The Sinus Bone Graft [3 ed.] 0867157917, 9780867157918

Table of contents :
Front Cover
Half Title Page
Dedication
Acknowledgments
Copyright ~ Library of Congress Cataloging-in-Publication Data
The Sinus Bone Graft, Third Edition -Edited by Ole T. Jensen, DDS, MS
Contents
Foreword
Preface
In Memoriam
Contributors
Introduction
The Preparation
The Sinus Procedure
Vascularized Osteotomies
The Future of Sinus Augmentations
Conclusion
Reference
Section I: Chapter 1: Bone Grafting Strategies for the Sinus Floor
Indications for Sinus Bone Grafting
Simultaneous Versus Delayed Implant Placement
Sinus Grafting Techniques
Bone Graft Materials
Conclusion
References
Chapter 2: Diagnosis and Treatment of Sinus Infections
Diagnosing Rhinosinusitis
Treatment of Acute and Chronic Infections
Other Causes of Sinus Infection
Considerations Prior to Sinus Augmentation Surgery
Conclusion
References
Chapter 3: Osteoperiosteal Flaps For Sinus Grafting
Posterior Maxillary Sandwich Osteotomy
Discussion
Conclusion
References
Chapter 4: The Alveolar Split Approach For Sinus Floor Intrusion
Alveolar Split for Width-Deficient Ridges
Case Studies
Conclusion
References
Chapter 5: Complex Techniques for Posterior Maxillary Reconstruction
Posterior Maxillary Sandwich Osteotomy Combined with Sinus Grafting
Maxillary Edentulous Le Fort I Osteotomy with Interposed Bone Graft
Titanium Shell Treatment of Severe Alveolar Defects
Conclusion
References
Section II: Chapter 6: Lateral Window Surgical Techniques for Sinus Elevation
Presurgical Sinus Assessment
Lateral Antrostomy Window Management
Alternatives to the Lateral Window
Sinus Membrane Elevation
Graft Placement
Closure
Conclusion
References
Chapter 7: Sinus Floor Augmentation Without Bone Grafting
Indications
Surgical Technique
Literature Review of Biologic and Histologic Aspects
Conclusions
References
Chapter 8: Intraoperative Complications with the Lateral Window Technique
Sinus Membrane Perforation
Intraoperative Bleeding
Other Complications
Conclusion
References
Chapter 9: Transcrestal Window Surgical Technique for Sinus Elevation
Treatment Strategies
Treatment Options
The Furcation Intrusion Procedure
Transcrestal Window Method for Sites with No Grafting
Transcrestal Approach with Graft Placement
Conclusion
References
Chapter 10: Transcrestal Sinus Augmentation with Oseeodensification
Challenges with the Posterior Maxilla
Osseodensification
TSAOD Protocols
Osseodensification and Osseointegration
Case Reports
References
Chapter 11: Transcrestal Hydrodynamic Piezoelectric Sinus Elevation
Clinical Goals of the Sinus Bone Graft Procedure
Lateral Wall Technique
Osteotome Technique
Using the Crestal Approach Sinus Kit
The Piezoelectric Transcrestal Approach for Sinus Augmentation
Conclusion
References
Section III: Chapter 12: Lateral and Transcrestal Bone Grafting with Short Implants
Treatment Recommendations
Lateral Sinus Bone Grafting with Immediate Implant Placement
Transcrestal Sinus Bone Grafting with Immediate Implant Placement
Discussion
Conclusion
References
Chapter 13: Transsinus Implants
Alternatives to Lateral Window Surgery
Nasal Anatomy
Using Transsinus Implants
Evidence-Based Support for the Transsinus Approach
Conclusion
References
Chapter 14: Guided Extrasinus Zygomatic and Pterygoid Implants
Zygomatic and Pterygoid Implant Treatment Options
Implant Positioning
Surgical Protocol
Complications
Conclusion
Acknowledgments
References
Chapter 15: Navigation for Transsinus Placement of Zygomatic Implants
Challenges with Zygomatic Implant Placement
Surgical Navigation
Accuracy Analysis
Case 1: Zygomatic Implant Classic Approach with Surgical Navigation System
Case 2: Zygomatic Implant Quad Approach with Surgical Navigation System
Conclusion
Acknowledgments
References
Chapter 16: Arch-length Threshold for Using Zygomatic Implants
Defining the Short Arch Length
Preoperative Evaluation: Imaging
Detailed Clinical Examination
Treatment Options for the Short-Arch-Length Maxilla
Conclusion
References
Chapter 17: Pterygoid Implants
Anatomical Considerations
Preoperative Evaluation and Patient Selection
Surgical Technique
Complications
Case Studies
Conclusion
References
Chapter 18: The Nazalus Implant
Surgical Procedure
Advantages of Nazalus Implants
Conclusion
References
Chapter 19: Ultrawide Implants in Molar Sites
Treatment Using Ultrawide Implants
Presurgical Planning
Surgical Technique
Case Examples
Conclusion
References
Chapter 20: Restoration and Abutment Options
Restoration Options
Abutment Selection
Conclusion
References
Section IV: Chapter 21: The Sinus Consensus Conference: Results and Innovations
Sinus Grafting Materials
Sinus Grafting Techniques
Combination Sinus and Alveolar Augmentation Grafts
Alternative Strategies for Bypassing the Need for Sinus Grafting
Conclusion
Acknowledgments
References
Chapter 22: Sharpey Fiber Biologic Model for Bone Formation
Embryomimetic Surgical Engineering
The Sharpey Fiber Matrix Network
Microanatomical Innovations
Clinical Applications
Conclusion
Acknowledgments
References
Chapter 23: Using BMP-2 to Increase Bone-To-Implant Contact
Animal Study
Human Study
Discussion
Conclusion
References
Chapter 24: Tissue-Engineered Bone and Cell-Conditiond Media
Approaches to Bone Regenerative Medicine Using TEB
CCM for Bone Regeneration
Conclusion
Acknowledgments
References
Chapter 25: Tissue Engineering of the Dental Organ for the Posterior Maxilla
Abnormal Odontogenesis
Dental Stem Cells for Dental Tissue Engineering
Important Cell Signaling Molecules for Dental Tissue Engineering
Conclusion
Acknowledgments
References
Index

Citation preview

The Sinus Bone Graft, Third Edition

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Dedication For my loving family: my wife, Marty, and my three children, Sverre, Trygve, and Autumn.

Acknowledgments I wish to acknowledge my surgical assistants, Cindy Formanek and Jennifer Chatting, and my auxiliary staff including Monique Stozek, Jenny Featheringill, Kathy Stenson, and Janet Zacharias. — Ole T. Jensen

Library of Congress Cataloging-in-Publication Data Names: Jensen, Ole T., editor. Title: The sinus bone graft / [edited by] Ole T. Jensen. Description: Third edition. | Batavia, IL : Quintessence Publishing Co Inc,     [2018] | Includes bibliographical references and index. Identifiers: LCCN 2018033872 | ISBN 9780867157918 (hardcover) Subjects: | MESH: Maxillary Sinus--surgery | Bone Transplantation--methods |     Dental Implantation--methods | Reconstructive Surgical Procedures--methods Classification: LCC RF421 | NLM WV 345 | DDC 617.5/2--dc23 LC record available at https://lccn.loc.gov/2018033872

© 2019 Quintessence Publishing Co, Inc Quintessence Publishing Co Inc 411 N Raddant Rd Batavia, IL 60510 www.quintpub.com 5 4 3 2 1 All rights reserved. This book or any part thereof may not be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, or otherwise, without prior written permission of the publisher. Editor: Marieke Zaffron Design: Sue Zubek Production: Sue Robinson Printed in China

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THE SINUS BONE GRAFT THIRD EDITION

Edited by

Ole T. Jensen, dds, ms Adjunct Professor Department of Oral and Maxillofacial Surgery School of Dentistry University of Utah Salt Lake City, Utah

Berlin, Barcelona, Chicago, Istanbul, London, Milan, Moscow, New Delhi, Paris, Prague, São Paulo, Seoul, Singapore, Tokyo, Warsaw

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CONTENTS Foreword by Tomas Albrektsson   vi Preface  vii In Memoriam: Carl Erwin Misch   viii Contributors  ix Introduction by Hilt Tatum Jr   xiii

Section I: Surgical Options for Bone Grafting 1 Bone Grafting Strategies for the Sinus Floor  1 Craig M. Misch

2 Diagnosis and Treatment of Sinus Infections  15 Ashish A. Patel | Eric J. Dierks

3 Osteoperiosteal Flaps for Sinus Grafting  23 Ole T. Jensen

4 The Alveolar Split Approach for Sinus Floor Intrusion  32 Len Tolstunov | Daniel R. Cullum | Ole T. Jensen

5 Complex Techniques for Posterior Maxillary Reconstruction  42 Nardy Casap | Heli Rushinek

Section II: Lateral and Transcrestal Sinus Elevation 6 Lateral Window Surgical Techniques for Sinus Elevation  48 Tiziano Testori | Riccardo Scaini | Matteo Deflorian | Stephen S. Wallace | Dennis P. Tarnow

7 Sinus Floor Augmentation Without Bone Grafting  66 Giovanni Cricchio | Lars Sennerby | Stefan Lundgren

8 Intraoperative Complications with the Lateral Window Technique  73 Stephen S. Wallace | Dennis P. Tarnow | Tiziano Testori

9 Transcrestal Window Surgical Technique for Sinus Elevation  92 Michael S. Block

10 Transcrestal Sinus Augmentation with Osseodensification  105 Salah Huwais | Ziv Mazor

11 Transcrestal Hydrodynamic Piezoelectric Sinus Elevation  118 Konstantin Gromov | Sergey B. Dolgov | Dong-Seok Sohn

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Section III: Implant Placement in the Resorbed Posterior Maxilla 12 Lateral and Transcrestal Bone Grafting with Short Implants  128 Rolf Ewers | Mauro Marincola

13 Transsinus Implants  140 Tiziano Testori | Gabriele Rosano | Alessandro Lozza | Stephen S. Wallace

14 Guided Extrasinus Zygomatic and Pterygoid Implants  151 Nardy Casap | Michael Alterman

15 Navigation for Transsinus Placement of Zygomatic Implants  159 Yiqun Wu | Feng Wang | Wei Huang | Kuofeng Hung

16 Arch-Length Threshold for Using Zygomatic Implants  169 Nicholas J. Gregory | Ole T. Jensen

17 Pterygoid Implants  175 Stuart L. Graves | Lindsay L. Graves

18 The Nazalus Implant  183 Pietro Ferraris | Giovanni Nicoli | Ole T. Jensen

19 Ultrawide Implants in Molar Sites  187 Costa Nicolopoulos | Andriana Nikolopoulou

20 Restoration and Abutment Options  199 Alexandre Molinari | Sérgio Rocha Bernardes

Section IV: Evolution and Innovations in Maxillary Bone Regeneration 21 The Sinus Consensus Conference: Results and Innovations  203 Vincent J. Iacono | Howard H. Wang | Srinivas Rao Myneni Venkatasatya

22 Sharpey Fiber Biologic Model for Bone Formation  213 Martin Chin | Jean E. Aaron

23 Using BMP-2 to Increase Bone-to-Implant Contact  227 Byung-Ho Choi

24 Tissue-Engineered Bone and Cell-Conditioned Media  235 Hideharu Hibi | Wataru Katagiri | Shuhei Tsuchiya | Masahiro Omori | Minoru Ueda

25 Tissue Engineering of the Dental Organ for the Posterior Maxilla  244 Fugui Zhang | Dongzhe Song | Ping Ji | Tong-Chuan He | Ole T. Jensen

Index  259

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FOREWORD

About 40 years ago, I defended my PhD thesis, Healing of Bone Grafts, under the tutorship of P-I Brånemark. I placed optical implants in bone tissue prior to grafting and in this manner was able to investigate what happened to the graft microvasculature after transplantation. Even if allogeneic or heterologous bone was available at the time (eg, in the Oswestry and Kiel bone banks), it was generally agreed that only autogenous bone provided adequate repair. Bank bone was mainly used for large orthopedic defects as a last resort. Some 20 years later, I participated in the consensus conference on sinus grafts arranged in the United States. At the same time, results of sinus grafts were so successful that it seemed irrelevant whether autogenous, allogeneic, or heterologous grafts were used. Lamentably, the clinical material available at the time was data collected from clinicians rather than data printed in peer-reviewed journals, and this seldom allows for a critical scientific analysis. Nevertheless, it was the first time I had heard colleagues claim that similar good clinical results could be achieved with types of grafts other than the conventionally used autograft. Today, of course, we have a large bulk of evidence that many types of bone grafts function very well when placed in sinuses. Admittedly, as evidenced in one chapter of the present volume, in some cases we do not necessarily see improved clinical results of implants after grafting compared to nongrafting—the preparation of bone tissue may provide a satisfactory supply of autogenous bone particles for clinical success. However, this type of very simple autografting may not work in severely resorbed clinical cases, and clinicians trying it in cases with 2 to 4 mm of bone thickness are advised to carefully check implant stability after placement. One commonly used source of sinus graft material today can be heterologous bone such as Bio-Oss (Geistlich). We investigated the long-term fate of sinus-grafted Bio-Oss particles 11 years after grafting and found them largely unchanged in size and morphology.1 These particles, like the implant, may represent a foreign body with osteoconductivity (ie, new bone growth that explains the good clinical results achieved). In fact, the clinical fate of autografts may be quite similar in behavior. We analyzed the histologic outcome of small autogenous bone columellas used to replace the ossicular bones in hearing impairment

in humans. The actual grafts had died, but they continued to function clinically with clear evidence that new live bone grew on the surfaces of the old grafts.2 The main reason why a volume such as the third edition of The Sinus Bone Graft is so important depends on the clinical reports made available. Sinus grafts are indeed most positive for patient treatment and have since long proven their clinical efficacy. Dr Jensen, the editor of this book, is one of very few in the world who has experience from more than 30 years working with sinus grafts, and I can think of no one more suited to be editor of this volume. He has put together a great number of excellent contributors to write about their experiences with sinus grafts under different conditions. This book is highly recommended to anyone using oral implants, and since major innovations have been presented in this third edition, I would even recommend it to those who already own the previous editions. Tomas Albrektsson, md, phd Professor Emeritus Department of Biomaterials Institute of Clinical Sciences Gothenburg University Gothenburg, Sweden Visiting Professor Faculty of Odontology Malmö University Malmö, Sweden

References 1. Mordenfeld A, Hallman M, Johansson CB, Albrektsson T. Histological and histomorphometrical analyses of biopsies harvested 11 years after maxillary sinus floor augmentation with deproteinized bovine and autogenous bone. Clin Oral Implants Res 2010;21:961–970. 2. Kylén P, Albrektsson T, Ekvall L, Hellkvist H, Tjellström A. Survival of the cortical bone columella in ear surgery. Acta Otolaryngol 1987;104:158–165.

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PREFACE

With each passing year, I continue to be amazed at how far we have come and how we continue to advance in the highly specialized procedure of sinus elevation and grafting. Only a few decades ago, the sinus elevation was performed in just one general dental office in Opelika, Alabama; it is now an international cross-specialty collaboration. As the techniques have evolved, so has this book. The third edition of The Sinus Bone Graft updates current scientific rationale and clinical practice for what continues to be a necessary procedure for posterior maxillary dental implant reconstruction. In this volume, attention is given to historical recognition of pioneers in this field, including Hilt Tatum, Philip Boyne, and Carl Misch. But there are countless contributors to sinus elevation, from the members of the 1996 Sinus Consensus Conference sponsored by the Academy of Osseointegration to the authors of the now over 2,000 publications concerning modifications related to sinus floor treatment. In 1986, I made the pilgrimage taken by many general dentist implantologists before me to visit Dr Hilt Tatum’s office and learn firsthand from the master clinician. After observing him over a few days, I remember leaving in a kind of daze wondering if a “sinus lift,” as he called it, could be real. It wasn’t until 10 years later that a group of 38 clinicians met in Boston to present their early sinus elevation results. After everyone had presented their data, including disparate methods and modifications to the original procedure, we came to understand quite remarkably that we all had success! We were stunned, almost to silence, that Dr Tatum’s work had so summarily been replicated. From that point forward, the world of implant dentistry changed as the sinus elevation was confidently recommended to patients.

A few years later, after having collaborated in Sweden, I had a discussion with P-I Brånemark and Ulf Lekholm, who still viewed the sinus procedure with skepticism. At the time, Dr Brånemark was hatching the idea of the zygomatic implant and told me that the sinus graft might not be necessary after all. I did not understand his meaning then, but I do now. In addition to an overview of the types of graft material and techniques, this book is filled with alternatives to the sinus graft. Among them are the use of the zygomatic implant and the idea that the sinus membrane should be reflected but not necessarily grafted, as Stefan Lundgren has shown. In 2011, I met separately with Tatum and Boyne, the two great innovators of the sinus floor bone graft, and recorded their independent creative thought processes firsthand. Interestingly, they both described inspiration being triggered by a problem of deficient interocclusal space. Though surgeons, they were thinking as restorative dentists, struggling with how to obtain room for crowns or a prosthesis, when the sudden thought occurred of developing bone “on the other side” (ie, on the sinus floor). Bone grafting had never solved a problem in this way before. Similarly, many of the innovators in this book—the best and the brightest minds throughout the world—continue to creatively solve a portion of the riddle that is regenerative medicine. This collection of prescient advancements in sinus graft technology would clearly not be possible without these innovators and scientists, the doctors of medicine and dentistry. However, we must also recognize all those who participate in the art of healing a human being: the surgical and research assistants, auxiliary staff, supportive families, and of course the patients themselves. Thank you for your devotion to this worthy cause. Ole T. Jensen

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IN MEMORIAM: Carl Erwin Misch, dds, mds

  Dr Carl Misch (left) and Dr Craig Misch (right) at the Academy of Osseointegration Annual Meeting, 2016.

“Being his brother I could feel I live in his shadow, but I never have and do not now. I live in his glow.”—Michael Morpurgo In 2017, the dental profession and implant field lost a true icon: my brother, Dr Carl E. Misch. Carl often stated that his professional goal was to elevate the standard of care in implant dentistry, and he worked tirelessly in pursuit of that achievement. He had a gift for organizing and simplifying information and used that gift to develop numerous principles and classifications that became integral concepts in the origins of modern implant dentistry. Carl had the good fortune to meet Dr Hilt Tatum in the late 1970s and to be taught sinus bone grafting techniques from one of the originators of the procedure. He had exceptional clinical skills and was one of the first prosthodontists in the United States to perform complex implant surgeries. In 1987, Carl published the first classification for managing the posterior maxilla based on the amount of bone below the sinus. These practical guidelines are still relevant today and were included in the second edition of The Sinus Bone Graft. He was also an early proponent of using bone substitutes for sinus grafting and presented his data alongside me at the first Sinus Consensus Conference at Babson College in 1996.

Carl had a passion for learning and sharing information. He founded the Misch Implant Institute, a continuing education program with an organized curriculum on implant dentistry. He was also on the faculty at several dental schools and served as director of one of the first university-based implant programs at the University of Pittsburgh from 1986 to 1993. His lectures— enthusiastic, authoritative, charismatic, and personal—always captured the audience’s attention. This text, Contemporary Implant Dentistry (Mosby/Elsevier, 1993), was one of the first books detailing sinus anatomy, physiology, and surgical approaches to manage the atrophic posterior maxilla. This text is now in its third edition and is considered by many as the most complete reference on surgical and prosthetic implant topics. Carl was a prolific author and published over 100 peer-reviewed articles on various implant-related topics. His commitment to the profession truly changed the lives of his students, colleagues, and patients. Dr Carl Misch was a true pioneer, leader, professor, and master clinician of implantology. He had a remarkable career, and we will all miss his influence and passion for implant dentistry. Craig M. Misch

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CHAPTER 19

CONTRIBUTORS Jean E. Aaron, phd

Daniel R. Cullum, dds

Bone Structural Biologist and Visiting Lecturer School of Biomedical Sciences University of Leeds Leeds, United Kingdom

Private Practice Limited to Oral and Maxillofacial Surgery Coeur d’Alene, Idaho

Michael Alterman, dmd Director of Outpatient Clinic Hadassah and Hebrew University Medical Center Jerusalem, Israel

Guest Lecturer Department of Oral and Maxillofacial Surgery Loma Linda University Loma Linda, California

Sérgio Rocha Bernardes, bds, msc, phd

Guest Lecturer Department of Oral and Maxillofacial Surgery University of California, Los Angeles Los Angeles, California

Head of New Product Development and Clinical Practice  Neodent Global

Matteo Deflorian, dds

Professor Latin American Institute of Dental Research and Education Curitiba, Brazil

Michael S. Block, dmd Private Practice Limited to Oral and Maxillofacial Surgery Metairie, Louisiana

Nardy Casap, dmd, md Professor and Chairman Department of Oral and Maxillofacial Surgery Hadassah and Hebrew University Medical Center Jerusalem, Israel

Martin Chin, dds Private Practice Limited to Oral and Maxillofacial Surgery San Francisco, California

Byung-Ho Choi, dds, phd Professor Department of Oral and Maxillofacial Surgery Wonju College of Medicine Yonsei University Wonju, South Korea

Giovanni Cricchio, dds, phd

Tutor at the Section of Implant Dentistry and Oral Rehabilitation Department of Biomedical, Surgical, and Dental Sciences School of Medicine University of Milan Milan, Italy

Eric J. Dierks, dmd, md Private Practice Limited to Head and Neck Surgery Portland, Oregon

Sergey B. Dolgov, dds, msd Private Practice Limited to Periodontics and Implant Dentistry Mankato, Minnesota

Rolf Ewers, md, dmd, phd Chairman Emeritus Department of Cranio-Maxillofacial and Oral Surgery Medical University of Vienna Vienna, Austria

Pietro Ferraris, md, dds Private Practice Limited to Oral and Maxillofacial Surgery and Prosthodontics Alessandria, Italy

Research Fellow Department of Oral and Maxillofacial Surgery Umeå University Umeå, Sweden

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Lindsay L. Graves, dmd

Kuofeng Hung, dds, ms

Resident Division of Oral and Maxillofacial Surgery UT Southwestern/Parkland Memorial Hospital Dallas, Texas

Department of Oral Maxillofacial Implantology Second Dental Clinic Ninth People’s Hospital School of Medicine Shanghai Jiao Tong University Shanghai, China

Stuart L. Graves, dds, ms Private Practice Limited to Oral, Maxillofacial, and Implant Surgery Burke, Virginia

Salah Huwais, dds

Private Practice Limited to Oral and Maxillofacial Surgery Monroe, Louisiana

Adjunct Assistant Clinical Professor Department of Restorative Sciences School of Dentistry University of Minnesota Minneapolis, Minnesota

Konstantin Gromov, dds

Private Practice Limited to Periodontics and Implantology Jackson, Michigan

Nicholas J. Gregory, dds

Private Practice Limited to Periodontics and Implant Dentistry Glenview, Illinois Private Practice Limited to Perioprosthodontics and Implant Dentistry Moscow, Russia

Tong-Chuan He, md, phd Associate Professor Department of Surgery Biological Sciences Division University of Chicago Associate Professor and Director Molecular Oncology Laboratory Department of Orthopaedic Surgery and Rehabilitation Medicine University of Chicago Medical Center Chicago, Illinois Chongqing Key Laboratory of Oral Diseases and Biomedical Sciences The Affiliated Hospital of Stomatology Chongqing Medical University Chongqing, China

Hideharu Hibi, dds, phd Professor and Chair Department of Oral and Maxillofacial Surgery Nagoya University Graduate School of Medicine Nagoya, Japan

Wei Huang, dds, ms Professor Department of Oral Maxillofacial Implantology Ninth People’s Hospital School of Medicine Shanghai Jiao Tong University Shanghai, China

Vincent J. Iacono, dmd SUNY Distinguished Service Professor, Tarrson Family Professor of Periodontology and Chair Department of Periodontology Director of Postdoctoral Education Stony Brook School of Dental Medicine Stony Brook, New York

Ole T. Jensen, dds, ms Adjunct Professor Department of Oral and Maxillofacial Surgery School of Dentistry University of Utah Salt Lake City, Utah

Ping Ji, dds, phd Professor and President Chongqing Key Laboratory of Oral Diseases National Clinical Research Center for Oral Diseases The Affiliated Hospital of Stomatology Chongqing Medical University Chongqing, China

Wataru Katagiri, dds, phd Associate Professor Division of Reconstructive Surgery and Oral and Maxillofacial Region Niigata University Graduate School of Medical and Dental Sciences Niigata, Japan

Alessandro Lozza, md Chief Assistant and Senior Consultant Neurophysiopathy Service, IRCCS Mondino Foundation Pavia, Italy

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Stefan Lundgren, dds, phd

Costa Nicolopoulos, bds, ffd

Professor and Chairman Department of Oral and Maxillofacial Surgery Umeå University Umeå, Sweden

Private Practice Limited to Oral and Maxillofacial Surgery Dubai, United Arab Emirates

Mauro Marincola, dds, ms Professor and Clinical Director International Implantology Center Department of Implant Dentistry University of Cartagena Cartagena, Colombia

Ziv Mazor, dmd Associate Professor Department of Implantology Titu Maiorescu University Bucharest, Romania Private Practice Tel Aviv, Israel

Craig M. Misch, dds, mds Clinical Associate Professor Department of Periodontics/Prosthodontics School of Dental Medicine University of Florida Gainesville, Florida Private Practice Limited to Oral and Maxillofacial Surgery and Prosthodontics Sarasota, Florida

Alexandre Molinari, dds, msc, phd Director Clinical Professional Relations and Education Neodent USA Andover, Massachusetts

Andriana Nikolopoulou, md Private Practice  Glyfada, Greece

Masahiro Omori, dds, phd Postdoctoral Researcher Department of Oral and Maxillofacial Surgery Nagoya University Graduate School of Medicine Nagoya, Japan

Ashish A. Patel, dds, md Consultant at a Private Practice Limited to Head and Neck Surgery Associate Professor Department of Oral and Maxillofacial Surgery School of Dentistry Oregon Health and Science University Portland, Oregon

Gabriele Rosano, dds, phd Oral Surgeon Lake Como Institute Como, Italy

Heli Rushinek, dmd Oral and Maxillofacial Surgeon Department of Dentistry Hadassah and Hebrew University Medical Center Jerusalem, Israel

Riccardo Scaini, dds

Visiting Professor Latin American Institute of Dental Research and Education Curitiba, Brazil

Tutor at the Section of Implant Dentistry and Oral Rehabilitation Department of Biomedical, Surgical, and Dental Sciences IRCCS Istituto Ortopedico Galeazzi University of Milan Milan, Italy

Srinivas Rao Myneni Venkatasatya, dds, ms, phd

Lars Sennerby, dds, phd

Assistant Professor Department of Periodontics Stony Brook School of Dental Medicine Stony Brook, New York

Giovanni Nicoli, md Maxillofacial Surgery Specialist ASST Vallecamonica Hospital Brescia, Italy

Professor Institute of Odontology Sahlgrenska Academy University of Gothenburg Gothenburg, Sweden

Dong-Seok Sohn, dds, phd Professor and Chair Department of Oral and Maxillofacial Surgery Catholic University Medical Center of Daegu Daegu, South Korea

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Dongzhe Song, dds, phd

Minoru Ueda, dds, phd

Molecular Oncology Laboratory Department of Orthopaedic Surgery and Rehabilitation Medicine University of Chicago Medical Center Chicago, Illinois

Professor Emeritus Department of Oral and Maxillofacial Surgery Nagoya University Graduate School of Medicine Nagoya, Japan

State Key Laboratory of Oral Diseases National Clinical Research Center for Oral Diseases West China Hospital of Stomatology Sichuan University Chengdu, China

Dennis P. Tarnow, dds Clinical Professor and Director of Implant Education College of Dental Medicine Columbia University Irving Medical Center New York, New York

Tiziano Testori, md, dds Head of the Section of Implant Dentistry and Oral Rehabilitation Department of Biomedical, Surgical, and Dental Sciences University of Milan Milan, Italy Private Practice Limited to Implantology Como, Italy Adjunct Clinical Associate Professor Department of Periodontics and Oral Medicine School of Dentistry University of Michigan Ann Arbor, Michigan

Len Tolstunov, dds, dmd Associate Clinical Professor School of Dentistry University of the Pacific Assistant Clinical Professor School of Dentistry University of California, San Francisco Private Practice Limited to Oral and Maxillofacial Surgery San Francisco, California

Shuhei Tsuchiya, dds, phd Assistant Professor Department of Oral and Maxillofacial Surgery Nagoya University Graduate School of Medicine Nagoya, Japan

Stephen S. Wallace, dds Clinical Associate Professor Department of Periodontics College of Dental Medicine Columbia University New York, New York Private Practice Limited to Periodontics Waterbury, Connecticut

Feng Wang, dds, md Assistant Professor Department of Oral Maxillofacial Implantology Ninth People’s Hospital School of Medicine Shanghai Jiao Tong University Shanghai, China

Howard H. Wang, dds, ms, mph, mba Private Practice Limited to Endodontics, Periodontics, and Implant Dentistry New York, New York

Yiqun Wu, dds, md Professor Department of Oral Implantology Ninth People’s Hospital Second Dental Clinic School of Medicine Shanghai Jiao Tong University Shanghai, China

Fugui Zhang, dds, phd Molecular Oncology Laboratory Department of Orthopaedic Surgery and Rehabilitation Medicine University of Chicago Medical Center Chicago, Illinois Chongqing Key Laboratory of Oral Diseases and Biomedical Sciences The Affiliated Hospital of Stomatology Chongqing Medical University Chongqing, China

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INTRODUCTION Hilt Tatum Jr, dds

When Dr Jensen contacted me about contributing to this third edition, I was uncertain. It had not been possible for me to participate in the Sinus Consensus Conference, and at the time I had not read his book. After reading the second edition, I realized it would be an honor to participate in this one.

The Preparation My journey leading to the sinus augmentation procedure started in 1956, when I attended the first course on oral implants given in an American dental school, the Emory University School of Dentistry. The course was presented by Col Roy Bodine. My clinical experience began with 2 years of service in the Marine Hospital located in Savannah, Georgia. The next 2 years were spent doing full-mouth restorative dentistry in Savannah before I joined my father, Hilt Tatum Sr, and brother, Crawford Tatum, DDS, in Opelika, Alabama. There, our practice quickly became oriented to extensive restorative dentistry. We recognized patients’ and our own dissatisfaction with free-end partial dentures and felt that this need could be met with the use of endosteal implants and fixed restorations. In an attempt to fix the problem, we acquired two sheets of commercially pure titanium, 0.25 inch thick and 0.75 inch thick. Using these sheets, we began to make and successfully use endosteal implants with different shapes that were designed to fit into the available bone found in different patients. After the implants were placed, we waited to load them until after a healing period similar to that used for mandibular fractures. However, because most of these patients had worn partial dentures for extended periods of time, we recognized the severe vertical bone loss and the need to restore the missing bone before the patients could receive implants.

The obvious answer to this need was to restore the missing bone volume with autogenous bone augmentation. However, as we began our preparation period before performing these surgeries, a startling event occurred. I had the chance to meet with Dr Frank Morgan, who had extensive experience doing bone grafting to treat battlefield wounds during the Vietnam War. When I discussed our plans with Frank, he shocked me with the following words: “Hilt, if you do this elective surgery on your private restorative patients, it will bury you with the complications you will encounter.” This completely stopped our efforts toward bone construction for some time. Don Tillery, an oral surgeon and close friend, was aware of the preparation we had done and the effect that Dr Morgan’s advice had on our plans. In early 1969, Don called and said that he had seen a technique that he thought would safely meet our goal. He told me about an oral surgeon, Dr James Alley, who had successfully done a series of preprosthetic bone augmentations on edentulous mandibles before denture construction. We contacted Dr Alley, and he invited us to visit his office. We spent a week with him, observed two surgeries, and were able to see several patients who were at different periods of time postsurgically. The technique consisted of placing an autogenous rib (with no screws) on an edentulous mandible. This was followed by a 6-month unloaded healing period and then the construction of a new mandibular denture. He reported no postoperative healing complications. The secret to Dr Alley’s success was in making two vertical incisions in the vestibule of each canine area, tunneling and mobilizing the soft tissue over the entire mandible, decorticating the crest of the mandible, shaping and placing the rib, and closing the remote incisions. The secret therefore was good asepsis, no incisions over the graft material, decortication, and an unloaded healing period. One patient who had worn the postoperative denture for 2 years appeared to have very little of the augmentation left.

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INTRODUCTION

Fig 1  Autogenous rib with one thickness (a) and two thicknesses (b) from 1970.

a

b Fig 2 (a and b) By 1980, we were using autogenous iliac bone for the maxilla and bilateral sinuses done with two vertical vestibular incisions.

a

b

These were our takeaways from this visit: •  Surgical asepsis would be critical. •  Decortication aided the augmentation union with the mandible. •  Remote incisions had prevented postoperative infections. •  Loading of the denture had largely destroyed the newly formed crestal bone. •  Placement of endosteal implants should not destroy the new crestal bone. •  Placement of endosteal implants should internally load and stimulate new crestal bone. •  Most importantly, we could safely begin to restore alveolar bone. In January of 1970, we performed the first of four successful autogenous rib augmentations on posterior edentulous mandibles (Fig 1) harvested by Dr William Lazenby. Following his suggestion, we later began using the ilium as a bone source. Over a period of 9 years, Dr Lazenby and Dr Doyle Hanes routinely harvested bone for our augmentation patients (Fig 2) until I relocated my practice to St Petersburg, Florida, in 1979. Because all of these patients were treated in a hospital environment with remote incisions and Millipore filters (MilliporeSigma) over the augmented bone, we experienced a very limited number of postoperative surgical complications. I have had the opportunity to give more than 2,000 podium presentations demonstrating these principles of creative remote incisions for all augmentation locations. These have been presented to a wide range of dental meetings, practitioners, and specialists. It surprised me that a large majority of alveolar augmentations have continued to be completed with crestal incisions over the augmentation material, sometimes resulting in complications. With good asepsis, remote incisions, adequate tissue mobilization, effective augmentation material, and precise tissue closures, complication rates will be significantly reduced.

We also found that augmented bone remained stable after implant placement, healing, and restoration. We did observe that when large augmentations were done within the esthetic zone, it was wise to maintain patients with provisional restorations in function for a period of 2 years before the definitive restorations were placed. This resulted in the most desirable esthetic results.

The Sinus Procedure As our augmentation experience progressed, we recognized that it was impossible to do a vertical onlay augmentation in a posterior maxilla with no vertical loss and a severely pneumatized sinus without infringing on the vertical space required for the dental restorations. For the longest time, this seemed an insurmountable challenge. Then, in 1974, the thought occurred to me that we were looking at the problem backward and should be putting the bone inside of the sinus rather than on the crest. Immediately after this epiphany, I had parallel feelings of both exhilaration and fear. I was exhilarated by the thought that it might be possible, but the fear was that which any dentist might have on considering contact with a maxillary sinus. During the remainder of 1974, we placed a number of posterior maxillary implants in the following way. We would either machine a titanium implant or cast a Vitallium implant that would fit into the medullary space between the sinus floor and the crest of the ridge (Fig 3). We also cast a try-in that had the same side dimensions but was longer than the implant. A remote palatal flap was lifted to expose the ridge crest, and curettes were used to prepare the implant site by removing bone to the floor of the sinus to match the dimension of the implant. The try-in was then fitted into this socket and lightly tapped to release the sinus floor. The floor and mucosal lining were vertically elevated a few millimeters, and some of the curetted bone was

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The Sinus Procedure

Fig 3 Custom-made implants elevating the sinus floor and custom-made root form from 1974.

Fig 4  Sinus floor elevated by compressing bone and without entering the sinus.

placed into the space around the elevated floor. The implant was then placed into the deepened socket and additional bone was placed over the implant to the crest of the ridge, with only the implant neck exposed. The flap was rotated and sutured on the palatal wall. The healing around each of these implants was uneventful, and they were restored. We have always referred to this procedure as a sinus lift. By 1980, we had modified the technique into compressing the cancellous bone threads into an intertwined mat that could elevate the floor as it deepened the socket without entering the sinus (Fig 4). We now use these bone manipulation osteotomes to form the sockets, compress the cancellous bone, and elevate the sinus floor. Our first sinus augmentation with autogenous, particulate, iliac bone was done in February of 1975. This, along with our next four augmentations, was done from the crest of the ridge and opened with a palatal flap. We then began to primarily use a crestal incision and prepare a sinus window anterior to the zygomatic buttress on the lateral wall of the maxilla. However, our fear of the word sinus was so strong that in the hospital operative notes, we would describe the operation as an inverted maxillary bone graft. At the 1976 Alabama Implant Congress meeting in Birmingham, Alabama, we reported on the sinus augmentation procedure and the results we had observed during the previous 15 months. I was invited to make a presentation in the fall of 1977 on sinus augmentation at the American Academy of Implant Dentistry annual meeting and asked Dr Philip Boyne to join me. In a 1994 meeting of the Alabama Implant Congress (at the same podium from which I first presented in 1976), he confirmed our success with this procedure before an audience of more than 300 attendees. During the first several years of sinus augmentations, we had limited instruments and relied heavily on modified Fogarty catheters to aid in the elevation of the sinus membrane. These were shortened to a few inches long and attached to a syringe. When slid under the sinus lining and gently inflated, they could safely lift the membrane (Fig 5). By 1978, we had created suitable instruments and no longer needed the Fogarty catheters. Until 1984, autogenous iliac bone was our primary augmentation material. However, from 1972 until 1982, we were furnished some frozen human allograft by Dr Bill Hiatt from the VA-funded

Fig 5  Inflated Fogarty catheter elevating the sinus membrane.

study, 1962–1982, for which he was a codirector. We established and maintained the same cryogenic banking capability as was used in the study and would always have a suitable human lymphocyte antigen match between the donor and recipient for anyone treated with this bone. Results comparable with autogenous bone were observed on the sinus augmentation patients treated with this allograft. From 1978 forward, we began to utilize a titanium root form system I had developed, which became the first titanium root form system with FDA marketing approval (Fig 6). This system also included a selection of designs that were used to elevate the sinus floor and used the curetted bone that was harvested during the socket preparation (Fig 7). From 1979 until 1983, we did the surgical cases for the US Food and Drug Administration (FDA) preclinical study on tricalcium phosphate ceramic (TCP) as a bone augmentation material. We evaluated and found this product to be successful for sinus augmentations, though slower in its replacement than human bone. In the summer of 1982, Martin Lebowitz, DDS, MS, left the chairmanship of the OMS Department at the University of Florida School of Dentistry to join me. Following this, many of the Le Fort I surgical cases also had simultaneous sinus augmentations. Martin was left-handed and I was right-handed, which allowed us to both operate at the same time with the following steps: •  Careful attention was given to achieve optimum asepsis within each nasal passageway during preparation and intubation. •  After maxillary downfracture, a careful, meticulous freeing of the nasal mucosa from bone to prevent tears in this tissue was done. This was important to protect the augmentation material from risk of contamination from bacterial flora occurring in the nose. •  We also provided a hyperbaric oxygen chamber within our office to aid in the management of potential anaerobic infections. In 1984, my son, Hilt Tatum III, DMD, joined our practice. During that same year, multiple augmentation products became available with the freeze-dried demineralized bone products reported as the most favorable. We used multiple products for

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INTRODUCTION

a

b

Fig 6  (a and b) Transmucosal implants and soft tissue reconstruction in augmented maxilla and bilateral sinuses.

sinus augmentations during this period, but by 1986, our clinical results were varied and confusing. We decided to evaluate each class of products by comparing results with histomorphometric evaluations taken from bilateral sinuses in the 4th postoperative month. We obtained three to five results from each type of the tested materials and were surprised by what we found. The best results (37% new bone) were obtained from irradiated cancellous human bone (ICB, Rocky Mountain Tissue Bank), and the second best was from 1- to 2-mm demineralized freeze-dried cortical bone chips (12% new bone). Since 1988, the ICB from Rocky Mountain Tissue Bank has been our product of choice for sinus augmentations. This recognition that ICB provided a sinus augmentation product comparable with autogenous bone permitted a readily available and reliable material for in-office surgical procedures. Also, this product allowed us to perform lateral wall augmentations and place root-form implants rather than the special sinus implants. The average amount that we have used for each sinus has been 7 g. In the mid-1990s, I designed and made a number of instruments to improve our ability to perform sinus procedures. These included flap retractors to fit over different shapes found on zygomatic buttresses and curettes made to fit the different anatomical areas found within sinuses. These instruments have significantly simplified and improved the precision of the surgeries. Even when following a strict protocol under exact specified patient conditions, complications may occur. When a tear is present in the mobilized mucosal lining, excess tissue is folded over the tear and stabilized with a shaped collagen tape just prior to placing the bone. The tape will momentarily adhere to the lining, and by placing the bone immediately against the tape, it will stabilize the tape and hold the torn tissue in position. When postoperative infections occur, they will typically become symptomatic within a few days after the surgical procedure. Immediate attention, including culture and sensitivity testing, modification or expansion of antibiotic coverage with therapeutic doses, and further modification as directed following sensitivity testing, has proven to be effective in the majority of patients. If this does not completely eliminate the symptoms within a period of 7 to 14 days, removal of all augmentation

Fig 7  Sinus implant selection and try-ins. This photograph shows 4 of the 16 sizes made.

material is usually indicated. If implants were placed during the augmentation procedure, this regimen would not be expected to be successful as a result of the biofilm-shielded bacterial colonies growing and shielded on the implants. In our 43 years of sinus augmentations, we have lost the grafts in less than 1% of the sinuses treated.

Vascularized Osteotomies By 1980, we recognized that sinus and interpositional bone augmentations as well as free-flap procedures were safer and more precise than onlay procedures. Hoping to demonstrate this, I took a training course in microvascular surgery. We then attempted to replace onlay autogenous procedures with freeflap microvascular procedures using autogenous iliac sources. Though we could make the microvascular connections, we found that developing the correct bone shapes in the precise locations needed on the alveolar ridges was like fitting a square peg in a round hole. Still, the idea fascinated me, and in early 1982, we did a maxillary vascularized osteotomy procedure attempting to achieve a free-flap result by using the natural alveolus with its blood supply and without the need for microvascular surgery. This was successful, so we published a paper on maxillary augmentations with the technique and have developed and expanded its utilization through the years.1 It instantly produces the results sought with a distraction osteogenesis procedure with minimal or no hardware. Typically, a long titanium screw (ie, 18 to 24 mm) is used to stabilize the vertically moved bone. ICB and irradiated corticocancellous (ICC) blocks are used for the interpositional material (Fig 8). Alterative vertical stabilization can be achieved with miniplates or ICC blocks. It is true that the shape of a healed alveolar ridge is not the shape of an alveolus surrounding teeth. However, the plasticity of vascularized alveolar bone, combined with the correct instruments, knowledge, and skill of bone manipulation, makes it possible to transform the vertically corrected but misshaped bone into a perfect socket. An implant can then be crestally positioned within the same location previously occupied by the root it is

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Vascularized Osteotomies

Fig 8  (a to d) Tatum vascularized osteotomy (TVO). The goal is to regain bone attachment in the mandible by using a vertical fixation screw and implants.

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b

c

d

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b

c

d

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d

Fig 9  (a to d) Bone expansion, implant, and restorative treatment by Dr Jose Pedroza.

Fig 10 (a to d) Bone expansion, implants, and restorative central crown restorations by Dr Ana Ayala.

replacing (Figs 9 and 10). The correct use of this concept will produce the safest, simplest, and most precise correction of a vertical deficiency. We have used this to perform office procedures with intravenous sedation and local anesthesia, including the following: •  Move healed implants (Fig 11) •  Move segments of teeth and bone (Fig 12) •  Correct single implant sites (Fig 13) •  Move multiple edentulous segments (Fig 14)

•  Correct vertical defects simultaneously with sinus augmentations (Fig 15) •  Move full maxillary arches (Fig 16) The safety lies in the maintained vascularity and vitality of the bone, surgical asepsis, the interpositional location of the augmentation material, and the remoteness of the incisions. We have described this procedure as a Tatum vascularized osteotomy (TVO).

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INTRODUCTION

Fig 11  (a to d) TVO used to move an implant.

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c

a

b

d

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Fig 12  (a) Preoperative maxillary extrusion and an extreme buccal relationship. (b) TVO to correct abnormality and with implants placed. (c) Completed case with restorations by Dr Jose Pedroza.

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b

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d

e

f

Fig 13  (a and b) Preoperative. (c to e) Using TVO. (f and g) Implant and restoration by Dr Jose Pedroza.

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The Future of Sinus Augmentations

Fig 14 (a and b) TVO correction before implant placement.

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b

a

b

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d

Fig 15 Simultaneous sinus augmentation and TVO, implants with bone expansion and manip­ ulation of gingiva. (a) Preoperative. (b) Postoperative.

Fig 16  (a to d) Full maxillary alveolus moved 8 mm down and 4 mm forward and crossbite correction all as in-office procedures.

The Future of Sinus Augmentations It is our opinion that the future of the sinus augmentation procedure will include the simultaneous correction of vertical deficiencies. For a number of years, over half of the sinuses we have augmented have had simultaneous vertical corrections. These have been accomplished with either a TVO or an onlay block, and we will describe both. When a block is to be placed, an incision is made one tooth and one papilla anterior to the edentulous area and the same palatally to the midline or beyond, and a full-thickness flap is rotated over this tooth to prevent any incision from being present over the block. This flap must be completely elevated from the maxilla, including a buccal cut through the periosteum.

When the TVO is indicated, it can be correctly done and the implants later placed with bone manipulation. The TVO is safer than an onlay and produces the most precise results. The greater challenge here is that this requires the implant placements to be done with bone manipulation; this is a skill and an art that requires patience and training. The further complication is that we have a limited number of instructors with these special skills.

The TVO technique Bone cuts are made with a set of microtomes that are designed for this procedure. The greater palatine vascularity to the soft tissue and bone should be preserved. The sinus elevation is completed as described previously and must be above the level of the hard palate. All bone cuts are made from the buccal without penetrating the palatal soft tissue and with progressive

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Two bone blocks (ICC block) Screw

INTRODUCTION

ICB bone

Collagen

Two bone blocks (ICC block) Screw

a

b

c

Fig 17  (a) After the elevation, collagen is placed against the lining. (b) ICB is placed, and a stent is added to allow placement of bone blocks with a screw for stabilization. (c) Palatal view of completed surgery and area to granulate.

ICB bone Two bone blocks (ICC block)

a

Screw

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Fig 18  Onlay block and sinus augmentation showing (a) incision, (b) remote vascularized flap elevation, and (c) occlusal view of block in place, palatal tissue, and area to granulate.

microtomes (5 mm, 7.5 mm, 10 mm, 12.5 mm, and 15 mm) to produce a straight cut. The anterior vertical cut is anterior to the vertical deficiency and is made through the alveolus to the level of the hard palate. Note that roots are never stripped of bone. A horizontal cut is made through the sinus and palatal slope just below the hard palate and anterior to the greater palatine foramen. The distal vertical cut is made through the tuberosity to the level of the hard palate or as a separation between the pterygoid plates and the maxilla to that level. A superficial horizontal bone cut to protect the greater palatine bundle is made with a wide microtome to the distal vertical cut in the area of the greater palatine foramen. The microtome is then rotated downward to complete the horizontal fracture. A periosteal elevator is slid through this horizontal cut (anterior to the greater palatine) to elevate and mobilize the soft tissue from the hard palate over to or across the midline (artery is safely within this tissue). A semicircular incision is made (facing the surgical site) in the tissue over the hard palate. This permits the segment to be moved downward as this flap slides laterally—the greater palatine artery is avoided and always protected. The exposed bone will granulate over in 2 weeks. The shaped collagen tape is placed against the sinus lining. A layer of ICB mixed with antibiotic is placed against the collagen tape to stabilize the collagen. A premade stent will be used to vertically position the mobilized bone, and it will be stabilized with ICC blocks, vertical screws, plates, and ICB to complete filling the sinus space below the elevated lining. A stent or

dressing will be placed to hold this advanced soft tissue flap against the hard palate to create a fibrin seal (Fig 17). When a vertically deficient maxilla is indicated for a sinus augmentation and the shape is not appropriate for a TVO, an ICC onlay block is indicated. The best results will be achieved by designing the flap to have no incisions over the augmentation and for the flap to be fully vascularized. There are a number of creative incision designs that can be used to provide access, maintain vascularity, reposition gingiva, or all of these tasks (Fig 18).

Conclusion In 1977, we included this quote in our presentation: “The goal of modern implantology is to accept for treatment a patient at any stage of dental disease, atrophy, or trauma and—with general health permitting—restore them to normal contour, comfort, function, esthetics, and health.” Carl Misch opened each of his books with these goals. After 42 years and our over 2,800 sinus augmentations, this procedure has allowed us and many others to achieve these goals for countless patients.

Reference 1. Tatum H Jr. Endosteal implants. CDA J 1988;16(2):71–76.

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Section I

CHAPTER 1

BONE GRAFTING STRATEGIES FOR THE SINUS FLOOR Craig M. Misch, dds, mds

A

primary diagnostic consideration of dental implant placement in the maxilla is the bone volume of the residual ridge. In the posterior maxilla, the maxillary sinus often limits the available bone for implant placement. The clinician can avoid the sinus by either selecting a shorter implant size or tilting the implant position away from the sinus cavity. Another option is to elevate the sinus mucosa to establish a new sinus floor at a more superior level. The goals of the sinus elevation procedure are to augment bone height in the posterior maxilla for dental implant placement, promote the development of a bone-to-implant interface contact, and enable long-term survival of the implants under prosthetic loading. This chapter discusses various strategies for managing the sinus floor, including surgical approaches, graft materials, and future directions.

Indications for Sinus Bone Grafting During growth of the facial skeleton, the sinus cavities expand in volume. The floor of the maxillary sinus is often in close approximation to the posterior tooth roots. When posterior teeth are lost, the sinus further expands, reducing the amount of residual bone. Following extraction of the posterior teeth, there is also a loss of facial bone, resulting in medial resorption of the maxillary ridge. In addition, the edentulous posterior maxilla often has poorer bone quality. These conditions can compromise the placement of dental implants for prosthetic support. The management of maxillary atrophy and sinus pneumatization for dental implant placement has evolved over the years. When sinus bone grafting was first developed, clinicians favored the use of longer dental implants. This was thought necessary for optimal biomechanical loading of the implant and prosthetic support. In addition, shorter machine-surfaced implants (< 10

mm) showed lower survival rates in the posterior maxilla.1 Under these constraints, it was often necessary to perform sinus bone grafting through a lateral window approach to allow placement of longer implants. An early classification protocol recommended lateral window sinus bone grafting when there was 8 mm or less of bone height below the sinus floor for placement of the maximum implant length (> 15 mm).2 However, improvements in implant materials, design, and surface properties have now led to the use of shorter dental implants. Many studies have even shown that the survival of short implants is the same as longer implants placed into grafted sinuses.3,4 Compared with short implants, sinus bone grafting has a higher incidence of complications, costs more, and requires additional surgical and healing time. However, short implants do have a higher risk of failure during the early healing period, which may be due to their reduced stability in softer bone.5 A clinical trend is to use shorter implant lengths in the posterior maxilla (Fig 1-1). This reduces the volume of bone grafting that is needed for implant placement and may even avoid the need for sinus augmentation. It may also allow the surgeon to consider an osteotome sinus floor elevation for short implant placement rather than using a lateral window technique.6 For example, a vertical bone height of 6 mm below the sinus floor would allow placement of a 6- to 9-mm implant via a transcrestal osteotome approach. Although there is no definitive bone dimension needed before considering sinus bone grafting, there is a lack of substantive long-term data on shorter implants (< 8 mm) in the posterior maxilla. The decision to place short implants versus sinus grafting for longer implants should be based on long-term studies, implant design, sinus pathology, surgical experience, and patient preferences.3 The need for sinus bone grafting is also reduced by using tilted implants to avoid the sinus and zygomatic implants that may be placed through or lateral to the maxillary sinus.

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Bone height below the sinus (mm)

1  BONE GRAFTING STRATEGIES FOR THE SINUS FLOOR

10

Standard implant 8

Transcrestal lift + implant 6

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Lateral window + bone graft + implant

Lateral window + bone graft

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Fig 1-1  Clinical guidelines for managing the posterior maxilla based on bone height below the sinus floor. Overlapping colors indicate that multiple options can be considered.

Delayed implant placement is performed after healing of a bone graft. The healing time may vary depending on the graft material used. Autogenous bone grafts heal faster, so using autograft as the sole material or combining it with bone substitutes can shorten the healing time requirements to 4 to 6 months.12 The use of a slow-resorbing graft material, such as bovine bone mineral or hydroxyapatite, may necessitate longer healing periods well exceeding 6 months.13 The bone graft material does not have to be completely incorporated before implant placement because additional healing time is allowed for implant integration, but the total healing period may still exceed 1 year with these slower resorbing graft materials. A systematic review revealed no significant differences in the survival of implants placed simultaneous with grafting or after graft healing.14 Therefore, the decision to place dental implants simultaneous with the graft or after healing is largely determined by the ability to achieve primary stability in native bone.

Sinus Grafting Techniques Simultaneous Versus Delayed Implant Placement The decision to place dental implants simultaneous with sinus bone grafting or staging placement after graft healing depends on several factors: the quantity and quality of bone below the sinus, implant design, clinical conditions, and experience of the surgeon. The advantages of simultaneous grafting and implant placement are decreased morbidity, lower costs, and shorter treatment duration. The edentulous posterior maxilla typically has a thin outer cortex with softer quality trabecular bone, and the sinus floor is a thin cortical shell. As such, the minimum bone height needed to place an implant simultaneous with grafting is approximately 4 to 5 mm.7 Experienced clinicians may be able to use methods to enhance primary implant stability in sites with less bone, such as underpreparing the osteotomy, osteotome expansion, osseodensification, and/or using tapered implants.8 Autogenous or allogeneic block bone grafts fixed to the sinus floor with implants have also been utilized.9 However, implant placement into sites with minimal residual bone may have higher risks of complications such as implant displacement and implant failure.10,11 If large sinus mucosa perforations are encountered during the augmentation procedure, it may be prudent to stage implant placement after graft healing. Grafting for simultaneous implant placement may be accomplished along the sinus floor via a lateral window or transcrestal approach. Another option is to place implants without any bone graft material, allowing the implant apices to tent the sinus membrane so blood clot or platelet concentrate alone can be used to provide enough matrix for bone ingrowth.

When inadequate bone volume is present below the sinus for implant support, the sinus floor can be augmented. Conventional radiographs, such as periapical and panoramic films, are useful for preliminary screening of potential implant sites. Cone beam computed tomography can better assess the available bone and further evaluate sinus health and morphology. Cross-sectional images are useful to evaluate the ridge width, bone quality, and sinus floor. The buccopalatal distance of the sinus can influence the amount of graft material needed for augmentation and healing time requirements.15 There are two surgical approaches that can be used to elevate the sinus mucosa and place graft material: the lateral window or direct sinus elevation and the transcrestal or indirect sinus floor elevation. These grafting techniques only address vertical bone deficiencies. The surgeon should also evaluate the residual ridge for facial bone loss and medial resorption following tooth loss. This may necessitate concomitant horizontal bone augmentation for ideal implant placement. In some cases, severe atrophy may also require vertical ridge augmentation (Fig 1-2).

Lateral window approach The lateral window approach is performed in the posterior maxilla by creating an osteotomy over the lateral sinus wall and leaving the sinus mucosa intact. There have also been reports on using a palatal approach.16 The osteotomy may be created using rotary burs or piezoelectric tips to create an ovoid bone flap or complete removal of the overlying bone, providing an access opening for mucosal elevation. This approach requires vertical releasing incisions with greater flap reflection and retraction than a transcrestal sinus floor elevation. This greater surgical access can result in increased postoperative pain, facial swelling,

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Sinus Grafting Techniques

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Fig 1-2  (a) A bone scraper is used to collect particulate autograft and expose the sinus mucosa. (b) Autogenous bone is placed along the sinus floor and used for vertical ridge augmentation. (c) Implants are placed 4 months after graft healing.

and ecchymosis. In addition, vessels within the lateral sinus wall may be disrupted during preparation of the bony window, causing intraoperative bleeding. There may also be a greater risk of sinus mucosa perforation using this approach compared with a transcrestal elevation.17 However, open access allows for direct repair of mucosal disruption. Serious infections are rare but can occur with this more invasive surgical approach. The main advantages of using a lateral window approach are superior access, visibility of the mucosal elevation, and direct access to the sinus floor. This allows for placement of larger volumes of graft material and greater vertical bone augmentation. For this reason, it is the preferred technique for managing the pneumatized sinus with minimal residual bone below the sinus floor (0 to 5 mm). It would also be the preferred approach if additional simultaneous horizontal or vertical ridge augmentation of the posterior maxilla were needed. The posterior maxilla resorbs medially following tooth loss, and this pattern of bone loss may result in an unfavorable ridge relationship with the opposing mandibular dentition. If there is adequate residual bone height, implants may be placed simultaneous with the graft. Otherwise, implants are placed after a period of graft healing. The lateral window technique may also be useful in cases where sinus bone septa would complicate an internal osteotome lift. In this instance, two windows can be created on each side of the septa and the sinus mucosa can be elevated around and over the bony projection. A lateral window approach also allows for the removal of sinus pathology in conjunction with sinus grafting. A systematic review on the lateral window sinus grafting technique including 59 articles and 13,162 implants found an overall implant survival of 93.6% (range: 61.2% to 100%).18 Evidencebased reviews have concluded that rough-surfaced implants have a significantly higher survival rate than machine-surfaced implants in lateral window sinus grafts. The use of a membrane to cover the window over the graft may also have a positive influence on implant survival. The use of a rough-surfaced implant and membrane coverage over the graft was found to improve implant survival to 98.6%.19 Chapters 6 and 8 have more information on the lateral window technique.

Transcrestal approach The transcrestal approach for sinus augmentation involves creating an osteotomy through the ridge crest of the posterior maxilla. This is usually done in conjunction with simulta­ neous implant placement. The osteotomy is typically prepared just short of the bony sinus floor. The thin layer of remaining bone can be gently upfractured and elevated with an osteotome or carefully reduced with a diamond bur or piezoelectric tip. Reverse-rotating osseodensification burs are another method to create the transcrestal osteotomy without disrupting the sinus mucosa (see chapter 10). This indirect method requires less flap manipulation, so it is less invasive than the lateral window technique. High patient satisfaction has been documented with this procedure.20 In cases where minimal additional bone height is needed for implant placement, it may not even be necessary to add graft material. The space between the implant apex and sinus mucosa fills with blood clot that heals into bone (see chapter 7). Platelet concentrate, such as platelet-rich fibrin (PRF), can also be used as a graft matrix. The fibrin clot is introduced into the osteotomy and compressed superiorly. The matrix of fibrin, embedded with platelet and leukocyte cytokines, can act as a cushion to protect the sinus membrane and facilitate bone healing. Larger amounts of bone augmentation can be achieved using particulate bone graft materials.6 Osteoconductive bone substitutes, such as bovine bone mineral or mineralized bone allograft or alloplasts, can be hydrated with sterile saline and placed into the osteotomy. The graft particles are gently compressed and elevated superiorly with an osteotome. Some slight resistance should be noted when the particles are compacted upward. Larger graft particles (> 1.0 mm) with irregular or sharp geometry are avoided because they may tear the sinus mucosa. Grafting via the indirect method is less invasive but has the disadvantage that detection and management of sinus mucosa perforations is limited. Disruption of the sinus mucosa can occur during drilling of the osteotomy, mucosal elevation, or graft and implant placement. Although mucosal perforation is reported to be less frequent than with the lateral approach, the

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elevation of the sinus membrane should be regarded as technique sensitive.17 A small disc curette can be inserted into the osteotomy to detect the sinus floor and assess the dissection of the sinus membrane. Valsalva maneuver has been used to test for membrane perforation. The presence of air bubbles appearing through the osteotomy indicates a loss of mucosal integrity. It is difficult to blindly repair a sinus tear through the osteotomy. If a large perforation is encountered, the procedure may need to be abandoned. Another option is to create a lateral window for better access to repair. Benign paroxysmal positional vertigo has been documented as an infrequent but unpleasant complication of the osteotome technique.17 The transcrestal sinus floor elevation is typically used with simultaneous implant placement and when less bone augmentation is needed. An endoscopic examination found the increase in height by an osteotome technique alone should be limited to approximately 3 mm.21 However, using the indirect approach, bone gains between 3 and 9 mm have been reported.22 Greater bone gains can be obtained by using graft material versus no grafting. Experienced surgeons proficient in the transcrestal technique may manage cases with minimal available bone. Devices have also been developed to assist transcrestal grafting using hydraulic pressure or a balloon catheter to elevate the sinus mucosa.23 Although there is no definitive measurement of residual bone to indicate one technique over the other, improvements in the transcrestal method and a trend toward using shorter implants have lessened the need for the lateral approach.24 If the residual alveolar bone height is 6 mm, a transcrestal approach to elevate the sinus floor and place an 8-mm implant may lead to fewer complications than using a lateral window approach to place a longer implant. A systematic review on the transcrestal osteotome technique including 34 studies and 3,119 implants found an overall implant survival of 96.7%.25 The vast majority of implant failures occurred early (< 1 year loading). Transcrestal sinus floor elevation was most predictable when the residual alveolar bone height was greater than 5 mm. Shorter implants (< 8 mm) demonstrated significantly lower cumulative survival rates than longer implants.25 For more information on the transcrestal approach, see chapter 9.

Bone Graft Materials In the first publication on the sinus bone graft technique in 1980, Boyne and James26 used autogenous cancellous marrow from the ilium. Early Swedish studies on the reconstruction of the atrophic maxilla used iliac bone grafts with machine-surfaced implants.27 Autogenous bone was considered the gold standard of graft materials for oral and maxillofacial reconstructive surgeries. In addition, there was a limited choice of bone substitutes and a paucity of research on these alternative materials. Over time, clinicians began to evaluate the use of various alternative bone materials for sinus augmentation. Tricalcium

phosphate was the first bone substitute used for sinus bone grafting.28 In 1996, the Academy of Osseointegration held the Sinus Consensus Conference to evaluate retrospective data from clinicians. The conference unanimously agreed that the sinus graft was an efficacious procedure.7 The overall implant survival rate was reported as 90%. The various materials used for grafting all seemed to perform acceptably, and it was not possible to state with certainty that one material was better than another. One limitation in evaluating the graft materials is that the residual bone below the sinus floor is often not reported. Dental implant survival may be a function of residual native bone supporting the implant rather than grafted bone.29 Since the first consensus conference, numerous graft materials have been used for sinus augmentation. The literature on sinus graft success is often evaluated by secondary outcomes, such as dental implant survival or histologic studies. However, there are inherent limitations in using these secondary measurements. For example, machine-surfaced implants have lower survival in grafted bone.18 A lower implant survival in a particular graft material could be interpreted as a poorer graft success. In addition, patients may suffer cluster implant failures due to factors unrelated to the graft material.30 Because of the variability in study design and numerous confounding variables, a direct comparison between published reports on graft materials is not possible. This section evaluates studies on sinus grafting and discusses the use of different choices for graft materials.

Autogenous bone Literature review The interpretation of the results with using autogenous bone for sinus grafting has been confusing and controversial. Many clinicians have incorrectly concluded that the use of autograft is associated with a lower implant survival or that bone substitutes provide better results. The 1996 Sinus Consensus Conference issued a consensus statement that autogenous bone is appropriate for sinus grafting.7 However, it was only a majority opinion of the group that bone substitutes may be effective as a graft material in selected clinical situations. A 2004 systematic review on sinus bone grafting by Del Fabbro et al14 concluded that bone substitutes are as effective as autogenous bone. Four years later, the same group published an updated review with additional data.18 Although the results were essentially unchanged, they altered their opinion and stated that survival rates for implants in bone substitutes and composite grafts were slightly better than implants in 100% autogenous grafts. However, in deriving this conclusion they combined the survival of both machine-surfaced and rough-surfaced implants in grafted sinuses. Their data clearly showed that machine-surfaced implants had significantly lower implant survival rates and that the majority of sinuses grafted with autograft had machine-surfaced implants18 (Fig 1-3). Contrarily, sinuses grafted with bone substitutes only had rough-surfaced implants, casting doubt on their comparative conclusions.

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Advantages and disadvantages Autogenous bone has been considered the gold standard of graft materials because it has superior biologic properties compared with bone substitutes. However, not all autogenous bone grafts have osteogenic qualities. Only viable bone-forming cells, found mostly in the cancellous marrow, can directly produce new bone. Extraoral donor sites with a significant cancellous component, such as the iliac crest or tibia, can provide this type of bone quality. Although intraoral donor sites are more convenient, they do not contain many bone-forming cells. The bone in the maxillary tuberosity is porous, and the outer cortical layer is thin. The mandibular symphysis and ramus are mostly cortical bone. However, bone morphogenetic proteins (BMPs) found in the cortical graft can recruit and induce mesenchymal stem cells (MSCs) to become osteoblasts. In addition, freshly harvested cortical chips contain viable osteocytes capable of controlling bone remodeling through a variety of additional growth factors that induce gene expression in mesenchymal progenitor cells.32 The cortical portion of the autogenous bone graft also acts as an osteoconductive scaffold for bone formation. Local autogenous bone can be easily harvested from the tuberosity or collected from a bone-scraping device passed over the lateral maxilla and zygomatic buttress. If additional autograft is desired, bone can be harvested from the mandibular body and ramus area with a scraping device or collection bur. Rarely would it be necessary to harvest bone from the mandibular symphysis, tibia, or ilium for straightforward sinus grafting because these sites can add morbidity. If the severely atrophic maxilla is reconstructed with an iliac bone graft, then cancellous bone may also be used for the sinus. However, mixing the particulate cancellous autograft with a slow-resorbing bone substitute, such as bovine bone mineral, should be considered to help maintain graft volume during healing.33 Some loss of augmentation volume always occurs after sinus grafting during early healing times. In general, less volume loss can be expected with bone substitutes than with 100% autogenous bone.33 However, the remodeling of an autogenous graft stabilizes, and the reduced volume does not seem to compromise implant placement or survival.33 The use of a barrier membrane over the sinus window has also been advocated when bone substitutes are used.34 Instead of using a

100

Implant survival rate (%)

Pjetursson et al31 performed a systematic review that evaluated bone grafting of pneumatized sinuses that had 6 mm or less residual bone height. When they focused on outcomes using only rough-surfaced implants, they found high implant survival rates (> 96%) for all types of grafts. However, rough-surfaced implants placed in particulate autogenous bone had a significantly higher estimated 3-year survival (99.8%). Therefore, it appears that the autogenous bone is not associated with a lower implant survival, given that rough-surfaced implants significantly improve outcome with sinus grafting. This does not imply that 100% autogenous bone is the preferred graft selection for sinus augmentation; it merely clarifies the misconception that it is an inferior material for use.

96.7% 95

94.9% 92.6%

89.6%

90 85 80

96.5%

84%

Autogenous

Combined

Substitutes

Machine-surfaced implants Rough-surfaced implants

Fig 1-3  Implant survival rates in sinus bone grafts using autogenous bone, bone substitutes, and combinations. (Data from Del Fabbro et al.18)

commercially produced membrane, a thin piece of cortical bone obtained from the tuberosity area can be used as an autologous barrier to cover the window35 (Fig 1-4). There are potential advantages in using autogenous bone in sinus grafts, especially when the sinus cavity is large and minimal bone remains below the sinus floor.36,37 The superior biologic properties of autogenous bone grafts can result in greater bone formation at earlier time periods than bone substitutes.38 Several studies have found an increase in bone formation when autogenous bone is used alone or added to other grafting materials in sinus grafts.39–43 Based on a review of histomorphometric studies, autogenous bone was found to result in the highest amount of new bone formation in comparison with the other sinus graft materials.12 There is conflicting evidence on improving bone formation with mixing a small amount of autograft and bovine bone mineral.40,44 A small volume of autogenous bone may not be biologically available when it is mixed within a large amount of bone substitute. A better strategy may be to layer the graft materials within the sinus.45 The bone substitute can be inserted first and elevated superiorly so the particulate autogenous bone can be placed along the sinus floor (Fig 1-5). This provides the autograft with a better environment for healing and bioavailability in close approximation to the native bone. Compared with bone substitutes, the healing time requirements of autogenous bone grafts are shorter, especially in larger pneumatized sinuses.15 The healing period for sinuses grafted with 100% autogenous bone can be as short as 3 to 4 months compared with the 8 to 10 months often recommended for bone substitutes.40,46 The addition of autogenous bone to composite bone grafts may also shorten healing times and influence bone remodeling patterns.40,47,48 This offers a potential advantage because patients often object to extended treatment lengths.49 Not only do autogenous bone grafts heal faster than bone substitutes; the biology of the regenerated bone may be improved.

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Fig 1-4 (a) Piece of cortical bone harvested from the maxillary tuberosity. (b) The cortical bone graft is used to cover the sinus window.

a

b Fig 1-5 (a) Bovine bone mineral is placed first and elevated superiorly as the first layer. (b) Mineralized bone allograft is used as the second layer. (c) Autogenous bone from the ramus and tuberosity is placed along the sinus floor and over the window. (d) Sinus and block bone graft after 4 months of healing.

a

b

c

d

Histologic studies have shown greater bone formation and higher bone-to-implant contact when autogenous bone grafts are used compared with allografts.42 This improved bone formation at an earlier time can allow for shorter implant healing periods than with the use of bone substitutes alone. The main disadvantage in using large amounts of autogenous bone for sinus floor grafting is the potential for complications from bone harvest. Local intraoral donor sites, such as the maxillary tuberosity and zygomatic buttress, incur minimal added morbidity. The mandibular body and ramus have a low incidence of complications, but a secondary surgical site is required.50 The mandibular symphysis and extraoral sites, such as the tibia or iliac crest, can significantly increase surgical risks and morbidity. The harvest of autogenous bone requires added surgical time and may require sedation. Iliac bone harvest requires an operating room and general anesthesia. Although using autogenous bone decreases graft material costs for the surgeon, it may be necessary to purchase equipment or instrumentation for bone harvest.

Bone substitutes There have been several evidence-based reviews evaluating various graft materials for sinus bone augmentation. They have essentially concluded that bone substitutes are as effective as autogenous bone for sinus grafting. As previously discussed, sinus bone graft success is often measured by a secondary outcome, such as the amount of vital bone formation. There are inherent limitations in using this measurement to evaluate graft success. Clinical studies have failed to identify the defined minimal amount of vital bone needed for implant integration and survival.12 Histomorphometric studies have shown a wide range of vital bone formation. For example, xenografts produce approximately 25% of vital bone formation by volume at 8 months healing.19 Although bone substitutes are associated with a lower percentage of vital bone than autografts, their implant survival rates are similar.51 The obvious advantages of using bone substitutes are decreased morbidity and shorter surgical time. They are also available as a sterile, uniform product in an unlimited supply. It is not feasible to review every bone substitute used as a graft

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material for sinus augmentation, nor is it possible to determine which bone replacement material provides the best results. There is a lack of randomized controlled clinical trials with sufficient statistical power comparing various grafting materials.19 In addition, there are too many confounding variables to account for in comparing materials. In some studies, graft products have even been combined. Furthermore, a lower percentage of the implants evaluated in systematic reviews on sinus grafting were placed in bone substitutes alone.18 In general, the implant survival rates are high with several types of bone replacement grafts with negligible differences. An ideal bone substitute for sinus grafting would fulfill several criteria, as follows: •  Particulate graft materials are much easier to use in sinus augmentation than block forms. •  The graft should provide a biocompatible osteoconductive scaffold for new bone formation. •  The product should be well documented with supportive clinical studies. •  The graft should have favorable handling characteristics with a particle size and geometry that provides adequate space for revascularization and bone ingrowth. •  The particles should not be too large or irregular in shape because this could risk sinus membrane disruption. •  A radiopaque graft material makes it easier to identify on postoperative radiographs. •  A slower resorbing material will provide a stable scaffold for bone formation and maintain graft volume during healing. •  A low to moderate cost would also be preferred. There are several graft products in all bone substitute categories (allograft, xenograft, alloplast) that satisfy the proposed criteria. Although some clinicians prefer to combine different bone substitutes, there is no evidence to support the benefits of this practice, and the use of one material simplifies inventory and surgery.

Xenografts Anorganic bovine bone mineral has been studied extensively and has the most clinical documentation for sinus grafting. This xenograft product has demonstrated very favorable clinical outcomes and high implant survival rates.19 It is a deproteinized, bovine cancellous product with a native crystalline structure that is very similar to human bone. Bovine bone mineral is a highly biocompatible and osteoconductive material that allows for deposition of vital bone directly on the surface of the xenograft particles. As such, the particles become integrated into the bone matrix and natural physiologic remodeling process. This provides added mineral density to the graft for dental implant placement and stability.19 Although one study suggested that a larger particle size may allow more bone ingrowth, another clinical evaluation found no difference between larger and smaller particle xenografts.52,53 Histologic evidence has shown that the xenograft particles do not interfere with the development of the

bone-to-implant interface.54 The slow-resorbing nature of bovine bone mineral maintains graft height and provides long-term volume preservation. There has been some concern raised regarding the possible risk of bovine spongiform encephalopathy from a xenograft product. To date, there has not been any reported case of disease transmission from bovine bone mineral. This risk can be essentially eliminated by stringent safety requirements by the manufacturer, chemical and physical purification of the product, and sterilization procedures.55

Allografts Although allograft bone substitutes are popular in the United States, many countries strictly regulate or prohibit their use in patient treatment. The main concerns associated with these materials are possible antigenicity and risk of disease transmission from donor to recipient. However, accredited tissue banks have essentially negated this risk through stringent donor screening, tissue recovery, and disinfection processes.56 Demineralized freeze-dried bone allografts may have limitations for sinus bone grafting. This material is not radiodense and can be more difficult to identify on postoperative films. Used alone in a pneumatized sinus, a demineralized graft has poor scaffolding properties and may be subject to loss of height during healing. Although it may contain some BMPs, the amounts are so miniscule that the clinical significance of its osteoinductive capacity has been questioned.57 Demineralized freeze-dried bone has also been found to provide lower implant survival rates than other bone substitutes.7,58 There is a clinical trend toward using mineralized bone allografts. These materials are radiopaque and provide better osteoconductive scaffolding for bone ingrowth and maintenance. The particulate mineralized products come in cortical, cancellous, and mixtures of these two forms. They have a faster turnover and more physiologic resorption profile than slower resorbing bovine bone mineral.59 A blind randomized controlled study on bovine bone mineral and mineralized bone allograft used for sinus grafting found that significantly more vital bone was formed in the allograft sites at 26 to 32 weeks healing (28% vs 12%).60 Another prospective randomized split-mouth study comparing a biphasic calcium phosphate alloplastic bone substitute with mineral allograft found at 9 months healing that the allograft had a higher osteoconductive value and less residual graft material.61

Alloplasts There are numerous different types of alloplastic materials that have been successfully used for sinus bone grafting, including hydroxyapatite, calcium sulfate, calcium phosphate, bioactive glass, titanium granules, and polymers.62 These materials are synthetically produced or derived from natural materials and processed. Tricalcium phosphate was the first bone substitute used for sinus bone grafting.28 Early experience was also reported on use of a dense nonresorbable hydroxlapatite.63 Because these graft materials are synthetic, there is no risk of disease transmission. They have osteoconductive properties that provide scaffolding for new bone ingrowth and/or replacement.

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They are available in resorbable and nonresorbable forms with various particle sizes, geometries, pore sizes, and porosity levels. An important factor to consider for sinus grafting is the rate of degradation for maintenance of vertical height. Much like xenografts, porous hydroxyapatite has been mixed with particulate autogenous bone to better maintain graft volume. Alloplastic materials may be quite useful in the future because they may be customized for cellular constructs and delivery of growth factors.

No graft The basic principles of bone regeneration require space maintenance for bone ingrowth and stability of the wound for blood clot formation and subsequent healing.64 In 2004, Lundgren et al65 published on a lateral window technique where the sinus mucosa was elevated for implant placement but no bone graft material was inserted. The implant apices supported the sinus mucosa, and a blood clot was allowed to form around the implants. Thereafter, the bone window was replaced. All of the implants integrated, and computed tomography showed new bone formation. However, the researchers noted that the bone levels peaked around the implants and did not cover the apices. Several subsequent studies have found that nongrafted sinus floor elevation using the lateral window and transcrestal approach seems to be characterized by new bone formation and high implant survival rates comparable to grafted sinus floor augmentation.66 The vast majority of implant failures with this technique are early during healing.25 Long-term comparative studies of no grafting versus grafting are lacking, so conclusions should be interpreted with caution.

Membranes During early development of the lateral window technique, graft material was placed along the sinus floor and the mucoperiosteal flap was repositioned and closed over the grafted site.67 Later on, the placement of a barrier membrane over the graft to cover the sinus window was proposed.68 It was theorized that a barrier membrane could prevent soft tissue cells from growing into the graft and facilitate the growth of bone tissue within the sinus. This was observed in one study in which biopsies were taken after 6 months of healing using mineralized bone allografts with or without expanded polytetrafluoroethylene (ePTFE) membranes over the window. Sinus grafts without the membrane had greater scarring and soft tissue.68 A follow-up study evaluated 12 patients undergoing bilateral sinus grafts and found that sinus grafts covered with ePTFE membrane had increased vital bone formation and had a positive effect on implant survival.34 The conclusion was that membrane placement should be considered for all sinus elevation procedures. However, there is conflicting evidence regarding routine use of a barrier membrane over a sinus graft, and the use of ePTFE led to a high rate of infection. Some systematic reviews support the idea that dental implant survival rates can be improved if a

membrane is placed over the sinus window.69 However, another review indicated that there was insufficient evidence on the effects of membranes to make definitive conclusions due to limited sample sizes, short follow-up periods, and a high risk of bias.70 A meta-analysis of 37 studies on the effect of using a barrier membrane on the histomorphometric outcomes of sinus augmentation determined that a membrane did not influence the amount of new vital bone formation.71 A randomized clinical trial comparing maxillary sinus augmentation with and without a membrane over the window found that the use of the membrane did not substantially increase the amount of vital bone over a period of 6 months.72 However, the use of a membrane did seem to reduce the proliferation of the connective tissue and the graft resorption rate. Similar findings were reported in a split-mouth prospective pilot study on bovine bone mineral sinus grafts.73 Another randomized clinical trial with a two-arm and split-mouth design comparing sinus grafts with and without membranes found that implant survival was not influenced by membrane coverage.74 There may be several factors that explain the different findings on this topic. As previously mentioned, there are many variations in study design and numerous confounding variables that do not allow direct comparison between published reports. For example, one study reported that a collagen barrier used to cover the window improved the survival rate of machine-­ surfaced implants in sinus grafts using bovine bone mineral.75 Using a rough-surfaced implant improves survival, and this may override the influence of a membrane. There is also a lack of studies differentiating the type of graft material used with membrane coverage. Osteoconductive bone substitutes may benefit from membrane coverage more than 100% autogenous bone would. When no bone graft is used, the access window is typically replaced to protect the clot. Sinuses grafted with recombinant human BMP-2 (rhBMP-2) and absorbable collagen sponge (ACS) are not covered with a barrier membrane to allow unimpeded chemotaxis, cell migration, and vascular ingrowth. Another factor that many impact this decision is the amount of bone below the sinus floor and size of the sinus cavity. It may be more beneficial to use a membrane when the sinus is wider or there is minimal residual bone. The size of the sinus access opening could also influence this decision. Smaller windows that maintain more bone to encase the graft have been shown to have a positive correlation with the maturation and consolidation of the bone graft76 (Fig 1-6). Incorporation of a sinus graft material may improve from placement of a barrier membrane over a larger window. The research does not support the opinion that routine membrane coverage of the lateral window is necessary in every case. The disadvantage is added cost if a commercial membrane is used. When coverage of the window was originally proposed, nonresorbable PTFE membranes were used.68 This type of membrane requires stabilization over the lateral maxilla with tacks or screws to prevent micromovement. Exposure of PTFE membranes is a potential problem that can negatively affect the result. A resorbable membrane has advantages because it

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Fig 1-6  (a) The sinus window opening is limited to maintain the bone walls. (b) The limited sinus access is wide enough to introduce a bone graft syringe.

a

does not require fixation and subsequent removal.68 Resorbable collagen membranes used for guided bone regeneration are well suited for this purpose. Another option is to harvest a thin piece of cortical bone as a natural resorbable barrier to cover the antrostomy. Some authors advocate replacement of the lateral window itself (see chapter 7). After performing the peripheral osteotomy to create the window, the piece of bone is removed intact and then repositioned over the grafted sinus.77 As discussed previously, another option is to procure a thin cortical graft from the tuberosity area and shape it to cover the window.35 Some clinicians have suggested using PRF over the window. However, a fibrin membrane is not a cell occlusive barrier, and there is no evidence this improves sinus graft healing.

Bioactive products Evidence-based reviews reveal that dental implant survival in grafted sinuses is very high and equal to or better than implants placed in native maxillary bone.19 As such, there is no significant margin for improvement in implant survival rates using new graft materials or bioactive products. In addition, studies have found that high implant survival rates can be obtained using bone substitutes that produce relatively low amounts of new vital bone.19 Therefore, a new strategy to improve vital bone formation using tissue-engineering products, such as cellbased therapies or signaling molecules, would also not necessarily improve outcomes. Future research on sinus bone grafting should therefore focus on shortening treatment duration by reducing the time needed for graft maturation and/or implant healing as well as minimizing patient morbidity. Although the use of autogenous bone for sinus grafting may accelerate new bone formation when compared with bone substitutes, the added morbidity from bone harvest is undesirable. The search for bioactive products that can decrease sinus graft healing time and minimize patient morbidity should be the goal of future clinical research.

Platelet concentrates Platelet concentrates are prepared following blood draw using a centrifuge device. There are various protocols that produce different forms of platelet-rich preparations. The platelets contain numerous growth factors that stimulate and accelerate

b

the tissue-repair process. Platelet concentrates have been used with bone substitutes for sinus bone grafting in an attempt to enhance bone regeneration. However, a number of systematic reviews have failed to provide evidence that platelet concentrates increase or accelerate new bone formation.78–81 Some researchers have claimed that newer generations of platelet-rich preparations (ie, PRF) contain different cell compositions and greater amounts of cytokines with better release kinetics. However, these formulations have also not shown any significant improvements when added to bone substitutes in sinus grafts.82–85 One randomized clinical trial did find that using a platelet concentrate with sinus bone augmentation resulted in significantly less pain, less swelling, and improved functional activities when compared with the control group.86 A clinical benefit of platelet-­ rich preparations is improved handling and containment of bone graft particles within the fibrin clot. The fibrin matrix has also been proposed as an autogenous membrane for the repair of sinus mucosa perforations.87 Some clinicians have advocated using PRF as the sole material for sinus grafting. PRF consists of an autogenous leukocyteand platelet-rich fibrin matrix containing cytokines and stem cells. A limited number of studies have shown favorable vertical bone gains and implant survival using both the lateral window and osteotome approaches for simultaneous implant placement with PRF.88,89 The fibrin clot may also serve as a cushion against the sinus mucosa over the implant apex. However, there is no evidence that PRF accelerates bone formation or produces better outcomes than a blood clot alone or other graft materials.

rhBMP BMPs are a group of growth factors that are chemotactic for MSCs and induce their differentiation into osteoblasts. Recombinant technology has produced proteins that can mimic this activity for bone regeneration in various clinical applications. The most actively studied of these cytokines is rhBMP-2. One issue with rhBMP-2 is that it is rapidly degraded by proteases, so larger amounts of the protein are required to initiate bone formation. The recombinant protein is packaged with an ACS as the carrier to release the growth factor into the site. The use of rhBMP-2/ACS for sinus bone grafting has been thoroughly investigated in two large randomized controlled clinical trials.90,91 Both studies compared outcomes between rhBMP-2/ACS and autogenous bone and concluded that dental implants placed in

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Fig 1-7 After a zygomatic implant failed, rhBMP-2/ACS was used to repair the bone defect.

rhBMP-2/ACS and autogenous bone graft groups performed similarly after functional loading (Fig 1-7). The use of rhBMP-2/ACS for sinus bone grafting has several disadvantages. Although the ACS has been found to be an optimal carrier for the rhBMP-2 molecule, it has poor scaffolding properties. As such, the collagen mass loses significant volume during healing when used for sinus augmentation. In addition, the collagen is not radiodense, so it is more difficult to identify on postoperative radiographs until bone mineralization has occurred. A large volume of this material is needed for sinus augmentation. The growth factor is very expensive and may be considered cost-prohibitive considering more economic graft products perform just as well. In the sinus bone graft study by Boyne et al,90 the rhBMP-2/ACS grafts had significantly less radiographic bone density than autograft sites at 4 months of healing. This difference is likely due to the mechanism of bone formation. The de novo bone formation by rhBMP-2 requires greater time for healing and mineralization. As such, the bone quality at implant placement may be less dense than mineralized bone grafts. The use of rhBMP-2 is associated with significant edema that compromises the postoperative experience for the patient. The swelling is unavoidable and is not reduced by measures such as steroid therapy and ice packs. The dental implant survival for rhBMP-2/ACS sinus grafts in two randomized controlled clinical trials was rather low (76% and 83%).90,91 When using rhBMP-2 for sinus grafting, the inclusion of a particulate mineralized graft material has been suggested to reduce volume loss from the collagen sponge. Adding graft material would also decrease the cost because less growth factor would be needed. Froum et al92 compared sinuses grafted with mineralized bone allograft alone and two different concentrations of rhBMP-2 (8.4 mg and 4.2 mg) mixed with mineralized bone allograft. All three groups had similar bone volume and graft shrinkage. Density measurements showed that allograft alone had statistically significant greater density at selected time points. The histologic results after 6 to 9 months of healing showed no statistically significant differences in the amount of vital bone between the two test groups compared with the control sinus group treated with allograft alone. It was also

noted that the growth factor accelerated resorption of the mineralized allograft particles. Another study comparing bone formation using bovine bone mineral with rhBMP-2 and bovine bone mineral alone found that the growth factor actually had a negative effect of bone formation. A pilot study comparing sinus augmentation with rhBMP-7 and bovine bone mineral versus bovine bone mineral alone found significantly less new bone formation in the rhBMP-7 grafts.93 In contrast, a comparison study of a different form of rhBMP-2, low-dose Escherichia coli–derived, showed an improved outcome (see chapter 23).94 This cytokine was not bound to a collagen sponge but was soaked with hydroxyapatite granules. Core biopsies obtained at 3 months found significantly more new bone formation with the low-dose BMP sinus grafts than bovine bone mineral alone (16.10% vs 8.25%). Although the use of rhBMP-2/ACS has been shown to induce bone formation in the sinus, it does not shorten healing time and increases postoperative morbidity with significantly higher costs. Other recombinant BMPs may prove to offer benefits in the future, but additional research is needed at this time.

rhPDGF Platelet-derived growth factor (PDGF) is a wound healing cytokine found in the α granules of platelets. It regulates cell mitosis and the formation of new blood vessels. The protein is chemotactic for MSCs, fibroblasts, and osteoblasts and enhances cell proliferation. A recombinant form of this growth factor (rhPDGF-BB) was approved for use in periodontal regeneration. Off-label use of rhPDGF-BB in sinus bone grafting has been evaluated in two studies.95,96 Froum et al95 assessed vital bone formation at 4 to 5 months and 7 to 9 months following sinus augmentation with bovine bone mineral with and without rhPDGF-BB. Vital bone formation was significantly greater in the earlier specimens containing rhPDGF-BB. At the later time period in 7 to 9 months, this difference had disappeared. In another study, Kubota et al96 treated 46 patients with sinus augmentation using bovine bone mineral and rhPDGF-BB. The residual bone below the sinus measured only 0.77 ± 0.28 mm. Implants were placed after 4 months of healing with favorable primary stability measurements at placement and after 8 weeks for a survival of 100%. These two clinical studies suggest that more rapid formation of vital bone with the addition of rhPDGF-BB may allow for earlier implant placement. However, additional research is needed to support this premise.

Stem cells Stem cells are undifferentiated with a capacity to differentiate into specialized cell lines when exposed to specific stimuli. Adult stem cells may be harvested from bone marrow, periosteum, adipose tissue, blood, and dental pulp. The number and concentration of transplanted stem cells are critical factors in producing a favorable clinical result. Bone marrow aspirates (BMA) from the ilium are a rich source of MSCs for bone regeneration. A centrifuge device can be used to concentrate the collected cells from the BMA. The stems cell may also be harvested, cultured,

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and expanded in the laboratory. The MSCs are usually seeded onto some type of scaffold that guides their growth and proliferation. Bone substitutes, such as bovine bone mineral or tricalcium phosphate, are often used as the scaffold for sinus grafting. There are several case series studies showing that the use of MSCs is clinically feasible for sinus bone grafting in preparation for implant placement.97–99 However, comparison studies with autogenous bone or autograft/bone substitute mixtures do not show superior histologic or clinical outcomes. A split-mouth study found no significant difference in new bone formation between the bone graft mineral with BMA and a control group with bone graft mineral alone.100 Another study compared bovine bone mineral with BMA and 100% autogenous bone for sinus augmentation. Dental implants were placed 4 months after graft healing. Although the stem cell grafts compared favorably with the autograft sites, the dental implant survival was lower (91% vs 100%).101 A clinical study comparing histologic results between bovine bone mineral mixed with either BMA or 30% autogenous bone found low new bone formation (< 15%) at 4 months and no significant difference between groups.102 A prospective controlled clinical trial evaluated new bone formation between sinuses grafted with bovine bone mineral mixed with BMA or autogenous bone harvested from the mandible. Biopsies taken at 14 weeks did find more new bone in the BMA grafts (17.7%) than sinuses with autograft (12%).103 One sinus graft study evaluated the use of cryogenically preserved allogeneic stem cells from cadavers.104 The authors compared allogeneic MSCs with mineralized bone allograft and mineralized bone allograft alone. Histologic cores taken at 3 to 4 months found significantly more vital bone formation with the allogeneic MSCs (32.5% vs 18.3%). This technique is not without challenges, however. The allogeneic MSCs must be shipped frozen and thawed before use within 4 hours. There is also a concern for possible disease transmission and the number of viable cells that survive harvest and processing. It appears that the use of MSCs may produce outcomes similar to autogenous bone grafts. Further clinical trials are needed to evaluate the potential benefits of MSCs in sinus grafting. However, the evidence that the sinus graft healing time is significantly reduced is not compelling considering the morbidity of cell harvest, additional surgical time, and added material costs.

Conclusion The sinus bone graft has proven to be one of the most predictable bone augmentation methods for dental implant placement and support. The decision to place dental implants simultaneous with a graft or after healing is largely determined by the ability to achieve primary stability in native bone. When minimal bone is present below the sinus floor, a lateral window provides superior access for mucosal elevation and placement of graft

materials for greater vertical bone augmentation. The transcrestal approach is more often used when modest augmenta­tion is needed in conjunction with simultaneous implant placement. The need for significant vertical bone augmentation in the posterior maxilla has been challenged by successful outcomes with shorter implants. In addition, the use of tilted and zygomatic implants may avoid the need to perform bone grafting procedures. There is currently sparse evidence that bioactive products can significantly decrease sinus graft healing time. Platelet concentrates can improve graft handling and containment, but they do not improve bone graft healing. Studies on rhBMP-2/ACS show that a longer time period is needed for bone maturation, and this product adds morbidity and significant cost. Additional clinical research is needed on rhPDGF-BB to validate that this growth factor may allow for earlier implant placement. Although MSC therapy may produce bone amounts similar to autogenous bone, a higher percentage of vital bone will not necessarily improve implant outcomes. The use of autogenous stem cells also adds morbidity, costs, and surgical time. Future research may find growth factors, cellular constructs, and/or scaffolds that enhance outcomes with sinus bone grafting. Clinicians will need to weigh the higher costs of these options against the possibility for an enhanced biologic response and potential for minimizing patient morbidity.

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75. Tawil G, Mawla M. Sinus floor elevation using a bovine bone mineral (Bio-Oss) with or without the concomitant use of a bilayered collagen barrier (Bio-Gide): A clinical report of immediate and delayed implant placement. Int J Oral Maxillofac Implants 2001;16:713–721. 76. Avila-Ortiz G, Wang HL, Galindo-Moreno P, Misch CE, Rudek I, Neiva R. Influence of lateral window dimensions on vital bone formation following maxillary sinus augmentation. Int J Oral Maxillofac Implants 2012;27:1230–1238. 77. Cho YS, Park HK, Park CJ. Bony window repositioning without using a barrier membrane in the lateral approach for maxillary sinus bone grafts: Clinical and radiologic results at 6 months. Int J Oral Maxillofac Implants 2012;27:211–217. 78. Arora NS, Ramanayake T, Ren YF, Romanos GE. Platelet-rich plasma in sinus augmentation procedures: A systematic literature review: Part II. Implant Dent 2010;19:145–57. 79. Del Fabbro M, Bortolin M, Taschieri S, Weinstein RL. Effect of autologous growth factors in maxillary sinus augmentation: A systematic review. Clin Implant Dent Relat Res 2013;15:205–216. 80. Pocaterra A, Caruso S, Bernardi S, Scagnoli L, Continenza MA, Gatto R. Effectiveness of platelet-rich plasma as an adjunctive material to bone graft: A systematic review and meta-analysis of randomized controlled clinical trials. Int J Oral Maxillofac Surg 2016;45:1027–1034. 81. Lemos CA, Mello CC, dos Santos DM, Verri FR, Goiato MC, Pellizzer EP. Effects of platelet-rich plasma in association with bone grafts in maxillary sinus augmentation: Systematic review and meta analysis. Int J Oral Maxillofac Surg 2016;45:517–525. 82. Peker E, Karaca IR, Yildirim B. Experimental evaluation of the effectiveness of demineralized bone matrix and collagenated heterologous bone grafts used alone or in combination with platelet-rich fibrin on bone healing in sinus floor augmentation. Int J Oral Maxillofac Implants 2016;31:e24–e31. 83. Nizam N, Eren G, Akcalı A, Donos N. Maxillary sinus augmentation with leukocyte and platelet-rich fibrin and deproteinized bovine bone mineral: A split-mouth histological and histomorphometric study. Clin Oral Implants Res 2018;29:67–75. 84. Cömert Kılıç S, Güngörmüs¸ M, Parlak SN. Histologic and histomorphometric assessment of sinus-floor augmentation with beta-tricalcium phosphate alone or in combination with pureplatelet-rich plasma or platelet-rich fibrin: A randomized clinical trial. Clin Implant Dent Relat Res 2017;19:959–967. 85. Miron RJ, Zucchelli G, Pikos MA, et al. Use of platelet-rich fibrin in regenerative dentistry: A systematic review. Clin Oral Investig 2017;21:1913–1927. 86. Del Fabbro M, Corbella S, Ceresoli V, Ceci C, Taschieri S. Plasma rich in growth factors improves patients’ postoperative quality of life in maxillary sinus floor augmentation: Preliminary results of a randomized clinical study. Clin Implant Dent Relat Res 2015;17:708–716. 87. Öncü E, Kaymaz E. Assessment of the effectiveness of platelet rich fibrin in the treatment of Schneiderian membrane perforation. Clin Implant Dent Relat Res 2017;19:1009–1014. 88. Mazor Z, Horowitz RA, Del Corso M, Prasad HS, Rohrer MD, Dohan Ehrenfest DM. Sinus floor augmentation with simultaneous implant placement using Choukroun’s platelet-rich fibrin as the sole grafting material: A radiologic and histologic study at 6 months. J Periodontol 2009;80:2056–2064. 89. Tajima N, Ohba S, Sawase T, Asahina I. Evaluation of sinus floor augmentation with simultaneous implant placement using platelet-rich fibrin as sole grafting material. Int J Oral Maxillofac Implants 2013;28:77–83.

90. Boyne PJ, Lilly LC, Marx RE, et al. De novo bone induction by recombinant human bone morphogenetic protein-2 (rhBMP-2) in maxillary sinus floor augmentation. J Oral Maxillofac Surg 2005;63:1693–1707. 91. Triplett RG, Nevins M, Marx RE, et al. Pivotal, randomized, parallel evaluation of recombinant human bone morphogenetic protein-2/absorbable collagen sponge and autogenous bone graft for maxillary sinus floor augmentation. J Oral Maxillofac Surg 2009;67:1947–1960. 92. Froum SJ, Wallace S, Cho SC, et al. Histomorphometric comparison of different concentrations of recombinant human bone morphogenetic protein with allogeneic bone compared to the use of 100% mineralized cancellous bone allograft in maxillary sinus grafting. Int J Periodontics Restorative Dent 2013;33:721–730. 93. Corinaldesi G, Piersanti L, Piattelli A, Iezzi G, Pieri F, Marchetti C. Augmentation of the floor of the maxillary sinus with recombinant human bone morphogenetic protein-7: A pilot radiological and histological study in humans. Br J Oral Maxillofac Surg 2013;51:247–252. 94. Kim HJ, Chung JH, Shin SY, et al. Efficacy of rhBMP-2/hydroxyapatite on sinus floor augmentation: A multicenter, randomized controlled clinical trial. J Dent Res 2015;94(9 suppl):158S–165S. 95. Froum SJ, Wallace S, Cho SC, et al. A histomorphometric comparison of Bio-Oss alone versus Bio-Oss and platelet-derived growth factor for sinus augmentation: A postsurgical assessment. Int J Periodontics Restorative Dent 2013;33:269–279. 96. Kubota A, Sarmiento H, Alqahtani MS, Llobell A, Fiorellini JP. The use of recombinant human platelet-derived growth factor for maxillary sinus augmentation. Int J Periodontics Restorative Dent 2017;37:219–225. 97. Zizelmann C, Schoen R, Metzger MC, et al. Bone formation after sinus augmentation with engineered bone. Clin Oral Implants Res 2007;18:69–73. 98. Shayesteh YS, Khojasteh A, Soleimani M, Alikhasi M, Khoshzaban A, Ahmadbeigi N. Sinus augmentation using human MSCs loaded into a beta-tricalcium phosphate/hydroxyapatite scaffold. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008;106:203–209. 99. Fuerst G, Strbac GD, Vasak C, et al. Are culture-expanded autogenous bone cells a clinically reliable option for sinus grafting? Clin Oral Implants Res 2009;20:135–139. 100. Wildburger A, Payer M, Jakse N, Strunk D, Etchard-Liechtenstein N, Sauerbier S. Impact of autogenous concentrated bone marrow aspirate on bone regeneration after sinus floor augmentation with a bovine bone substitute: A split-mouth pilot study. Clin Oral Implants Res 2014;25:1175–1181. 101. Rickert D, Vissink A, Slot WJ, Sauerbier S, Meijer HJ, Raghoebar GM. Maxillary sinus floor elevation surgery with BioOss mixed with a bone marrow concentrate or autogenous bone: Test of principle on implant survival and clinical performance. Int J Oral Maxillofac Surg 2014;43:243–247. 102. Sauerbier S, Rickert D, Gutwald R, et al. Bone marrow concentrate and bovine bone mineral for sinus floor augmentation: A controlled, randomized, single-blinded clinical and histological trial—Per-protocol analysis. Tissue Eng Part A 2011;17:2187–2197. 103. Rickert D, Sauerbier S, Nagursky H, Menne D, Vissink A, Raghoebar GM. Maxillary sinus floor elevation with bovine bone mineral combined with either autogenous bone or autogenous stem cells: A prospective randomized clinical trial. Clin Oral Implants Res 2011;22:251–258. 104. Gonshor A, McAllister BS, Wallace SS, Prasad H. Histologic and histomorphometric evaluation of an allograft stem cell-based matrix sinus augmentation procedure. Int J Oral Maxillofac Implants 2011;26:123–131.

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CHAPTER 2

DIAGNOSIS AND TREATMENT OF SINUS INFECTIONS Ashish A. Patel, dds, md | Eric J. Dierks, dmd, md

S

inusitis or rhinosinusitis is defined as a collection of inflammatory disorders affecting the paranasal sinuses and nasal cavity. In the United States alone, the prevalence is estimated to be 30 million cases annually. To best understand the pathophysiology and subsequent management of infectious rhinosinusitis as it relates to dentoalveolar reconstruction, it is critical to understand the anatomy and various etiologies that contribute to these disorders. Furthermore, rhinosinusitis can also be classified based on its temporal relationships to symptoms.

The ostiomeatal complex is a common channel that links the anterior group of paranasal sinuses (ie, maxillary, frontal, and anterior ethmoid) into the middle meatus. It is composed of five distinct anatomical structures: the maxillary ostium, infundibulum, ethmoid bulla, uncinate process, and hiatus semilunaris. Patency of this unit is critical in normal sinonasal function and health (Fig 2-1). Anatomical obstruction of the ostiomeatal complex is a major predisposing factor toward the development of rhinosinusitis because this results in stasis of mucous secretions with proliferation of sinus flora within the antrum.

Diagnosing Rhinosinusitis

Predisposing factors

Anatomy of the sinus The maxillary sinus is the largest of the paired paranasal sinuses and eponymously known as the antrum of Highmore. Each maxillary sinus is a pyramid-shaped cavity with its apex oriented posteriorly. It occupies approximately 15 cubic centimeters of volume within the midface and is lined by pseudostratified ciliated columnar epithelium with mucous-producing goblet cells. The cilia beat in harmony at upward of 22 beats per second toward the ostiomeatal complex to allow non-gravity-dependent expulsion and drainage of mucous and collected debris into the nasal cavity. The maxillary sinus ostium lies beneath the middle turbinate, at the superior portion of the medial sinus wall, approximately halfway between the anterior and posterior sinus walls, and drains into the infundibulum via an elliptical aperture that is 2.4 mm in diameter on average. A properly functioning sinus membrane is critical to the health of the maxillary sinus.

