Implants and Oral Rehabilitation of the Atrophic Maxilla: Advanced Techniques and Technologies 3031127544, 9783031127540

Table of contents :
Acknowledgements
Contents
About the Contributors
Part I: Theory and Rational Bases
1: General Considerations on the Surgical Techniques in the Treatment of the Atrophic Maxilla
1.1 Introduction
1.2 The Impact of Edentulism on the Quality of Life
1.3 Techniques and Technologies for Implant Rehabilitation
1.4 Indications of Treatment Techniques Based on the Degree and Location of Bone Atrophy
1.5 Reasons for This Book
References
2: Surgical Anatomy of the Atrophic Maxilla
2.1 Introduction
2.1.1 Cone-Beam Computed Tomography (CBCT): The Second Level of Image-Guided Diagnosis
2.2 The Physiopathology of Edentulism
2.3 The Anatomical and Radiological Aspects of the Edentulous Maxilla
2.3.1 Premaxilla
2.3.2 Midmaxilla
2.3.2.1 Surgical Anatomy of the Midmaxilla
2.3.2.2 Iuxtameatal Implants
2.3.3 Posterior Maxilla
2.3.3.1 Radiological Landmarks
2.3.3.2 Implants in the Pterygoid Region, Radiological Diagnosis and Planning
References
3: Integrating Modern Diagnostic Tools with Digital Engineering
3.1 Introduction to Applied Digital Technologies
3.1.1 Medical Imaging
3.1.1.1 Short Basics of CT and CBCT Technology
Computed Tomography (CT)
Cone-Beam Computed Tomography (CBCT)
3.1.1.2 Radiation Dose
3.1.1.3 Generic Imaging Protocols
3.1.1.4 Accuracy of 2D and 3D Measurements
3.1.1.5 Image-Based Classification of Bone Quality
3.1.1.6 Digital Imaging and Communications in Medicine (DICOM)
3.1.2 Computer-Aided Design (CAD)
3.1.3 Finite Element Analysis (FEA)
3.1.4 Additive Manufacturing
3.2 The Method of Concurrent Anatomical Engineering
3.2.1 Image Acquisition
3.2.2 Image Processing
3.2.3 Interfacing CAD, FEA, and AM
3.3 Potential of Digital Engineering in Clinical Practice
References
4: Surgical Planning Softwares and Computer Guided Implantology
4.1 The Importance of 3-D Diagnosis and Treatment Planning in the Atrophic Maxilla
4.2 Bone Grafting Surgical Protocols Using Three-Dimensional Technologies
4.2.1 Ganz–Rinaldi Sinus Augmentation Lateral Approach Protocol
4.2.1.1 Special Cases
4.2.1.2 Post-operative Use
4.2.2 Ganz–Rinaldi Protocol for Bone Harvesting from Mandibular Symphysis or Body Ramus
4.2.3 Ganz–Rinaldi Reconstructive Surgery Protocol
4.2.4 Ganz–Rinaldi Zygomatic implants Protocol
4.2.4.1 Introduction
4.3 Ganz–Rinaldi Bone Grafting Surgical Protocols Using Three-Dimension Technologies
4.3.1 Clinical Innovation: Lateral Sinus Lift Surgical Guide—Digital Workflow
4.3.1.1 Summary
4.3.2 Clinical Innovation: Ramus Harvest Guide—Digital Workflow
4.3.2.1 Summary
4.4 Conclusion
References
5: Dynamic Navigation Systems for the Rehabilitation of the Atrophic Maxillae
5.1 Introduction and Historical Background of Guided Surgery
5.2 An Overview of Dynamic Navigation
5.3 Dynamic Navigation Workflow(s) and Key Concepts
5.3.1 Workflow: Stent, Scan, Plan, and Place
5.3.1.1 Stent and Scan
5.3.2 Workflow Improvements: The Trace Registration (TR) Protocol
5.3.2.1 Plan
5.3.2.2 Trace
5.3.2.3 Place
5.3.3 Full-Arch Implant Prosthetic Treatment Workflow
5.3.3.1 Workflow for Transitioning the Terminal Natural Dentition to an Implant-Supported Full-Arch Prosthesis
5.3.3.2 Use of a Mini Implant
5.3.3.3 Use of Mini Screws
5.3.4 Potential Sources of Guidance Errors
5.4 Discussion
5.5 Pterygoid Implants for Totally Edentulous Patients
5.6 Conclusions
References
6: Robotics for Implant Reconstruction of the Edentulous Maxilla
6.1 An Overview of Robotic Surgery
6.2 Computer-Guided Surgery Options for Implant Placement in the Edentulous Maxilla
6.3 Workflow of Robotic Surgery for the Edentulous Maxilla
6.4 Extramaxillary Applications in Robotic Surgery
References
7: Tilted Implants
7.1 Introduction and a Brief History of the Development of the Malo Protocol
7.1.1 1990: Establishment of the Immediate Load Protocol
7.1.2 1993: The First Case of the All-on-4 Standard Mandible
7.1.3 1996: The First AO4 Standard Maxilla
7.1.4 2004: Beginning of the Development of the All-on-4 Hybrid and Double Zygoma
7.1.5 2005: Adaptation of the All-on-4 Concept to Guided Surgery
7.2 Malo Classification of the Edentulous Maxilla
7.3 The Biomechanics of AO4
7.4 The Malo Protocol—AO4: Rehabilitation for the Edentulous Maxilla
7.5 The Malo Bridge
7.6 Maintenance
References
8: Short® Implants and TRINIA® Full-Arch Prostheses for the Rehabilitation of the Atrophic Maxilla
8.1 Introduction to Implant Reconstructions in the Edentulous Maxilla: Current Status and Materials Perspective
8.2 Introduction to SHORT® Tapered Implants
8.2.1 Atrophic Maxilla: Introduction
8.2.2 Materials and Methods
8.2.3 Patient Group with Four Implants
8.2.4 Results
8.2.5 Case Reports
8.2.5.1 “All on Four” with Full-Arch TRINIA® Prosthesis
Front and Premolar Region Implants
8.2.6 Patient Group with Three Implants
8.2.7 Results
8.2.8 Case Reports
8.2.8.1 “All on Three” with Full-Arch TRINIA® Prosthesis
Nasopalatine and Premolar Region Implants
8.2.9 Patient Group with One Implant
8.2.10 Results
8.2.11 Case Report
8.2.11.1 “All on One” with Nasopalatine Implant and Full-Arch TRINIA® Prosthesis
8.2.11.2 Minimal Crestal Widening and Spreading After Epiperiosteal Preparation in the Premolar Region
8.2.11.3 Tuber Implants
8.3 Discussion
8.4 Conclusion of the Three Study Groups
References
9: Bone Grafting
9.1 Introduction
9.2 Graft Types
9.2.1 Autologous Bone Donor Sites
9.2.2 Bone Grafts Cellular Healing
9.2.3 Morphological Structure of Donor Sites
9.3 Bone Grafts from the Iliac Crest
9.3.1 Background
9.3.2 Anatomic Evaluation
9.3.3 Pharmacological Aspects
9.3.4 Surgical Techniques
9.3.5 Iliac Crest Surgical Harvesting Techniques
9.3.6 Surgical Procedures for Grafting in the Upper Maxilla
9.3.6.1 Sinus Lift with Iliac Crest Graft
9.3.6.2 Onlay Blocks
9.3.6.3 Titanium Mesh
9.3.6.4 Interpositional Blocks (Inlay Technique)
9.3.7 Complications
9.3.7.1 Harvesting Issues
9.3.7.2 Graft Positioning Issues
9.3.8 Discussion
9.4 Bone Grafts from the Mandible
9.4.1 Background
9.4.1.1 Osteoconduction
9.4.2 Anatomic Evaluation
9.4.3 Pharmacological Aspects
9.4.4 Surgical Technique
9.4.4.1 Graft Harvesting
9.4.4.2 Mandibular Branch
9.4.4.3 Chin Symphysis
9.4.4.4 Edentulous Mandibular Areas
9.4.5 Graft Positioning
9.4.6 Surgical Procedures for Grafting in the Upper Maxillae
9.4.7 Complications
9.4.8 Discussion
9.5 Bone Grafts from the Calvaria
9.5.1 Background
9.5.2 Anatomic Evaluation
9.5.3 Pharmacological Aspects
9.5.4 Surgical Technique
9.5.4.1 Graft Harvesting
9.5.5 Graft Positioning
9.5.6 Complications
9.5.7 Augmentation Methods
9.5.8 Discussion
References
10: Post-oncological and Post-traumatic Maxillary Reconstruction
10.1 Introduction
10.2 Diagnostics
10.3 Clinical Case I (Surgery by Rolf Ewers and Clemens Klug): Point-to-Point Navigation-Assisted Repositioning of the Zygoma by Means of Pre-bent Osteosynthesis Plates
10.3.1 Preoperative Planning
10.3.2 Surgical Procedure
10.4 Clinical Case II (Surgery by Arnulf Baumann): An Orbito-Zygomatico-Maxillary Complex (OZMC) Fracture Is Corrected by Using a Combination of Titanium Mesh and Synthetic Material, Accompanied by Intraoperative Navigation
10.4.1 Preoperative Planning
10.4.2 Surgical Procedure
10.5 Clinical Case III (Surgery by Franz Watzinger): Correction of Midfacial Deformity (Hypoplasia) by Means of Individualized Polyether-Ether-Ketone (PEEK) Implants
10.5.1 Preoperative Planning
10.5.2 Surgical Procedure
10.6 Clinical Case IV (Surgery by Emeka Nkenke): Maxillary Reconstruction with Prefabricated Vascularized Free Fibula Flap with Dental Implants Already Inserted Before Harvesting the Flap
10.6.1 Preoperative Planning
10.6.2 Surgical Procedure
10.7 Discussion
References
11: Zygomatic Implants. The ZAGA Concept
11.1 Indications
11.2 Technique Evolution
11.2.1 PI Brånemark Original Technique
11.2.2 The Slot Technique
11.2.3 The Extra-Sinus, Exteriorized, and Extra-Maxillary Approach
11.2.4 The Zygoma Anatomy-Guided Approach (ZAGA)
11.3 The ZAGA Concept
11.3.1 The ZAGA Classification
11.3.2 The ZAGA Zones
11.3.3 The ZAGA Concept
11.3.3.1 The ZAGA “Tunnel Osteotomy” for a Round Implant Design
11.3.3.2 The “ZAGA Channel Osteotomy” and Flat Implant Design
11.4 The ZAGA Flat and ZAGA Round Zygomatic Implants: The Story of a Breakthrough
11.4.1 The Clinical Pain Points to Solve
11.4.2 ZAGA and Adapted Implant Design
11.4.3 A Design Becoming a Reality
11.5 ORIS Criteria to Evaluate Zygomatic Implant Rehabilitation
11.6 The use of ZAGA Concept and the New Zygomatic Implant Designs on the Extremely Atrophied Maxilla
11.7 Zygomatic Implant Network: www.zagacenters.com
11.7.1 What Is the Goal of the ZAGA Center Network?
11.7.2 Benefits and Responsibilities Associated with the ZAGA Network
11.7.3 Educational Programs
11.8 Conclusions
References
12: Additively Manufactured Subperiosteal Jaw Implant (AMSJI)
12.1 Introduction: Subperiosteal Implants and the AMSJI Concept
12.1.1 Introduction
12.1.2 Macroscopic, Morphological, and Structural Characteristics of the AMSJI
12.1.3 Microscopic Surface Characteristics of the AMSJI
12.1.4 Structural and Biomechanical Characteristics of the AMSJI
12.2 Surgical and Prosthetic Procedures
12.2.1 Scan Prosthesis
12.2.2 Surgical Technique
12.2.2.1 Instrumentation
12.2.2.2 Flap Incision and Dissection
12.2.2.3 Exposure of Maxillary Bone and Implant Placement
12.2.2.4 Connect the Interim Superstructure
12.2.2.5 Screw Fixation of the AMSJI
12.2.2.6 Suture of the Flaps
12.2.2.7 Assembly of the Temporary Prosthetic Structure
12.2.2.8 Final Prosthetic Structure
12.2.2.9 Double Structure
12.2.2.10 Aftercare (from AMSJI® Manual 2019)
12.3 Resection Guides for AMSJI: VOG and HOG
12.4 Consensus Online Meeting Report, Gent, September 14, 2020
12.4.1 Introduction
12.4.2 Number of Screw Holes per Wing
12.4.3 Different Types/Brands of Osteosynthesis Screws
12.4.4 Space Between the Arms and Loop Crossing the Maxillary Crest
12.4.5 Position of the Buccal Horizontal Part of the Main Frame and Configuration of the Screw Holes in the Posterior Wing
12.4.6 Shape of the Posts
12.4.7 Retention of the Temporary Restoration
12.4.8 Prevention and Management of Local Infection
12.4.8.1 Preoperative Prophylactic Antibacterial Protocol
12.4.8.2 Post-operative Prophylactic Antibacterial Protocol
12.4.8.3 Treatment of Dental Peri-Implant Mucositis
12.4.8.4 Treatment of Chronic Periodontitis and Dental Peri-Implantitis
12.4.8.5 Treatment of Infected Orthopedic and Craniofacial Implants
12.4.9 Buccal Recessions and Gingival Biotype
12.4.10 Vertical and Horizontal Ostectomy Guides
12.4.11 Biomechanical Evaluation Using Finite Element Analysis
12.4.12 A Simplified Temporary and Definitive Suprastructure for Acrylic Coverage
References
Part II: Clinical Cases and Surgical Techniques
1.1 Introduction
13: Clinical Case No. 1: Computer Aided Implantology, Tilted Implants
13.1 Medical and Clinical Picture
13.2 Preoperative Considerations
13.3 Surgical Procedures
13.4 Postoperative Considerations
14: Clinical Case No. 2: Full Arch Guided Surgery - Immediate Load
14.1 Medical and Clinical Picture
14.2 Preoperative Considerations
14.3 Surgical Procedures
14.4 Postoperative Considerations
15: Clinical Case No. 3: All-on-4
15.1 Medical and Clinical Picture
15.2 Preoperative Considerations
15.3 Surgical Procedures
15.4 Postoperative Considerations
16: Clinical Case No. 4: All-on-4
16.1 Medical and Clinical Pictures
16.2 Preoperative Considerations
16.3 Surgical Procedures
16.4 Postoperative Considerations
17: Clinical Case No. 5: All-on-4, Immediate Loading
17.1 Medical and Clinical Picture
17.2 Preoperative Considerations
17.3 Surgical Procedures
17.4 Postoperative Considerations
18: Clinical Case No. 6: Dynamic Navigation, Pterygoid Implants
18.1 Medical and Clinical Pictures
18.2 Preoperative Considerations
18.3 Surgical Procedures
18.4 Postoperative Considerations
19: Clinical Case No. 7: Robotic Surgery, Immediate Loading
19.1 Medical and Clinical Picture
19.2 Preoperative Considerations
19.3 Surgical Procedures
19.4 Postoperative Considerations
References
20: Clinical Case No. 8: Robotic Surgery, Full Arch
20.1 Introduction
20.2 Medical and Clinical Picture
20.3 Preoperative Considerations
20.4 Surgical Procedures
20.5 Postoperative Considerations
References
21: Clinical Case No. 9: Extra Short Implants, Immediate Loading
21.1 Medical and Clinical Picture
21.2 Preoperative Considerations
21.3 Surgical Procedures
21.4 Prosthetic Procedures
21.5 Postoperative Considerations
22: Clinical Case No. 10: Tilted Implants, Iuxtameatal Implants, Immediate Loading
22.1 Preoperative Considerations
22.2 Surgical Procedures
22.3 Postoperative Considerations
22.3.1 Prosthetic Phase
23: Clinical Case No. 11: Zygomatic Implants, Immediate Function
23.1 Medical and Clinical Considerations
23.2 Preoperative Considerations
23.3 Surgical Procedures
23.4 Postoperative Considerations
24: Clinical Case No. 12: Zygomatic Implants, Computer Guided Approach
24.1 Medical and Clinical Picture
24.2 Preoperative Considerations
24.3 Surgical Procedures
24.4 Postoperative Considerations
25: Clinical Case No. 13: Dynamic Navigation, Pterygoid Implants
25.1 Medical and Clinical Picture
25.2 Preoperative Considerations
25.3 Surgical Procedures
25.4 Postoperative Considerations
26: Clinical Case No. 14: Zygomatic Implants in Cleft Palate Patient
26.1 Medical and Clinical Picture
26.2 Preoperative Considerations
26.3 Surgical Procedures
26.4 Postoperative Considerations
References
27: Clinical Case No. 15: Zygomatic Robotic Implant Surgery
27.1 Medical and Clinical Picture
27.2 Preoperative Considerations
27.3 Surgical Procedures
27.4 Postoperative Considerations
References
28: Clinical Case No. 16: Double Zygoma, Zaga Flat
28.1 Medical and Clinical Picture Resume
28.2 Preoperative Considerations
28.3 Surgical Procedures
28.3.1 Right Side
28.3.2 Left Side
28.4 Postoperative Considerations
29: Clinical Case N° 17: Zygoma Quad, Zaga 4
29.1 Medical and Clinical Picture Resume
29.2 Preoperative Considerations
29.3 Surgical Procedures
29.4 Postoperative Considerations
30: Clinical Case N° 18: Zygoma Quad, Dynamic Navigation
30.1 Medical and Clinical Picture
30.2 Preoperative Considerations
30.3 Surgical Procedures
30.4 Postoperative Considerations
31: Clinical Case N° 19: Short Implants, Incisal Foramen, Trio-Trinia
31.1 Medical and Clinical Picture
31.2 Preoperative Considerations
31.3 Surgical Procedures
31.4 Possible Pitfalls and Complications
31.5 Postoperative Considerations and Conclusion
References
32: Clinical Case N° 20: Short Implants, Trio-Trinia
32.1 Medical and Clinical Picture
32.2 Preoperative Considerations
32.3 Surgical Procedures
32.4 Postoperative Considerations
33: Clinical Case N° 21: Bone Grafting, Sinus Augmentation, Reconstructive Surgery
33.1 Medical and Clinical Picture
33.2 Preoperative Considerations
33.3 First Intervention
33.3.1 Surgical Procedures
33.4 Second Intervention
33.4.1 Preoperative Considerations
33.5 Surgical Procedures
33.6 Third Intervention
33.6.1 Preoperative Considerations and Surgical Procedures
33.7 Final Prosthesis
34: Clinical Case No. 22 Zygoma Quad, Computer Guided Implantology
34.1 Medical and Clinical Picture
34.2 Preoperative Considerations
34.3 Surgical Procedures
34.4 Postoperative Considerations
35: Clinical Case No. 23: Hemimaxillectomy, Zygomatic Implant, Computer Guided Approach
35.1 Preliminary Remarks
35.2 Medical and Clinical Pictures
35.3 Preoperative Considerations
35.4 Surgical Procedures
35.5 Postoperative Considerations
36: Clinical Case No. 24: AMSJI, Patient Specific Implants, Subperiosteal Implant
36.1 Medical and Clinical Picture
36.2 Preoperative Considerations
36.3 Surgical Procedures
36.4 Postoperative Considerations
37: Clinical Case No. 25: AMSJI, Patient Specific Implants, Subperiosteal Implant
37.1 Medical and Clinical Picture
37.2 Preoperative Considerations
37.3 Surgical Procedures
37.4 Postoperative Considerations
38: Clinical Case No. 26: AMSJI, Patient Specific Implants, Cutting Guide VOG and HOG
38.1 Medical and Clinical Picture
38.2 Preoperative Considerations
38.3 Surgical Procedures
38.4 Postoperative Considerations
39: Clinical Case No. 27: AMSJI, Patient Specific Implants, Cutting Guide VOG and HOG
39.1 Medical and Clinical Picture
39.2 Preoperative Considerations
39.3 Surgical Procedures
39.4 Postoperative Considerations
40: Clinical Case No. 28: AMSJI, Temporomandibular Joint Prosthesis, Patient Specific Implants
40.1 Medical and Clinical Picture
40.2 Preoperative Considerations
40.3 Surgical Procedures
40.4 Postoperative Considerations

Citation preview

Implants and Oral Rehabilitation of the Atrophic Maxilla Advanced Techniques and Technologies Marco Rinaldi Editor

123

Implants and Oral Rehabilitation of the Atrophic Maxilla

Marco Rinaldi Editor

Implants and Oral Rehabilitation of the Atrophic Maxilla Advanced Techniques and Technologies

Editor Marco Rinaldi Dr Marco Rinaldi Dental Clinic Bologna, Italy Clinica Privata Villalba GVM Care & Research Bologna, Italy

ISBN 978-3-031-12754-0    ISBN 978-3-031-12755-7 (eBook) https://doi.org/10.1007/978-3-031-12755-7 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

To my wife Cristina, my son Francesco, and to my daughter Chiara

Acknowledgements

I thank the friends and colleagues of the CAI Academy (https://www.yourcaiacademy.org), many of whom are also coauthors of this book. The CAI Academy is the oldest academy dedicated to computer-assisted and digital applications in surgical and prosthetic implantology. The events of the CAI Academy have been moments of meeting and training with many of the authors of this book.

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Contents

Part I Theory and Rational Bases 1 General  Considerations on the Surgical Techniques in the Treatment of the Atrophic Maxilla��������������������������������������   3 Marco Rinaldi 2 Surgical  Anatomy of the Atrophic Maxilla������������������������������������  23 Michele Manacorda and Raffaele Vinci 3 Integrating  Modern Diagnostic Tools with Digital Engineering��������������������������������������������������������������������������������������  47 Panos Diamantopoulos and Gerlig Widmann 4 Surgical  Planning Softwares and Computer Guided Implantology������������������������������������������������������������������������������������  65 Scott D. Ganz and Marco Rinaldi 5 Dynamic  Navigation Systems for the Rehabilitation of the Atrophic Maxillae������������������������������������������������������������������ 111 Luigi Vito Stefanelli and George A. Mandelaris 6 Robotics  for Implant Reconstruction of the Edentulous Maxilla���������������������������������������������������������������������������������������������� 129 Jeffrey Ganeles, Uday N. Reebye, Frederic J. Norkin, and Liliana Aranguren 7 Tilted Implants �������������������������������������������������������������������������������� 145 Paulo Malo, Andreia Filipa Fontoura de Castro Rodrigues, and Tiago Miguel Bravo Estêvão 8 Short® Implants and TRINIA® Full-­Arch Prostheses for the Rehabilitation of the Atrophic Maxilla������������������������������ 183 Rolf Ewers and Estevam A. Bonfante 9 Bone Grafting ���������������������������������������������������������������������������������� 209 Raffaele Vinci 10 P  ost-oncological and Post-­traumatic Maxillary Reconstruction���������������������������������������������������������������������������������� 231 Kurt Schicho and Godoberto Guevara Rojas

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11 Zygomatic  Implants. The ZAGA Concept������������������������������������ 247 Carlos Aparicio, Andrew Dawood, and Cemal Ucer 12 Additively  Manufactured Subperiosteal Jaw Implant (AMSJI)������ 277 Marco Rinaldi and Maurice Y. Mommaerts Part II Clinical Cases and Surgical Techniques 13 Clinical  Case No. 1: Computer Aided Implantology, Tilted Implants �������������������������������������������������������������������������������� 319 Marco Rinaldi 14 Clinical  Case No. 2: Full Arch Guided Surgery - Immediate Load�������������������������������������������������������������� 327 Scott D. Ganz 15 Clinical  Case No. 3: All-on-4 ���������������������������������������������������������� 339 Paulo Malo, Ezio Costa, and Beatrice Costa 16 Clinical  Case No. 4: All-on-4 ���������������������������������������������������������� 343 Paulo Malo, Ezio Costa, and Beatrice Costa 17 Clinical  Case No. 5: All-on-4, Immediate Loading ���������������������� 347 Paulo Malo, Ezio Costa, and Beatrice Costa 18 Clinical  Case No. 6: Dynamic Navigation, Pterygoid Implants�������� 351 Luigi Vito Stefanelli 19 Clinical  Case No. 7: Robotic Surgery, Immediate Loading �������� 357 Jeffrey Ganeles, Frederic J. Norkin, and Liliana Aranguren 20 Clinical  Case No. 8: Robotic Surgery, Full Arch�������������������������� 373 Uday N. Reebye, Brandon D. Kofford, Benjamin T. Vanderkwaak, and Lauren R. Hattrich 21 Clinical  Case No. 9: Extra Short Implants, Immediate Loading �������������������������������������������������������������������������������������������� 381 Mauro Marincola and Rolf Ewers 22 Clinical  Case No. 10: Tilted Implants, Iuxtameatal Implants, Immediate Loading�������������������������������������������������������� 393 Michele Manacorda and Raffaele Vinci 23 Clinical  Case No. 11: Zygomatic Implants, Immediate Function�������������������������������������������������������������������������������������������� 401 Paulo Malo, Ezio Costa, and Beatrice Costa 24 Clinical  Case No. 12: Zygomatic Implants, Computer Guided Approach ���������������������������������������������������������������������������� 405 Marco Rinaldi 25 Clinical  Case No. 13: Dynamic Navigation, Pterygoid Implants�������������������������������������������������������������������������������������������� 419 Luigi Vito Stefanelli

Contents

Contents

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26 Clinical  Case No. 14: Zygomatic Implants in Cleft Palate Patient ���������������������������������������������������������������������������������������������� 425 Andrea Tedesco and Marco Rinaldi 27 Clinical  Case No. 15: Zygomatic Robotic Implant Surgery�������� 433 Uday N. Reebye, Brandon D. Kofford, Benjamin T. Vanderkwaak, and Lauren R. Hattrich 28 Clinical  Case No. 16: Double Zygoma, Zaga Flat ������������������������ 439 Carlos Aparicio, Peter Simon, and Madalina Simon 29 Clinical  Case N° 17: Zygoma Quad, Zaga 4���������������������������������� 453 Carlos Aparicio and Natalia Barluenga 30 Clinical  Case N° 18: Zygoma Quad, Dynamic Navigation���������� 467 Luigi Vito Stefanelli and Fabrizio Grivetto 31 Clinical  Case N° 19: Short Implants, Incisal Foramen, Trio-Trinia���������������������������������������������������������������������������������������� 479 Rolf Ewers, Michael Truppe, and Boyd J. Tomasetti 32 Clinical  Case N° 20: Short Implants, Trio-Trinia ������������������������ 493 Marco Rinaldi 33 Clinical  Case N° 21: Bone Grafting, Sinus Augmentation, Reconstructive Surgery ������������������������������������������������������������������ 503 Marco Rinaldi 34 Clinical  Case No. 22 Zygoma Quad, Computer Guided Implantology������������������������������������������������������������������������������������ 521 Marco Rinaldi 35 Clinical  Case No. 23: Hemimaxillectomy, Zygomatic Implant, Computer Guided Approach������������������������������������������ 533 Marco Rinaldi 36 Clinical  Case No. 24: AMSJI, Patient Specific Implants, Subperiosteal Implant �������������������������������������������������������������������� 547 Marco Rinaldi 37 Clinical  Case No. 25: AMSJI, Patient Specific Implants, Subperiosteal Implant �������������������������������������������������������������������� 563 Marco Rinaldi 38 Clinical  Case No. 26: AMSJI, Patient Specific Implants, Cutting Guide VOG and HOG ������������������������������������������������������ 577 Marco Rinaldi 39 Clinical  Case No. 27: AMSJI, Patient Specific Implants, Cutting Guide VOG and HOG ������������������������������������������������������ 593 Marco Rinaldi 40 Clinical  Case No. 28: AMSJI, Temporomandibular Joint Prosthesis, Patient Specific Implants��������������������������������������������� 611 Maurice Y. Mommaerts

About the Contributors

Carlos Aparicio, MD, DDS, MSc, MSc, DLT, PhD received his Bachelor of Medicine and Surgery degree with Summa Cum Laude from the University of Navarra in 1978. Thereafter, he completed postgraduate studies in Dentistry in 1983 at the University of Barcelona. He became a Dental Laboratory Technician in 1983 at Ramon y Cajal School in Barcelona. Dr. Aparicio received a Diploma in Implant Dentistry in 1984 from the University of Gothenburg (with Prof. P-I Brånemark as tutor), and he was awarded a Master of Materials Science at the University of Barcelona in 1990 before receiving his Diploma in Periodontics from the University of Gothenburg in 1995 (Profs. Jan Lindhe and Jose Javier Echeverría as tutors). He was awarded a Master’s in Biomedical Research from the University of Barcelona in 2010, and in 2013, Dr. Aparicio received a PhD in medicine with Summa Cum Laude and International Mention. The thesis title was “on Zygomatic implants: state of the art and criteria for success” and this was defended at the University of Barcelona (Profs. Tomas Albrektsson, Jan Lindhe, Xavier Gil, Jose M Suarez, and Mariano Monzo as Jury). He is a fellow researcher with the Handicap Research Group in the Department of Biomaterials at the University of Gothenburg (Prof. Tomas Albrektsson as tutor) and became an International Teaching Scholar at Indiana University School of Dentistry, Indianapolis, USA, in 2021. He has written numerous articles for international journals. In 2012, he was the editor of the book Zygomatic Implants. The Anatomy-Guided Approach (ZAGA). He has served as referee at European J. of Oral Implantology and J. of

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Clinical Implant Dentistry and Related Research. He is a Fellow of the Royal Society of Medicine in England and became an academic at the Royal European Academy of Doctors in 2016. Dr. Aparicio is a past president 2003–2004 of the Osseointegration Foundation of the American Academy of Osseointegration. From 2003 to 2005, he served as a Board Member of the European Academy of Osseointegration. He was President of the European Association Barcelona meeting, in Barcelona in 2007. He also founded and is the honorific President of the Spanish Society of Minimally Invasive Dentistry. Dr. Aparicio received the Fonseca Award from the Spanish Society of Periodontics three times and was awarded the Simo Virgili Prize by the Catalonian Society of Odonto-Stomatology twice. In his latest endeavor, he founded the Zygoma ZAGA Centers Network in 2018 (www. zagacenters.com) with the goal of spreading the ZAGA philosophy globally. Currently, he is sharing his knowledge as a Zygomatic implants Senior Consultant at Hepler Bone Clinic in Barcelona, Spain. Liliana  Aranguren, DDS, MDSc  received her dental degree from the University of Zulia, in Maracaibo, Venezuela. After briefly practicing there, she emigrated to the USA and completed a residency in Advanced Education in General Dentistry, followed by a residency and master’s degree in Periodontics at the University of Connecticut. She is a Diplomate of the American Board of Periodontology, Fellow of the ITI, and early adopter of Yomi Robotic Guided Surgery. She has written and lectured on implant dentistry, periodontics, technology innovations, management of peri-implantitis, and dental esthetics. Currently, she practices periodontics and implant dentistry in Boca Raton, FL, with the South Florida Center for Periodontics and Implant Dentistry.

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Natalia  Barluenga 1997–2000, Bachelor’s Degree in Nursing, Univesitat Internacional de Catalunya-UIC, Spain 2000–2005, Bachelor’s Degree in Dentistry, Universitat Internacional de Catalunya-UIC, Spain 2005–2007 University Master’s Degree in Esthetic and Restorative Dentistry, Doctoral Program in Clinical and Lab Techniques in Dentistry, Universitat Internacional de CatalunyaUIC, Spain 2008–2009 Diploma in Implant Dentistry, Clinica Aparicio in collaboration with Gothenburg University, Sweden 2009–2010 Diploma in Aesthetic Dentistry, Clinica Aparicio in collaboration with UIC, Spain 2014–2015 Diploma in Clinical Periodontology, Clinica Aparicio in collaboration with Gothenburg University, Sweden Private practice and special field: oral surgery, implantology, restorative and aesthetics Estevam  A.  Bonfante, DDS, MS, PhD, has developed a specific background in prosthodontic reconstructions conventionally and implant supported. During his master’s (2003–2005) and PhD (2005–2009) in Oral Rehabilitation, efforts were devoted to the understanding of the application of biomaterials and restorative materials used in dentistry. He has been a full-time Associate Professor in the Department of Prosthodontics and Periodontology at the University of São Paulo—Bauru School of Dentistry since 2013. Besides reviewing for highimpact indexed journals, he is part of the selected board of reviewers of the International Journal of Prosthodontics. He has, along with a team of collaborators, been responsible for several grants, especially from the Fundação de Amparo a Pesquisa do Estado de São Paulo (FAPESP# 2012/19078-7 and 2021/06730-7) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq# 307255/2021-2/). He is a member of the International Association for Dental Research and has participated in scientific publications, book chapters, seminars, and international courses.

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Beatrice  Costa, DDS, work at the “Ezio Costa-Malo Dental Clinic,” in Verona, where she deals with oral surgery, implantology, and smile aesthetics. She is a trainer in “Academy EC,” the first practical course on Perioral Aesthetics.

Ezio Costa, MD, DDS,  is an adjunct professor of “Aesthetics of perioral tissues” at the University of Roma-Tor Vergata. He is a speaker at international courses and congresses on Aesthetic Therapy of the Face and Smile. He directs “Clinica Ezio Costa-Malo Dental,” in Verona, where he starts “Academy EC,” the first practical course on Perioral Aesthetics.

Andrew  Dawood, MRD, RCS, MSc, BDS  Specialist in Periodontics and Prosthodontics Andrew devotes his time to dental implant surgery at the Dawood and Tanner Specialist Dental Practice. His research interests include implant design and manufacture, 3D technologies, and treatment planning and longevity in implant and restorative dentistry. Andrew is an Honorary Consultant at University College Hospital London where he provides implantbased reconstructions for oncology patients. Andrew carries out surgery for both referring colleagues and for patients of The Dawood and Tanner Practice. He utilizes the latest technology to plan and implement both simple and advanced reconstructions, working closely with general dental practitioners and other specialists. He particularly enjoys the collaborative aspect of treatment, helping the general dental practitioner to bring the benefits of implant treatments to their patients and their working life. Andrew has a particular interest in the implant rehabilitation of patients who have atrophic jaws, particularly those who have suffered implant failure or extensive bone loss. Andrew has a passion for technology and ceramics and is the Clinical Director of Cavendish Imaging, an independent CBCT imaging center and medical modeling facility, and founder of

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www.additive.xyz—a 3D printing studio. He is a recreational potter. Panos  Diamantopoulos, DPhil, Dr. Eng. is a Research Professor and Director of the Medical 3D Printing and Computer Guided Surgery Unit at Physiology Laboratory of Athens University Medical School. He received a Degree in Mechanical Engineering (BEng) with focus on implant biomechanics from the University of Brighton (1995). He completed a master’s program (MPhil) in Computational Implant Biomechanics and received his doctoral degree (DPhil) in Biomedical Modeling from the University of Sussex (2001). His doctoral thesis demonstrated the practical integration of medical imaging with computer-aided design (CAD), finite element simulation (FEA), and rapid prototyping (RP), setting the underlying technological framework utilized nowadays by computer-guided surgery. As a research professor at the University of Sussex, he founded one of the first Biomedical Modeling Units in the world and pioneered the application of digital technologies (scanning, design, simulation, manufacturing) for preoperative planning, surgical guidance, and implant customization. He has collaborated with many leading universities including Oxford, UCL, Leuven, Padova, EPFL, and lately Athens. He has also worked with many hospitals and private practices for the clinical introduction of “digital technologies,” including CBCT, computer-guided implantology, and medical 3D printing procedures. He has worked on a very large number of clinical cases in many medical disciplines and has acted as a consultant and instructor for many companies in the underlying fields. Dr. Diamantopoulos is committed to proving and promoting the benefits of digital engineering in clinical practice. He has been recognized as a “Distinguished Researcher” and has contributed to many peer-reviewed scientific journals, conferences, seminars, and workshops. During the COVID-19 pandemic, he has been coordinating Medical 3D Printing activities on behalf of the Greek Ministry of Health. He was recently elected as the next President of the Computer Aided Implantology (CAI) Academy, the international scientific organization that pioneered the application of “digital technology” in dentistry.

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Tiago  Estêvão received his master’s degree in Dental Medicine in 2009 at Instituto Superior de Ciências da Saúde Egas Moniz. He worked in Malo Clinic from 2009 to 2020. He has been working in Malo Dental since 2020, in Dr. Sobczak Klinika since 2021, and in Clinica Médica Dentária Dr Orlando Estêvão since 2021. He has exclusive practice in Oral Surgery and Implantology. He is an expert in complex surgeries of total rehabilitation specially with All-on-4, unitary implants, complex extractions, and periodontal surgery. He is a speaker at national and international courses and congresses. Rolf  Ewers  is currently Chairman of the CMF Institute Vienna, Austria. Raised in Dresden and Stuttgart, Germany, his final school year was spent as an exchange student in San Diego, USA.  He studied Medicine and Dentistry in Freiburg, Germany. His Residency was started as a first-year surgery resident at the Downstate University in Brooklyn, USA, continuing his training as a Cranio-, Maxillofacial and Oral Surgeon and finishing with his PhD in Freiburg, Germany. For 9 years, he was Deputy Chairman of the University Hospital for Oral-Maxillofacial Surgery in Kiel, Germany. Until October 2012, for 23 years he was Chairman of the University Hospital of Cranio-, Maxillofacial and Oral Surgery in Vienna, Austria, and is also since that time chair of the CMF Implant Institute in Vienna, which he continues to be until now. All other information and full-size bio: http:// www.cmf-vienna.com/en/the-institute/our-teamof-specialists/cv. Jeffrey  Ganeles, DMD  After receiving a Bachelor of Science from Cornell University, he received his DMD from Boston University Goldman School of Graduate Dentistry. Following dental school, he completed a general practice residency at the Hospital of the University of Pennsylvania, then was awarded a research position and received specialty training in periodontics and a Certificate in Advanced Graduate Studies from the University of Pennsylvania College of Dental Medicine. Dr. Ganeles is a Diplomate of the American Board of Periodontology, Fellow of the ITI, Academy of Osseointegration, American College

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of Dentists, and International Society of Periodontal Plastic Surgery. He holds faculty positions at Nova Southeastern University College of Dental Medicine and Boston University Goldman School of Dental Medicine. Dr. Ganeles lectures widely on implant dentistry, immediate loading, technology innovations, and periodontal regeneration and is well published in these fields. He is believed to have performed the first robotic implant surgical procedure worldwide. Currently, he practices periodontics and implant dentistry in Boca Raton, FL, with the South Florida Center for Periodontics and Implant Dentistry. Scott D. Ganz  is well published in many scientific journals (over 125 articles) and contributed to 15 professional textbooks. He continues to deliver presentations both nationally and internationally as a featured speaker on the prosthetic and surgical phases of implant dentistry and is considered one of the world’s leading experts in the field of computer utilization for diagnostic, graphical, interactive treatment planning, CBCT, and CAD CAM applications in dentistry. He has been a featured speaker for most major dental organizations, currently serves as Editor-in-Chief of “digital” International Magazine, and serves on the editorial staff of several other publications. Dr. Ganz is a Past President of the N.J. Section of the American College of Prosthodontists, Past President of the CAI Academy (Computer-Aided Implantology Academy), serves as adjunct faculty of Rutgers School of Dental Medicine and the Hackensack University Medical Center, the Board of Directors of the Clean Implant Foundation, Digital Dentistry Society, and Past Board of Directors of MINEC and the ICOI. He is a Fellow of the Academy of Osseointegration and the International College of Dentists and coDirector of Advanced Implant Education providing live hands-on surgical programs several times each year (AIE—www.aiedental.com). He maintains a private practice for prosthodontics, maxillofacial prosthetics, and implant dentistry in Fort Lee, NJ, USA, and Director of Oral Restoration at Park40, a facility dedicated to full-arch dental implant reconstruction in the heart of Manhattan, New York, USA.  He can be reached via email: [email protected].

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Fabrizio  Grivetto graduated in Medicine and Surgery at Università di Torino in 1995. His Academic Specialization is in Maxillo-Facial Surgery at Università di Torino in 2000. He is first-level medical manager of the Maxillo-Facial Surgery Unit at Azienda OspedalieroUniversitaria Maggiore della Carità in Novara. He is a specialist in complex restorations using zygomatic and pterygoid implants. He lectures nationally and internationally as well as addresses conferences. Godoberto  Guevara Rojas, PhD, has several years of experience in the field of 3D printing in Maxillofacial Surgery, combining his expertise in Engineering and Radiography. He is a lecturer at the University of Applied Sciences in Vienna and has implemented the Course in 3D Printing in Medical Applications for Radiographers. He has participated in various research projects and has several publications in the field of 3D printing in medicine, including a patent in this area. He has been a guest lecturer at various universities across Europe and at national and international congresses. Lauren R. Hattrich  earned her B.S. in Human Biology with highest distinction from North Carolina State University in June 2021. During her undergraduate years, she was a University Ambassador and received certifications in Radiology, Nitrous Oxide, Adult and Pediatric First Aid/CPR/AED, and Phlebotomy. In 2020– 2022, Lauren was an intern at Triangle Implant Center in Durham, NC, working as an anesthesiologist assistant alongside Uday N. Reebye MD, DMD, gaining valuable knowledge and clinical experience. She is currently working as a surgical assistant at Carolina Centers for Oral and Maxillofacial Surgery with hopes of attending dental school in the near future.

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Brandon D. Kofford, DMD, MS, FACP, graduated cum laude from Case Western Reserve University School of Dental Medicine in 2008 and was inducted into the Omicron Kappa Upsilon Honors society. He trained to become a prosthodontist with the United States Air Force from 2008 to 2011. Upon completing his prosthodontics residency in 2011, he successfully challenged the American Board of Prosthodontics that same year becoming a Fellow in the American College of Prosthodontists and a Diplomate of the American Board of Prosthodontics. He completed his U.S.  Air Force obligation while stationed at Royal Air Force Lakenheath in Suffolk, England, obtaining the rank of Major. Dr. Kofford is one of four owners in seven dental practices and a dental laboratory. His focus has been full-arch rehabilitation with a particular emphasis on implant-based solutions. Dr. Kofford developed the separable fastener and Smart Denture Conversions protocol. Dr. Kofford’s immediate-load protocol was published in the February 2021 Journal of Prosthodontics. He mentors graduate students in their research activities and lectures around the United States. He continues to test and develop restorative products, procedures, and protocols that simplify the treatment of the edentulous arch. Dr. Kofford resides in Apex, North Carolina, with his wife and six children. Paulo Malo, DDS, PHD,  is the Founder of Malo Dental & Malo Dental International and Founder of Malo Clinic. He is the inventor of immediate load single implant and small bridges (published in 1996); inventor of All-on-4®, Malo protocol for edentulous; Malo Protocol Zygomatic implants 0°, external protocol; trans-sinus implant protocol; para nerve implant protocol; Malo Bridge, CAD-CAM bar with ceramic or acrylic individually teeth; speedy implant (first bone level and expansion implant); CC parallel implant; inventor of the special soft bone implant WP/RP connection; Zygoma 0° implant; Malo Guide; Step Drills for Implantology; ITA abutment (first platform shifting abutment); angled abutments 45, 60; Zygoma Elevator (Hu-Friedy); and inventor of many patent products commercialized by various companies globally.

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He has over 100 international publications and over 1000 lectures internationally. He has also 23 international awards, as a Scientist and Entrepreneur, including the Prize “Rubrum Lilium 2022,” Florence University, for distinction in Science and Humanity; Portuguese Leader 2020, Mercury Prize; Personality Value Award 2013; Portuguese National Champion European Business Award 2013/14; Innovator of the Year 2011—Mediazone Group; Santiago 2008 for the significant journey and contribution on Oral Rehabilitation, Personality of the year 2007. Michele  Manacorda, DMD, DDS1 is an Oral Surgeon who received his DMD degree from Milano State University, Italy, in 1985. He is Adjunct Professor of Oral Surgery and Oral Implantology at Vita-Salute S. Raffaele University in Milano. He received his bachelor’s degree in Dental Hygiene and master’s degree in Dentistry. He is Adjunct Professor at Oral Surgery Postgraduate School at Vita-Salute University, Milano. He is Scientific Consultant and Clinical Tutor at the Dentistry Unit of San Raffaele Hospital, Milano (Dental Clinic). He is in charge of Digital Diagnosis and Computer Aided Implantology at San Raffaele Hospital, Milano (Dental Clinic). He is Chief Medical Doctor and Director of Smart Dental Clinic at Palazzo della Salute (Istituto Clinico S.  Ambrogio, Milano). He is Clinical Researcher in Digital Dentistry at the Center for Oral Pathology and Implantology in IRCCS Ospedale San Raffaele. He is Private Dentist in Milano where he works as Implantologist and Oral Surgeon applying new technologies for mini-invasive surgery. Dr. Michele Manacorda is also consultant for the development of innovative technology in the field of computer-aided implantology and guided surgery for more than 15 years. He is the author of several scientific papers and coauthor of scientific textbooks. He teaches postgraduate courses and is a speaker in national and international congresses. He is an active member of CAI Academy (Computer Aided Implantology Academy), SidCO (Italian Society of Oral Surgery), and Co-founder of the

Vita-Salute San Raffaele University, Milan, Italy

1 

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Implant Research Association San Raffaele (ACRIS). George  A.  Mandelaris, DDS, MS, FACD, FICD  attended the University of Michigan from undergraduate through dental school. He completed a postgraduate residency program at the University of Louisville, School of Dentistry, where he obtained a certificate in the specialty of Periodontology as well as a Master of Science (M.S.) degree in Oral Biology. Dr. Mandelaris is a Diplomate of the American Board of Periodontology and Dental Implant Surgery and has served as an examiner for Part II (oral examination) of the American Board of Periodontology’s certification process. He is an Adjunct Clinical Assistant Professor in the Department of Graduate Periodontics at the University of Illinois, College of Dentistry (Chicago, IL), as well as the University of Michigan, School of Dentistry, Department of Periodontics and Oral Medicine (Ann Arbor, MI). He is a Fellow in both the American and International College of Dentists. Dr. Mandelaris serves as an ad-hoc reviewer for the Journal of Periodontology, the International Journal of Periodontics and Restorative Dentistry, and the International Journal of Oral and Maxillofacial Implants. He has published over 30 scientific papers in peerreviewed journals and has authored eight chapters in seven different textbooks used worldwide on subjects related to computer-guided implantology, CT/CBCT diagnostics, and surgically facilitated orthodontic therapy (SFOT). Dr. Mandelaris is one of the recipients of the 2017 American Academy of Periodontology’s (AAP) Clinical Research Award, an award given to the most outstanding scientific article with direct clinical relevance in periodontics. A nationally recognized expert, he was appointed by AAP to co-chair the Best Evidence Consensus Workshop on the use of CBCT Imaging in Periodontics as well as coauthor the national guidelines. In 2018, he was recognized with American Academy of Periodontology’s Special Citation Award. Dr. Mandelaris is the 2018 recipient of The Saul Schluger Memorial Award for Clinical Excellence in Diagnosis and Treatment Planning.

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Dr. Mandelaris is a Past President of the Illinois Society of Periodontists and has served on several committees for the American Academy of Periodontology and is one of the AAPs recommended speakers on topics related to periodontics-orthodontics and imaging/implant surgery. He is a key opinion leader for several industry leaders and holds memberships in many professional organizations, including the American Academy of Periodontology, Academy of Osseointegration, American Academy of Restorative Dentistry, and the American Society of Bone and Mineral Research. Dr. Mandelaris is in private practice at Periodontal Medicine and Surgical Specialists, LTD in Chicago, Park Ridge, and Oakbrook Terrace, Illinois. He limits his practice to periodontology, dental implant surgery, bone reconstruction, and tissue engineering surgery. He can be reached at 630.627.3930 or gmandelaris@ periodontalmedicine.org. Mauro  Marincola, DDS, MSD, currently serves as clinical director of the “International Center of Oral Implantology” and professor at the dental school, University of Cartagena, Colombia, where he is clinically active and professor since 1997 and since 1998 in charge as a scientific research coordinator for Bicon Dental Implants, Boston, MA.  He graduated at “La Sapienza University” Rome, Italy, and received his Italian and German doctor degree in Dentistry and Dental Prosthetics. He then received his master’s degree in Stomatology with focus on Implant Dentistry from the “Center of Research and Postgraduate Studies,” Medical Academy of Rome, and his title as Specialist in Implantology from the “Order of Physicians and Dentists” in Koblenz, Germany. He served also as visiting professor at several dental schools like Beijing University, Nanjing University, University of Rome and Verona, and MWU of AZ. He is a co-developer of innovative surgical and restorative techniques of the mentioned plateau-designed sub-crestally placed and bacterially sealed implant system. He speaks fluent Italian, German, English, and Spanish. He is the author and coauthor of numerous scientific

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articles in international dental journals. He lectures extensively in Europe, Asia, USA, and South America on short implant related topics. Maurice  Y.  Mommaerts  is professor at VUBrussels, head of the European Face Centre at the University Hospital Brussels, consultant at ZAS Hospital in Antwerp and in private practice at the Face Ahead Clinic in Antwerp. His focus is on orthognathic and orthofacial surgery, facial makeover—aesthetic facial surgery, facial feminization–masculinization surgery, congenital craniofacial malformation surgery, and patient-specific implants (TMJ prosthesis, AMSJI–facial contouring implants), with special expertise in secondary rhinoplasty and eyelid surgery. Frederic  J.  Norkin, DMD After receiving a Bachelor of Arts degree from Emory University, he received his DMD from Tufts University School of Dental Medicine. Following dental school, he completed a general practice residency at the Veterans Administration Medical Center in Miami, Florida, then received specialty training in Periodontics and a Certificate in Advanced Graduate Studies from Nova Southeastern University, Ft. Lauderdale, FL. Dr. Norkin is a Diplomate of the American Board of Periodontology, Fellow of the ITI, and early adopter of Yomi Robotic Guided Surgery. He has written and lectured on implant dentistry, immediate loading of implants, technology innovations, dental management of medically complex patients, and minimally invasive periodontal regenerative procedures. Currently, he practices periodontics and implant dentistry in Boca Raton, FL, with the South Florida Center for Periodontics and Implant Dentistry. Uday N. Reebye, MD, DMD  received his DMD from Boston University Goldman School of Dental Medicine, then completed an Oral and Maxillofacial Surgical internship in several Boston hospitals before receiving his MD from the University of North Carolina School of Medicine. He then completed a surgical internship at UNC Hospitals before finishing his Oral and Maxillofacial Surgical Certificate at Long

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Island Jewish Medical Center and Stony Brook University Medical Center. Dr. Reebye is a Diplomate of the American Board of Oral and Maxillofacial Surgery. He is a Principal Investigator in several research projects including robotic dental implant surgery and inflammatory mediators in maxillofacial surgery. He is a well-published author and frequently lectures on topics including robotic dental implant surgery, oral medicine and pathology, and reconstructive procedures with implant dentistry. He is the founder and currently practices with Triangle Implant Center, Durham, NC. Marco  Rinaldi, MD, DMD He has developed specific experience in reconstructive surgery, using 3D technologies. He has contributed to international studies and research on computer-guided implantology and stereolithographic models. He was the President of Computer Aided Implantology Academy in 2015–2016, Director of Italian Computer Aided Implantology Academy, President of SimPlant Academy Italy in 2012, active member of IADDM and of Academy of Osseointegration, and Honorary Member of CAI Academy. He is a member of the editorial board of several scientific magazines. As an international speaker, he has taken active part in national and international courses, seminars, and congresses, and he is the author of a large number of scientific publications and of some books including Computer Guided Applications for Dental Implants, Bone Graft and Reconstructive Surgery published by Elsevier USA in 2016 and translated into Spanish and Chinese. Dr. Rinaldi works as Oral Surgeon in Bologna, at Clinica Privata Villalba GVM Care & Research, and in his Dental Clinic. Andreia Rodrigues  received her master’s degree in Dental Medicine in 2009 at the Faculdade de Medicina Dentária da Universidade de Lisboa. She also received an intensive master in OroFacial Harmonization by the European Face Institute and Miguel Cervantes University in 2019–2020. She worked in Malo Clinic from 2009 to 2020. She has been clinical director of Malo Dental Lisboa since 2021. She has exclusive practice in prosthodontics and dentistry. She is an

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expert in aesthetic complex rehabilitation over teeth and implants, full arch rehabilitation, veneers, crowns, and overlays. She is a speaker at national and international courses and congresses. Kurt Schicho, MD, DSc • Study of Mathematics at University of Klagenfurt, Austria (MSc) and at the Technical University of Vienna, Austria (DSc). Special focus on applied mathematics in biomedical engineering (simulation and modeling of neurophysiologic processes at synapses) • Study of Medicine at the Medical University of Vienna (MD) • Habilitation (Venia docendi) in Biomedical Engineering (Medical University of Vienna) •  Professor for Biomedical Engineering at the Medical University of Vienna, Department of Oral and Maxillofacial Surgery; Expert for high technology in medicine/Founder of “Facial Esthetics Engineering” group: Biomedical engineering, computer assisted surgery, telemedicine •  Board-Certified specialist in Plastic, Aesthetic and Reconstructive Surgery with private office in Carinthia •  Main fields of research:      –  Surgical planning and simulation in esthetical facial surgery     –  Biomedical engineering     –  Telemedicine     – Photobiomodulation/Low level light therapy (LLLT) • >160 scientific publications, book chapters, and lectures at international conferences •  >60 scientific publications in peer-reviewed international journals • May–June 2012: Visiting professor at the Università degli Studi di Padova, Italy

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• Before the scientific career: reporter for private radio and TV stations for many years (mainly working in the fields of culture and society) Madalina  Simon, DDS, MSc, MSc  joined her husband’s office in 1994 and specialized in implantology and periodontology. She took her Master of Science in implantology in 2004 and in aesthetic dentistry in 2007. She is (from the beginning) a member of the ZAGA Centers Network. She is also a member of GAK, DGÄZ, DGP, Dental School, BDIZ, EAO, and FOR. The office is awarded as Excellence Center for All-on-4® (Gold Member) by Nobel Biocare. Peter  Simon, DDS He already specialized in dental implantology in the 70s. He is a specialist for dental implantology for DGZI, DGOI, ICOI, and BDIZ. He is (from the beginning) a member of the ZAGA Centers Network, BDIZ, and DGOI and a gold member of ICOI and DGZI. The office is awarded as Excellence Center for All-on-4® (Gold Member) by Nobel Biocare. He was vice president of DGZI and DGOI. He was an international speaker on seminars and congresses. He has taken active part on international courses about sinus lifting. Luigi  Vito  Stefanelli, DDS, PhD, has developed specific experience in digital dentistry. He has received two degrees, one in civil engineering at Politecnic of Turin and the second one in dental science at “Sapienza,” University of Rome. He has also received a PhD on head and maxillofacial district diseases from “Sapienza,” University of Rome. He, also, teaches pterygoid, nasal and zygomatic implants in several courses at cadaver lab. He was a professor at the implant master of second level at “Sapienza,” University of Rome, 2014–2016. He was also professor at the prosthesis master of second level at “Sapienza,” University of Rome, since 2015–2022. He is president of Dynamic Navigation Society EMEA; master clinical trainer and opinion leader of Navident, Claronav; active member of Digital

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Dentistry Society; active member of Digital Implant and Restorative Academy; author of several patents on static guided surgery; and author of several papers on guided surgery. Andrea Tedesco  received a degree in Dentistry and specialized in Oral Surgery, Maxillofacial Surgery Department, University of Florence, Italy. Later he obtained a postgraduate degree at the Oral and Maxillofacial Department, Guy’s and St. Thomas’ Hospital, London, UK. Registered at GDC London, UK, he works essentially for zygomatic implants surgery. He is a Fellow of the Royal Society of Medicine, London, UK, and member of the American Academy of Oral Surgery, Association of Dental Implantology, London, UK, and the International Association of Oral and Maxillofacial Surgeon Speaker for training courses and further zygomatic implantology education in Italy and abroad. He is the author of national and international publications. In 2016 he was awarded with the Prize for best Oral Communication at the Royal Society of Medicine, London, UK, on “Advances in Maxillofacial Surgery: the treatment of atrophic maxilla using zygomatic implants: a new Minimally Invasive Technique.” He has won “Best Dentist—Zygomatic Implantologist,” World Dental and Oral Health Congress House of Commons Parliament London, UK, 2019; and “The king of Zygomatic implantology,” World Dental and Oral Health Congress, Chennai, India, 2019. After about 20 years of interest in zygomatic implants and over 500 surgeries performed, he published his first book: “Gli impianti zigomatici:attualità nelle riabilitazioni implantoprotesiche dei mascellari atrofici” Ed. Quintessence Publishing. He is a Research Fellow on “Atrophic maxilla treatment using zygomatic implants.” He is a Lecturer at “Zygomatic Implants Master,” Oral Surgery Department, University of Pisa, Italy. He is the

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owner of a private clinic in Florence, Italy; he is the first President and founder of the Italian Society of Zygomatic and Pterygoid Implantology. Boyd J. Tomasetti  is a graduate of the University of Vermont and Tufts University School of Dental Medicine. He completed his OMS training at Kings County—Downstate Medical Center. Dr. Tomasetti is a Board-Certified OMS. He has been in a private group practice in Littleton Colorado and presently an Attending Surgeon at the Denver Health OMS Residency Program in Denver, Colorado. He has served on numerous hospital committees and was President of the Colorado Society of OMS.  He is a Past President of the AAOMS and has also served on the Executive Committee of the IAOMS.  Dr. Tomasetti is a Clinical Associate Professor at the University of Colorado School of Dentistry and is an Attending Surgeon in the Denver Health and Hospitals OMS Residency Program. He has authored numerous scientific papers and book chapters and is the coeditor of a book on short implants with Prof. Rolf Ewers. He lectures both nationally and internationally on a variety of subjects. Michael  Truppe, MD, studied Medicine and Dentistry in Vienna, Austria. In 1974 he was for a Clinical Traineeship in Oakland, California. At the University Hospital of Cranio-Maxillofacial and Oral Surgery in Vienna he was a resident from 1981 to 1989. There he started to develop a system for image-guided surgery based on augmented reality visualization; for this purpose he was from 1992 to 1994 in Salt Lake City, USA. Several patents were issued in the USA. The unique technology used video streams with embedded synchronous 3D sensor data of surgical instruments to visualize in 3D at remote locations the image-guided surgery procedure in real time for teleconsultation. In 1995 the clinical trials started at the University Hospital of Cranio-, Maxillofacial and Oral Surgery in Vienna (Chairman Prof. Ewers). In 2005 the clinic was awarded the Harry Archer award from the American Association of Oral and Maxillofacial Surgery Society for teleconsultation worldwide.

About the Contributors

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The current field of research is to improve dental implant teleconsultation with artificial intelligence (IBM Watson). Michael Truppe has since 2006 a private practice in Vienna. Cemal  Ucer, BDS MSc PhD MFDS RCS, FDTFEd,  a specialist Oral Surgeon, graduated from Manchester Dental School in 1982. He established a private hospital referral practice for implantology in 1988. He was awarded one of the first MSc certificates in implantology in the UK in 1995. This was followed by a PhD from Manchester University for his clinical study investigating the factors affecting the survival of implants in iliac bone grafts and osteoporotic patients. Cemal’s clinical and research interests include the role of bone quality, quantity and major bone grafting on the success of implants, 3D surgical navigation, hard and soft tissue oral reconstructive surgery and sinus grafting, as well as rehabilitation of the severely atrophic maxilla with zygomatic and 3D printed customized implants. Cemal has directed a nationally renowned multi-system postgraduate certificate course in implantology since the 1990s. He has a professorial appointment as academic lead of the MSc program in Implantology at the University of Salford. Cemal is a past president (2011–2013) and honorary life member of the UK Association of Dental Implantology (ADI) and clinical director of Manchester Postgraduate Dental Institute at ICE Hospital. He has contributed to the scientific literature with numerous guidelines, position and research papers, and general peer-reviewed publications. Cemal is a Fellow of the Faculty of Dental Trainers at the Royal College of Surgeons of Edinburgh, a Fellow of the British Association of Oral & Maxillofacial Surgeons, a Fellow of the International Team for Implantology (ITI), Fellow of College of General Dentistry (UK),

About the Contributors

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and a member of the Faculty of Examiners for the RCSEd Diploma in Implant Dentistry at the Royal College of Surgeons, Edinburgh. Cemal is clinic director of the Manchester ZAGA Centre for Zygomatic Implants. Benjamin  T.  Vanderkwaak is a pre-medical student who earned a B.S. in Biology with highest distinction from the University of North Carolina at Chapel Hill in May 2022. As an undergraduate student, he worked in the lab of Dr. Jeffrey Dick undergoing research. His first project revealed a more cost-efficient method for nanoparticle deposition for use in energy conversion systems resulting in a publication in the Nanoscale journal of the Royal Society of Chemistry. He also participated in another project probing the cellular effects of PFOS, a chemical found in some drinking water that is linked to disease and cancer. In 2021–2022, Benjamin was an intern at Triangle Implant Center in Durham, NC, working as a surgical assistant and gaining valuable clinical experience under the guidance of Uday Reebye, MD, DMD. As of January 2023, he is within the medical school application process and works as a medical assistant at Forest Dermatology in Asheville, NC. Raffaele  Vinci, MD, DMD, MFS  is Associate Professor of Oral Diseases since 2016 at the Dental School, University Vita Salute San Raffaele in Milano; his teaching fields and courses are advanced oral implantology, preimplant surgery, and general oral surgery. Currently Dr. Vinci is director of the postgraduate program in Oral Surgery at Vita-Salute University, Milan, Italy. Since 2004 he has been working as a scientific consultant for the Dental Clinic at the San Raffaele Hospital in Milano where he has been in charge of managing the Advanced Oral Surgery Unit. Dr. Raffaele Vinci graduated in Medicine and Surgery in 1980 and completed the board specialization in Oral and Maxillofacial Surgery in 1985. From 1984 to 1997, he served as assis-

About the Contributors

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tant surgeon and then as senior registrar at the Department of Maxillofacial Surgery—“Spedali Civili” Brescia University Hospital. From 1997 to 2003, he was Chief Director at the Maxillofacial Department of the Istituto Stomatologico Italiano in Milan. From 2004 he has been Clinical Professor in Oral Surgery, Dental School, VitaSalute University, Milan, Italy. In 1993/1994 he was Senior Lecturer at the Post-graduate School in Maxillofacial Surgery, University of Ferrara. Dr. Vinci is fellow of the Italian College of Professors in Dentistry and Maxillofacial Surgery, President of Italian Society of Odontostomalogic Surgery (SIdCO) 2020–2021, active fellow of the Italian Academy of Osteointegration (IAO), fellow of the Italian Association for Dentistry and Maxillofacial Surgery (SIOCMF), and active fellow of Italian Implanto-prosthetic Academy (AIIP). He published over 150 scientific papers and reviews in the fields of oral and maxillofacial surgery in Italian and international journals and books. He has been invited as a guest speaker at national and international courses and meetings. Since 1987 he performed more than 4000 surgical interventions under general anesthesia regarding the surgery and the pathology of the oral and cranio-facial district, in particular preprosthetic and implant surgery. Gerlig  Widmann, MD, PD, MSc, EBIR,  is a radiologist who specializes in head and neck radiology, thoracic radiology, and interventional oncology. Dr. Widmann graduated from the Medical University of Innsbruck and completed his radiology residency at the University Hospital Innsbruck. He completed a fellowship in interventional radiology and holds certifications from the Austrian Society of Interventional Radiology and European Board of Interventional Radiology. Dr. Widmann obtained his postdoctoral lecture qualification in Radiology from the Medical University of Innsbruck and graduated from the University of Applied Health Sciences in Hall in Tirol. He currently holds the position as the asso-

About the Contributors

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ciate director and clinical risk manager of the Department of Radiology of the Medical University of Innsbruck. He is head of the Section of Computed Tomography and chief of Head & Neck Radiology, Thoracic Radiology, and Oncologic Radiology. Dr. Widmann is a board member of the Austrian Roentgen Society, chair of the radiology examination council, chair of the working group head and neck radiology of the Austrian Roentgen Society, and past president of Computer Aided Implantology Academy. His research interests in the field of head and neck radiology include computer-aided implantology, ultra-low dose CT and radiomics in oncology. He lives in Innsbruck with his wife and two adolescent children.

Part I Theory and Rational Bases

1

General Considerations on the Surgical Techniques in the Treatment of the Atrophic Maxilla Marco Rinaldi

1.1 Introduction

bone atrophy (Chap. 2). When the teeth are missing, the tissue collapses, the reflection in the mirWhen my son was in elementary school, he wrote ror puts on age, the smile becomes embarrassing, in an essay, “My father is very good because he chewing becomes difficult, and even life’s social fixes dental implants into unlucky folk who have aspects can alter (Figs. 1.1 and 1.2). However, a lost their teeth, and can’t eat or smile anymore”. lot can still be done to help these patients recover This phrase provoked a touch of irony because, at their aesthetics and functions; we can be as my the time, dental implants were not included in son wrote, “good doctors, helping these patients social and medical assistance and were still con- to resolve their problems”. sidered a luxury. However, as specialists, we follow a long One must always bear in mind the fact that a period of preparation because the surgical techpatient with no teeth has severe problems to niques are varied and we need to become familiar resolve, even though greater ones might eventu- with them in order to offer advice and resolve the ally crop up in life. We have carried out post-­ various needs of each patient. We must avoid prooncological and post-traumatic implant posing only those techniques that we are most rehabilitation (Chap. 10), but the fact is that a familiar with and those that are mainly publipatient with maxillary atrophy who turns to a cized. With clinical experience, one realizes that specialist and is prepared to undergo complex although probably there is not one technique bettreatment does so because he/she is unable to ter than the other, there is probably one that is cope with the severe disadvantage of the lack of more appropriate. A younger patient is different teeth. In such cases, in which preventive dentistry from an elderly one, bad health is not the same as has failed, the patient personally experiences good health, and patients have various needs and functional changes, aesthetic consequences different expectations. related to tooth loss, and consequences of gradual

M. Rinaldi (*) Dr. Marco Rinaldi Dental Clinic, Bologna, Italy Clinica Privata Villalba, GVM Care & Research, Bologna, Italy e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 M. Rinaldi (ed.), Implants and Oral Rehabilitation of the Atrophic Maxilla, https://doi.org/10.1007/978-3-031-12755-7_1

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a

b

Fig. 1.1  Maxillary edentulism, lateral view (a), decrease in vertical height, prognathism, and changes of the soft tissues. Frontal view (b)

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Fig. 1.2  Maxillary edentulism; bone resorption has resulted in an alteration of the relationship between the lower dental arch and the upper alveolar ridge. Lateral view (a) and frontal view (b)

1.2 The Impact of Edentulism on the Quality of Life Edentulism is an important public health problem and is a debilitating and an irreversible condition representing one of the principle world health problems. The decline in the number of edentulous patients by 10% every 10  years in the American population is compensated by the increase in the adult population—giving rise to an even greater request for total mobile ­prosthesis [1]. The number of edentulous patients, even with different percentages associated with different geographical areas and social conditions, is still high [2]. In the United States, in 2010, it was reported that the number of edentulous persons was about 12.2 million [3]. The Lancet, in 2010,

reported that about 158  million persons in the world were suffering from edentulism [4]. Edentulism causes impairment, functional limitation, and physical, psychological, and social disabilities. It affects oral and general health and the quality of life. The loss of bone support gradually makes the dentures more unstable, causing chewing problems, which, in turn, determine alimentary choices, which can have a negative effect on diet. The condition of the oral mucosa is often compromised in those wearing dentures, which can cause stomatitis and alterations of various degrees of soft tissues. Tooth loss also influences general health through the lack of certain essential food, such as fruit and vegetables, in diet. Different research studies have revealed an association between tooth loss

1  General Considerations on the Surgical Techniques in the Treatment of the Atrophic Maxilla

and the quality of diet. A major increase in obesity has been reported, along with the risk of heart diseases, increase in gastrointestinal problems, lack of sleep, and obstructive sleep apnea syndrome (OSAS) [5, 6]. In patients who seek implant rehabilitation, the impact that the lack of teeth and maxillary atrophy have on the quality of their life is evident; in fact, the instability of the dentures and alteration of the face can cause embarrassment while communicating with others, while smiling and speaking—worsening ­outside relationships and encouraging social isolation [7–9]. Many people have difficulty accepting the loss of their teeth (Figs. 1.3 and 1.4) or implants (Fig. 1.5), feeling less secure, inhibited in everyday activity, and less able to accept the facial alteration that the loss of teeth and bone atrophy cause. Studies on the emotional aspects

Fig. 1.3  Tooth extraction is a highly emotionally traumatic event

a

5

of edentulism should not be underestimated because about half of the subjects in question have reported a great difficulty in accepting the loss of their teeth [10]. Tooth loss and bone atrophy therefore have deleterious consequences on oral and general health and should be given more consideration in prevention programs and in the development of new possibilities in rehabilitation. The strong demand by patients and the notable interest shown by specialists in implant surgery have nourished a trend that has increased the commerce of dental implants throughout the world. In 2015, the European market in dental implants was estimated at about two million dollars [11]. In 2020, despite the negative impact of the coronavirus disease-19 (COVID-19) pandemic, a further expansion in the market of dental implants was foreseen for North America. This positive trend is favored by the greater knowledge that patients have regarding implant treatments, and this should continue and sustain an increase in the market—in the forecast made for as far ahead as 2029 [12]. This study on marketing shows that the substitution of one or more teeth with implants is considered a valid option. In 2015, the World Health Organization reported an average life expectancy of more than 80 years in many industrialized countries [13]. In a revision in 2015, the United Nations calculated the world population at about 7.3 milliard persons, representing about double the world population of 1970 [14]. b

Fig. 1.4  Terminal periodontal disease (a), where the teeth must be extracted. Frequently, there is also a loss of the alveolar bone, which makes implant placement difficult or impossible (b)

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a

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Fig. 1.5  Like natural teeth, rehabilitations with implants, which are extremely common today, can fail (a, b); in these cases, an advanced atrophy of the maxillary bone often remains

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Fig. 1.6  Computer tomography (a) and cone-beam computer tomography (b) are indispensable diagnostic tools today

Therefore, an increase in life expectancy and population determines (at least in a country with high income) an increase in the request for implantary treatment that permits complete aesthetic and functional rehabilitation. The loss of teeth causes relevant functional consequences, both aesthetic and psychological, that successive bone atrophy can only worsen (Chap. 1). Scientific research has demonstrated that implants can, for some time, support a fixed denture and easily resolve the problems of edentulous patients [15]. Today, for dental implant rehabilitation, we have at our disposal modern technology and excellent diagnostic instruments. A cone-beam

computed tomography (CBCT)/computed tomography (CT) exam (Fig.  1.6) represents the survey of choice in order to evaluate the bone volumes available for implants. Hounsfield and Cormack were awarded the Nobel Prize in 1979 [16] for having set up the first apparatus, CT Scan (1971). In dentistry, the first use of the CT-scan began in 1987—and, in the previous year, Chuck Hull patented the first machine for stereolithography [17]—whereas the first implantology software dates back to 1993. The combined use of these techniques in the field of oral surgery has encouraged the rise of computer-assisted implantology. Many years have passed and the precision of

1  General Considerations on the Surgical Techniques in the Treatment of the Atrophic Maxilla

diagnostic methods and three-dimensional (3D) printing has greatly improved, reaching a much higher level of reliability, well-reported in the scientific literature (Chaps. 3 and 4) [18]. Using implant planning software, we can perform simulations of the treatment plan on the patient’s CT scan and evaluate the anatomical obstacles and every therapeutic possibility (Fig.  1.7). In the case of severe atrophy, implant treatment could become highly complex (Fig. 1.8).

7

Extreme maxillary atrophy presents the most difficult challenge of today, and, because of this, many patients wear dentures or carry on with wobbly old bridges because they believe they will not be able to have dental implants. Almost always, these patients have already seen dentists, who have explained that they are having to cope with dentures due to bone loss. However, a few stray words, a bit of research on the Internet, an article in the newspaper, a talk on TV, and an odd piece of publicity all of

a

b

Fig. 1.7 Computerized implant planning with six implants; the more posterior ones have the apex tilted forward to avoid the maxillary sinuses (a). Computerized

implant planning with implants tilted forward and backward so as not to involve the sinus cavities (b)

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Fig. 1.8  In case of advanced atrophy of the maxilla, it is impossible to insert dental implants, as evidenced in the 3D images (a) and in the oblique sagittal ones (b)

these can restore hope and bring about another consultation. In web search engines, the terms “implants without bone” and “maxillary atrophy” are spewed about and are often used for publicity purposes by doctors and dental clinics that really are not able to adequately treat people with severe maxillary bone atrophy. In many cases, hopes get squashed anew and patients believe that their problems are insoluble. This book is dedicated to those patients and their doctors and proposes to be an investigation into the surgical techniques and technologies available today, which can be used for treating patients with advanced bone atrophy. Bone loss can be of different severity and can have different localizations; consequently, the surgical techniques can be more or less complex. In general terms, the choice of any surgical technique should fall upon the one that is the least invasive amongst those available to guarantee long-term success. This is the nodal point of “invasiveness risk and success”. It would not make sense to reduce the invasiveness in order to achieve a non-optimal or non-lasting result. Therefore, we should try to define certain concepts more clearly—what are we talking about when we

discuss clinical ­success, duration over time, and invasiveness, i.e., in other words, what are the objectives and what are the risks. Granted that the answer is not so unexpected if we reason amongst the specialists, but it gets even more complicated if we include in the reasoning another variable subject— the patient. In fact, it is a question of evaluating the techniques, the success, and the risks but above all understanding which technique is the most suitable for that person. Patients involved in clinical decision-making may not make the best medical decision but the best medical decision may not be for the patient. Often, patients choose the least invasive, faster, and less expensive techniques; this is understandable but represents only one aspect of the problem. In many fields of medicine, where difficult choices are at stake regarding the patient’s quality and risk of life, “shared decision-making” (SDM) [19] between the therapist and the patient is increasingly followed. Careful collaborations and decision-making freedom are the fundamental elements of a shared therapeutic path when different therapeutic options exist; these should be explained to the patient and if possible compared, and every

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Fig. 1.9  Use of the residual bone: angled and short implants in an atrophic jaw, panorex X-ray vision (a). Implants inserted into the bone are available in the edentulous maxilla (b)

clinical decision should be made while considering three fundamental elements—the state of the patient’s health, scientific evidence about the efficacy and safety of this surgical technique, and the objective and preference of the patient [20]. Our patients are not all the same and, above all, represent a complex entity that most certainly cannot be reduced to the morphology of their jaws. They can be elderly, suffering from other pathologies, or, simply, would prefer a simpler, cheaper treatment, and, in many cases, a simple but satisfactory solution can be found using the little residual bone (Fig.  1.9). (Chap. 8). However, informing the patient is now considered a physician’s duty, and shared decision-

making (SDM) is considered an optimal approach to making health-care decisions [21, 22].

1.3 Techniques and Technologies for Implant Rehabilitation With clinical practice and experience, new needs and new therapeutical therapies are born. For example, in the case of tilted implants (Chap. 7), after the first cases were carried out free hand, it was realized that computer-assisted technology, in fact, represented a more satisfactory and less

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Fig. 1.10  Tilted implants: computerized planning of six angled implants in front of and behind the sinus cavities; a panorex CT view (a), a 3D view including planning of

the angled abutments (b), and a transparent 3D planning image (c)

empirical approach to the placement of tilted implants in front of the maxillary sinus (Fig. 1.10). Some research has considered that the patientcentered outcome has demonstrated that patients prefer flapless implant placement (Fig. 1.11) techniques because they are less invasive than the open flap technique (Fig.  1.12) [23, 24]. The patient’s point of view is important, but we know that there are highly frequent cases in which it is preferable to open a flap and not follow the preferences of the patients in order to offer them better treatment in the long run. We have always preferred to elevate a flap and use bone-supported surgical guides (Fig. 1.13) whenever the thickness of the alveolar ridge was not abundant (remember the precision limits of computer-­guided implantology), when visual control of the operating field was necessary (Fig. 1.14), or when we had to perform bone grafts (Fig.  1.15) or remodeling

(Fig. 1.16). Treating these cases, we are used to using stereolithographic models and to three dimensionally evaluate the patient’s anatomy (Fig.  1.17). Little by little, we are beginning to face more complex cases, with more advanced levels of atrophy. We began with bone grafts (Chap. 9) taken from the mandibular symphysis and ramus for sectorial reconstructions (Fig. 1.18), and, then, we began to treat entire maxillaries using the iliac crest as the donor site (Fig. 1.19). We defined protocols (Ganz–Rinaldi) that used stereolithographic models to plan reconstructive surgeries (Chap. 4) [25]. However, the long times that they require and the not always predictable results of the bone grafts pushed us to find simpler and quicker solutions. Then, we began to use zygomatic implants (Chap. 11); also, in this case, we defined a protocol to perform zygomatic implants using a computer-assisted method

1  General Considerations on the Surgical Techniques in the Treatment of the Atrophic Maxilla

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Fig. 1.11  Implant placement using a mucosa-supported SurgiGuide (flapless technique): the mucosa-supported surgical guide for six implants (a); three pins fix the guide to the bone in the correct position (b); insertion of the

implants through the surgical guide (c, d); removal of the guide (e); and the two implants anterior inserted with the flapless technique (f) (WINSIX® K Implants BIOSAF IN, Italy)

(Chap. 4) (Fig. 1.20). When the atrophy is really extreme, even the positioning of four zygomatic implants can be highly complicated, and, so, we began to use the subperiosteal technique Additively Manufactured Subperiosteal Jaw Implant (AMSJI) (Fig. 1.21) (Chap. 12). With this technique, we are entering into the fascinating world of personalized implants, specifically built for that Patient Specific Implants (PSI), a world of new technology, with new professional collaborations, which will presumably represent the future in many fields of surgery. The collaboration of medical and engineering competencies, originating from the beginning of the twentieth century, has become even more indispensable in response

to the increase in diagnostic and therapeutic needs. The requests for an even more complex technology requires competence that one single doctor cannot have. Many techniques and technologies are already being used in the treatment of patients with maxillary atrophy such as computer-assisted implantology (Chap. 4), dynamic navigation (Chap. 5), and robotic navigation (Chap. 6). Some techniques have reached maturity and scientific validity, whereas others are at the beginning of the course; but it could be the future techniques, which will very probably change the scenario of treatment possibilities. Let us say that it is important to follow the indications and needs of the patients, but, in the same manner,

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a

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Fig. 1.12  Implant placement using a bone-supported SurgiGuide (flap technique): flap openings to expose the alveolar bone (a); positioning of the bone-supported surgical guide (b); the guide has only one position of stabil-

ity; preparation of the implant sites through the surgical guide (c); insertion of the implants (d) can be done free hand or through the guide; and six implants inserted (e) (NobelActive, Nobel Biocare)

we must use our own experience, as specialists, to direct them toward the technique that we believe to be the most suitable. The choice is not always easy, as you will realize while reading the different chapters (Part I) and looking at the clinical cases (Part II) of this textbook. Different techniques can be applied to similar levels of bone atrophy. Therefore, conflict can arise over various approaches—is it better to carry out bone grafts or zygomatic implants or to use short implants or custom-made subperiosteal implants? I will not

give you an answer as it is extremely important to get to know all the techniques through direct experience in order to be able to weigh the different indications—that the case of advanced atrophy can be determined in apparent detail with a gingival biotype, the value of the angle between the zygomatic bone and the alveolar ridge, or, still further, with the presence of the bone in unexpected areas such as the pterygoid and the nasopalatine channel. When the atrophy is severe and the bone is completely absorbed, many techni-

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Fig. 1.13  Implant placement using a bone-supported SurgiGuide (flap technique): in the case of a thin bone, we prefer the flap technique, exposure of the bone (a); the alveolar ridge is thin, positioning of the bone-supported

surgical guide (b); preparation of the implant sites through the surgical guide (c); and six implants inserted (d) (NobelSpeedy, Nobel Biocare)

cians have to throw in the towel and surrender because there is nothing else to be done. Today, the rehabilitation of the atrophic jaw presents a challenge not without risks, the therapeutic setup has many possible options, and the decidable process is more complicated and extremely different from the fabrication of a set of dentures, which for more than a 100  years has represented the only therapeutical option. For this reason, The Academy of Osseointegration organized a summit to develop guidelines (Clinical Practice Guidelines, CPGS) for the treatment of the edentulous maxilla using a systematic revision of the literature available [26]. Five sections of the problem were considered: the role of bone grafts, the role of the design and implant systems, the role of the images in guiding the insertion of the implants, the role of biologics, and the role of prosthetic

management. In a revision of the literature, it was reported that the level of clinical evidence was rather weak. A work group set out to elaborate the clinical advice used for guidelines but were well aware that they could alter with further development of science and technology and consolidation of clinical experience. The management of the edentulous maxilla is a controversial topic because many specialists consider it as “one size fits all”; in other words, they prefer to carry out the same old surgical techniques. It appears that the problem is technology, which advances so rapidly that we do not have sufficient time to evaluate techniques and material in an objective manner. In other words, when we have studied at length one technique, up comes another new technique, which is probably better. Here is the problem: the consolidated or the novelty. For scientific

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progress, the most dangerous phrase is “we’ve always done it this way.” We must remember that many techniques that are currently utilized today when first proposed were without any scientific evidence. In 1988, when Branemark used the first zygomatic implants, there was no specific literature—this came about in the following years.

Fig. 1.14  Zygomatic implantology. Guided preparation of the implant site for a zygomatic implant; in these cases, a visual inspection of the drills is absolutely necessary

a

However there is always a beginning when every new technique must face up to its first criticism before being accepted or abandoned—before the critic becomes a supporter, it is the emotional cycle of change, the Kubler-Ross curve can be applied to science as well as to business. For every change, there are always enthusiastic supporters, while the skeptics wait around the touch line on the edge of the field. All that research can do is keep on providing proof until the skeptics are convinced and they themselves get criticized for using obsolete techniques. At the beginning of their development, even dental implants were frowned upon in many academic circles. Visionary and creative doctors have always favored the development of medical science because they imagine the future. Many innovations—consolidated and developed—are the result of the genius intuition of passionate researchers and dreamers. The Time on 13 June 1938 [27] published on its cover the transoceanic flyer Charles Lindberg and the engineer Alexis Carrel with their pump, one of the first prototypes of an artificial heart and of a heart and lung machine [28]. On 6 May 1953, the heart and lung machine developed by John Gibbon and IBM engineers was used in an open heart operation [29]. Many fascinating events in the history of the medical scientific progress of the last century recount and teach us that the rapport between medicine and biomedical technol-

b

Fig. 1.15  Reconstruction of an atrophic maxilla with iliac bone grafts (a); healing and graft integration after 4 months (b)

1  General Considerations on the Surgical Techniques in the Treatment of the Atrophic Maxilla

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Fig. 1.16  The alveolar bone must be exposed every time to the alveolar ridge (a, b) or the bone grafts (c) need to be remodeled

Fig. 1.17  A stereolithographic model of an edentulous maxilla in which a double sinus augmentation was simulated

ogy is consolidated and is irreplaceable for the development of new therapeutic possibilities. Some techniques and technologies used for the treatment of maxillary atrophy can, little by little, prove to be r­eliable and thus provide new therapeutic possibilities. Claude Bernard, however, puts us on our guard—“Men who show an excessive trust in their theories and new ideas are not only poorly predisposed into making new discoveries, but generally make the most useless remarks” [28]. However, let us not forget that an excellent technique is probably not suitable for all patients; in fact, “a one size does not fit all.”

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a

Fig. 1.18  A stereolithographic model in which a bone graft and a maxillary sinus lift were simulated (a). During the dissection of the Schneiderian membrane, the simula-

Fig. 1.19  A case of reconstructive surgery with iliac bone grafts and double sinus lifts that used the protocol for reconstructive surgery and sinus lifting guides. The clinical case was published in 2007 (Headlines, Materialise, 2007)

b

tion on the model allows understanding the internal morphology of the maxillary sinus (b)

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Fig. 1.20  A computer-assisted approach to zygomatic implantology. Simulation of the insertion of two zygomatic implants in the stereolithographic model and our first studies for a design of the zygomatic guide (years 2013–2014) (a). The model was scanned and superimposed on the CT scan of the maxilla to represent the computerized planning and preview of the zygomatic guide

a

Fig. 1.21  AMSJI, a personalized subperiosteal implant (CADskills, Gent, Belgium). The custom-made implant is fixed to the frame of the pyriform opening and to the body of the zygomatic bone. It is made with an additive tech-

(b). A stereolithographic model with surgical guides for the insertion of zygomatic implants (c) (Materialise, Leuven). Clinical use of the zygomatic guide for the preparation of implant sites (d); the guide rests stably on the body of the zygomatic bone and allows visual control of the drill. Zygomatic implants inserted with a computer-­ assisted technique but always with visual control (e)

b

nique and allows immediate rehabilitation with fixed prostheses or overdentures in cases of extreme bone atrophy (Cawood-Howell V-VIII) (a). The AMSJI implant fixed to the maxillary bone (b)

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M. Rinaldi

1.4 Indications of Treatment Techniques Based on the Degree and Location of Bone Atrophy In the second part of this book, we have gathered clinical cases, trying to put in “competition” or rather in comparison the different technologies applied to the jaw with similar degrees of bone atrophy. In the variability of the anatomical situations, we wanted to distinguish some typical situations that directly affect the decision tree of the surgical strategies to be applied. We have adopted, for its practicality, the classification proposed by Bedrossian et  al. [30], which distinguishes a radiographic criterion for rehabilitation with fixed prostheses in the edentulous maxillae. These authors distinguish three areas in the edentulous jaw: zone 1, the premaxilla or anterior maxilla, from cuspid to cuspid, and for each side; zone 2, the bicuspids, premolar region; and zone 3, the molars, the most posterior (Fig.  1.22). In fact, the presence or absence of a bone that can be used for implant placement in each of these anatomical areas strongly conditions the surgical technique that can be used. In fact, if there is a bone in zones 1, 2, and 3, then it will be possible to insert traditional axial implants. If we have a bone in zones 1 and 2, then we can tilt the implant (Fig.  1.23) so as not to involve the maxillary sinus (Chap. 6). If we have a bone in only zone 1, the anterior one, then we can use zygomatic implants (Fig.  1.24) (Chap. 9) associated with anterior axial implants or we can carry out bone and sinus grafting (Fig. 1.25). Finally, in the most

Fig. 1.23  A tilted implant in case of availability of a bone in the anterior and premolar zones

Fig. 1.24  Two zygomatic implants in case of availability of a bone only in the anterior area

difficult situation, when we have no bone available in any of the three zones, we can use four zygomatic implants (quad technique) (Fig. 1.26), bone grafts, or other particular techniques (AMSJI in our experience) (Fig.  1.27) (Chap. 12). In some patients, short implants may represent a minimally invasive therapeutic alternative (Fig.  1.28). We have tried to divide the clinical cases in this book into three sections, following this classification, in order to try and group together the clinical cases carried out on patients with similar levels of atrophy. However, as you can see, there are many exceptions in these subdivisions. In fact, in the treatment of the edentulous maxilla, we can use many techniques: tilted, short, and zygomatic implants, bone grafting, and

Fig. 1.22  Maxillary zones. Classification (Bedrossian, Sullivan, Malo), which distinguishes a radiographic criterion for rehabilitation with fixed prostheses in the edentulous maxillae, three zones: molars, bicuspids, and anterior

1  General Considerations on the Surgical Techniques in the Treatment of the Atrophic Maxilla

Fig. 1.25  Bone grafting in case of lack of a bone in all areas where we can use reconstructive surgery with bone grafts. We can also use the grafts in previous cases; the choice depends on the clinical indications and the preferences of the surgeon and the patient and must be carefully evaluated case by case

Fig. 1.26  Four zygomatic implants (quad technique) in case of lack of a bone in all areas

Fig. 1.27  AMSJI in case of extreme maxillary atrophy

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reconstructive surgery. Often, some surgical techniques, originating from a specific application, can be applied in other contexts. For example, the sinus fenestration for zygomatic implants is similar to that carried out for sinus augmentation. A reconstruction with bone graft could require tilted implants, and, often, the long zygomatic implants are associated with short anterior implants.

1.5 Reasons for This Book This book originates from the clinical experience of many years, in which we have used various surgical techniques for the treatment of the edentulous maxilla with various degrees of atrophy: inclined implants, bone grafts, zygomatic implants, short implants, and subperiosteal implants. Above all, in the most advanced atrophy, I have faced the problem of a choice of one technique over another, and I realized that I would have liked to share the decision tree or process of which technique to adopt with someone who has more expertise than myself and has carried a surgical technique to its very limits. So, I have begun to seek advice and contributions from the great specialists, the masters whom we all know, and have collaborated in the development of this textbook. I am honored to have been able to utilize the experiences, suggestions, and hints of the doctors—all visionaries and innova-

Fig. 1.28  Short implants planned in the little remaining bone may be a viable alternative in some cases

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tors—who have never ceased to search for solutions to the problems, and, to them, we extend our most grateful thanks.

References 1. Douglass CW, Shih A, Ostry L. Will there be a need for complete dentures in the United States in 2020? J Prosthet Dent. 2002;87:5–8. 2. Muller F, Naharro M, Carlsson G. What are the prevalence and incidence of tooth loss in the adult and elderly population in Europe? Clin Oral Implants Res. 2007;18(Suppl. 3):2–14. 3. Slade GD, Akinkugbe AA, Sanders AE. Projection of U.S. edentulism prevalence following 5 decades of decline. J Dent Res. 2014;93(10):959–65. 4. Vos T, et  al. Years lived with disability (YLDs) for 1160 sequelae of 289 diseases and injuries 1990-­ 2010: a systematic analysis for the Global Burden of Disease Study 2010. Lancet. 2012;380(9859):2163–96. https://doi.org/10.1016/ S0140-­6736(12)61729-­2. 5. Dietrich T, Webb I, Stenhouse L, Pattni A, Ready D, Wanyonyi KL, White S, Gallagher JE. Evidence summary: the relationship between oral and ­cardiovascular disease. Br Dent J. 2017;222(5):381– 5. https://doi.org/10.1038/sj.bdj.2017.224. PMID: 28281612. 6. Emani E, Freitas de Souza R, Kabawat M, Feine JS.  The impact of edentulism on oral and general health. Int J Dent. 2013, 2013:498305., , 7 pages. https://doi.org/10.1155/2013/498305. 7. Nitschke I, Müller F. The impact of oral health on the quality of life in the elderly. Oral Health Prev Dent. 2004;2(Suppl 1):271–5. PMID: 15646585 8. Albaker AM. The oral health-related quality of life in edentulous patients treated with conventional complete dentures. Gerodontology. 2013;30(1):61–6. https://doi.org/10.1111/j.1741-­2358.2012.00645.x. Epub 2012 Feb 27. PMID: 22369662. 9. Hahnel S, Schwarz S, Zeman F, Schäfer L, Behr M. Prevalence of xerostomia and hyposalivation and their association with quality of life in elderly patients in dependence on dental status and prosthetic rehabilitation: a pilot study. J Dent. 2014;42(6):664–70. https://doi.org/10.1016/j.jdent.2014.03.003. Epub 2014 Mar 14. PMID: 24632475. 10. Davis D, Fiske J, Scott B, et al. The emotional effects of tooth loss: a preliminary quantitative study. Br Dent J. 2000;188:503–6. https://doi.org/10.1038/ sj.bdj.4800522. 11. Millennium Research Group’s European Markets for Dental Implants 2011. 12. Medtech Insights report, Dental Implants-Market Insights-North America. 13. World Health Organization statistics, Life expectancy.

M. Rinaldi 14. United Nations, Department of Economic and Social Affairs, Population Division. World population prospects: the 2015 revision, DVD edition; 2015. 15. Howe MS, Keys W, Richards D. Long-term (10-year) dental implant survival: a systematic review and sensitivity meta-analysis. J Dent. 2019;84:9–21. https:// doi.org/10.1016/j.jdent.2019.03.008. Epub 2019 Mar 20. PMID: 30904559. 16. The Nobel Prize in Physiology or Medicine 1979. NobelPrize.org. 17. United States Patent, number 4,575,330. 18. D’haese J, Ackhurst J, Wismeijer D, De Bruyn H, Tahmaseb A.  Current state of the art of computer-­ guided implant surgery. Periodontol 2000. 2017;73(1):121–33. https://doi.org/10.1111/ prd.12175. PMID: 28000275. 19. Charles C, Gafni A, Whelan T.  Shared decision-­ making in the medical encounter: what does it mean? (or it takes at least two to tango). Soc Sci Med. 1997;44(5):681–92. https://doi.org/10.1016/s0277-­ 9536(96)00221-­3. PMID: 9032835. 20. Elwyn G, Cochran N, Pignone M.  Shared decision making-the importance of diagnosing preferences. JAMA Intern Med. 2017;177(9):1239–40. https:// doi.org/10.1001/jamainternmed.2017.1923. PMID: 28692733. 21. Shay LA, Lafata JE.  Where is the evidence? A systematic review of shared decision making and patient outcomes. Med Decis Making. 2015;35(1):114– 31. https://doi.org/10.1177/0272989X14551638. Epub 2014 Oct 28. PMID: 25351843; PMCID: PMC4270851. 22. Joosten EA, DeFuentes-Merillas L, de Weert GH, Sensky T, van der Staak CP, de Jong CA. Systematic review of the effects of shared decision-making on patient satisfaction, treatment adherence and health status. Psychother Psychosom. 2008;77(4):219–26. https://doi.org/10.1159/000126073. Epub 2008 Apr 16. PMID: 18418028. 23. Nkenke E, Eitner S, Radespiel-Tröger M, Vairaktaris E, Neukam FW, Fenner M.  Patient centred outcomes comparing transmucosal implant placement with an open approach in the maxilla: a prospective, non-randomized pilot study. Clin Oral Implants Res. 2007;18:197–203. https://doi. org/10.1111/j.1600-­0501.2006.01335.x. 24. Vercruyssen M, van de Wiele G, Teughels W, Naert I, Jacobs R, Quirynen M. Implant- and patient-centred outcomes of guided surgery, a 1-year follow-up: An RCT comparing guided surgery with conventional implant placement. J Clin Periodontol. 2014;41:1154– 60. https://doi.org/10.1111/jcpe.12305. 25. Rinaldi M, Ganz SG, Mottola A.  Computer-guided applications for dental implants, bone grafting, and reconstructive surgery. Elsevier; 2016. 26. Current best evidence for management of the edentulous maxilla. Int J Oral Maxillofac Implants. 2016;31(Suppl):s6–15. https://doi.org/10.11607/ jomi.16suppl.ovw.

1  General Considerations on the Surgical Techniques in the Treatment of the Atrophic Maxilla 27. The Time Magazine June 13, 1938/Vol. XXXI, No. 24. 28. Borghi L.  Umori, il fattore umano nella storia delle discipline biomediche. Roma: Società Editrice Universo; 2012. 29. Le Fanu J.  The rise & fall of modern medicine. BMJ. 1999;319:1276. https://doi.org/10.1136/ bmj.319.7219.1276.

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30. Bedrossian E, Sullivan R, Malo P.  Fixed-prosthetic implant restoration of the edentulous maxilla: a systematic pretreatment evaluation method. J Oral Maxillofac Surg. 2008;66:112–22.

2

Surgical Anatomy of the Atrophic Maxilla Michele Manacorda and Raffaele Vinci

2.1 Introduction The edentulous maxilla tends to atrophy and, by definition, loses volume, meaning that the bone is reduced in quantity while the whole maxilla structure is architecturally modified, changing the ratio between the cortical and medullar percentage, usually towards a decrease in the bone density of the bone in the cancellous bone tissue. The cortical plates of the alveolar processes tend to decrease in thickness and range, till total disappearance. It has been less frequently observed that the bone walls tend to collapse from the vestibular to the palatal area, with no cancellous bone interposition. The decrease in bone percentage involves not only the alveolar processes but also extends to the basal bone, probably because of an inadequate endosteal stimulation due to the absence of function. Maxillary bone atrophy, in terms of quantity as well as quality, significantly impacts its feasible use as a site of M. Manacorda (*) Department of Dentistry, San Raffaele Hospital, Postgraduate School of Oral Surgery, Vita-Salute University, Milan, Italy e-mail: [email protected] R. Vinci Department of Dentistry, San Raffaele Hospital, Postgraduate School of Oral Surgery, Vita-Salute University, Milan, Italy Postgraduate School of Oral Surgery, Vita-Salute University, Milan, Italy e-mail: [email protected]

implants. This is because, generally, a reduced value in the fixtures’ bone impact contact (BIC) decreases the implants’ holding function and eventually affects the prognosis of implant prosthetic rehabilitation. The physiological process leading to bone regress has different causes, among which bone resorption is relevant and frequent due to periodontal pathology, which involves and compromises the alveolar structure even before partial edentulism. Moreover, failure to replace the extracted dental elements in time inevitably leads to in situ bone atrophy due to the crestal bone portion’s resorption. Dentoalveolar trauma, prolonged use of inadequate removable prosthesis, nutrition deficiency-induced systemic pathologies, vitamin deficiency and osteoporosis are among the contributory causes of maxilla bone resorption, up to extreme atrophy.

2.1.1 Cone-Beam Computed Tomography (CBCT): The Second Level of Image-­ Guided Diagnosis Cone-beam computed tomography (CBCT) produces three-dimensional reconstructions of maxillary anatomical structures using a single scan, offering multiple views with a low radiation. To date, according to the American Academy of Oral and Maxillofacial Radiology, CBCT should be

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 M. Rinaldi (ed.), Implants and Oral Rehabilitation of the Atrophic Maxilla, https://doi.org/10.1007/978-3-031-12755-7_2

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considered as the method of choice for three-­ dimensional evaluation of the maxillary bone to plan an implant treatment [1]. In particular, volumetric data acquired by CBCT show a high accuracy of measurements with a relative error below 1% compared with the same measurements taken in vivo as demonstrated by Veyre-Goulet et al. [2]. A CBCT scan allows the evaluation of the quality and quantity of the remaining bone, which is crucial for interactive implant planning at any given site. Cone-beam computed tomography (CBCT) studies have revolutionized craniofacial imaging and have aided in understanding the anatomical and morphometric variability of the edentulous maxilla. These unique challenges have led to special considerations and novel surgical techniques in oral maxillary surgery and dental restoration.

M. Manacorda and R. Vinci

subject to individual, morphological and structural variables, local as well as systemic, and it appears in different extents and modalities. The kind of resorption depends on the individual bone structure and dentoalveolar proportions, the patient’s age, local tissue trophism, individual bone metabolism and various related systemic pathologies. Dental treatments can also affect the type and grade of post-extractive atrophy: atypical resorption situations, pronounced or asymmetrical, are often seen in long-time edentulous patients who wear inadequate removable dentures. In the completely edentulous maxilla (or made edentulous for rehabilitation), the socalled centripetal bone resorption and remodelling is generally observed. This means that the whole upper jaw tends to contract and reduce its size by diameter and height, with obvious levelling of the palatal roof, often along with sinus pneumatization [4]. This effect is due to the alveolar processes’ volume progressive reduction 2.2 The Physiopathology until disappearance, and it is then combined with of Edentulism the consequent shrinking of the upper basal bone. In a frontal or cross-sectional view disBone tissue resorption due to the loss of a dental played by a CT image of the maxilla, it has been element is initially concerned with the alveolar observed that the alveolar processes’ morpholborder of the maxilla basal bone, involving a ogy—from the buccal marginal bone crest to the small part of the crest, and then advances to phys- dental elements—tends to move up with a deciiological remodelling, with a progressive con- sive gradient towards the midline, until shrinktraction of the volume of the bone, which is no age of the maxillary basal bone, which has a longer being subjected to functional stimulation. definite narrower basis compared to the extenThe belated remodelling of the alveolus extended sion of the alveolar processes. to the extra-alveolar bone section leads to anatMaxillary alveolar processes diverge downomy panels, which extend to the maxilla basal wards and outwards from their basis to guarantee bone in physiopathological stays known as post-­ support to the dental elements positioned at difextraction atrophy [3]. ferent overjet degrees to contribute to proper The early post-extraction tissue healing occlusion and optimal dissipation of the funcresponse is highly variable, and it usually depends tional loading. on the dental elements’ condition, the presence of Generally, the long axis of the tooth in the inflammation in the root apparatus and the global maxillary arch is on the bisector of the angle status of the periodontal tissue, which can already between the jaw and its elevator muscles’ force have undermined a significant portion of the bone vector, and it is the most effective in dissipating volume, with important horizontal deficits. After mechanical stress along the craniofacial skeletal about a 3-month period, and mostly because of a structure’s support pillars. So, the major axis of non-functional situation, a progressive alteration the maxillary teeth is obliquely placed, extending of the remaining bone structure takes place, from the vestibule towards the palate, and it through structural remodelling of the bone tissue, matches the occlusal forces’ vector occurring at typically in a regressive manner. This regress is that precise point (Fig. 2.1).

2  Surgical Anatomy of the Atrophic Maxilla

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a

c

b

d

Fig. 2.1  Effects of tooth loss on the bone structure of the jaw. Resorption in the upper arch generally leaves a spongy bone, except in the canine, zygomatic and pterygoid pillars. The collapse in the maxilla is not the same as that in the mandibular bone where horizontal resorption is

not followed by a centripetal involution. The sequence of 3d CT reconstruction images (a, b complete skull; c coronal section in complete skull; d, coronal section in edentulous skull) shows the difference of bone resorption between maxilla and mandibula

Along with the pronounced premaxillary alveolar crests’ vestibular inclination, due to the optimization of the apparatus’s efficiency, the dental roots’ position is otherwise placed with regard to the alveolus cortical plates. In the front teeth, from canine to canine, the teeth’s major axis is not parallel to the major axis of the alveolar process (Fig. 2.2).

In summary, the conformation of maxillary, alveoli and dental elements submits to functional adjustment rules so as to give the stomatognathic apparatus a proper functionality [5]. The alveolar bone at the vestibular side of the roots is often merely cortical, with no cancellous bone [6, 7].

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Fig. 2.2  Cross sections from CBCT scans. The front teeth’s roots, generally, immediately lie under the cortical vestibular plate, with no interposition of the cancellous

M. Manacorda and R. Vinci

bone. The major teeth axis is not parallel to the axis of the alveolar process. After tooth extraction, the root position influences the bone atrophy

2  Surgical Anatomy of the Atrophic Maxilla

The vestibular cortical, normally thin or fenestrated because of post-extractive odontogenic infective foci, often shows a fast and significant resorption. Therefore, an evident precocious collapse of the remaining alveolar crest with preeminent preservation of the palatal cortical and its adherent cancellous bone can be observed. Maxillary atrophy endures a centripetal resorption vector. Combined with horizontal resorption, a consequent reduction of the maxillary arch’s width is observed, with variable vestibular–palatal thickness of the remaining bone basis [8]. It is not unusual to find remaining alveolar crests of diminished thickness, sometimes insufficient for implant positioning, so that

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a specific surgical intervention—such as split crest—or a regenerative technique—such as bone grafting—is required. Increasing the bone volume to make it suitable for implant fixtures will deeply affect the treatment plan both in terms of managing the timing for the prosthesis and for rehabilitation. It is clear that waiting for the bone graft to integrate means dramatically stretching the timing of recovery, requesting removable temporary prosthesis and regular monitoring to handle possible dehiscence and check the stability of the removable prosthetic basis. “One-stage” implant prosthetic surgery is a better option (Fig. 2.3).

a

b

Fig. 2.3  A radiological study of the edentulous maxilla in a pseudo panoramic X-ray (a), CT axial view display (b) and cross section (c). Different two-dimensional (2D)

c

projections allow for an accurate analysis for a bone evaluation of the edentulous maxilla before an implant surgery

M. Manacorda and R. Vinci

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Latest generation implant prosthetic rehabilitation should opt for the use of the remaining alveolar bone and atrophic maxilla’s base bone, identified by accurate exams, via mini-­ invasive surgical techniques along with immediate loading prosthesis [9].

2.3 The Anatomical and Radiological Aspects of the Edentulous Maxilla To study the edentulous or partially edentulous maxilla, three different anatomical areas are to be identified. A front section called the premaxilla has two halves that meet at the midline, and, therefore, the intermaxillary suture is located below the pyriform opening at the front portion of the nasal floor, bilaterally extends up to the surface of the canine ridge and includes the midline symphysis, the central and lateral incisors’ alveolar processes and the corresponding palatal process. The adjacent portion of the maxillary bone, along the remaining alveolar crest, is called the midmaxilla and includes the canine ridge up to the front limit of the maxillary sinus’ antral hollow. This maxillary portion includes the bone volume of the canine and the two premolars, but it is individually highly variable because, often at the second premolars, due to maxillary sinus’ pneumatization, the remaining bone’s vertical deficit can be extremely significant. The midmaxilla can then be limited to a restricted area of the remaining bone between the premaxilla and the posterior section. Despite its limited extension into the atrophic maxilla, the midmaxilla is an exceptional pillar of implant support; here, there is a solid basal bone, a proper bone height for longer implants and a strong cortical for the implants’ anchorage, widely used over the years in the “All-on-4” technique. Distally moving along the remaining crest, we find the third area, the posterior maxilla. Owing to the location of the molars, it is frequently affected by important atrophic effects along with deficits of the qualitative, remaining basal bone. According to an anatomical–surgical interpreta-

tion, the posterior maxilla, nevertheless, includes bone portions apart from the maxillary bone. Distally located at the convex portion of the tuber maxillae is the sphenoid’s joint to the pterygoid process, while palatally, at the posterior margin of the palatal vault, there is the palatal bone with its pyramidal process; this process palatally delimitates the tuberal area. Although not part of the maxillary bone, here, these are considered and included in the anatomical study for their feasible use as an anchorage for implants (Fig. 2.4a, b).

a

b

Fig. 2.4 (a) Premaxilla: in classical anatomy, it extends from the alveolar crest to the nasal floor and laterally until the lateral margin of the pyriform opening, with the canine ridge excluded (A). Midmaxilla: from the canine ridge to the premolar area. The cranial extension of the bone extension is bounded by the maxillary sinus’ anteroinferior margin. It also includes the maxillary zygomatic process (B). The posterior maxillary is made of the alveolar crest of the molars’ area, the tuber maxillae and—surgically—it includes the sphenoid’s pterygoid process and the nasal bone’s pyramidal process (C). (b) The edentulous maxilla in an axial display via CT.  The edentulous maxilla in the axial section should be correctly displayed after aligning the scanning, both on the sagittal and the coronal planes. This allows evaluating the eventual asymmetries of the two hemi-arches and the remaining bone portion related to a proper plan, usually parallel to the hypothetical occlusal plan

2  Surgical Anatomy of the Atrophic Maxilla

2.3.1 Premaxilla Anatomically, the premaxilla consists, by definition, of the most frontal portion of the maxillary bones, the palatal processes, the frontal process and the alveolar processes anterior to the zygomatic process. Due to the peculiar aspects of this part of the skeleton in an edentulous patient with maxillary atrophy, and because of the different surgical approaches in order to position implants in this specific section, the premaxilla is divided in two separate anatomical–surgical areas of interest. We have established as the anterior ­maxilla or premaxilla only the segment that goes from the midline suture, below the anterior nasal spine, extending laterally and posteriorly till the pyriform opening’s side wall. The most posterior maxillary skeletal segment—from the canine ridge to the zygomatic process’ vestibular surface—is defined as the midmaxillary area. In the premaxilla, vascularization of the bone structures and teeth is granted by vessels of small diameter within the upper mid and anterior alveolar arteries, intrabony branches moving from the intraorbital artery along the homonymous canal. The palatal process of the premaxilla, posteriorly extending upwards from the teeth’s alveolar processes, receives blood from the nasopalatine artery, the terminal branches of the main palatal artery and from small separate vessels of the anterior upper alveolar artery [10]. In the toothed adult, at the premaxilla, the average extension of the alveolar process and that of the basal bone (from the marginal crest to the nasal floor) is 18  mm (in males) and 17 (in females) [11], whereas the average distance between the central incisors’ apex and the lateral incisors from the nasal cavity is 10 and 13 mm, respectively [1]. The vestibular side of the premaxilla presents a reduced physiological amount of the cortical bone, decreasing in thickness from the canine premolar area to the incisors, where it is usually thin and adherent to the dentoalveolar ligament, with no interposed cancellous bone at the incisors [6]. Anatomically, this implies that a ­significant part of the vestibular bone tissue is lost shortly after extraction (about 2–3 mm) [2].

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The premaxilla encounters serious post-­ extraction resorption, reduction of the alveolar processes’ volume and off the upper soft tissues, progressive and deteriorating in time, leading to significant deficits concerning smile aesthetics, often implying difficulty in the implant-­supported prosthetic stage. It is fair to say that atrophy in the anterior maxilla always implies not only functional but also aesthetical effects. The implant planning in this area has to always be associated with an interdisciplinary study so as to preliminarily evaluate the rehabilitation plan [12] (Fig. 2.5a). Therefore, in normal conditions, such as in immediate or delayed post-extraction implantology, the bone portion receiving a fixture in the anterior maxilla is not challenging, but it becomes so if the post-extraction loss of bone is early and significant in the affected area. Moreover, the implant insertion axis must consider the quantity of the remaining basal bone, often found along the premaxilla palatal process and therefore offset with regard of the extracted tooth. A paraxial CBCT scan can be used to determine how to protect the remaining bone walls and avoid vestibular fenestrations and to calculate the matching of the fixture’s positioning with the prosthetic axis. In edentulous patients, the average thickness of the remaining crest is calculated as 3.8  mm, and measuring at 3 mm from the crest margin, it is 4  mm, with an average reduction of 50% in thickness compared to toothed patients. Nevertheless, anatomical differences are so variable that a 3D radiological evaluation is essential in long-standing edentulism. Most often, horizontal atrophies, extending to the basal bone, can be adjoined to minimal height reductions with absolutely negligible remaining crest thickness (Fig. 2.5b). The incisor canal, or nasopalatine, is the main obstacle to premaxilla implant surgery manoeuvres in this area. It is a neurovascular canal connecting the nasal and oral cavities. It includes the nasopalatine nerve, which carries sensitive fibres from the palatal mucosa and frontal group’s gums till the canine, and also the incisor artery, with the final stretch originating from the main palatal artery and sphenopalatine anastomosis.

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M. Manacorda and R. Vinci

a

b

Fig. 2.5 (a) With the use of innovative software, it is possible to match bone structures with soft tissue profiles and a digital mock-up of overimplant prosthesis. Virtual planning of a correct fixture and abutment fits the prosthetic connection for an easy immediate loading. (b) The cross-­

sectional view provides the surgeon with an accurate image of the third dimension of the residual bone. When the thickness in not sufficient, it is also possible to plan in advance a bone graft solution or a split crest surgery

The channel arises from the anterior maxilla’s nasal side in two separate foramina alongside the nasal septum—Stenson’s foramen—and runs the alveolar process along the suture in the lower anterior direction to end in the incisive fossa behind the central incisors under the posterior incisive papilla. Its dimensions are usually wide, about 5 mm, but can expand its diameter after losing the teeth [13]. From a CBCT scan, it is possible to evaluate—in the midsagittal section—both dimensions and localization of the canal, also noting different anatomical typologies such as separate or united channels diverging on the surface of the palatal wall [14, 15] (Figs. 2.6 and 2.7).

Clinically, the nasopalatine channel’s course can interfere in choosing the positioning of the osseointegrated implants in 11 and 21 areas. This the reason why, usually, surgeons prefer the lateral incisors’ site for implant-supported full-arch rehabilitations. Moreover, in the All-on-4 technique, putting distance between the two anterior fixtures improves the prosthetic load distribution. The anterior maxilla is anyway an implant site with scarce bone thickness, where the remaining craniocaudal extension is often reduced, as well as vestibular–palatal thickness. Fixtures measuring 6/9  mm can hold better with an anchorage on the nasal floor cortical, which guarantees primal stability for the immedi-

2  Surgical Anatomy of the Atrophic Maxilla

a

31

b

Fig. 2.6  CBCT volume rendering of the atrophic edentulous maxilla. The length of the incisor channel is proportionally reduced according to the atrophy level, whereas

its diameter tends to increase (b). Owing to radiological diagnosis software, it is possible to visualize the vascular nerve bundles’ progression during surgical planning (a)

Fig. 2.7  A view on the axial and midsagittal planes of the incisor channel with two accessory channels. Right: rear-­ incisive axial projection where the two Stenson foramen

entrances on the inferior meatus’ floor and their junction in a single channel before reaching the palatine foramen are highlighted

ate implant load. The nasal floor cortical bone is usually easily identified, and it naturally stops the neo-alveolus drilling during implant site preparation. It is therefore quite rare to have a perforation of the floor, with its consequent post-surgical symptoms. There have been a few cases of rhinitis with nasal congestion and rhinorrhoea with a deep perforation passing through the nasal mucous extruding into the cavity. If the apical cortical anchorage remains below the periosteum

on the nasal side of the floor, then an intervention can be planned and performed successfully without consequences [15, 16]. In Fig.  2.8, planning of two implants in the premaxilla of an extremely atrophic maxilla is described: the correct distance between the nasopalatine channel and the apical anchorage for a proper and satisfactory stability even with a 9  mm implant passing through a poor bone marrow.

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M. Manacorda and R. Vinci

Fig. 2.8  Digital implant planning in the premaxilla by the incisive canal. Note the palatal insertion axis due to the deep resorption of the vestibular flange that reduced the alveolar component of the premaxillary bone to zero

2.3.2 Midmaxilla The skeletal midmaxillary section goes from the nose lateral wall to the anterior wall of the maxillary sinus, including the remaining canine and premolar alveolar process downwards and the maxillary zygomatic process vestibularly. The midmaxilla can also be identified as the bone triangle behind the canine as in the study by Ganz (2006) [17, 18]. Anatomically, the midmaxilla can be identified as the lower portion of the intraorbital area, which is the most caudal segment below the intraorbital foramen ridge. This bone district,

belonging to the maxillary bone body, has been widely studied for its relevance in edentulous patients with significant posterior atrophy needing implants. As a matter of fact, the remaining bone often provides an usable implant site in a well-preserved and depicted basal bone (Fig. 2.9).

2.3.2.1 Surgical Anatomy of the Midmaxilla In edentulous patients, the bone district, even with different atrophy degrees, can be depicted as a pyramid with a triangular basis and a severed apex. The vague triangular basis, pointing downwards, is made of the remaining alveolar process,

2  Surgical Anatomy of the Atrophic Maxilla

Fig. 2.9  An ex vivo (freshly frozen) dissection of the mid maxillary area. The vestibular wall of the maxillary sinus has been removed to show the anteromedial wall. Normally, in these cases of atrophy, between the nose and sinus, we find a good amount of the basal bone for inserting a tilted iuxtameatal implant. Note the absence of the canine crest and the great bone loss in the molar area

a

Fig. 2.10 (a) Parasagittal view of an edentulous maxilla. Severe atrophy is evident in the complete loss of alveolar bone under a hyper pneumatized maxillary sinus. Although, in this volume there often is a good amount of bone for implant placement. At the centre of the arrows we can see a poligon of bone surrounded by nose floor and residual alveolar crest, maxillary sinus and piryform mar-

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and it is distally wider in the premolar area. It mesially shrinks towards the incisor, where the vestibular–palatal atrophy is wider. The basis is the entrance point of the implants, which reach— usually with a mesio-palatal tilt—a good bone thickness in the canine pillar. The distal side of the pyramid, which is the posterior edge of the midmaxilla, is often definitely concave, due to the maxillary sinus anterior border. Cranially, it shrinks dramatically, following the maxillary frontal process. The vestibular side matches the maxillary bone anterolateral wall, and it includes the canine ridge and fossa. This is the only evident side of the pyramid with a dissected flap during surgery. The remaining of the alveolar processes, the maxillary palatal process and— apically—the exterior border of the nasal cavity are the medial side of the polygon (Fig. 2.10). The vascularity and innervation of the midmaxilla have a large individual variability. Basically, the small vascular nerve bundles originate from the intraorbital channel, where they spread down-

b

gin. (b) Paracoronal section at bicuspid level on CBCT (the reference axis is tilted along the blue line in the image “a”). The palatal process, the nose floor and the cortical plate are the margins of a large amount of bone volume to be used for a tilted implant placement. Without these multiplanar images, it is impossible to define nor measure the individual anatomy

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M. Manacorda and R. Vinci

wards and forward, with an intrabony course to get to the alveolar processes, the periodontal structures and the palatine and buccal mucous membranes. In their course, the anastomotic joints are often created between the superior posterior alveolar artery, the upper middle and anterior alveolar artery bundles and the sinuous channel. While it is a normal that the upper anterior alveolar artery and nerve reach the territory of the frontal teeth from canine to canine, their involvement in the innervation of some areas of the maxillary sinus’ anterior wall or of some distal districts usually reached by posterior or middle bundles has been proven. Canalis sinuosus is another vessel frequently noted in maxillary pre-surgical planning. It is an intrabony channel with a winding path, starting from the intraorbital channel and going forward and downwards until the maxillary sinus’ ante-

rior wall. Then, the channel goes mesially to the lateral wall of the pyriform opening. On reaching the pyriform opening, it keeps a low profile until getting into the premaxilla and dividing itself into many terminal branches. The canal ends with the little foramina palatally at lateral incisors or along the interincisive suture and carries sensitive fibres belonging to the anterior alveolar superior nerve [10, 19] (Fig. 2.11). Its involvement in implant surgery bears no consequences, except for a few cases of post-­ surgical persistent pain [20]. The upper and middle arteries and alveolar nerves elapse distribute their terminal branches in the midmaxilla. They separately reach the upper premolars and the adjacent mucosa; nevertheless, only in a few cases is a sharp distinction of their courses observed, confirming the great variability of bundles in the maxillary area [21].

Fig. 2.11  Canalis sinuosus: a CBCT views of the neurovascular bundle along the path from the infraorbital canalis to the spongy bone under the nose base. The canalis

sinuosus is tracked owing to an advanced tool of 3Diagnosys 5.0 Software (3Diemme, Cantù. Italy)

2  Surgical Anatomy of the Atrophic Maxilla

a

35

b

Fig. 2.12  In this CBCT panoramic reconstruction (a), the blue line indicates the parasagittal cut shown in the cross-­sectional view (b). If we tilt this line on the panoramic image in the cross-sectional view, then we can see

exactly the tilted implant axis and the bone availability. Fixture length and width are planned easily because of a correct visualization of the individual anatomy

For its bone thickness, the palatal process’ height and the existing cortical in the nasal wall, this area of the midmaxilla generally offers a proper anchorage to medially tilted implants. With a frontal or cross-sectional view from CBCT, the available bone thickness and the vestibular–palatal axis for the implants’ fixture insertion are visible. Diagnostic imaging provides all the information essential to the best use of the cortical anchorage, which is necessary for a correct torque insertion to guarantee an immediate loading (Fig. 2.12). Since Krekmanov et  al. and Aparicio et  al. presented their first papers describing a combination of axial and tilted implants, inserted in this skeletal segment, this methodology has become a valid alternative to pre-implant surgery with maxillary sinus lifting or bone grafts [22, 23]. Recently, pre-surgical diagnosis has become more accurate owing to 3D radiodiagnostic techniques, which have expanded the planning accuracy and therefore applicability of the surgical implant procedure even in significantly atrophic cases. Through the diagnostic software’s multiplanar view matched with the implants’ virtual position, a more accurate, individual and three-­ dimensional study of the remaining bone is now possible. Implant surgery, also computer-assisted, can use the best part of the midmaxillary remaining bone without involving adjacent areas such as the maxillary sinus or the nasal cavity. Other surgical techniques such as sinus lifting, trans-sinus

implantology or bone splitting are necessary only in extreme atrophic patients.

2.3.2.2 Iuxtameatal Implants When the remaining alveolar bone and the quality of its cancellous bone are not enough for loading the implants, it is possible to use the better features of the midmaxillary basal bone. A fixture is generally inserted with a medial tilting between 30° and 45° in the frontal process of the maxillary bone, the apex of which can reach the lateral nasal wall fixing itself in the thick cortical bone of the lower meatus. Along the implant’s extra-­ sinus path, the maxillary front process walls and the palatal process walls provide sufficient primary stability and improve the implant’s site quality. Previewing the implant position through multi-layered reconstructions of the edentulous area certainly provides substantial support in using the otherwise unseen remaining bone at its best (Figs. 2.13 and 2.14). These implants, hereby defined as iuxtameatal implants, can almost always be positioned, even in deep atrophy cases, without involving the maxillary sinus in elevation and grafting surgery [9]. All the fixtures reach the nasal base to be placed into the cortical plate and guarantee a high insertion torque sufficient to guarantee an immediate loading. Using cross-sectional images, the surgeon can plan the correct dimension and position of the drills. In this case, a bone-supported surgical template has been used for an accurate implant positioning.

M. Manacorda and R. Vinci

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a

b

c

e

Fig. 2.13  Implant planning in a severe atrophic maxilla. This “basal bone implant project” has been conducted to place four implants as an “All-on-4” project. No alveolar bone in the posterior areas and huge resorption in the midmaxilla and anterior maxillary bone. The project allows the placement of four implants, 3.3 mm in diameter and

d

f

11 and 9  mm in length (Winsix TTx, Biosafin, Ancona, Italy). Panoramic and cross-sectional view of 2.5 implant positioning planning (a, b). Iuxtameatal 1.5 implant planning in panoramic and cross-sectional view (c, d). Occlusal and nasal view of implant positiong planning in a 3d visualization (e, f)

2  Surgical Anatomy of the Atrophic Maxilla

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Fig. 2.14  Digital project: rendering 3D views in a posterior maxillary edentulism case. Note the big resorption of the alveolar bone under the sinus. The posterior fixture, tilted medially and palatally, enters deeply into the midmaxilla basal bone till it reaches the cortical plate of the

nose floor. The anterior fixture in position 1.4 is shorter and straight. Moreover, note the project for the abutments: they emerge parallel to each other to allow a screwretained anchorage with the prosthetic rehabilitation. The implant project form four different angles in 3d images

2.3.3 Posterior Maxilla

this area is not the first choice for the placement of dental implants. However, if the maxillary sinus is not largely extended into the tuber maxillae and a sufficient volume of bone remains in the posterior maxilla, then this area can be used for implant placement. The tuber maxillae are composed of a thin or absent cortical layer of compact bone surrounding an internal portion of the sparse trabeculae and large lacunae. Therefore, implants in this maxillary area with extremely spongy bone quality need to be placed involving the compact bone of the pterygomaxillary region to provide retention and guarantee implant stability. The survival rate of pterygomaxillary implants confirms that this technique is a predictable alternative for treatment in atrophic patients [24].