In addition to normal ciliary motility and adequate nasal drainage of the maxillary sinus, many other factors are known to play an important role in the development of or predisposition to rhinosinusitis. Inflammatory disease of the paranasal sinuses, particularly allergic rhinitis, has recently been shown to be an important predisposing factor to recurrent acute sinusitis. Exposure to environmental factors such as tobacco or noxious chemicals or factors like nasal packing, nasogastric tubes, and nasal surgery may also increase the risk for developing rhinosinusitis. In addition, autoimmune vasculitidies (eg, granulomatosis with polyangiitis, polyarteritis nodosa) or immunosuppressive states have been well associated with rhinosinusitis. Genetic factors and altered host anatomy also contribute, including cystic fibrosis, immotile cilia syndrome, septal deviation or spurs, concha bullosa, and paradoxical turbinates.1,2 Concha bullosa is the pneumatization and subsequent enlargement of the middle turbinate—historically, this was believed to be a source of ostiomeatal complex obstruction, which resulted in a higher incidence of sinusitis, but newer studies

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Ethmoid bulla Hiatus semilunaris Infundibulum Maxillary sinus ostium Uncinate process

Fig 2-1  Healthy ostiomeatal complex without obstruction. Note the chronic oroantral fistula.

Fig 2-2  Large obstructive concha bullosa with ipsilateral opacification of the maxillary sinus.

demonstrate that this relationship is nebulous. Several anatomical and computed tomography (CT) studies actually demonstrate a correlation between concha bullosa and nasal septal deviation, the latter of which has been positively correlated with the development of rhinosinusitis in several reports.3,4 Other studies, however, positively correlate concha bullosa and not nasal septal deviation with the development of rhinosinusitis5 (Fig 2-2). Though the relationship between these endonasal anatomical abnormalities and the development of sinusitis is not clearly defined, there does appear to be a trend toward increased incidence of rhinosinusitis.

respiratory infections will have concomitant sinusitis. These symptoms generally do not last more than 10 days and do not continue to get worse as the virus is cleared. Because these viruses are air- and particle-borne and are highly infectious, school-aged children are at the highest risk. Careful hand hygiene via hand washing or use of alcohol-based hand sanitizers is perhaps the most effective and efficient way of reducing transmission. Though there are many over-the-counter supplements and decongestants, none have been proven efficacious in preventing or reliably reducing the duration of upper respiratory infections.

Signs and symptoms

Bacterial rhinosinusitis

Diagnosis of rhinosinusitis requires the presence of either (1) two major factors, or (2) one major and two minor factors as listed in Box 2-1. It is important to recognize that the distinction between acute and chronic rhinosinusitis depends not only on the symptoms, but also the temporal sequence of events. Acute rhinosinusitis has signs and symptoms that persist for up to 4 weeks; however, chronic disease is defined as lasting at least 12 weeks. It is also possible to have acute exacerbations of chronic rhinosinusitis with worsening severity of symptoms in individuals who suffer from chronic rhinosinusitis. This is different from recurrent acute sinusitis, which is characterized by at least four annual episodes of acute rhinosinusitis, each lasting longer than 7 days in duration.

Though less common than its viral counterpart, bacterial sinusitis poses a more complex problem because it can contribute to the development of chronic or recurrent rhinosinusitis. Unlike viruses, bacteria (particularly gram-negative rods) can form a sinonasal biofilm. This results in a tenacious layer of bacteria partially protected from antibiotic penetration and mechanical lavage. Biofilm-producing bacterial strains, such as pseudomonas, can be quite recalcitrant and result in chronic or recurring infections. The most common bacterial pathogens isolated from patients with acute sinusitis are Haemophilus influenzae, Moraxella catarrhalis, Staphylococcus aureus, and Streptococcus pneumoniae. Vaccines are available against H influenzae and S pneumoniae and are recommended by the Centers for Disease Control and Prevention to be administered to all children. Bouts of acute bacterial sinusitis typically follow a viral upper respiratory tract infection (URTI). Though many of the URTI symptoms improve, sinus-associated symptoms persist past 10 days and then worsen over the course of a week. These symptoms may last for up to 4 weeks. Unlike acute viral sinusitis, which is generally self limited, bacterial sinusitis oftentimes requires medical therapy including the use of systemic antibiotics.

Viral rhinosinusitis The most common infectious etiology of rhinosinusitis is attributed to viruses. Viral infections that contribute to the common cold or upper respiratory infections are the major culprits for the development of acute sinusitis. These include adenovirus, parainfluenza, influenza, rhinovirus, and respiratory syncytial virus. Up to 90% of people suffering from upper

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Diagnosing Rhinosinusitis

Fungal rhinosinusitis Although uncommon, fungal sinusitis is usually seen as a chronic disease, and it occurs mostly in diabetic patients. Aspergillus is the most commonly isolated organism in these cases, and it forms a mycetoma or aspergilloma, otherwise known as a fungus ball. This is a mass of fungal hyphae arranged concentrically forming a sphere-like structure and is best seen on CT or magnetic resonance imaging (MRI) scans, although in some patients it can be seen on nasal endoscopy. Fortunately, aspergilloma is generally self-contained and does not exhibit the invasive properties of acute fungal sinusitis. Both clinically and radiographically, there is generally a sharp demarcation between the aspergilloma and surrounding normal sinus tissue as it is sequestered from the body. Endoscopic removal of the mycetoma with or without systemic antifungals is effective, though recurrent or recalcitrant cases may also benefit from the addition of systemic antifungal therapy. Chronic fungal rhinosinusitis often recurs, and this fact must be considered in dental treatment plans that include maxillary sinus floor grafting or other invasive procedures involving the maxillary sinus. Fungal sinusitis represents a minority of acute sinusitis cases, but its clinical course and features can be the most aggressive. Unlike bacterial and viral sinusitis, acute fungal sinusitis (also known as invasive fungal rhinosinusitis) almost exclusively affects individuals with compromised immune systems. Patients under active oncologic treatment or those with hematologic malignancies, diabetes mellitus, chronic steroid use, or AIDS are most at risk for developing this potentially devastating and fatal form of fungal sinusitis. There have been several fungal species isolated from patients with acute fungal sinusitis, but the two most prevalent responsible pathogens are Mucor and Aspergillus. The clinical features and presentation are more dramatic than that of bacterial and viral sinusitis and can sometimes be confused with rapidly evolving malignant processes of the paranasal sinuses. In addition to the signs and symptoms outlined in Box 2-1, patients suffering from acute fungal rhinosinusitis can also exhibit visual changes, facial neuropathy or paresthesia, facial or orbital swelling and edema, and epistaxis. Furthermore, oral manifestations are more common in those with fungal sinusitis and may include palatomaxillary edema, erythema, and paresthesia. In advanced cases, there may be an oroantral communication from palatal necrosis. Anterior rhinoscopy and nasal endoscopy can reveal frank mucosal necrosis. Both CT and MRI scans are useful in delineating the extent of this disease. In addition to the typical findings of mucosal edema and air-fluid levels in the antrum, invasive fungal sinusitis can demonstrate tissue necrosis, bone erosion, and cranial nerve/foramina enhancement. Though these signs seen on advanced sinus imaging may arouse suspicion for invasive fungal sinusitis, definitive diagnosis rests on tissue biopsy to confirm these findings. In a recent series of 13 patients with invasive fungal sinusitis, only 1 had preoperative CT imaging suggesting bony erosion; however, 6 patients had gross bony invasion noted intraoperatively.6

Box 2-1  Diagnostic criteria of rhinosinusitis

Major Minor Fever (acute) Fever (nonacute) Nasal purulence Dental pain Nasal obstruction Ear pain/fullness Facial congestion/fullness Cough Facial pain/pressure Headache Hyposmia/anosmia Halitosis

Invasive fungal sinusitis involving the sphenoid sinus is particularly worrisome because involvement of the adjacent cavernous sinus is almost always fatal. Death occurs due to direct intracranial extension and brain abscess, internal carotid rupture, subarachnoid hemorrhage, and sepsis.7,8 The treatment for confirmed invasive fungal sinusitis is hinged both on aggressive surgical debridement and systemic antifungal therapy. This is generally completed in an inpatient setting because patients may require multiple debridements and washouts as well as long-term intravenous antifungals. As suggested by its name, invasive fungal sinusitis is destructive and may result in irreversible damage to critical structures of the nasal cavity, oral cavity, paranasal sinuses, orbit, and intracranial space. Surgical or prosthetic reconstruction of lost tissue is carried out in a delayed fashion once the active infection has resolved (Table 2-1).

Medical workup Like other diseases of the human body, careful history and physical examination are the first tools in making a diagnosis of rhinosinusitis. This includes anterior rhinoscopy with a nasal speculum and may include office nasal endoscopy as well as subjective olfactory testing. In addition to the presence of two major or one major and two minor signs and symptoms (see Box 2-1), imaging can be most helpful in confirming the diagnosis. A CT scan of all the paranasal sinuses (including the ostiomeatal complex) is standard practice. Both wide-field cone beam CTs (CBCTs) as well as medical-grade paranasal sinus CT scans are acceptable, but limited-scope dental CBCT is not helpful. Patients with characteristics of sinus inflammation alone, suggestive of viral rhinosinusitis, without the presence of clinical signs and symptoms, do not always warrant imaging or medical or surgical intervention. Sinus CT alone may have false positive rates of 20% to 60% in the diagnosis of sinonasal disorders. Children under 8 years old, in particular, are prone to having incidental mucosal abnormalities in the absence of symptoms on CT examination. This may be due to frequent URTIs in children with residual sinonasal mucosal inflammation.

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Table 2-1  Characteristics of rhinosinusitis Type of rhinosinusitis

Duration

Pathogens

Treatment

Acute viral

Less than 4 weeks

Adenovirus, parainfluenza, influenza, rhinovirus, respiratory syncytial virus

Best supportive care, nasal steroids

Acute bacterial

Symptoms worsen 10 days after URTI, total course less than 4 weeks

H influenzae, M catarrhalis, S aureus, S pneumoniae

Antibiotics, nasal steroids

Acute fungal

Less than 4 weeks

Mucor, Aspergillus

Antifungals, surgical debridement

Chronic bacterial

At least 12 weeks

Mixed, may include pseudomonas

Nasal steroids, sinus hygiene, consider FESS, consider guided antibiotics

Chronic fungal

At least 12 weeks

Aspergillus

Surgical excision of fungus ball, consider antifungals

FESS, functional endoscopic sinus surgery

Although it might seem logical to obtain cultures and antimicrobial sensitivity testing from nasal secretions, this is generally inaccurate in the diagnosis and management of bacterial sinusitis. The nasal vault is colonized by upper respiratory flora as well as S aureus. Purulent-appearing nasal secretions do not always represent what is happening within the antrum. Generally, empiric antibiotic coverage for a clinically diagnosed bacterial sinusitis is sufficient. In refractory cases of bacterial sinusitis or recurrent acute bacterial sinusitis, maxillary sinus cultures are indicated. In these cases, it is imperative to obtain cultures from the lumen of the antrum and not the nose. This can be accomplished via transnasal endoscopic approaches to the maxillary sinus or transmucosal or transoral needle aspiration through the anterior sinus wall utilizing an 18-gauge needle. Interestingly, the color of nasal and sinus secretions is not associated with the severity of sinus disease nor with the level of infection. In addition, purulent discharge does not necessarily signify bacterial infection, but rather is indicative of the presence of leukocytes.

Treatment of Acute and Chronic Infections Antibiotics Systemic oral antibiotic therapy remains at the core of the treatment algorithm for patients with acute bacterial sinusitis. Similar to dentoalveolar infections, the first-line antibiotic of choice is penicillin based: amoxicillin with or without clavulanic acid

for a 5- to 7-day course.9–13 The rationale for the addition of a β-lactamase inhibitor (ie, clavulanic acid) depends on the suspicion of β-lactamase-producing organisms (namely S pneumoniae, and to a lesser degree H influenzae). Patients who fail to respond to amoxicillin or have sinus cultures demonstrating β-lactamase activity may be candidates for amoxicillin with clavulanic acid. Doxycycline or fluoroquinolones (eg, ciprofloxacin, levofloxa­ cin) may be considered for patients with penicillin-resistant bacterial infections or allergies to penicillin.11–13 Macrolide use (eg, clindamycin, azithromycin) is quite common among surveyed medical providers for the treatment of sinusitis, but it should be reserved for penicillin-allergic or second-line therapy because there is growing antibiotic resistance to erythromycin.9,10 Though uncommon, methicillin-resistant S aureus can contribute to acute bacterial sinusitis and would require clindamycin, sulfamethoxazole and trimethoprim, or linezolid for adequate coverage, depending on the results of sinus culture and sensitivity. Antibiotic therapy for the treatment of chronic sinusitis should ideally be culture directed. The antibiotics of choice are the same as that of acute bacterial sinusitis; however, the sinus flora and bacterial colonization are usually more complex, are more likely to include anaerobes, and may have resistant organisms if the patient has previously been treated with antibiotics. The use of intravenous antibiotics is reserved for patients with severe infections resulting in systemic inflammatory response syndrome, sepsis, or septic shock. The principles of antibiotic therapy are the same as for orally administered treatment, but management of hemodynamics and end-organ function—particularly in those patients who are immunosuppressed—is critical for positive outcomes.

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Other Causes of Sinus Infection

Intranasal steroids Over the last few years, several clinical trials have demonstrated the efficacy of intranasally delivered topical glucocorticoids for the treatment of acute and chronic rhinosinusitis. Some of these products are now available over the counter and can play a critical role in the treatment of rhinosinusitis. Glucocorticoids inhibit the production of several inflammatory mediators and reduce the inflammatory response at the transcription level. This results in improvement of nasal and sinus mucosal edema and engorgement and translates into reduction in clinical symptoms of both acute and chronic sinusitis as demonstrated by multiple clinical trials.14 Budesonide, fluticasone, and triamcinolone are available over the counter via nasal mist and should be used for a 1-month course. Unlike systemic corticosteroids, intranasal applications demonstrate no systemic adverse effects due to lack of meaningful systemic absorption. Local adverse reactions are mild and most frequently result in epistaxis or nasal dryness.

Sinonasal lavage Nasal saline administration via a neti pot or sinus douche using hypertonic saline has been shown to be effective in reducing the severity and symptoms associated with chronic sinusitis. Unlike nasal saline sprays and mists, the use of a modern neti pot or sinus douche lavages the maxillary sinus via retrograde irrigation through the middle meatus and ostiomeatal complex. In addition to appropriate antibiotic therapy, sinus lavage with saline is an important and effective tool in treating chronic rhinosinusitis.

these will persist when there is a baseline deficiency of normal sinonasal drainage due to chronic sinusitis or impaired ostiomeatal complex outflow. Pooling of dependent secretions at the site of the oroantral communication will inevitably result in breakdown of the suture line and refistulization. These refractory cases can require functional endoscopic sinus surgery (FESS), including nasal antrostomy to restore adequate sinus drainage while closing the fistula with a robust local tissue flap such as a buccal fat pad flap or palatal island flap. Other dental insults to the integrity of the maxillary sinus, such as sinus elevation with bone grafting or the placement of zygomatic implants, are usually well-tolerated by a healthy maxillary sinus with a well-functioning ostiomeatal complex. Patients with borderline function of these areas may not be able to recover from such procedures without postoperative infection resulting from obstruction of maxillary sinus drainage. The most common complication of maxillary sinus elevation surgery is perforation of the sinus membrane. Using the open lateral window technique, clinically evident perforations occur in up to 44% of cases.15,16 Though small perforations (> 5 mm) may repair themselves via a fibrin plug or fold over the membrane, larger perforations (up to 10 mm) may require direct repair if possible and full-thickness coverage with a resorbable collagen membrane. It is critical to isolate the bone graft material from the lumen of the maxillary sinus to prevent ongoing contamination or mobilization of graft particles through the ostiomeatal complex. Perforation of the sinus membrane during sinus elevation does not necessarily lead to poor dental implant survival when managed appropriately. In patients with healthy maxillary sinuses and a functionally adequate ostiomeatal complex, repaired sinus membrane perforations using a resorbable collagen membrane did not adversely affect dental implant survival.17,18

Other Causes of Sinus Infection Odontogenic sinusitis Sinonasal infections associated with dentoalveolar manipulation and insult In addition to the common bacterial, fungal, and viral pathogens that contribute to infectious rhinosinusitis, infections of the paranasal sinuses may be iatrogenic in nature. Transoral surgery of the maxillary alveolus or floor of the maxillary sinus can result in postoperative infections. Furthermore, acute infections of maxillary posterior teeth with root apices inside the maxillary sinus can result in acute or subacute sinusitis. Perhaps the most common cause of iatrogenic maxillary sinus pathology from an oral surgical procedure is extraction of a posterior maxillary tooth resulting in an oroantral communication. These are troublesome to patients because they may result in nasal regurgitation of fluids, foul taste or odor, and discomfort or sensitivity to the local area. Though many of these small perforations close spontaneously, larger openings require adjacent tissue transfer to seal the defect. Unfortunately, a number of

Infections of the maxillary sinus attributed to odontogenic sources may be responsible for up to one-third of all cases of rhinosinusitis. Using radiographic and CT criteria, reported rates of an odontogenic source of rhinosinusitis range from 10% to 40%.19 Typically, such cases are unilateral as they are associated with a periapical granuloma or cyst from a necrotic maxillary molar or premolar or large periodontal infections traversing the sinus floor.20,21 The palatal roots from first molars are the roots most frequently associated with odontogenic sinusitis (Fig 2-3), followed by the mesiobuccal roots from the second molars. Interestingly, Eberhardt et al22 used CT scans in cadavers to demonstrate that the apex of the mesiobuccal root of the second maxillary molar was closest to the sinus floor with a mean distance of 1.97 mm. First premolar root apices, on the contrary, were an average of 7.5 mm away from the sinus floor in the same specimens. Symptomatology is also quite variable depending on the insult to the floor of the sinus and efficiency of the ostiomeatal

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Fig 2-3  Odontogenic sinusitis. Note the bone changes in the alveolus from a failing endodontially treated maxillary molar and resultant maxillary sinus membrane thickening, possibly with a fluid component.

of the maxillary sinus prior to the sinus bone graft. Though CT evidence of a thickened sinus mucosal membrane alone is not always indicative of infectious sinusitis (Fig 2-4), it does indicate the presence of sinus inflammation. This should be considered prior to a sinus elevation to reduce the risk of surgical complications. The radiographic presence of a commonly encountered mucous retention phenomenon, often but inaccurately referred to as a mucocele (Fig 2-5), does not require specific presurgical consideration. If this thickening is due to obstructed outflow via an abnormal ostiomeatal complex, this may pose problems postoperatively unless the anatomical problem is corrected. Elevation of the sinus membrane during sinus floor augmentation temporarily inhibits normal ciliomotor function, and within a compromised sinus with obstructed nasal outflow tract, this can be a cause for postoperative infection and bone graft failure.

Timing of sinus floor augmentation complex. Patients may experience vague symptoms or no pain at all in early cases of odontogenic sinusitis, but it can still progress to fulminant acute rhinosinusitis if left untreated. The microbiology of odontogenic sinusitis differs from conventional rhinosinusitis in that it is predominated by oral flora and pathogens that are responsible for odontogenic infections. Like most other dental infections, mixed aerobic and anaerobic bacteria are present, with streptococcal species predominating.23 In contrast to the treatment for conventional sinusitis, the eradication of odontogenic sinusitis requires source control, (ie, removal of the infected tooth). Antibiotic choices are similar to that of acute sinusitis, with penicillin-based therapy preferred and clindamycin as the first choice for patients with a penicillin allergy.

Considerations Prior to Sinus Augmentation Surgery

In patients with abnormal sinus findings on history and physical examination or on CT evaluation, it is prudent to consider otolaryngology consultation prior to sinus floor augmentation, zygomatic implant placement, or other invasive surgeries in the maxillary sinus. Patients should be considered for optimization of sinonasal health prior to preprosthetic sinus surgery if they have a history suspicious for chronic sinusitis; episodes of recurrent acute sinusitis; or CBCT findings of sinus mucosal thickening, large mucous retention phenomena, or obstructed ostiomeatal complex with opacity involving the surrounding ethmoid sinuses. This may involve a course of nasal steroids, antibiotics, and/or sinus lavage or FESS to relieve obstruction at the middle meatus and uncinate process before proceeding with maxillary sinus elevation. Patients with a history of allergic rhinitis may be prone to sinusitis during high allergen seasons, particularly spring and fall. Such patients usually know their “bad seasons,” and careful history taking can determine a time of year when their allergies are quiescent to minimize the chances of an acute flare of allergic rhinosinusitis in the perioperative period.

Evaluation of paranasal sinuses The crux of sinus diagnosis rests on a thorough, focused history and physical examination. In patients who are planned to undergo maxillary sinus floor augmentation, it is critical to elicit a proper history and to perform a focused physical examination on the paranasal sinuses and associated structures. Patients who are afflicted with at least one major sinus infection every year merit consideration of full CT evaluation. Box 2-1 summarizes the most common signs and symptoms associated with rhinosinusitis. In addition, findings such as pain with palpation or percussion over the paranasal sinuses, hearing changes, maxillary dental pain, periorbital discomfort, sinus headache, or turbinate hyperemia may indicate sinusitis. CT imaging—most often CBCT—is of utmost importance in evaluating both the maxillary edentulous ridge and the health

Preconsultation communication with otolaryngologist Prior to otolaryngology consultation, there are several important points to discuss with the otolaryngologist regarding the patient’s care. First, describe the planned procedure (eg, maxillary sinus floor augmentation, zygomatic implants, Le Fort I downgraft) and send illustrations or reprints that highlight the associated anatomical changes. It is also important to note that the procedure is carried out through a transoral approach and does not violate the maxillary sinus ostium. (Most otolaryngologists are unfamiliar with sinus elevation or zygomatic implants.) Second, relay your goals for the patient and a plan to establish optimal sinus health with adequate drainage through the

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References

Fig 2-4 Chronic maxillary sinusitis. There is circumferential thickening of the right antral membrane with outflow tract obstruction and ipsilateral concha bullosa. This should be addressed prior to preprosthetic surgery involving the maxillary sinus.

ostiomeatal complex prior to sinus elevation or other surgery. It should be noted that the sinus membrane will ideally remain intact; however, there may be gross or microscopic perforations from manipulation. In zygomatic implant placement or Le Fort I osteotomy with interpositional bone graft, the sinus membrane will normally be grossly violated. These are rarely problematic if baseline sinus health and drainage is sufficient. Third, prepare your patient for the fact that their otolaryngology consultation may culminate in a recommendation for preemptive endoscopic sinus surgery. Because preprosthetic surgery of the maxillary sinus is elective, preventable complications due to sinonasal infection should be minimized.

Conclusion Rhinosinusitis is a widely prevalent acute and chronic disease that can affect individuals of all age groups. There are welldescribed evidence-based treatment protocols for this process that should be taken into consideration prior to preprosthetic surgery involving the maxillary sinus. With proper diagnosis and treatment of acute and chronic sinonasal infections, postsurgical complications associated with maxillary sinus preprosthetic surgery can be markedly reduced.

References 1. Karatas D, Koc A, Yuksel F, Dogan M, Bayram A, Cihan MC. The effect of nasal septal deviation on frontal and maxillary sinus volumes and development of sinusitis. J Craniofac Surg 2015;26:1508–1512.

Fig 2-5 Confluent small mucous retention phenomena at the floor of the left maxillary sinus (arrow). Note that the remainder of the sinus appears healthy without membrane thickening or fluid levels.

2. Orlandi RR. A systematic analysis of septal deviation associated with rhinosinusitis. Laryngoscope 2010;120:1687–1695. 3. Kucybała I, Janik KA, Ciuk S, Storman D, Urbanik A. Nasal septal deviation and concha bullosa—Do they have an impact on maxillary sinus volumes and prevalence of maxillary sinusitis? Pol J Radiol 2017;82:126–133. 4. Koo SK, Kim JD, Moon JS, Jung SH, Lee SH. The incidence of concha bullosa, unusual anatomic variation and its relationship to nasal septal deviation: A retrospective radiologic study. Auris Nasus Larynx 2017;44:561–570. 5. Kaya M, Çankal F, Gumusok M, Apaydin N, Tekdemir I. Role of anatomic variations of paranasal sinuses on the prevalence of sinusitis: Computed tomography findings of 350 patients. Niger J Clin Pract 2017;20:1481–1488. 6. Slonimsky G, Slonimsky E, Yakirevitch A, et al. The significance of computed tomography in invasive paranasal mucormycosis. Rhinology 2018;56:54–58. 7. Murosaki T, Nagashima T, Honne K, Aoki Y, Minota S. Invasive sphenoid sinus aspergillosis mimicking giant cell arteritis. Int J Rheum Dis 2014;17:476–478. 8. Lee DH, Yoon TM, Lee JK, Joo YE, Park KH, Lim SC. Invasive fungal sinusitis of the sphenoid sinus. Clin Exp Otorhinolaryngol 2014;7:181–187. 9. Benninger MS, Holy CE, Trask DK. Acute rhinosinusitis: Prescription patterns in a real-world setting. Otolaryngol Head Neck Surg 2016;154:957–962. 10. Chow AW, Benninger MS, Brook I, et al. IDSA clinical practice guideline for acute bacterial rhinosinusitis in children and adults. Clin Infect Dis 2012;54:e72–e112. 11. Rosenfeld RM. Clinical practice. Acute sinusitis in adults. N Engl J Med 2016;375:962–970. 12. Rosenfeld RM, Piccirillo JF, Chandrasekhar SS, et al. Clinical practice guideline (update): Adult sinusitis executive summary. Otolaryngol Head Neck Surg 2015;152:598–609. 13. Rosenfeld RM, Piccirillo JF, Chandrasekhar SS, et al. Clinical practice guideline (update): Adult sinusitis. Otolaryngol Head Neck Surg 2015;152(2 suppl):S1–S39. 14. Zalmanovici Trestioreanu A, Yaphe J. Intranasal steroids for acute sinusitis. Cochrane Database Syst Rev 2013;12:CD005149.

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15. Danesh-Sani SA, Loomer PM, Wallace SS. A comprehensive clinical review of maxillary sinus floor elevation: Anatomy, techniques, biomaterials and complications. Br J Oral Maxillofac Surg 2016;54:724–730. 16. Zijderveld SA, van den Bergh JP, Schulten EA, ten Bruggenkate CM. Anatomical and surgical findings and complications in 100 consecutive maxillary sinus floor elevations. J Oral Maxillofac Surg 2008;66:1426–1438. 17. Froum SJ, Khouly I, Favero G, Cho SC. Effect of maxillary sinus membrane perforation on vital bone formation and implant survival: A retrospective study. J Periodontol 2013;84:1094–1099. 18. Viña-Almunia J, Peñarrocha-Diago M, Peñarrocha-Diago M. Influence of perforation of the sinus membrane on the survival rate of implants placed after direct sinus lift. Literature update. Med Oral Patol Oral Cir Bucal 2009;14:E133–E136.

19. Patel NA, Ferguson BJ. Odontogenic sinusitis: An ancient but under-appreciated cause of maxillary sinusitis. Curr Opin Otolaryngol Head Neck Surg 2012;20:24–8. 20. Ferguson M. Rhinosinusitis in oral medicine and dentistry. Aust Dent J 2014;59:289–295. 21. Shanbhag S, Karnik P, Shirke P, Shanbhag V. Association between periapical lesions and maxillary sinus mucosal thickening: A retrospective cone-beam computed tomographic study. J Endod 2013;39:853–857. 22. Eberhardt JA, Torabinejad M, Christiansen EL. A computed tomographic study of the distances between the maxillary sinus floor and the apices of the maxillary posterior teeth. Oral Surg Oral Med Oral Pathol 1992;73:345–346. 23. Saibene AM, Vassena C, Pipolo C, et al. Odontogenic and rhinogenic chronic sinusitis: A modern microbiological comparison. Int Forum Allergy Rhinol 2016;6:41–45.

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CHAPTER 3

OSTEOPERIOSTEAL FLAPS FOR SINUS GRAFTING Ole T. Jensen, dds, ms

A

lthough the sinus graft offers a major benefit for gaining bone mass for osseointegration, it does not in itself address deficient alveolar form.1 Guided bone regeneration, block grafting, and alveolar split graft combined with sinus grafting have been used successfully, but there are few reports in the literature describing a combination of sinus and alveolar grafting.2–4 The use of the sandwich osteotomy graft to raise the residual alveolus crestally in combination with sinus grafting is an additional technique for improving alveolar form for implant placement. This approach not only results in an increase in bone but also leads to a relatively stable alveolar crest morphology when compared with alternative approaches.5–8 Though technically challenging, a sandwich osteotomy can be performed from access through the lateral sinus osteotomy site.9–11 Similarly, an alveolar split graft (ie, book flap) made over the sinus cavity provides access to the sinus floor from a transalveolar approach.12 Through these methods, an increase in both height and width can be obtained simultaneously. A third approach, the intra-alveolar split osteotomy performed after the horizontal segment cut of the sandwich osteotomy, increases the height and width of the alveolar process. However, sufficient bone must be available to allow the intra-alveolar split, usually a minimum of 4 mm. Interpositional bone grafting with all of these approaches extends upward into the sinus floor beneath the previously elevated sinus membrane. Relatively modest intra-alveolar expansion and sinus membrane elevation create a large cavity that is particularly well suited to placement of a recombinant human bone morphogenetic protein 2 (rhBMP-2) graft.13 The great advantage of the sandwich osteotomy technique is that it provides a relatively stable alveolar crest and a considerable amount of bone mass for osseointegration.8 Primary wound closure is usually easily obtained because the incision is made in

the vestibule for the sandwich graft and palatocrestally for the split graft, sites that are both easily mobilized to obtain closure for modest gaps of 5 mm or less. Because these are vascularized osteoperiosteal flaps, incision sites heal well, and the alveolar reconstruction is less likely to break down.

Posterior Maxillary Sandwich Osteotomy Surgical technique It can be difficult for surgeons to obtain access to perform this osteotomy in partially dentate individuals. The surgeon must be able to visualize the posterior lateral maxilla clearly to perform a transsinus osteotomy procedure. If access is limited, the procedure should not be attempted. The incision is a standard vestibular incision that extends the length of the edentulous space. This procedure is a good choice when both premolars and molars are absent. A much more difficult case arises when only molars are absent, and the risk of the procedure may outweigh benefits. After the vestibular incision is made, reflection is minimal crestally but enough to access the lateral maxilla to create a window for elevation of the sinus membrane (Figs 3-1a and 3-1b). Once the sinus elevation is completed, a horizontal osteotomy cut is made forward and backward, tapering to the alveolar crest (Fig 3-1c). Next, a transsinus downward curving osteotomy is made, connecting at the alveolar crest with laterally made cuts (Fig 3-1d). This palatal osteotomy is done with an oscillating saw or sometimes a piezoelectric knife. If it cannot be completed, an osteotome is used to complete the cut, and the segment is downfractured toward the palate.

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Incision line

Outer wall of maxilla cut

Location of sinus membrane

Sinus membrane

Periosteum Gingiva

Site of sinus window

Osseous window hinge raises sinus membrane

Atrophy of alveolar process of maxilla

a

b

c

Palatine process of maxilla cut Cut lines joined to free bone

Rigid fixation plate

Desired alveolar plane

d

e

f

Bone graft deposited

g

h

i

Fig 3-1  (a) A lateral window osteotomy is made for sinus grafting after a vestibular incision is minimally elevated toward the alveolar crest. (b) Following elevation of the sinus membrane, a lateral horizontal osteotomy is made forward and backward, curving toward the alveolar crest. (c) A transsinus palatal connecting osteotomy is made, freeing at least a 5-mm (vertical) segment of alveolar bone. An oscillating saw or piezoelectric knife is used in conjunction with spade osteotomes. (d) The connection at the alveolar crest is made blindly beneath the flap so the mucoperiosteum does not detach from the alveolar segment. (e) Vertical elevation of the segment is usually limited to 5 mm before significant palatal deflection occurs. A bone plate is fixed in place. (f) A cross-sectional view of sinus elevation from the lateral approach. A transsinus bone cut of the palate tapers to connect with the lateral cut and frees the segment.

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Posterior Maxillary Sandwich Osteotomy

j

k

l

Fig 3-1  (cont) (g) The interpositional graft is placed after bone plate fixation. The combination of interpositional and sinus floor grafting has considerable capacity for bone mass expansion. (h) Following placement of the bone plate and grafting in the defect, the bone plate is bent (arrow) to torque the alveolus into axial alignment. (i to l) Implants are placed 4 to 6 months after grafting, often through an alveolar split approach to normalize alveolar dimension. The definitive restoration is placed 4 months after implant placement.

The mobilized segment is displaced crestally about 5 mm (Fig 3-1e). To maintain blood supply, no palatal releasing incisions are made (Fig 3-1f). A bone plate is placed to hold the alveolus in a crestally elevated position (Fig 3-1g). If the alveolus deflects significantly palatally, this can be corrected by an alveolar split graft at the time of implant placement 4 months later. Following bone plating, the alveolus is torqued toward axial alignment by using a wire twister in a circular crimping action to bend the bone plate (Fig 3-1h). When internal alveolar splitting is used as a strategy to gain width, plate torquing is critical to establishing an axial alveolar position. Combined with sinus elevation, the osteotomy usually provides 10 to 15 mm of vertical space for bone grafting (Figs 3-1i and 3-1j). This is an excellent setting for the use of rhBMP2.8 The graft is placed, and the wound is closed primarily in the vestibule. Following 4 to 6 months of healing, the alveolus is approached from the alveolar crest. If the crest is inclined palatally, an alveolar split bone flap can bring the buccal segment into a lateral position while implants are placed transalveolarly in the sinus graft consolidation. After another 4 months, the definitive restoration is placed (Figs 3-1k and 3-1l).

Case 1: Posterior sandwich osteotomy with sinus floor grafting A 51-year-old woman was missing her maxillary left molars. A prominent sinus was associated with vertical atrophy of

approximately 12 mm (Fig 3-2a). A vestibular incision with minimal elevation toward the alveolar crest was used to create a lateral antrostomy window for elevation of the sinus membrane. Horizontal osteotomies were made forward and backward, curving toward the alveolar crest. These cuts were connected with a horizontal curving osteotomy of the palatal bone made through the sinus. The cut was completed with an osteotome. The segment was moved crestally about 5 or 6 mm and then fixed in place with a bone plate (Fig 3-2b). The plate was used to torque the segment laterally. Interpositional and sinus floor grafts were placed using autogenous bone graft, the wound was closed with resorbable sutures, and the grafts were left to consolidate for 4 months. After 4 months, the bone plate was removed, and two implants were placed (Figs 3-2c and 3-2d). The implants were restored 4 months after placement (Figs 3-2e and 3-2f).

Case 2: Posterior sandwich osteotomy with internal alveolar split A 48-year-old woman presented with loss of the maxillary left molars and vertical loss of 5 or 6 mm of alveolar bone. The sinus was prominent, although 4 or 5 mm of basal bone was still present (Fig 3-3a). Following sinus elevation and alveolar osteotomies to move the alveolus to the alveolar plane, the 6-mm-wide alveolus was internally split and fixed with a bone plate in a widened alveolar position (Fig 3-3b). Autogenous

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a

b

c

d

e

f

Fig 3-2  (a) A 51-year-old woman is missing her maxillary left molars and has a 12-mm vertical alveolar deficiency. (b) A combined sandwich osteotomy and sinus floor graft are used to move the segment downward 5 to 6 mm. The segment is fixed still short of the alveolar plane. (c) The radiograph reveals good consolidation of the segment 4 months after grafting. (d) The site is approached through a crestal incision, and the titanium bone plate is removed, revealing well-healed bone. (e) Two implants are placed in the healed site, and the definitive restoration is placed 4 months later. (f) The final radiograph shows a stable bone level.

a

b

d

c

e

Fig 3-3  (a) Two left molars are missing, and there is a 7-mm vertical defect as well as a 4- to 5-mm horizontal defect. The sinus is prominent, and minimal bone is available for osseointegration. (b) A vestibular incision is used to elevate the sinus floor through a lateral antrostomy. The alveolar segment is moved downward 5 to 6 mm via a sandwich osteotomy, which is also split internally to widen the alveolus, and the segment is fixed in position with a bone plate. (c) Immediate postoperative radiograph showing combined sinus and intra-alveolar bone graft. (d) Two implants are placed 4 months after the osteotomy was made. (e) The implants are restored 4 months after implant placement.

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Posterior Maxillary Alveolar Split and Sinus Graft

Incision Sinus floor Bone cuts

a

Sinus intrusion ~ 7–8 mm

Original location of sinus membrane

b

Implants

c

d

e

Bone graft

Original location of sinus membrane

Fig 3-4  (a) A crestal incision is minimally reflected, and the alveolus is split sagittally. Vertical stop cuts are made anteriorly and posteriorly. (b) The sinus floor is elevated the entire length of the alveolar split as an osteoperiosteal flap. (c) For multitooth sites, graft material is placed to maintain alveolar width. (d) Four months later, implants are placed into the sinus graft through the alveolar split site. (e) The implants have a more axial position and are restored.

bone and xenograft mixed with platelet-derived growth factor BB were applied between the alveolar plates and in the sinus floor (Fig 3-3c). After 4 months, there was excellent consolidation. The titanium plate was removed, and implants were placed so that the implant platform was nearly level with the alveolar plane (Fig 3-3d). Definitive restoration proceeded 4 months after implant placement (Fig 3-3e).

Posterior Maxillary Alveolar Split and Sinus Graft Surgical technique In the partially edentulous posterior region of the maxilla, when alveolar height is sufficient but the alveolar ridge is narrow and a prominent sinus cavity is present, an alveolar split osteotomy

can be combined with transalveolar sinus floor elevation. The incision is a palatal-crestal incision that is minimally reflected, leaving mucoperiosteal attachment on the buccal plate. Following alveolar split osteotomy in the form of a book osteoperiosteal flap (Fig 3-4a), sinus floor access is gained transalveolarly, and blunt osteotomes are used to infracture the sinus floor the entire length of the edentulous space (Fig 3-4b). When a two- or three-tooth segment of sinus floor is mobilized, the segment can be easily elevated up to 10 mm; however, a modest elevation of several millimeters is usually sufficient. For a single-tooth site, a 4- to 5-mm elevation is carried out without bone grafting. Implants placed in conjunction with an alveolar split technique end up in a more axial location. Bone graft material is placed to maintain alveolar width and fill the defect in multitooth sites for delayed placement (Fig 3-4c). Four months after grafting, implants are placed transalveolarly in a single-stage protocol and then restored 4 months after placement (Figs 3-4d and 3-4e).

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a

c

b

Fig 3-5 (a) Loss of a maxillary first molar has led to loss of buccal bone as well as limited vertical bone because of sinus prominence. (b and c) An alveolar split technique (book flap) is combined with sinus floor intrusion to allow placement of an implant without added bone grafting. (d and e) The implant is positioned more axially within the alveolus and level with the alveolar plane.

d

e

a

c

b

d

Fig 3-6  (a) A 46-year-old woman has severe periodontal disease in the maxilla and extensive loss of the buccal plate of bone. In the process of extraction of all remaining teeth, the alveolus is split, the sinus floor is intruded the entire length of the edentulous space, and then the site is bone grafted. (b) Four months after grafting, implant sites are prepared in the widened alveolus. (c) A post­ operative panoramic radiograph demonstrates alveolar and sinus floor augmentation at the time of transgingival implant placement. (d) The combined procedures have restored alveolar width and increased vertical bone mass sufficiently to obtain osseointegration. The remaining vertical alveolar deficiency is addressed with a prosthetic strategy that is acceptable to the patient.

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Posterior Maxillary Alveolar Split and Sinus Graft

a

d

b

c

e

f

Fig 3-7  (a) A palatal approach to the combined posterior maxillary segmental osteotomy and sinus graft must avoid the greater palatine artery. (b and c) Piezoelectric surgery is used to make the osteotomy cuts after sinus elevation through the vault. (d) The segment is osteotomized transsinus, connecting a lateral osteotomy cut to a palatal cut that tapers together at the posterior and anterior margins of the edentulous crest. (e) The rhBMP-2 graft material is placed interpositionally and the segment retained with rigid fixation. (f) The wound is closed primarily.

Case 3: Alveolar split grafting combined with transalveolar sinus grafting A 35-year-old woman was missing her maxillary left first molar (Fig 3-5a). Buccal plate collapse was combined with a prominent sinus. Round osteotomes were used to expand the buccal plate and intrude the sinus floor. Immediate implant placement was completed without the use of additional bone graft material, allowing the implant to be placed in an axial location and restored 4 months later (Figs 3-5b to 3-5e).

Case 4: Alveolar split sinus floor intrusion combined with dental extractions A 46-year-old woman exhibited severe periodontal disease that required extraction of all of her maxillary teeth. The alveolus was split because of the severe buccal bone loss (Fig 3-6a). The sinus floor was intruded and then grafted with autograft and xenograft. Implants were placed 4 months after the osteotomy

(Figs 3-6b and 3-6c). After 1 year in function, the definitive restoration reveals adequate alveolar width; the remaining vertical deficiency was addressed prosthetically (Fig 3-6d).

Case 5: Palatal approach sinus grafting and segmental osteotomy A final variation to consider is a palatal approach to sinus elevation14 and segmental osteotomy.8,9 When a combined procedure is done from a lateral approach, it always results in deflection of the segment toward the palate. The palatal approach, in contrast, facilitates easier lateralization of the alveolar crest. The technique is difficult to master, even with the use of piezoelectric surgery (Fig 3-7), but it may hold promise with the development of better instrumentation. The reason for this is the common finding throughout the atrophic maxillary arch of centripetal alveolar bone loss, which is not as easily addressed by buccalrather than palatal-based osteoperiosteal flaps.

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g

h

Fig 3-7  (cont) (g and h) Comparison of the preoperative and postoperative situation reveals an improved alveolar position. The segment deflected favorably in the buccal direction (arrow).

Discussion One of the outgrowths of the various alveolar segmental osteotomies, such as the smile osteotomy for the treatment of posterior mandibular atrophy, is application of these procedures in locations that are difficult to assess. As in orthognathic surgery planning, the surgeon must return to the use of articulated mounted casts or stereolithographic models for planning the surgical procedure.15 By using so-called model surgery and a diagnostic wax-up, the entire restorative team can evaluate and approve the surgical treatment plan prior to surgery, based on the goals of the esthetic control cast.1,16 There are both technical and biologic limitations to surgical movements. Excess movement can compromise blood supply or lead to relapse.17–19 Wounds closed under tension usually result from overaggressive treatment planning goals.20 It is better to make alveolar segmental moves in small increments of 5 or 6 mm.21 Often, even a 3- or 4-mm segmental move provides sufficient improvement to proceed with a nearly ideal prosthetic restoration. Once the bony base has been altered to an optimal alveolar position, soft tissue or minor osseous augmentation is often achievable at the time of implant placement.22–24 Shaping of gingivoalveolar form is therefore finalized at stage-two surgery rather than at the time of the osteotomy.9 Complications from this procedure are almost all caused by disturbance of the palatal soft tissue pedicle. When the soft tissue is perforated or torn, the bone segment can become partly exposed or an oroantral fistula may result.25 Interruption of the soft tissue pedicle generally results from misuse of hand instruments such as osteotomes rather than the oscillating saw or piezoelectric unit. Bone exposure develops despite a vital osteoperiosteal segment. When this occurs, exposed bone will have to be removed, and a secondary reparative surgery will likely be needed. Therefore, this procedure should not be attempted by surgeons who are not familiar with orthognathic surgery.26

Another complication to avoid is entry into the palatal vasculature.14 To avoid this problem, the palatal osteotomy cut should be made within the alveolus at least 10 mm from the greater palatine foramen. Because only a 5-mm segment height is required to elevate the alveolus toward the alveolar plane, a more superiorly placed palatal osteotomy cut is not needed. If significant bleeding is encountered in a sedated patient, an intact sinus membrane prevents airway compromise.15 One technical consideration is evaluation of interocclusal space on articulated stone or resin casts.1 Compensation by the opposing arch may mean that there is not enough interocclusal space to move the alveolus to the alveolar plane, despite the presence of vertical alveolar atrophy.27 In such cases, compromises will have to be made. On the other hand, when there is excess interocclusal space, implants placed without alveolar elevation lead to high crown-to-implant ratios and less-thanideal restorative schemes.13 In patients with a high smile line, the posterior region of the alveolar ridge can sometimes be exposed, creating an unesthetic restoration.28

Conclusion In general, elevation of a segment about 5 mm vertically toward the alveolar plane in conjunction with sinus grafting is an excellent, achievable strategy that is very stable and has fewer complications than onlay grafting.8 Complications associated with the alveolar split graft or book flap apply to a combined sinus graft and alveolar widening procedure.29 Excessive periosteal stripping destabilizes the buccal plate of bone, but when this occurs, it does not appear to substantially affect the sinus floor portion of the graft. A combination of sandwich osteotomy and sinus grafting or a combination of transalveolar widening and sinus floor intrusion provides a way to perform posterior maxillary alveolar reconstruction through the use of vascularized osteotomies,

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References

a much more stable approach to alveolar augmentation than open flap approaches. Alveolar height can be increased with a sandwich osteotomy, and alveolar width can be increased with a split graft approach that incorporates a book flap. The sinus membrane is elevated either from the lateral side or transalveolarly from the crest, and graft material is placed in the sinus floor and interpositionally. Model-based presurgical planning is important. Biomimetics are well suited for use in this setting, which requires a delayed implant placement protocol.

References 1. Zinner ID, Small SA, Landa LS. Prosthetic management of the sinus graft patient. In: Jensen OT (ed). The Sinus Bone Graft, ed 2. Chicago: Quintessence, 2006:75–85. 2. Weingart D, Bublitz R, Petrin G, Kalber J, Ingimarsson S. Combined sinus lift procedure and lateral augmentation. A treatment concept for the surgical and prosthodontic rehabilitation of the extremely atrophic maxilla [in German]. Mund Kiefer Gesichtschir 2005;9:317–323. 3. Neyt LF, De Clercq CA, Abeloos JV, Mommaerts MY. Reconstruction of the severely resorbed maxilla with a combination of sinus augmentation, onlay bone grafting, and implants. J Oral Maxillofac Surg 1997;55:1397–1401. 4. De Clercq C, Neyt L, Mommaerts M, Abeloos J, Deryckere F. Reconstruction of the extremely atrophic maxilla with onlay and inlay bone graft techniques in combination with implants. Acta Stomatol Belg 1994;91:5–15. 5. Jensen OT, Leopardi A, Gallegos L. The case for bone graft reconstruction including sinus grafting and distraction osteogenesis for the atrophic maxilla. J Oral Maxillofac Surg 2004;62:1423– 1428. 6. Baker RD, Terry BC, Davis WH, Connole PW. Long-term results of alveolar ridge augmentation. J Oral Surg 1979;37:486–489. 7. Davis WH, Delo RI, Ward WB, Terry B, Patakas B. Long term ridge augmentation with rib graft. J Oral Maxillofac Surg 1975;3:103– 106. 8. Jensen OT. Dentoalveolar modification by osteoperiosteal flaps. In: Fonseca RJ, Turvey TA, Marciani RD (eds). Oral and Maxillofacial Surgery, vol 1, ed 2. Philadelphia: Saunders, 2008:471–478. 9. Jensen OT, Kuhlke L, Bedard JF, White D. Alveolar segmental sandwich osteotomy for anterior maxillary vertical augmentation prior to implant placement. J Oral Maxillofac Surg 2006;64:290– 296. 10. Jensen OT. Alveolar segmental “sandwich” osteotomies for posterior edentulous mandibular sites for dental implants. J Oral Maxillofac Surg 2006;64:471–475. 11. Jensen J, Simonsen EK, Sindet-Pedersen S. Reconstruction of the severely resorbed maxilla with bone grafting and osseointegrated implants: A preliminary report. J Oral Maxillofac Surg 1990;48:27–32. 12. Cullum DR, Jensen OT. Trans-alveolar sinus elevation combined with ridge expansion. In: Jensen OT (ed). The Sinus Bone Graft, ed 2. Chicago: Quintessence, 2006:251–262.

13. Li XJ. Different osteogenic pathways between rhBMP-2/ACS and autogenous bone graft in 190 maxillary sinus floor augmentation surgeries [abstract]. J Oral Maxillofac Surg 2007;65(suppl):36.e2. 14. Garcia AG, Martin MS, Vila PG, Saulacic N, Rey JM. Palatal approach for maxillary alveolar distraction. J Oral Maxillofac Surg 2004;62:795–798. 15. Perciaccante VJ, Bays RA. Maxillary orthognathic surgery. In: Miloro M (ed). Peterson’s Principles of Oral and Maxillofacial Surgery, vol 2, ed 2. Shelton, CT: People’s Medical Publishing House-USA, 2004:1179–1204. 16. Salinas TJ. Implant prosthodontics. In: Miloro M (ed). Peterson’s Principles of Oral and Maxillofacial Surgery, vol 1, ed 2. Shelton, CT: People’s Medical Publishing House-USA, 2004:251–274. 17. Van Sickels JE. Prevention and management of complications in orthognathic surgery. In: Miloro M (ed). Peterson’s Principles of Oral and Maxillofacial Surgery, vol 2, ed 2. Shelton, CT: People’s Medical Publishing House-USA, 2004:1247–1266. 18. Dodson TB, Bays RA, Neuenschwander MC. Maxillary perfusion during Le Fort I osteotomy after ligation of the descending palatine artery. J Oral Maxillofac Surg 1997;55:51–55. 19. Epker BN. Vascular consideration in orthognathic surgery. II. Maxillary osteotomies. Oral Surg Oral Med Oral Pathol 1984; 57:473–478. 20. Ackerman M, Sarver D. Database acquisition and treatment planning. In: Miloro M (ed). Peterson’s Principles of Oral and Maxillofacial Surgery, vol 2, ed 2. Shelton, CT: People’s Medical Publishing House-USA, 2004:1087–1110. 21. Valencia E, Hernandez M, Jaramillo J. Le Fort I segmental osteotomy. In: Fonseca RJ, Turvey TA, Marciani RD (eds). Oral and Maxillofacial Surgery, vol 3, ed 2. Philadelphia: Saunders, 2008:192–204. 22. Kassolis JD, Rosen PS, Reynolds MA. Alveolar ridge and sinus augmentation utilizing platelet-rich plasma in combination with freeze-dried bone allograft: Case series. J Periodontol 2000;71: 1654–1661. 23. Levin L, Ophir S, Schwartz-Arad D. Atrophic ridge augmentation using intra-oral onlay bone grafts—Expanding the limits [in Hebrew]. Refuat Hapeh Vehashinayim (1993) 2006;23:31–35. 24. Wilkert-Walter C, Jänicke S, Spüntrup E, Laurin T. Maxillary sinus examination after sinus floor elevation combined with autologous onlay osteoplasty [in German]. Mund Kiefer Gesichtschir 2002; 6:336–340. 25. Pikos MA. Complications of maxillary sinus augmentation. In: Jensen OT (ed). The Sinus Bone Graft, ed 2. Chicago: Quintessence, 2006:103–114. 26. Hull D, Fonseca R. The biologic, physiologic, and psychosocial basis of facial skeletal surgery. In: Fonseca RJ, Turvey TA, Marciani RD (eds). Oral and Maxillofacial Surgery, vol 3, ed 2. Philadelphia: Saunders, 2008:60–86. 27. Landes CA, Glasl B, Kopp S, Sader R, Ludwig B. Microanchor mediated upper molar intrusion in deep posterior bite after longterm edentulousness for prosthetic reconstruction with dental implants. Oral Maxillofacial Surg 2008;12:155–158. 28. Pollack AS, Doundoulakis J. Interdisciplinary treatment of a severe maxillary aesthetic defect: A case report. Pract Proced Aesthet Dent 2004;16:157–164. 29. Jensen OT, Ellis E. The book flap: A technical note. J Oral Maxillofac Surg 2008;66:1010–1014.

This chapter has been reprinted with permission from Jensen OT (ed). The Osteoperiosteal Flap: A Simplified Approach to Alveolar Bone Reconstruction. Chicago: Quintessence, 2010:175–188.

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CHAPTER 4

THE ALVEOLAR SPLIT APPROACH FOR SINUS FLOOR INTRUSION Len Tolstunov, dds, dmd | Daniel R. Cullum, dds | Ole T. Jensen, dds, ms

I

mplant dentistry is further complicated by a lack of available bone stock in the posterior maxilla. Inadequate bone quantity from sinus pneumatization and buccal bone collapse as well as poor bone quality often make it difficult to successfully place and restore implants in that area.1–5 Among the variety of surgical implant-related techniques that have been described for the posterior maxillary region, there are very few that improve bone volume and bone density. One surgical technique that does accomplish this is the transcrestal ridge-split combined with sinus floor intrusion. The goal of the combined ridge-split technique is to expand the bone in both a horizontal and vertical direction. This chapter covers simultaneous horizontal and vertical expansion in the posterior maxilla related to placement of endosseous root-form dental implants, a minimally invasive surgical technique.

Alveolar Split for Width-Deficient Ridges When a tooth is removed, the alveolar ridge undergoes bone atrophy through resorption due to loss of function (nonuse atrophy) and loss of mechanical strain.6,7 Bone atrophy is mainly horizontal, resulting in narrowing of the alveolar ridge in the buccopalatal direction, with resulting bone collapse from a normal 10 to 12 mm to often 3 to 5 mm of alveolar ridge width.8–11 The alveolar split technique is designed for these width-deficient cases with a goal to improve the horizontal dimension of the collapsed alveolar ridge for restoratively driven implant placement. The split approach is targeted to a specific goal. The objective is to reposition the collapsed buccal plate facially and graft the

intersplit compartment. The split interface maintains vascularization via osteoperiosteal flaps. During the alveolar split, the buccal plate is outfractured and repositioned facially with a particulate graft placed interpositionally. Dental implants are sometimes placed into the ridge immediately depending on the prospect for primary implant stability. The important consideration in the posterior maxilla is sinus proximity best addressed by sinus floor intrusion done through the split site. The interpositional and sinus floor areas are then grafted simultaneously. There are three main surgical approaches to the pneumatized sinus in implant dentistry: lateral through the modified Caldwell-­Luc approach introduced by Tatum,12 the transalveolar from the crest using osteotomes developed by Summers,13 and the alveolar split. It is accepted that a residual bone height of 4 to 5 mm is a borderline height to choose one technique or another.14 Less that this amount (eg, 3 mm) of vertical bone in cases of severe sinus pneumatization is the most common indication for a lateral sinus elevation technique, usually with a bone graft and delayed implant placement. If there is 4 to 8 mm of vertical bone, a mild-to-moderate sinus pneumatization case, this is an indication for crestal access for sinus floor intrusion commonly accompanied by simultaneous implant placement. There are a variety of techniques for minimally invasive transcrestal sinus elevation procedures with a goal to carefully elevate the sinus membrane off the sinus floor, add bone grafting material into the created sinus pocket, and insert a transalveolar implant at the same time. The third method is the alveolar split combined with the sinus floor intrusion using osteotomes, a method in which the sinus membrane is not elevated away from the sinus floor. Vertical bone can vary with this technique from 3 to 10 mm. The technique can extend segmentally from the canine to the tuberosity region and is a form of an osteoperiosteal flap.

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Alveolar Split for Width-Deficient Ridges

Fig 4-1 (a and b) Widening of the ridge by the alveolar split first followed by the transcrestal sinus elevation leads to a volumetric surgical bone augmentation that creates a bone stock necessary for implant placement.

a

Width augmentation in the posterior maxilla The alveolar split can be done for horizontal augmentation alone or combined with vertical augmentation in the sinus.15 The interpositional bone graft is used to restore alveolar morphology. Combining both techniques can improve both width and height of the alveolar ridge for immediate or delayed implant placement. Widening of the ridge by the alveolar split first (Fig 4-1a) followed by transcrestal sinus elevation (Fig 4-1b) leads to a volumetric bone expansion that creates bone stock necessary for implant placement. A few publications on this topic, including extraction of teeth with immediate alveolar split and transcrestal sinus elevation, have been published.16–18 When extraction of teeth is done with an alveolar split, implant placement is usually delayed for 4 months. When these procedures are done for the edentulous maxillary posterior ridge, implants can sometimes be placed immediately if primary stability will be achieved.

Reestablishment of alveolar anatomy Atrophy of the alveolar ridge after extraction consists of progressive resorption of both cortical and trabecular bone, resulting in progressive loss of alveolar width. The goal of the alveolar split is to reposition the residual buccal cortex approximate to where it was prior to the tooth loss and expand the intercortical marrow space using graft material. By doing this, the cortical-­ trabecular anatomy can be restored to its original anatomical form and function. This anatomically driven concept of restoring a collapsed alveolar ridge to its original form from inside out is one of the most important physiologic advantages of this technique.

b

This is opposite to the healing principle of onlay block grafting, which is largely conducted in a relatively ischemic environment. Transcrestal sinus floor elevation may function as a vascularized bone segment or cortical fragments that receive some blood supply from intact sinus membrane. The split site extending up into the sinus graft is an excellent environment favorable for bone healing and osseointegration.

Osteocondensation In the process of bone manipulation during the alveolar split, adjacent trabecular fragments of bone are slightly compressed or condensed.19 It is especially apparent in the maxilla because of less bone density. In the process of bone manipulation during the transcrestal sinus elevation, Summers13 observed that “osteotomes conserve osseous tissue and may improve bone density around the implant.” Therefore, mild bone compression may improve primary implant stability and early implant loading.20–22

Revascularization as a biologic rationale Both procedures—alveolar split and transcrestal sinus floor intrusion—are preparatory to horizontal and vertical expansion of the alveolar envelope. The split corrects horizontal deficiency, and floor elevation corrects vertical deficiency. Both procedures are nearly flapless procedures that use available bone and avoid donor site morbidity. These procedures are also associated with an easy recovery and limited postoperative discomfort and swelling, as both surgical procedures have the inherent biologic basis of osteoperiosteal flaps to provide vascularization.

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4  THE ALVEOLAR SPLIT APPROACH FOR SINUS FLOOR INTRUSION

Lingual flap Buccal osteoperiosteal flap

Plane of split

Periosteum (vascularization)

b

a

Figs 4-2  Book flap (Jensen): Schematic illustration (a) and clinical intraoperative photograph (b) of the hinged modification of the ridge-split procedure.

Bone graft

Lingual flap

Plane of split

Buccal osteoperiosteal flap

Periosteum (vascularization)

a

b

Fig 4-3  Island flap (Jensen): Schematic illustration (a) and clinical intraoperative photograph (b) of the displaced modification of the ridge-split procedure.

Osteotomized bone segment The alveolar split is an osteoperiosteal flap with a unique physiologic basis that defines graft success. Vascularization of the segment of the ridge split is paramount for the procedure to be effective. The groundbreaking work of Dr William H. Bell through animal and clinical studies in the 1960s and 1970s on bone vascularization, bone healing, and pulp vitality helped to establish the biologic basis for segmental osteotomies in orthognathic surgery.23–27 Dr Bell demonstrated that the vitality of the segment of a jaw to be osteotomized would be preserved if the soft tissue pedicle could be kept intact. This principle of

preservation of bone vascularization of the osteotomy segment through an intact periosteum was adapted from Bell’s segmental maxillary osteotomies and subsequent researchers who explored the possibilities of smaller alveolar osteotomies. Many early dental implant innovators (eg, Tatum, Simion, Pikos, Scipioni) followed and proposed multiple modifications of the alveolar split osteotomy where the adapted principle of vascularization of osteotomized bone segments played a key role. In 1994, Scipioni et al28 commented that “the essential feature of edentulous ridge expansion technique is the partial-thickness flap with preservation of its buccal blood supply … the integrity of the periosteum must be maintained.”

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Case Studies

This points to the importance of preservation of the integrity of the periosteum and maintenance of vascularization to the bone segment being osteotomized. In 1998, Bruschi, et al29 demonstrated successful (ie, 97.5%) use of “localized management of the sinus floor” based on placement of 499 implants where the edentulous ridge expansion procedure was followed by trans­crestal sinus floor elevation and simultaneous implant placement. In 2008 and 2010, Jensen differentiated two designations of the alveolar split: the book flap, a hinged outfractured alveolar split (Fig 4-2) and the island flap, a bone flap fully separated from its bony base but still connected to the periosteum (Fig 4-3).30,31 Periosteal blood supply to the osteotomized buccal bony fragment is preserved in both flaps. The combined hard and soft tissue flap is called a vascularized mucoosteoperiosteal flap that has preserved periosteal (peripheral) blood supply to all its components essential to success of this surgical technique. The differences in the two bone flaps are based on the degree of osteomobilization needed in a particular case. In 2013, Jensen18 also described a segmental alveolar split combined with dental extraction and osteotome sinus floor intrusion for the posterior maxilla using bone morphogenetic protein 2 (BMP-2) with allograft. Both Bruschi29 and Jensen18 demonstrated that interpositional bone augmentation techniques, like ridge-split and transcrestal sinus elevation, have similar biologic bases that determine their success. Thus, the unique biologic mechanism of the osteoperiosteal flap procedure is that in the process of the surgery, the split and repositioning of the buccal bone fragment occurs with a continuous intact vasculation. In addition, the periosteum provides osteogenic cells in conjunction with the blood supply needed for bone consolidation.32 Nutritional qualities of the periosteum toward the adjacent bone are well known, with the periosteum contributing 70% to 100% of the alveolar blood supply.32 The osteoperiosteal flap, as one integral unit, consists of the mucosal layer, the periosteum, and a buccal osteotomized mobile segment of bone.31,33,34 This provides ongoing vascularization to the osteotomized segment of bone through the entire procedure, early postoperative healing period, and late-term remodeling.

Interpositional particulate bone graft Both the transcrestal sinus elevation and alveolar split use particulate bone graft for interpositional grafting. It is similar to a ridge preservation procedure when an extraction socket is filled with a particulate graft. In both cases, the particulate grafting is done as an internal graft. Cancellous bone is known to more rapidly and completely revascularize through both appositional modeling and creeping substitution remodeling starting with woven bone formation and proceeding directly to formation of lamellar bone.34,35 In a systematic review, Aghaloo and Moy36 stated that guided bone regeneration using particulate graft is the only well-documented surgical technique used for localized ridge augmentation. However, by creating a well-vascularized

environment with particulate grafts for both the alveolar split and transcrestal sinus elevation, successful augmentation occurs with revascularization. Osseointegration of dental implants follows within vital bone.

Successful osseointegration The intercortical marrow is trabecular or spongy, a source of blood supply mandatory for proper healing heavily dependent on oxygen and nutrients. It is the place where an endosseous implant is inserted in the process of the alveolar split (or later) and where osseointegration occurs.37,38 Early in healing after the alveolar split, the internal coagulum is quickly converted into woven bone in the protected bicortical environment using vascularization from both sides of the split. In contrast, after a block graft, the implant is placed into a cortical environment that may not be well vascularized. Therefore, an endosseous dental implant is placed into newly vascularized woven or lamellar bone similar to delayed implant placement in a grafted extraction site. Similarly, during the transcrestal sinus elevation, endosseous implants are placed into a grafted space with nearly ideal vascularization and a protected environment for successful osseointegration.

Case Studies Ridge expansion and transcrestal sinus floor intrusion in the posterior maxilla A 63-year-old man presented for extraction of his failing maxillary left molars (Fig 4-4a). The radiograph showed close proximity of the sinus floor to the apices of roots of both molars (Fig 4-4b). The sinus floor was intruded through both sockets and grafted. An alveolar split throughout the socket was made to gain alveolar ridge width. Both intersocket alveolar split and transsocket sinus floor intrusion helped to volumetrically augment the alveolar ridge beyond its existing dimensions as preparation for the delayed placement of two implants after 4 months. Figures 4-4c to 4-4f show the exterior procedure, sinus floor intrusion by osteotome, and split expansion of the alveolus. Figure 4-4g demonstrates a split gap of about 7 mm between the palatal and fractured buccal portions of the sockets as well as an intact sinus membrane that can be seen at the bottom of the split. Rounded-end osteotomes were then used for the sinus elevation (Figs 4-4h and 4-4i). Light gentle tapping was required to atraumatically intrude the sinus floor 4 to 5 mm. After the sockets were both vertically and horizontally expanded, they were grafted with particulate graft (0.5 g of Bio-Oss particulate xenograft, Geistlich Pharma) and covered with a membrane (Ossix Volumax resorbable collagen membrane, Datum Dental), and 4-0 silk sutures were placed on top (Figs 4-4j and 4-4k). Primary closure is not mandatory in these cases.

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a

c

b

d

g

j

e

h

k

f

i Fig 4-4 (a) Preoperative clinical photograph of failing first and second molars. (b) Preoperative radiograph of failing first and second molars. (c) Immediate postextraction intraoral photograph. (d to f) Ridge-split procedure with fracture of the buccal segment of both sockets and their facial displacement. (g) Sockets of the first and second molars after ridgewidening procedure; the sinus membrane can be seen at the bottom of both sockets. (h and i) Sinus osteotomes are used for the crestal transsocket sinus elevation. (j) Particulate bone grafting material is placed into expanded (in width and height) sockets of both molars. (k) A resorbable membrane is placed to isolate and protect the grafting material; secondary closure is achieved with 4-0 chromic gut sutures.

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Case Studies

a

b

c

d

e

f

Fig 4-5  (a) Preoperative radiograph demonstrating bone and sinus dimensions. (b) Intra­ operative view of the edentulous first molar area at the initiation of the ridge-split expan­ sion procedure; crestal osteotomy can be seen. (c) Intraoperative view of final osteotome for expansion and floor intrusion, showing expan­ sion next to the anterior vertical osteotomy. (d) Intraoperative view of the first molar implant placed at the corner of crestal and anterior vertical osteotomies right after ridge expansion and transcrestal sinus elevation. (e) Immediate postoperative result demong h strating use of a mesial-based finger flap for primary closure and transgingival healing. (f) Postoperative CBCT scan of the first molar implant placed immediately after ridge expansion with simultaneous transcrestal sinus elevation. (g and h) The 2-year postrestoration clinical photograph and radiograph showing excellent bone and soft tissue contours.

Ridge expansion and transcrestal sinus floor elevation with simultaneous implant placement in the posterior maxilla This 55-year-old woman presented with an edentulous left maxillary molar region and wanted implant reconstruction at the first molar site. The edentulous area demonstrated horizontal alveolar deficiency and inadequate vertical height to the sinus floor due to sinus pneumatization, as seen on the panoramic radiograph (Fig 4-5a). A buccal-based palatal incised flap was developed posterior to the tuberosity for planned apical positioning. Bone osteotomies (transcrestal and anterior vertical) were completed with piezoelectric surgical OT7S4 inserts at the palatal implant margin from anterior to posterior and beveled posteriorly and laterally at the tuberosity region (Fig 4-5b).

Custom designed chisels and tapered osteotomes were used to expand the crestal alveolus below the sinus floor (Fig 4-5c). The sinus osteotomes were then used to upfracture the floor to allow placement of a 9.0 × 5.8–mm tapered implant (Tapered Plus, BioHorizons), which was advanced into position showing 3 to 4 mm of ridge expansion (Fig 4-5d). Intraoperative periapical radiographs were used to confirm trial length and implant position. The site was overgrafted mostly to the distal to enhance and preserve long-term bony contours with apical flap positioning, followed by a mesial-based finger flap that was created for primary closure around the healing cap (Fig 4-5e). The immediate postoperative cone beam computed tomography (CBCT) image (Fig 4-5f) showed good implant position after the 3 to 4 mm of ridge expansion and sinus floor elevation of 3 mm. The 2-year postoperative results can be seen in Figs 4-5g and 4-5h, demonstrating the implant and crown

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Sinus membrane

Bone cuts a

b

Facial plate

Raised sinus floor

Elevated sinus floor Osteotome

c

d

Bone graft fills center of book flaps

Lateral book flap pivoted

Implant with abutment e

f

Prosthesis

Fig 4-6  (a) Without flap reflection, crestal and limiting vertical cuts are made. (b) The facial plate is outfractured buccally, usually about 4 mm. (c) In the posterior maxilla, the book flap provides intra-alveolar access to intrude the sinus floor. (d) The sinus floor is raised front to back as an osteoperiosteal flap attached to sinus membrane. (e) Following ossification, dental implants are fixed and left to heal 4 months. (f) The final restoration gains adequate width and height. (g) The combined procedures established a mature facial plate as well as adequate bone for long-term osseointegration.

g

with excellent surrounding bone and soft tissue contours. Ridge expansion with implant placement is most predictable with thick bone flaps and overgrafting if a full-thickness flap is used.

The advantages of this application are a single-stage procedure, optimized keratinized tissue, and long-term stability, as well as minimal postoperative discomfort.39–42

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Case Studies

Bone cuts

+ 5–6 mm desired

Sagittal view of anterior maxilla

Buccal bone margin

+ 3–4 mm desired

+ 3–4 mm desired

Sinus floor intruded

Fractures

Palatal bone margin

a

Posterior canine region

b

Greenstick outfracture

Bone cut (buccal bone margin)

c

Palatal bone margin

d

Osteotome sinus intrusion and elevation

Fractures

Spontaneous fracture e

f

Fig 4-7  (a and b) The full maxillary arch alveolar split osteotomy allows for significant alveolar widening as well as access for transalveolar sinus grafting. Shown here is an atrophic maxilla with sufficient height anteriorly and at the posterior palatal plate but with a deficient buccal plate. (c and d) Alveolar split is done creating a greenstick outfracture near the level of the sinus floor. The segment is widened 5 mm using the book bone flap technique. (e and f) Island flaps are created to free the osseous attachment while still maintaining periosteal attachment. Spontaneous separation usually occurs in the canine areas to create three or more separate island flaps.

Similarly, when a segmental, multitooth posterior segment is intruded, the entire sinus floor can be elevated 5 mm or more (Figs 4-6 and 4-7). In fully edentulous settings, the entire maxilla can be split grafted with sinus floor intrusion. This

requires island flap mobilization of the buccal fragments. In general, the greater the length of the sinus floor being intruded, the easier it is to elevate and perforate the membrane.

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Alveolar plane

g

h

Level alveolar plane

j

i Fig 4-7  (cont) (g) Without an island flap approach, the final alveolar split restoration would not have a level alveolar plane. (h and i) With island flap leveling and width gain, implants are placed in the axial alignment, and the alveolar plane is restored. (j) Spade osteotomes are used to outfracture the entire maxilla in an extended U-shaped book flap. (k) In the posterior region, blunt osteotomes are used to intrude the sinus floor, creating an extended sinus floor osteoperiosteal flap.

Conclusion The alveolar split transcrestal sinus floor intrusion procedure is unique from a biologic standpoint. The technique is essentially an alveolar ridge osteoplasty that has a solid physiologic ration­ ale due to the vascularization of both the osteotomized bone segments and favorable revascularization environment of the internal grafting site. Using this method at the time of tooth extraction provides a fast and efficient way of gaining added bone mass by creating a volumetrically enlarged socket conducive to bone healing and implant osseointegration. Particulate graft material placed as an interpositional graft into this bony environment simulates the development of natural trabecular vascularized bone similar to extraction socket healing. Endosseous dental implant osseointegration is highly favorable in this setting. The primary benefit of the alveolar split sinus intrusion procedure is that it is minimally invasive with a marked absence of

k

morbidity. There is no need for an autogenous donor site. Postsurgical healing is notable for lack of postoperative discomfort. Overall, there is a shortened treatment time due to frequent simultaneous implant placement. All of these factors make this procedure an important option to consider in cases of horizontal ridge deficiency in the posterior maxilla.

References 1. Morand M, Irinakis T. The challenge of implant therapy in the posterior maxilla: Providing a rationale for the use of short implants. J Oral Implantol 2007;33:257–266. 2. Tolstunov L. Implant zones of the jaws: Implant location and related success rate. J Oral Implantol 2007;33:211–220. 3. He J, Zhao B, Deng C, Shang D, Zhang C. Assessment of implant cumulative survival rates in sites with different bone density and related prognostic factors: An 8-year retrospective study of 2,684 implants. Int J Oral Maxillofac Implants 2015;30:360–371.

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References

4. Truhlar RS, Orenstein IH, Morris HF, Ochi S. Distribution of bone quality in patients receiving endosseous dental implants. J Oral Maxillofac Surg 1997;55(12 suppl 5):38–45. 5. Farré-Pagés N, Augé-Castro ML, Alaejos-Algarra F, Mareque-­ Bueno J, Ferrés-Padró E, Hernaández-Alfaro F. Relation between bone density and primary implant stability. Med Oral Patol Oral Cir Bucal 2011;16:e62–e67. 6. Mihalko WM, May TC, Kay JF, Krause WR. Finite element analysis of interface geometry effects on the crestal bone surrounding a dental implant. Implant Dent 1992;1:212–217. 7. Cornette R, Tresset A, Herrel A. The shrew tamed by Wolff’s law: Do functional constraints shape the skull through muscle and bone covariation? J Morphol 2015;276:301–309. 8. Pietrokovski J, Massler M. Alveolar ridge resorption following tooth extraction. J Prosthet Dent 1967;17:21–27. 9. Pietrokovski J, Starinsky R, Arensburg B, Kaffe I. Morphologic characteristics of bony edentulous jaws. J Prosthodont 2007;16:141–147. 10. Schropp L, Kostopoulos L, Wenzel A. Bone healing following immediate versus delayed placement of titanium implants into extraction sockets: A prospective clinical study. Int J Oral Maxillofac Implants 2003;18:189–199. 11. Carlsson GE, Persson G. Morphologic changes of the mandible after extraction and wearing of dentures. A longitudinal, clinical, and x-ray cephalometric study covering 5 years. Odontol Revy 1967;18:27–54. 12. Tatum H Jr. Maxillary and sinus implant reconstructions. Dent Clin North Am 1986;30:207–229. 13. Summers RB. A new concept in maxillary implant surgery: The osteotome technique. Compendium 1994;15:152–156. 14. Mazor Z, Peleg M, Garg AK, Chaushu G. The use of hydroxyapatite bone cement for sinus floor augmentation with simultaneous implant placement in the atrophic maxilla. A report of 10 cases. J Periodontol 2000;71:1187–1194. 15. Jensen OT, Cottam J. Sinus graft combined with osteoperiosteal flaps. In: Jenson OT (ed). The Osteoperiosteal Flap. Chicago: Quintessence, 2010:175–188. 16. AlGhamdi AS. Management of combined ridge defect and osteotome sinus floor elevation with simultaneous implant placement: A 36-month follow-up case report. J Oral Implantol 2009;35:225–231. 17. Jensen OT, Kuhlke KL, Leopardi A, Adams MW, Ringeman JL. BMP-2/ACS/allograft for combined maxillary alveolar split/sinus floor grafting with and without simultaneous dental implant placement: Report of 21 implants placed into 7 alveolar split sites followed for up to 3 years. Int J Oral Maxillofac Implants 2014;29:e81–e94. 18. Jensen OT. Segmental alveolar split combined with dental extractions and osteotome sinus floor intrusion in posterior maxilla using BMP-2/ACS allograft for alveolar reconstruction: Technical note and report of three cases. J Oral Maxillofac Surg 2013;71:2040–2047. 19. Scipioni A, Bruschi GB, Calesini G, Bruschi E, De Martino C. Bone regeneration in the edentulous ridge expansion technique: Histologic and ultrastructural study of 20 clinical cases. Int J Periodontics Restorative Dent 1999;19:269–277. 20. Nishioka RS, Kojima AN. Screw spreading: Technical considerations and case report. Int J Periodontics Restorative Dent 2011;31:141–147. 21. Khayat PG, Arnal HM, Tourbah BI, Sennerby L. Clinical outcome of dental implants placed with high insertion torques (up to 176 Ncm). Clin Implant Dent Relat Res 2013;15:227–233.

22. Nevins M, Nevins ML, Schupbach P, Fiorellini J, Lin Z, Kim DM. The impact of bone compression on bone-to-implant contact of an osseointegrated implant: A canine study. Int J Periodontics Restorative Dent 2012;32:637–645. 23. Bell WH. Revascularization and bone healing after anterior maxillary osteotomy: A study using adult rhesus monkeys. J Oral Surg 1969;27:249–255. 24. Bell WH, Levy BM. Revascularization and bone healing after anterior mandibular osteotomy. J Oral Surg 1970;28:196–203. 25. Bell WH, Levy BM. Revascularization and bone healing after posterior maxillary osteotomy. J Oral Surg 1971;29:313–320. 26. Bell WH. Biologic basis for maxillary osteotomies. Am J Phys Anthropol 1973;38:279–289. 27. Bell WH, You ZH, Finn RA, Fields RT. Wound healing after multisegmental Le Fort I osteotomy and transection of the descending palatine vessels. J Oral Maxillofac Surg 1995;53:1425–1433. 28. Scipioni A, Bruschi GB, Calesini G. The edentulous ridge expansion technique: A five-year study. Int J Periodontics Restorative Dent 1994;14:451–459. 29. Bruschi GB, Scipioni A, Calesini G, Bruschi E. Localized management of sinus floor with simultaneous implant placement: A clinical report. Int J Oral Maxillofac Implants 1998;13:219–226. 30. Jensen OT, Ellis E. The book flap: A technical note. J Oral Maxillofac Surg 2008;66:1010–1014. 31. Jensen OT, Mogyoros R, Owen Z, Cottam JR, Alterman M, Casap N. Island osteoperiosteal flap for alveolar bone reconstruction. J Oral Maxillofac Surg 2010;68:539–546. 32. Chanavaz M. Anatomy and histophysiology of the periosteum: Quantification of the periosteal blood supply to the adjacent bone with 85Sr and gamma spectrometry. J Oral Implantol 1995;21:214–219. 33. Jensen OT, Cullum DR, Baer D. Marginal bone stability using 3 different flap approaches for alveolar split expansion for dental implants: A 1-year clinical study. J Oral Maxillofac Surg 2009;67: 1921–1930. 34. Casap N, Brand M, Mogyros R, Alterman M, Jensen OT. Island osteoperiosteal flaps with interpositional bone grafting in rabbit tibia: Preliminary study for development of new bone augmentation technique. J Oral Maxillofac Surg 2011;69:3045–3051. 35. Oppenheimer AJ, Tong L, Buchman SR. Craniofacial bone grafting: Wolff’s Law revisited. Craniomaxillofac Trauma Reconstr 2008;1:49–61. 36. Aghaloo TL, Moy PK. Which hard tissue augmentation techniques are the most successful in furnishing bony support for implant placement? Int J Oral Maxillofac Implants 2007;22(suppl):49–70. 37. Adell R, Lekholm U, Rockler B, Brånemark PI. A 15-year study of osseointegrated implants in the treatment of the edentulous jaw. Int J Oral Surg 1981;10:387–416. 38. Ohta K. SEM-studies on the osseous healing and changes of the microvascular architecture in supporting tissues of endosseous implants [in Japanese]. Nihon Hotetsu Shika Gakkai Zasshi 1990;34:294–308. 39. Cullum DR, Jensen OT. Trans-alveolar sinus elevation combined with ridge expansion. In: Jensen OT (ed). The Sinus Bone Graft, ed 2. Chicago: Quintessence, 2006:251–262. 40. Cullum DR. Advances in bone manipulation: Part 1—Osteotome site development and minimally invasive sinus elevation. Select Read Oral Maxillofac Surg 2010;18(4):1–47. 41. Cullum DR. Advances in bone manipulation: Part 2: Osteomobilization for horizontal and vertical implant site development. Select Read Oral Maxillofac Surg 2010;18:1–44. 42. Cullum DR. Ridge expansion combined with trans-alveolar sinus elevation. In: Cullum DR, Deporter D (eds). Minimally invasive dental implant surgery. Hoboken, NJ: Wiley, 2016:311–333.

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CHAPTER 5

COMPLEX TECHNIQUES FOR POSTERIOR MAXILLARY RECONSTRUCTION Nardy Casap, dmd, md | Heli Rushinek, dmd

B

one defects in the posterior maxilla can result from congenital or developmental deformities, disuse atrophy, trauma, tumor resection, and degenerative diseases. The resulting morphology of the residual alveolar ridge may preclude ideal implant positioning and rehabilitation, and the deficit may be classified as vertical, horizontal, or combination. Reconstruction for large bony defects in the maxillofacial region remains a major surgical challenge. Unrepaired bone defects can result in devastating consequences ranging from loss of function to distorted facial appearance. The introduction of reliable endosseous implants has extended the scope and effectiveness of preprosthetic reconstructive surgery. Despite the variety of materials and surgical techniques available for bone augmentation, augmentation of the extremely atrophic jaw is still considered a difficult, unpredictable task and is commonly associated with complications. In the posterior maxilla, insufficient height may be associated with sinus pneumatization, vertical resorption of the crest, or a combination of the two. Cawood and Howell, in their classification of resorption patterns for edentulous jaws, demonstrated that bone resorption progresses tridimensionally. Accordingly, a reduction in alveolar ridge width is also frequently present. Resorption of the maxillary alveolar process eventually leads to a relatively posterior and cranial position of the maxilla, resulting in a reversed intermaxillary relationship and increased vertical intermaxillary distance. Facial alterations that accompany reduction of alveolar bone include collapse of facial muscles leading to obtuse nasolabial angle, decreased commissure width, loss of nasolabial and labiomental support, and decreased lower face height.1,2 If insufficient bone volume is related only to sinus pneumatization, a sinus graft may be indicated; however, the sinus may not need to be grafted if the bone defect is related to vertical

resorption of the crest. Instead, vertical reconstruction to recreate adequate interarch distance may be the treatment of choice. The atrophic posterior maxilla should be evaluated in terms of residual bone height and width, but also intermaxillary relationship. Sinus grafting may therefore represent only part of the reconstructive procedure necessary to achieve orthoalveolar form with adequate bone volume and intermaxillary space for optimization of implant placement and prosthetic rehabilitation.3 Early attempts to onlay-graft the class VI maxilla did not stand the test of time; rapid resorption commonly occurred with disappointing results. Interpositional bone graft methods appear to be more stable over time.1 Autogenous bone grafts from the iliac crest in particular have long been considered the gold standard because of their ability to transplant viable osteogenic cells and contribute osteoconduction and osteoinduction in the formation of viable new bone. However, autogenous grafts have an inherent risk of intraoperative donor site morbidity, including blood loss, nerve injury, damage to adjacent tissues, and fractures, as well as postoperative morbidity such as paresthesia, gait disturbance, infection, prolonged pain, or prolonged healing.4 Employing off-the-shelf materials to perform major vertical alveolar reconstructions that are currently treated with iliac bone grafting can reduce morbidity, increase operative simplicity, and make care accessible to more patients. In addition, it provides the reconstructive surgeon with a technique that can recover alveolar form in a highly specified morphology based on jaw relation, interocclusal space, need for expanded bone stock for implant support, and establishment of esthetic osseogingival form (ie, orthoalveolar form). A paradigm shift from grafting to regeneration involves components of the tissue engineering triad, namely inductive growth factors combined with a matrix and stem cells, together with osteotomies or devices designed

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Posterior Maxillary Sandwich Osteotomy Combined with Sinus Grafting

b

a

d

c

e

Fig 5-1  (a) A posterior maxillary edentulous segment. The posterior alveolar plane is out of conformity with the anterior maxilla, requiring that implants be placed at a relatively high level. This would necessitate restoration with long clinical crowns and a high crown-to-implant ratio. (b) The lateral maxilla is approached with a vestibular incision for Caldwell-Luc access to elevate the sinus membrane. (c and d) A lateral osteotomy cut is made anterior and posterior to the sinus window access and tapers to the alveolar crest. These cuts are made without substantial reflection of the crestal mucosa. (e) The palatal wall is freed using an oscillating saw transsinus. This cut also tapers to the crest anterior and posterior from within the sinus cavity. After the cuts are made, an osteotome is used to free the segment. (f) The segment is downfractured while pedicled to the palatal and crestal mucosa and then fixed in place with a miniature titanium fixation plate. (g) Interpositional bone graft material fills not only the osteotomy site but the floor of the sinus.

for space maintenance. Thus, current concepts of reconstruction must emulate bone development in that reconstruction should recapitulate the developmental processes.

Posterior Maxillary Sandwich Osteotomy Combined with Sinus Grafting The technique of posterior maxillary segmental sandwich osteotomy is generally indicated when the anterior teeth are sound and there is sufficient intraoral opening to perform the operation in the face of alveolar height insufficiency and a prominent sinus cavity.5 Following local and intravenous anesthesia, a vestibular incision is made and reflected superiorly (minimally inferiorly) to expose the lateral wall of the maxilla adjacent to the maxillary sinus (Figs 5-1a and 5-1b). A lateral approach is done by elevating the sinus membrane to provide space for

f

g

grafting. A horizontal osteotomy is then created anterior and posterior to the sinus access osteotomy; anteriorly, this tapers to the alveolar crest just behind the most posterior tooth, and in the posterior area it reaches to just in front of the pterygomaxillary suture (Figs 5-1c and 5-1d). This buccal cut is then connected transsinus with a similar palatal bone cut using a piezoelectric surgical device or a curved sagittal saw (Fig 5-1e). An osteotome is needed to free the segment so it can be downfractured 5 mm or more. Once the segment has been moved down to the appropriate alveolar level, it is fixed with a bone plate (Fig 5-1f). Once fixed, the bone plate can be used to compensate for the palatal pull of the palatal mucosa. The plate can be twisted with a wire twister to torque or force the segment laterally. If the segment is still too far to the palatal, this must be addressed at a later time. Once the segment is stabilized, bone morphogenetic protein 2 in an absorbable collagen sponge carrier (BMP-2/ACS) and 20% allograft or a xenograft is placed into the sinus floor and the interpositional graft zone (Fig 5-1g). The wound is then closed in two layers with resorbable sutures.

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5  COMPLEX TECHNIQUES FOR POSTERIOR MAXILLARY RECONSTRUCTION

a

b

Fig 5-2  (a) Cone beam computed tomography scan showing bone graft material filling the sinus floor and the osteotomy site. (b) Implants are placed after consolidation is complete, usually about 6 months later. The implant platforms are located at an improved alveolar plane.

After 4 to 6 months, with a crestal incision located slightly to the palatal, the lateral maxilla is exposed and the bone plate is removed. Implants are placed according to a surgical guide. When the ridge is too far to the lingual, guided bone regeneration or an alveolar split osteotomy can be done to bring the buccal plate laterally, with implants placed simultaneously (Fig 5-2). The definitive restoration is placed 4 months later. Because of the pull of the palatal mucosa, a 5- or 6-mm vertical movement is usually all that can be obtained (unless the segment includes four or more teeth, in which case up to 10 mm vertical movement can be obtained). The disadvantage of sandwich grafting is the necessity of surgical experience and technical expertise. Reflection or release of palatal tension or releasing incisions are not advised because a torn pedicle can cause the complete loss of the segment.

Maxillary Edentulous Le Fort I Osteotomy with Interposed Bone Graft When the maxilla is extremely resorbed, a Le Fort I downgraft procedure is indicated. The use of iliac bone grafting for the Le Fort I downgraft is used to gain not only vertical dimension but also horizontal width. Le Fort I osteotomies for the simultaneous improvement of the intermaxillary relationship and provision of bone volume for implant placement have been performed for almost 30 years. The original idea was put forward by Sailer, who proposed simultaneous osteotomy, grafting gaps with corticocancellous block grafts, and implant placement. Cawood et al1 suggested performing the delayed implant surgery to allow for bone healing, which facilitated more accurate implant placement. This strategy was also followed by others.6–13 The Le Fort I technique involves making a vestibular incision and horizontal osteotomy cuts after elevation of the sinus

membranes bilaterally through lateral window access (Fig 5-3a). The pterygoid sutures and nasal septum are freed, and the maxilla is downfractured in a standard manner. Following downfracture, the maxilla is mobilized forward using disimpaction forceps and then repositioned and bone plated in a down and forward position (Fig 5-3b). A general rule of thumb is 10 mm forward and 10 mm downward. Fixation provides a very large interpositional graft zone for bone grafting (Fig 5-3c). Grafting proceeds by first grafting the sinus floor with particulate marrow and then grafting the anterior nasal floor, followed by block mortising and overgrafting the bone-plated regions to gain width. Once the graft is in place, which entails the combination of particulated bone marrow deep and corticocancellous blocks fixed with screws as overgraft, the wound is closed in two layers with slowly resorbing suture material. Six months later, an incision is made 3 to 4 mm palatal to the alveolar crest around the arch for implants to be placed. The advantage of the Le Fort I downgraft is greatly increased bone mass available for osseointegration, but the disadvantage is that alveolar height may not be achieved and the position of the maxilla is never ideal. It often ends up 5 to 10 mm retropositioned despite advancement. Also, these cases require a lot of bone graft material, often necessitating posterior hip harvest. Grafts can be expanded with allografts or alloplasts, but this may add additional risk for infection if the graft site becomes exposed. The greatest disadvantage is the need for a secondary harvest site, which is not always possible in elderly patients or patients with back or extremity osteoarthritis. Therefore, the procedure may be relatively contraindicated in those older than 60 years unless the patient is in excellent health. This suggests a great need to treat these not uncommon atrophic findings with an alternative method such as the use of BMP-2 expanded with mineralized adjuncts.14 The power of BMP in intra-alveolar/ sinus floor location is formidable and does not carry the risk of exposure associated with iliac block or allogeneic particulate grafts.15 Also, the rate of infection is lower.

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Titanium Shell Treatment of Severe Alveolar Defects

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b

c

Fig 5-3  (a) Bilateral sinus membrane elevations done in conjunction with a Le Fort I osteotomy. (b) The maxilla is brought forward and downward and fixated with plates and screws. (c) Interpositional grafting is done with BMP-2/ACS.

Titanium Shell Treatment of Severe Alveolar Defects In the past, the major reconstructive effort has been directed at regaining continuity or increasing bone mass for dental implants. Now there is a new concept to consider: orthoalveolar form. This is a surgical prosthetic treatment planning ideal, an effort to reconstruct bone structure of the jaw to a specified size and shape that enables optimal dental implant reconstruction. Titanium mesh for bone graft containment has been used since 1970 when it was introduced by Boyne.16 Boyne popularized the use of titanium mesh for alveolar grafting using iliac particulate graft, also described by others.16–19 Handcrafted mesh, especially when made from medical models, can shape a near ideal alveolar form, but rapid prototype methodology better overcomes anatomical limitations and can more accurately obtain complex shapes for adaptation over osseous defects. In these settings, recombinant human BMP-2 (rhBMP-2) with ACS as osteoinductive graft material plus mineralized conductive product has been demonstrated to form bone to the desired bone morphology.20,21 The first step in producing a rapid prototype titanium shell is a design phase that begins with program-input of a threedimensional (3D) computed tomography (CT) scan with minimum artifacts derived from CT digital imaging and communications in medicine (DICOM) files. The 3D CT is converted into a 3D computerized design program format. The shell is designed to 0.8-mm thickness. The existing bone is subtracted from the model to ensure a perfect fit with the patient’s jaw morphology (Fig 5-4a). In some cases, a plaster mold or a stereolithographic (STL) print model can be used to aid in the design. The final design is converted into an STL file, which is sent for 3D sinter-printing using titanium powder (Fig 5-4b). Surgery is done under intravenous sedation or general anesthesia. A mucoperiosteal flap is elevated by crestal or sulcular

incision. The flap is developed such that watertight closure is obtained without tension. The rhBMP-2/ACS is then prepared according to manufacturer’s standards, including 20 minutes of protein binding to the collagen. The rhBMP-2/ACS is fragmented and mixed with allograft in a 1:1 ratio by volume. The titanium shell is first placed into the site and fit accurately without need of adjustment. The shell is then removed and filled with the rhBMP-2/ACS allograft composite regenerative material, and the filled shell is pushed into place and secured by screws (Fig 5-4c). The wound is then closed in layers with resorbable sutures (Fig 5-4d). After 4 months, a crestal incision is made and the shell is cut in half at the crest using a metal cutting disc and removed. Following removal of the shell, the wound is approximated, except in areas where the titanium shell had been exposed. Implants are placed 5 months after initial grafting (Fig 5-4e) and restored 4 months later. Wound dehiscence at the terminal vasculature occurs in almost every case in which significant vertical augmentation is attempted. Angiogenesis precedes osteogenesis in the healing of critical size defects. Angiogenesis of a vertical augmentation defect, such as within a titanium shell, is similar to callus formation and occurs early from unreflected periosteum, while reflected periosteum and basal bone make later contributions. Yet, the most significant proportion of neovascularization originates peripherally from unreflected periosteum, as the reflected periosteum is highly traumatized and is sometimes unable to sustain terminal blood supply to the overlying mucosa, contributing to early wound breakdown. The titanium shell also serves as a conductive matrix for bone formation, as a layer of bone forms underneath and sometimes above the titanium, migrating around the entire surface of the shell. Wound dehiscence stops this conductive migration and bone does fill completely under the shell. However, deeper below the exposed titanium shell surface, callus-like bone development continues, and by 6 to 8 weeks newly formed osteoid is mature enough to resist breakdown, allowing for early removal of the shell. This should be done carefully at this early stage to avoid dislodging the

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5  COMPLEX TECHNIQUES FOR POSTERIOR MAXILLARY RECONSTRUCTION

a

c

b

d

e

Fig 5-4  (a) A 3D CT reconstruction demonstrating the posterior maxillary defect. (b) A maxillary titanium shell design. The shell is designed to fit the natural continuity of the existing ridge and to simulate the preexisting ridge. (c) The titanium shell is placed into the site and fit accurately without needing adjustment. The filled shell is pushed into place and secured with screws. (d) The wound is closed in layers with resorbable sutures. (e) Implants are placed 5 months after initial grafting.

graft from basal bone. Because BMP-2/ACS/allograft provides an accelerated bone formation environment, early removal of the shell (at about 6 to 8 weeks) prevents prolonged percolation from oral fluids and deep extension of superficial infection, while still preserving the majority of the developing osteoid. By this time, the bone graft integrity remains intact except at the site of dehiscence. The advantages to the surgeon and the patient of computer-­ planned bone forms with BMP-2 grafting are evident: ease of use, accuracy of fit, decreased surgical time, no need for second site bone harvest, and increased accuracy in the alveolar augmentation plan for placement of dental implants. The disadvantages are the high cost and inaccessibility of this new technology. The titanium shells can be placed in conjunction with sinus floor augmentation, which may be best to do from a transcrestal approach.

Conclusion The use of interpositional bone grafts with various jaw osteotomies and the smaller segmental osteoperiosteal flaps is becoming more commonly prescribed in the edentulous setting for augmentation and implant site preparation. The sandwich approach is more stable with less resorption at the crest, provided there is adequate width to the caudal segment. The

interpositional graft technique eliminates the need for vertical alveolar distraction in most cases, limiting the use of distraction to vertical movements of 10 mm or more. Full-arch alveolar atrophy of the mandible and maxilla can often be treated without augmentation grafting by using All-on-4 technology and/or computer-guided implant strategies. However, when the maxilla is extremely resorbed, a Le Fort I downgraft procedure is indicated. Although onlay procedures have shown success, especially when combined with sinus floor grafting, the advantage of a Le Fort I downgraft is maxillary repositioning into a more biomechanically advantageous implant platform. The titanium shell, the segmental sandwich graft, and the Le Fort I interpositional graft variations have all shown favorable implant success rates when done using a delayed implant placement strategy. Orthognathic surgery done using small, precise osteotomy movements that are well fixed may heal without significant relapse. This experience in the dentate setting may not be fully achieved in parallel for the edentulous patient, but the use of an osteoperiosteal flap approach, perhaps mildly overcorrected to allow for reductive remodeling, should enhance outcomes for the challenge of reconstruction of missing or ablated jaw bone structure. Although posterior augmentation with titanium mesh has been successfully done using iliac particulate graft, en bloc iliac bone can resorb more than 50%. In light of this, the use of titanium shell–protected morphogen-enhanced grafting shows great promise.

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References

References 1. Cawood JI, Stoelinga PJ, Brouns JJ. Reconstruction of the severely resorbed (Class VI) maxilla. A two-step procedure. Int J Oral Maxillofac Surg 1994;23:219–225. 2. Cawood JI, Howell RA. A classification of the edentulous jaws. Int J Oral Maxillofac Surg 1988;17:232–236. 3. Chiapasco M, Casentini P. Implant-supported dental restorations in compromised edentulous sites: Optimization of results with a multidisciplinary integrated approach. In: Khoury F, Antoun H, Missika P (eds). Bone Augmentation in Oral Implantology. Chicago: Quintessence, 2006:29–52. 4. Marx RE, Armentano L, Olavarria A, Samaniego J. rhBMP-2/ACS grafts versus autogenous cancellous marrow grafts in large vertical defects of the maxilla: An unsponsored randomized open-label clinical trial. Int J Oral Maxillofac Implants 2013; 28:e243–e251. 5. Jensen OT, Cottam J. Posterior maxillary sandwich osteotomy combined with sinus grafting with bone morphogenetic protein-2 for alveolar reconstruction for dental implants: Report of four cases. Int J Oral MaxIllofac Implants 2013;28:e415–e423 6. Sailer HF. A new method of inserting endosseous implants in totally atrophic maxillae. J Craniomaxillofac Surg 1989;30:299–305. 7. Krekmanov L. A modified method of simultaneous bone grafting and placement of endosseous implants in the severely atrophic maxilla. Int J Oral Maxillofac Implants 1995;10:682–688. 8. Stoelinga PJ. Reconstruction of the severely atrophied (class VI) maxilla. A review. Dtsch Zahnarztl Z 1996;51:2. 9. Issaksson S, Ekfeldt A, Alberius P, Blomqvist JE. Early results from reconstruction of severely atrophic (class VI) maxillas by immediate endosseous implants in conjunction with bone grafting and Le Fort I osteotomy. Int J Oral Maxillofac Surg 1993;22:144–148. 10. Nyström E, Nilson H, Gunne J, Lundgren S. Reconstruction of the atrophic maxilla with interpositional bone grafting/Le Fort I osteotomy and endosteal implants: A 11–16 year follow-up. Int J Oral Maxillofac Surg 2009;38:1–6. 11. Chiapasco M, Brusati R, Ronchi P. Le Fort I osteotomy with interpositional bone grafts and delayed oral implants for the rehabilitation of extremely atrophied maxillae: A 1–9-year clinical follow-up study on humans. Clin Oral Implants Res 2007;18: 74–85.

12. Kahnberg KE, Nilsson P, Rasmusson L. Le Fort I osteotomy with interpositional bone grafts and implants for rehabilitation of the severely resorbed maxilla: A 2-stage procedure. Int J Oral Maxillofac Implants 1999;14:571–578. 13. Soehardi A, Meijer GJ, Hoppenreijs TJ, Brouns JJ, de Koning M, Stoelinga PJ. Stability, complications, implant survival, and patient satisfaction after Le Fort I osteotomy and interposed bone grafts: Follow-up of 5–18 years. Int J Oral Maxillofac Surg 2015;44:97–103. 14. Jensen OT, Ringeman JL, Cottam JR, Casap N. Orthognathic and osteoperiosteal flap augmentation strategies for maxillary dental implant reconstruction. Dent Clin North Am 2011;55: 813–846. 15. Jensen OT, Kuhlke KL, Leopardi A, Adams MW, Ringeman JL. BMP-2/ACS/allograft for combined maxillary alveolar split/sinus floor grafting with and without simultaneous dental implant placement: Report of 21 implants placed into 7 alveolar split sites followed for up to 3 years. Int J Oral Maxillofac Implants 2014; 29:e81–e94. 16. Boyne PJ. Autogenous cancellous bone and marrow transplants. Clin Orthop Relat Res 1970;73:199–209. 17. Gongloff RK, Cole M, Whitlow W, Boyne PJ. Titanium mesh and particulate cancellous bone and marrow grafts to augment the maxillary alveolar ridge. Int J Oral Maxillofac Surg 1986;15:263– 268. 18. Sbordone C, Toti P, Guidetti F, Califano L, Santoro A, Sbordone L. Volume changes of iliac crest autogenous bone grafts after vertical and horizontal alveolar ridge augmentation of atrophic maxilla and mandibles: A 6 year computerized tomographic follow-up. J Oral Maxillofac Surg 2012;70:2559–2565. 19. Tideman H, Samman N, Cheung LK. Immediate reconstruction following maxillectomy: A new method. Int J Oral Maxillofac Surg 1993;22:221–225. 20. Jensen OT, Lehman H, Ringeman JL, Casap N. Fabrication of printed titanium shells for containment of BMP-2 composite graft materials for alveolar bone reconstruction. Int J Oral Maxillofac Implants 2014;29:e103–e105. 21. Lehman H, Casap N. Rapid prototype titanium bone-forms for vertical alveolar augmentation using bone morphogenetic preotien-2: Design and treatment planning objectives. Int J Oral Maxillofac Implants 2014;29:e259–e264.

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Section II

CHAPTER 6

LATERAL WINDOW SURGICAL TECHNIQUES FOR SINUS ELEVATION Tiziano Testori, md, dds | Riccardo Scaini, dds | Matteo Deflorian, dds | Stephen S. Wallace, dds | Dennis P. Tarnow, dds

M

axillary sinus augmentation has been part of the implant surgical armamentarium for over 40 years.1 Many changes in surgical protocols have occurred over this time as a result of ongoing clinical and scientific research, the development of new products and technologies, the desire for higher procedural success rates and reduced complication rates, and the demand for minimally invasive surgical approaches. Today, it is easy to forget that sinus elevation began as a hospital-based procedure that incorporated the use of extraoral autogenous bone grafts.2 It should also be remembered that while there has been a groundswell of transcrestal sinus elevation techniques presented, there will always be a need for the lateral window technique in cases of extreme atrophy that require extensive elevation, when there is difficult anatomy, or for access to repair large perforations. This chapter describes the present-day therapeutic options that have resulted from the evolutionary forces mentioned above. The chapter begins with a discussion of presurgical sinus assessment and preoperative diagnosis protocols. Therapeutic options are then presented in a stepwise manner from flap entry through final flap closure. The chapter concludes with a rationale for the preservation of the lateral window approach as an essential component of sinus surgery armamentarium.