The posterior maxilla is the region of the upper jaw from the molar area to the junction with the pterygoid process. This bone volume is the result of the fusion of different bones including the maxilla, palatine, sphenoid and zygomatic bones. In the edentulous alveolar process, the width of the molar region is generally larger than that of the premolar region but it is often narrower than that in the dentate maxilla. The height of the bone in the posterior maxilla is generally reduced because of sinus pneumatization and alveolar height loss. The effect of atrophic resorption is generally massive and causes an insufficient amount of bone for implant positioning. After extraction and resorption, the bone structure in

M. Manacorda and R. Vinci

38

Knowledge of the anatomy of the pterygoid– palatal–maxillary region is needed to fully comprehend the technique of implant positioning in this region and the risks associated with it. The posterior maxilla can be defined as the pterygoid–palatal–maxillary region because it consists of several bone structures: maxillary tuberosity, pyramidal process of the palatine bone and pterygoid plates of the sphenoid bone [25]. Although the tuberosity region of the maxilla features poor bone quality and, consequently, is often considered the cause of lower success rates in osseointegrated implant placements as compared to the other regions of the jaw, the fusion between the previously mentioned bone structures represents a highly interesting area from a mechanical point of view in implantology [26] (Fig. 2.15). The tuber maxillae are located in the lower and posterior part of the upper jaw, posteriorly to the third molar. The tuber maxillae medially articulate with the pyramidal process of the palatine bone and, in the atrophic maxilla, often

a

reduce this bone amount and height because of sinus pneumatization. Posteriorly, the maxillary tuber joins the pterygoid process of the sphenoid bone forming the pterygomaxillary junction. Cranially, at the end of the junction between these two bones, we find the lowest point of the pterygopalatine fossa. Composed of a low-density cancellous bone, this represents an implant site when used in combination with pterygoid implants. The pterygoid process of the sphenoid bone originates from the junction between the body and the greater wing of the sphenoid, and, at its base, it is crossed by the pterygoid canal, which gives passage to the Vidian nerve and vessels. There, it bifurcates into medial and lateral pterygoid plates. The medial plate forms, with their medial face, and the posterior part of the lateral walls of the nasal cavities, with its lateral face delimit the pterygopalatine fossa. The lateral plate, with its lateral face, contributes to the formation of the infratemporal fossa, and, with the medial face, it laterally delimits the pterygopalatine fossa.

b

Fig. 2.15  A view of the posterior maxillary region in an atrophic dry skull. Note the junction between the tuberosity of the maxillary bone and the pterygoid process from the sphenoid bone. The pterygomaxillary fissure starts at the junction and continues to the pterygomaxillary fossa.

On the external surface of tuberosity are the visible foramina of the posterior superior alveolar artery (a). On the inferior view (b), note the horizontal plate of the palatine bone and great palatine artery emergency 3d rendering and actual picture

2  Surgical Anatomy of the Atrophic Maxilla

39

The internal pterygoid muscle originates from the pterygomaxillary fossa, between the two plates. The pterygomaxillary junction is formed by the maxillary tuberosity and the pterygoid process of the sphenoid bone. The variability of this anatomical structure is high: it has been demonstrated that this junction can remain as a fissure separating the maxillary tuberosity from the pterygoid plate (88% of the cases) or it can be a synostosis fusing the two bones together (12%) [27]. Knowing the height of this junction is fundamental in order to detect the pterygopalatine fossa and plan the implant position, avoiding neurovascular injuries. The pterygopalatine fossa is a small, fat-filled space in the shape of an inverted pyramid located under the apex of the orbital cavity. It is bounded by the maxillary tuberosity anteriorly, the pterygoid process of the sphenoid bone posteriorly and the perpendicular plate of the palatine bone medially. Laterally, through the pterygomaxillary fissure, it communicates with the infratemporal fossa. Despite its small size, the pterygopalatine fossa is a complex space that serves as a neurovascular crossroad between the nasal cavity, oral cavity, masticator space, orbit and middle cranial fossa. The pterygopalatine segment of the maxillary artery travels through this fossa, and it is embedded in fat; it crosses between 10 and 23.5  mm above the pterygomaxillary suture [28], and its

terminal branches supply the nasopharynx and the superior nasal meatus via the sphenopalatine foramen. Posterior to the maxillary artery, the sphenopalatine ganglion, the maxillary division of the trigeminal nerve, which exits the middle cranial fossa via the foramen rotundum, the Vidian nerve, which exits the middle cranial fossa via the pterygoid canal and the greater palatine nerve all reside in the neural structures of interest. This neural structure leaves the sphenopalatine ganglion and travels up to the greater palatine foramen, where it exits with its artery to supply the palate [24] (Fig. 2.16). The palatine bone forms part of the floor of the posterior hard palate and the lateral wall of the nose and takes part in the medial wall of the pterygopalatine fossa with its pyramidal process. The pyramidal process is located between the maxillary tuberosity and the medial pterygoid process of the sphenoid bone (Fig. 2.17). Anatomically, it appears to be fused to the anterior surface of the pterygoid process at the passage between the horizontal and pyramidal process. It is part of the wall of the pterygopalatine canal and often contains the smaller palatine artery and its duct. The region of the posterior maxilla is supported by several other arteries of surgical interest. The posterior superior alveolar artery, for example, originates from the maxillary artery in the pterygopalatine fossa and enters into the tuberosity to support the teeth and maxillary sinus. These

Fig. 2.16  Coronal and parasagittal views of a CBCT image showing the pterygopalatine canal (white arrows) during its path from the pterygopalatine fossa to the hard

palate. The canal generally bifurcates into greater and smaller palatine canals and ends in greater and smaller palatine foramina (red arrows)

40

branches often form an anastomosis with the anterior superior alveolar artery or with the infraorbital artery located on the bone surface of the sinus or in narrow canals in the cortical bone. They run anteriorly along the sinus surface, and, during surgery, is important to avoid intra- and postoperative bleeding complications, for example, in sinus floor elevation procedures (Fig. 2.18) [20].

M. Manacorda and R. Vinci

2.3.3.1 Radiological Landmarks For the placement of pterygomaxillary implants, it is imperative to have a thorough knowledge of the anatomy involved because the nearby vital structures can be injured during surgery. Special attention should be paid to the internal maxillary artery [26]. A three-dimensional evaluation of the pterygomaxillary region’s characteristics for implant placement is highly recommended. Recognition of individual anatomy allows the surgeon to fix implants with good bone quality and to avoid injuries. Stereolithographic models are extremely useful before an implant surgery to analyze patient-specific anatomy [29]. Point of entries, mesiodistal and buccopalatal angulations of the fixtures are essential before an implant surgery in this area because the space available for implant placement can vary according to the displaceable bone and the anatomical variants of each individual (Figs. 2.19 and 2.20).

Fig. 2.17  Occlusal and palatine views of the pyramidal process of the palatine bone. The thin cortical bone is connected to the medial pterygoid process posteriorly and to the palatal side of the tuber maxillae anteriorly. 3D reconstruction from Multislice CT (a 3D rendering by Real Guide Software, Cantù, Italy)

2.3.3.2 Implants in the Pterygoid Region, Radiological Diagnosis and Planning Although over the last few years, implantology has made major progresses, it remains certain that, in case of severe bone atrophy, the rehabilitation of the posterior segments of the maxillary bones often presents a challenge. Concerning the upper jaw, the cause is related to the presence of the maxillary sinus and low-density bone in the posterior area. Many alternatives, including sinus

Fig. 2.18  Individual localization of the arteries on the external surface of the maxillary sinus. Anastomoses between the posterior superior alveolar artery, the anterior

superior alveolar artery and the infraorbital artery are often present on the bone surface of the sinus or in narrow canals in its cortical bone. 3d rendering and actual picture

2  Surgical Anatomy of the Atrophic Maxilla

41

a

b

Fig. 2.19 (a) A panoramic reconstruction from CBCT in a fully dentate patient (thickness 0.2  mm). Anatomical differences between an atrophic edentulous arch and a

patient with complete dentition. (b) In an atrophic patient, the panoramic view does not offer enough information on the pterygomaxillary region for implant planning

lift, guided bone regeneration (GBR) grafting and zygomatic implants, have been proposed to overcome these difficulties. In order to avoid the complications related to these surgical techniques, a more predictable alternative has been described. Implants positioned at the tuberosity of the maxilla have been proposed by many authors as a valid and predictable alternative. Tuberal implants are positioned at the posterior-­most area of the maxillary bone, distally at the posterior wall of the tuber maxillae. In many patients, this area is not occupied by the sinus and is mostly composed of an extremely poor cancellous bone with an extremely thin crestal cortical plate [26]. In 1992, Tulasne introduced the concept of pterygomaxillary implants, specifically tilted implants placed through the tuber region of the posterior maxilla and tethered to the pterygoid

plate of the sphenoid bone [30]. In the literature, we can find different terms for this surgical procedure, “pterygoid implants”, “tuberosity implants” or “pterygomaxillary implants”, but the correct definition should be “tuberosity implants with pterygoid anchorage”. This definition correctly describes the placement of these types of implants, mostly in the maxillary bone, often with poor bone density, but with the apex engaged in the hard and thin cortical bone of the pterygoid plate, or the pyramidal process of the palatine bone, close to its junction with the distal palatal region of the tuber maxillae. However, it must be kept in mind that the simplest solution with the least associated risks is always preferable, which is why, when it is possible, depending on the tuberosity’s dimensions and quality, we place an implant completely within

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42

a

c

b

d

Fig. 2.20 (a) A lateral view of 3D rendering of the atrophic maxilla in an edentulous patient: (A) tuber maxillae; (B) pterygomaxillary junction; (C) lateral plate of the lateral pterygoid process; (D) pterygopalatine fossa; and (E) maxillary sinus. (b) A posterior view of the atrophic maxilla. (A) Medial plate of the pterygoid process; (B) lateral plate; (C) pterygoid hook; (D) horizontal process of the

palatine bone; and (E) insertion of the medial pterygoid muscle. (c) An occlusal view in CBCT 3D rendering. (A) Medial plate; (B) minor palatine artery emergency; (C) pyramidal process of the palatine bone; (D) incisive canal; and (E) atrophic alveolar process and zygomatic process (d) virtual impant positioning in the pterygoid region of an atrophic maxilla (posterior view)

this anatomical region (avoiding angling the implant apex more distally). If the height, length and/or width of the tuberosity are not adequate, then the implant can be angled and the apex made to engage the pterygoid process, the pyramidal plate of the palatine bone or both [25]. In Fig. 2.21, a schematic illustration describes the different options for pterygomaxillary implants, depending on the individual anatomy of the residual bone. Given the fact that a panoramic view is not sufficient for planning a tuberal or p­ terygomaxillary implant, it is necessary to conduct a CBCT examination to determine the individual length, width and angulation of implants. With an axial view, it is possible to determine the width of the tuber

maxillae and scroll images cranially on the viewer to see the extension of the sinus till the pterygoid junction. Along the palatal side, it is possible to detect the great palatine artery path and the emergency on the palatal vault. Specific software can show the density of the cancellous and cortical bone to plan the bone drilling diameter in order to attain good primary stability (Fig. 2.22). In the “panoramic view”, we can plan the length and the angulation of the tilted implant to avoid sinus membrane perforation and also plan to reach the pterygoid process for implant stability. In this projection, we can also establish the bone quality along the parasagittal view on a multiplanar selected view (Fig. 2.23).

2  Surgical Anatomy of the Atrophic Maxilla TUBEROSITY IMPLANTS

Maxillary sinus Pterygoid process of sphenoid bone Pterygopalatine fossa

TUBEROSITY IMPLANTS WITH PTERYGOID ANCHORAGE

Maxillary sinus Pterygoid process of sphenoid bone Pterygopalatine fossa

43 TUBEROSITY-PTERYGOIDPYRAMIDAL IMPLANTS

Maxillary sinus Pterygoid process of sphenoid bone Pterygopalatine fossa

Fig. 2.21  A schematic view of different lengths and angulations of implants in the posterior maxilla

Fig. 2.22  An axial view of the edentulous atrophic maxilla in the area where the tuber is connected to the pterygoid process (the pterygomaxillary joint). The pink segment in (a) indicates the bone density in the corresponding bone segment

Fig. 2.23  A pseudo panoramic view is necessary to plan the angulation of the tilted implant, its length and the extension on the cortical bone of the pterygoid plate

44

M. Manacorda and R. Vinci

Fig. 2.24  On the left, the multiplanar section (in red) chosen for implant planning with an extremely poor amount of bone in the tuber maxillae. The cross section shows the real path of the implant and the anatomy around

the site. On the right, a virtual implant positioning after a radiographic analysis of the implant. Surgical guides can help the surgeon place the fixture in the planned position

On the coronal view, it is possible to decide the buccopalatal inclination, maintaining a safety distance between the artery and the palatine nerve and the implant. It is necessary to select, using dedicated software, a tilted plane of the parasagittal section with the required distal inclination. A

cross-sectional view is the correct place to plan the implant site (Fig. 2.24). An accurate study of CBCT images and a virtual implant positioning before the surgery can help the surgeon in preparing an implant site that is generally sensitivity-dependent and semi-­

2  Surgical Anatomy of the Atrophic Maxilla

blinded, potentially with a high risk of encroachment of the vital structures [31].

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45 13. Wang KH, Heike CL, Clarkson MD, Mejino JL, Brinkley JF, Tse RW, Birgfeld CB, Fitzsimons DA, Cox TC. Evaluation and integration of disparate classification systems for clefts of the lip. Front Physiol. 2014;5:163. 14. Bornstein MM, Balsiger R, Sendi P, von Arx T.  Morphology of the nasopalatine canal and dental implant surgery: a radiographic analysis of 100 consecutive patients using limited cone-beam computed tomography. Clin Oral Implants Res. 2011;22:295–301. 15. Mardinger O, Namani-Sadan N, Chaushu G, Schwartz-Arad D. Morphologic changes of the nasopalatine canal related to dental implantation: a radiologic study in different degrees of absorbed maxillae. J Periodontol. 2008;79:1659–62. 16. Raghoebar GM, den Hartog L, Vissink A. Augmentation in proximity to the incisive foramen to allow placement of endosseous implants: a case series. J Oral Maxillofac Surg. 2010;68:2267–71. 17. Ganz SD. The reality of anatomy and the triangle of bone. Inside Dent. 2006;2:72–7. 18. Ganz SD.  Using interactive technology: in the zone with the Triangle of Bone. Dent Implantol Update. 2008;19:33–8. 19. von Arx T, Lozanoff S, Sendi P, Bornstein MM.  Assessment of bone channels other than the nasopalatine canal in the anterior maxilla using limited cone beam computed tomography. Surg Radiol Anat. 2013;35:783–90. 20. 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;3:255–8. 21. Heasman PA. Clinical anatomy of the superior alveolar nerves. Br J Oral Maxillofac Surg. 1984;22:439–47. 22. Krekmanov L, Kahn M, Rangert B, Lindström H.  Tilting of posterior mandibular and maxillary implants for improved prosthesis support. Int J Oral Maxillofac Implants. 2000;15:405–14. 23. 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. 24. Lopes LF, da Silva VF, Santiago JF Jr, Panzarini SR, Pellizzer EP.  Placement of dental implants in the maxillary tuberosity: a systematic review. Int J Oral Maxillofac Surg. 2015;44(2):229–38. 25. Rodríguez X, Rambla F, De Marcos Lopez L, Méndez V, Vela X, Jiménez Garcia J. Anatomical study of the pterygomaxillary area for implant placement: cone beam computed tomographic scanning in 100 patients. Int J Oral Maxillofac Implants. 2014;29(5):1049–52. 26. Salinas-Goodier C, Rojo R, Murillo-González J, Prados-Frutos JC.  Three-dimensional descriptive study of the pterygomaxillary region related to pterygoid implants: a retrospective study. Sci Rep. 2019;9(1):16179. 27. Dadwal H, Shanmugasundaram S, Krishnakumar Raja VB. Preoperative, postoperative CT. Scan assessment

46 of pterygomaxillary junction in patients undergoing Le Fort I osteotomy: comparison of pterygomaxillary disjunction technique and trimble technique—a pilot study. J Maxillofac Oral Surg. 2015;14:713–9. 28. Rodríguez X, et  al. Anatomical and radiological approach to pterygoid implants: a crosssectional study of 202 cone beam computed tomography examinations. Int J Oral Maxillofac Surg. 2016;45:636–40. 29. Bidra AS, Huynh-Ba G.  Implants in the pterygoid region: a systematic review of the literature. Int J Oral Maxillofac Surg. 2011;40(8):773–81.

M. Manacorda and R. Vinci 30. Tulasne JF.  Osseointegrated fixtures in pterygoid region. In: Worthington P, Branemark PI, editors. Advanced osseointegration surgery: application in the maxillofacila region. Chicago: Quintessence; 1992. p. 182. 31. 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(1):7–14.

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Integrating Modern Diagnostic Tools with Digital Engineering Panos Diamantopoulos and Gerlig Widmann

3.1 Introduction to Applied Digital Technologies 3.1.1 Medical Imaging Medical imaging is the creation of a visual representation of the human anatomy. It has been an important diagnostic tool since the discovery of X-rays by Roentgen in 1895. Techniques other than simple planar radiographs have become available during the last 50 years. These include, in historical order, radioisotope nuclear medicine (NM), ultrasound (US), computed tomography (CT), and magnetic resonance (MR) imaging. As a subject, it has grown enormously over the past few decades. One of the major developments has been the development of techniques for constructing images representing slices through three-dimensional (3D) objects. These techniques are called tomography and are based on the idea that an object may be constructed from projections. The theory of reconstruction from projections predates the construction of any P. Diamantopoulos Medical 3D Printing Unit, Laboratory of Experimental Physiology, Medical School, University of Athens, Athens, Greece e-mail: [email protected] G. Widmann (*) Department of Radiology, Medical University of Innsbruck, Innsbruck, Austria e-mail: [email protected]

actual scanner for computed tomography. It is generally accepted that the problem was first analyzed by Radon in 1917 [1]. An account of the method and the first system for reconstructing X-ray medical images probably originated from Russia [2, 3], although it is the work of Hounsfield in 1972 [4] that led to the first commercially developed system. It was the first system to produce section images of high quality and paved the way to tomographic and three-dimensional imaging techniques. The success of CT depended largely though on the development of a fast and accurate image reconstruction algorithm by Cormack in 1980 [5]. This, in turn, generated a general interest in reconstruction algorithms and digital imaging. It is important to keep in mind that the data acquired by the system detectors represent spatial distribution of intensity. This distribution can be mathematically described as a two-dimensional (2D) function f(x,y), where x and y are spatial coordinates and the value of f at any point (x,y) is proportional to the brightness or gray value of the data at that point. To create a digital image, a sampling process occurs that creates discrete finite picture elements (called pixels) and assigns to them both a location (x,y coordinates) and a color or gray value (f-value) (Fig. 3.1). This process is known as digital imaging or digitizing [6]. The picture elements are directly stored in the computer into a 2D matrix, also called an array or a frame, using analog-to-digital converters

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 M. Rinaldi (ed.), Implants and Oral Rehabilitation of the Atrophic Maxilla, https://doi.org/10.1007/978-3-031-12755-7_3

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PIXEL (2D) VOXEL (3D)

Fig. 3.1  An image slice is represented by pixels and voxels depicting the acquired spatial intensity in different shades of gray. The sum of pixels and voxels is known as resolution

(ADCs). Typically, a two-dimensional image is made up of M rows, each of N pixels. A value is assigned to each of them, representing either the integrated or the average image intensity across the pixel or a sampled value at the center of the pixel. A three-dimensional image is made up of K slices or planes each containing M rows, each of N pixels. The elements in this case are called voxels (volume elements). Pixels are invariably square, but voxels are not always cubic because it depends on the image thickness during image acquisition. In general, a typical digital medical imaging system process includes (a) image digitization, (b) image storage, (c) image display, and (d) image processing and analysis. Digital radiographic systems present advantages in all these steps as well as dose reduction. However, it is a fact that most imaging data is presented in a

two-­dimensional black and white format. They are grayscale images without actual color. Multiple color, three-dimensional visualization can be achieved using the high-specification workstations accompanying the medical scanners. In this case, the applied colors are also artificial and are thus called pseudo-colors, with the intention of making intensity differences more apparent. Such weaknesses have often been limiting the application potential. In addition, medical scanners have generally been “closed systems,” scanner to workstation, which offer limited or no external access to their data. Transferring data to external systems has been a particularly demanding task, requiring specific hardware, software, and special expertise. As a result, the potential of utilizing medical imaging information in other scientific domains, such as biomechanical engineering, has not yet been fully realized. In maxillofacial surgery, 3D imaging using computed tomography (CT) or, most recently, cone-beam computed tomography (CBCT), has become an essential prerequisite for modern presurgical evaluation, treatment planning, digital engineering, and computer-guided surgery. A summary of the most important imaging aspects relevant to the maxillofacial practice is provided below:

3.1.1.1 Short Basics of CT and CBCT Technology Computed Tomography (CT) In CT, the subject is scanned using a helical rotating X-ray beam. Multislice detectors opposite to the X-ray beam record the information, which is transformed into digital images using filtered back projection or iterative reconstructive techniques. The volumetric data can be displayed in axial or multiplane image reconstructions. Furthermore, curved plane reconstructions including cross-sectionals and panoramic reconstructions as well as 3D reconstructions using volume rendering or cinematic volume rendering techniques are available. Modern CT scanners

3  Integrating Modern Diagnostic Tools with Digital Engineering

are multifunctional, high-tech machines for diagnostics of the entire body. CT has become a diagnostic mainstay in acute medicine, trauma, and oncology. Cone-Beam Computed Tomography (CBCT) In CBCT, the subject is scanned using a 180–360° rotating beam-shaped X-ray, which is recorded by an opposite flat-panel detector to generate CT-like images [7]. Compared with CT scanners, CBCT machines are more compact and smaller and can be installed in dental offices. The scan range is limited to the head area, and there is no soft tissue imaging. However, CBCT has a high spatial resolution and an excellent bone image quality [8]. Due to the longer scan time, motion artifacts can be a possible source of errors.

3.1.1.2 Radiation Dose Medical societies and legislative directives demand strict adherence to evidence-based imaging guidelines and patient’s informed consent. Surgery and implant rehabilitation in the atrophic maxilla is a clear indication for CT/CBCT imaging. Dose management should follow the principle of “as low as reasonably achievable” (ALARA) and “as low as diagnostically acceptable” (ALADA) [9]. For benchmarking of CT radiation doses across institutions and scanners, diagnostic reference levels (DRLs) are provided by national radiological societies [7]. Regular excess of DRLs may attract local reviews and audits with the assistance of medical physicists. DRLs are given as phantom-based dose estimates such as the volume CT dose index, CTDIvol (mGy), and the dose length product, DLP (mGy × cm), which are documented in the Digital Imaging and Communications in Medicine (DICOM) dose report [8]. CTDIvol refers to the dose within one radiated slice (a nominal beam width) and considers the ratio of the nominal beam width and table feed (pitch). DLP is the product of CTDIvol and scan length. The effective dose (E) of an examination can be estimated using DLP and a conversion factor (k)

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(E  =  k  ×  DLP) [10]. Following the current International Commission on Radiation Protection (ICRP) 103 recommendations, a conversion factor of 0.0019 mSv/mGy × cm is used for CT of the head and 0.0051 mSv/mGy × cm for examinations of the head and neck area [11]. CBCT is erroneously considered a low-dose modality, based on comparisons of doses from CBCT with an extremely limited scan range and CT doses using head protocols. More recently, ultra-low-dose (CTDIvol 8 mm) with sinus lifting in atrophic posterior maxilla: a meta-analysis of RCTs. Clin Implant Dent Relat Res. 2017;19(1):207–15. 41. Anitua E, Flores J, Flores C, Alkhraisat MH.  Long-­ term outcomes of immediate loading of short implants: a controlled retrospective cohort study. Int J Oral Maxillofac Implants. 2016;31(6):1360–6. 42. Bechara S, Kubilius R, Veronesi G, Pires JT, Shibli JA, Mangano FG.  Short (6-mm) dental implants versus sinus floor elevation and placement of longer (≥10 mm) dental implants: a randomized controlled trial with a 3-year follow-up. Clin Oral Implants Res. 2017;28:1097. 43. Chana H, Smith G, Bansal H, Zahra D. A retrospective cohort study of the survival rate of 88 zygomatic implants placed over an 18-year period. Int J Oral Maxillofac Implants. 2019;34(2):461–70. 44. Petrungaro PS, Kurtzman GM, Gonzales S, Villegas C.  Zygomatic implants for the management of severe alveolar atrophy in the partial or completely edentulous maxilla. Compend Contin Educ Dent. 2018;39(9):636–45. 45. Davó R, Felice P, Pistilli R, Barausse C, Marti-­ Pages C, Ferrer-Fuertes A, Ippolito DR, Esposito M.  Immediately loaded zygomatic implants vs conventional dental implants in augmented atrophic max-

L. V. Stefanelli and G. A. Mandelaris illae: 1-year post-loading results from a multicentre randomised controlled trial. Eur J Oral Implantol. 2018;11(2):145–61. 46. Baggi L, Capelloni I, Di Girolamo M, Maceri F, Vairo G.  The influence of implant diameter and length on stress distribution of osseointegrated implants related to crestal bone geometry: a three-­ dimensional finite element analysis. J Prosthet Dent. 2008;100(6):422–31. 47. Tulasne JF.  Implant treatment of missing posterior dentition. In: Albrektson T, Zarb G, editors. The Brånemark osseointegrated implant. Chicago, IL: Quintessence; 1989. p. 103–58. 48. Tulasne JF. Osseointegrated fixtures in the pterygoid region. In: Worthington P, Brånemark PI, editors. Advanced osseointegration surgery, applications in the maxillofacial region. Chicago, IL: Quintessence; 1992. p. 182–8. 49. 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(6):798–804. 50. Rodríguez X, Lucas-Taulé E, Elnayef B, Altuna P, Gargallo-Albiol J, Peñarrocha Diago M. Hernandez-­ Alfaro F2. 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(5):636–40. 51. Stefanelli LV, Graziani U, Pranno N, Di Carlo S, Mandelaris GA.  Accuracy of dynamic navigation surgery in the placement of pterygoid implants. Int J Periodontics Restorative Dent. 2020;40(6):825–34. https://doi.org/10.11607/prd.4605. 52. Bidra AS, Huynh-Ba G.  Implants in the pterygoid region: a systematic review of the literature. Int J Oral Maxillofac Surg. 2011;40(8):773–81. 53. Candel E, Peñarrocha D, Peñarrocha M. Rehabilitation of the atrophic posterior maxilla with pterygoid implants: a review. J Oral Implantol. 2012;38 Spec No:461–6. 54. Araujo RZ, Santiago Júnior JF, Cardoso CL, Benites Condezo AF, Moreira Júnior R, Curi MM.  Clinical outcomes of pterygoid implants: systematic review and meta-analysis. J Craniomaxillofac Surg. 2019;47(4):651–60. 55. Graves SL.  The pterygoid plate implant: a solution for restoring the posterior maxilla. Int J Periodontics Restorative Dent. 1994;14(6):512–23. 56. Stefanelli LV, Mandelaris GA, Franchina A, Di Nardo D, Galli M, Pagliarulo M, Testarelli L, Di Carlo S, Gambarini G.  Accuracy evaluation of 14 maxillary full arch implant treatments performed with Da Vinci Bridge: a case series. Materials (Basel). 2020;13(12):2806. https://doi.org/10.3390/ ma13122806.

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Robotics for Implant Reconstruction of the Edentulous Maxilla Jeffrey Ganeles, Uday N. Reebye, Frederic J. Norkin, and Liliana Aranguren

6.1 An Overview of Robotic Surgery Robotic technology in the operating room has advanced from exotic to routine in the past 35  years. The first documented robot-assisted surgery occurred in 1985, when the PUMA 560 (Programmable Universal Machine for Assembly) (Unimation, Danbury, Connecticut) assisted sur-

J. Ganeles (*) South Florida Center for Periodontics and Implant Dentistry, Boca Raton, FL, USA American Board of Periodontology, Chicago, IL, USA Nova Southeastern University, College of Dental Medicine, Fort Lauderdale, FL, USA Boston University Goldman School of Graduate Dentistry, Boston, MA, USA e-mail: [email protected] U. N. Reebye Triangle Implant Center, Durham, NC, USA American Board of Oral and Maxillofacial Surgery, Chicago, IL, USA University of North Carolina, Adams School of Dentistry, Adjunct Faculty, Chapel Hill, NC, USA F. J. Norkin · L. Aranguren South Florida Center for Periodontics and Implant Dentistry, Boca Raton, FL, USA American Board of Periodontology, Chicago, IL, USA e-mail: [email protected]; [email protected]

geons in performing a neurosurgical biopsy. Later, the PROBOT and ROBODOC surgical systems were designed to improve the accuracy of prostate surgery and hip replacement surgery, respectively. As researchers recognized the potential of robotics in laparoscopic surgery, the da Vinci Surgical System (Intuitive Surgical Systems, Inc., Sunnyvale, California) and the Zeus Robotic Surgical System (Computer Motion, Inc., Goleta, California) were created to assist physicians in minimally invasive procedures. The Zeus Robotic Surgical System for endoscopy was created with a voice-activated user interface, namely, AESOP (Automated Endoscopic System for Optimal Positioning) [1]. Significant improvements in the da Vinci Surgical System have addressed some previous limitations of laparoscopic surgery [2]. As the field of robotic surgery advanced, medical robots were classified according to their autonomy: passive, remote, semi-active, and active systems [3]. Passive robotic systems provide support to the surgeon for various tasks. Remote systems are dependent on surgeon control and are also known as surgical extenders. Due to their lack of preprogrammed elements, the da Vinci and Zeus platforms fall under this classification, in which the laparoscopic instruments manipulated by the robot replicate the surgeon’s movements. With semi-active, or semi-autonomous, robotic platforms, surgeons work alongside a predetermined element of the

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system. Finally, active platforms work autonomously and do not require a direct feedback from the surgeon. The Mako (Stryker, Kalamazoo, MI) semi-­ autonomous robotic surgical system was developed in 2004. The NAVIO Surgical System (Navigation Input/Output) (Smith & Nephew, Inc., Andover, MA) is also a semi-autonomous robotic system used in orthopedic surgery for total and partial hip and knee arthroplasty. The NAVIO system is imageless, relying upon real-­ time characterization of the bone and cartilage through landmark collection and point mapping. NAVIO provides the surgeon with realtime feedback by modulating bur speed based upon the preoperative plan. Both the NAVIO and Mako systems reduce surgical time and blood loss by allowing for minimally invasive techniques and reduced surgical time versus conventional techniques. Although both systems offer similar 1-year results, the Mako system is less invasive and is associated with lower blood loss [4]. Mako integrates preoperative computed tomography (CT) scan of the patient’s knee or hip and three-dimensional planning to size and orient implants prior to bone resection. Unique to Mako’s system is its integration of haptic feedback beyond which movement is limited, enabling the surgeon with robotic assistance to

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perform accurate bone shaping through minimally invasive incisions for partial or complete knee and hip replacements. The haptic feedback provides the surgeon with real-time information about the three-dimensional position of a bur tip for precise, preplanned cuts. Systematic reviews of Mako robotic-assisted unicompartmental knee arthroplasty (UKA) concluded that “implant positioning with robotic-assisted UKA is more accurate and more reproducible than that performed manually” [5]. Similarly, total knee arthroplasty performed with the Mako robotic system demonstrated reduced postoperative pain, improved implant positioning, and slightly improved functional outcomes compared to conventional techniques 1 year after surgery [6]. The novel Yomi platform (Neocis Inc., Miami, FL) is the first semi-autonomous robot designed for dental implant placement (Fig. 6.1a, b). Like the Mako system, Yomi integrates and provides computed tomography, presurgical planning, and real-time haptic feedback to the surgeon to prevent deviation from the preoperative plan (Fig. 6.2) [7]. The surgeon will experience resistance from the robot if the handpiece is not in the correct location, orientation, or depth. If needed, the surgeon can modify the surgical plan mid-­ procedure “on-the-fly” through the laptop computer attached to the robot. This can be used to address unexpected anatomical or surgical anom-

b

Fig. 6.1 (a) A Yomi robot from Neocis, Inc. with the working arm partially extended and monitors. (b) The surgeon holds and guides the handpiece, which is attached to the robotic surgical arm

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Fig. 6.2  The robotic arm uses haptic signals to guide the surgeon exactly to the planned osteotomy position and then maintains the orientation to precisely drill or place an implant

alies intraoperatively without having to abandon the guided system and be forced to proceed free-handed. In 2017, the United States Food and Drug Administration cleared the use of Yomi for dental implant surgical procedures in partially edentulous patients, and, in 2020, it cleared the use of Yomi in fully edentulous patients.

6.2 Computer-Guided Surgery Options for Implant Placement in the Edentulous Maxilla Osseointegration has paved the way for modern implant dentistry [8]. In most situations, dental implants are the preferred method to anchor and support prostheses for replacement of missing teeth due to their predictable outcomes, minimal complication risk, and improved quality of life following the procedure [9–11]. The prevalence estimates in the United States indicates a substantial increase in the utilization of implants for dental rehabilitation over the last two decades, with projections indicating a near doubling of the implant market between 2021 and 2028 [12]. The patient demographic typically in need of extensive dental rehabilitation is most often older adults who often exhibit unique challenges in the

maxillary arch such as alveolar resorption, limited bone volume, pneumatization of the posterior alveolar ridge, reduced bone quality, systemic health challenges, and reduced healing potential [13]. The unique difficulties with implant placement in the resorbed maxillary arch are described in greater detail in other sections of this book. However, these anatomical and physiological difficulties create a greater need for precise implant planning and placement. Advancements in implant therapy continue to become more sophisticated and patient-oriented, in part due to the advent of three-dimensional computer modeling and technology [14]. The use of computed tomography (CT) has permitted surgeons to implement a precise and accurate approach when virtually planning and physically performing implant placement. There are two general technological categories for computer-­ guided implant surgery: static and dynamic [15, 16]. The static guide approach typically utilizes a printed or stereolithographically produced surgical template created from imaging derived from CBCT data [Digital Imaging and Communications in Medicine (DICOM) files], an intraoral scan of the patient [stereolithography (STL) files], a digital wax-up of the planned restoration, and a digitally designed surgical guide. This printed guide has plastic or metal sleeves and keys that restrict

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drill positioning and depth when used as planned. The guides may be tooth-, tissue-, or bone-­ supported and are used for osteotomy preparation as well as implant placement [17]. Static guides have been validated to improve placement accuracy in comparison to freehand, laboratory-­ fabricated, and partially guided methods [18]. Static guides have some challenges and limitations. There is an inherent manufacturing time delay for static guides, meaning that spontaneously guided surgical procedures cannot be performed unless the surgeon has the design and printing capabilities in-house. Additionally, once the osteotomy positions are established and printed in the guide, those three-dimensional positions are fixed. Intraoperative corrections can be performed by the surgeon free hand, but they are unguided. Printed guides must necessarily have some bulk for strength and stability. This may impede the surgeon’s ability to see the surgical site. Additionally, there are concerns of excessive heat from the friction between the twist drills, metal sleeves in the surgical template, and guide handles during osteotomy preparation. The presence of a surgical template can prevent proper cooling of the twist drill as it enters the osteotomy site, leading to excessive heat generation, which may result in bone necrosis and failure of the implant to osseointegrate [19–21]. Guide accuracy is also sensitive to sleeve length, sleeve tolerance, and distance of the sleeve above the osteotomy [22]. The further the sleeve is from the osteotomy, the lower the tolerance is between the sleeve and the drill diameter, and the shorter is the sleeve, the less accurate the guide. This becomes particularly important when considering zygomatic implants, pterygoid implants, and distally tilted implants. In some anatomical circumstances, such as limited interarch space or distally tilted implants, it can be highly challenging to the surgeon to be able to use a static guide due to physical space limitations. When using a static guide, if the surgeon wants to deviate from the preplanned osteotomy position, then it must be done free hand. Other concerns have been raised about seating implants through a guide as the carrier can bind on it, caus-

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ing the surgeon to lose tactile sensation and possibly leading to over-torquing or stripping of the osteotomy, thus reducing implant stability. The functional differences between static and dynamic surgery will be more fully discussed in the chapter on surgical navigation. Dynamic guided surgery was introduced to the dental implant surgery field in the early 2000s [23, 24]. It overcame many of the limitations of static guides using different technologies and strategies. Dynamic navigation systems were the first platforms in the field, integrating three-­ dimensional diagnosis and a subsequent presurgical plan with real-time visual feedback to the implant surgeon. The next iteration of dynamic guidance was robotics (introduced by Neocis Inc., Miami, FL), which received FDA approval for implant placement in 2017. They share similar workflows and strategies to overcome some limitations of static guides. They use motion tracking technology of the patient and the surgeon’s drill in concert with real-time data from CBCT scans and the surgical plan to guide implant placement. Dynamic navigation utilizes fiducial landmarks placed adjacent to the alveolar bone of the patient to trace the implant placement [25]. The software allows the clinician to plan the three-­ dimensional implant placement prior to surgery and then ensure accurate positioning of the planned implant [26]. Innovations in dynamic navigation-guided implant surgery seek to alleviate static guide limitations while implementing a plan in a patient seamlessly [27].

6.3 Workflow of Robotic Surgery for the Edentulous Maxilla The goal of robotic implant surgery is to precisely mimic the presurgical plan at the time of surgery in an accurate, actionable, and reproducible manner. To accomplish this goal, the implant surgical team, the restorative dentist, or the prosthodontist and/or the laboratory technician, in concert with the implant surgeon, generates a pretreatment digital plan. Although the steps may vary based upon the clinician’s preferences, they essentially follow a similar pathway.

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The implant team obtains a digital or analog implant positions as needed at this time or anyimpression and bite registration of the patient, time during the procedure (Fig. 6.7). which is converted to an .stl file, for subsequent The robot is moved into a position over the digital planning. Facial and intraoral photographs patient so that the surgical area is within the can be integrated as additional information for working radius of the robot. Indicators in the the technician regarding lip position and smile robot software assist in patient and robot posiline and vertical height. From this information, a tioning in this process (Fig.  6.8a, b). Once an digital wax-up of the anticipated final prosthesis acceptable positioning is confirmed, the splint, is created. which was originally used to attach the fiduciary Once a presurgical cone-beam CT scan (a array, is attached to a tactile tracking arm from DICOM file) is obtained, it is merged with the the robot via a sterile effector (a connector). This digital wax-up in the planning software, provid- allows the robot software to precisely, three-­ ing the implant team with a prosthetically ori- dimensionally locate and track the patient in real ented means to plan implant placement [28]. The time. It also allows the robot to sense and adjust surgeon can now visualize both bony anatomy to patient movements and instantly adjust the disand soft tissue surfaces to effectively plan the played images and robotic arm to those moveprocedure. During this stage, Yomi software will ments (Fig. 6.9) [29, 30]. highlight the bone density surrounding the virtual A landmark verification step is needed to implants and provide warnings in case of proxim- complete the setup. In the software, a known anaity between the implants and the nerves or sinuses tomical and radiographic landmark is assigned. much like other planning software in implant Often, this is the center of a fixation screw or dentistry. Ultimately, this preoperative plan cusp tip of an existing tooth. A drill of known should allow for implant placement, promoting length and diameter is confirmed and placed into an easily delivered final restoration (Fig. 6.3a, b). the handpiece attached to the robot arm and then At the time of surgery, a fixation device, called moved to touch the landmark (Fig. 6.10a, b). If a splint, is attached to the arch being treated with this is successfully completed, then a cross-­ three to five fixation screws for rigid skeletal hatched image on the drill tip in the software anchorage and splint stability (Figs. 6.4 and 6.5). turns green, indicating successful verification The splint serves several purposes. First, it is and an accurate setup (Fig. 6.11). If not, then the used to anchor radiographic markers to the previous steps need to be rechecked before propatient as the patient needs to be re-scanned using ceeding with osteotomy preparation. A successCBCT to orient the patient to the standardized ful verification means that the virtual plan radiographic objects that are incorporated into matches the actual measurements and conditions, the fiducial array (Fig. 6.6). The software recog- indicating that accurate guidance can be expected. nizes this pattern and matches its three-­ During the surgical procedure, it is helpful to dimensional position to the patient. Once this have an assistant managing the laptop that conscan is completed, the fiducial array is removed. trols the robot. He or she cycles through the softThe second purpose of the splint is to connect the ware, entering information as the surgery patient to the robot via a tactile tracking arm, progresses. This includes drill dimensions meawhich will be described below. sured from the face of the handpiece to the tip of The new scan is uploaded to the laptop com- the drill and tooth number being treated. Other puter associated with the robot and is then over- “commands” that are entered include allowing layed with the original digital surgical plan. the handpiece and robotic arm to move freely Landmarks are identified on the pre-op scan and (“free”) or to be in the “guided” mode. The the new fiduciary scan. Once the scans are guided mode is activated when the drill is relaaligned, the software merges them so that the tively close to the intended osteotomy, which is original plan now appears on the fiduciary scan. viewed by the surgeon on the monitor displaying The surgeon can fine-tune the plan and adjust the robotic software or by looking into the mouth

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a

b

Fig. 6.3 (a, b) Planning software showing a CBCT .dicom image overlayed with a .stl image from intraoral scan displays’ implant positions three-dimensionally

at the surgical site. When the “guided” mode is enabled, indicators in the software advise the surgeon regarding which directions to move to align to the intended osteotomy site. Directions on the monitor advise the surgeon to bodily move the handpiece anteriorly, posteriorly, laterally, or medially as well as into the correct angulation

(Fig. 6.12). The robot also provides haptic feedback, encouraging the surgeon to move the handpiece in the correct direction, while making it more difficult to deviate away from the intended position. When the drill is properly aligned over the osteotomy site in terms of position and angula-

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Fig. 6.4  An edentulous “splint”, which requires fixation with at least three screws to rigidly anchor the robotic tracking arm to the arch being treated

Fig. 6.5 A maxillary edentulous “splint” placed transmucosally

Fig. 6.6  A new CBCT scan taken of the patient after the splint is attached with a radiographic marker array in place

tion, the robotic arm locks the handpiece orientation in place and restricts movement to apicocoronal (vertical drilling) movements (Fig.  6.13). Once the full osteotomy depth is reached, the robot restricts further apical drilling. This process is repeated for each osteotomy until they are completed according to the surgical plan. The robot can then be switched into an implant placement mode so that the implants can be robotically inserted fully guided. The implants must be delivered with the handpiece in order to use this feature (Fig.  6.14). Measurements are taken from the handpiece face to the top of the implant and entered into the robotic software. Each implant can then be precisely and accurately robotically guided into position according to the plan. Some discretion and caution should be exercised with full robotic insertion in poor quality bone as it is possible to strip an osteotomy by over-torquing an implant since the surgeon’s tactile sense of resistance to insertion torque is diminished. In other circumstances, with denser bone or under-drilled osteotomies, this fully guided approach can be used. Once all the implants are seated, the robot is detached from the patient by loosening the screw between the effector and the splint. The robot is wheeled away, and the splint and fixation screws

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Fig. 6.7  The pre-op/planning CBCT scan is overlayed onto the new scan with the fiduciary markers to transfer the planned implant positions to the scan. The software

confirms successful overlay with an indicator on the bottom right of the screen

are removed. Normal procedures to complete the surgical procedure should proceed as per the surgeon’s protocol. It should be noted that the case reports accompanying this chapter clearly illustrate this process. The reader will also note that the splint

shown is large and bulky. This was the first design of the edentulous splint to be approved by the US Food and Drug Administration, and newer, more compact, and user-friendly versions are in ­development and will likely be in use prior to publication.

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a

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Fig. 6.8 (a, b) Robot positioning is assisted with indicators in the setup software to ensure that the patient is within the range of robotic arm movements

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138 Fig. 6.9  A robot with a sterile drape setup. The tracking arm is attached to the splint using an effector (under the triangular light blue marking). The robotic arm with a handpiece is paused in the resting mode, waiting for the surgeon for activation and movement

a

b

Fig. 6.10 (a, b) The drill length is measured from the drill face to the tip in order to set the software. An easily visible verification point is created in the planning software to confirm functional accuracy

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Fig. 6.11  The indicator turns green when a successful verification is accomplished, which permits progression to guided drilling. An unsuccessful verification will block

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progression and require repeating the setup steps to complete the process

Fig. 6.12  In the “guided” mode, the software provides visual and haptic assistance to get the surgeon to place the handpiece and drill in exact alignment with the planned orientation

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Fig. 6.13 Once correct positioning is achieved, the robotic arm maintains the correct orientation and limits movement to vertical changes. When a correct depth is

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accomplished, handpiece movement is restricted and audible and visible signals confirm the full depth

Fig. 6.14  Implants can be placed with full guidance using audible, visible, and haptic feedback to ensure correct positioning

6  Robotics for Implant Reconstruction of the Edentulous Maxilla

6.4 Extramaxillary Applications in Robotic Surgery Advanced bone resorption can often leave inadequate bone needed for implant anchorage, leading to bone grafting with autogenous or alloplastic bone materials [31]. Unfortunately, this can lead to a longer rehabilitation process [32]. Zygomatic implants were first introduced by Brånemark to effectively manage severe atrophy of the edentulous maxilla. Brånemark’s protocol fixes two to four implants into the anterior maxilla [33, 34]. With an intrasinus technique, the zygomatic implants pass through the sinuses and anchor themselves onto the zygoma. Another technique, the extramaxillary zygomatic implant surgical protocol, was first described by Maló et al. in 2008 [35]. With this protocol, the implant is placed extramaxillary to increase bone-to-­ implant contact [36]. The implant head is also positioned close to the maxillary crest, which allows for correct positioning of the prosthetics [37]. Due to the specific drill path, the length of the drill compared to that of the guiding sleeve, the distance between the location of the guide (the anterior maxilla) and the osteotomy site (the zygoma), and the accuracy of static surgical guides may not be adequate for zygomatic implants [38–40]. Challenges still exist in placing zygomatic implants using the intrasinus technique. There is a limited and obstructed surgical view of the zygoma. Additionally, zygomatic implants are longer than conventional dental implants. Small errors in angulation upon insertion can affect the neighboring anatomy, including the infraorbital nerve. More recently, a 6 degrees of freedom (DOF) robot has been designed to improve the accuracy and safety of zygomatic implant placement. Its system includes a planning and navigation system as well as a control system [41]. Along with zygomatic implants, pterygoid implants can be utilized to address the limitations of advanced bone resorption. Pterygoid implants were first introduced by Tulasne et al. [42] due to the stability of the bone over time. They allow for anchorage in the posterior maxilla without the

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use of sinus lifts or grafting procedures [43]. Additionally, the dense cortical bone of the pterygoid processes can stabilize the implants. Similar to zygomatic implants, pterygoid implants require specific techniques and surgical skills due to difficulty of surgical access and their proximity to vital anatomical structures [44]. In 2020, Stefanelli et al. reported that the accuracy of pterygoid implants placed with dynamic navigation systems was higher than that of freehand methods [45]. In general, zygomatic and pterygoid implants need to be placed with a higher accuracy and precision, in the surgical field, in comparison to ­conventional implants. Early indications are that using robotic technology, a surgeon can preoperatively plan and be guided toward the specific location at which implant heads should be placed to avoid difficulty during prosthetic restoration of the maxilla. Since zygomatic and pterygoid implants are placed “blind” with few anatomical landmarks for visual guidance, robotic technology allows for better virtual visualization during the procedure, which can improve the overall safety.

References 1. Lane T.  A short history of robotic surgery. Ann R Coll Surg Engl. 2018;100(6_sup):5–7. https://doi. org/10.1308/rcsann.supp1.5. 2. Boubaker O, editor. Control theory in biomedical engineering: applications in physiology and medical robotics. 1st ed. Amsterdam: Elsevier; 2020. 3. Moustris GP, Hiridis SC, Deliparaschos KM, Konstantinidis KM.  Evolution of autonomous and semi-autonomous robotic surgical systems: a review of the literature. Int J Med Robot Comput Assist Surg. 2011;7(4):408. https://doi.org/10.1002/rcs.408. 4. Leelasestaporn C, Tarnpichprasert T, Arirachakaran A, et  al. Comparison of 1-year outcomes between MAKO versus NAVIO robot-assisted medial UKA: nonrandomized, prospective, comparative study. Knee Surg Relat Res. 2020;32:13. 5. Robinson PG, Clement ND, Hamilton D, Blyth MJG, Haddad FS, Patton JT. A systematic review of robotic-­ assisted unicompartmental knee arthroplasty. Bone Jt J. 2019;101-B:838–47. 6. Batailler C, Fernandez A, Swan J, et  al. MAKO CT-based robotic arm-assisted system is a reliable procedure for total knee arthroplasty: a system-

142 atic review. Knee Surg Sports Traumatol Arthrosc. 2020;29(11):3585–98. 7. Rawal S, Tillery D Jr, Brewer P.  Robotic-assisted prosthetically driven planning and immediate placement of a dental Implant. Compend Contin Educ Dent. 2020;41(1):26–30. 8. Brånemark P-I, Breine U, Adell R, Hansson BO, Lindström J, Ohlsson Å. Intra-osseous anchorage of dental prostheses: I.  Experimental studies. Scand J Plast Reconstr Surg. 1969;3(2):6699. https://doi. org/10.3109/02844316909036699. 9. Buser D, Sennerby L, De Bruyn H. Modern implant dentistry based on osseointegration: 50 years of progress, current trends and open questions. Periodontology 2000. 2017;73(1):12185. https://doi. org/10.1111/prd.12185. 10. Hong DGK, Oh J. Recent advances in dental implants. Maxillofac Plast Reconstr Surg. 2017;39(1):132. https://doi.org/10.1186/s40902-­017-­0132-­2. 11. Elani HW, Starr JR, Da Silva JD, Gallucci GO. Trends in dental implant use in the U.S., 1999–2016, and projections to 2026. J Dent Res. 2018;97(13):2567. https://doi.org/10.1177/0022034518792567. 12. Grandview Research. Dental implant market size, share and trends analysis report by implants type (titanium, zirconium), by region (North America, Europe, Asia Pacific, Latin America, MEA), And Segment Forecasts, 2021–2028. https:// www.grandviewresearch.com/industry-­a nalysis/ dental-­implants-­market. 13. Mueller F, Barter S.  Implant therapy in the geriatric patient. ITI treatment guide, vol. 9. Chicago: Quintessence Publishing; 2016. 14. Surovas A. A digital workflow for modeling of custom dental implants. 3D Print Med. 2019;5(1):46. https://doi.org/10.1186/s41205-­019-­0046-­y. 15. D’haese J, Ackhurst J, Wismeijer D, De Bruyn H, Tahmaseb A.  Current state of the art of computer-­ guided implant surgery. Periodontol 2000. 2017;73(1):121–33. https://doi.org/10.1111/ prd.12175. 16. Jung RE, Schneider D, Ganeles J, Wismeijer D, Zwahlen M, Hammerle CHF, Tahmaseb A. Computer technology applications in surgical implant dentistry: a systematic review. Int J Oral Maxillofac Implants. 2009;24(Suppl):92–109. 17. Geng W, Liu C, Su Y, Li J, Zhou Y. Accuracy of different types of computer-aided design/computer-aided manufacturing surgical guides for dental implant placement. Int J Clin Exp Med. 2015;8(6):8442–9. 18. Vercruyssen M, Coucke W, Naert I, Jacobs R, Teughels W, Quirynen M.  Depth and lateral deviations in guided implant surgery: an RCT comparing guided surgery with mental navigation or the use of a pilot-drill template. Clin Oral Implants Res. 2015;26:1315–20. 19. Orgev A, Gonzaga L, Martin W, Morton D, Lin WS.  Addition of an irrigation channel to a surgical template to facilitate cooling during implant osteotomy. J Prosthet Dent. 2020;126(2):164–6.

J. Ganeles et al. 20. Gargallo-Albiol J, Salomo-Coll O, Lozano-Carrascal N, Wang H-L, Hernandez-Alfaro. Intra-osseous heat generation during implant bed preparation with static navigation: multi-factor in  vitro study. Clin Oral Implants Res. 2021;32(5):590–7. 21. Frosch L, Mukaddam K, Filippi A, Zitzmann NU, Kuhl S.  Comparison of heat generation between guided and conventional implant surgery for single and sequential drilling protocols—an in  vitro study. Clin Oral Implants Res. 2019;30:121–30. 22. Koop R, Vercruyssen M, Vermuelen K, Quirynen M.  Tolerance within the sleeve inserts of different surgical guides for guided Implant surgery. Clin Oral Implants Res. 2013;24(6):630–4. 23. Panchal N, Mahmood L, Retana A, Emery R.  Dynamic navigation for dental implant surgery. Oral Maxillofac Surg Clin N Am. 2019;31(4):1. https://doi.org/10.1016/j.coms.2019.08.001. 24. Mandelaris G, Stefanelli L, DeGroot B. Dynamic navigation for surgical implant placement: overview of technology, key concepts, and a case report. Compend Contin Educ Dent. 2018;39(9):614–21. 25. Franchina A, Stefanelli LV, Gorini S, Fedi S, Lizio G, Pellegrino G.  Digital approach for the rehabilitation of the edentulous maxilla with pterygoid and standard implants: the static and dynamic computer-aided protocols. Methods Protoc. 2020;3(4):84. https://doi. org/10.3390/mps3040084. 26. Pellegrino G, Tarsitano A, Taraschi V, Vercellotti T, Marchetti C.  Simplifying zygomatic implant site preparation using ultrasonic navigation: a technical note. Int J Oral Maxillofac Implants. 2018;33(3):6270. https://doi.org/10.11607/jomi.6270. 27. Wu Y, Wang F, Fan S, Chow JK-F.  Robotics in dental implantology. Oral Maxillofac Surg Clin N Am. 2019;31(3):13. https://doi.org/10.1016/j. coms.2019.03.013. 28. Ansari R.  Robotically-guided dental implant placement: extending surgical expertise, vol. 24. Toronto: Oral Health Group; 2020. 29. Bolding SL, Reebye UN. Accuracy of haptic robotic guidance of dental implant surgery for completely edentulous arches. J Prosthet Dent. 2021;2021:48. https://doi.org/10.1016/j.prosdent.2020.12.048. 30. Grant B-T. Implant surgery with robotic guidance— digital workflows for patient care. Toronto: Oral Health; 2019. 31. Ferrara ED, Stella JP.  Restoration of the edentulous maxilla: the case for the zygomatic implants. J Oral Maxillofac Surg. 2004;62(11):36. https://doi. org/10.1016/j.joms.2004.06.036. 32. Aparicio C, Manresa C, Francisco K, et al. Zygomatic implants: indications, techniques and outcomes, and the zygomatic success code. Periodontol 2000. 2014;66(1):38. https://doi.org/10.1111/prd.12038. 33. Araújo PPT, Sousa SA, Diniz VBS, Gomes PP, da Silva JSP, Germano AR. Evaluation of patients undergoing placement of zygomatic implants using sinus slot technique. Int J Implant Dent. 2016;2(1):35. https://doi.org/10.1186/s40729-­015-­0035-­x.

6  Robotics for Implant Reconstruction of the Edentulous Maxilla 34. Hirsch J-M, Öhrnell L-O, Henry PJ, et al. A clinical evaluation of the zygoma fixture: one year of follow­up at 16 clinics. J Oral Maxillofac Surg. 2004;62:30. https://doi.org/10.1016/j.joms.2004.06.030. 35. Maló P, de Araujo NM, Lopes I. A new approach to rehabilitate the severely atrophic maxilla using extramaxillary anchored implants in immediate function: a pilot study. J Prosthet Dent. 2008;100(5):237. https:// doi.org/10.1016/S0022-­3913(08)60237-­1. 36. Maló P, de Araújo NM, Lopes A, Ferro A, Moss S.  Five-year outcome of a retrospective cohort study on the rehabilitation of completely edentulous atrophic maxillae with immediately loaded zygomatic implants placed extra-maxillary. Eur J Oral Implanatol. 2014;7(3):267–81. 37. Blanc O, Shilo D, Emodi O, Rachmiel A.  Extramaxillary zygomatic implants for maxillary prosthetic rehabilitation. Int J Oral Maxillofac Surg. 2017;46:333. https://doi.org/10.1016/j. ijom.2017.02.333. 38. Magic M, Wang F, Fan S, Wu Y. Dynamic navigation guidance for bone reduction in maxilla: case report. Int J Oral Maxillofac Implants. 2021;36(1):e1–6. https://doi.org/10.11607/jomi.8555. 39. 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

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Surg. 2003;32(1):337. https://doi.org/10.1054/ ijom.2002.0337. 40. 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(5):74. https://doi.org/10.1563/ AAID-­JOI-­D-­09-­00074. 41. Cao Z, Qin C, Fan S, et al. Pilot study of a surgical robot system for zygomatic implant placement. Med Eng Phys. 2020;75:72–8. https://doi.org/10.1016/j. medengphy.2019.07.020. 42. Tulasne J.  Implant treatment of missing posterior dentition. In: Albrektsson T, Zarb G, editors. The Branemark osseointegrated implant. Chicago: Quintessence Publishing; 1989. p. 103–16. 43. Candel E, Peñarrocha D, Peñarrocha M. Rehabilitation of the atrophic posterior maxilla with pterygoid implants: a review. J Oral Implantol. 2012;38(S1):200. https://doi.org/10.1563/AAID-­JOI-­D-­10-­00200. 44. Bidra AS, Huynh-Ba G.  Implants in the pterygoid region: a systematic review of the literature. Int J Oral Maxillofac Surg. 2011;40(8):7. https://doi. org/10.1016/j.ijom.2011.04.007. 45. Stefanelli LV, Mandelaris GA, Franchina A, et  al. Accuracy evaluation of 14 maxillary full arch implant treatments performed with Da Vinci bridge: a case series. Materials (Basel). 2020;13(12):806. https:// doi.org/10.3390/ma13122806.

7

Tilted Implants Paulo Malo, Andreia  Filipa Fontoura de Castro Rodrigues, and Tiago Miguel Bravo Estêvão

7.1 Introduction and a Brief History of the Development of the Malo Protocol It is my intention to describe here in summary the history of the All-on-4. This is a surgical technique that literally improves the lives of millions of people around the globe. It is important to say that this surgical procedure was the logical extension of the previous innovation procedure, “immediate load on single teeth and small bridges,” which I developed in 1990 and published in 1998 for the first time. After the first All-on-4 (previously called the Malo surgical procedure for edentulous patients) procedure was conducted in 1993, a number of products and other surgical and prosthodontic procedures were developed in order to improve the rehabilitation of edentulous patients. Many P. Malo (*) Oral Surgery Department, MaloDental Portugal and International, Lisbon, Portugal e-mail: [email protected] A. F. F. de Castro Rodrigues Prosthodontic Department, MaloDental, Lisbon, Portugal T. M. B. Estêvão Oral Surgery Department, MaloDental, Lisbon, Portugal Oral Surgery Department, Dr Sobczak Kliniki, Warsaw, Poland

other innovative products and techniques were also developed in a logical and creative sequence to not only improve edentulous rehabilitation but also to try to solve or improve the outcome of the rehabilitation of other challenging cases. To help the reader to better understand the sequence of events here is a chronological description: In 1989, a study was initiated to establish an immediate load protocol for single tooth and small bridges. The protocol of loading single implants was, until 1989, not to load immediately. It was advised to wait 4–6 months to place the crowns. In 1990, a protocol was established for immediate loading, after a primary study, for single tooth and small bridges.

7.1.1 1990: Establishment of the Immediate Load Protocol Different types of implants were tested to understand which type would deliver the maximum primary stability. Implants with more threads responded better to immediate loading as a higher number of threads indicate that more stability and therefore a higher anchorage could be achieved. Cylindrical implants with parallel walls were better than a conical design because they

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have more volume per size and therefore have the capability to expand the bone more. A higher number of threads also increase the surface of the implant, thus increasing the primary stability. The surgical protocol was also altered, in order, to achieve a higher primary stability. It was possible due to bicortical anchorage and underpreparation of the implant site. Studies revealed that the stability of implants with bicortical anchorage decreases more slowly under high loads [1] and that this reduces the stress in the native bone [2]. Bicortical anchorage increases the primary stability, a prerequisite for an immediate function with dental implants. The results of bicortically anchored implants placed in immediate function are similar to those of the classical two-stage surgical approach. In the rehabilitation of the posterior edentulous maxilla, when anticipating high occlusal loads and encountering a low-density bone, the use of bicortical anchorage (via the crest and the cortical bone of the sinus to achieve a high primary stability) can play a vital role in allowing immediate function [3].

7.1.2 1993: The First Case of the All-on-4 Standard Mandible The challenge was: can we perform a procedure to deliver an immediate fixed bridge to those patients for whom grafting was the only solution? AO4 was developed to avoid bone grafting. The first case in 1993 was performed on the mandible, and the need for the correct placement of the implants was immediately identified. AO4 is extremely critical to the position of the implants. An AO4 surgery implies that most cases have a cantilever and that if there is a cantilever, then the amount of pressure on the last implant is extremely high. So, it is particularly important to decrease the size of the cantilever. Just having one molar would be enough for aesthetics and for efficient masticatory capability. The bridge should have 12 teeth. In some cases, this was not enough to reduce the cantilever. Another solution was to tilt the implant. So, instead of placing an implant on the first PM and

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having two teeth in the cantilever, inclining the implant in a posterior direction would reduce the cantilever. The inclination of the implant between 30° and 45° could either reduce the cantilever or avoid it. It was understood that a guide would be extremely important in ensuring the correct placement of the implants. A guide was developed that could be used in the mandible and maxilla, could be sterilized, and adapted for different sizes and shapes of the arches and also with parallel marks, allowing the placement of parallel implants. In the mandible, it also helps to keep the tongue away from the surgical site; this guide is known as the Malo guide. By 1993, the guide, drilling sequence, protocol for surgery, and bridge were developed. After 3  years and after performing more than a 100 cases, the surgical protocol was established with a success rate of 99%. The challenge now was the development of a bridge with a passive fit and enough resistance to the cantilevers. A bridge made of acrylic, a flexible material, with a cantilever that could be delivered on the same day of the surgery was tested. An acrylic bridge can have a passive fit; the problem is the mechanical resistance, especially in long cantilevers. Up to one or two teeth in the cantilever, if there is enough acrylic thickness, is safe, but, if the thickness is not enough, then it will break. This situation would work better for patients with large bone loss. The disadvantages of an all acrylic bridge is that it cannot have long cantilevers, can easily get stained, and has a low mechanical resistance. The risk of implant failure is reduced in single-­ tooth reconstructions when using full-arch reconstructions as the reference. A systematic review registered a higher survival rate for single-tooth reconstructions when compared to fixed dental prosthesis after 10  years of follow-up. Biomechanically, single-tooth reconstructions benefit from the presence of adjacent teeth, whereas full-arch reconstructions depend on the distribution of load on all the implants [4–6]. According to a systematic review, an occlusal overload, associated with parafunctional habits such as bruxism, was considered the primary etiological factor in biomechanical implant treatment complications [7].

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7.1.3 1996: The First AO4 Standard Maxilla

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was developed by Nobel Biocare. It is a CAD/ CAM titanium bar of a horseshoe-type with a maximum passive fit. The teeth can be acrylic or ceramic and are cemented on top of the framework one by one in the case of the ceramic teeth.

There is a significant difference in bone density between the maxilla and the mandible. In the maxilla, due to a lower bone density, an immediate loading in this jaw region is perceived as a greater challenge than that in the mandible. 7.1.4 2004: Beginning of the Development Implant anchorage in the totally edentulous maxof the All-on-4 Hybrid illa is often restricted owing to bone resorption, and Double Zygoma which is especially frequent in the posterior region of the maxillary arch, where bone grafting is often indicated. The use of tilted implants in The challenge was in those cases in which there the maxilla has been demonstrated to be an alter- was not enough bone to place four implants. The native to bone grafting [8–11]. By tilting the dis- answer to the challenge was to introduce the tal implant, a more posterior implant position can zygoma approach to the surgical protocol. be reached, and improved implant anchorage can Zygomatic implants and AO4 were combined to be achieved by benefiting from the cortical bone create an All-on-4 hybrid and an All-on-4 double zygoma. of the wall of the sinus and the nasal fossa. Different techniques are used to gain suffiThe challenge of the soft bone has led to the addition of a new tool to the concept: a novel cient bone volume before implant placement implant design. This implant merged three sig- (sinus lifts and intraoral grafts are the most comnificant features: the implant’s macrodesign mon) [2–6]. Bone augmentation is usually rec(shape and threads) allowing to condense the ommended first, and delayed implant insertion is bone instead of cutting it; the new apex design suggested to increase the success rate of the final made it possible to engage the sinus or nasal fos- restoration [15–19]. These procedures require sae cortical, allowing bicortical anchorage; and long treatment times, sometimes with multiple because the implant is fully threaded from the surgical sites and interventions, possible severe apex to the head, the whole implant aims to complications, and high morbidity, thus reducing patient acceptance [20, 21]. The success rates of achieve a higher primary stability [12]. A narrow tip of the implant facilitated inser- these bone augmentation techniques range from tion into underprepared sites by acting as an 60 to 90% [22]. In 1988, Brånemark et al. introduced the use osteotome, allowing the implant to be inserted into narrow ridges. This seemed particularly of zygomatic implants combined with convenimportant when dealing with rehabilitations per- tional fixtures to support dental prostheses [23]. formed in extreme situations, where the out- His technique included an entry point on the comes remained positive with a 95.7% implant palatal side of the residual crest and an implant survival rate for the implants inserted in the pres- path through the sinus cavity. In all, 28 patients ence of dehiscences, fenestrations, post-­were treated with a total of 52 zygomatic extraction sockets, or periodontally compromised implants, and an implant success rate of 96.2% areas with follow-ups up to 3 and 5 years for the was achieved after 5  years of function [23]. maxilla and mandible, respectively [13]. The However, the percentage of sinusitis was notable implant design features resulted in a good (14%). Furthermore, with this technique, the mechanical anchorage of the implant, which palatal emergence of the implant heads causes makes it especially suitable for soft bone situa- interference with phonetics and difficulty in the maintenance of hygiene. tions and immediate function protocols [14]. A new implant design and a different approach In 1999, the NobelSpeedy™ implant and the have been developed to overcome the ­complications Malo bridge were developed. The Malo bridge

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occurring with the Brånemark technique. This approach consists of starting osteotomy at the level of the residual crest and inserting the zygomatic implants external to the sinus membrane, thus preserving its integrity [24]. The main difference of the extramaxillary technique or the Malo protocol for zygomatic surgery is that it has better anchorage in the zygoma and better emergency of the prosthetic screw on the bridge. This can be achieved by controlling the placement of the head of the implant in relation to the bridge and avoiding having the screw exit too palatal. A new zygomatic implant was developed with a 0° head and a conical apex as well as no threads at the coronal end of the implant.

7.1.5 2005: Adaptation of the All-on-4 Concept to Guided Surgery With the development of guided surgery, new products needed to be introduced, specially angulated abutments with no engagement. In 2006, the NobelZygoma implant was developed. A new zygomatic implant with a 0° head, a conical apex, and threads only in the apical third was developed. In 2007, step drills, specifically designed to deliver Speedy implants or any implant with an apex, were developed. In 2007, it was proved that short implants are as effective as long implants and an article showing that was published: Short Implants Placed One-Stage in Maxillae and Mandibles: A Retrospective Clinical Study with 1 to 9 Years of Follow-Up. In 2007, long implants of length 20, 22, and 25  mm for the tuberosity and transsinus technique as well as soft bone cases were developed. These two developments allowed the treatment of extreme cases. In 2010, 45° abutments for more complex cases and 60° abutments for extreme cases were

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developed. These abutments were developed to allow the placement of 0° implants in severe reabsorbed maxillae. In 2014, the NobelParallel CC implant was developed. This implant is similar to Speedy implants but with an internal connection. Throughout all these years, several articles were published. Because of the development of immediate loading of single-tooth implants and the All-on-4, 25 products were developed in order to guarantee the success of these new techniques or to improve the results of the established protocols. All-on-4 is a surgical technique that uses the minimum amount of bone to deliver a fully fixed bridge. It is the result of years of research, experience, and knowledge. The most important techniques developed are as follows 1. Immediate loading of single tooth and small bridges. 2. AO4. 3. Transsinus implant protocol. 4. Malo protocol for zygomatic implants and 0° zygomatic implants. 5. CAD/CAM full-arch bridge with individual ceramic crowns and the Malo bridge. 6. Half AO4. The most important products developed are as follows 1. Edentulous guide and the Malo guide. 2. Angulated abutments, 45° and 60°. 3. Speedy implants. 4. NobelParallel CC implant. 5. ITA abutment platform shifting (immediate temporary abutments). 6. Zygomatic implant, 0°. 7. Titanium bar for full-arch rehabilitation. 8. Step drills. 9. Long implants (20/22/25). 10. Special implants for the soft bone (RP/WP). 11. Long drills. 12. Non-engaging 30° abutments.

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7.2 Malo Classification of the Edentulous Maxilla

If there is full bone volume, then up to six parallel implants can be placed from molar to molar or All-on-4.

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If a bone is not available in the molar region to place a straight implant, then there are two options: placement of parallel implants having a

bridge with a molar in the cantilever or avoiding an All-on-4 cantilever.

If a bone is not available in the molar and second premolar regions to place a straight implant, then the best solution is to perform an All-on-4 and ending up with one tooth in the cantilever or

no teeth in the cantilever depending on the amount of bone available and the inclination of the anterior wall of the sinus.

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If a bone is not available in the molar, second, and first premolar regions to place a straight implant, then performing an All-on-4 is the best

surgical approach because there is no need for bone grafting and the bridge will have one or two teeth in the cantilever.

If the only remaining bone is from the lateral incisor to the lateral incisor, then the All-on-4 standard can no longer be performed and a hybrid All-on-4 is the best solution. This is a combina-

tion of two implants in the central or lateral position and two implants outside of the maxilla that can be in the zygoma.

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If there is no bone even in the frontal area to place an implant, then a double zygoma is the gold standard technique.

In some cases, the zygoma is not big enough to place two implants or if the zygomatic implants fail, then bone grafting should be considered.

7.3 The Biomechanics of AO4 Biomechanical analyses indicate that the most anterior and posterior implants supporting a full mouth reconstruction take the major load share at

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cantilever loading, irrespective of the number of intermediate implants [25]. For a given distance, between the anterior and the posterior implants, the load supported by the most heavily loaded implant (the distal implant) is virtually independent of the total number of implants that support the restoration. These ­theoretic findings are supported by in vivo measurements [26]. Good clinical outcomes from studies using protocols in which four implants were placed to support a full-arch prosthesis indicate that the placement of larger numbers of implants may not be necessary for successful implant treatment of edentulous jaws [27, 28]. The use of implant tilting in the maxilla has been demonstrated to be an alternative to bone grafting [8–10, 29]. By tilting the distal implant, a more posterior implant position can be reached reducing the cantilever, and an improved implant anchorage can be achieved by benefiting from the cortical bone of the wall of the sinus and the nasal fossae. The use of four implants in the maxilla is encouraged by results from in vivo implant load analyses demonstrating that favorable load distribution for complete-arch prostheses can be achieved with four implants provided that they are placed as “cornerstones”: two posterior and two anterior and well-spread [26]. In addition, using a finite element analysis model to compare the coronal stress when applying an occlusal load, it is possible to conclude that there is a biomechanical advantage to using implants tilted distally, as opposed to using axial implants supporting a larger number of cantilever teeth [30, 31]. Previous systematic reviews [32] and meta-­ analyses [33, 34] did not reveal differences in marginal bone loss and implant failure rates between axial and tilted implants in short- and medium-term outcomes. The few available longer-­term outcomes support these results for the mandible [35, 36] and the maxilla [9, 37], showing no significant differences in marginal bone-level change and implant survival rates between the axial and tilted implants over 5  years of follow-up, assuming no additional risk of implant failure using tilted implants posteriorly [38].

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7.4 The Malo Protocol—AO4: Rehabilitation for the Edentulous Maxilla The “All-on-4” treatment concept is based on the insertion of four implants into the anterior region of completely edentulous jaws to support an immediate implant-supported fixed prosthesis: the two most anterior implants are placed axially, whereas the two posterior implants are placed with a distal tilting of up to 45°, allowing the connection of prostheses with up to 12 teeth [39]. The “All-on-4” treatment concept was developed to maximize the use of the available residual bone in atrophic jaws, allowing immediate function and avoiding regenerative procedures (such as bone grafting) that increase treatment costs, patient morbidity, and complications inherent to these procedures [40]. The concept benefits from the use of tilted implants that relate to several surgical and prosthetic advantages previously described: the possibility of placing longer implants with improvement of bone anchorage by engaging the apex of the implant with the cortical bone of the anterior wall of the sinus, the reduction of the need for bone grafting, the possibility of reaching a more posterior implant position and avoiding long cantilevers, and a good anterior–posterior spread with the possibility of increasing the distance between the anterior and posterior abutments, resulting in an improvement of the load distribution [8, 31, 41– 46]. The All-on-4 concept was further validated in the short- and midterm outcomes, considering the results of two systematic reviews that reported high survival rates in the rehabilitation of completely edentulous patients [47–49]. The surgical procedures are normally performed under local anesthesia, but they can also be performed under general anesthesia. For local anesthesia, carticaine chlorhydrate (72 mg/1.8 mL) with epinephrine (0.018 mg/1.8 mL; 1:100,000) is used. All patients are sedated with diazepam 10  mg prior to surgery. Antibiotics (amoxicillin 875  mg  +  clavulanic acid 125  mg) should be administered 1  h prior to surgery and daily for 6  days thereafter. Cortisone medication (prednisone 5  mg) is administered daily in a regression

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mode (15–5 mg) from the day of the surgery until 4  days postoperatively. Anti-inflammatory medication (ibuprofen 600  mg) is administered for 4 days postoperatively starting on day 4. Analgesics (clonixin 300 mg) are administered on the day of the surgery and postoperatively for the first 3 days if needed. Antacid medication (omeprazole 20 mg) is administered on the day of the surgery and daily for 6 days postoperatively [9]. The teeth are extracted, when needed, at the time of surgery before implant placement. A flap design is performed to have a correct view of our surgical field. In the upper jaw, the flap should be made slightly more palatal with relieving incisions on the buccal aspect in the molar area. This flap should be a full-thickness flap, and it should allow us to have a good view of the limits of our surgery, meaning the contour of the anterior wall of the sinus and the nasal fossa. After the mucoperiosteal flap, bone reduction can be performed if needed. The amount of reduction should be calculated, before starting the surgery, by evaluating the maximum smile and the occlusion of the patient. If any gingiva is shown in the smile, then bone reduction should be performed to hide the transition zone between the prosthesis and the natural gingiva. Crestal bone recontouring can be performed with a rongeur or bur, depending on the degree of irregularity of the alveolar ridge. A small window can be opened to the sinus using a round bur for identification of the exact position of the anterior sinus wall. The implants and abutments are placed in one position at a time, starting with the posterior ones. A special guide should be used to assist implant and abutment placement. This guide is placed into a 2-mm osteotomy made at the midline of the jaw, and the titanium band is bent so that the occlusal centerline of the opposing jaw is followed. By doing this, it is possible to guide the implants to be placed at the center of the opposing prosthesis and at the same time finding the optimal position and inclination for the best implant anchorage and prosthetic support. The insertion of the implants follows standard procedures, except that under preparation it can be used to achieve an insertion torque of at least 35 Ncm before the final seating of the implant. The

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preparation is typically performed by a full drill depth with a 2-mm twist drill followed by a 2.4/2.8  mm and 3.2/3.6  mm twist step drills (depending on the bone density). In cases of high-density bone, the 3.8/4.2 mm step drills can be used only in the cortical bone. The implant neck is aimed to be positioned at the bone level, and bicortical anchorage is established whenever possible. Posterior implant tilting allows a position shift on the implant head from a vertically placed implant in the canine/first premolar region to a tilted implant in the second premolar/first molar region, following the anterior sinus wall up to 45° of inclination. Angulated abutments of 30° are connected to the implant, correcting the inclination to a maximum of 15°. The anterior implants are oriented vertically by a guide pin replacing the edentulous guide. Care should be taken in the selection of the anterior implant positions so as to not to come into conflict with the apex of the tilted posterior implants, which normally reach the canine area. With this implant arrangement is aimed a good implant anchorage, a large inter-­ implant distance, and a short cantilever length with the posterior implants typically emerging at the second premolar/first molar position. Multi-unit abutments are connected to the implants: 30 angulated abutments connected to the two posterior tilted implants and straight (0) or angulated (17) connected to the anterior implants. The flap is closed and sutured using 3-0 non-resorbable sutures, and the abutments are accessed by means of a punch (a mechanical soft tissue punch). And impression copings are placed (Figs.  7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 7.10, 7.11, 7.12, 7.13, 7.14, 7.15, 7.16, 7.17, 7.18, 7.19, 7.20, 7.21, 7.22, 7.23, 7.24, 7.25, 7.26, 7.27, 7.28 and 7.29). When the quantity of the alveolar crest bone between the canines is, at least, 7 mm in height and 4 mm in width (C-VI, Cawood and Howell classification), two straight implants in the maxilla and two implants with a zygomatic anchorage should be placed (All-on-4 hybrid). In patients for whom the anterior residual crestal bone does not fulfill the minimum prerequisite to allow a conventional maxillary implant placement proxi-

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Figs. 7.1–7.3  Open the flap

Figs. 7.4–7.5  Flap raising

Fig. 7.6  Bone reduction

mal to the midline (more than C-VI, Cawood and Howell classification), four implants with a zygomatic anchorage should be used, with two implants bilaterally (All-on-4 double zygoma). After the medication is administered and anesthesia is performed with the same protocol as the standard All-on-4, a linear incision should be made slightly toward the palate, from the molar area to the contralateral side, with two vertical incisions over the zygomatic process. A mucoperiosteal flap is raised in the same way as for a Le Fort I exposure, providing a direct vision

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Figs. 7.7–7.24  Drilling sequence and implant placement

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Figs. 7.7–7.24 (continued)

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Figs. 7.7–7.24 (continued)

Fig. 7.26  Impression copings screwed to the abutments Fig. 7.25  Suture and placement of the healing caps

of the piriform rim and of the body of the zygomatic bone with its inferior edge. Isolation of the infraorbital nerve and identification of the masseter muscle insertion represent the superior and inferior limits, respectively, for the zygomatic fixtures. The palatal mucosa needs to be reflected to avoid interference during the drilling phase. When necessary and depending on the morphology of the residual alveolar process, regularization of the ridge should be performed with rongeur or rotary instruments to remove knife edge ridges. Zygomatic implant lengths and positions are determined perioperatively and are dependent on the anatomy of the region. The “channel” osteotomy begins as posteriorly as possible at the maxillary crest level with a channel drill directed along the planned implant direction, which maintains a minimum safe distance of approximately

3  mm from the posterior-inferior edge of the zygomatic bone, avoiding damaging the membrane of the sinus. The sinus membrane is then carefully elevated from the internal wall of the sinus. This “channel” facilitates access and an optimal path to the zygomatic bone for the implant drills without any tissue interference and typically helps counterfort the implant against the lateral maxillary wall. Next, a round bur and then the 2.9-mm zygoma twist drill is used to start and then define the extramaxillary zygomatic osteotomy. During this procedure, the surgeon’s finger should be positioned on the external surface of the upper edge of the zygoma to feel the preparation of the external cortical bone (superior edge) as it nears completion in order to not damage the overlying soft tissues. Subsequently, a depth indicator is used to assess the correct length of the implant. The extramaxillary

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Figs. 7.27–7.29  Impression copings screwed to the abutments and connected for an accurate impression

implant length is measured from the posteriorsuperior cortical aspect of the zygoma to the vestibular aspect of the residual crestal ridge. Then, according to the thickness and density of the zygoma, some variations of the successive drills are used—3.5 mm, 4.0 mm, and 4.4 mm twists. Particular attention should be paid to the infraorbital nerve and the base of the orbit to avoid damaging these anatomical structures during implant site preparation, especially in “double zygoma” cases. The zygomatic implants inserted through the extramaxillary technique should be placed with an insertion torque of at least 30 Ncm for sufficient primary stability. For the surgical procedures performed with two zygomatic implants in the same zygoma, either unilateral or bilateral, a minimum distance of approximately 5  mm is

between the two implants, with the anterior implant serving as the reference. The orbit, infraorbital nerve, and bone anatomy are factors in determining implant directions. The head of the distal implant emerges usually around the first molar/second premolar region, and the head of the anterior implant emerges usually in the canine-to-lateral-incisor region. This protocol allows the implant’s head to be positioned near the buccal aspect of the residual crest and be less palatal, compared with the surgical protocol described by Brånemark et  al. [23]. The edges of the flaps are reapproximated tension-free with interrupted sutures. Buccal keratinized gingiva is preserved whenever possible, especially around the implants. The “All-on-4” concept is a treatment protocol for rehabilitating edentulous arches through a

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fixed prosthesis supported by four implants, with the posterior implants placed at an angle and put into immediate function [39]. Specifically, this concept has demonstrated good treatment outcomes in the short, medium, and long terms, with cumulative implant survival rates ranging between 96.7% and 99.7% and a 100% prosthetic survival for both arches [11, 29, 35, 39, 50–61].

7.5 The Malo Bridge Full-arch fixed implant hybrid prostheses, in function for more than 40 years, require frameworks to splint the implants together for support, an assembly considered as one of the keys to long-term clinical success [62, 63]. The historical perspective of framework materials includes the evolution from cast noble (gold, silver, etc.) or base metal alloys (nickel and chromium) to the modern milled titanium and zirconium frameworks, with the latter providing high biocompatibility, corrosion resistance, and

Figs. 7.30–7.32  Immediate prosthesis

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the possibility of computer-assisted design/ computed-assisted manufacturing (CAD/CAM), an important improvement to achieve a better fit between the framework and the dental implants [62, 64, 65]. The fabrication of the immediate implant-­ supported prosthesis follows standard procedures. After suturing, an impression with putty material is made in a custom open tray. After tray removal, healing caps are placed to support the peri-implant mucosa during the fabrication of the prosthesis. A high-density acrylic resin prosthesis with titanium cylinders is manufactured at the dental laboratory and inserted on the same day usually 2–3  h post-surgically. Anterior occlusal contacts and canine guidance during lateral movements are preferred in the provisional prosthesis (Figs. 7.30, 7.31 and 7.32). Four months after the surgery, it is time to begin planning the final rehabilitation. However, if some changes need to be made to the immediate bridge, then it is always preferable to develop a second provisional bridge in which some

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adjustments can be made in terms of aesthetics, phonetics, and comfort in order to serve as a replica for the final prosthesis. So, the initial step is to take impressions at the implant level in the frontal implants and at the abutment level in the posterior implants, allowing the technician to adjust the position of the abutment to improve the phonetics, parallelism between the implants, abutment level, and aesthetics. The impression is taken by splinting the impression copings using pattern resin and metal bars (orthodontic wires, old burs) and using light and putty silicone material in a custom open tray to record the position of the soft tissues (Figs. 7.33, 7.34 and 7.35). In a subsequent appointment, a facebow record and an interocclusal record is made using

Fig. 7.33  Impression copings screwed to the abutments and connected for an accurate impression of the second provisional bridge

the fixed provisional prostheses. The master casts are mounted on a semi-adjustable articulator. Denture acrylic teeth are used in the esthetic and functional positioning of teeth, and, after obtaining the patient’s approval, these are processed as a second interim prosthesis using pink acrylic resin and temporary abutment-level cylinders (Figs. 7.36, 7.37, 7.38, 7.39, 7.40 and 7.41). The manufacturing process of the definitive prostheses is started once the patient is comfortable with the esthetic and functional aspects, 4  weeks following the delivery of the second prosthesis. A silicone mask index is made with the maxillary and mandibular interim prostheses removed from the patient and screwed onto the master casts to serve as a guide for the final restoration. A resin framework template (GC Pattern Resin; GC Co, Alsip, IL) is fabricated according to the contour of the maxillary second interim prosthesis with individual abutment preparations to accommodate the corresponding individual ceramic crowns. Reduction in the abutment component of the framework allows for optimal crown thickness, with a minimum of 1.5 mm on all aspects. This pattern is scanned, and CAD is designed. A titanium screw-retained bar is manufactured after CAM processing. Only the stone model is scanned for margin information. The wax pattern is scanned for final contour information. A light-curing opaque liner is applied to the abutment components of the titanium bar. A silicone impression is made on the bar and poured into extra-hard gypsum. An individual full-­

Figs. 7.34–7.35  Impression using light and putty silicone material in a custom open tray

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contour wax-up is completed. Once each individual crown is double-scanned for both abutment and outer contour, pre-crystalized lithium disilicate-­ reinforced glass ceramic crowns are

Fig. 7.36 An interocclusal record of the immediate prosthesis

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fabricated. A try-in of the maxillary titanium substructure, pre-crystallized individual crowns, and mandibular acrylic prosthesis is performed before finishing the rehabilitation. The crowns are later crystallized, custom-trimmed, and stained following the manufacturer’s instructions and according to the patient’s individual characteristics and esthetic expectations. Crowns are cemented according to an adhesive cementation protocol. Gingival anatomy is waxed up for a try­in. Following the patient’s approval, the prosthesis with the waxed gingival form is invested in the lower half of a flask. Once the plaster is set, the prosthesis is spruced and the pink acrylic resin is injected according to the manufacturers’ protocol. In the mandible, a metal–acrylic hybrid prosthesis is fabricated, using a titanium bar as infrastructure, acrylic teeth, and pink acrylic resin. All the prosthetic screws are given a final torque of 15 Ncm. The occlusion is evaluated and adjusted to a mutually protected occlusion scheme, mimicking natural dentition and respect-

Figs. 7.37–7.40  Teeth try-in for the second provisional bridge

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ing the patient’s centric relation. Follow-up visits are scheduled every 6  weeks during the first 3 months, 6 months after the insertion of definitive prostheses, and every 6  months after that. Further follow-ups are carried out at 12 and 18 months after delivery (Figs. 7.42, 7.43, 7.44, 7.45, 7.46, 7.47, 7.48, 7.49, 7.50, 7.51, 7.52, 7.53, 7.54, 7.55, 7.56, 7.57, 7.58, 7.59, 7.60, 7.61, 7.62, 7.63, 7.64, 7.65, 7.66, 7.67, 7.68, 7.69, 7.70, 7.71, 7.72 and 7.73). The choice of materials plays an important role in the final outcome. The lack of resilience due to the absence of a periodontal ligament in implant-supported restorations demands the use of highly sophisticated materials when trying to overcome fatigue resistance due to occlusal loading. In a complex biomechanical system, in which implants, abutments, frameworks, screws, and esthetic veneering materials share masticatory stress conduction, porcelain is the material

Fig. 7.41  The second provisional bridge

Figs. 7.43–7.44  Master casts for the definitive bridge

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most commonly prone to failure with immediate esthetic consequences [66–68]. Throughout the years, clinicians and laboratory technicians have overcome this limitation through different strategies. One strategy is a compatible material section between the maxillary and mandibular arches, prior to the combination of a maxillary ceramic prosthesis with a mandibular metal– acrylic prosthesis in full-arch rehabilitations. This reduces the overall stiffness of the prosthetic elements as a whole, dramatically reducing mechanical complication [67]. Protecting the restorations with an occlusal splint “night guard” is another method typically used to protect restorations, particularly when parafunctional habits are present. Another strategy to address the mechanical failure of porcelain is to design individual full-contour crowns to be cemented on a titanium

Fig. 7.42  Impression using light and putty silicone material for the definitive bridge

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Figs. 7.45–7.46  Articulation of the second provisional bridge

Figs. 7.47–7.49  The silicone mask index made with the maxillary and mandibular second prostheses

alloy screw-retained bar [69]. The benefit of this concept is based on the ability to remove and repair (or even replace) an individual fractured crown without the need to remove the entire structure, which in turn allows a lower cost. As reported in the literature, firing a full-arch ceramic prosthesis after years in the oral cavity

may prove catastrophic, with resultant air bubbles visible throughout the ceramic’s outer surface [70–72]. There are some advantages and disadvantages of processing the plastic acrylic after the crowns have been cemented. On one hand, this procedure allows hiding of the crown margins.

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Figs. 7.50–7.55  The verticulator used to duplicate the bridge

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Fig. 7.60  A titanium screw-retained bar manufactured after CAM processing

Fig. 7.61  A light-curing opaque liner applied to the abutment components of the titanium bar Figs. 7.56–7.58  Resin framework template fabrication

Fig. 7.62  Silicone impression made over the titanium bar Fig. 7.59  A scan image of the resin framework template

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In addition, the sealing of the acrylic resembles the esthetics of the anatomical gingival sulcus and allows removal of the excess cement before processing the pink esthetics. On the other hand,

Fig. 7.63  A stone model of the crown preparation

Figs. 7.64–7.65  An individual full-contour wax-up

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this procedure might represent a disadvantage when replacing an individual crown, where it may force replacement of the entire pink acrylic in order to avoid a different color patch of the new acrylic. Among the range of commercially available ceramic systems, lithium disilicate-reinforced glass ceramic has generated considerable interest throughout the last decade, due to the material’s physical properties, excellent esthetic features, ability to comply to adhesive cementation protocols, and a versatile fabrication process (either the lost-wax technique or CAD/CAM) [73–75]. The development of different pre-crystallized ceramic CAD/CAM blocks of different translucencies has allowed for the production of monolithic full-contour anatomical crowns that could later be crystallized and characterized for customization. Monolithic crowns offer a flexural

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Fig. 7.68  Teeth try-in for the MaloCeramic bridge and the MaloAcrylic bridge Fig. 7.66 Pre-crystalized lithium disilicate-reinforced glass ceramic crowns

Fig. 7.67  Crystalized lithium disilicate-reinforced glass ceramic crowns over the titanium bar

strength of 360 MPa compared to 90 MPa offered by the veneering ceramic in veneered zirconia crowns, reducing the odds of porcelain chipping [76–79]. Alumina crowns have optimal esthetic properties; however, their mechanical properties contraindicate their use in implant-supported restorations. Zirconia has proved to be superior in terms of its mechanical stability but poses an esthetic problem due to its white opaque nature. Moreover, the absence of chemical bonding between zirconia and the layering porcelain remains a concern regarding reliability [80].

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Figs. 7.69–7.73  The MaloCeramic bridge and the MaloAcrylic bridge

7.6 Maintenance The patients are instructed to consume a soft food diet for the first 4  months post-surgery. Ten days after the surgery, the sutures are removed and hygiene and implant stability (clinical mobility and suppuration by finger pressure) are checked. The occlusion is rechecked according to the initial protocol, a procedure that is repeated after 2 and 4 months. Usually, at around 4 months, the prosthe-

ses are removed, jet-cleaned (using AIRFLOW powder), and disinfected (using 0.2% chlorhexidine) and the implants are checked for anchorage (clinical mobility), suppuration, and pain. After the connection of the definitive prostheses, the patients are evaluated after 6 months (clinically) and 1 year of function (clinical and radiographically). The following tables show the protocols established for the patients’ home care and clinical appointments.

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Protocol for maintenance of rehabilitation with immediate function implants performed by the patient 0 - 10th day Oral Hygiene:

Morning & Evening: • Use a Post-operative tooth brush and a 0.2% hyaluronic acid gel; • Rinse with hyaluronic acid mouthrinse

10th – 60th day Oral Hygiene

Morning & Evening • 0 - 10th day indications + use of other mechanical means of dental plaque removal

60 – 120 day Oral Hygiene th

th

Morning & Evening • Brush with a medium toothbrush and chlorhexidine gel • Use other mechanical means of dental plaque removal

Protocol for maintenance of rehabilitation with immediate function implants- clinical appointments Day 0 • Oral Hygiene:

• Oral hygiene; • Explanation of treatment phases and maintenance procedures to the patient; • Application of a chlorhexidine gel and hialuronic acid gel after the surgery; • Control of occlusion; • Information that should not overload the structure

Protocol for maintenance of rehabilitation with immediate function implants- clinic appointments Day 10 • Oral Hygiene:

• Panoramic x-ray; • Periapical X-ray; • Removal of the prosthesis for disinfection and cleaning; • Removal of suture; • Control of mobility • Control of suppuration by finger pressure; • Modified Plaque index • Modified Bleeding index • Application of a hyaluronic acid gel (0.2%) in the surgical wound; • Polish the abutments with ruber cup and chlorhexidine gel; • Information that should not overload the structure; • Check for any fracture or loosening of prosthetic components. • Control of occlusion.

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Protocol for maintenance of rehabilitation with immediate function implants- clinic appointments Day 60 • Oral Hygiene:

Day 120 • Oral Hygiene:

• Oral Hygiene; • Removal of prosthesis for cleaning and desinfecting; • Control of suppuration by finger pressure; • Control of the mobility • Modified plaque index • Modified bleeding index • Probing the peri-implant sulcus • Polish with a chlorhexidine gel; • Control of occlusion; • Check for any fracture or loosening of prosthetic components. • Oral hygiene (all the above clinical indexes); • Periapical X-ray;

References 1. Xiao JR, Li YQ, Guan SM, Kong L, Liu B, Li D. Effects of lateral cortical anchorage on the primary stability of implants subjected to controlled loads: an in vitro study. Br J Oral Maxillofac Surg. 2012;50:161–5. https://doi.org/10.1016/j.bjoms.2011.01.010. 2. Huang HL, Fuh LJ, Ko CC, Hsu JT, Chen CC.  Biomechanical effects of a maxillary implant in the augmented sinus: a three dimensional finite element analysis. Int J Oral Maxillofac Implants. 2009;24:455–62. 3. Maló P, de Araujo Nobre M, Lopes A, Moss S. Posterior maxillary implants inserted with bicortical anchorage and placed in immediate function for partial or complete edentulous rehabilitations. A retrospective clinical study with a median follow-up of 7 years. Oral Maxillofac Surg. 2014;19:19–27. 4. Fu JH, Hsu YT, Wang HL.  Identifying occlusal overload and how to deal with it to avoid marginal bone loss around implants. Eur J Oral Implantol. 2012;5:S91–S103. 5. Johansson A, Omar R, Carlsson GE.  Bruxism and prosthetic treatment: a critical review. J Prosthodont Res. 2011;55:127–36. 6. Maló P, de Araujo Nobre M, Guedes CM, Almeida R.  Outcomes of immediate function implant prosthetic restorations with mechanical complications: a retrospective clinical study with 5 years of follow-up. Eur J Prosthodont Restor Dent. 2017;25:26–34. 7. Maló P, de Araujo Nobre M, Guedes CM, Almeida R, Silva A, Sereno N, Legatheaux J.  Short-term report of an ongoing prospective cohort study evaluating the outcome of full-arch implant-supported fixed hybrid polyether ether ketone-acrylic resin prostheses and the All-on-Four concept. Clin Implant Dent Relat Res. 2018;20:1–11. 8. Krekmanov L, Kahn M, Rangert B, Lindström H.  Tilting of posterior mandibular and maxillary

implants of improved prosthesis support. Int J Oral Maxillofac Implants. 2000;15:405–14. 9. 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. 10. Fortin Y, Sullivan RM, Rangert BR.  The Marius implant bridge: surgical and prosthetic rehabilitation for the completely edentulous upper jaw with moderate to severe resorption: a 5-year retrospective clinical study. Clin Implant Dent Relat Res. 2002;4:69–77. 11. Maló P, Rangert B, de Araujo 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):S88–94. 12. Maló P, de Araujo Nobre M, Lopes A.  The rehabilitation of completely edentulous maxillae with different degrees of resorption with four or more immediately loaded implants: a 5 years retrospective study and a new classification. Eur J Oral Implantol. 2011;4(3):227–43. 13. Malo P, de Araujo Nobre M, Lopes A. Immediate rehabilitation of completely edentulous arches with a four-­ implant prosthesis concept in difficult conditions: an open cohort study with a mean follow-up of 2 years. Int J Oral Maxillofac Implants. 2012;27:1177–90. 14. Malo P, de Araujo Nobre M, Lopes A, Ferro A, Gravito I.  Complete edentulous rehabilitation using an immediate function protocol and an implant design featuring a straight body, anodically oxidized surface, and narrow tip with engaging threads extending to the apex of the implant: a 5-year retrospective clinical study. Int J Oral Maxillofac Implants. 2016;31(1):1–9. 15. Del Fabbro M, Rosano G, Taschieri S.  Implant survival rates after maxillary sinus augmentation. Eur J Oral Sci. 2008;116:497–506. 16. Pjetursson BE, Tan WC, Zwahlen M, Lang NP.  A systematic review of the success of sinus floor eleva-

7  Tilted Implants tion and survival of implants inserted in combination with sinus floor elevation. J Clin Periodontol. 2008;35:216–40. 17. Sjostrom M, Sennerby L, Nilson H, Lundgren S.  Reconstruction of the atrophic edentulous maxilla with free iliac crest grafts and implants: a 3-year report of a prospective clinical study. Clin Implant Dent Relat Res. 2007;9:46–59. 18. Nystrom 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. 19. Louis PJ.  Vertical ridge augmentation using titanium mesh. Oral Maxillofac Surg Clin N Am. 2010;22:353–68. 20. Chiapasco M, Casentini P, Zaniboni M.  Bone augmentation procedures in implant dentistry. Int J Oral Maxillofac Implants. 2009;24(Suppl):237–59. 21. Li J, Wang HL.  Common implant-related advanced bone grafting complications: classification, etiology, and management. Implant Dent. 2008;17:389–401. 22. Agliardi EL, Romeo D, Panigattib S, de Araujo Nobre M, Malo P. Immediate full-arch rehabilitation of the severely atrophic maxilla supported by zygomatic implants: a prospective clinical study with minimum follow-up of 6 years. Int J Oral Maxillofac Surg. 2017;46(12):1592–9. 23. Brånemark PI, Gröndahl K, Ohrnell LO, Nilsson P, Petruson B, Svensson B, Engstrand P, Nannmark U.  Zygoma fixture in the management of advanced atrophy of the maxilla: technique and long-term results. Scand J Plast Reconstr Surg Hand Surg. 2004;38:70–85. 24. Maló P, de Araujo Nobre M, Lopes I. A new approach to rehabilitate the severely atrophic maxilla using extramaxillary anchored implants in immediate function: a pilot study. J Prosthet Dent. 2008;100:354–66. 25. Rangert B, Jemt T, Jörneus L. Forces and moments on Brånemark implants. Int J Oral Maxillofac Implants. 1989;4:241–7. 26. Duyck J, Van Oosterwyck H, Vander Sloten J, De Cooman M, Puers R, Naert I. Magnitude and distribution of occlusal forces on oral implants supporting fixed prostheses: an in vivo study. Clin Oral Implants Res. 2000;11:465–75. 27. Cooper LF, Rahman A, Moriarty J, Chafee N, Sacco D. Immediate mandibular rehabilitation with endosseous implants: simultaneous extraction, implant placement, and loading. Int J Oral Maxillofac Implants. 2002;17:517–25. 28. Brånemark P-I, Svensson B, van Steenberghe D. Ten-­ year survival rates of fixed prostheses on four or six implants ad modum Brånemark in full edentulism. Clin Oral Implants Res. 1995;6:227–31. 29. Malo P, de Araujo Nobre M, 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;8:223–32.

179 30. Zampelis A, Rangert B, Heijl L.  Tilting of splinted implants for improved prosthodontic support: a two-­ dimensional finite element analysis. J Prosthet Dent. 2007;97:S35–43. 31. Maló P, de Araujo Nobre M, Lopes A, Francischone C, Rigolizzo M. “All-on-4” immediate-function concept for completely edentulous maxillae: A clinical report on the medium (3 years) and long-term (5 years) outcomes. Clin Implant Dent Relat Res. 2012;14:e130–50. 32. Del Fabbro M, Bellini CM, Romeo D, Francetti L. Tilted implants for the rehabilitation of edentulous jaws: a systematic review. Clin Implants Dent Relat Res. 2012;14:612–21. 33. Monje A, Chan HL, Suarez F, Galindo-Moreno P, Wang HL. Marginal bone loss around tilted implants in comparison to straight implants: a meta-analysis. Int J Oral Maxillofac Implants. 2012;27:1576–83. 34. Chrcanovic BR, Albrektsson T, Wennerberg A. Tilted versus axially placed dental implants: a meta-­analysis. J Dent. 2015;43:149–70. 35. Malo P, de Araujo Nobre M, Lopes A, Moss SM, Molina GJ.  A longitudinal study of the survival of All-on-4 implants in the mandible with up to 10 years of follow-up. J Am Dent Assoc. 2011;142:310–20. 36. Francetti L, Romeo D, Corbella S, Taschieri S, Del Fabbro M. Bone level changes around axial and tilted implants in full-arch fixed immediate restorations. Interim results of a prospective study. Clin Implant Dent Relat Res. 2012;14:646–54. 37. Koutouzis T, Wennstrom JL.  Bone level changes at axial- and non- € axial-positioned implants supporting fixed partial dentures. A 5-year retrospective longitudinal study. Clin Oral Implants Res. 2007;18:585–90. 38. Hopp M, de Araujo Nobre M, Malo P. Comparison of marginal bone loss and implant success between axial and tilted implants in maxillary All-on-4 treatment concept rehabilitations after 5 years of follow-up. Clin Implant Dent Relat Res. 2017;19:849–59. 39. Maló P, Rangert B, de Araujo Nobre M. “All-on-Four” immediate-function concept with Brånemark system implants for completely edentulous mandibles: a retrospective clinical study. Clin Implant Dent Relat Res. 2003;5:S2–9. 40. Babbush CA, Kanawati A, Kotsakis GA, Hinrichs JE.  Patient-related and financial outcomes analysis of conventional full-arch rehabilitation versus the All-on-4 concept: a cohort study. Implant Dent. 2014;23:218–24. https://doi.org/10.1097/ ID.0000000000000034. 41. Fermergard 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;10:62–9. 42. Agliardi EL, Pozzi A, Stappert CF, Benzi R, Romeo D, Gherlone E.  Immediate fixed rehabilitation of the edentulous maxilla: a prospective clinical and radiological study after 3 years of loading. Clin Implant Dent Relat Res. 2012;9:292–302. https://doi. org/10.1111/j.1708-­8208.2012.00482.x.

180 43. Hsu Y, Fu J, Hezaimi K, Wang H.  Biomechanical implant treatment complications: a systematic review of clinical studies of implants with at least 1 year of functional loading. Int J Oral Maxillofac Implants. 2012;27:894–904. 44. Wood MR, Vermilyea SG. A review of selected dental literature on evidence-based treatment planning for dental implants: report of the committee on research in fixed prosthodontics of the academy of fixed prosthodontics. J Prosthet Dent. 2004;92:447–62. 45. Gross MD. Occlusion in implant dentistry. A review of the literature of prosthetic determinants and current concepts. Aust Dent J. 2008;53(suppl 1):S60–8. 46. Maló P, de Araújo NM, Lopes A, Rodrigues R. Preliminary report on the outcome of tilted implants with longer lengths (20–25 mm) in low-density bone: one-year follow-up of a prospective cohort study. Clin Implant Dent Relat Res. 2013;17:e134–42. https:// doi.org/10.1111/cid.12144. 47. Patzelt SB, Bahat O, Reynolds MA, Strub JR. The all-­ on-­four treatment concept: a systematic review. Clin Implant Dent Relat Res. 2014;16:836–55. https://doi. org/10.1111/cid.12068. 48. Soto-Penaloza D, Zaragozí-Alonso R, Penarrocha-­ Diago M, Penarrocha-Diago M. The all-on-four treatment concept: systematic review. J Clin Exp Dent. 2017;9:e474–88. https://doi.org/10.4317/jced.53613. 49. Maló P, de Araujo Nobre M, Lopes A, Ferro A, Nunes M. All-on-4 concept for full-arch rehabilitation of the edentulous maxillae: a longitudinal study with 5–13 years of follow-up. Clin Implant Dent Relat Res. 2019;21(4):538–49. 50. Maló P, Rangert B, Dvärsäter L. Immediate function of Brånemark implants in the esthetic zone: a retrospective clinical study with 6 months to 4 years of follow-­up. Clin Implant Dent Relat Res. 2000;2:138–46. 51. Maló P, Friberg B, Polizzi G, Gualini F, Vighagen T, Rangert B.  Immediate and early function of Brånemark system implants placed in the esthetic zone: a 1-year prospective clinical multicenter study. Clin Implant Dent Relat Res. 2003;5:S37–46. 52. Maló P, Rangert B, de Araújo Nobre M.  The all-­ on-­4 concept for edentulous jaws. Quintessence Int. 2006;1:1–10. 53. Jensen OT, Adams MW. The maxillary M-4: a technical and biomechanical note for all-on-4 management of severe maxillary atrophy—report of 3 cases. J Oral Maxillofac Surg. 2009;67:1739–44. 54. Jensen OT, Adams MW. All-on-4 treatment of highly atrophic mandible with mandibular V-4: report of 2 cases. J Oral Maxillofac Surg. 2009;67:1503–9. 55. Jensen OT, Adams MW, Cottam JR, Parel SM, Phillips WR III. The all on 4 shelf: mandible. J Oral Maxillofac Surg. 2011;69:175–81. 56. Butura CC, Galindo DF, Jensen O.  Mandibular all-­ on-­4 therapy using angled implants: a three-year clinical study of 857 implants in 219 jaws. Oral Maxillofac Surg Clin N Am. 2011;23(4):289–300. 57. Babbush CA, Kutsko GT, Brokloff J.  The All-on-­ Four immediate function treatment concept with

P. Malo et al. nobel active implants: a retrospective study. J Oral Implantol. 2011;37(4):431–45. 58. Pomares PC.  A retrospective study of edentulous patients rehabilitated according to the “all-on-4” or the “all-on-6” immediate function concept using flapless computer-guided implant surgery. Eur J Oral Implantol. 2010;3:155–63. 59. Agliardi E, Clericò M, Cinancio P, Massironi D.  Immediate loading of full-arch fixed prostheses supported by axial and tilted implants for the treatment of edentulous atrophic mandibles. Quintessence Int. 2010;41:285–93. 60. Khatami AH, Smith CR. “All-on-Four” immediate function concept and clinical report of treatment of the edentulous mandible with a fixed complete denture and milled titanium framework. J Prosthodont. 2008;17:47–51. 61. Agliardi E, Panigatti S, Clericò M, Villa C, Maló P.  Immediate rehabilitation of the edentulous jaws with full fixed prostheses supported by four implants: interim results of a single cohort prospective study. Clin Oral Implants Res. 2010;21:459–65. 62. Drago C, Howell K. Concepts for designing and fabricating metal implant frameworks for hybrid implant prostheses. J Prosthodont. 2012;21:413–24. https:// doi.org/10.1111/j.1532-­849X.2012.00835.x. 63. Drago C, Gurney L.  Maintenance of implant hybrid prostheses: clinical and laboratory procedures. J Prosthodont. 2013;22:28–35. https://doi. org/10.1111/j.1532-­849X.2012.00899.x. 64. Maló P, de Araújo NM, Borges J, Almeida R. Retrievable metal ceramic implant-supported fixed prostheses with milled titanium frameworks and all-­ ceramic crowns: retrospective clinical study with up to 10 years of follow-up. J Prosthodont. 2012;21:256–64. https://doi.org/10.1111/j.1532-­849X.2011.00824.x. 65. Maló P, de Sousa ST, De Araújo NM, et  al. Individual lithium disilicate crowns in a full-arch, implant-­ supported rehabilitation: a clinical report. J Prosthodont. 2014;23:495–500. https://doi. org/10.1111/jopr.12137. 66. Jemt T, Henry P, Linden B, et al. Implant-supported laser-welded titanium and conventional cast frameworks in the partially edentulous law: a 5-year prospective multicenter study. Int J Prosthodont. 2003;16:415–21. 67. Kim Y, Oh TJ, Misch CE, et  al. Occlusal considerations in implant therapy: clinical guidelines with biomechanical rationale. Clin Oral Implants Res. 2005;16:26–35. 68. Kinsel RP, Lin D. Retrospective analysis of porcelain failures of metal ceramic crowns and fixed partial dentures supported by 729 implants in 152 patients: patient-specific and implant-specific predictors of ceramic failure. J Prosthet Dent. 2009;101:388–94. 69. Jemt T, Back T, Petersson A. Precision of CNC-milled titanium frameworks for implant treatment in the edentulous jaw. Int J Prosthodont. 1999;12:209–15. 70. Sousa S, Pragosa A, Crispim P. Assessment of prosthetic complications in full-arch implant supported

7  Tilted Implants zirconia bridges: a retrospective analysis of 59 consecutive cases with a 12–29 month follow-up. Clin Oral Implants Res. 2009;20:1056–61. 71. Ozcan M. Fracture reasons in ceramic-fused-to-metal restorations. J Oral Rehabil. 2003;30:265–9. 72. Blum IR, Jagger DC, Wilson NH.  Defective dental restorations: to repair or not to repair? Part 2: All-­ ceramics and porcelain fused to metal systems. Dent Update. 2011;38:150–8. 73. Guess PC, Zavanelli RA, Silva NR, et al. Monolithic CAD/CAM lithium disilicate versus veneered Y-TZP crowns: comparison of failure modes and reliability after fatigue. Int J Prosthodont. 2010;23:434–42. 74. Makarouna M, Ullmann K, Lazarek K, et al. Six-year clinical performance of lithium disilicate fixed partial dentures. Int J Prosthodont. 2011;24:204–6. 75. Giannetopoulos S, van Noort R, Tsitrou E. Evaluation of the marginal integrity of ceramic copings with dif-

181 ferent marginal angles using two different CAD/CAM systems. J Dent. 2010;38:980–6. 76. Magne P, Schlichting LH, Maia HP, et  al. In vitro fatigue resistance of CAD/CAM composite resin and ceramic posterior occlusal veneers. J Prosthet Dent. 2010;104:149–57. 77. Sahin S, Cehreli MC, Yalcin E. The influence of functional forces on the biomechanics of implant-­supported prostheses—a review. J Dent. 2002;30:271–82. 78. Bindl A, Luthy H, Mormann WH. Strength and fracture pattern of monolithic CAD/CAM-generated posterior crowns. Dent Mater. 2006;22:29–36. 79. Wolfart S, Eschbach S, Scherrer S, et al. Clinical outcome of three-unit lithium-disilicate glass-ceramic fixed dental prostheses: up to 8 years results. Dent Mater. 2009;25:e63–71. 80. Denry I, Holloway J.  Ceramics for dental applications: a review. Materials. 2010;3:351–68.

8

Short® Implants and TRINIA® Full-­Arch Prostheses for the Rehabilitation of the Atrophic Maxilla Rolf Ewers and Estevam A. Bonfante

8.1 Introduction to Implant Reconstructions in the Edentulous Maxilla: Current Status and Materials Perspective

advocated in several studies as the standard of care in full-arch scenarios [4, 5]. Further technologies have fostered the use of all-ceramic systems such as yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP) polycrystalline ceramics, Estevam Bonfante initially as a suprastructure material, due to their favorable biocompatibility, biological, and high Full-arch implant-supported prostheses are a pre- mechanical properties (σ: 1200  MPa, Kic: dictable treatment option used to reestablish mas- 6  MPa  m1/2, E: 210  GPa) [4–8]. Although high ticatory function, quality of life, esthetics, and survival rates have been reported [4, 5, 8], the phonetics [1, 2]. Prostheses survival, usually most common technical complication, mainly for defined as the prostheses remaining in situ with 3Y-TZP reconstructions, is chipping/fracture of or without modification for the observation the veneering material commonly observed in the period, has shown to be above 90% for implant-­ low-toughness veneering porcelain (Kic: supported full-arch fixed dental prostheses 0.7  MPa  m1/2 for Y-TZP and 1.1  MPa  m1/2 for (FA-FDP) [3]. Unlike the mandible, the maxilla metal ceramic) [9], with approximately 11 to may receive implants in anterior and posterior 50% reported chipping after 5 years for porcelain-­ positions, but considering pneumatization of the fused to zirconia FA-FDPs [4, 8]. maxillary sinus and the desire to avoid grafting According to the latest Oral Reconstruction procedures, the use of short implants in the eden- Foundation (ORF) Consensus published in 2021, tulous maxilla may be advantageous for patients, in cases of severe atrophy of the edentulous maxalthough it has been suggested that their perfor- illa, the literature suggests as valid procedures: mance is yet to be investigated [3]. From a mate- bone augmentation including onlay bone grafts, rial’s perspective, porcelain fused to metal and lateral sinus floor elevation, vertical distraction acrylic over a metallic suprastructure have been osteogenesis, and Le Fort I interpositional grafting. As an alternative to bone grafting, two to four anterior parallel implants and two distally R. Ewers (*) CMF Institute, Vienna, Austria tilted implants have been indicated. It has also e-mail: [email protected] been suggested that short implants may be used E. A. Bonfante only in conjunction with standard implants in Department of Prosthodontics and Periodontology, splinted configurations, where regardless of University of São Paulo—Bauru School of Dentistry, being fixed or removable, should result in a prosBauru, SP, Brazil theses supported by at least 4–6 implants [10]. e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 M. Rinaldi (ed.), Implants and Oral Rehabilitation of the Atrophic Maxilla, https://doi.org/10.1007/978-3-031-12755-7_8

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The rationale for the increased level of technical complications for implant-supported ­rehabilitations may lie on the absence of periodontal ligament and its inherent micromotion that helps dampen occlusal forces, as well as mechanoreceptors and their feedback mechanism that differentiate food hardness and consistency [11–13]. Hence, technological improvements in the materials science have focused on the development/improvement of biomechanically favorable restorative systems with occlusal forces dampening features to meet the functional and esthetic demands of dental reconstructions [11, 12, 14–19]. According to the ORF Consensus, prosthetic material selection in implant-­supported edentulism should be done based on the required mechanical stability of the prosthesis and the use of a completely or partially digital or an analogic workflow [20]. Fiber-reinforced composites (FRCs) have emerged as promising systems in several aerospace, aeronautical, and biomedical applications, particularly for their favorable strength and stiffness-­to-weight ratios [17–19, 21, 22]. Dental FRCs are generally composed of a highvolume fraction of reinforcement compounds, carbon or glass fibers, bonded to a polymeric matrix by a coupling agent, where the fiber reinforcement bears the loads and increases the energy needed for crack propagation, known as resistance curve (R-curve) behavior, as well as increase the stiffness and strength of the material (σ: 540-­740 MPa, Kic: 9 MPa m1/2, E: 15–30 GPa) [16, 17, 23]. Such properties of FRC composites are directly dependent on the fiber type and composition, fiber geometry and orientation, fiber volume fraction, polymer matrix, and quality of the fiber–matrix interface [16, 24]. Given the typical anisotropic nature of conventional FRC reconstructions properties, the framework dimension and design as well as its three-dimensional position, usually following a structural relationship with occlusal forces distribution through a parallel alignment with the maximum principal stress direction, are key factors to obtain the maximum performance of FRC prostheses [16–19, 22].

R. Ewers and E. A. Bonfante

There are several FRC materials available in the market but, in this chapter, one specific material (TRINIA®, Bicon LLC, Boston, MA, USA) will be discussed not only because comprehensive engineering efforts have been devoted in its research and development over a decade ago, but also due to the fact that relevant clinical mid and long term as well as laboratory researches are available in major peer-reviewed journals [18, 25–31]. TRINIA is composed of a tailored balance between predominant reinforcing glass fibers bonded to an epoxy resin matrix (Fig. 8.1). Fibers are aligned as meshes and layers in a disk or blocks, suitable for designing and milling in any computer-aided design, and computer-­assisted manufacturing (CAD/CAM) system [31]. It is available as a framework material in two shades to optimize the dental technician layering of esthetic material: (1) pink, where its shade easily matches the gum interface also allowing esthetic layering of tooth structures; and (2) ivory, which is tailored to mimic natural tooth shades and also allows gum regions to be veneered for an esthetic interface with soft tissues. TRINIA’s fracture toughness (defined as resistance to crack propagation from a sharp notch or flaw [32]) is high (9.7  MPa/ m1/2) compared to zirconia (6–9  MPa/m1/2) or even cast metal Co-Cr (6 MPa/m1/2). With such a high fracture toughness, subsequent mechanical properties have been tailored to provide advanced function and biomimetics where some degree of flexing may exist according to its design and dimensions since TRINIA’s Young’s modulus of elasticity of 18.8 GPa is very similar to bone (14.8–20  GPa) when compared to 200  GPa for zirconia and up to 240  GPa for Co-Cr. Considering TRINIA’s similarity in modulus of elasticity to bone, the rise of a paradigm shift is naturally expected regarding its use not only in routine cases, but specially in very complex biomechanical scenarios of unconventional lengths of implant-supported free end distal extensions (cantilever). In extreme cases, literature suggests that cantilever length for metal or ceramic frameworks should be no longer than

8 Short® Implants and TRINIA® Full-Arch Prostheses for the Rehabilitation of the Atrophic…

a

185

c

b

Fig. 8.1  Polarized light microscopic images of the (a) top and (b) side sections of a TRINIA FRC disc displaying the fiber orientation. (c) Scanning electronic micro-

scopic side view depicts a unique fiber mesh entanglement and their close bond to the polymeric matrix that results in a distinct anisotropy

20 mm [33], with a recommended and preferable length of less than 15 mm [34], equivalent to two teeth distal to the most posterior abutment, usually premolars [35, 36]. Results from clinical studies have shown high survivals of TRINIA cantilever lengths of more than 25 mm [26, 27]. Therefore, FRC ­rehabilitations may offer significant clinical advantages due to their lower elastic modulus and increased resilience compared to metallic/zirconia rehabilitations, which may favor chewing forces absorption and stress distribution and improve the biomechanical performance of the restorations, particularly for implant-supported reconstructions [11, 12, 18, 19], as well as favorable cost effectiveness, chemical adhesion to resin composite and resin cement, and easy reparability with conventional in-office direct restorative procedures [16, 17, 21, 24, 37]. It is unequivocal that CAD/CAM technologies have revolutionized the use of FRC-based prostheses fabrication, improving their clinical per-

formance and range of indication [14, 38]. TRINIA is an FRC disk industrially fabricated under controlled conditions of temperature, heat, and pressure resulting in a decreased defect population and increased material reliability [14, 38–41]. With TRINIA use targeted as a framework, one must bear in mind that any finalized ceramic restorative material (milled and sintered or crystallized or pressed) can be bonded to it. For instance, a feldspathic porcelain, lithium disilicate ceramics, zirconia, or hybrid ceramics crowns or acrylic teeth may be bonded to TRINIA. The FRC framework may be designed and milled as a tooth-prepared shape framework where a subsequent milled crown would be bonded to the framework resulting in a major advantage for future individual replacement, should fracture occur. In such case, instead of entire restoration replacement, individual crown replacement and bonding to the TRINIA framework or even chairside repair with resin composite could extend prostheses function.

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8.2 Introduction to SHORT® Tapered Implants Rolf Ewers Initially, osseointegrated implants were used for the treatment of edentulous patients only and were placed in the anterior mandible [42, 43]. It was not long before implants were being used in the maxilla and as single-tooth replacements. At this time, implants were still fairly long (13– 16 mm), but many companies were beginning to produce shorter ones. By the mid- to late-1980s, 10–11  mm implants were being used, and research was beginning on even shorter implants. Short implants, those that were 8–10 mm, initially were the purview of the smaller implant companies. MegaGen, Bicon, Jeneric, and BTI among others began to develop these 8–10  mm implants. It was not long before the larger implant companies  – Nobel, Astra, and Straumann  – released their research and development of short implants. The next obvious question was how short can be an implant and still have long-term success? The result was the development of the ultrashort 5 mm long and also diameter reduced 3 mm narrow Bicon SHORT® osseointegrated implants (Fig. 8.2). Implants are now produced with 5–6  mm lengths, obviating the need for extensive grafting. Short and narrow implants allow the practitioner to place implants in  locations that would have been impossible 10–15  years ago. Many practitioners are still skeptical of the ultrashort implants, but recent research has shown success similar to short (8–10 mm) and traditional (above 10 mm) length implants [44–48]. In many cases, the use of short and ultrashort implants has obviated the need for grafting.

8.2.1 Atrophic Maxilla: Introduction Rehabilitation of the severely atrophic maxilla is always an incredibly challenging task for both

Fig. 8.2  4.0 x 5.0 mm extra short bicon implant

surgical and prosthetic clinicians. The early loss of the dentition and long-lasting edentulism lead to atrophy throughout the maxilla. Especially, the early loss of molars leads to a significant atrophy of the alveolar process and an extensive pneumatization of the maxillary sinus [49] and the septa, which Zuckerkandl first described get larger [50] and more dangerous for the surgeon. Since Tatum’s lecture about the so-called sinus lift [51], many methods have been reported to solve these problems with excellent long-term results [52– 55]. With more experience and treatments being performed, these procedures became minimally invasive [56–58]. During the last decade, short and ultrashort implants have become more commonly used as an alternative to conventionally long implants in conjunction with bone augmentation procedures [59, 60]. To avoid extensive surgical vertical and horizontal augmentation procedures, such as sinus lifts, in 2010, a prospective cohort study was initiated at our University Hospital with four 4.0 × 5.0 mm, posteriorly placed implants. When thin anterior alveolar ridges necessitated,

8 Short® Implants and TRINIA® Full-Arch Prostheses for the Rehabilitation of the Atrophic…

3.0  ×  8.0  mm calcium phosphate-coated (CP) locking taper implants (Integra-CP) [61] were placed. In complex cases, it was observed that the options for augmentation and implant placements in the anterior maxilla were extremely limited due to the narrow width and limited height of the alveolar crest. Therefore, currently there is a prospective cohort study with three ultrashort 4.0 × 5.0 mm CP-coated locking taper implants (Integra-CP) for the severely atrophic maxilla in concert with the longer existing mandibular study of three ultrashort implants [62]. Depending on the size and form of the incisive foramen and nasopalatine canal [63], 4.5- up to 6.0-mm diameter ultrashort implants were used [64]. To determine if it would be possible to insert an ultrashort implant into the incisive foramen and the nasopalatine canal, a preoperative Cone-Beam Computed Tomography (CBCT) is essential [65–67]. The middle ultrashort implant is inserted into the incisive foramen and nasopalatine canal, where there is usually one cavity with two nerves [68], since this is the thickest boney site in the atrophic premaxilla where an implant can be placed. Most incisive foramen has one cavity in which two incisive nerves are situated [68–71]. For Le Fort I Osteotomies [72] and for Horseshoe Le Fort I Osteotomies with free iliac crest bone block transplants [73, 74], the incisive nerve and vessel structures are always cut without any permanent clinical effects. This fact is also true for the placement of an implant into the nasopalatine canal, despite most authors denying this fact [75]. De Mello et al. [76] have shown in a largescale systematic review and meta-analysis of 238 articles, where they cited ten articles with references to 91 implants being inserted into the incisive foramen with a success rate of 84.6– 100%, with only one permanent nerve disturbance being reported after the lateralization of the nerve. For all the twelve-unit full-arch implant-­ loaded prostheses [77], TRINIA® (Bicon), a metal-free, fiber-reinforced hybrid resin CAD/ CAM material was used.