Presurgical Sinus Assessment Diagnosing pathologic conditions of the maxillary sinus The clinician can lower the risk of postoperative complications if maxillary sinus elevation is performed starting in a healthy sinus.3,4 It is advisable to perform an extensive anamnestic,

clinical, and radiographic assessment prior to sinus augmentation surgery to investigate sinus health and subsequent sinus compliance to avoid unnecessary postsurgical complications. The first consultation should include collection of a complete history of potential conditions affecting the maxillary sinus, such as nasal obstructions, facial trauma, sinus infections, allergic symptoms, smell and taste dysfunction, pressure-related discomfort, chronic respiratory diseases, previous nasosinusal surgery, facial deformities, scars, and mouth breathing. If the anamnesis is positive or there are symptoms of sinusitis, it is advisable to refer for an otolaryngology assessment. The same assessment should be made in cases that present signs of radiopacity, previous sinus treatments, a history of impaired nasal breathing, or chronic respiratory diseases (see chapter 2). Box 6-1 shows an example form with questions for a specific maxillary sinus anamnesis as well as basic requirements of a computed tomography (CT) scan. In addition to the general contraindications for oral surgery, Mantovani5 lists specific contraindications for maxillary sinus augmentation surgery. These are divided into two categories: reversible and irreversible (Table 6-1). A prospective clinical study evaluated this approach and confirmed its reliability with 34 patients evaluated.6 None presented presumably irreversible ear, nose, and throat (ENT) contraindications, but 38.2% presented potentially reversible ENT contraindications that were consequently treated, and no complications after sinus elevation surgery were noticed (Table 6-2). A sinus elevation procedure can be impaired by preexisting odontogenic sinusitis. Odontogenic sinusitis has been reported to represent 10% of all cases of maxillary sinusitis, but it is estimated that the real incidence could be between 25% and 40%.7–10 A survey of 93 board-certified otolaryngologists and rhinologists reported that an odontogenic source is a common cause of maxillary sinusitis and that the clinicians treated an average of

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Presurgical Sinus Assessment

Box 6-1  Sample medical history and radiologic evaluation questions Medical history

• Have you ever had allergies? • Have you ever had chronic respiratory diseases? • Can you breathe normally using both nostrils? • Have you ever had ear, nose, and throat (ENT) diseases? • Do you use nasal sprays? • Have you ever had chronic or acute sinusitis? • Have you ever had ENT or maxillofacial surgery? • Can you compensate pressure through the ears, such as when you fly on a plane? • Is there ever a bitter taste at the back of your throat? • Do you have or have you ever had any facial fillers or facelift? (This is important during flap management because facial fillers may cause problems in soft tissue handling.)

Radiologic evaluation

• Does the computed tomography (CT) allow a correct visualization of the ostiomeatal complex? • Is the ostiomeatal complex patent? • Are there any signs of radio-opacity in the maxillary sinus?

Final evaluation

• Ask for ENT assessment. • Is the patient eligible for maxillary sinus elevation?

Table 6-1  Contraindications for maxillary sinus augmentation

Anatomical-structural alterations

Presumably irreversible ENT contraindications

Potentially reversible ENT contraindications

Serious deformities and posttraumatic, postsurgical, and postradiotherapy scarring on the nasal-sinus walls and/or mucosa lining.

Stenosis of the drainage-ventilation pathways in the maxillary sinus (sustained by one or more of the following anatomical alterations): • Septal deviation • Paradox curve of the middle turbinate bone • Conchae bulla • Hypertrophy of the agger nasi cell • Presence of Haller cell • Postsurgical scars or synechiae on the ostiomeatal complex • Oroantral fistula All these alterations can be resolved by surgery. The maxillary sinus appears to be well ventilated thanks to a partial uncinectomy.

Inflammatory-infective processes

Recurring or chronic sinusitis, with or without polyps, which cannot undergo resolution because it is associated with congenital mucociliary clearance alterations (eg, cystic fibrosis, primary ciliary dyskinesia, Young syndrome), to intolerance of acetyl­salicylic acid (triad: nasal polyps, asthma, intolerance to acetylsalicylic acid), and to immunologic deficiency (eg, AIDS, pharmacologic immunosuppression).

Acute viral or bacterial rhinosinusitis, allergy-­related rhinosinusitis, mycotic sinusitis (noninvasive forms), acute repeating and chronic sinusitis sustained by one of the anatomical alterations listed above that obstruct the sinus drainage-ventilation pathways, by endoantral foreign bodies, or by nasal polyps. Functional endoscopic surgery is clearly indicated.

Tumor-related

• Locally aggressive benign tumors (eg, inverted papilloma, myxoma, ethmoidal-­maxillary fibro­ matosis) in antrum. • Nasal-sinus malignant tumors (epithelum, neuro­ ectodermal, bone, soft tissue, odontogenous, lymphomatosis, metastatic-originated) of the maxillary sinus and/or adjacent structures.

Nonobstructive nasal-sinus benign tumors, both before and after the sinus elevation, could affect the sinus drainage-ventilation pathways. When removal does not affect the mucociliary transportation system (eg, mucosa cysts, cholesterinic granuloma, antrochoanal polyp), all are easily subject to correction by functional endoscopic surgery.

Nasal-sinus manifestations of specific systemic granulomatous diseases

Wegener’s granulomatosis, idiopathic midline granuloma, and sarcoidosis.

NA

NA, not applicable. Modified with permission from Mantovani.5

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6  LATERAL WINDOW SURGICAL TECHNIQUES FOR SINUS ELEVATION

Table 6-2  Prophylaxis and postoperative drug therapy in sinus elevation patient Prophylaxis

Postoperative therapy

Patient not allergic to penicillin

Amoxicillin (875 mg) with clavulanic acid (125 mg) twice per day by mouth starting 24 hours before surgery

Amoxicillin (875 mg) with clavulanic acid (125 mg) twice per day by mouth for 7 days

Patient allergic to penicillin

Clarithromycin (Biaxin, AbbVie) 250 mg twice per day and metronidazole 500 mg three times per day by mouth starting 24 hours before surgery

Clarithromycin (Biaxin) 250 mg twice per day and metronidazole 500 mg three times per day by mouth for 7 days

Fig 6-1  CT scan of a drug abuser. The lateral wall of the nose is missing.

through the nose may have a deleterious effect on the mucosa (Fig 6-1). In a systematic review addressing hard palate perforation in cocaine abusers, sinusitis is confirmed as one of the most common side effects.14,15 The sinus membrane in these patients is extremely thin and fragile, requiring great attention when detaching. Smoking is also a well-known risk factor for implant survival.16 A retrospective evaluation on the survival rate of implants placed in grafted sinuses found that smoking more than 15 cigarettes per day was significantly correlated with implant failure.17 Optimizing sinus ventilation is an essential requisite of sinus health and is a fundamental prerequisite before attempting a maxillary sinus elevation procedure.

Preoperative diagnosis, planning, and evaluation of case difficulty

2.9 patients per year with odontogenic maxillary sinusitis who were initially misdiagnosed.11 Otolaryngologists also perceived that radiologists rarely consider dental pathology when scanning the maxillary sinus using CT. The exact pathogenesis of odontogenic sinusitis is still not fully understood, although impaired sinus membrane integrity due to maxillary dental infections or trauma, odontogenic disease of maxillary bone, tooth extractions, implantology, or endodontic treatment is always present. Microbiologic sampling of sinusitis of odontogenic origin reveals a different bacterial flora than that found in rhinogenic sinusitis.12 Usually odontogenic sinusitis is a polymicrobial infection and anaerobic species from the oral cavity and upper respiratory tract are predominant. The development of sinusitis in patients with predisposing odontogenic disease is variable; however, a recent review suggested the possible role of the bacterial biofilm in relation to severity and progression of the odontogenic sinusitis.13 Sinus elevation procedures could be affected by a number of behavioral and environmental conditions that affect the normal physiology of the maxillary sinus. The use of cocaine inhaled

During the diagnostic phase, an important parameter to assess is the degree of resorption in the alveolar crest. This variable must be evaluated in the apicocoronal (sinus to crestal bone floor), vestibulopalatal, and residual crestal dimensions with respect to the occlusal plane (interarch distance). The classic indication for sinus elevation is moderate atrophy in the maxilla without skeletal alteration. In these cases, it is possible to perform an implant-prosthetic rehabilitation with premolars and molars of average size18 (Fig 6-2a). A three-dimensional (3D) analysis of the edentulous ridge will determine the type of surgery needed to restore vertical and/or horizontal bone volume. In clinical cases with increased interarch distance and/or an alveolar ridge with a thickness of less than 6 mm in the vestibulopalatal direction, ideal treatment would be by reconstructive surgery18 (Fig 6-2b). The quantity of crestal bone available in the apicocoronal direction can influence the choice of the surgical approach. Many clinicians would accept 4 mm as the threshold determining whether to perform sinus elevation from a crestal or lateral approach. An analysis of quality and quantity of available bone is a useful parameter to predict primary stability. Such considerations determine the choice of whether to perform sinus surgery with simultaneous implant placement or a delayed protocol. Although it may be technically possible to stabilize implants with minimal residual crestal bone heights of 1 to 3 mm, the

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Presurgical Sinus Assessment

Fig 6-2 (a) Classic indication for maxillary sinus elevation: vertical bone atrophy is secondary to sinus pneumatization and there are no 3D discrepancies between the edentulous ridge and the mandible. (b) Severe bone atrophy with deficiencies on the horizontal and vertical planes that requires 3D reconstruction of the edentulous ridge associated with maxillary sinus elevation. (Reprinted with permission from Giannì et al.18)

a

a

c

b

b

d

e

Fig 6-3  (a) A 3D reconstruction of anatomical details using dedicated software. Note the course of the alveolar antral artery. (b to e) Surgical stent for the antrostomy design.

risk of early implant failure is high prior to graft consolidation. Therefore, in cases with residual crestal bone of 3 mm or less, it is advisable to plan a delayed approach after graft consolidation. To carry out a cemented restoration, the minimum distance between the crestal bone and occlusal plane should be at least 7 mm to allow sufficient space for restorative components. However, in clinical practice, prosthetic crowns are usually longer in the apicocoronal direction to compensate for bone resorption. Some clinical parameters that can be evaluated preoperatively with regard to procedures for home care include emergence profile of prosthetic restoration, adequate quantity of peri-implant keratinized mucosa, and sufficient arch depth. Preoperative radiologic examinations recommended include a

cone beam computed tomography (CBCT) scan extended to the ostiomeatal complex for the assessment of ostium patency and investigating the possible presence of disease in the paranasal sinuses. When compared with orthopantomography, CBCT allows for a more accurate assessment of septal anatomy, the diameter and course of blood vessels, possible bone dehiscence, and sinus disease.19 Using dedicated software, graft volume can be determined and surgical guides for the antrostomy and implant positioning can be fabricated (Fig 6-3). Once a thorough preoperative evaluation and surgical diagnosis is completed, it is possible to assess surgical risk. The maxillary sinus elevation difficulty score worksheet assigns difficulty points for a number of clinical situations that may be encountered20–22 (Fig 6-4). A score determines surgical difficulty.

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A  Extra-intraoral evaluation A1

A2

Face type Long or normal face* Short face† Surgical access (ease to retract cheeks) A2-1  Dimensions of the mouth:

A2-2  Thickness of the cheeks:

A2-3  Sinus elevation patient side: A3

0 pt 2 pt Wide Regular Narrow Normal Thick Very thick (usually bruxers) Left side for right-handed surgeon Right side for left-handed surgeon

0 pt 1 pt 2 pt 0 pt 1 pt 2 pt 1 pt 1 pt

Type of edentulism Fully edentulous Partially edentulous (missing premolars and molars) Partially edentulous (missing only molars or missing 1 tooth in between natural teeth)

0 pt 1 pt 2 pt

B  Radiographic evaluation B1

Wall thickness:

B2

Sinus membrane thickness:

B3

Septa direction:

B4

Septa location:

B5

Alveolar antral artery diameter‡:

B6

Angle between buccal and palatal wall:

B7

Zygomatic process morphology §:

B8

Osteoma/exostosis:

B9

Bone dehiscence:

B10

Palatonasal recess:

Thin: ≤ 1 mm Medium: 1 to 2 mm Thick: > 2 mm 1 to 2.5 mm < 1 mm > 2.5 mm Absent Bucconasal direction Mesiodistal direction Middle recess Posterior recess Anterior recess < 1 mm 1 to 2 mm > 2 mm > 30 degrees < 30 degrees Apically positioned Coronally positioned Absent Present Absent Present at the level of the buccal wall Present at the level of the ridge Present at the level of the nasal wall Absent Present

0 pt 1 pt 2 pt 0 pt 1 pt 2 pt 0 pt 1 pt 2 pt 0 pt 1 pt 2 pt 0 pt 1 pt 2 pt 0 pt 1 pt 0 pt 1 pt 0 pt 1 pt 0 pt 1 pt 2 pt 3 pt 0 pt 1 pt

Total Simple case

Most difficult case

Green 0

Orange 6

Red 12

23

*Long face usually has thin sinus wall and the zygomatic process is more apically positioned (see B7). † Short face has thicker sinus wall and zygomatic process more coronally oriented (see B7). ‡ Alveolar antral artery diameter important only if artery interferes with execution of antrostomy; if artery not involved, 0 pt. § The zygomatic process of the maxilla could be apically or more coronally located with respect to the ridge. If it is apically located and there is a vertical wall, it is easier for the clinician to perform the antrostomy. If it is coronally located, there is an inclined wall and it is more difficult for the surgeon to perform the antrostomy.

Fig 6-4  Maxillary sinus elevation difficulty score.20–22

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Lateral Antrostomy Window Management

Prophylaxis and medical management Sinus surgery is a procedure that should be carried out under antibiotic prophylaxis and postoperative drug therapy as seen in Table 6-2. This pharmacologic regimen is based on clinical experience to reduce infections.23,24 Corticosteroid therapy is commonly used as well. The goal of prophylaxis and postoperative antibiotic therapy, along with aseptic surgical conditions, is to protect the patient by preventing or minimizing infection by reducing the introduction of microbial contamination to sterile fields, sterile equipment, and the operative site. Once the preparation of the operating room has been completed and the patient rinses with 0.2% chlorhexidine solution for 1 minute to reduce bacteria concentration, disinfection of the perioral skin with povidone-iodine is completed and sterile drapes are positioned (Fig 6-5). The protocols for the preparation of the patient, the medical staff, and operating field aim to avoid contamination of the surgical site by bacteria normally not found in the oral flora, especially by bacteria on the skin of the patient and medical staff. Antibiotics administered before the operation and chemical control of plaque are not enough to guarantee a sterile operation site, but they do significantly reduce the flora. When a graft is placed, it is appropriate to carry out the procedure under as aseptic conditions as possible because the graft, lacking vascular supply, will not immediately benefit from antibiotic treatment. Additionally, in extended operations, the prolonged surgery time may lead to increased risk of contamination. The superiority of aseptic operating conditions over clean conditions in terms of success rate in implant surgery is controversial. Operating under clean conditions may be viable in traditional implantology procedures, but aseptic operating conditions are recommended in complex surgery because following an aseptic control protocol has been shown to lower infection rate from 5.6% to 2.1% (Testori et al, unpublished data).25

Lateral Antrostomy Window Management Flap management Access for a lateral window antrostomy is accomplished via a full-thickness mucoperiosteal flap. Flap design must keep in mind the principles of atraumatic flap management, adequate blood supply, access to the antrostomy site, postoperative protection of the surgical site, and effective primary closure. The flap design should include broad-based vertical incisions for adequate vascular supply. The crestal incision should be made in keratinized gingiva for more stable suturing. Generally, the incision should be made midcrestal if possible or in a position that would best favor positioning the flap around immediately

Fig 6-5 Sterile setting for the sinus elevation procedure; adhesive drapes are positioned to mark the cleaned perioral area.

placed implants. If the window will be close to the crest due to the presence of only a minimal amount of crestal bone, the incision should be moved somewhat toward the palate. The incisions should expose the area where the window is planned and at least an additional 3 to 4 mm so that suturing will not occur over the window or the membrane. This will most likely avoid the possibility of membrane exposure, which may compromise the integrity of the graft (Fig 6-6). Vertical releasing incisions should be to the bone level to avoid tearing the periosteum. When making the anterior releasing incision, keep in mind the position of the infraorbital nerve and its branches. In cases with severe alveolar loss, these branches may be quite close to the window location (Fig 6-7). Depending on the window location, the distal releasing incision may be shortened. Longer releasing incisions may be less traumatic than trauma of overzealous flap retraction. The lateral antrostomy should provide access to the sinus cavity in the best possible location to allow for the successful elevation of the sinus membrane. Factors that should be considered are the thickness of the lateral wall, the location of the posterior superior alveolar (PSA) artery, the location of the sinus floor and anterior sinus wall, the internal sinus anatomy (septa number and location and mediolateral sinus width), and the proposed anteroposterior (AP) graft dimension.

Window characteristics Window size A large window will provide better access for the elevation of the sinus membrane, especially if septa are present. However, a large window reduces vascular supply to the graft. Avila-Ortiz et al26 have shown there to be an inverse relationship between window size and vital bone production, but there is no significant effect on implant survival because the absolute minimal amount of vital bone required for successful osseointegration remains unknown.

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a

b

c

Fig 6-6  (a) Vertical releasing incision should be placed 3 to 4 mm mesial to the planned antrostomy. (b) Dissection via Metzenbaum scissors could be a proper way to avoid neurologic injuries. (c) Flap design and proper elevation allow excellent control of hemostasis. Fig 6-7  (a) Cadaver dissection of the infraorbital nerve. (b) In vivo view of a branch of the infraorbital nerve.

a

a

b

b

c

Fig 6-8  (a to c) Window location depends on the sinus anatomy. The antrostomy is placed both mesial and distal to the septum.

Window location The location of the window should be dictated by limiting the incidence of bleeding and membrane perforation. It has been shown that membrane perforations are more likely to occur in areas of restricted anatomy, such as the narrow anterior portion of the sinus.22 An acute angle between the medial and lateral walls at the sinus floor results in the need for significantly greater manipulation of sinus curettes in a narrow, restricted-access area. When this occurs, the anterior window access should be enlarged. Therefore, an anterior location most often provides direct visual access and enables significantly less manipulation. Likewise, making the window close to the sinus floor reduces the coronal movements required to reach the sinus floor. Therefore, a window 3 mm distal to the anterior sinus wall and 2 to 3 mm apical to the sinus floor is recommended. The size of the

window is determined by internal sinus anatomy and the size of the proposed graft (Fig 6-8). The presence of a septum also influences the AP location of the window. It is best to have the window straddle the septum so that sinus curettes can be used in a lateral to medial direction on both the anterior and posterior aspects of the septum. Modifications are frequently made with rotary window techniques to protect the integrity of the PSA artery. This is less of a problem with the advent of piezoelectric techniques that protect the integrity of the vasculature even while carefully working directly over it.

Window design There have been many lateral window designs proposed over the years. The choice may be that of operator preference; however,

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Lateral Antrostomy Window Management

Fig 6-9 The antrostomy is made with a surgical handpiece (1:3 ratio) mounted on an implant drilling unit. (a) A carbide bur with eight cutting blades is used at the beginning of the procedure. (b) The surgeon switches to a diamond bur when approaching the sinus membrane.

a

b

a

b

c

d

Fig 6-10 At completion of the antrostomy, the window is elevated, leaving an island of thin cortical bone at the center of the osteotomy. This is done starting from the apical part (a), moving distally (b), then mesially (c), and finally moving toward the nasal wall of the sinus (d).

certain designs do offer succinct advantages. Among the designs are the elevated hinge, elevated island, island removed, complete osteotomy via osteoplasty, transcrestal approach, palatal approach, and a new technique termed the simplified antrostomy design (SAD; see page 59). The early technique of Boyne was actually a complete elimination of the window via osteoplasty with a laboratory carbide bur.2 The hinge osteotomy was first presented in 1988 in a rotary bur technique by Wood and Moore.27 In this technique, the two lateral and the coronal osteotomy cuts go directly to the membrane while the apical cut is partial or consists of small isolated bone perforations to the membrane level. The window is then infractured by tapping the window at the coronal aspect, creating the superior hinge. One must take care when internally elevating the released window because the sharp edges can potentially cause membrane perforation.

Preparation techniques Rotary window preparation

The technique has been modified to first use low-speed implant motors outlining the window with a round carbide bur and to then use of diamond burs of various sizes (Fig 6-9). The island osteotomy is a modification to the hinge technique that avoids the previously mentioned tapping, which could result in a membrane tear, by completing the osteotomy circumferentially with a rotary or piezoelectric device. The window can then be elevated as with the hinge osteotomy, or it can be removed completely with a curette (Fig 6-10). While rotary instrumentation with carbide or diamond burs has been used successfully for many years, there are inherent complications associated with this technique. Intraoperative complication rates of bleeding (2% to 4%) and membrane perforation (20% to 25%) are relatively high with this technique due to the inability of a rotary instrument to differentiate between hard and soft tissues. The piezoelectric and Dentium Advanced Sinus Kit (DASK) surgical techniques for window preparation and membrane elevation are less atraumatic to soft tissues, reducing the incidence of complication (see page 57). One method for using these new methods is performing a complete osteoplasty for antrostomy access.28

In 1980, Boyne2 published a case of maxillary sinus elevation with window preparation using a laboratory-sized carbide bur.

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Fig 6-11 (a and b) Piezoelectric osteoplasty indicated in case of thick lateral wall.

a

b

a

b

c

Fig 6-12  (a to c) Piezoelectric outline technique indicated in case of thin lateral wall.

a

b

c

Fig 6-13  (a to c) DASK drills used for the osteotomy.

a

b

c

Fig 6-14  (a to c) DASK elevator used for detaching the sinus membrane from the bone walls.

Piezoelectric window preparation Piezoelectric techniques have been very well documented in the literature. Low-frequency ultrasonic vibrations (29 KHz, 2.8 to 16 w power, modulations of 10/30/60 cycles/min, 60 to 200 µm micrometric vibration) selectively cut hard tissues without damaging adjacent soft tissues.29 This technique has been applied in both oral and orthopedic surgical procedures. In oral surgery, it has been found to be especially useful in maxillary sinus elevation where the integrity of both the internal branch of the PSA artery and the sinus membrane can be predictably maintained.30 Perforation rates with piezoelectric surgery reported in the literature range from 3.6% to 5%, which is much lower

than with rotary techniques.31–33 This safety factor is due in part to the fact that ultrasonic vibration does not produce the drag or tearing effect that is produced by traditional rotary instrumentation. Furthermore, the technique introduced a unique trumpet-shaped elevator that can provide approximately 2 mm of circumferential internal membrane release. This allows hand instruments to be safely introduced to the sinus without accidently stretching and tearing the sinus membrane. This internal elevator is used at a low power setting with cavitating water spray. The cavitation effect of piezoelectric devices maintains a blood-free operating field that further enhances instrument control and procedural safety.

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Alternatives to the Lateral Window

Fig 6-15  (a to d) Patient with bone dehiscence on the lateral wall of the sinus. The periosteum is carefully detached from the sinus membrane.

a

b

c

d

There are two distinct protocols for performing a piezoelectric antrostomy: an osteoplasty technique and an osteotomy outlining technique (Figs 6-11 and 6-12). The outlining technique should be restricted to cases where the lateral wall is 1 mm thick or less because this technique can be quite time-consuming when the wall is thick and will quickly wear out the diamond inserts. The osteoplasty is performed with a spoon-shaped metal insert, which is more efficient when there is a thick lateral wall. In cases where the wall is very thick, such as in the area of the malar eminence, it is appropriate to consider reduction of the bulk of the thickness with rotary instrumentation prior to completing window preparation with piezoelectric osteoplasty. A study by Stacchi et al34 showed the osteoplasty technique to have the lowest perforation rate.

DASK window preparation The DASK technique is a low-speed (800 to 1,200 rpm) modification of the rotary technique that uses a 6- or 8-mm diamond dome-shaped drill to perform a lateral bone-planing antrostomy. DASK can be used to create a small 6- or 8-mm round window by using an up-and-down motion. It can also be used in a lateral direction to shape a window that is reflective of internal sinus anatomy. An additional modification uses a trephine drill to remove a bone core from the lateral wall to very near the membrane. The core is then gently removed with a curette or an elevator and the membrane elevation is started with a 180-degree back-angled elevator. The DASK drill is used at 800 to 1,200 rpm to create an osteotomy exposing a portion of the membrane. A dome-shaped elevator, either the hand- or motor-controlled version with irrigation, can then be used to circumferentially free the membrane from the window margin prior to further enlarging the site with a dome-shaped drill (Fig 6-13). The combination of slow speed

and very broad surface area allows the drill to safely contact the membrane without creating membrane perforation. Membrane elevation is then completed with standard hand instrumentation (Fig 6-14). Because the window can be relatively small, the first membrane release is circumferential on the lateral wall. This is simplified by the utilization of a unique elevator that turns back 180 degrees to reach the lateral wall adjacent to the window. The perforation rate with the DASK technique is similar to that of piezoelectric surgery at 5.6%.35

Alternatives to the Lateral Window In certain instances, access to the sinus via a lateral window antrostomy can be hindered due to anatomical factors such as lateral wall fenestrations from prior extractions or previous attempts at window preparation, the presence of a large artery, or a septum that runs in an AP direction. An additional hindrance to access might be a previously placed graft that did not extend to the medial wall, leaving a void in the proposed implant site. In these cases, one might consider alternate window locations such as the alveolar crest or even the palatal wall.

Crestal window When there is a defect in the lateral wall as a result of prior traumatic extraction or previous failed lateral window attempts, the periosteum and sinus membrane are joined over the opening with multiple adhesions present around the bony circumference (Fig 6-15). This would result in the need for a careful split-thickness dissection and a difficult membrane elevation. Similarly,

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a

b

Fig 6-16  (a and b) Case with crestal window.

a

b

c

Fig 6-17  (a) Incomplete sinus grafting. (b) Reentering from the palatal aspect. (c) Implant placed in the correct position. (Courtesy of Dr Cho Sang-Choon, New York, New York.)

a defect may be present on the crest that would make elevation of the sinus membrane difficult with a lateral approach, as the sinus membrane and crestal mucosa are conjoined in the crestal area. Manipulation of a large-diameter PSA artery could also be avoided with a transcrestal approach (Fig 6-16). A disadvantage of this procedure is the possible breakdown of the crestal split-thickness closure, exposing the underlying barrier membrane and graft and thereby introducing the risk of graft contamination.

Palatal window There are additional situations in which a lateral window may not be an appropriate choice. Consider the case of a previous lateral window that failed to elevate the sinus membrane fully across the sinus floor and up the medial wall. The resulting situation would be a very thick lateral wall with insufficient medial height to place an implant (Fig 6-17). A palatal approach would eliminate the need to obliterate the previous graft and newly formed bone by providing direct access to the medial void.36

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Alternatives to the Lateral Window

Fig 6-18  Incomplete sinus grafting. The implant is placed in the available bone (alternate therapy).

a

b

c

Fig 6-19  SAD virtual planning on CT scans. (a) A small window 3 × 6 mm is made just distal to the anterior sinus wall (light blue oval). (b) The window is then expanded anteriorly to locate the anterior sinus wall within the antrum (dark blue circle). (c) The window can be enlarged to address internal anatomy (eg, septa) and the number of implants to be placed (red oval).

Another solution could be to place the implants in the available bone and correct the indication with an angulated abutment (Fig 6-18). Another situation where a palatal approach might be indicated is that of a high and long AP septum. Depending on the location of the septum, a graft might only be needed in the medial sinus compartment to place an implant. Utilization of a lateral approach would necessitate making a “window within a window” to reach the medial compartment. In studies by Stübinger et al,37,38 results were similar to those of the lateral approach with regard to implant survival and perforation rates (19%). There was less postoperative inflammation and less scarring in the palatal tissue than that observed in the vestibular incision group.37,38 For a palatal approach to be considered as an option, the CT scan should show sufficient vertical access to the sinus between the residual crestal bone and the palatal vault. This would generally be the case with extensive pneumatization and a high palatal vault. A CT study by Wagner et al39 showed that the palatal approach is generally feasible in 93.6% of sinuses with alveolar bone heights up to 4 mm, while sinuses with crestal heights of 5 mm or greater or those with thick palatal walls limit this approach.40

Simplified antrostomy design A modification of the lateral window procedure for the placement of transsinus implants was presented by Testori et al41 for use with the All-on-4 procedure. In this technique, a small sinus elevation against the anterior wall allows for tilting of the posterior implants into an anterior wall sinus graft to increase the AP spread. A small window is all that is required for this procedure; it is appropriate to start the window at the anterior wall rather than starting distal to it and reaching forward. This technique is simple and worth considering as the starting point for the majority of lateral window procedures. From this starting point, the window could be expanded as required to adapt to varying internal sinus anatomy. The SAD is accomplished as a three-step procedure as follows (Fig 6-19): 1. Using the best CBCT and clinical measurements available, a small window 3 mm wide by 6 mm is made just distal to the anterior sinus wall.

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a

b

c

Fig 6-20  (a to c) Elevators are used on both the anterior and posterior aspects of the septum.

Membrane elevation varies from technically quite simple to extremely difficult depending on anatomical factors relating to the width of the sinus, the presence of septa, the residual crestal bone height, and the location of the antrostomy.

pinch the membrane, compressing it against the internal aspect of the sinus wall and tearing it on the first effort at reflection. This can be avoided by the use of piezoelectric trumpet-shaped elevators. This device is used at a low power setting with a cavitating water spray. This will yield a predictable circumferential membrane separation of about 2 mm that will allow the next elevator to be placed in direct contact with the bone, avoiding any possibility of perforation. An unpublished study at New York University has shown that membranes with a thickness of 1 mm or less (as shown on CBCT) have a perforation rate 2.5 times greater than those that are thicker, hence the greater need for care and accuracy of elevation technique with thin membranes. Other published studies are in agreement; however, a systematic review by Monje et al42 reported inconclusive data to correlate membrane thickness with perforation rate with thicker membranes more prone to perforation (P = .14).43–47 Elevation should continue from lateral to medial with either the 45- or 90-degree piezoelectric sinus elevators; alternatively, it can be accomplished with sharp hand elevators. Dull elevators have the potential to roll over a membrane as opposed to elevating it, resulting in a tear. When firm adhesions of the membrane are present on the sinus floor, it may be appropriate to use a sharp dissection to free the membrane. When using sharp elevators, it is imperative to keep them in direct contact with the bone surface at all times to avoid perforating the membrane. When elevating the membrane from septa, one should gain window access on both sides of the septum (anterior and posterior) so that elevation can be performed lateral to medial as opposed to AP (Fig 6-20). This is because it is difficult to keep an elevator in contact with bone while moving in an AP direction over a sharp septal spine. The membrane is then elevated moving medially in a slow progression from each side in succession. There are some factors that directly contribute to membrane perforations (Box 6-2).

Operator technique and instrumentation

Managing membrane perforation

The first entry into the sinus when starting membrane elevation can cause an immediate problem. It is possible for the elevator to

Many elevators used for sinus elevation are improperly designed. The only part of the elevator that should touch the sinus walls

Box 6-2  Factors influencing perforation rate • Bony dehiscences • Membrane thickness • Sinus septa, direction and location • Sinus anatomy – Buccal wall thickness – Angle between the buccal and palatal wall – Osteoma or exostosis – Nasopalatal recess • Operator skill • Instrumentation used – Piezoelectric – DASK – Burs

2. The window is then extended anteriorly to locate the anterior sinus wall within the antrum. 3. The window can be enlarged to address internal anatomy (septa) and the number of implants to be placed. The final window extends coronally to be 2 to 3 mm from the sinus floor and roughly 10 mm in the AP direction.

Sinus Membrane Elevation

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Graft Placement

Fig 6-21  (a and b) Sinus membrane perforation repaired via resorbable suture and collagen membrane.

a

is the tip because this is how the surgeon gains haptic feedback. If the instrument has a long shank, this shank may contact the window entrance and make it difficult to determine contact at the tip, increasing the chance for inadvertent perforation. In the event of perforation, it is still possible to proceed cautiously and continue the elevation. The direct area of the perforation should be avoided as a weak spot because the perforation is likely to expand if disturbed. The membrane elevation should continue at a distance from the perforation, going completely around it. The perforation will likely get smaller as tension on the membrane is relieved. Another way to facilitate further elevation is to cover the perforation with a collagen membrane. A membrane with a rough side, such as a Bio-Gide membrane (Geistlich Pharma) or use of leukocyte- and platelet-rich fibrin, if available, will work well to stabilize the tear (Fig 6-21). It should be mentioned that large perforation repair is best made with a somewhat stiffer membrane such as BioMend (Zimmer Biomet Dental) that is able to maintain its shape and better resist packing pressure.

Graft Placement The most common postoperative infection following sinus augmentation is an infected sinus graft. Sinus graft infections may result from bacterial contamination from untreated periapical lesions near the sinus floor or by external contamination from untreated periodontal lesions and/or local oral flora. Preoperative antibiotic therapy is essential to establish effective antibiotic blood levels before the surgical procedure. A 7- to 10-day course of a penicillin-based outbreak should be given starting prior to surgery (or an alternative medication in case of a penicillin allergy). While fluoroquinolones such as ciprofloxacin have a very broad spectrum, the untoward side effects of tendon rupture, tendonitis, arrhythmias, gastrointestinal perforations, and peripheral neuropathies must be considered when prescribing these drugs.48–53 The placement of antibiotics such as clindamycin within the graft is not recommended.54 Choukroun et al55 published a CT study to determine the effectiveness of the inclusion of a low dose of metronidazole in the sinus graft to reduce contamination by anaerobic bacteria. The test group did not show the postoperative presence of air bubbles (tomodensitometric change)

b

within the graft that were present in the control patients without metronidazole inclusion. However, the presence of air bubbles is not considered sensitive and may result from the packing procedure itself. For now, the use of antibiotic impregnation in the graft is not warranted by published evidence. When placing particulate grafts into the sinus, it is important to fill the space entirely and not to leave voids. The osteoconductive graft material is also a more favorable space maintainer than a blood clot and therefore better at maintaining volume. Another consideration when placing graft material in the maxillary sinus is the possible effect of packing pressure on the volume that is created. Volumetric studies show that there is a loss of volume from the time of graft placement to the time of graft maturation.56 Loss of graft volume has even been observed with nonresorbable graft materials such as xenografts.57 Some of the volume loss may be due to compression of the graft from intrasinus pressure at the expense of interparticle space. In a comparison of vital bone production with xenografts of different particle size, it was shown that more vital bone was formed when large-particle xenograft was used.58 The difference is likely due to the reduced compression of interparticle space with more favorable maintenance of volume. A potential downside of large graft particles may result from less-than-adequate perforation repair. Escaped large graft particles could potentially block a smaller-sized ostium and result in a postoperative sinusitis or infection. In addition to preoperative treatment of adjacent pathologies and the administration of perioperative antibiotics, a sterile protocol should be used to prevent local contamination at the time of graft placement. Steps taken may include flushing the sinus with saline after membrane elevation, surrounding the window with gauze to prevent salivary contamination, using a syringe to place the graft material, and having the patient remain with the mouth open until the flap is sutured over the graft site (Fig 6-22). A major source of graft contamination is the use of nonsterile instruments to manipulate the particulate graft material. Instruments that have been sterilized before the procedure do not retain sterility once they are introduced into the oral cavity. A common procedural error is to use the same instrument for periosteal elevation and for graft placement. This simple breakdown of sterile technique should be avoided. One way to do this is to have separate surgical trays and suction tips for instrumenting flap reflection and for sinus grafting.

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a

b

c

Fig 6-22  (a) Isolation with gauze. (b) Rinse with sterile saline. (c) The graft is placed into the sinus with a syringe. Fig 6-23  (a and b) Membrane placed inside the window.

a

b

Placement and stabilization of membrane In early histomorphometric investigations of lateral window sinus elevations using particulate grafts, horizontal cores from the apical portion of the graft were used to evaluate vital bone formation.59,60 The lateral part of the core often contained soft tissue extending into in the lateral portion of the graft. Without the use of barrier membranes, soft tissue invaginated into the grafted site.61,62 Early studies comparing the effect of membrane placement over the lateral window revealed greater formation of vital bone with membrane placement.60,63,64 Further, these studies showed that comparable positive results were achieved with both nonresorbable and resorbable membranes.62,63,65 However, recent studies indicate that the placement of a membrane has no significant effect on vital bone formation within the central area of the sinus.66–68 One study found that that membrane placement has no beneficial effect for bone formation with a negative effect on osteoid formation.69 While controversy exists regarding vital bone formation, membrane placement does deter soft tissue encleftation and graft material migration. It is quite possible that the differences observed in vital bone formation between the earlier studies (positive membrane effect) and the later studies (neutral membrane effect) are the result of differences in location of the core harvest. Due to Institutional Review Board limitations, raising a vestibular flap for core harvesting is now prohibited. Later cores, taken from the crestal implant receptor sites, will most likely be taken close to the bony walls and will therefore show a higher percentage of vital bone.

The membrane is typically placed to cover the borders of the window by approximately 2 to 3 mm. This allows for complete coverage in the event of a minor membrane displacement from flap manipulation during suturing. It is prudent to avoid placing the membrane beneath an incision line to reduce the possibility for membrane exposure from wound dehiscence (Fig 6-23). Nonresorbable membranes, such as expanded polytetrafluoroethylene (ePTFE), are generally stabilized via tacking. This is both to prevent movement including lifting and soft tissue invagination into the graft space. It is not uncommon to dissect ePTFE membranes from surrounding soft tissues to remove them at stage-two surgery. It is obvious that a resorbable membrane, because of its adaptability and lack of requirement for fixation and subsequent removal, allows for a less demanding surgical protocol. This makes sense if the outcomes of vital bone formation and implant survival are similar. A prospective study by Tarnow et al63 showed no significant differences between nonresorbable (eg, Gore-Tex) and resorbable (eg, Bio-Gide) membranes for either vital bone formation or implant survival. Resorbable membranes generally require no stabilization if a membrane with the proper handling characteristics is used. The best membrane would be one that, once hydrated, conforms and adheres to the irregular bony surface. Some membranes are too thick and rigid to conform, so they may slide out of position or lift off the surface and allow soft tissue invagination. Alternatively, resorbable membranes can be stabilized using overlying horizontal mattress suturing or by changing the membrane placement location. Testori et al70 published a protocol for placing the cut-to-size collagen membrane inside the window, covering the graft material and being stabilized internally against the lateral wall.

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References

a

b

Fig 6-24  (a) Sutures are made apical to coronal on the vertical releasing incision to move the flap coronally. (b) Primary intention closure.

Closure The surgeon should establish a tension-free primary closure. However, periosteal releasing incisions are rarely made because a split-thickness releasing incision increases patient morbidity. In the severely resorbed maxilla, damage to the branches of the infraorbital nerve can occur. Releasing incisions are only needed in cases of simultaneous ridge augmentation where the alveolar dimension is enlarged. Either interrupted or continuous suturing techniques may be used. Resorbable or combinations of resorbable and nonresorbable sutures can also be used. The vertical incisions are best closed with finer resorbable sutures because suture removal in the vestibule is uncomfortable for the patient (Fig 6-24).

Conclusion The lateral window sinus elevation procedure continues to evolve. As reported in multiple evidence-based reviews, it has proven to be a remarkably successful preprosthetic surgical procedure.71–73 However, the importance of the lateral antrostomy method has been reduced by the use of the osteotome transcrestal approach, the use of ultrashort implants, and now the multiple variations of minimally invasive methods that sometimes avoid the sinus completely. The options of the transcrestal approach and ultrashort implants have shown high success rates. As these recent solutions became more popular, the lateral window procedure evolved to become less invasive. It is no longer a hospital-based procedure dependent on autogenous bone harvest; it is now an office-based procedure requiring no harvesting of donor bone. Furthermore, techniques using

smaller access windows and therefore smaller flaps have further reduced morbidity. The lateral window technique still offers advantages not present with other techniques. It allows for greater access to work around obstacles (eg, septa), it requires one surgery for multiple implant sites, it can be used regardless of residual crestal bone height, and it allows for repair if something goes wrong during the procedure (eg, perforation). The surgeon should not be biased by personal preference. To obtain regeneration in the sinus floor, one must deliver the most appropriate therapy possible with the least intervention. In some cases, this may best be done with the lateral window approach.

References 1. Tatum H. Lecture presented to the Alabama Implant Congress. 1976. 2. Boyne PJ, James RA. Grafting the floor of the maxillary sinus with autogenous marrow and bone. J Oral Surg 1980;38:613–616. 3. Timmenga NM, Raghoebar GM, Liem RS, van Weissenbruch R, Manson WL, Vissink A. Effects of maxillary sinus floor elevation surgery on maxillary sinus physiology. Eur J Oral Sci 2003;111:189– 197. 4. Torretta S, Mantovani M, Testori T, Cappadona M, Pignataro L. Importance of ENT assessment in stratifying candidates for sinus floor elevation: A prospective clinical study. Clin Oral Implants Res 2013;24(suppl A100):57–62. 5. Mantovani M. Otorhinolaryngological contraindications in augmentation of the maxillary sinus. In: Testori T, Del Fabbro M, Weinstein R, Wallace S (eds). Maxillary Sinus Surgery. Chicago: Quintessence, 2009:29–34. 6. Kim MJ, Jung UW, Kim CS, et al. Maxillary sinus septa: Prevalence, height, location, and morphology. A reformatted computed tomography scan analysis. J Periodontol 2006;77:903–908.

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6  LATERAL WINDOW SURGICAL TECHNIQUES FOR SINUS ELEVATION

7. Lopatin AS, Sysolyatin SP, Sysolyatin PG, Melnikov MN. Chronic maxillary sinusitis of dental origin: Is external surgical approach mandatory? Laryngoscope 2002;112:1056–1059. 8. Mehra P, Murad H. Maxillary sinus disease of odontogenic origin. Otolaryngol Clin North Am 2004;37:347–364. 9. Melen I, Lindahl L, Andréasson L, Rundcrantz H. Chronic maxillary sinusitis. Definition, diagnosis and relation to dental infections and nasal polyposis. Acta Otolaryngol 1986;101:320–327. 10. Albu S, Baciut M. Failures in endoscopic surgery of the maxillary sinus. Otolaryngol Head Neck Surg 2010;142:196–201. 11. Longhini AB, Branstetter BF, Ferguson BJ. Otolaryngologists’ perceptions of odontogenic maxillary sinusitis. Laryngoscope 2012;122:1910–1914. 12. Saibene AM, Vassena C, Pipolo C, et al. Odontogenic and rhinogenic chronic sinusitis: A modern microbiological comparison. Int Forum Allergy Rhinol 2016;6:41–45. 13. Taschieri S, Torretta S, Corbella S, et al. Pathophysiology of sinusitis of odontogenic origin. J Investig Clin Dent 2017;8(2). 14. Blanksma CJ, Brand HS. Cocaine abuse: Orofacial manifestations and implications for dental treatment. Int Dent J 2005;55:365–369. 15. Silvestre FJ, Perez-Herbera A, Puente-Sandoval A, Bagán JV. Hard palate perforation in cocaine abusers: A systematic review. Clin Oral Investig 2010;14:621–628. 16. Heitz-Mayfield LJ, Huynh-Ba G. History of treated periodontitis and smoking as risks for implant therapy. Int J Oral Maxillofac Implants 2009;24(suppl):39–68. 17. Testori T, Weinstein RL, Taschieri S, Del Fabbro M. Risk factor analysis following maxillary sinus augmentation: A retrospective multicenter study. Int J Oral Maxillofac Implants 2012;27:1170– 1176. 18. Giannì AB, Monteverdi R, Baj A, Carlino F, Tomic O. Maxillary atrophy: Classification and surgical protocols. In: Testori T, Del Fabbro M, Weinstein R, Wallace S. Maxillary Sinus Surgery and Alternatives in Treatment. Chicago: Quintessence, 2009. 19. Harris D, Horner K, Gröndahl K, et al. E.A.O. guidelines for the use of diagnostic imaging in implant dentistry 2011. A consensus workshop organized by the European Association for Osseointegration at the Medical University of Warsaw. Clin Oral Implants Res 2012;23:1243–1253. 20. Insua A, Monje A, Urban I, et al. The sinus membrane-maxillary lateral wall complex: Histologic description and clinical implications for maxillary sinus floor elevation. Int J Periodontics Restorative Dent 2017;37:e328–e336. 21. Rosano G, Taschieri S, Gaudy JF, Del Fabbro M. Maxillary sinus vascularization: A cadaveric study. J Craniofac Surg 2009;20:940– 943. 22. Cho SC, Wallace SS, Froum SJ, Tarnow DP. Influence of anatomy on Schneiderian membrane perforations during sinus elevation surgery: Three-dimensional analysis. Pract Proced Aesthet Dent 2001;13:160–163. 23. Dohan Ehrenfest DM. How to optimize the preparation of leukocyte- and platelet-rich fibrin (L-PRF, Choukroun’s technique) clots and membranes: Introducing the PRF box. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010;110:275–278. 24. Elian N, Wallace S, Cho SC, Jalbout ZN, Froum S. Distribution of the maxillary artery as it relates to sinus floor augmentation. Int J Oral Maxillofac Implants 2005;20:784–787. 25. Wallace SS. Complications in lateral window sinus elevation surgery. In: Froum SJ (ed). Dental Implant Complications: Etiology, Prevention, and Treatment. Hoboken, NJ: Wiley-Blackwell, 2010:284–309.

26. Avila-Ortiz G, Wang HL, Galindo-Moreno P, Misch CE, Rudek I, Neiva R. Influence of lateral window dimensions on vital bone formation following maxillary sinus augmentation. Int J Oral Maxillofac Implants 2012;27:1230–1238. 27. Wood RM, Moore DL. Grafting of the maxillary sinus with intraorally harvested autogenous bone prior to implant placement. Int J Oral Maxillofac Implants 1988;3:209–214. 28. Wallace SS, Tarnow DP, Froum SJ, et al. Maxillary sinus elevation by lateral window approach: Evolution of technology and technique. J Evid Based Dent Pract 2012;12(3 suppl):161–171. 29. Vercellotti T. Technological characteristics and clinical indications of piezoelectric bone surgery. Minerva Stomatol 2004;53:207–214. 30. Vercellotti T, De Paoli S, Nevins M. The piezoelectric bony window osteotomy and sinus membrane elevation: Introduction of a new technique for simplification of the sinus augmentation procedure. Int J Periodontics Restorative Dent 2001;21:561–567. 31. Wallace SS, Mazor Z, Froum SJ, Cho SC, Tarnow DP. Schneiderian membrane perforation rate during sinus elevation using Piezosurgery: Clinical results of 100 consecutive cases. Int J Periodontics Restorative Dent 2007;27:413–419. 32. Blus C, Szmukler-Moncler S, Salama M, Salama H, Garber D. Sinus bone grafting procedures using ultrasonic bone surgery: 5-year experience. Int J Periodontics Restorative Dent 2008;28: 221–229. 33. Toscano NJ, Holtzclaw D, Rosen PS. The effect of piezoelectric use on open sinus lift perforation: A retrospective evaluation of 56 consecutively treated cases from private practices. J Periodontol 2010;81:167–171. 34. Stacchi C, Vercellotti T, Toschetti A, Speroni S, Salgarello S, Di Lenarda R. Intraoperative complications during sinus floor elevation using two different ultrasonic approaches: A two-center, randomized, controlled clinical trial. Clin Implant Dent Relat Res 2015;17(suppl 1):e117–e125. 35. Lozada JL, Goodacre C, Al-Ardah AJ, Garbacea A. Lateral and crestal bone planing antrostomy: A simplified surgical procedure to reduce the incidence of membrane perforation during maxillary sinus augmentation procedures. J Prosthet Dent 2011; 105:147–153. 36. Florio S, Suzuki T, Cho SC. The palatal window for treating an incompletely augmented maxillary sinus. Implant Dent 2017; 26:328–331. 37. Stübinger S, Saldamli B, Seitz O, Sader R, Landes CA. Palatal versus vestibular piezoelectric window osteotomy for maxillary sinus elevation: A comparative clinical study of two surgical techniques. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2009;107:648–655. 38. Stübinger S, Saldamli B, Landes CA, Sader R. Palatal piezosurgical window osteotomy for maxillary sinus augmentation. Int J Oral Maxillofac Surg 2010;39:606–609. 39. Wagner F, Dvorak G, Pillerstorff R, et al. Anatomical preconditions for the palatal sinus floor augmentation—A three-dimensional feasibility study. J Craniomaxillofac Surg 2015;43:1303–1308. 40. Jensen OT, Perkins S, Van de Water FW. Nasal fossa and maxillary sinus grafting of implants from a palatal approach: Report of a case. J Oral Maxillofac Surg 1992;50:415–418. 41. Testori T, Mandelli F, Mantovani M, Taschieri S, Weinstein RL, Del Fabbro M. Tilted trans-sinus implants for the treatment of maxillary atrophy: Case series of 35 consecutive patients. J Oral Maxillofac Surg 2013;71:1187–1194. 42. Monje A, Diaz KT, Aranda L, Insua A, Garcia-Nogales A, Wang HL. Schneiderian membrane thickness and clinical implications for sinus augmentation: A systematic review and meta-regression analyses. J Periodontol 2016;87:888–899.

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References

43. Al-Dajani M. Incidence, risk factors, and complications of Schneiderian membrane perforation in sinus lift surgery: A meta-analysis. Implant Dent 2016;25:409–415. 44. Lin YH, Yang YC, Wen SC, Wang HL. The influence of sinus membrane thickness upon membrane perforation during lateral window sinus augmentation. Clin Oral Implants Res 2016;27:612–617. 45. Irinakis T, Dabuleanu V, Aldahlawi S. Complications during maxillary sinus augmentation associated with interfering septa: A new classification of septa. Open Dent J 2017;11:140–150. 46. Schwarz L, Schiebel V, Hof M, Ulm C, Watzek G, Pommer B. Risk factors of membrane perforation and postoperative complications in sinus floor elevation surgery: Review of 407 augmentation procedures. J Oral Maxillofac Surg 2015;73:1275–1282. 47. Moreno Vazquez JC, Gonzalez de Rivera AS, Gil HS, Mifsut RS. Complication rate in 200 consecutive sinus lift procedures: Guidelines for prevention and treatment. J Oral Maxillofac Surg 2014;72:892–901. 48. Liu X, Ma J, Huang L, et al. Fluoroquinolones increase the risk of serious arrhythmias: A systematic review and meta-analysis. Medicine (Baltimore) 2017;96:e8273. 49. Hsu SC, Chang SS, Lee MG, et al. Risk of gastrointestinal perforation in patients taking oral fluoroquinolone therapy: An analysis of nationally representative cohort. PLoS One 2017;12: e0183813. 50. Singh S, Nautiyal A. Aortic dissection and aortic aneurysms associated with fluoroquinolones: A systematic review and meta-analysis. Am J Med 2017;130:1449–1457. 51. Zabraniecki L, Negrier I, Vergne P, et al. Fluoroquinolone induced tendinopathy: Report of 6 cases. J Rheumatol 1996;23:516–520. 52. McGarvey WC, Singh D, Trevino SG. Partial Achilles tendon ruptures associated with fluoroquinolone antibiotics: A case report and literature review. Foot Ankle Int 1996;17:496–498. 53. Kuehn BM. FDA warning and study highlight fluoroquinolone risks. JAMA 2013;310:1014. 54. Misch CE. Contemporary Implant Dentistry, ed 3. St Louis: Mosby Elsevier, 2008. 55. Choukroun J, Simonpieri A, Del Corso M, Mazor Z, Sammartino G, Dohan Ehrenfest DM. Controlling systematic perioperative anaerobic contamination during sinus-lift procedures by using metronidazole: An innovative approach. Implant Dent 2008;17: 257–270. 56. Shanbhag S, Shanbhag V, Stavropoulos A. Volume changes of maxillary sinus augmentations over time: A systematic review. Int J Oral Maxillofac Implants 2014;29:881–892. 57. Mazzocco F, Lops D, Gobbato L, Lolato A, Romeo E, del Fabbro M. Three-dimensional volume change of grafted bone in the maxillary sinus. Int J Oral Maxillofac Implants 2014;29:178–184. 58. Testori T, Wallace SS, Trisi P, Capelli M, Zuffetti F, Del Fabbro M. Effect of xenograft (ABBM) particle size on vital bone formation following maxillary sinus augmentation: A multicenter, randomized, controlled, clinical histomorphometric trial. Int J Periodontics Restorative Dent 2013;33:467–475. 59. Froum SJ, Tarnow DP, Wallace SS, Rohrer MD, Cho SC. Sinus floor elevation using anorganic bovine bone matrix (OsteoGraf/N) with and without autogenous bone: A clinical, histologic, radiographic, and histomorphometric analysis—Part 2 of an ongoing prospective study. Int J Periodontics Restorative Dent 1998; 18:528–543.

60. Jensen OT, Greer RO. Immediate placement of osseointegrating implants into the maxillary sinus augmented with mineralized cancellous allograft and Gore-Tex: Second stage surgical and histological findings. In: Laney WR, Tolman DE (eds). Tissue Integration in Oral, Orthopedic & Maxillofacial Reconstruction. Chicago: Quintessence, 1991:321–333. 61. Jensen OT. Guided bone graft augmentation. In: Buser D, Dahlin C, Schenk RK (eds). Guided Bone Regeneration in Implant Dentistry. Chicago: Quintessence, 1994:235–264. 62. Avera SP, Stampley WA, McAllister BS. Histologic and clinical observations of resorbable and nonresorbable barrier membranes used in maxillary sinus graft containment. Int J Oral Maxillofac Implants 1997;12:88–94. 63. Tarnow DP, Wallace SS, Froum SJ, Rohrer MD, Cho SC. Histologic and clinical comparison of bilateral sinus floor elevations with and without barrier membrane placement in 12 patients: Part 3 of an ongoing prospective study. Int J Periodontics Restorative Dent 2000;20:117–125. 64. Tawil G, Mawla M. Sinus floor elevation using a bovine bone mineral (Bio-Oss) with or without the concomitant use of a bi­ layered collagen barrier (Bio-Gide): A clinical report of immediate and delayed implant placement. Int J Oral Maxillofac Implants 2001;16:713–721. 65. García-Denche JT, Wu X, Martinez PP, et al. Membranes over the lateral window in sinus augmentation procedures: A two-arm and split-mouth randomized clinical trials. J Clin Periodontol 2013;40:1043–1051. 66. Suárez-López Del Amo F, Ortego-Oller I, Catena A, et al. Effect of barrier membranes on the outcomes of maxillary sinus floor augmentation: A meta-analysis of histomorphometric outcomes. Int J Oral Maxillofac Implants 2015;30:607–618. 67. Choi KS, Kan JY, Boyne PJ, Goodacre CJ, Lozada JL, Rungcharassaeng K. The effects of resorbable membrane on human maxillary sinus graft: A pilot study. Int J Oral Maxillofac Implants 2009;24:73–80. 68. Bresaola MD, Matsumoto MA, Zahoui A, Biguetti CC, Nary-Filho H. Influence of rapid- and slow-rate resorption collagen membrane in maxillary sinus augmentation. Clin Oral Implants Res 2017;28:320–326. 69. Schulten EA, Prins HJ, Overman JR, Helder MN, ten Bruggenkate CM, Klein-Nulend J. A novel approach revealing the effect of a collagenous membrane on osteoconduction in maxillary sinus floor elevation with β-tricalcium phosphate. Eur Cell Mater 2013;25:215–228. 70. Testori T, Mandelli F, Valentini P, Wallace S. A novel technique to prevent the loss of graft material through the antrostomy after sinus surgery: Technical note. Int J Oral Maxillofac Implants 2014;29:e272–e274. 71. Wallace SS, Froum SJ. Effect of maxillary sinus augmentation on the survival of endosseous dental implants. A systematic review. Ann Periodontol 2003;8:328–343. 72. Pjetursson BE, Tan WC, Zwahlen M, Lang NP. A systematic review of the success of sinus floor elevation and survival of implants inserted in combination with sinus floor elevation. J Clin Periodontol 2008;35(8 suppl):216–240. 73. Aghaloo TL, Moy PK. Which hard tissue augmentation techniques are the most successful in furnishing bony support for implant placement? Int J Oral Maxillofac Implants 2007;22(suppl):49–70.

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CHAPTER 7

SINUS FLOOR AUGMENTATION WITHOUT BONE GRAFTING Giovanni Cricchio, dds, phd | Lars Sennerby, dds, phd | Stefan Lundgren, dds, phd

W

hen there is insufficient residual bone height in the edentulous posterior maxilla, an alternative approach for prosthetic rehabilitation with dental implants is the graftless sinus floor elevation technique. For decades, the standard approach has been a two-stage sinus elevation technique using bone grafts inserted in the sinus cavity after membrane elevation. With this technique, the graft material (which could be both autogenous or bone substitute alone or mixed together) is left to heal for a period of 4 to 6 months before dental implant placement.1–10 The graft works as a scaffold for tissue regeneration and therefore contributes to new bone formation mainly thanks to osteoconductive properties, eventually resulting in favorable conditions for dental implant placement. In 2004, a new graftless alternative technique to increase the available bone height in the posterior maxilla was described.11 The authors showed that the mere raising of the sinus membrane and the creation of a void space in which blood clot formation could take place resulted in formation of new bone. The implants were placed simultaneously using an undersized drilling technique to obtain primary stability. The tips of the implants also acted as support for the elevated membrane. A similar approach to the sinus has been indicated in earlier studies and further investigated by others.12–31 The new bone was probably formed in accordance with the principles of guided bone regeneration (GBR). This biologic method was tested by Dahlin et al32 for regeneration of critical bone defects in a rat model.32–35 GBR developed based on the principle of guided tissue regeneration (GTR) investigated by Nyman and Karring36 and deals with the regeneration of a desired tissue in a secluded space created using a barrier membrane.36–45 GTR and GBR are based on wound healing process knowledge. From the 1950s to the 1970s, several authors showed that the formation and the subsistence of a stable coagulum is the first and the main step for a predictable healing result.46–48

The environment created under the elevated sinus membrane presents favorable biologic features for favorable healing. It is a secluded space surrounded by the residual bone and maintained by well-positioned implants, which creates the perfect condition for coagulum formation and undisturbed wound healing process (Fig 7-1).

Indications Graftless lateral sinus elevation is indicated when it is impossible to place dental implants in an acceptable position for prosthetic rehabilitation using a standard technique and/or by the transcrestal sinus floor elevation technique. This may be caused by a low residual amount of bone crest that impaired primary stability and/or unsafe sinus membrane elevation management. In cases of crestal approach, endoscopically controlled studies have shown that the higher the amount of elevation, the higher the risk of membrane perforation.49–52 When the performed elevation is more than 4 mm, there is a high risk of membrane damage. As yet, there is no consensus on the recommended residual bone crest height for selecting the transcrestal or lateral sinus floor elevation approach and technique. As a rule of thumb, it has been suggested that the lateral approach is a suitable technique where the residual bone in the floor of the sinus is of lesser height compared with the planned elevation. The graftless lateral sinus elevation technique with simultaneous implant placement to support the elevated sinus membrane always depends on the possibility of achieving primary implant stability for healing of implants.53 Primary implant stability is the main factor in the choice to use graftless sinus elevation but may vary depending on bone height and width, as well as on bone density and type of implant used.53

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Surgical Technique

a

b

c

d

e

f

Fig 7-1  Schematic drawings of cross-sectional aspect in buccolingual direction. (a) Before surgery. (b) Dissected bone flap after osteotomy. (c) Implant in place working as a tent pole. (d) Replaced bone flap. (e) Coagulum formation. (f) New bone formation.

The anatomical condition of the planned implant site must have such characteristics that at the end of implant seating, primary implant stability is sufficient for uneventful healing. The quantity and quality of residual bone are both important factors influencing primary implant stability. As is often seen in the clinical situation, a limited amount of residual bone develops from apparent fusion of the outer alveolar cortex and the sinus floor cortex. This situation can be more favorable to obtain implant stability than situations with higher amounts of residual bone and low bone density with less cortical content. Dental implants available in the market today have a large variety in micro and macro design. The design of the neck of the implant plays an important role in obtaining primary implant stability. The less residual bone height, the more important is the role played by implant marginal micro and macro design in obtaining primary stability. It is paramount to choose a dental implant that will result in the best performance of the technique, especially in conditions where it is difficult to obtain primary implant stability.

Surgical Technique After a midcrestal incision and vertical releasing incisions, a mucoperiosteal flap is elevated to expose the sinus lateral wall. The extension of the planned bone window is marked with a small round bur, and the window is cut with a reciprocal

microsaw or a piezotome device (Fig 7-2). The inferior margin of the window created should always be cut at least 5 mm above the sinus floor to maintain a three-wall compartment to protect the blood coagulum and to maintain the bone strength to avoid accidental bone fracture during implant placement. The saw or tip is tilted to create a tapered osteotomy to ensure the stability of the window when it is replaced after surgery. The bone window is dissected free from the underlying sinus membrane with a dissector, and after removal it is kept in saline. The sinus membrane is elevated to create a secluded compartment for the implants. The level of the sinus membrane elevation is determined by the intrasinus protrusion of the implant, visualized by the use of a depth gauge or direction indicator. After the elevation is finished and instruments are removed from the prepared cavity, the planned implant positions are marked with a pilot bur. To achieve optimal primary implant stability, the implant sites are prepared in accordance with a drilling protocol that is undersized compared with the recommendations from standard protocols. The diameter of the final drill used should be selected based on the type of implant used and on the quality and quantity of the residual bone crest with the aim of obtaining adequate primary stability for implant healing. Wider implants can be used to replace standard implants with insufficient primary stability. The implant is placed without irrigation and without raising the sinus membrane, as the distance to the membrane is previously determined with the aid of a depth gauge (Fig 7-3a). The bone window is then replaced and secured by closure of the oral mucosal flap (Fig 7-3b). If

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7  SINUS FLOOR AUGMENTATION WITHOUT BONE GRAFTING

a

b

a

b

Fig 7-2  (a) The extension of the bone window is marked by drilling with a small round bur. (b) The bone window is cut with a reciprocal microsaw or a piezotome device.

Fig 7-3  (a) Implant in position supporting the elevated sinus membrane. (b) Replaced bone window stabilized by the tapered osteotomy.

there is insufficient stability of the bone wall, a few drops of N-butyl-2-cyanoacrylate glue could be used at the bone window osteotomy sites for stabilization.53

bone morphologic protein 6 and 7. Kim et al56 analyzed cells in culture retrieved from human maxillary sinus membrane specimens collected from patients who had undergone orthognathic surgery. The results suggested that there are multipotent MSCs in human maxillary sinus membrane tissue that can differentiate into osteoblasts under osteogenic induction.56 Srouji et al57,58 also demonstrated that the maxillary sinus membrane has osteogenic potential. Using histologic analysis of in vivo subcutaneous transplants of human maxillary sinus membrane– derived cells in athymic nude mice, they showed evidence of the formation of ectopic bone at the transplantation site. They also reported that after subcutaneous transplantation of the folded sinus membrane with or without an additional fibrin clot, new ectopic bone formation was detected. These authors concluded that the sinus membrane appears to play an important role in bone formation after elevation, thanks to both its osteogenic properties and its function as a barrier membrane protecting the blood clot after surgery.57,58 On the other hand, in a couple of studies in primates, Scala et al27,28 reported that the sinus membrane is not involved in new bone formation during the first 20 days after surgery. They found that new bone originates from the sinus wall and from septa. Similar conclusions have been outlined by Jungner et al24 in a histologic and immunohistochemical study on early bone formation events in primates after membrane elevation in the maxillary sinus (Fig 7-5). In particular, the 10-day specimens showed that osteoblasts could be observed forming mineralized tissue at existing bone and bone fragments and near vessels as solitary islets. In another recent histomorphometric study in rabbits, Sohn et al31 compared sinus membrane elevation without bone grafting and a repositioned lateral bone window (test group) with sinus membrane elevation with additional xenogeneic bone graft in which the lateral bone window was substituted with a resorbable

Literature Review of Biologic and Histologic Aspects Bone formation In a study on primates, Boyne54 showed that sinus membrane elevation and implant placement with the apical part protruding in the sinus cavity under the elevated mucosa results in spontaneous bone formation. In an experimental study by Palma et al,26 machined and oxidized implants were placed in conjunction with sinus membrane elevation using the replaceable bonewindow technique. One sinus was filled with autogenous bone grafts and served as a control for the elevated side where no grafts were used. Histology was performed after 6 months of healing and showed bone formation around the implants at both sides with no apparent differences (Fig 7-4a). The raised sinus membrane lined the new bone, and the apex of the implant showed no signs of inflammatory infiltrates or irritation (Fig 7-4b). The surface-modified oxidized implants showed more direct bone-to-implant contacts than did machined implants, regardless of treatment. The specific role of the sinus membrane in bone formation during the early healing phase has been widely investigated, and some authors have suggested that the sinus membrane may play a direct role in the bone-formation process. Gruber et al55 showed in an in vitro study that the sinus membrane contains mesenchymal stem cells (MSCs), which respond to

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Literature Review of Biologic and Histologic Aspects

Fig 7-4 (a) Light micrograph after 6 months of healing showing bone formation around the implants. (b) Light micrograph featuring interaction between the apical part of the implant and the sinus membrane without signs of morphologic alteration (Toluidine blue staining).

Sinus membrane

Implant

1 mm

a

b

100 µm

Fig 7-5  (a) Light microscopy image of a specimen 10 days after membrane elevation. The implant is penetrating marginal residual bone and protruding into the sinus cavity. In the area close to the implant on the sinus floor where the membrane was elevated is the region of interest. (b) Close up of a. New bone formation is first seen on the existing residual bone close to the implant. (Toluidine blue and pyronin Y staining.)

1000 µm

b

a

collagen membrane (control group). The authors histologically analyzed the bone healing phases at 1, 2, 4, 6, and 8 weeks after sinus membrane elevation. They found new bone formation at the floor of the replaced bony window and at the elevated sinus membrane after 1 week. More new bone was seen on the surface of the elevated sinus membrane and the floor of the repositioned bony window than at the central area of the augmented sinus. They also showed that the replaceable bony window can serve as an autogenous barrier and new bone formation early in the healing phase is accelerated compared with using a collagen membrane placed over a bone graft. The authors also noted that bone formation was accelerated in sinuses that had undergone sinus membrane elevation without bone grafting (test group) compared with those that were augmented with additional xenogeneic bone graft (control group). It is also possible that the absence of additional grafting materials in the test group may reduce the healing time.59 In a clinical histologic study, Johansson et al23 found no differences when comparing lateral sinus floor elevation with and

500 µm

without autogenous bone grafts, regarding bone formation and bone-to-implant contacts.

Implant survival It has been clearly demonstrated by multiple authors and studies that creating a void space for blood clot formation below the elevated sinus can result in successful bone formation and implant survival.13–28,30,53,60,61 For instance, Cricchio et al18 reported that 96 maxillary sinus membrane elevation procedures and the simultaneous placement of 239 oxidized implants, without bone grafts or bone substitutes, resulted in predictable bone formation with a high implant survival rate of 98.7% during a follow-up period of 1 to 6 years after functional loading (Fig 7-6). Riben and Thor60 evaluated 83 implants placed during 53 sinus membrane elevation procedures and reported a survival rate of 94.3% after a mean follow-up time of 4.6 years. Ellegaard et al21 reported on sinus membrane elevation and simultaneous

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a

b

c

Fig 7-6  Intraoral radiographic showing new bone formation. (a) Preoperative. (b) Immediately after surgery. (c) Follow-up after 10 years.

implant therapy in 68 periodontally compromised patients. The 5-year follow-up results showed an implant survival rate of 90% despite compromised periodontal health in all of the patients and the fact that more than 60% of the patients were smokers at the time of implant surgery.21

Intrasinus responses Cricchio et al18 found intrasinus bone formation at all implant sites, which amounted to an average of 5.3 mm at 6 months after implant surgery. As evaluated in periapical radiographs, the amount of bone mineralization seemed to increase with time. In general, new bone was more easily distinguished at time points of 1 year and later than at earlier time points. There was a positive correlation between the amount of bone formation and the implant length in the maxillary sinus (ie, the higher the sinus membrane elevation, the more bone created). This is in line with the findings of Thor et al.61 They found more bone in sites with only 2.0 to 5.5 mm of residual bone than in sites with more bone and drew the conclusion that this was a result of the longer implant length present in sinuses with less residual bone. In a split-mouth design, Borges et al16 compared sinus membrane elevation without (test side) and with the use of autogenous bone graft. They found no statistically significant differences in new bone formation between the two groups. A significant positive correlation was found between the protruded implant length and bone gain. In addition, absence of sinusitis was correlated with implant survival.

Complications Sinus membrane perforation is an intraoperative complication observed with the graftless lateral sinus floor elevation technique. However, although an intact membrane is desirable, perforation does not seem to prevent bone formation. In a study on 239 implants placed in 96 elevation procedures, 6 minor perforations (< 5 mm) and 5 major perforations (> 5 mm) occurred. Of the 25 implants placed in the sinuses with

membrane perforation, only 1 failed, giving a survival rate of 96% for implants in perforated sites. The six minor perforations were left to heal, while the five major perforations were sutured to the adjacent bone wall.18 Bone formation was observed in all perforated sites, which has also been confirmed in experimental studies in which minor membrane perforation seemed to have no consequence on the formation of new bone.19,26 Early exposure of the cover screw is another complication observed with this technique, particularly in situations with minimal height of the residual crest, that could be further influenced by the chosen implant type and its marginal macro design. However, exposure of the cover screw does not seem to lead to increased risk for implant failure, although some marginal bone resorption can be expected.20

Conclusions The graftless lateral sinus floor elevation technique is a valid alternative to sinus floor augmentation when the residual subantral crest allows for firm implant stability at the time of elevation. The primary implant stability depends on the height, width, density, and type of implant used. Compared with sinus elevation technique using grafts of autogenous bone or a bone substitute either with a staged or direct placement of implants, the graftless technique is a less invasive and an overall costeffective technique.

References 1. Boyne PJ, James RA. Grafting the floor of the maxillary sinus with autogenous marrow and bone. J Oral Surg 1980;38:613–616. 2. Wood RM, Moore DL. Grafting of the maxillary sinus with intraorally harvested autogenous bone prior to implant placement. Int J Oral Maxillofac Implants 1988;3:209–214. 3. Kent JN, Block MS. Simultaneous maxillary sinus floor bone grafting and placement of hydroxylapatite-coated implants. J Oral Maxillofac Surg 1989;47:238–242.

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References

4. Raghoebar GM, Brouwer TJ, Reintsema H, Van Oort RP. Augmentation of the maxillary sinus floor with autogenous bone for the placement of endosseous implants: A preliminary report. J Oral Maxillofac Surg 1993;51:1198–1203. 5. Lundgren S, Moy P, Johansson C, Nilsson H. Augmentation of the maxillary sinus floor with particulated mandible: A histologic and histomorphometric study. Int J Oral Maxillofac Implants 1996;11:760–766. 6. Tulasne JF. Commentary on maxillary pre-implant rehabilitation. A study of 55 cases using autologous bone graft augmentation [in French]. Rev Stomatol Chir Maxillofac 1999;100:265–266. 7. Moy PK, Lundgren S, Holmes R. Histomorphometric analysis of grafting materials for maxillary sinus floor augmentation. J Oral Maxillofac Surg 1993;51:857–862. 8. Lindgren C, Sennerby L, Mordenfeld A, Hallman M. Clinical histology of microimplants placed in two different biomaterials. Int J Oral Maxillofac Implants 2009;24:1093–1100. 9. Hallman M, Sennerby L, Lundgren S. A clinical and histologic evaluation of implant integration in the posterior maxilla after sinus floor augmentation with autogenous bone, bovine hydroxylapatite, or a 20:80 mixture. Int J Oral Maxillofac Implants 2002;173:635–643. 10. Mordenfeld A, Lindgren C, Hallman M. Sinus floor augmentation using Straumann BoneCeramic and Bio-Oss in a split mouth design and later placement of implants: A 5-year report from a longitudinal study. Clin Implant Dent Relat Res 2016;18:926–936. 11. Lundgren S, Andersson S, Gualini F, Sennerby L. Bone reformation with sinus membrane elevation: A new surgical technique for maxillary sinus floor augmentation. Clin Implant Dent Relat Res 2004;6:165–173. 12. Hatano N, Sennerby L, Lundgren S. Maxillary sinus augmentation using sinus membrane elevation and peripheral venous blood for implant-supported rehabilitation of the atrophic posterior maxilla: Case series. Clin Implant Dent Relat Res 2007;9:150–155. 13. Brånemark PI, Adell R, Albrektsson T, Lekholm U, Lindström J, Rockler B. An experimental and clinical study of osseointegrated implants penetrating the nasal cavity and maxillary sinus. J Oral Maxillofac Surg 1984;42:497–505. 14. Ellegaard B, Kølsen-Petersen J, Baelum V. Implant therapy involving maxillary sinus lift in periodontally compromised patients. Clin Oral Implants Res 1997;8:305–315. 15. Balleri P, Veltri M, Nuti N, Ferrari M. Implant placement in combination with sinus membrane elevation without biomaterials: A 1-year study on 15 patients. Clin Implant Dent Relat Res 2012; 14:682–689. 16. Borges FL, Dias RO, Piattelli A, et al. Simultaneous sinus membrane elevation and dental implant placement without bone graft: A 6-month follow-up study. J Periodontol 2011;82:403–412. 17. Chen TW, Chang HS, Leung KW, Lai YL, Kao SY. Implant placement immediately after the lateral approach of the trap door window procedure to create a maxillary sinus lift without bone grafting: A 2-year retrospective evaluation of 47 implants in 33 patients. J Oral Maxillofac Surg 2007;65:2324–2328. 18. Cricchio G, Sennerby L, Lundgren S. Sinus bone formation and implant survival after sinus membrane elevation and implant placement: A 1- to 6-year follow-up study. Clin Oral Implants Res 2011;22:1200–1212. 19. Cricchio G, Palma VC, Faria PE, et al. Histological findings following the use of a space-making device for bone reformation and implant integration in the maxillary sinus of primates. Clin Implant Dent Relat Res 2009;11(suppl 1):e14–e22.

20. Cricchio G, Imburgia M, Sennerby L, Lundgren S. Immediate loading of implants placed simultaneously with sinus membrane elevation in the posterior atrophic maxilla: A two-year follow-up study on 10 patients. Clin Implant Dent Relat Res 2014;16:609– 617. 21. Ellegaard B, Baelum V, Kølsen-Petersen J. Non-grafted sinus implants in periodontally compromised patients: A time-to-event analysis. Clin Oral Implants Res 2006;17:156–164. 22. Jeong SM, Choi BH, Li J, Xuan F. A retrospective study of the effects of sinus membrane elevation on bone formation around implants placed in the maxillary sinus cavity. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009;107:364–368. 23. Johansson LA, Isaksson S, Bryington M, Dahlin C. Evaluation of bone regeneration after three different lateral sinus elevation procedures using micro-computed tomography of retrieved experimental implants and surrounding bone: A clinical, prospective, and randomized study. Int J Oral Maxillofac Implants 2013;28:579–586. 24. Jungner M, Cricchio G, Salata LA, et al. On the early mechanisms of bone formation after maxillary sinus membrane elevation: An experimental histological and immunohistochemical study. Clin Implant Dent Relat Res 2015;17:1092–1102. 25. Lin IC, Gonzalez AM, Chang HJ, Kao SY, Chen TW. A 5-year follow-up of 80 implants in 44 patients placed immediately after the lateral trap-door window procedure to accomplish maxillary sinus elevation without bone grafting. Int J Oral Maxillofac Implants 2011;26:1079–1086. 26. Palma VC, Magro-Filho O, de Oliveira JA, Lundgren S, Salata LA, Sennerby L. Bone reformation and implant integration following maxillary sinus membrane elevation: An experimental study in primates. Clin Implant Dent Relat Res 2006;8:11–24. 27. Scala A, Botticelli D, Faeda RS, Garcia Rangel Jr I, Américo de Oliveira J, Lang NP. Lack of influence of the Schneiderian membrane in forming new bone apical to implants simultaneously installed with sinus floor elevation: An experimental study in monkeys. Clin Oral Implants Res 2012;23:175–181. 28. Scala A, Botticelli D, Rangel Jr IG, de Oliveira JA, Okamoto R, Lang NP. Early healing after elevation of the maxillary sinus floor applying a lateral access: A histological study in monkeys. Clin Oral Implants Res 2010;21:1320–1326. 29. Schweikert M, Botticelli D, de Oliveira JA, Scala A, Salata LA, Lang NP. Use of a titanium device in lateral sinus floor elevation: An experimental study in monkeys. Clin Oral Implants Res 2012;23:100–105. 30. Sohn DS, Lee JS, Ahn MR, Shin HI. New bone formation in the maxillary sinus without bone grafts. Implant Dent 2008;17:321– 331. 31. Sohn DS, Moon JW, Moon KN, Cho SC, Kang PS. New bone formation in the maxillary sinus using only absorbable gelatin sponge. J Oral Maxillofac Surg 2010;68:1327– 1333. 32. Dahlin C, Linde A, Gottlow J, Nyman S. Healing of bone defects by guided tissue regeneration. Plast Reconstr Surg 1988;81:672– 676. 33. Dahlin C, Sennerby L, Lekholm U, Linde A, Nyman S. Generation of new bone around titanium implants using a membrane technique: An experimental study in rabbits. Int J Oral Maxillofac Implants 1989;4:19–25. 34. Dahlin C, Gottlow J, Linde A, Nyman S. Healing of maxillary and mandibular bone defects by a membrane technique: An experimental study in monkeys. Scand J Plast Reconstr Surg Hand Surg 1990;24:13–19.

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35. Seibert J, Nyman S. Localized ridge augmentation in dogs: A pilot study using membranes and hydroxyapatite. J Periodontol 1990;3:157–165. 36. Nyman S, Karring T. Regeneration of surgically removed buccal alveolar bone in dogs. J Periodontal Res 1979;14:86–92. 37. Nyman S. Bone regeneration using the principle of guided tissue regeneration. J Clin Periodontol 1991;18:494–498. 38. Karring T, Nyman S, Lindhe J. Healing following implantation of periodontitis affected roots into bone tissue. J Clin Periodontol 1980;7:96–105. 39. Karring T, Nyman S, Lindhe J, Sirirat M. Potentials for root resorption during periodontal healing. J Clin Periodontol 1984;11: 41–52. 40. Nyman S, Karring T, Lindhe J, Plantén S. Healing following implantation of periodontitis affected roots into gingival connective tissue. J Clin Periodontol 1980;7:394–401. 41. Nyman S, Gottlow J, Karring T, Lindhe J. The regenerative potential of the periodontal ligament. An experimental study in the monkey. J Clin Periodontol 1982;9:257–265. 42. Nyman S, Lindhe J, Karring T, Rylander H. New attachment following surgical treatment of human periodontal disease. J Clin Periodontol 1982;9:290–296. 43. Nyman S, Lindhe J, Karring T. Reattachment: New attachment. In: Lindhe J (ed). Textbook of Clinical Periodontology, ed 2. Philadelphia: Saunders, 1989:450–473. 44. Gottlow J, Nyman S, Karring T, Lindhe J. New attachment formation as the result of controlled tissue regeneration. J Clin Periodontol 1984;11:494–503. 45. Gottlow J, Nyman S, Lindhe J, Karring T, Wennström J. New attachment formation in the human periodontium by guided tissue regeneration. Case reports. J Clin Periodontol 1986;13:604– 616. 46. Urist MR, McLean FC. The local physiology of bone repair with particular reference to the process of new bone formation by induction. Am J Surg 1953;85:444–449. 47. Amler MH. The time sequence of tissue regeneration in human extraction wounds. Oral Surg Oral Med Oral Pathol 1969;27:309– 318. 48. Melcher AH. On the repair potential of periodontal tissues. J Periodontol 1976;47:256–260. 49. Lundgren S, Cricchio G, Hallman M, Jugner M, Rasmusson L, Sennerby L. Sinus floor elevation procedures to enable implant placement and integration: Techniques, biological aspects and clinical outcomes. Periodontol 2000 2017;73:103–120.

50. Engelke W, Deckwer I. Endoscopically controlled sinus augmentation. A preliminary report. Clin Oral Implants Res 1997:8:527– 531. 51. Nkenke E, Schlegel A, Schultze-Mosgau S, Neukam FW, Wiltfang J. The endoscopically controlled osteotome sinus floor elevation: A preliminary prospective study. Int J Oral Maxillofac Implants 2002;17:557–566. 52. Berengo M, Sivolella S, Majzoub Z, Cordioli G. Endoscopic evaluation of the bone-added osteotome sinus floor elevation procedure. Int J Oral Maxillofac Surg 2004;33:189–194. 53. Lundgren S, Cricchio G, Palma VC, Salata LA, Sennerby L. Sinus membrane elevation and simultaneous insertion of dental implants: A new surgical technique in maxillary sinus floor augmentation. Periodontol 2000 2008;47:193–205. 54. Boyne PJ. Analysis of performance of root-form endosseous implants placed in the maxillary sinus. J Long Term Eff Med Implants 1993;3:143–159. 55. Gruber R, Kandler B, Fuerst G, Fischer MB, Watzek G. Porcine sinus mucosa holds cells that respond to bone morphogenetic protein (BMP)-6 and BMP-7 with increased osteogenic differentiation in vitro. Clin Oral Implants Res 2004;15:575–580. 56. Kim MJ, Jung UW, Kim CS, et al. Maxillary sinus septa: Prevalence, height, location, and morphology. A reformatted computed tomography scan analysis. J Periodontol 2006;77:903–908. 57. Srouji S, Kizhner T, Ben David D, Riminucci M, Bianco P, Livne E. The Schneiderian membrane contains osteoprogenitor cells: In vivo and in vitro study. Calcif Tissue Int 2009;84:138–145. 58. Srouji S, Ben-David D, Lotan R, Riminucci M, Livne E, Bianco P. The innate osteogenic potential of the maxillary sinus (Schneiderian) membrane: An ectopic tissue transplant model simulating sinus lifting. Int J Oral Maxillofac Surg 2010;39:793–801. 59. Sohn DS, Kim WS, An KM, Song KJ, Lee JM, Mun YS. Comparative histomorphometric analysis of maxillary sinus augmentation with and without bone grafting in rabbit. Implant Dent 2010;19:259–270. 60. Riben C, Thor A. Follow-up of the sinus membrane elevation technique for maxillary sinus implants without the use of graft material. Clin Implant Dent Relat Res 2016;18:895–905. 61. Thor A, Sennerby L, Hirsch JM, Rasmusson L. Bone formation at the maxillary sinus floor following simultaneous elevation of the mucosal lining and implant installation without graft material: An evaluation of 20 patients treated with 44 Astra Tech implants. J Oral Maxillofac Surg 2007;65(7 suppl 1):64–72.

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CHAPTER 8

INTRAOPERATIVE COMPLICATIONS WITH THE LATERAL WINDOW TECHNIQUE Stephen S. Wallace, dds | Dennis P. Tarnow, dds | Tiziano Testori, md, dds

M

axillary sinus elevation surgery has become an integral part of the preprosthetic surgical armamentarium since its first presentation by Tatum in 1976 and its first publication by Boyne and James in 1980.1,2 It is now considered an invaluable tool as the most predictable of the preprosthetic site development or bone augmentation procedures that are currently employed.3 This high level of predictability has been demonstrated in two ways. The outcome measures of both procedural success and implant survival, as reported in evidence-based reviews, have been shown to be remarkably high.4–7 In addition, complications are infrequent and those that occur during and after sinus grafting procedures are usually localized and readily remedied.8–12 It should be noted that many of the complications that occur arise from an incorrect preoperative diagnosis. The recognition of preexisting sinus pathology and the many variations of internal sinus anatomy that exist are factors that should be incorporated into surgical decision making for every patient. Any list of potential intraoperative complications would be quite extensive given the broad scope of this surgical procedure. It is therefore important to understand that the relative frequency of most of these complications is quite low and most occur as a result of surgical difficulties encountered during the augmentation procedure. These may happen because of complex anatomy (eg, thin membranes; incomplete, thick, or convex lateral walls or crests; presence of septa; presence of large cysts), the choice of less predictable treatment options, inadequate preoperative systemic or local anatomical diagnosis, or operator error. Zijderveld et al12 reported on complications in 100 consecutive sinus elevations. Intraoperative complication rates were 11% membrane perforations and 2% bleeding. A recent systematic

review by Stacchi et al13 reported an overall membrane perforation rate of 20.1% and a bleeding incidence of 0.4% with no other complications reported. Clearly, the most common intraoperative complication reported is membrane perforation.12–14 Other less common intraoperative complications reported include bleeding, nerve injury, perforation or tear of buccal flap, perforation of the medial wall, damage to inferior orbit wall, fracture of alveolar ridge, inadvertent grafting of the nasal passage, obstruction of the ostium, damage to adjacent teeth, and inadequate graft placement.

Sinus Membrane Perforation Etiology and incidence Perforation of the sinus membrane is the most common intraoperative complication in sinus elevation surgery.12–14 The reported incidence in the literature varies from lows of 8.6% to a high of 56% with variations depending on the surgical technique used. Most experienced clinicians estimate their perforation rate to be approximately 20% to 25% when using conventional rotary instruments.15,16 In retrospective computed tomography (CT) scan studies performed at the New York University Department of Periodontology and Implant Dentistry, the perforation rate was shown to be related to membrane thickness and—to a lesser degree—to the presence of septa. The perforation rate was 41% when the membrane thickness was less than 1.5 mm and 16.6% when thickness was greater than or equal to 1.5 mm. In a separate study of 136 sinus elevations, the perforation rate was 44.2% when a septum was present and 35.7% when septa

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a

b

Fig 8-1  (a) An acute angle at the sinus floor of the anterior region. (b) Acute angle in the palatonasal recess at the junction of the alveolus and the medial wall.

were absent. A recent classification of maxillary sinus septa by Irinakis et al17 showed that the presence of interfering septa on preoperative cone beam CT (CBCT) scans was significantly associated with the occurrence of intrasurgical sinus membrane perforations. In a retrospective CT study by Cho et al,18 the perforation rate was also shown to be related to sinus width or, to be more specific, the angle made by the medial and lateral walls at the floor of the sinus. The perforation rates were 62.5% for the narrow anterior part of the sinus (angle < 30 degrees), 28.6% for the wider middle part of the sinus (angle 30 to 60 degrees), and 0% for the widest posterior portion (angle > 60 degrees) (Fig 8-1a). A recent CT study by Chan et al19 identified another angle made where the alveolus meets the medial wall of the sinus. This angle defines the shape of the palatonasal recess, and it must also be taken into consideration when elevating the sinus membrane from the medial wall (Fig 8-1b). If this angle is acute and is located within approximately 10 mm from the sinus floor (the area in which graft material is likely to be placed), care must be taken to keep the elevator in direct contact with the bone surface to avoid trapping, stretching, and tearing the membrane. Any of the following maneuvers that must be performed during sinus elevation surgery may place the sinus membrane at risk: •  Flap elevation (placing an elevator through a thin crest or lateral wall or through a previous oroantral fistula that has healed with soft tissue only) •  Preparation of the lateral window (specifically with rotary instruments) •  Elevation of the sinus membrane with hand instruments (narrow sinus, acute angles, thin membrane, and in close proximity to septa)

•  Placement of graft material (excessive pressure against elevated membrane)

Prevention A thorough knowledge of the three-dimensional (3D) anatomy of the sinus is essential if the perforation rate is to be kept to a minimum. A CT analysis will give information relating to the thickness of the crest and lateral walls; presence of discontinuities in the bony walls; width of the sinus; slope of the anterior sinus wall; membrane thickness; and the presence, size, and location of septa. Clinicians will also gain information relative to sinus health and patency of the osteiomeatal complex. This evaluation may also indicate the need for presurgical treatment that can avoid complications such as postoperative sinusitis and infection. Figure 8-2 shows a defect in the lateral sinus wall created during a failed sinus elevation. Likewise, crestal and lateral wall defects may be created during the extraction of teeth (Fig 8-3). It is possible that an aggressive full-thickness flap elevation may cause a tear in the membrane at this location. If a discontinuity is known to exist, a split-thickness flap dissection over the site will avoid a laceration of the sinus membrane. It should be noted that there will likely be multiple adhesions of the enjoined sinus membrane and periosteum complex along the perimeter of the existing defect. The authors advise that the tissue left behind following the split-thickness flap be trimmed close to the defect. A piezoelectric device should then be used to make a slightly larger window where possible, thereby allowing the membrane elevation to be performed with less membrane disruption by avoiding the adhesions around previous antrostomy. Having 3D knowledge of the existence, location, and anatomical form of any septa will also help determine the best location for the antrostomy to facilitate an uneventful membrane

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a Fig 8-2  Defect in lateral wall following failed sinus elevation.

a

b

Fig 8-3  (a) Cross-sectional CT scan showing a defect in the lateral wall. Note the acute angle in the palatonasal recess. (b) Cross-sectional CT scan showing a defect at the crest following extraction and healed oroantral fistula.

b

c

Fig 8-4  (a) Axial CBCT view of a septum close to the sinus floor. (b) Axial CBCT view of the same septum taken at a more coronal level. Note spine on left medial wall. (c) Clinical view of the septum.

Fig 8-5  Exceptionally wide septum.

elevation. A septum may initially be seen as a ridge crossing the sinus floor, but it will generally continue as a spine, reaching its highest extent on the medial wall. The 3D configuration of the septum can be visualized by viewing the axial slices sequentially in an apicocoronal direction (Fig 8-4). Septa can be quite large, but they can be circumvented with proper access (Fig

Fig 8-6  Multiple septa.

8-5). Multiple septa may be present, but this is uncommon (4% of cases) (Fig 8-6). In rare instances, the septum can be high enough to divide the sinus, at least at the augmentation level, into two separate compartments (see Fig 8-8c). Once inside the sinus, good access and good vision will greatly facilitate membrane elevation. The location of the

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Fig 8-7 (a) Trapezoidal window design following anterior wall. (b) The osteotomy is begun.

a

b Fig 8-8 (a) Panoramic CBCT showing multiple septa. (b) Axial view showing 16-mm height of anterior septum. (c) Window design exposing septum for membrane elevation.

a

b

c

lateral window and its size will affect the clinician’s ability to safely elevate the membrane. Having the window in a location that gives the best access to areas where instrument angulation—and hence membrane elevation—is difficult will have a profound effect on the operator’s ability to keep his or her hand instruments directly on the bone surface. Changes in instrument angulation are required to go across the floor and up the anterior and medial sinus walls. The anterior portion of the sinus can be very narrow, requiring coordination and visibility to prevent inadvertent membrane perforation. Many experienced clinicians feel that the ideal location for the window is 3 mm superior to the sinus floor and 3 mm distal to the sloping anterior wall, which allows a controlled membrane elevation to be accomplished while keeping the elevating instruments on the bone surface at all times (Fig 8-7). Zijderveld et al12 encountered 11 perforations; of these, 5 were in relation to septa and 4 were made when releasing the membrane anteriorly with poor visibility. The superior extent of a sloping anterior wall may require the window to be far from a traditional oval

or rectangular window. The shape of the window in this type of case should be trapezoidal with the superior osteotomy cut being longer and more anterior than the inferior osteotomy, always keeping the window within 3 mm of the anterior wall. The anterior sinus wall may then be viewed as an extension of the sinus floor, and the most predictable way to reach it during membrane reflection is by following the floor in an anterior and superior direction. When septa are known to be present, it is advisable to lengthen the window in the anteroposterior direction so that the window is located both anterior and posterior to the septum. This allows for a lateral to medial elevation of the membrane from both sides of the septum. It must be realized that it is extremely difficult to elevate a membrane from a sharp septum in a mesial to distal direction while keeping the elevator on the bony surface at all times. While making two separate windows has been proposed for this task, some explanation is required.12,20 It is likely that the two separate windows will be so decreased in size that access and vision will be made even more difficult with this technique.

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Fig 8-9  (a) Thin window outlined with a piezoelectric diamond insert. (b) Thin window with hinge or “island” has been elevated. (Reproduced with permission from Wallace et al.22)

a

In practice, creating one large window with improved access to both sides of the septum may be a more practical solution. A useful technique is to perform a complete osteotomy, which entails removal of the lateral window by osteoplasty or careful lifting and removal of the bony window. This will readily reveal the location of a septum and allow for its removal and subsequent membrane elevation from both sides (Fig 8-8). While enlarging the window will improve both access and visualization, it must be mentioned that a recent study by Avila-Ortiz et al21 has shown a significant inverse correlation between window size and vital bone formation. However, there is no evidence that this reported difference has any clinical significance with respect to the outcome measure of implant survival. Evolution in surgical protocols has resulted in two techniques for window preparation that most authors and clinicians have found to result in substantially decreased membrane perforation rates. These techniques involve the use of either piezoelectric surgical inserts or Dentium Advanced Sinus Kit (DASK) drills.

Use of piezoelectric surgery Piezoelectric inserts have proven to be safe near soft tissue thanks to their specifically designed low-frequency ultrasonic vibration. In a series of 100 consecutive sinus elevations using piezoelectric surgery, Wallace et al22 reported a membrane perforation rate of 7%. In this series, all perforations occurred when the elevation was completed via hand instruments; none occurred with the piezoelectric inserts. Blus et al23 reported 2 perforations in 53 sinus elevations for a 3.8% perforation rate using two different piezoelectric devices. In a report of 56 consecutive sinus elevations, Toscano et al24 reported a 3.6% perforation rate using piezoelectric surgery. A systematic review by Atieh et al14 showing comparable results regarding membrane perforations for both rotary and piezoelectric techniques is based on only four studies (one favoring each technique and two with comparable results), with operator experience being a greater factor in the results than the actual surgical technique. A recent meta-analysis by Geminiani et al25 reported that the use of alternative techniques like osteotomes (five studies), piezoelectric surgery (four studies), sonics (one study), and trephines (one study) did not reduce the incidence of intra- and postoperative complications. Conflicting data were reported by Barone

b

et al,26 who reported on 13 bilateral cases using piezoelectric surgery on one side and a rotary diamond window preparation on the other as a within-patient control. The perforation rate was 30% with piezoelectric surgery compared with 23% with the diamond bur control. The results of Barone and the reviews of Atieh14 and Geminiani25 are in contradiction to the other publications and the positive clinical experience with piezoelectric sinus elevation surgery at both the New York University Department of Periodontology and Implant Dentistry and the Columbia University Division of Periodontics over the past 12 years. The conflicting results may be due to differences in window antrostomy techniques used in the study. Piezoelectric surgical techniques may differ depending on the thickness and shape of the lateral sinus wall. If the window is thin, a diamond insert can be used to make a superior hinge or a free-floating bone island attached to the membrane22 (Fig 8-9). This is then elevated horizontally. If the lateral wall is thick, or if it becomes convex in the malar eminence area, the entire lateral wall in the window area can be eliminated via osteoplasty (Fig 8-10). The clinician will be looking directly at the sinus membrane, which can then be elevated with a combination of piezoelectric and manual elevators. Working directly against the membrane may seem to place it at risk for perforation, but the membrane may be even more susceptible to damage from the sharp edges of an elevated bony window. There has not yet been a histologic comparison of vital bone formation with these two techniques, but clinical evidence from the author’s 14-year experience with this technique does not show a difference in outcome as measured by implant survival rate. Stacchi et al27 compared the techniques of outlining the window via osteotomy with that of eliminating the window via osteoplasty with regard to membrane perforation rates. The lowest perforation rate of 4% was achieved with the osteoplasty reduction technique.

Use of DASK drilling The DASK technique employs a 6- or 8-mm-diameter domeshaped diamond drill to make the lateral window. The drill runs on a conventional implant motor at a speed of 800 to 1,200 rpm with internal irrigation. The window can be made to have a round shape by using an up-and-down motion, or it

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a

b

c

d

e

f

Fig 8-10  (a) Thick lateral wall with osteoplasty insert in place. (b) Reduction via osteoplasty. (c) Refining window. (d) Posterior superior alveolar (PSA) artery exposed. (e) Initial membrane elevator. (f) Elevator in place.

a

b

c

d

e

f

Fig 8-11  (a) An 8-mm DASK drill in place over lateral wall. (b) Removal of all but paper-thin layer of bone. (c) Dome-shaped elevator. (d) Domeshaped elevator in place. (e) Initial membrane elevation in progress. (f) Elevation completed up medial wall. (Reprinted with permission from Wallace et al.28)

can be made to any size or shape desired by moving the drill in a lateral direction. This technique results in a complete osteotomy (ie, total removal of window) in a safe manner as the large drill diameter and slow speed do not seem to cause the drag or stretching that is detrimental to membrane integrity. The drill appears to selectively cut bone, leaving the exposed membrane intact. Membrane elevation then begins with either

a motor- or hand-operated instrument that is similar in shape to the familiar trumpet-shaped piezoelectric elevator28 (Fig 8-11). This technique, described as a lateral bone-planing antrostomy, has been shown in a preliminary study by Lozada et al29 to result in a perforation rate of 5.6%. An additional study by Nishimoto et al presented 50 consecutive cases with a perforation rate 4% (unpublished data).

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Sinus Membrane Perforation

Graft containment An intact or repaired sinus membrane is essential for graft containment when a particulate autogenous or particulate bone replacement graft is used as a grafting material. Elevation of the sinus membrane helps to form a compartment in which the particulate graft material can be placed and confined. The elevated membrane forms the distal and superior walls of this compartment, while the bony sinus walls form the inferior (crest), anterior, medial, and lateral walls. Proussaefs et al30 showed that failure to contain the particulate graft due to membrane perforation will result in decreased bone formation (14.2% vs 33.6%) and a decreased implant survival rate (70% vs 100%). However, this is not necessarily the case when using block grafts.31,32 Should the sinus membrane be torn or perforated, the remaining membrane becomes more fragile, and more care and attention are required to complete the elevation. This is best accomplished by elevating the membrane around and away from the location of the perforation, thereby releasing tension on the perforated area of the membrane, as opposed to working directly in the weakened area of the perforation. It is still necessary to complete the sinus membrane elevation from the floor, medial, and anterior bony walls to allow the blood supply from the bony walls to vascularize the graft. Some clinicians opt to make a small repair to stabilize the damaged area before completing the elevation. If this is done, the repair should be evaluated for stability before placing the graft material.

Perforation repair Many techniques have been reported for repair of perforated or torn sinus membranes.33–38 The most common method of repairing a perforated sinus membrane is to use a bioabsorbable collagen barrier membrane as a patch. Other techniques involve the use of lamellar bone sheets, sutures (sometimes difficult) to close the perforation, or growth factor–enriched biologic barrier membranes such as leukocyte- and platelet-rich fibrin (L-PRF) (if blood is drawn at the time of surgery). Techniques are specifically chosen based on both the size and location of the perforation and the perceived need to stabilize the repair to keep it securely in place. Without stabilization, it is possible for the repair to shift in position or even be drawn up through the perforation into the body of the sinus during or after graft material placement. The choice of a specific repair material will be based on the previously mentioned factors as well as the physical characteristics of the material. Zijderveld et al12 and Shlomi et al38 preferred to use lamellar bone sheets for repairs, owing to the rigidity of the material. The following generalizations should be helpful when attempting repairs: •  Very small perforations may self-repair by membrane foldover or clot formation.

•  Large perforations will require large repairs for stability. •  Large repairs tend to tent superiorly when grafts are placed. •  Repair membranes placed near the lateral wall tend to shift medially when graft material is placed. •  Repair membranes that are soft and shapeless when wet are not ideal for large repairs.

Small It is not uncommon to perforate the sinus membrane with highspeed rotary instruments (eg, diamond burs) when performing a lateral window osteotomy. With careful membrane elevation, it is possible that these perforations will remain small. When the elevation is completed, the small perforation will either disappear in the folds of the elevated membrane or—more likely—self-repair with a small blood clot. In this type of case, a separate repair procedure is not indicated because the goal of graft material containment has been biologically achieved. If a very small perforation is still evident, it can be repaired with a biologic L-PRF fibrin repair (Intraspin, Intra-Lock), or it can be covered with a soft repair membrane such as CollaTape (Zimmer Biomet) or Gelfilm (Pfizer).

Large If the perforation is larger (ie, > 5 mm), the clinician should use a bioabsorbable membrane that retains its shape (eg, Bio-Gide Compressed, Geistlich Pharma), or better, remains stiff when wet such as BioMend (Zimmer Biomet Dental), OsseoGuard (Zimmer Biomet Dental), Dentium Collagen Membrane (Dentium), or similar membranes. The amount of stability that can be achieved with the repair is directly proportional to the amount of coverage over the intact portion of the sinus membrane. There is no reason to avoid making a large repair, creating a “new roof” over the graft material compartment with the repair membrane. It has been shown in animal studies that the elevated sinus membrane plays a secondary role in vascularization and bone formation within the graft.39–42 Figures 8-12 and 8-13 show two examples using a collagen repair membrane that forms a new roof in the damaged graft material compartment. Note that the sinus membrane has been elevated to the horizontal position, demonstrating sinus membrane release from the medial wall maximizing vascular supply to the graft.

Extreme As perforations become still larger (> 10 mm), nonstabilized repairs become unpredictable as they tend to shift medially while packing the graft material and may even rise upward, through the tear, with partial or complete loss of the graft material into the sinus cavity. This untoward event may lead to blockage of the ostium, postoperative sinusitis, or a sinus infection. A major loss of graft material containment may necessitate a reentry for removal of all-particulate graft material.

Difficult locations Repair techniques have been developed to address both larger tears and tears in difficult locations. If, after final membrane

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Fig 8-12  (a) Small perforation. (b) Nonstabilized collagen repair forming a new roof to confine the particulate graft.

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b Fig 8-13 (a and b) CBCT showing multiple septa on left. (c) Membrane elevation with perforation. (d) Collagen membrane in place.

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elevation, the perforation resides close to the lateral, superior aspect of the window preparation, it is quite common for the repair membrane to shift medially while the particulate graft material is being placed. This is due to the convex shape of the lateral wall in the malar eminence (ie, first molar) area, the upward tenting of the membrane when packing, and the likelihood that the repair membrane is not sufficiently wide to reach the medial wall. To counteract this shifting tendency, use a large membrane (typically an adjusted 20 × 30– or 30 × 40–mm size) and leave a portion of it outside the window folded in a superior direction and have it rest on the medial wall37 (Fig 8-14). This is a simple repair modification that will prevent any medial or superior shifting of the membrane with concomitant loss of graft material into the sinus proper. In some instances, further stabilization can be achieved by a combination of the previously described folding technique with external tacking and/or internal suturing. Again, the membrane elevation from the floor and walls must be completed to expose the bony walls and their vascular supply before completion of the repair. It must also be realized that the torn sinus membrane is very fragile and all suturing must be accomplished with small needles with minimal tension on the remaining membrane.