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Previously, for severely atrophic maxillae, a Horseshoe Le Fort I Osteotomy with a free iliac crest bone transplant was performed [74]. However, after the favorable mandibular results reported by Kern [78] and others [79], only one ultrashort implant which was inserted through the incisive foramen into the nasopalatine canal was used to retain an overdenture on a single Brevis™ abutment [80].

8.2.2 Materials and Methods In this book chapter, we report about a “prospective cohort study” which was approved by the institution’s ethical committee under the number “EK 018/2011” of the Medical University of Vienna/Austria. The prospective study was designed according to the Declaration of Helsinki, as well as the Good Clinical Practice guidelines. The results are reported according to the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) criteria [81]. The study is designed as a bicentric cooperation between the University Hospital for Cranio-Maxillofacial and Oral Surgery Vienna/ Austria and the CMF Institute Vienna/Austria. Consecutively, all edentulous patients with pronounced maxillary atrophy Class V and VI according to Cawood and Howell [82], in consideration of the common criterion of exclusion and after a written consent were included. Patients with Bisphosphonate/Denosumab-anamnesis, heavy smokers with more than ten cigarettes per day and adolescents were excluded.

8.2.3 Patient Group with Four Implants All 18 patients, 54–80 years of age (12 women; mean age, 66.9  ±  9.0  year; range, 54.0 to 79.7  year; 6 men; mean age, 67.6  ±  5.3  year; range, 61.4–76.5  year; there was no significant age difference between female and male patients) had been treated with four 4.0  ×  5.0  mm ultra-

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short CP-coated locking taper implants (Bicon, LLC). For patients with very thin maxillary anterior alveolar crests, 3.0 × 8.0 mm locking taper implants were placed [83]. The healing time for the implants was 6 months. During the uncovering session, the impressions and the bite registration were made. For the prosthetic rehabilitation, a 12-unit full-arch CAD/CAM-produced prosthesis fabricated with TRINIA® metal-free fiberglass-­reinforced hybrid resin material was used, which was either cemented onto the abutments or attached with screws and fixed-­ detachable abutments. After finishing their prosthetic treatment, patients had been evaluated yearly in a recall program, which included panoramic radiographs.

8.2.4 Results Of the 18 patients with 72 implants which were previously reported [62], only 12 patients are still remaining in the recall program, due to severe illnesses or demise. The longest evaluation is 98 months (8.2 years). For the 48 implants inserted in these 12 patients, 4 implants have been lost (8.33%). The four patients who lost an implant, were able to function on their three remaining implants until the fourth one was replaced. There have been no observed fractures of the 12 TRINIA® prostheses. As previously reported [64], radiographs reveal only slight marginal bone loss.

8.2.5 Case Reports 8.2.5.1 “All on Four” with Full-Arch TRINIA® Prosthesis Front and Premolar Region Implants As patient example, we show a 69-year-old patient [59] who now came to the office for the 7.4 years recall. The panoramic radiograph shows in Fig. 8.3a the initial situation and Fig. 8.3b the

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situation at starting to load. First, the patient had a cemented solution on four abutments as shown in Fig. 8.3c–g. Later the patient wished a removable telescopic solution which Fig. 8.3h–k show after his 7.4 years of loading. Figure 8.3h, j show the intraoral view after 7.4  years. Note on this image the new telescopic TRINIA® prosthesis with four individually milled telescopic abutments and copings, which accommodated the patient’s request after 4  years for a full-arch TRINIA® removable prosthesis with short distal extensions. The second demonstration is of a 69-year-old male patient, who had not only a pronounced maxillary atrophy class V-VI [82] in vertical dimension, but also a very thin alveolar process in the premaxilla and premolar region. Therefore, bilaterally in the frontal region a 3.0  ×  8.0  mm Bicon Integra-CP Implant was placed. For the very narrow alveolar crests in the premolar region, after a supra-periosteal tissue preparation and a widening or spreading of the alveolar crest, were performed before inserting the 4.0 × 5.0 mm Bicon implant. The panoramic radiograph in Fig. 8.4a shows his initial situation, Fig. 8.4b at time of loading, and Fig. 8.4c at his 6-year recall. Figure 8.4d shows the situation intraorally after 6 years of loading. Concluding the presentation of four Bicon implants panoramic radiographs of implants with 6.5 and 7 years of loading is shown (Fig. 8.5). On the left side are their preoperative images, in the middle are their images at initial loading, and on the right side are their latest recall radiographs. Images in the upper row are of a 64-year-old female patient with 7 years loading, images in the middle row are of a 65-year-old female also with 7 years of loading, and images in the lower row are of a 67-year-old male with 6.5  years of loading. Interestingly, there always appears to be a visible stability of the bone levels around the implants. Although all the implants are splinted and are not individually loaded, there is no peri-­ implant bone loss visible.

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Fig. 8.3 (a) Magnified section of a panoramic radiograph of a 69-year-old male patient with extensive maxillary atrophy with a splint and two metal points incorporated for navigation help. (b) Magnified section of a panoramic radiograph with four inserted 4.0 x 5.0  mm SHORT® Bicon Integra-CP implants. (c) Parallelized four Universal Titanium Abutments for cementation on stone model. (d) Finalized full-arch 12-piece TRINIA® prosthesis with four cementing abutments ready placed to be inserted into the implants. (e) Intraoral view at four inserted abutments for cementation after the implants had been uncovered 6 months post-insertion and finalizing the technical laboratory work. (f) Intraoral view of the finalized, cemented 12-piece full-arch TRINIA prosthesis with the absence of

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an acrylic arch. (g) Magnified section of a panoramic radiograph with four inserted 4.0  ×  5.0  mm SHORT® Bicon Integra-CP implants cemented on four abutments 6  months after implant insertion. (h) Intraoral situation after 7.4 years loading with individually milled telescopic abutments. (i) Undersurface of the TRINIA® prosthesis with four individually milled telescopic copings and short extensions since distal implants could be inserted more posteriorly. (j) Intraoral view after 7.4  years of loading. (k) Magnified section of a panoramic radiograph with a TRINIA® prosthesis fixed on four individually milled telescoping abutments and copings after 7.4  years loading

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Fig. 8.4 (a) Magnified section of a panoramic radiograph of a 69-year-old male patient with pronounced class V-VI maxillary atrophy. (b) Magnified section of a panoramic radiograph after insertion of two 3.0 × 8.0 mm and two 4.0 × 5.0 mm Bicon Integra-CP implants and after incor-

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porating a cemented TRINIA® full-arch prosthesis at the time of loading. (c) Magnified section of a panoramic radiograph after 6 years of loading, revealing no marginal bone loss. (d) Intraoral appearance after 6  years of loading

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Fig. 8.5  Sections of panoramic radiographs. Left side before implant insertion. Middle column at initial loading and right side most recent recall. Upper row a 64-year

female with 7 years of loading, middle row a 65-year-old female with 7 years of loading and lower row a 67-year-­ old male with 6.5 years of loading

8.2.6 Patient Group with Three Implants

of and in the incisive foramen and nasopalatine canal and a 4.5- up to 6.0-mm diameter calcium phosphate-coated Bicon implant (Integra-CP) [25, 62, 64] in the incisive foramen and nasopalatine canal. In very thin premolar regions, an alveolar crest widening or splitting procedure after a supra-periosteal preparation was performed [84]. The anatomical peculiarities and the special oper-

Eleven patients aged between 55 and 86 years old with extreme maxillary atrophy class V to VI according to Cawood and Howell [82] were included in this study group. All patients had been treated with a 4.0 × 5.0 mm implant on each side

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ative techniques have been previously described [64, 65]. The healing time for the implants was 6 months. The prosthetic rehabilitation was with a 12-unit full-arch CAD/CAM-produced prosthesis fabricated with TRINIA® metal-free fiberglassreinforced hybrid resin material.

8.2.7 Results Of the 11 patients with 33 implants, six were women (58.2–68.7  years) and five were men (63.4–81.6 years). They all had been in a twice per year recall regimen. The mean observation period is 34.2 months, and the longest observation period is 66 months (5.5 years). In the premolar region, 22 calcium phosphate-coated locking taper Bicon (Integra-CP) implants were placed. For the incisal foramen and nasopalatine canal, four 4.5 × 6.0 mm, four 5.0 × 6.0 mm, and three 5.0  ×  5.0  mm calcium phosphate-coated locking taper Bicon (Integra-CP) implants were placed. During the observation period of 5.5 years, all Bicon implants remained osseointegrated and only two implants (6.06%) were lost. The loss rate is relevant considering the following: the advanced age of both patients, the extreme maxillary atrophy, the relatively large diameter of incisive foramen and nasopalatine canal, and the surgeon’s experience with the new surgical placement techniques. The wider the foramen, the more difficult it is to insert an implant. Surprisingly, both patients were able to very carefully use their TRIIA® prosthesis on only two implants, during the osseointegration time of their replacement implant. None of the 11 twelve-unit TRINIA® prosthesis showed any fracture of the TRINIA material. As reported with four implants [61], there were only minor changes in the marginal bone levels with three implants.

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8.2.8 Case Reports 8.2.8.1 “All on Three” with Full-Arch TRINIA® Prosthesis Nasopalatine and Premolar Region Implants The treatment of 65-year-old patient, which was previously reported [25, 64] presented at his 4-year reevaluation is being shown. Figure 8.6a shows a Cone-Beam CT in transverse projection before extraction of his teeth 6 through 10 with massive lone loss around the teeth. Figure  8.6b reveals the severe bone defect of premaxillary bone. Only around the incisive foramen and the nasopalatinal canal is bone left. Figure  8.6c shows the insertion of three implants. Figure 8.6d shows the Cone-Beam CT in sagittal projection after insertion of the middle Bicon implant through the incisive foramen into the nasopalatine canal. Figure 8.6e shows a section of a panoramic radiograph at initial loading with the prosthesis onto the three fixed-detachable abutments. Figure  8.6f shows the intraoral situation at his 4-year recall and Fig. 8.6g shows the radiologic appearance at the 4-year recall visit. Note: there is no apparent change of marginal bone level around the Bicon implants. Concluding the reporting of the study with three implants, a panoramic radiograph survey of three patients with 4- and 3.5-year loading time is being shown (Fig.  8.7). On the left side are images before the implant’s insertions. In the middle column, at their initial loading; and on the right side, at their last recall. In the upper row is an 86-year-old female patient (one of the oldest) with a 4-year loading; in the middle row, a 70-year-old male patient also with a 4-year loading; and in the lower row, a 68-year-old female patient with a 3.5-year loading. Interestingly,

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Fig. 8.6 (a) Cone-Beam CT in transverse projection revealed massive bone loss around teeth 6 through 10 prior to their being extracted. (b) Cone-Beam CT in transverse projection after extraction of the teeth reveals extensive bone loss, except for an area around the nasopalatine canal where there is some remnant bone. (c) In Cone-­ Beam CT in transverse projection, only two of the three implants are seen. (d) Cone-Beam CT in sagittal projec-

tion after inserting the middle Bicon implant through the incisive foramen into the nasopalatinal canal. (e) Section of a panoramic radiograph at initial loading with the TRINIA® prosthesis onto the three fixed-detachable abutments. (f) Intraoral situation at his 4-year recall. (g) Section of a panoramic radiograph with screw-retained full-arch TRINIA® prosthesis on three fixed-detachable abutments at the 4-year recall

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Fig. 8.7  Sections of panoramic radiographs. Left side— before implant insertion. Middle column—at initial loading and right side—most recent recall. Upper row images — an 86-year-old female patient with 4-year recall, middle

row—a 70-year-old male patient also with 4-year recall, and lower row—a 68-year-old female patient with a 3.5year recall

there always is a visible stability of the bone levels around the implants. Although all implants are splinted and not individually loaded, there is no peri-implant bone loss visible.

rehabilitation was with a full-arch CAD/CAM produced partially cover denture prosthesis fabricated with the metal-free fiberglass-reinforced hybrid resin material. The prostheses were fixed to the single implant with a Brevis™ (Bicon) attachment and abutment. During the short observation period of 35  months, no complications were observed, and all patients are incredibly happy with their prosthetic solution. Importantly, the patients have the feeling that their prosthesis is not loose and not in danger of inadvertently slipping out of their mouth—despite their extreme maxillary atrophy.

8.2.9 Patient Group with One Implant Based on the gained experience and the successful results of the studies with “all on four” and “all on three” (and according to the suggestions and reported good results in the mandible by Kern et  al. [78]), it was decided to try to insert only one ultra-SHORT® implant in the maxilla through the incisive foramen into the nasopalatine canal to support a TRINIA® overdenture in the atrophic maxilla. Proportionally to the width of the nasopalatine canal, ultrashort Bicon implants with diameters up to 6.0 mm were used.

8.2.10 Results On five patients aged of 62–76  years, implants were inserted through the incisive canal and into the nasopalatine canal. The implants used ranged from a 4.5 mm up to 6.0 × 5.0 mm and 6.0 mm calcium phosphate-coated locking taper implants with a healing time of 6 months. The prosthetic

8.2.11 Case Report 8.2.11.1 “All on One” with Nasopalatine Implant and Full-Arch TRINIA® Prosthesis A 75-year-old female patient was diagnosed with an extreme maxillary atrophy class VI (Fig. 8.8a, b) and a mild mandibular atrophy class III-IV [82] (Fig.  8.8a) after being edentulous for 57 years. All these factors together resulted in a severe Class III relationship (Fig. 8.8c). The only region of the maxilla with sufficient bone for an implant is the premaxilla with two incisive foramina and nasopalatine canal in the middle (Fig. 8.8d).

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Fig. 8.8 (a) Panoramic radiograph of a 75-year-old female patient with extreme maxillary atrophy class VI and a mild mandibular atrophy class III-IV [82], after being edentulous for 57  years. (b) Frontal section of a Cone-Beam CT with extreme bilateral atrophy of the alve-

Fig. 8.9  Section of panoramic radiograph after the insertion of three 4.0  ×  5.0 Bicon CP-coated locking taper (Integra-CP) implants

Initially, the mandible was treated by inserting three 4.0  ×  5.0  mm Bicon CP-coated locking taper implants (Integra-CP) (Fig. 8.9). After 2 months, one 5.0 × 6.0 mm CP-coated locking taper implant was placed through the

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olar crests in the premolar region, class VI [82]. (c) Sagittal Section of a Cone-Beam CT showing an extreme progenic Angle class III bite relationship. (d) Transverse section of a Cone-Beam CT showing the premaxilla with two incisive foramina and the nasopalatine canal

incisive foramen into the nasopalatine canal (Fig. 8.10a). The postoperative Cone-Beam CT images in Fig. 8.10b, c reveal a satisfactory position of the implant in the premaxilla. During the 6 months of osteointegration of the maxillary implant, the mandibular implants were uncovered, and at the same session, the impression and the bite registration were made. The facial position of the impression posts is noted (Fig. 8.11a). After the Perpetuini Dental Laboratory had fabricated the full-arch CAD/CAM prosthesis with metal-free fiberglass-reinforced hybrid resin material, the problem of the too facially positioned implants due to the progenic class III malposition was solved. The three sleeves and screws

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Fig. 8.10 (a) Intraoperative view during the insertion of a 5.0 × 6.0 mm Bicon CP-coated locking taper (Integra-CP) implant with the Implant Inserter/Retriever instrument on a Threaded Straight Handle. (b) Frontal section of a Cone-­

Beam CT after insertion of a 5.0  ×  6.0  mm Bicon CP-coated locking taper (Integra-CP) implant. (c) Sagittal section of a Cone-Beam CT after insertion a 5.0 × 6.0 mm Bicon CP-coated locking taper (Integra-CP) implant

were positioned in front of the canines and incisors (Fig. 8.11b, c). The position of the fixed-detachable abutments (Fig.  8.11d) clearly reveals an extreme progenic class III malocclusion situation. Figure 8.11e shows the full-arch prosthesis fixed with three screws in the screw-detachable abutments. Figure 8.11f reveals the long bilateral extensions (cantilevers) due to the extreme labial positioning of the screws. The entire prosthesis is a distal extension (cantilever). Ten years ago, the authors experienced facially positioned implants in a progenic class III relationship for a 59-year-old female patient, whose four 4.0  ×  5.0  mm CP-coated locking taper implants had been tilted too far labially (Fig. 8.12a). Their position necessitated that the sleeves and screws are positioned far in front of the canines and incisors. The panoramic radiograph (Fig. 8.12b) reveals the exceptionally long extensions (cantilevers). Left is 21.0 mm and the

right 19.0 mm. Once again, the entire prosthesis is a distal extension (cantilever). The lateral cephalometric radiograph also reveals the distinctly long bilateral extensions (cantilevers) of 21.0  mm on the left side and 19.0  mm on the right side of the prosthesis (Fig. 8.12a). Figure 8.12c shows the intraoral situation at the 9-year recall revealing the successful resolution of the facially angled implants. Despite the extreme loading during the 9 years of prosthetic wear, there was no fracture of the prosthesis and no apparent bone loss visible on the panoramic radiographs (Fig. 8.12d). Continuing with the discussion above with the 75-year-old female patient, whose implants were uncovered after 6  months is presented. During the same session, the impressions and the bite registration were made (Fig. 8.13a). A few days later, another bite registration was made at the try-in session with the prepared overdenture base providing fixation for the orienta-

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Fig. 8.11 (a) Intraoral image after the uncovering the implants and insertion of the impression posts. The too facially positioned impression posts reveal progenic (Angle class III) relation. (b) Fig.  8.11b Finished TRINIA® full-arch prosthesis with three sleeves for abutment screws resolved the treatment of the class III malocclusion. The distance arrows indicate 19.0- and 20.0-mm-long extensions (cantilevers) of the canines, premolar, and molar teeth. (c) Final TRINIA® full-arch prosthesis, fixed with three screws to their abutments in the analog implants within the stone model. The frontal position of the three screws and sleeves is positioned in

front of the canines, premolar, and molar teeth. (d) Intraoral situation after inserting the fixed-detachable abutments to the three Bicon implants. The extreme progenic class III position is clearly evident. (e) Intraoral situation after fastening the TRINIA® full-arch prosthesis with three screws to the fixed-detachable abutments. The bores in the prosthesis are covered with a provisional resin for easier maintenance. (f) Section of a panoramic radiograph after fastening the TRINIA® full-arch prosthesis with three screws, revealing long bilateral extensions (cantilevers)

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Fig. 8.12 (a) Lateral cephalometric radiograph reveals the apparently unfavorable position of the implants due to their labial tilting and the exceedingly long (left 21.0 mm and right 19.0 mm) distal extensions (cantilevers) of the TRINIA® prosthesis. (b) Section of panoramic radiograph after fastening the TRINIA® full-arch prosthesis on four

Bicon implants and fixed-detachable abutments. The long extensions (cantilevers) of left 21.0 mm and right 19.0 mm are obvious. Figure  8.12c Intraoral situation at 9-year recall. (c) Intraoral situation at 9-year recall. (d) Section of panoramic radiograph taken at more than 9-year loading. No peri-implant bone loss is visible

tion. The green plastic impression sleeve fits precisely onto the titanium impression post to ensure a precise try-in and bite registration (Fig. 8.13b). Image of the finished prosthesis was fabricated by Paolo Perpetuini. Figure  8.13c shows the single Brevis™ attachment fixed in the implant analog of the master model. Figure 8.13d shows the finished prosthesis and Fig. 8.13e the prosthesis from below with the Brevis™ attachment in the middle. Despite the class III bite relationship due to the extensive maxillary and mandibular atrophy, it was possible to achieve an adequate overjet and overbite by increasing the vertical dimension

(Fig.  8.13f). Lateral image confirms the result (Fig. 8.13g). Figure 8.13h, i reveal a very satisfied patient with an aesthetic appearance with only a slight progenic chin and Fig. 8.13j shows the intraoral situation with a single Brevis abutment seated in a SHORT Bicon implant, inserted through the incisal foramen into the nasopalatinal canal. According to the patient’s opinion, she has been given a very satisfactory functional and aesthetic result. She can chew her food without any difficulties since her upper prosthesis does not wiggle anymore and keeps its position securely in her mouth.

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Fig. 8.13 (a) Intraoral situation with plastic impression sleeve fixed over the titanium impression post after uncovering the implant for immediate impression making and bite registration. (b) Prepared overdenture prosthesis being used as fixation and orientation for the try-in and the bite registration. (c) Master model showing the single Brevis™ attachment fixed in the implant analog. (d) Finished TRINA® overdenture prosthesis. (e) Finished TRINA® overdenture prosthesis from below with the Brevis™ attachment in the middle. (f) Intraoral situation

showing a normal overbite and overjet, achieved by increasing the vertical dimension of occlusion despite the class III bite relationship caused by the extensive atrophic maxilla and mandible. (g) Lateral view. (h) Facial image of an incredibly happy patient. (i) Lateral image showing only a slight progenic chin position. (j) Intraoral view with a single Brevis abutment seated in a Bicon implant inserted through the incisal foramen into the nasopalatinal canal at two-year recall

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8.2.11.2 Minimal Crestal Widening and Spreading After Epiperiosteal Preparation in the Premolar Region In extremely atrophied maxilla, Class V to VI according to Cawood and Howell [82], the alveolar ridge in the premolar region is often very thin. In situations like this, we prefer to prepare the mucosa epiperiosteal (supra-periosteal) [split thickness flap], (Fig.  8.14) so the mobilized or split buccal crestal cortical bone will remain vascularized as it is covered by periosteum which would not be if a full thickness flat is prepared [84]. After condensing (osseodensification) and mobilizing the buccal bone by widening or spreading, the implants are inserted at least 2–3  mm subcrestal immediately and covered with mucosa by primary suture closure. The bony gap between the bone segments may be covered with resorbable augmentation material like Synthograft® or phycogenic Algoss® materials.

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This procedure we demonstrate on an 82-year-­ old female patient with extremely atrophied maxilla, Class V to VI according to Cawood and Howell [82]. As the crestal bone in the premolar region was in addition to the minimal vertical bone height very thin (Fig. 8.15a, b) (better DVT section), there was the indication for a minimal bone condensing, widening, and spreading. After epiperiosteal (supraperiosteal) soft tissue preparation, we perform following step–by-step procedure: 1. Marking the desired implant position with a round burr. 2. Cutting the cortical bone of the alveolar crest about 4–5 mm on both sides. 3. Deepening this osteotomy with the Beaver knife. 4. Gentle widening the osteotomy gap with a chisel. 5. During widening the osteotomy gap with the chisel, starting to drill the osteotomy with the

Fig. 8.14 Graphic visualization of separating the periosteum from the mucosa and submucosa tissue layers with a 15c scalpel in a 45° position

Spongy Bone Cortical Bone Periosteum Submucosa Mucosa Split Thickness Flap

Supra-periostal Preparation

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Fig. 8.15 (a) Section of a Cone-Beam image in the premolar region. The right alveolar crest is noticeably short and narrow, Class VI according to Cawood and Howell

pilot drill in a low speed without irrigation only perforating the cortical bone. 6. Then starting to widen and condensing the spongy bone by widening very gently and slow (to tribute to the viscous elasticity to living bone) the osteotomy gap and moving the buccal cortex buccally. For this procedure, we use the Bicon Hand Reamers in ascending diameter. 7. As the Bicon Hand Reamer has one cutting edge and the rest is round, the round part always should be toward the buccal side. Gently you insert the instrument, and sometimes you use very gently the mallet to deepen the osteotomy. 8. In order to widen the osteotomy and to mobilize the buccal cortical bone segment, it is worthwhile to wiggle the Hand Reamer, so the osteotomy diameter increases. 9. As soon as you reached your desired diameter with the Hand Reamer, you keep the gap open again with a small chisel and insert the SHORT implant. As always it should be positioned 2–3 mm subcrestal. 10. Then insert the polyethylene healing cap which had been shortened to the desired length (Fig. 8.16). 11. The remaining gap you may augment with resorbable augmentation material. 12. At the end primary soft tissue closure. Figure 8.16 shows the intraoperative situation after inserting the SHORT implant about 3 mm subcrestal and inserting the polyethylene

[82]. (b) Section of a panoramic radiograph of an atrophic maxilla. The radiograph was taken with an acrylic splint with 4 metal balls for better orientation

Fig. 8.16  Intraoperative situation after separating the palatal and buccal crestal alveolar bone and widening the gap to insert a 4.0 × 5.0 mm SHORT implant in 3 mm subcrestal position. Implant closed with polyethylene healing plug

healing plug. In this operation, we decided not to augment the existing gap. The panoramic radiograph of Fig.  8.17a and the Cone-Beam section (Fig. 8.17b) show an excellent position of the right lateral implant after a bone widening procedure. Six months later the impression taking follows immediately the uncovering procedure (Fig.  8.18). The panoramic radiograph after incorporating the 12-piece full-arch TRINIA prosthesis reveals an excellent result including the well-positioned right lateral implant due to minimally invasive crestal widening after epiperiosteal (supra-periosteal) tissue preparation (Fig.  8.19). Figure  8.20a–c show the clinical situation at the 5-year recall session and Fig.  8.20d the panoramic radiograph with this long-lasting stable result.

8 Short® Implants and TRINIA® Full-Arch Prostheses for the Rehabilitation of the Atrophic…

a

Fig. 8.17 (a) Post-operative section of a panoramic radiograph revealing well-positioned 4.0  ×  5.0  mm SHORT implants. Note the subcrestal position of the right

Fig. 8.18  Intraoral situation after uncovering the implant 6 months after the insertion and primary suturing. In the same session, the three titanium impression post and the plastic impression sleeves are in situ for the impression taking

Fig. 8.19  Section of panoramic radiograph after incorporating the full-arch TRINIA prosthesis

8.2.11.3 Tuber Implants In some very atrophic maxilla, there is the possibility to use the tuber region for an implant position if in the premolar region is less bone. Also, the spongy bone is very soft and filled with a great amount fatty tissue that the osseointegration is possible probably due to the high vascularity of this bone region. As this bone is so soft, we perform the osteotomy only with Hand Reamer instruments.

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b

lateral implant after minimally crestal widening. (b) Post-­ operative Cone-Beam section. Note the wider crestal bone with the inserted right SHORT implant

We demonstrate this procedure on a 73-female patient with an atrophic maxilla, Class V–VI according to Cawood and Howell [82] (Fig. 8.21a). As the alveolar crest in the front was very thin, we applied the front implants in the canine region and the posterior implants in the tuber region. The intraoperative image (Fig.  8.21b) demonstrates the situation of performing the osteotomy. With the hand Reamer which is a cutting instrument when turning right, we turn left, and with this procedure, you can perform an osseodensification. As the spongy bone is so soft, you do not need a mallet to get depth. Your pushing force is enough to get the desired 7–8 mm depth of your osteotomy. The following insertion of the SHORT implant is performed without any pressure (Fig. 8.21c). The post-operative panoramic radiograph reveals a perfect position of the right implant in the tuber region. After 6 months, there was the uncovering of the implants, the impression taking and finalizing a full-arch TRINIA prosthesis fixed on four screw-detachable abutments (Fig. 8.21e). The clinical image at the 6-year recall shows a very satisfying result after treating such a difficult situation (Fig.  8.21f), and the panoramic radiograph also at the 6-year recall shows a stable situation without bone loss as well on the other side of the tuber implant (Fig.  8.21g). It is surprising that this soft and fatty spongy bone in the tuber region seems to be so excellent vascularized that a stable and long-lasting osseointegration is possible.

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a

b

c

d

Fig. 8.20 (a) Intraoral situation at patients’ 5-year recall. (b) Intraoral situation at patients’ 5-year recall. Palatal view with free hard gum. (c) Intraoral situation after

unscrewing the detachable full-arch TRINIA prosthesis. Note the infect-free peri-implant mucosa tissue. (d) Section of a panoramic radiograph at 5-year recall

a

c

b

d

e

f

g

Fig. 8.21 (a) Section of a panoramic radiograph with atrophic maxilla, Class V–VI according to Cawood and Howell [82]. Very excessive pneumatization of the maxillary sinus and some remnant bone in the tuber region. (b) Intraoperative image performing in the tuber region the osteotomy. Using a Hand Reamer which has one cutting edge and turning it counterclockwise, you are able to perform an osseodensification as the spongy bone is very soft

in this region. (c) Intraoperative image of inserting the SHORT implant in the tuber region with the Threaded Offset Handle. (d) Postoperative section of panoramic radiograph of well-positioned SHORT implants also in the tuber region. (e) Section of a panoramic radiograph taken with the incorporated full-arch TRINIA prosthesis. (f) Intraoral situation at 6-year recall. (g) Section of panoramic radiograph at 6-year recall

8 Short® Implants and TRINIA® Full-Arch Prostheses for the Rehabilitation of the Atrophic…

8.3 Discussion The aim of this study was to investigate the possibility of treating patients with extreme maxillary atrophy by means of short and ultrashort implants, without the necessary time and cost of intensive augmentation procedures and to minimize the morbidity and complication risks of using augmentation procedures. The full-arch prostheses were CAD/CAM produced out of TRINIA®, a metal-free glass fiber-reinforced hybrid resin material, and were fixed on 4.0 × 5.0 mm and 3.0 × 8.0 mm ultra-SHORT® implants. The implant-based survival rate with a surveillance time of up to 8.2 years was 91.67%. These survival rates are comparable with the survival rates of standard long implants—especially if you take into consideration that all the presented patients showed a pronounced maxillary atrophy and were elderly. This study shows that it is possible to treat the very atrophic maxilla of elderly patients with the “all-on-four” concept with four ultrashort and narrow diameter Bicon implants [25, 53]. These results are comparable with reports about standard long implants of other authors [6, 7]. After 2 years of experience, cemented prostheses were substituted with screw-retained prostheses, which are also recommended by the S3 guidelines [85]. For the prosthetic rehabilitation with four implants, the focus was on providing a precise occlusal rehabilitation with the opposing jaw. A centric premolar and molar occlusion with minimal or no anterior contact was always sought. For eccentric movements, canine guidance or group guidance was sought. Additionally, steep inclinations were avoided. Furthermore, emphasis on the curve of Spee to achieve a balanced axial loading of the implants was always a goal. When treating patients with severe maxillary atrophy with a new prosthesis, one must emphasize a correct vertical dimension of occlusion, for which it is highly likely that it has been reduced due to the loss of teeth, with subsequent repositioning of the joint. Increasing the vertical dimension of occlusion may improve the Angle class III relationship, which many long-term edentulous patients with massive jaw atrophy have. Due to the advanced

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age of the patients, it is easier for them to clean a removable prosthesis than a fixed, because of their compromised tactile visual capabilities. Furthermore, the study has shown that treating patients with a CAD/CAM-produced prosthesis fabricated with metal-free fiberglass-reinforced hybrid resin material did not show any complications [25]. All four patients who had to wait for osseointegration of their replaced implant were able to use their prosthesis on three implants, which means a 100% prosthetic success. The results using short and narrow Bicon implants are encouraging for the treatment of the extremely atrophic maxilla without extensive augmentation procedures, which not only saves the patient time and money, but more importantly with less pain and morbidity. Since the study of the atrophic maxilla with four ultrashort Bicon implants showed such good results [27, 61, 86, 87], it was considered to use only three implants, contrary to the meta-­analysis [85] and the suggestions of the S3 guidelines [88]. However, the treatment followed the principle of “triangular stability.” Initially the three-­ implant study started in the mandible without any problems [89] and subsequently in the maxilla [25]. To reduce the implant number to three in the maxilla, however, one probably must insert the middle implant through the incisive foramen and into the nasopalatine canal. Due to the author’s many years of operating experience with the Le Fort I osteotomy [72] and the Horseshoe Le Fort I osteotomy [73, 74], he knew that this procedure would have no sensational disturbances of the incisive nerves. De Mello et al. [76] confirm these observations in his review and meta-analysis report. The implant survival rates are comparable with the results of standard long implants in combination with augmentation procedures. The implant survival for up to 5.5 years is 93.94%. This shows that it is possible to treat the highly atrophic maxilla with the “all on three” concept with ultrashort Bicon implants [25, 44, 64]. The studies are comparable with studies of other authors [47–49, 90]. Furthermore, this study also shows that the use of metal-free fiber-­ reinforced resin hybrid CAD/CAM prostheses did not show any problems or complications [83].

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These results are reassuring as they had to be performed in some cases with alveolar crest widening and splitting due to the extreme maxillary atrophy. By inserting the middle Bicon implant through the incisive canal and into the nasopalatine canal, wider implants were able to be used. The prosthetic treatments were performed in the same manner as for the patients with four implants. With the “triangular stability,” there were fewer tilting effects on the abutments. Since ridge-lap prostheses require greater hygiene, it is better to use fixed removeable prostheses for elderly patients because of their compromised capabilities. Due to the recommended and widely published method of Kern et al. [78] and other positive reports about treating the mandible with only one implant [79], it was decided to use these novel concepts in the maxilla. The anecdotal evidence for an observation period of 28  months, without the loss of a single implant, is far too short to discuss this treatment as a successful modality and certainly not to recommend it. However, the extreme satisfaction of the patients with partially stable maxillary full-arch prosthesis with only one implant encourages the continued use of this method. Just considering the benefits of is able to properly masticate one’s food, which leads to healthy digestion and nutrition. Referring to the review and meta-analysis of removable and fixed implant-supported prostheses in edentulous jaws [88] and the systematic S3 guidelines [85], this report contributes to the long-discussed reduction of implant numbers to four implants and even to the use of only three implants. Due to the locking taper Bicon implant system without a bacterial film at the implant abutments interface, no soft tissue problems or peri-­ implantitis were observed. Interestingly, in all of the panoramic radiographs, there appears to be a visible stability of the bone levels around the implants. Although all of the implants were splinted and not individually loaded, there is no observed peri-implant bone loss visible. Probably, one explanation of this phenomenon is due to the fact that the TRINIA® material is flexible. The

R. Ewers and E. A. Bonfante

flexibility between the splinted implants during functional loading may be the beneficial factor according to Wolff’s law, [91] which provided the accelerated mineralization and possible bone gain. Additionally, and notably, the flexibility of the TRINIA material, which by definition cannot be a lever or cantilever, provided the opportunity of using apparently excessively long distal extensions (cantilevers). In these study groups, we also experienced some additional difficult situations that we had to apply a minimal invasive bone-spreading procedure after epiperiosteal preparation to guarantee undamaged vascularization for a perfect osseointegration of the SHORT implant. Some cases forced us even to perform implant insertions in the tuber region also with good stable results, and also the spongy bone is incredibly soft in this very posterior region.

8.4 Conclusion of the Three Study Groups Initially in 2010, the author was very skeptical when he started to treat his patients with four ultrashort Bicon implants—even though the Bicon system had been widely used and phenomenally successful for 25 years by that time. Since there had been no reports about the use of 4.0 × 5.0 mm implants in very atrophic jaws, he started first in the mandible and, after seeing successful results, he continued with maxillary treatments. Considering the challenging anatomy of highly atrophic maxillae with minimal bone volumes and without complex and costly augmentation procedures, he can state that the initial use of four and subsequently three ultrashort Bicon locking taper implants shows after an extended observation period, equivalent results as standard long implants with complex augmentation methods. Additionally, implant placement in the incisive foramen and nasopalatine canal did not lead to any complication and seems to be a sound procedure. The presented treatments contradict the S3 guidelines [85]. Therefore, there should be discussions about the presented methods as a practi-

8 Short® Implants and TRINIA® Full-Arch Prostheses for the Rehabilitation of the Atrophic…

cal way of reducing the number of implants due to the excellent results shown. Additionally, successful use of narrower implants has been shown, which offer significant surgical benefits. The medium-term observations of more than 8 years in the maxilla and more than 10 years in the mandible are satisfactorily compelling, especially considering the advanced age of the studied patients with their evident difficulties with implant and prosthetic maintenance issues [92]. We significantly exceeded the initial goal of enhancing the quality-of-life elderly patients. As a positive side effect, it must be mentioned that their improved mastication has provided for their having an improved and well-balanced nutrition. Furthermore, the good results seem not only be influenced by the learning curve of the operating surgeons [93]. Reports concerning the long-term results with only three and four ultrashort implants are still scarce. Similar prospective studies with long observation periods are recommended. Much to the delight of needful patients, it seems practical to treat the very atrophic maxilla with only one implant for an implant-­ stabilized full-arch TRINA® prosthesis. However, further long-term studies are also recommended. Acknowledgment/Declaration  Part of this article has been published as follows: Ewers et  al. Versorgung des atrophen Oberkiefers mit vier oder drei ultrakurzen Implantaten bzw. Einem ultrakurzen Implantat. Implantologie 2020;28(4):327–342. With friendly permission by Quintessenz Publishing.

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208 tine canal in implant-prosthetic treatment: a pilot study dent. Dent J (Basel). 2020;8:30. https://doi. org/10.3390/dj8020030. 76. de Mello JS, Faot F, Correa G, Chagas Júnior OL.  Success rate and complications associated with dental implants in the incisive canal region: a systematic review. Int J Oral Maxillofac Surg. 2017;46:1584–91. 77. Ewers R, Perpetuini P, Morgan V, Marincola M, Wu R, Seemann R.  TRINIA™—metal-free restorations. Implant Dent. 2017;1:2–7. 78. Kern M, Att W, Fritzer E, Kappel S, Luthardt RG, Mundt T, Reissmann DR, Rädel M, Stiesch M, Wolfart S, Passia N.  Survival and complications of single dental implants in the edentulous mandible following immediate or delayed loading: a randomized controlled clinical trial. J Dent Res. 2018;97:163–70. 79. Asami M, Kanazawa M, Lam TV, Thu KM, Sato D, Minakuchi M. Preliminary study of clinical outcomes for single implant-retained mandibular overdentures. J Oral Sci. 2020;62(1):98–102. 80. Ewers R, Marincola M, Perpetuini P. Versorgung des atrophen Oberkiefers mit vier oder drei ultrakurzen Implantaten bzw. einem ultrakurzen Implantat. Implant Dent. 2020;28(4):327–42, Quintessenz Verlag Berlin. 81. Vandenbroucke JP, Von Elm E, Altman DG, et  al. Strengthening the reporting of observational studies in epidemiology (STROBE): explanation and elaboration. Gac Sanit. 2009;23:158, (in Spanish). 82. Cawood JI, Howell RA. A classification of the edentulous jaws. Int J Oral Maxillofac Surg. 1988;17:232–6. 83. Ewers R, Marincola M, Perpetuini P, Seemann R, Morgan V, Wu R.  Leichtgewicht im Praxistest-­ Restaurationen bei schwierigen Situationen und atrophen Kiefern. Z Oral Implant. 2017;1(17):28–36. 84. Ewers R.  Pedicled Sandwich Osteotomy  – surgical technique for vertical and horizontal alveolar bone deficiency. Vortrag auf dem International Bone Symposium in Implant Dentistry in San Francisco/ USA am 30.3.2017.

R. Ewers and E. A. Bonfante 85. Kern JS, Terheyden H, Wolfart S.  Implantat-­ prothetische Versorgung des zahnlosen Oberkiefers. S3-Leitlinie. AWMF-Registernr. 083–010. 2017, Report No.: AWMF-Registernr. 083–010: AWMF. 86. Seemann R, Marincola M, Seay D, Perisanidis C, Barger N, Ewers R. Preliminary result of fixed, fiber-­ reinforced resin bridges on four 4- x 5- mm ultrashort implants in compromised bony sites: a pilot study. J Oral Maxillofac Surg. 2015;73:630–40. 87. Ewers R, Perpetuini P, Seemann R, De Witt T, Sarvan I, Coetzer M, Pisarik K. Atrophic maxillary ridges. In: Morgan VH, editor. The bicon short implant: a thirty-­ year perspective. Chicago: Quintessence Publishing; 2017. p. 199–213. 88. Kern JS, Kern T, Wolfart S, Heussen N.  A systematic review and meta-analysis of removable and fixed implant-supported prostheses in edentulous jaws: post-loading implant loss. Clin Oral Implants Res. 2016;27:174–95. 89. Ewers R, Seemann R. TRINIA™ trio – “all-on-three” – metallfreie glasfaserverstärkte Kunststoffprothese auf drei ultrakurzen Bicon-Implantaten. Zahn Krone. 3/17:11–17. 90. Vazouras K, Barbisan de Souza A, Gholami H, Papaspyridakos P, Pagni S, Weber H-P.  Effect of time in function on the predictability of short dental implants (≤6mm): a meta-analysis. J Oral Rehabilit. https://onlinelibrary.wiley.com/doi.org/10.1111/ joor.12925. 91. Wolff J. Das Gesetz der Transformation der Knochen. Berlin: Verlag von August Hirschwald; 1892. 92. Schlegel KA, Schmitt CH, Möst T. Implantate beim hochbetagten Patienten?! Fallserie hochbetagter Patienten Implantologie. 2020;28(2):157–66. 93. Knöfler W, Barth T, Graul R, Krampe D, Schmenger K. Beobachtung von 10.000 Implantaten über 20 Jahre-­ eine retrospektive Studie. Einfluß von Implantatlänge, durchmesser und -typ auf die Überlebensrate. Implant Dent. 2017;25:413–21.

9

Bone Grafting Raffaele Vinci

9.1 Introduction

The purpose of this chapter is to focus on autologous bone grafts. The main sites and techIn severe atrophy of the jaw bones (Cawood and niques of harvesting, the preparation of the graft Howell classes V and VI), the traditional implant-­ and its fixation in the receiving site, morbidity prosthetic rehabilitation cannot be used due to based on the type of surgery performed and comthe amount of bone available; for this reason vari- plications that may occur will therefore be ous more complex therapeutic alternatives have described in this chapter. been proposed over time to rehabilitate the parEverything is based on our clinical experience tially or totally edentulous patient. and the state of the art of literature. Various bone augmentations techniques for increasing bone volumes have been described over time, including bone regeneration methods 9.2 Graft Types with biomaterials, membranes and bone grafts. Although the success of these therapeutic Over the years, various solutions have been tested alternatives has been amply demonstrated, our for bone defects reconstruction, namely autoloclinical experience teaches us that the best thera- gous, homologous and heterologous grafts. Paul peutic solution is the most predictable one, for Tessier stated the superiority of autologous one in this reason the use of the patient’s native bone comparison to other bone substitutes on a bioshould always be preferred, even using alterna- logical, immunological and medico-legal basis. tive strategies. These include the placement of The mechanical, osteogenic and morphologic angled/short implants to bypass relevant anatom- properties make it the gold standard. ical structures, bone expansion, condensation techniques and transposition of the IAN to exploit residual bone volume. 9.2.1 Autologous Bone Donor Sites However, it may not always be possible for the above-mentioned techniques to be used, there- Various types of donor sites have been described fore, bone volume increase techniques are in the literature, which we distinguish mainly needed. into extraoral and intraoral. The first group includes the parietal bone of the skull, the tibia and the iliac crest, which are generally selected R. Vinci (*) Postgraduate School of Oral Surgery, Dental School, for larger bone reconstructions. Department of Dentistry, Vita-Salute San Raffaele University, Milan, Italy

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The second group includes tuberosity of the maxilla, palatal bone, torus and the mandibular sites, i.e. the ramus and the retromolar area, which are considered the gold standard since the observed resorption of that site is less than the one observed in the other areas. Generally, the intraoral sites are chosen if a small amount of bone is needed or in localized bone atrophies.

9.2.2 Bone Grafts Cellular Healing All types of autologous bone grafts follow a similar regenerative process and their success completely depends on the quality, intensity and, most importantly, speed of revascularization; the more rapidly the vascular connection occurs, the greater the survival of the graft and the better its regeneration. The revascularization process begins within a few hours after placing the graft thanks to the osteoclasts that create a passage for the formation of new blood vessels. The maximum time in which the cells present inside the graft can survive corresponds to about 4 days: if the revascularization does not occur within this time, the bone cells undergo a process of necrosis with loss of the biological component and permanence of the mineral part, however, to act as a guide for the osteoblasts present in the newly formed capillaries inside the graft. To ensure the survival of the bone cells within the graft, all the blood vessels present in the affected region are used, including those deriving from the periosteum and other tissues. For this reason, it is recommended not to use membranes in the recipient sites as they would lead to a delay in bone healing with the risk of necrosis of the more superficial cells of the graft with a consequent late resorption of the graft.

9.2.3 Morphological Structure of Donor Sites Autologous bone grafts have the great advantage of following the healing process along three main paths: osteogenesis, osteoconduction and osteoinduction. The first, as Wolff stated in 1863, is

directly related to the survival of the osteoblasts within the bone block, without which it would not be possible to obtain the success of bone regeneration. The latter, however, does not seem to be solely due to the number of surviving osteoblasts within the bone block, in fact, as described in the osteoconduction theory by Barth in 1893, these bone cells must proliferate in the receiving bone tissue guided by the residual inorganic skeleton following necrosis of the transplant bone cells. Lastly, in 1997, Boyne said that, according to the osteoinduction theory, the pluripotent cells guided by hormones and morphogenetic bone cells differentiate into osteogenic cells capable of transforming into osteocytes. Each of these pathways leading to bone regeneration can be more or less represented according to the characteristics of the donor site of the graft, for example, the one withdrawn from the iliac crest mainly presents features of osteogenesis and osteoinduction thanks to the large amount of cancellous bone with a consequent high capacity for revascularization responsible for the survival of large quantities of bone cells. Conversely, the one withdrawn from the mandible mainly presents characteristics of osteoconduction due to the higher presence of the cortical component. There are therefore excellent requirements for the osseointegration of implants due to the excellent bone quantity and quality.

9.3 Bone Grafts from the Iliac Crest 9.3.1 Background According to the literature, hip has long been used as a donor site in the reconstruction of maxillary bones affected by severe atrophy. The augmentation of bone volumes using iliac crest grafts is considered a predictable and reliable technique thanks to several characteristics that distinguish it, namely, the accessibility of the surgical site, the possibility to perform the sampling and positioning of the bone block in the same surgical session, the ease of modelling the shape of the sample and the amount of cortical and cancellous

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bone available [1]. In fact, as previously stated, the iliac crest bone is characterized by a large component of cancellous bone tissue, which contains cells promoting osteoconductivity, osteoinductivity and osteoproliferative effects.

9.3.2 Anatomic Evaluation Before selecting this technique as the most suitable based on the case you are dealing with, a careful analysis of the patient’s general health is necessary, as well as a meticulous assessment of both the recipient and donor sites. This consists of an intraoral inspection including both clinical and radiographical examination to accurately evaluate the position of the nearby anatomical structures to design the following implant-prosthetic rehabilitation and an extraoral evaluation to analyse factors including facial harmony and soft tissue consistency.

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There are various alternatives regarding the harvest of bone from the iliac crest, as it can be harvested in the form of monocortical block, bicortical block or particulate bone. Based on the characteristics of the recipient site where it has to be positioned, the bone block can be designed in shape and volume [3].

9.3.5 Iliac Crest Surgical Harvesting Techniques

After establishment of endotracheal general anaesthesia, a sand bag is placed under the ipsilateral buttock to elevate shoulder and hip. The most important reference points to identify before incising the skin are the anterior superior (ASIS) and posterior superior iliac spines, which represent the limits for bone harvesting. These two points are marked with a demographic pen and the incision is made 1  cm posterior to ASIS in order to avoid any damage to the lateral femoral cutaneous nerve. The incision runs 9.3.3 Pharmacological Aspects approximately 5  cm parallel to the hip margin towards the posterior iliac spine. Prior to the surgical procedure, the patient underThe incision is deepened through the skin and goes prophylactic broad-spectrum antibiotic subcutaneous tissue up to the fascia-lata, which is treatment with Amoxicillin (3  g/day) or then cut to expose the iliac crest via a lateral or Clindamycin if allergic to penicillin. The treat- medial reflection. The medial approach is safer ment is continued for 10 days. and with less complications, but a drain should be Half an hour prior to surgery the patient is placed in situ before closing to avoid the risk of given 8  mg of dexamethasone and 4  mg on the haematoma. same evening to avoid oedema. Ketorolac, metoOne cut is made in the middle third of the clopramide and H2 receptor antagonists are also crest with an osteotome and two vertical cuts administered to prevent the most frequent post-­ on either side of the crest in order to gain surgical symptoms. access to the cancellous bone (Figs.  9.1, 9.2, Buprenorphine is used intravenously for at and 9.3). At this point the cancellous bone least 6 h in the postoperative period. chips are harvested from the inside of the crest with a spoon and a strip of cellulose is placed on the exposed medullary bone to obtain better 9.3.4 Surgical Techniques haemostasis. If a bicortical block has to be harvested, both The main reason why the iliac crest is one of the lateral and medial approaches are required to most commonly used site for autogenous bone expose the iliac crest. If only cancellous bone is grafting is due to the copious amount of cortical needed, for example for the titanium membrane and cancellous bone that composes it. As needed, technique, a small portion of cortical bone is cut a combination of both can be harvested in abun- on the most superficial part of the crest in order to dance [2]. expose the medullary material and then reposi-

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Fig. 9.1  The iliac crest is a rich harvesting site, suitable for extended withdrawals that are usually made posterior to the anterior superior iliac spine. To expose this area, a full-thickness or partial thickness surgical flap (as in this case) is raised. The cortico-medullary withdrawal is then made with a piezoelectric device

Fig. 9.3  Iliac crest harvested bone block

After surgery, drain is removed when the contents decreased to 5–10  ml after 48–72  h and sutures are removed after 10 postoperative days in case of satisfactory wound healing at the site.

9.3.6 Surgical Procedures for Grafting in the Upper Maxilla Once the sample has been harvested, the intraoral positioning in the upper maxilla mainly consists of the following: Fig. 9.2  The bone block is then removed exactly of the shape and size required by the recipient area. The iliac crest also represents a donor area of large quantities of particulate bone, which however does not have the same osteogenetic, osteoconductive and osteoinductive characteristics of the calvaria

• • • •

tioned in situ and sutured to keep the hip morphology intact. The periosteal layer, fascia-lata and subcutaneous layers are usually closed using resorbable sutures (3–0 vicryl) and the skin with 3–0 silk. A different surgical technique is necessary when a greater amount of bone is needed and consists in the harvesting of the sample from the posterior half. The surgical procedure is more difficult, takes longer and the patient is placed face down. For these reasons, this technique is rarely used for maxillary reconstructions.

9.3.6.1 Sinus Lift with Iliac Crest Graft This technique of sinus lifting and positioning of bone harvested from the hip is usually performed in patients with large pneumatization of the maxillary sinuses where bone augmentation with artificial substitutes is not recommended. Usually, the residual bone height is less than 3 mm and it is therefore mandatory to place the implants after some time. The bone blocks can be adapted and inserted into the subantral cavity after a large sinus fenestration is prepared, in this case, the implants are placed in the same session. This variant is

Sinus lift with bone graft Onlay grafts Titanium mesh with cancellous bone Inlay grafts

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advantageous because it consists of only one surgical procedure, but it is more complex and longer than the bone marrow grafting technique. Adding inorganic bovine bone, as reported by the literature, seems to help maintain the volume of the entire graft during the remodelling of the autogenous portion [4]. From a clinical point of view, the consistency of regenerated bone at 6 months corresponds to a class 2 of Albrektsson. The use of PRP (platelet-­ rich plasma) mixed with autologous bone and bovine inorganic bone does not seem to improve the final result.

9.3.6.2 Onlay Blocks This surgical procedure involves the positioning of cortico-cancellous bone blocks above an atrophic ridge with a horseshoe technique or on a residual vestibular lamina of an atrophic bridge that still maintains a vertical component. After the elevation of a full-thickness flap, the recipient site is exposed and the cortical lamina is milled with a round bur under saline solution to increase the blood supply and to adapt as well as make the recipient bed to the blocked graft. After modelling the block according to the desired shape the bone blocks are screwed according to the “lag-screw” technique with fixation-­compression to the residual bridge; in this way, we avoid any micro-movement that could compromise the integration of the graft [5]. All residual gaps between graft and recipient site must be filled with bone chips to avoid the growth of soft tissue in those spaces. This type of technique, as will be explained in the course of this chapter in the description of the membranous bone grafts, is difficult to apply in the grafts of endochondral derivation due to the poor representation of cortical bone for which there is sinking of the head in the absence of compression. Positioning a thin layer of inorganic bovine bone above the graft can reduce physiological resorption by up to 50%. The fixation screws are removed 3/4  months later and the implants can be placed.

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9.3.6.3 Titanium Mesh Prior to surgery, a polyether impression of the jaw is made and the wax placed to simulate the desired bone effect. The model is duplicated in acrylic and this replica has the ideal jaw shape. The titanium mesh is applied on the replica to get the right shape. After the elevation of a full-thickness flap, the titanium mesh is filled with cancellous bone harvested from the hip using the technique described above and then screwed onto the palate using a pair of transcortical screws. The bone can be mixed with particles of bovine inorganic bone in a 1:1 proportion in order to maintain the volume. It is essential to release the soft tissues with periosteum incisions in order to cover the substantial increase created and achieve a complete closure. The mesh has to be removed 5  months after surgery. 9.3.6.4 Interpositional Blocks (Inlay Technique) This procedure is limited to extreme atrophies of the edentulous maxilla in which the relationship between the upper and lower jaw must be restored both in a vertical and in a sagittal plane due to extreme resorption. Lateral and frontal cephalometric radiographs are needed to make the traces. A full-thickness flap is elevated from the first upper molar to the first contralateral molar and a Le-Fort I is made. The bone blocks harvested from the iliac crest can be modelled using the replica as a guide and positioned on the jaw bone. Although implant placement can be combined with bone graft, a deferred technique after 4–6 months is preferable. The inlay technique is more complex and increases postoperative morbidity; therefore, it is not recommended in older patients.

9.3.7 Complications Though rehabilitation of bone defects of the jaws through the use of grafts and implants is a sophisticated procedure, the surgical technique is relatively simple [1], but using it carries a risk of

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complications both in the harvesting (including gait disturbances, neurologic injury and ilium fracture [2]) and graft positioning steps.

9.3.7.1 Harvesting Issues After harvesting iliac crest bone the minor complications include prolonged pain, hypersensitivity and buttock anaesthesia [2]. Postoperative morbidity is easily reduced with a gentle and precise technique, however, complications including infections are possible [6]. Major complications that have been described are meralgia paraesthetica described by Yamamoto et al. in 2001 [7], herniation [8], disturbance of gait and ureteral injury [9]. Another rare but serious complication of iliac grafts is postoperative adynamic or paralytic ileus [8]. 9.3.7.2 Graft Positioning Issues Careful soft tissue management can ensure a tension-­ free closure thus reducing the risk of bone exposure. Localized exposure of the graft can easily be treated by cleaning the soft tissues, prescribing the patient an antibiotic therapy and rinsing with chlorhexidine. Attempting to mobilize the soft tissues, a second time to obtain a primary closure should be avoided as it can result in a second exposure of a greater volume of the graft. The risk of graft necrosis is very low due to the rapid revascularization of the iliac bone.

9.3.8 Discussion When performing a surgical technique, the doubt always lies in the long-term results. Iliac crest grafts have been used for many decades for the reconstruction of jaw bone defects, but only in the last 20 years they have been used simultaneously with the positioning of implants. Many studies confirm the reliability of this donor site and in literature it has been shown that resorption of the graft around the implants after surgery can occur after 3 years, showing an attitude similar to that of the native bone. One of the most debated problems is how to reduce the bone resorption of the grafts by limit-

ing the extra-axial forces after connecting the implants to a prosthetic framework. Although the literature is not yet uniform regarding the influence of a non-passive fit on bone resorption, the authors have analysed hip grafts and Toronto bridge or overdenture restorations by observing that when the prosthetic framework has no passive fitting, the resorption over time (5 years) is double. In conclusion, according to the international literature and our clinical trials, nowadays the block grafts withdrawn from the iliac crest seem to be a suitable solution to reconstruct segments of the mandibular arch, as previously mentioned, thanks to the great amount of withdrawable samples, the easy access to the surgical field, the bone quality, the revascularization potential and the consequent discrete integration. Even so, when compared with calvaria bone graft for the cell viability performance, the iliac crest bone graft does not seem to be an ideal solution, especially after a long period from the grafting [10].

9.4 Bone Grafts from the Mandible 9.4.1 Background The success of engraftment is directly related to the phenomenon of osteoconduction. For this process to take place, most, if not all of the graft surface must be in close contact with the recipient site. This situation accounts for more than half of the healing process. In this regard, it is therefore necessary to briefly describe the process even if formerly mentioned in the introduction of this chapter.

9.4.1.1 Osteoconduction This phenomenon basically consists in the colonization of the graft that results in a real scaffold, inside which the osteoblasts penetrate both through the newly formed vessels deriving from the recipient site, and through the surrounding bone thanks to the ability of the graft itself to attract osteoblasts.

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The rapid vascularization and regeneration of the graft limit the action of the osteoclasts that invade the site to remove dead cells, preventing new ones from colonizing the graft leading to a resorption of a large part of the graft before ­possible regeneration. Clinically, this resorption begins in the most distant part of the graft at the recipient site, the last to be reached by the new blood vessels. Many authors emphasize that regeneration was shown to be influenced by autologous bone chips. If small, it leads to greater and more mature regeneration after 2–4 weeks compared to larger particulates. However, it must be remembered that the bone particulate for the reconstruction of an alveolar arch is unstable and the use of a membrane is not recommended due to the risk of exposure and infections.

9.4.2 Anatomic Evaluation In order to proceed with the surgery, it is necessary to have anatomical knowledge of all the possible sampling areas of the jaw to carry out a safe and predictable operation, thus avoiding the possible onset of complications. Pre-operative clinical and radiographic evaluation of the nerves, musculature, dentition and donor site is therefore extremely necessary. In particular, the areas of greatest interest are represented by the inferior alveolar nerve, the masseter muscle and the lower posterior teeth [11]. The Inferior Alveolar Nerve, with all its anatomical variables, must be studied and radiographically examined by means of level II radiographic examinations (CBCT) to evaluate its position within the mandibular canal and its neurovascular bundle thickness, to ensure a complete safety surgical manoeuvres with any neurosensory and vascular complications [12]. The Masseter Muscle consisting of two subunits [13]: 1. The superficial head originating from a thick tendinous aponeurosis of the zygomatic bone and from the anterior two-thirds of the lower edge of the zygomatic arch. Its muscle bundles pass down and back and then enter

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the outer portion of the mandibular angle, while in the lower portion they enter the lower half of the lateral surface of the mandibular branch. 2. The deep head deriving from the posterior third of the lower edge of the zygomatic arch and from its medial face. Its muscle bundles move forward and downward, crossing those belonging to the superficial part, inserting themselves in the upper half of the branch until they reach the coronoid process. Lower Posterior Teeth, including mainly premolars, characterized by having the longest root in the mandibular posterior sextant (14–15 mm), followed by first and second molars (13–14 mm), then third molars (10–11 mm) [14].

9.4.3 Pharmacological Aspects Antibiotic prophylaxis, except for patients with systemic conditions that require it, is not strictly necessary. The administration of antibiotics after surgery is mandatory in healthy patients for a period of 7–10 days, as is the use of 0.2% chlorhexidine in combination with analgesics three times a day for a week.

9.4.4 Surgical Technique 9.4.4.1 Graft Harvesting The mandibular bone harvest is performed under local anaesthesia, usually accompanied by intravenous sedation. For larger types of reconstructions, such as reconstructions by means of sampling from multiple donor sites or for surgeries lasting 3 or more hours, the surgery is performed under general anaesthesia. There are essentially three possible areas of mandibular bone block harvesting: • Mandibular branch • Chin Symphysis • Edentulous areas

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9.4.4.2 Mandibular Branch Prior to the surgical procedure, a careful clinical examination has to be performed (Fig. 9.4), then a type of vestibular and lingual plexus a­ naesthesia is recommended, avoiding the IAN block in order to reduce the risk of compromising it in surgical manoeuvres. The incision consists of a triangular incision (Fig.  9.5) followed by the elevation of a full-thickness mucoperiosteal flap in order to expose the bone of the external oblique crest for a length of about 3–4 cm and about 2 cm in depth (Fig. 9.6). Then the bone block is harvested under abundant saline irrigation and its volume depends mainly on the extension of the external oblique ridge and the amount of bone required for the process (Fig.  9.7). The harvest can be performed using burrs, diamond discs and piezoelectric device (Fig. 9.8). With the diamond disc, the nec-

Fig. 9.6  Exposure of the retromolar area, mandibular body and upright branch, note the oblique line

Fig. 9.7  Osteotomy cut design Fig. 9.4  Donor area clinical view

Fig. 9.8  Bone block harvesting Fig. 9.5  Surgical incision

9  Bone Grafting

Fig. 9.9 Donor area, note the neurovascular bundle exposure

essary osteotomies are performed, delimited by the position of the inferior alveolar nerve (Fig. 9.9). The block taken from the mandibular branch is of the cortico-medullary type, since generally in addition to a well-represented cortical component, it also has a layer of medullary bone adhering to the internal part. In order to avoid intraoperative complications, the mandibular lingual border must be carefully protected at all times. Usually, the donor site is covered with a layer of collagen that has haemostatic properties that lead to better healing. If you decide to place filling material in the site, it is necessary to use collagen between the latter and the bone in order to avoid the migration of this material near the nerve, with the consequent risk of degenerative neurological lesions. The harvesting procedure ends with the suture of the surgical site (Fig. 9.10). Radiographically, the surgical results disappear in a period of time between 6 and 12 months based on the regenerative potential of the donor site.

9.4.4.3 Chin Symphysis Prior to the surgical procedure, lateral teleradiographs provide clear information regarding bone volume, and mandibular anterior teeth apex position and root angulation. A loco-regional anaesthesia is performed with the mental nerve block followed by vestibular

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Fig. 9.10  Donor site sutures

and lingual plexus infiltration of the anterior mandibular region. The surgical procedure begins with a vestibular incision with the elevation of a full-thickness mucoperiosteal flap towards the base of the chin. In the case of an edentulous mandible, the incision is made on the upper part of the crest allowing good exposure of the crestal bone and at the same time, if necessary, the insertion of implants. The harvesting of the bone block, once exposed, can be obtained with osteotomes. The lower limit of the sampling area must preserve the lower mandibular edge, while maintaining a safety margin of about 3–5  mm for aesthetic reasons. Symphysis bone defects should be filled with biomaterials and stabilized with membranes. The resorbable biomaterial is placed on the outside, while the collagen on the inside. A good regeneration of the site is achieved 12 months after the intervention.

9.4.4.4 Edentulous Mandibular Areas Once local anaesthesia is performed with vestibular and lingual infiltration, a trapezoidal incision with the consequent elevation of a full-thickness mucoperiosteal flap is made in order to expose the sampling area. In the upper part it must begin approximately 5 mm below the alveolar ridge to preserve the upper contour. In these cases, it is possible to harvest apical bone blocks from the region where they will then be grafted.

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9.4.5 Graft Positioning The graft positioning surgical procedure of the mandibular bone block includes the preparation of the recipient site and the graft fixation. To prepare the recipient site, the bone marrow has to be exposed, since it represents a source of osteoclasts and bone vessels, provides haematopoietic and reticuloendothelial information. In order to do so, perforation of the cortical bone has to be performed [15, 16]. Although the role of the recipient bed has not yet been fully described, the first osteogenesis phase in the healing of autogenous grafts consists in bone cells formation, originating by the survived cells in the marrow of the graft itself and by the cells in recipient bed marrow [17, 18]. Once the graft is fixed, the bone healing process begins in the first week. This occurs with a single necessary condition, namely, that the graft is completely stabilized in order to avoid microor macro-movements (>100 μ). In case of complete fixation, new blood vessels would begin to form and consequently the revascularization of the graft [17–22]. In the presence of micro-movements, on the contrary, there would be an absence of nutritional supply and consequently a high risk of graft failure. In case of macro-movements there could even be an immune response with consequent rejection of the graft. Intramembranous bone transplant showed less resorption compared with endochondral bone origin and greater volume maintenance when the transplant was rigidly fixed. Regarding the flap management, it is important to obtain coverage of the graft by the periosteum or muscle. The first, if properly passivated, is safer since the possible presence of intermittent stress due to continuous muscle movements could have a negative effect on the integration of the graft itself, including the dehiscence of the wound [23]. Furthermore, it is reported that the iliac onlay graft under a submuscular site is subjected to a greater resorption maybe because of a superior revascularization which can lead to an early bone remodelling [24].

9.4.6 Surgical Procedures for Grafting in the Upper Maxillae Mandibular grafts can be installed in the form of blocks (cortical or cortico-medullary) or particulate. There are two types of graft positioning in the upper maxillae, which can be divided mainly into onlay and inlay grafts. The first one consists of positioning of the bone block in the recipient area (alveolar crest or vestibular region of the atrophic alveolar ridge), subsequently fixed with screws (Fig. 9.11). The second one involves the positioning of the bone block under the floor of the maxillary sinus or the nasal passages to correct the deficiencies in height and width. The particulate medullary grafts can be placed under guided bone regeneration membranes, meshes of titanium or into bone cavities. As a therapeutic alternative in order to stabilize the bone particulate, Fouad Khoury suggests a thin block of cortical bone, fixed by using screws at the necessary distance from the native bone to determine the new shape and width of the arch. Subsequently, the interposed space is filled with the carefully prepared particulate (Fig. 9.12) in order to avoid spaces that would cause the proliferation of fibroblasts [25]. The surgical flaps are then repositioned by means of a resorbable suture (Fig.  9.13) and at

Fig. 9.11  Bone blocks positioning

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and with a high potential for osseointegration due to the presence of the bone cortex. The detailed explanation of the surgical techniques has already been described in the iliac crest grafts paragraph.

9.4.7 Complications

Fig. 9.12  Completion with bone chips obtained from the donor area beveling

Fig. 9.13  Recipient’s area surgical wound and sutures

As for the mandibular branch samples, the infection of the donor site is a very rare complication (in the literature it is reported as less than 1% of cases). If performed with care, the sampling technique hardly leads to sensory damage, which, however, resolves in a period of 1–5 months. In case of fractures of one of the bone walls, it is still possible to fix the wall again using osteosynthesis screws. Concerning graft removal in the mandibular symphysis area, complications are more frequent (2.5%) and sometimes sensory problems of the mandibular anterior incisors have also been found, which may therefore be affected by anaesthesia/ paresthesia for a shorter or longer period of time. This is mainly due to the possible tearing of the anterior branches of the mandibular nerve during the bone graft surgery. The use of this technique is therefore recommended in patients who have edentulous anterior mandibular area or with a large protuberance of the chin with short incisal roots.

9.4.8 Discussion

Fig. 9.14  Clinical check-up 1 month after surgery

the one-week follow-up visit, good tissue healing can already be assessed (Fig. 9.14). From this technique derives a graft rich in cancellous bone with a high regenerative potential

In conclusion, as reported by the literature and based on our clinical experience, the intraoral sampling sites represent qualitatively satisfactory bone sampling sites. In addition to the structure, the high concentration of promoter and osteoprogenitor morphogenetic proteins make these grafts a predictable therapeutic choice for the rehabilitation of severe atrophy of the jaw bones. Bone healing time, especially in mandibular branch harvesting with intramembranous component, appears to have a shorter healing time compared to other types of bone regeneration. All these can also be determined by the fact that intramembranous autologous bone trans-

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plants and intraoral recipient sites share the same embryological ectomesenchymal origin, intramembranous ossification, biochemical and biological similarities that certainly improve the revascularization of the graft and potential for incorporation [26]. Overall, it must be said that it is rather challenging to reconstruct a severely atrophic upper jaw for implant-prosthetic purposes, except for a few selected cases that cannot undergo rehabilitation with a reduced number of implants.

9.5 Bone Grafts from the Calvaria 9.5.1 Background As stated in the literature, calvarial grafts are indicated in interventions requiring more than 30 mL of cortical bone volume. The main advantages of this harvesting technique are the possibility of obtaining a large amount of good-quality bone and facilitating rapid vascularization of the graft [26]. In fact, a significant quantity of cortical and cancellous bone may be harvested from the parietal region, utilizing the split in situ calvarial graft as originally proposed by Tessier in 1982, who gave a systematic description of the various methods for harvesting and grafting parietal bone in craniofacial reconstruction [27].

9.5.2 Anatomic Evaluation The region of the calvaria comprises the skull vault, extending antero-posteriorly from the frontal bone along the parietal bones to reach the squama occipitalis and laterally to the superior temporal line of the parietal bone. There are several layers from the top to the deeper plane: Pensler and McCarthy showed that the thickness of the calvaria in the parietal region has a mean value of 7.45 ± 1.03 mm [28]. The superficial plane, with a total thickness of about 4–5  mm, is represented by the skin (par-

ticularly thick in this area), the subcutaneous connective tissue and the pericranial aponeurosis, also called galea capitis which are strongly connected. The subcutaneous connective tissue is characterized by the following structures: • The parietal and auricular posterior arteries, with their numerous anastomoses. • The parietal veins. • Lymphatic vessels, which mainly drain into the retro-auricular lymph nodes. • Some diverging rami from the auriculotemporal nerve, which give sensitive innervation of the zone.

9.5.3 Pharmacological Aspects Before surgery patient undergoes prophylactic broad-spectrum antibiotic treatment with penicillin and clavulanic acid (3 g/day). The treatment is then continued for 10 days. During surgery, the patient is given 8  mg of dexamethasone and 4 mg on the same evening to avoid oedema. Ketorolac, metoclopramide and H2 receptor antagonists are also administered to prevent the most frequent post-surgical symptoms, while buprenorphine is used intravenously for at least 6 h in the postoperative period.

9.5.4 Surgical Technique 9.5.4.1 Graft Harvesting The Galea capitis is a fibrous lamina that covers the mid-part of the cranial vault and joins together the frontal and occipital muscles. Under this layer, there is lax subaponeurotic connective tissue, called supraperiosteal Merkel space, which allows the Galea to slide over the periosteum, also called pericranium. The last layer is formed of two types of compact bone (outer and inner tables) with an interposed layer of cancellous bone called diploe, which is highly vascularized by rami of the parietal artery exocranially, and endocranially by the rami arteriae meningeal media.

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Fig. 9.15  Before undergoing surgery, the scalp is cleaned up three times with povidone-iodine solution. Once the operating field is prepared, an infiltration with cold water is performed in order to obtain the mechanical detachment of the galea capitis

The postero-medial region of the parietal bone near the lambda suture, at least 2  cm from the medial line, laterally outside the temporal muscle insertion and anteriorly behind the coronal suture is the most favourable and safe donor site because of its thickness. There are no posterior limits to the donor site, which may thus extend to the occipital bone especially if a large quantity of bone is needed. When exposing the cranial vault, the fascia temporalis superficial, which covers the muscle, is revealed by the tenacity of the insertion on the bony table. The area surrounding the incision line is carefully disinfected and dried with sterile gauze, then infiltrated with generous amounts of physiological solution (Fig. 9.15).

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Fig. 9.16  Full-thickness incision of the scalp, detachment with single layer of the tissue (skin, soft tissues and galea capitis) and positioning of the hemostatic clips without blood vessels cauterization to preserve the follicles’ integrity

The incision, at least 10  cm long, is always made with a scalpel to avoid damaging hair bulbs and in the sagittal direction. Sometimes is better an irregular incision line, which can mask the scar easily (Fig. 9.16). Once the first incision has been made, the scalp can be detached from the underlying pericranium for several centimetres, via sub-fascial access: at this point, the Raney disposable scalp clips are carefully positioned to provide haemostasis, with the dual advantage of greatly reducing operative time and maintaining the hair bulbs (Fig. 9.17). When the donor site is completely exposed, the outline of the first strip is drawn with a round 2 mm diameter bur under abundant irrigation with refrigerated physiological solution (Fig.  9.18). Particular care must be taken to

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Fig. 9.17  Image of the parietal theca with the coronal suture and the frontal bone. The operating field must be located as described in the text at least 2  cm from the median line, away from the sutures, on the parietal bone to the insertion of the temporal muscle

stop at the point when resistance to advancement of the bur lessens and slight bleeding occurs. When the fragment is completely drawn to the chosen depth, it can be slightly detached using a metal hammer and different angled scalpels (Figs.  9.19, 9.20, 9.21, 9.22, and 9.23). The margin of the donor sites should be blunted with bone scrapers, in order to gain large amounts of bone chips which are extremely useful for the following surgical procedures (Figs. 9.24, 9.25, 9.26, and 9.27).

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Fig. 9.18  The first bone sample, a splitting in situ calvarial graft, is drawn using a piezoelectric device or a drilling instrument as described. The groove of the first sampling must be quite wide in order to allow the insertion of the osteotome chisels

Finally, if soft tissues are detached correctly, the pericranial layer is sutured using 3/0 slow-­ resorption sutures. For suturing the skin flaps, metal clips or 3–4/0 silk or synthetic suture thread may be used, according to the surgeon preference especially when the incision lies entirely above the hairline. In case of little hair or where the incision is below the hairline, an intra-dermal suture with 4–5/0 synthetic tread is preferable (Figs. 9.28 and 9.29). After closure and cleaning of the surgical wound, sterile gauze is placed and covered with

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Fig. 9.19  First fragment withdrawal from which it is possible to know the bone morphology and then proceed more quickly in the subsequent phases of the surgery

Fig. 9.20  Image magnification of the parietal graft morphology where the spongious and the cortical component ratio are clearly evident (graft thickness more than 4 mm)

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Fig. 9.21  Using curved chisels it is possible to proceed without making large grooves inside the graft and therefore without losing bone substrate to proceed to pick up the subsequent fragments

Fig. 9.22  During each phase of the surgery it is possible to obtain large quantities of particulate bone (the bone scraper is chamfering the margin of the donor site)

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Fig. 9.23  After the initial grafting, is possible to use straight chisels in order to perform the bone grafting

Fig. 9.24  After the splitting, into the donor site visible full-thickness bone islands are left to promote a better healing. The perimeter area is beveled with a bone scraper in order not to make the sampling area perceptible to the patient Fig. 9.25  The bone grafts

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Fig. 9.26  Bone-particles for the reconstructive phase

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Fig. 9.28  Hemostasis control by collagen cloth, resorbable sutures in the lower layers with interrupted suture in the deep layers. Metal grafts are used in the most superficial part

Fig. 9.29  At the end of the surgery a compressive medication of the scalp is placed for 2 days without drains

Fig. 9.27  Part of the bone particle is repositioned inside the sampled site to reduce the perception of the sampling area. Note the wide bevel over the entire circumferential margin of the sample

cotton and an elastic bandage for 24  h. An ice pack directly on the bandage above the harvest area is also indicated in the first few hours after surgery.

9.5.5 Graft Positioning The recipient site must be subjected to a careful clinical examination; in the illustrated case, as in

the vast majority of cases treated with this type of surgery, the atrophy of the alveolar ridge (Cawood and Howell class IV/V) is clearly observed. (Fig. 9.30). After having performed the local anaesthesia, as previously described, the surgical flap is lifted through a crestal access started anteriorly from the canine region and posteriorly from the tuberous region. An antrostomy is then performed by removing the lateral wall of the maxillary sinus, followed by the elevation of the sinus membrane according to classical sinus elevation techniques (Fig. 9.31). Two slots are made, respectively, in correspondence of the anterior canine recess and of the tuberosity region. The trapezoidal bone block is then inserted in order to reconstruct the new floor

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of the sinus (the cortical portion of the graft is directed upwards in contact with the raised membrane while the trabecular portion is turned downwards) (Fig. 9.32). The inferior portion is then filled with the bone chips previously collected from the residual alveolar bone crest. Once positioned and stabilized, according to the lag-screw technique, the space between the bone blocks must be filled with bone chips and covered with collagen tissue (Fig.  9.33). The flap is then repositioned and sutured, granting a complete covering of the regenerated area avoiding any tension (Figs. 9.34 and 9.35).

Fig. 9.30  Intraoral aspect of alveolar ridge with Cawood and Howell atrophy class IV/V

Fig. 9.31  Crestal access with vertical releasing incisions. Antrostomy through lateral sinus wall removal (2  cm  ×  1.5  cm) is followed by elevation of the sinus membrane

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Fig. 9.32  Performing of the two slots and insertion of a trapezoidal bone block (the cortical side of the graft upwards in contact with the elevated sinus membrane and spongious face down)

Fig. 9.33  Positioning of the bone chips previously collected and initial reconstruction of the residual alveolar ridge

Fig. 9.34 Positioning and stabilization of the bone blocks according to the lag-screw technique, followed by filling of any residual free space with bone chips and covering with collagen tissue

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bone grafts show good resistance to infection and can be successfully handled using local wound treatment, cleansing with disinfectant solutions and antibiotic treatment. In sinus bone grafting, symptoms of transient sinusitis are frequent and can usually be successfully treated with decongestants and antibiotics. If necessary, a drainage should be performed crestally or with a nasal antrostomy. Fig. 9.35  Flap repositioning in order to cover the regenerated area without tensions

9.5.6 Complications Although the majority of studies reported in the literature have shown no complications at the donor sites [29, 30], Kline and Wolfe investigated various complications associated with cranial bone grafts, which can be divided into generic and neurological complications [31]. Among the generic complications, they listed • Exposure and laceration of the dura mater • Serohaematoma • Infection of the surgical wound The exposure of the dura mater occurs in 10% of cases and does not constitute a complication, and can be avoided by covering the exposure with bone chips. In case of dural laceration, the neurosurgeon should suture and suspend the dura mater. The onset of serohaematoma can be avoided using a pressure dressing kept in place for 24–36 h. Infection of the surgical wound is usually due to sepsis of the alloplastic materials used to achieve haemostasis. The incidence of neurological complications is extremely rare (0.02% of cases) and consists of extradural, subdural and intracerebral haematoma and are operator-dependent [31]. The most frequent complication is represented by wound dehiscence, especially if the suture site is under tension after wound closure. Membranous

9.5.7 Augmentation Methods The most important condition in order to achieve success in bone grafting is a total balance between the rigid fixation of the graft and the adequate vascularization of the recipient site, which must be free of infections. Rigid fixation is usually obtained with the lag-­ screw technique [32], which consists of fully threaded maxillofacial screws placed through the first hole in the near cortex and a threaded hole in the far cortex. Great care must be taken to achieve perfect fixation and stabilization of the bone grafts, which must be fully covered with soft tissue, avoiding tensions. Some studies determined that the compression between the two bone surfaces, by reducing the interface gap, produces better and more rapid healing because it reduces the need for osteogenesis. Bone chips should be interpositioned in the gap, improving coaptation between the two bony interfaces. In knife-edge edentulous alveolar ridges (Cawood class IV atrophy) [33] which is most frequent in the maxilla, the main indication is transversal ridge reconstruction via lateral bone block grafts, while in Cawood & Howell atrophy classes V and VI, vertical bone grafting by overlapping grafts is the most suitable method for the reconstruction of the basal bone. In some cases, sinus floor rebuilding is required, and in this case, an incision of the vestibular mucosa at 6  mm from the insertion line of the attached mucosa should be performed. After a large antrostomy, more than 2 cm in diameter and the subsequent

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sinus mucosa detachment, two slots should be made into the nasal and zygomatic buttresses of the external wall of the maxilla, in order to offer a good stabilization of the new antral floor bone graft. The bone box under the new floor should be filled with previously harvested bone chips. The antrostomy can be closed with a resorbable membrane sited above the muco-periosteum, or with a graft to enlarge the alveolar ridge horizontally. The oral mucosa is sutured with 4/0 nylon or silk. In any case, temporary removable prostheses are to be avoided in these cases to prevent mechanical stress and bone resorption.

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for the formation of bone. Membranous bone heals with the road-like characteristics of cortical bone, with a greater number of thicker trabeculae, as well as lower connectivity than endochondral bone. Integration of an intramembranous graft with the recipient membranous bone is characterized by the presence of osteogenic cells that do not pass through an intermediate cartilaginous stage. We believe that lag-screw fixation of autogenous calvarial grafts represents the gold standard for reconstruction of large bony defects of the jaws, where the recipient site is vascularized and the defect itself can be covered with the help of the surrounding soft tissues. Finally, both morphologic analysis and immu9.5.8 Discussion nohistochemical analysis as stated by the literature, suggest a continuous and effective new bone Four months after bone grafting, the majority of formation and remodelling, a consequent full patient undergo dental implant treatment. At this integration of the calvarial graft with the host tispoint, biopsies of the grafted bone have shown sue, thus making this kind of intervention the that calvarial grafts are well incorporated into the most suitable for bone grafts not only by the clinbasal bone [34]. At the radiographical analysis, ical and biomechanical criteria but also by a biocortical bone maintains its density: radiolucency molecular point of view [36]. increases in cancellous bone, showing an increase In the clinical cases we treated with the calin density, and the gaps between grafts and/or varial grafts, the implants were inserted only between the graft and the recipient site disappear. after 4–6 months. In this way it was possible to Prosthodontic treatment begins after place a considerable amount of submerged 3–4  months with provisional prostheses, while implants in the grafted bone. The loading of the the final rehabilitation is placed after a period of implants took place from 3 to 4 months after their progressive and functional loading, which will positioning, after all the osseointegration proguarantee a stable interface of the grafted bone. cesses occurred. Lastly the definitive prostheses The fate of a bone graft depends on many factors have been placed 4, 6 months later. including the local environment, periosteal presAs described in a retrospective study we conervation, mechanical forces and micro-­ducted with 10-year follow-up [37], primary and architecture features. secondary outcomes have been considered. The primary determinant of bone graft behaviour is the interaction between the micro-­ • The primary ones, which resulted of a 97.10% architectural features of the bone graft and the survival rate, were related to the dental local mechanical environment in which the bone implants survival, based on the examination of graft is placed. several aspects including clinical mobility, Survival is optimal when bone grafts closely peri-implant radiolucency, pain or suppuration duplicate the architecture of the recipient site in the implant sites and signs of peri-­ [34]. At this point, graft fixation with lag screws implantitis; success rate, defined as implant is extremely important to minimize any micro-­ survival plus marginal bone loss less than 1, movements, which could lead to early resorption 5 mm after 1 year of loading and no more than of the graft and fibrosis [35]. If minimal deforma0.2  mm of loss between any two follow-up tion exists from the start, the conditions are met appointments after the first year of function;

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6. Tayapongsak P, Wimsatt JA, LaBanc JP, Dolwick MF.  Morbidity from anterior ilium bone harvest. A comparative study of lateral versus medial surgical approach. Oral Surg Oral Med Oral Pathol. 1994;78(3):296–300. 7. Yamamoto T, Nagira K, Kurosaka M.  Meralgia paresthetica occurring 40 years after iliac bone graft harvesting: case report. Neurosurgery. 2001;49(6):1455–7. 8. Nodarian T, Sariali E, Khiami F, Pascal-Mousselard H, Catonné Y. Iliac crest bone graft harvesting complications: a case of liver herniation. Orthop Traumatol Surg Res. 2010 Sep;96(5):593–6. 9. Lementowski PW, Lucas P, Taddonio RF.  Acute and chronic complications of intracortical iliac crest bone grafting versus the traditional corticocancellous technique for spinal fusion surgery. Orthopedics. 2010;33(4). Postoperative implant failures included peri-­ 10. Tetè S, Vinci R, Zara S, Zizzari V, De Carlo A, Falco G, Tripodi D, Cataldi A, Mortellaro C, Gherlone E. Long-­ implantitis, clinical mobility and paresthesia, term evaluation of maxillary reconstruction by iliac while graft complications that occurred included bone graft. J Craniofac Surg. 2011;22(5):1702–7. wound dehiscence, phlogosis, pressure ulcers https://doi.org/10.1097/SCS.0b013e31822e5cbd. and graft failure. PMID: 21959416. In conclusion, due to the greater invasiveness 11. Aalam A-A, Nowzari H.  Mandibular cortical bone grafts part 1: anatomy, healing process, and and higher costs, interventions involving bone influencing factors. Compend Contin Educ Dent. harvesting from extraoral sites are less suitable 2007;28(4):206–12; quiz 213. compared to less invasive techniques; however, 12. Kieser J, Kieser D, Hauman T. The course and distribution of the inferior alveolar nerve in the edentulous they are specifically indicated for the treatment of mandible. J Craniofac Surg. 2005;16:6–9. extreme atrophy of the jaws. Previous reports 13. Rosse C, Gaddum-Rosse P. Hollinshead’s textbook of explored the predictability of minimally invasive anatomy. 5th ed. Philadelphia: Lippincott and Raven techniques for full-arch rehabilitations supported Co; 1997. by axial and tilted implants. However, in extreme 14. Ash M, Nelson S. Wheeler’s dental anatomy, physiology and occlusion. 8th ed. Missouri: Saunders Co; bone atrophy, the alternative approach is extra2003. p. 1–515. oral grafting, of which calvaria seems to be the 15. Gray JC, Elves MW.  Donor cells’ contribution to most predictable site [37]. osteogenesis in experimental cancellous bone grafts. Clin Orthop Relat Res. 1982;163:261–71. 16. Burwell RG.  Studies in the transplantation of bone. VII.  The fresh composite homograft autograft of References cancellous bone; an analysis of factors leading to osteogenesis in marrow transplants and in marrow-­ 1. Shaw KA, Griffith MS, Shaw VM, Devine JG, containing bone grafts. J Bone Joint Surg Br. Gloystein DM.  Harvesting autogenous cancellous 1964;46b:110. bone graft from the anterior iliac crest. JBJS Essent 17. Fonseca RJ, Clark PJ, Burkes EJ Jr, et  al. Surg Tech. 2018;8(3):e20. Revascularization and healing of onlay particulate 2. Hall MB, Smith RG. The medial approach for obtainautologous bone grafts in primates. J Oral Surg. ing iliac bone. J Oral Surg. 1981;39(6):462–5. 1980;38:572–7. 3. Sudhakar KNV, Mohanty R, Singh V.  Evaluation of 18. Kusiak JF, Zins JE, Whitaker LA. The early revascudonor site morbidity associated with iliac crest bone larization of membranous bone. PlastReconstr Surg. harvest in oral and maxillofacial, reconstructive sur1985;76:510–6. gery. J Clin Diagn Res. 2017;11(6):ZC28–ZC33. 19. Albrektsson T. Repair of bone grafts. A vital micro4. Del Fabbro M, Wallace SS, Testori T.  Long-term scopic and histologic investigation in the rabbit. implant survival in the grafted maxillary sinus: a sysScand J Plast Reconstr Surg. 1980;14:1–12. tematic review. Int J Periodontics Restorative Dent. 20. Enneking WF, Burchardh H, Puhl JJ, et  al. Physical 2013;33(6):773–83. and biological aspects of repair in dog cortical bone 5. Prein J. Manual of internal fixation in the cranio-facial transplants. J Bone Joint Surg Am. 1975;57:237–52. skeleton. Berlin, New York: Springer; 1998.

and restoration success determined as the absence of fractures of prosthetic elements even if one or more implants supporting the restoration were removed. On a total of 207 fixtures positioned, only 6 failed but have been removed and replaced. • The secondary outcomes which resulted of a 96.88% survival rate included graft survival and incidence of postoperative complications. Only in a single case, partial removal of the graft was necessary due to an inflammatory reaction of a possible infectious aetiology that did not respond to antibiotic therapy.

230 21. Alberius P, Dahlin C, Linde A. Role of osteopromotion in experimental bone grafting to the skull: a study in adult rats using a membrane technique. J Oral Maxillofac Surg. 1992;50:829–34. 22. Hedbom E, Heinegard D. Interaction of 59-kDa connective tissue matrix protein with collagen I and II. J Biol Chem. 1989;264:6898–905. 23. Pikos MA. Atrophic posterior mandibular reconstruction utilizing mandibular block autografts: risk management. Int J Oral Maxillofac Implants. 2003;18:765–6. 24. Ermis I, Poole M. The effects of soft tissue coverage on bone graft resorption in the craniofacial region. Br J Plast Surg. 1992;45:26–9. 25. Khoury F, Antoun H, Missika P. Bone augmentation in oral implantology. Quintessence; 2007. 26. Milinkovic I, Cordaro L. Are there specific indications for the different alveolar bone augmentation procedures for implant placement? A systematic review. Int J Oral Maxillofac Surg. 2014;43(5):606–25. 27. Tessier P. Autogenous bone grafts taken from the calvarium for facial and cranial applications. Clin Plast Surg. 1982;9(4):531–8. 28. Pensler J, McCarthy JG.  The calvarial donor site: an anatomic study in cadavers. Plast Reconstr Surg. 1985;75(5):648–51. 29. Cenzi R.  Zuccarino L Gli innesti di calvaria in chirurgia cranio-maxillo-facciale. In: Renda A, Masciariello S, Gagliardi C, Landi M, editors. Scritti in onore di Costantino Giardino. Napoli: Giuseppe De nicola. Editore; 2004. 30. Tulasne JF, Renouard F. La complexiti anatomique en implantologie. J Periodontol. 1992;11:193.

R. Vinci 31. Kline RM, Wolfe SA. Complications associated with the harvesting of cranial bone grafts. Plast Reconstr Surg. 1995;95:5–13. 32. Atik F, Atac MS, Ozkan A, Kilinc Y, Arslan M. Biomechanical analysis of titanium fixation plates and screws in mandibular angle fractures. Niger J Clin Pract. 2016;19(3):386–90. 33. Cawood JL, Howell RA.  A classification of the edentulous jaws. Int J Oral Maxillofac Surg. 1988;17(4):232–6. 34. Manson PN.  Facial bone healing and bone grafts. A review of clinical physiology. Clin Plast Surg. 1994;21(3):331–48. 35. Vinci R, Rebaudi A, Capparè P, Gherlone E.  Microcomputed and histologic evaluation of calvarial bone grafts: a pilot study in humans. Int J Periodontics Restorative Dent. 2011;31(4):e29–36. PMID: 21837297. 36. Tetè S, Vinci R, Zara S, Zizzari V, Cataldi A, Mastrangelo F, Mortellaro C, Gherlone E.  Atrophic jaw reconstruction by means of calvarial bone graft: long-term results. J Craniofac Surg. 2010;21(4):1147– 52. https://doi.org/10.1097/SCS.0b013e3181e484a7. PMID: 20613590. 37. Vinci R, Teté G, Lucchetti FR, Capparé P, Gherlone EF.  Implant survival rate in calvarial bone grafts: a retrospective clinical study with 10 year follow-up. Clin Implant Dent Relat Res. 2019;21(4):662–8. https://doi.org/10.1111/cid.12799. Epub 2019 May 28. PMID: 31140209.

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Kurt Schicho and Godoberto Guevara Rojas

10.1 Introduction

of planning data with the corresponding postoperative outcome cannot be accomplished with Reconstructive surgery in the maxillary region is sufficient reliability: This is obvious from theoa sophisticated task in terms of three-dimensional retical estimations because considering the error spatial sense during diagnosis and preoperative propagation throughout this process reveals that planning as well as in terms of surgical complex- the order of magnitude of the evaluation process ity, e.g. when free flaps (such as fibula grafts) are is comparable to the intended soft-tissue change required. Considering the specific anatomy close itself. by the maxilla, besides the delicate vascular and Nevertheless, preoperative computer-assisted nervous structures in the nasal, zygomatic and planning and simulations in the maxillary region infraorbital region, particularly, the thin infraor- can provide valuable support for the surgeon bital skin hampers mathematical soft-tissue sim- throughout the reconstructive treatment. Not only ulations. Consequently, predictions of the does the simulation procedure itself allow the postoperative look by means of simulations of physician to “virtually immerse into the complex soft-tissue changes according to variations of the anatomy”. Moreover, we can derive accurate 3D subjacent bony structures are notably demand- datafiles (typically in -.stl format) from the planing. In particular, quantitative evaluations of soft-­ ning for the fabrication of individualized implants. tissue predictions at and caudally to the In this article, we illustrate four distinct but infraorbital rim by means of imaging data fusion paradigmatic treatment workflows, all of them based on computer-assisted planning, in order to Based on original research published with/by Arnulf reveal the full integration of medical imaging, Baumann, Rolf Ewers, Clemens Klug, Emeka Nkenke, virtual reality, rapid prototyping and intraoperaFranz Watzinger. tive navigation. These examples also reveal the progress of 3-dimensional planning in reconstructive K. Schicho (*) procedures. Department of Oral and Maxillofacial Surgery, The presented treatment workflows (clinical Medical University of Vienna, Vienna, Austria cases) are as follows: e-mail: [email protected] G. Guevara Rojas University of Applied Sciences, FH Campus Wien, Wien, Austria e-mail: [email protected]

1. Point-to-point navigation-assisted repositioning of the zygoma by means of pre-bent osteosynthesis plates.

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2. Complex orbital reconstruction (orbito-­ are involved, in case the surgeons themselves zygomatico-­maxillary complex, OZMC) after are not trained with the planning software. In a comminuted fracture using a combination of any case, a tight coordination and communicatitanium mesh and synthetic material, accomtion also with the radiologist, respectively, the panied by intraoperative navigation. radiological technologists are required. 3. Correction of midfacial deformity (hypopla- 3. Decision on and detailed planning of the treatsia) by means of individualized polyether-­ ment strategy, such as ether-­ketone (PEEK) implants. (a) Reconstruction by means of autologous 4. Maxillary reconstruction with prefabricated bone graft or biocompatible materials manvascularized free fibula flap with dental ufactured in a rapid prototyping procedure. implants already inserted before harvesting (b) Application of surgical templates (e.g. the flap. cutting guides), step-by-step “haptic simulation” of surgery and preforming of In addition to these selected examples (casuosteosynthesis plates on a 3D stereolithoistics), up-to-date computer planning even graphic skull model of the patient. allows for insertion of implants into bone grafts (c) Intraoperative computer-assisted navigabefore harvesting them. However, the intention tion and/or use of 3D templates and rapid of this article is to sketch some very basic conprototyping guides. cepts for the implementation of virtual planning and intraoperative navigation in the maxillary Following, we describe the treatment workregion. These concepts can individually be flow as mentioned above in three examples. adapted and modified according to other specific problems [1–4].

10.3 Clinical Case I (Surgery by Rolf Ewers and Clemens 10.2 Diagnostics Klug): Point-to-Point Navigation-Assisted In computer-assisted maxillary reconstruction, Repositioning of the Zygoma diagnostic analysis is substantially (the same) as in by Means of Pre-bent conventional procedures (approaches). Computed Osteosynthesis Plates tomography is the standard diagnostic tool (imaging modality). In consideration of subsequent virtual planning and rapid prototyping concepts, specific radiographic protocols may be required. Overall, post-oncological as well as post-­ traumatic (in many respects both in fact are a similar task in terms of computer-assisted planning) are based on the following: 1. 3D analysis of the specific (i.e. deficient) anatomy. 2. Virtual design and simulation of the acquired (aspired) anatomy, which means mirroring from the contralateral, intact side. Various wellengineered software solutions are commercially available for routine clinical application. However, in-depth experience and technical skills are mandatory to take benefit from this technology. Frequently, also planning engineers

Zygomatic fractures are a frequent kind of trauma. When the healing occurs in a deficient position, not only aesthetic but also functional issues arise (diplopia). Repositioning of the zygoma has to be done precisely, otherwise the functional restraints cannot be resolved. In [5, 6] a straight-forward concept has been described, based on preoperative planning using a stereolithographic skull model of the patient for pre-­ bending of the osteosynthesis plates. By means of intraoperative navigation, the holes for the osteosynthesis plates are drilled exactly according to the plan before the malpositioned zygoma is being mobilized. In this manner, the holes for fixation of the osteosynthesis material are already finished when the zygoma is osteotomized, and the pre-bent plates immediately fit exactly, without needing intraoperative adaption.

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10.3.1 Preoperative Planning See Figs. 10.1, 10.2, and 10.3.

Fig. 10.1  As preparation, an occlusal resin splint with several (e.g. about 8–10) tiny metallic markers for registration is fabricated and attached to the patient before computed tomography (CT)

Fig. 10.3  In the next step, the zygoma is moved back into its deficient position and mounted, e.g. using a glue. The drill holes for the (now already bent) osteosynthesis plates are stored within the surgical navigation system. For this purpose, a reference frame (representing a coordinate system) has to be connected to the skull model

10.3.2 Surgical Procedure Intraoperatively, the procedure is straight-­ forward, without any need for repeated adaptions of the plates to the bony requirements: A dynamic reference frame (serving as coordinate-system for navigation) is connected to the drill handle, the instrument is registered and the holes for the plates are being positioned according to the stored coordinates (Fig. 10.4).

Fig. 10.2  According to the CT data, a stereolithographic skull model including also the positions of the markers as in the splint is printed. The design of the stereolithographic model with the marker positions is subject to engineering considerations. Therefore, the reference landmarks are integrated in small “bars” at the surface and the whole model does not reflect the “look” of the patient wearing the occlusal splint. Now, osteotomy and repositioning of the zygoma can be simulated with haptic impression at the skull model, allowing the bending of the plates. Having finished this procedure, the plates are removed and sent to sterilization

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Fig. 10.4  After mobilization of the zygoma, the plates immediately fit and the zygoma can be fixed in the definite position

10.4 Clinical Case II (Surgery by Arnulf Baumann): An Orbito-­ Zygomatico-­Maxillary Complex (OZMC) Fracture Is Corrected by Using a Combination of Titanium Mesh and Synthetic Material, Accompanied by Intraoperative Navigation

The patient has undergone a treatment of a comminuted fracture of the right zygoma with affection of the orbit, maxilla and the lacrimal drainage system. The outcome was not adequate and a secondary reconstruction was wished by the patient. The CT scan is analysed using the Materialise Mimics™ software (Figs. 10.5, 10.6, 10.7, 10.8, 10.9, 10.10, and 10.11).

10.4.1 Preoperative Planning

10.4.2 Surgical Procedure

Fracture of the OZMC must be optimally diagnosed and reconstructed. The interruption of this normal anatomical situation results in aesthetic constraint and functional impairments. Secondary corrections in this region are complex out of involvement of hard and soft tissue. The first step will be to reconstruct the bony structure. Therefore, a 3D analysis is necessary based on a CT scan. In this case, dislocated bone fragments, already-inserted osteosynthesis materials and scarring aggravate the preoperative planning [7, 8].

Intraoperative navigation using commercial image-guided surgery equipment can facilitate the reconstruction according to the preoperative planning. Already a very basic “point-to-point” navigation, i.e. just displaying the position of defined “landmarks” such as edges and corners of the implants relatively to the patient’s anatomy, supports the realization of the planning. The imaging data from the preoperative simulation can be used for navigation. In this area, landmarks suitable for the registration procedure are easily identifiable (Fig. 10.12).

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Fig. 10.5  Standard coronal, axial and sagittal views from computed tomography within the Materialise Mimics™ software in a 3D view. Patient’s anatomy can be better

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analysed, segmented and discussed as by conventional treatment settings

b

Fig. 10.6 (a) Segmentation of the defect provides an illustrative view that supports the preoperative assessment and can also be used as a tool to explain for the patient the need and complexity of the reconstructive procedure. The

visualization can be rotated arbitrarily. (b) Various cutting planes can be defined for a precise quantitative analysis of anatomical details

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a

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Fig. 10.7 (a) Mirroring from the intact (i.e. left) side gives an approximation of the favoured geometry and leads to the design of an implant. Numerous automatized, respectively, semi-automatized procedures are available in the software. Segmentation, planning and implant design are still a demanding tasks, requiring technical

knowledge and skills. (b) The planned PEEK (polyether-­ ether ketone) for reconstruction of the lateral part of the orbit, zygoma and the infraorbital rim. The final version of the implant design can be transferred to a manufacturing site as an -.stl (stereolithography format) file

Fig. 10.8  A titanium mesh is planned to reconstruct the orbital floor and the medial wall

Fig. 10.9  The mesh can be viewed and rotated three-­ dimensionally. An -.stl file defines its geometry exactly and can be sent to a manufacturing site

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Fig. 10.10  Both simulations are done, i.e. for the PEEK implant at the lateral regions (right picture, red) as well as for the titanium mesh of the medial wall and orbital floor (left picture, yellow)

Fig. 10.11  Final step of the preoperative planning and implant design in this complex case: Fusion of the two implants, showing the planned reconstruction. Due to threshold settings some overlay artefacts have occurred. Mainly the edges and corners should be considered for positioning of the implants. Before surgery, these implants are manufactured according to the -.stl files

Fig. 10.12  Intraoperatively the fixation of both implants can be supported by means of basic point-to-point navigation to verify the correspondence of the actual implant positions with the corresponding planning

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10.5 Clinical Case III (Surgery by Franz Watzinger): Correction of Midfacial Deformity (Hypoplasia) by Means of Individualized Polyether-­ Ether-­Ketone (PEEK) Implants In midfacial hypoplasia is the aim to gain symmetry of the face. In contrast to the situation in case 2, in this situation, the prediction of the soft tissue is the essential aspect. Further, as aesthetic considerations are dominating, the invasivity, respectively, the extent of surgery has to be minimized. The plan was to do an onlay grafting with an individualized PEEK implant instead of a midfacial osteotomy, which might give more prediction for

a

Fig. 10.13 (a, b) Female patient with congenital midfacial hypoplasia. She declined extensive osteotomy, therefore, the described alternative approach based on onlay

the symmetry of the face. To acquire the design of the biocompatible onlay grafts, the desired postoperative outcome is visualized by soft-­ tissue simulations according to virtual movements of the (virtually) osteotomized bone. Having gained the desired facial surface within the simulation, the “difference” between the original and the desired situation is being calculated. Finally, this “difference” defines the design and geometry of the customized PEEK implant. This procedure is described for the correction of congenital midface hypoplasia [9].

10.5.1 Preoperative Planning See Figs. 10.13, 10.14, 10.15, 10.16, 10.17, and 10.18.

b

grafting has been chosen. (a) … conventional 2D photo; (b) … 3D photo

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Fig. 10.14  To enable an illustrative, realistic view (particularly also for patient information), the 3D renderings from computed tomography data were merged with conventional (2D) photos, which is possible, e.g. in Materialise Mimics™

a

b

Fig. 10.15  Virtual osteotomy, using Materialise SurgiCase™; (a) … original situation, (b) … after movement of the osteotomized segment

Fig. 10.16  The difference is being calculated …

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240 Fig. 10.17  Resulting in the 3D design of the PEEK implant for onlay grafting

a

Fig. 10.18 (a) To make the preparations more “vivid” and illustrative, in addition to the virtual planning and computer graphics also a classic 3D rapid prototyping skull model with the designed onlay grafts has been built. (b) Modifications of the graft design and position can be

b

made easily and integrated into the computer planning in an iterative procedure. This haptic feeling supports the surgeons’ imagination as well as the patient’s informed consent

10.5.2 Surgical Procedure To avoid scars in the facial region, the grafts were implanted through a coronary approach, which is particularly demanding regarding spatial orientation. Consequently, also in this case a navigation system was used during surgery in order to verify the exact correspondence between the ­pre-­planned and the actual graft positions (Figs. 10.19, 10.20, and 10.21).

Fig. 10.19  Intraoperative site, navigation (using electromagnetic tracking in this example) allows exact verification of graft position and orientation, although reliable anatomical landmarks are hardly identifiable

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Fig. 10.20  As a very basic but efficient method for navigation-­assisted implant orientation, the final version of the PEEK implant had been attached in the optimum position at the stereolithographic skull model and scanned in computed tomography again. Therefore, the “bone” as well as the onlay graft present this homogenous colour. This CT dataset was used for intraoperative navigation

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after a standard registration procedure, which is possible due to the exact correspondence between the model and the real patient. Quantitative aspects in this context are investigated separately in [6]. The centre of the cross hairs indicates the tip of the pointing instrument intraoperatively in real time

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a

b

Fig. 10.21 (a) Before and (b) 3 weeks postoperatively. Although some swelling is still present, a very natural result could be achieved. (Surgery by Franz Watzinger). Details in [9]

10.6 Clinical Case IV (Surgery by Emeka Nkenke): Maxillary Reconstruction with Prefabricated Vascularized Free Fibula Flap with Dental Implants Already Inserted Before Harvesting the Flap In tumour patients undergoing wide en-bloc resection at the maxilla as well as in cases of congenital irregularities, a free fibula flap is an established method for reconstruction. Optimization of the surgical workflow can be achieved by preparing the fibula flap with the dental implants already being inserted before harvesting the fibula. Consequently, the complete reconstruction including the implants can be accomplished simultaneously [8, 10–16]. As a clinical example, we summarize an exemplary treatment workflow of a female patient suffering from rhabdomyosarcoma (Figs.  10.22 and 10.23).

Fig. 10.22  Intraoral view

Fig. 10.23  Panoramic X-ray

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10.6.1 Preoperative Planning Preoperative computed tomography of the skull as well as of the fibula low leg is the base for simulation and planning. And, similar to the former examples, also this workflow can utilize 3D rapid prototyping: For both, the maxilla and the fibula, a rapid prototyping model can be manufactured. Impressions from the maxilla and the mandibula are taken in order to fabricate plaster casts. The cast of maxillary dentition is used for the preparation of a template, respectively, a surgical guide for the insertion of the dental implants using a thermoplastic sheet. Implant analogues are placed into a segment of the 3D fibula model. Tumour resection and subsequent reconstruction using the fibula segment are simulated on the cast model by means of the surgical templates. Alternative versions (i.e. various extent) of resection and appropriate reconstruction can immediately be considered on this cast model. Implant analogues placed in the fibula model enable the preparation of a surgical template for intraoperative application.

Fig. 10.24  Implants inserted into the fibula before osteotomy. Osteotomy at the maxilla as well as of the harvested fibula segment are performed using cutting guides as prepared on the models

10.6.2 Surgical Procedure Main steps of surgery itself do not differ from the conventional procedure, apart from the application of a surgical guide to insert the dental implants into the fibula exactly corresponding to the preoperative simulation immediately before osteotomy (Figs.  10.24, 10.25, and 10.26). Fig. 10.25  Fibula after osteotomy by means of the prefabricated cutting guide, resulting in the desired geometry “straight forward”, i.e. without need for iterative adaptions and modifications

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Fig. 10.26  Postoperative panoramic X-ray

10.7 Discussion Today, virtual planning and simulation are an established way to support and optimize complex surgical reconstructions in the maxillary region. Although the essential planning and navigation principles remain rather basic even in complex cases, their adaption to specific, individual situations is mentionable challenging and requires an interdisciplinary collaboration between surgeons and planning experts. Due to the fact that—in many settings—planning data for the design of customized implants have to be transferred to the manufacturing site, and the finished implants are returned to the hospital, data security issues have to be taken into consideration. Further, the involvement of different sites and stakeholders (surgical department, radiology department, planning engineer, implant manufacturer, sterilization unit) requires profound quality management and the implementation of clear standard operating procedures.

References 1. Wagner F, Figl M, Cede J, Schicho K, Sinko K, Klug C.  Soft tissue changes in patients undergoing intraoral quadrangular Le Fort II osteotomy versus conventional Le Fort I osteotomy. J Oral Maxillofac Surg. 2018;76(2):416–25. https://doi.org/10.1016/j. joms.2017.07.158. Epub 2017 Jul 25. PMID: 28822722. 2. Willinger K, Cede J, Guevara-Rojas G, Sinko K, Figl M, Schicho K, Nemec S, Klug C. Midfacial advancement line—a comparative evaluation of a new mea-

K. Schicho and G. Guevara Rojas surement method in orthognathic surgery. J Oral Maxillofac Surg. 2020;78(2):286.e1–9. https://doi. org/10.1016/j.joms.2019.10.013. Epub 2019 Oct 28. PMID: 31778641. 3. Willinger K, Guevara-Rojas G, Cede J, Schicho K, Stamm T, Klug C.  Comparison of feasibility, time consumption and costs of three virtual planning systems for surgical correction of midfacial deficiency. Maxillofac Plast Reconstr Surg. 2021;43(1):2. https://doi.org/10.1186/s40902-­020-­00284-­1. PMID: 33411020; PMCID: PMC7790928. 4. Willinger K, Guevara-Rojas G, Cede J, Schicho K, Stamm T, Klug C. Accuracy of soft tissue prediction of 2 virtual planning systems in patients undergoing intraoral quadrangular Le Fort II osteotomy. Plast Reconstr Surg Glob Open. 2021;9(2):e3326. https:// doi.org/10.1097/GOX.0000000000003326. PMID: 33680633; PMCID: PMC7929711. 5. Klug C, Schicho K, Ploder O, Yerit K, Watzinger F, Ewers R, Baumann A, Wagner A.  Point-topoint computer-assisted navigation for precise transfer of planned zygoma osteotomies from the ­ stereolithographic model into reality. J Oral Maxillofac Surg. 2006;64(3):550–9. https://doi. org/10.1016/j.joms.2005.11.024. PMID: 16487823. 6. Schicho K, Figl M, Seemann R, Ewers R, Lambrecht JT, Wagner A, Watzinger F, Baumann A, Kainberger F, Fruehwald J, Klug C. Accuracy of treatment planning based on stereolithography in computer assisted surgery. Med Phys. 2006;33(9):3408–17. https://doi. org/10.1118/1.2242014. PMID: 17022237. 7. Baumann A, Sinko K, Dorner G.  Late reconstruction of the orbit with patient-specific implants using computer-aided planning and navigation. J Oral Maxillofac Surg. 2015;73(12 Suppl):S101–6. https://doi.org/10.1016/j.joms.2015.06.149. PMID: 26608137. 8. Ploder O, Klug C, Voracek M, Backfrieder W, Tschabitscher M, Czerny C, Baumann A. A computer-­ based method for calculation of orbital floor fractures from coronal computed tomography scans. J Oral Maxillofac Surg. 2001;59(12):1437–42. https://doi. org/10.1053/joms.2001.28278. PMID: 11732031. 9. Guevara-Rojas G, Figl M, Schicho K, Seemann R, Traxler H, Vacariu A, Carbon CC, Ewers R, Watzinger F.  Patient-specific polyetheretherketone facial implants in a computer-aided planning workflow. J Oral Maxillofac Surg. 2014;72(9):1801–12. https://doi.org/10.1016/j.joms.2014.02.013. Epub 2014 Feb 15. PMID: 24679957. 10. Jaquiéry C, Rohner D, Kunz C, Bucher P, Peters F, Schenk RK, Hammer B. Reconstruction of maxillary and mandibular defects using prefabricated microvascular fibular grafts and osseointegrated dental implants—a prospective study. Clin Oral Implants Res. 2004;15(5):598–606. https://doi.org/10.1111/ j.1600-­0501.2004.01065.x. PMID: 15355403.

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11. Nkenke E, Agaimy A, Vairaktaris E, Lell M, von FW, Stamminger M.  Three-dimensional analyWilmowsky C, Eitner S. Case history report: immesis of changes of the malar-midfacial region after diate rehabilitation with a prefabricated fibula flap LeFort I osteotomy and maxillary advancement. following removal of a locally aggressive maxillary Oral Maxillofac Surg. 2008;12(1):5–12. https://doi. tumor. Int J Prosthodont. 2016;29(1):53–8. https:// org/10.1007/s10006-­008-­0094-­8. PMID: 18600355. doi.org/10.11607/ijp.4010. PMID: 26757329. 15. Nkenke E, Vairaktaris E, Schlittenbauer T, Eitner 12. Nkenke E, Eitner S.  Complex hemimaxillary rehaS.  Masticatory rehabilitation of a patient with cleft bilitation with a prefabricated fibula flap and cast-­ lip and palate malformation using a maxillary full-­ based vacuum-formed surgical template. J Prosthet arch reconstruction with a prefabricated fibula flap. Dent. 2014;111(6):521–4. https://doi.org/10.1016/j. Cleft Palate Craniofac J. 2016;53(6):736–40. https:// prosdent.2013.07.028. Epub 2013 Dec 19. PMID: doi.org/10.1597/15-­051. Epub 2015 Nov 17. PMID: 24360016. 26575963. 13. Nkenke E, Vairaktaris E, Hanke S, Hoffmann B, 16. Rohner D, Jaquiéry C, Kunz C, Bucher P, Maas Schlittenbauer T. Skeletal stability and complications H, Hammer B.  Maxillofacial reconstruction with in transantral maxillary distraction in patients with prefabricated osseous free flaps: a 3-year expecleft lip and palate. J Craniofac Surg. 2014;25(2):689– rience with 24 patients. Plast Reconstr Surg. 93. https://doi.org/10.1097/SCS.0000000000000607. 2003;112(3):748–57. https://doi.org/10.1097/01. PMID: 24621725. PRS.0000069709.89719.79. PMID: 12960855. 14. Nkenke E, Vairaktaris E, Kramer M, Schlegel A, Holst A, Hirschfelder U, Wiltfang J, Neukam

Zygomatic Implants. The ZAGA Concept

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Carlos Aparicio, Andrew Dawood, and Cemal Ucer

11.1 Indications The maxilla presents a particular challenge for the anchorage of dental implants. Even in the absence of present or historical disease, anatomical bone volume may already be limited and bony topography irregular, particularly posteriorly. Lack of posterior maxillary anchorage for dental implants is a relatively common problem which may be managed with a staged or simultaneous graft of bone harvested from a second surgical site or with a bone scaffold material. Grafting will extend, perhaps greatly extend the treatment period, and where a second site is involved results in a more invasive treatment which may be seen as more complex and daunting to the patient. Medically compromised or elderly patients may not be deemed to be fit for C. Aparicio (*) ZAGA Center Barcelona, International Teaching Scholar, Indiana University School of Dentistry, Indianapolis, IN, USA Zygomatic Unit at Hepler Bone Clinic, Barcelona, Spain e-mail: [email protected] A. Dawood Dawood and Tanner Central London, ZAGA Center London, London, UK C. Ucer University of Salford and ICE Postgraduate Dental Institute, Salford, UK ZAGA Center Manchester, Manchester, UK

extensive grafting procedures or repeated interventions. By angling the distal implant in a full-arch reconstruction to project beyond the anterior wall of the maxillary sinus many patients with moderate maxillary atrophy may be treated without the extra intervention and the inherent delay of a graft procedure. The use of an angled implant will broaden the distribution of the implant support for full-arch fixed bridgework, and make it possible to use longer implants so that immediate loading becomes more practical. However, in situations where the sinus extends anteriorly, or where the alveolar ridge is poorly developed or atrophic, useful distal extension of implant support may not be available. Zygomatic implants (ZI) are longer implants which extend beyond the maxilla to anchor into the zygomatic bone to offer secure support for implant-based reconstructions [1]. The zygomatic bone is generally available and able to offer robust implant anchorage, even where there has been a great deal of maxillary atrophy (Fig.  11.1a, b), and in more extreme situations, where the maxilla has been resected or irradiated. ZI, either on their own or sometimes in conjunction with regular dental implants (Fig. 11.2), are generally used to support a full-arch prosthesis. In a quadruple distribution, four ZI will provide support for a full-arch reconstruction even where there is a total absence of anchorage sites for regular dental implants (Fig. 11.3). There is a

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 M. Rinaldi (ed.), Implants and Oral Rehabilitation of the Atrophic Maxilla, https://doi.org/10.1007/978-3-031-12755-7_11

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a

b

Fig. 11.1 (a, b) Tomographic cut (a) and radiological profile (b) showing an extreme maxillary atrophy

Fig. 11.2  Panoramic radiological view of a patient with the presence of some bone in the premaxillary area, canine to canine, and the absence of bone in the premolar and molar areas. The installation of a combination of regular with zygomatic implants was chosen

Fig. 11.3  Panoramic radiological view of a patient with insufficient bone in the anterior, premolar, and molar maxillary zones. The installation of four zygomatic implants was chosen

considerable body of scientific evidence to support the use of ZI, with success rates that compare favorably with graft surgery in combination with dental implants [2]. However, when compared with treatment with dental implants, zygomatic implant reconstructions may present with an additional array of complications. Surgical protocols,

implant design, and surface characteristics have evolved over a 20-year period, and each element of change may impact upon the biological and mechanical stability of the implant and the prosthesis it supports. Changes in design and surgical protocols mean that few genuine long-term studies are available. As with any dental implant treatment, changes in health and circumstances and advancing age may affect prognosis, and so a carefully considered and cautious approach should be adopted when planning treatment. Certainly, the use of ZI should be reserved for situations where the use of conventional dental implants in a standard protocol is ruled out (Fig. 11.1a, b). From the patients’ perspective the functional outcome of an implant treatment incorporating grafting procedures, or treatment with zygomatic implants is similar. As with any implant treatment, properly informed consent is a key tenet, and patients must be made aware of the various alternatives and associated complications and limitations of both graft and zygomatic implant surgeries. When faced with the choice between a multi-step grafting process or a single-stage procedure with the added benefit of immediate loading of a provisional prosthesis, many individuals appear to have a strong preference for the zygomatic implant approach (Fig. 11.2). A history of sinusitis, smoking, and the presence of a parafunctional habit will all impact upon or influence the outcome of both grafting and zygomatic implant treatments. The argument for the use of zygomatic implant treatment is more compelling:

11  Zygomatic Implants. The ZAGA Concept

• As the impact of protracted or multiple treatments becomes more onerous, as with an elderly or medically compromised patient. Treating a patient with zygomatic implants in their 80s is clearly less likely to result in long-­term complications than treating a patient in their 50s. • As the extent of bone loss becomes more extreme, where donor site morbidity is more of a concern, or where grafting and implant placement cannot take place simultaneously; all leading to an increase in the number of surgical interventions, and an extended treatment period. • With increasing loss of function. Inability to manage a removable prosthesis, or the need to avoid wearing a prosthesis during lengthy and complex grafting procedures may make such prolonged treatment untenable. • Where an extensive implant and/or graft treatment has previously failed (Fig. 11.4). • Where a patient will not accept the loss of their teeth or tolerate a removable denture as a step towards graft treatment. • In oncology, where a maxillectomy or a partial maxillectomy has taken place. The zygomatic bone can usually be easily accessed at the time of resection.

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It may be preferable to consider alternative approaches to zygomatic implants: • In a younger patient. • Where lack of bone is less extreme, and the situation can be improved with minimal intervention—less extensive grafting, simultaneous grafting, and implant placement. • If front teeth (or implants) remain and appearance can be maintained or made acceptable to the patient, albeit on a provisional basis, such that grafting can take place without a great impact on quality of life, perhaps in preparation for more comprehensive treatment once a graft has matured. • When the need for the extra support offered by the zygomatic implant is marginal, and other alternatives such as angled, short, or narrow implants may be available, or where the dental arch may be shortened without much compromise to appearance or function. Zygomatic implants are most commonly used in full-arch treatments, where rigid splinting to other dental or zygomatic implants stabilizes the long, tilted, and apically anchored implant. This approach provides consistently predictable

Fig. 11.4  Radiological 2D cut and 3D image of a patient with a failing implant treatment

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results and has been well supported by the literature. The use of zygomatic implants for the support of short-span prosthesis is less well-studied. In this sort of situation, the patient may still have front teeth and may find their appearance to be acceptable despite the lack of back teeth. Temporization with a removable partial denture stabilized by the remaining teeth may be more manageable for the patient than in a full-arch treatment. Under these circumstances, use of a zygomatic implant for support of short-span bridge work may be more difficult to justify, particularly, in a healthy younger individual where graft treatment is straightforward. Nonetheless, the use of zygomatic implants in unilateral cases has the benefit of immediacy and may have a role in following extensive consultation with the patient. In oncology, where resection of the maxilla has taken place, the zygoma, including the lateral and infraorbital rim, can be an exceptionally useful site for implant anchorage. Possibilities include the use of a variety of zygomatic implants, special ‘oncology’ implants, customized implants, and standard dental implants with custom abutments. The implants can be used with overdenture attachments, or more ideally, splinted with milled bars to support obturators, or where closure of nasal or sinus openings has been carried out, with fixed bridgework. In this way, patients can appreciate a rapid and near complete return to full function without a need for microvascular anastomosis and free-flap surgery. Zygomatic implants can also be used as anchorage for a nasal prosthesis or where the radiation dose delivered to the alveolus excludes the possibility of reconstruction with regular dental implants.

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severely atrophied or discontinuous maxillae [3– 7], a long-term study on onlay bone grafting and simultaneous placement, the zygoma fixture was introduced by PI Brånemark et  al. in 2004 [1]. Twenty-eight consecutive patients were included. A total of 52 zygoma fixtures and 106 conventional fixtures were installed. Bone grafting was deemed necessary in 17 patients (60%). All patients were followed for between 5 and 10  years. The procedure indicated a “window” antrostomy in the uppermost lateral aspect of the anterior maxillary wall (Fig.  11.5). The sinus mucosa was then reflected and no special effort was made to keep it intact. According to PI Brånemark, “the direction of the zygoma fixture was selected to provide optimal stability over prosthetic requirements.” In other words, the original implant trajectory had, depending on the maxillary wall curvature, a more or less palatal entrance to achieve an intra-­ sinus path allowing for optimal implant anchorage in the zygomatic bone. Due to the palatal position of the zygoma fixtures, the palatal flap was thinned, and the fat tissue eliminated to prevent soft tissue inflammation around the abutments. Despite the palatal position of the heads of the ZI, in the case of concave maxillary walls, resulting in a prosthesis which may impinge upon

11.2 Technique Evolution 11.2.1 PI Brånemark Original Technique After several short-term initial communications reporting the possibility of the use zygomatic anchorage for dental prosthetic fixation in

Fig. 11.5 The skull image is showing the original Brånemark protocol for zygomatic surgery: “the direction of the zygoma fixture was selected to provide optimal stability over prosthetic requirements.” In other words, the implant trajectory had, depending on the maxillary wall curvature, a more or less palatal entrance to achieve an intra-sinus path allowing for optimal implant anchorage in the zygomatic bone

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occupying the tongue space, no patient discomfort and/or speech difficulties was reported [1]. Brånemark’s long-term study [1] reported 3 ZI failures and a survival rate for individual implants of 94.2%. The overall prosthetic rehabilitation rate was 96% at five years. A total of 8 out of the 28 patients experienced late sinusitis during the follow-up period (28.50%). Four patients (14.25%) presented recurrent sinusitis. They were treated by improving drainage from the sinuses through a new ostium inside the inferior turbinate. Radiographically diagnosed sinusitis with, clinically, symptom-free maxillary sinuses were found in another four patients (14.25%). In those cases, no treatment was required and regarded as necessary. Those results were consistent with the sinus reactions observed by Davo in 2008 on 71 immediately loaded ZI, that were followed for a 13 to 42  months of period [8]. In 2010, Bedrossian et al. reported a prospective follow-up of 36 patients followed from 5 to 7 years, treated using the immediate load protocol with a survival rate of 97.2% [9]. Aparicio et al. in 2012, reported on a long-term prospective study, 22 consecutive patients that were followed for at least 10  years after loading. The original two-stage ad modum Brånemark protocol and turned titanium-threaded implants were used. Two ZI were partly removed due to peri-­ implant infection at year nine. A cumulative survival rate of 95.12% was obtained (10  years CSR  =  95.12%). All patients maintained functional prostheses. In 2013, Davó et al. reported on a 5-year prospective study of immediately loaded zygomatic implants. The implant surfaces were either commercially pure titanium (machined) (44 implants) or porous titanium oxide (37 implants). The 5-year survival rate of immediately loaded zygomatic implants was 98.5% (68/69).