Most often, it is not possible to suture the tear completely closed. When this is the case, it is possible to use the sutures as struts upon which to rest the repair membrane. The sutures can course between two sections of torn membrane or between the membrane and small holes drilled in the lateral wall37 (Figs 8-15a and 8-15b). Figures 8-15c to 8-15e show evidence of radiographic and histologic success of the repair procedure after 9 months. In extreme situations, there may be insufficient membrane fragments remaining to retain a suture. At this point, a decision has to be made whether to abort the procedure or perform a more extensive repair. In the following case (Fig 8-16), the technique developed by Dr Pikos, sometimes referred to as the Pikos technique or the Loma Linda technique, was used along with additional stabilization tacks to create a complete container for placement of the graft material.35,37 A large 40 × 60–mm Bio-Gide membrane was pushed through the window to create an internal sinus pouch to hold and confine the graft material. The edges of the membrane were left outside the window to hold it in position. Two tacks were also required to keep the entire membrane from slipping into the sinus and through the perforation.

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Sinus Membrane Perforation

Fig 8-14  (a) Repair membrane from the torn sinus membrane on medial wall to holes stabilized by folding outside the window. (b) Graft material in place. (Reprinted with permission from Testori et al.37)

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Fig 8-15 (a) Suture repair from a torn sinus membrane to holes made in the lateral wall. (b) Membrane resting on suture struts with additional fold and tack stabilization. (c) Panoramic CT scan 9 months postoperative. (d) Cross-sectional CT view 9 months postoperative. (e) Histology after 9 months showing over 30% vital bone. (Parts a, b, c, and e reprinted with permission from Testori et al.37)

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d e

Bioabsorbable membranes The choice of a particular repair membrane will often be made by operator preference. General guidelines as to the type and location of the defect will be helpful in making this choice. In most cases, a membrane that retains its stiffness and shape when wet is advisable. This membrane will stabilize by contact with the remaining intact sinus membrane. With a Loma Linda–type repair, there is minimal or no remaining sinus membrane. In this case, a soft, moldable membrane is desired to reach an intimate

contact with the available bony walls and create the pouch-like space for the particulate graft material. Another repair technique involves the use of autogenous L-PRF membranes fabricated with the IntraSpin System and protocol. The patient’s blood is drawn and spun in a calibrated centrifuge, and a fibrin clot is then obtained by compression. The compressed fibrin clot is resilient, pliable, and tacky, and it can be cut or pieced together to make a biologically active repair membrane that is rich in platelets, leukocytes, growth factors, and cytokines.43–45 The prepared membranes have a

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a

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c Fig 8-16 (a) Large membrane tear. (b) The 40 × 60–mm BioGide membrane in position. (c) Bio-Oss graft in place. (d) Panoramic CBCT 6 months post­ operative. (e) CBCT cross section. (f) Histology after 6 months show­ ing new bone formation (purple). (Parts a to d and f reprinted with permission from Testori et al.37)

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f

strong adhesiveness, allowing them to join together to facilitate the repair of large perforations. The fibrin membranes have sufficient tensile strength that makes it convenient to join them together via suturing (Fig 8-17).

Effects of membrane perforation There is a relatively large literature base pertaining to implant survival following perforation and repair of the sinus membrane. Papers by Proussaefs,30 Jensen,46 and Khoury47 state that implant survival is negatively affected by membrane perforations. Hernández-Alfaro et al48 report that the implant survival rate is inversely proportional to the size of the membrane perforation. Other researchers present data showing that survival rates are not affected by perforations.37,49–51 In the authors’ clinical experience, perforations have not impacted implant survival when proper repairs are made and they remain intact throughout

e

the postsurgical healing period. As opposed to the Proussaefs study,30 a study by Froum et al52 reported the average percentage of vital bone as 26.3% ± 6.3% in repaired perforated sinuses versus 19.1% ± 6.3% in the nonperforated sinuses. While this difference was significant, there was not a significant difference in implant survival rates. The presence of a bioabsorbable repair membrane against the elevated sinus membrane does not impede the blood supply to the graft, as the reflected membrane does little to provide a blood supply. The Loma Linda pouch technique, however, presents a theoretic problem in that the repair membrane completely surrounds the graft and is likely at least to delay the vascularization of the graft from the lateral sinus walls. The vital bone formation in the two large pouch repairs presented previously was 30% and 32% by volume, respectively, which is considered a favorable result when using 100% xenograft.37 The Testori paper37 presents results from 20 cases with large perforation repairs. All patients had minimal postoperative symptoms and

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Sinus Membrane Perforation

Fig 8-17  (a) L-PRF as it is removed from centrifuge, prior to removing red blood cells. (b) Compressed to form an L-PRF membrane. (c) Multiple sinus membrane perforations. (d) Perforation biologically sealed. (Courtesy of Dr Robert J. Miller, Delray Beach, Florida.)

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Fig 8-18  (a) Split-thickness flap over previous window location. (b) Periosteum remains over window area. (c) Periosteum trimmed to window margins. (d) Elevation of conjoined periosteum and sinus membrane.

all cases showed clinical, histologic, and radiographic evidence of successful sinus elevation with 100% implant survival. If repair procedures do not appear to give a stable result, it may be necessary to abort the grafting procedure and allow the sinus membrane to heal. Becker et al53 in a study of 201 sinus elevations with 41 perforations (20%) reported that all but 4 (10%) could be repaired. A reasonable waiting time, confirmed by ear, nose, and throat (ENT) physicians, should be in the vicinity of 4 months (or 2 months for smaller perforations). Should this be the treatment of choice, the placement of a

bioabsorbable barrier membrane over the window may prevent soft tissue encleftation into the sinus cavity. It will most likely be necessary to raise a split-thickness reentry flap over the window owing to the likelihood that the periosteum may be joined to the newly formed membrane in the window area. The residual small amount of soft tissue is then elevated along with the membrane to create the roof of the graft material compartment. This can be covered with a bioabsorbable collagen barrier membrane to isolate this small amount of connective tissue from the graft (Fig 8-18).

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Fig 8-19  Blood supply to the lateral sinus wall.

Intraoperative Bleeding Etiology and incidence Intraoperative bleeding results from severing or damaging branches of the vascular supply to the lateral wall of the sinus and the surrounding soft tissues. This bleeding is usually minor and of relatively short duration, but in some instances, it can be profuse and difficult to control. Solar et al54 described the blood supply to the lateral wall of the maxillary sinus in cadaver specimens. It consists of the intraosseous and extraosseous branches of the posterior superior alveolar (PSA) artery, which form a double arterial arcade by anastomosing with the infraorbital artery (Fig 8-19). Bleeding may occur either from the soft tissue (ie, extraosseous branch) during flap elevation or directly from the lateral bony wall (ie, intraosseous branch) during preparation of the lateral window via rotary instrumentation. Rosano et al55 have described the intra- and extraosseous pathways of the PSA artery as well as its diameter in both a cadaver and CBCT study. The artery is present in 100% of cases and can be identified in the lateral wall in 47% of cases. The canal diameter was less than 1 mm in 55.3% of cases, 1 to 2 mm in 40.4% of cases, and 2 to 3 mm in 4.3% of cases. There is also the possibility of bleeding from the medial wall of the sinus if the posterior lateral nasal artery is damaged.56 The PSA, infraorbital, and posterior lateral nasal artery are all branches of the maxillary artery that provide a source for vascularization for the sinus graft.

Prevention Although bleeding does not occur on every occasion that the PSA artery is damaged, it seems prudent to use 3D planning as a means of avoiding an encounter with the internal arterial branch while performing the antrostomy whenever possible (Fig 8-20). Kang et al57 reported visualization of the PSA

Fig 8-20 PSA artery visualized in cross-sectional (paraxial) images of the lateral wall.

artery using CBCT in 64.3% of sinuses. A systematic review and meta-analysis by Varela-Centelles et al58 reported that the artery can be detected by CT and CBCT in at least some of the cross-sectional views of the lateral wall in 51% and 78% of cases, respectively. In some cases, the artery can be visualized within the lateral wall after elevation of the flap (Fig 8-21a). In many instances, a window can be made coronal to the location of the artery and the superior portion of the membrane elevation can be performed internally to the required height (Fig 8-21b). Again, it should be noted that the artery is not always located within the lateral wall. It can be located just internal or even external to the lateral wall and may pass in and out of the bony wall throughout its anteroposterior course in the lateral sinus wall.58 When located outside the lateral wall, it is susceptible to damage from both rotary and hand instruments. The external branch of the PSA artery may also be severed when making vertical releasing incisions for flap elevation. Once it is anticipated that the possibility of a bleeding complication exists, it is prudent to locate the position of the artery on the cross-sectional CT images and then use antrostomy instruments that can respect the integrity of vascular and other soft tissues while still creating the window in the ideal location for access to and elevation of the sinus membrane. If rotary instruments are used, in the authors’ experience, diamond burs are preferable to carbide burs because they are less likely to catch and tear the membrane. Piezoelectric surgery, the concept of ultrasonic bone surgery developed by Vercellotti and specifically adapted for sinus elevation surgery,59 provides a means of avoiding this complication almost entirely. Piezoelectric surgery uses low-frequency ultrasonic vibrations (range of 24 to 32 kHz for the various commercial systems) to perform cutting (osteotomy) and grinding (osteoplasty) procedures on bone. This low-frequency, selective cutting action provides safety for soft tissues because if used correctly, it is incapable of cutting blood vessels or disrupting the membrane. Piezoelectric surgery has been used successfully to avoid soft tissue complications (both vascular and neural) in

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Intraoperative Bleeding

Fig 8-21 (a) Artery visualized in the lateral wall after flap reflection. (b) Lateral window created coronal to the artery.

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Fig 8-22  (a) Large PSA artery. (b) Ligation of severed PSA artery.

numerous oral surgical procedures such as Le Fort osteotomies and mandibular sagittal split osteotomies.60,61 The piezoelectric surgery technique has seen widespread use in Europe for over 18 years, and today at least six piezoelectric surgery devices are available in the United States. Since the introduction of this technique to the United States in 2005, numerous clinicians have realized its advantages in sinus elevation surgery. Piezoelectric surgery has minimized bleeding episodes and membrane perforations during preparation of the lateral window. The selective cutting action (bone cutting only) allows the operator to dissect the PSA artery from the bony window area, leaving it completely intact (see Fig 8-10).

Treatment Many techniques exist to control vascular bleeding in sinus elevation surgery, as follows: •  Direct pressure on the bleeding point •  Use of a localized vasoconstrictor •  Bone wax •  Crushing the bone channel around the vessel (hemostat) •  Use of electrocautery (with care near membranes) •  Suturing of the vessel proximal to the bleeding point The use of a vasoconstrictor (1:50,000 epinephrine) is more effective in controlling soft tissue bleeding that may occur when making releasing incisions before elevation of the mucoperiosteal flap, and electrocautery is more effective in controlling a bone bleed from the cut lateral wall. It should be kept in mind that electrocautery may result in membrane damage when

used to control vascular bleeding from bone in the vicinity of the sinus membrane and should therefore be used with caution. Crushing the bleeding end of an intrabony vascular channel to compress the bone and vessel may be effective, but care must be taken to avoid membrane perforation by direct pressure. This can be accomplished by carefully releasing the sinus membrane immediately internal to the vessel (making the window slightly larger while diverting the blood flow with a suction tip to provide better vision) and then clamping the vessel with a hemostat for a period of a few minutes. Bleeding encountered during sinus elevation will usually be gently flowing in nature. In some instances, however, bleeding may be pulsating. In general, the appearance is worse than the severity of the condition. Bleeding, even of the pulsating variety, may stop spontaneously or after several minutes of direct pressure as a result of clot formation within the bone channel surrounding the artery. One technique that may be used is to have the surgical assistant place a high-volume, narrow-tipped evacuator close to the bleeding point to eliminate blood flow into the surgical field. Window preparation, membrane elevation, and grafting can be completed while diverting bleeding in this manner. The bleeding usually stops by the time the grafting is completed, and postoperative bleeding is usually not encountered after closure. Note that suction is used only to create adequate visibility. Suturing the vessel is another method sometimes employed to stop persistent bleeding. If access to the artery can be established adjacent to the bleeding point via osteoplasty, the vessel can be tied off with a resorbable suture. It may also be performed proactively in the event that a large-diameter vessel might be in a compromising location62 (Fig 8-22).

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Fig 8-23 (a) Location of the infraorbital foramen on a dry skull. (b) Infraorbital nerve dissection on a cadaver specimen.

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Fig 8-24  (a and b) Healthy sinus with patent ostium.

The following are best clinical practices: •  Obtain preoperative CT images to locate the vessel. •  Visualize the vessel clinically. •  Avoid the vessel, if appropriate, when designing the window. •  Use piezoelectric surgery to avoid trauma to the vessel. •  Have materials on hand to control bleeding (eg, electrocautery, local with 1:50,000 epinephrine, bone wax).

flap may be thin in the area of release and that the direction of the bone surface changes in the area of the malar eminence.

Injury to infraorbital nerve branches

Complications such as tears in the buccal flap and injury to the infraorbital nerve generally result from poor surgical technique.

Blunt or pressure injury to the infraorbital nerve may result during flap retraction. If the flap elevation extends superiorly to this position, the exit of the nerve from the bone can be visualized and retraction placed to avoid injury. It is also possible to sometimes injure this nerve during sharp dissection to release the flap for primary closure. The exit point of the nerve from the skull is just below the infraorbital notch (Fig 8-23). Locating this anatomical structure is crucial before performing these procedures, especially in patients with short faces.

Buccal flap tears

Mucous retention cysts

Buccal flap tears may result from attempts to release the flap to achieve primary closure. This is usually an unnecessary procedure in a typical sinus elevation. Because there is no change in external dimensions, the flap will close tension free without release. Loss of primary closure is more often a problem when simultaneous ridge augmentation is performed. Note that the

Mucous retention cysts are a fairly common occurrence in the maxillary sinus. In a tomographic study by Maestre-Ferrín et al,63 radiographic abnormalities were observed in 38% of cases, and 10% were mucous retention cysts. These cysts are not complication or contraindication for maxillary sinus elevation in themselves; they may become problematic if large when they

Other Complications

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Other Complications

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Fig 8-25  (a) Panoramic view of mucous retention cyst. (b) Paraxial view of mucous retention cyst. (c) Polyp arising from sinus wall.

are elevated during sinus grafting and block sinus drainage through the ostium. A preoperative CT analysis can help predict the likelihood of this adverse outcome. The presence of cysts is readily detected, and they can be classified into three categories: incidental (small volume); manageable at the time of surgery by aspiration; and complex, a large volume that must be treated via functional endoscopic sinus surgery (FESS) prior to sinus elevation surgery. Complex lesions are unlikely to respond to antibiotic or anti-inflammatory medications alone, so it is prudent to refer the patient to an ENT specialist to diagnose and treat these conditions prior to sinus augmentation surgery. A healthy sinus with a thin membrane and patent ostium is shown in Fig 8-24. Figure 8-25 radiographically demonstrates mucous retention cysts and a polyp. Mucous retention cysts and polyps can be differentiated from each other by form and location. Cysts are typically dome-shaped and arise from the sinus floor. Polyps typically have a pedunculated base and arise from the sinus walls. The presence of a yellow, serous fluid aspirant is pathognomonic for a sinus cyst. A generalization can be made that a cyst that occupies two-thirds of the total sinus volume is likely to block drainage through the ostium if it is elevated during the course of the procedure (Fig 8-26). If it is determined that elevation of the cyst will lead to a complication (eg, postoperative sinusitis due to blockage of sinus drainage), there are two distinct treatment

Fig 8-26 Large cyst is likely to block ostium (red arrow) when elevated for graft placement. If the ostium is divided into thirds, the cyst occupies two-thirds.

options. The first is FESS prior to sinus elevation to remove or marsupialize the cyst. A second option is to aspirate the contents of the cyst at the time of sinus elevation surgery. A lateral window is created by a complete osteotomy technique involving total removal of the window. Access is now present for the insertion of a 22-gauge needle through the sinus membrane and into the cyst to remove the contents via aspiration (Fig 8-27). Postoperative CBCT after sinus graft and implant placement reveals that the cyst has not reformed. A question remains as to whether intraoperative aspiration, which leaves the cyst lining in place, can be as effective as endoscopic marsupialization, which removes a majority or all of the cyst lining. A study by Hadar et al64 that followed up on endoscopic cyst removal showed reformation of the cyst in 3% of the cases. A study by Testori et al65 followed cases treated by intraoperative cyst aspiration for 1 to 3 years during maxillary sinus elevation. Only cysts bigger than 1 cm along the long axis and located in the area to be elevated were included in the study. The study included 15 patients with a mean follow-up time of 8 years, and no intra- or postoperative complications occurred. Postoperative disappearance of antral cysts was radiologically documented in 12 patients whose postoperative mucosal thickness ranged from 1 to 2 mm by CT scan analysis after a 6-month healing period (Fig 8-28). In the remaining three patients, a 6-month postoperative CT scan showed the

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Fig 8-27  (a) Cross-sectional view of cyst on sinus floor. (b) A 22-gauge needle is inserted through the sinus membrane into the cyst. (c) Typical yellow aspirant. (d) The 2-year postoperative CBCT cross section. (e) The 2-year postoperative panoramic CBCT scan.

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Fig 8-28  (a) Preoperative cross sections of sinus with dome-shaped cyst present. (b) Same sinus 1 year after simultaneous cyst aspiration, sinus elevation, and implant placement.

presence of residual antral cysts with a reduced size that were asymptomatic and did not affect implant survival. There was no occurrence of sinusitis after deflation and no new complications occurred intra- or postoperatively. The implants (31 total; 5 in a single-stage and 26 in a two-stage procedure) were placed 6 months after the sinus surgery with only 1 failure occurring 1 month after placement. At the conclusion of the study, the cumulative implant survival rate was 96.8%.

Inadvertent nasal floor grafting In cases of severe maxillary atrophy, it is possible to find the nasal passage in a crestal location where one would expect to find the maxillary sinus. The preoperative CT scan shows that there is no residual crestal bone and that the proposed restoration in cross section 97 (Fig 8-29a) will not be located below the sinus but beneath the nasal floor. The postoperative axial view shows that, in addition to a posterior sinus graft, the nasal passage has also been grafted (Fig 8-29b). In this particular case, no remedial therapy was advised, as the ostium remained patent and the nasolacrimal duct was undisturbed. This sinus

was grafted with allograft. The entire graft resorbed and the sinus regrafted 14 months later. Best clinical practices for avoiding intraoperative complications include the following: •  Perform presurgical diagnosis with CT scans to disclose difficult anatomy, vessel location, sinus pathology, and presence of cysts. •  Make the window in the best available location (3 mm from the floor and anterior wall). •  Use piezoelectric surgery or DASK for lateral osteotomy and initial membrane elevation. •  Elevate the membrane from lateral to medial, keeping the elevators on bone at all times. •  Repair perforations with collagen barrier membranes or biologic L-PRF membranes. •  Use a collagen repair membrane that remains rigid when wet to achieve the most stable repair. L-PRF is both resilient and adhesive. •  All repairs must be stable. •  Aspirate mucous retention cysts if elevation might block sinus drainage.

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References

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Fig 8-29  (a) Cross-sectional CBCT view indicating that the proposed restoration (slice 97) is not below the sinus. (b) Postoperative CBCT axial view showing the graft in both the sinus and the nasal floor.

Conclusion Postoperative edema, ecchymosis, mild to moderate discomfort, minor nosebleed, minor bleeding at the incision line, and mild congestion are within the scope of expected patient responses to this procedure. Some are caused by manipulation of the facial flap and others by the manipulation of the sinus membrane. A consensus conference by the Academy of Osseointegration3 concluded that the maxillary sinus elevation was the most predictable of the preprosthetic augmentation procedures. They further concluded that complications were relatively few and were generally localized and easily remedied. While this is for the most part true, it should be noted that improper handling of intraoperative complications may result in procedural failure or more serious adverse postoperative outcomes. There are two fundamental principles in achieving the positive results reported with maxillary sinus augmentation. The first is a thorough knowledge of the 3D anatomy of the sinus by the operating surgeon. This allows for strategic decision making in the multiple stages of this procedure. The second is to ensure that the sinus is healthy at the start of the procedure. The term sinus compliance refers to the intrinsic potential of recovery of the normal maxillary sinus homeostasis after sinus floor elevation. This depends on the baseline anatomophysiologic condition of the sinus. In other words, the better the starting condition (high compliance), the lower the risk of complication. It is appropriate to recognize pathology that may result in complications and, if possible, address it prior to sinus surgery.66 The prevention of an intraoperative complication suggests the advisability of obtaining preoperative CBCT analysis.

References 1. Tatum H. Lecture presented to the Alabama Implant Congress. 1976. 2. Boyne PJ, James RA. Grafting the floor of the maxillary sinus with autogenous marrow and bone. J Oral Surg 1980;38:613–616. 3. Aghaloo TL, Moy PK. Which hard tissue augmentation techniques are the most successful in furnishing bony support for implant placement? Int J Oral Maxillofac Implants 2007;22(suppl):49–70. 4. Pjetursson BE, Tan WC, Zwahlen M, Lang NP. A systematic review of the success of sinus floor elevation and survival of implants inserted in combination with sinus floor elevation. J Clin Periodontol 2008;35(8 suppl):216–240. 5. Del Fabbro M, Wallace SS, Testori T. Long-term implant survival in the grafted maxillary sinus: A systematic review. Int J Periodontics Restorative Dent 2013;33:773–783. 6. Wallace SS, Froum SJ. Effect of maxillary sinus augmentation on the survival of endosseous dental implants. A systematic review. Ann Periodontol 2003;8:328–343. 7. Del Fabbro M, Testori T, Francetti L, Weinstein R. Systematic review of survival rates for implants placed in the grafted maxillary sinus. Int J Periodontics Restorative Dent 2004;24:565–577. 8. Ziccardi VB, Betts NJ. Complications of maxillary sinus augmentation. In: Jensen OT (ed). The Sinus Bone Graft. Chicago: Quintessence, 1999:201–208. 9. Misch CE. Contemporary Implant Dentistry, ed 3. St Louis: Mosby Elsevier, 2008. 10. Pikos MA. Complications of maxillary sinus augmentation. In: Jensen OT (ed). The Sinus Bone Graft, ed 2. Chicago: Quintessence, 2006:103–114. 11. Wallace SS, Testori T. Complications in lateral window sinus elevation. Periodontology 2000 (in press). 12. Zijderveld SA, van den Bergh JP, Schulten EA, ten Bruggenkate CM. Anatomical and surgical findings and complications in 100 consecutive maxillary sinus floor elevations. J Oral Maxillofac Surg 2008;66:1426–1438.

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13. Stacchi C, Andolsek F, Berton F, Perinetti G, Navarra CO, Di Lenarda R. Intraoperative complications during sinus floor elevation with lateral approach: A systematic review. Int J Oral Maxillofac Implants 2017;32:e107–e118. 14. Atieh MA, Alsabeeha NH, Tawse-Smith A, Faggion CM Jr, Duncan WJ. Piezoelectric surgery vs rotary instruments for lateral maxillary sinus floor elevation: A systematic review of and metaanalysis of intra- and postoperative complications. Int J Oral Maxillofac Implants 2015;30:1262–1271. 15. Schwarz L, Schiebel V, Hof M, Ulm C, Watzek G, Pommer B. Risk factors of membrane perforation and postoperative complications in sinus floor elevation surgery: Review of 407 augmentation procedures. J Oral Maxillofac Surg 2015;73:1275–1282. 16. Kasabah S, Krug J, Simu˚ nek A, Lecaro MC. Can we predict maxillary sinus mucosa perforation? Acta Medica (Hradec Kralove) 2003;46;19–23. 17. Irinakis T, Dabuleanu V, Aldahlawi S. Complications during maxillary sinus augmentation associated with interfering septa: A new classification of septa. Open Dent J 2017;11:140–150. 18. Cho SC, Wallace SS, Froum SJ, Tarnow DP. Influence of anatomy on Schneiderian membrane perforations during sinus elevation surgery: Three-dimensional analysis. Pract Proced Aesthet Dent 2001;13:160–163. 19. Chan HL, Monje A, Suarez F, Benavides E, Wang HL. Palatonasal recess on medial wall of the maxillary sinus and clinical implications for sinus augmentation by the lateral approach. J Periodontol 2013;84:1087–1093. 20. Betts NJ, Miloro M. Modification of the sinus lift procedure for septa in the maxillary antrum. J Oral Maxillofac Surg 1994;52:332– 333. 21. Avila-Ortiz G, Wang HL, Galindo-Moreno P, Misch CE, Rudek I, Neiva R. Influence of lateral window dimensions on vital bone formation following maxillary sinus augmentation. Int J Oral Maxillofac Implants 2012;27:1230–1238. 22. Wallace SS, Mazor Z, Froum SJ, Cho SC, Tarnow DP. Schneiderian membrane perforation rate during sinus elevation using piezosurgery: Clinical results of 100 consecutive cases. Int J Periodontics Restorative Dent 2007;27:413–419. 23. Blus C, Szmukler-Moncler S, Salama M, Salama H, Garber D. Sinus bone grafting procedures using ultrasonic bone surgery: 5-year experience. Int J Periodontics Restorative Dent 2008; 28:221–229. 24. Toscano NJ, Holtzclaw D, Rosen PS. The effect of piezoelectric use on open sinus lift perforation: A retrospective evaluation of 56 consecutively treated cases from private practices. J Periodontol 2010;81:167–171. 25. Geminiani A, Tsigarida A, Chochlidakis K, Papaspyridakos PV, Feng C, Ercoli C. A meta-analysis of complications during sinus augmentation procedure. Quintessence Int 2017;48:231–240. 26. Barone A, Santini S, Marconcini S, Giacomelli L, Gherlone E, Covani U. Osteotomy and membrane elevation during the maxillary sinus augmentation procedure. A comparative study: Piezoelectric device vs. conventional rotary instruments. Clin Oral Implants Res 2008;19:511–515. 27. Stacchi C, Vercellotti T, Toschetti A, Speroni S, Salgarello S, Di Lenarda R. Intraoperative complications during sinus floor elevation using two different ultrasonic approaches: A two-center, randomized, controlled clinical trial. Clin Implant Dent Relat Res 2015;17(suppl 1):e117–e125. 28. Wallace SS, Tarnow DP, Froum SJ, et al. Maxillary sinus elevation by the lateral window approach: Evolution of technology and technqiue. J Evid Based Dent Pract 2012;12(3 suppl):161–171.

29. Lozada JL, Goodacre C, Al-Ardah AJ, Garbacea A. Lateral and crestal bone planing antrostomy: A simplified surgical procedure to reduce the incidence of membrane perforation during maxillary sinus augmentation procedures. J Prosthet Dent 2011; 105:147–153. 30. Proussaefs P, Lozada J, Kim J, Rohrer MD. Repair of the perforated sinus membrane with a resorbable collagen membrane: A human study. Int J Oral Maxillofac Implants 2004;19:413–420. 31. Triplett RG, Schow SR. Autologous bone grafts and endosseous implants: complementary techniques. J Oral Maxillofac Surg 1996;54:486–494. 32. Keller EE, Eckert SE, Tolman DE. Maxillary antral and nasal onestage inlay composite bone graft: Preliminary report on 30 recipient sites. J Oral Maxillofac Surg 1994;52:438–447. 33. Vlassis JM, Fugazzotto PA. A classification system for sinus membrane perforations during augmentation procedures with options for repair. J Periodontol 1999;70:692–699. 34. Fugazzotto PA, Vlassis JM. A simplified classification and repair system for sinus membrane perforations. J Periodontol 2003;74: 1534–1541. 35. Proussaefs A, Lozada J. The “Loma Linda pouch”: A technique for repairing the perforated sinus membrane. Int J Periodontics Restorative Dent 2003;23:593–597. 36. Wallace SS, Froum SJ, Tarnow DP. Use of barrier membranes in sinus augmentation. In: Jensen OT (ed). The Sinus Bone Graft, ed 2. Chicago: Quintessence, 2006:229–239. 37. Testori T, Wallace SS, Del Fabbro M, et al. Repair of large sinus membrane perforations using stabilized collagen barrier membranes: Surgical techniques with histologic, and radiographic evidence of success. Int J Periodontics Restorative Dent 2008;28:9–17. 38. Shlomi B, Horowitz I, Kahn A, Dodriyan A, Chaushu G. The effect of sinus membrane perforation and repair with Lambone sheet on the outcome of maxillary sinus floor augmentation: A radiographic assessment. Int J Oral Maxillofac Implants 2004;19:559– 562. 39. Hürzeler MB, Quiñones CR, Kirsch A, et al. Maxillary sinus augmentation using different grafting materials and dental implants in monkeys. Part 1. Evaluation of anorganic bovine bone-derived bone matrix. Clin Oral Implants Res 1997;8:476–486. 40. Haas R, Baron M, Donath K, Zechner W, Watzek G. Porous hydroxyapatite for grafting the maxillary sinus. Int J Oral Maxillofac Implants 2002;17:337–346. 41. Scala A, Lang NP, Velez JU, Favero R, Bengazi F, Botticelli D. Effects of a collagen membrane positioned between augmentation material and the sinus mucosa in the elevation of the maxillary sinus floor. An experimental study in sheep. Clin Oral Implants Res 2016;27:1454–1461. 42. Iida T, Carneiro Martins Neto E, Botticelli D, Apaza Alccayhuaman KA, Lang NP, Xavier SP. Influence of a collagen membrane positioned subjacent the sinus mucosa following the elevation of the maxillary sinus. A histomorphometric study in rabbits. Clin Oral Implants Res 2017;28:1567–1576. 43. Dohan Ehrenfest DM, Rasmusson L, Albrektsson T. Classification of platelet concentrates: From pure platelet-rich plasma (P-PRP) to leucocyte- and platelet-rich fibrin (L-PRF). Trends Biotechnol 2009;27:158–167. 44. Dohan Ehrenfest DM. How to optimize the preparation of leukocyte- and platelet-rich fibrin (L-PRF, Choukroun’s technique) clots and membranes: Introducing the PRF box. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010;110:275–278.

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References

45. Simonpieri A, Choukroun J, Del Corso M, Sammartino G, Dohan Ehrenfest DM. Simultaneous sinus-lift and implantation using microthreaded implants and leukocyte- and platelet-rich fibrin as sole grafting material: A six-year experience. Implant Dent 2011;20:2–12. 46. Jensen OT, Shulman LB, Block MS, Iacono VJ. Report of the Sinus Consensus Conference of 1996. Int J Oral Maxillofac Implants 1998;13(suppl):11–45. 47. Khoury F. Augmentation of the sinus floor with mandibular bone block and simultaneous implantation. Int J Oral Maxillofac Implants 1999;14:557–564. 48. Hernández-Alfaro F, Torradeflot MM, Marti C. Prevalence and management of Schneiderian membrane perforations during sinus-lift procedures. Clin Oral Implants Res 2008;19:91–98. 49. Ardekian L, Oved-Peleg E, Mactei EE, Peled M. The clinical significance of sinus membrane perforation during augmentation of the maxillary sinus. J Oral Maxillofac Surg 2006;64:277–282. 50. Karabuda C, Arisan V, Özyuvaci H. Effects of sinus membrane perforation on the success of dental implants placed in the augmented sinus. J Periodontol 2006;77:1991–1997. 51. Schwartz-Arad D, Herzberg R, Dolev E. The prevalence of surgical complications of the sinus graft procedure and their impact on implant survival. J Periodontol 2004;75:511–516. 52. Froum SJ, Khouly I, Favero G, Cho SC. Effect of maxillary sinus membrane perforation on vital bone formation and implant survival: A retrospective study. J Periodontol 2013;84:1094–1099. 53. Becker ST, Terheyden H, Steinriede A, Behrens E, Springer I, Wiltfang J. Prospective observation of 41 perforations of the Schneiderian membrane during sinus floor elevation. Clin Oral Implants Res 2008;19:1285–1289. 54. Solar P, Geyerhofer U, Traxler H, Windish A, Ulm C, Watzak G. Blood supply to the maxillary sinus relevant to sinus floor elevation procedures. Clin Oral Implants Res 1999;10:34–44. 55. Rosano G, Taschieri S, Gaudy JF, Weinstein T, Del Fabbro M. Maxillary sinus vascular anatomy and its relation to sinus lift surgery. Clin Oral Implants Res 2011;22:711–715. 56. Flanagan D. Arterial supply of maxillary sinus and potential for bleeding complication during lateral approach sinus elevation. Implant Dent 2005;14:336–338.

57. Kang SJ, Shin SI, Herr Y, Kwon YH, Kim GT, Chung JH. Anatomical structures in the maxillary sinus related to lateral sinus elevation: A cone beam computed tomographic analysis. Clin Oral Implants Res 2013;24(suppl A100):75–81. 58. Varela-Centelles P, Loira-Gago M, Seoane-Romero JM, Takkouche B, Monteiro L, Seoane J. Detection of the posterior superior alveolar artery in the lateral sinus wall using computed tomography/cone beam computed tomography: A prevalence metaanalysis study and systematic review. Int J Oral Maxillofac Surg 2015;44:1405–1410. 59. Vercellotti T, De Paoli S, Nevins M. The piezoelectric bony window osteotomy and sinus membrane elevation: Introduction of a new technique for simplification of the sinus augmentation procedure. Int J Periodontics Restorative Dent 2001;21:561–567. 60. Beziat JL, Vercellotti T, Gleizal A. What is Piezosurgery? Two-years experience in craniomaxillofacial surgery [in French]. Rev Stomatol Chir Maxillofac 2007;108:101–107. 61. Geha HJ, Gleizal AM, Beziat JL. Sensitivity of the inferior lip and chin following mandibular bilateral sagittal split osteotomy using Piezosurgery. Plast Reconstr Surg 2006;118:1598–1607. 62. Testori T, Rosano G, Taschieri S, Del Fabbro M. Ligation of an unusually large vessel during maxillary sinus floor augmentation. A case report. Eur J Oral Implantol 2010;3:255–258. 63. Maestre-Ferrín L, Galán-Gil S, Carrillo-García C, Peñarrocha-­ Diago M. Radiographic findings in the maxillary sinus: Comparison of panoramic radiography with computed tomography. Int J Oral Maxillofac Implants 2011;26:341–346. 64. Hadar T, Shvero J, Nageris BI, Yaniv E. Mucus retention cyst of the maxillary sinus: The endoscopic approach. Br J Oral Maxillofac Surg 2000;38:227–229. 65. Testori T, Mantovani M, Wallace SS, et al. Maxillary sinus elevation with simultaneous cyst deflation: A clinical prospective study. Int J Periodontics Restorative Dent (in press). 66. Torretta S, Mantovani M, Testori T, Cappadona M, Pignataro L. Importance of ENT assessment in stratifying candidates for sinus floor elevation: A prospective clinical study. Clin Oral Implants Res 2013;24(suppl A100):57–62.

Portions of this chapter, including text and figures, have been reprinted with permission from Wallace SS, Testori T. Complications in lateral window sinus elevation surgery. In: Froum SJ (ed). Dental Implant Complications: Etiology, Prevention, and Treatment, ed 2. Hoboken, NJ: John Wiley & Sons:396–426.

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9  TRANSCRESTAL WINDOW SURGICAL TECHNIQUE FOR SINUS ELEVATION

CHAPTER 9

TRANSCRESTAL WINDOW SURGICAL TECHNIQUE FOR SINUS ELEVATION Michael S. Block, DMD

B

one availability is the key to successful placement of endosseous implants in the posterior maxilla. When the vertical height of the bone between the maxillary sinus and the alveolar crest is limited, increasing bone height by grafting will provide support for implants and prosthetic restoration. Patients who require a maxillary molar extraction will often want this tooth replaced with a dental implant, and this should be accomplished with minimal chair time, minimal pain, and minimal loss of time from work. Clinicians and patients of course also want to avoid complications. Perforation of the maxillary sinus membrane can occur secondary to the tethering of the membrane to the sinus floor for iatrogenic reasons or in the locations of previous root tips, septa, or thin membranes. By elevating the bone in the furcation region at the time of tooth extraction, an appropriate amount of vertical bone height can be established to allow a simple and low-morbidity second intrusion procedure to place implants of sufficient length without using a lateral window approach. This chapter focuses on how to manage the maxillary molar site at the time of tooth removal to place an implant either at the same time or delayed after the site heals. A technique using a precise osteotomy within the maxillary molar socket allows the clinician to mobilize a segment of bone and superiorly raise it to provide increased alveolar bone height using grafting.1–3 This eliminates the need for lateral window surgery.

Treatment Strategies A patient presents with a maxillary molar in need of extraction secondary to loss of structure, root fracture, failed endodontic therapy, or bone loss. To place an implant, there must be sufficient bone to stabilize the implant in position. After determination of the patient’s medical history, pretreatment evaluation

begins with a cone beam computed tomography (CBCT) scan. Two-dimensional radiographs are not sufficient to determine the amount of bone available because they do not show the degree of sinus membrane thickening or the presence of other intrasinus pathology. The sinus is inspected on the CBCT scan. It is common to have sinus membrane thickening in patients with maxillary molar problems.4 If the sinus membrane thickness is limited to less than 6 mm, then sinus elevation is performed. If it is greater than 6 mm, then a consultation is done for treatment of a potential sinus infection. However, if sinus membrane thickness is associated with an unhealthy molar, the tooth is removed and the socket grafted, followed by a new CBCT scan 3 months postoperatively. In many patients, the sinus membrane thickness decreases after tooth extraction.4 Patients who smoke cigarettes are staged with tooth extraction and grafting the sockets, but without immediate sinus elevation. If purulent exudate is present, then the procedure is staged with tooth extraction followed by sinus elevation after resolution of the infection. Patients with a history of radiation to the mouth, autoimmune therapy, steroid use, uncontrolled diabetes, or other systemic disease that would adversely affect bone healing are staged with straightforward socket grafting without sinus elevation at the time of tooth extraction. Reconstructed cross-sectional views from the CBCT scan show the bone height around each molar root. Roots often extend above the sinus floor. The furcation can protrude within the sinus or exist at the level of the floor with minimal bone, if any, apical to the tooth root (Figs 9-1 and 9-2). The amount of available furcation bone will need to be measured within the furcal region. Bone thickness in the furcation is often much less than what is needed for implant stability (Fig 9-3). Even if root sockets are grafted, there will still be a deficit of vertical bone within the center of the planned implant site due to interradicular pneumatization. After the radiographic evaluation is made, the surgeon can develop a treatment plan.

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Treatment Options

a

b

c

Fig 9-1  (a) Cross-sectional reconstruction of maxillary left first molar showing buccal and palatal roots very close to the sinus floor. (b) Cross-sectional reconstruction of site in part a showing bone formation following intrusion of furcation bone. (c) Cross-sectional reconstruction of site showing implant placement with additional sinus floor elevation through implant preparation site.

8.01 mm

a

b

c

Fig 9-2 (a) Cross-sectional reconstruction of maxillary left second molar with apex of root through the sinus floor adjacent to the sinus membrane. (b) Cross-­ sectional reconstruction of edentulous site of maxillary first molar showing 3 mm bone thickness. (c) Cross-sectional reconstruction of site following removal of tooth and grafting socket with allograft. (d) Cross-sectional reconstruction of site following transcrestal window method to intrude bone and membrane with defect grafting. There is now 10 mm of bone thickness available for implant placement.

10.01 mm

d

Treatment Options Presence of purulent drainage and gross loss of gingiva may require tooth extraction with a delayed grafting approach. If necessary, the tooth can be removed allowing resolution of the infection. The surgeon can reenter the site (usually 4 to 6 weeks later) and elevate the furcation bone if needed. Figure 9-4 shows

an extraction site with a small oroantral fistula and sinus congestion 2 weeks after extraction of a maxillary molar. This site was allowed 2 months for resolution of the sinus problems prior to crestal elevation of the floor and grafting. The following scenarios may be encountered when the clinician is considering removing a maxillary molar and replacing it with an implant-supported restoration.

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a

b

c

8.71 mm

d

e

f

Fig 9-3  (a) CBCT of a 35-year-old woman with a nonrestorable maxillary left first molar with 5 mm of bone in the furcation. (b) After exposing the tooth and crest sites, the first molar was removed. A piezoelectric surgery cutting tip was used to create osteotomies connecting the three root sites. (c) A blunt-tipped osteotome was used to elevate the furcation bone 5 mm. Xenograft was placed into the apical region and allograft in the crestal portion of the socket. (d) After placing the graft, the incision was closed by advancing the buccal mucosa. (e) Cross-sectional view immediately after surgery. The left cross section shows almost 9 mm of bone thickness at the first molar location. (f) View 5 months after placement of the definitive restoration showing bone to the apical region of the implants.

a

b

c

Fig 9-4  (a) Panoramic radiograph showing loss of right first molar with severe sinus congestion following removal of the tooth by a general dentist. (b) Cross section showing minimal bone on the ridge with acute sinusitis. The patient had a patent oroantral fistula immediately after tooth extraction, which closed with antibiotics and decongestants. (c) Cross section of same site 6 weeks after initial presentation with resolution of the sinus congestion.

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Treatment Options

e

d

f

9 mm

g

h

i

Fig 9-4  (cont) (d) This view shows the crest after elevation of a flap and creation of osteotomies through the floor to form a rectangular piece of bone attached to the sinus membrane. (e) The mobilized crestal window was gently tapped superiorly to allow 9 mm of graft placement. (f) The graft was placed carefully, avoiding excessive pressure on the elevated segment of crestal bone. (g) The incisions were closed without tension. (h and i) The radiographs show 9 mm of bone height awaiting implant placement.

Greater than 9 mm of bone within the furcation The patient presents with a broken down, nonrestorable molar with at least 9 mm of bone thickness in the furcation. For these patients, the surgical protocol includes sulcular incisions with flap elevation as necessary and extraction of the tooth preserving the buccal, furcal, and palatal bone. This may require the use of piezoelectric surgery periotome-style tips to separate the tooth from the bone or the use of a drill to section the tooth for extraction of each root separately. The goal is preservation of the bone (Fig 9-5). The implant should be chosen to provide stability after placement and to avoid excessive sinus perforation. The center of the implant should be equidistant from the adjacent teeth. The facial-palatal position should allow for screw retention or cementation as determined by the treating team. It is important to maintain at least 2 mm of buccal bone thickness after the implant has been placed. Navigation methods can be used to provide increased precision and accuracy of implant placement.5,6 Initiation of the implant site can be accomplished by a round or a tapered bur. The subsequent preparation should be performed preserving as much bone as possible. Drills that compact bone rather than remove it may be useful to result

in a well-defined osteotomy (see chapter 10). The implant is placed 0.5 to 1.0 mm subcrestally to allow for appropriate bone coverage and emergence. The root sockets can be grafted with allograft per clinician preference. Healing abutments are used to allow for gingival healing without the need for exposure surgery (see Fig 9-5). If the sinus membrane is perforated during implant preparation, the socket can be grafted and allowed to heal in preparation for delayed implant placement. This may avoid problems from sinus irritation.

7 to 9 mm of bone within the furcation In this situation, there will be sufficient bone after grafting the root sockets for implant placement combined with transcrestal elevation of the bone at the time of implant placement. If the implant site is prepared in the center of the extraction site at the time of tooth removal, the sinus membrane will be encountered. Because of the relatively small area of the furcation, it will be difficult to elevate the membrane and still have sufficient bone for implant stability. In this situation, the extraction site is grafted and an implant is placed after 4 months with transcrestal elevation of the bone, now sufficient to stabilize the implant.

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a

Fig 9-5 (a) Intraoral photograph of maxillary first molar with fractured distal cusp with the fracture within the bone. The tooth was not restorable. (b) Cross section of tooth showing 9 mm of bone available for implant placement. (c) Navigation planning was performed prior to tooth extraction with a virtual implant placed in the ideal position. (d) The tooth was removed with preservation of the buccal and interseptal bone. The site was prepared using reverse-­ turning drills to compact bone rather than removing it (see chapter 10). (e) The implant was placed into the prepared site with excellent stability. (f) Postoperative cross section showing appropriate placement of the implant. The healing abutment was removed and bone trimmed to allow for reseating of the abutment.

b

c

d

e

The tooth is removed and allograft is placed within the socket. A buccal flap is advanced to cover at least the buccal root sockets. A small piece of a fast-resorbing collagen material is placed over the palatal root socket to facilitate soft tissue migration. After 4 months of healing, there will be 7 mm of bone. It is important to determine the amount of bone within the furcation prior to surgery. If the surgeon extracts the tooth and places allograft within the root sockets, there may be insufficient bone in the furcation region. Though the surgeon may elect to place

f

an implant into one of the root sockets, such as the palatal root socket, this will lead to nonideal implant placement with resultant compromise in the restoration (Fig 9-6).

5 to 7 mm of bone within the furcation The surgical placement of the implant involves navigated implant site preparation to within 1 mm of the sinus floor.

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Treatment Options

5.4 mm

7.2 mm

a

b

d

10.5 mm

c

e

5.4 mm

Fig 9-6  (a) Cross section showing 5.4 mm of bone within the furcation. (b) Panoramic reconstruction of CBCT scan showing the maxillary right first molar prior to extraction. Note the furcation region, which has less vertical bone availability than the root sites. (c) Cross section radiograph after grafting the sockets with allograft. (d) This panoramic reconstruction shows the grafted socket with less bone in the furcation site. The furcation site is the ideal location for an implant but does not have as much vertical bone as the palatal socket. (e) Restored implant that was placed in the region of available bone. Note that this implant would have been more ideally located slightly mesially, which would have placed it within the furcation region. Regardless, it has functioned well for 3 years.

a

b

c

Fig 9-7  (a) Preoperative panoramic reconstruction showing maxillary left first and second molars in need of extraction, grafting, and later implant placement. (b and c) Cross sections showing 7 mm of bone in furcation in the first and second molars.

This preparation is taken to the regular diameter of the drills of the implant diameter chosen, which is usually 5 to 6 mm in diameter. A round osteotome is used to upfracture the floor of the sinus. Graft material is placed into the preparation site and gently elevated using the osteotome to a depth consistent with final implant length. The implant and healing abutment are placed. This procedure is well tolerated by patients with minimal downtime and minimal morbidity (Fig 9-7).

Less than 5 mm of bone within the furcation Invagination of the sinus into the furcation of nonrestorable maxillary molars may result in less than 5 mm of bone available in the central fossa region of the proposed implant site. If the molar with less than 5 mm of bone is removed and the root sockets are grafted, there will still be a lack of vertical bone for

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d

e

g

f

h

i

Fig 9-7  (cont) (d) Cross section of first molar site showing 7 mm bone height. (e) Panoramic radiograph showing the two molar sites with 7 to 8 mm bone height. (f) A navigation plan was developed 3 months after the extractions and graft to place 9-mmlong implants with sinus elevation from the crestal approach with osteotomes. Allograft was planned as the graft. (g and h) Cross sections of the implants in the first molar and second molar sites, respectively. The allograft is minimally visible at the apex as expected. (i) Postoperative panoramic radiograph showing implants in correct positions prior to restoration.

simultaneous implant placement and sinus elevation methods through the implant preparation site.

The Furcation Intrusion Procedure Jensen et al1 reported a technique that used osteotomes to create an island of bone within the maxillary molar extraction socket. This mobilized bone was gently tapped to raise it superiorly, creating increased vertical height of the alveolar bone in the molar extraction site 4 months later. No grafts were placed and patients had implants placed after bone had formed. Modification of the technique includes an osteotomy created with piezoelectric surgery serrated blades of the bone bordered by the root sockets.2,3 This technique eliminates the need for lateral window surgery because the resultant grafted vertical bone thickness results in at least 5 mm, and often 9 mm in height.

The concept is a relatively low-morbidity method to restore the bone height in the entire maxillary molar site. When the tooth in need of removal has limited vertical alveolar height of bone present in the furcation area prior to tooth extraction, the plan is to intrude the furcation bone into the sinus. By intentionally intruding the bone superiorly and grafting the deepened socket, the result is sufficient bone for routine implant placement or to provide bone height that can be elevated again when the implant is placed.

Treatment steps Local infiltration is used for anesthesia. A sulcular incision is made with vertical release incisions while avoiding the papilla on the adjacent teeth. A flap is elevated only on the facial aspect to expose the junction of the tooth and labial bone. A periosteal

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Transcrestal Window Method for Sites with No Grafting

release is performed to allow for passive flap rotation to cover the mesial and distal buccal root sockets. The tooth is removed with the aid of a piezoelectric surgery unit with a periotome tip to preserve the bone. If necessary, the tooth is sectioned with a small fissure bur with care to avoid loss of the labial cortical bone. After the tooth roots have been removed, granulation tissue is carefully removed while taking care to avoid damage to the sinus membrane if it is visible through the root sockets (see Fig 9-3). The piezoelectric surgery unit is used to create precise osteotomies. The serrated tip is used to gently cut through the bone between the two buccal root sockets and then connect the cuts to the palatal root socket. Care is taken to cut through the bone but not through the membrane. Loss of resistance is used to limit the depth of the cuts. The bone segment bordered by the root sockets should be mobile at this point of the procedure. If not, the osteotomy cuts are checked and additional cutting is performed, taking care to avoid perforating the membrane. An osteotome with a flat tip is used to very gently superiorly raise the bone segment 4 to 5 mm, resulting in a socket deeper than 7 mm. The vertical bone height can be raised further when the implant is placed through a simple implant site preparation sinus elevation.3 After the segment of bone is mobilized and gently elevated, the graft is placed. After placement of the initial layer of the graft, the wide flat-surfaced osteotome can be used to gently elevate the graft into the elevated area. To avoid membrane perforations, no effort is made to peripherally elevate the membrane. Because the root sockets are simultaneously grafted, the result will be a flat but thickened alveolus with adequate dimensions for implant placement. The graft material used may be allograft alone, xenograft alone, allograft mixed with recombinant bone morphogenetic protein, or xenograft in the deep portion with allograft in the crestal alveolus. However, evidence-based discrimination between graft materials has not been adequately evaluated at this time. The gingival flap is closed with minimal tension. If the flap is difficult to advance to the palate, a piece of fast-resorbing collagen is placed over the palatal root socket, which has been grafted with an osteoconductive material with the edge of the flap covering the buccal root sockets. The patient is given sinus precautions, instructions, and antibiotics, and he or she is advised to spray the nose with a decongestant aerosol to maintain the opening of the os for drainage. Once the site heals, the patient can usually have implants placed with intra-alveolar sinus elevation for another 3 to 4 mm of bone height development. There might also be sufficient height for routine implant placement.

Evidence-based results Jensen et  al1 reported their experiences with intentional intrusion of the interradicular bone after the extraction of 20 maxillary molars. They used straight osteotomes to create the osteotomies and elevated the bone with a round osteotome using

gentle tapping. When found, sinus perforations were covered with oxidized cellulose. After 4 months of healing, implants were placed and later restored successfully. The technique increased vertical dimension approximately 4 mm on average as measured by periapical radiographs, allowing placement of longer endosseous implants. In Block’s report,2 there were 10 consecutive patients treated with this method who had vertical height measurements made using cross-sectional CBCT images. The furcations of the molars were identified and vertical bone height was measured. Measurements were made immediately after intrusion of the bone at the time of tooth extraction and 3 months after the procedure to verify bone height before implant placement. Patients had a mean bone height of 4.4 mm before extraction, with a standard deviation (SD) of 1.3 mm. Immediately after extraction, the mean bone height was 9.3 mm, SD 2.1 mm. After 3 months, mean bone height was 8.7 mm, SD 2.4 mm. Implant lengths also were recorded. Five patients had 9-mm-long implants, one patient had a 10-mm-long implant, and four patients had 11-mm-long implants placed and restored. All patients required small secondary sinus floor elevation through the implant preparation site.2,3 No implants were lost, and no patients required lateral window approaches for sinus augmentation. Implant placement follow-up ranged from 6 months to 2 years. No long-term CBCT scans were taken to avoid excessive radiation to the patient.

Transcrestal Window Method for Sites with No Grafting The transcrestal osteotome method can be used to place maxillary implants and to increase vertical bone thickness. This method avoids extensive membrane manipulation and may have a lower rate of complications.7 However, most crestal techniques involve removal of bone to reach the sinus floor, which is then elevated (Fig 9-8). The concept discussed in the following section does not remove crestal bone but instead creates an island of bone vascularized by the sinus membrane, which is elevated into the sinus as a new floor. The crestal alveolar defect is then filled in with crestal grafting.

Bone thickness If the vertical bone thickness is 6 mm or greater, then the sinus floor is usually elevated from the crestal approach through the implant preparation site. The implant chosen is usually 3 to 4 mm longer than the height of the residual bone. If the bone thickness is 6 mm, then a 9- to 10-mm-long implant is used. If the floor thickness is 8 mm, then an 11- to 12-mm-long implant is chosen.

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12.8 mm 10 mm 4.8 mm

a

b

c

9.90 mm

d

e

f

g

Fig 9-8  (a) Preoperative panoramic radiograph showing missing maxillary left first molar. Note the septa within the site. (b) Cross section of preoperative site. Note the residual height of 4.8 mm, the intended height of 10 mm, and the width measurement of 12.8 mm. (c and d) These radiographs show the creation of a dome with xenograft placed through a transcrestal approach. Drills with stops were used from 4 mm to a 4.3-mm diameter. The osteotome was used to fracture the floor. Xenograft was placed, and the osteotome was gently tapped to elevate the segment to 10 mm. Additional graft was placed gradually and compacted into the elevated membrane site with a total of 0.5 mL of graft material placed. (e and f) These radiographs were taken 4 months after the augmentation, showing consolidation of the graft with minimal loss of height or width. (g and h) These radiographs show the 10.5-mm-long implant in place. h

If the vertical alveolar height is less than 6 mm, there are two transcrestal methods that are suggested. The transcrestal osteotome method is first used to increase the thickness of a 4-mm ridge an additional 4 mm. Four months later, a second crestal approach is used with simultaneous implant placement to eliminate the need for a lateral window approach.

Transcrestal approach with no graft placement Elevation of the sinus membrane without graft placement from a lateral window or transcrestal approach has been shown to result in bone formation between the elevated membrane and intact floor of the sinus. Maintenance of the space created after membrane elevation may be important for bone formation to occur.8–13 The decision to use the transcrestal approach allows elevation of the membrane with or without graft placement, which can result in adequate bone function for long-term

implant success7 (see also chapter 7). Six studies report bone gains ranging from 1.8 to 5.7 mm using a transcrestal approach with no graft placement.9,10,12–15 However, deviations in reporting and data collection prevent a meaningful statistical analysis.

Transcrestal Approach with Graft Placement There are studies that evaluated augmentation of the ridge using allograft and xenograft, with vertical increases ranging from 3.5 to 6.0 mm.11,16,17 These studies confirm that placing material to maintain space will result in apparent bone gain. Bone gain using the osteotome technique from the crestal approach ranges from 3 to 6 mm, with or without grafting.9,10,12–19 Different grafting materials do not seem to affect implant success rates.7,17 In a series of over 120 patients who were treated with

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the transcrestal approach, there were no differences reported comparing the use of allograft or autograft.7 In general, a narrow sinus will result in more predictable bone augmentation with the transcrestal approach than a wide sinus.20 A study comparing radiofrequency analysis values for different approaches and healing times did not review differences in implant stability after bone had formed.21 Data comparing lateral window and crestal approaches using no graft or different graft materials in a single study is not available. Therefore, a thorough review of publications is required to reveal consistencies. What is the reported success rate when using the crestal osteotome approach to place implants? When there is greater than 5 mm of bone, the success rate for implants placed immediately using the crestal approach without a graft ranges from 86% to 98%.7,14–18,22 The success rates of the placement of implants from the crestal approach with the osteotome technique and the conventional placement with a two-stage lateral window approach are similar.16,21 When there is less than 5 mm of bone prior to transcrestal approach, the implant success rate varies.7,19 The success rate when using the osteotome technique does improve when there is greater than 5 mm initial bone thickness compared with more deficient ridges that used the technique of grafting and immediate implant placement.7 As an alternative, or in cases where less than 8 mm was formed, the use of shorter implants resulted in favorable clinical outcomes, but long-term follow-up has not been reported.19 For now, based on the published reports and the consistency of the bone gain and implant success rates, the following is a suggested algorithm that may clarify when and how to use a crestal osteotome approach.

Transcrestal osteotome strategies Bone height 9 mm or greater Implants are placed without a graft. Based on clinician preference, the floor can be elevated during the implant preparation process to place slightly longer implants.23–25

Bone height 5 to 8 mm Because long-term evidence is inconclusive with the use of ultrashort implants (4 to 6 mm long) in the posterior maxilla, clinicians may choose to place implants 8 mm or longer. When CBCT cross sections show 5 to 8 mm vertical height, the sinus floor can be elevated during implant preparation, with simultaneous implant placement.7,14–16,22 There is evidence that sinus membrane elevation with no graft material placed may result in bone formation between the membrane and sinus floor.10–13

Bone height less than 5 mm In this situation, a clinical decision is made to use a transcrestal or lateral window approach based on the difficulty of raising the sinus membrane without perforation. If a molar has been recently removed in the presence of intraradicular pneumatization, the membrane may be difficult to elevate because it may

adhere to the intraradicular site. If there are septa or remnants from a mucocele or other sinus pathology present, this may also make the membrane more difficult to elevate. The lateral window approach has more evidence-based research than the transcrestal approach for this crestal bone height.26–30 If the lateral window approach is used, the resultant bone height for implant placement may exceed 11 mm on a predictable basis. If the transcrestal approach is used in this clinical scenario, the resultant 6 to 9 mm of bone height may require a second transcrestal elevation at the time of implant placement.

Technique 1: Creation of a crestal concavity in healed edentulous sites prior to crestal elevation of the sinus floor In an edentulous site in the posterior maxilla, the following technique can be used for bone thickness of 3 mm or greater (Fig 9-9). A cross-sectional image from the CBCT is used to measure the distance from the crest to the sinus floor. Local anesthesia is administered and an incision is made slightly palatal to the crest with vertical release incisions. The reflection identifies the buccal and palatal edges of the crest. A round bur is used to mark the initial preparation of the crest. Using increasing-diameter drills with stops controls the depth of the preparation. The drill length is chosen to be 1 mm less than the measured thickness of the maxillary crest. The diameters of the drills with the stop increase until the desired final preparation site diameter is reached. A small amount of graft material is then placed into the preparation site, and a flat-surfaced osteotome is used to fracture the floor of the sinus. The osteotome can be taken to the desired elevation gently and slowly and elevated with graft in place in a sequential manner. The graft is placed and gently elevated with an osteotome. A xenograft is chosen in the elevated site within the sinus.26 Multiple sites in an edentulous arch can be grafted simultaneously as needed. The created crestal defect is then grafted with allograft or xenograft depending on clinician preference. The incision is closed. Patients receive antibiotics and precaution to avoid Valsalva maneuvers.

Technique 2: Creation of an alveolar crest island of bone prior to elevation of the sinus floor When choosing a lateral window approach for sinus augmentation, several surgeons advocate using a round bur to outline an “island” of bone on the lateral maxillary wall (Fig 9-10; see also Figs 9-2 and 9-4). The sinus membrane is elevated to allow for rotation of the lateral wall island to form a new floor as the superior border of the sinus augmentation. After the graft is placed, there is excellent healing of the lateral wall. However, the difficulty at the time of surgery is elevation of the membrane without tearing it along the floor.

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5.22 mm

a

b

c

d

Fig 9-9 (a and b) Preoperative radiographs showing the limited furcation bone on the maxillary left first molar. (c and d) The tooth was removed and osteotomies were created connecting the three root sockets. The furcation bone was tapped to intrude it superiorly 5 mm. Xenograft was placed deep near the sinus membrane and allo­graft within the crestal portion. (e and f) Four months after the furcation intrusion, the graft appears well consolidated with sufficient bone for routine implant placement. (g and h) Postoperative views showing the implant in position within the newly formed bone.

8.72 mm

e

g

f

h

The same approach has been used at the crest (ie, a crestal window) with excellent results. Rather than removing a bone core to access the sinus floor, a crestal island is formed and tapped superiorly, raising the floor of the sinus as well as the membrane as an osteoperiosteal flap. After local anesthesia infiltration, an incision is made along the palatal border of the crest with anterior and posterior release several millimeters from the planned window site. The flap must be raised with no perforations. If the flap is perforated, a lateral approach is indicated. After the flap has been elevated exposing the crest, a piezoelectric surgery serrated cutting tip

is used to create an osteotomy through the crest. The cuts are made to create a square or rectangle of bone. The bone is then gently tapped superiorly 4 to 5 mm and the graft is placed. An initial layer of graft is placed followed by gentle pressure using a wide flat-based osteotome to move the graft superiorly. After the graft is placed, the incisions are closed. The patient is given sinus precautions and antibiotics and is advised to use a nasal spray decongestant to avoid congestion. A postoperative CBCT scan is taken to confirm accurate displacement of the alveolar crest segment without migration of graft material into the sinus. After bone healing, implants can be placed.

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Transcrestal Approach with Graft Placement

a

b

c

d

f

i

e

g

h

j

k

Fig 9-10  (a) Preoperative cross section image of the maxillary left first molar. This tooth is fractured and has a past history of multiple endodontic procedures including apicoectomy. (b) Preextraction panoramic reconstruction showing the first molar as the terminal abutment of a three-unit fixed partial denture. The second premolar was extracted 15 years previously. (c and d) Radiographs showing bone height in the molar location after extraction of the tooth with allograft placed within the root sockets. The furcation had not been elevated because of the extensive erosion of the buccal bone and presence of gingival hyperplasia. (e) Four months after tooth extraction, the edentulous site was well healed with epithelial coverage. (f) A crestal incision was made with vertical release and a flap was elevated. A piezoelectric cutting tip was used to create osteotomies through the crestal bone. Tactile sensation was used to judge when the piezoelectric surgery tip went through the crestal bone. (g) The bone island was then gently tapped superiorly, elevating the sinus floor and membrane. No obvious perforation was noted. (h) Xenograft was placed as the graft with gentle compression to maintain the position of the elevated bone segment. (i) The incision was closed with resorbable sutures. The patient received antibiotics and was asked to avoid blowing her nose or other Valsalva maneuvers. (j and k) These images show the increased bone created in the posterior maxilla, which will allow two implants to be placed with minimal additional bone augmentation. Compare the height with part c.

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Conclusion Careful planning and diagnosis of the available bone in the maxilla will allow the surgeon to choose an appropriate procedure for bone augmentation. The use of transcrestal approaches with a crestal window allow the possibility to intrude furcation bone and raise up the floor without the morbidity associated with other procedures.

References 1. Jensen OT, Brownd C, Baer D. Maxillary molar sinus floor intrusion at the time of dental extraction. J Oral Maxillofac Surg 2006;64:1415–1419. 2. Block MS. Sinus augmentation at the time of molar tooth removal: Modification of Jensen technique. J Oral Maxillofac Surg 2015;73:1078–1083. 3. Block MS. Maxillary sinus grafting. In: Block MS. Color Atlas of Dental Implant Surgery. St Louis: Elsevier, 2015:235–241. 4. Block MS, Dastoury K. Prevalence of sinus membrane thickening and association with unhealthy teeth: A retrospective review of 831 consecutive patients with 1662 cone beam scans. J Oral Maxillofac Surg 2014;72:2454–2460. 5. Block MS, Emery RW, Lank K, Ryan J. Implant placement accuracy using dynamic navigation. Int J Oral Maxillofac Implants 2017;32:92–99. 6. Block MS, Emery RW, Cullum DR, Sheikh A. Implant placement is more accurate using dynamic navigation. J Oral Maxillofac Surg 2017;75:1377–1386. 7. Rosen PS, Summers R, Mellado JR, et al. The bone-added osteotome sinus floor elevation technique: Multicenter retrospective report of consecutively treated patients. Int J Oral Maxillofac Implants 1999;14:853–858. 8. Boyne PJ. History of maxillary sinus grafting. In: Jensen OT (ed). The Sinus Bone Graft, ed 2. Chicago: Quintessence, 2006:1–12. 9. Kanayama T, Horii K, Senga Y, Shibuya Y. Crestal approach to sinus floor elevation for atrophic maxilla using platelet-rich fibrin as the only grafting material: A 1-year prospective study. Implant Dent 2016;25:32–38. 10. Pérez-Martínez S, Martorell-Calatayud L, Peñarrocha-Oltra D, García-Mira B, Peñarrocha-Diago M. Indirect sinus lift without bone graft material: Systematic review and meta-analysis. J Clin Exp Dent 2015;7:e316–e319. 11. Isidori M, Genty C, David-Tchouda S, Fortin T. Sinus floor elevation with a crestal approach using a press-fit bone block: A case series. Int J Oral Maxillofac Surg 2015;44:1152–1159. 12. Nedir R, Nurdin N, Vazquez L, Abi Najm S, Bischof M. Osteotome sinus floor elevation without grafting: A 10-year prospective study. Clin Implant Dent Relat Res 2016;18:609–617. 13. Brizuela A, Martín N, Fernández-Gonzalez FJ, Larrazábal C, Anta A. Osteotome sinus floor elevation without grafting material: Results of a 2-year prospective study. J Clin Exp Dent 2014;6:e479– e484.

14. Fermergård R, Astrand P. Osteotome sinus floor elevation and simultaneous placement of implants: A 1-year retrospective study with Astra Tech implants. Clin Implant Dent Relat Res 2008;10:62–69. 15. Schleier P, Bierfreund G, Schultze-Mosgau S, Moldenhauer F, Küpper H, Freilich M. Simultaneous dental implant placement and endoscope-guided internal sinus floor elevation: 2-year post-loading outcomes. Clin Oral Implants Res 2008;19:1163– 1170. 16. Zitzmann NU, Schärer P. Sinus elevation procedures in the resorbed posterior maxilla. Comparison of the crestal and lateral approaches. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1998;85:8–17. 17. Toscano P, Toscano C, Del Fabbro M. Mini-invasive implant placement in combination with maxillary sinus membrane perforation during transcrestal sinus floor elevation: A retrospective study. Int J Periodontics Restorative Dent 2016;36:199–211. 18. Emmerich D, Att W, Stappert C. Sinus floor elevation using osteotomes: A systematic review and meta-analysis. J Periodontol 2005;76:1237–1251. 19. Deporter D, Todescan R, Caudry S. Simplifying management of the posterior maxilla using short, porous-surfaced dental implants and simultaneous indirect sinus elevation. Int J Periodontics Restorative Dent 2000;20:476–485. 20. Spinato S, Bernardello F, Galindo-Moreno P, Zaffe D. Maxillary sinus augmentation by crestal access: A retrospective study on cavity size and outcome correlation. Clin Oral Implants Res 2015;26:1375–1382. 21. Patel S, Lee D, Shiffler K, Aghaloo T, Moy P, Pi-Anfruns J. Resonance frequency analysis of sinus augmentation by osteotome sinus floor elevation and lateral window technique. J Oral Maxillofac Surg 2015;73:1920–1925. 22. Cavicchia F, Bravi F, Petrelli G. Localized augmentation of the maxillary sinus floor through a coronal approach for the placement of implants. Int J Periodontics Restorative Dent 2001;21:475– 485. 23. Toffler M. Sinus elevation: Osteotome-mediated approach. In: Sonick M, Hwang D (eds). Implant Site Development. West Sussex, UK: Wiley-Blackwell, 2012:270–291. 24. Summers RB. Osteotome technique for site development and sinus floor augmentation. In: Jensen OT (ed). The Sinus Bone Graft, ed 2. Chicago: Quintessence, 2006:263–272. 25. Ferrigno N, Laureti M, Fanali S. Dental implants placement in conjunction with osteotome sinus floor elevation: A 12-year life-table analysis from a prospective study on 588 ITI implants. Clin Oral Implants Res 2006;17:194–205. 26. Jensen OT, Shulman LB, Block MS, Iacono VJ. Report of the Sinus Consensus Conference of 1996. Int J Oral Maxillofac Implants 1998;13(suppl):11–45. 27. Boyne PJ, James RA. Grafting the floor of the maxillary sinus with autogenous marrow and bone. J Oral Surg 1980;38:613–616. 28. Misch CE. Maxillary sinus augmentation for endosteal implants: Organized alternative treatment plans. Int J Oral Implantol 1987;4:49–58. 29. Block MS, Kent JN. Maxillary sinus grafting for totally and partially edentulous patients. J Am Dent Assoc 1993;124:139–143. 30. Block MS, Kent JN, Kallukaran FU, Thunthy K, Weinberg R. Bone maintenance 5 to 10 years after sinus grafting, J Oral Maxillofac Surg 1998;56:706–715.

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CHAPTER 10

TRANSCRESTAL SINUS AUGMENTATION WITH OSSEODENSIFICATION Salah Huwais, dds | Ziv Mazor, dmd

Challenges with the Posterior Maxilla Historically, the posterior maxilla has been associated with higher implant failure rates.1–4 Following tooth loss, the posterior maxilla presents several challenges in implant site instrumentations because of low trabecular bone density and alveolar bone deficiency caused by ridge resorption and maxillary sinus pneumatization. Several surgical methods have been documented to treat the deficient edentulous maxilla, including the lateral window direct approach and the transcrestal approach.5 The lateral sinus elevation procedure was introduced by Boyne and James.6,7 Predictable clinical results were reported by Wallace and Testori but with a degree of morbidity as well as risk for membrane perforation, delayed healing, and postoperative infection.8–10 On the other hand, the transcrestal approach described by Summers11 has lower morbidity and is less invasive. However, the risk of membrane perforation was reported to be as high as 26%, and it is related to the experience of the surgeon.12,13 Mazor et al14 reported a 3-year follow-up of 10 implants placed with the transcrestal approach using osteotomes. Membrane perforation was observed in 4 out the 10 implant sites. They stated that the membrane tear was mainly due to the irregularity of the overlaying bone and the small access, which allowed limited surgical control.14 Piezoelectric surgery, balloon, hydraulic pressure, and noncutting tip reamers with modified osteotomes can reduce the risk of membrane perforation when compared with the explosive force produced by the osteotome, which may cause unintentional membrane perforation. These surgical approaches allow

the surgeon to elevate the membrane, but there is still a need for predictability to reduce the risk for perforation.15–17 Additionally, the traditional transcrestal approach requires a minimum of 4 to 5 mm of vertical residual alveolar bone height to safely and predictably elevate the membrane to simultaneously place an implant with sufficient stability.18 Several clinical strategies and bone instrumentation techniques are reported in the literature to increase posterior maxillary bone density and enhance implant stability. Osteotomy underpreparation to place a wider tapered implant and a malleted osteotome to facilitate osseous and condensation have been used with a variable success.11,12,19 Rosen et al19 have reported a 95% survival rate of 174 implants using osteotomes to achieve osteocompression in combination with membrane elevation in a multicenter 20-month follow-up study. The success rate dropped to 85% in sites with subcrestal alveolar height 4 mm or less.19 Del Fabrro et al20 performed a systematic review and reported a reduced implant survival rate in sites with less than 5 mm. Meanwhile, Toffler21 reported a 95.7% survival rate over 18 months of follow-up of 202 implants placed with the same method. Bone instrumentation as part of the augmentation method occupies very little attention in the literature despite the need for improvement in bone drilling instrumentation.22,23 Though recent work has focused on drilling and instrumentation to enhance osseointegration, the majority of these methods are subtractive in which bone is removed. 24–27 Collagen determines trabecular bone plasticity and toughness—the bone’s ability to dissipate energy—and bone subtractive drilling deteriorates collagen integrity.28,29 Bone plastic deformation depends on time and strain rate history.30,31 Bone fluid content also affects viscoelasticity.32,33 To maintain functional plasticity and enhance bone toughness, it is necessary to rethink subtractive drilling.

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10  TRANSCRESTAL SINUS AUGMENTATION WITH OSSEODENSIFICATION

Fig 10-1 The Densah Bur (Versah) has different diameters to facilitate osteotomy preparation simultaneously with subcrestal sinus augmentation.

a

b

Fig 10-2  The Densah Bur is a dual-action tool. The recommended technique for TSAOD is to use the burs in OD mode (counterclockwise rotation at 800–1,200 rpm) with a pumping motion and copious irrigation. (a) OD mode. (b) Cutting mode.

Osseodensification Huwais recently described a new concept termed osseodensifi­ cation.34,35 It is a novel and dynamic biomechanical bone instrumentation method that allows for creation of an osteotomy without subtractive drilling. Drilling occurs in a gradual, incremental process to preserve collagen to enhance bone plasticity.34 It is facilitated by novel burs that have lands with a large negative rake angle, which work without cutting to densify trabecular bone by compaction autografting.34,35 (Fig 10-1). Densifying burs are designed with a chisel edge and a tapered shank that progressively increases diameter, controlling the expansion process.35 The burs are labeled according to average size but range in actual diameter (eg, the Versah Densah Bur [2.0] is 1.5 mm at the tip and 2.5 mm at the top). These burs are used with a standard surgical motor and irrigation but rotate in a noncutting direction, counterclockwise at 800 to 1,200 rpm for densification. The burs are dual action and can also be used in the cutting direction (clockwise at 800 to 1,200 rpm) in cutting mode.

The recommended technique for transcrestal sinus augmentation wth osseodensification (TSAOD) is to use the burs in the osseodensifying (OD) mode with a pumping motion with copious irrigation (Fig 10-2). Copious irrigation provides lubrication between the bur and bone surfaces and eliminates overheating. The fluid pumping method coupled with high-speed counterclockwise rotation induces a hydrodynamic wave termed the compression wave ahead of the point of contact.35 Huwais et al have retrospectively evaluated 222 patients who were treated with TSAOD and simultaneous implant placements (261 total implants) (unpublished data, 2017). Follow-up evaluation ranged from 6 to 64 months, and there was a 97% implant survival rate with no observed sinus membrane perforations. Osseodensification effectively facilitated sinus augmentation in cases with residual bone heights as low as 2 mm without the disadvantages inherent in both the lateral window and the transcrestal osteotome techniques. There was a limitation of this technique in cases of residual bone dimension less than 2 mm height with only 4 mm width.36 Kumar and Narayan37 reported a 100% implant survival rate over 1 year for 22 implants placed in 20 patients who received transcrestal osseodensification. They also reported successful sinus augmentation in cases with minimal residual bone dimension without detection of membrane perforation. Osseodensification has the capacity to prepare the implant site while predictably elevating the sinus membrane with low risk of perforation while also facilitating autogenous bone grafting to enhanced implant stability. These capabilities are based on a combination of the following technical processes: •  Hydrodynamic wave action from fluid pumping coupled with high-speed counterclockwise drill rotation induces effluence ahead of the point of contact. Once the sinus floor is penetrated by the densifying bur, irrigation solution and bone debris serve to hydraulically elevate the sinus membrane. •  Hydraulic compression coupled with bur-to-bone contact generates an opposing axial reactive force proportional to the intensity of the force applied by the surgeon. Haptic feedback enables the surgeon to control the force based on the perceived bone density encountered, allowing for controlled plastic deformation.35

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TSAOD Protocols

a

b

c

d

e

Fig 10-3  Radiographic illustration of TSAOD with 8 mm residual bone. (a) There is a distance of 8 mm to the sinus floor. (b) Pilot to 1 mm below the sinus floor. (c and d) The Densah Bur is used rotating at 1,200 rpm in densifying mode. (e) Two 11.5-mm-long implants are placed with sinus autograft.

•  Lateral compaction of small fragments of displaced trabecular bone pushed laterally and apically within the implant preparation site facilitates intraosseous densification.34,38–40 •  Plastic bone deformation persists from the relative atraumatic osteotomy preparation that enables the inner walls of the osteotomy to “spring back” toward the center of the osteotomy. This subsequently generates increased biomechanical energy for bone-to-implant contact.34 •  Intraosseous nucleation by devitalized bone fragments increases the potential for greater peri-implant bone mineral density in both early- and late-stage osseointegration due to increased biomass within the trabecular space.38–40

TSAOD Protocols Situation with 6 mm residual bone When the minimum vertical bone height is 6 mm or greater with at least 4 mm alveolar width, a stepwise protocol using

Denash Burs in full step increments is done as shown in Fig 10-3.

Stepwise treatment 1. Measure bone height to the sinus floor. Flap the soft tissue, then measure the crestal bone height below the sinus floor to determine the working depth. This should be correlated with radiographic imaging (Fig 10-3a). 2. Pilot drill depth to 1 mm below the sinus floor. In cases where posterior residual alveolar ridge height is 6 mm or greater and additional vertical depth is desired, drill to the depth determined within an approximate safety zone of 1 mm from the sinus floor using the pilot drill (clockwise drill speed 800 to 1,500 rpm with copious irrigation). Confirm the pilot drill position with a radiograph. 3. Use a Densah Bur (2.0) in OD mode to the sinus floor. Depending on the implant type and diameter selected for the site, begin with the narrowest Densah Bur (2.0). Change the drill motor to OD mode and begin running the bur into the osteotomy. When you feel the dense sinus floor bone, stop and confirm the first Densah Bur vertical position with a radiograph (Fig 10-3b).

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a

b

c

d

e

f

Fig 10-4  (a) Measure the crestal bone height below the sinus floor, the working depth, using calibrated radiographic imaging. (b) Use a Densah Bur (2.0) in OD mode to the sinus floor. (c) After entering with the Densah Bur (3.0) up to 3 mm past the sinus floor, Densah Burs (4.0 and 5.0) are used in OD mode up to 3 mm past the sinus floor. (d) Fill the final prepared osteotomy with well-hydrated allograft added. (e) Use the last Densah Bur used in step 4 in OD mode with speed of 150 to 200 rpm with no irrigation to advance the allograft into the sinus. (f) Place the implant.

4. Enter with a Densah Bur (3.0) in OD mode up to 3 mm past the sinus floor. Use the next wider Densah Bur (3.0) in OD mode and advance it into the previously created osteotomy, modulating pressure with a pumping motion. When the bur reaches the dense bone, modulate pressure with a gentle pumping motion to advance past the sinus floor in 1-mm increments. Maximum possible advancement past the sinus floor at any stage must not exceed 3 mm. As the next wider Densah Burs advance in the osteotomy, additional autogenous bone will be pushed apically, achieving additional vertical depth to a maximum membrane elevation of 3 mm. Vertical bur position is confirmed by radiograph (Figs 10-3c and 10-3d). 5. Place the implant. Placement of the implant into the osteotomy is done using the drill motor at slow speed to tap the implant into place, according to the placement torque maximum. The implant is seated to depth with a torque wrench (Fig 10-3e).

Situation with 4 mm residual bone When the minimum vertical bone is 4 to 5 mm with at least 5 mm of horizontal width, a stepwise protocol using Densah Burs in full step increments is done as shown in Fig 10-4. Avoid using a pilot drill.

Stepwise treatment 1. Measure bone height to sinus floor. Flap the soft tissue and measure the crestal bone height below the sinus floor to determine the working depth. This is done using calibrated radiographic imaging (Fig 10-4a). 2. Use a Densah Bur (2.0) in OD mode to the sinus floor. Avoid using a pilot drill. Depending on the implant type and diameter selected for the site, begin with the narrowest Densah Bur (2.0). Change the drill motor to reverse (ie, OD mode). Begin running the bur into the osteotomy until you

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Osseodensification and Osseointegration

Regular drilling

Osseodensification 0 weeks

500 µm

500 µm

3 weeks

500 µm

500 µm

6 weeks

a

500 µm

b

500 µm

Fig 10-5  (a) Optical micrographs taken from samples at 0, 3, and 6 weeks from the group using regular drilling. (b) Optical micrographs taken from samples at 0, 3, and 6 weeks from the OD drilling group.

reach the dense sinus floor. Confirm the bur position with a radiograph (Fig 10-4b). 3. Enter with a Densah Bur (3.0) in OD mode up to 3 mm past the sinus floor. Use the next wider Densah Bur (3.0) and advance it into the previously created osteotomy with modulating pressure and a pumping motion. When the bur reaches the sinus floor, modulate pressure with a pumping motion to advance past the sinus floor in 1-mm increments, up to 3 mm. (Maximum bur advancement past the sinus floor, at any stage and in any diameter, must not exceed 3 mm). Bone fragments will be pushed toward the apical end and will begin to gently raise the membrane up to 3 mm. Confirm bur vertical position with a radiograph. 4. Use Densah Burs (4.0 and 5.0) in OD mode up to 3 mm past the sinus floor. Use the sequential wider Densah Burs in OD mode with a pumping motion to achieve additional width with maximum membrane elevation of 3 mm to reach final desired width for implant placement (Fig 10-4c) 5. Add the allograft. After achieving the final planned osteotomy diameter, fill the osteotomy with a well-hydrated, mainly cancellous allograft. Use the last Densah Bur used in step 4 in OD mode with speed of 150 to 200 rpm with no irrigation to propel the allograft into the sinus. The Densah Bur facilitates allograft material compaction to further elevate the sinus membrane and not advance beyond the sinus floor more than 2 to 3 mm. Repeat the grafting step to facilitate additional membrane elevation as needed according to implant length (Figs 10-4d and 10-4e). 6. Place the implant. Place the implant into the osteotomy. If the drill motor is being used to tap the implant into place, the unit

may stop when it reaches the placement torque maximum. Finish placing the implant to depth with a torque-indicating wrench (Fig 10-4f).

Osseodensification and Osseointegration Osseodensification promises to increase both safety and efficacy for minor sinus floor grafting procedures using the transcrestal approach. The sinus membrane is elevated without hand instrumentation as required from the transcrestal osteotome and lateral sinus approaches. Operator tactile skill is enhanced, leading to fewer instances of membrane perforation and resulting in a relatively less invasive procedure. The osseodensification within the trabecular space results in displaced bone fragments that have the potential to increase bone mass for osseointegration.38–40 Osseodensification used in the spine for plate fixation has shown in both clinical and animal studies to result in markedly stabilized screw fixation with superior bone-to-titanium surface contact when compared with a standard drilling technique38 (Figs 10-5 and 10-6). Bone densification around a loaded dental implant occurs naturally in function with time via the mechanostat when favorable bone strain leads to increased bone mineral density near the interface surface of an immobile dental implant.44–46 However, increased mineral density does not always occur and is not always maintained if sufficient bone mass to maintain fixation

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Regular drilling

Fig 10-5 (cont) (c) Higher magnification optical micrographs of regular drilling samples at 0, 3, and 6 weeks. (d) Higher magnification optical micro­ graphs of OD drilling samples at 0, 3, and 6 weeks. White arrows show residual bone chips from surgical instrumentation, and yellow arrows show remodeling sites. (Reprinted with permission from Lopez et al.38)

Osseodensification 0 weeks

200 µm

200 µm

3 weeks

200 µm

200 µm

6 weeks

200 µm

c

a

100

80

60

40

20

R

80

60

40

20

0

OD b

Bone area fraction occupancy (%)

100

Bone area fraction occupancy (%)

Bone area fraction occupancy (%)

100

0

200 µm

d

0

3

Weeks

80

60

40

20

0

6

0

c

3

R

6

0

3

6

OD

Fig 10-6  Bone area fraction occupancy mean and standard deviation (ie, percentage of bone quantity in the area of the open screw thread). (a) As a function of drilling technique (collapsed over time). (b) As a function of time in vivo. (c) Time points within each group (regular vs OD). R, standard drilling; OD, osseodensification. (Reprinted with permission from Lopez et al.38)

is not present to allow for subtractive remodeling.1 Therefore, osseointegration is less predictable in highly trabecular bone, which may undergo fatigue fractures within trabeculae without coupled repair.39,41 In the posterior maxilla, a lack of bone and no augmentation grafting can lead to implant failure—one of the most common causes of failure in maxillary implants.42 A starting point of significant lateral compaction autografting via osseodensification or compaction of added allogeneic bone suggests facilitation for intraosseous densification by remodeling substitution with greater potential for increased bone mass within the alveolar space for biomechanical function.43

Case Reports Case 1 This 53-year-old patient presented with a missing maxillary right first molar with evident sinus pneumatization with crestal alveolar bone height deficiency (Fig 10-7).

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Case Reports

4.2 mm

a

b

c

d

e

f

g

h

i

j

k

l

Fig 10-7  Representative clinical case with 5-year clinical and radiographic follow-up. (a) Initial radiograph with 4 mm of alveolar ridge height in area of maxillary right first molar. (b) Radiograph of densifying bur (3.0) entering the sinus cavity, facilitating autogenous bone grafting into the sinus, and elevation of the membrane up to 3 mm. (c) Occlusal clinical view of the osteotomy created by densifying bur (4.0) expanding the osteotomy and depositing autograft into the sinus up to 3 mm. (d) Occlusal clinical view of the final osteotomy created and filled with particulate allograft. (e) Radiograph of densifying bur (5.0) used in a counterclockwise direction at 100 to 200 rpm with no irrigation propelling the allograft into the sinus and elevating the membrane to achieve additional lift and grafting beyond the initial 3 mm. (f) Radiograph of the implant in place at the time of surgery. (g) Radiograph of the implant 3 years after placement. (h) Clinical buccal view of the implant 3 years after placement. (i) Radiograph of the implant 5 years after placement. (j) Occlusal clinical view of the implant 5 years after placement. (k) Cone beam computed tomography (CBCT) sagittal section at 5-year follow-up. (l) CBCT cross section at 5-year follow-up.

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5.5 mm

4 mm

6 mm

b

c

d

e

f

g

h

i

a

Up to 4 mm

Pilot: 1.7 mm

Fig 10-8  Clinical case with 4-year clinical and radiographic follow-up. (a) Occlusal view of edentulous left maxilla with missing molars and second premolar. (b) Maxillary sinus pneumatization was evident with crestal height deficiency and irregular sinus floor. Crestal bone height to the maxillary sinus floor ranged from 4 to 6 mm. (c) Open flap. Site revealed alveolar ridge width deficiency at area of second premolar with poor bone quality in areas of molars. Note root tip remnants. (d) Periapical radiograph showing initial pilot osteotomy to 4-mm depth (1 mm below the sinus floor in area of second premolar). (e) Densah Bur VT2535 (3.0) entering the sinus up to 3 mm, elevating the membrane, and grafting autogenous bone below the elevated membrane. (f) Clinical occlusal view showing both lateral ridge expansion and the intact elevated sinus membrane with autogenous bone particles in the area of the second premolar. The Densah Bur VT3545 (4.0) was used as the last bur to achieve the lateral and vertical expansion. (g) Occlusal clinical view demonstrating an intact membrane with autogenous bone particles underneath the intact elevated sinus membrane in the area of the first molar. (h) Radiograph of the 11.5 × 4.7–mm implant that was placed with adequate transcrestal sinus augmentation in the area of the second premolar. The first molar area is demonstrating adequate allograft containment, which is an indication of intact lifted membrane using the Densah Bur VT4555 (5.0) according to the recommended protocol. (i) Radiograph showing both the second premolar implant and the 11.5 × 5.7–mm first molar implant with adequate transcrestal sinus augmentation.

Case 2 This 62-year-old patient presented with missing maxillary left molars and second premolar with sinus pneumatization and crestal alveolar bone deficiency (Fig 10-8).

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Case Reports

j

k

l

m

n

o

p

q

r

s

t

u

Fig 10-8  (cont) (j) Autogenous graft from the site was used to develop the necessary hard tissue in the buccal of the premolar implant. (k) A collagen membrane was placed for guided bone regeneration. (l) Primary closure was obtained. (m) Reentry after 4 months demonstrating that adequate bone was regenerated around both the premolar and molar implants. (n) Healing abutments at the uncover stage. (o) Periapical radiograph after 4 months of healing. (p) Definitive restoration at 5 months after surgery. (q) Definitive restorations at 3-year follow-up. (r) Apical radiograph demonstrating a stable crestal bone height and sinus graft at 3-year follow-up. (s) Coronal section view demonstrating a stable crestal bone width in areas of implants at 4-year follow-up. (t) CBCT cross-sectional view demonstrating a stable crestal bone height and sinus graft in area of second premolar at 4-year follow-up. (u) CBCT cross-sectional view demonstrating a stable crestal bone height and sinus graft in area of first molar at 4-year follow-up.

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a

b

c

e

d f

h

g

Fig 10-9  Clinical case with 3-year clinical and radiographic follow-up. (a) Clinical view of preoperative site. (b) TSAOD with osteotomy preparation. (c) Graft administration. (d) Preoperative panoramic view taken from the CBCT scan. (e) Preoperative CBCT showing 4 mm of residual crestal bone height. (f) CBCT 5 months postoperative. (g) Panoramic view taken from the CBCT 5 months postoperative. (h) Panoramic radiograph 3 years postoperative. (i) Clinical view 3 years postoperative.

i

Case 3

Case 4

The patient is 63 years old and has missing maxillary right molars and a missing second premolar with sinus pneumatization and crestal alveolar bone deficiency with 4 mm of residual bone height (Fig 10-9).

The patient is a 43-year-old man with missing maxillary right molars with severe sinus pneumatization and crestal alveolar bone deficiency with 2 mm of residual bone height (Fig 10-10).

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a

b

c

d

e

Fig 10-10  Clinical case with 2-year clinical and radiographic follow-up. (a) Clinical view of the preoperative site. (b) Preoperative CBCT. (c) Preoperative CBCT demonstrating 2 mm residual bone height. (d) Subcrestal sinus elevation using OD drill. (e) Implant placement.

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g

f

h

Fig 10-10  (cont) (f) CBCT scan 5 months postoperative. (g) Panoramic view from CT scan 5 months postoperative. (h) Radiograph 2 years postoperative with stable crestal height and sinus augmentation.

References 1. Jaffin RA, Berman CL. The excessive loss of Branemark fixtures in type IV bone: A 5-year analysis. J Periodontol 1991;62:2–4. 2. Friberg B, Jemt T, Lekholm U. Early failures in 4,641 consecutively placed Brånemark dental implants: A study from stage 1 surgery to the connection of completed prostheses. Int J Oral Maxillofac Implants 1991;6:142–146. 3. Esposito M, Hirsch JM, Lekholm U, Thomsen P. Biological factors contributing to failures of osseointegrated oral implants. (I). Success criteria and epidemiology. Eur J Oral Sci 1998;106:527–551. 4. Engquist B, Bergendal T, Kallus T, Linden U. A retrospective multicenter evaluation of osseointegrated implants supporting overdentures. Int J Oral Maxillofac Implants 1988;3:129–134.

5. Kher U, Ioannou AL, Kumar T, et al. A clinical and radiographic case series of implants placed with the simplified minimally invasive antral membrane elevation technique in the posterior maxilla. J Craniomaxillofac Surg 2014;42:1942–1947. 6. Tatum H Jr. Maxillary and sinus implant reconstructions. Dent Clin North Am 1986;30:207–229. 7. Boyne PJ, James RA. Grafting the floor of the maxillary sinus with autogenous marrow and bone. J Oral Surg 1980;38:613–616. 8. Wallace SS, Froum SJ. Effect of maxillary sinus augmentation on the survival of endosseous dental implants. A systematic review. Ann Periodontol 2003;8:328–343. 9. Wallace SS, Mazor Z, Froum SJ, Cho SC, Tarnow DP. Schneiderian membrane perforation rate during sinus elevation using Piezosurgery: Clinical results of 100 consecutive cases. Int J Periodontics Restorative Dent 2007;27:413–419.

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References

10. Testori T, Weinstein RL, Taschieri S, Del Fabbro M. Risk factor analysis following maxillary sinus augmentation: A retrospective multicenter study. Int J Oral Maxillofac Implants 2012:27:1170– 1176.
 11. Summers RB. A new concept in maxillary implant surgery: The osteotome technique. Compendium 1994;15:152–156. 12. Horowitz RA. The use of osteotomes for sinus augmentation at the time of implant placement. Compend Contin Educ Dent 1997;18:441–447. 13. Pjetursson BE, Lang NP. Sinus floor elevation utilizing the transalveolar approach. Periodontol 2000 2014;66:59–71. 14. Mazor Z, Peleg M, Gross M. Sinus augmentation for single-tooth replacement in the posterior maxilla: A 3-year follow-up clinical report. Int J Oral Maxillofac Implants 1999;14:55–60. 15. Kfir E, Goldstein M, Yerushalmi I, et al. Minimally invasive antral membrane balloon elevation: Results of a multicenter registry. Clin Implant Dent Relat Res 2009;11(suppl 1):e83–e91. 16. Vercellotti T, Pollack AS. A new bone surgery device: Sinus grafting and periodontal surgery. Compend Contin Educ Dent 2006; 27:319–325. 17. Vercellotti T, De Paoli S, Nevins M. The piezoelectric bony window osteotomy and sinus membrane elevation: Introduction of a new technique for simplification of the sinus augmentation procedure. Int J Periodontics Restorative Dent 2001;21:561–567. 18. Wang HL, Katranji A. ABC sinus augmentation classification. Int J Periodontics Restorative Dent 2008;28:383–389. 19. Rosen PS, Summers R, Mellado JR, et al. The bone-added osteotome sinus floor elevation technique: Multicenter retrospective report of consecutively treated patients. Int J Oral Maxillofac Implants 1999;14:853–858. 20. Del Fabbro M, Corbella S, Weinstein T, Ceresoli V, Taschieri S. Implant survival rates after osteotome-mediated maxillary sinus augmentation: A systematic review. Clin Implant Dent Relat Res 2012;14:e159–e168. 21. Toffler M. Site development in the posterior maxilla using osteocompression and apicalalveolar displacement. Compend Contin Educ Dent 2001;22:775–780. 22. Coelho PG, Jimbo R, Tovar N, Bonfante EA. Osseointegration: Hierarchical designing encompassing the macrometer, micrometer, and nanometer length scales. Dent Mater 2015;31:37–52. 23. Natali C, Ingle P, Dowell J. Orthopaedic bone drills—Can they be improved? Temperature changes near the drilling face. J Bone Joint Surg Br 1996;78:357–362.

 24. Galli S, Jimbo R, Tovar N, et al. The effect of osteotomy dimension on osseointegration to resorbable media-treated implants: A study in the sheep. J Biomater Appl 2015;29:1068–1074. 25. Giro G, Marin C, Granato R, et al. Effect of drilling technique on the early integration of plateau root form endosteal implants: An experimental study in dogs. J Oral Maxillofac Surg 2011;69: 2158–2163. 26. Sarendranath A, Khan R, Tovar N, et al. Effect of low speed drilling on osseointegration using simplified drilling procedures. Br J Oral Maxillofac Surg 2015;53:550–556. 27. Yeniyol S, Jimbo R, Marin C, Tovar N, Janal MN, Coelho PG. The effect of drilling speed on early bone healing to oral implants. Oral Surg Oral Med Oral Pathol Oral Radiol 2013;116:550–555. 28. Ritchie RO, Buehler MJ, Hansma P. Plasticity and toughness in bone. Phys Today 2009;62(6):41–47. 29. Wang X, Shen X, Li X, Agrawal CM. Age-related changes in the collagen network and toughness of bone. Bone 2002;31:1–7.

30. Panjabi MM, White AA 3rd, Southwick WO. Mechanical properties of bone as a function of rate of deformation. J Bone Joint Surg Am 1973;55:322–330. 31. Carter DR, Hayes WC. The compressive behavior of bone as a two-phase porous structure. J Bone Joint Surg Am 1977;59:954– 962. 32. Hansen U, Zioupos P, Simpson R, Currey JD, Hynd D. The effect of strain rate on the mechanical properties of human cortical bone. J Biomech Eng 2008;130:011011. 33. Pugh JW, Rose RM, Radin EL. Elastic and viscoelastic properties of trabecular bone: Dependence on structure. J Biomech 1973;6:475–485. 34. Huwais S, Meyer EG. A novel osseous densification approach in implant osteotomy preparation to increase biomechanical primary stability, bone mineral density, and bone-to-implant contact. Int J Oral Maxillofac Implants 2017;32:27–36. 35. Huwais S [inventor]. Huwais IP Holding LLC, assignee. Fluted osteotome and surgical method for use. US patent 9,737,312. 22 Aug 2017. 36. Huwais S, Mazor Z, Ioannou A, Gluckman H, Neiva R. A multi-­ center retrospective clinical analysis of 261 implants with up to 5 years follow-up placed via osseodensification transcrestal sinus augmentation. Int J Oral Maxillofac Implants (in press). 37. Kumar BT, Narayan V. Minimally invasive crestal approach sinus floor elevation using Densah burs, and hydraulic lift utilizing putty graft in cartridge delivery. Clin Oral Implants Res 2017; 28(suppl 14):203. 38. Lopez CD, Alifarag AM, Torroni A, et al. Osseodensification for enhancement of spinal surgical hardware fixation. J Mech Behav Biomed Mater 2017;69:275–281. 39. Lahens B, Neiva R, Tovar N, et al. Biomechanical and histologic basis of osseodensification drilling for endosteal implant placement in low density bone. An experimental study in sheep. J Mech Behav Biomed Mater 2016;63:56–65. 40. Trisi P, Berardini M, Falco A, Podaliri Vulpiani M. New osseo­ densification implant site preparation method to increase bone density in low-density bone: In vivo evaluation in sheep. Implant Dent 2016;25:24–31. 41. Karami KJ, Buckenmeyer LE, Kiapour AM, et al. Biomechanical evaluation of the pedicle screw insertion depth effect on screw stability under cyclic loading and subsequent pullout. J Spinal Disord Tech 2015;28:E133–E139. 42. Jemt T, Häger P. Early complete failures of fixed implantsupported prostheses in the edentulous maxilla: A 3-year analysis of 17 consecutive cluster failure patients. Clin Implant Relat Res 2006;8:77–86. 43. Gonzáles-García R, Monje F, Moreno C. Alveolar split osteotomy for the treatment of severe narrow ridge maxillary atrophy: A modified technique. Int J Oral Maxillofac Surg 2011;40:57–64. 44. Frost HM. Wolff’s Law and bone’s structural adaptation to mechanical usage: An overview for clinicians. Angle Orthod 1994; 64:187–212. 45. Frost HM. Structural adaptation to mechanical usage (SATMU): 1. Redefining Wolff’s law: The bone modeling problem. Anat Rec 1990;226:403–413. 46. Carter DR, Blenman PR, Beaupré GS. Correlations between mechanical stress history and tissue differentiation in initial fracture healing. J Orthop Res 1988;6:736–748.

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CHAPTER 11

TRANSCRESTAL HYDRODYNAMIC PIEZOELECTRIC SINUS ELEVATION Konstantin Gromov,* dds | Sergey B. Dolgov, dds, msd | Dong-Seok Sohn, dds, phd

O

ral surgery, periodontics, and implant dentistry have developed varying treatment modalities and techniques for the same conditions. Many surgical concepts emerged empirically while others evolved over time based on clinicians’ preferences, research, experience, and armamentarium. This chapter compares several variations of sinus grafting techniques that have evolved toward the use of a transcrestal approach with piezoelectric surgery or hydrodynamics. Dental implant–supported restorations have proven to be an effective treatment solution for partially and fully edentulous cases. When placing dental implants in the posterior maxilla, attention is paid to volume and quality (density) of the available bone.1 Likewise, the restorative treatment plan impacts the surgical phase by guiding which specific surgical techniques are used. Historically, clinicians have used various concepts and strategies to manage edentulous conditions with maxillary sinus proximity and bone deficiencies. Early on, they understood the necessity of augmenting the sinus to accommodate dental implants. Preference was given to longer dental implants when the surgical site allowed. In fact, many clinicians considered implants shorter than 12 mm to be less reliable and augmented the potential implant site to accommodate implants 12 mm or longer. This is explained by significant differences in surface

properties of implants and available surgical and restorative components of the early implant devices. Options for bone grafting evolved over the years into a wide range of choices, from autogenous bone, allografts, xenografts, platelet-rich fibrin (PRF), advanced PRF, synthetic materials, and combinations.

Clinical Goals of the Sinus Bone Graft Procedure The clinical goals for optimal treatment when vertical bone is deficient include the following: •  Adequate bony environment to accommodate implants •  Minimal invasiveness to avoid morbidity •  Long-term stability of graft sites •  A repeatable and consistent operator-friendly working protocol •  Simultaneous implant placement when possible •  Immediate implant placement in the vicinity of the maxillary sinus •  Cost and time efficiency

*Dr Gromov dedicates this chapter to his only son, Ivan Gromov (2001–­2017). “I wish it need not have happened in my time.” / “So do I, and so do all who live to see such times. But that is not for them to decide. All we have to decide is what to do with the time that is given us.” – J.R.R. Tolkien

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To achieve these goals, there are different approaches to sinus graft procedures, which are generally divided into the lateral wall and transcrestal approaches.

Lateral Wall Technique Lateral approach sinus grafting was introduced in 1976 by Tatum for the placement of dental implants, whereas Philip J. Boyne used the sinus elevation procedures in the 1960s to increase interarch restorative space for removable prostheses.2–4 Boyne’s technique involved grafting the sinus floor from the lateral approach using autogenous bone followed some months later by posterior ridge reduction. Boyne’s and Tatum’s approaches evolved over the years and are now the basis for advancements in the field of sinus floor augmentation. While the literature favors the lateral wall surgical technique as highly successful and predictable with long-term stable results, there are several considerations worth mentioning: •  Sinus membrane perforations and tears are common (10% to 20% of the time) for the lateral approach.5 Complicating factors include membrane thickness, presence of septa, presence of pathology, operator skills, and armamentarium. •  The vasculature of the maxillary sinus can include an endosseous anastomosis from the posterior superior alveolar (PSA) artery and the infraorbital artery via the alveolar antral artery (AAA), a risk for intraoperative bleeding. The incidence of AAA anastomosis has been reported as up to 100%.6,7 This artery must be properly identified by cone beam computed tomography (CBCT) diagnostics. Extrabony positioning of the AAA is not detectable in the CBCT. When present outside the bone, two bony windows to isolate and bypass the blood vessel may be required using piezoelectric instrumentation. •  Vertical incisions facilitate full periosteal flap elevation to provide adequate surgical access to the lateral sinus wall; however, vertical incisions lead to more edema.8 •  The surgical time of the procedure is generally longer for a lateral wall approach than a transcrestal approach, especially for single-implant cases. On the other hand, the lateral wall technique provides direct visualization of the maxillary sinus and allows for evaluation of the sinus membrane.