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shortcomings of the original Brånemark technique and to reduce post-operative pain. They claimed that in an already-resorbed maxilla, a sinus window can further compromise the precarious bone support of the remaining dental alveolus. They proposed a reduced antrostomy in the shape of a slot as opposed to the standard window osteotomy. The slot was drilled prior to implant placement following the planned path of the implant (Fig. 11.6). The palatal mucosa was reflected so that only the crest of the ridge was exposed. A rounded tungsten carbide drill was used to prepare a hole in the lateral wall of the maxillary sinus at the upper extreme contour of the zygomatic buttress. The zygomatic implant depth gauge was placed in the hole and positioned to simulate the angle of approach of the implant twist drill. A second hole was made on this line 5 mm above the crest of the ridge. A slot was then made connecting the 2 holes. A rounded drill was used to mark the implant anchoring zone on the maxillary crest at the first molar level. Through this perforation, the first 2.9-mm

11.2.2 The Slot Technique In 2000 Stella and Warner [10] described the sinus-slot technique in a technical note. The goal was to provide a solution to the prosthodontic

Fig. 11.6  Clinical picture showing a “slot” antrostomy. Note that since the slot is made before implant placement, the slot is not matching the final implant path. (Courtesy of Prof. Dr. Miguel Peñarrocha, ZAGA Center Valencia)

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drill was introduced and directly visualized through the prepared sinus slot. The drill was advanced superiorly towards the junction of the lateral orbital rim and zygomatic arch. In the same way, the pilot drill and 3.5-mm twist drill were also directed through the center of the sinus slot. The depth of the preparation was again confirmed with the zygomatic implant depth gauge, and the appropriate length implant was chosen [11]. Authors recommended for the first time a more conservative approach: incision, dissection, and osteotomy to achieve a better anatomical emergence of the ZI. The slot results in a smaller antrostomy and serves to orient the twist drills for implant placement under direct visualization [12]. Although the slot technique represented an improvement regarding prosthesis design, the technique had some drawbacks. For instance, the authors did not provide specific criteria for possible variations of the slot anatomical limits or implant path. The precision for the slot to completely match the implant shape was limited (Fig. 11.6). In other words, bone-to-implant contact (BIC) was not optimized. Slot antrostomy, prior to implant placement, may be unnecessary in the presence of maxillary wall concavities. Criteria relating the crestal implant entry point to the type of atrophy at the sinus floor were not provided either.

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mum follow-up period was at least 3  years. A total of 36 zygomatic implants, smooth turned titanium surfaces (Nobel Biocare AB, Göteborg, Sweden) were used (Fig. 11.7). According to the authors, the original indication for this approach was the presence of buccal concavities in the lateral wall of the maxillary sinus, which precluded the intra-sinus trajectory of zygomatic fixtures while positioning the implant head within a distance of 10 mm from the top of the alveolar crest. The implant site was prepared, with respect to the alveolar bone, drilling from the palatal side of the crest pointing to the zygomatic arch without making an opening into the maxillary sinus thus preserving the sinus membrane integrity (Fig. 11.7a). One concern with the technique may be the long-term effect of exposed threads directly adjacent to the soft tissues at the lateral aspect of the zygomatic implants. Aparicio et  al., however, reported healthy mucosa covering the extra-sinus part of the zygomatic implants in all patients. An explanation may be found on the use of this technique solely in patients with concave lateral maxillary walls and in taking surgical care to preserve the remaining alveolar bone volume (Fig. 11.7). They informed no signs of maxillary sinus infection with all implants maintaining stability and no implant failures observed during the follow­up period. The extra-sinus technique resulted in an emergence of the collar of the zygomatic fixture closer to the crest of alveolar bone of the maxilla, this was considered beneficial from a 11.2.3 The Extra-Sinus, Exteriorized, cleaning and patient-comfort point of view. and Extra-Maxillary Approach Later in 2008, Maló et  al. in a pilot study, using 5-mm diameter ZI with different pre-­ The next evolutionary technique that emerged established implant head angulations, described was the extra-sinus approach. The 1-year results a zygomatic implant technique where the reconfor this new technique were first described in the touring of the remaining crestal bone at the maxEnglish literature by Aparicio’s group in 2006 illary alveolus was systematically performed in [13]. Miglioranza et  al. also in 2006 [14] also order to achieve “only zygomatic anchorage of described a similar approach in Portuguese the implant.” When the patients presented with named the exteriorized technique in Portuguese. an over contoured external maxillary sinus wall, In a 3-year prospective study in 2008, Aparicio the maxillary sinus membrane was inevitably et al. [15] reported the results of the extra-sinus perforated, as it was in the pathway of drill direcplacement of the zygomatic implant (mid-­ tion. Out of the 18 patients that underwent the portion) on 20 consecutive patients recruited 1-year follow-up, four patients had sinus infecfrom October 2004 to October 2005. The mini- tion (22% of sinusitis if dropouts are consid-

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a

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b

Fig. 11.7 (a) Channel type of osteotomy used at the initial stages of the extra-sinus technique. The initial indication for the extra-sinus technique was limited only to just pronounce maxillary concavities [16]. (b) Prosthetically

driven extra-sinus implant placement respecting the remaining alveolar bone. Note the implant design corresponds to the original threaded, turned titanium Brånemark fixture

ered). This type of approach was called the “Extra-maxillary” technique. In a subsequent study, extending the previous one, Malo et  al. (2012) retrospectively reported 3-year use, 5-mm diameter, extra-­ maxillary zygomatic implants placed in 39 consecutive patients from January 2006 to October 2009 [17]. The maxillary alveolar bone was prepared to allow direct access by the drill to the entry point at the inferior aspect of the zygomatic bone, and the alveolar bone was not used for anchoring the extra-maxillary implant coronally. Six patients with sinus complications were reported (18%). Malo group further reported a long-term 7-year follow-up of the extra-­maxillary technique. In contrast to their earlier study, which included a total of 39 patients observed from January 2006 to October 2009 [17], a substantially higher number of patients were included in the new study (313 new patients in 2 years and 9 months) [18]. Reasons for much reduced incidence of sinus infections (8%) observed in the new study compared with the previously reported higher rates (18–22%) were not explained. A possible explanation for this improvement in the prevention of sinus infections may be related to a few surgical modifications the authors made in the latter study:

(ii) Moreover, the authors appear to have abandoned the previously reported technique of alveolar bone recontouring. (iii) As well as avoiding the exclusive use of 5-mm-diameter zygomatic implants.

(i) The use of a previously described “channel osteotomy” was introduced to minimize surgical damage occurring to the maxillary sinus membrane during extra-maxillary ZI bed preparation.

Nevertheless, the authors reported a high incidence of mechanical complications in 156 ZI patients (44%). This may be because the extra-­ maxillary implants, in this study, were retained by zygomatic bone anchorage only and/or because the implants were placed too parallel to each other thus increasing the prosthetic cantilevering. In the absence of a rigid alveolar crestal support, unfavorable stress distribution would have predisposed to these mechanical failures. According to Freedman et  al., 2015, occlusal stresses are higher than lateral stresses when there is lack of robust alveolar bone support for the implant neck. Despite the extra-maxillary implant allocation, none of Malo’s previously quoted studies [17–19] reported complications regarding soft tissue dehiscence or recession around zygomatic implants. Miglioranza et al. [20] retrospectively reported on the treatment of 75 patients with conventional implants compared with 150 zygomatic implants placed using the extra-maxillary (extra-sinus) approach. Although a life chart of the implants and dropout information were not reported, the implants were followed up for at least a year. Surgical technique involved using a round drill to penetrate the residual alveolar ridge near the crest, entering it from the palatal side and exiting

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on the buccal aspect of the ridge, then following an extra-sinus path before entering the zygomatic bone superiorly. Survival rate was estimated at 98.7%. Two implants showed slight soft tissue dehiscence with no inflammation.

11.2.4 The Zygoma Anatomy-Guided Approach (ZAGA) The clinical scenario of the severely atrophic maxilla is represented by a thin (≤2  mm) bone separating the maxillary sinus from the overlying oral soft tissue. In such cases, an implant perforating the palatal sinus floor would scarcely achieve adequate BIC (bone to implant contact) thus making it difficult to achieve and maintain osseointegration along its coronal section. The absence of adequate peri-implant crestal bone seal would predispose to the formation of late oral-antral communication between the maxillary sinus and the mouth. In order to preserve maxillary sinus integrity and to prevent possible sinus infections, implant position may be buccally offset to avoid perforation into the sinus cavity when placing ZI.  Nevertheless, new soft tissue-related complications have also been observed in these situations where the implant platform is positioned buccal to the crest of the alveolar bone outside the lateral wall of the maxillary sinus. The presence of the zygoma implant directly beneath the vestibular depth may lead to vascular compression, soft tissue necrosis, and/or erosion of the mucosa leading to exposure of the implant (Fig. 11.8). The occurrence of soft tissue dehiscence, in the absence of adequate alveolar bone supporting the implant head, is difficult to prevent and eventually could lead to peri-implant infections. Indeed, implant design and implant macro and micro surface characteristics will crucially influence bone and soft tissue maintenance at the zygomatic implant critical zone (ZICZ). The concept of zygomatic anatomy-guided approach (ZAGA) was described by Aparicio [21, 22] as a refinement of the extra-maxillary technique. The concept seeks for a “patient-­ specific therapy” and applies not only to patients with extreme buccal concavities but to all varia-

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tions of the maxillary anatomy. The placement of the ZI is guided by an anatomically and prosthetically driven approach. The technique relies on the recognition of the existence of the inter-­ individual anatomical differences as well as the intra-individual variations. By following specific criteria developed by Aparicio et al., the intraoral entrance point for the ZI is determined accurately, based on two main factors: the volume and architecture of the alveolar/basal process and on the anterior maxillary wall curvature. The fundamental principle of this, evidence-­ based, new concept is to design the placement of ZI in an anatomically and prosthetically guided approach in order to • Maximize the bone-to-implant contact at the zygomatic anchor zone (ZAZ), the ZICZ and, if possible, at mid-point. Maximized BIC will contribute to bone sealing and stability. • Achieve maximum structural zygomatic stabilization by a precise under preparation and subsequent implant insertion through four cortical of the maxillary zygomatic process and zygomatic bone. • Prevent the most frequent late complications such as oral-antral communication or soft tissue dehiscence. The first principle of the ZAGA Concept is to place the implant within the alveolar bone, following the Brånemark protocol, to minimize the risk of late soft tissue complications. Indeed,

Fig. 11.8  Soft tissue dehiscence bacterial plaque and inflammation around zygomatic implants. (Image taken from internet)

11  Zygomatic Implants. The ZAGA Concept

whenever the alveolar bone architecture at the sinus floor level is found to be sufficient to house the implant neck (>4 mm height and 6 mm wide), attempts should be made to maintain this bone and to place the implant through it minimizing the risk of late soft tissue complications. In the event that inadequate residual bone architecture is noticed, the coronal osteotomy should be buccally offset to prevent future sinus complications, such as oral-antral or nasal oral communications, occurring. Eventually, the latter situation requires careful planning to prevent soft tissue complications. These concepts will be analyzed deeply in the next sections.

11.3 The ZAGA Concept 11.3.1 The ZAGA Classification To better understand the influence of the maxillary wall anatomy and the alveolar crest on a prosthetically driven implant trajectory, Aparicio in 2011 [21] described the “ZAGA Classification,” an anatomical classification that is based on the prosthetically driven position of the ZI trajectory with reference to the amount of the remaining alveolar crest and maxillary sinus wall curvature (Fig. 11.9). The classification described by Aparicio ranges from ZAGA 0 (Fig.  11.9a) (Straight-­ Convex lateral maxillary wall with the implant head on the crest and mid-portion of the zygoma implant in the sinus) to ZAGA 4 (Fig.  11.9e), which is the most extreme resorption of the maxillary alveolar ridge together with or without a significant concavity of the lateral maxillary sinus wall. The ZAGA 4 situation represents extreme bone resorption at the sinus floor and subsequent decrease of the transversal and anteroposterior palatal dimensions as occurs in the severely atrophic maxilla. As shown by ongoing anatomy studies of Chow’s group (personal communications), the number of Type 0 cases increases as the entry location of the Zygomatic implant is moved further distally in the maxilla. The maxillary wall contour is more convex around the Zygomatic

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buttress region, which is usually above the first molar location. Indeed, if the entry site is located at the first molar, more patients will present with type 0 when compared to an entry site at the second premolar.

11.3.2 The ZAGA Zones As previously stated the success of the ZI treatment is based on the identification of the patient anatomical characteristics, specifically the surgeon must be familiar with the characteristics, physiology, and function(s) of the structures that the oblique plane of the planned osteotomy intersects. With a didactic intention, we are differentiating three main zones of the zygomatic implant path: • The “Zygomatic Implant Critical Zone”. • The “Antrostomy Zone”. • The “Zygomatic Anchor Zone”. The “Zygomatic Implant Critical Zone” (ZICZ) is the complex formed by maxillary bone, soft tissue, and the zygoma implant at the coronal level where the first contact with maxillary bone occurs (Fig.  11.10). The rationale for correct positioning of the ZICZ can be found in the ZAGA Concept and will be discussed later. Residual alveolar bone and soft tissue preservation/augmentation at the coronal level of the zygomatic implant are critical to prevent late complications. Indeed, bone and soft tissue maintenance at the ZICZ should be one of the main goals of our surgical approach. The Antrostomy zone (AZ) is the area where the drill penetrates into the maxillary sinus cavity (Fig.  11.11). ZAGA recommends a minimally invasive osteotomy procedure intended to maximize BIC using an under preparation of the designed implant trajectory. Prior to implant placement no previous “window” or “slot” osteotomy/antrostomy is performed nor required. As it will be later explained, depending on the maxillary anatomy, the antrostomy zone will be located either at the internal side of the remaining alveolar bone (Tunnel Osteotomy) or apically from the

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256 Fig. 11.9 (a–e) ZAGA Classification [21], expressing the different positions in which a prosthetically driven posterior zygomatic implant may be placed in relation to different maxillary wall curvatures and remaining alveolar bone crest

a

b

c

d

e

ZICZ when there is not enough alveolar bone, and the osteotomy trajectory is buccally offset (Channel Osteotomy). As a rule of thumb, the antrostomy should be located as far away as possible from the ZICZ. Excluding ZAGA Types 0 and 1 when the ZI perforates the sinus floor, the AZ is ­usually located at the zygomatic process of the maxilla, below the zygomatico-maxillary suture. ZAGA Concept uses anatomic, prosthodontic, numerical, and 3D implant design crite-

ria to determine the ZICZ position. The location of the antrostomy will depend on the zygoma buttress curvature and on the position of the coronal entrance point. The Zygomatic Anchoring Zone (ZAZ) is the section of the zygomatic bone where the implant reaches its maximal primary stability (Fig.  11.12). The zygomatic bone is variable in quality and quantity between patients. It has been described by Nkenke et al. [23] as it consists of

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trabecular bone with unfavorable features for implant placement. To maximize primary stability, the ZAGA Concept uses a tangential zygomatic bone-to-implant intersection, penetrating the four cortical of the maxillary zygomatic ­process and zygomatic bone to achieve optimum structural zygomatic stabilization.

11.3.3 The ZAGA Concept The ZAGA Concept is in continuous evolution as a systematic protocol. It represents a combination of key criteria that define the success of the ZI treatment: identification of the patient anatomy; establishment of the prosthetically driven zygomatic implant trajectory including the entry and exit points of the osteotomy at ZICZ and ZAZ; sinus antrostomy location; identification of a new portfolio of zygomatic implant designs capable of adapting to patients anatomy; associated procedures to prevent complications (e.g., use of the buccal fat pad and connective tissue grafting); and a systematic method to evaluate the success or failure of a zygomatic implant-related rehabilitation (ORIS Criteria) [24]. A thorough preoperative 3D radiographic evaluation protocol and a full understanding of the ZAGA classification and implant design [25] are essential to determine the final ZI position Fig. 11.11  The clinical picture illustrates two channel-­ while anticipating possible complications. Once type ZAGA osteotomies. The circles are showing the the anatomical and prosthodontic features of Antrostomy Zone (AZ) as the zone where the drill peneeach individual patient have been carefully investrates the antrum tigated, the ZAGA Concept provides the clinician with surgical decision-making criteria needed to establish the key landmarks for positioning the coronal ZICZ at the alveolar process, and the apical entry point into the zygomatic bone. These factors described elsewhere are fundamental for reducing long-term complications such as chronic rhinosinusitis and achieving a successful outcome [25]. The evidence shows that the ideal position for a prosthetically optimum, implant head location is at or near the crest of the alveolar bone, with a mesiodistal space between implants carefully calculated to minimize the anterior– Fig. 11.12  The clinical picture illustrates the measuring posterior cantilevering. By following specific gauge trespassing the Zygomatic Anchor Zone (ZAZ) prosthetic, biomechanical, and anatomical criteFig. 11.10  The clinical picture illustrates a Straumann ZAGA®-Flat zygomatic implant in its final position. The yellow circle marks the Zygomatic Implant Critical Zone (ZICZ) as the complex formed by maxillary bone, soft tissue, and the zygoma implant at the coronal level where the first contact with maxillary bone occurs

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ria, the chosen location of ZI contact or entry points at the ZICZ depends on the vertical and horizontal resorption and architecture of the ­alveolar bone and on the anterior maxillary wall curvature. Guided by these factors, the intraoral preparation can start either on the bone crest or in cases of severe resorption the first perforation, after grooving the buccal maxillary wall, may be performed extra-maxillary, on the zygomatic buttress (e.g., ZAGA 4). Table  11.1 represents the osteotomy goals according to the minimally invasive ZAGA Concept. The understanding of the ZAGA concept helps the clinician to better use the available crestal bone allowing for the following: (i) bone integration (bone sealing) at the Table 11.1  ZAGA Concept: the goals of minimally invasive zygomatic implant osteotomy preparation  • Achieve maximal implant primary stability  • Accomplish a prosthetically driven implant trajectory placing the implant head at the optimal restorative position  • Preserve as much bone as possible at the lateral maxillary wall and alveolar bone for optimum bone seal and stability  • Maximize the bone-to-implant contact along the length of the whole implant. This includes alveolar, maxillary wall, and zygomatic bone  • Completely seal the osteotomy for achieving a stable soft and hard tissue coverage  • Protect the sinus integrity at the implant head/neck level to prevent late oral-antral communication  • Prevent soft tissue dehiscence Fig. 11.13  On the right CBCT postoperative cut 2D image. On the left the 3D image of the same implant shows the implant path from the inner side. Both 2D and 3D images illustrate the final implant positioning. Orange circles correspond to the ZICZ, green circles to the AZ and yellow one to the ZAZ. Note how the implants are penetrating four corticals

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implant neck and body level in most of the ZAGA types and (ii) better soft tissue control to predictably cover the ZI in comparison with an exclusively extra-maxillary technique (soft tissue sealing). Once the crestal site for the ZICZ has been established, the ZAGA Concept proposes anatomic, prosthodontic, and implant design criteria to achieve maximal implant primary stability and avoid complications. Since zygomatic bone consists of trabecular bone with unfavorable features for implant placement, according to Nkenke et al. [23], structural zygomatic stabilization will be maximized by the penetration of four corticals of the maxillary zygomatic process and zygomatic bone. To avoid fracture of the zygomatic bone during or after the drilling procedure, a minimum amount of 3 mm of bone thickness was left externally to the implant at the zygoma level (Fig.  11.13). In that sense the use of ZI with reduced diameter becomes of extreme importance, especially in the cases of quadruple ZI installation. Accordingly, in cases where an extra-sinus implant path was decided, the final position of the antrostomy was in relation to the number of implants to be placed and the type of the zygoma buttress curvature. The flatter the zygomatic buttress, the more inferior the perforation for the antrostomy was located. In the opposite situation, the more pronounced the buttress

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curvature is, the higher the entrance was performed. When treatment planning, attention to the prevention of the most common late complications, i.e., oral-antral or nasal communications or soft tissue recession/infection, is mandatory for achieving a long-lasting successful outcome in zygomatic implant surgery. To preserve sinus integrity and prevent soft tissue complications such as mucosal dehiscence, guidelines have been developed to perform implant osteotomy in the pattern of a tunnel or a channel depending on the architecture of the residual alveolar bone forming the sinus floor and the contours of the maxillary lateral wall. Bone-to-implant contact/support must be achieved for better load distribution in both, tunnel and channel osteotomy types [26, 27].

11.3.3.1 The ZAGA “Tunnel Osteotomy” for a Round Implant Design According to patient-specific, ZAGA zygomatic implant concept, the ZI should enter the sinus cavity directly through the alveolar crest provided that there is sufficient residual bone volume of a minimum 4–5  mm high and 6–7  mm wide bone is still present below the floor of the maxillary sinus cavity (Table  11.2). In other words, whenever bone architecture at the sinus floor level is sufficient to circumferentially enclose the implant neck with at least 3–4 mm of bone, attempts should be made to maintain this bone and to place the implant through it, to minimize the risk of late soft tissue complications (Fig. 11.14a–c). Providing the clinician feels comfortable controlling the drilling direction a lateral “window”-shaped osteotomy is not recom­ mended to minimize bone injury. The entry point should preferably be located in a position close to the middle part of the crest regardless of the maxillary wall anatomy attaining to place the implant neck fully surrounded by the adequate thickness of pristine bone. The circular osteotomy for implant placement will penetrate at least

259 Table 11.2  The ZAGA anatomically and prosthetically guided ZI placement concept ZAGA tunnel osteotomy Indications:    (a) Intra-sinus path: Adequate residual alveolar bone volume below the maxillary sinus (e.g., in ZAGA 0 & 1)      Osteotomy has an entry point to the maxillary sinus through sufficient alveolar bone which is used to embrace the implant neck      Osteotomy direction is determined by the anatomy of the zygoma and the number of implants to be placed, independently of maxillary wall curvature      Antrostomy is placed at the sinus side of the tunnel osteotomy. Additional facial (window) antrostomy or sinus lift are not recommended (e.g., in ZAGA 0 & 1)     Straumann ZAGA® round implant section is recommended    (b) Extra-sinus path: Residual alveolar bone below the maxillary sinus has a triangular architecture, inadequate to host a regular implant and is concomitant with pronounced maxillary wall concave curvature (e.g., in ZAGA 3 and some 2 types)      Osteotomy has its entry and exit points within the residual alveolar bone      Osteotomy direction is determined by the anatomy of the zygoma and the number of implants to be placed, independently of maxillary wall curvature      Antrostomy location is determined by the number of implants to be placed and the curvature of the zygomatic buttress     Straumann ZAGA® round implant section is recommended ZAGA Channel osteotomy Indications:    Advanced alveolar bone atrophy. Alveolar bone has inadequate volume and architecture to host the neck of the ZI (e.g., in ZAGA 4 and some 2 types)      Osteotomy is buccally offset through the residual of alveolar bone and maxillary wall      Osteotomy direction is determined by the anatomy of the zygoma and the number of implants to be placed, independently of maxillary wall curvature      Antrostomy location is placed as far as possible from the ZICZ, in relation to the number of implants to be placed and the zygoma buttress curvature     Straumann ZAGA® flat implant section is recommended

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a

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Fig. 11.14 (a) Providing the alveolar sinus floor thickness is >4 mm, ZAGA Concept recommends piercing thorough alveolar bone to reach the zygomatic bone. Sinus entrance will be performed prosthetically driven, regardless of maxillary wall anatomy and sinus lining integrity. Although the cassical “window” antrostomy is not considered strictly necessary, clinicians must decide whether or not to use it. This type of perforation is known as “ZAGA Tunnel Osteotomy.” In this figure, a tunnel osteotomy has been virtually performed in a ZAGA type 0 anatomy. (b) Radiographic cut on 2D and 3D visions representing a tunnel osteotomy that has been virtually performed in a ZAGA type 1 maxilla. The prosthetically driven circular “ZAGA

Tunnel Osteotomy” enters the sinus through a 4-mm alveolar thickness, yet around one-third of the implant body is placed outside the sinus cavity. No slot or window antrostomy, previous to implant placement, is recommended. (c) Radiographic cut on 2D and 3D visions representing a tunnel osteotomy virtually performed in a ZAGA type 3 maxilla. The prosthetically driven circular “ZAGA Tunnel Osteotomy” is placed through the alveolar bone. Maximum respect for alveolar bone remaining is mandatory to allow connective tissue fibers to attach and prevent soft tissue dehiscence. The implant body is placed outside the sinus cavity, no slot or window antrostomy, previous to implant placement, are necessary

4–5 mm of crest, with no special effort to maintain sinus membrane integrity and will adopt either a total, partial, or extra-sinus path on its mid-part until reaching the zygoma bone. The final determination of the relationship between implant and maxillary anterior wall will be determined by the external wall shape. In tunnel osteotomy, performing an antrostomy on the facial side of the maxillary wall is not considered necessary and the ZI enters the sinus cavity directly through the remaining alveolar bone regardless of maxillary wall anatomy/curvature. Actually, the antrostomy is made on the sinus side of the perforated alveolar bone. The rationale to perforate the sinus lining is based on the need to support the neck of the ZI in adequate alveolar bone while reaching a prosthetically

optimum implant position. Moreover, with the achievement of optimal stabilization of the implant on the ZAZ will facilitate osseointegration of the neck of the implant at ZICZ (Fig. 11.14a–c). There is no empirical evidence of what the minimum amount of residual bone is able to long term withstand the different masticatory loads applied from the zygomatic implant to the sinus floor bone-implant junction. Indeed, circumstances affecting BIC quality and maintenance at the piercing level can dramatically differ from one patient to the next, i.e., drilling and implant insertion precision, degree of zygomatic implant anchorage/stability allowing or not for micromovements, quality of soft tissue attachment, type of oral hygiene maintenance, history of periodontitis, habits, etc. In other words, if a

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theoretically suitable thickness of circumferential alveolar bony support at the zygoma implant platform may be attained, this should be the first option. Nevertheless, given the absence of evidence on this matter, in order to minimize jeopardizing implant movements zygoma implants must be splinted to other conventional or zygoma implants in a rigid “cross arch stabilization system,” from the beginning of the treatment, if possible [28–31]. Other authors [32] have proposed an extended sinus lift with extended bone window, such that zygomatic implants are placed outside the intra-­ sinus displaced maxillary sinus wall as a method to avoid the risk of maxillary sinusitis related to ZI placement. Probable bone formation around zygomatic implants underneath the elevated sinus membrane was also suggested. Again, sinus floor thickness evaluation is mandatory to prevent sinus complications. It is important to note that if the preceding method fails in the purpose of maintaining the integrity of the sinus lining, the risk of sinus-related complications may be increased.

a

Authors of this chapter propose to name the circular osteotomy, described above, as a “Tunnel Osteotomy” because, at the coronal osseous entrance, it has a floor, lateral walls, and more or less complete roof. ZAGA Concept recommends aiming for “tunnel osteotomy” whenever possible, regardless of the maxillary wall curvature (Table 11.2). The rationale being a stable ZI, with a suitable threaded neck profile, surrounded by sufficient bone at the coronal entrance, appropriately anchored on the zygomatic bone and stabilized by adequate prostheses, will achieve osseointegration capable to seal the sinus entrance for the long term. A tunnel can be achieved depending on the existing height and architecture of the remaining alveolar bone at the prosthetically chosen entrance point. This type of osteotomy is typical of ZAGA Type 0, 1, 2, and 3 maxillary wall situations accompanied by an adequate thickness and architecture of alveolar bony support circumferential to the implant neck. The ZAGA Tunnel Osteotomy, by definition, has a circular profile entrance that needs to be sealed by an implant having a round section (Fig. 11.15a, b).

b

Fig. 11.15 (a) Clinical picture representing a tunnel osteotomy performed in a ZAGA type 3 concave maxilla. The prosthetically driven circular “tunnel osteotomy” is placed through the alveolar bone. The integrity of the residual alveolar bone has been preserved to allow connective fibers to attach and prevent soft tissue dehiscence. Note that, in ZAGA Tunnel Osteotomy, no slot or window

antrostomy is necessary to accurately perform the ZI placement through the maxillary sinus cavity. (b) Clinical picture illustrating how a ZAGA implant circular section design (Straumann ZAGA®-Round) is sealing a “tunnel osteotomy” accomplished in a ZAGA type 3 concave maxilla. (In collaboration with Drs. Simon, ZAGA Center Stuttgart)

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11.3.3.2 The “ZAGA Channel Osteotomy” and Flat Implant Design It is not uncommon to find patients presenting with reduced bone height/thickness or poor architecture at the alveolar crest level, not enough or adequate to allow for an osteotomy capable of achieving and maintaining intimate bone to implant contact all around the neck of the ZI implant. Instead of perforating through a thin crestal or palatal bone the ZAGA Concept recommends displacing the initial entry point of ZI, from the crest of the atrophic alveolar crest towards the buccal aspect of the ridge, aiming to move the osteotomy as far as possible away from the thin crestal bone; in order to maintain sinus membrane integrity at this anatomically compromised point. As previously described [25], the current authors of this chapter suggest to name this technique as the “ZAGA Channel Osteotomy” (Table  11.2). In atrophic cases (e.g., ZAGA types 2 & 4), the ZAGA Channel technique therefore involves preparing the ZI bed on the buccal aspect of the alveolar crest along the lateral maxillary wall whilst avoiding a formal antrostomy at this point. This maximizes the BIC and implant support as the implant is placed in a channel shaped osteotomy that is designed to provide as much congruence as possible within the lateral sinus wall (Fig. 11.16a, b). The ZAGA Channel Osteotomy (Table 11.2) is a groove made on the coronal alveolar bone, and sometimes also in the lateral maxillary wall and zygomatic buttress. As a waterway or channel, it has floor, lateral walls with more or less height, but no roof. When a “ZAGA Channel Osteotomy” is performed, bone is not covering the buccal implant mid-part nor its neck. It is indicated in anatomical situations where the implant mid-body and neck could not be fully positioned with adequate coverage of bone.

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The rationale for this ZAGA Concept recommendation is based on the fact that in patients with minimal crestal bone around implant piercing, under function and in time, bone may resorb. As a consequence, sinus sealing that is performed by a weak hemidesmosome junction may be jeopardized, i.e., inadequate hygiene, use of water pressure devices against the gingival junction, inadequate use of dental probe, etc. [33] speculated that the lack of bony support would end up in transversal mobility of the long coronal part of the zygomatic implant facilitating oro-­ sinus communication that is in accordance with Freedman FEA studies [26, 27]. On the contrary, placing the zygoma implant platform partially or outside of the sinus with just lateral maxillary bony support/contact would allow for better prosthetically positioned together with a more conservative approach regarding sinus integrity preservation. It is important to remark that in such an extremely resorbed anatomy model, a strong recommendation is made to, if possible, locate the antrostomy at least 15 mm up from the coronal area of the ​​ platform. Indeed, it is also recommended to preserve sinus membrane integrity and as much bone thickness as possible at crest level. To prevent soft tissue injury when placing the implant laterally to the maxillary wall, it is recommended grooving buccal bone to house the implant body as laterally submerged as possible into bone crest in such a way that it does not protrude against mucosal position so that it does not compress soft tissue vascularity. The digging limit is membrane integrity at this level. A bony canal having a circumference arc section, would, ideally, be sealed by an implant showing a circumference arc section too (Fig. 11.17a–c). Accordingly, a recommendation for the use of a flat implant section design that fits into a channel minimizing its buccal impact against soft tissue is made.

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Fig. 11.16 (a) The 2D radiographic visions are characterizing an extremely resorbed ZAGA Type 4 posterior maxilla. The inclined CBCT cut represents the chosen spot for implant placement. A virtual round implant has been placed into a “ZAGA Channel type” osteotomy. A flat implant body design would better adapt to this osteotomy contour minimizing capillary soft tissue compression. Sinus lining should be preserved at the coronal level. (b) The 2D radiographic visions are postoperatively characterizing the implant positioning of (a) To respect sinus integrity, the implant has been displaced laterally in an extra-maxillary position. Lateral walls of the “ZAGA Channel osteotomy” are of minimal height. As the virtual

round profile implant is not surrounded by an alveolar bone it may compress soft tissues and future dehiscence should be expected. (c) A flat implant body design (Aparicio 2017) is better adapted to the contour of Channel osteotomy. This allows the remaining alveolar bone to be preserved, and the implant neck to be medially surrounded by bone. The sinus lining can be preserved at the coronal level as perforating the thin covering of the alveolar bone is avoided for positioning of the head of the ZI at the palatal aspect or mid-point of the crest when there is inadequate bone remaining at this important anatomical location

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Fig. 11.17 (a) Clinical picture exemplifying the result of moving laterally the osteotomy. Sinus lining integrity is unspoiled. Roof and lateral walls of the “channel type” osteotomy have been preserved for: soft tissue fibers to attach and for more uniform distribution of the pressure against soft tissues. (b) Detail of implant design (Straumann ZAGA-Flat®) during its insertion in an alveolar and maxillary wall “ZAGA Channel type” osteotomy. Implant neck is provided with micro threads just on the bony side to help in the long-term bony maintenance at

the coronal level. (In collaboration with Drs. Simon, ZAGA Center Stuttgart). (c): Clinical picture illustrating how a ZAGA implant flat section design (Straumann ZAGA-Flat®) is sealing a “channel osteotomy” accomplished in a ZAGA type 4 maxilla. Flat surface intends to better distribute the eventual implant to soft tissue compression by increasing the contact area and decreasing the buccal diameter. (In collaboration with Drs. Simon, ZAGA Center Stuttgart)

11.4 The ZAGA Flat and ZAGA Round Zygomatic Implants: The Story of a Breakthrough

• The eventual lack of volume in the zygomatic bone, especially when performing quad surgeries. • The steric problem of implant transporters usually breaking the bony crest, so valuable for soft tissue maintenance. • The interference of wide implant transporters with anterior hard bone or another implant in a compromised maxilla. • The lack of strong primary stability in the zygoma area. • The difficulty for soft tissue anchoring at the crest level. • The high tension of the soft tissue when placing the implant extra-maxillary in ZAGA Types 2 and 4. • The bacterial adhesion to implant rough surfaces.

This section dives into the genesis of the new portfolio of “adapted to the anatomy” new zygomatic implants, from design to manufacturing, up until reaching the patients. With two different implant designs: Straumann ZAGA®-Round and ZAGA®-Flat many unique features, this system clearly stands as a breakthrough for the growing field of zygomatic implant rehabilitation. The invention, design, industrial technology transfer, and in fine commercialization is a textbook story from start to finish.

11.4.1 The Clinical Pain Points to Solve Born from the clinical requirements of the end-­ user in mind, the Straumann ZAGA zygomatic implant system designed by Dr. Carlos Aparicio is described for the first time in a book chapter aiming at solving specific pain points of the oral surgeons:

11.4.2 ZAGA and Adapted Implant Design ZAGA, the acronym for Zygoma Anatomy-­ Guided Approach, is the concept used to place zygomatic implants in a prosthetically driven man-

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ner and according to the anatomy of the patient. Clearly, the zygomatic implant systems back in the ending of the last century and in the first decade of the current one needed to further adapt to the patient’s anatomy and to the current surgical requirements. Adapting the implant design to the anatomy of each patient is critical to reaching clinical success and patient satisfaction, or should we say happiness with a new smile, free of complications. Indeed, if we were to summarize all late pitfalls, they would fall into one of the two following categories: soft tissue complications and rhinosinusitis complications. The use of the ZAGA protocol as well as the design of the ZAGA®-Flat and ZAGA®-Round Straumann zygomatic implants aims at preventing these complications.

11.4.3 A Design Becoming a Reality A thorough global professional journey around the world-led Dr. Aparicio from his drawing on a desk to the industrial technology transfer of the ZAGA designs by the hand of Graham Blackbeard CEO at Southern Implants. Originally as five different models (Fig.  11.18), a set of two were selected to best solve the clinical limitations of zygomatic implants and adapt to all ZAGA classifications but also to connect to the industrial reality (Figs. 11.19 and 11.20). Along with patent protection (https://uspto. report/patent/app/20190254781) for the most innovative features of the implants, the portfolio

Fig. 11.18  Initial drawings of zygomatic implants to be adapted to all ZAGA types of maxillary anatomy as presented to Nobel Biocare in 2014 as early as 2014. After almost three years without getting an effective DesignerCompany communication, its production was discarded

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also includes aspects already proven to be appreciated by the oral surgeons. The final ZI design then includes the following: • A narrower 3.4  mm apex diameter. This is possible as implants are fabricated with special cold-worked Grade 4 titanium, shown in bench experiments to increase fatigue strength. • A rough tapered apex portion to enhance primary stability and match the minimally invasive ZAGA osteotomies. • A turned machined implant body and head to prevent bacterial adhesion. • A 55° angle correction on the implant platform optimizing prosthetic versatility. • A model with a flat mid-portion section to reduce soft tissue tension when placed extra-maxillary. • A model with a round mid-portion section to fit a tunnel type osteotomy when placed intra-sinus. • A transporter with the same outer diameter as the implant to ease implant placement and preserve the bone crest. Backed by its scientific approach and building on its legacy of innovation, Straumann® now takes the election for the final design (Fig. 11.21) and the universal distribution of the ZAGA®-Flat and ZAGA®-Round Straumann zygomatic implants. The correct use and indication for zygomatic implant rehabilitation along with several ways to prevent long-term complications represent the main objective of this achievement.

by the Company. Some weeks later, the Company put on the market two new zygomatic implant models: one of 5mm diameter without angulation correction and one with 45° correction, both with roughened surface and threaded only in their apical part

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b Fig. 11.19 (a) One of the ZAGA Prototypes iterations in collaboration with Southern Implants. Initially, implants were named as ZAGA Tunnel and ZAGA Channel. (b) Detail of the implant transporter designed to avoid interference with bone or other implants during insertion

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Fig. 11.20  ZAGA Flat tapered design evolution and apex interations

Fig. 11.21  Straumann zygomatic implants ZAGA Flat and ZAGA round characteristics

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11.5 ORIS Criteria to Evaluate Zygomatic Implant Rehabilitation There is a tendency to validate, and subsequently use, the same diagnostic methods to evaluate the status of teeth and oral implants. The relevance of the periodontal index applied to the peri-implant evaluation of conventional implants has been questioned [34]. Its use in zygomatic implant dentistry may even be less successful. Currently, there is a tendency to consider and evaluate a zygomatic implant in the same way as a conventional implant. However, zygomatic implants differ from traditional implants in biomechanics, clinical procedures, outcomes, and eventual complications. Hence, zygomatic implants are different from regular ones and to consistently evaluate the success of the treatment, compare and in fine enhance the quality of the procedure, criteria of success have been proposed in the literature and used clinically [24, 35]. The multi-aspect evaluation of the treatment success is vital to ensure recovering the quality of life of each patient. Aparicio et  al. [36] compared the outcomes in rehabilitating the atrophic maxilla using the original zygomatic technique versus the Zygoma Anatomy-Guided Approach (ZAGA). Twenty-­ two consecutive zygomatic patients operated on from 1998 to 2002 and 80 consecutive zygomatic patients operated on from 2004 to October 2009 were selected. All included patients were in a maintenance program. For the first time in a zygoma-related article, sinus health was radiographically and clinically assessed according to the Lund–Mackay system and Lanza and Kennedy survey recommended by Task Force on Rhinosinusitis for research outcomes. The clinical use over time revealed room for improvement in several aspects, leading to the adaptation and creation of the ORIS success criteria [24]. The ORIS acronym is suggested to name four specific criteria to systematically describe the outcome of zygomatic Implant rehabilitation:

Fig. 11.22  The 2D radiographic vision is characterizing the lateral offset of a ZI placed in an extremely resorbed ZAGA Type 4 posterior maxilla: line “a” means the distance between middle palate and the center of the alveolar crest; line “b” means the distance between middle palate and the center of the implant head. The difference of a-b should be as close as possible to 0 mm

1. Offset: evaluation of prosthetic success based on final positioning of the zygomatic implant with respect to the center of the alveolar crest (Fig. 11.22). 2. Rhino-sinus status report: a presurgical and postsurgical CBCT comparative approach to evaluate whether sinuses are healthy (Fig. 11.23). 3. Infection permanence related to dehiscence: an evaluation of soft tissue signs of infection or dehiscence on a grading scale based on referenced photographs obtained (Fig. 11.8). 4. Stability report: accepting as criteria of success some mobility until dis-osseointegration signs of rotation or apical pain appear. The use of the ORIS criteria of success over time as a follow-up tool is key to evaluate the long-term, multi-aspect success of the treatment.

11  Zygomatic Implants. The ZAGA Concept Fig. 11.23 (a) The circle on the 2D CBCT cut is pointing out a discrete inflammation of the right sinus right after the surgery. (b) The comparison with the preoperative CBCT shows that the inflammation was already present. In this case the Lund– Mackay test would be negative. (c) CBCT of the same implant taken after a period of 24 months, the inflammation had disappeared

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11.6 The use of ZAGA Concept and the New Zygomatic Implant Designs on the Extremely Atrophied Maxilla In our daily practice, it is not uncommon to receive patients presenting very reduced bone height and thickness or poor architecture at the crest level, that does not allow us to perform an osteotomy capable of achieving and maintaining

an intimate bone to implant contact surrounding the overall implant neck profile. Indeed, the indications for zygomatic implants have been broadened since they are used not only in cases of lack of bone in the posterior maxilla but also in clinical cases of extreme anterior and posterior maxillary atrophy. Then, four implants anchored in the zygomatic bone ZI are placed. In these new situations, the indication for reaching the zygomatic bone using an intra-nasal implant path, in the same manner as an intra-sinus path that was pre-

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scribed on the original technique cannot be extrapolated. As previously explained, The Zygomatic Implant Critical Zone (ZICZ) is the complex formed by the maxillary bone, the soft tissue, and the implant coronal neck at the place where it contacts for the first time with the maxilla. In the presence of extreme atrophy, ZAGA Concept recommends to buccally offset the ZICZ with the aim of sinking the implant neck/body as much as possible into the alveolar and lateral maxillary wall bone while maintaining the sinus lining integrity with no membrane perforation at the ZICZ level. Implants surrounded by minimal thickness of bone at their entry point may present bone resorption under function and within time. A subsequent oral-antral fistula would appear if bone failed to seal antrum entrance. Indeed, the amount of bone to implant contact (BIC) may be jeopardized by different circumstances, i.e., periodontal disease history, inadequate oral hygiene, use of water pressure devices at the gingival junction, inadequate use of the dental probe, etc. Moreover, it has been speculated that the lack of crestal bone support would end up in transversal mobility of the long coronal part of the zygomatic implant facilitating oral-sinus communication. Placing the zygoma implant platform outside of the sinus, and with a lateral maxillary bone support/contact, would allow a better prosthetic positioning together with a more conservative approach regarding sinus/nasal integrity preservation. In order to prevent soft tissue dehiscence when placing the implant laterally to the maxillary wall, it is recommended to groove the buccal bone to house the implant body with as much lateral submergence as possible into bone, in such a way that it does not protrude against the mucosal position and does not compress the soft tissue vascularity. The depth limit for the canal digging is the sinus membrane integrity at this level. The use of a flat section implant adapted to this osteotomy type, i.e., the Straumann ZAGA Flat would help the surgeon to prevent soft tissue complications.

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The Antrostomy Zone (AZ) is represented by the position where the antrum entrance occurs. In a ZAGA type 4 case, typically found in a quadruple ZI installation, the AZ should be located as far as possible from the ZICZ.  The opposite situation for us to imagine would be the one represented by the ZAGA Type 0. Here, the residual alveolar bone is adequate in architecture and height (more than 4 mm height and 6 mm wide) for a “tunnel” type perforation able to maintain bone sealing over time. In this ZAGA type 0 case, the AZ will be located just at the sinus side of the tunnel osteotomy. A tunnel osteotomy is also recommended in cases of concave maxillary wall where there is less bone height but the zygomatic antrostomy zone (ZAZ) is foreseen to be performed far from the ZICZ after an exteriorized implant path (i.e., ZAGA Type 3). The rationale being a ZI, with an appropriate threaded neck profile, surrounded by sufficient bone at the coronal entrance and stabilized by adequate apical anchorage, and prostheses, will achieve osseointegration at the neck level capable to seal the sinus entrance for the long term. A tunnel can be achieved depending on the existing height and architecture of the remaining alveolar bone at the chosen entry point. Tunnel osteotomy, by definition, has a circular profile entrance that needs to be sealed by an implant having a round section, i.e., the Straumann ZAGA®-Round design (Fig. 11.24). In a Quad situation, the Zygomatic Anchor Zone (ZAZ) is also represented by the portion of the zygomatic bone where the implant gets its maximal primary stability. As in the double zygoma, the positioning of the ZAZ will vary with respect to the anatomy and specifically with the curvature of the zygomatic buttress. Since the zygomatic bone consists mainly of trabecular bone, structural zygomatic stabilization will be achieved when the four cortical are perforated. The ZAGA Concept does not recommend performing a slot not a “window” previous to implant positioning. There is no need to “see” the implant on its path inside the zygomatic buttress. Indeed, the classic opening of the maxillary wall on its upper part close to the suture zygomatic maxilla is reducing the capability for implant sta-

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Fig. 11.24  The ZAGA concept and the reasoning for the choice of the implant according to the specific anatomy of each site

bilization and in some situations is decreasing the tapered effect of the implant design. The recommendation is to raise a flap enough to discover the zygomatic bone, its limits, and to be able to place a retractor on the angle formed by the temporal and frontal apophysis.

11.7 Zygomatic Implant Network: www.zagacenters.com The patient with a primary indication for fixed oral rehabilitation anchored to zygomatic implants presents maxillary atrophy in both the anterior and posterior sectors. This patient will only have one chance to receive this treatment. One chance means that if we fail, the patient will be condemned to a removable prosthesis for the rest of his life. That is, if we do not cause additional complications. On the other hand, the number of patients indicated for zygomatic implant placement that a normal-sized clinic identifies is low. This means that the surgeon responsible for that clinic has too long a learning curve.

ZAGA Centers arise in response to the patient’s need to be able to easily select centers whose priority is the patient himself; that have accumulated experience with zygomatic implants; that practice a long-term predictable zygomatic implant placement technique (ZAGA Concept); and that use the most appropriate implants and tools for each patient. ZAGA Centers are dental practices that are experts in the treatment of severe jaw atrophy with zygomatic implants. Each ZAGA Center undergoes a strict selection process prior to certification. Criteria include clinical and patient care aspects. Once certified, they participate in the network’s activities, which include scientific, clinical, and industrial activities. The ZAGA Center is locally exclusive and is part of a worldwide network of zygomatic implants (Fig.  11.25). They are local reference centers for patients and other dental clinics. They have and accumulate experience in this treatment. Above all, they are here to respond to each patient’s individual problem. If zygomatic implant treatment is the indicated solution, they will thoroughly explain and adapt the treatment

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Fig. 11.25  The ZAGA Centers Network global map

plan. In fact, from the diagnosis to the surgical procedure, ZAGA Centers adapt to the characteristics and anatomy of each patient, individualizing the treatment. The ZAGA Center becomes part of a worldwide network. As such, they actively participate in scientific research activities around zygomatic implants. In addition, they have several opinions to help provide the best possible care for each patient. Most ZAGA professionals are authors of peer-reviewed scientific publications. Finally, clinicians harmonize and improve best practices in the field by sharing experiences and advice. In addition, the ZAGA Centers SL network offers valuable tools for patients such as an informative portal that includes frequently asked questions and testimonials: www.zygomaticimplants.org The portal is available in more than ten languages. Therefore, if a person is looking for information as a patient, he or she will be recommended to visit the Patient Portal.

11.7.1 What Is the Goal of the ZAGA Center Network? To recognize and support professionals with expertise in the rehabilitation of the atrophic maxilla using zygomatic implants in a unique geographic area. The professionals we intend to support have the following characteristics: Their practice is patient-centered, meaning that it focuses on the patient’s well-being. They use the ZAGA concept for the treatment of severe maxillary atrophy. They are willing to share their expertise in zygomatic implants to improve treatment outcomes. Both internally (within the network) through meetings, congresses, courses, etc., and externally, by sharing their knowledge through scientific publications. Being a member of the network implies obtaining a series of benefits, but also acquiring some responsibilities.

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11.7.2 Benefits and Responsibilities Associated with the ZAGA Network Differentiation as unique and exclusive members in a global network of experts in zygomatic implants. Identification by potential patients as a local leader in the treatment of zygomatic implants versus other centers in the same geographic area. Standardization of practice and protocols, making treatment results more predictable, thus encouraging and increasing patient referrals from other professionals. The goal of our scientific meetings and co-authored publications is precisely to improve our standardized protocols. Social and ethical responsibility perspective, which is facilitated by collaboration in a group of professionals with similar ethics, philosophy, and social orientation that becomes an influential group. This perspective is nurtured and encouraged by the ZAGA team, for example, with the recent creation of a research grant in zygomatic implants. Although we consider the above four points to be the main pillars of ZAGA’s value proposition for its members, there are other advantages and benefits that can be obtained by belonging to the network, which we at ZAGA headquarters are working hard to facilitate. For example, discounts on materials (implants, 3D models, instruments, etc.), promotion of the network and its members to potential patients, periodic analysis of each center’s web positioning, advice, etc.

11.7.3 Educational Programs ZAGA Centers network is committed to sharing and transmitting the philosophy of the ZAGA Concept and in addition to scientific publications, it does so through two major interrelated activities: the theoretical and practical training and the mentoring program.

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There are different educational programs organized by ZAGA Centers SL.  The ZAGA Zygomatic Implants course is the most well known. It describes our experience of more than 25 years with zygomatic implants in the rehabilitation of the extremely resorbed maxilla. The course is a three-day intensive zygomatic implant course. Participants gain knowledge about the use of this advanced treatment in different anatomies. In addition, they learn about the related prosthetic rehabilitation. We also review different surgical techniques, their benefits, and limitations, including the classic intra-sinus technique, the extra-sinus technique up to the ZAGA philosophy. Precisely, we provide detailed information on the latter to prevent surgical and prosthetic complications. The hands-on training includes the placement of implants on real 3D patient models. After the practice, the trainee will see the actual surgery of the patient corresponding to his 3D model. In addition, the participant receives the DICOM images of his “patient” for virtual planning before starting. After that he will place implants in the 3D model of his cryopreserved donor and finally, the surgical training is completed by placing implants in cryopreserved human heads. ZAGA Centers also have a mentoring program created to bridge the gap between the theoretical course and the first surgeries with patients. The mentoring program is available on the ZAGA Centers website www.zagacenters.com for both practitioners interested in being supervised by a mentor, while performing surgery and practitioners interested in observing a mentor performing surgery. The mentorship program is open to any surgeon who wishes to learn from mentors.

11.8 Conclusions While zygomatic implants are a predictable alternative to bone grafting techniques, in patients who present with moderate maxillary bone atrophy, they are the first choice of

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treatment for the rehabilitation of patients with severe bone atrophy, oncology patients as well as patients with full-arch implant failures and associated bone defects. Alternatives, such as bone grafting procedures, have significant disadvantages that include the risk of complications inherently associated with regenerative techniques that require multiple surgical interventions that span over a much-prolonged overall treatment time. Emerging evidence including a recent randomized clinical trial comparing zygomatic implants and regenerative therapies showed that zygomatic implants are a better rehabilitation modality [2]. The ZAGA technique has evolved to standardize the zygomatic implant surgery by adopting an individualized, anatomically and prosthetically guided, implant placement approach to reduce complications and to improve the predictability of long-term treatment outcomes. At the heart of the ZAGA concept is the use of a modified surgical technique according to individual variations in maxillo-zygomatic anatomy; the ZAGA tunnel osteotomy in Zaga types 0, 1, & 3 and channel osteotomy technique in ZAGA 4 cases. The ultimate objective is to achieve maximum stability for the ZI by engaging the three key anchorage points: the crest of the alveolar bone, lateral wall of the maxilla, and the denser zygomatic bone whenever possible, while aiming to achieving optimal prosthodontic emergence profile as well as protecting the integrity of the maxillary sinus by preserving the residual alveolar bone and sinus lining and avoiding vascular compression of the covering soft tissues in extra-sinus pathways. This has, recently, led to the development by Aparicio of a modified portfolio of Zygomatic implants best suited for different anatomical situations according to the above-described ZAGA concept; the round and flat Straumann ZAGA ZI.  These implants with slimline profiles allow the correct coronal positioning of the implant head while preserving the reduced volume of residual alveolar bone. The round ZI has been designed to be used in tunnel osteotomies where the remaining alveolar bone may embrace the implant neck. The flat variant is more suitable for

channel osteotomies to seal the sinus wall and achieve the best possible BIC without compressing the soft tissue on its buccal side. Acknowledgments  It is with great pleasure that we acknowledge the work done by Drs. Edmond Bedrossian and SepehrZarrine in collaboration with Dr. Carlos Aparicio to improve the efficiency of the drills required for zygomatic surgery contained in the Straumann cassette.

References 1. Brånemark P-I, Gröndahl K, Ohrnell L-O, Nilsson P, Petruson B, Svensson B, et al. Zygoma fixture in the management of advanced atrophy of the maxilla: technique and long-term results. Scand J PlastReconstr Surg Hand Surg. 2004;38(2):70–85. 2. Davó R, Bankauskas S, Laurincikas R, Koçyigit ID, Sanchez M, de Val JE. Clinical performance of zygomatic implants-retrospective multicenter study. J Clin Med. 2020;9(2):480. 3. Higuchi KW.  The zygomaticus fixture: an alternative approach for implant anchorage in the posterior maxilla. Ann R Australas Coll Dent Surg. 2000;15:28–33. 4. Bedrossian E, Stumpel L, Beckely ML, Indresano T. The zygomatic implant: preliminary data on treatment of severely resorbed maxillae. A clinical report. Int J Oral Maxillofac Implants. 2002;17(6):861–5. 5. Malevez C, Abarca M, Durdu F, Daelemans P. Clinical outcome of 103 consecutive zygomatic implants: a 6-48 months follow-up study. Clin Oral Implants Res. 2004;15(1):18–22. 6. Aparicio C, Brånemark PI, Keller EE. Reconstruction of the premaxilla with autogenous iliac bone in combination with Osseointegrated implants. Int J Oral Maxillofac Implants. 1993;8:61–7. 7. Stevenson AR, Austin BW.  Zygomatic fixtures--the Sydney experience. Ann R Australas Coll Dent Surg. 2000;15:337–9. 8. Davó R, Malevez C, López-Orellana C, Pastor-Beviá F, Rojas J.  Sinus reactions to immediately loaded zygoma implants: a clinical and radiological study. Eur J Oral Implantol. 2008;1(1):53–60. 9. Bedrossian E.  Rehabilitation of the edentulous maxilla with the zygoma concept: a 7-year prospective study. Int J Oral Maxillofac Implants. 2010;25(6):1213–21. 10. Stella JP, Warner MR.  Sinus slot technique for simplification and improved orientation of zygomaticus dental implants: a technical note. Int J Oral Maxillofac Implants. 2000;15(6):889–93. 11. Peñarrocha M, Uribe R, García B, Martí E. Zygomatic implants using the sinus slot technique: clinical report

11  Zygomatic Implants. The ZAGA Concept of a patient series. Int J Oral Maxillofac Implants. 2005;20(5):788–92. 12. Peñarrocha M, García B, Martí E, Boronat A.  Rehabilitation of severely atrophic maxillae with fixed implant-supported prostheses using zygomatic implants placed using the sinus slot technique: clinical report on a series of 21 patients. Int J Oral Maxillofac Implants. 2007;22(4):645–50. 13. 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(3):114–22. 14. Migliorança R, Ilg JP, Serrano AS, Souza RP, Zamperlini MS. Sinus exteriorization of the zygoma fixtures: a new surgical protocol. Implant News. 2006;3:30–5. 15. Aparicio C, Ouazzani W, Aparicio A, Fortes V, Muela R, Pascual A, et al. Extra sinus zygomatic implants: three year experience from a new surgical approach for patients with pronounced buccal concavities in the edentulous maxilla. Clin Implant Dent Relat Res. 2010;12(1):55–61. 16. Aparicio C, Ouazzani W, Hatano N.  The use of zygomatic implants for prosthetic rehabilitation of the severely resorbed maxilla. Periodontol. 2000;2008(47):162–71. 17. Maló P, de Nobre M, Lopes A, Francischone C, Rigolizzo M.  Three-year outcome of a retrospective cohort study on the rehabilitation of completely edentulous atrophic maxillae with immediately loaded extra-maxillary zygomatic implants. Eur J Oral Implantol. 2012;5(1):37–46. 18. Maló P, de Nobre M, Lopes A.  Immediate loading of “all-on-4” maxillary prostheses using trans-sinus tilted implants without sinus bone grafting: a retrospective study reporting the 3-year outcome. Eur J Oral Implantol. 2013;6(3):273–83. 19. Maló P, de Nobre M, A, Lopes I. A new approach to rehabilitate the severely atrophic maxilla using extramaxillary anchored implants in immediate function: a pilot study. J Prosthet Dent. 2008;100(5):354–66. 20. Migliorança RM, Coppedê A, Dias Rezende RCL, de Mayo T. Restoration of the edentulous maxilla using extrasinus zygomatic implants combined with anterior conventional implants: a retrospective study. Int J Oral Maxillofac Implants. 2011;26(3):665–72. 21. 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(3):269–75. 22. Aparicio C. Zygomatic implants: the anatomy-guided approach. London, UK: Quintessence; 2012. 23. Nkenke E, Hahn M, Lell M, Wiltfang J, Schultze-­ Mosgau S, Stech B, et  al. Anatomic site evaluation

275 of the zygomatic bone for dental implant placement. Clin Oral Implants Res. 2003;14(1):72–9. 24. Aparicio C, López-Piriz R, Albrektsson T.  ORIS criteria of success for the zygoma-related rehabilitation: the (revisited) zygoma success code. Int J Oral Maxillofac Implants. 2020;35(2):366–78. 25. Aparicio C. Zygomatic Implants: The Anatomyguided Approach. 1st ed. London,UK: Quintessence Pub Co; 2012. 26. Freedman M, Ring M, Stassen LFA. Effect of alveolar bone support on zygomatic implants in an extra-sinus position--a finite element analysis study. Int J Oral Maxillofac Surg. 2015 Jun;44(6):785–90. 27. Freedman M, Ring M, Stassen LFA.  Effect of alveolar bone support on zygomatic implants: a finite element analysis study. Int J Oral Maxillofac Surg. 2013;42(5):671–6. 28. Davo R, Malevez C, Rojas J.  Immediate function in the atrophic maxilla using zygoma implants: a preliminary study. J Prosthet Dent. 2007 Jun;97(6 Suppl):S44–51. 29. Davó R. Zygomatic implants placed with a two-stage procedure: a 5-year retrospective study. Eur J Oral Implantol. 2009;2(2):115–24. 30. Brunski J.  Biomechanical aspects of tilted regular and zygomatic implants. In: Aparicio C, editor. The anatomy guided approach. Berlin: EdQuintessence; 2012. p. 25–45. 31. Skalak R.  Biomechanical considerations in osseointegrated prostheses. J Prosthet Dent. 1983;49(6):843–8. 32. Chow J, Wat P, Hui E, Lee P, Li W.  A new method to eliminate the risk of maxillary sinusitis with zygomatic implants. Int J Oral Maxillofac Implants. 2010;25(6):1233–40. 33. Becktor JP, Isaksson S, Abrahamsson P, Sennerby L. Evaluation of 31 zygomatic implants and 74 regular dental implants used in 16 patients for prosthetic reconstruction of the atrophic maxilla with cross-­ arch fixed bridges. Clin Implant Dent Relat Res. 2005;7(3):159–65. 34. Coli P, Christiaens V, Sennerby L, Bruyn HD.  Reliability of periodontal diagnostic tools for monitoring peri-implant health and disease. Periodontol. 2000;73(1):203–17. 35. Aparicio C, Manresa C, Francisco K, Claros P, Alández J, González-Martín O, et  al. Zygomatic implants: indications, techniques and outcomes, and the zygomatic success code. Periodontol 2000. 2014;66(1):41–58. 36. Aparicio C, Manresa C, Francisco K, Aparicio A, Nunes J, Claros P, et  al. Zygomatic implants placed using the zygomatic anatomy-guided approach versus the classical technique: a proposed system to report rhinosinusitis diagnosis. Clin Implant Dent Relat Res. 2014;16(5):627–42.