Osteotome Technique Osteotome sinus grafting was suggested by Summers in 1994 as an alternative to lateral approach sinus grafting to minimize surgical trauma and facilitate dental implant placement.9 The

technique involves the elevation of the floor of the sinus via the actual implant osteotomy. The armamentarium includes special osteotomes with various diameters and tips as well as a surgical mallet. The osteotome technique has some variations but generally involves approaching the antral floor by using implant drills under a tactile and radiographic control. The osteotomy stops at approximately 1 mm from the floor of the sinus. The remaining bone and the floor of the sinus are infractured by a gentle tapping with a surgical mallet on the handle of the osteotome. The sinus membrane is elevated by means of the osteotomes, sometimes indirectly by pushing the graft material into the created opening. Although this is considered a less invasive and successful approach by many clinicians, the osteotome technique has certain limitations and considerations, as follows: •  Atrium floor elevation is performed blind with a questionable control of membrane integrity. •  Aside from the infraction of the bony floor, membrane elevation is unpredictable too as demonstrated under a nasal endoscopy.10 •  Minimum bone required is about 5 mm with expected elevation of 3 to 5 mm, so an 8- to 10-mm dental implant can be placed. •  Benign paroxysmal positional vertigo has been reported after osteotome sinus grafts.11,12 Successful osseointegration requires that the implant be surrounded by vital bone with most of the implant loading occurring at the cervical 5 mm of the implant.13–17 Therefore, if alveolar bone height is 3 to 6 mm, a transcrestal approach to elevating the sinus lining and placing 8-mm implants may be adequate treatment. The following modifications are suggested for the transcrestal approach to improve its predictability: •  The use of drills with stoppers (metal sleeves of different working lengths) is suggested for the drilling set. In addition, the working end tip of the drill may be diamond coated with an internal irrigation port or rounded flutes to prevent cutting through sinus membrane. Also, a bony plug in a shape of an inverted cone is created between the spinning flutes, which provides extra protection for the elevated sinus membrane (Fig 11-1). •  Instead of the blind osteotome method, hydraulic pressure by a saline-filled balloon or cavitation by piezoelectric surgery was developed. Additionally, the use of a cannula without a balloon creates hydraulic pressure that spreads evenly in a horizontal direction for optimal membrane separation (Fig 11-2). •  Implant thread and body design play a significant role in the primary implant stability, suggesting an aggressive thread at the cervical portion of the implant.

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b

a

c

d

Fig 11-1  (a) The crestal approach sinus (CAS) kit safety drill with an 8-mm stopper attached. (b) The CAS drill tip has an inverse cone shape that will form a conical bone chip when drilling to safely raise the membrane. (c) Note the bone chip formation between the cutting blades. Bone particles generated during drilling will discharge upward. (d) Intraoperative periapical radiograph confirming CAS drill positioning to initiate membrane elevation.

a

b

c

Fig 11-2  (a to c) The CAS kit hydraulic lifter placed in the osteotomy. The hydraulic lifter requires a sterile saline solution, which is dispensed from the attached disposable syringe.

•  Wide healing abutments provide additional stabilization of implants to prevent implant migration into the maxillary sinus. Two-piece contoured polyetheretherketone (PEEK) healing abutments provide stabilization of the socket graft material if a tooth extraction and an immediate implant placement has been done (Fig 11-3).

•  Graft delivery instruments include an amalgam carrier to deliver bone graft and special pluggers with depth sleeves as are used on a safe cutting drills. A “funnel” modification allows delivery of graft material. A rotary spreader is used to distribute the bone graft inside the elevated sinus at low rpm (Fig 11-4).

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Fig 11-3 (a) Contoured PEEK healing abutments have several internal connection designs and sizes compatible with most major dental implant platforms. (b) Immediate implant placement in the maxillary first molar extraction socket. The positioning of the flat surface of the internal hexagon connection parallel to the buccal aspect of the molar allows for optimal orientation of the asymmetrical contoured healing abutment. (c) Particulate bone xenograft is packed and condensed around the implant. There is a temporary cover screw to prevent the particles of the bone graft from entering the screw chamber. (d) The contoured healing abutment is attached to the implant and has several very important functions: additional mechanical stabilization of the implant, obliteration of the extraction socket to contain the bone graft, and development of the ideal emergence profile for the definitive restoration.

a

b

c

d

Fig 11-4  (a and b) Particulate bone graft delivery with a large amalgam carrier. (c and d) Particulate bone graft delivery with a special funnel and a plugger (a variation of the CAS kit) (e) Implant placement in the sinus bone graft under the elevated membrane. (f) Postoperative occlusal view of the healing abutments and a universal surgical guide confirming the optimal distribution of the implants.

a

b

e

c

d

f

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Table 11-1  Comparison of lateral and transcrestal approach sinus elevation techniques with simultaneous implant placement Lateral approach

Transcrestal approach Cosci technique

Access and visibility

Best

Limited

Flap size

Large both mesiodistally and apicocoronally with one or two verticals

Minimal, comparable with a simple implant flap: no verticals, minimal apicocoronal and mesiodistal dimensions

Intraoperative complications

Membrane perforation, severing of a PSA branch, fracture of the buccal wall when the implant osteotomy and the window located too close to each other

Lower membrane perforation risk

Postoperative complications: swelling, bruising, extra pain

Occasional, more frequent

Rare, comparable with a simple implant placement

Surgical time

Longer: bigger flap, additional bony window creation

Shorter: no need to create a lateral window

Placement of multiple implants

Facilitated

More time consuming because multiple membrane elevations and graft placements will be required

Biomaterials

Bone graft and a collagen membrane

Bone graft only, less bone graft needed (approximately 0.5 to 1 mL for a single implant)

Amount of bone lifted above the floor

10 mm on average

3 to 5 mm on average

Using the Crestal Approach Sinus Kit Surgical access After adequate local anesthesia, the incision is made at the palatal crest. Reflecting a flap one or two teeth mesially and distally is sufficient for access. No vertical releasing incisions are required, and the buccal flap is smaller apicocoronally compared with the lateral window approach.

Osteotomy preparation and entrance to the sinus This part of the procedure is the most crucial because most sinus membrane perforations occur at this stage. The osteotomy can be prepared using a drilling method just short of the sinus floor. Once the sinus floor is reached with the implant drills, an osteotome is used to infracture the sinus floor. The sinus floor is usually a dense cortical bone approximately 1 mm in thickness and may require a significant tapping force to break through. This is why the osteotomes used for the sinus tent procedure must be rather concave or flat. A tent of the sinus

membrane can easily occur. Therefore, the ultimate advantage of the sinus elevation kit over the osteotome technique is the ability to enter the sinus cavity while leaving the membrane intact. This is accomplished by using a non-end-cutting drill with crestal stoppers, termed the Cosci technique. A clinical trial comparing both techniques in a split-mouth design showed that 13 out of 15 patients preferred the Cosci technique over the osteotome method. Less postoperative morbidity was reported in the Cosci group, which required less surgical time: 24 minutes versus 33 minutes. The transcrestal approach is definitely less invasive than a lateral approach as noted in Table 11-1. All other parameters related to implant survival and success were equal. Various transcrestal approach sinus elevation kits for the Cosci technique are available on the market today (Fig 11-5). All are designed to be used with an implant handpiece and employ non-end-cutting burs. The osteotomy is started with a diamond or a needle bur. The pilot drill is then advanced until just before the sinus floor is felt. The osteotomy is enlarged to the desired diameter. (The distance from the crest of the bone to the sinus membrane or sinus floor must have been measured on the CT scan preoperatively.) Note that larger drill diameters have a lower likelihood of membrane perforation, so the widest appropriate crestal approach sinus (CAS) drill kit is used with a stopper 1 mm short of the sinus floor as measured on the CBCT. After completion of the osteotomy, an instrument with a blunt tip is used to

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Using the Crestal Approach Sinus Kit

carefully sound and determine the sinus membrane versus the sinus floor. If the surface appears solid, the sinus floor is not completely removed. In this case, the same CAS drill is used with a stopper equal to the measurement on the CBCT until the cortical bone is removed and the sinus is entered without perforating the membrane. From the authors’ experience, in most cases it takes a stopper that makes the drill length 1 or even 2 mm more than the CBCT-based measurement. For example, if the measurement is 5 mm from the crest to the sinus floor, it is usually necessary to drill with a stopper 6 mm in length. This is usually explained by mesial and distal bony peaks close to the adjacent teeth that do not allow for tight adaptation of the sleeve to the crest of the bone. After confirming that the floor is removed, a Valsalva maneuver is done to confirm that the membrane is intact. This is done using a dental mirror to observe air flow or even bubbles from the osteotomy, which indicates perforation. Sometimes the integrity of the membrane can be assessed visually with a mirror when the native bone is only a few millimeters and the sinus is located closer to the crest (see Fig 11-5c). If no perforation is noticed, the clinician may proceed to the next step. If there is a perforation, the tear repair must be completed before proceeding.

a

b

Membrane elevation and graft placement Membrane elevation can be done using various techniques: balloon, hydraulic, or pushed with the bone graft itself. This step is also crucial because perforating the membrane with a bone graft is still possible. The most basic way of elevating the membrane is by introducing the bone graft itself. Graft material is carefully placed in small quantities into the osteotomy with the aid of osteotomes by gentle mallet tapping and is pushed to the depth of the sinus floor but not deeper. With each addition of graft material, the aim is to raise the membrane approximately 1 mm above the floor. This means that there will be three to five portions of the graft material sequentially introduced into the osteotomy and carefully pushed above the floor. The amount of bone graft needed is determined by the amount of elevation needed. Radiographic control at this stage may aid in determining the amount of bone elevation. In most cases, 0.5 mL introduced into the osteotomy is enough. Implant placement will add additional volume because it will push the graft apically.

c Fig 11-5 (a and b) CAS kit modification with the funnels for bone graft delivery. (c) An intraoperative view of the intact sinus membrane after using the CAS kit.

a healing abutment of a wider diameter than the osteotomy to prevent postoperative migration of the implant into the sinus (eg, a 6-mm healing abutment on a 5-mm-diameter implant). Placement of the healing abutment at the time of the initial surgery will eliminate the necessity to perform the second stage of surgery. Insertion torque is dependent on bone height, bone quality, implant macro design, and undersizing of the osteotomy.

Implant placement

Complications

An implant is placed according to the manufacturer’s protocol and is often bicortically stabilized despite low bone mass. Studies recommend having 3 to 5 mm of native bone for simultaneous implant placement to obtain primary stability and avoid migration of the implant into the sinus cavity (Fig 11-6). Adequate insertion torque will allow the operator to simultaneously place

Complications can be classified as intraoperative and postoperative. Intraoperative complications include membrane perforations, which can lead to nose bleeding in the early postoperative period. Late postoperative complications include persistent nose bleeding, pain, swelling, and migration of the implant into the sinus.

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a

b

c

Fig 11-6  (a) Periapical radiograph of the initial clinical situation. The edentulous maxillary first molar site has 3.5 mm of crestal bone present under the floor of the sinus. (b) Postoperative periapical radiograph. A CAS kit and particulate allograft were used to augment the sinus, and an 8 × 4.5–mm implant was placed with a 5 × 5–mm standard healing abutment (not shown). Note the well-defined dome of the allograft, suggesting the integrity of the sinus membrane after the elevation. (c) A periapical radiograph with the definitive restoration in place 1 year after surgery. There has been remodeling and noticeable settling of the graft, a new cortical floor of the elevated sinus, and overall stable clinical situation. (Periodontist: Konstantin Gromov, DDS; Restorative dentist: Ye Wang, DMD.)

Tear repair technique

A resorbable collagen barrier approximately 15 × 15 mm is hydrated, folded, and carefully inserted in the osteotomy to the depth of the sinus floor. It is preferable to use a bone putty graft than particulate in this setting to minimize the chance of graft migration.

The Piezoelectric Transcrestal Approach for Sinus Augmentation The piezoelectric surgical system uses ultrasonic microvibration to create the implant osteotomy. Piezoelectric energy does not cut soft tissue, which virtually eliminates trauma to the sinus mucosa.18–20 Piezoelectric surgery also allows precise and tactile control with a very low rate of sinus membrane perforation when performing either the transcrestal or lateral window technique.21–23 In addition, ultrasonic vibration provides a tactile sensation of the sinus mucosa when the sinus floor is penetrated, so a very minimal rate of mucosal perforation occurs.

PISE technique The piezoelectric internal sinus elevation (PISE) technique was introduced in 2003.19,20 This approach uses a piezoelectric surgical tip instead of osteotomes, but bone graft condensation is still required to elevate the sinus membrane because hydraulic pressure from the external irrigation is not enough to elevate the sinus mucosa. In the PISE technique, a cylindric carbide PISE tip with external irrigation or any compatible piezoelectric tip, connected to a piezoelectric device (Surgybone, Silfradent), is used to break through the sinus floor (see Figs 11-7a and 11-7b). The working head of the PISE tip (S028E tip) is 2.8 mm wide and 4 mm high.

A piezoelectric carbide-type tip is more powerful and effective than a diamond-coated tip for creating an osteotomy. After penetrating the sinus floor, bone graft condensing elevates the sinus mucosa. Gel-conditioned or putty bone graft material is preferred. To prepare gel- or putty-conditioned bone graft, use a mix of bovine bone powder (BioCera, Oscotec) and gel-conditioned allograft (OrthoBlast II, SeaSpine). The bovine bone acts as a radiopaque marker, and the gel allograft acts as a buffer during membrane elevation. An amalgam carrier is used when placing the graft into the socket. A narrow-diameter osteotome (usually 2 mm in diameter) or PISE tip is inserted to compact the graft into the osteotomy site. The PISE tip is more beneficial to place bone graft through the osteotomy site because it uses vibration preforming a gentle condensation. After the membrane is elevated, a standard-diameter implant is placed (ie, 3.7 to 4.0 mm wide and tapered) without additional drilling. To place a wide-body implant, the osteotomy should be underprepared with an intermediate drill to accommodate the implant with good stability (Fig 11-7).

Hydrodynamic PISE Hydrodynamic PISE (HPISE) is an updated version of PISE. This technique was introduced in 2008 and uses ultrasonic piezoelectric vibration to transgress the sinus floor similar to PISE.12 However, unlike PISE and other conventional transcrestal approach techniques, HPISE does not rely on bone graft condensation to elevate the sinus membrane but rather uses hydraulic pressure from internal irrigation. Hydraulic pressure from internal irrigation facilitates gentle and broad elevation of the sinus membrane before bone grafting up to 20 mm. When the sinus membrane is elevated sufficiently and an implant is placed simultaneously, bone graft is not needed in a new compartment under the elevated sinus mucosa in most cases.24–26 According to a 5-year prospective study on transcrestal sinus augmentation without grafting, bone regeneration in the sinus

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The Piezoelectric Transcrestal Approach for Sinus Augmentation

a

d

b

c

e

f

g

h

Fig 11-7  (a) Ultrasonic piezoelectric device (Surgybone). (b) A cylindric carbide PISE tip with an external irrigation. (c) The sinus floor was penetrated with a PISE tip. (d) A PISE tip was inserted through the osteotomy site, and the sinus floor was penetrated directly to expose the sinus mucosa. (e) The mixture of bovine bone (BioCera) and gel-conditioned bone (OrthoBlast II) was placed through the osteotomy site to elevate the sinus membrane. Bone condensing was performed by an osteotome to elevate sinus mucosa. (f) A 12 × 4.8–mm dental implant (EBI Implant) was placed simultaneously as a single-stage procedure. (g) A postoperative CBCT reveals approximately 5 mm of vertical sinus elevation. (h) Posterioranterior radiograph of the molar site after delivery of definitive restoration and 12 years of loading.

was predictable with favorable long-term results.25 As alternative bone graft, gelatin sponge, autologous venous blood, and fibrin block with concentrated growth factors (CGFs) are also recommended to accelerate bone reformation in the sinus after performing HPISE.27,28 However, when implants are not placed simultaneously, bone graft is needed in the sinus for space maintenance.

HPISE surgical technique As the first step, a 2.0-mm-wide round HPISE tip with an internal irrigation is used to penetrate the sinus floor and to elevate the sinus mucosa concurrently. The round insert has depthindicating lines marked at 2-mm intervals to measure the exact residual bone height from the alveolar crest to the sinus floor. In

addition, this tip has a set of stoppers (sleeves) at 2-mm intervals to prevent accidental mucosal perforation when approaching the sinus floor (Fig 11-8). After entering the sinus floor, the piezoelectric tip is kept in the osteotomy, applying hydraulic pressure on the sinus membrane for an additional 10 to 20 seconds. The sinus membrane is easily elevated through this procedure in most cases. Then, a 2.8-mm-wide cylindric HPISE tip is used to enlarge the osteotomy. While enlarging the osteotomy with the cylindric HPISE tip, elevation of sinus mucosa is achieved by the hydraulic pressure. After the removal of this tip from the osteotomy, a surgeon can observe up-and-down excursions of the sinus membrane during breathing. A cylindric HPISE tip is the final osteotomy tip to accommodate a 3.7- to 4.2-mm-wide tapered implant for good primary stability. To place a wide-body

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11  TRANSCRESTAL HYDRODYNAMIC PIEZOELECTRIC SINUS ELEVATION

a

b

c

d

e

f

g

h

i

j

k

Fig 11-8  (a) A set of 2.0-mm-wide round HPISE tips with a working length of 10 mm. These tips are mounted with stoppers to prevent accidental mucosal perforation when approaching the sinus floor. White stopper: 2-mm working length; red stopper: 4-mm; blue stopper: 6-mm; yellow stopper: 8-mm. (b) A 2-mm-wide round HPISE tip is used to break sinus floor. Sinus mucosa is elevated after applying hydraulic pressure for 10 to 20 seconds. (c) A clinical intraoral view showing a 2-mm-wide round HPISE tip using hydraulic pressure. (d) A 2.8-mm-wide cylindric HPISE is used to enlarge the osteotomy site and to elevate the sinus mucosa further with hydraulic pressure. (e) A clinical intraoral view showing a 2.8-mm-wide cylindric HPISE tip. This tip is the final osteotomy tip to accommodate tapered implants 3.7 to 4.2 mm wide. (f) CGF or bone graft is placed in the new compartment under the elevated sinus mucosa. (g and h) Clinical intraoral views showing placement of CGF alone in the sinus. (i) Postoperative panoramic CBCT after performing bilateral sinus augmentation using HPISE. Note 10-mm mucosal elevation in the right sinus and 25-mm sinus elevation in the left sinus. (j and k) Periapical radiographs before performing the HPISE procedure and 3 years in function.

implant, an intermediate implant drill is used to widen the osteotomy site. Bone graft material is by surgeon preference. A fibrin clot with CGF alone or bone graft material can be delivered through the osteotomy site after the membrane elevation. The authors prefer to place CGF alone instead of placing bone graft in the sinus when implants are placed simultaneously because more vital bone is regenerated in the sinus. When

sufficient sinus elevation is not achieved with the hydraulic pressure or an implant is not placed simultaneously, bone graft material is used to facilitate sinus membrane elevation and stabilization. Kim et al29 evaluated a total of 250 sinus augmentations using HPISE with or without bone graft. They reported the total success rate of 97.2% after an average of 69.3 weeks of

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References

loading. No severe complications were recorded. According to the clinical study, the HPISE technique can be applied to augment edentulous posterior maxilla and results in favorable success rate, minimal postoperative discomfort, and predictability. It is a minimally invasive sinus augmentation method that does not involve using a surgical mallet to break the sinus floor. Therefore, this technique reduces the possibility of benign positional vertigo, membrane perforation, and postoperative patient discomfort. In addition, this technique does not rely on rotary instrumentation or bone graft condensing to elevate the sinus membrane. HPISE is a viable alternative surgical method to the lateral sinus augmentation technique as well. One further advantage is that it can be used with or without bone graft material.

Conclusion Based on several concepts and techniques for the transcrestal approach to sinus grafting reviewed in this chapter, the authors suggest making a balanced decision in each clinical situation based on the skills, experience, and armamentarium of the operator. Although minimal invasiveness is not the only and ultimate goal of the dental implant therapy, the hydrodynamic piezoelectric method satisfies the goal of sinus augmentation for implant placement with minimal morbidity.

References 1. Truhlar RS, Orenstein IH, Morris HF, Ochi S. Distribution of bone quality in patients receiving endosseous dental implants. J Oral Maxillofac Surg 1997;55(12 suppl 5):38–45. 2. Tatum H Jr. Maxillary and sinus implant reconstructions. Dent Clin North Am 1986;30:207–229. 3. Chanavaz M. Maxillary sinus: Anatomy, physiology, surgery, and bone grafting related to implantology—Eleven years of surgical experience (1979–1990). J Oral Implantol 1990;16:199–209. 4. Boyne PJ, James RA. Grafting of the maxillary sinus with autogenous marrow and bone. J Oral Surg 1980;38:613–616. 5. Del Fabbro M, Testori T, Francetti L, Weinstein R. Systematic review of survival rates for implants placed in the grafted maxillary sinus. Int J Periodontics Restorative Dent 2004;24:565–577. 6. Solar P, Geyerhofer U, Traxler H, Windish A, Ulm C, Watzak G. Blood supply to the maxillary sinus relevant to sinus floor elevation procedures. Clin Oral Implants Res 1999;10:34–44. 7. Traxler H, Windisch A, Geyerhofer U, Surd R, Solar P, Firbas W. Arterial blood supply of the maxillary sinus. Clin Anat 1999;12: 417–421. 8. Zucchelli G, Mele M, Mazzotti C, Marzadori M, Montebugnoli L, De Sanctis M. Coronally advanced flap with and without vertical releasing incisions for the treatment of multiple gingival recessions: A comparative controlled randomized clinical trial. J Periodontol 2009;80:1083–1094. 9. Summers RB. The osteotome technique: Part 3—Less invasive methods of elevating the sinus floor. Compendium 1994;15:698–708. 10. Berengo M, Sivolella S, Majzoub Z, Cordioli G. Endoscopic evaluation of the bone-added osteotome sinus floor elevation procedure. Int J Oral Maxillofac Surg 2004;33:189–194.

11. Nedir R, Bischof M, Vazquez L, Nurdin N, Szmukler-Moncler S, Bernard JP. Osteotome sinus floor elevation technique without grafting material: 3-year results of a prospective pilot study. Clin Oral Implants Res 2009;20:701–707. 12. Sammartino G, Mariniello M, Scaravilli MS. Benign paroxysmal positional vertigo following closed sinus floor elevation procedure: Mallet osteotomes vs. screwable osteotomes. A triple blind randomized controlled trial. Clin Oral Implants Res 2011;22:669–672. 13. Testori T, Szmukler-Moncler S, Francetti L, Del Fabbro M, Trisi P, Weinstein RL. Healing of Osseotite implants under submerged and immediate loading conditions in a single patient: A case report and interface analysis after 2 months. Int J Periodontics Restorative Dent 2002;22:345–353. 14. Akça K, Cehreli MC, Iplikçioglu H. A comparison of threedimensional finite element stress analysis with in vitro strain gauge measurements on dental implants. Int J Prosthodont 2002;15:115–121. 15. Pierrisnard L, Renouard F, Renault P, Barquins M. Influence of implant length and bicortical anchorage on implant stress distribution. Clin Implant Dent Relat Res 2003;5:254–262. 16. Renouard F, Nisand D. Short implants in the severely resorbed maxilla: A 2-year retrospective clinical study. Clin Implant Dent Relat Res 2005;7(suppl 1):S104–S110. 17. Tawil G, Younan R. Clinical evaluation of short, machined-surface implants followed for 12 to 92 months. Int J Oral Maxillofac Implants 2003;18:894–901. 18. Vercellotti T. Piezoelectric surgery in implantology: A case report— A new piezoelectric ridge expansion technique. Int J Periodontics Restorative Dent 2000;20:358–365. 19. Sohn DS (ed). Piezoelectric Bone Surgery [Proceedings of the 12th Taipei Congress of Oral Implantologists, 27–29 Dec 2003, Taipei]. Taipei: Congress of Oral Implantologists, 2003. 20. Sohn DS, Ahn MR, Jang BY. Sinus bone graft using piezoelectric surgery. J Korean Acad Oral Maxillofac Implantol 2003;9:48–55. 21. Sohn DS. Innovative Implant Dentistry. Seoul: Koonja, 2003:228– 269. 22. Sohn DS (ed). Clinical Applications of Piezoelectric Bone Surgery [8th International Congress of Oral Implantologists, 28 Aug 2004, Singapore]. Singapore: International Congress of Oral Implantologists, 2004. 23. Robiony M, Polini F, Costa F, Vercellotti T, Politi M. Piezoelectric bone cutting in multipiece maxillary osteotomies. J Oral Maxillofac Surg 2004;62:759–761. 24. Sohn DS, Lee JS, Ahn MR, Shin HI. New bone formation in the maxillary sinus without bone grafts. Implant Dent 2008;17:321–331. 25. Nedir R, Nurdin N, Vazquez L, Szmukler-Moncler S, Bischof M, Bernard JP. Osteotome sinus floor elevation technique without grafting: A 5-year prospective study. J Clin Periodontol 2010; 37:1023–1028. 26. Sohn DS, Heo JU, Kwak DH, et al. Bone regeneration in the maxillary sinus using an autologous fibrin-rich block with concentrated growth factors alone. Implant Dent 2011;20:389–395. 27. Sohn DS, Moon JW, Moon KN, Cho SC, Kang PS. New bone regeneration in the maxillary sinus using only absorbable gelatin sponge. J Oral Maxillofac Surg 2010;68:1327–1333. 28. Moon JW, Sohn DS, Heo JU, Shin HI, Jung JK. New bone regeneration in the maxillary sinus using peripheral venous blood alone. J Oral Maxillofac Surg 2011;69:2357–2367. 29. Kim JM, Sohn DS, Heo JU, et al. Minimally invasive sinus augmentation using ultrasonic piezoelectric vibration and hydraulic pressure: A multicenter retrospective study. Implant Dent 2012;21:536–542.

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CHAPTER 12

Section III

LATERAL AND TRANSCRESTAL BONE GRAFTING WITH SHORT IMPLANTS Rolf Ewers, md, dmd, phd | Mauro Marincola, dds, ms

P

artially or completely edentulous patients often do not have enough bone available in the vertical or horizontal dimension in the posterior maxilla for standard-length dental implants. Sinus floor bone grafts have often been prescribed as a solution, but they are not always required. Sinus mucosa elevation or sinus elevation has been advocated to avoid augmentation of the alveolar crest. The term sinus bone graft describes filling the resulting cavity in the alveolar recess with augmentation material.1,2 In this chapter, the term sinus elevation will also be used. There are different varieties of sinus grafting depending on the amount of residual bone available and what length of implant is used. Careful imaging investigation with the panoramic radiograph (Fig 12-1a), digital volume tomography (DVT) (Fig 12-1b), or dental computed tomography (CT) (Figs 12-1c and 14-1d) is performed before treatment can begin.3 In rare cases, a cephalometric radiograph must be taken to decide whether the maxilla lies too far dorsally (Fig 12-1e).

Treatment Recommendations Based on vertical bone height (Fig 12-2), we propose the following two algorithms for using standard-length or short implants.3–5

Standard-length implant recommendations •  For less than 1 mm alveolar height: Horizontal horseshoe Le Fort I osteotomy with interpositional autogenous iliac crest graft. •  For 1 to 5 mm: Sinus floor bone grafting with staged implant placement. •  For 5 to 8 mm: Sinus floor grafting with simultaneous implant placement. •  For 8 mm or more: Minimally invasive sinus floor intrusion with simultaneous implant placement.

Short implant recommendations When using short (≤ 8 mm) or ultrashort (< 6 mm) implants, the indication changes dramatically4,5: •  For less than 1 mm alveolar height: Horizontal horseshoe Le Fort I osteotomy with interpositional autogenous iliac crest graft, lateral sinus elevation, or transcrestal sinus elevation with titanium mesh. •  For less than 3 mm: Transcrestal window sinus elevation or lateral sinus elevation. •  For 3 to 7 mm: Transcrestal (internal) sinus elevation with immediate implant placement. •  For 7 mm or more: Place short or ultrashort implants without a sinus procedure.

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Treatment Recommendations

a

b

c

d

e

Fig 12-1  (a) Panoramic radiograph showing pronounced atrophy of the maxilla on both sides with 1 to 3 mm residual bone. (b) DVT of an edentulous lateral maxilla. Top right shows the views that are taken. Top left is a top view into the maxillary sinus lumen at the purple plane; bottom left is the sagittal panoramic reformatting at the level of the blue plane; bottom right shows a transverse section at the level of the green plane. (c) Overall view of the dental CT with coronal section, three reformatted panoramic and 44 reformatted orthoradial slices. (d) Reformatted panoramic view (section) of a dental CT scan, showing the left maxillary sinus and a maxillary sinus septum. (e) Section of the cephalometric radiograph (yellow dots indicate the most ventral points in the maxilla and mandible). The maxillary bone atrophy is increased because of the residual dentition in the mandible. (Reprinted with permission from Ewers.3)

Fig 12-2 Recommended procedures are dictated by alveolar crest height, implant size, and the surgi­ cal capabilities of the clinician. (a) For crest heights ≤ 1 mm, a horizontal horseshoe Le Fort I osteot­ omy may be recommended. (b) For crest heights between 1 and 3 mm, transcrestal or lateral sinus elevations are both options. (c) For crest heights between 3 and 7 mm, implants can be placed si­ multaneously with the internal sinus lift (ISL). (d) For crest heights greater than 7 mm, a sinus elevation does not need to be used with a short implant. (Modified with permission from Ewers.3)

1.0–3.0 mm a

≤ 1.0 mm

b

> 7.0 mm

3.0–7.0 mm c

d

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12  LATERAL AND TRANSCRESTAL BONE GRAFTING WITH SHORT IMPLANTS

Palatal

Sinus floor

Buccal a

Fig 12-3 Preoperative illustration of maxilla with a vertical RBH of 1.0 to 3.0 mm with a cut through the mucosa and periosteum in the middle of the crest. (Reprinted with permis­ sion from Marincola et al.4)

b

Fig 12-4  Preparing a bone trough approximately 4 to 5 mm in height. (a) The trough is first prepared with a rough metal bur. (Reprinted with permission from Marincola et al.4) (b) Intra­ operative view.

Fig 12-5 (a) As the sinus mucosa is ap­ proached, the rough metal bur is replaced by a diamond bur. (b) When the bone almost has been removed and the sinus mucosa be­ comes visible, the trough is finalized with a diamond bur until all bone is removed from the sinus mucosa. (Reprinted with permission from Marincola et al.4)

a

b Fig 12-6  (a) Finalized trough without mucosa perforation. (Reprinted with permission from Marincola et al.4) (b) When all the bone is removed, the sinus mucosa becomes visible without perforation preferably.

a

b

Lateral Sinus Bone Grafting with Immediate Implant Placement

the transcrestal approach shows fewer implant losses, whereas other authors recommend the lateral approach, especially if there is less than 4 mm residual bone height (RBH) present.11–13

Since 1976, this method of augmentation of the alveolar recess of the maxillary sinuses has established itself and become standard.6 The transcrestal approach has also been used since the publications of Defrancq and Vanassche and others.7–9 Engelke et al10 also reported a minimal lateral approach, the subantroscopic laterobasal sinus floor augmentation (SALSA). Since that time, there has been continuous discussion regarding which of these approaches is better. Some authors are convinced that

Surgical procedure The standardized operating method for a lateral sinus graft is shown in Figs 12-3 to 12-18. The following steps are taken: 1. Cut through the mucosa and the periosteum (Fig 12-3) and prepare a mucoperiosteal flap to open the lateral aspect of the alveolar crest.4

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Lateral Sinus Bone Grafting with Immediate Implant Placement

a Fig 12-7  View through an arthroscope. Ele­vat­ ing the maxillary sinus mucosa after dissect­ ing it away from the maxillary sinus septum. (Reprinted with permission from Marincola et al.4)

b

Fig 12-8  (a) Elevating the maxillary sinus mucosa from the alveolar recess bone with special elevating instruments. (Reprinted with permission from Marincola et al.4) (b) Starting to very carefully elevate the sinus mucosa with a special sinus elevation instrument.

Fig 12-9  (a) Filling the cavity with a syringe of augmentation material. (b) Carefully packing the augmentation material with sinus eleva­ tion instruments under the sinus mucosa into the alveolar recess. (Reprinted with permis­ sion from Marincola et al.4)

a

b

a

b

Fig 12-10  (a) The maxillary alveolar recess is completely filled with augmentation material, and the implant socket is drilled with the pilot drill. As the sinus mucosa is elevated by the augmentation material, there is no danger of perforating the sinus mucosa. (Reprinted with permission from Marincola et al.4) (b) Starting to drill the implant socket with the pilot drill until the augmentation material is reached.

2. Prepare a bone trough approximately 4 to 5 mm wide and about 10 mm long for one implant or 20 mm long for two implants in the region where the implants will be placed. First use a surgical carbide bur (Fig 12-4) and then continue with a diamond bur (Fig 12-5). The trough should be located directly at the lateral lower edge of the floor of the maxillary sinus (Fig 12-6). 3. Special care has to be taken if there is a septum in the maxillary recess (as first described by Zuckerkandl14 in 1877).The preparation must be very careful around the recess to prevent perforation of the sinus mucosa (Fig 12-7).

4. Elevation of the maxillary sinus through the trough is done with special instruments designed for sinus elevation operations15 (Fig 12-8). 5. Fill the resulting cavity with an augmentation mixture such as SynthoGraft (Bicon) or Symbios (Dentsply) with a special syringe (Fig 12-9a) and then pack it with special instruments (Fig 12-9b). 6. Drill the implant socket with the pilot drill. Because the sinus mucosa is elevated and protected by the augmentation material, there is no danger of damaging the sinus mucosa (Fig 12-10). 7. Continue with latch reamers up to the desired width to enlarge the cortical cavity (Fig 12-11).

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Fig 12-11 (a) Widening the implant socket with latch or hand reamers. (Reprinted with permission from Marincola et al.4) (b) Oste­ otomy being enlarged with the 4-mm hand reamer.

a

a

b

b

c

Fig 12-12  (a) Hand reamer with collected bone. (b) Collected bone on a Freer instrument. (c) Collected bone being applied into the osteoto­ my hole with sinus elevation instrument. (Reprinted with permission from Marincola et al.4)

11. Because the trough is so small, it is not necessary to cover the augmentation material with a membrane, but this can be done if the clinician wishes. The suture may be a singleknot suture with resorbable suture material (Fig 12-15). 12. If the remnant cortical bone is very thin and there is concern whether the implant will retain its position, a special sinus elevation abutment can be used (Fig 12-16).

Fig 12-13  A 5 × 4–mm implant with a 2.5-mm well is placed into the osteotomy with a 2.5-mm implant inserter/retriever.

8. Fill the cavity with the bone collected from the latch or hand reamer and place the short dental implant. As the autogenous bone is pressed into the augmentation material, the surface on the tip and around the dental implant always is covered with autogenous bone (Fig 12-12). 9. Place the short implants (Fig 12-13). 10. To finalize the implant operation, cover the implant and the healing plug with the remaining autogenous bone collected from the latch or hand reamer (Fig 12-14).

To prepare the bone trough, either rotary instruments or piezoelectric surgical instruments may be used.16 With both methods, it is imperative to ensure that all the bone chips are collected with a suitable bone collector so they can then be mixed with the bone-forming material SynthoGraft or Symbios. The small bone trough is particularly effective when the mucosa of the maxillary sinus has to be dissected away from the septa of the sinuses, as first described by Zuckerkandl.14 This procedure is not possible with the transcrestal approach where a sinus mucosa perforation may go unnoticed. In the lateral approach procedure, a perforation is easily observed and can be covered with a resorbable collagen membrane to provide protection of the sinus mucosa17,18 (Fig 12-17). Also, only a small amount of augmentation material is placed into the alveolar process because there is risk that material will be displaced into the vestibule when the patient blows his or her nose. Therefore, it is recommended that the patient be instructed not to blow his or her nose. Postoperative radiologic control images show the sinus elevation and augmentation (Fig 12-18a), which should mineralize after few months (Fig 12-18b).

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Lateral Sinus Bone Grafting with Immediate Implant Placement

Fig 12-14 (a) The implant is covered with collected bone so it will be surrounded with autogenous bone. (b) Illustra­ tion of implant completely sur­ rounded by autogenous col­ lected bone. (Reprinted with permission from Marincola et al.4) (c) Implant is completely covered with autogenous col­ lected bone. a

b

c

Fig 12-15  (a) Finalized situation after place­ ment of implants covered with autogenous collected bone and sutured. (Reprinted with permission from Marincola et al.4) (b) Intra­ operative view after wound closure with singleknot sutures of the mucosa and the perios­ teum.

a

b

a

b

a

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a

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Fig 12-16  (a) Bicon implant in situ with sinus elevation abutment, if necessary. (b) Final situ­ ation of Bicon implant covered with sinus el­ evation abutment and suture. (Reprinted with permission from Marincola et al.4)

Fig 12-17  (a) Sinus mucosa perforation seen through the trough. (b) Covering of the sinus mucosa perforation with a resorbable colla­ gen membrane.

Fig 12-18 (a) Postoperative radiograph fol­ lowing a lateral sinus elevation and bone graft in the alveolar recess with a “hood” over the implant, which is seen as a hallmark of a successful lateral sinus elevation procedure. (b) Post­operative radiograph after 5 months re­ vealing newly formed bone with a better visi­ ble hood. (Reprinted with permission from Marincola et al.4)

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12  LATERAL AND TRANSCRESTAL BONE GRAFTING WITH SHORT IMPLANTS

a

c

b

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Fig 12-19  (a) Preoperative radiograph of a 36-year-old man with missing maxillary left premolars. Alveolar bone is less than 2 mm at the position of the first premolar. (b) Postoperative radiograph after lateral sinus elevation with augmentation and placement of two 5 × 4–mm Bicon implants. (c) Postoperative image of two integrated abutment crown restorations (Bicon). (d) Two-year postoperative radiograph with very good mineralization around the two implants and bone gain in the maxillary recess, especially above the first premolar implant. (Reprinted with permission from Marincola et al.4)

Case example Figure 12-19 illustrates the treatment of a 36-year-old man. The panoramic radiograph shows the lack of crestal bone with less than 2 mm of bone in the maxillary sinus region (Fig 12-19a). The postoperative panoramic radiograph (Fig 12-19b) shows two implants in good position. Six months later, two single crowns were used to restore the implants (Figs 12-19c and 12-19d). The panoramic radiograph shows mineralization around the tips of the implants, which is a precondition to osseointegration.

Transcrestal Sinus Bone Grafting with Immediate Implant Placement In 1994, Summers introduced the maxillary internal sinus lift (ISL) technique by the use of osteotomes, in which bone is added to the apical part of the implant to improve primary implant stability.19,20 This technique was shown to be less invasive, less

time-consuming, and less painful for the patient postoperatively than the lateral window approach. ISL is indicated when RBH is between 5 and 7 mm. Other authors perform ISL with bone levels as low as 4 mm.21 There is an increasing debate whether a bone graft is needed beneath the elevated membrane to maintain the space for new bone formation. In Summers’ original report, autogenous, allogenic, or xenogeneic grafting materials were placed.22 Recently, Nedir et al23 showed no differences (P > .05) between ISL procedures performed with or without bone graft. However, the main clinical challenge arises when a bone graft is placed and the bone around the implant-abutment interface needs to be maintained. Rammelsberg et al24 performed ISL without bone graft in a retrospective study in 66 patients with 101 dental implants in 2015. They used radiographs to determine bone changes over time and determined that mesial and distal mean apical bone gain were 0.5 mm and 0.4 mm, respectively, indicating that implants placed in combination with ISL without graft material would still have bone gain. Likewise, Nedir et al21,23 compared dental implants plus ISL placed in combination with and without bone graft in 2013. They concluded that, although more bone is observed when the grafting material is used (5

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Transcrestal Sinus Bone Grafting with Immediate Implant Placement

a

b

Fig 12-20 (a) Clinical condition of the alveolar ridge that shows the edentulous area of the premolars and first molar prior to the surgical procedure. (b) Preopera­ tive patient assessment: Radiograph of the edentulous space showing maxillary sinus pneumatization. (c) Crest­ al incision and blood collection with a sterile syringe for further bone graft. (d) Pilot drilling at the site of dental implantation with simultaneous ISL. (e) A 2.5-mm latch reamer with no cutting edge is used to start osteoto­ my widening at the crestal bone. (f) The latch reamer perforation in the bone starts the osseous widening. (g) Radiograph showing RBH of 4.24 mm and the 2.5-mm latch reamer insertion into the bone.

e

mm) in comparison with nongrafted sites (3 mm, P < .05), this was not required to promote endosinus gain. Although there is no consensus whether bone graft should be placed or not, this option remains highly recommended due to the benefit of long-term osseous maintenance.

Surgical procedure After clinical and radiograph evaluation (Figs 12-20a and 12-20b), intrasulcular incision is used to raise a full-thickness flap to perform the ISL (Fig 12-20c). A 2-mm-diameter pilot drill is used to achieve cortical perforation and extends 1 to 2 mm as determined by RBH measurement.25 A high-speed drill (ie, 1,100 rpm) with a cutting edge at the apical portion is used with external water irrigation (Fig 12-20d). The pilot osteotomy should be 1 to 2 mm shorter than the calculated bone height measured on the periapical radiograph. The following steps are achieved with latch reamers at 50 rpm without water irrigation. The reamer consists of two vertical cutting edges that stop 2 mm before the apical portion. The apex is tapered with no cutting edge to avoid sinus membrane perforation. A 2.5-mm latch (mechanical) reamer is inserted to start the widening of the crestal cortical bone and to deepen the bur with finger pressure toward the cortical bone of the sinus floor. The pressure allows the noncutting edge to be pressed through the smooth cancellous bone but stops at the cortex of the sinus floor (Figs 12-20e and 12-20f). With this 2.5-mm latch reamer, a radiograph is taken to determine the remaining final

c

d

f

g

length before sinus floor (Fig 12-20g). The RBH is measured to determine the final drilling length, and the latch reamer series with 0.5-mm diameter increments is used until the 4.5-mm implant diameter is reached. Next follows the microfracture of the sinus floor. With the 3.5-mm hand reamer that has a single vertical cutting edge and ends with a knife edge at the apex of the reamer, a mallet is used to tap the hand reamer at four different points along the buccopalatal and mesiodistal axes to facilitate microfracture of the sinus floor. The first fracture point is at the lowest residual bone level as determined by periapical radiograph. The fracture is started at the distal aspect of the osteotomy. The second and fourth fracture points are buccal and palatal because of higher pneumatization toward the buccal. The third point in this case is the mesial aspect (Figs 12-20h to 12-20j). A synthetic and bacteriostatic grafting material (eg, SynthoGraft) can be mixed with collected blood until a putty consistency is reached, as shown in Fig 12-20k. A 4.0-mm bone graft syringe is used to place bone graft material into the apical portion of the osteotomy (Fig 12-20l). Once resistance against the sinus membrane is detected, the syringe is slowly retracted with continuous injection. After the bone graft material is injected, a 3.5-mm osteotome is used to gently push the material into the depth of the osteotomy. With the graft material in place, the osteotome is advanced via gentle tapping until the cortical bone is fully fractured, elevating the sinus mucosa (Figs 12-20m to 12-20o). A 6.0 × 4.5–mm implant is placed into the grafted osteotomy site first using an implant inserter in a straight handle and then by gently tapping with a seating tip (Figs 12-20p to 12-20s).

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12  LATERAL AND TRANSCRESTAL BONE GRAFTING WITH SHORT IMPLANTS

2

3

Second microfracture at buccal with the 3.5-mm hand reamer

1

Third microfracture at mesial with the 3.5-mm hand reamer

First microfracture at distal with the 3.5-mm hand reamer

Cortical bone

4

Fourth microfracture at palatal with the 3.5-mm hand reamer

Cortical bone

h

i

j

k

l

m

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Fig 12-20  (cont) (h) Illustration of the microfracture points along the cortical zone performed with the 3.5-mm hand ream­ er. The first microfracture is at the distal, the second microfracture is at buccal, the third microfracture is at the mesial, and the fourth microfracture is at the palatal. (Reprinted with permission from Marincola et al.4) (i and j) Clinical pictures show­ ing the 3.5-mm hand reamer performing microfractures. (k) Illustration of the grafting material inside the cavity. (Reprinted with permission from Marincola et al.4) (l) The grafting material is injected. (m) The 3.5-mm osteotome inserted into the osteotomy pushing the material against the sinus membrane. (n) Radiograph showing the osteotome position and the grafting material. (o) A 4.0-mm osteotome performing the greenstick fracture.

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Transcrestal Sinus Bone Grafting with Immediate Implant Placement

p

q

t

r

s

u

w

v

x

Fig 12-20  (cont) (p to r) The implant is placed into the osteotomy with the straight handle and the 3.0-mm seating tip. (s) Clinical picture showing the implant position after its placement via gentle tapping. (t) Implant in place with the healing plug. (u) View after the healing plug has been cut. (v) Autologous bone graft over the implant with the bone that was collected during the osteotomy. (w) Immediate final radiograph of the implant placed together with the ISL pro­ cedure. The grafting material is visible on the apical portion of the implant. (x) View of the definitive restoration after 4.5 years.

If there is more than 3 mm of remaining bone, the first plateaus following the sloping shoulder of the implant will be engaged against the osteotomy walls, and this press-fit implant will not move during healing because primary stability will be achieved. When the bone level is 3 mm or less, a sinus elevation abutment needs to be placed to avoid implant displacement into the sinus floor. If this is not required, a healing plug is used (Figs 12-20t and 12-20u). This implant design cannot have primary stability in this setting along the osteotomy walls because it is placed 2 mm under the crest, and the implant body will be fully submerged into the grafting material. Plateau root form

implants with healing chambers between the plateaus (ie, Bicon implants) do not need primary stability, but the internal sinus abutment stabilizes the implant into its final prosthetic position. More grafting material is applied (Fig 12-20v), and single sutures with polyglycolic acid are used to close the mesial and distal relieving incisions. After implant placement, an immediate postoperative radiograph is taken (Fig 12-20w). The definitive restoration for this patient is shown in Fig 12-20x. Patients should receive postoperative and homecare instructions, and antibiotics (eg, amoxicillin) and analgesics can be prescribed to avoid infections and pain or swelling.

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Discussion Dental implantation is still the most effective approach to replace a missing tooth according to the observed survival rates over time. However, sometimes the anatomical conditions restrict implant placement into an optimal position, limiting prosthetic options.26 Maxillary sinus pneumatization occurs as the result of the maxillary posterior tooth loss. Therefore, ISL has been documented as one of the surgical approaches to accomplish implant placement in the same surgical procedure.27 Results of this case example suggest that ISL and simultaneous implantation can be successfully performed on patients with no intraoperative or early postoperative complications. The need for sinus grafting in conjunction with the ISL procedure is still open to debate. According to Summers’ recommendation, autogenous, allogenic, or xenogenic grafting materials will maintain the space for new bone formation. However, several studies have suggested that sinus membrane elevation by itself promotes bone regeneration by means of the formation of a fibrin clot in the created space. This clot, which is stabilized and protected from external trauma and intrasinus pressure, has the potential to stimulate bone formation (see chapter 7).28,29 It is important to note that this option is highly susceptible to membrane perforation or membrane invagination around the implant apex, leading to loss of bone supporting volume over time. The placement of a synthetic material (eg, purephase tricalcium phosphate) into the created space to avoid the collapse of the membrane around the exposed implant will promote bone formation during the osseointegration period also around the implant apex. Associated complications with sinus augmentation procedures are well described in the literature. The most common complication is membrane perforation with a prevalence of between 7% and 44%. Hemorrhage, infection, and rhinosinusitis are also described as expected complications.30 However, none of them occurred in this case study, indicating a successful surgical procedure that is specifically developed for novice clinicians with little or no experience in the sinus elevation procedure. Implant survival in conjunction with ISL has also been well reported in the literature, ranging from 94% to 100%.31,32 Nevertheless, the most critical issue is crestal bone level maintenance over time. This is favored by placing an implant in a subcrestal (ie, submerged) fashion and by using an implant with a convergent crest profile represented by sloping shoulder geometry to enhance platform switching. Platform switching allows for an increase in residual crestal alveolar bone volume around the neck of the implant, repositions the papilla to a more esthetic and apposite level, reduces mechanical stress in the crestal alveolar bone area, and assists in enhancing the vascular supply to hard and soft tissue in cases of reduced interdental space.33 ISL is a reliable method to use when the proper protocol is followed. It is a less time-consuming option with a low rate of complication that can be considered in patients with decreased

bone stock in the posterior maxilla. The procedure outlined allows for implant placement in a nontraumatic way and without complication during the procedure or the postoperative time period.

Conclusion Ever since Tatum’s innovation in 1976, there have been modifications of this procedure with many publications, demonstrating that there is not just one method to treat sinus graft patients.3 The best option depends on the severity of the bone deficiency, the age and medical condition of the patient, and the ability of the operating surgeon. The possibility to minimize surgical intervention by the use of short and ultrashort implants in accordance with the height of the missing bone in the alveolar crest should be a consideration given the success of posterior maxillary short and ultrashort implants.

References 1. Ewers R. Maxilla sinus grafting with marine algae derived bone forming material: A clinical report of long-term results. J Oral Maxillofac Surg 2005;63:1712–1723. 2. Frost HM, Jensen OT. Vital biomechanics of bone and bone grafts. In: Jensen OT (eds). The Sinus Bone Graft, ed 2. Chicago: Quintessence, 2006:27–39. 3. Ewers R. Implant surgery. In: Lambrecht JT (ed). Oral and Implant Surgery: Principles and Procedures: Chicago: Quintessence, 2009:350–360. 4. Marincola M, Daher S, Ewers R, Lehrberg J. Sinus lift techniques. In: Morgan VJ (ed). The Bicon Short Implant: A Thirty-Year Per­ spective. Chicago: Quintessence, 2017:151–180. 5. Neugebauer J, Vizethum F, Berger C, et al. Short, angulated and diameter-reduced implants. Guidelines of the 11th European Consensus Conference. Eur J Dent Implantol 2016;12:16–19. 6. Tatum H. Lecture presented to the Alabama Implant Congress. 1976. 7. Defrancq J, Vanassche B. Less invasive sinus lift using the tech­ nique of Summers modified by Lazzara [in French]. Rev Belge Med Dent (1984) 2001;56:107–124. 8. D’Amato S, Borriello C, Tartaro G, Itro A. Maxillary sinus surgical lift. Summers’ technique versus lateral surgical approach [in Ital­ ian]. Minerva Stomatol 2000;49:369–381. 9. Baumann A, Ewers R. Minimally invasive sinus lift. Limits and possibilities in the atrophic maxilla [in German]. Mund Kiefer Gesichtschir 1999;3(suppl 1):S70–S73. 10. Engelke W, Schwarzwäller W, Behnsen A, Jacobs HG. Subantro­ scopic laterobasal sinus floor augmentation (SALSA): An up-to5-year clinical study. Int J Oral Maxillofac Implants 2003;18:135– 143. 11. Felice P, Pistilli R, Piattelli M, Soardi E, Barausse C, Esposito M. 1-stage versus 2-stage lateral sinus lift procedures: 1-year post-loading results of a multicentre randomised controlled trial. Eur J Oral Implantol 2014;7:65–75.

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References

12. Zitzmann NU, Schärer P. Sinus elevation procedures in the re­ sorbed posterior maxilla. Comparison of the crestal and lateral approaches. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1998;85:8–17. 13. Pal US, Sharma NK, Singh RK, Met al. Direct vs. indirect sinus lift procedure: A comparison. Natl J Maxillofac Surg 2012;3:31–37. 14. Zuckerkandl E. Zur Morphologie des Gesichtsschädels. Stuttgart: Ferdinand Enke, 1877. 15. Kirsch A, Ackermann KL, Hürzeler M, Hutmacher D. Sinus graft­ ing with porous hydroxyapatite In: Jensen OT (ed). The Sinus Bone Graft. Chicago: Quintessence, 1999:79–94. 16. Vercellotti T. Essentials in Piezosurgery: Clinical Advantages in Dentistry. Chicago: Quintessence, 2009. 17. Lambrecht JT, Glaser G, Meyer J. Bacterial contamination of filtered intraoral bone chips. Int J Oral Maxillofac Surg 2006;35: 996–1000. 18. Chung KM, Salkin LM, Stein MD, Freedman AL. Clinical evalua­ tion of a biodegradable collagen membrane in guided tissue regeneration. J Periodontol 1990;61:732–736. 19. Summers RB. A new concept in maxillary implant surgery: The osteotome technique. Compendium 1994;15:152–156. 20. Summers RB. The osteotome technique: Part 3—Less invasive methods of elevating the sinus floor. Compendium 1994;15:698– 704. 21. Nedir R, Nurdin N, Khoury P, et al. Osteotome sinus floor eleva­ tion with and without grafting material in the severely atrophic maxilla. A 1-year prospective randomized controlled trial. Clin Oral Implants Res 2013;24:1257–1264. 22. Brizuela A, Martín N, Fernández-Gonzalez FJ, Larrazábal C, Anta A. Osteotome sinus floor elevation without grafting material: Results of a 2-year prospective study. J Clin Exp Dent 2014;6: e479–e484. 23. Nedir R, Nurdin N, Abi Najm S, El Hage M, Bischof M. Short implants placed with or without grafting into atrophic sinuses: The 5-year results of a prospective randomized controlled study. Clin Oral Implants Res 2017;28:877–886.

24. Rammelsberg P, Mahabadi J, Eiffler C, Koob A, Kappel S, Gabbert O. Radiographic monitoring of changes in bone height after implant placement in combination with an internal sinus lift without graft material. Clin Implant Dent Relat Res 2015;17 (suppl 1):e267–e274. 25. Marincola M, Urdaneta R, Bär A, Günther J. Implantation mit gleichzeitigem Sinuslift bei geringer Knochenresthöhe. Implan­ tologie J 2009;17:44–50. 26. Calvo-Guirado JL, Gómez-Moreno G, López-Marí L, Ortiz-Ruiz A, Guardia-Muñoz J. Atraumatic maxillary sinus elevation using threaded bone dilators for immediate implants. A three-year clinical study. Med Oral Patol Oral Cir Bucal 2010;15:e366–e370. 27. Gabbert O, Koob A, Schmitter M, Rammelsberg P. Implants placed in combination with an internal sinus lift without graft material: An analysis of short-term failure. J Clin Periodontol 2009;36:177–183. 28. Lundgren S, Andersson S, Gualini F, Sennerby L. Bone reforma­ tion with sinus membrane elevation: A new surgical technique for maxillary sinus floor augmentation. Clin Implant Dent Relat Res 2004;6:165–173. 29. Hatano N, Sennerby L, Lundgren S. Maxillary sinus augmentation using sinus membrane elevation and peripheral venous blood for implant-supported rehabilitation of the atrophic posterior maxilla: Case series. Clin Implant Dent Relat Res 2007;9:150–155. 30. Boffano P, Forouzanfar T. Current concepts on complications associated with sinus augmentation procedures. J Craniofac Surg 2014;25:e210–e212. 31. Shalabi MM, Manders P, Mulder J, Jansen JA, Creugers NH. A meta-analysis of clinical studies to estimate the 4.5-year survival rate of implants placed with the osteotome technique. Int J Oral Maxillofac Implants 2007;22:110–116. 32. Uckan S, Tamer Y, Deniz K. Survival rates of implants inserted in the maxillary sinus area by internal or external approach. Implant Dent 2011;20:476–479. 33. Aparna IN, Dhanasekar B, Lingeshwar D, Gupta L. Implant crest module: A review of biomechanial considerations. Indian J Dent Res 2012;23:257–263.

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CHAPTER 13

TRANSSINUS IMPLANTS Tiziano Testori, md, dds | Gabriele Rosano, dds, phd | Alessandro Lozza, md | Stephen S. Wallace, dds

I

mplant rehabilitation in the edentulous maxilla can be achieved with either fixed or removable prostheses. In completely edentulous patients, fixed implant rehabilitation shows higher survival rates than removable prostheses.1 The possibility of rehabilitating an arch with a fixed prosthesis with predictable long-term success has been an important goal in dentistry.2 However, the rehabilitation of a completely edentulous maxilla is often associated with anatomical limitations from decreased bone volume, especially in the premolar and molar regions. Bone atrophy progresses rapidly during the first year after tooth loss and continues thereafter and is affected by long-term use of removable prostheses and relative maxillary sinus pneumatization.3 The sinus is largest at age 20 to 30 years, with changes observed following tooth extractions due to alveolar change.4 Subjective data gathered by patient questionnaires do not establish the number of elements perceived for “normal” functioning.5–7 A reduced number of functional units is not a source of functional deficiency in elderly patients and does not result in an increased incidence of temporomandibular disorders.8,9 Functionality of the stomatognathic apparatus as it relates to the patient’s age range has been correlated with the number of teeth present termed optimal, suboptimal, or minimal function. An optimal level is considered 12 pairs of occlusal units in function for the age range 20 to 50 years. A suboptimal level is 10 occlusal pairs for an age range between 40 and 80 years. A minimal level is 8 pairs of occlusal units in the age range between 70 and 100 years.

Alternatives to Lateral Window Surgery When reconstructing the maxilla, insufficient bone volume in the lateroposterior sectors is not in itself an indication for performing a lateral window maxillary sinus augmentation.

Alternatives to invasive surgery should be considered in cases of systemic diseases, sinus pathologies, advanced age, or psychologic reasons. When bone volume is insufficient for implant placement, bone regeneration techniques or alternative treatments may be considered, such as implants in the maxillary tuberosity, pterygoid implants, zygomatic implants, tilted implants, and short implants.10–20 These alternative treatments may be indicated for patients who cannot undergo complex surgery for various psychologic or clinical reasons. An example of an alternative treatment would be the All-on-4 protocol in which maxillary posterior implants are placed with the apex angled anteriorly at 30 degrees, just missing the anterior wall of the sinus cavity. This provides increased length and greater anteroposterior (AP) spread and often eliminates the need for bone grafting of the sinus floor.21–23 For moderate to severe maxillary atrophy, in the presence of surgically challenging sinus anatomy, the apex of the posterior implants can be angled anteriorly, passing transsinus, to apically fix at the lateral piriform rim into the lateral nasal wall. The most important bone for apical fixation of implants in this setting is the lateral nasal bone mass with the maximum available bone found at the piriform rim above the nasal fossa.24–26 This area, designated the M point, can often also engage two implants placed at 30-degree angles. The transsinus implants are then grafted and possibly placed into immediate function, depending on the level of crestal stability present. In patients with severe maxillary atrophy presenting with reduced lateral nasal wall thickness or even absence, there is insufficient bone to use the transsinus approach. In such cases, a zygomatic implant can be considered.27,28 However, in the vast majority of patients, the lateral nasal wall will be 2 mm or greater in thickness, enough to engage a transsinus implant. Note that this method is only practical if there is also sufficient bone at the alveolar crest to stabilize the implant. The aim of this chapter is to present the alternative of anterior sinus grafting in conjunction with transsinus implant placement.

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Nasal Anatomy

Fig 13-1  Lateral nasal wall bone where the apical fixation of a transsinus implant should be placed (arrow).

Fig 13-2  Sinus medial wall. Small branches deriving from the posterior lateral nasal arteries have been found to perforate the nasal wall laterally and reach the mucosa of the maxillary sinus. The course of the posterior lateral nasal artery is indicated by arrows.

Nasal Anatomy

nasal wall laterally to reach the mucosa of the maxillary sinus29 (Fig 13-2). The medial wall of the maxillary sinus, therefore, is vascularized and innervated by the posterior lateral nasal arteries that pass through the wall in an AP direction to innervate the sinus mucosa. The posterior lateral nasal artery is close to the sphenopalatine artery and may anastomose with the facial or other nasal arteries. It has been found to course close to or within the medial wall of the sinus. This distribution presents the potential for bleeding during lateral approach sinus elevation surgery with simultaneous transsinus implant placement because these branches can be intraosseous or disturbed by curettage or osteotomy. Bleeding may be controlled with head elevation and tamponade or (rarely) electrocauterization.32,33

The lateral nasal wall is vascularized by branches deriving from the posterior lateral nasal artery and is in anatomical relation to the nasolacrimal duct (NLD) and the canalis sinuosus (CS).29 The thickness of the nasal mucosa varies between 0.3 and 5.0 mm, depending on the development of the cavernous plexus and the mucosal glands. It is found to be thickest over the medial surface of the middle and inferior nasal conchae.30 Ideally, apical fixation of a transsinus implant should be limited to the confines of the lateral nasal wall bone (Fig 13-1) and not protrude into the nasal cavity. Clinical experience, however, has shown that a slight protrusion of 1.0 to 1.5 mm through the anterior nasal septum is acceptable. This is possible because the epithelium at the anterior septum is underlined by a 1.5-mm-thick tissue of convoluted vessels that may contain the implant and act as a further barrier for protrusion into the airway space. Dental implants that extend into the nasal cavity may remain asymptomatic but add risk for airway and implant health. When complications do occur, the most prevalent symptoms are hematomas and unilateral mucopurulent nasal discharge. Pain, discomfort, headache, or congestion may occur on the affected side.31 Patients complaining of nasal discharge after transsinus implant placement should be thoroughly examined for penetration into the nasal cavities. As reported in a cadaver study, small branches coming from the posterior lateral nasal arteries are found to perforate the

The nasolacrimal duct Another anatomical structure that may potentially be damaged during transsinus implant placement is the NLD. The lacrimal sac and upper part of the NLD are housed in the bony lacrimal sac fossa or the sulcus lacrimalis, which is bounded anteriorly and posteriorly by the respective lacrimal crests (Fig 13-3). The bony lacrimal sac fossa continues downward as the nasolacrimal canal, which is formed by the maxilla, lacrimal bone, and inferior nasal concha. It transmits the NLD, which opens into the inferior meatus. In a recent cadaver study, the mean AP and transverse diameters of the entrance of the bony NLD were 5.7 and 4.7 mm,

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13  TRANSSINUS IMPLANTS

a

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Fig 13-3  (a to d) The lacrimal sac and upper part of the NLD are housed in the bony lacrimal sac fossa or the sulcus lacrimalis; the sulcus lacrimalis continues downward and transmits the NLD, which opens into the inferior meatus.

a

b

Fig 13-4  (a and b) Bilateral CS leaving the bilateral infraorbital canals.

respectively, and the mean distance of the NLD opening from the anterior nasal spine and limen nasi (ridge marking the boundary between the vestibule of the nose and the nasal cavity proper) were 22.2 and 18.9 mm, respectively.34 Cadaver studies of the lacrimal drainage system provide useful insights into the understanding of the anatomy of the bony lacrimal landmarks. Damage of the NLD near the opening at the inferior meatus leads to obstruction and could occur by transsinus implant placement leading to epiphora.

The canalis sinuosus Recent publications have drawn attention to radiographically visible accessory canals that may carry neurovascular structures to the anterior maxilla.35 More than half of these accessory bone

canals communicate with the CS.36 The CS is a tortuous bone channel originating from the infraorbital canal slightly posterior to the infraorbital foramen and coursing in an anterolateral direction to the anterior wall of the nasal antrum below the orbital margin.37 The CS turns medially to course below the infraorbital foramen toward the lateral wall of the nasal fossa and curves sharply downward along the piriform aperture (Fig 13-4), where apical fixation of the transsinus implant is achieved. The double-curved course of the CS, which runs for about 55 mm through the maxilla, is characterized by a thin overlying bone, making it more susceptible to injury in case of trauma. The CS carries a major branch of the infraorbital nerve, the anterior superior alveolar nerve (ASAN), and corresponding arteries.38 The ASAN follows this intraosseous course through the anterior maxilla to innervate the incisors and canines.

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Using Transsinus Implants

a

b

c

Fig 13-5  (a to c) Reformatted CBCT images in coronal plane put in evidence an accessory canal curving downward from the CS into the alveolar ridge.

The anterior superior alveolar nerve Intraoperative injuries to this plexus of nerves that innervate the canine pillar may result in postoperative paresthesia. Though rarely seen, transsinus implant placement has the potential to injure this neurologic bundle by transection or compression with resultant sensory disturbances. An accurate and precise understanding of the anatomical course of the ASAN through the midface is required for proper management of surgical interventions. According to Olenczak et al,39 starting at the point at which the ASAN is 25 mm inferior to the medial margin of the infraorbital rim, the ASAN is 3.4 mm (standard deviation 0.5 mm) lateral to the piriform aperture. From this point, the ASAN maintains a curvilinear course mirroring the contour of the piriform aperture. At the inferior extent of the CS, the ASAN terminates in dental branches that innervate the anterior teeth. To avoid iatrogenic injury to the ASAN, it is essential to obtain as much information as possible, especially from cone beam computed tomography (CBCT) scans and radiographs (Fig 13-5).

Anatomical considerations for surgery The ASAN is more likely to result in midface pain after craniofacial trauma than after dentoalveolar procedures. Olenczak et al39 postulate this to be the case because common maxillofacial and dentoalveolar procedures result in surgical transection of the ASAN, whereas craniofacial trauma, resulting in comminuted midface fractures, makes the nerve vulnerable to crush and avulsion injuries. Complex injury becomes a more significant impediment to healing and creates an environment more susceptible to neuroma formation and dysesthesia. Despite anatomical proximity of the ASAN, lasting sensory disturbances after transsinus implant placement have not been reported. Neurapraxia usually recovers within 3 months

following surgical intervention, possibly because there are multiple neurologic connections in the lower third of the piriform rim where the nerve may potentially be damaged by a transsinus implant. This results in a redundancy that guarantees continued sensory perception to the skin and anterior teeth in case of injury.

Using Transsinus Implants Patient selection Modern dentistry, especially in the field of implant-prosthetic rehabilitation, employs digital diagnosis, treatment planning, guided surgery, and prosthetic finalization. CBCT is the radiography of choice in the diagnostic phase. In all sinus surgery, this examination must be extended to include the ostiomeatal complex (OMC). CBCT supplies information on the anatomy and physiology of the maxillary sinus, and particular attention must be paid to ensure the patency of the OMC, absence of inflammation in the sinus membrane, absence of anatomical alterations that could represent a contraindication to any sinus surgery, visualization of the course of the alveolar antral artery, and the presence of Underwood septa. Encountering sinus disease in the course of the examination must prompt consultation with an ear, nose, and throat specialist before planning surgery.40 However, because the transsinus implant approach requires only a minor displacement of the sinus membrane (the average volume created by the intervention is less than 1 mL), this approach can still be pursued in the presence of chronic sinus disease. Clinicians opting to perform transsinus implant placement need experience both in tilted implant placement and sinus elevation techniques. This must be considered an advanced procedure requiring significant clinical experience. Employment

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13  TRANSSINUS IMPLANTS

a

b

c

d

e

f

g

h

Fig 13-6  (a to e) Views of two different procedures in the same patient. A standard four-implant approach requires two cantilevered teeth on each side. (f to h) A transsinus implant allows only one cantilever at each side. The grafted area in the anterior recess of the maxillary sinus does not exceed a volume of 1 mL.

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Using Transsinus Implants

of guided surgery will enhance accuracy of implant placement and reduce surgical time with subsequent reduction in postoperative complications. Use of bone-supported guides in edentulous patients and tooth-supported guides in partially edentulous patients is advisable. Clinical indications for the transsinus approach include the following: •  Advanced sinus pneumatization with residual crestal bone height 4 mm or less in the first premolar position •  A requirement to tilt a traditionally placed implant greater than 30 degrees to obtain an adequate AP spread •  Bone dehiscence of the edentulous crest in the second premolar and molar areas and its replacement by fibrous scar tissue, precluding implant placement in those sites In addition, the transsinus method should be considered in setting of short alveolar arch length where AP spread would be less than 10 mm for standard implant placement. Exclusion criteria include the following: •  The presence of systemic, uncontrolled diseases that could represent a general contraindication to implant dentistry •  Irradiation in the head and neck region within the last 12 months •  Severe bruxism or clenching habits •  Pregnancy •  Poor oral hygiene and motivation

Preparation According to the authors, transsinus implants may be classified as type 1 if tricortical layer stabilization is achieved: the cortical layers at the osseous crest of the alveolar process, the floor and anterior wall of the maxillary sinus, and the nasal wall. Type 2, or bicortical stabilization, designates an implant fixed without the nasal wall. Type 2 transsinus implants may be indicated when there is a thin layer of cortical bone between the nose and the anterior wall as seen on a CBCT scan and there is substantial risk for implant protrusion into the nasal airway. By performing sinus membrane distal deflection with the placement of transsinus implants, a 12-unit fixed implant restoration with a single-tooth cantilever can be achieved. This is more biomechanically favorable than a 10-unit restoration or a 12-unit restoration with two cantilevered teeth (Fig 13-6). Surgical intervention is performed with antibiotic prophylaxis using amoxicillin and clavulanic acid (Augmentin, GlaxoSmithKline) 1 g every 12 hours starting from the day before the surgery. The surgery is performed under local anesthesia with articaine 1:100,000 (Ultracaine D-S Forte, Sanofi-Aventis).

Procedure An incision is made along the crest with vertical releasing incisions to obtain access to the lateral and anterior walls of the sinus. The extension of the flap is smaller than for a traditional sinus elevation. Once a full-thickness flap is elevated, a small antrostomy is made parallel to the anterior sinus wall starting 3 mm distal to it and then extending anteriorly to reach the anterior sinus wall. The antrostomy is usually 4 to 6 mm mesiodistally and 7 to 8 mm apicocoronally. This simplified antrostomy design is preferred because extension of the antrostomy to the anterior wall renders the membrane elevation procedure simpler and safer by providing direct visual access to the narrow anterior portion of the sinus, resulting in a reduced membrane perforation rate (Fig 13-7). The approach is accomplished by using the following threestep procedure: 1. Make a small window 3 mm wide by 6 mm long just distal to the location of the anterior sinus wall correlated with the CBCT scan. 2. Extend the window in the anterior direction to locate the anterior sinus wall. 3. Detach the sinus membrane from the anterior wall, always maintaining instrument contact with the bone, and push the membrane distally. Distal displacement of the sinus membrane allows for the placement of an implant with a distal tilt of 30 degrees (Fig 13-8). The direction of the first implant drill can be observed through the antrostomy. The preparation of the implant site extends apically through the anterior sinus wall into the cortical layer of the often adjoining lateral nasal wall. After verification of the implant axis using direction indicators, the drilling sequence is finalized and a bone substitute is inserted (on average, 1 mL of graft material is needed). The implant is then inserted through the residual crestal bone into the grafted sinus where the membrane has been previously displaced distally. It engages apically at the M point, the confluence of three cortical walls (Fig 13-9). In some cases, it may be possible to obtain satisfactory implant stability without engaging the lateral nasal wall cortex. This approach further simplifies the surgical procedure. If four implants are planned, the anterior implants are placed in the lateral incisor positions. If six implants are planned, the central and lateral incisor positions are the preferred locations. The decision to place four versus six implants is based on the availability of bone in the first molar areas. The implants are placed 1 mm subcrestally and submerged. The patients may then use their full dentures that have been relined with a soft conditioner. After 6 months, the implants are uncovered, impressions are made, and the prosthesis is delivered after soft

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Fig 13-7 (a and b) A small antrostomy is made close to the sinus mesial wall, a membrane is detached, a small amount of xenograft is placed, and a transsinus implant is positioned.

a

b Fig 13-8  (a and b) The antrostomy is parallel to the anterior sinus wall. The membrane has been distally displaced, and the nasal mucosa is gently elevated to allow implant site preparation. An implant probe is used to visualize the axis of the future implant.

a

b

a

b

c

Fig 13-9  (a) An implant is placed at a 30-degree angle. (b) A sinus elevation instrument is used to check the level of the final position of the implant apex. A slight protrusion of the implant covered by mucosa can be a clinically accepted solution for gaining good primary stability. (c) CT scan showing the transsinus implant and its relationship with the nose.

a

b

c

Fig 13-10  (a to c) Abutments are screwed into the implants and the definitive restoration is cemented.

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Evidence-Based Support for the Transsinus Approach

Fig 13-11  (a) Preoperative sagittal CBCT scan. (b) Postoperative sagittal CBCT scan. (c and d) Sagittal CBCT scan and periapical radiograph of the definitive restoration in place.

a

b

c

d

tissue maturation. A similar protocol is followed in partially edentulous patients. The definitive fixed screw-retained prosthesis for the edentulous group is fabricated using a titanium framework with acrylic resin teeth. The definitive restoration in partially edentulous patients is typically a 3- or 4-unit fixed partial prosthesis (Figs 13-10 and 13-11).

Outcome evaluations The following are outcome evaluations for this procedure: •  The prosthesis is considered a success when it is delivered as planned and its function is maintained even if an implant fails. •  Implant success is based on lack of peri-implant radiolucency and no recurrent or persistent peri-implant infection, pain, neuropathy, or paresthesia. Crestal bone loss should not exceed 1.5 mm by the end of the first year of loading and 0.2 mm per year in the subsequent years. •  Prosthetic complications include fracture of abutment screws, framework, or occlusal material. •  Patient satisfaction is evaluated by a questionnaire after 1 year of function. The patient rates qualities including esthetics, phonetics, ease of maintenance, and functional efficiency, and each subject is rated as excellent, good, satisfactory, or poor. •  Marginal bone-level changes can be calculated by radiographic evaluation using image analysis software (Scion Image, Scion Corporation). All measurements are made by an independent evaluator who is not involved in the clinical procedures.

Evidence-Based Support for the Transsinus Approach Treatments for 51 patients are reported in part in Table 13-1 (21 men, 30 women; mean age at surgery, 59.2 ± 9.5 years) who subsequently underwent prosthetic rehabilitation. There were 251 implants placed in patients who received a full-arch fixed prosthesis supported by axial and transsinus tilted implants. All transsinus implants had a diameter of 4 mm, and 95.3% were 15 mm long and 4.7% were 13 mm long. The decision to place four or six implants was based on the available bone. Six implants were placed if a minimum interimplant distance of 3 mm was attainable. Three patients each received two implants for 3- or 4-unit fixed restorations. Of the patients, 11 were smokers; 9 were light smokers (≤ 10 cigarettes per day) and 2 were heavy smokers (> 10 cigarettes per day). Sixteen patients had mild systemic diseases controlled by pharmacologic therapy. The cumulative implant survival rate was calculated only for the full-arch fixed prosthesis group and was 98.41% (see Table 13-1). The present data are in agreement with the literature on smoking as a risk factor in implant therapy.41–43 In the failure analysis, four implants failed before loading. All failed implants were axially placed implants. They were not replaced, and the prosthesis was finalized on the remaining five implants. Crestal bone loss averaged 0.9 ± 0.4 mm for axial implants and 0.8 ± 0.5 mm for tilted implants at the 12-month evaluation. No significant difference was recorded in bone-level changes

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Table 13-1  Life table analysis of 51 patients with 251 implants Time interval (years)

Patients

Implants

Dropouts

Interval failures

Interval survival rate

Cumulative survival rate

0–1

51

251

0

4

98.41%

98.41%

1–2

49

247

0

0

100%

98.41%

2–3

46

236

0

0

100%

98.41%

3–4

41

218

0

0

100%

98.41%

4–5

37

203

0

0

100%

98.41%

5–6

34

192

0

0

100%

98.41%

6–7

32

184

2

0

100%

98.41%

7–8

27

154

0

0

100%

98.41%

8–9

22

122

0

0

100%

98.41%

9–10

20

108

2

0

100%

98.41%

10–11

17

90

0

0

100%

98.41%

11–12

14

72

0

0

100%

98.41%

12–13

10

50

0

0

100%

98.41%

13–14

5

20

0

0

100%

98.41%

Table 13-2  Satisfaction evaluation questionnaire at the 1-year follow-up Excellent

Good

Satisfactory

Poor

75%

21.4%

3.6%

––

Function

69.2%

30.8%

––

––

Ease of maintenance

35.7%

42.9%

14.3%

7.1%

70%

15.7%

14.3%

––

Esthetics (teeth and smile)

Phonetics ––, none.

between the two implant groups. A postoperative scan was taken in 10 patients to assess the volume necessary for the placement of tilted implants using the transsinus technique; the average graft volume required was 0.7 ± 0.2 mL. The mean length of the cantilevered tooth was 7.2 mm, depending on the opposing dentition and the esthetic demands of the patient. All patients confirmed that their overall quality of life improved after the treatment (Table 13-2). Biologic complications at the implant level included one implant with peri-implantitis and three implants with mucositis. No patients developed a sinus infection. The prosthetic complications encountered were screw

loosening, which occurred in 17.5% of cases, and chipping of tooth restorations (30% of cases). These complications were easily resolved chairside and did not lead to prosthetic failure. Swelling and bruising were rare in the postoperative period. This finding is likely due to the decreased extension of the mucoperiosteal flap elevation when compared with a traditional sinus procedure. The requirement to expose only the anterior wall of the sinus for a small antrostomy and the reduced overall surgical time contributed to a reduced morbidity when compared with traditional lateral sinus elevation.

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References

A significant difference has been found in the stress generated at tilted implants with 15-mm versus 5-mm cantilever extensions.44 The prostheses in the present edentulous study population had an average distal cantilever of 7.2 mm. It is possible to reduce the cantilever by decreasing the number of fixed teeth on a prosthesis, as proposed by Kanno and Carlsson.45 In that study, dentitions were limited to 10 teeth; however, not all patients will accept a shortened dental arch. A shortened arch rehabilitation could be contraindicated in patients with a broad smile and high esthetic expectations. Furthermore, an arch with only 10 units may cause extrusion of mandibular molars if they are present and unopposed. A recent clinical study has proposed a similar transsinus surgical technique with very promising short-term results.25 Further clinical investigations with a larger sample size are advisable to confirm the results of the presented protocol.

Conclusion The rationale for the tilted implant protocol was to place implants in conjunction with sinus membrane elevation. A number of studies have emphasized that bone density is an important factor for implant success.46,47 For this technique, the tilted implant transgresses three planes of cortical bone. It has been shown that most of the functional load is exerted at the collar of an implant, so in tilted implants, the load shifts distally.48 In the study population described previously, the tilted implants were placed with the implant platform entirely surrounded by bone. It is also important to consider the positive effect of the decreased distal cantilever in the tilted implant protocol.

References 1. Jemt T, Book K, Lindén B, Urde G. Failures and complications in 92 consecutively inserted overdentures supported by Brånemark implants in severely resorbed edentulous maxillae: A study from prosthetic treatment to first annual check-up. Int J Oral Maxillofac Implants 1992;7:162–167. 2. Adell R, Eriksson B, Lekholm U, Brånemark PI, Jemt T. Long-term follow-up study of osseointegrated implants in the treatment of totally edentulous jaws. Int J Oral Maxillofac Implants 1990;5:347– 359. 3. Rossetti PH, Bonachela WC, Rossetti LM. Relevant anatomic and biomechanical studies for implant possibilities on the atrophic maxilla: Critical appraisal and literature review. J Prosthodont 2010;19:449–457. 4. Jun BC, Song SW, Park CS, Lee DH, Cho KJ, Cho JH. The analysis of maxillary sinus aeration according to aging process; volume assessment by 3-dimensional reconstruction by high-­ resolutional CT scanning. Otolaryngol Head Neck Surg 2005; 132:429–434.

5. Käyser AF. Limited treatment goals: Shortened dental arches. Periodontology 2000 1994;4:7–14. 6. Witter DJ, De Haan AF, Käyser AF, Van Rossum GM. A 6-year follow-up study of oral function in shortened dental arches. Part II: Craniomandibular dysfunction and oral comfort. J Oral Rehabil 1994;21:353–366. 7. Witter DJ, van Palenstein Helderman WH, Creugers NH, Käyser AF. The shortened dental arch concept and its implications for oral health care. Community Dent Oral Epidemiol. 1999;27:249– 258. 8. Meeuwissen JH, van Waas MA, Meeuwissen R, Käyser AF, van ‘t Hof MA, Kalk W. Satisfaction with reduced dentitions in elderly people. J Oral Rehabil 1995;22:397–401. 9. Sarita PT, Witter DJ, Kreulen CM, van ‘t Hof MA, Creugers NH. Chewing ability of subjects with shortened dental arches. Community Dent Oral Epidemiol 2003;31:328–334. 10. Khayat P, Nader N. The use of osseointegrated implants in the maxillary tuberosity. Pract Periodont Aesthet Dent 1994;6:53–61. 11. Venturelli A. A modified surgical protocol for placing implants in the maxillary tuberosity: Clinical results at 36 months after loading with fixed partial dentures. Int J Oral Maxillofac Implants 1996;11:743–749. 12. Balshi TJ, Wolfinger GJ, Balshi SF II. Analysis of 356 pterygomaxillary implants in edentulous arches for fixed prosthesis anchorage. Int J Oral Maxillofac Implants 1999;14:398–406. 13. Ferrara ED, Stella JP. Restoration of the edentulous maxilla: The case for the zygomatic implants. J Oral Maxillofac Surg 2004; 62:1418–1422. 14. Calandriello R, Tomatis M. Simplified treatment of the atrophic posterior maxilla via immediate/early function and tilted implants: A prospective 1-year clinical study. Clin Implant Dent Relat Res 2005;7(suppl 1):S1–S12. 15. Aparicio C, Perales P, Rangert B. Tilted implants as an alternative to maxillary sinus grafting: A clinical, radiologic, and periotest study. Clin Implant Dent Relat Res 2001;3:39–49. 16. Del Fabbro M, Bellini CM, Romeo D, Francetti L. Tilted implants for the rehabilitation of edentulous jaws: A systematic review. Clin Impl Dent Rel Res 2012;14:612–621. 17. Testori T, Galli F, Fumagalli L, et al. Assessment of long-term survival of immediately loaded tilted implants supporting a maxillary full-arch fixed prosthesis. Int J Oral Maxillofac Implants 2017;32:904–911. 18. Fan T, Li Y, Deng WW, Wu T, Zhang W. Short implants (5 to 8 mm) versus longer implants with sinus lifting in atrophic posterior maxilla: A meta-analysis of RCTs. Clin Implant Dent Relat Res 2017;19:207–215. 19. Lee SA, Lee CT, Fu MM, Elmisalati W, Chuang SK. Systematic review and meta-analysis of randomized controlled trials for the management of limited vertical height in the posterior region: Short implants (5 to 8 mm) vs longer implants in vertically augmented sites. Int J Oral Maxillofac Implants 2014;29:1085–1097. 20. Monje A, Fu JH, Chan HL, et al. Do implant length and width matter for short dental implants ( 95%) over medium- to long-term follow-up.3 In addition, zygomatic implant–supported prosthe­ ses have had very few technical and biologic complications when compared with advanced bone grafting approaches.4

Challenges with Zygomatic Implant Placement In the situation of Cawood and Howell Class VI, a technique using multiple zygomatic implants was proposed in an attempt to provide a graft-free procedure in the anterior maxilla while minimizing the risk of standard implant failure.5,6 Data from the latest systematic review that identified three studies with a total of 196 implants placed in 49 patients suggest that maxil­ lary rehabilitation by four zygomatic implants with no anterior support is a reliable approach.7 However, due to the limited

width of the zygomatic bone, poor intraoperative visibility, and anatomical intricacies of the curved zygomatic bone, the poten­ tial risks of complications increase. Furthermore, making the best possible use of the available zygomatic bone volume makes zygomatic implant placement much more difficult. To promote minimally invasive surgery and accurate place­ ment of zygomatic-directed implants, the use of computer-aided surgery (CAS) has been proposed to transfer the preoperative information to the surgical site. Several computer-aided naviga­ tion systems have recently been presented for oral implantology. Meanwhile, some model and human studies have demonstrated improvements in quality and minimization of risks with this approach to implant placement.8,9 A small angular or position entrance error may result in signif­ icant positional errors at the tip of the drills, especially when placing zygomatic implants longer than 35 mm. Stereolitho­ graphic templates, either bone- or mucosa-supported, have been used to place zygomatic implants in the planned position based on computer-assisted planning. However, there is no effective mechanism to physically control the drilling trajectory for the zygomatic implants. Another consideration is dynamic navigation, which can provide interactive control during implant placement. In 2000, Schramm et al10 first reported the use of a computer-assisted navigation system to place zygomatic implants. Since that initial report, there have been several attempts to use dynamic guided surgery for zygomatic implant placement. Modifications during an implant procedure based on preoperative imagery are import­ ant when drilling up to 50 mm for zygomatic implant bed prepa­ ration. With the help of dynamic guided surgery, intraoperative application of 3D image data can be realized so that the precision achieved in the planning phase can be transferred to the patient.

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15  NAVIGATION FOR TRANSSINUS PLACEMENT OF ZYGOMATIC IMPLANTS

Preoperative CBCT data

3D reconstruction with software • Preoperative planning • 3D geometric measurement based on anatomical landmarks • Optimization design of the position and orientation of zygomatic implants

maxillary denture can be displayed, and according to the zygo­ matic anatomy-guided approach (ZAGA) presented by Apari­ cio,12 the intraoral coronal entrance points for the zygomatic implant are designed at or near the top of the alveolar crest with the guidance of a prefabricated denture (Fig 15-2). Patients presenting with severe resorption of the maxilla lack­ ing bone volume anterior to the wall of the sinus, in the piriform rim region, and/or in the nasal crest region are candidates for the zygomatic implant approach. The inclusion criteria for the zygomatic implant classic approach (ie, one zygomatic implant on each side of the zygomatic bone with two to four standard implants in the anterior maxilla) are as follows:

Fiducial marker insertion and new CBCT data

Registration • Registration method • Calculation of the coordinate of fiducial markers • Registration algorithm

Real-time navigation • Calibration and visualization of the surgical instruments • Algorithms for tracking the movements of the surgical instruments and patients • 2D and 3D interactive image rendering • Calculation of the deviation from the preoperative plan Fig 15-1 Time line of real-time navigation in zygomatic implant placement.

Surgical Navigation The framework of real-time navigation starting with cone beam computed tomography (CBCT) is shown in Fig 15-1.11

Presurgical planning The usual medical and dental workup must be completed for the patient. Patients have to receive an extraoral and intraoral examination, and the degree of bone resorption is estimated from preoperative panoramic radiography and CBCT scanning. Digital imaging and communications in medicine (DICOM) data extracted from the CBCT scan are imported into software for preliminary planning. With this software, the prefabricated

•  Presence of maxillary posterior bone height ranging from 1 to 3 mm in the premolar and molar regions (Cawood and Howell Class VI)5 •  Anterior maxillary height of at least 10 mm to allow place­ ment of at least two standard implants without additional bone grafting The inclusion criteria for a quad approach (ie, two zygomatic implants on each side of the zygomatic bone without standard implants) are as follows: •  Presence of maxillary posterior bone height ranging from 1 to 3 mm in the premolar and molar regions (Cawood and Howell Class VI and worse)5 •  Insufficient width in the anterior maxilla to place regular implants of at least 3.75 mm diameter without additional bone grafting or insufficient height to allow the placement of implants shorter than 10 mm even with a titled approach Patients are excluded if they have local or systematic contra­ indications for implant placement, untreated maxillary sinusitis or a maxillary sinus cyst, poor oral hygiene, heavy smoking habits (ie, more than 20 cigarettes per day), pregnancy, or any history of chemotherapy or radiotherapy. For the single zygomatic implant approach, the entrance point of the zygomatic implant is in the second premolar or first molar site. If the quad approach is chosen, the anterior zygomatic implant is at the level of the lateral incisor to canine region, and the posterior zygomatic implant is in the second premolar to first molar region. The extraoral apical exit point of the zygomatic implant is on the zygomatic bone outer surface. For the quad approach, when placing the zygomatic implants at the apical exit point on the zygomatic bone outer surface, a minimum distance of 3 mm is maintained to ensure sufficient bone around each zygomatic implant. The path of a zygomatic implant should be ensured without going through the critical anatomical structures, and the length of a zygomatic implant is determined by preoperative digital planning according to the distance between the entrance and exit points. The treatment plan is designed to make optimal use of available bone volume while protecting critical anatomical structures.

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Surgical Navigation

Fig 15-2 (a) With the NobelClinician software (Nobel Biocare), the potential zygomatic implant length and position can be selected and placed according to the ZAGA approach for the patient with a quad approach. (b) Zygomatic implant angulation and the appropriate abutment can both be displayed prior to surgery.

a

Fig 15-3 A total of eight registering screws are used for point-to-point registration. The distribution of these screws is polygon spanned.

b

Fig 15-4  In the planning navigation software, a different color of cylindroid trajectories can simulate the drilling path for zygomatic implants. The length and position of planned zygomatic implants can be determined, while the relationship between the zygomatic implant and maxillary sinus can also be displayed.

Registration As a crucial part of navigation surgery, registration is defined as the determination of the spatial relationships between the virtual coordinate system and the intraoperative patient coordinate system, and its precision is vital to the actual navigation surgery. Registration methods can be divided into two groups: invasive bone-anchored screw markers and noninvasive adhesive mark­ ers (dental splints). Compared with noninvasive techniques, the advantage of an invasive technique is its precision.13 After preliminary planning of zygomatic implant placement is completed, registering titanium screws are inserted in the maxilla under local anesthesia to serve as fiducials, and a mini­ mum of six registering screws are inserted to be used for pointto-point registration. The distribution of these miniature screws must be in noncritical areas that can provide bone anchorage and not interfere with implant insertion. For geometric consid­ eration, a polygon spanned by the screws should be as large as possible to achieve a wide field to maximize accuracy (Fig

15-3). After placement of the registered screws, a second 3D data set is acquired with CBCT scanning. The data are then imported into preoperation planning navigation software. The software can simulate the drilling path for zygomatic implants, and all miniature screws are marked as registration points for intraoperation imaging registration (Fig 15-4).

Surgical technique After general anesthesia, the reference base is rigidly secured to the skull. The reference array is then secured to the base assem­ bly with three reflective marked spheres (Fig 15-5). The reflec­ tive marked sphere is a referencing device that enables flexible and accurate patient tracking by a camera during the navigation procedure. A positioning probe is used to collect the coordinates of the fiducial titanium screw markers so that registration is automatically accomplished (Fig 15-6). After registration, the available sagittal, coronal, axial, and 3D reconstruction images

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15  NAVIGATION FOR TRANSSINUS PLACEMENT OF ZYGOMATIC IMPLANTS

Fig 15-5 The skull reference base is a bone-anchored device and is assembled with three reflective marked spheres.

Fig 15-7  A custom-made rigid bracket integrating with three reflective marked spheres is fixed with a zygoma drilling handpiece.

a

Fig 15-6  After finishing collecting the position of eight fiducial screws, registration is automatically accomplished by the software.

Fig 15-8 For transsinus zygomatic implants, a vertical window is created, and the sinus membrane is elevated. However, with navigation guidance, it is not always necessary to expose the inferior border of the zygoma before the drilling procedure.

b

Fig 15-9  (a and b) In the drilling process for zygomatic implant bed preparation with navigation, the target drillings can all be clearly identified on the reconstructed 3D skull model on the screen.

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Accuracy Analysis

Fig 15-10 The handpiece with the drill and three reflected spheres is recalibrated with the calibration tool (iPlan Navigator, Brainlab) after the initial drilling is finished.

are displayed on a screen. Then, a custom-made rigid bracket integrating the reference array is fixed with the zygoma drilling handpiece so that constant visualization of drilling trajectory can be displayed in real time (Fig 15-7). A midcrestal incision and vertical releasing incisions are made in the midline and at the maxillary tuberosity region. Mucoperi­ osteal flap elevation is conducted, and the lateral sinus wall and a part of zygomatic complex are exposed. If a transsinus path for the implant body has been designed according to preoperative planning, a window approximately 5 × 10 mm is made in the lateral aspect of the sinus wall. The sinus mucosa is reflected, and no special efforts are made to keep it intact. The window is not used for providing direct vision of the roof of the sinus or enabling the optimal point for entrance of the drill into the zygomatic bone, but serves only for cooling during drilling (Fig 15-8). Target drilling can be clearly identified on the reconstructed 3D skull model on the screen (Fig 15-9). During the drilling procedure, after the handpiece is calibrated, the spatial position of the planned trajectories and drill are shown on the screen. Following the instruction of the real-time image display, the entrance point is located and the drilling direction oriented. In addition, the distance between the exit point and drill tip are constantly displayed on the screen to remind operators when the drill tip is approaching the exit point. For the next drill change during implant bed preparation, the handpiece with the drill is recalibrated with the calibration tool to decrease tool calibration error (Fig 15-10). The whole drilling procedure follows the trajectories from the entrance point to the exit point as planned. After implant bed preparation, zygomatic implants (Brånemark system, Nobel Biocare) are placed (Fig 15-11). Multiunit abutments and healing caps are placed on the implants. If the insertion torque of each implant is more than 35 Ncm, immediate loading is performed within 72 hours. If a sufficient level of implant anchorage or stability cannot be achieved at surgery, delayed loading is employed instead. Delayed loading is also used when the patient presents with

Fig 15-11  Four zygomatic implants have been placed. Notice the two fiducial screws in the anterior nasal spine. They were removed before wound closure.

significant parafunctional activity or with uneasily controlled occlusal factors. The flaps are closed with resorbable sutures. All patients are given 5-day prescriptions of antibiotics, analgesics, and 0.12% chlorhexidine mouthwash solution. A postoperative CBCT scan is taken to evaluate the implant position within 72 hours after surgery. If immediate loading is undertaken, a prefabricated metal-reinforced acrylic resin interim prosthesis is secured to the implants, and the prosthetic screws are tightened to 15 Ncm.

Accuracy Analysis Surgical template A surgical template is regarded as a reliable method for guid­ ing the placement of a standard dental implant. However, for patients with a severely atrophic maxilla, it is difficult to main­ tain a surgical template that is stable throughout the entire drill­ ing procedure. Chrcanovic et al14 reported the placement of 16 zygomatic implants with the guidance of a stereolithographic surgical template on human cadavers, with an angle deviation of the long axis between the planned and placed implants of 8.06 ± 6.40 degrees for the anterior posterior view and 11.20 ± 9.75 degrees for the caudal-cranial view, of which one emerged in the infratemporal fossa and one emerged inside the orbit. Another study reported the placement of zygomatic implants with the guidance of a surgical template on patients with entry deviations and apical emergence of the zygomatic implants of 2.77 mm (1.0 to 7.4 mm) and 4.46 mm (0.3 to 9.7 mm), respectively. Additionally, two of the implants failed, which was attributable to excess apical emergence.15 Thus, for placement of an implant with a length greater than 35 mm, a slight deviation in the entry point or initial direction may result in a magnifying deviation at the exit point. A surgical template should presumably be used to locate the entry point of the zygomatic implant, but the

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same template may no longer be practical to guide the drilling procedure when operating the zygomatic implant.

Navigation system The accuracy of intraoperative navigation is very important for CAS in terms of reliability. The accuracy of navigation systems depends on parameters such as the CT layer thickness, the voxel size, the CT image resolution, the registration accuracy, the precision of the optical tracking system, and the precision of manufacturing and calibration of the rigid bracket assem­ bly equipped with retro-reflective balls for tracking.16 After the registration procedure, information can be provided regarding the target registration error (TRE). This value represents the error between corresponding points other than fiducial points after registration, and it is the most representative indicator of registration accuracy.17

Fiducial markers In previous studies, it has been demonstrated that the shape of the configuration of fiducial points is an important factor governing TRE in point-based rigid registration, and relatively small values of TRE may be achieved by using widely spread fiducial markers and/or placing the centroid of the markers near the target.18 In a clinical setting, the entrance of a zygomatic implant is at the alveolar crest, and the end of the drilling is on the surface of the zygomatic bone. That means the ideal spreading of fiducial markers would be in the maxillary alveolar ridge and around the orbital area for full field coverage. Occlusal splints for fiducial points in a severely atrophic maxilla are not feasible because of poor stability of the full denture. Percuta­ neous insertion of bone-anchored fiducial implants, typically self-drilling screws, has been shown to be a viable referencing method. However, in patients with a severely atrophic maxilla, the type and placement of fiducials—as well as the manner in which they are localized—are limited by the residual bone volume for which bone anchorage could be provided. There­ fore, the distribution of these fiducials has to make good use of some uncritical areas. For geometric considerations, the polygon spanned by the screws is as large as possible to achieve a wide field for maximum accuracy. In an in vitro study by the authors, the accuracy of fiducial registration for zygomatic implant treatment and the most reli­ able configuration registration, including numbers and posi­ tions intraorally, were detected.19 A scattered distribution with a polygon span with at least five fiducial markers in the eden­ tulous maxilla for registration seems to achieve an acceptable TRE value with a high accuracy for navigation in zygomatic implant placement. However, in clinical procedures, the anchor­ age of bone screws is always limited by the remaining bone quantity and quality (stability). Some of the fiducial markers may displace or split off during open flap surgeries. Therefore,

it is recommended to check rigid anchorage of bone screws after placement or to insert two more bone screws in regions with sufficient bone to ensure high accuracy for registration if necessary.

In vitro and in vivo conditions Regarding the use of a navigation system for the placement of zygomatic implants in vitro, the entry and exit deviations of implants were 1.36 ± 0.59 mm and 1.57 ± 0.59 mm on the models and were 1.30 ± 0.8 mm and 1.7 ± 1.3 mm on the cadav­ ers.11 However, compared with the resulting data in the clinical case report, the precision should theoretically be much higher in the in vitro experiment. This is because it is not possible to mimic the difficulty of drilling under in vivo conditions. During the actual surgery, several factors can compromise the surgeon’s ability to accurately transfer the plan to the actual surgical site. These include the irregular and porous bone structure, the inherent intricacies of the morphology of the bone surface, the changes in bone density along the implant socket, the limited intraoperative visibility, and the possible displacement of the bracket. However, most of these factors fall under the category of nonsystematic errors, and the devia­ tion may differ significantly each time under different in vivo conditions. In clinical practice, the authors’ modification for zygomatic implant placement is a custom-made rigid bracket that integrates the reference array fixed with the zygoma drilling handpiece, which makes the surgery possible and facilitates the guidance of the drilling trajectory. In a recent prospective study, 10 patients received 40 zygo­ matic implants using a quad approach with surgical navigation. The entry deviation, exit deviation, and angle deviations were 1.35 ± 0.75 mm, 2.15 ± 0.95 mm, and 2.05 ± 1.02 degrees, respectively.19 The differences among all deviations were not significant, regardless of the lengths or locations of the implants. They were also similar to the deviations obtained from the implants placed in models and cadavers.19 Although no significant difference was found between the anterior and posterior implants, there was a slight tendency to have larger apical deviations for the posterior implants than the anterior implants.19 This observation could be attributed to the length of the drill, the distortion of the drill during performance, the patients’ limited mouth opening, and the mandibular dentition affecting the drilling access of the posterior implants. Because of the limited width of the zygomatic bone and anatomical differences among individuals, navigation accu­ racies of 1 mm or less during zygomatic implant surgery are ideal but still challenging. Some modifications can be made to increase the registration accuracy, including the establishment of adequate layer thickness, the voxel size, image resolution of CBCT scanning, and modification to bone-anchored registra­ tion screws to decrease the fiducial localization error, which is the difference between reality and display, while localizing fiducials with a pointer.

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Case 1: Zygomatic Implant Classic Approach with Surgical Navigation System

a

b

c

Fig 15-12 (a) According to the ZAGA approach, the zygomatic implant entrance point is planned in the alveolar crest of the first molar site. (b) The length of the zygomatic implant and the relationship between the zygomatic implant and maxillary sinus are easily determined in the software. (c) Seven miniature screws were anchored as fiducial points for the navigation. The maxillary right lateral incisor and canine were extracted before flap elevation. (d) Zygomatic implant planning in the navigation software. The cylindroid trajectory indicates the drilling path for the zygomatic implant.

d

Case 1: Zygomatic Implant Classic Approach with Surgical Navigation System A 50-year-old man who is a nonsmoker was referred for reha­ bilitation of his dentition. He had been diagnosed with severe chronic periodontitis and lost his teeth more than 5 years prior. He had been wearing partial dentures, and his chief complaint was discomfort in connection with his maxillary denture. All conditions were medically controlled and stable. The clinical inspection intraorally revealed missing maxillary right premolars and molars and maxillary left molars. Periodon­ tal examination revealed probing depths in the range of 5 to 6 mm for the right canine and lateral incisor. The patient received his first preoperative CBCT (i-CAT, Imaging Sciences International) scan with a resolution of 0.39 mm/pixel and 0.2-mm slice thickness. DICOM data were imported into NobelClinician (Nobel Biocare) for preliminary planning (Figs 15-12a and 15-12b). As shown in the CBCT, maxillary posterior bone height ranged from 1 to 2 mm in the right premolar and molar regions. A zygomatic implant was planned for the patient to avoid lateral sinus grafting to decrease

the treatment time. The right lateral incisor and canine were to be extracted and replaced with one standard implant. The zygomatic implant entrance point was planned in the first molar site, and the exit point was on the outer surface of the zygomatic bone. When the path of the zygomatic implant was decided, the length of the implant was also determined as 50 mm using the transsinus routine. Meanwhile, the position, length, and diameter of the standard implant in the central incisor area were also confirmed with the software. On the day of surgery, titanium registration screws (length: 9.0 mm; diameter: 1.6 mm) were inserted intraorally under local anesthesia to serve as fiducials. A total of seven registration screws were inserted, including two in the maxillary tuberosity bilaterally, two in the midline palatine suture, and three in the anterior basal bone (Fig 15-12c). A second preoperative CBCT scan (i-CAT) was taken with the registration screws at a resolu­ tion of 0.39 mm/pixel and 0.2-mm slice thickness. The CBCT data were then imported into preoperation planning navigation software (iPlan Navigator). The software provides cylindroid trajectories that could simulate the drilling path for zygomatic implants (Fig 15-12d). On the same day, after general anesthesia, the skull reference base assembly with three reflective marked spheres was rigidly secured to the skull with a self-tapping miniature screw 1.5 mm

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e

f

g

h

Fig 15-12  (cont) (e and f) During the drilling procedure, the reference array was fixed in the handpiece and real-time visualization of the drilling trajectory could be displayed on the screen, which helped the surgeon to follow the planned routine and direction to prepare the implant bed. (g) The zygomatic implant was inserted with a transsinus approach, and the standard implant was placed in the site of the lateral incisor. In the left posterior maxilla, a lateral window approach was used. (h) Postoperative panoramic radiograph.

in diameter (iPlan Navigator). A positioning probe was used to collect all seven fiducial screw markers so that registration was automatically accomplished. After registration, the recon­ struction images were displayed on the screen. The bracket integrating the reference array was fixed with a zygoma drilling handpiece so that constant visualization of the drilling trajec­ tory could be displayed on the screen in real time. During the drilling procedure, any deviation of the drill could be displayed with a red line, which helps the surgeon to correct any devia­ tions. When each drill reached the planned exit point, the drill­ ing trajectory was shown in green, which meant the planned routine was finished (Figs 15-12e and 15-12f). Then, zygomatic implants with the planned lengths were placed. The standard implant was placed freehand (Figs 15-12g and 15-12h).

Case 2: Zygomatic Implant Quad Approach with Surgical Navigation System A 50-year-old woman presented with the chief complaint that her complete maxillary denture was unstable. She had been

previously diagnosed with aggressive periodontitis and received periodontal treatment and maintenance regularly; however, due to the progress of the disease, she had lost most of her teeth during the past 10 years. The patient was in good health and did not smoke. A clinical examination was performed, revealing a full denture in the maxilla. Removal of the denture revealed that the morphology of the posterior maxillary alveolar ridge was not obvious with a very shallow vestibule. A panoramic radiograph was obtained for initial evaluation, revealing horizontal and vertical bone resorption. Very limited bone height was present for standard implant placement in the premolar and molar area of the maxilla. A maxillary denture was made as a radiographic guide. Tooth positions were filled with resin containing barium sulfate (70% tooth-color light-cured resin to 30% barium sulfate). The patient received her first preoperative CBCT scan with the radiographic guide. The guide was then scanned separately. Using NobelCli­ nician, the potential zygomatic implant sites could be visualized in relation to the proposed tooth position. A quad approach was designed for the patient with the anterior zygomatic at the level of the canine and the posterior zygomatic in the second premolar to first molar region according to the desired prosthesis-driven position (Figs 15-13a and 15-13b).

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Case 2: Zygomatic Implant Quad Approach with Surgical Navigation System

Fig 15-13 (a and b) With the prefabricated denture, using the quad approach, the intraoral coronal entrance points of anterior and posterior zygomatic implants are designed in the positions of the canine and second premolar to first molar, respectively. (c) The software interface of iPlan Navigator for implant planning. The relationship between the sinus and planned zygomatic implants can be visualized in the interface. With the prefabricated denture with barium sulfate, the entrance point of zygomatic implant in the alveolar ridge can be easily determined. (d) The patient underwent the quad approach. The flap has exposed the lateral wall of the sinus, and a lateral window has been made. It is not necessary to expose the buttress of the area of zygomatic bone and inferior border of the zygoma to enhance visualization of the surgical site with navigation. The position of the head of the anterior zygomatic implant is in the palatal of the canine region. (e) All four zygomatic implants achieved good primary stability, and immediate loading was performed with a rigid connection of four zygomatic implants.

a

b

c

d

On the day of surgery, fiducial screws were inserted intra­ orally under local anesthesia in the maxilla. The patient wore the surgical guide for the second CBCT. Afterward, the data were imported to iPlan Navigator software. Within the soft­ ware, cylindroid trajectories were displayed with different colors simulating the drilling path for zygomatic implants. The length of cylindroid trajectories could be determined according to the preplanned length in NobelClinician. The software interface of iPlan Navigator is different from NobelClinician in that it cannot provide program detection of zygomatic implant angu­ lation with abutments and the image of the denture cannot be imposed onto the CBCT scan of the patient. However, with the tooth positions filled with resin containing barium sulfate,

e

it became easy to recognize the zygomatic implant entrance positions in the alveolar bone level (Fig 15-13c). The registration and drilling procedures were the same as those in the previous treatment using the classic approach. Both windows were made in the lateral aspect of the sinus wall, and the sinus mucosa was reflected. The whole drilling procedure followed the trajectories in the path as planned. Four zygo­ matic implants were placed: the two posterior implants were transsinus and the two anterior implants were extrasinus (Fig 15-13d). The insertion torque of each zygomatic implant was more than 35 Ncm, so immediate loading was performed within 72 hours for the patient (Fig 15-13e).

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Conclusion Due to the anatomical complexity of the operation sites and potential risk for critical structural injury, the placement of zygomatic implants, especially in the quad approach, represents a significant challenge for clinicians. A real-time surgical navi­ gation approach has thus been proposed and tested to achieve precise 3D placement of the zygomatic implant with minimal invasiveness. Through over 10 years of work on decreasing registration deviation from both in vitro and in vivo studies, critical modifications have been rationalized and made in multi­ ple navigation fixtures to make zygomatic navigation surgery more feasible and reliable. This ensures that real-time surgical navigation for zygomatic implant placement may proceed with a high level of accuracy with minimal positional deviations, improving precision.

Acknowledgments We would like to thank Prof Zhiyong Zhang (Department of Oral Implan­ tology, Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University, School of Medicine) for his full support and valuable suggestion in the cases presented. We would like to extend our gratitude to the collaborators Prof Xiaojun Chen (Institute of Biomedical Manufacturing and Life Quality Engineer­ ing, School of Mechanical Engineering, Shanghai Jiao Tong University) and Prof Shigang Wang (School of Mechanical Engineering, Shanghai Jiao Tong University) for their fundamental research work on the image-guided oral implantology system.

References 1. Nyström E, Ahlqvist J, Gunne J, Kahnberg KE. 10-year follow-up of onlay bone grafts and implants in severely resorbed maxillae. Int J Oral Maxillofac Surg 2004;33:258–262. 2. Esposito M, Grusovin MG, Rees J, et al. Effectiveness of sinus lift procedures for dental implant rehabilitation: A Cochrane systematic review. Eur J Oral Implantol 2010;3:7–26. 3. Esposito M, Worthington HV. Interventions for replacing missing teeth: Dental implants in zygomatic bone for the rehabilitation of the severely deficient edentulous maxilla. Cochrane Database Sys Rev 2013;9:CD004151. 4. Aparicio C, Ouazzani W, Hatano N. The use of zygomatic implants for prosthetic rehabilitation of the severely resorbed maxilla. Periodontol 2000 2008;47:162–171.

5. Cawood JI, Howell RA. A classification of the edentulous jaws. Int J Oral Maxillofac Surg 1988;17:232–236. 6. Bothur S, Jonsson G, Sandahl L. Modified technique using multiple zygomatic implants in reconstruction of the atrophic maxilla: A technical note. Int J Oral Maxillofac Implants 2003; 18:902–904. 7. Wang F, Monje A, Lin GH, et al. Reliability of four zygomatic implant-supported prostheses for the rehabilitation of the atrophic maxilla: A systematic review. Int J Oral Maxillofac Implants 2015;30:293–298. 8. Block MS, Emery RW. Static or dynamic navigation for implant placement—Choosing the method of guidance. J Oral Maxillofac Surg 2016;74:269–277. 9. Ohba S, Yoshimura H, Ishimaru K, Awara K, Sano, K. Application of a real-time three-dimensional navigation system to various oral and maxillofacial surgical procedures. Odontology 2015; 103:360–366. 10. Schramm A, Gellrich NC, Schimming R, Schmelzeisen R. Computer-­ assisted insertion of zygomatic implants (Brånemark system) after extensive tumor surgery [in German]. Mund Kiefer Gesichtschir 2000;4:292–295. 11. Xiaojun C, Ming Y, Yanping L, Yiqun W, Chengtao W. Image guided oral implantology and its application in the placement of zygoma implants. Comput Methods Programs Biomed 2009;93:162–173. 12. Aparicio C. A proposed classification for zygomatic implant patient based on the zygoma anatomy guided approach (ZAGA): A cross-sectional survey. Eur J Oral Implantol 2011;4:269–275. 13. Lübbers HT, Matthews F, Zemann W, Grätz KW, Obwegeser JA, Bredell M. Registration for computer-navigated surgery in edentulous patients: A problem-based decision concept. J Craniomaxillofac Surg 2011;39:453–458. 14. Chrcanovic BR, Oliveira DR, Custódio AL. Accuracy evaluation of computed tomography–derived stereolithographic surgical guides in zygomatic implant placement in human cadavers. J Oral Implantol 2010;36:345–355. 15. Vrielinck L, Politis C, Schepers S, Pauwels M, Naert I. Image-based planning and clinical validation of zygoma and pterygoid implant placement in patients with severe bone atrophy using customized drill guides. Preliminary results from a prospective clinical follow-up study. Int J Oral Maxillofac Surg 2003;32:7–14. 16. Ewers R, Schicho K, Undt G, et al. Basic research and 12 years of clinical experience in computer-assisted navigation technology: A review. Int J Oral Maxillofac Surg 2005;34:1–8. 17. West JB, Fitzpatrick JM, Toms SA, Maurer CR Jr, Maciunas RJ. Fiducial point placement and the accuracy of point-based, rigid body registration. Neurosurgery 2001;48:810–816. 18. West JB, Maurer CR Jr. Designing optically tracked instruments for image-guided surgery. IEEE Trans Med Imaging 2004;23:533– 545. 19. Hung KF, Wang F, Wang HW, Zhou WJ, Huang W, Wu YQ. Accuracy of real-time surgical navigation system for the placement of quad zygomatic implants in the severe atrophic maxilla: A pilot clinical study. Clin Implant Dent Relat Res 2017;19:458–465.

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CHAPTER 16

ARCH-LENGTH THRESHOLD FOR USING ZYGOMATIC IMPLANTS Nicholas J. Gregory, dds | Ole T. Jensen, dds, ms

T

he atrophic maxilla has been a long-standing challenge for clinicians. The severely atrophic maxilla offers little in the way of cortical bone for anchorage of dental implants. Many bone grafting procedures have been developed and proven effective in the management of maxillary atrophy.1–3 The zygomatic implant was originally introduced in 1988 by Professor Per-Ingvar Brånemark. Its success has been documented in the literature in both delayed and immediate loading protocols.4,5 The use of the zygomatic implant allows an opportunity to simplify the surgical treatment of patients with severely atrophic maxillae. Patients who are not candidates for extensive bone grafting procedures, have had failed bone grafts or traditional implants, or wish to avoid multiple surgical procedures may well be adequately reconstructed with zygomatic implants. Immediate function of dental implants for full-arch maxillary rehabilitation in the patient with the atrophic edentulous maxilla improves the patient’s oral health quality of life. Erkapers et al6 demonstrated this in a prospective study of 51 patients with atrophic edentulous maxillae, with 45 patients being followed for 3 years showing the most improvement in oral health quality of life at 12 months and remaining high for 3 years. Anchoring the zygomatic implant within the body of the zygomatic bone allows for immediate function of the implants with transmittance of the load via the infrazygomatic crest to the frontal and temporal portions of the bone.7 When approaching the treatment of the short-arch-length maxilla with the goal of immediate function in mind, there are multiple biomechanical considerations that can help guide the clinician in the best treatment for the patient. The clinician should know when to use zygomatic implants to satisfy the biomechanical requirements for immediate function, but it is equally important to appreciate when the placement of zygomatic implants can be avoided.

Defining the Short Arch Length The maxilla with 45 mm of bone or less available for osseointegration between the most anterior extents of the maxillary sinuses is defined as having short alveolar arch length. This measurement is determined digitally by a spline on the axial view of the computed tomography scan from the most anterior projections of the maxillary sinuses near mid-alveolar level, which is an approximation of the planned All-on-4 bone shelf 8 (Fig 16-1). The short-arch-length maxilla is typically found in elderly patients or patients with long-term partial or complete edentulism. In instances of few locations for adequate cortical bone fixation, immediate functional loading becomes burdensome.9 Because of the minimal bone quantity in the posterior maxilla, there is also often a challenge in obtaining adequate anterior posterior (AP) spread. The decreased AP spread will limit the extent of the cantilever on the full-arch restoration.10 In such cases, this may lead to inadequate esthetics, function­ality, and patient satisfaction with the full-arch implant-­supported prosthesis. The clinician preparing for the treatment of the short-arch-length maxilla should be prepared to execute multiple different treatment modalities to obtain the best distribution of implants within the arch.

Preoperative Evaluation: Imaging Preoperative imaging should be used to narrow treatment options before any surgery. A panoramic radiograph may be used as an initial screening tool for maxillary atrophy, but cone beam computed tomography (CBCT) imaging is crucial

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16  ARCH-LENGTH THRESHOLD FOR USING ZYGOMATIC IMPLANTS

Fig 16-1  A preoperative cone beam computed tomography (CBCT) axial slice of the maxilla showing the spline measurement of the arch between the anterior-most projections of the maxillary sinuses at the mid-alveolar level of the expected All-on-4 bone shelf. The shortarch-length maxilla measures less than 45 mm.

a

b

Fig 16-2  The preoperative CBCT coronal slice provides inspection of paranasal sinuses for presence of disease, evaluation of the zygomatic bones, and the preoperative measurement of the path of the zygomatic implant. This can aid the clinician in selecting the correct length of the zygomatic implant.

to the proper evaluation of the atrophic maxilla prior to implant surgery. Particular interest is paid to the evaluation of the M point, V point, presence of teeth (especially first molars), pterygomaxillary junction, zygomatic bones, and presence of paranasal sinus disease (Figs 16-2 and 16-3). Evaluation should be done radiographically to determine if there is sufficient cortical bone present for adequate primary stability of the implants. Using the complete arch site classification for All-on-4 immediate function, the short-arch-length maxilla is a Class C or Class D maxilla11 (Fig 16-4). The point of maximum bone mass at the lateral piriform rim about the nasal fossa is the M point. The V point is the point of maximum bone mass in the midline of the maxilla, usually within the nasal crest approximating the junction with the vomer. These are important locations because they are surgical aiming points for the apical anchorage of tilted dental implants in the atrophic maxilla.11 The goal of immediate loading of a full-arch hybrid prosthesis allows for some treatment variations during the surgery that are largely dependent on the quality of bone available for implant stability. This variable requires the surgeon to be prepared for insufficient composite insertion torque values, requiring additional implants or alternative fixation sites. The CBCT scan should be reviewed for possible secondary or tertiary implant locations such as the palatal root of a first molar when removed during surgery, the pterygomaxillary junction, or the zygoma.

Fig 16-3  (a) A preoperative panoramic radiograph of a patient with a short-arch-length maxilla. Note the bone isolated to the anterior maxilla. (b) The preoperative CBCT axial slice of the same patient with the spline measurement of the arch length. Note the bone stock in the pterygoid region, which may be used as implant anchorage sites.

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Treatment Options for the Short-Arch-Length Maxilla

a

15 mm 15 mm 10–15 mm

20 mm b

Fig 16-4  (a) Class C maxilla. (b and c) Class D maxilla. (Reprinted with permission from Jensen.11)

c

Detailed Clinical Examination The past medical history of the patient should be thoroughly reviewed with special attention given to any history of sinus disease. Any sinus disease needs to be managed preoperatively. If there is acute sinus disease, this is a contraindication to transsinus implants and zygomatic implants. Chronic sinus disease that is well controlled is not a contraindication for transsinus implants or zygomatic implants. It is prudent to have a patient with poorly controlled sinus disease first evaluated by an otolaryngologist to optimize the sinuses before extensive implant surgery. Evaluating for position of the prosthesis transition line is crucial to the success of the implant-supported fixed hybrid prosthesis.12 In the short-arch-length maxilla, bone leveling to achieve the All-on-4 shelf is all that is required; significant bone reduction is usually not necessary to gain adequate restorative space. Evaluation of the maximum opening and mandibular dentition is important in planning the management of the shortarch-length maxilla. This can help the clinician to assess the operative difficulty of properly accessing bone stock in areas such as the pterygomaxillary junction or the difficulty of using the long zygomatic implant instrumentation.

Treatment Options for the ShortArch-Length Maxilla There are several options for treatment of the short-arch-length maxilla to obtain a full-arch implant-supported prosthesis. Traditionally, five or six implants were placed in the maxilla either during or after maxillary sinus grafting and allowed to

osseointegrate followed by delayed loading with a completearch prosthesis.13 As dental implants continued to prove their success, techniques were developed to allow for an abbreviated number of implants as well as reduction in the number of procedures for sinus grafting. The All-on-4 technique, which allows for avoidance of anatomical limiting factors by using tilted implant placement, has been a great advancement and has become popular both in the maxilla and mandible.14 Several strategies have been developed in the management of the short-arch-length maxilla with the presence of posterior maxillary atrophy, pneumatized maxillary sinuses, and minimal incisive bone. These techniques have involved the use of paranasal bone including subnasal basal bone, lateral piriform, and nasal crest as well as maxillary sinus grafting, nasal floor grafting, pterygoid implants, and zygomatic implants.15–20 These have all been used to successfullly treat difficult cases in the maxilla requiring complete-arch dental rehabilitation. Of these, the most frequently used treatments include the following: •  Bilateral sinus grafting with delayed implant placement •  Implant placement in a V-4 placement strategy with or without transsinus implants and simultaneous bone grafting •  Two anterior implants with immediate implants at the first molar sites with or without sinus intrusion •  Two anterior implants with bilateral zygomatic implants •  Two anterior implants with bilateral zygomatic implants and pterygoid implants •  Quad zygomatic implants

Zygomatic implants When planning treatment for the short-arch-length maxilla for an immediate function complete arch prosthesis, there is a defining strategy that can be followed to avoid unnecessary

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16  ARCH-LENGTH THRESHOLD FOR USING ZYGOMATIC IMPLANTS

Adequate zone I and II bone

Adequate zone I bone No

Yes

Patient desires immediate function?

Yes

Inadequate maxillary alveolar bone

V-4 pattern implant placement

Quad zygomatic implant placement

Two anterior implants

No Anterior sinus grafting with delayed M-4 pattern implant placement

Adequate AP spread?

No

Yes

Adequate composite insertion torque?

No

Yes

Yes Stable for immediate function

First molar implant site?

No

Place first molar site implant

Pterygoid implant site?

No

Place zygomatic implant ± pterygoid implant

Yes Adequate composite insertion torque?

Yes

No

Anterior implant to posterior implant site > 20mm?

Yes

No Stable for immediate function

Place pterygoid site implant

Fig 16-5 This flow chart describes the approach to treatment planning the short-arch-length maxilla. The balance between simplicity and efficacy should always be considered when approaching the difficult short-arch-length maxilla.

treatment. There are cases when it is clear that the patient has severe maxillary atrophy and requires quad zygomatic implants with two in each zygoma to achieve immediate function for the complete arch prosthesis. This technique has been presented in the literature by Maló et al21 and Bedrossian et al.22 This method would be the treatment strategy for the Class D maxilla when immediate function was desired. Hung et al23,24 have

published work with real-time CT-guided navigation for zygomatic implant placement. This technique will likely see more use as the technology becomes more available to surgeons and continues to improve. In cases where the indications for zygomatic implants are not absolute, it is valuable to be prepared to place zygomatic implants if necessary to provide adequate composite insertion

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33.67 mm

22.53 mm 44.19 mm

a

b

c

Fig 16-6 (a) Preoperative arch length measurement on axial view CBCT. Note the opacification of the right maxillary sinus, indicating the presence of sinus disease. This patient was referred to an otolaryngologist for evaluation and management prior to surgery. (b) Three-dimensional reconstruction of postoperative CBCT showing V-4 implant placement, bilateral zygomatic implants, and left pterygoid implant. The V-4 placement did not satisfy the appropriate AP spread or the composite torque value of 120 Ncm, thus progressing to placement of a pterygoid implant that provided adequate AP spread but due to poor bone quality did not provide significant increase in composite torque value. Bilateral zygomatic implants were then placed, achieving adequate AP spread and composite torque. (c) Postoperative CBCT axial slice with AP spread measurements.

torque for immediate loading. Both the patient and surgeon benefit from exploring other options before making the decision to use zygomatic implants. Secondary implant anchorage sites should be identified preoperatively to be efficient during the surgical procedure (Fig 16-5).

followed by placement of an 8- to 10-mm-long tapered implant. This may decrease the length of the cantilever or even negate the need for a cantilever.

The V-4 placement strategy

If the patient lacks molar site availability, the pterygoid should be evaluated for implant placement.25 Using four anterior implants that may have minimal AP spread with the addition of pterygoid implants allows for restoration of posterior dentition, avoids the use of cantilevers, and provides favorable biomechanical dispersal of load.26

Around 20% of short-arch-length maxillary cases can be successfully managed with a V-4 implant placement. V-4 placement strategy uses four standard-length implants in the maxilla angled at 30 degrees toward the midline with the posterior implant apex at the M point and the anterior implant apices at the V point. A disadvantage is that the AP spread of implants in the V-4 placement strategy is often reduced and may approach 10 mm or shorter. In cases of V-4 placement when adequate AP spread cannot be obtained or a composite insertion torque of 120 Ncm is not obtained, options for additional implants should be evaluated.11 Potential implant sites more distal in the arch would be the first molar palatal root site or the pterygomaxillary junction.

Implants in the first molar site When a patient has a first molar that is to be extracted, this provides a potential site for immediate implant placement even if the remaining posterior maxilla is severely atrophic. An implant osteotomy can typically be prepared with round osteotomes, allowing for simultaneous sinus floor intrusion about 3 to 4 mm

Pterygoid implants

Combination of techniques When the pterygoid region is deficient in quantity or quality of bone, the zygomatic bone provides a relatively distal implant anchorage point that can satisfy the requirements for the immediate-function complete arch prosthesis.5 Having two to four implants in the anterior maxilla with zygomatic implants offering support for the posterior maxilla allows for an increase in both insertion torque and implant distribution. Both composite insertion torque and AP spread can be increased with the addition of pterygoid or zygomatic implants and occasionally first molar site implants. In most short-arch-length cases, a combination of four to six implants will gain adequate composite insertion torque and AP spread; in rare cases, additional implants may be warranted (Fig 16-6).

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Conclusion Long-standing indications for zygomatic implant use in the atrophic posterior maxilla have been well documented in the literature. The severely atrophic maxilla necessitates the quad zygomatic implant placement strategy. When addressing the short alveolar arch length maxilla with adequate incisive bone for placement of two to four traditional implants, there is no well-established measurement to indicate when to use zygomatic implants. The clinician can look for adequate bone for osseointegration of traditional implants in a first molar extraction site or pterygoid region; if these sites do not offer satisfactory bone for implant placement, the zygomatic implant should be employed. The guideline of 45 mm of alveolar arch length can be used as the decision threshold measurement for when a zygomatic implant should be considered.

References 1. Adell R, Lekholm U, Rockler B, Brånemark PI. A 15-year study of osseointegrated implants in the treatment of the edentulous jaw. Int J Oral Surg 1981;10:387–416. 2. Boyne PJ, James RA. Grafting the floor of the maxillary sinus with autogenous marrow and bone. J Oral Surg 1980;38:613–616. 3. Isaksson S, Ekfeldt A, Alberius P, Blomqvist JE. Early results from reconstruction of severely atrophic (class VI) maxillas by immediate endosseous implants in conjunction with bone grafting and Le Fort I osteotomy. Int J Oral Maxillofac Surg 1993;22:144– 148. 4. Aparicio C, Ouazzani W, Garcia R, Arevalo X, Muela R, Fortes V. A prospective clinical study on titanium implants in the zygomatic arch for prosthetic rehabilitation of the atrophic edentulous maxilla with a follow-up of 6 months to 5 years. Clin Implant Dent Relat Res 2006;8:114–122. 5. Tuminelli FJ, Walter LR, Neugarten J, Bedrossian E. Immediate loading of zygomatic implants: A systematic review of implant survival, prosthesis survival and potential complications. Eur J Oral Implantol 2017;10(suppl 1):79–87. 6. Erkapers M, Segerström S, Ekstrand K, Baer RA, Toljanic JA, Thor A. The influence of immediately loaded implant treatment in the atrophic edentulous maxilla on oral health related quality of life of edentulous patients: 3-year results of a prospective study. Head Face Med 2017;13:21. 7. Ujigawa K, Kato Y, Kizu Y, Tonogi M, Yamane GY. Three-dimensional finite elemental analysis of zygomatic implants in craniofacial structures. Int J Oral Maxillofac Surg 2007;36:620–625. 8. Jensen OT, Adams MW, Cottam JR, Parel SM, Phillips WR 3rd. The all-on-4 shelf: Maxilla. J Oral Maxillofac Surg 2010;68:2520– 2527. 9. Jensen OT, Ringeman JL, Adams MW, Gregory N. Reduced archlength as a factor of 4-implant immediate function in the maxilla: A technical note and report of 39 patients followed for 5 years. J Oral Maxillofac Surg 2016;74:2379–2384. 10. McAlarnmey ME, Stravropoulos DN. Theoretical cantilever lengths versus clinical variables in fifty-five clinical cases. J Prosthet Dent 2000;83:332–343.

11. Jensen OT. Complete arch site classification for all-on-4 immediate function. J Prosthet Dent 2014;112:741–751. 12. Garber DA, Belser UC. Restoration-driven implant placement with restoration-generated site development. Compend Contin Educ Dent 1995;16:796–804. 13. Jensen OT, Shulman LB, Block MS, Iacono VJ. Report of the Sinus Consensus Conference of 1996. Int J Oral Maxillofac Implants 1998;13(suppl):11–45. 14. Maló P, Rangert B, Nobre M. All-on-4 immediate-function concept with Brånemark System implants for completely edentulous maxillae: A 1-year retrospective clinical study. Clin Implant Dent Relat Res 2005;7(suppl 1):S88–S94. 15. Jensen OT, Cottam J, Ringeman J, Adams M. Trans-sinus dental implants, bone morphogenetic protein 2, and immediate function for all-on-4 treatment of severe maxillary atrophy. J Oral Maxillofac Surg 2012;70:141–148. 16. Piere F, Aldini NN, Fini M, Marchetti C, Corinaldesi G. Immediate fixed implant rehabilitation of the atrophic edentulous maxilla after bilateral sinus floor augmentation: A 12 month pilot study. Clin Implant Dent Relat Res 2012;14(suppl 1):e67–e82. 17. Testori T, Mandelli F, Mantovani M, Tashieri S, Weinstein RL, Del Fabbro M. Tilted trans-sinus implants for the treatment of maxillary atrophy: Cases series of 35 consecutive patients. J Oral Maxillofac Surg 2013;71:1187–1194. 18. Jensen OT, Adams MW. Anterior sinus grafts for angled implant placement for severe maxillary atrophy as an alternative to zygomatic implants for full arch fixed restoration: Technique and report of 5 cases. J Oral Maxillofac Surg 2014;72:1268–1280. 19. Camargo IB, Oliveira DM, Fernandes AV, Van Sickels JE. The nasal lift technique for augmentation of the maxillary ridge: Technical note. Br J Oral Maxillofac Surg 2015;53:771–774. 20. Jensen OT, Cottam JR, Ringeman JL, Graves S, Beatty L, Adams MW. Angled dental implant placement into the vomer/nasal crest of atrophic maxilla for All-on-Four immediate function: A 2 year clinical study of 100 consecutive patients. Int J Oral Maxillofac Implants. 2014;29:30–35. 21. Maló P, Nobre Mde A, Petersson U, Wigren S. A pilot study of complete edentulous rehabilitation with immediate function using a new implant design: Case series. Clin Implant Dent Relat Res 2006;8:223–232. 22. Bedrossian E, Rangert B, Stumpel L, Indresano T. Immediate function with the zygomatic implant: A graftless solution for the patient with mild to advanced atrophy of the maxilla. Int J Oral Maxillofac Implants 2006;21:937–942. 23. Hung KF, Wang F, Wang HW, Zhou WJ, Huang W, Wu YQ. Accuracy of real-time surgical navigation system for the placement of quad zygomatic implants in the severe atrophic maxilla: A pilot clinical study. Clin Implant Dent Relat Res 2017;19:458–465. 24. Hung K, Huang W, Wang F, Wu Y. Real-time surgical navigation system for the placement of zygomatic implants with severe bone deficiency. Int J Oral Maxillofac Implants 2016;31:1444–1449. 25. Bidra AS, Huynh-Ba G. Implants in the pterygoid region: A systematic review of the literature. Int J Oral Maxillofac Surg 2011;40:773–781. 26. Cucchi A, Vignudelli E, Franco S, Corinaldesi G. Mimimally invasive approach based on pterygoid and short implants for rehabilitation of an extremely atrophic maxilla: Case report. Implant Dent 2017;26:639–644.

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CHAPTER 17

PTERYGOID IMPLANTS Stuart L. Graves, dds, ms | Lindsay L. Graves, dmd

Because of inadequacies in both the quantity and quality of available bone in the posterior maxilla, this area can be uniquely challenging for dental rehabilitation using osseointegrated implants.1,2 Implant placement is often limited by pneumatization of the maxillary sinuses, which increases with both age and tooth loss. Alveolar ridge height is also lost with time in an edentulous state. In addition to the frequent issue of bone quantity, bone quality presents a challenge because the posterior maxilla is made up of low-density cancellous bone (Lekholm and Zarb type 3 and 4).3,4 However, these anatomical obstacles can often be overcome without the use of grafting through the use of the pterygoid plate implant, first described by Tulasne in 1989.5 Since the advent of roughened implant surfaces, the survival rate of pterygoid implants has been reported as 96% to 99%.6–10 This is comparable with that of traditional nonangled implants and higher than that of maxillary implants placed in grafted bone, making them an excellent and predictable alternative to sinus elevations and posterior alveolar bone grafting. The goal of using the pterygomaxillary region for implant placement is to avoid sinus elevation and alveolar grafting procedures while still obtaining molar occlusion. This is done by first attempting to use existing bone, which is advantageous for both the patient and practitioner due to decreased cost and chair time.5 Additionally, fewer surgical procedures means fewer opportunities for unforeseen morbidity and postoperative pain. A distinct advantage of pterygoid implants over sinus elevation and grafting techniques is the possibility for immediate loading. In fact, it has been shown that immediate loading increases the success rate for pterygoid implants when compared with a traditional two-stage approach.11 Zygomatic implants represent another alternative to grafting; however, this is a more complex surgical procedure that is potentially more prone to complications. Also, the surgical procedure for zygomatic implant placement generally requires sedation, while pterygoid implants may be placed quickly with relative ease under local anesthesia.12

Anatomical Considerations The success of implants placed in the pterygoid region is due to engagement of a dense pillar of bone comprising the tuberosity of the maxilla, the pyramidal process of the palatine bone, and the pterygoid process of the sphenoid bone (Fig 17-1).13 In contrast to the cancellous type 3 or 4 bone in the tuberosity, the pyramidal and pterygoid processes are made up of cortical type 1 and 2 bone, which is 139% denser than that of the tuberosity.14 Engagement of dense bone results in increased primary stability, a key determining factor in implant survival.15 Because this long vertical pillar is engaged, longer implants have a greater survival rate than shorter implants; therefore, implants should have a minimum length of 15 mm.16 The implant apex should ideally penetrate into the pterygoid fossa by at least 2 mm for maximal cortical stabilization.13 The pyramidal-pterygoid junction has an average width of 6.0 to 6.7 mm, so a regular-platform 4-mm-diameter implant is ideal to thread this junction for maximal bone encasement.13,17 The thickest area of supporting bone is located in the middle part of the pterygoid process between the plates, about 3 to 4 mm medial to the alveolar ridge. An implant must therefore be angled slightly palatally to bisect this dense junction of bone in the pterygoid region.13 Placement of pterygoid implants is technique sensitive and may be daunting to the new user, but it is a generally safe procedure because the implant path does not contain vital structures. Depending on implant angulation and the posterior extent of maxillary sinus pneumatization, the implant may pass transsinus through the posterior aspect of the sinus en route to the pterygoid process without adverse sequelae, and transsinus placement does not require bone grafting. The maxillary artery is located 10 mm above the pterygomaxillary suture (which these implants penetrate) as it enters the pterygopalatine fossa (Fig 17-2). In the case of a Le Fort I osteotomy, this suture is

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Fig 17-1  (a) There is a dense pillar of bone consisting of the tuberosity of the maxilla, the pyramidal process of the palatine bone, and the pterygoid process of the sphenoid bone. (b) The implant should pass through the bone into the fossa by at least 2 mm.

a

b Fig 17-2  (a and b) The pterygoid fossa is bordered by plates medial and lateral to the pterygoid. Branches of the posterior superior alveolar nerve pass through this region. There are no major arteries in this immediate area. The thickest part of the buttress is 4 to 5 mm lateral to the hamular process.

a

b

completely cut without fear of maxillary artery severance.18 The greater palatine artery branches off the maxillary within the pterygopalatine fossa and dives into its canal, which emerges palatal to the region of the first or second molar. Excessive palatal inclination (ie, more than 40 degrees) could result in transection of the greater palatine artery, vein, and nerve within the canal, potentially causing excessive bleeding.5,19,20 Cases of severe bleeding have been reported; however, this is a rare adverse event related to inaccurate placement.14 A palatal inclination of 10 to 15 degrees is suggested. This angle may be smaller (ie, more vertical) in cases of the severely atrophied maxilla, as more bone volume is lost on the buccal and the tuberosity; therefore, the entry point moves medially to align more with the stationary pterygoid pillar.

Preoperative Evaluation and Patient Selection Candidates for use of pterygoid implants are those patients with nonrestorable or missing posterior dentition (specifically

second molar to first premolar at least) with inadequate height for standard implant placement. Because the implant is not oriented perpendicularly to the occlusal plane, it must be used in a multiunit treatment plan (fixed partial denture or full-arch restoration) splinted to anterior implants to dissipate off-axis occlusal forces that would otherwise be unfavorably concentrated on a mesial cantilever. Though surgical planning for a pterygoid implant may be adequately accomplished via panoramic radiograph, cone beam computed tomography (CBCT) is becoming standard for screening and treatment planning in most contemporary oral surgery practices and is ideal, especially in the case of severe maxillary atrophy. The degree of pneumatization of the maxillary sinus determines anteroposterior insertion and angulation of the implant. CBCT also allows for measurement of the height and width of the tuberosity and the pterygoid plates, visualization of the position of lateral plates in relation to the hamular process, as well as suggestion of bone density in the area. The CT occlusal view of the maxilla is used to determine the optimal angle of implant placement to obtain a fixed implant for possible immediate function. Printing of a three-dimensional stereolithic model from the CBCT via computer-aided design/computerassisted manufacturing is often helpful for visualization and

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Surgical Technique

a Fig 17-3  Typical pterygoid implant insertion. (a) Preoperative clinical situation. (b) A linear incision is made midcrestal to the pterygoid notch. Slight vertical relaxing incision posterior and buccal mark on the tuberosity approximately in the second molar region. (c) The starter drill is placed at a 45-degree angle to the occlusal plane. (d) This is followed by the long 2-mm twist drill. Using the hamular process as a guide, the drill is aimed 5 mm to the buccal of this structure and is inserted its full length. Note it is very important to feel the drill hit dense bone and slow at 10 to 15 mm insertion depth. (e) The osteotomy is prepared for 18.0 × 4.3–mm implant, which is inserted in the usual manner. Torque from 30 to 40 Ncm is usually obtained when dense buttress bone has been engaged. (f) The implant is placed to bone level with no countersinking. Usually a 17- or a 30-degree multiunit abutment is placed for easy restoration. (g) The incision is closed, keeping care to maintain attached gingiva on the buccal.

b

c

d

e

f

g

allows the surgeon to plan and practice via model surgery prior to the actual live patient surgery. Rarely, inadequate height of the tuberosity below and behind the sinus is a contraindication to pterygoid implant placement. This results in excessive flattening of the implant angle, making the implant unable to engage the height of the vertical pyramidal-pterygoidal pillar and resulting in a less favorable restorative angle.

Surgical Technique Figure 17-3 demonstrates the surgical technique. Adequate local anesthesia is obtained through blockade at the greater palatine artery and nerve and local infiltration in the buccal vestibule as well as posterolateral to the tuberosity. A full-thickness incision is made 2 to 3 mm palatally to the alveolar crest from the estimated location of the pterygomaxillary fissure, over the tuberosity, to the premolar region, and a relaxing incision is placed anteriorly. A mucoperiosteal flap is then elevated buccally, exposing the tuberosity in its entirety, and a guide hole is placed in approximately the second molar area of the tuberosity with a no. 4 or 6 round bur.14

To establish angulation, a long-shaft 2-mm twist drill on an extension is used. The pterygoid hamulus is palpated, and the drill is directed 5 mm laterally to this landmark. The angle is approximately 45 degrees to the occlusal plane.13,19,21 This process is the primary guide used to determine the thickest part of the pterygoid pillar of bone. If the correct path is followed, the twist drill will encounter the dense cortical bone of the pterygomaxillary suture area at a depth of 10 to 14 mm. The drill will slow down noticeably, then speed up again after it passes through pterygoid cortical bone, entering the pterygoid fossa. The drill is removed, and a probe is placed in the hole to attempt to feel for the sinus cavity. If a large perforation has occurred, a new site must be located at least 3 mm posterior to the original one. Sequential long-shaft drills on extenders are used to enlarge the osteotomy while maintaining the palatal trajectory toward the pterygoid hamulus. With each drill, it is important to pass completely through the pterygoid plate buttress of bone. There is no countersinking. The operator may elect to underprepare the site in cases of less dense bone. Care should be taken not to underprepare in the dense pterygoid pillar because the implant could “bottom out” if the osteotomy hole is too small. That is, when the implant reaches the dense bone, it may be unable to

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a

b

c

d

Fig 17-4  (a) Preoperative radiograph demonstrating 4 to 7 mm vertical bone height in the maxillary ridge. (b and c) Postoperative imaging with completed prosthesis. Note the angles of the pterygoids in relation to the vertical and lateral. (d) Clinical view of definitive screw-retained prosthesis. Note the screw access hole visible for all six implants.

continue to self-tap into the pillar, halting forward motion, and with sustained rotation strip the previously tapped less dense bone of the tuberosity that surrounds it. After the implant site has been completely prepared, a depth probe with an enlarged tip is used to explore the site and determine the length of implant to be used. The implant should pass completely through the pterygoid process to establish bicortical stabilization. An implant is selected that will extend roughly 2 mm past the pterygoid process. This is generally a self-tapping implant 15 mm or longer. It is easily placed with a long fixture mount or with use of a long-shaft straight hand-torque “onion” driver. The implant should be seated so that half of the head is buried in the cortex of the tuberosity. A goal of 30 to 40 Ncm of torque should be expected. A cover screw or straight abutment is then placed. Where angulation exceeded 60 degrees, an angled abutment is used. An alternative method of placement is more vertical with only a 15- to 20-degree angulation forward relying on the posterior sinus wall and the pterygoid places. With this approach, insertion torque exceeds 50 Ncm and immediate function is assured. Soft tissue plasty or tuberosity reduction is often performed at wound closure to reduce extraneous thick tissue.14 This allows for better access for restorative treatment and correction of an

inverse alveolar plane. The incision is closed with 3-0 resorbable sutures on a no. 6 cutting needle in continuous fashion. The restorative dentist may at this time make impressions for a provisional fixed denture prosthesis. The prosthesis should be designed without excursive contacts to promote osseointegration during the healing period of 6 months. The patient is placed on antibiotics for 1 week. Augmentin (GlaxoSmithKline) is the antibiotic of choice due to potential involvement of the sinuses, though amoxicillin or penicillin may be used. In the case of penicillin allergy, clindamycin or a cephalosporin is used. At reentry in 6 months, the implant is reverse-torque tested to 10 Ncm to ensure osseointegration.

Complications As previously mentioned, complications of pterygoid buttress implant osteotomies include bleeding, sinus perforation, and restorative issues from thick local mucosa. However, these are rare and usually minor or avoidable with proper technique.5,14,19,20 The biggest reason for failure to achieve primary stability is inability to engage the cortical bone of the pterygoid

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Case Studies

a

b

d

c

e

Fig 17-5  (a) Preoperative panoramic radiograph. (b and c) After 3 months, healing appeared to be as good as can be expected. The oroantral fistulae were still open. (d) Model surgery was completed on the stereolithic model. (e) Postoperative stereolithic model demonstrates the position of the implant. Note that both oroantral communications are open in the model.

plates. This is due to either an error in angulation or inadequate implant length. The 2-mm twist bur should be the operator’s first indicator of proper placement—increased resistance should be felt by approximately 14 mm. If this is not the case, landmarks should be checked, the bur reoriented, and the site reosteomatized before proceeding to wider drill bits, which may destroy bone needed for stabilization. It may be helpful to take a CT scan to verify position of the drill prior to sizing up. The roottip pick or other long probe is excellent for angle visualization and palpation of the cavity. If an implant in the pterygoid region fails to integrate, it tends to not lead to significant bone loss. The bone of the tuberosity and pterygoid region is not important for alveolar function, nor will it cause a gross alveolar deformity intraorally if an implant is lost. Because of the limited volume of bone, another pterygoid implant is generally not considered. Instead, the operator may use either a zygomatic implant or traditional sinus elevation to achieve posterior occlusion. In some cases, two pterygoid-directed implants can be placed on the same side.

Case Studies Case 1 This 55-year-old woman had been edentulous in the maxilla for 20 years (Fig 17-4). The sinuses were quite pneumatized, and there was minimal alveolar ridge. Workup included a stereolithic model and model surgery. It was decided to place six implants: two pterygoid implants, two zygomatic implants, and two piriform rim implants.

Case 2 This 72-year-old woman had a subperiosteal implant placed 25 years previously. She presented with secondary infection of the framework and two large oroantral communications (Fig 17-5). The appliance was removed, and 3 months were allowed for healing. During this time, she could not wear a maxillary denture due to the oroantral openings.

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f

g

h

i

j

k

l

Fig 17-5 (cont) (f to h) Immediate postoperative scan consisting of the following implants: one vomer, two zygomatic, and two pterygoids. The oroantral fistulae were not attempted to be closed at this time. (i) Final impression consisting of abutments on the vomer, zygomatic, and pterygoid implants. (j) Metal-ceramic prosthesis incorporating the five implants. (k and l) Definitive prosthesis in place.

a

b

Fig 17-6  (a and b) Preoperative scans.

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Case Studies

d

c

e

f

g

Fig 17-6 (cont) (c and d) Model surgery on stereolithic model. (e) Placement of implants visible are the following: two vomer, two zygomatic, and two pterygoid implants. (f) Postoperative scan. (g) Definitive prosthesis screwed in place. Note the screw access holes. (h and i) Preoperative photographs. (j and k) Postoperative photographs.

h

i

j

Case 3 This 65-year-old man had been wearing maxillary and mandibular dentures for 45 years. He had several consults with oral maxillofacial surgeons saying that he needed a hip graft to

k

the maxilla for any implants to be placed. Note that there are extremely large pneumatized sinuses bilaterally (Fig 17-6). There is also virtually no vertical height between the floor of the nose and the alveolar ridge.

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a

b Fig 17-7 (a and b) The right side has two pterygoid implants, one 3.5 mm in diameter and one 4.3 mm in diameter.

Case 4 This is a 37-year-old woman with a severely pneumatized sinus. The patient had recurrent bouts of chronic right sinusitis that could not be cleared. It was decided to place a double pterygoid on the patient’s right side in lieu of a zygomatic implant, as this would prevent sinus violation. Double pterygoid implants were placed on the right side approximately 2 mm apart (Fig 17-7).

Conclusion Osseointegrated implant placement in the pterygoid buttress of bone offers a predictable and safe option for restoring posterior dentition. The practitioner and patient may both find the modality more efficient and preferable to other options such as the sinus elevation or zygomatic implants due to shortened implant placement time without the need for sedation and shortened overall treatment time with a relative dearth of complications and the option of immediate loading.

References 1. Jaffin RA, Berman CL. The excessive loss of Branemark fixtures in type IV bone: A 5-year analysis. J Periodontol 1991;62:2–4. 2. DaSilva JD, Schnitman PA, Wohtle PS, Wang HN, Koch GG. Influence of site on implant survival: 6 year results [abstract]. J Dent Res 1992;71:256.

3. Balshi TJ. Single, tuberosity-osseointegrated implant support for a tissue-integrated prosthesis. Int J Periodontics Restorative Dent 1992;12:345–357. 4. Lekholm U, Zarb GA. Patient selection and preparation. In: Brånemark PI, Zarb GA, Albrektsson T (eds). Tissue-Integrated Prostheses: Osseointegration in Clinical Dentistry. Chicago: Quintessence, 1985:199–209. 5. Tulasne JF. Implant treatment of missing posterior dentition. In: Albrektsson T, Zarb GA (eds). The Brånemark Osseointegrated Implant. Chicago: Quintessence, 1989:103. 6. Balshi SF, Wolfinger GJ, Balshi TJ. Analysis of 164 titanium oxide-surface implants in completely edentulous arches for fixed prosthesis anchorage using the pterygomaxillary region. Int J Oral Maxillofac Implants 2005;20:946–952. 7. Balshi SF, Wolfinger GJ, Balshi TJ. A prospective study of immediate functional loading, following the Teeth in a Day protocol: A case series of 55 consecutive edentulous maxillas. Clin Implant Dent Relat Res 2005;7:24–31. 8. Curi MM, Cardoso CL, Ribeiro Kde C. Retrospective study of pterygoid implants in the atrophic posterior maxilla: Implant and prosthesis survival rates up to 3 years. Int J Oral Maxillofac Implants 2015;30:378–383. 9. Peñarrocha M, Carillo C, Boronat A, Peñarrocha M. Restrospective study of 68 implants placed in the pterygomaxillary region using drills and osteotomes. Int J Oral Maxillofac Implants 2009;24:720– 726. 10. Rodríguez X, Méndez V, Vela X, Segalà M. Modified surgical protocol for placing implants in the pterygomaxillary region: Clinical and radiologic study of 454 implants. Int J Oral Maxillofac Implants 2012;27:1547–1553. 11. Balshi TJ, Wolfinger GJ, Slauch RW, Balshi SE. A retrospective comparison of implants in the pterygomaxillary region: Implant placement with two-stage, single-stage, and guided surgery protocols. Int J Oral Maxillofac Implants 2013;28:184–189. 12. Bidra AS, Balshi TJ, Wolfinger GJ. American College of Prosthodonists. Use of implants in the pterygoid region for prosthodontic treatment [position paper]. https://www.prosthodontics.org/assets/ 1/7/Use_of_Implants_in_the_Pterygoid_Region.pdf. Accessed 8 May 2018. 13. Graves SL. The pterygoid plate implant: A solution for restoring the posterior maxilla. Int J Periodontics Restorative Dent 1994;14:512–523. 14. Rodríguez X, Lucas-Taulé E, Elnayef B, et al. Anatomical and radiological approach to pterygoid implants: A cross-sectional study of 202 cone beam computed tomography examinations. Int J Oral Maxillofac Surg 2016;45:636–640. 15. Bahat O. Osseointegrated implants in the maxillary tuberosity: Report of 45 consecutive patients. Int J Oral Maxillofac Implants 1992;7:459–467. 16. Balshi TJ, Wolfinger GJ, Slauch RW, Balshi SF. Brånemark system implant lengths in the pterygomaxillary region: A retrospective comparison. Implant Dent 2013;22:610–612. 17. Lee SP, Paik KS, Kim MK. Anatomical study of the pyramidal process of the palatine bone in relation to implant placement in the posterior maxilla. J Oral Rehabil 2001;28:125–132. 18. Turvey T, Fonseca R. The anatomy of the internal maxillary artery: Its relationship in maxillary surgery. J Oral Surg 1980;38:92–95. 19. Uchida Y, Yamashita Y, Danjo A, Shibata K, Kuraoka A. Computed tomography and anatomical measurements of critical sites for endosseous implants in the pterygomaxillary region: A cadaveric study. Int J Oral Maxillofac Surg 2017;46:798–804. 20. Suzuki M, Omine Y, Shimoo Y, et al. Regional anatomical observation of morphology of greater palatine canal and surrounding structures. Bull Tokyo Dent Coll 2016;57:223–231. 21. Bidra AS, Huynh-Ba G. Implants in the pterygoid region: A systematic review of the literature. Int J Oral Maxillofac Surg 2011;40:773–781.

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CHAPTER 18

THE NAZALUS IMPLANT Pietro Ferraris, md, dds | Giovanni Nicoli, md, dds | Ole T. Jensen, dds, ms

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mmediate loading of maxillary denture prostheses in the context of severe bone atrophy is complicated by posterior implant placement, sometimes requiring zygomatic or pterygoid implants with extra-alveolar placement that increases surgical and prosthetic complexity. To overcome this complexity, a new extra-long implant (20 to 24 mm) was developed with an angulated 24-degree platform (Nazalus, Southern Implants). A study was done to evaluate these implants as an alternative to zygomatic implants in the setting of severe maxillary bone atrophy. The main limitation to immediate loading of dental implants for complete arch rehabilitation in the maxilla is inadequate cortical bone to place implants.1 Disuse atrophy results in vertical bone loss, leading to deficient alveolar arch length and therefore limiting options for placement of posterior maxillary implants. For this reason, bone augmentation is commonly prescribed, including sinus floor and alveolar augmentation followed by delayed implant placement.2 To provide immediate function and avoid complex bone grafting procedures, zygomatic and pterygoid implants have been advocated.3 But these surgical approaches have some limitations and potential for complications. For example, the pterygoid implant results in a relatively unfavorable prosthetic position (ie, second and third molars), and the zygomatic implant may be complicated by chronic oroantral communication.3–6 The Nazalus implant was developed to overcome the limitations of pterygoid and zygomatic implants. Instead of extramaxillary anchorage, the Nazalus implant is anchored into cortical bone mass found at M point at the lateral nasal wall.3,7 In addition to bicortical anchorage at the residual palatoalveolar ridge and the nasal wall, bone grafting of the sinus floor may be done as needed. Nazalus implants are designed for transsinus placement with an angled platform to improve fixation at the alveolar process. To study the use of the Nazalus implant, 33 patients with completely edentulous maxillae were enrolled in a study. Patients qualified if there was less than 5 mm posterior maxillary bone height and if the anterior sinus wall angle to the

sinus floor approximated 90 degrees as viewed by cone beam computed tomography (CBCT).

Surgical Procedure The Nazalus implant placement protocol merges three different techniques: angulated implant placement, maxillary sinus floor augmentation, and the short alveolonasal criteria for the use of zygomatic implants.1,8,9 A preoperative CBCT scan should be taken to simulate implant position and measure the distance between the nasal wall and the residual alveolar crest at the approximate second premolar position. This establishes the length of implant required. The surgical technique begins with a crestal incision made around the arch with a posterior releasing incision at the first molar area. A buccal mucoperiosteal flap reflection exposes the nasal fossa and lateral sinus wall. According to the Bedrossian classification, a sinus floor bone graft should be done when the crestal bone is 3 mm or less10 (Fig 18-1). If so, a lateral antrostomy window is created for access using a triangular-shaped sinus membrane reflection where the sides of the triangle include the sinus floor and nasal wall to enhance vascularization of the bone graft. Options for sinus bone graft material include xenograft (ie, substitutive bovine bone [OCS-B Xenomatrix, Nibec] mixed with platelet-rich fibrin) or allograft, autograft, or bone morphologic protein 2.11 The implant osteotomy at the crest is increased to 3.4 mm diameter unless the crestal bone is very thin (ie, 1 mm or less). In that case, a 4-mm-diameter osteotomy is prepared to avoid bone fracture during implant placement. If the alveolar crestal bone is greater than 3 mm, bone grafting is not done.12–14 The final length of the implant is determined after measuring the osteotomy, which is usually longer than 20 mm.15 The Nazalus implants are 20, 22, and 24 mm in length, with a 24-degree offset platform in a conical shape with an external hexagon connection.

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Fig 18-1  (a) The Bedrossian classification. (b) In cases of crestal bone greater than 3 mm, the bone graft is not required. (c) In cases of severe bone atrophy with residual crestal bone 3 mm or less, a bone graft has been applied.

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Primary implant stability should be assessed by insertion torque, percussion test, and postsurgical CBCT.16 Two implants are also placed into the anterior maxilla. A screw-retained acrylic interim denture prosthesis should be placed within 24 hours after the implants are placed. In the initial pilot study of 33 patients, 24 (72.7%) underwent immediate loading. Of this group, 16 patients were men and 8 were women, and the mean age was 65 years (standard deviation: 9.73 years). The total number of implants placed was 115, ranging from 4 to 6 implants for each patient. Of these implants, 46% (53 implants) were Nazalus. Two patients smoked more than 10 cigarettes a day and three patients had cardiac comorbidity. Fourteen patients (58.3%) had sinus floor xenografts done (8 bilateral and 6 unilateral). All immediate-function implants achieved at least 30 Ncm insertion torque, and 10 implants achieved higher torque (40 Ncm in three implants and 45 Ncm in seven implants). Nine patients (27.3%) were treated with a delayed loading protocol, for a total of 29 implants, of which 12 (41.4%) were Nazalus. All delayed loaded implants osseointegrated and were in prosthetic function within 6 months. One nasal wall–directed implant (2%) failed during the follow-up period. All the remaining Nazalus implants (n = 52, 98%) were placed into function. There were no significant complications at the 6-month or lateterm follow-up of this preliminary study.

Advantages of Nazalus Implants The zygoma-directed implant is a technique that can be applied in patients with severe bone atrophy but can lead to oroantral fistula and other complications.4,5,15,17 Moreover, the technique

is challenging, it may require general anesthesia, and it has not been fully proven in efficacy over alternative bone augmentation techniques such as the sinus floor bone graft for treating atrophic maxillae.6 Potential complications include sinusitis (the most common), oronasal fistula, orbital injury, extraoral fistula, and intraoral soft tissue hyperplasia around the implant (ie, peri-implantitis). These complications may occur even if the surgeon is experienced and knowledgeable.15,18 The complementary technique of pterygoid plate–directed implantation requires only local anesthesia and therefore may be a more accessible treatment for patients.19,20 However, the emergence of the pterygoid implant platform in the second or third molar location renders prosthetic procedures more difficult. Moreover, pterygoid implant placement risks include excessive bleeding and inadequate bone quality or quantity for implant stability.19,21,22 The use of 20- to 24-mm-long implants appears to be a valid alternative to zygomatic or pterygoid implants. Compared with standard-length implants, the transsinus placement method results in an increased anterior posterior spread. Nazalus implants may find application in between the zygomatic and pterygoid implants not only because of anatomical position, but also in terms of difficulty of placement. Extra-long implants may increase the available armamentarium for addressing the treatment challenge of severe maxillary atrophy, particularly when there is a short arch length available for osseointegration.18,19 The extra-long implant protocol has two main advantages (see chapter 16). First, it can often be safely applied even in the presence of severe bone atrophy.15,21 Second, the Nazalus implant is less invasive and easier to place than the zygomatic implant. The Nazalus implant has been found to be stable over time where engaged with the lateral nasal wall and to form apparent osseointegration when viewed on CBCT (Figs 18-2 and 18-3). From a prosthetic point of view, the Nazalus implant introduces

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Advantages of Nazalus Implants

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Fig 18-2  (a) This 48-year-old man received four maxillary implants, including two Nazalus implants. (b to d) The right crestal bone thickness was less than 3 mm, so he required a bone graft on this side. (e) The left crestal bone thickness was greater than 3 mm, so he did not require a graft on this side. (f) This CBCT scan was taken 28 months after surgery. Fig 18-3 (a to e) This 60-year-old woman received six im­plants, two of which were Nazalus implants. Her crestal bone thickness was greater than 3 mm, so she did not require a graft. This CBCT scan was taken 24 months after surgery.

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a novelty by its design principle: In addition to increased length, the implant platform allows for a more central alveolar position for restoration than alternatives. As shown in Fig 18-4,

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the implant platform is in an optimal position when parallel to the residual crestal bone, avoiding the need for an angulated abutment and keeping the platform itself out of the sinus cavity.

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Fig 18-4 This is the optimal position of the Nazalus implant platform, avoiding the need for an angulated abutment and keeping the platform itself out of the sinus cavity.

Conclusion The use of Nazalus implants appears to be a safe alternative to zygomatic and pterygoid implants. Extra-long implants placed angulated transsinus into M point at the lateral nasal wall are shown to have a low failure rate with an absence of complications during a clinical study follow-up from 16 to 61 months. The approach adds a new option for addressing moderate to severe maxillary atrophy and enables improved posterior implant position by increasing anterior posterior spread. The use of extra-long implants could potentially increase the number of patients seeking complete arch treatment. Nevertheless, this short-term study requires long-term verification to be considered comparable to available techniques such as zygomatic and pterygoid implants even though there is strong scientific foundation for transsinus grafted implant placement.

References 1. Bedrossian E, Stumpel L, Beckely ML, Indresano T, Indersano T. The zygomatic implant: Preliminary data on treatment of severely resorbed maxillae. A clinical report. Int J Oral Maxillofac Implants 2002;17:861–865. 2. Beretta M, Poli PP, Grossi GB, Pieroni S, Maiorana C. Long-term survival rate of implants placed in conjunction with 246 sinus floor elevation procedures: Results of a 15-year retrospective study. J Dent 2015;43:78–86. 3. Jensen OT, Cottam JR, Ringeman JL, Graves S, Beatty L, Adams MW. Angled dental implant placement into the vomer/nasal crest of atrophic maxilla for All-on-Four immediate function: A 2 year clinical study of 100 consecutive patients. Int J Oral Maxillofac Implants. 2014;29:30–35. 4. Davó R, Pons O. Prostheses supported by four immediately loaded zygomatic implants: A 3-year prospective study. Eur J Oral Implantol 2013;6:263–269.

5. Fernández H, Gómez-Delgado A, Trujillo-Saldarriaga S, Varón-Cardona D, Castro-Núñez J. Zygomatic implants for the management of the severely atrophied maxilla: A retrospective analysis of 244 implants. J Oral Maxillofac Surg 2014;72:887–891. 6. Esposito M, Worthington HV. Interventions for replacing missing teeth: Dental implants in zygomatic bone for the rehabilitation of the severely deficient edentulous maxilla. Cochrane Database Sys Rev 2013;9:CD004151. 7. Jensen OT, Cottam J, Ringeman J, Adams M. Trans-sinus dental implants, bone morphogenetic protein 2, and immediate function for all-on-4 treatment of severe maxillary atrophy. J Oral Maxillofac Surg 2012;70:141–148. 8. Kurtzman GM, Dompkowski DF, Mahler BA, Howes DG. Off-axis implant placement for anatomical considerations using the co-axis implant. Inside Dent 2008;4. https://www.aegisdentalnetwork. com/id/2008/05/off-axis-implant-placement-for-anatomicalconsiderations-using-the-co-axis-implant. Accessed 4 May 2018. 9. Wallace SS, Tarnow DP, Froum SJ, et al. Maxillary sinus elevation by lateral window approach: Evolution of technology and technique. J Evid Based Dent Pract 2012;12(3 suppl):161–171. 10. Bedrossian E, Sullivan RM, Fortin Y, Malo P, Indresano T. Fixed-prosthetic implant restoration of the edentulous maxilla: A systematic pretreatment evaluation method. J Oral Maxillofac Surg 2008;66:112–122. 11. Ali S, Bakry SA, Abd-Elhakam H. Platelet-rich fibrin in maxillary sinus augmentation: A systematic review. J Oral Implantol 2015;41:746–753. 12. Abi Najm S, Malis D, El Hage M, Rahban S, Carrel JP, Bernard JP. Potential adverse events of endosseous dental implants penetrating the maxillary sinus: Long-term clinical evaluation. Laryngoscope 2013;123:2958–2961. 13. Jung JH, Choi BH, Zhu SJ, et al. The effects of exposing dental implants to the maxillary sinus cavity on sinus complications. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2006;102:602–605. 14. Petruson B. Sinuscopy in patients with titanium implants in the nose and sinuses. Scand J Plast Reconstr Surg Hand Surg 2004;38:86–93. 15. Chrcanovic BR, Abreu MHNG. Survival and complications of zygomatic implants: A systematic review. Oral Maxillofac Surg 2013;17:81–93. 16. Atsumi M, Park SH, Wang HL. Methods used to assess implant stability: Current status. Int J Oral Maxillofac Implants 2007;22:743– 754. 17. Bothur S, Jonsson G, Sandahl L. Modified technique using multiple zygomatic implants in reconstruction of the atrophic maxilla: A technical note. Int J Oral Maxillofac Implants 2003;18:902– 904. 18. Pi Urgell J, Revilla Gutiérrez V, Gay Escoda CG. Rehabilitation of atrophic maxilla: A review of 101 zygomatic implants. Med Oral Patol Oral Cirugia Bucal 2008;13:E363–E370. 19. Bidra AS, Huynh-Ba G. Implants in the pterygoid region: A systematic review of the literature. Int J Oral Maxillofac Surg 2011;40:773–781. 20. Graves SL. The pterygoid plate implant: A solution for restoring the posterior maxilla. Int J Periodontics Restorative Dent 1994;14:512–523. 21. Curi MM, Cardoso CL, Ribeiro Kde C. Retrospective study of pterygoid implants in the atrophic posterior maxilla: Implant and prosthesis survival rates up to 3 years. Int J Oral Maxillofac Implants 2015;30:378–383. 22. Candel E, Peñarrocha D, Peñarrocha M. Rehabilitation of the atrophic posterior maxilla with pterygoid implants: A review. J Oral Implantol 2012;38(spec no):461–466.

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CHAPTER 19

ULTRAWIDE IMPLANTS IN MOLAR SITES Costa Nicolopoulos, bds, ffd | Andriana Nikolopoulou, md

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he posterior maxilla is considered an area of added risk for dental implants because of higher occlusal forces, inferior bone quality, and often limited bone quantity.1,2 After maxillary molar extraction, immediate molar replacement with an implant presents a challenge to the implant surgeon because of the following factors:

•  Multiple root anatomy with irregular extraction socket morphology •  Multiple osseous defects perimetrical to an immediate maxillary molar implant leading to inadequate primary stability  •  Sinus pneumatization resulting in limited vertical bone volume •  Poor bone quality  •  Large socket dimension (The average anatomical dimension of a maxillary molar at the cementoenamel junction is 8 × 11 mm.)3,4 •  High occlusal forces These conditions often dictate a delayed implant placement protocol for socket healing, resulting in alveolar bone loss and the need for a sinus bone graft. A socket preservation technique can be performed in the minority of cases without sinus grafting where adequate vertical socket height exists. However, rather than sinus elevation treatment with added treatment time, added cost, and increased patient treatment resistance, placement of an ultrawide implant just short of the sinus may be preferable.5 To compensate for the shorter implant length, bone-to-implant contact area for osseointegration can be achieved by placing an ultrawide implant.6–8 Most studies found no difference in survival rates between immediate and delayed placement, including one study that found less bone loss when wide implants were placed immediately.9–15

Treatment Using Ultrawide Implants Ultrawide implants are defined as implants with diameters of 7 to 9 mm. These implants have been specifically designed to overcome the challenges and limitations associated with immediate molar replacement. Designed by the South African prosthodontist Dr Andrew Ackermann (for which he received the 2007 Academy of Osseointegration Award for best clinical innovation in implant dentistry), ultrawide implants (Southern Implants) are engineered to overcome the limitations associated with molar extraction sockets. They feature an aggressive taper, moderately rough surface (ie, Sa value of 1.34 μm), 0.8-mm thread pitch, and built-in platform switching of 0.25 mm on the horizontal and a further 0.35 mm at 45 degrees. They are available in varying diameters and lengths as well as in external and internal connection options (Fig 19-1). With an adapted drilling protocol, these features allow wide implants to be inserted in limited bone height, not requiring sinus grafting and with excellent primary stability. This offers the possibility of immediate loading, especially in a cross-arch stabilization treatment protocol.16,17 This decreases morbidity, complications, added time, and cost associated with sinus grafting. Patient treatment acceptance and satisfaction is also improved.18 Ultrawide implants achieve these benefits in extraction sockets by engaging the socket wall.19–21 Box 19-1 outlines the benefits of using ultrawide implants in maxillary molar sites from a surgical, prosthodontic, and patient perspective.18,19,22

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Fig 19-1  (a) Ultrawide Max Implants (Southern Implants) in 6- to 10-mm diameters. (b) Ultra­ wide Max Implants in various external and internal connections.

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Box 19-1  Benefits of using ultrawide implants Surgical benefits • Cortical fixation • Enhanced primary stability • Increased contact surface area for osseointegration • Possibility for immediate loading Prosthodontic benefits • More favorable distribution of occlusal forces • Opportunity to use wider and stronger prosthetic components • Development of proper root and crown contours while avoiding nonhygienic ridge lap profiles • Ability to use higher torque forces • Reduced screw loosening • Decreased incidence of technical problems Patient benefits • Avoidance of sinus floor grafting procedures • Decreased morbidity • Decreased cost • Decreased treatment time • Increased treatment acceptance • Increased patient satisfaction

Presurgical Planning Molar extraction site classification Smith and Tarnow23 classify molar extraction sites for immediate dental implant placement into three categories: types A, B, and C. •  Type A. The type A socket allows for the implant to be placed completely within the septal bone, leaving no gaps between the implant and the socket walls. There is adequate septal bone to circumferentially contain the coronal portion of the implant completely within the bone. •  Type B. The type B socket has enough septal bone to stabilize but not completely surround the implant, leaving gaps between one or more surfaces of the implant and the socket walls. The implant is stabilized but not fully contained by the septal bone. •  Type C. The type C socket has little or no septal bone, requiring the implant to engage the periphery of the socket. It may be impossible to achieve implant stability without engaging the perimeter walls of the socket. Ultrawide Max Implants (Southern Implants) are always indicated in type C sockets and sometimes in type B sockets but seldom in type A sockets. Type A sockets may be treated with conventional 5- or 6-mm-diameter implants housed completely within the septal bone, whereas some type B and almost all type C sockets require ultrawide Max Implants to engage perimeter walls of the socket for primary stability.

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Presurgical Planning

Fig 19-2  Thin biotypes are contraindicated and may lead to recession.

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Fig 19-3  Never attempt a molar extraction.

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Fig 19-4  (a to c) Always first decoronize the molar and then remove the roots separately.

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Fig 19-5  Intact alveolar walls.

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Fig 19-6  (a) Stay mesial to avoid the thin interradicular bone between the first and second molar. (b and c) Incorrect placement with risk of violating the thin interradicular bone (arrowheads) between the first and second molar.

Cardinal rules for Max Implant placement The following guidelines should be followed if a Max Implant is planned: •  Select patients with medium or preferably thick biotypes. A thin biotype is a contraindication (Fig 19-2). •  Never attempt a normal extraction because the buccal plate may fracture and the site will no longer be suitable (Fig 19-3). •  Always decoronize the molar first and then separate and remove the roots (Fig 19-4).

•  Only attempt ultrawide implant placement if the four alveolar walls of the extraction socket are intact (Fig 19-5). •  For the first molar, start the implant osteotomy 1 to 2 mm more mesial than the center in order to stay away from the thin interradicular bone between the first and second molars (Fig 19-6). •  Place the Max Implant 1 to 2 mm away from the buccal plate (Fig 19-7) and 1 to 2 mm deeper than the crest of the buccal plate (Fig 19-8).

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Fig 19-7 (a) This implant is incorrectly positioned too close to the buccal plate. (b) Correct implant placement is 1 to 2 mm away from the buccal plate.

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b Fig 19-8 (a) This implant is incorrectly positioned because it is not placed deep enough. Exposed threads are visible. (b) Correct implant depth: 1 to 2 mm deeper than the buccal plate.

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Fig 19-9 Decoronize, section, and remove the roots.

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Fig 19-10 Decoronize and drill through the tooth.

Surgical Technique There are two techniques for implant site drilling: 1. Decoronize and remove roots (Fig 19-9). 2. Decoronize and drill through the tooth (Fig 19-10).

Decoronize and remove roots In this technique, the molar crown is sectioned with crown cutters and removed. The roots are then separated, carefully wedged, and removed with elevators, preserving alveolar bone and the buccal plate. The implant osteotomy is started with a round bur and then carried out with the drilling sequence

Fig 19-11  Drill may fall out of thin interradicular bone septa, resulting in unstable drilling.

using progressively wider tapered drills per the manufacturer’s guidelines. In type B and C sockets with thin or missing interradicular bone septa (Fig 19-11), the round bur and subsequent initial drills tend to fall out of the thin bone septum, resulting in unstable drilling and drill chatter. In this situation, further drilling will damage the implant osteotomy, resulting in an unusable or suboptimal implant site. This is the reason for using the technique of drilling through the tooth.

Drill through the tooth In this technique, again the molar crown is sectioned with crown cutters and removed. The remaining tooth is used as a drilling platform.

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Case Examples

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Fig 19-12  (a) Drill through the tooth starting mesially. (b) Roots sectioned from each other. (c) Straight elevator is used to split, wedge, and elevate the roots into the osteotomy site. (d) Osteotomy is shaped and finalized with the final dedicated drill. (e) Max Implant tapped into place.

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The implant osteotomy drilling is started with the round bur drilling through a stable platform instead of a thin interradicular bony strut (Fig 19-12a). Further drilling through the sectioned tooth is carried out using progressively wider tapered drills per the manufacturer’s instructions, resulting in a progressively bigger round hole in the remaining decoronized tooth. After using the second to last drill, a fissure bur is used to section the roots (Fig 19-12b). A straight elevator is then used to split and separate the roots from each other. The individual roots are then wedged and elevated into the osteotomy for delivery (Fig 19-12c). The implant osteotomy that has been created by drilling through the tooth serves not only to prepare the implant site but also to facilitate the extraction because it creates a large gap into which each separated root can be subluxed. After the roots have been removed, the extraction site is inspected, degranulated, and debrided. The last drill is then used to finalize the drilling procedure (Fig 19-12d). Once drilling is complete, screw tapping can be used when necessary in sites of dense bone to avoid the implant getting stuck before it reaches the desired depth. A periapical radiograph can be taken at any stage to verify position and depth. The ultrawide implant is placed using a low-speed handpiece (Fig 19-12e). Seating to final depth is performed with a ratchet wrench or zygomatic implant inserter if access permits. Insertion torque can be measured with a torque wrench and typically reaches high levels. With respect to osseous gaps between the

e

implant and the adjacent plate of bone, gaps less than 2 mm are generally not grafted, whereas data suggests that if the gap is greater than 2 mm, the site should be grafted.24,25 Other investigators have shown that success may be achieved even without grafting and without primary closure.26–29 Therefore, grafting is not generally done.

Case Examples Case 1 A 56-year-old man presented with multiple failing teeth, requiring five extractions including both maxillary second molars where the available bone was adequate in width but suboptimal in height due to sinus pneumatization (Fig 19-13a to 19-13c). The medical history was noncontributory other than smoking 20 cigarettes per day. The treatment plan was to extract and perform immediate molar replacement with ultrawide site-specific implants for immediate function. The right second molar was extracted and immediately replaced with an ultrawide implant (7 × 9 mm) as part of a four-unit screw-retained partial denture. The left second molar was extracted and immediately replaced with an ultra­wide implant (9 × 8 mm) to support a single screw-retained molar

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Fig 19-13 (a) Preoperative right second molar. (b) Preoperative right first premolar. (c) Preoperative left second molar. (d) Maxillary right first molar 3 years postoperative. (e) Maxillary left second molar 3 years postoperative. (f) Maxillary right second molar 3 years postoperative. (g) Maxillary right first premolar 3 years postoperative. (h) Maxillary left second molar 3 years postoperative. (Restorations by Dr Fotis Melas, Glyfada, Greece.)

restoration. Thanks to appropriate osteotomy drilling and aggressive implant taper, good primary stability was achieved with both ultrawide implants with insertion torques in excess of 100 Ncm. All of the implants in this case, including the ultrawide molar implants, were loaded immediately with provisional screwretained prostheses within 1 day and definitive screw-retained prostheses in 7 days. The 3-year follow-up shows excellent soft tissue health as well as minimal bone loss with stable bone levels (Figs 19-13d to 19-13h). The exceptional bone stability may be attributed to platform switching as well as excellent fit of the prosthodontic components, resulting in microgaps of less than 2 μm.

Case 2 A healthy 61-year-old woman presented with a nonrestorable right maxillary first molar. Due to festooning of the maxillary sinus between the molar roots, the available alveolar bone height was only 6 mm (Fig 19-14a). This molar was removed and immediately replaced with an ultrawide molar replacement implant (11 × 9 mm) with simultaneous internal sinus elevation. This implant was loaded immediately at 45 Ncm with a definitive screw-retained zirconia restoration that has never been removed. The 6-year follow-up reveals excellent health of the soft tissues as well as stable bone levels (Fig 19-14b and 19-14c).

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Case Examples

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Fig 19-14  (a) Preoperative radiograph showing only 6 mm height. (b) The 6-year postoperative radiograph. (c) The 6-year postoperative clinical view. (Restorations by Dr Fotis Melas, Glyfada, Greece.)

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Fig 19-15  (a) Preoperative radiograph. (b) Postoperative radiograph after 2 years. (c) Postoperative clinical view after 2 years. (Restorations by Dr Fotis Melas, Glyfada, Greece.)

Case 3

Case 4

A 40-year-old woman in good health was referred for removal and immediate replacement of a nonrestorable maxillary right first molar (Fig 19-15a). The drill-through-the-tooth drilling protocol was used, and the molar was removed and immediately replaced with an ultrawide 9 × 7–mm implant with high insertion torque. Immediate loading was performed with a permanent screw-retained zirconia tooth. At the 2-year follow-up, an excellent and stable result was observed (Fig 19-15b and 19-15c).

A 47-year-old woman was referred for removal of her symptomatic maxillary left first molar that had undergone apicoectomy 15 years previously. At the time of referral, she was experiencing recurrent buccal discomfort and mild swelling. A thick biotype was evident (Fig 19-16a), but festooning of the sinus between the molar roots was noted on the radiograph (Fig 19-16b). Cone beam computed tomography assessment revealed 4 to 5 mm available bone height (Fig 19-16c). A partial buccal plate deficiency was noted in the region of the previous apicoectomy, but a margin of continuous buccal plate was still evident crestally.

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After cutting off the crown, the drill-through-the-tooth protocol was used. The roots were sectioned and removed (Fig 19-16d). After thorough debridement and degranulation, the osteotomy was shaped (Fig 19-16e). The sinus floor was reached and an internal sinus elevation was performed. The buccal socket wall defect resulting from the previous apicoectomy and recurrent chronic infection was identified, degranulated, and grafted with particulate allograft as was the internal sinus elevation (Fig 19-16f). An ultrawide implant (9 × 8 mm)

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f Fig 19-16 (a) Thick biotype. (b) Sinus festooning between the molar roots. (c) Available bone height is 4 to 5 mm. (d) Removal of roots after drill-through-the-tooth technique. (e) Osteotomy shape after using the dedicated final drill. (f) Grafting with allograft. (g) A 9 × 8–mm Max Implant was placed. (h to j) The 4-year follow-up shows stable bone levels and good bone consolidation. (Restoration by Dr Safa Tahmasebi, Dubai, United Arab Emirates.) 

was placed with excellent primary stability in excess of 75 Ncm and was immediately loaded with a definitive screw-retained zirconia restoration (Fig 19-16g). The prosthetic screw was torqued to 45 Ncm, and the crown has never been removed. The 4-year follow-up showed good bone consolidation around the implant as well as in the area of the internal sinus elevation. The crestal bone levels are well maintained, and the thick biotype soft tissues showed excellent health with stability (Fig 19-16h to 19-16j).

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Case Examples

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Fig 19-17  (a) Terminal maxillary dentition. (b) Pneumatized maxillary left sinus. (c) Wide ridge suitable for Max Implant. (d) Same day acrylic screw-retained provisional. (e) Definitive metal-ceramic prosthesis 7 days postoperative.

Case 5 A 57-year-old man in good health was referred for removal of his terminal maxillary dentition followed by complete-arch implant reconstruction and immediate function (Fig 19-17a). To avoid a delayed loading protocol associated with time-consuming and costly sinus bone grafting, an accelerated protocol was used with immediate molar replacement at the same time as extraction of the maxillary left second molar (Figs 19-17b and 19-17c). Using an adapted drilling protocol, an ultrawide implant (7 × 8 mm) was placed in the appropriately shaped left second molar extraction socket with very good primary implant stability by engaging the cortical fixation area of the molar socket

wall. In combination with an implant placed in a tilted fashion anterior to the left maxillary sinus wall engaging the piriform maximum bone mass (M point) with cortical fixation, it was possible to achieve high primary stability for immediate loading.30 A complete cross-arch splinted screw-retained provisional acrylic prosthesis was placed on the same day (Fig 19-17d). A definitive metal-ceramic screw-retained prosthesis was delivered 7 days later (Fig 19-17e). The 2-year follow-up of this accelerated treatment protocol shows an excellent result both clinically and radiographically (Fig 19-17f to 19-17h). This patient treatment demonstrates the benefit of using a combination of a tilted implant and an ultrawide implant to avoid sinus grafting where appropriate.

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g Fig 19-17  (cont) (f) The 2-year clinical view of the definitive prosthesis. (g and h) The 2-year postoperative imaging shows excellent stable bone levels. (Restoration by Dr Safa Tahmasebi, Dubai, United Arab Emirates.)

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a

b

c

d

Fig 19-18  (a and b) Preoperative imaging. (c) Same day acrylic screw-retained provisional. (d) The 4-year postoperative panoramic radiograph.

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Conclusion

e

f

g

h

Fig 19-18  (cont) (e) The 4-year postoperative right periapical radiograph. (f) The 4-year postoperative left periapical radiograph. (g) The 4-year postoperative frontal intraoral clinical view. (h) The 4-year postoperative smile. (Restoration by Dr Safa Tahmasebi, Dubai, United Arab Emirates.)

Case 6 A healthy 52-year-old woman received a treatment plan for full-mouth immediate implant placement and immediate function (Figs 19-18a and 19-18b). She insisted on second molar occlusion with immediate function, so the treatment plan had to include implants in the molar regions to restore with 14 teeth per arch. Sinus bone grafting procedures were excluded from the treatment plan to allow for an accelerated protocol. It was possible to avoid sinus grafting procedures by placing ultrawide molar implants in the molar extraction sockets bilaterally, achieving good primary stability. A complete crossarch splinted screw-retained provisional acrylic prosthesis was placed on the same day (Fig 19-18c). A definitive metal-ceramic screw-retained prosthesis was delivered 7 days later. The 4-year follow-up showed an excellent clinical and radiographic result with stable bone levels around all implants, including around the ultrawide molar replacement implants that were used to avoid sinus bone grafting (Fig 19-18d to 19-18h).

Conclusion Although the posterior maxillary region is considered a highrisk zone for implant placement due to high occlusal forces, poor bone quality, and often limited vertical bone, it is often possible for wide-body immediate molar replacement implants to manage these challenges. Rather than treating with a staged, costly, and time-consuming approach, the placement of an ultrawide implant in a molar extraction socket is preferable. Despite the often compromised bone status in these cases, investigators have reported survival rates of ultrawide implants as comparable to normal implants. Indeed, placement of an ultrawide implant in an immediate molar extraction socket may be a better alternative than the sinus floor bone graft, but caution is advised regarding immediate loading.31–33 The success of the ultrawide implant may be related to increased implant surface area, aggressive taper, excellent primary stability, and built-in platform switching, all factors that are highly favorable to immediate loading even for single-tooth restorations.34 Correct case selection and appropriate surgical protocol using the adaptive drilling technique are essential because immediate molar implant placement is highly technique sensitive. If the biotype is thin, if the buccal plate is missing, or if primary stability cannot be achieved, a delayed protocol should be followed.

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19  ULTRAWIDE IMPLANTS IN MOLAR SITES

References 1. Muftu A, Chapman RJ. Replacing posterior teeth with freestanding implants: Four-year prosthodontic results of a prospective study. J Am Dent Assoc 1998;129:1097–1102. 2. Truhlar RS, Orenstein IH, Morris HF, Ochi S. Distribution of bone quality in patients receiving endosseous dental implants. J Oral Maxillofac Surg 1997;55(12 suppl 5):38–45. 3. Kerns DG, Greenwell H, Wittwer JW, Drisko C, Williams JN, Kerns LL. Root trunk dimensions of 5 different tooth types. Int J Periodontics Restorative Dent 1999;19:82–91. 4. Scheid RC, Weiss G. Woelfel’s Dental Anatomy, ed 8. Philadelphia: Lippincott Williams and Wilkins, 2012. 5. Renouard F, Nisand D. Impact of implant length and diameter on survival rates. Clin Oral Implants Res 2006;17(suppl 2):35–51. 6. Eckert SE, Meraw SJ, Weaver AL, Lohse CM. Early experience with Wide-Platform Mk II implants. Part I: Implant survival. Part II: Evaluation of risk factors involving implant survival. Int J Oral Maxillofac Implants 2001;16:208–216. 7. Ivanoff CJ, Gröndahl K, Sennerby L, Bergström C, Lekholm U. Influence of variations in implant diameters: A 3- to 5-year retro­ spective clinical report. Int J Oral Maxillofac Implants 1999;14: 173–180. 8. Ivanoff CJ, Sennerby L, Johansson C, Rangert B, Lekholm U. Influence of implant diameters on the integration of screw implants. An experimental study in rabbits. Int J Oral Maxillofac Surg 1997;26:141–148. 9. Peñarrocha-Diago M, Carrillo-Garcîa C, Boronat-Lopez A, García-Mira B. Comparative study of wide-diameter implants placed after dental extraction and implants positioned in mature bone for molar replacement. Int J Oral Maxillofac Implants 2008;23:497–501. 10. Gomez-Roman G, Kruppenbacher M, Weber H, Schulte W. Immediate postextraction implant placement with root-analog stepped implants: Surgical procedure and statistical outcome after 6 years. Int J Oral Maxillofac Implants 2001;16:503–513. 11. Botticelli D, Renzi A, Lindhe J, Berglundh T. Implants in fresh extraction sockets: A prospective 5-year follow-up clinical study. Clin Oral Implants Res 2008;19:1226–1232. 12. Cafiero C, Annibali S, Gherlone E, et al. Immediate transmucosal implant placement in molar extraction sites: A 12-month prospective multicenter cohort study. Clin Oral Implants Res 2008;19:476–482. 13. Fugazzotto PA. Implant placement at the time of maxillary molar extraction: Treatment protocols and report of results. J Periodontol 2008;79:216–223. 14. Gelb DA. Immediate implant surgery: Three-year retrospective evaluation of 50 consecutive cases. Int J Oral Maxillofac Implants 1993;8:388–399. 15. Krump JL, Barnett BG. The immediate implant: A treatment alternative. Int J Oral Maxillofac Implants 1991;6:19–23. 16. Luongo G, Di Raimondo R, Filippini P, Gualini F, Paoleschi C. Early loading of sandblasted, acid-etched implants in the posterior maxilla and mandible: A 1-year follow-up report from a multicenter 3-year prospective study. Int J Oral Maxillofac Implants 2005;20:84–91. 17. Abboud M, Koeck B, Stark H, Wahl G, Paillon R. Immediate loading of single-tooth implants in the posterior region. Int J Oral Maxillofac Implants 2005;20:61–68.

18. Morand M, Irinakis T. The challenge of implant therapy in the posterior maxilla: Providing a rationale for the use of short implants. J Oral Implantol 2007;33:257–266. 19. Langer B, Langer L, Herrmann I, Jorneus L. The wide fixture: A solution for special bone situations and a rescue for the compromised implant. Part 1. Int J Oral Maxillofac Implants 1993; 8:400–408. 20. Lee JH, Frias V, Lee KW, Wright RF. Effect of implant size and shape on implant success rates: A literature review. J Prosthet Dent 2005;94:377–381. 21. Lazzara RJ. Criteria for implant selection: Surgical and prosthetic considerations. Pract Periodontics Aesthet Dent 1994;6:55–62. 22. Siamos G, Winkler S, Boberick KG. Relationship between implant preload and screw loosening on implant-supported prostheses. J Oral Implantol 2002;28:67–73. 23. Smith RB, Tarnow DP. Classification of molar extraction sites for immediate dental implant placement: Technical note. Int J Oral Maxillofac Implants 2013;28:911–916. 24. Akimoto K, Becker W, Persson R, Baker DA, Rohrer MD, O’Neal RB. Evaluation of titanium implants placed into simulated extraction sockets: A study in dogs. Int J Oral Maxillofac Implants 1999;14:351–360. 25. Wilson TG Jr, Schenk R, Buser D, Cochran D. Implants placed in immediate extraction sites: A report of histologic and histometric analyses of human biopsies. Int J Oral Maxillofac Implants 1998;13:333–341. 26. Schwartz-Arad D, Chaushu G. The ways and wherefores of immediate placement of implants into fresh extraction sites: A literature review. J Periodontol 1997;68:915–923. 27. Wöhrle PS. Single-tooth replacement in the aesthetic zone with immediate provisionalization: Fourteen consecutive case reports. Pract Periodontics Aesthet Dent 1998;10:1107–1114. 28. Smith RB, Tarnow DP, Brown M, Chu S, Zamzok J. Placement of immediate implants and a fixed provisional restoration to replacethe four mandibular incisors. Compend Contin Educ Dent 2009;30:408–415. 29. Tarnow DP, Chu SJ. Human histologic verification of osseointegration of an immediate implant placed into a fresh extraction socket with excessive gap distance without primary flap closure, graft, or membrane: A case report. Int J Periodontics Restorative Dent 2011;31:515–521. 30. Jensen OT. Complete arch site classification for all-on-4 immediate function. J Prosthet Dent 2014;112:741–751. 31. Vandeweghe S, Ackermann A, Bronner J, Hattingh A, Tschakaloff A, De Bruyn H. A retrospective, multicenter study on a novo wide-body implant for posterior regions. Clin Implant Dent Relat Res 2012;14:281–292. 32. Atieh MA, Payne AG, Duncan WJ, de Silva RK, Cullinan MP. Immediate placement or immediate restoration/loading of single implants for molar tooth replacement: A systematic review and meta-analysis. Int J Oral Maxillofac Implants 2010;25:401–415. 33. Vandeweghe S, Hattingh A, Wennerberg A, Bruyn HD. Surgical protocol and short-term clinical outcome of immediate placement in molar extraction sockets using a wide body implant. J Oral Maxillofac Res 2011;2:e1. 34. Vandeweghe S, De Bruyn H. A within-implant comparison to evaluate the concept of platform switching: A randomised controlled trial. Eur J Oral Implantol 2012;5:253–262.

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CHAPTER 20

RESTORATION AND ABUTMENT OPTIONS Alexandre Molinari, dds, msc, phd | Sérgio Rocha Bernardes, bds, msc, phd

S

urgical procedures for dental implant placement have one aim: to prosthetically restore the patient’s edentulous areas. Therefore, the success of certain practices should be measured by their capacity for allowing functional and esthetic restorations, and prosthetic workflow should be as accurate, clean, and careful as any surgical procedure. Abutment selection, impression, clinical procedures, and dental materials should be precisely defined to properly rehabilitate the oral cavity. This chapter aims to describe meticulous prosthetic procedures that are important for the success of sinus directed implants in the short and long term.

Restoration Options Abutment selection has recently gained more interest thanks to the idea of “one abutment–one time.”1,2 In addition, the implant-abutment connection, type of prosthesis retention, platform switching, abutment height, alloy composition, and final implant position have been shown to have a strong impact in relation to peri-implant tissues, long-term maintenance, and emergence profile.3–10 Regardless of whether the prosthesis is cement- and screw-retained or placed with nickel-titanium alloy (ie, nitinol) sleeves, a certain distance from the abutment margin of the restoration should be respected in relation to the bone to avoid peri-implant tissue remodeling. According to this principle, the abutment selection step becomes very important, particularly in grafted settings when grafted bone is less stable than native alveolar bone. Single restorations can be done as cement- or screw-retained or by nitinol-locking abutments. Multiple restorations (ie, partial dentures) are strongly recommended to be screwretained or nitinol-locking because of retrievability. A minimum width of 3 mm of peri-implant mucosa is necessary to create a mucosal barrier around the dental implant. This consists of an average depth for the sulcus of 0.16 mm, junctional epithelium

of 1.88 mm, and connective tissue attachment of 1.05 mm, for approximately 3 mm total. In addition, the establishment of a biologic seal around implants is considered an important natural phenomenon.11–14 Depending on the remaining thickness of the mucosa, common practice results in prosthetic procedures in which peri-implantitis is more likely to occur because the dentist is unable to execute the one abutment–one time concept.1,2,15 The one abutment–one time concept has proven to result in significantly less bone remodeling when compared with standard implant-level workflow where disturbance of the implantabutment interface occurs from abutment disconnection and reconnection.1,2,4,16,17 To optimize hard and soft tissue maintenance, implants can be placed subcrestally, resulting in less bone remodeling. There are three important factors that help to maintain peri-implant tissues: (1) bone adaptation over the implant coronal third area; (2) greater abutment collar height; (3) easier reestablishment of the biologic peri-implant width.4,7,9,10 However, implants placed at this position must not have a significant microgap or mobility between the abutment and implant itself. The use of a Morse taper connection promotes vertical friction between the abutment and implant wall, resulting in a significant reduction of microgap or mobility and nearly creating a bacterial seal. This mechanical design for reducing the microgap and micromovement between parts creates a better environment for both soft and hard tissues. The abutment fit inside the implant should have an internal angle of 3 to 8 degrees per side or 6 to 16 degrees.18

Abutment Selection After deciding how the restoration is to be retained, the goal is to check if a straight or angled abutment is needed and measure the depth from the top of the implant to the mucosal margin

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a

b

c

Fig 20-1  (a) Screw-retained stock abutment. (b) Cement-retained stock abutment. (c) Custom abutment.

0.8

1.0 to 3.0 mm maximum

1.5

2.5

3.5

4.5

1.5 mm minimum

Fig 20-2  The restoration margin needs to be at least 1.5 mm from the crestal bone and not more then 1 to 3 mm intrasulcus.

Fig 20-3  Collar height can vary from 0.8 mm up to 6.5 mm, though this can differ among dental implant systems.

with respect to biologic width (Fig 20-1). Specific depth is evaluated using a try-in abutment to evaluate optimal collar height as well as horizontal and vertical space and implant position in relation to the occlusal plane. A periapical radiograph is taken to see where the implant is located within the crestal bone. The restorative margin should ideally be at least 1.5 mm above the crestal bone but not more than 3 mm intrasulcus, as illustrated in Figs 20-2 to 20-4. The margin of the restoration defines the abutment collar height as determined chairside. Laboratorial work is then initiated.

7. Remove the try-in and place and torque the definitive stock abutment with the recommended torque. 8. Make a provisional restoration over the abutment. 9. After mucosa healing, take an impression at the abutment level and send it to the laboratory to make a definitive restoration.

Chairside sequence for abutment selection 1. Remove the healing abutment. 2. Place the height measure over the implant (preferably one provided by the manufacturer). 3. Measure the mucosa collar height. 4. Use a try-in abutment with a collar height smaller than the value measured to avoid exposure of the transmucosal metal. This height should coincide with the mucosa margin or maximum of 3.0 mm below it. 5. Keep the try-in abutment in position and take a periapical radiograph. 6. Check the radiograph to see if the margin of the restoration is at least 1.5 mm from crestal bone.

Laboratory workflow 1. Remove the healing abutment. 2. Place the height measure over the implant. 3. Measure the mucosa collar height. 4. Use a try-in abutment with a collar height smaller than the value measured to avoid exposure of the transmucosal metal. The height should coincide with the mucosa margin or a maximum of 3.0 mm below it. 5. Keep the try-in abutment in position and take a periapical radiograph. 6. Check the radiograph to see if the margin of the restoration is at least 1.5 mm from the crestal bone. 7. Make an impression at the implant platform level and send the selected abutment to the laboratory or make a custom abutment with the collar height required from the measurement. Stock abutments are usually offered in different diameters, shapes, and cementable heights that have to be defined as well. Figure 20-5 shows situations where wrong abutment selections

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Abutment Selection

Fig 20-4 (a) Example of a right abutment section in an immediate loading procedure. A screw-retained abutment for a full-arch prosthesis that maintains the distance between bone and the margin of the component. (b) Follow-up after 4 months without any tissue retraction.

a Fig 20-5  (a and b) The collar height places the restorative margin too close to the crestal bone, possibly causing bone and soft tissue remodeling. (c) This restorative margin respects the biologic width regarding the intra­ sulcus distance and distance from the crestal bone, possibly creating an ideal environment to promote less remodeling of bone and soft tissue.

b Collar height 0.8 mm

a

Collar height 2.5 mm

b

a

d

Collar height 1.5 mm

c

b

c

e

f

Fig 20-6  (a) Preoperative panoramic radiograph. (b) The 2.5-mm CM abutment in place. (c) Periapical radiograph on the day of the surgery. (d) Definitive restoration 11 months later. (e and f) Definitive crown 8 years later.

were done. Once the final abutment is selected, impressions, clinical try-in, and placement of the prosthesis are completed. When making an implant-level impression for custom abutments, it is crucial to keep the communication between the dentist and technician clear regarding the desired collar height because the laboratory does not have the option to check implant position in relation to peri-implant bone.

Clinical case A single implant at the first molar requires immediate loading after the sinus elevation procedure. A 13 × 4.3–mm Cone Morse (CM) Alvim implant (Neodent, Straumann) received a CM abutment with a 2.5 mm collar height (Neodent). The selection performed during the surgery is shown in Fig 20-6.

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This procedure makes the selection easier because the bone and abutment margin can be easily observed. The definitive restoration was placed and at the follow-up 4 months later, the emergence profile was well established due to the immediate loading protocol. A regular prosthetic workflow was done for abutment-level reconstructions.

Conclusion There are different ways to restore oral implants: on the implant level or on the abutment level. There are also different types of prosthetic retention: by screws, cement, or attachments. However, regardless of the type of retention, the best workflow to reconstruct implants in grafted areas is on the abutment level. The abutment-level workflow, especially when doing one abutment–one time, results in less potential of tissue losses in the follow-up, particularly in grafted settings when grafted bone is less stable than alveolar bone. This is why abutment selection is a key step and implant/abutment connections play a significant role in the local biologic response. Due to their mechanism, cone Morse connections optimize biologic results found on abutment-level restorations.

References 1. Degidi M, Nardi D, Piattelli A. One abutment at one time: Nonremoval of an immediate abutment and its effect on bone healing around subcrestal tapered implants. Clin Oral Implants Res 2011;22:1303–1307. 2. Atieh MA, Tawse-Smith A, Alsabeeha NHM, Ma S, Duncan WJ. The one abutment-one time protocol: A systematic review and meta-analysis. J Periodontol 2017;88:1173–1185. 3. Macedo JP, Pereira J, Vahey BR, et al. Morse taper dental implants and platform switching: The new paradigm in oral implantology. Eur J Dent 2016;10:148–154. 4. Castro DS, Araujo MA, Benfatti CA, et al. Comparative histological and histomorphometrical evaluation of marginal bone resorption around external hexagon and Morse cone implants: An experimental study in dogs. Implant Dent 2014;23:270–6. 5. Wittneben JG, Millen C, Brägger U. Clinical performance of screw- versus cement-retained fixed implant-supported reconstructions: A systematic review. Int J Oral Maxillofac Implants 2014;29(suppl):84–98.

6. Di Girolamo M, Calcaterra R, Di Gianfilippo R, Arcuri C, Baggi L. Bone level changes around platform switching and platform matching implants: A systematic review with meta-analysis. Oral Implantol (Rome) 2016;9:1–10. 7. Galindo-Moreno P, León-Cano A, Monje A, Ortega-Oller I, O’Valle F, Catena A. Abutment height influences the effect of platform switching on peri-implant marginal bone loss. Clin Oral Implants Res 2016;27:167–173. 8. Alrabeah GO, Knowles JC, Petridis H. The effect of platform switching on the levels of metal ion release from different implant-abutment couples. Int J Oral Sci 2016;8:117–125. 9. Novaes AB Jr, Barros RR, Muglia VA, Borges GJ. Influence of interimplant distances and placement depth on papilla formation and crestal resorption: A clinical and radiographic study in dogs. J Oral Implantol 2009;35:18–27. 10. Barros RR, Novaes AB Jr, Muglia VA, Iezzi G, Piattelli A. Influence of interimplant distances and placement depth on peri-implant bone remodeling of adjacent and immediately loaded Morse cone connection implants: A histomorphometric study in dogs. Clin Oral Implants Res 2010;21:371–378. 11. Berglundh T, Lindhe J. Dimension of the periimplant mucosa. Biological width revisited. J Clin Periodontol 1996;23:971–973. 12. Abrahamsson I, Berglundh T, Lindhe J. The mucosal barrier following abutment dis/reconnection. An experimental study in dogs. J Clin Periodontol 1997;8:568–572. 13. Cochran DL, Hermann JS, Schenk RK, Higginbottom FL, Buser D. Biologic width around titanium implants. A histometric analysis of the implanto-gingival junction around unloaded and loaded nonsubmerged implants in the canine mandible. J Peridontol 1997;68:186–198. 14. Lazzara RJ, Porter SS. Platform switching: A new concept in implant dentistry for controlling postrestorative crestal bone levels. Int J Peridontics Restorative Dent 2006;26:9–17. 15. Hjalmarsson L, Smedberg JI, Pettersson M, Jemt T. Implant-­ level prostheses in the edentulous maxilla: A comparison with conventional abutment-level prostheses after 5 years of use. Int J Prosthodont 2011;24:158–167. 16. Koutouzis T, Fetner M, Fetner A, Lundgren T. Retrospective evaluation of crestal bone changes around implants with reduced abutment diameter placed nonsubmerged and at subcrestal positions: The effect of bone grafting at implant placement. J Periodontol 2011;82:234–242. 17. Degidi M, Nardi D, Daprile G, Piattelli A. Nonremoval of immediate abutments in cases involving subcrestally placed postextractive tapered single implants: A randomized controlled clinical study. Clin Implant Dent Relat Res 2014;16:794–805. 18. Bozkaya D, Müftuü S. Efficiency considerations for the purely tapered interference fit (TIF) abutments used in dental implants. J Biomech Eng 2004;126:393–401.

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Section IV

CHAPTER 21

THE SINUS CONSENSUS CONFERENCE: RESULTS AND INNOVATIONS Vincent J. Iacono, dmd | Howard H. Wang, dds, ms, mph, mba | Srinivas Rao Myneni Venkatasatya, dds, ms, phd

T

he 1996 Report of the Sinus Consensus Conference validated a relatively novel technique for bone augmentation in the maxillary sinus cavity.1 Because the procedural parameters that impacted the success of sinus grafting were poorly defined at the time, the report attempted to clarify these parameters. Data from a total of 1,000 cases including 3,554 implants placed by 38 clinicians were analyzed for bone and implant survival as the primary outcomes. The results revealed a 3- to 5-year survival rate of 90%; however, certain factors were found to impact the survival rate, including poor primary stability, poor provisional prostheses, smoking, and occlusal trauma.1 One of the most important factors related to implant success was the type of grafting material used. The success of 11 different grafting materials was evaluated over a 3-year period, and varying implant survival rates were found among the grafting materials used. The greatest number of failed implants was in the autograft/xenograft group with a 54% failure rate. However, it is important to note that only 13 patients received this combination of grafting. The next highest failure rate was found in the allograft/xenograft and autograft/allograft groups, both with failure rates of 36%. The three top performing graft materials were the autograft/allograft/alloplast group, the alloplast only group, and the alloplast/xenograft group. These each had failure rates of less than 10%.1 In addition to studying the effects of different grafting materials on implant survival rate, the consensus report also investigated the survival rate of simultaneous versus delayed implant placement in the context of different grafting materials. Delayed implant placement is defined as placing the implants approximately 6 to 9 months after the grafting procedure. In general, the type of grafting material did not affect implant success, regardless of the time of placement. One notable exception to

this finding was the pure autograft group; there was a higher success rate with the delayed approach (P = .037).1 While the 1996 Report of the Sinus Consensus Conference provided evidence for the use of sinus floor grafting for the placement of implants and confirmed that the novel procedure could no longer be considered experimental in nature, it failed to provide the scientific rationale behind the data that were generated. Since then, a large volume of literature pertaining to the sinus elevation graft has been published. Four key advancements have occurred in this area in the past 20 years, namely (1) improved sinus grafting materials, (2) new surgical sinus grafting techniques, (3) introduction of sinus floor grafting combined with alveolar augmentation bone grafts, and (4) alternative strategies to a sinus graft. The advances in each of these topics are reviewed in this chapter.

Sinus Grafting Materials The 1996 Report of the Sinus Consensus Conference analyzed the success of various grafting materials and found that bone replacement grafts such as alloplasts and xenografts increased the implant success. Conversely, the report stated that autogenous block grafts may negatively impact implant prognosis.1 Since then, large meta-analyses have reviewed the effects of various sinus grafting materials on implant success. Pjetursson et al2 performed an extensive meta-analysis of 175 articles. In this study, the survival of 12,020 dental implants was assessed over a 3-year period. An initial analysis revealed that that the highest implant survival rates were observed in those placed in the autogenous bone and bone substitute combination group (95.7%), followed by bone substitutes alone (92.5%).

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21  THE SINUS CONSENSUS CONFERENCE: RESULTS AND INNOVATIONS

Fig 21-1  (a) Preoperative computed tomography (CT) scan. (b) Postoperative CT scan 6 months following surgical placement of a BMP-2/ ACS. (c) CT scan following implant placement.

a

b

Implants placed in autogenous particulated bone grafts and those in autogenous block bone grafts had the lowest survival rates (84.3% and 80.1%, respectively). However, a second meta-analysis performed on rough-surfaced implants specifically found that the 3-year survival rates were similar for all types of grafting materials, ranging from 96.3% to 99.8%, with autogenous particulated bone graft having the highest implant survival.2 Importantly, more recent studies on sinus bone grafting materials have suggested that the lower survival rates of implants in sinuses grafted with autogenous bone is due to the lack of surface modifications of implants in early studies.3 For example, the use of machine-surfaced implants served as a confounding variable in the earlier analyses for the effect of different sinus bone grafting materials because machine-surfaced implants intrinsically have a statistically significant lower implant survival rate (82.4%) than rough-surfaced implants (95.2%).3 It is now known that roughened surfaces are superior because they induce clot stabilization, allowing for contact osteogenesis. In contrast, machined surfaces cause clot destabilization and retraction, leading to distance osteogenesis. Thus, current evidence shows that there is no significant difference between implants placed in the sinus grafted with autogenous bone and bone replacement grafts. However, bone replacement grafts may be more ideal for sinus elevation procedures in the atrophic maxillary sinus.4

Biologic materials In addition to grafting materials, other biologic materials have been shown to impact the success of sinus grafting.5 A large multicenter study involving 20 sites and 160 patients compared sinus grafting procedures using either recombinant human bone morphogenetic protein 2/absorbable collagen sponge (rhBMP-2/ACS) or autogenous bone grafts. The authors found

c

that although rhBMP-2 was both safe and effective for maxillary sinus augmentation, it resulted in less bone height gain and increased graft shrinkage compared with the autogenous bone graft.5 Of note, the graft shrinkage persisted even when combined with well-established graft materials such as xenografts and allografts. However, the use of rhBMP2/ACS demonstrates de novo bone formation, which has been shown to increase in density after the placement of dental implants as shown in Fig 21-1. Since then, other biologic materials such as recombinant human plateletderived growth factor (rhPDGF) and mesenchymal stem cells and osteoprogenitors have been investigated. In one study, histomorphometric analysis of patients who received bilateral maxillary sinus grafting with either anorganic bovine bone matrix (ABBM) alone or ABBM mixed with rhPDGF showed a statistically significant difference in the amount of vital bone growth at 4 to 5 months: 11.8% vital bone and 33.6% residual graft material compared with 21.1% vital bone and 24.8% residual graft material, respectively.6 Further studies found that the addition of native mesenchymal stem cells and osteoprogenitors to an allograft cellular bone matrix (ACBM) allowed for significantly more vital bone growth and decreased residual graft material compared with ACBM alone. A study of biopsies taken following an average healing time of 3.7 months found that the patients treated with sinus grafts composed of ACBM impregnated with native mesenchymal stem cells and osteoprogenitors had 32.5% vital bone and 4.9% residual graft material. In contrast, sinuses grafted with ACBM alone exhibited 18.3% vital bone and 25.8% residual graft material.7 In separate studies, the use of platelet-rich plasma (PRP) and platelet-rich fibrin (PRF) were investigated. When mixed with bone grafting material, PRP and PRF may accelerate the remodeling of allografts, but no significant differences in implant survival are seen.8 In addition, sinus grafting is appropriate to correct oroantral communication as demonstrated in Fig 21-2.