Additively Manufactured Subperiosteal Jaw Implant (AMSJI)

12

Marco Rinaldi and Maurice Y. Mommaerts

12.1 Introduction: Subperiosteal Implants and the AMSJI Concept

lateral walls of the maxillary sinuses [3]. Subsequently, various authors [4] modified the implants design in order to involve bone areas of greater density. In 1951, the technique of direct 12.1.1 Introduction bone impression was introduced to improve the precision of the implants which improved the Subperiosteal implants were proposed by Dhal in precision but required a specific intervention to 1943 [1]. They reached a significant diffusion in expose the bone and take the impression [5]. the 1950s and 1960s, but thereafter they were From the 1980s, there were the first attempts [6] gradually abandoned giving way to osseointe- to use computed tomography and CAD-CAM grated endosseous implants which subsequently techniques to build three-dimensional models on spread all over the world. The reasons for this which to manufacture subperiosteal implants. decline are many [2] including the difficulty in Nevertheless, for many years, digital technolobuilding the implants, the difficulty in taking pre- gies were not precise enough, and the direct bone cise impressions of the bone surface and the impression technique was still more reliable [7]. design of the implants itself. First implants were First implants were not made of titanium but conceived to be supported by the alveolar bone Vitallium®, which has a low osseointegration surface, but it was soon clear that, due to the joint capacity. The design of the implant structures effect of the masticatory load and the post-­ was not adequate to prevent peri-implantitis as extraction bone resorption, the implants col- the relationship between bacterial microflora and lapsed into the maxillary bone, not particularly periodontitis was not yet understood in the 1950s stiff, up to perforate and broke the caudal and and 1960s. Very variable survival rates of subperiosteal implants have been published in the literature. M. Rinaldi (*) Dr. Marco Rinaldi Dental Clinic, Bologna, Italy Some studies indicate quite high survival rates, while others lower percentages. 10-year survival Clinica Privata Villalba, GVM Care & Research, Bologna, Italy values ​​vary between 79% and 95% in the mandie-mail: [email protected] ble [8, 9] and between 65% and 93% for maxilM. Y. Mommaerts lary implants [10]. Bodine and Yanase [11] report Face Ahead Day Clinic, Antwerp, Belgium 93% success at 5 years, 64% at 10 years, and only European Face Centre, Universitair Ziekenhuis 54% at 15  years. Complications include bone Brussel, Brussels, Belgium subsidence and recurrent infections that only e-mail: [email protected]

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resolve by the removal of the entire subperiosteal implant [12]. The high incidence of ­complications led to the progressive abandonment of the technique. Subperiosteal implants have no longer been taught in the Universities and are mentioned only from a historical point of view. Few companies produce them and the quantity of implants produced is not in the least comparable to that of endosseous implants. In parallel with the decline of subperiosteal implants, there was a notable development of diagnostic and engineering technologies. Godfrey Hounsfield and Allan Cormack constructed the first CT equipment and won the Nobel Prize for Medicine in 1979. The first use of CT in dentistry dates back to 1987, a year earlier Chuck Hull filed the patent for stereolithography (3D Systems, Rock Hill, SC, USA). Many years have passed since then, and the precision of diagnostic methods and 3D printing have significantly improved, reaching a very high degree of reliability, widely reported in scientific literature (see Chap. 2). These technologies find application in many fields of medicine providing new therapeutic possibilities. Three-dimensional anatomical models are used in many fields of surgery as diagnostic and operative tools. Furthermore, 3D printing allows the creation of patient-specific alloplastic implants (PSI) used for the replacement of different skeletal parts, such as cranioplasty [13], reconstructions of the orbital floor [14], prostheses of the temporomandibular joint [15], facial implants for the correction of asymmetries and deformities [16, 17], and replacement of vertebrae [18], just to mention some of the many applications of 3D printing. The greater accuracy of three-dimensional diagnostic tools (CT) and the use of technologies such as stereolithography, numerical control milling (CNC), topological optimization (TO), and finite element analysis (FEA) allow to reconsider therapeutic possibilities that had been abandoned. Indeed, in subperiosteal implantology, these new technologies enable to plan the fixation of implants in areas less subject to resorption, such as the zygoma and mid-facial pillars. These anatomical areas would be impossible to detect with an impression but can be carefully studied using today’s technologies. The first AMSJI® was cre-

M. Rinaldi and M. Y. Mommaerts

ated for a case of cleft lip and palate through the know-how gained in the field of patient-­specific implants (PSI). The acronym AMSJI® means additively manufactured subperiosteal jaw implant and defines a subperiosteal implant made with current techniques and concepts. This implant, custommade for the patient, could represent an alternative technique to large bone reconstructions or zygomatic implants in the treatment of extreme atrophies of the maxillary bone [19, 20]. We want to make clear from the start that in this book, we will deal exclusively of the AMSJI® subperiosteal implant for some fundamental reasons: this is the only subperiosteal implant used by the authors, and therefore, the only one about which they can write from direct experience. We also think that, in the field of subperiosteal implants, the construction and design technologies are so important that they can make devices very different from each other. Therefore, even with the common denomination of subperiosteal implants, there are different design and construction characteristics that could significantly affect many aspects of their clinical behavior. For example, a different structure design can result in a different way of transferring the masticatory load to the bone surface. Differences in the shape of the mainframe, arms, fixation systems, connections, and other macro- and microscopic construction details could influence the clinical behavior of the different implants. We certainly do not want to discredit products that we simply do not know. AMSJI® has some patents that protect it from a commercial point of view, but here we are interested in underlining the fact that nowadays, new technologies have made abandoned solutions interesting again, and we should be ready to reconsider and study them, in their clinical indications, without dogmatic attitudes [21]. The implant treatment of maxillary extreme bone atrophy is really a challenge for the surgeon, and the available solutions [22] are never risk-free [23] and easy to be performed so we must be able to evaluate risks and benefits of each technique and which one is the most suitable for the patient. In our experience, AMSJI has opened a new way and constitutes a concrete therapeutic possibility for many patients with advanced maxillary atrophy [24].

12  Additively Manufactured Subperiosteal Jaw Implant (AMSJI)

12.1.2 Macroscopic, Morphological, and Structural Characteristics of the AMSJI The AMSJI implant (CADskills BVBA, Ghent, Belgium) consists of two parts, one right and one left, which rest on the bone surface and are fixed with osteosynthesis screws. The two implants are joined by the prosthetic structure (Fig.  12.1). Each implant consists of a main body (mainframe), which branches and rests on the bone surface. Two extensions originate from the main structure, the wings which extend to the maxillary zygomatic process and to the edge of the pyriform opening. Each wing has two holes for the osteosynthesis screws for fixation of the implant to the bone. The arms depart from the main structure for the prosthetic connection which takes place, by means of screws, at the level of the Posts (Fig. 12.2). The arms are very smooth to avoid the accumulation of bacterial plaque and ensure the epithelial seal. The Posts are hand polished with pink ceramic disks, rubber tips, white and brown (Edenta, St. Gallen, Switzerland) and polishing paste, water and fat free (Luxi Green Polishing Compound, HS Walsh & Sons, Biggin Hill, United Kingdom), with rotating bristles (Bison, Renfert, Hilzingen, Germany). They are designed in such a way that any arm can be cut individually in case of recurrent infections (Fig. 12.3). The pink anodization (Viktor Hegedüs, Wehingen, Germany) of the arms makes them more similar in color to that of

Fig. 12.1  3D rendering of the AMSJI for Hybrid Bridge

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the gingival tissue and, therefore, less visible if over time they get exposed by the retraction of the gingival tissues. The body of the zygomatic bone and the edge of the pyriform opening represent the fixing areas of the AMSJI. These areas are stable over time, chosen specifically for their poor bone resorption. The implant is fixed with two osteosynthesis screws at each end of the wings (Wings). Therefore, eight screws are

Fig. 12.2  The parts of the AMSJI: main structure (salmon pink), loops (red), wings (blue), arms (green), and prosthetic connections (yellow)

Fig. 12.3  Branches of the arms with areas of weakness (dark gray) for their possible removal

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280 Fig. 12.4  Scheme of fixation screws: the lengths of the osteosynthesis screws are indicated 13 mm

13 mm 13 mm

13 mm 9 mm

9 mm

9 mm

9 mm

needed to fix the two AMSJI implants to the maxillary bone. The Mimics Medical 22.0 software (Materialise, Leuven, Belgium) is used to assess the location and length of the osteosynthesis screws. Each AMSJI is delivered to the physician accompanied by instructions of the position and length of the fixation screws (Fig. 12.4).

12.1.3 Microscopic Surface Characteristics of the AMSJI

Fig. 12.5  Porosity of the internal surface to promote osseointegration

The mainframe internal surface, the one in contact with the bone, has diamond-shaped cells, with porosities of 500 μm, to enhance secondary stability, which is obtained as a result of the bone growth inside the structure [9] (Fig.  12.5). The micro-roughness of the internal surface is obtained with 297 μm alumina sandblasted and etched with oxalic acid (2% mass/volume solution for 10 min).

12.1.4 Structural and Biomechanical Characteristics of the AMSJI In the design of the AMSJI, biomechanical and structural aspects are carefully studied. The design of the implant structure is in fact made using the topological optimization (TO) method. This mathematical method improves the geometry of the material within the design for certain sets of loads and constraints, with the aim of increasing the mechanical performance of the system. Topological optimization is performed by implementing an initial project through the Altair Inspire software (solidThinking Inc., Troy MI, USA) in which fixed areas, where the project cannot be modified, and editable areas, are defined. Then the material prop-

Fig. 12.6  Topological optimization of the general design of the AMSJI

erties are set out (Ti6Al4V, tensile strength 920 MPa, E modulus 116,000 MPa, Poisson’s ratio 0.31). The AMSJI is topologically optimized for loads in boundary conditions (Fig.  12.6). It has been shown [25] that when using 3D-printed Ti6Al4V, no fatigue failure of the implant occurs up to ten million chewing cycles, with stresses up

12  Additively Manufactured Subperiosteal Jaw Implant (AMSJI)

to 200 MPa and in the absence of structural defects. The AMSJI has been designed to work for at least 15  years. Assuming an average number of 1100 chewing cycles per day, we obtain an estimate of 15  years  ×  365  days/year  ×  1100  cycles/ day = 6,000,000 cycles. The maximum admissible stresses, in the optimization phase are 200  MPa. Therefore, there should be no fatigue failures of the system in the established period of operation. The elastic deformation of the implant under masticatory load should somehow follow the deformation of the bone on which it rests. To match the elasticity of the AMSJI to that of the bone, finite element analysis (FEA) is performed on the bone by means of computer simulation. With an equally distributed load of 100 N, vertically oriented on the bone, displacements between 0.03 and 0.1 mm occurred. When the same load was applied to only one side of the bone, displacements were about 0.2  mm. Starting from these results, a maximum vertical displacement of 0.1 mm was imposed at the most

Fig. 12.7  FEA analysis

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frontal and most posterior points, to the left and right of the bridge. Four different load situations were applied on the implant: four vertical forces of 25 N on the left side, four vertical forces of 25 N on the right side, five vertical forces of 20 N on the front of the bridge, and nine vertical forces of 11 N evenly distributed on the bridge. During the application of these forces, all screw holes were found fixed and immobile. It was determined to place four screws for each AMSJI implant and frame thickness of 1 mm, although, according to the FEA study, a single screw per each wing would have been sufficient. In the event that screw stability is not found during the intervention, the presence of a second hole can be very useful: for this reason, each wing has two holes for the osteosynthesis screws (see also Consensus Meeting Gent 2020). Two finite element analyses were carried out to check the complete system. Each AMSJI is delivered to the physician accompanied by an accuracy report (Fig. 12.7). The precision in the prosthetic

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connection is 0.02  mm and is obtained by CCN (computer numerical control) milling. The connection with the suprastructure further increases the stiffness of the whole system.

12.2 Surgical and Prosthetic Procedures 12.2.1 Scan Prosthesis The realization of an AMSJI implant requires a careful preliminary study. The evaluation of the maxillary bone morphology is of fundamental importance, but the study from the prosthetic point of view is also very important because the AMSJI implant is made together with the prosthetic structure. It is possible to choose between a removable overdenture type prosthesis and a fixed hybrid type prosthesis. The construction of the AMSJI takes place according to a reverse engineering principle; that is, it starts with the prosthesis to build the subperiosteal implant accordingly, following the change in philosophy from “bone driven” to “restoration driven.” All prosthetic information is given by the scan prosthesis [26] worn by the patient while undergoing to the CT scan. The manufacturer of the AMSJI receives all information relating to the prosthesis through the DICOM files of the CT of the scan prosthesis. For a better morphological definition of the temporary prosthesis, it is also advisable to send the STL file of the optical scan of the scan prosthesis so that it can be coupled to the DICOM files. The vision obtained is more realistic than that obtained from computed tomography alone and 3D printing will also be more accurate. If the patient already has a removable prosthesis and it is planned to create an overdenture, the procedure is simple because, if the existing prosthesis is suitable from an aesthetic, functional and occlusal point of view, it can be duplicated to build the scan prosthesis. In this way, the overdenture, built together with the AMSJI, will be very similar to the patient’s original prosthesis. In the event that the prosthesis used by the patient is not suitable, we recommend

M. Rinaldi and M. Y. Mommaerts

making a new one from which the Scan Prosthesis can be subsequently obtained. The transition from a removable to a fixed prosthesis requires a more accurate study. The occlusion, the shape of the teeth, and the relationship with the gingival tissues in fixed prostheses have their own characteristics that should be evaluated and incorporated the scan prosthesis. It represents the tool for bringing the final prosthetic project onto the CT images and, in the case of the AMSJI, for defining its construction characteristics from the beginning. The scan prosthesis, therefore, represents a fundamental moment because it will define the shape of the final structure. In designing scan prosthesis for a Hybrid Prosthesis, the main problem is to connect the teeth of the prosthesis to the boney alveolar crest, avoiding excessive prominences, which could cause stagnation of food, but at the same time provide adequate support to the lip. The position of the teeth of a removable prosthesis almost never meets the morphological requirements necessary for a fixed-type prosthesis due to the centripetal direction of bone resorption (Cawood-Howell). A decision criterion has been proposed to evaluate the indication for a fixed prosthesis or an overdenture in edentulous maxillae using a virtual implant planning [27]. These authors identify some points on the scan prosthesis at the level of the anterior teeth: Central Cervical Point (C-Point), Acrylic Flange Border (F-Point), and the Implant Platform Buccal End (I-Point). Starting from these points, they measure these distances: FLHeight (vertical distance from C-Point to F-Point), which indicate the flange height; MucCov (vertical distance from I-Point to F-Point) representing the coverage of the mucosa from the acrylic flange above implant neck; CID (distance from C-Point to I-Point), this measure is important for the emergence profile of prosthetic reconstruction and need for artificial soft-­ tissue replacement; ProsthProfile (buccal profile of the prosthesis is determined by the angle between the tangential line connecting C-Point, I-Point, and the horizontal plane) that represent the angular aspect of

12  Additively Manufactured Subperiosteal Jaw Implant (AMSJI)

the buccal profile. These measurements are representative for the emergences profile and tissue volume. The authors describe three classes: A, B, and C. Class A: a fixed prosthesis with crowns without the need for artificial gingiva is indicated. Class B: a fixed prosthesis with artificial gingiva (hybrid design) is indicated. Class C: it is recommended by overdentures with buccal flanges. Other authors [28] claim that an angle between implants and prostheses greater than 45° would compromise the labial movements during the smile and would create accumulation of food with problems of hygiene maintenance. These studies indicate some evaluation criteria to predict the design of the future prosthesis. These evaluations are predictive and not absolute but can be useful to avoid misunderstandings, excessive aesthetic expectations, and technical difficulties. The choice between overdenture and hybrid prostheses is multifactorial and the role of the patient decisive, but (and) it can be very useful to discuss some prosthetic aspects in the initial diagnostic phase. Implant design software packages are generally not sufficient to evaluate the labial support, the smile line, and the support of the perioral tissues. Therefore, it is necessary to evaluate many parameters clinically using a traditional or digital wax-up. The following parameters must be considered: vertical dimension, midline, occlusal plane, length and shape of the teeth, width of the oral arch, lip line, lip support, naso-labial angle, and occlusion. When everything is evaluated and decided, this information will be used in the construction of the scan prosthesis. In traditional computer-­ assisted implantology, there are basically two types of scan protocols: the single-scan protocol using a radiopaque scan prosthesis (Fig.  12.8) and the double-scan protocol which uses a radiolucent scan prosthesis with radiopaque marks (Fig.  12.9). Decomposable (modular) Scan Prostheses can be made in particular post-­ extraction cases [29]. The scan prosthesis can be built in various ways: by mounting radio-opaque teeth, ready-­ made, or manufactured in the dental laboratory by mixing barium sulfate in the dental resin part,

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in a ratio of 1 part BaSO4 for two parts acrylic powder; through resin duplication of the diagnostic wax-up; through a digital wax-up (Fig. 12.11 digital wax-up), using specific software (3Shape, Exocad); and 3D printing of the wax-up. The resin wax-up, obtained in a traditional way or with 3D printing, is mounted on a prosthetic base and tried in the mouth to check and verify all the previously mentioned parameters. The aesthetic evaluation by the patient is also very important (Fig. 12.10a, b). If changes are needed, the wax-­up can be modified it and tried again. Only when all the parameters are satisfactory, it will be possible to proceed with the

Fig. 12.8  Scan prosthesis for single scan

Fig. 12.9  Scan prosthesis for double scan

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a

b

Fig. 12.10 (a) Digital wax-up printed in resin. (b) Try the wax-up in the mouth

a

b

c

Fig. 12.11 (a) Digital design of a scan prosthesis. (b) Design of the scan prosthesis and the radiopaque markers are seen. (c) Scan prostesis built with 3D printing and ready for CT/CBCT exam

construction of the scan prosthesis (Fig. 12.11a– c). We recommend taking photographs of the scan prosthesis in the patient’s mouth (Fig. 12.13 scan prosthesis in the mouth). The data of this important preliminary study will be stored and

used to create the coating final framework of the AMSJI (Fig. 12.12). In the case of digital waxup, the file will be printed milled in PMMA or in micro-loaded composite and applied to the prosthetic framework.

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Fig. 12.12  The scan-prothesis file is imported into the design software

12.2.2 Surgical Technique 12.2.2.1 Instrumentation The specific components for the AMSJI technique are the following (Fig. 12.13): • Two subperiosteal AMSJI implants, right and left. • Temporary suprastructure. • Temporary 3D-printed denture. • Incision Guide. • Container with tools: spiral drills, screwdrivers, osteosynthesis screws and rescue screws, Torque wrench, GC dispenser, and cartridge for Fuji Temp LT cement. • Hybrid bridge, double structure, or Dolder bar for final prosthetic solution with screws and screwdriver. Surgical tools necessary for the positioning of the AMSJI depend on the preferences of each operator because basically it is necessary to simply open and then suture a gingival flap. For the correct placement of the AMSJI implants, we also use the Tampers Martin metal plungers (KLS Martin, Tuttlingen, Germany) (Fig. 12.14) and a Partsch hammer. The positioning of an AMSJI

can be performed under local anesthesia or under general anesthesia depending on the clinical indications and preferences of the doctor and the patient.

12.2.2.2 Flap Incision and Dissection The incision for the dissection of the full-­ thickness flap is guided by the “Incision Guide”, provided with the AMSJI. It is possible to choose between two types of flaps: Paracrestal and crestal. According to preferences, two different types of incision guides can be requested. Originally, the guide indicated a buccal paracrestal incision, to facilitate closure when the palatal flap had shifted palatally (Fig. 12.15a, b). Later, the crestal incision was introduced (Fig. 12.16a, b). Incision guides have been conceived because when the surgeon performs the gingival incisions, he does not have a precise idea of ​​the position in which the prosthetic connections will be. The incision guide was then designed to give an incision line which is close to the gingival emergencies of the Posts. Subsequently, given the importance of the mucous seal, it was thought to make a guide that can indicate, with greater precision, the individual position of the posts at the gingival level. The incision guide indicates the posterior extension

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Fig. 12.13  The components of the AMSJI, and the box with specific surgical instruments

Fig. 12.14  Surgical instruments used for the positioning of an AMSJI (Dr. Rinaldi)

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a

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b

Mucogingival border Incision line option 1 Incision line option 2

Fig. 12.15 (a) Guide for paracrestal incision. (b) Using the paracrestal incision guide

a

b

Fig. 12.16 (a) Guide for crestal incision. (b) Using the crestal incision guide

of the crestal incision and the vertical relaxation incision. Since the redraping of the buccal flap around the posts consumes flap edge length, it is important to have the vertical relaxation incision made 8 mm or more posteriorly to the distal post. Otherwise, the latter will not be fully engaged by keratinized mucosa. The resulting defect in the buccal sulcus can easily be closed by advancing the posterior margin. Hence, following the Incision Guide indicators is important to obtain cover of the posterior wing and to circle the posterior post with keratinized mucosa. The crestal guide, in fact, brings the pillars for the prosthetic connections, printed in resin.

In this way, the incision of the gingival tissue will be conducted exactly to the point where the Posts will be located. According to our experience, the crestal incision guide allows to trace the incision line in correspondence with the abutments, considerably facilitating the suturing of the flaps. The use of the crestal guide essentially avoids having an excessive discrepancy between the position of the prosthetic connections and the incision line used to expose the bone (Fig.  12.17), thus, avoiding the risk of excessive lengthening of the flaps which can put in tension the suture and favor tissue dehiscences. In any case, the crestal incision guide,

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288 Fig. 12.17  Discrepancy between the incision line and the position of the posts

Fig. 12.18  Guide for two separate flaps, with incision lines slightly palatal

showing on the gingival tissue positions that the Posts will have, allows the surgeon to make any choice regarding the design of the flap. Sometimes, a more palatally incision (Fig. 12.18) could result in a gain of fixed keratinized mucosa on the buccal side (Fig.  12.19). Depending on the clinical situation, it is possible to carry out two separate flaps, one on the right and the other on the left, with relaxing incisions in the front and posteriorly, or a single flap to expose the entire maxillary arch. In the latter case, an incision is used along the entire arch with two relaxing incisions posteriorly and a median one anteriorly (Fig. 12.20).

12.2.2.3 Exposure of Maxillary Bone and Implant Placement All the bone that will be used as a support for the AMSJI must be carefully exposed and freed from any residual soft tissue so that the implant can rest completely on the bone surface. The flap must be detached with great care, and it must be always locate the position of the infraorbital foramen, the emergency point of the homonymous nerve. The detachment at the level of the zygomatic body and at the edge of the piriform opening must be large enough to allow freedom of movement to the handpiece for the preparation of the holes for the osteosynthesis screws. It should be emphasized

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Fig. 12.19  Six weeks after placement with incision palatally to the crest: gain of fixed keratinized mucosa at the buccal side

Fig. 12.20  Incision line for two separate flaps (right side) and incision line for a single flap in order to expose the entire maxillary arch (left side). On the left the sutures around the posts are indicated

that once the infraorbital foramen has been located, the tissue retractor must be kept well away from the emergence of the nerve during all the procedures for drilling and screwing the osteosynthesis screws. In fact, while in zygomatic implantology,

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a large detachment of the flap is required only at the level of the zygomatic body, in the case of AMSJI, the two points of implantation are placed at the ends of an ideal line that passes very close to the infraorbital hole (Fig. 12.21). It is, therefore, easier than, trying to expose the bone surface, the retractor can be moved toward the infraorbital nerve. In our experience, we had a case of temporary paresthesia in the right half face due to stretching of the infraorbital nerve which regressed completely after about a month. If this extensive detachment of the soft tissues is not necessary, it would be preferable to keep completely covered the area of the canine fossa high up to the infraorbital nerve, to protect it from trauma caused by a wound retractor. We recommend proceeding immediately with the execution of the periosteal incisions to lengthen the gingival flaps (Fig. 12.22) so that they can easily cover the alveolar bone crest. Performing this procedure in this phase allows to aspirate immediately the blood that comes out of the relaxation incisions and to prevent it to accumulate below the flaps, thus, reducing the post-­operative hematoma. The two AMSJI implants, on the right and left, must be carefully tried in their position. In order to facilitate their insertion, it may be useful to use a metal plunger (Fig.  12.23). The surgeon must check that the entire implant is adherent to the bone (Fig.  12.24), especially in the areas of fixation, where it is necessary to check, through the hole for the screws that there is no interposed soft tissue. In general, the correct position of the implants on the bone is easily to be found and so stable that often the implants remain in the correct position even without being fixed with screws (Fig. 12.25).

12.2.2.4 Connect the Interim Superstructure The temporary prosthetic structure must be screwed to the two AMSJI implants before fixing them to the bone through the osteosynthesis screws (Fig.  12.26). This precaution is very important to avoid that any small inaccuracies or tensions generated during the placement of the screws could prevent the correct insertion of the structure of the subperiosteal implants. The connection between the Post and the prosthetic struc-

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Fig. 12.21  Line drawn between the fixation points of the AMSJI and its relationship with the infraorbital foramen. Care must be taken not to damage the infraorbital nerve with tissue retractors

Fig. 12.22  Bone exposure and flap elongation incisions

Fig. 12.23  The metal tampers are useful for finding the precise housing of the AMSJI

ture is very precise, made with CNC technique, with a tolerance of only 0.02 mm. The screwing of the structure must be complete even if it does not matter that the screws are tightened strongly. The temporary prosthesis is then placed on the suprastructure, and the patient is brought into centric occlusion (Fig. 12.27). At this stage, the whole system, consisting of AMSJI implants, temporary structure, and prosthesis, is assembled and constitutes a single structure. The surgeon must now check once again that the wings, with the holes for the osteosynthesis screws, have no interposed soft tissue and that they are adherent to the bone surface. The structure must be stable and have no tilting.

12.2.2.5 Screw Fixation of the AMSJI Before fixing the AMSJIs, the suprastructure is connected to the AMSJIs using 4 torx screws. The provisional prosthesis is mounted and the lower dentition put into occlusion. The mandible is manually supported until the osteosynthesis is accomplished. We recommend using only the osteosynthesis screws delivered with the components of the AMSJI. Screws diameter is 2.3 mm (Surgi-Tec NV, Ghent, Belgium). Their length is variable and is indicated in the surgical planning (Fig.  12.4). Since biomechanical studies of the project are performed with these screws, it should be avoided to introduce variable elements not conforming to the original project. Holes for the

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Fig. 12.26  The temporary prosthetic structure must be screwed to the implants before their fixation to the maxillary bone

Fig. 12.24  The implant must adhere well to the bone surface

Fig. 12.25  AMSJI implants in the correct position must be adherent and stable on the bone

Fig. 12.27  The provisional prosthesis in centric occlusion, before fixation with the osteosynthesis screws

osteosynthesis screws are drilled with 1.6–mm-­ diameter drills, mounted on a straight or contra-­ angle handpiece (Fig. 12.28). We generally start with the fixation points at the level of the body of the zygomatic bone, which require a greater detachment of the flap. We prepare first the seat for the lower osteosynthesis screw (Fig.  12.29) which is soon screwed completely. The implant is now already fixed to the bone and the hole for the second zygomatic screw can be easily prepared (Fig. 12.30). We then prepare the holes and insert the two screws also at the level of the edge of the

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Fig. 12.28  The bur prepares the hole for the osteosynthesis screw in the lower zygomatic area

Fig. 12.29  Tightening of the first screw (Surgi-Tec NV, Gent, Belgium)

Piriform opening (Fig.  12.31). If the implant is very stable and adherent to the bone, to speed up the procedure, we can also prepare the seats of several screws at the same time and then screw them in quick succession. The AMSJI fixation procedure continues on the other side of the mouth in the same way, but there are no precise rules to follow in the AMSJI fixation sequence. In general, it is not necessary to tighten the osteosynthesis screws too much, and it is sufficient that they come into contact with the surface of the implant and tighten only a little to prevent them from stripping the bone once reached the end stop. If a screw is not stable, a 2.5  mm rescue screw, slightly wider than the standard 2.3  mm screw, can be used. In addition to all the screws for its fixation, some spare screws and some res-

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Fig. 12.30  Screwing in the second zygomatic screw

Fig. 12.31  Screwing of the two screws at the level of the pyriform opening frame

cue screws with a larger diameter are delivered with the implant. At this point of the procedure, the AMSJI is fixed to the bone and connected with the temporary prosthetic structure. Gingival flaps are still open (Fig. 12.32).

12.2.2.6 Suture of the Flaps In order to proceed with the suture of the gingival flaps, it is necessary to remove the prosthesis and unscrew the temporary suprastructure. If a crestal incision guide has been used, there should not be many problems in suturing the flaps as the gingival incision was conducted on the crest at the level of the prosthetic connections which should, therefore, be located between the palatal and vestibular flaps (Fig.  12.33). Those who prefer a palatal

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paracrestal incision may need to extend the vestibular flaps a little more. An excessively buccal incision on the other hand may be far from the Posts and require extemporaneous changes in the suturing technique (Fig. 12.17). The palatal and vestibular flaps can be sutured with various techniques, but at the level of the Posts, we suggest mattress or purse string sutures, so that the tissue is well tightened around the posts themselves. Between each post and the next one, running sutures or detached stitches, can be used. The important concept is to try to obtain a stable and tension-free suture so that the entire subperiosteal implant is well covered by gingival tissue. Absorbable sutures are always used in order to avoid to disassemble prosthetic structure to remove the sutures in the first 2 months.

Fig. 12.32  The AMSJI was fixed to the bone, joined to the temporary prosthetic structure and the gingival flaps are still open

Fig. 12.33  Suture of the gingival flaps. The use of the crestal incision guide made it possible to have the incision line in correspondence with the prosthetic connections

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12.2.2.7 Assembly of the Temporary Prosthetic Structure At the end of the suture (Fig. 12.34), only the six posts for the connection of the prosthetic structures emerge from the gingival tissue. The temporary structure is then reassembled by fixing it with its screws to the AMSJI.  The tightening of the screws must be checked with the Torque ­controller, supplied with the AMSJI and must be approximately 15 Ncm (Fig. 12.35). The temporary prosthesis, 3D printed, must be cemented to the temporary suprastructure using a small amount of GC glass-ionomer adhesive (Fig.  12.36), once again bringing the maxillaries into centric occlusion. In the 2021 concept, cementing is not required anymore, as the temporary suprastructure is glued into the 3D-printed provisional denture. Periodontal dressing (Coe-­Pak, GC Europe) can

Fig. 12.34  The suture has been completed, and the six posts for the prosthetic connection are visible

Fig. 12.35  Tightening the prosthetic screws with the torque controller

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be used bucally and palatally to protect the wound for approximately 2  weeks. The use of the periodontal pack is a personal choice of the surgeon since there are reasons for or against its use. Small occlusal adjustments are usually necessary to ensure proper chewing. The occlusion must be checked several times during the first period of use of the prosthesis. The patient will be able to chew immediately but he must have a balanced chewing and keep a soft diet during the first 2 months. Postoperative check-ups are recommended, and the completion of a PROMS questionnaire [30] can be useful to evaluate the patient’s opinion on the treatment performed.

Fig. 12.36  Cementation of the temporary prosthesis with glass ionomer cement

a

12.2.2.8 Final Prosthetic Structure After about 2  months, the temporary prosthetic structures can be removed. At the beginning, the prosthesis were cemented to the titanium structure of the AMSJI and had to be detached with a bridge remover in order to access the screws and remove the titanium bar. Later, with the development of the method, prosthesis was provided with holes at the level of the fixing screws, to allow the prosthesis and the bar to be removed together without detaching the prosthesis. The latter also pertains for the glued 2021 feature. This methodic facilitates mounting and removing operations and also facilitates the procedures of periodic checks (Fig. 12.37a, b). After removing the prosthetic components, an impression is taken using the impression copings (Fig.  12.38) supplied with the open (recommended) or closed tray technique. Implant analogs are fixed to the impression copings to build the plaster model (class III gypsum). Obviously, the impression of the mandibular arch is also required. The final prosthetic structure, delivered with the AMSJI, is screwed onto the model, with the certainty that it will fit perfectly, because the connections are identical to those of the temporary structure, which has already been in the patient’s mouth. At this point, various techniques can be adopted to complete the prosthetic work.

b

Fig. 12.37 (a) The holes on the temporary prosthesis facilitate disassembly and carrying out periodic checks. Bottom view. (b) Temporary prosthesis seen from above, you can see the space for housing the temporary bar

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ture is suitable for a CAD-CAM-made coating, the files that were stored for the scan prosthesis can be used to make the white and pink PMMA coating (Figs. 12.12, 12.40a, b, 12.41a, b, 12.42a, b). The prosthesis is mounted (Fig. 12.43), by screwing it to the posts of the AMSJI implant, with a torque of 35 Ncm.

Fig. 12.38  Impression coping to take the impression

Fig. 12.39  Try the final prosthetic structure in the mouth

The final structure can be positioned by screwing it to the AMSJI Posts (Fig. 12.39), and then the occlusion is recorded with wax or dedicated materials. Alternatively, to be closer to the original project, if this has been well accepted by the patient during the first 2 months of use, the occlusion is recorded with the temporary prosthesis, which is removed and re-mounted on the plaster model prepared with the analogs, to be placed in the articulator with the two models in centric occlusion. The final prosthetic structure in titanium has been delivered to the physician together with the AMSJI components, and only the white and pink acrylic resin coating (acrylic polymerized) is to be built. Alternatively, this component is provided to the restorative dentist. The dental laboratory can make a wax-up of the suprastructure to be tried intraorally in order to verify, occlusion, shape, color, lip posture, and phonetics. If the tests are satisfactory, the wax-up can be reproduced in composite resin. If the prosthetic struc-

12.2.2.9 Double Structure The double structure consists of a structure directly screwed onto the AMSJI connections and a secondary structure in turn fixed to the primary structure (Fig.  12.44). The two structures are stabilized both by means of a primary fixation by friction (under 4° milled primary and secondary structure) and by means of secondary retentions (snap-pin or Teflon ® attachment system). After taking the impression, the two structures are positioned on the plaster model, and waxes for the bite registration and an individual impression tray are made for the construction of the mobile prosthesis. 12.2.2.10 Aftercare (from AMSJI® Manual 2019) Good follow-up is essential for a successful short- and long-term result of an AMSJI treatment, as is the case with conventional endosseous dental implant treatment [31, 32]. It is recommended to see the patient 1 week after treatment to remove the dressing, to carry out an initial cleaning and to provide brushing instructions with interdental brushes. A second check is performed 3  weeks after the intervention and later according to the needs. Two months after the placement of the implants, the patient is referred for definitive prosthetic care. When the implant treatment is completed and the final suprastructure is placed, periodic inspection must take place at least twice a year. It has been found that patients who have lost their teeth by periodontal disease have an increased risk of peri-implantitis [33]. These patients need more follow-up with shorter intervals. In those in whom cleansing is more difficult [32], as those with a hybrid bridge, follow-up should be more frequent. During the periodic inspection, both the prosthetic structure and peri-implant tissue must

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a

b Fig. 12.40 (a) Virtual coupling of the scan prosthesis image (see Fig. 12.12) to that of the scan of the prosthetic structure. (b) CAD design of the covering in frontal view

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b Fig. 12.41 (a) Scan of the prosthetic structure is imported into the software. (b) CAD design of the veneer in occlusal view

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Fig. 12.42 (a) Final prosthesis in occlusal view. (b) Final prosthesis in frontal view

Fig. 12.43  Final prosthesis in the mouth screwed to the prosthetic connections of the AMSJI

be checked. The examination of a fixed dental prosthesis focuses on occlusion and articulation, wear, mobility, and breakage of parts. The check of a removable prosthetic structure (double structure and overdenture) focuses on the following aspects: occlusion and articulation, wear of the occlusal surfaces, mobility, wear and breakage of the secondary structure, retention of overdenture, and secondary structure and anchoring elements of the overdenture [32]. The investigation of the peri-implant tissue focuses on the following aspects: the presence of plaque and tartar, depth of the connector pocket, degree of bleeding and the presence of pus on probing, clinical attachment level, and mobility of AMSJI [32, 34]. Periodic clinical examination must be supported by X-ray examination. Immediately after placing the suprastructure, it is recommended to make a CBCT in order to have a reference to identify changes of the peri-implant bone level

Fig. 12.44  Double structure

over time. Moreover, with the CBCT, it is possible to assess the fit of the suprastructure. Thereafter, extra radiographs are made on a ­routine basis [31, 32]. It is recommended to perform a CBCT after 1 year, 5 years, 10 years, etc. (taken into account the ALARA principle) to assess peri-implant bone level and peri-implant radiolucencies [32].

12.3 Resection Guides for AMSJI: VOG and HOG Not all patients come to our observation completely edentulous and with an advanced degree of bone atrophy. Frequently, they still have roots or residual teeth, often in a state of advanced periodontal disease, or have recently lost their teeth, and the alveolar bone has not been still completely resorbed. They wear mixed, fixed-­

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mobile prostheses with different levels of bone atrophy between the areas with teeth and the edentulous ones. Therefore, the CT/CBCT investigation could highlight the presence of bone defects in height and thickness that do not allow the use of standard dental implants but at the same time, it shows areas where the bone is still present. The Cawood–Howell class IV [35] is not suitable for AMSJI because the presence of thin-­ edged bone would lead to the creation of a main structure (mainframe) with sharp edges that would favor the dehiscence of the gingival tissue (see Consensus Conference). Therefore, we often find ourselves in this paradoxical situation: not having enough bone for other implant solutions but at the same time not having a sufficiently advanced degree of bone atrophy for an AMSJI. In fact, if the alveolar bone has not yet completely reabsorbed, the mainframe would rest on a bone surface that will face a contraction in volume, thus leaving a space under the structure that would easily lead to the formation of a dehiscence. We know that the alveolar bone resorption, after the loss of teeth, takes place rapidly, both vertically and horizontally, while the basal bone does not undergo to significant changes and is more stable over time [36]. In these kind of situations, it would be necessary to wait for complete bone resorption before to consider to carry out of an AMSJI implant. With the aim of extending the use of the technique also to class IV atrophies and in all situations in which the alveolar bone is not yet completely resorbed, we described a protocol which provides the use of bone resection guides [37]. In general terms, they constitute a tool to surgically anticipate the natural post-­ extraction bone resorption process and make the bone surface more suitable for receiving an AMSJI implant. Cutting guides can be used in many different clinical situations [38]. In post-­ extraction, where extractions, bone remodeling, and placement of the AMSJI could be carried out simultaneously; in Cawood–Howell class IV cases, to eliminate residual bone with a sharp edge; in all cases where there are bony parts to be removed or smoothed. The horizontal ostectomy

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Guides (HOG) and vertical ostectomy guides (VOG) allow to perform guided and calibrated osteotomies based on the pre-surgical CT/CBCT study and can be used for the remodeling of bone segments that affect both the support area of the ​​ AMSJI and areas outside of these. The VOG and HOG guides can be used simultaneously with implant placement or can be used in a pre-­ prosthetic surgery that will precede the of the AMSJI implant by a few months. The factors to consider for the choice between the simultaneous or deferred approach are many, such as the presence of infections, the need to perform dental extractions, extractions of teeth with prominent roots at the level of the buccal bone plate [39], or teeth with roots penetrating the sinus cavity, the need to remove standard or zygomatic implants. The HOG and VOG guides can also be used to improve the morphology of the bone surface that will support AMSJI.  The protocol provides that the DICOM data, obtained from the CT exam, are imported in the software Mimics (Materialise, Heverlee, Belgium). In case there are teeth to be extracted, and a virtual edentulation was performed through different density thresholds with Geomagic Freeform Plus (3D-systems GmbH, USA). Post-­extraction bone resorption takes place both vertically and horizontally. Therefore, in order to simulate the natural post-extraction resorption, a vertical and a horizontal osteotomy are hypothesized (Using Geomagic Freeform Plus), and then a vertical osteotomy guide (VOG) (Fig.  12.45a, b) and a horizontal osteotomy guide (HOG) (Fig. 12.46a, b) are designed. The path of the osteotomies is planned on the basis of specific considerations on each individual clinical case. They are performed virtually by evaluating and choosing between different options (Fig.  12.47a, b). The maxillary sinuses are colored to highlight the position of the sinus floors so that they are not reached by the cut. We recommend leaving at least 3 mm of bone above the osteotomy at the level of the sinus floors (Fig. 12.48). The VOG and HOG guides are made with 3D printing in titanium alloy (SLM Solutions, Lubeck, Germany) (Fig.  12.49). The

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a

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Fig. 12.45 (a) VOG design before osteotomy. (b) VOG design after vertical osteotomy

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Fig. 12.46 (a) HOG design before osteotomy. (b) HOG design after horizontal osteotomy

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Fig. 12.47 (a) Cutting options: angled osteotomy lines. (b) Cutting options: straight osteotomy line

vertical guide (VOG) has a posterior platform that rests on the alveolar bone crest to facilitate the correct positioning of the guide. Furthermore, being made of titanium, the guides have a considerable strength, so they can also be positioned using light hammer blows. Once the right posi-

tion has been found, the guides can be fixed to the bone with osteosynthesis screws to facilitate the cutting procedures (Fig. 12.50). The two guides (VOH and HOG) use the same holes for the fixation screws. This detail allows to verify the accuracy of the first osteotomy and the correct

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Fig. 12.48  Highlighting of the maxillary sinuses in red

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Fig. 12.50  VOH in working position, the guide is fixed with osteosynthesis screws

Fig. 12.51  Guided vertical osteotomy performed with a piezosurgical instrument Fig. 12.49  VOH and HOG in titanium on stereolithographic models

positioning of the second guide. In fact, if the first osteotomy (Fig. 12.51) was performed correctly, the second guide (Fig. 12.52) will fit perfectly and the holes in the bone for the fixation screws of the first guide will correspond to those of the second. The handle of the guides must have a shape or an angle that does not interfere with the reciprocating saw or with the piezo handpiece (Figs. 12.51 and 12.52). The use of the VOG and HOG guides potentially extends the indications of the AMSJI to the IV Cl of Cawood–Howell and to all cases in which more favorable bone morphology must be created for the subperiosteal implant. We believe that the use of deferred technique does not (should not) cause particular problems. It should be emphasized, however, that in the simultaneous approaches, the shape of the bone

Fig. 12.52  HOG in position and guided horizontal bone remodeling. This second guide is fixed in the same holes as the previous guide for vertical ostectomy

after ostectomy directly influences the design of the AMSJI. Therefore, in the planning of osteotomies, it should be avoided the formation of sharp corners that would lead to sharp edges also in the mainframe structure and that over time could favor tissue dehiscences. For this reason, we rec-

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ommend a greater use of the HOG guide and to round off the bone edges as much as possible. To conclude this chapter, dedicated to the AMSJI® subperiosteal implant, we report in full the results of the 2020 International Consensus Meeting which should have been held in Amsterdam but due to the pandemic situation SARS-CoV-2 and Covid-19 was held online on September 14. During the meeting, experts of these techniques analyzed and tried to give solutions, suggestions and remedies to potential problems, obstacles, and complications related to the use of the AMSJI®.

phy. Continuous evaluation of the concept, both clinically and radiographically, has resulted in a second series of modifications [20]. In this chapter, a third series of modifications is discussed, based on the input of a survey conducted by the international steering group, by observations from experienced users and observations of the dental technician/AMSJI product manager of CADskills BV and a third finite element analysis by the R&D officer and a master student at the Department of Biomechanical Engineering of the KULeuven. The discussed topics have been randomly ordered.

12.4 Consensus Online Meeting Report, Gent, September 14, 2020

12.4.2 Number of Screw Holes per Wing

(Concerns about and suggested remedies for potential problems, obstacles, and complications with additively manufactured subperiosteal jaw implants (AMSJI®) in the maxilla) Maurice Y. Mommaerts1,2,3,5, Benoit de Smet1, Stijn Huys1,4, Eline De Moor4, Marco Rinaldi2,3, Björn De Neef2, Erik Nout2,3, Hylke Schouten2, Geert Klomp2,3, Casper Van den Borre5. CADskills BV1, AMSJI key-opinion leaders2, International Steering Group ASMJI in the maxilla3, Department of Biomechanical engineering  - Katholieke Universiteit Leuven4, Doctoral school, Vrije Universiteit Brussel5.

12.4.1 Introduction Additively manufactured subperiosteal jaw implants (AMSJI®) are three-dimensionally (3D) titanium-printed, patient-matched, juxta-osseous implants that can be installed through a minimally invasive technique [19]. The concept allows for immediate masticatory, aesthetic, and phonetic function. It is an alternative to zygomatic implants or full-arch bone augmentation and subsequent endosseous implant surgery in case of Cawood–Howell V-VIII maxillary atro-

The thickness of the boney frame surrounding the piriform aperture may vary and the problem of bone-thread stripping has been encountered a few times. This happened despite individual analysis of the bone quantity by Mimics Medical 22.0 (Materialise, Heverlee, Belgium). It was suggested that an extra screw hole could be provided, to be used in case of stripping of the other(s) (Fig. 12.53a, b). Topological (Discovery, Ansys Inc., Canonsburg, PA, USA), and mechanical optimization [40] have demonstrated that one screw per wing suffices to primarily stabilize the AMSJI frame. Adding another hole in the anterior wing does not have a direct influence on implant safety or stress shielding. The advantages of adding screw holes are that primary fixation is even more likely to succeed when two or even three screws engage. If a screw hole fails, an additional safety hole remains available for that purpose but has not to be used in case the other screws engage properly. Disadvantages may be that the edge of the longer wing may be seen or felt through the integument, and that fixation may be more difficult. Also degloving would more extensive. Care should be taken, using Mimics Medical 22.0, to avoid blocking the nasolacrimal duct or pierce into the nose and irritate the lower turbinate. Extra advantages would be that more

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Fig. 12.53 (a) Anterior wing with two screw holes. (b) Anterior wing with three screw holes

12.4.3 Different Types/Brands of Osteosynthesis Screws The steering group had decided in April 2018 to allow only the 2.3-mm-diameter Surgi-Tec osteosynthesis screws (Surgi-Tec NV, Gent, Belgium) to reduce the number of variables in the prospective registry. As per mid-September 2020, other types and brands are allowed. Specification in the study questionnaires is required. The main stay is still the trusted 2.3-mm-diameter screw.

12.4.4 Space Between the Arms and Loop Crossing the Maxillary Crest Fig. 12.54  Teflon engagements as means of retention

extensive cosmetic paranasal augmentation can be considered, and that forceful removal of the provisionally cemented prosthesis will less likely loosen the anterior wing. This advantage may only be present in the future in a limited number of indications, as removal by untightening the prosthetic screws or by making use of polytetrafluoroethylene engagements (Fig.  12.54) will avoid removal of the provisional prosthesis from the suprastructure intraorally with a Miller crown remover.

It was questioned if the distance between the posterior arms and loop crossing from buccally to palatally is sometimes not too short in relationship with the soft-tissue flap that needs to adhere to the bone in between the arms and basal loop frame. The distance is partially related to the position of the posts and partially to the location of the posterior loop. The location of the posts can be 2, 4, 6 or 3, 5, 6 or 3, 5, 7 in both first and second quadrant of the maxilla. Position 2 is in the aesthetic zone and in an area with thin gingival biotype. Location 7 does not allow for comfortable introduction of the cross-fit screw in the prosthesis. Hence, positions 3, 5, and distal 6 are the preferred ones. The posterior loop should be located at least 5  mm from the arms extending to the post at position 6 (Fig. 12.55).

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12.4.5 Position of the Buccal Horizontal Part of the Main Frame and Configuration of the Screw Holes in the Posterior Wing The horizontal part of the main frame, from which rises the anterior and posterior wings, contains a scaffold for boney ingrowth at its inner aspect. The lower it is located the easier it is to install the system when using only local anesthesia. Hence, the recommendations in 2018 were to have it designed at the level of the anterior nasal spine (Fig. 12.56a). This low position is disadvantageous when ascending mucositis is present. The main frame could become infected before the affected arm is removed. It was decided to keep it above the nasal spine level

(Fig. 12.56b). At the same time, the position of the screw holes in the posterior arm is changed from horizontally to vertically, because of the designer experience that this conforms bone quantity underneath, and because of the user’s experience of facilitating access to the screw holes (Fig. 12.57a, b).

12.4.6 Shape of the Posts The posts extending above the platform were 1.715 mm high with a conicity of 10°. The diameter at the platform was 3.8 mm. Prosthodontists reported difficulties in mounting the suprastructure and strain between the three structures. It was decided to reduce the height of the post to 1.2 mm, to provide a conicity of 30°. A reduction in height of the post has important consequences. A shorter prosthetic torx-type screw needs to be produced, which is easier to insert with mouth-­ opening limitations (Fig.  12.58a, b). More patients will become candidate for a double-­ structure denture as well.

12.4.7 Retention of the Temporary Restoration

Fig. 12.55  Submento-vertical view on the palate with bilateral AMSJI, with yellow arrows indicating the minimal 5 mm distance between the basal loop frame and the posterior posts

a

Initially, the temporary restoration was cemented with glass ionomer on a non-retentive CNC-­ milled suprastructure. Only a few droplets of cement were used to facilitate removal and cleansing. Removal of the temporary restoration b

Fig. 12.56 (a) Cephalad part of the basal loop frame at the level (rede line) of the anterior nasal spine (2018 design). (b) Cephalad part of the basal loop frame above the 2018 level (red line)

12  Additively Manufactured Subperiosteal Jaw Implant (AMSJI)

becomes awkward when too much glass ionomer was used. Consequently, a shift toward eugenol-­ free zinc oxide cement was made on a Dolder bar structure. Patients complained of frequent loosening of the temporary prosthesis. In a later phase, holes in the temporary prosthesis above the torx-type fixation screws allowed removal by untightening the screws. Still, the temporary prosthesis has to be detached from the Dolder bar structure outside of the oral cavity. Fracture of the temporary prosthesis may occur. Even with a copy always available, this solution is considered not to be the ideal one. Ultrasonic equipment and cement solvents are not available in every dental office. A new concept is now elaborated making use of polytetrafluoroethylene precision attachments (Fig.  12.54). This solution will allow for a

b

Fig. 12.57 (a) 2018 horizontal configuration of the screw holes in the posterior wings. (b) 2020 vertical configuration of the screw holes in the posterior wings Fig. 12.58 (a) Lateral view on 2018 (A) and 2020 (B) post-design. (b) Translucent lateral view indicating the longer torx screw in the 2018 (A) design and the shorter one in the 2020 (B) design

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easy separation but will not always be technically feasible to incorporate.

12.4.8 Prevention and Management of Local Infection Reference is made to dental and orthopedic implant literature. AMSJI implantation is considered clean-contaminated surgery. There is consensus that all effort should be made, by designer and operator, not to enter the maxillary sinus with drill or screw shaft. The wings and main frame should be in full contact with the boney surfaces. After installment, rinsing with 3% peroxide is recommended, to free all debris (bone dust, titanium powder) and to act against anaerobic bacterial species that have been introduced in the wound cavity by surgical manipulation.

12.4.8.1 Preoperative Prophylactic Antibacterial Protocol Meta-analyses report a statistically significantly lower number of dental implant failures when antibiotics are administrated pre-operatively [41–43]. Evidence suggests that administering ­antibiotics pre- rather than post-operatively following routine dental implant placement is the protocol of choice [44]. The most effective protocol is 3 g orally of amoxicillin administered 1 h pre-­ operatively in case of surgery using local anesthesia only [45]. In orthopedic literature, a prophylactic single dose of a first-generation cephalosporine is the gold standard [46]. In knee a

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12.4.8.4 Treatment of Chronic Periodontitis and Dental Peri-Implantitis Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Prevotella intermedia, and Treponema denticola are important etiologic 12.4.8.2 Post-operative Prophylactic agents of chronic periodontitis and are most susAntibacterial Protocol ceptible to the amoxycillin and metronidazole The US Center for Disease Control and combination [54, 55]. Cossé (2017) [56] recomPrevention recommended in its 2017 Guideline mends probing with a soft-tip probe for culture for the Prevention of Surgical Site Infection to and sensitivity testing. The biofilm is removed administer pre-operatively a single dose of anti- after flap raising with a soft Teflon tip piezo-­ biotics and no post-operative antibiotics for total device. The wound is irrigated for 2 min with 3% joint replacement [48]. The American Association peroxide. The exposed titanium is treated for of Hip and Knee Surgeons disagrees with this 2 min with phosphoric acid 35%. Take care not to recommendation because it contradicts interna- touch bone or soft tissues. The gingiva is thinned tional standards of care with limited evidence. and replaced. The cavity is rinsed with aqueous The Foundation for Arthroplasty Research and chlorhexidine solution. The open/close or apical Education is conducting a prospective, random- transposition technique is according to the surized study to establish level I evidence for single-­ geon’s wish, as is vital bone grafting. Antibiotic dose versus 24-h antibiotic prophylaxis in coverage after this mechanical debridement is not primary total knee arthroplasty [49]. Also, in proven necessary [57]. In contrast, Australian periclean-contaminated head and neck surgery in odontists US systematic antibiotics in 72% of the general, prolonging antibiotic prophylaxis for cases, with a combination of amoxicillin and met24–48  h after surgery was associated with the ronidazole, are reported by the same authors [58]. highest prevention rate of surgical site infection [50]. The antibiotics of choice were cefazolin, 12.4.8.5 Treatment of Infected amoxicillin-clavulanate, and ampicillin-­ Orthopedic and Craniofacial sulbactam. Clindamycin-treated patients showed Implants a higher infection rate that ampicillin-sulbactam-­ Antibiotics are necessary to treat infections after treated ones. orthopedic implantation when hardware needs to be retained [59]. Treatment with rifampin combi12.4.8.3 Treatment of Dental Peri-­ nations in staphylococcal infections is crucial. Implant Mucositis Quinolones can be combined with rifampicin Besides professional mechanical debridement, against susceptible staphylococci, as demonthe use of an oral irrigator with 0.06% aqueous strated in vitro, in animal studies and in clinical chlorhexidine solution reduces peri-implant trials [60]. Increasing antibacterial resistance mucositis over a 3-month period [51]. However, requires culture and sensitivity tests. Chronic simple rinsing with chlorhexidine solution did infection necessitating removal of craniofacial not enhance the clinical results of mechanical osteosynthesis plates is caused by biofilm and debridement [52]. Removal of the suprastructure cured by plate removal and antibiotic therapy during professional mechanical plaque removal [61]. Also, the flora is polymicrobial which points considerably reduces bacterial levels at the abut- at the necessity of culture and sensitivity testing. ment level [53]. Yeast may be suspected as well. and hip arthroplasty, no statistical difference was found for superficial and deep surgical site infections between the intraoperative rinsing with diluted povidone-iodine, chlorhexidine gluconate solution and saline solution [47].

12  Additively Manufactured Subperiosteal Jaw Implant (AMSJI)

Suggestions for infection prevention and cure in case of AMSJI:

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buccally to one post and an asymptomatic palatal fistula (Fig.  12.59). This case was treated with the removal of arm and post. This leads us to con• Rinsing the wound with anything else than sider the local gingival biotype. Thin periodontal saline solution is not proven to be more biotypes are of greater risk of developing receseffective. sions around natural teeth [62]. A thin gingival • A single, preoperative (30–60  min) dose of biotype is predisposed also to buccal recessions, amoxycillin (3 g) serves as proper prophylaxis. reduced periodontal health, and peri-implantitis • Prolonging antibiotic therapy (amoxicillin-­ [63, 64]. A crestal incision is more palatally clavulanate or ampicillin-sulbactam) for located than the top of the crest, and beveled 24–48 h is reasonable. (Fig.  12.60) is introduced, and follow-up is • Treatment of peri-post mucositis entails included in the open-study survey. Another solumechanical debridement (supra- and subgin- tion could exist in obliterating the spaces between gival) with temporary removal of the arms and loops using bone substitute material of supra-structure. bovine origin. This should be evaluated. To • Treatment of subperiosteal peri-post mucosi- exclude patients with a thin gingival biotype, tis requires specific, open sky, mechanical ASMJI would also exclude them from any other debridement and may benefit from post-­ implant-based solution. operative amoxicillin and metronidazole therapy. • Treatment of deep soft-tissue infections 12.4.10 Vertical and Horizontal requires culture and testing, and immediate Ostectomy Guides amoxicillin and metronidazole therapy. Quinolone (e.g., ciprofloxacin—beware hepa- The use of vertical ostectomy guides (VOG, totoxicity) and rifampicin therapy can be con- Figs.  12.45a, b and 12.61a) has the potential to sidered second choice when culture shows extend the use of AMSJI® to all cases in which resistance against penicillin or allergy is pres- there are still terminal teeth to be removed, or ent. Removal of hardware (sectioning of an where boney ridges are yet to be resorbed. This infected post, arm(s) or loop, even a wing) approach can be used to reduce the time of the may be considered when antibiotic treatment rehabilitation [37]. The shape of the bone after fails to be successful. ostectomy dictates the design of the AMSJI®. Therefore, it is important to avoid sharp angles in the implant structure at the resection platform 12.4.9 Buccal Recessions using a horizontal ostectomy guide (Figs. 12.46a, and Gingival Biotype b and 12.61b). Sharp corners can cause soft-tissue dehiscence over time (Fig. 12.62). These are An indefinite number of cases in the clinical sur- not necessarily symptomatic but need extra care vey organized by the International Steering and attention. A correct position of the VOG is Group showed stabile buccal gingival recessions mandatory for proper subsequent correct posiat the posts. None of the palatal sides showed a tioning of the AMSJI.  A proposal is made to recession. One case showed an ascending infec- include extra holes in the VOG for markings that tion, successfully treated with ciprofloxacin, have to coincide with screw holes in the AMSJI. which resulted in a persistent peri-post-mucositis

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b

Fig. 12.59  Case with cured ascending peri-post mucositis. (a) Intraoral view. The yellow arrow points at residual chronic peri-post inflammation. The red arrow points at a palatal perforation. (b) Corresponding design render

12.4.11 Biomechanical Evaluation Using Finite Element Analysis

Fig. 12.60  Section through a right-sided part of the maxilla, with maxillary antrum, alveolar recess, and nasal cavity. The incision (indicated in red) is beveled and palatally located to the mid-crest. As a consequence, a wider strip of keratinized mucosa is shifted buccally to cover the buccal aspect of the posts. The black arow indicates the mucogingival border

The current AMSJI design is an evolution of various design iterations that were based on various extensive optimizations. When the idea of a subperiosteal jaw implant was revisited, a general shape was designed, which was optimized afterwards. This was done by using topological optimization, which is a numerical method that starts from a very rough and basic design and reduces the amount of used material to achieve the best balance between implant safety and over dimensioning the implant. This has several advantages, under which reducing the overall implant thickness, for example, favors the aesthetic results, and avoidance of stress shielding is a phenomenon that causes the underlying bone to resorb because most of the chewing forces are absorbed by the metal implants causing the

12  Additively Manufactured Subperiosteal Jaw Implant (AMSJI)

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b

Fig. 12.61 (a) A vertical ostectomy guide (VOG), used to resect residual sharp/irregular crest without or after simultaneous edentulation of terminal dentition. (b) A

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horizontal ostectomy guide (HOG), used to smoothen the buccal aspect of the residual ridge, after vertical trimming

b

Fig. 12.62  A knee in an arm perforating a thin biotype of keratinized mucosa. Sharp angles sin arms or basal loop frame should be avoided at all costs. (a) Intraoperative

view. The yellow arrow points at a knee in the basal looped frame. (b) Intraoral view, 1 year post-operatively, pointing at the same knee, now perforating mucosa

underlying bone to remain unloaded and, thus, allowing it to resorb. To prevent this, the implants are being optimized by subdividing a general design in two areas: an area that may be altered (red/brown area in Fig.  12.63 and an area that may not be altered (gray area). Next, a set of boundary and loading conditions is applied which closely mimics the real-life situation, for example, forces, friction, fixation methods, etc. Using these parameters, together with the appropriate material properties, a mathematical computer analysis is done, which results in a new general design with a maximized performance

(Fig.  12.64). It is also during this optimization that the weaknesses in the arms were introduced to be able to easily remove a connection if necessary. Every individual design can also be subjected to its own finite element analysis or FEA, which is a mechanical analysis of the specific design. Again, using boundary conditions, a set of loads and the appropriate material properties, the design can be mathematically verified. This way, one can visualize and inspect the areas with the largest stresses and strains and check if they need to be reinforced or not and, thus, if there are potential problem areas or not. Furthermore, the

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Fig. 12.63  Subdivided design in preparation of the topological optimization

Fig. 12.64  Design result after topological optimization

maximum deformation and the loading of the bone (to prevent bone resorption) can also be simulated. But these results should be interpreted with care since these are only simulations based on, for example, correct placement during implantation. But checking every individual design be itself is very time consuming and computationally expensive. Even with a general and safe concept lay-out as shown in Fig. 12.64, the variance in designs between different cases makes it difficult to interpret the exact working of the AMSJI concept. This is why an extensive evaluation of the AMSJI concept offers a better understanding of the biomechanical behavior and the accompanying risks. Finite element methods/analyses (FEM/FEA) are gaining in popularity thanks to being a non-­ destructive research method, their broad field of use, and immense capabilities. Using these computer simulations, more accurate predictions can be done (for indications, ranging Cawood/Howell Class V–VIII) regarding failure/fatigue of the implants structure, stress shielding, osseointegration, and the potential occurrence of further bone resorption. To do so, various loading condi-

M. Rinaldi and M. Y. Mommaerts

tions based on activities of daily living were used, under (average and maximum) occlusal forces and bruxism forces (clenching and grinding). When considering average occlusion forces (200  N), no failure or fatigue of the AMSJI implants is expected (Fig. 12.65). Furthermore, no stress shield would occur (Fig. 12.66). If this occlusion force is increased to 1000 N, still no plastic deformation or fracture would occur, but due to microstrains exceeding the physiological window, stress shielding and overloading occur (Fig.  12.67). In both aforementioned loading cases, all micromotions are minor (