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Sinus Grafting Materials

a

b

c

d

e

f

g

h

i

Fig 21-2 Sinus grafting to correct oroantral communication by using a barrier of PRF. (a to c) Preoperative CT scan and clinical photograph of oroantral communication. (d) Incision design. (e) Oroantral communication. (f) Lateral window creation. (g to i) Sinus membrane elevation.

In this protocol, sinus membrane oroantral communication is occluded using a barrier of PRF. Thus, the addition of biologic materials to maxillary sinus grafts tends to increase the rate of vital bone formation, allowing for earlier implant placement.

Barrier membranes In addition to biologic materials, studies have evaluated the effect of barrier membranes on implant success. This approach offers significant benefits, as the addition of a barrier membrane over the lateral antrostomy increases vital bone formation,

prevents soft tissue ingrowth, and has a positive effect on implant survival.8,9 In 39 studies, the implant survival rates with the use of a membrane ranged from 92% to 100%. Survival rates in the absence of a membrane were 61.2% to 100%, suggesting that use of a membrane may improve implant success.10 Of note, the use of nonresorbable membranes such as expanded poly­ tetrafluoroethylene (ePTFE), resorbable collagen membranes, and PRF have all been used without any reported complications. Thus, the available evidence suggests that deproteinized bovine bone mineral with slow resorption profiles is well suited for the maintenance of bone after the sinus graft procedure.

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j

l

k

m

n

o

Fig 21-2  (cont) (j and k) View of PRF. (l and m) Oroantral communication and lateral window occluded using a barrier of PRF and flap sutured. (n and o) Preoperative and postoperative radiographs.

Sinus Grafting Techniques

Comparing treatment options

Improved understanding of the biology of the maxillary sinus in the past 20 years has allowed for development of innovative sinus grafting techniques. Research in a murine model has demonstrated that ectopic subcutaneous transplantation of the membrane allowed for de novo bone formation.11 This finding of the innate osteogenic potential of the sinus membrane has important clinical implications and suggests that any method of elevating the sinus membrane will lead to new bone formation as long as the space is maintained.10,11 The 1996 Report of the Sinus Consensus Conference described only the lateral approach with a Caldwell-Luc antrostomy; however, if a bone height of 4 mm or greater is present, then a transcrestal approach with osteotomes can be performed. The clinician has the option of placing the implant using a simultaneous or delayed approach when performing a sinus graft procedure. Traditionally, delayed implant placement is recommended in cases with less than 4 to 5 mm of residual bone. However, the expertise of the clinician plays a large role in deciding whether simultaneous implant placement can be carried out. This decision is based on the available bone quantity and quality, type of implant used, and the ability to achieve primary stability.10

Current innovations in drilling protocols and implant designs (such as underpreparing the osteotomy and using tapered implants) have allowed for increased predictability of achieving good primary stability when placing implants in compromised sites with minimal residual bone height. Successful implant placement into severely pneumatized sinuses with 1 to 2 mm of residual bone height is reported with success rates similar to those placed in residual bone height of greater than 5 mm when cases are carefully planned and surgeries are performed meticulously.12 However, if a simultaneous approach is used in a severely pneumatized sinus with only 1 to 2 mm of residual bone height, then it is advised to perform two-stage implant surgery. Performing a single-stage implant surgery in this setting can compromise the site because of biologic width remodeling, leading to crestal bone resorption and loss of implant stability. Advances in cone beam computed tomography (CBCT) technology can aid in case planning and determining the appropriate surgical approach.13 The lateral approach via Caldwell-Luc antrostomy remains one of the most widely used procedures for sinus grafting when the remaining bone height is 4 mm or less. Additional modifications have been made in antrostomy creation and membrane elevation to decrease technique sensitivity and intraoperative

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Fig 21-3 Sinus augmentation lateral window via piezoelectric surgery. (a) A diamond-coated sinus augmentation osteotome is used to pre­ vent damage to the sinus membrane. (b) A sinus membrane separator cone compressor is used to separate the sinus membrane. (c) The lateral wall is removed, exposing the septum. (d) Atraumatic elevation of the sinus membrane around a septum. a

b

c

d

complications. The osteotomy can be created using conventional rotary instruments at 800 to 40,000 rpm with copious irrigation. However, piezoelectric surgery using an ultrasonic technique is more precise and allows for selective cutting of either hard or soft tissue.14 This technique reduces bleeding, induces minimal trauma, and thereby improves the healing response.14

Surgical tools for success Piezoelectric instruments include osteotomes to create the osteotomy as well as cone compressors to elevate the membrane. This decreases the risk of perforation and is particularly useful around Underwood septa compared with traditional hand instrumentation techniques. Piezoelectric instruments allow the clinician to isolate and maintain the intraosseous branches of the maxillary artery on the sinus membrane without risk of laceration. In both the traditional rotary and piezoelectric surgery techniques (Fig 21-3), the clinician has the option of thinning out the lateral wall or creating a hinged door access to preserve the bony window. In addition, numerous products are currently on the market to aid in the sinus graft procedure. These include improved membrane elevation instruments as well as trephines and large diamond-coated drills to either thin out or trephine an access into the sinus. Another novel technique includes the use of a silicone balloon inflated by diluted contrast liquid to passively elevate the sinus membrane.15 When used in conjunction with piezoelectric surgery for the initial osteotomy, this technique may overcome the difficulty of performing a transcrestal approach sinus elevation with a sloped sinus floor. A large multicenter

clinical trial has shown this procedure to have a 97.3% success rate (ie, no sinus membrane perforation during the procedure), with a 95% implant survival rate observed at 6 to 9 months.15

Transcrestal technique The transalveolar or transcrestal technique, introduced in 1994, requires the use of successive osteotomes and a mallet to elevate the membrane with or without bone graft material. This technique simultaneously increases the density and volume of spongy bone at the apicocoronal and buccolingual dimensions through osseous compression.16 It is a less invasive procedure that may be able to improve primary stability from bone compression of the osteotomy walls. Indications include adequate crestal bone width, a flat sinus floor with residual bone height of at least 4 to 5 mm, and no apparent signs of Underwood septa. Subsequently, variants of the transalveolar technique were developed, including the modified trephine osteotome technique and transcrestal core elevation technique.17,18 The literature reports that the transcrestal technique is able to increase bone height up to 7 mm. However, the mean bone height gain is approximately 3.5 mm in the absence of graft material and 4.1 mm when grafting material is used. The reported implant survival rates are similar to that of the lateral approach at 92.8% with 3 years of follow-up.19 Similar to the lateral approach, piezoelectric surgery was adopted to increase the ease of the transcrestal technique. Because it has selective cutting for either bone or soft tissue, the likelihood of membrane perforation is minimized. Many

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a

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d

e

f

Fig 21-4  Combination sinus and alveolar augmentation grafts. (a and b) Preoperative CT scan and clinical photograph. (c and d) Stage-one implant surgery, 4 months later. CT scan after combined sinus and alveolar augmentation and clinical view during implant placement. (e and f) Stage-two implant uncovering, 6 months after stage one. CT scan and clinical image. (Courtesy of Dr Juan Francisco Pardo, Lima, Peru.)

other devices and techniques have been created to improve both the efficiency and safety of the transcrestal approach. For example, sequential use of diamond-coated drills functions as osteotomes, allowing for direct drilling up to the sinus membrane without the need for the use of the mallet. After the drills are used, the sinus membrane is elevated using the dome-shaped sinus curette, and graft material is introduced into the cavity.

Summary Because the armamentaria for both lateral and transcrestal approach sinus elevations are rapidly increasing, it is of utmost importance for the practicing clinician to understand the biologic basis for the procedures. Any clinician who is adopting new techniques must be aware of the advantages, limitations,

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Alternative Strategies for Bypassing the Need for Sinus Grafting

and possible complications. For example, the use of osteotomes and mallets for the transcrestal approach has been shown to induce benign paroxysmal positional vertigo with an incidence of 3%. The use of piezoelectric surgery or other types of minimally invasive techniques eliminates this sequela. Therefore, this may be a determining factor for selecting one technique or another.20 Importantly, mastery of these techniques allows the clinician to appropriately plan the best treatment approach for each individual patient.

Combination Sinus and Alveolar Augmentation Grafts The combined sinus and alveolar graft technique is often necessary to create orthoalveolar form and is indicated when there is insufficient buccolingual width of the alveolus to receive the dental implant. Moreover, it aids in proper placement of the implant in relation to the existing dentition. This concept has gained importance as dental implant placement is prosthetically driven and is no longer dictated by the availability of the alveolar bone. If the surgical site is amenable to lateral or vertical ridge augmentation, then it is advised to attempt this technique simultaneously with the sinus augmentation to decrease the number of surgeries, healing time, and morbidities. The combined sinus and alveolar graft technique may be particularly important for posterior maxillae that have lost significant vertical bone height, as the definitive restoration in the absence of this technique may be overcontoured and difficult for patients to maintain. A study using the combined sinus and alveolar graft technique examined maxillary sinus augmentation performed using autogenous particulate bone combined with vertical ridge augmentation. Autogenous harvested bone blocks were placed on the crest from either the iliac crest, mandibular ramus, or chin. The results showed an average gain of 13.4 mm of bone height from an initial mean of 1.8 mm residual bone height at the 1-month postoperative visit. Notably, the bone height remained at 10.8 mm at 15-month and later follow-up visits after bone resorption and remodeling. A total of 20 implants were placed, and only 1 implant failure occurred. The final crown-to-implant ratios were all within acceptable ranges.21 Another study investigated the success of simultaneous sinus elevation and lateral ridge augmentation in the placement of 284 implants using autogenous bone from the iliac crest in 57 patients.22 Although partial bone graft dehiscence was reported in three cases, all implants survived at the time of stage-two surgery. In addition, the alveolar split combined with sinus floor intrusion has been reported.22 Combining sinus grafting with lateral or vertical ridge augmentation is predictable in facilitating ideal implant placement and decreasing both treatment time and complications after restoration.23 The combination of sinus and lateral alveolar

ridge augmentation using guided bone regeneration is shown in Fig 21-4. The use of interpositional grafts combined with sinus grafts has also been employed.24

Alternative Strategies for Bypassing the Need for Sinus Grafting Numerous strategies have been proposed to bypass the need for sinus grafting, and these techniques have success rates similar to sinus graft–directed implants. These strategies include dental implant placement in the zygoma or pterygoid process, tilted implants, and—more recently—the placement of short implants (ie, < 8 mm). These procedures do not include a healing period for sinus grafting and therefore accelerate treatment time. With regard to tilted implants and implants placed in the zygoma or pterygoid process, a reduced number of implants may be needed for the final fixed implant prosthesis as compared with conventional implant treatment involving either sinus augmentation or shorter implants (see chapter 14).25,26

Implants placed in the pterygoid process and zygoma Dental implant placement in the pterygoid process was first described in 1989 by Tulasne.27 These implants differ from standard implants in that the length typically ranges from 10 to 16 mm, depending on jawbone atrophy and angle of placement. Pterygoid-directed implants are placed through the maxillary tuberosity and pyramidal process of the palatine bone and engage apically into the pterygoid process. Pterygoid implants can also be placed vertically through the pterygoid maxillary junction. A review of 13 articles reporting a total of 1,053 pterygoid implants in 676 patients with a minimum of 1 year follow-up showed that the cumulative survival rate was 90.7%.28 Other authors have reported 10-year survival rates of 94.7%, but implants attempted and not placed are usually not included in these studies. Common surgical and postoperative complications are comparable to conventional implant placement procedures with increased likelihood for slight venous bleeding. Minor trismus pterygoid implant fracture has also been reported.29 See chapter 17 for more information on pterygoid implants. Zygomatic implants were first introduced in the 1990s and gained popularity for rehabilitation in patients with insufficient bone in the posterior maxilla due to trauma, maxillectomy related to tumor resection, or congenital defects.30 These implants have a high success rate and may not need any bone grafting procedure in either the anterior or posterior maxilla. Therefore, this treatment approach remains an option for implant-supported restorations for dental patients who do not wish to undergo extensive bone augmentation procedures.

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Zygomatic implants may be used in conjunction with two standard implants in the anterior maxilla and one or two zygomatic implants bilaterally in each maxillary posterior quadrant. If it is not viable to place standard implants in the anterior maxilla, two zygomatic implants can be placed bilaterally in the posterior maxilla to support a fixed prosthesis. Zygomatic implant lengths range between 30 to 57.5 mm, and implant platform to abutment angles range from 30 to 60 degrees. While there are several advantages to using zygomatic implants, the procedure is highly technique sensitive because the drill path is close to vital anatomical structures such as the infraorbital nerve, maxillary sinus, orbit, and nasal cavity. In addition, surgical access and visibility is limited. Postoperative complications may include failure of osseointegration, periimplantitis, sinusitis (which may occur immediately or many years later), soft tissue infection, paresthesia, and oroantral fistulae. There have also been reports of a cutaneous fistula developing at the zygomatic-orbital area due to sinus communication or bone necrosis at the apical part of the implant.31 In addition, the loss of one implant in a bilateral zygomatic rehabilitation may lead to a total loss of the prosthesis. In a systematic review that included 68 studies and 4,556 zygomatic implants, the 12-year cumulative survival rate was reported to be 95.1% with failures primarily occurring shortly after implant placement. However, the success criteria of zygomatic implants is not well defined.32 See chapters 15 and 16 for more information about zygomatic implants. Unfortunately, the existing literature for extramaxillary implants such as pterygoid and zygomatic implants does not incorporate a single randomized clinical trial. Only case series are published to elucidate outcomes. While placement of these implants may be viable by a skilled surgeon, it must be noted that there are several shortcomings that warrant additional investigation. The use of CBCT-guided surgery is not predictable for controlling drilling trajectory for zygomatic implants because drill deviation is always anticipated.33 In addition, it may be difficult to assess radiographic bone loss and peri-implant health of these types of implants due to the anatomical location and placement.34 Also, the absolute need for zygomatic implants has not been well defined, although Jensen et al34 suggested a 45-mm alveolar length measured on a CT spline occlusal view from anterior sinus wall to anterior sinus wall as the threshold indication for posterior zygomatic implant placement. In the event that an implant has to be removed, it can be very traumatic and may entail significant postoperative morbidity.35

Tilted (angled) implants Standard implants can be placed at a 15- to 30-degree angle to avoid involvement of the maxillary sinus.25 Although axially placed implants are more widely accepted for rehabilitation of the dentition, research has shown that despite angulated placement, these implants have similar patterns of bone loss and overall success as axially placed implants. A systematic review

of 44 publications, including a total of 5,029 tilted implants and 5,732 nontilted implants, showed that failure rates were similar at 1.63% and 1.81%, respectively. Additionally, there was no statistically significant effect of implant angulation on marginal bone loss or implant survival.36 Tilted implants have been shown to resist antiaxial occlusal forces. The concept of angulated implants was introduced in 1993, and this concept is applied to form implant fixed-denture rehabilitation treatment plans in which two tilted or axial implants are placed anteriorly and two tilted implants are placed at 30 degrees posteriorly to support a fixed implant-supported prosthesis.26 Advantages include circumventing the need for sinus grafting, reduction in the length of cantilevers, and decreased number of implants needed for a complete arch restoration. Immediate provisionalization may be possible. The disadvantage is that it is highly technique sensitive; however, this can be simplified with the aid of CBCT-guided surgery. See chapter 13 for further research on tilted implants.

Short implants Historically, clinicians were reluctant to place short implants due to concerns that they may induce excessive biomechanical forces and lead to loss of osseointegration. In addition, many feared that even mild peri-implantitis would result in the failure of short implants. Although the length of a short implant has not historically been well defined, the general consensus in the literature is that a short implant is 8 mm in length or shorter. The effectiveness of short implants has been shown to be comparable to standard-length implants. Accordingly, a meta-analysis of 2,631 short dental implants placed in both the mandible and maxilla in a total of 1,269 patients with up to 10 years of follow-up reported no significant differences of implant survival, marginal bone loss, prosthetic failures, or complications. However, additional stratification of the data may be needed to fully understand the impact of dental implant length to success or survival in future studies. It is important to note that a subanalysis of short implants that were 4 to 7 mm in length revealed a significant increase in failures (P < .02), although the number of failures of 4-mm dental implants may skew the data for the whole stratification of 4- to 7-mm implants.32,37 Another more recent meta-analysis of seven randomized clinical trials compared the survival rate of 265 short implants (5 to 8 mm) and 289 standard-length implants (> 8 mm) in patients who required sinus grafting in the atrophic posterior maxilla with a 1- to 3-year follow-up. This study found no difference in implant survival rate between the two groups. However, the short implant group had a significantly lower rate of complications, as standard-length implant placement was associated with more extensive bone grafting procedures and more invasive surgical procedures such as the sinus elevation.38 Thus, the available evidence suggests that short implants may function just as well as standard-length implants in the posterior maxilla,

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References

although there may be an increased risk of failure as the implant becomes shorter. Additionally, studies that take into account the patient’s systemic health, quality of the residual alveolar bone, primary stability, and platform switching will be of value in determining the indications for short implant use. See chapter 12 for more information on short implants.

Conclusion The high success rate of sinus grafts as reported in the 1996 Sinus Consensus Conference has been repeatedly confirmed in the literature. That conference resulted in confidence to restore the posterior maxilla with functional implants. In addition, it has been shown that deproteinized bovine bone mineral is effective in the regeneration and maintenance of bone and that it may be considered a material of choice for sinus floor grafting. While there are increasing numbers of innovations in grafting materials, methods of graft placement, and surgical techniques, no grafting material or technique has been shown to be ideal for all situations. Clinical judgment based on evidence is required for idealized treatment planning on a case-by-case basis.

Acknowledgments The authors would like to thank Dr Juan Francisco Pardo, DDS, MS, for sharing the clinical and CT scan images of Fig 21-4. Dr Padro is a periodontist at Pardo Y Bellido Dentistas Asociados in Lima, Peru.

References 1. Jensen OT, Shulman LB, Block MS, Iacono VJ. Report of the Sinus Consensus Conference of 1996. Int J Oral Maxillofac Implants 1998;13(suppl):11–45. 2. Pjetursson BE, Tan WC, Zwahlen M, Lang NP. A systematic review of the success of sinus floor elevation and survival of implants inserted in combination with sinus floor elevation. J Clin Periodontol 2008;35(8 suppl):216–240. 3. Wallace SS, Froum SJ. Effect of maxillary sinus augmentation on the survival of endosseous dental implants. A systematic review. Ann Periodontol 2003;8:328–343. 4. Esposito M, Grusovin MG, Coulthard P, Worthington HV. The efficacy of various bone augmentation procedures for dental implants: A Cochrane systematic review of randomized controlled clinical trials. Int J Oral Maxillofac Implants 2006;21:696–710. 5. Triplett RG, Nevins M, Marx RE, et al. Pivotal, randomized, parallel evaluation of recombinant human bone morphogenetic protein-2/absorbable collagen sponge and autogenous bone graft for maxillary sinus floor augmentation. J Oral Maxillofac Surg 2009;67:1947–1960.

6. Froum SJ, Wallace S, Cho SC, et al. A histomorphometric comparison of Bio-Oss alone versus Bio-Oss and platelet-derived growth factor for sinus augmentation: A postsurgical assessment. Int J Periodontics Restorative Dent 2013;33:269–279. 7. Gonshor A, McAllister BS, Wallace SS, Prasad H. Histologic and histomorphometric evaluation of an allograft stem cell-based matrix sinus augmentation procedure. Int J Oral Maxillofac Implants 2011;26:123–131. 8. Esposito M, Felice P, Worthington HV. Interventions for replacing missing teeth: Augmentation procedures of the maxillary sinus. Cochrane Database Syst Rev 2014;(5):CD008397. 9. Jensen OT, Greer RO. Immediate placement of osseointegrating implants into the maxillary sinus augmented with mineralized cancelllous allograft and Gore-Tex: Second stage surgical and histological findings. In: Laney WR, Tolman DE (eds). Tissue Integration in Oral, Orthopedic & Maxillofacial Reconstruction. Chicago: Quintessence, 1991:321–333. 10. Jensen SS, Terheyden H. Bone augmentation procedures in localized defects in the alveolar ridge: Clinical results with different bone grafts and bone-substitute materials. The Int J Oral Maxillofac Implants 2009;24(suppl):218–236. 11. Srouji S, Ben-David D, Lotan R, Riminucci M, Livne E, Bianco P. The innate osteogenic potential of the maxillary sinus (Schneiderian) membrane: An ectopic tissue transplant model simulating sinus lifting. Int J Oral Maxillofac Surg 2010;39:793–801. 12. Peleg M, Garg A, Mazor Z. Predictability of simultaneous implant placement in the severely atrophic posterior maxilla: A 9-year longitudinal experience study of 2132 implants placed into 731 human sinus grafts. Int J Oral Maxillofac Implants 2006;21:94–102. 13. Angelopoulos C, Aghaloo T. Imaging technology in implant diagnosis. Dent Clin North Am 2011;55:141–158. 14. Vercellotti T, De Paoli S, Nevins M. The piezoelectric bony window osteotomy and sinus membrane elevation: Introduction of a new technique for simplification of the sinus augmentation procedure. Int J Periodontics Restorative Dent 2001;21:561–567. 15. Kfir E, Goldstein M, Yerushalmi I, et al. Minimally invasive antral membrane balloon elevation: Results of a multicenter registry. Clin Implant Dent Relat Res 2009;11(suppl 1):e83–e91. 16. Summers RB. A new concept in maxillary implant surgery: The osteotome technique. Compendium 1994;15:152–156. 17. Toffler M. Site development in the posterior maxilla using osteocompression and apicalalveolar displacement. Compend Contin Educ Dent 2001;22:775–780. 18. Fugazzotto PA. The modified trephine/osteotome sinus augmentation technique: Technical considerations and discussion of indications. Implant Dent 2001;10:259–264. 19. Pjetursson BE, Lang NP. Sinus floor elevation utilizing the transalveolar approach. Periodontol 2000 2014;66:59–71. 20. Sammartino G, Mariniello M, Scaravilli MS. Benign paroxysmal positional vertigo following closed sinus floor elevation procedure: Mallet osteotomes vs. screwable osteotomes. A triple blind randomized controlled trial. Clin Oral Implants Res 2011;22:669– 672. 21. Shibuya Y, Takeuchi Y, Asai T, Takeuchi J, Suzuki H, Komori T. Maxillary sinus floor elevation combined with a vertical onlay graft. Implant Dent 2012;21:91–96. 22. Jensen OT, Kuhlke KL. Maxillary full-arch alveolar split osteotomy with island osteoperiosteal flaps and sinus grafting using bone morphogenetic protein-2 and retrofitting for immediate loading with a provisional: Surgical and prosthetic procedures and case report. Int J Oral Maxillofac Implants 2013;28:e260–e271.

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23. Weingart D, Bublitz R, Petrin G, Kalber J, Ingimarsson S. Combined sinus lift procedure and lateral augmentation. A treatment concept for the surgical and prosthodontic rehabilitation of the extremely atrophic maxilla [in German]. Mund Kiefer Gesichtschir 2005;9:317–323. 24. Jensen OT. Alveolar segmental “sandwich” osteotomies for posterior edentulous mandibular sites for dental implants. J Oral Maxillofac Surg 2006;64:471–475. 25. Asawa N, Bulbule N, Kakade D, Shah R. Angulated implants: An alternative to bone augmentation and sinus lift procedure: Systematic review. J Clin Diagn Res 2015;9:ZE10–ZE13. 26. Maló P, Rangert B, Nobre M. All-on-4 immediate-function concept with Brånemark system implants for completely edentulous maxillae: A 1-year retrospective clinical study. Clin Implant Dent Relat Res 2005;7(suppl 1):S88–S94. 27. Tulasne JF. Implant treatment of missing posterior dentition. In: Albrektsson T, Zarb GA (eds). The Brånemark Osseointegrated Implant. Chicago: Quintessence, 1989:103. 28. Candel E, Peñarrocha D, Peñarrocha M. Rehabilitation of the atrophic posterior maxilla with pterygoid implants: A review. J Oral Implantol 2012;38(spec no):461–466. 29. Valerón JF, Valerón PF. Long-term results in placement of screwtype implants in the pterygomaxillary-pyramidal region. Int J Oral Maxillofac Implants 2007;22:195–200. 30. Tamura H, Sasaki K, Watahiki R. Primary insertion of implants in the zygomatic bone following subtotal maxillectomy. Bull Tokyo Dent Coll 2000;41:21–24.

31. Tzerbos F, Bountaniotis F, Theologie-Lygidakis N, Fakitsas D, Fakitsas I. Complications of zygomatic implants: Our clinical experience with 4 cases. Acta Stomatol Croat 2016;50:251–257. 32. Chrcanovic BR, Abreu MH. Survival and complications of zygomatic implants: A systematic review. Oral Maxillofac Surg 2013;17:81–93. 33. Chow J. A novel device for template-guided surgery of the zygomatic implants. Int J Oral Maxillofac Surg 2016;45:1253–1255. 34. Jensen OT, Ringeman JL, Adams MW, Gregory N. Reduced arch length as a factor for 4-implant immediate function in the maxilla: A technical note and report of 39 patients followed for 5 years. J Oral Maxillofac Surg 2016;74:2379–2384. 35. Esposito M, Worthington HV. Interventions for replacing missing teeth: Dental implants in zygomatic bone for the rehabilitation of the severely deficient edentulous maxilla. Cochrane Database Sys Rev 2013;(9):CD004151. 36. Chrcanovic BR, Albrektsson T, Wennerberg A. Tilted versus axially placed dental implants: A meta-analysis. J Dent 2015;43:149– 170. 37. Lemos CA, Ferro-Alves ML, Okamoto R, Mendonça MR, Pellizzer EP. Short dental implants versus standard dental implants placed in the posterior jaws: A systematic review and meta-analysis. J Dent 2016;47:8–17. 38. Fan T, Li Y, Deng WW, Wu T, Zhang W. Short implants (5 to 8 mm) versus longer implants with sinus lifting in atrophic posterior maxilla: A meta-analysis of RCTs. Clin Implant Dent Relat Res 2017;19:207–215.

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CHAPTER 22

SHARPEY FIBER BIOLOGIC MODEL FOR BONE FORMATION Martin Chin, dds | Jean E. Aaron, phd

R

econstruction of skeletal disorders may be approached with a wide variety of techniques, but all treatment methods require a positive reaction from the common biologic system. A successful outcome depends on how well the patient’s physiology responds to surgical incursion. An understanding of the physiology of bone and how bone operates is the foundation upon which all treatments of skeletal disorders are designed and new technologies developed. The study of the bone-forming construct offers new insights into how bone may work.1 This tested surgical model proposes the inclusion of previously overlooked contributory factors in explaining how living bone behaves with respect to familiar aspects of formation, remodeling regulation, response to surgery, and deterioration with aging. Innovations from several independent research centers are combined into a single working program, resulting in a treatment protocol that can be applied to a range of clinical disorders. This stepwise protocol is based on novel bone regulation concepts and can be used to analyze the healing potential of proposed procedures before treatment is started. Clinical examples illustrate how a healing response can be predicted by comparing how well the surgical plan conforms to the requirements indicated by the basic principles of the model. This protocol also provides a means to analyze and learn from past treatment failures. Innovative clinicians can use these principles to craft new treatments for disorders that were previously considered impossible to treat or to likely yield unsatisfactory outcomes.

Embryomimetic Surgical Engineering The underlying strategy of this surgical design is to harness the primitive biologic pathways that form the fetal skeleton.2

Embryonic development is an elegant and inadequately understood demonstration of the self-assembly of the anatomical system. The fetal facial skeleton is formed without external direction and using only local substrate. All of the cells are recruited from the adjacent tissues and undergo morphogenesis to meet their skeletal requirements. The complex structural architecture is assembled and then continuously reassembled as the fetus grows. The possibility of de novo self-assembly is not in question because embryos consistently demonstrate the process with near flawless precision throughout a wide range of living organisms. The challenge is to reverse engineer the sequential events to provide a depth of understanding that can be incorporated into treatment designs.

Transition from hypothesis to clinical practice Formulating a treatment protocol that can be applied to real patient problems requires a stepwise process of discovery and verification. First, a plausible mechanism must be defined that can explain how the embryo effects morphogenesis and assembly of a skeletal system without external regulation. The subsequent hypothesis needs verification through identification of the physiologic and anatomical mechanisms that achieve the resultant skeletal formation. The second task is to verify that the proposed embryonic mechanism of choice is preserved in the adult. This requires histologic evidence that the fetal systems are retained within the adult anatomy and continue to function in controlling the skeletal physiology. The third step is to design practical surgical treatments that depend on the working model. These procedures should correct those clinically relevant disorders that especially challenge patients and providers. The fourth step is to confirm that the reconstructed skeletal units function just like their normal counterparts and that they will remain stable for many years.

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The mechanisms of interest are likely to have developed early in evolution when they were structurally integrated into primitive organisms. Even in the simplest single-celled organism, there would have been a survival advantage in the ability to form particular structural components. The need to fabricate skeletal systems becomes increasingly crucial as the complexity and size of the organism evolves. To form and maintain the fetal and adult skeleton, the process of regulation must extend from the individual cells to the organism as a whole. A hierarchy of regulation affords the ability to synthesize a major structural skeletal system. The premise is that a system has to be in place to coordinate the activity of each cell to the net benefit of the organization of the complex organism. The key to reverse engineering fetal skeletal development is the recognition of how each component of the regulatory system accomplishes its global objective. Wolff3 and Moss and Salentijn4 recognized the effects of an underlying regulatory process but were unable to identify a mechanism that could explain the outcome. A working theoretical model has to explain how this system operates and provide experimental and anatomical verification that these processes remain operational in the adult. The premise of this approach is that the embryonic regulatory system directs the physiology and structural architecture of the adult skeleton over a lifetime.

The Sharpey Fiber Matrix Network Insufficient understanding of how bones form and function is the primary constraint in designing new reconstructive surgeries and understanding why existing treatments fail. The current state of knowledge is often defined by limitations in the ability to image the fine structural anatomy of mature skeletal bone. The calcified architecture of skeletal systems provides the organism with a protective barrier from damaging external forces but also hides from view the histologic details of how the tissue components interact. Established methods to capture and image the complex interrelationships of bone structure and ultrastructure are often inadequate to determine in detail the biologic events taking place in vivo. Traditional processing of resected bone specimens can compromise evidence about how the underlying system operates. Some of the inevitable limitations of routine histologic methods may be reduced by the application of complementary technologic advances, enabling insight into macromolecular composition. These advances may assist progress toward new frontiers by identifying target features with the objective of constructing a new surgically relevant biologic model that takes into account how normal bone forms, functions, and deteriorates with age and disease. Contained within the skeleton is a largely unrecognized network of highly specialized collagen fibers that apparently participate in mechanobiologic behavior5 (Fig 22-1). This new anatomical and physiologic finding has recently received attention because the specialized fibers seem to be an essential

component of early bone initiation. In textbooks, such fibers have been confined to outer skeletal surfaces as Sharpey fibers that supply periosteal anchorage and are associated with muscle attachments, innervated muscle fibers, periodontal ligaments, and cranial sutures. However, because the technology was not available in the past, it was rarely recognized that the familiar Sharpey fiber system of short regular insertions extends beyond the superficial bone surface to permeate the deeper underlying microarchitecture5 (Fig 22-2). Current visualization of an apparently extensive Sharpey network within the bony tissue generally requires special specimen cryoprocessing, specific antibodies, and immunohistochemical labeling. Aaron et al6,7 adopted and developed this primarily soft tissue technology for hard tissues to investigate fetal skeletal assembly and showed fetal bones that apparently formed in relation to a Sharpey collagen matrix precursor framework7 (Fig 22-3). They also found that adult skeletal wounds healed using a Sharpey fiber mechanism that was histologically similar to the fetal bone-forming process, which confirms that the functional potential is conserved throughout life. Details of this process are outlined in the rest of the chapter, together with an accompanying description of a separate anomaly prevalent in the literature relating to the origins and assembly of the mineral phase of bone. The two aspects combine to suggest that the extracellular matrix is an interactive system of greater biologic complexity than was previously thought. There have been two advances in bone histology that relate to the matrix (organic and inorganic phases respectively) and that may aid future therapeutic interpretation and translation into innovative orthopedic surgery.

Organic phase Traditionally the organic bone matrix is a construct of woven and lamellar collagen Type I defining well-recognized remodeling patterns and with a narrow intervening boundary of histochemical specificity separating outer intramembranous expansion from core endochondral growth. Enveloping and lining the tissue are the apparently unremarkable periosteum and endosteum, respectively. Now immunohistochemically evident in thin sections of intramembranous bone are polarized, periosteal Sharpey fiber arrays of collagen Type III that permeate the matrix and disperse into fine networks toward the inner endosteum, and in some instances beyond into the marrow tissue. Their abundance as persistently uncalcified fiber is greater than needed historically for shallow anchorage. After raising little attention, other than that of dentists concerned with the periodontal ligament, the possibility that they play a pivotal role in the signaling and mechanosensitivity essential to skeletal maintenance has been considered, as follows.5 Sharpey fibers exist beneath and extending from the periosteum at the skeletal surface. Neuromuscular and endocrine processes combine with the Sharpey fibers to influence bone

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The Sharpey Fiber Matrix Network

30 µm Fig 22-1  Photomicrograph of collagen Type III–rich Sharpey fiber network (green fluorescence) extending from the peri­osteum across the extracellular human bone matrix demonstrating longitudinal and cross-sectional orientation of fibers, approximately 10 μm thick. Fluorescein isothiocyanate immunostain, fresh cryomicrotomy section, ultraviolet epifluorescence microscopy.

Fig 22-2  Photomicrograph of three periosteal Sharpey fibers (black arrows) in the human proximal femur extending vertically in parallel from the periosteum (P) into the bone cortex (B) toward the endosteum and marrow cavity (MC). A small real microcrack is visible (white arrow). En bloc gentian violet stain. Undecalcified plastic-embedded section, plain light microscopy. (Reprinted with permission from Aaron.5)

Fig 22-3  Photomicrograph of part of an early de novo skeletal framework of periosteal Sharpey fibers (some continuous with rudimentary tendon and ligament insertions) in developing vertebrate spongiosa of the lamb fetus. A coarse collagen fiber (F) is shown branching into finer elastin-containing fibers upon which new cuboidal-shaped osteoblasts (arrow) are assembled for intramembranous trabecular generation. Decalcified plastic-embedded section, Verhoeff’s elastin stain, Nomarski optics. Original magnification ×800. (Reprinted with permission from Aaron and Skerry.7)

15 µm

remodeling. Periosteal Sharpey fibers are a feature of intramembranous bone formation (see Figs 22-1 to 22-4) but not endochondral bone formation. The development of specific immunofluorescent antibody procedures combined with advances in hard tissue cryomicrotomy has been instrumental to their identification (see Fig 22-1). These fibers fan out from the periosteum (see Fig 22-2) and unlike the surrounding collagen Type I, the periosteal Sharpey fibers consist of collagen Type III and are 15 to 25 μm wide and birefringent in polarized light. They are not featureless fibers but are regularly beaded with the developmental organizer molecule tenascin. Without this, fibrous dysplasia would occur. Additionally, they are encircled by collagen Type VI, a dumbbell-shaped molecule that blocks calcification. This notable impediment ensures the stability and longevity of the Sharpey fibers by protecting them from osteoclastic resorption, as osteoclasts normally resorb only

calcified tissue. An indented profile of the Sharpey fibers adds to their complexity. Some disperse into a fine network (see Fig 22-3) while others traverse in parallel to interconnect with the endosteum, which is a thin lamina also rich in collagen Type III (Fig 22-4). Retraction of the monitoring network from its matrix is associated with aging and estrogen decline where it apparently fades away before bone volume is lost; its augmentation is stimulated by physical activity. From the outset, the presence of Sharpey fibers in the embryonic femoral anlagen functions as a discrete proximal framework (ie, scaffold) upon which the osteoblasts assemble and ossification is shaped. In fracture healing, a similar scaffold bridges the gap and stabilizes callus formation. When an experimental cylindric osteotomy (by means of a 1-cm-diameter trephine) is created in a sheep model, the amputated ends of the matrix-embedded Sharpey fibers extend concentrically into the lumen of the

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a

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Fig 22-4 Photomicrographs of human iliac bone with associated marrow tissue immunostained for collagen Type III (a and b) in plain light showing interconnected cortical and trabecular bone and (c and d) by ultraviolet epifluorescence microscopy showing collagen Type III staining extended to the endosteal membrane (ie, not confined to the periosteum). Plastic-embedded section. (Courtesy of Dr A. Al-Qtaitat, PhD dissertation, Leeds 2007.)

defect.7 During the next 5 to 21 days, bone formation follows extension of the fibers in an initial pattern of radiating primary rods followed by a secondary pattern of bridging cross-struts. The new bone forms in the space that has a Sharpey fiber scaffold and the buttressing effect of the osteotomy wall. The cut bone surface is rich in cytokines and is the source and stimulant of substrate cells. This microenvironment contains all of the critical elements of a bone-forming construct and is completed within 90 days. There is a source of cells (ie, bone), a stabilized enclosure (ie, the osseous wall), and regulatory signaling (ie, via Sharpey fibers). The findings from the cylindrical osteotomy sheep model have implications for the healing dental implant preparations and therefore for a direct application to surgical healing and osseointegration. The porcine mandible has been similarly described as an ideal model for investigation of the periosteum because of its exceptionally powerful musculotendinous insertions.8 Birefringent Sharpey fibers were classified as horizontal (more common with age), oblique (most common in youth), or vertical (least common) and also designated as superficial, transcortical, and intertrabecular (ie, deep, coarse, and vertical). With age, the periosteum-to-bone ratio fell significantly. The fibers became fewer, fragmented, and shortened, while calcified particles encroached to progressively harden the periosteum, further reducing its function, illustrating a general phenomenon.

Inorganic phase Traditionally, the inorganic bone matrix tends to be regarded primarily in terms of crystal chemistry and precipitation (ie, as homogeneous sheets of needle- or plate-like apatite crystallites of uniform electron density dependent on collagen fibers for their nucleation). The growth of the crystallites is restricted by organic crystal “ghosts,” an organic enclosure evident by demineralization. However, there are features consistent with a more heterogeneous biodynamic interpretation, as follows.

Calcified microspheres The previous view underestimates the extent of cell-directed energetic intervention into the laws of physical chemistry and crystal growth. It also neglects the ultrastructural changes introduced by rigorous preparative procedures (eg, dehydration, fixation, electron-dense staining). Thus, when the inorganic phase is disassembled, it separates not into isolated apatite crystals but a myriad of organically contained calcified objects approximately 1 μm in diameter with lower density centers. In each substructure is a cluster of sinuous beaded filaments, each electron-dense strand 5 nm wide. The fundamental nature of the microspheres (including lipid and noncollagenous proteins) and their variable elemental composition (including traces of Si, Mg, and Fe) influences turnover rate and contributes to their

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The Sharpey Fiber Matrix Network

Fig 22-5 The evolutionary bedrock of bone. Photomicrographs of microspherical objects, approximately 1 μm diameter, calcified with phosphate. (a) Intracellular fabrication in juxtanuclear vesicle (Vs) in the protozoan bone cell model of the Spirostomum ambiguum. Thin, plastic-embedded section with von Kossa stain for bone salt and methylene blue for cell detail. (b) Populations of organically enshrouded micro­ spheres, discrete and in aggregates extruded from the burrowing protozoan. Nomarski optics. (c) Ultrastructure of an individual protozoan microsphere transmission electron microscopy (TEM), showing radiating beaded filaments (encircled) 5 nm thick (white for density) and surrounding a less dense center (arrow). (d) Similar populations of microspheres extracted from bone matrix. Nomarski optics. (e) Ultrastructure of an individual bone microsphere (black arrow; TEM), showing clusters of beaded filaments, 5 nm thick, surrounding a less dense center. (Parts c and e courtesy of Dr V. Fallon and Melanie Cowdy, Leeds, United Kingdom.)

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property as independent microscopic mechanobiologic units (Fig 22-5). In situ, their optical granularity and aggregation into a mosaic of specific and subtly variable domains (resembling bacterial colonies) is clearest at the calcification front or at sites deficient in minerals.9 In mature bone, the microspheres tend to be masked by their considerable compression, deformity, and collagen compaction, appearing as a dense continuum and restored in configuration by an inherently plastic nature when released from the matrix (eg, chemically, enzymatically by digestive fungi, or mechanically by milling).10 By interlinking into convoluted bridged assemblies around collagen fibers, they constitute a supporting microskeleton that is coarser in some anatomical locations and finer in others. In addition, they change with age and pathology, the microspherical particles

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tending to be smaller and smoother in osteoporosis (0.5 to 0.7 µm) and larger and rougher in osteoarthritis (0.5 to 4.0 µm).11 These differences will affect mechanical properties of particle slip and crystal fracture as well as fluid flow, which will be greater between larger particles.12 Implications for bioimplant compatibility are also anticipated because rigorous processing, including deproteination, enables filaments to fuse into fenestrated plates. This potentially risks unmasking a broad and capricious antigenicity that is an indigenous immunologic property of apatite crystals.13 The following describes evidence for the intracellular fabrication of populations of organically enshrouded calcified microspheres as biologic objects with a primordial history.

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Fig 22-6  The evolutionary bedrock of bone. Diagram of microspherical objects, about 1 μm diameter, calcified with phosphate (black dots) as mechanosensitive fabrications. Acute osteocyte response to external stimuli evolved from a primordial protozoan mechanobiology. (a) A silt burrowing protozoan S ambiguum (2 to 3 mm long; meganucleus red) as a mechanosensory paradigm for (b) stressed segment of the osteocyte syncytium (each cell 20 to 30 μm long; nuclei red). Within both, the large black, mineral-loaded juxtanuclear Golgi body and integral Golgi cisternae (green) “switch on” to assemble copious, compressionresistant, mineralized microspheres aligned axially relative to force in the protozoan and exported from the bone cell syncitium to consolidate the calcification front before Golgi “switch off.”

Golgi-directed calcified microspheres The bone-forming cellular response is intrinsic and primitive. For a bone-forming model to be valid, the individual cells must have an intrinsic ability to respond to extrinsic signaling within the stabilized, bone-forming environment. Ingber14,15 showed how this worked. The cell is structurally configured to respond to external mechanical forces. This concept, termed tensegrity, is derived from evidence that cells contain an internal skeleton consisting of nanotubules that support and anchor the cell wall and organelles. Subtle distortion of the cell exerts forces on the nanotubular network. The tubules and anchored organelles respond with specific upregulation of protein synthesis. The result may be a variety of cellular responses including morphogenesis, which probably emerged millions of years ago in response to specific environmental pressures. These primitive mechanisms have been preserved through evolution and are the foundation of skeletal formation and maintenance. The process is also preserved in modern single-celled organisms. A return to primordial skeletal roots is not purely academic and can provide novel insight into the governing factors directing advanced bony tissue behavior. In particular are the calcifying protozoa, exemplified by Spirostomum ambiguum (a cigar-shaped ciliate visible to the naked eye), which is unusual in that it calcifies primarily with phosphate rather than the more common carbonate. Stress induces this organism to fabricate micron-sized calcified microspheres resembling those in bone. These are assembled in the Golgi apparatus (juxtanuclear body) and align along axes of force in the cytoplasm,

enabling the large fragile creature (2 to 3 mm in length) to remain compression-resistant when tunneling in silt and simultaneously storing essential phosphate. When the ciliate adopts a gentler aqueous-swimming mode, the mineral particles diminish in number and realign transaxially. Using identical advanced fluorescence-tagged Golgi markers, the process can be seen as it recapitulates cyclic events evident in young osteocytes at the calcification front. The large, “simpler,” easily cultured organism demonstrates a conserved mechanosensitive process that has withstood the test of evolutionary time and serves as a convenient paradigm for the less accessible bone cell syncytium (Fig 22-6). On the basis of its primordial particulate bone salt fabrication, the origin of backbones has been attributed to such an organism16,17 (Fig 22-7). The Golgi-directed intracellular accumulation provides the delicate silt-embedded ciliate and the equally vulnerable entombed osteocyte with essential compression resistance.18,19 In addition, in the contractile ciliate, the bone mineral particles are in close proximity to intracellular muscle myonemes (early contractile fibrils). The convergence of the two may be a preliminary step in the ancient advance toward an integrated musculoskeletal unit.20 It seems likely that all cells, both in soft and in hard tissues, possess this Golgi-directed compression-resistant capacity for mineral fabrication but to a lesser degree than that found in the osteocyte lineage.9 Without this dynamic function, cellular bone will lack a central aspect of its acute resilience. However, this survival trait is unnecessary in acellular bone (eg, fish scales) where the mechanobiologic priority is one of sustained passive

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Microanatomical Innovations

Fig 22-7  The evolutionary bedrock of bone. Acute bone mechanosensitivity postulated from ancient history. Diagram of matrix mechanobiology factors and primordial roots in a stressed protozoan (Pr). Stress mediators include Sharpey fibers (Sf) for tension and osteocytes (Oc) “switched on” (green) for compression-resistant calcified microsphere fabrication and trafficking as 1-µm particles (black dots) consolidating those of the complex mineral microskeleton (Ms). Early evolutionary events are evoked, promoting mobility in a sessile protozoan (bottom center) by calcification along axes of biomechanical force, transferring low-stress swimming (bottom left) to high-stress tunneling in silt (bottom right).

protection rather than episodic active support. There is evidence that Golgi-formed silicon granules may augment the biomineralization process with silicification as an archaic prelude to calcification, perhaps explaining the orthopedic activity of silicon.21 From a modest organism as well as from bony tissue, it may be possible to harvest bone mineral particles for future innovative mechanobiologic fillers and bone analogs (see Fig 22-7). Further identified discrepancies of the calcifying Golgi apparatus and the clinical consequences may be the next orthopedic frontier. Both the organic Sharpey network and the inorganic microskeletal assembly described previously are biologic phenomena that influence the tensile and compression properties of the extracellular matrix, thereby contributing to bone structural quality and skeletal fragility independent of bone quantity (ie, mass). As novel complementary interactive aspects of mechanobiology, they may be exploited as future instruments of surgical innovation. In this way, the microscopic fabric serves to illustrate that bony tissue is not inherently homogeneous in its behavior. Rather, an age-diminished heterogeneous indigenous mosaic of discrete domains of microanatomical diversity is tailored to meet the diversity of gross biomechanical demand.

Microanatomical Innovations The specialized hard tissue laboratory implementing procedures ranging from the microanatomical to the macromolecular was

Tension

Quiescence

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established in 1969 under the auspices of the Medical Research Council and its flagship Mineral Metabolism Unit. Located in the Faculty of Biological Sciences, the team at the University of Leeds developed and extrapolated on the previously described histologic imaging techniques to investigate influential properties of bone quality.22 It has emerged that of particular relevance to current orthopedics are the extensive periosteal matrix fibers that apparently constitute intraosseous avenues of interconnection (see Fig 22-4) with a postulated regulatory role of clinical relevance to menopause, aging, exercise, and possibly bisphosphonate response.8,23 Nevertheless, fundamental research of this nature can sometimes appear distant from any future orthopedic application even while adding to the lexicon of knowledge. Exceptions to this may be maxillofacial disorders. Here intervention has led to positive evidence-based outcomes in cases where traditional avenues have failed. It seems that the bone biology advances from the laboratory are demonstrably meeting with success in the operating room where they are remarkably compatible with and directly applicable to the correction of maxillofacial disorders. Bony tissue is resorbed and replaced as part of normal remodeling; however, the Sharpey fiber matrix remains relatively stable throughout because the collagen fibers of this network are not calcified and are therefore protected. This ability to remain intact as a stable anatomical and physiologic system while the structural bone around them turns over enables the potentially continuous regulation of the skeleton over a lifetime. The mature skeleton maintains a steady state through constant

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Meckel cartilage

Mandible

Mylohyoid muscle

Fig 22-8 Coronal section of a 500-mm human fetus showing a mandible developing within a bone growth–promoting environment established by Meckel cartilage and the mylohyoid muscle. (Adapted with permission from Hamilton et al.25)

interaction between the periosteal Sharpey fiber network and structural bone. Neuromuscular and endocrine processes influence bone remodeling either by a direct effect on bone or indirectly through the Sharpey network. Degradation of skeletal structural integrity with age or disease may be related to changes in the periosteal Sharpey network, and the attenuation and disruption of the existing arrangement by injury results in a response to restore the prior steady state.5,7,22 The Sharpey fiber matrix network apparently directs the assembly of structural bone tissue generated in response to injury. It therefore has a direct application to surgical healing including osseointegration.

Cellular response Another critical component of this bone-forming method is the role of the physical environment within which the ossicle forms. Harvold24 recognized that skeletal formation occurs within an anatomical volume adjacent to a structure that provides mechanical stability of the soft tissue. He theorized that precursor cells are only susceptible to morphogenesis when contained within a mechanically sheltered tissue volume.24 As an example, consider that the mandible forms in the embryo adjacent to Meckel cartilage. This is a soft tissue volume that is mechanically stabilized by the cartilage bar25 (Fig 22-8). Stimulation of the cells within the tissue volume is required to undergo morphogenesis and

Fig 22-9  Coronal section of a 50-mm human fetus showing that the mandible (yellow outline) develops with a volume stabilized by Meckel cartilage (blue outline) and under the mechanical influence of the mylohyoid muscle (red outline). The green arrow indicates the direction of the muscle fiber orientation. (Adapted with permission from Hamilton et al.25)

regulation to modulate the appropriate structural architecture. Harvold’s observation is consistent with the principles of tensegrity. Attenuation of the forces exerted on the cell membrane has a direct effect on intracellular metabolism. Aaron’s team9 observed that the single-celled aquatic organism S ambiguum responds by Golgi-directed mineral fabrication when burrowing and surrounded by a high-viscosity silt environment, suggesting that this property of compression resistance is primitive and preserved in evolution. The mineral synthesized by the protozoan is chemically identical to and therefore appropriate for structural bone mineral formation. Fetal bone formation depends on a periosteal Sharpey fiber matrix precursor scaffold. Muscle fibers seem to be a source of a proportion of the Sharpey fibers because there is the consistent presence of a developing muscle in alignment with the developing bone. The extending fibers convey regulatory direction for bone formation and are then retained as the embedded fibers of the muscle attachment. Harvold recognized the relationship of muscle attachments and bone development26 (Fig 22-9). It is likely that innervated muscle fibers are the source of Sharpey fibers that make up the periosteal Sharpey fiber matrix bone precursor. The primitive fibers are probably preserved as the tendinous muscle attachments in the adult. Through this assembly strategy, the Sharpey network serves as an intermediary between the nervous system and structural bone. Harvold recognized that developmental skeletal anomalies

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Clinical Applications

Fig 22-10  Membranous healing stages of a cylindric osteotomy defect. Sharpey fibers grow into the defect before trabecular bone formation occurs. (Reprinted with permission from Chin.1)

were consistently related to neuromuscular deficiencies. The functional and anatomical links between the nervous system, muscles, tendon insertions, and embedded Sharpey network suggest a possible common path by which regulatory signals are conveyed. Experimental work confirmed that principle. When an experimental cylindric osteotomy is created in the sheep model, the amputated ends of the embedded Sharpey fibers extend into the lumen of the defect1,7 (Fig 22-10). Bone formation follows extension of the fibers but in a specific pattern. Bone forms in the volume that has both the presence of the Sharpey fibers and the mechanical buttressing effect of the osteotomy wall. The cut surface of the bone is also the source of substrate cells. This microenvironment contains each of the critical elements of a bone-forming construct. There is a source of cells (bone), stabilized environment (osteotomy wall), and regulatory signaling (Sharpey fibers). The results from the sheep cylindric osteotomy model have obvious application to our understanding of healing of dental implant preparations.

Clinical Applications Clinical situation A 65-year-old woman presented for management of missing maxillary right molars. Radiographs of the site revealed that

the maxillary sinus had descended into the alveolus, leaving a thin layer of bone at the ridge crest (Fig 22-11). If the treatment objective is crowns supported by dental implants, a volume of vital bone must be established. Standard treatment would be to first place a graft involving a sinus elevation to prepare the site for placement of endosseous implants once the graft is consolidated.

Alternative option As an alternative approach, the patient underwent evaluation to determine if a bone-forming construct could be assembled to generate a volume of vital bone and simultaneously position dental implants within it. As the first step, a deliberate analysis of the existing bone regulatory mechanisms was undertaken. This is a critical step in the diagnostic phase that must precede the process of surgical design. The theoretic basis of this surgical design method is the principle that the morphology and structural architecture of the bone is under the regulation of the embedded Sharpey network. The Sharpey network fills the volume of existing bone (Fig 22-12). Rather than focusing on the volume of deficient bone, this method depends on identifying the presence and integrity of the systems that maintain and regulate the existing bone. The fiber system extends beyond the border of the skeleton as the periodontal ligaments inserting into the dental roots. Other Sharpey fibers extend into the periosteum, anchoring the gingiva and sinus membrane (Fig

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Fig 22-11 Radiograph shows thin sinus floor lacking bone to place dental implants with augmentation.

Fig 22-12  Sharpey fibers fill the volume of the residual bone.

Fig 22-13  Sharpey fibers extending from the periosteum, sinus membrane, and periodontal ligaments are of particular importance in designing a bone-forming construct.

Fig 22-14 If the sinus membrane elevation is the proposed treatment, then raising the membrane creates a space for bone construction. Elevating the sinus membrane also severs the anchoring Sharpey fibers. The amputated fiber ends project into the bone construction chamber.

22-13). Tendon-anchoring muscle attachments are extensions of the Sharpey network. The formation and maintenance of bone performs at the direction of the Sharpey network. In this clinical situation, it is useful to focus on the fibers that anchor the sinus membrane. When the sinus membrane is elevated, severed Sharpey fibers are displaced superiorly (Fig 22-14). The fibers are critical in the formation of new bone because they have the potential to deliver regulatory signals that direct morphogenesis and organization of the skeletal architecture. Design of an effective bone-forming construct also requires physical stabilization of the future bone-formed volume along with a source of cells. One possible configuration for a bone-forming construct is illustrated in Fig 22-15. After initial conception, the design proposal must be examined to determine if it meets the essential requirements for a bone-forming construct. Positioning a dental implant in the center of the bone construction site and fixating the cylinder with a bone plate provides mechanical stability. In this design, the space created

by elevation of the sinus membrane is filled with recombinant human bone morphogenetic protein 2 (rhBMP-2) carried on a resorbable collagen sponge (Fig 22-16). This device has the ability to provide cells with bone-forming capability. Budding Sharpey fibers derived from the severed fibers that anchored the sinus membrane to the osseous sinus cortex provide regulatory instructions for the immature cells furnished by the rhBMP-2 device.26 Maintaining integrity of the sinus membrane during the elevation maneuver provides an anatomical barrier to bacterial incursion from the sinus and nasal cavities. This minimizes the risk of bacterial colonization of the site before bone has an opportunity to organize. The components of the bone-forming construct complement each other, decreasing the requirements of each component. The manufacturer’s recommended rhBMP-2 dose of 1.5 mg per mL can be reduced to 0.25 mg per mL and remain effective. The properly designed and assembled bone-forming construct would be expected to perform in a predictable and reproducible manner. Sharpey fibers from the

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Clinical Applications

Fig 22-15  Possible design of a bone-forming construct. The dental implants stabilized by the bone plate serve to provide mechanical attenuation of forces within the bone-forming chamber. The amputated ends of the severed Sharpey fibers bud into the chamber to transmit regulatory signals from the remaining network. The intact sinus membrane resists bacterial incursion from the sinus cavity. Bone-forming cells may be recruited from the denuded bone of the sinus floor or augmented with a graft.

Fig 22-16  In this proposed surgical design, rhBMP-2 carried on a resorbable collagen sponge is to be placed into the sinus elevation chamber to enhance the population of cells with bone-forming potential. This plan must be analyzed to verify that it meets all the requirements for a bone-forming construct before proceeding to surgery: (1) cells, (2) environment, (3) signaling, and (4) absence of pathology.

Fig 22-17  As the amputated Sharpey fibers of the elevated sinus membrane bud and extend into the sinus elevation space, they encounter cells with bone-forming potential. In the presence of a mechanically sheltered region, the combination of circumstances results in bone formation and organization.

Fig 22-18 The result is a volume of organized, structural bone with normal trabecular architecture, a cortical sinus floor, and a fully functioning Sharpey network capable of regulating the bone volume though normal cycles of turnover and remodeling.

sinus membrane and the denuded sinus floor should extend into the sinus elevation bone-forming chamber. Cells that find regulatory direction from the fiber network and are positioned in a mechanically sheltered region of the bone-construction chamber would be expected to develop new bone because all the requirements for a bone-forming construct would be in place. Bone should fill following extension of Sharpey fibers into a potential bone-forming space. The stabilized implant cylinder will provide the constructed region with mechanical stability. As the space below the elevated sinus membrane fills with tissue, the region adjacent to the stabilized implant cylinder becomes an ideal bone-forming site (Fig 22-17). It meets all the criteria

for bone formation: (1) cells, (2) signals, (3) environment, and (4) absence of pathology. If the objective is long-term stability, the surgical design must include a strategy to provide maintenance of the reconstruction with continued regulation of the constructed bone physiology and architecture. In this plan, the constructed bone volume should be maintained by the extension of the existing Sharpey network system from the adjacent bone. Recruiting Sharpey network regulation from adjacent, healthy periodontal systems or muscle insertions will improve the predictability of the reconstruction (Fig 22-18).

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Fig 22-19 (a) Following verification of the integrity and validity of the surgical plan, the patient undergoes a sinus elevation procedure through a lateral window. Camlog implants were chosen for this patient. (b) A titanium bone plate is attached to the implant and secured to the adjacent bone with two miniature screws because there is inadequate bone in the sinus floor to stabilize the implant. (c) Four months after placement of the implants and fabrication of the bone-forming construct, the site is opened to remove the bone plate. (d) The bone adjacent the polished collars of the implant is resorbed. The roughened and acid-etched surface of the implant is clinically healed. (e) The implants are restored. (f) Radiographic appearance 5 years postoperative demonstrates features of functional bone construction and implant osseointegration. There is a distinct cortical outline at the sinus floor, indicating physiologic remodeling.

Transitioning from surgical design to surgical procedure Only after the design proposal has been analyzed and shown to meet all of the requirements of a bone-forming construct does case management proceed to surgery. In this case, a sinus elevation procedure was completed through a lateral window (Fig 22-19a). The osteotomy for implant placement was created through the alveolar ridge. The implant cylinders were positioned with the distal implant extending into the sinus elevation void and lacking any primary stability. The cylinder was secured by attaching a titanium bone plate beneath the implant cover screw and then affixing the plate to the alveolar bone with two miniature screws (Fig 22-19b). Collagen sponges saturated with rhBMP-2 at 0.25 mg per mL were packed around the implant body within the sinus elevation cavity. A total of 1 mL of rhBMP-2 was used, which delivered a total dose of 0.25 mg rhBMP-2 to the site.26 The wound was closed primarily with interrupted 4-0 Vicryl sutures (Johnson and Johnson). Four months after surgery, the site was opened for abutment connection (Fig 22-19c). The bone plate was removed

and the stability of the implant verified (Fig 22-19d). After 3 weeks of healing with gingiva formers in place, the implants were restored (Fig 22-19e). Five years later, the radiographic appearance verifies successful performance of the bone-forming construct (Fig 22-19f). The radiograph shows development of a distinct osseous cortex at the sinus floor. Below the cortical outline is bone exhibiting normal trabecular architecture. All of the bone that formed initially apical to the implant cylinders has been resorbed as it is outside of the stabilized environment. This case demonstrates the effective and efficient use of materials and procedures to achieve a stable and functional result.

Conclusion Clinicians create surgical procedures based on their beliefs about how biology works, which results in an essential paradox of clinical practice. Current views on how bone and supporting tissues heal are the sum of basic science and clinical experience. The plans for definitive surgical incursion are based on

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References

an incomplete understanding of the how the biologic system works. Although the parameters of geometry and physics are clear, the forces that control performance of individual cells are still in the realm of conjecture. How millions of individual cells coordinate their function to bring about successful healing and maintenance of hemostasis is largely unknown. If all of the processes governing the formation, maintenance, and repair of the body were clear, then design of surgical procedures would be much less challenging. Biologic theories are created to provide guidelines that will direct clinicians and students to meet the challenge of deciding what to do. These theories help fill in the gaps of definitive understanding so that a useful treatment strategy can be formed. This knowledge base, although substantial, is imperfect and constantly evolving. As clinicians and scientists, we must always question the assumptions we were obligated to accept in order to complete the synthesis of the working theories upon which we base our treatment decisions. Expanding our understanding of how bone works is the most important step in the process of improving and innovating new skeletal reconstructive procedures. Typical clinical practice employs standardized technical protocols for surgical treatment. This approach is valuable because it limits unexpected outcomes arising from the wide range of providers’ technical abilities and preferences. However, it should never be assumed that achieving a good outcome is equivalent to having a complete understanding of the underlying biologic processes. The scientific approach always looks for flaws in the existing set of knowledge assumptions. Recognizing small inconsistencies between the expected and realized outcomes is the first step in enabling our understanding of nature to evolve. To the curious investigator, an unexpected result is an opportunity to look beyond existing theory in a direction that may yield further insight into basic biology. Contradictions to our assumptions deserve consideration and reconciliation according to the basic principles of the scientific process. The primary objective of this chapter is to offer an alternative window through which basic scientists and clinicians might view a patient outcome that cannot be explained by conventional theories. In some cases, a bad clinical outcome occurs despite rigorous adherence to the correct protocol in a patient without any compromising features. In other cases, a successful outcome is realized despite clear violation of multiple protocol requirements. These clinical anomalies are more than curiosities—these cases provide valuable clues about unexplained complexities in the biologic model. Aiming to understand the processes better in the most challenging exceptional case is the responsibility of all clinicians and fundamental scientists. These cases appear to defy the rules set down by currently accepted dogma and protocols. Interpreting more precisely what we see may be possible if the situation is assessed from the perspective of the underlying bone biology to help understand the outcomes we cannot otherwise explain. Like the process of biologic evolution, there is a sequence of knowledge evolution derived from progress by iteration. The potential for deliberate and incremental improvement in our knowledge and treatment

outcomes may overcome limitations created by automatically following traditional rote protocols. Designing novel treatments incorporating newly explored mechanisms of bone biology provides an opportunity to improve patient care. Reconstructing disorders of the facial skeleton can be accomplished through the use of bone-forming constructs. Application of this treatment method requires recognition of the mechanisms that regulate bone formation and maintenance. Instead of initiating replacement of a missing bone volume by filling the void with some foreign material, this approach recruits the existing biologic processes that are already operating in tissue adjacent to the defect. The same mechanisms that maintain the remaining anatomy can be used to potentiate replacement of the missing skeletal volume. The newly constructed skeletal unit incorporates the existing regulatory mechanism into the replacement volume and becomes integrated into the global patient physiology. No single material or simple procedure can replace the deliberate assembly of a bone-forming construct containing all of the essential elements for successful regeneration. Long-term stability requires that provisions be included in the surgical design for continued regulation of bone physiology over many years. To be successful, the bone-forming construct should include (1) a source of cells with bone-forming potential, (2) a mechanically stabilized environment, (3) a regulatory signaling source, and (4) control of incursion from infection. The manner in which each of these requirements is met depends on the specific nature of the deficiency under reconstruction, available materials, and the creativity of the surgeon. For example, a surgical design that deliberately takes account of and incorporates the regulatory potential of the embedded Sharpey network can yield results that are either improved or sometimes otherwise not possible at all. Beginning to appreciate how evolution has resulted in this elegant and complex system is the first step to novel improvement and more appropriate treatments. It is the responsibility of all clinicians to question what is assumed to be fact and to constantly seek better solutions.

Acknowledgments Appreciation is extended to Lauren K. Chin, RDHAP, for her assistance in writing this chapter and for providing the graphic illustrations of the clinical case presentations.

References 1. Chin M. Surgical Design for Dental Reconstruction with Implants: A New Paradigm. Chicago: Quintessence, 2015. 2. Chin M. Establishing and maintaining osseointegration within the functional matrix. Int J Periodontics Restorative Dent 2016;36:29–37.

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3. Wolff J. The Law of Bone Remodelling. Berlin: Springer-Verlag, 1986. 4. Moss ML, Salentijn L. The primary role of functional matrices in facial growth. Am J Orthod 1969;55:566–577. 5. Aaron JE. Periosteal Sharpey’s fibers: A novel bone matrix regulatory system? Front Endocrinol (Lausanne) 2012;12:98. 6. Aaron JE, Carter DH. Rapid preparation of fresh-frozen undecalcified bone for histological and histochemical analysis. J Histochem Cytochem 1987;35:361–369. 7. Aaron JE, Skerry TM. Intramembranous trabecular generation in normal bone. Bone Miner 1994;25:211–230. 8. Al-Qtaitat A, Shore RC, Aaron JE. Structural changes in the ageing periosteum using collagen III immuno-staining and chromium labelling as indicators. J Musculoskelet Neuronal Interact 2010;10:112–123. 9. Aaron JE. Cellular ubiquity of calcified microspheres: A matter of degree, ancient history and the Golgi body? J Biomed Sci 2016;5:3. 10. Aaron JE, Oliver B, Clarke N, Carter DH. Calcified microspheres as biological entities and their isolation from bone. Histochem J 1999;31:455–470. 11. Linton KM, Hordon LD, Shore RC, Aaron JE. Bone mineral “quality”: Differing characteristics of calcified microsphere populations at the osteoporotic and osteoarthritic femoral articulation front. J Biomed Sci Eng 2014;7:739–755. 12. Aaron JE. Bone turnover and microdamage. Adv Osteoporot Fract Manage 2003;2:102–110. 13. Carter DH, Scully AJ, Heaton DA, Young MP, Aaron JE. Effect of deproteination on bone mineral morphology: Implications for biomaterials and aging. Bone 2002;31:389–395. 14. Ingber DE. Tensegrity: The architectural basis of cellular mechanotransduction. Ann Rev Physiol 1997;59:575–599. 15. Ingber DE. Tensegrity I. Cell structure and hierarchical systems biology. J Cell Sci 2003;116:1157–1173.

16. Pautard FG. Calcium phosphate and the origin of backbones. New Sci 1961;12:364–366. 17. Pautard FGE, Williams RJP. Biological minerals. Chem Brit 1982;18:14–16. 18. Fallon V, Carter DH, Aaron JE. Mineral fabrication and Golgi apparatus activity in the mouse calvarium. J Biomed Sci Eng 2014;7:769–779. 19. Fallon V, Garner PE, Aaron JE. Mineral fabrication and Golgi apparatus activity in Spirostomum ambiguum: A primordial paradigm of the stressed bone cell? J Biomed Sci Eng 2017;10:466– 483. 20. Garner PE, Fallon V, Aaron JE. Spirostomum ambiguum: A protozoan model for primordial musculoskeletal exchange. Bone 2011;48:S140. 21. Linton KM, Tapping CR, Adams DG, Carter DH, Shore RC, Aaron JE. A silicon cell cycle in a bacterial model of calcium phosphate mineralogenesis. Micron 2013;44:419–432. 22. Aaron JE, Shore PA, Itoda M, et al. Mapping trabecular disconnection “hotspots” in aged human spine and hip. Bone 2015; 78:71–80. 23. Hordon LD, Itoda M, Shore PA, et al. Preservation of thoracic spine microarchitecture by alendronate: Comparison of histology and microCT. Bone 2006;32:444–449. 24. Harvold EP. The theoretical basis for the treatment of hemifacial microsomia. In: Harvold EP (ed). Treatment of Hemifacial Microsomia. New York: Alan R. Liss, 1983. 25. Hamilton WJ, Boyd JD, Mossman HW. Alimentary and respiratory systems, pleural and peritoneal cavities. In: Hamilton WJ, Mossman HW (eds). Hamilton, Boyd and Mossman’s Human Embryology, ed 4. Baltimore: Williams and Wilkins, 1972. 26. Chin M, Ng T, Tom WK, Carstens M. Repair of alveolar clefts with recombinant human bone morphogenetic protein (rhBMP-2) in patients with clefts. J Craniofac Surg 2005;16:778–789.

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CHAPTER 23

USING BMP-2 TO INCREASE BONE-TO-IMPLANT CONTACT Byung-Ho Choi, dds, phd

A

ugmentation of bone around the maxillary sinus is an important procedure for implant placement in the atrophic posterior maxilla.1 Researchers have described various maxillary sinus floor augmentation techniques for the management of severe bone loss in the posterior maxilla.2–4 Despite evidence of the benefits of sinus floor elevation, an extended healing period is required for the osseointegration of dental implants in severely atrophic maxillae.5–7 Adequate new bone formation following sinus augmentation is achieved only after 6 to 8 months of healing.8 Authors have investigated the use of different growth factors to overcome this limitation.9,10 Bone morphogenetic protein 2 (BMP-2) is considered a promising factor for the acceleration of bone regeneration.11 Studies have focused on how BMP-2 affects the volume of new bone in animal sinus models, but more research is still needed on the effects of adding BMP-2 to graft materials on the extent of bone-to-implant contact (BIC).12–15 Joo et al12 reported no significant difference in BIC when BMP-2 and a synthetic bone substitute were used in the maxillary sinus of rabbits. To provide more comprehensive data, an animal study was designed to determine the effect of BMP-2 on BIC when used in sinus augmentation. In addition, the effects of the addition of BMP-2 to graft materials on bone formation and implant stability in the early stages of healing have rarely been studied, particularly in patients with severely atrophic maxillae.9,10 Thus, a clinical study was conducted to evaluate the effects of BMP-2 on bone formation and implant stability during early-stage healing in this population.

Animal Study

Preparation of BMP-2-loaded collagen matrix Escherichia coli–derived BMP-2 (Novosis) was provided by the CGBio Institute. This BMP-2 was diluted in saline to a concentration of 0.25 mg/mL, and 250 mg of Bio-Oss collagen (Geistlich Pharma) was loaded with 600 μL of either BMP-2 or saline (control). BMP-2 was loaded in a sterilized culture dish using an auto pipette and was allowed to adsorb to the surface of the Bio-Oss collagen for 10 minutes. Subsequently, the experimental and control collagen samples were placed into the maxillary sinuses.

Surgical procedures All surgical procedures were performed under general anesthesia (ketamine, 5 mg/kg; xylazine, 2 mg/kg). The maxillary premolars and molars of each dog were bilaterally extracted before surgery. After 3 months, the edentulous region was opened with a buccal incision. The mucoperiosteal flap was reflected onto the buccal cortical plate, extending from the first maxillary premolar to the second maxillary molar. The lateral bone wall (10 × 15 mm) was subsequently removed using a round bur. After elevating the sinus membrane, Bio-Oss collagen soaked with saline was placed on one side of the maxillary sinus as a control, while Bio-Oss collagen loaded with BMP-2 was placed on the other side, called the BMP side (Fig 23-1a). The side on which the BMP and control collagen samples were placed was randomly selected in each animal. After bone grafting, a 10 × 4–mm UF(II) implant (DIO Implant) was placed in the maxillary sinus such that it penetrated the bone of the maxillary sinus floor (Fig 23-1b). After grafting and implant placement, the mucoperiosteal flap was replaced and sutured.

Animals Nine adult female mixed-breed dogs (weight, 15 to 20 kg) were used in this experiment.

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a

b

Fig 23-1  (a) View of the maxillary sinus showing that the space between the elevated sinus membrane and sinus floor was filled with Bio-Oss collagen. (b) View of Bio-Oss collagen immediately after placement in the maxillary sinus.

a

b

c

d

Fig 23-2  View of specimens. (a and b) On the BMP-2 side, the grafted particles were primarily surrounded by a layer of newly formed bone and there was a large amount of new bone on the lateral surface of the implant in direct contact with the implant. (c and d) On the control side, the particles were primarily surrounded by connective tissue and only small amounts of new bone were in direct contact with the implant (hematoxylin-eosin stain; original magnification ×5).

Sample preparation After a healing period of 3 months, the dogs were sacrificed and the bone blocks containing the implants were excised. The bone blocks were dehydrated in ethanol, embedded in methacrylate, and subsequently cut parallel to the implant axis in

the buccolingual plane. Histologic sections 20 μm thick were prepared using a cutting-grinding method and stained with hematoxylin and eosin. The histologic slides were observed, and images were captured digitally using a light microscope (BX50, Olympus).

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Animal Study

a

b

Fig 23-3  View of specimens. (a) On the BMP-2 side, a trabecular pattern of the new bone was observed on the top surface of the implants in direct contact with the implant surface. (b) On the control side, there was no direct deposition of bone on the surface of the implant (hematoxylin-eosin stain; original magnification ×5).

Table 23-1  Mean osseointegration and new bone formation rates on the BMP-2 and control sides of the dog study BMP-2 side

Control side

P values

Osseointegration rate

63.5% ± 15.4%

38.7% ± 8.8%

< .05

New bone formation rate

61.8% ± 8.9%

39.3% ± 8.4%

< .05

Histomorphometric analysis

Results

Morphometric assessment using an image analysis system (Image-Pro Plus, Media Cybernetics) was used to quantify the newly formed bone around the implants. To calculate the area of the newly formed bone in the graft sites, four sites on each slide were randomly selected. The area captured in each photograph was 3 × 3 mm. The new bone formation rate, defined as the area of newly formed bone divided by the total area of the site, was calculated. The calculation required outlining the newly formed bone. The BIC rate (measured in percentage), defined as the length of the bone surface border in direct contact with the implant perimeter, was also calculated.

At the time of surgery, the animals showed no clinical signs of sinus disorders. Postoperative healing was uneventful in all cases. Three months after sinus augmentation, an examination of the bone specimens revealed that on the BMP-2 side, the grafted particles were primarily surrounded by a layer of newly formed bone (Fig 23-2a). The new bone formation rate was 61.8% ± 8.9%. Furthermore, the new bone was in direct contact with the implants, enhancing the BIC (Fig 23-2b), and the mean BIC rate was 63.5% ± 15.4%. On the control side, the grafted particles were primarily surrounded by connective tissue (Fig 23-2c), and only a small amount of the new bone was in direct contact with the implants (Fig 23-2d). The new bone formation rate was 39.3% ± 8.4%, and the mean BIC rate was 38.7% ± 8.8%. The newly formed bone was barely visible on the top surface of the implants on the control side. On the BMP-2 side, a trabecular pattern of the new bone was observed on the top surface of the implants in direct contact with the implant (Fig 23-3). The quantitative morphometric analysis showed significantly more BIC and new bone formation on the BMP-2 side than on the control side (Table 23-1).

Statistical analysis The Mann-Whitney U test was used to calculate statistical differences between the two treatment groups. P < .05 was considered significant.

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23  USING BMP-2 TO INCREASE BONE-TO-IMPLANT CONTACT

Fig 23-4  Surgical template design.

Human Study Patient selection There were 38 adult patients who participated in this study (20 men and 18 women; mean age, 48.3 years; range, 37–66 years). Patient selection was based on the availability of computed tomography (CT) studies. The following inclusion criteria were used: •  Patients requiring implant treatment in the posterior maxilla •  Residual bone height of 1 to 3 mm at the estimated implant positions Patients were excluded if they had acute or chronic sinus disease, were pregnant, had insulin-dependent diabetes, were taking medications or receiving treatments known to affect bone turnover, or had a disease affecting bone metabolism.

Preparation of the BMP-2-loaded collagen matrix The BMP-2-loaded collagen matrix was prepared as described previously.

Virtual planning The sinus elevation technique was performed by a sinus augmentation procedure using a hydraulic sinus elevation instrument (DIO Flapless Crestal Sinus Kit, DIO Implant) via the transcrestal approach combined with computer-guided flapless implant surgery. Before surgery, cone beam CT (CBCT) data acquisition of the maxilla and mandible was performed using

a Point 3D Combi 500C dental CT scanner (PointNix). When the scan was complete, digital impressions of both arches were obtained using an intraoral scanner (TRIOS, 3Shape). Digital stereolithography (STL) files generated from the intraoral scan were imported into virtual implant planning software (Implant Studio, 3Shape). Digital imaging and communications in medicine (DICOM) data acquired from the CBCT scan were imported into the virtual implant planning software and were merged with the STL files. Image fusion of the intraoral scan data and DICOM data was performed via semiautomatic three-dimensional (3D) object adjustment. After image fusion, a prosthetically driven implant surgical plan was executed in the fused virtual model using virtual implant planning software. Once implant planning was complete, the generated data were used to design a surgical template (Fig 23-4). After completion of the virtual surgical template, the actual surgical template was printed using a 3D printer (ProJet 3510 MP, 3D Systems).

Surgical procedure Antibiotic prophylaxis (ie, amoxicillin) was provided to patients approximately 1 hour before surgery and was continued for 3 days after surgery. Computer-guided flapless implant surgery was performed under local anesthesia. First, the surgical guide was placed in the patient’s mouth. The tissue punch was the first drill used in the sequence (Fig 23-5a). An implant osteotomy was then prepared up to 1 mm short of the sinus floor (Fig 23-5b). The drilling depth was controlled by a drill stop in the shank that corresponded to the sum of the implant length, gap between the guiding sleeve and implant, and guiding sleeve height (see Fig 23-6). After drilling to 1 mm short of the sinus floor, a dome-shaped transcrestal approach bur was used to eliminate the remaining bone below the sinus floor (Fig 23-5c). The bur was used at a speed of less than 10 rpm. During drilling, the drill depth was controlled with drill stops and surgical guides. After puncturing the sinus floor, hydraulic pressure was used to elevate the sinus membrane. The hydraulic pressure was generated by injecting saline into the sinus floor through the drill hole. First, the nozzle of the hydraulic membrane lifter was positioned in the opening of the drill hole and secured in place. Subsequently, 0.6 mL of saline was slowly injected to separate the sinus membrane from the bony sinus floor and to push the membrane upward (Fig 23-5d). The sinus membrane integrity was tested immediately after elevation. All of the injected saline was drawn back up, and the syringe showed negative pressure, suggesting that the membrane was not perforated. After the sinus membrane was elevated, the bone grafting procedure was performed. Bio-Oss collagen loaded with BMP-2 was cut into pieces and inserted into the sinus cavity through the drill hole using a bone plugger (Fig 23-5e). The amount of grafting material inserted was determined by the height of the membrane elevation. To elevate the membrane by 5 mm, 250 mg of Bio-Oss collagen was inserted, and to elevate by

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Human Study

a

b

c

d

e

f

Fig 23-5  Sinus augmentation procedure using a hydraulic sinus elevation instrument with the transcrestal approach combined with computer-guided flapless implant surgery. (a) Tissue punch. (b) Drilling to 1 mm short of the sinus floor. (c) A dome-shaped transcrestal approach drill eliminated the remainder of the bone below the sinus floor. (d) Saline was injected to separate the sinus membrane from the bony sinus floor. (e) The graft material was inserted into the maxillary sinus using a bone plugger. (f) The implant and bone graft were placed simultaneously.

Fig 23-6  Drilling through the surgical template.

Fig 23-7  Immediate restoration with prefabricated resin provisional crowns. The occlusion and articulation of the crowns were adjusted out of contact with the opposing teeth.

10 mm, 500 mg of Bio-Oss collagen was inserted. Before the placement of the implant, final drilling was performed 1 mm beyond the sinus floor through the surgical guide to enlarge the sinus floor. The osteotomy was enlarged to 1.8 mm less than the anticipated implant diameter to increase implant stability. The implants were subsequently placed with guidance from the surgical template (Figs 23-5f and 23-6). When more than two

implants were placed in one side of the maxillary sinus, they were splinted to each other using customized abutments and a provisional restoration that was fabricated before surgery (Fig 23-7). The restoration process followed the immediate nonfunctional loading concept by adjusting the crown to avoid contact with the opposing teeth.

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a

b

Fig 23-8  Typical coronal CT images before (a) and 3 months after (b) maxillary sinus augmentation. Note in part a the minimum amount of residual crestal bone (≤ 3 mm).

a

b

Fig 23-9  Typical sagittal CT images before (a) and 3 months after (b) maxillary sinus augmentation.

Endosinus bone height assessment

Implant stability measurement

The endosinus bone height was assessed using CT scans acquired preoperatively and 3 months after placement of the BMP-2-loaded collagen matrix and dental implants. The height of the endosinus bone gain, defined as the mean height of the new bone on the buccal and palatal aspects of the implant, was measured.

The implant stability was examined 3 months postoperatively using the Periotest device (Medizintechnik Gulden). The Periotest value (PTV) ranged from –8 to 50.

Bone quality analysis The density of the newly formed bone was assessed using CT scans obtained 3 months after placement of the BMP-2-loaded collagen matrix and dental implants. Four rectangular areas (1×1 mm) were marked over the image, which excluded the cortical bone. All areas were at least 2 mm away from the dental implant. Bone density readings were subsequently obtained from the areas and recorded in Hounsfield units (HU). The bone density was averaged for the four rectangular areas of all graft sites.

Results During surgery, initial stabilization was achieved for all implants with an insertion torque of 15 Ncm or greater, and membrane perforation did not occur in any of the cases. All patients underwent unilateral sinus surgery. Although most patients received two implants into the grafted sinus, five patients received three implants and two received one implant. All implants were 5 mm in diameter and 10 mm in length. No patients showed signs of inflammation or other adverse tissue reactions during the experimental period. Figures 23-8 and 23-9 present CT scans from patients treated with the BMP-2-loaded collagen matrix. The scans revealed that in all patients, the augmented sinus had a dome-shaped appearance. The mean bone height was 8.4 ±

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Conclusion

1.6 mm (range: 6.5 to 12.4 mm). The recorded HU at the graft sites ranged from 643 to 1,201 HU (average: 887 ± 177 HU), indicating a high level of bone density. The PTV ranged from –6 to +1 (average: –3.0 ± 2.1), indicating good implant stability.

Discussion The animal and human studies revealed that maxillary sinus floor augmentation with the BMP-2-loaded collagen matrix yielded a well-formed sinus bone, an improvement in BIC, a high level of bone density, and good implant stability in the early stage of healing. These results indicated that the BMP-2loaded collagen matrix allows successful implantation with sinus augmentation, even when the bone height is minimal. These observations are not in concordance with findings of previous animal experiments and clinical studies.10,12 Joo et al12 placed a synthetic bone substitute loaded with BMP-2 in the maxillary sinus of rabbits simultaneously with implant placement and observed no difference in the BIC between the BMP and control sides. Boyne et al10 placed an absorbable collagen sponge (ACS) loaded with BMP-2 into the maxillary sinus without implant placement and reported that BMP-2/ACS yielded lower gain in bone formation and bone density than did a bone graft alone. The most likely explanation for the inconsistency in these results is the carrier material. BMP requires a carrier material that serves as a scaffold for cellular growth and attachment.16 In the present study, Bio-Oss collagen was used as a carrier for BMP-2; it is commonly used as a sponge-type grafting material and is composed of 90% calf cancellous bone and 10% pig collagen. Although collagen sponge is the best carrier for BMP-2, it may not be suitable for maintaining the space under the elevated sinus membrane because it can be quickly resorbed.17 However, the Bio-Oss collagen sponge is suitable because Bio-Oss bone particles maintain their shape without rapid resorption once inside the sinus cavity.18 Moreover, structural and morphologic characteristics favor the proliferation of blood vessels and migration of bone cells, and the qualities of hemostasis, proangiogenesis, and flexibility allow for better material accommodation.19–22 In addition, the authors in this study performed simultaneous sinus elevation and implantation. When an implant was placed with grafting material, it could help maintain the elevated sinus membrane. This might be a reason why adequate new bone formation was achieved in the sinus; the average bone height was 8.4 ± 1.6 mm.

Considerations with BMP-2 An interesting finding of the animal study was that BIC at the early stage of healing was improved by new bone growth between threads on the BMP-2 side. The sites between the threads were the most distant from osteogenic sources, such as the parental

bone and sinus membrane, resulting in a relative lack of new bone formation. In the present study, the BMP-2-loaded collagen matrix seemed to facilitate angiogenesis in areas distant from the osteogenic sources by providing an appropriate environment for rapid revascularization. This observation demonstrated that BMP-2 could result in earlier and increased bone regeneration in the maxillary sinus, offering improved BIC at the early stage of healing and reducing the healing time. Dental implants can be placed either simultaneously in a single-stage procedure or in two stages when the atrophic posterior maxilla is to be augmented by sinus floor elevation.23 If primary stability of the implant is achievable, the single-stage technique may be preferred because it reduces the overall treatment period and makes the second stage for implant placement uncessary.24 About 4 to 5 mm of alveolar bone height is the minimum amount of bone necessary to provide initial implant stability.24 Therefore, when the alveolar bone height is less than 4 to 5 mm, a two-stage procedure is recommended. The present study revealed that it was possible to perform simultaneous implant placement with sinus elevation in a single-stage procedure when the alveolar bone height was 1 to 3 mm. However, there are two primary concerns: the initial stability of the implant and maintenance of that stability. Improvements in surgical techniques make it easier to achieve good initial implant stability. In the present study, initial implant stability with 1 to 3 mm of residual bone height was achieved using both a surgical template and an undersized drilling procedure (1.8 mm less than the anticipated implant diameter). The use of a surgical guide optimized the drilling procedure by preventing drill wobbling. Furthermore, it optimized the implant placement by guiding the implants. The implants were placed as planned in all cases, which facilitated immediate provisional restoration of the implants. Stability maintenance could be achieved by splinting implants together with a provisional prosthesis fabricated before surgery. The fact that the prefabricated prosthesis was placed onto the implants demonstrated the clinical efficiency of the described approach. To reduce potential implant overload, the prosthetic crowns were prepared away from occlusion. A wide range of BMP-2 concentrations has been used in preclinical sinus augmentation models.25,26 High-dose BMP-2 in clinical practice may contribute to the numerous adverse effects observed in humans.27 Therefore, the use of BMP-2 at lower doses may reduce the side effects.28 The low concentration of BMP-2 (0.25 mg/mL) used in the present animal and human studies successfully accelerated bone regeneration without adverse tissue reactions.

Conclusion The addition of BMP-2 to Bio-Oss collagen in sinus augmentation can increase osseointegration, bone formation, bone density, and implant stability in the early stage of healing, thereby reducing

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the healing time. Transcrestal sinus augmentation using a BMP-2 and collagen matrix allograft and simultaneous implant placement seem effective for enhanced bone formation in the early stages of healing in patients with a severely atrophic maxilla, offering improved implant stability.

References 1. Kahnberg KE, Ekestubbe A, Gröndahl K, Nilsson P, Hirsch JM. Sinus lifting procedure. I. One-stage surgery with bone transplant and implants. Clin Oral Implants Res 2001;12:479–487. 2. Wetzel AC, Stich H, Caffesse RG. Bone apposition onto oral implants in the sinus area filled with different grafting materials. Clin Oral Implants Res 1996;6:155–163. 3. Acocella A, Bertolai R, Nissan J, Sacco R. Clinical, histological and histomorphometrical study of maxillary sinus augmentation using cortico-cancellous fresh frozen bone chips. J Craniomaxillofac Surg 2011;39:192–199. 4. Zhang Y, Tangl S, Huber CD, Lin Y, Qiu L, Rausch-Fan X. Effects of Choukroun’s platelet-rich fibrin on bone regeneration in combination with deproteinized bovine bone mineral in maxillary sinus augmentation: A histological and histomorphometric study. J Craniomaxillofac Surg 2012;40:321–328. 5. Nishibori M, Betts NJ, Salama H, Listgarten MA. Short-term healing of autogenous and allogeneic bone grafts after sinus augmentation: A report of 2 cases. J Periodontol 1994;65:958–966. 6. Wallace SS, Froum SJ, Tarnow DP. Histologic evaluation of a sinus elevation procedure: A clinical report. Int J Periodontics Restorative Dent 1996;16:46–51. 7. Lorenzetti M, Mozzati M, Campanino PP, Valente G. Bone augmentation of the inferior floor of the maxillary sinus with autogenous bone or composite bone grafts: A histologic-­ histomorphometric preliminary report. Int J Oral Maxillofac Implants 1998;13:69–76. 8. Wallace SS, Froum SJ. Effect of maxillary sinus augmentation on the survival of endosseous dental implants. A systematic review. Ann Periodontol 2003;8:328–343. 9. Triplett RG, Nevins M, Marx RE, et al. Pivotal, randomized, parallel evaluation of recombinant human bone morphogenetic protein-2/absorbable collagen sponge and autogenous bone graft for maxillary sinus floor augmentation. J Oral Maxillofac Surg 2009;67:1947–1960. 10. Boyne PJ, Lilly LC, Marx RE, et al. De novo bone induction by recombinant human bone morphogenetic protein-2 (rhBMP-2) in maxillary sinus floor augmentation. J Oral Maxillofac Surg 2005;63:1693–1707. 11. Jung RE, Weber FE, Thoma DS, Ehrbar M, Cochran DL, Hämmerle CH. Bone morphogenetic protein-2 enhances bone formation when delivered by a synthetic matrix containing hydroxyapatite/tricalciumphosphate. Clin Oral Implants Res 2008;19: 188–195. 12. Joo MJ, Cha JK, Lim HC, Choi SH, Jung UW. Sinus augmentation using rhBMP-2-loaded synthetic bone substitute with simultaneous implant placement in rabbits. J Periodontal Implant Sci 2017;47:86–95.

13. Kim JS, Cha JK, Cho AR, et al. Acceleration of bone regeneration by BMP-2-loaded collagenated biphasic calcium phosphate in rabbit sinus. Clin Implant Dent Relat Res 2015;17:1103–1113. 14. Choi Y, Yun JH, Kim CS, Choi SH, Chai JK, Jung UW. Sinus augmentation using absorbable collagen sponge loaded with Escherichia coli–expressed recombinant human bone morphogenetic protein 2 in a standardized rabbit sinus model: A radiographic and histologic analysis. Clin Oral Implants Res 2012; 23:682–689. 15. Park JB. Use of bone morphogenetic proteins in sinus augmentation procedure. J Craniofac Surg 2009;20:1501–1503. 16. Seeherman H, Wozney J, Li R. Bone morphogenetic protein delivery systems. Spine (Phila Pa 1976) 2002;27:16–23. 17. Lee J, Susin C, Rodriguez NA, et al. Sinus augmentation using rhBMP-2/ACS in a mini-pig model: Relative efficacy of autogenous fresh particulate iliac bone grafts. Clin Oral Implants Res 2013;24:497–504. 18. Fontana F, Rocchietta I, Dellavia C, Nevins M, Simion M. Biocompatibility and manageability of a new fixable bone graft for the treatment of localized bone defects: Preliminary study in a dog model. Int J Periodontics Restorative Dent 2008;28:601–607. 19. Acil Y, Terheyden H, Dunsche A, Fleiner B, Jepsen S. Threedimensional cultivation of human osteoblast-like cells on highly porous natural bone mineral. J Biomed Mater Res 2000;51:703– 710. 20. Heinemann F, Hasan I, Schwahn C, Bourauel C, Mundt T. Bone level change of extraction sockets with Bio-Oss collagen and implant placement: A clinical study. Ann Anat 2012;194:508–512. 21. Rohner D, Hailemariam S, Hammer B. Le Fort I osteotomies using Bio-Oss collagen to promote bony union: A prospective clinical split-mouth study. Int J Oral Maxillofac Surg 2013;42: 585–591. 22. Araújo M, Linder E, Wennstroöm J, Lindhe J. The influence of Bio-Oss collagen on healing of an extraction socket: An experimental study in the dog. Int J Periodontics Restorative Dent 2008;28:123–135. 23. Jensen OT, Shulman LB, Block MS, Iacono VJ. Report of the Sinus Consensus Conference of 1996. Int J Oral Maxillofac Implants 1998;13(suppl):11–45. 24. Peleg M, Mazor Z, Chaushu G, Garg AK. Sinus floor augmentation with simultaneous implant placement in the severely atrophic maxilla. J Periodontol 1998;69:1397–1403. 25. Hanisch O, Tatakis DN, Rohrer MD, Wöhrle PS, Wozney JM, Wikesjö UM. Bone formation and osseointegration stimulated by rhBMP-2 following subantral augmentation procedures in nonhuman primates. Int J Oral Maxillofac Implants 1997;12: 785–792. 26. Gutwald R, Haberstroh J, Stricker A, et al. Influence of rhBMP-2 on bone formation and osseointegration in different implant systems after sinus-floor elevation. An in vivo study on sheep. J Craniomaxillofac Surg 2010;38:571–579. 27. Kaneko H, Arakawa T, Mano H, et al. Direct stimulation of osteoclastic bone resorption by bone morphogenetic protein (BMP)-2 and expression of BMP receptors in mature osteoclasts. Bone 2000;27:479–486. 28. Cha JK, Lee JS, Kim MS, Choi SH, Cho KS, Jung UW. Sinus augmentation using BMP-2 in a bovine hydroxyapatite/collagen carrier in dogs. J Clin Periodontol 2014;41:86–93.

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CHAPTER 24

TISSUE-ENGINEERED BONE AND CELL-CONDITIONED MEDIA Hideharu Hibi, dds, phd | Wataru Katagiri, dds, phd | Shuhei Tsuchiya, dds, phd | Masahiro Omori, dds, phd | Minoru Ueda, dds, phd

P

ractitioners who perform dental implant surgery in the oral and maxillofacial field use a variety of materials for sinus grafting, including allogenic bone, xenogenic bone-derived materials, synthetic materials, and more. While autogenous bone is considered the best overall option in terms of efficacy and safety, this type of bone grafting may cause patients additional issues at their donor site, limiting its application. In an effort to overcome these limitations, researchers have extensively studied bone regeneration to identify improved approaches. The authors have carried out translational research on bone regeneration using tissue-engineered bone (TEB), a complex of autogenous mesenchymal stem cells (MSCs) and platelet-rich plasma (PRP) prepared from bone marrow aspirates and the peripheral blood.1 The clinical applications of this research were included in the section “Looking to the Future” in the previous edition of this book. This chapter includes a change in concepts and new techniques developed through work concerning bone regenerative medicine.

Approaches to Bone Regenerative Medicine Using TEB TEB is composed of osteogenic cells differentiated from MSCs, growth factors contained in platelets, and the fibrinous network of plasma. These components provide the respective elements required for tissue regeneration: functional cells, appropriate growth signals, and a support scaffold. An overview of the standard methodology for the preparation and use of TEB is shown in Fig 24-1. Prior to initiating the protocol, the eligibility of a patient should be considered based on predetermined criteria

such as whether the patient is suffering from anemia or any infections. Once the patient has been screened and admitted to the protocol, either 200 or 400 mL of peripheral blood is collected approximately once per month for 3 months. The serum is then separated from the blood sample and cryopreserved for subsequent cell culturing. In addition to peripheral blood, a few milliliters of bone marrow aspirate from the iliac crest are collected using a bone puncture needle under local anesthesia. The wall-adherent cells are separated from the bone marrow aspirate and cultured in basal medium with the autogenous serum for approximately one month. Once the cell count has reached a planned level, the bone marrow cells are differentiated into osteogenic cells for approximately one week. Following the collection and processing of the sera and bone marrow cells, peripheral blood is collected to prepare the PRP. The PRP and the cultured cells are combined, allowing the formation of a complex between the cells and the PRP. Gelatinization of this complex with thrombin and calcium chloride results in the formation of TEB. The TEB is prepared fresh at the time of use and is applied with a syringe to fill the bonedefect cavity. When TEB is applied to the space created at the time of maxillary sinus floor elevation, the amount of newly formed bone remains sufficient to support dental implants even 2 years later.2 This is based on the findings from 16 sinuses in 12 patients, which had an average elevation height of 8.8 ± 1.6 mm.2 The procedure is also effective in patients with vertical ridge resorption or an alveolar cleft greater than 10 mm.3,4 It is even possible to guide unerupted or impacted teeth to a proper position using this technology. As a whole, these results demonstrate TEB as a promising graft material for bone augmentation.

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a

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Fig 24-1  Cell-based therapy for bone regeneration with TEB. (a) Iliac bone marrow aspiration under local anesthesia. (b) Technician culturing cells. (c) Processing of autogenous marrow fluid and serum. (d) Incubation of samples. (e) MSCs in culture. (f) Mixing of osteogenic cells differentiated from MSCs and PRP. (g) Gelatinized TEB ready for use.

Changes in the environment of bone regenerative medicine Despite the known efficacy of TEB, it remains unlikely that its use will become widespread unless it can be made more cost effective. Human allogenic MSCs were first marketed in the United States for bone augmentation in the oral and maxillofacial field in 2010. In Japan, a bovine-derived bone substitute was approved in 2011 for periodontal use only, nearly 20 years after approval in the United States and Europe. While these products sell for several hundred dollars, TEB products cost more than $5,000 for the materials alone. In addition, the cost for construction of a cell-processing facility can be $2 million with annual maintenance and operation expenses exceeding $600,000. An alternative to large-scale cell-processing facilities is new generation of cell preparation equipment, including isolators and automatic culture machines. However, while the cost of installing and operating cell-based equipment has been reduced, it remains in the hundreds of thousands of dollars. Further research provided insight into the efficacy of TEB as a regenerative material, and the authors found that bone regeneration outcomes using TEB depend largely on the morphology of the defects. When the number of bony walls surrounding the defect is decreased, the amount of regenerated bone decreases proportionately. No specific relationship is observed between the number of cells applied to the bone defect site and the

amount of regenerated bone. Furthermore, autogenous cells cultured ex vivo have substantially lower survival rates following their return to the donor. These cells often regenerate tissues indirectly rather than directly. To be more precise, they recruit endogenous stem cells and precursor cells via paracrine effects, with the recruited cells regenerating the tissue at a higher rate.5,6

Changes in strategy for achieving success in bone regenerative medicine As the mechanisms of tissue regeneration became clearer, researchers began to consider alternative strategies for bone regeneration without the use of cell culture. A German group conducting similar studies using osteogenic cells derived from the periosteum demonstrated limitations in bone regeneration.7,8 In response, they developed a new approach that used autogenous bone marrow concentrate rich in mononuclear cells in conjunction with bovine bone mineral.9 The graft procedure may be completed in an operating room without the need for culturing or a specialized cell-processing facility. Because of the previously noted problems, along with tighter legal regulations on regenerative medicine, future studies employed a different strategy regarding bone regenerative medicine.10 Recent studies show that implanted cells contribute to tissue regeneration through both pluripotency and paracrine

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CCM for Bone Regeneration

Autogenous cells

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Fig 24-2 Strategy changes for achieving regenerative medicine success. (a) Cell-based therapy faces problems associated with the conventional concepts of returning cultured autogenous cells back into the body. (b) Cell-free therapy may use both autogenous and allogenic CCM, which contain growth factors and matrices released from cells. These factors recruit endogenous stem cells and precursor cells that work to regenerate tissue. The identification of the active components in CCM and their formulation as drugs will solve many problems associated with cell-culture-based therapy.

effects.11 Therefore, a different approach to bone regeneration was investigated. This approach still used cultured cells but did not reintroduce the cells back into the donor.5,6,11 Instead, the focus was switched to using cell-conditioned media (CCM), not the conditioned cells themselves (Fig 24-2). Because cells release various growth factors and substrates, the authors instead created a product of the cells (ie, CCM). The hypothesis was that the application of the CCM will recruit endogenous stem cells and precursor cells into the bone defect site and result in regeneration of the bone. This approach excludes reintroducing cultured cells. In addition, the identification of active components in the CCM may serve as the basis for synthesis and formulation of drugs independent of cell culture. This could not only allow for more controlled treatments, but it may also solve problems associated with the use of cell culture.

CCM for Bone Regeneration

approxi­mately 2,000 proteins, including growth factors and extracellular matrix (ECM) proteins associated with bone formation, such as collagen-1, bone sialoprotein-2, osteopontin, osteocalcin, fibronectin, vascular endothelial growth factor A (VEGF-A), decorin, and others.11–19 Interestingly, commercially available bone morphogenetic protein (BMP), platelet-derived growth factor BB, and fibroblast growth factor 2 are not detected even though they are reported to be effective in bone formation. CCM applied to the bone defect site with agarose gel or collagen sponge as a scaffold stimulates stem cell and precursor cell migration, resulting in vascularization of the tissue bed and bone regeneration.6,13–21 These findings provide insight into the mechanisms of bone regeneration with CCM. The authors’ studies with CCM also include investigation of its use in clinical settings of bone regeneration related to titanium (Ti) implants, membrane-guided regeneration, and graft materials.12,13,17,18 These preclinical laboratory studies translated to initial clinical studies looking to regenerate bones with the combined use of autogenous CCM and calcium phosphate–based granules and have subsequently advanced to the use of allogenic CCM.

Comprehensive analyses of bone marrow–derived CCM and dental pulp–derived stem cell–conditioned media have identified

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Box 24-1  Preparation of CCM 1. The stem cells are cultured in basal medium. 2. They reach 70% to 80% confluency following passages of the cell culture. 3. The medium is refreshed with serum-free Dulbecco’s Modified Eagle’s Medium (Sigma-Aldrich). 4. Cells are incubated for 48 hours. 5. The CCM is collected. 6. The CCM is centrifuged. 7. The CCM is filtered. 8. The CCM is processed.

b

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Fig 24-3  Preparation of MSC-CM for implantation with different scaffolds. (a) Dissolving lyophilized MSC-CM in saline just before application. (b) Infiltrating MSC-CM into porous β-TCP granules. (c) Atelocollagen sponge. (Reprinted with permission from Katagiri et al.22)

Preparation of CCM The standard method for the preparation of CCM is depicted in Box 24-1. Stem cells with mesenchymal characteristics (derived from bone marrow, dental pulp, or other appropriate sources) are cultured and processed at 37°C, 5% CO2 in basal medium using standard methods. When the cells reach 70% to 80% confluency following the final round of passage, the medium is refreshed with serum-free Dulbecco’s Modified Eagle’s Medium (Sigma-Aldrich) and incubated for an additional 48 hours. The cell culture medium is then collected and clarified by centrifugation, and the supernatant is recovered. Following a second centrifugation, the supernatant is passed through a 0.22-µm filter to remove any remaining cells or cellular debris. The processed supernatant at this point is the final CCM. The CCM can be stored at 4°C, or it may be lyophilized with ethanol through step-by-step centrifugation and stored at –80°C until use.

Clinical application of CCM to graft material Based on the preclinical experimental studies, the authors applied CCM generated from cultured human bone marrow– derived MSCs (MSC-CM) to sinus graft material in a preliminary clinical study.22,23 Six partially edentulous patients were enrolled in the study and divided into experimental (n = 4) and control (n = 2) groups. To identify potential allergies to the MSC-CM, a safety evaluation in the experimental group was performed before application of the MSC-CM. The evaluation included a

skin patch test and the drug lymphocyte stimulation test, and all safety results were negative. OSferion (Olympus Terumo Biomaterials), a pure porous β-tricalcium phosphate (β-TCP), was used as scaffold in both groups. The experimental group was implanted with scaffold material plus MSC-CM, while the controls were implanted with scaffold material only. Just prior to application, lyophilized MSC-CM was reconstituted in saline22 (Fig 24-3). For the experimental group, 1 g β-TCP was soaked in 3 mL of MSC-CM for at least 5 minutes. In the control group, the β-TCP was instead soaked in saline. For the subjects in each group, the corresponding graft material was applied to the sinus floor elevation cavity formed from the standard lateral window technique. Neither systemic nor local clinical complications were observed. The lack of clinically observed complications was consistent with results from computed tomography (CT) and blood tests that were used to check for inflammation, allergic reactions, and organ dysfunction both before and after treatment application. After 6 months, the grafts were biopsied with a trephine bur during implant surgeries and evaluated histologically22 (Figs 24-4 and 24-5). Remnants of β-TCP were observed at the edge of the specimens along with new bone formation in each specimen. Grafts from the experimental group contained lamellar bone, while the control group grafts consisted mainly of woven bone with infiltration of inflammatory cells. Osteoblasts and osteoclasts were present around the new bone and β-TCP remnants in both groups, but the number of cells and the amount of newly formed bone replacing the β-TCP were greater in the experimental group. Additionally, more vascularization was present in the experimental group, especially in the central regions of the specimens. Histomorphometric analysis revealed that the

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Fig 24-4 A 46-year-old woman in the experimental group implanted with scaffold material plus MSC-CM. (a) Implant and cavity created by sinus floor elevation. (b) Scaffold β-TCP granules containing MSC-CM filled into the cavity. (c) Six-month-old graft biopsied with a trephine bur during implant uncovering surgery. (d) CT image prior to application. (e) CT image 3 months after application. (f) CT image 6 months after application. (Reprinted with permission from Katagiri et al.22)

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Fig 24-5 Histology of specimens from the experimental group implanted with scaffold material plus MSC-CM (a to d) and control group implanted with scaffold material only (e to h). (a and e) Outline of the specimen (original magnification ×12.5). (b and f) Alveolar side of the specimen (original magnification ×100). (c and g) Center of the specimen (original magnification ×100). (d and h) Sinus side of specimen (original magnification ×100). Hematoxylin-eosin stain. Black arrows, osteoblasts; green arrows, osteoclasts; arrowheads, inflammatory cells; AB, alveolar bone; NB, newly formed bone; TCP, β-TCP granules; V, blood vessel. (Reprinted with permission from Katagiri et al.22)

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N-PBS

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Fig 24-6  In vitro analysis of cell attachment to Ti disks. (a) Quantitation of the number of MSCs attaching on Ti disks 1 and 24 hours after seeding. *P < .05, **P < .01. (b to e) Confocal micrographs of MSCs 24 hours after seeding on Ti disks. 4’,6-diamidino-2-phenylindole stain for nuclei (blue) and rhodamine phalloidin stain for actin filaments (red). (Reprinted with permission from Omori et al.25)

newly formed bone area was significantly larger in the experimental group than the control group, especially at the center of the specimens. Previous studies revealed that MSC-CM contains several cytokines, including insulin-like growth factor 1 (IGF-1), VEGF, and transforming growth factor β1 (TGF-β1).11–19 Each of the agents has its own effect on bone regeneration. IGF-1 regulates the migration of osteoblasts and MSCs. Sustained systemic or local infusion of IGF-1 enhances osteogenesis. VEGF is the main regulator of angiogenesis, enhancing survival and differentiation of endothelial cells and promoting osteogenesis. TGF-β1 enhances the migration of osteoprogenitor cells and regulates cellular proliferation, differentiation, and ECM production. In addition to their individual activities, these growth factors act synergistically to promote cell migration, angiogenesis, and osteogenesis. Recent studies also reveal that MSC-CM promotes bone formation through enhancing endogenous stem cell migration, osteogenic differentiation, and angiogenesis in vitro and in vivo.6,12–21 In a rabbit model of sinus augmentation, cell proliferation and vascularization significantly increased by 2 weeks after graft implantation with MSC-CM, indicating that MSC-CM is effective in the early phase of angiogenesis and osteogenesis and that early vascularization enhances proliferation and migration of osteoprogenitor cells into the centers of the augmented areas with limited blood supply.17 BMP-2 is commercially available and has been used widely in sinus augmentation with a relatively high level of efficacy. Achieving a sufficient volume of bone formation requires high doses of BMP-2, which accordingly is dose dependent. However,

local concentrations greater than physiologic levels may cause adverse events such as facial edema due to a localized inflammatory response.24 The MSC-CM used in this study contained IGF-1, VEGF, and TGF-β1 at pg/mL levels, which is approximately 1/1,000 of the concentration of the BMP-2. These lowerdose combinations of multiple growth factors in the MSC-CM may be beneficial in avoiding inflammatory responses as well as preventing other adverse events. MSC-CM can effectively shorten the time required for the degradation and replacement of β-TCP with new bone without triggering unfavorable reactions and potentially promising safe clinical application for sinus grafts.

Application of CCM to the pretreated implant surface Atmospheric pressure plasma (APP) is effective in the antiaging of implant surfaces, similar to ultraviolet light and hydrothermal treatments. Stem cells from human exfoliated deciduous teeth (SHED) are highly proliferative, postnatal stem cells capable of differentiating into odontoblasts, adipocytes, neural cells, and osteogenic cells. SHED cells have even greater bio­­ active capabilities than do bone marrow–derived MSCs. Therefore, the authors studied the effects of APP treatment and SHED-CM on the osseointegration and osteogenesis around Ti implants.12,19,25 APP-treated or nontreated Ti specimens of disks and implants were soaked and agitated in SHED-CM or phosphate-buffered

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CCM for Bone Regeneration

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Fig 24-7  Radiologic analysis on bone formation around Ti implants in vivo. Micro-CT images of Ti implants in canine femur 4 weeks (a to h) and 8 weeks (i to p) after implantation. (Reprinted with permission from Omori et al.25)

saline (PBS) for 24 hours at 37°C. This resulted in four experimental groups: •  Non-APP treated Ti soaked in PBS (N-PBS) •  APP-treated Ti soaked in PBS (P-PBS) •  Non-APP treated Ti soaked in SHED-CM (N-CM) •  APP-treated Ti soaked in SHED-CM (P-CM) A controlled number of MSCs were seeded onto the Ti disks and cultured at 37°C, 5% CO2 for either 1 or 24 hours. Cell counts were done to quantify the number of cells attached to each disk. The number of attached cells did not significantly differ among the four experimental groups after 1 hour in culture, but after 24 hours the P-CM group had more cells attached than did the other groups25 (Fig 24-6). The four groups of Ti implants were inserted into canine femurs and evaluated by micro-CT. Radiopacity indicating calcified tissue formation around the implants was higher in the P-CM group than the

other groups at both 4 and 8 weeks postimplantation25 (Fig 24-7). As seen in Fig 24-8, histologic analysis revealed that newly formed bone around the implant was continuous in the P-CM group but sparse in the other groups.25 Both the boneto-implant contact (BIC) and bone area fraction occupancy (BAFO) values were also higher in the P-CM group compared with the other three groups after 4 and 8 weeks of implantation. The APP pretreatment facilitated hydrocarbon removal from the Ti surface, and the refreshed Ti surface efficiently adsorbed soluble factors from the SHED-CM, including calcium phosphate components and ECM proteins, among others. Their immobilized surfaces actively recruited endogenous MSCs, and the incoming MSCs exerted their biologic effects both in the immediate area and more distally around the implants. This contributed to earlier osseointegration and greater osteogenesis. This study suggests that immobilizing SHED-CM by APP pretreatment may be a promising application when using implants for elevating the sinus floor membrane.

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Fig 24-8  Histologic evaluation of bone formation around Ti implants in vivo. Micrographs of specimens at 4 weeks (a to d) and 8 weeks (e to h) after implantation. (Toluidine blue stain, original magnification ×100.) (i) Average histomorphometric values of BIC. (j) Average histomorphometric values of BAFO. *P < .05, **P < .01. (Reprinted with permission from Omori et al.25)

Conclusion Studying bone regeneration with autogenous MSCs and PRP has shown its effectiveness, but several unavoidable problems associated with cell-based therapies were also encountered. Cells naturally secrete various growth factors and substrates required for or supportive of the cells and their survival, both in vivo and in vitro. Therefore, the authors focused on CCM

and introduced two types of application for implant materials as new concepts for regenerative medicine that alleviate these problems: CCM and APP. The secretions in the CCM recruit multiple types of endogenous cells. These cells cooperatively and consecutively work to efficiently form new tissue. Neogenesis of tissue proceeds from corresponding cascades, utilizing the natural healing ability in vivo. On the other hand, due to dose dependency, use of commercially available growth factors alone may only function

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References

at limited action points. Indeed, higher doses drive the cells to work harder, but side effects also occur with higher doses resulting in corresponding limited tissue formation. As further studies reveal the precise active components within the mechanism of action for CCM, we may be able to better manipulate endogenous cells to form new bone more efficiently and safely analogous to using specifically formulated drugs.26,27

Acknowledgments This work was supported by the Japanese Ministry of Education, Culture, Sports, Science and Technology and Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research.

References 1. Yamada Y, Ueda M, Hibi H, Nagasaka T. Translational research for injectable tissue-engineered bone regeneration using mesenchymal stem cells and platelet-rich plasma: From basic research to clinical case study. Cell Transplant 2004;13:343–355. 2. Yamada Y, Nakamura S, Ito K, et al. Injectable tissue-engineered bone using autogenous bone marrow–derived stromal cells for maxillary sinus augmentation: Clinical application report from a 2–6-year follow-up. Tissue Eng Part A 2008;14:1699–1707. 3. Ueda M, Yamada Y, Kagami H, Hibi H. Injectable bone applied for ridge augmentation and dental implant placement: Human progress study. Implant Dent 2008;17:82–90. 4. Hibi H, Yamada Y, Ueda M, Endo Y. Alveolar cleft osteoplasty using tissue-engineered osteogenic material. Int J Oral Maxillofac Surg 2006;35:551–555. 5. Shohara R, Yamamoto A, Takikawa S, et al. Mesenchymal stromal cells of human umbilical cord Wharton’s jelly accelerate wound healing by paracrine mechanisms. Cytotherapy 2012;14:1171– 1181. 6. Osugi M, Katagiri W, Yoshimi R, Inukai T, Hibi H, Ueda M. Conditioned media from mesenchymal stem cells enhanced bone regeneration in rat calvarial bone defects. Tissue Eng Part A 2012;18:1479–1489. 7. Schmelzeisen R, Schimming R, Sittinger M. Making bone: Implant insertion into tissue-engineered bone for maxillary sinus floor augmentation–A preliminary report. J Craniomaxillofac Surg 2003;31:34–39. 8. Schimming R, Schmelzeisen R. Tissue-engineered bone for maxillary sinus augmentation. J Oral Maxillofac Surg 2004;62:724–729. 9. Sauerbier S, Rickert D, Gutwald R, et al. Bone marrow concentrate and bovine bone mineral for sinus floor augmentation: A controlled, randomized, single-blinded clinical and histological trial—Per-protocol analysis. Tissue Eng Part A 2011;17:2187–2197. 10. Hibi H. Clinical review of bone regenerative medicine and maxillomandibular reconstruction. Oral Sci Int 2016;13:15–19. 11. Ando Y, Matsubara K, Ishikawa J, et al. Stem cell-conditioned medium accelerates distraction osteogenesis through multiple regenerative mechanisms. Bone 2014;61:82–90. 12. Tsuchiya S, Hara K, Ikeno M, Okamoto Y, Hibi H, Ueda M. Rat bone marrow stromal cell-conditioned medium promotes early osseointegration of titanium implants. Int J Oral Maxillofac Implants 2013;28:1360–1369.

13. Katagiri W, Osugi M, Kawai T, Ueda M. Novel cell-free regeneration of bone using stem cell-derived growth factors. Int J Maxillofac Implants 2013;28:1009–1016. 14. Inukai T, Katagiri W, Yoshimi R, et al. Novel application of stem cell-derived factors for periodontal regeneration. Biochem Biophys Res Commun 2013;430:763–768. 15. Kawai T, Katagiri W, Osugi M, Sugimura Y, Hibi H, Ueda M. Secretomes from bone marrow-derived mesenchymal stromal cells enhance periodontal tissue regeneration. Cytotherapy 2015;17: 369–381. 16. Ogata K, Katagiri W, Osugi M, et al. Evaluation of the therapeutic effects of conditioned media from mesenchymal stem cells in a rat bisphosphonate-related osteonecrosis of the jaw-like model. Bone 2015;74:95–105. 17. Katagiri W, Osugi M, Kinoshita K, Hibi H. Conditioned medium from mesenchymal stem cells enhances early bone regeneration after maxillary sinus floor elevation in rabbits. Implant Dent 2015;24:657–663. 18. Tsuchiya S, Omori M, Hara K, et al. An experimental study on guided bone regeneration by using a polylactide-co-glycolide membrane-immobilized conditioned medium. Int J Oral Maxillofac Implants 2015;30:1175–1186. 19. Sugimoto K, Tsuchiya S, Omori M, et al. Proteomic analysis of bone proteins adsorbed onto the surface of titanium dioxide. Biochem Biophys Rep 2016;7:316–322. 20. Fujio M, Xing Z, Sharabi N, et al. Conditioned media from hypoxic-cultured human dental pulp cells promotes bone healing during distraction osteogenesis. J Tissue Eng Regen Med 2017;11:2116–2126. 21. Ogata K, Katagiri W, Hibi H. Secretomes from mesenchymal stem cells participate in the regulation of osteoclastogenesis in vitro. Clin Oral Investig 2017;21:1979–1988. 22. Katagiri W, Osugi M, Kawai T, Hibi H. First-in-human study and clinical case reports of the alveolar bone regeneration with the secretome from human mesenchymal stem cells. Head Face Med 2016;12:5. 23. Katagiri W, Watanabe J, Toyama N, Osugi M, Sakaguchi K, Hibi H. Clinical study of bone regeneration by conditioned medium from mesenchymal stem cells after maxillary sinus floor elevation. Implant Dent 2017;26:607–612. 24. US Food and Drug Administration. Life-threatening complications associated with recombinant human bone morphogenetic protein in cervical spine fusion. http://www.tccortho.com/pdf/ FDAPublic%20Health%20Note.pdf. Accessed 28 August 2018. 25. Omori M, Tsuchiya S, Hara K, et al. A new application of cell-free bone regeneration: Immobilizing stem cells from human exfoliated deciduous teeth-conditioned medium onto titanium implants using atmospheric pressure plasma treatment. Stem Cell Res Ther 2015;6:124. 26. Sakaguchi K, Katagiri W, Osugi M, Kawai T, Sugimura-Wakayama Y, Hibi H. Periodontal tissue regeneration using the cytokine cocktail mimicking secretomes in the conditioned media from human mesenchymal stem cells. Biochem Biophys Res Commun 2017;484:100–106. 27. Katagiri W, Sakaguchi K, Kawai T, Wakayama Y, Osugi M, Hibi H. A defined mix of cytokines mimics conditioned medium from cultures of bone marrow–derived mesenchymal stem cells and elicits bone regeneration. Cell Prolif 2017;50. doi:10.1111/ cpr.12333. [Epub 2017 Jan 30.]

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CHAPTER 25

TISSUE ENGINEERING OF THE DENTAL ORGAN FOR THE POSTERIOR MAXILLA Fugui Zhang, dds, phd | Dongzhe Song, dds, phd | Ping Ji, dds, phd | Tong-Chuan He, md, phd | Ole T. Jensen, dds, ms

T

he sinus floor bone graft will be the future depository for dental follicles, enamel organs, and even fully formed teeth that will be bioengineered for tooth replacement in the not-too-distant future. Alveolar bone will still need to be prepared, including the sinus floor graft in anticipation of autogenous dental organ transplants. An example of this was reported in 1987 by Pogrel1 who used an alveolar split osteoperiosteal flap to widen the alveolus preparing a reception site for auto-transplant of a newly extracted tooth. The idea that alveolar bone will somehow be optimally developed by implantation of the enamel organ only, no matter the stage of tooth development, will likely not be possible without prior augmentation, as suggested by this book, including use of the lateral widow, alveolar split, alveolar osteotome intrusion, or some form of osseodensification used to develop alveolar height and width prior to definitive tissue engineering. This chapter describes the relatively few genetic defects currently identified that lead to agenesis, duplication, or malformation of dentate development, including the many craniofacial syndromes. Once tissue engineering has advanced to form implantables, a relatively mature osseous environment will be required to be conducive to coupled bone formation. Said in another way, space must be created, maintained, and remodeled biofunctionally prior to (or simultaneous to) implantation in adult patients. Even as technology for excision of genetic defects becomes more widespread, there will still be developmental, traumatic, and tumor extirpation loss of tissue. This will particularly complicate posterior maxillary reconstruction where aeration of the midface presents an exceptional challenge almost without parallel in the body. Given this theory—that sinus floor modification will continue to be important for regeneration—a future

edition of this book, perhaps as early as 10 to 15 years away, may describe implantation of tissue-engineered products reaching well beyond the experimental stage we now find ourselves in. Therefore, this future-thinking chapter is included in this third edition as a reminder of where we are going in the future as we continue regenerative efforts to restore what is missing. Today, that includes alveolar bone, gingival connective tissue, and sinus floor elements penetrated by biomechanical titanium osseointegration. In the future, treatment of what is missing will instead be by implantation of autogenous ex vivo constructs that will biointegrate seamlessly within the previously prepared alveolus and sinus floor milieu, sans titanium, sans osseointegration, and sans prosthetic machination.

Abnormal Odontogenesis Tooth development or odontogenesis consists of a series of morphogenetic stages and is a complex but well-orchestrated process through which teeth form from dental progenitor cells, grow, and erupt into the mouth.2–6 A precise balance of progenitor cell proliferation, differentiation, and apoptosis is essential for dental tissue homeostasis throughout tooth development, and a healthy oral environment of human teeth requires all parts of the tooth to develop during appropriate stages of fetal development.4 Uncontrolled proliferation of certain populations of the dental progenitors may lead to the formation of odontomas or ameloblastomas, and under some pathologic conditions, if teeth do not start to develop at or near the correct time, they will never develop, resulting in hypodontia or anodontia.

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Fig 25-1  Clinical and radiographic representations of odontomas. (a) Compound odontoma in mandibular premolars. (b) Macroscopic image of compound odontoma consisting of a capsule of fibrous tissue and multiple denticles. (c) Periapical projection of complex odontoma. (d) Complex odontoma in the area of mandibular premolars. (e and f) Histopathology of complex odontoma, disorganized mass of dentin-like material and enamel prisms. (Reprinted with permission from Barba et al.8)

Odontoma An odontoma, also known as an odontome, is a hamartoma composed of irregularly grown but normal dental tissue.7 This hamartoma is composed of both epithelial and mesenchymal elements and may show varied degrees of inductive change with regard to formation of dental hard tissues. While the etiology is not clear, the odontoma is a benign tumor of odontogenic origin closely linked to tooth development and associated with local trauma, infection, or genetic factors.

Compound odontoma versus complex odontoma Odontomas are classified as compound odontomas and complex odontomas. Compound odontomas are twice as frequent as complex odontomas, which usually contain mesenchymal and epithelial dental elements8 (Fig 25-1). Epidemiologically, odontomas are the most frequent benign odontogenic tumors, accounting for almost all maxillary tumors, often found in children and adolescents. The average age of individuals found with an odontoma is 14 years old, and they are commonly discovered in the second and third decades of life.

Histologically, compound odontomas are composed of different dental tissues, including enamel, dentine, cement, and sometimes pulp tissue. The lesions are usually unilocular and contain multiple radiopaque, miniature tooth-like structures known as denticles. The tumors may present a lobulated appearance without definitive demarcation of separate tissues between the individual toothlets or denticles, and they are usually located in the anterior maxilla, over the crowns of unerupted teeth, or between the roots of erupted teeth. If a compound odontoma forms multiple irregular tooth-like structures, the tumors may enlarge and cause airway obstruction of affected newborns. Complex odontomas are usually indistinguishable from normal dental tissues, presenting as a radiopaque area with varying densities. Complex odontomas are usually found in the posterior mandible or maxilla over impacted teeth. The lesions are unilocular and separated from normal bone by well-defined corticalization. Histologically, complex odontomas form amorphous calcification with dysplastic dentin covered by enamel. Multiple odontoma (MO) is characterized by numerous odontomas involving up to four quadrants of the arches. MO can also occur with other malformations, such as stenosis of the

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esophagus. The terms odontomatosis and odontoma syndrome are used to describe MO. However, MO is rare and little is known about its comprehensive clinical features. In addition to the compound odontomas and complex odontomas, dens invaginatus, or tooth-within-a-tooth, is a developmental anomaly resulting from invagination of a portion of the crown forming within the enamel organ during odontogenesis. The most extreme form of dens invaginatus is known as dilated odontoma, which is an infrequent developmental alteration that appears in any area of the dental arches in primary, permanent, and supernumerary teeth.

Clinical manifestations and treatment Odontomas are usually clinically asymptomatic but often associated with temporary or permanent tooth eruption disturbances, such as delayed tooth eruption. Most cases are found impacted within the jaw, although odontomas can erupt into the oral cavity, such as the exposure of the tumor through the oral mucosa. This can cause pain, inflammation of the adjacent soft tissues, or infection associated with suppuration. Both compound and complex odontomas usually occur as solitary lesions in the jaw. Radiologic diagnosis is a standard means for a single or multiple compound odontomas based on the presence of characteristic tooth-like structures, although multiple and massive complex odontomas may require differential diagnoses, which constitute a diagnostic and therapeutic challenge. Once the diagnosis is established, the treatment option is usually surgical removal of the lesions followed by histopathologic evaluations to confirm the diagnosis.

Ameloblastoma Ameloblastoma is a rare and slow-growing neoplasm of odontogenic origin involving the mandible (80%) and maxilla, often found at the site of the third molar.9–11 Ameloblastomas may become aggressive and spread locally to the nose, eye socket, and skull. Conservative treatment results in a high recurrence rate. Ameloblastoma occurs in men more often than in women and can be diagnosed at any age, although it is most often found in adults in their 30s and 40s. Ameloblastoma shows variable geographic prevalence. The global incidence has been estimated at 0.5 cases per million person-years, with most cases diagnosed in patients 30 to 60 years of age.9–11

Clinical manifestations Ameloblastoma can be asymptomatic in some affected individuals. The most common presentation for ameloblastoma is a painless swelling of the mandible or maxilla, which can cause facial distortion.9–11 The tumors usually grow slowly over months or years, and the affected individuals may experience tooth or jaw pain. However, ameloblastoma can be very aggressive, causing swelling and pain and/or uprooting teeth. Under rare conditions, ameloblastoma cells can spread to other areas of the body, such as the lymph nodes in the neck and the lungs.

Thus, it is important for ameloblastoma to be diagnosed and treated early.

Histopathology and pathogenesis Histopathologic examination reveals that ameloblastoma resembles normal odontogenic or enamel epithelium and ectomesenchyme, which are derived from the neural crest, and the oral cavity lining epithelium.11 The cause of ameloblastoma is not well understood. Risk factors may include injury to the mouth or jaw, infections of the teeth or gums, or inflammation of these areas. At the cellular level, ameloblastoma begins in the cells that form the protective enamel lining on the teeth. Interestingly, ameloblastoma shares many similarities with that of basal cell carcinoma at an early developmental stage. Ameloblastoma and basal cell carcinoma are both typically composed of uniform basaloid cells in nests with peripheral palisading surrounded by variable stroma. Until recently, little was known about the molecular aberrations driving ameloblastoma, due both to the rarity of the tumor and to the technical challenges to query the tumor genome.9–11 Nonetheless, it has been recently reported that through profiling ameloblastoma via DNA sequencing, the vast majority of ameloblastoma tumors contain somatic mutations impacting the mitogen-activated protein kinase signaling pathway through the FGFR2-RAS-BRAF axis, which is known to control cell proliferation.12 There is a high frequency of BRAF V600E activating mutations at high allele frequencies in ameloblastomas, especially for those exclusively located in the mandible. It was shown that the BRAF-mutated ameloblastoma cells were exquisitely sensitive to vemurafenib, a V600E-targeted small molecule inhibitor that is approved by the US Food and Drug Administration for metastatic melanoma.13 It was also reported that a high percentage of the mutant BRAF-negative maxillary ameloblastomas harbored activating mutations in Smoothened (SMO) in the sonic hedgehog (SHH) pathway, which is also frequently mutated in basal cell carcinomas.11 Furthermore, the activated SMO mutation could be blocked by select pharmacologic inhibitors of SHH signaling, such as KAAD-cyclopamine and arsenic trioxide. These findings may be consistent with current evidence suggesting that the SHH pathway is instrumental in the formation of the tooth bud. Interestingly, SMO and BRAF mutations were nearly always mutually exclusive, occurring predominantly in tumors of the maxilla and mandible, suggesting that there may be unrecognized divertent tooth developmental pathways and/ or mutational processes in the maxilla versus the mandible. Nonetheless, there are also other less common mutations in ameloblastomas, such as PIK3CA (of the PI3-kinase pathway that controls cell survival), CTNNB1 (of the Wnt signaling pathway that controls cell proliferation), and SMARCB1 (involved in chromatin remodeling).11

Diagnosis and treatment If untreated, ameloblastoma can grow to a very large size and pose an airway risk and lead to metabolic abnormalities.11

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a

c

b

d

e

Fig 25-2  (a to e) Hypodontia. This female patient presented with several common features of hypodontia. Note the agenesis of the maxillary lateral incisors and the second premolars, the retained primary mandibular molars, the generalized spacing, and the deep bite. (Reprinted with permission from Al-Ani et al.16)

Ameloblastoma can be detected by regular radiograph, magnetic resonance imaging, and/or computed tomography imaging. A biopsy confirms diagnosis. Surgical removal of the affected tissue is the preferred treatment, as chemotherapy drugs and radiation do not seem to have much effect on most noncancerous ameloblastomas. A wide margin of healthy tissue is removed from the treated area to keep the chance of tumor regrowth to a minimum. If the tumor does recur, surgery can be performed again. If there is malignant spread of the tumor, radiation therapy is the treatment choice as cancer chemotherapy is usually not effective in these malignant tumors. Prognosis for ameloblastoma largely depends on the age of the patient, tumor size, extent of disease, location of tumor, and histologic type. It is conceivable that a better understanding of the pathogenic roles of signaling pathways (eg, FGFR2-RAS-BRAF and SHH) in ameloblastoma development could lead to the clinical use of targeted therapies, improving the outcomes.

Tooth agenesis Tooth agenesis, or hypodontia, is one of the most common dentofacial malformations in humans having both known mutations (such as in MSX1, PAX9, AXIN2, WNT10A, and EDA) and unknown genetic alterations, in which tooth agenesis occurs as part of a recognized genetic syndrome or as a nonsyndromic

isolated trait4,14–16 (Fig 25-2). Tooth agenesis can cause masticatory dysfunction, speech alteration, esthetic problems, and malocclusion. Tooth agenesis is classified by the number of missing teeth as hypodontia, oligodontia, or anodontia. Hypodontia refers to the condition with an absence of up to five permanent teeth (excluding third molars), whereas six or more missing teeth (excluding third molars) is termed oligodontia. Total agenesis of teeth is known as anodontia.4,15,16 Oligodontia can be further classified into nonsyndromic oligodontia and syndromic oligodotia.4 Nonsyndromic oligodontia is more common and occurs independently. Syndromic oligodontia occurs in association with other genetic syndromes, such as the following: •  Incontinentia pigmenti •  Down syndrome •  Rieger syndrome •  Ectodermal dysplasia/hypohidrotic ectodermal dysplasia •  Tooth and nail syndrome (Witkop syndrome and Fried syndrome) •  Wolf–Hirschhorn syndrome •  Van der Woude syndrome •  Ectrodactyly–ectodermal dysplasia–cleft syndrome •  Ankyloblepharon-ectodermal defects •  Cleft lip/palate •  Cranioectodermal dysplasia

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•  Limb–mammary syndrome •  Oral-facial-digital syndrome type I •  Rapp–Hodgkin syndrome In these cases, oligodontia is associated with abnormalities of the skin, nails, eyes, ears, and skeleton.15

Epidemiology As the most common tooth agenesis, hypodontia occurs in primary dentition at a prevalence ranging from 0.1% to 1.5% without gender difference. In the permanent dentition, the prevalence of hypodontia varies from 1.6% to 36.5% depending on the population studied, with females affected approximately 1.5 times more than males.4,15 Oligodontia is relatively rare and estimated ranging from 0.08% to 0.30% in Western countries and approximately 0.25% in China. Anodontia occurs very rarely and only in some cases of ectodermal dysplasia. The most common missing tooth is the permanent third molar, which is missing in more than 20% of the general population.4 The mandibular second premolar is the second frequently missing permanent tooth (at a prevalence rate from 3% to 4%), followed by the maxillary lateral incisors (1% to 2.5%) and the maxillary second premolars (1% to 2%). Conversely, the maxillary central incisor is the least commonly missing (< 0.01%), followed by the mandibular first molar (< 0.02%) and the mandibular canine (0.01% to 0.03%).

Genetic alterations Tooth agenesis can occur at many stages of odontogenesis, such as a failure in the origination of tooth formation, reduced odontogenic potential of the dental lamina, or arrested development during an early stage.4,15 It is generally recognized that tooth agenesis is caused by a multifactorial etiology involving both genetic defects and environmental factors, of which genetic defects play a vital role.15 Nonsyndromic oligodontia can be inherited through autosomal dominant, autosomal recessive, or X-linked dominant mutations. Mutations in MSX1, PAX9, AXIN2, and EDA are the most common causes for nonsyndromic oligodontia, although mutations in WNT10A, EDAR, EDARADD, IKBKG (NEMO), and KRT17 are also implicated in nonsyndromic oligodotia. MSX1. MSX1 is a transcription factor that is expressed in con­­ densing ectomesenchyme of the tooth germ. It has been well established that MSX1 mutations are associated with tooth agenesis. Biologically, MSX1 is involved in epithelial-mesenchymal interactions and functions as a transcriptional repressor during embryogenesis through interactions with the key transcription complex and homeoproteins to determine the shape and position of teeth. Mice lacking Msx1 exhibit a cleft palate, deficient mandibular and maxillary alveolar bones, and failure of tooth development. Several family pedigree studies revealed that specific MSX1 mutations (mostly missense or nonsense mutations) may cause nonsyndromic hypodontia or oligodontia.

These MSX1 mutations mostly affect the formation of second premolars and third molars. Interestingly, a novel intronic mutation in MSX1 was recently implicated with autosomal dominant nonsyndromic oligodontia. PAX9. PAX9 is a member of the PAX gene family, which encodes transcription factors vital for the development of vertebrate organs. PAX9 is widely expressed in the tooth mesenchyme during tooth morphogenesis. PAX9 missense mutation, nonsense mutation, frameshift mutation, or same-sense mutation can lead to oligodontia. Homozygous Pax9-deficient mice die soon after birth and exhibit unsuccessful tooth formation at the bud stage. Heterozygous mutations of PAX9 in humans have been associated with nonsyndromic tooth agenesis. AXIN2. AXIN2 is a negative regulator of the canonical Wnt signaling pathway and involves the targeted degradation of β-catenin. AXIN2 is expressed in the dental mesenchyme, odontoblasts, and enamel knot. In humans, mutations in AXIN2 have been identified in patients with syndromic or nonsyndromic tooth agenesis and can cause tooth agenesis affecting permanent teeth—predominantly the permanent molars, mandibular incisors, and maxillary lateral incisors. EDA. The EDA gene encodes ectodysplasin A, a soluble protein member of the tumor necrosis factor (TNF) superfamily composed of a transmembrane domain, a furin cleavage site, a collagen type area, and a C-terminal TNF-like structure. EDA receptor activation through interactions between its death domain and an adaptor protein called EDARADD results in nuclear factor-κB (NF-κB) translocating into the nucleus, where it induces the transcription of the essential genes for the initiation and differentiation of ectodermal derived tissues, such as the skin, hair, and teeth. More recently, mutations in EDA lead to X-linked hypohidrotic ectodermal dysplasia, which is characterized by sparse hair, fewer and smaller teeth, and a lack of sweat glands. EDA mutations have also been implicated in missing maxillary lateral incisor cases.

Treatment The treatment plan of tooth agenesis is complicated and comprehensive, usually involving orthodontic treatment, restorative treatment, periodontal treatment, endodontic treatment, dental transplantation, dental implants, and dental extraction. Common challenges in treating oligodontia patients include space management, uprighting and aligning teeth, management of deep overbite, and retention. The treatment plan is usually personalized and dependent on age of the patient, degree of inherent crowding, state of the primary teeth, and type of malocclusion. It is conceivable that the arrival of three-dimensional (3D) printing and tissue engineering technologies could significantly facilitate the clinical management of tooth agenesis in the near future.

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a

b

c

Fig 25-3  Typical radiographic presentations in cleidocranial dysplasia. (a) Cone-shaped thorax. (b) Clavicular hypoplasia and aplasia on both sides. (c) Deformity of the skull, hypoplastic midface, and supernumerary teeth. (Reprinted with permission Shen et al.19)

Cleidocranial dysplasia Cleidocranial dysplasia (CCD) is also known as Marie and Sainton disease, Scheuthauer-Marie-Sainton syndrome, or mutational dysostosis17–19 (Fig 25-3). CCD is an autosomal dominant skeletal dysplasia disorder with high penetrance transmission. Originally thought to affect membranous-derived bones of the skull and clavicles only, CCD affects the skeleton in general and should be considered as dysplasia rather than dysostosis. Based on its clinical manifestations, CCD can be classified as typical CCD, light CCD, and isolated tooth dysplasia.

Epidemiology and pathogenesis CCD is a rare but well-known skeletal disorder with a prevalence of approximately 1 per million worldwide without gender or ethnicity predilections.17,18 It has been well documented that mutations (including insertions, deletions, nonsense, and missense mutations) of RUNX2 are implicated in skeletal and dental abnormalities in CCD development, although approximately 40% of the cases of CCD occur spontaneously with no apparent genetic cause or known etiology. Located at chromosome 6p21, RUNX2 is a key regulator of skeletal development and differentiation of osteoblasts by regulating the epithelialmesenchymal interactions that control tooth morphogenesis and histodifferentiation of the epithelial enamel organ. The papillary mesenchyme is the most common RUNX2 gene expression site during odontogenesis. Experimentally, mice lacking Runx2 fail to develop bone and tooth structures, whereas mice with mutant Runx2 genes exhibit arrested tooth development. Specifically, an absence of Runx2 expression in mice results in deficiency of osteoblastic differentiation and in reduction in the capacity of periodontal ligament cells to induce active osteoclastic differentiation, which may partly explain the delayed tooth eruption patterns in patients with CCD. Interestingly, Runx2 overexpression in mice also caused dysplasia and resulted in suffering from osteopenia

along with bone fractures. Thus, the molecular pathogenesis underlying CCD development remains to be fully understood.

Clinical manifestations and treatment CCD has a broad range of clinical manifestations, including pathognomonic deformity of the skull (such as persistent and open cranial sutures with bulging calvaria), hypoplasia, or aplasia of one or both the clavicles, delayed ossification of the fontanelles, frontal and parietal bossing, undue mobility of the shoulders, wide pubic symphysis, dental anomalies, a short middle phalanx in the fifth finger, associated vertebral anomalies, poor development of the premaxilla and pseudoanodontia, axial and appendicular skeletal defects, central nervous system anomalies, slight stature, spinal malalignment, genu valgum (knock knees), pes planus (flat feet), and hearing loss17–19 (see Fig 25-3). Hyperdontia is the most common dental abnormality of CCD, which can affect both primary and permanent dentition, leading to dental impaction, overcrowding, and malocclusion. In some cases, articulation and mastication may be affected as well. Supernumerary teeth may be normal or malformed and located in front, behind, or within the normal rows of teeth. The excess teeth may be arranged regularly in double rows or located chaotically within the arches. Teeth may be fully formed, bifid, or may present as small tuberosities on the alveolar ridges. Hyperdontia results from hyperactivity of the fetal dental lumina and the formation of excess tooth germs. The diagnosis of CCD is usually established by clinical and radiologic findings. Clinical dental management in CCD aims at realizing optimum functional and cosmetic outcome by early adulthood with a personalized multidisciplinary approach, which usually involves maxillofacial surgeons, orthodontists, and prosthodontists. Correction of malocclusion may involve surgical repositioning of teeth and the provision of dental prostheses. Orthodontic treatment is usually used to direct the eruption of the malposed teeth combined with orthognathic surgery.

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Permanent tooth Permanent tooth Deciduous Deciduous tooth tooth Enamel Enamel

DentinDentin

Dental pulp Dental pulp SHED SHED

Dental pulp DPSCs

Dental pulp DPSCs

Gingiva GMSCs

Gingiva GMSCs

Dental follicle (iv) DFPCs Cementum Alveolar bone ABMSCs Alveolar bone

ABMSCs a

b

Cementum

Periodontal ligament PDLSCs Apical papilla SCAP

Dental follicle (iv) DFPCs Periodontal ligament PDLSCs Apical papilla SCAP

Fig 25-4  Various types of dental stem cells and their locations in primary teeth (a) and permanent teeth (b). (Reproduced with permission from Zhang et al.6)

Speech therapy is sometimes required. The core purposes remain the restoration of craniofacial and dental function together with esthetics.

Dental Stem Cells for Dental Tissue Engineering Dental and craniofacial abnormalities caused by dysregulated odontogenesis almost always require some sort of surgical reconstruction.15,20 For example, the current practice for replacement of missing teeth is based on external materials. However, along with 3D printing technology, dental tissue engineering may offer the potential to replace missing teeth with a bioengineered tooth or to regenerate the damaged dental tissue. Thus, tooth regeneration is a stem cell–based regenerative medicine procedure in the field of tissue engineering and stem cell biology to replace damaged or lost teeth by regrowing them from autogenous stem cells.20–22 Dental tissues are a rich source of dental-derived mesenchymal stem cells (DMSCs), which may be suitable for dental tissue engineering because they have the potential to differentiate into several cell types, including odontoblasts, neural progenitors, osteoblasts, chondrocytes, and adipocytes.20 More recently, stem cells have been generated from human somatic cells into a pluripotent stage, resulting into so-called induced pluripotent stem cells, allowing the creation of patient- and disease-specific stem cells. Thus, the multipotency, high proliferation rates,

and accessibility make DMSCs an attractive source of MSCs for tissue regeneration.6 DMSCs are isolated from various dental tissues. Currently, at least seven types of DMSCs have been identified, including dental pulp stem cells (DPSCs), stem cells from apical papilla (SCAPs), stem cells from human exfoliated deciduous teeth (SHEDs), dental follicle precursor cells (DFPCs), periodontal ligament stem cells (PDLSCs), alveolar bone-derived MSCs (ABMSCs), and gingival MSCs (GMSCs)6,20,23–28 (Fig 25-4). DPSCs. These are multipotent stem cells that reside in the cellrich zone of both adult pulp tissue and primary tooth pulp and apical papilla.29,30 DPSCs can be readily isolated from discarded or extracted teeth and can differentiate along multiple cell lineages and promote the regeneration of dental pulp, dentin, and cementum, such as the generation of complete or partial tooth structures as biologic implants.31,32 Interestingly, human DPSCs also exhibit major neuroregenerative activities, demonstrating that tooth-derived stem cells may provide therapeutic benefits for treating spinal cord injury.33 SCAPs. These stem cells are isolated from soft tissue at the apices of developing permanent teeth and share significant similarities with DPSCs. Clinical attempts to preserve the remaining DPSCs and SCAPs lead to canal revascularization and completion of root maturation in young permanent teeth.34 SHEDs. These cells are derived from the pulp tissue of an exfoliating primary tooth and represent a postnatal stem cell population with high proliferative capacity, easy accessibility, high

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viability, and multilineage differentiation potential (eg, osteoblasts, neural cells, and odontoblasts).35,36 Therefore, SHEDs have been widely used for oromaxillofacial bone regeneration.37 DFPCs. These stem cells are derived from ectomesenchymal tissue surrounding enamel organ and dental papillae of developing tooth prior to eruption.38 DFPCs are potential stem cells for cementoblasts, osteoblasts, and periodontal ligament cells. They interact with Hertwig epithelial root sheath (HERS) cells during tooth root formation.39 When cocultured with HERS cells, DFPCs exhibited a greater tendency to form mineralized nodules and higher levels of cementoblast/osteoblast differentiation.40 PDLSCs. These stem cells are derived from DFPCs and are isolated from the mixed cell populations in the periodontal ligament space. Human PDLSCs possess high osteogenic and cementogenic differential ability.38 ABMSCs. These cells also originate from DFPCs and are dental progenitor cells of alveolar osteoblasts.38 GMSCs. These are ideal stem cells for repairing damaged periodontal tissues, muscle, and tendon, but it remains unclear if PDLSCs and GMSCs could form a dentin-pulp-like structure.23 Because dental stem cells share many characteristics with MSCs, there has been considerable interest in wider applications to treat disorders using mesenchymal cell derivatives.32 Although DMSCs present some common markers, such as CD105, CD146, and STRO-1, stem cells derived from various dental tissues exhibit heterogeneous capabilities of proliferation, clonogenicity, and differentiation potential.20 Furthermore, other embryonic stem cell features were reported in both DPSCs and SHEDs, although specific conditions to maintain the ability of DMSCs to initiate whole tooth formation may be required.41 Thus, DMSCs have a vast repertoire of differentiation (eg, osteogenic, odontogenic, adipogenic, and neurogenic). A regenerated tooth must be vascularized, innervated, and appropriately anchored in bone with pulp vascularization dependent on the differentiation capability of pulp and apical and periodontal stem cells.15,42

Important Cell Signaling Molecules for Dental Tissue Engineering Tooth morphogenesis involves extensive epithelial-mesenchymal interactions, which are tightly regulated by several highly conserved signaling pathways, such as bone morphogenetic proteins (BMPs), Wnt/β-catenin, Hedgehog (HH), Notch, fibroblast growth factors (FGFs), transforming growth factor β (TGFβ) and ectodysplasin A (EDA), to name a few.43 Fine-tuning the

activity of these conserved signaling pathways controls many aspects of tooth formation. For example, a supernumerary tooth forms in front of the first molar in several mutant mouse lines when signaling activity is modulated.43 These teeth form from activation of the development of a vestigial tooth rudiment found in wild-type mice in the diastema and represent premolars lost during the evolution of rodents.43 The relative sizes of the mouse molars are influenced by activation and inhibition between successionally developing teeth; the size and number of mouse incisors is affected by fine-tuning BMP signaling in the placodes; and the continuous growth and enamel deposition in incisors can be modulated by the levels of FGF, activin, and BMP signaling in the epithelial stem cell niche.43 Furthermore, crosstalk between signaling pathways can affect each pathway synergistically in maintaining cell survival, apoptosis, proliferation, and differentiation as well as other cellular processes of DMSCs.43 The cellular signaling network that governs tooth development has been thoroughly reviewed.43 This section focuses on the BMP and Wnt signaling pathways and their crosstalk in DMSCs because these pathways may have important implications in dental stem cell–based tissue engineering.

BMP signaling in dental stem cells BMP signaling plays an essential role in regulating the development of calcified tissues by directing MSC differentiation during development and throughout adulthood.44–50 BMPs belong to the TGF-β superfamily of proteins.50,51 More than 20 BMP-like molecules have been identified in vertebrates and invertebrates, several of which are of great importance to dental engineering.52,53 TGF-β/BMP plays an essential role in bone development by activating BMP receptor (BMPR) serine/threonine kinases.50 Mutations of TGF-β/BMP activity are linked to many clinical disorders, such as skeletal disorders, extraskeletal anomalies, autoimmune disorders, cancer, and cardiovascular diseases. Tooth development requires synchronous and spatially different BMP expression and interaction.54 BMPs perform their biologic functions through the canonical and noncanonical pathways. In the canonical pathway, BMPs initiate the signal transduction cascade by binding to BMPRs and forming a heterotetrameric complex comprised of two dimers of type I and type II serine/threonine kinase receptors6,51 (Fig 25-5). At least seven type I receptors (ALK1 to ALK7) have been identified for the ligands of TGF-β family. Three of these bind BMPs: type 1A BMPR (or BMPR-1A or ALK3), type 1B BMPR (or BMPR-1B or ALK6), and type 1A activin receptor (or ActR-1A or ALK2).55 BMP ligands are known to bind to their receptors and activate downstream mediators with high promiscuity. For example, BMP-6 and BMP-7 interact with BMPR-2 and recruit BMPR-1, whereas BMP-2 and BMP-4 preferentially bind BMPR-1 and recruit BMPR-2.56 Phosphorylation of TGF-β (I/II) or BMP-Rs activates Smads.6 This signaling network in skeletal development and bone formation is tightly regulated in a tempospatial specific fashion.57

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Dental mesenchyme/dental epithelium LRP4

Wise

Activin

WNT

BMP

Msx1/2

RI

Syndecan

Fzd

RII rac1

P

Smad2/3

FrzB

Wif

SFRP

Tenascin

Smad4

LRP5/6

Follistatin

Dsh GSK3

miR-26a

P p38MAPK

miR-200 c/141

-catenin TCF LEF

CREB

P P

ERK

Smad1/5/8

Smad4

P

P

Msx1

Amelogenin E-cadherin

APC

JNK

Smad4 Smad1/5/8

Akt

-catenin

Alkaline phosphatase

Runx2 DVR

TCF LEF

Noggin

Axin

Osterix

Nfic CyclinD1

Osteocalcin Osteopontin

Fig 25-5  Simplified Wnt and BMP signaling crosstalk in regulating dental stem cell proliferation and differentiation. Green lines indicate stimulatory effects while black lines indicate inhibitory actions. (Reproduced with permission from Zhang et al.6)

Tooth development affected by disruptions of BMP signaling Disruptions of BMP signaling cause early arrested tooth development.58 Cranial neutral crest–specific inactivation of BMPR-1A arrests tooth development at the bud/early cap stages.59 Substitution of BMPR-1A by constitutively active form of BMPR-1B in neural crest cells rescues molar and maxillary incisor development, although the rescued teeth exhibit delayed odontoblast and ameloblast differentiation.59 BMPR-1B, BMPR-2, and ActR-1 are detected in dental follicular and HERS cells at day 6 of periodontal development and later more diffusely in the periodontium.60 While BMP signaling plays a pivotal role in craniofacial organ and tooth development, canonical BMP signaling may not

operate in early developing teeth. Although pSmad1 is highly expressed in the dental follicle, HERS, and the periodontium, the absence of the pSmad1/5/8-Smad4 complex may be caused by saturation of Smad4 by pSmad2/3 in the dental mesenchyme.58,60 Silencing Smad2/3 or overexpression of Smad4 activates canonical BMP signaling in dental mesenchymal cells.58 Tight regulation of BMPR-1A signaling is essential in tooth development.61 Juglone-mediated inhibition of PIN1 augments the osteogenic medium-induced activation of BMPs, Wnt/βcatenin, extracellular signal-regulated kinase (ERK), JNK, and NF-κB pathway, suggesting that PIN1 may function as an important modulator of odontogenic and adipogenic differentiation of DPSCs.62 Deletion of Smad4 leads to defective odontoblast differentiation and dentin formation.63 On the other hand,

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BMP signaling is modulated by various factors and pathways.57 ADSCs from caALK2+/- mice had increased BMP signaling and activated pSmad 1/5.64 Extracellular phosphate (Pi) regulates BMP-2 expression via cAMP/PKA and ERK 1/2 pathways in human DPSCs.65 Negative regulators of BMP signaling can block the signal transduction at multiple levels, including decoy receptors, inhibitory intracellular binding proteins, and inducers of BMP ubiquitination.66 Furthermore, several noncanonical, Smad-independent signaling pathways for BMPs have been identified. For example, BMP-4 was found to activate TAK-1 signaling.67 It has also been demonstrated that BMPR-1 and BMP-2 may principally regulate FSHB expression in LβT2 cells via noncanonical activation of Smad2/3 signaling.68

may arrest this process by inhibiting cementogenic and osteogenic BMPs.60 Nonetheless, epithelial stem cell proliferation in cervical loops is controlled by an integrated regulatory network consisting of activin, BMPs, FGFs, and follistatin within incisor stem cell niches.89 Mesenchymal FGF3 stimulates epithelial stem cell proliferation, and BMP-4 represses FGF3 expression.89 Activin inhibits the repressive effect of BMP-4 and restricts FGF3 expression to labial dental mesenchyme.89 Follistatin limits the number of lingual stem cells and contributes to the asymmetry of mouse incisors.89

Diverse roles of BMPs in regulating osteogenic/ odontogenic differentiation

The Wnt family consists of at least 19 Wnt ligands encoded in both human and mouse genomes6,90–94 (see Fig 25-5). Wnt signaling regulates cell proliferation, migration, differentiation, apoptosis, and in epithelial-mesenchymal interactions involved in dental and periodontal tissue morphogenesis.95 Wnt responsiveness in craniomaxillofacial tissues were mapped, and the patterns of Wnt signaling colocalize with stem cell populations in rodent incisor apex, dental pulp, alveolar bone, periodontal ligament, cementum, and oral mucosa.96 Wnts are secreted lipid-modified glycoproteins and shortrange ligands to activate canonical and noncanonical signaling pathways.94,97 The hallmark of the canonical pathway is the activation of β-catenin-mediated transcriptional activity.6 The canonical pathway is initiated by binding of Wnt ligand to receptor complex containing Frizzled (Frz) protein and a coreceptor for low-density lipoprotein receptor-related protein (LRP)5/6. Binding of Wnts to Frz and LRP-5/6 activates distinct signaling pathways.80,94,97 Mutations in LRP-5 adversely affect skeletal development and bone mass.98 Ligand–receptor inter­ action is transmitted through Dishevelled (Dsh) proteins, leading to the inhibition of a multiprotein complex containing protein Axin, APC, PP2A, GSK3, and casein kinase 1α.94,99 Without ligand binding, this complex facilitates phosphorylation of β-catenin, resulting in its degradation via the ubiquitin– proteasome pathway. Thus, Wnt binding leads to an increase in cytoplasmic and nuclear β-catenin level, which complexes with T cell factor/lymphoid enhancer factor (TCF/LEF) trans­ cription factors and other coactivators regulating downstream target genes.94,100–104 Many extracellular secreted inhibitors can modulate Wnt signaling by binding either to Wnt ligands (eg, Wif and secreted Frz-related protein) or coreceptors LRP5/6 (eg, Dkk, Wise/Sost).100 Canonical Wnt signaling regulates tooth number in mice and humans, while its role in tooth replacement requires further research for clarification.97 Canonical Wnt target genes (eg, LEF1 and AXIN2) are continuously expressed in dental lamina tip and surrounding mesenchymal cells.105 The canonical Wnt/β-catenin signaling pathways were found to play a critical role in BMP-9-induced osteogenic differentiation of MSCs.80 BMP-9-induced ectopic bone formation and matrix mineralization are significantly inhibited by both FrzB overexpression and

BMP-2 has been detected in HERS cells, dental follicular cells, and differentiated periodontal cells.60 Local application of BMP-4 in epithelium of molar territories stimulates Islet1 expression, while inhibition of BMP signaling results in a loss of Islet1 expression.69 BMP-7 has been detected in HERS cells, dental follicular cells, and differentiated periodontal cells.60 Through a comprehensive analysis of the 14 types of human BMPs, the authors demonstrated that BMP-9 (aka, GDF2) is one of the most potent BMPs in promoting osteoblastic differentiation of MSCs both in vitro and in vivo.44,45,48,50,70,71 Nonetheless, BMP-9 is one of the least studied BMPs, and it has been demonstrated to interact with ALK1 and ALK2 type I receptors and upregulate a panel of critical downstream mediators that are involved in promoting the early stage of progenitor expansion and the late stage of terminal osteogenic differentiation of MSCs.72–78 For example, growth hormone (GH) is a direct early target of and upregulated by BMP-9 signaling.77 Furthermore, exogenous GH synergizes with BMP-9 for inducing osteogenic differentiation through insulin-like growth factor 1 (IGF1) signaling, which can be significantly blunted by JAK-STAT inhibitors.77 One potential mechanistic explanation of the potent osteogenic activity of BMP-9 is that BMP-9 can outcompete BMP antagonist noggin much more effectively than can other osteogenic BMPs such as BMP-2, BMP-4, BMP-6, and BMP-7.79 Furthermore, BMP-9 synergizes with several important signaling pathways, including WNTs, IGFs, EGF, Notch, and retinoic acid signaling pathways, in promoting osteogenic differentiation of MSCs.48,80–85 More recently, research demonstrated that BMP-9 effectively induces osteo/odontoblastic differentiation of the stem cells of dental apical papilla (SCAPs).86 BMP-2 was also used as a surface coating on scaffolds, decreasing pore size and causing better adhesion and reduced proliferation of BMP-MSCs.87 Recombinant human BMP-2 (rhBMP-2) is effective in establishing complete regeneration of a bony defect by 4 to 6 months, as assessed by intraoperative observations and histologic studies.88 It should be pointed out that as an inhibitor of bone formation, BMP-3 expression can be detected after day 13 of periodontal development. It is conceivable that BMP-3

Wnt signaling in dental stem cells

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β-catenin knockdown, suggesting that the canonical Wnt/βcatenin pathway is a critical mediator of BMP-9-mediated osteogenic signaling.80 The noncanonical Wnt signaling of the planar cell polarity (PCP) pathway is thought to transduce through NRH1, Ryk, PTK7, or ROR2 without interacting with LRP-5/6. The PCP pathway is also activated via the binding of Wnt to Frz and its coreceptor. The receptor complex then recruits Dsh to interact with Dsh-associated activator of morphogenesis 1 (DAAM1). DAAM1 activates small G-protein Rho and then Rho-associated kinase (ROCK). Dsh also forms a complex with Rac1 and mediates profilin binding to actin. Rac1 activates JNK and leads to actin polymerization.91,106 It remains to be fully investigated whether noncanonical Wnt signaling plays any important roles in tooth development and in regulating the proliferation and differentiation of dental stem cells.

Crosstalk between Wnt and BMP signaling pathways in dental stem cells The development of an individual tooth involves signaling networks, particularly in the BMP and Wnt signal pathways through positive and negative feedback loops6,107 (see Fig 25-5). At an embryonic age (E) 9.5 days, BMP-4 expression is detected in the epithelium of the dental lamina, follicle, and papilla and decreases rapidly on E10.5 or E11.5. BMP-2 expression is not prominent until E13.5, after which the signal is widespread throughout the neural-crest mesenchyme.108 BMP-4 was shown to induce a translucent mesenchymal zone similar to that induced by dental epithelium.109 MSX1 is required for BMP-4 expression transition from dental epithelium to mesenchyme and for LEF1 expression.5 Induced activity of canonical Wnt, FGF, and SHH signaling pathways rescues development of arrested mouse diastemal tooth germs as it was reported that BMP-4 and Msx1 act in a positive feedback loop to drive sequential tooth formation.110 Physical interaction between Wise, an extracellular protein that binds BMP ligands, and Wnt-modulator LRP4 acts as a direct link the two pathways at an extracellular level.6 Mutations in either Wise or Lrp4 in mice produced similar abnormalities in tooth development that are associated with alterations in BMP and Wnt signaling.111 During tooth development, LRP4 is expressed exclusively in epithelial cells while Wise is mainly in mesenchymal cells. Wise and LRP4 act together to coordinate BMP and Wnt signaling activities in epithelial-mesenchymal cell communication during development.111 Thus, LRP4 modulates and integrates BMP and canonical Wnt signaling during tooth development by binding Wise.112 During tooth and jawbone formation, TGF-β/BMP signaling regulates the fate of multipotent cranio neural crest (CNC) cells and directs these cells differentiating into odontoblasts and osteoblasts.6 Deleting Smad4 led to defects in odontoblast differentiation and dentin formation and upregulation of canonical Wnt signaling 63, indicating that Smad4 critically

regulates crosstalk between TGFβ/BMP and Wnt signaling to ensure proper CNC cell fate. Using iSCAP cells, we found that Wnt3A effectively induced early osteogenic markers, which were reduced by β-catenin knockdown.113 Furthermore, the iSCAP stimulation with both BMP-9 and Wnt3A exhibited more mature and highly mineralized trabecular bone, while knockdown of β-catenin in iSCAPs reduced BMP-9 or BMP-9/ Wnt3A-induced ectopic bone formation in vivo.113 Nonetheless, it has also been shown that overactivation of the Wnt/β-catenin pathway delays differentiation and growth of inner dental epithelium, resulting in permanent teeth presenting with altered size, morphology, and mineralization due to delayed differentiation and prolonged proliferation of the dental mesenchyme.114 BMPR-1A depletion at the differentiation stage switches differentiation of crown epithelia to root lineage, giving rise to ectopic cementum-like structures.115 This phenotype is related to activated Wnt/β-catenin signaling and epithelial-mesenchymal transition (EMT). Epithelial β-catenin depletion during the differentiation stage causes variable enamel defects and precocious/ectopic formation of fragmented root epithelia.115 Concomitant epithelial β-catenin depletion was shown to rescue EMT and ectopic cementogenesis caused by BMPR-1A depletion, suggesting that BMP and Wnt/β-catenin pathways interact antagonistically in regulating root lineage differentiation and EMT.115 Thus, proper crosstalk between BMP and Wnt signaling pathways is essential for tooth development6 (see Fig 25-5).

Conclusion With the rapid expansion of the understanding of oral stem cells, it is conceivable that the regrowth of human teeth should be within our reach in foreseeable future. Exploration of dental stem cell–based strategies to treat oral and dental diseases may make this a reality. The advantages for using dental tissuederived stem cells for tooth regeneration include highly accessible attainment, reproducibility, capability of self-renewal and large-scale expansion, less immune rejection, avoidance of ethical controversy, and readiness for making iPS cells.6 However, while there is a great need to establish cost-effective and safe protocols for exploiting DMSCs in clinical use, significant challenges must be addressed before the dental stem cells reach any clinical applications.116 Until then, the generation of fully functional teeth from the oral progenitor cells remains an elusive long-term goal.6 Future investigations should be directed to address the following questions: •  How can we efficiently and reproducibly isolate and maintain dental stem cells in culture? •  How can we effectively and safely expand isolated stem cells? •  What are the exact mechanisms underlying the functions of BMPs or Wnts in regulating dental stem cell proliferation and differentiation?

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•  Can Wnt-BMP crosstalk be further exploited to establish potent, synergistic biofactors for dental tissue engineering? •  What are the biocompatible scaffold materials that can be used for biofactor-programmed stem cell therapies for regenerative dentistry? •  What might the bioengineering approach be for tooth regeneration in the anterior versus posterior jaw? We may expect to get some satisfactory answers to these questions in the next 5 to 10 years.

Acknowledgments We apologize to the researchers whose original work cannot be cited due to space constraints. The authors wish to thank Mia Spezia, Scott Du, and Akhila Vuppalapati for the critical reading of the manuscript. The research work in the authors’ laboratories was supported in part by research grants from the National Institutes of Health (CA226303 to Dr He), Scoliosis Research Society to Dr He, the National Key Research and Development Program of China (2016YFC1000803 and 2011CB707906 to Dr He), and the National Natural Science Foundation of China (#81400493 to Dr Zhang). Dr Zhang and Dr Song received scholarship funding from the China Scholarship Council. Funding sources were not involved in the study design; in the collection, analysis, and interpretation of data; in the writing of the report; or in the decision to submit the chapter for publication.

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114. Aurrekoetxea M, Lopez J, Garcia P, Ibarretxe G, Unda F. Enhanced Wnt/β-catenin signalling during tooth morphogenesis impedes cell differentiation and leads to alterations in the structure and mineralisation of the adult tooth. Biol Cell 2012;104:603–617. 115. Yang Z, Hai B, Qin L, et al. Cessation of epithelial Bmp signaling switches the differentiation of crown epithelia to the root lineage in a β-catenin-dependent manner. Mol Cell Biol 2013;33:4732– 4744. 116. Rosa V, Toh WS, Cao T, Shim W. Inducing pluripotency for disease modeling, drug development and craniofacial applications. Expert Opin Biol Ther 2014;14:1233–1240.

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INDEX Page numbers followed by “f” denote figures; “t” tables; and “b” boxes.

A Absorbable collagen sponge description of, 8 rhBMP-2 and bone formation using, 204, 204f, 222, 223f description of, 9–11, 45 Abutments chairside sequence for, 200 collar height of, 200f Cone Morse, 201, 201f screw-retained, 200f selection of, 199–202 stock, 200 transsinus implants, 146f zygomatic implants, 163 ACS. See Absorbable collagen sponge. Acute rhinosinusitis, 16 Allergic rhinitis, 15 Allograft(s) autogenous bone grafts versus, 6 demineralized freeze-dried bone, 7 platelet-rich plasma/fibrin effects on, 204 risks associated with, 7 Allograft cellular bone matrix, 204 All-on-4 protocol, 140, 170 Alloplasts, 7–8 Alveolar bone atrophy of, 32, 46 defects of, titanium shell for, 45–46, 46f Alveolar crest bone loss of, 147 defects of, 74 height requirements for, for sinus floor elevation, 66 resorption of, 50 Alveolar crest island, 101, 103f Alveolar ridge atrophy of, after tooth extractions, 33 expansion of. See Ridge expansion. horizontal augmentation of, 33 vertical augmentation of, 33 width-deficient, alveolar split approach for, 32–35, 33f Alveolar segmental osteotomy, 30 Alveolar split approach alveolar anatomy, 33 benefits of, 40 case studies of, 35–40, 36f–40f definition of, 34

horizontal augmentation uses of, 33 implant placement with, 32 objective of, 32 osseointegration after, 35 osteocondensation in, 33 osteotomized bone segment, 34–35 revascularization, 33 summary of, 40 tooth extractions with, 33 for width-deficient alveolar ridge, 32–35, 33f Alveolar split osteoperiosteal flap, 244 Alveolar split osteotomy complications of, 30 history of, 35 illustration of, 34f, 39f implant placement with, 27, 27f, 29 modifications to, 34 sinus floor intrusion with, 28f, 29 transalveolar sinus floor elevation and, 27 transalveolar sinus grafting and, 29 Ameloblastoma, 246–247 Angiogenesis, 45 Angled implants. See Tilted implants. Anodontia, 247 Anorganic bovine bone matrix, 204 Anterior superior alveolar nerve, 142–143, 143f Antibiotics prophylactic uses of, 53, 61, 178, 230 rhinosinusitis treated with, 18 Antral cysts, 87–88 Antrostomy cortical bone as barrier over, 9 lateral window. See Lateral window antrostomy. Apical papilla, stem cells from, 250 ASAN. See Anterior superior alveolar nerve. Autogenous bone grafts advantages of, 5–6 allografts versus, 6 bone substitutes versus, 5, 9 complications of, 6 composite bone graft with, 5 disadvantages of, 5–6, 42 donor sites for, 5 as gold standard, 4–5, 42 harvesting of, 5–6 healing of, 2, 5 implant survival rates, 204 literature review regarding, 4–5 from maxillary tuberosity, 5, 6f Sinus Consensus Conference findings, 4, 203

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B Bacterial rhinosinusitis, 16, 18t Barrier membranes bone substitutes and, 5, 6f, 8 expanded polytetrafluoroethylene, 8, 62, 205 implant survival rates with, 8, 205 over sinus window, 5, 6f, 8, 9f, 62, 62f placement and stabilization of, 62, 62f sinus bone grafting with, 8–9 Sinus Consensus Conference findings, 205 Bedrossian classification, 183, 184f Benign paroxysmal positional vertigo, 209 β-catenin, 254 β-Lactamase inhibitors, for rhinosinusitis, 18 Bioactive products platelet concentrates, 9 rhBMP, 9–11 rhPDGF, 10–11 stem cells, 10–11 Biofilm, bacterial, 16 Bio-Oss, 35, 230–231 Biphasic calcium phosphate alloplasts, 7 Bleeding in lateral window sinus elevation, 84f–85f, 84–86, 119 from pterygoid implants, 157 Blood clot formation, 69, 138 BMP. See Bone morphogenic protein(s). BMP-2. See also rhBMP-2. adverse effects of, 233, 240 bone-to-implant contact effects of, in sinus augmentation animal study of, 227–229, 228f–229f description of, 227 human study of, 230f–232f, 230–233 summary of, 233 carrier material for, 233 concentrations of, 233 description of, 35, 43 endosinus bone height assessments, 232 scaffolding uses of, 253 Bone formation fetal, 220, 220f after implant placement, 68–69, 70f rhBMP-2/absorbable collagen sponge for, 204, 204f, 222, 223f Sharpey fiber matrix network for. See Sharpey fiber matrix network. titanium implants and, 241f–242f Bone grafts. See also Sinus bone graft(s). alternative materials, 4, 209–211 autogenous. See Autogenous bone grafts. implants in, survival rates for, 4, 5f, 203 interpositional in alveolar ridge widening, 33 description of, 23, 25f Le Fort I osteotomy with, in edentulous maxilla, 44, 45f, 46 options for, 118 particulate, 121f placement of, 61–62, 62f Sinus Consensus Conference findings, 4, 203 Bone morphogenetic protein(s) biologic functions of, 251 definition of, 9 description of, 5, 251 in osteogenic/odontogenic differentiation, 253 recombinant, 9–10. See also rhBMP-2. signaling of, in dental stem cells, 251–254, 252f Bone morphogenetic protein receptors, 251

Bone regeneration, 66, 140 Bone substitutes advantages of, 6–7 allografts, 6–7, 204 alloplasts, 7–8 autogenous bone grafts versus, 5, 9 ideal characteristics of, 7 implant survival rates with, 6 membranes with, 5, 6f, 8 osteoconductive, 3 platelet concentrates with, 9 Sinus Consensus Conference findings, 4, 203 xenografts, 7 Bone-forming construct criteria for success of, 225 embryomimetic surgical engineering, 213–214 Sharpey fiber matrix network for. See Sharpey fiber matrix network. Book flap, 34f, 35. See also Alveolar split osteotomy. Bovine bone mineral bone marrow aspirates with, 11 description of, 2, 7 Brånemark technique, 151, 152f Buccal flap tears, 86 Burs, for lateral window antrostomy preparation, 55, 55f

C Calcified microspheres description of, 216–217 Golgi-directed, 218–219 Caldwell-Luc approach, 32, 206 Canalis sinosus, 141–142, 142f Chronic rhinosinusitis, 16 Clarithromycin, 50t Cleidocranial dysplasia, 249f, 249–250 Cocaine abuse, 50, 50f Collagen membrane, for sinus membrane perforation coverage, 61, 61f Combination sinus and alveolar augmentation grafts, 208f, 209f Complex odontomas, 245f, 245–246 Composite bone grafts, autogenous bone added to, 5 Compound odontomas, 245f, 245–246 Compression wave, 106 Computed tomography maxillary edentulous ridge evaluations, 20 rhinosinusitis evaluations, 17, 20 Computer-aided surgery, for zygomatic implants, 159 Concha bullosa, 15–16, 16f Cone beam computed tomography anterior superior alveolar nerve evaluations, 143, 143f maxillary edentulous ridge evaluations, 20 maxillary molar pre-extraction evaluations, 92 Nazalus implant stability evaluations, 184, 185f pterygoid implants, 176 rhinosinusitis evaluations, 17 sinus augmentation on, 232f Cosci technique, 122 Crestal approach sinus kit, 120f, 122–123, 123f–124f Crestal window, 57, 57f–58f. See also Transcrestal approach. Cytokines, in mesenchymal stem cell-conditioned media, 240

D DASK. See Dentium Advanced Sinus Kit drilling. Delayed implant placement, 2–3, 203

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Demineralized freeze-dried bone allografts, 7 Dens invaginatus, 246 Densah Burs, 106f, 107–109, 108f Dental extractions alveolar split sinus floor intrusion with, 29 maxillary molars. See Maxillary molar extractions. Dental follicle precursor cells, 250–251 Dental pulp stem cells, 250, 252 Dental stem cells advantages of, 254 bone morphogenetic protein signaling in, 251–254, 252f future of, 254–255 types of, 250–251 Wnt signaling in, 252f, 253–254 Denticles, 245 Dentium Advanced Sinus Kit drilling in lateral window antrostomy, 55–57, 56f sinus membrane perforation prevention using, 77–78, 78f DFPCs. See Dental follicle precursor cells. DICOM. See Digital imaging and communications in medicine. Digital imaging and communications in medicine, 160, 230 Dilated odontoma, 246 Disuse atrophy, 183 Doxycycline, for rhinosinusitis, 18 DPSCs. See Dental pulp stem cells.

E Ectodermal dysplasia, 248 Ectodysplasin A, 248 Edentulous maxilla. See Maxilla, edentulous; Posterior maxilla, edentulous. Elevators, 60, 60f Embryomimetic surgical engineering, 213–214 Endoscopic marsupialization, of mucous retention cysts, 87 ePTFE membranes. See Expanded polytetrafluoroethylene membranes. Expanded polytetrafluoroethylene membranes, 8, 62, 205 Extractions alveolar split sinus floor intrusion with, 29 maxillary molars. See Maxillary molar extractions. Extra-long implants. See Nazalus implants.

F FESS. See Functional endoscopic sinus surgery. Fetal bone formation, 220, 220f Fetal facial skeleton, 213 FGFs. See Fibroblast growth factors. Fibrin clot, 9 Fibroblast growth factors, 253 Fistula, oroantral, 30, 93, 94f–95f, 179f Fluoroquinolones, for rhinosinusitis, 18 Fracture healing, 215 Functional endoscopic sinus surgery, 19 Functionality, 140 Fungal rhinosinusitis, 17, 18t Furcation intrusion procedure, 98–99

G GBR. See Guided bone regeneration. Gingival mesenchymal stem cells, 250–251 Glucocorticoids, for rhinosinusitis, 19

GMSCs. See Gingival mesenchymal stem cells. Golgi-directed calcified microspheres, 218–219 Graftless sinus floor elevation complications of, 70 history of, 66 implant placement with, 66–67 implant survival, 69–70, 70f indications for, 66–67 intrasinus responses, 70 sinus membrane perforation caused by, 70 summary of, 70 surgical technique for, 67–68, 68f Greater palatine artery, 176 GTR. See Guided tissue regeneration. Guided bone regeneration, 66 Guided tissue regeneration, 66

H Haemophilus influenzae, 16 Hand hygiene, 16 Hinge osteotomy, 55 HPISE. See Hydrodynamic piezoelectric internal sinus elevation. Human exfoliated deciduous teeth, stem cells from, 250 Hydrodynamic piezoelectric internal sinus elevation, 124–127, 126f Hydroxyapatite, 2, 7–8 Hyperdontia, 249 Hypodontia, 247f, 247–248

I IGF-1. See Insulin-like growth factor. Ilium autograft harvesting from, 5 mesenchymal stem cells harvested from, 10 Implant(s) alveolar crest bone height for, 50 alveolar split osteotomy with, 27, 27f apical fixation of, 140, 141f bone densification around, 109 extra-long. See Nazalus implants. immediate placement of. See Implant placement, immediate. machine-surfaced, 4, 5f Nazalus. See Nazalus implants. placement of. See Implant placement. posterior maxilla challenges for, 175, 187, 197 failure of, 105 maxillary sinus effects on, 1 rough-surfaced, 4–5 short in posterior maxilla, 1, 2f recommendations for, 128 sinus bone grafting versus, 1 Sinus Consensus Conference findings, 210–211 simultaneous placement of. See Implant placement, simultaneous. sinus membrane elevation supported with, 68f smoking effects on, 50 standard-length, 128 subcrestal placement of, 199 survival rates of barrier membrane effects on, 8, 205 bone grafting effects on, 4, 5f, 9 bone substitutes and, 9

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internal sinus elevation and, 138 short implants, 210 Sinus Consensus Conference findings, 203 sinus membrane perforation effects on, 82 tilted. See Tilted implants. with transcrestal sinus bone grafting, 134–137, 135f–137f ultrawide. See Ultrawide implants. zygomatic. See Zygomatic implants. Implant placement with alveolar split approach, 32 bone formation after, 68–69, 70f crestal approach sinus kit, 123, 124f delayed, 2–3, 203 with graftless sinus floor elevation, 66–67 immediate description of, 183 with lateral window approach for sinus bone grafting, 130f–131f, 130–134 after maxillary molar extractions, 187 pterygoid implants, 175 ultrawide implants, 192 limiting factors on, in posterior maxilla, 175 after maxillary molar extractions challenges associated with, 187 delayed, 93, 187 description of, 92 in 5 to 7 mm of bone within furcation, 96–97, 97f, 101 in greater than 9 mm of bone within furcation, 95, 96f, 101 in less than 5 mm of bone within furcation, 97–98, 101 in 7 to 9 mm of bone within furcation, 95–96, 97f simultaneous indications for, 11, 233 ridge expansion and transcrestal sinus floor intrusion with, 37f–40f, 37–39 with sinus bone grafting, 2 with sinus membrane elevation, 69 with transcrestal sinus augmentation with osseodensification, 106 with transcrestal sinus floor elevation, 4 single-stage, 233 sinus pneumatization effects on, 175 V-4, for short-arch-length maxilla, 173 Infraorbital canals, 142f Infraorbital nerve illustration of, 54f injury to branches of, during lateral window sinus elevation, 86, 86f Insulin-like growth factor, 240 Internal alveolar split, posterior maxillary sandwich osteotomy with, 25–27, 26f Internal sinus lift, 134–135, 135f, 137f, 138 Interocclusal space, 30 Interpositional bone graft/grafting in alveolar ridge widening, 33 description of, 23, 25f Le Fort I osteotomy with, in edentulous maxilla, 44, 45f, 46 Intra-alveolar split osteotomy, 23 Intranasal steroids, for rhinosinusitis, 19 Invasive fungal rhinosinusitis, 17 ISL. See Internal sinus lift. Island flap, 34f, 39, 40f

L Lacrimal sac, 142f Lateral floor approach advantages of, 63 presurgical sinus assessment, 48–53, 49b, 49t–50t, 50f–52f Lateral nasal wall anatomy of, 140, 141f vascularization of, 141 Lateral wall technique. See Lateral window sinus elevation. Lateral window antrostomy access for, 53, 54f alternatives to, 57–60, 57f–60f crestal window versus, 57, 57f–58f flap management for, 53, 54f palatal window versus, 58–59, 58f–59f preparation techniques, 55–57, 55f–57f vertical releasing incisions for, 53, 54f window in Dentium Advanced Sinus Kit preparation of, 55–57, 56f design of, 54–55, 76f location of, 54, 54f, 76 piezoelectric preparation of, 56f, 56–57, 77, 77f–78f, 207f rotary preparation of, 55, 55f simplified antrostomy design of, 55, 59f, 59–60 size of, 53 Lateral window approach for sinus bone grafting Caldwell-Luc antrostomy for, 206 description of, 1–3, 11 immediate implant placement with, 130f–131f, 130–134 osteotomy technique as alternative to, 119, 120f–121f surgical procedure for, 130f–131f, 130–134 Lateral window osteotomy, 23f Lateral window sinus elevation advantages of, 62 alternatives to, 140 antrostomy. See Lateral window antrostomy. closure of, 63, 63f complications of anatomic knowledge for prevention of, 74, 89 bleeding, 84f–85f, 84–86, 119 buccal flap tears, 86 inadvertent nasal floor grafting, 88, 89f infraorbital nerve branch injuries, 86, 86f mucous retention cysts, 86f–87f, 86–88 posterior superior alveolar artery damage, 84, 84f–85f prevention of, 88 sinus membrane perforation, 73–83, 74f–83f, 119. See also Sinus membrane perforation. summary of, 89 crestal bone height requirements, 66 graft placement, 61–62, 62f history of, 73, 105, 118 membrane placement and stabilization, 62, 62f summary of, 62 vasoconstrictors in, 84, 84f–85f Le Fort I osteotomy with interposed bone graft advantages of, 44 in edentulous maxilla, 44, 44f, 46 sinus membrane elevations with, 45f pterygomaxillary suture in, 175 Leukocyte- and platelet-rich fibrin membranes, 79, 81–82, 83f Loma Linda technique, 80, 82

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M M point, 140, 145, 170, 183, 195 Mandible embryonic development of, 220, 220f symphysis, autogenous bone harvesting from, 5–6 Marie and Sainton disease. See Cleidocranial dysplasia. Maxilla. See also Posterior maxilla. atrophy of description of, 1, 129f, 140, 169 zygomatic implants for. See Zygomatic implants. Class C, 171f Class D, 171f edentulous implant options for, 140 Le Fort I osteotomy with interposed bone graft for, 44, 44f, 46 Nazalus implants for, 183–186 pterygoid implants for, 178f, 179 resorption of, 160 short-arch-length defining of, 169, 170f first molar site implant for, 173 preoperative imaging of, 169–170, 170f–171f pterygoid implant for, 173 treatment options for, 171–173, 172f V-4 implant placement strategy for, 173 zygomatic implants for, 171–173, 172f Maxillary artery, 175 Maxillary molar extractions cone beam computed tomography before, 92 description of, 92 first molar, 96f furcation intrusion procedure, 98–99 implant placement after challenges associated with, 187 delayed, 93, 187 description of, 92 in 5 to 7 mm of bone within furcation, 96–97, 97f, 101 in greater than 9 mm of bone within furcation, 95, 96f, 101 immediate, 187 in less than 5 mm of bone within furcation, 97–98, 101 in 7 to 9 mm of bone within furcation, 95–96, 97f ultrawide. See Ultrawide implants. oroantral fistula with, 93, 94f–95f site classification for, 188 strategies for, 92 transcrestal approach in with graft placement, 100–101, 102f–103f osteotome strategies in, 101 for sites with no grafting, 99–100 type A socket, 188 type B socket, 188 type C socket, 188 ultrawide implants after. See Ultrawide implants. Maxillary sinus anatomy of, 15, 141f augmentation of. See Sinus augmentation. elevation of. See Sinus elevation. floor of, 1 iatrogenic pathology of, 19 infections of, 157 medial wall of, 141f mucosa of, 141 ostiomeatal complex of, 15, 16f ostium of, 15 pathologic conditions of, 48–50, 49t

pneumatization of. See Sinus pneumatization. posterior maxilla implants affected by, 1 Maxillary sinus elevation difficulty score, 51, 52f Maxillary sinus membrane. See Sinus elevation; Sinus membrane perforation. Maxillary sinusitis. See Rhinosinusitis. Maxillary tuberosity, autogenous bone grafts from, 5, 6f Meckel cartilage, 220 Medical history, 49b Membranes. See Barrier membranes. Mesenchymal stem cell(s) alveolar bone-derived, 250–251 dental-derived, 250–251 description of, 5, 10–11, 68, 235–236 gingival, 250–251 osteogenic differentiation of, 253 Mesenchymal stem cell–conditioned media, 238f–239f Methicillin-resistant Staphylococcus aureus, 18 Metronidazole, 61 MO. See Multiple odontoma. Model surgery, 30 Modified trephine osteotome technique, 207 Molar extractions. See Maxillary molar extractions. Morse taper connection, 199 MSCs. See Mesenchymal stem cell(s). MSED score. See Maxillary sinus elevation difficulty score. Mucous retention cysts, 86f–87f, 86–88 Mucous retention phenomenon, 21f Multiple odontoma, 245–246 Mutational dysostosis. See Cleidocranial dysplasia. Mycetoma, 17

N Nasal floor grafting, inadvertent, 88, 89f Nasal septal deviation, 16 Nasal-sinus tumors, 49t Nasolacrimal duct, 141–142 Navigation surgery, for zygomatic implant placement accuracy of, 164 case studies of, 165f–167f, 165–167 classic approach with, 160, 165–166, 165f–166f fiducial markers, 164 presurgical planning, 160, 161f quad approach with, 160, 166–167, 167f registration, 161, 161f software used in, 161f surgical technique, 161–163, 162f–163f target registration error, 164 time line for, 160f vertical releasing incisions, 163 in vitro and in vivo conditions, 164 Nazalus implants advantages of, 184–185, 185f cone beam computed tomography of, 184, 185f length of, 183 stability of, 184 surgical procedure for, 183–184, 184f Neurapraxia, 143 Nonsyndromic oligodontia, 247–248 Noris drilling guide description of, 157 for pterygoid implants, 156f for zygomatic implants, 155f

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O Odontogenesis, defined, 244 Odontogenesis abnormalities ameloblastoma, 246–247 cleidocranial dysplasia, 249f, 249–250 description of, 244 hypodontia, 247f, 247–248 odontomas, 245f, 245–246 Odontogenic differentiation, 253 Odontogenic sinusitis, 19–20, 20f, 48, 50 Odontoma(s), 245f, 245–246 Odontoma syndrome, 246 Odontomatosis, 246 Oligodontia, 247 Optimal function, 140 Oroantral communication, 19, 179, 179f, 205f–206f Oroantral fistula, 30, 93, 94f–95f, 179f Orthoalveolar form, 45 Osseodensification lateral compaction autografting via, 110 osseointegration and, 109–110 technique for, 106–107 in trabecular space, 109 transcrestal sinus augmentation. See Transcrestal sinus augmentation with osseodensification. Osseointegration after alveolar split approach, 35 BMP-2 effects on, 229, 229t methods to improve, 105 osseodensification and, 109–110 requirements for, 119 Osteocondensation, 33 Osteoconductive bone substitutes, 3 Osteogenesis, 45 Osteogenic differentiation, 253 Osteotome sinus grafting, 119, 120f–121f Osteotomy alveolar segmental, 30 alveolar split. See Alveolar split osteotomy. hinge, 55 instrumentation for, 105, 106f in lateral window approach, 2 palatal, 30 sandwich. See Sandwich osteotomy. in transcrestal approach, 3 Ostiomeatal complex, 143 anatomy of, 15, 16f obstruction of, 15 Otolaryngologist, 20–21

P Palatal approach lateral window antrostomy versus, 58–59, 58f–59f sinus grafting via, 29, 29f, 58, 58f–59f Palatal osteotomy, 30 Palatal window, 58–59, 58f–59f Paranasal sinuses computed tomography of, 17 evaluation of, before sinus augmentation, 20 PDGF. See Platelet-derived growth factor. Periapical granuloma, 19 Peri-implantitis, 210 Periodontal disease, 28f

Periodontal ligament stem cells, 250–251 Piezoelectric internal sinus elevation history of, 124 hydrodynamic, 124–127, 126f procedure for, 124, 125f Piezoelectric surgery in furcation intrusion procedure, 99 history of, 85 instruments in, 207, 207f lateral window sinus elevation applications of bleeding prevention, 84–85 illustration of, 207f sinus membrane perforation prevention, 77, 77f–78f window preparation, 56f, 56–57 silicone balloon with diluted contrast liquid used with, 207 sinus membrane perforation prevention using, 77, 78f technique variations, 77, 77f–78f transcrestal approach, 124–127, 125f–126f, 207 Pikos technique, 80 PISE. See Piezoelectric internal sinus elevation. Platelet concentrates, 9 Platelet-derived growth factor definition of, 10 recombinant human, 10–11, 204 Platelet-rich fibrin, 3, 204, 206f Platelet-rich plasma, 204, 235 PLSCs. See Periodontal ligament stem cells. Polyetheretherketone healing abutments, 120, 121f Posterior lateral nasal artery, 141f Posterior maxilla. See also Maxilla. alveolar ridge width augmentation in, 33, 33f atrophy of description of, 1, 129f, 140, 169 zygomatic implants for. See Zygomatic implants. bone defects in, 42 bone density in, strategies to improve, 105 edentulous anatomical limitations associated with, 140 bone quality in, 1 characteristics of, 2 illustration of, 43f implant options for, 140 Nazalus implants for, 183–186 sinus floor elevation in, 101, 102f implant placement in challenges for, 175, 187, 197 failure of, 105 maxillary sinus effects on, 1 sinus bone grafting in lateral window approach for, 2–3 transcrestal approach for, 3–4 Posterior maxillary alveolar split and sinus graft, 27, 27f Posterior maxillary sandwich osteotomy indications for, 43 internal alveolar split with, 25–27, 26f lateral window osteotomy, 23f sinus floor grafting with, 25, 26f, 30, 43f, 43–44 surgical technique of, 23, 24f–25f technique for, 43, 43f Posterior maxillary segmental osteotomy, 29, 29f Posterior superior alveolar artery bleeding from, during lateral window sinus elevation, 84, 84f–85f, 119 description of, 53 endosseous anastomosis from, 119 PRF. See Platelet-rich fibrin. Prosthetic retention, 202

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Pterygoid fossa, 176f Pterygoid implants advantages of, 175 anatomical considerations for, 175–176, 176f angulation of, 177 antibiotic prophylaxis in, 178 bleeding from, 157 case studies of, 178f–182f, 179–182 complications of, 178–179 cone beam computed tomography of, 176 disadvantages of, 183 goals of, 175 history of, 151 immediate loading of, 175 length of, 175 Noris drilling guide for, 156f patient selection for, 176–177 placement of, 209 preoperative evaluation of, 176–177 short-arch-length maxilla treated with, 173 Sinus Consensus Conference findings, 209–210 in sinus pneumatization, 176, 181f–182f surgical guide for, 156f surgical planning for, 176 surgical technique for, 177f, 177–178 survival rates for, 175 zygomatic implants versus, 175 Pterygoid process, of sphenoid bone, 175, 176f Pterygomaxillary junction, 170 Pterygomaxillary suture, 175, 176f Pyramidal-pterygoid junction, 175

R Recombinant human BMP-2. See rhBMP-2. Recombinant human platelet-derived growth factor, 10–11, 204 Recurrent acute rhinosinusitis, 16 Registration, 161, 161f Restorations, 199 Reverse-rotating osseodensification burs, 3 rhBMP-2. See also BMP-2. description of, 9–11 in posterior maxillary sandwich osteotomy, 25 rhBMP-2/absorbable collagen sponge bone formation using, 204, 204f, 222, 223f description of, 8–11, 45 Rhinosinusitis acute, 16 antibiotics for, 18 bacterial, 16, 18t characteristics of, 18t chronic, 16, 18, 21f computed tomography of, 17 concha bullosa and, 15–16, 16f environmental factors associated with, 15 fungal, 17, 18t genetic factors, 15 intranasal steroids for, 19 invasive fungal, 17 medical workup for, 17–18 odontogenic, 19–20, 20f, 48, 50 otolaryngologist referral for, 48 predisposing factors for, 15–16 recurrent acute, 16 signs and symptoms of, 16, 17b, 20

sinonasal lavage for, 19 sinus anatomy, 15 viral, 16, 18t zygomatic implant-associated, 156, 184 rhPDGF. See Recombinant human platelet-derived growth factor. Ridge expansion and transcrestal sinus floor intrusion, in posterior maxilla case studies of, 35–40, 36f–40f simultaneous implant placement with, 37–39, 37f–40f

S SAD. See Simplified antrostomy design. SALSA. See Subantroscopic laterobasal sinus floor augmentation. Sandwich osteotomy access for, 23 advantages of, 23 alveolar height increased with, 31 posterior maxillary internal alveolar split with, 25–27, 26f lateral window osteotomy, 23f sinus floor grafting with, 25, 26f, 30 surgical technique of, 23, 24f–25f SCAPs. See Stem cells from apical papilla. Scheuthauer-Marie-Sainton syndrome. See Cleidocranial dysplasia. Screw-retained abutments, 200f Segmental osteotomies, 34 Sharpey fiber matrix network calcified microspheres description of, 216–217 Golgi-directed, 218–219 clinical applications of, 221–224 description of, 214 illustration of, 215f inorganic phase of, 216–219 microanatomical innovations, 219–221 organic phase of, 214–216 periosteal, 215, 215f surgical design to surgical procedure transition, 224 SHEDs. See Stem cells from human exfoliated deciduous teeth. Short implants in posterior maxilla, 1, 2f recommendations for, 128 sinus bone grafting versus, 1 Sinus Consensus Conference findings, 210–211 Short-arch-length maxilla defining of, 169, 170f first molar site implant for, 173 preoperative imaging of, 169–170, 170f–171f pterygoid implant for, 173 treatment options for, 171–173, 172f V-4 implant placement strategy for, 173 zygomatic implants for, 171–173, 172f Simplified antrostomy design, 55, 59f, 59–60, 145 Simultaneous implant placement indications for, 11, 233 ridge expansion and transcrestal sinus floor intrusion with, 37f–40f, 37–39 with sinus bone grafting, 2 with sinus membrane elevation, 69 with transcrestal sinus augmentation with osseodensification, 106 with transcrestal sinus floor elevation, 4 Sinonasal infections, 19 Sinonasal lavage, for rhinosinusitis, 19

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Sinus augmentation alternatives to, 140 alveolar augmentation and, 208f, 209 bone grafts for. See Bone grafts. bone volume considerations, 140 bone-to-implant contact, BMP-2 effects on animal study of, 227–229, 228f–229f description of, 227 human study of, 230f–232f, 230–233 summary of, 233 complications of, 138. See also Lateral window sinus elevation, complications of. cone beam computed tomography of, 232f contraindications for, 49t infection after, 61 lateral window, 207f otolaryngologist consultation before, 20–21 paranasal sinuses evaluation before, 20 piezoelectric transcrestal approach for, 124–127, 125f–126f sinus elevation instrument for, 231f sinus graft infection after, 61 subantroscopic laterobasal, 130 timing of, 20 Sinus bone graft(s). See also Bone grafts. cultured human bone marrow-derived mesenchymal stem cells applied to, 238 definition of, 128 future of, 244 healing of, implant placement after, 2–3 options for, 183 placement of, 61–62, 62f radiographic evaluations, 128, 129f Sinus bone grafting alternatives to, 209–211 barrier membranes with, 8–9 goals of, 118 implants and short implants, 1 simultaneous placement, 2 incomplete, 58f–59f indications for, 1 indirect method of, 3 internal sinus lift with, 134–135, 135f, 137f, 138 lateral window approach description of, 1–3, 11 immediate implant placement with, 130f–131f, 130–134 osteotomy technique as alternative to, 119, 120f–121f surgical procedure for, 130f–131f, 130–134 materials for, 235 mesenchymal stem cells for, 11 osteotome technique, 119, 120f–121f palatal approach, 29, 29f posterior maxillary sandwich osteotomy with, 25, 26f, 30 radiographic evaluations, 128, 129f rhBMP-2/ACS for, 10 short implants versus, 1 Sinus Consensus Conference findings, 203, 206–209, 207f–208f summary of, 11 techniques for, 1, 3–4, 11 transcrestal description of, 3–4, 11, 118–127 immediate implant placement with, 134–137, 135f–137f tricalcium phosphate for, 4 vertical ridge augmentation with, 209 Sinus compliance, 89

Sinus Consensus Conference barrier membranes, 205 biologic materials, 204 bone grafts, 4, 203 combination sinus and alveolar augmentation grafts, 208f, 209f description of, 203 pterygoid implants, 209–210 short implants, 210–211 sinus grafting materials, 203–205 techniques, 206–209, 207f–208f tilted implants, 210 zygomatic implants, 209–210 Sinus elevation antibiotic prophylaxis for, 50t, 53 aseptic techniques for, 53, 53f blood clot formation, 68–69, 70f, 138 complications of, 19 difficulty score for, 51, 52f environmental factors that affect, 50, 50f graftless complications of, 70 history of, 66 implant placement with, 66–67 implant survival, 69–70, 70f indications for, 66–67 intrasinus responses, 70 sinus membrane perforation caused by, 70 summary of, 8, 70 surgical technique for, 67–68, 68f illustration of, 205f implant placement with illustration of, 68f simultaneous, 69 survival rates for, 69 indications for, 50 lateral window. See Lateral window sinus elevation. medical history before, 49b medical management of, 53 operator technique and instrumentation for, 60, 60f osteotome, for short implant placement, 1 perforations during. See Sinus membrane perforation. postoperative drug therapy for, 50t preoperative diagnosis and planning, 50–51 prophylactic drug therapy for, 50t, 53 radiologic examinations before, 51 sinus assessment before, 48–53, 49b, 49t–50t, 50f–52f sinus membrane perforation during, 19 transalveolar, 27 transcrestal with alveolar split approach. See Alveolar split approach. description of, 4 endosseous implant placement after, 35 as vascularized bone segment, 33 vertical augmentation uses of, 33 Sinus floor elevation. See Sinus elevation. Sinus floor intrusion alveolar split osteotomy with, 28f, 29 transcrestal, with alveolar split. See also Alveolar split approach. description of, 32 ridge expansion and, 35–40, 36f–40f Sinus floor microfracture, 135, 136f Sinus inflammation, 20, 21f Sinus lift. See Sinus elevation. Sinus membrane elevation. See Sinus elevation.

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Sinus membrane perforation collagen membrane coverage of, 61, 61f contributing factors, 60, 60b delayed implant placement after healing of, 95 effects of, 82–83, 83f etiology of, 73–74 in graftless sinus floor elevation, 70 high-risk maneuvers for, 74 illustration of, 61f, 75f, 133f incidence of, 73–74, 119 large, 79 management of, 60–61 prevention of anatomic considerations in, 74, 89 Dentium Advanced Sinus Kit drilling for, 77–78, 78f methods for, 74–77, 105 piezoelectric surgery for, 77, 78f septa identification for, 74–76, 75f–76f, 80f repair of bioabsorbable membranes in, 79–82 in difficult locations, 79–80, 81f failure of, 83 implant survival after, 82 leukocyte- and platelet-rich fibrin membranes for, 79, 81–82, 83f Pikos technique, 80 size-based approaches to, 79, 80f split-thickness graft indications in, 83, 83f sutures, 81f sinus floor elevation as cause of, 19 sinus width and, 74, 74f small, 79, 80f during transcrestal approach, 105 Sinus pneumatization case studies of, 181f–182f causes of, 138 description of, 1 implant placement affected by, 175 posterior maxilla bone volume insufficiency related to, 42 pterygoid implants in, 176, 181f–182f surgical approaches to, 32 transcrestal sinus augmentation with osseodensification in patients with, 112, 112f–116f, 114 Sinus window, barrier membrane over, 5, 6f, 8, 9f Sinusitis. See Rhinosinusitis. Smads, 251–252, 254 Smoking, 50 Soft tissue plasty, 178 Sphenoid bone, pterygoid process of, 175, 176f Sphenoid sinus, 17 Sphenopalatine artery, 141 Spirostomum ambiguum, 217f, 218 Staphylococcus aureus, 16, 18 Stem cells dental. See Dental stem cells. future of, 254–255 harvesting of, 10 mesenchymal. See Mesenchymal stem cell(s). periodontal ligament, 250–251 Stem cells from apical papilla, 250 Stem cells from human exfoliated deciduous teeth, 250 Sterile technique, 61 Streptococcus pneumoniae, 16, 18 Subantroscopic laterobasal sinus floor augmentation, 130 Suboptimal function, 140 Sulcus lacrimalis, 142f Sutures, for lateral window sinus elevation closure, 63, 63f

Symbios, 132 Syndromic oligodontia, 247–248 SynthoGraft, 132

T TEB. See Tissue-engineered bone. Tensegrity, 218 Tibia, autograft harvesting from, 5 Tilted implants sinus bone grafting versus, 1 Sinus Consensus Conference findings, 210 stress generated at, 149 Tissue-engineered bone bone regeneration with cell-conditioned media for, 237–241, 238b, 238f cell-based therapy for, 235, 236f efficacy of, 236 methodology for, 235, 236f strategies for, 237f success in, 236–237 composition of, 235 costs of, 236 Titanium implants, bone formation around, 241f–242f Titanium shell alveolar defects treated with, 45–46, 46f fabrication of, 45, 46f Tooth agenesis. See Hypodontia. Tooth extractions alveolar ridge atrophy after, 33 alveolar split sinus floor intrusion with, 29 alveolar split with, 33 maxillary molars. See Maxillary molar extractions. Transalveolar sinus floor elevation alveolar split osteotomy and, 27 description of, 32 Transalveolar sinus grafting, 29 Transalveolar technique, 207 Transcrestal approach description of, 207 indications for, 207 in maxillary molar extractions with graft placement, 100–101, 102f–103f osteotome strategies in, 101 for sites with no grafting, 99–100 modifications to, 119, 120f–121f osteotomes added to, 209 piezoelectric, 124–127, 125f–126f, 207 for sinus bone grafting description of, 3–4, 11, 118–127 immediate implant placement with, 134–137, 135f–137f sinus membrane perforation risks, 105 Transcrestal hydrodynamic piezoelectric sinus elevation, 118–127 Transcrestal sinus augmentation with osseodensification case reports of, 110–116, 111f–116f Densah Burs, 106f, 107–109, 108f in 4 mm residual bone, 108f, 108–109 illustration of, 107f osseodensification, 106–107 posterior maxillary challenges, 105 protocols for, 107–108 simultaneous implant placement with, 106 in sinus pneumatization, 112, 112f–116f, 114 in 6 mm residual bone, 107f, 107–108

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Transcrestal sinus floor elevation with alveolar split approach. See Alveolar split approach. crestal bone height requirements, 66 description of, 4 endosseous implant placement after, 35 as vascularized bone segment, 33 vertical augmentation uses of, 33 Transforming growth factor β1, 240 Transsinus implants abutments, 146f apical fixation of, 140, 141f evidence-based support for, 147–149 illustration of, 144f indications for, 145 lateral nasal wall bone, 140, 141f nasal anatomy, 141–143, 142f–143f outcome evaluations, 147 patient selection for, 143, 145 preparation for, 145 procedure for, 145–147, 146f simplified antrostomy design for, 59f, 59–60 Tricalcium phosphate, 4, 7 TSAOD. See Transcrestal sinus augmentation with osseodensification.

U Ultrawide implants benefits of, 188b biotypes contraindicated for, 189, 189f case studies of, 191–197, 192f–197f definition of, 187 features of, 187, 188f guidelines for, 189, 189f–190f illustration of, 188f immediate loading of, 192 Max, 189, 189f–190f molar extraction site classification, 188 osseous gaps with, 191 placement of, 191, 191f surgical technique for drill-through-the-tooth protocol, 190–191, 191f, 194f root decoronization and removal, 190, 190f Upper respiratory infections, 16

V V-4 implant placement strategy, for short-arch-length maxilla, 173 V point, 170 Vascular endothelial growth factor, 240 Vascularized mucoosteoperiosteal flap, 35 Vasoconstrictors, 84, 84f–85f VEGF. See Vascular endothelial growth factor. Vertical augmentation sinus grafting with, 209 transcrestal sinus floor elevation for, 33 Vertical releasing incisions for lateral window antrostomy, 53, 54f, 63f for zygomatic implant placement, 163 Viral rhinosinusitis, 16, 18t

W Wnt signaling, in dental stem cells, 252f, 253–254 Wound dehiscence, 45

X Xenografts, 7, 61, 183

Z Zygomatic anatomy-guided approach (ZAGA), 160, 161f Zygomatic implants abutments, 163 accuracy analysis of, 163–164 advantages of, 210 Brånemark technique for, 151, 152f case studies of, 165–167, 165f–167f challenges associated with, 159 complications of, 156–157, 184, 210 computer-aided surgery for, 159 contraindications for, 151 disadvantages of, 183 dynamic navigation of, 159 entry and exit points for, 154 extramaxillary, 157 extrasinus protocol for, 152f history of, 151, 159, 169, 209 indications for, 140, 151, 172, 174 length of, 155–156, 157f, 210 maxillary sinus infections associated with, 157 mispositioning of, 153, 153f navigation surgery for accuracy of, 164 case studies of, 165–167, 165f–167f classic approach with, 160, 165–166, 165f–166f fiducial markers, 164 presurgical planning, 160, 161f quad approach with, 160, 166–167, 167f registration, 161, 161f software used in, 161f surgical technique, 161–163, 162f–163f target registration error, 164 time line for, 160f vertical releasing incisions, 163 in vitro and in vivo conditions, 164 Noris drilling guide for, 155f positioning of, 153–155 pterygoid implants versus, 175 rhinosinusitis associated with, 156, 184 short-arch-length maxilla treated with, 171–173, 172f single, 160 Sinus Consensus Conference findings, 209–210 standard implants with, 210 surgical guides for, 154–155, 155f surgical protocol for, 155–156, 156f surgical template for, 163–164 vector of, 153, 153f virtual planning of, 154–155, 154f–155f

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