Surgical and Radiologic Anatomy for Oral Implantology 9780867155747, 2013027568, 0867155744

Table of contents :
COVER
Cover
Frontmatter
Copyright
To the Anonymous Donors
Contents
Chapter 1: Arteries, Veins, and Innervation of the Maxilla and theMandible
Chapter 2: Muscles of Facial Expression and Mastication
Chapter 3: Posterior Maxilla
Chapter 4: Anterior Maxilla
Chapter 5: Posterior Mandible
Chapter 6: Anterior Mandible
Chapter 7: Bone Density and Adjacent Teeth
Chapter 8: Anatomy for Surgical Emergencies
Chapter 9: Topographic Anatomy of the Maxillaand the Mandible
Chapter 10: Venipuncture
Dedication
Contributors
Preface
Acknowledgments
CH01
Arteries, Veins,and Innervationof the Maxillaand the Mandible
External Carotid Artery
Maxillary Artery
Pterygopalatine Fossa
Veins of the Head
Trigeminal Nerve
References
CH02
Muscles of Facial Expression
Muscles of Mastication
CH03
Greater and Lesser Palatine Foramina
Greater Palatine Artery and Nerve
The Maxillary Sinus
The Buccal Fat Pad
Inadequate Bony Structure in the Posterior Maxilla
References
CH04
The Nasal Cavity
Infraorbital Foramen
Maxillary Incisive Foramen and Canal
Inadequate Bony Structure in the Anterior Maxilla
References
CH05
Mandibular Ramus
Lingual Nerve
Inferior Alveolar Canal/Nerve
Submandibular Fossa
Inadequate Bony Structure in the Posterior Mandible
Clinical Management of Mandibular Alveolar BoneDeficiency
References
CH06
Mental Foramen/Nerve and Its Anterior Loop
Mandibular Incisive Canal
Accessory Lingual Foramina of the Mandible
Harvesting a Block Graft from the Anterior Mandible
Inadequate Bony Structure in the Anterior Mandible
References
CH07
Bone Density
Adjacent Teeth/Roots
Conclusion
References
CH08
Intrasurgical Bleeding
Hemorrhage of the Floor of the Mouth
Cricothyrotomy
References
CH09
TopographicAnatomy of theMaxilla andthe MandibleThe illustrations
CH10
Anatomy of the Systemic Circulation
Arteries and Veins of the Upper Limb
Venous Physiology
BACK COVER
Louie Al-Faraje

Citation preview

Surgical and Radiologic Anatomy for Oral Implantology

Surgical and Radiologic for Oral Implantology

Louie Al-Faraje, DDS Founder and Director California Implant Institute San Diego, California With contributions by Christopher Church, MD Arthur Rathburn, LFD

Quintessence Publishing Co, Inc Chicago, Berlin, Tokyo, London, Paris, Milan, Barcelona, Beijing, Istanbul, Moscow, New Delhi, Prague, São Paulo, Seoul, Singapore, and Warsaw

Library of Congress Cataloging-in-Publication Data Al-Faraje, Louie, author. Surgical and radiologic anatomy for oral implantology / Louie Al-Faraje. p. ; cm. Includes bibliographical references. ISBN 978-0-86715-574-7 I. Title. [DNLM: 1. Dental Implantation, Endosseous--methods. 2. Anatomic Landmarks--radiography. 3. Dental Implants. 4. Jaw--anatomy & histology. 5. Jaw--surgery. WU 640] RK667.I45 617.6’93--dc23 2013027568

© 2013 Quintessence Publishing Co, Inc Quintessence Publishing Co, Inc 4350 Chandler Drive Hanover Park, IL 60133 www.quintpub.com 5 4 3 2 1 All rights reserved. This book or any part thereof may not be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, or otherwise, without prior written permission of the publisher. Editor: Leah Huffman Design: Ted Pereda Production: Angelina Sanchez Printed in China

To the Anonymous Donors We are respectful of and deeply indebted to the six anonymous individuals whose cadaver sections are shown in this book. They have made a donation to science that will enrich the fundamental knowledge base of human anatomy and will benefit today’s students and clinicians of oral implantology. Future generations can then build on this foundational knowledge. I have done all in my power to preserve, protect, and maintain the dignity of these individuals. We did not know them in life but studied them in death; whoever they were, we honor their remains and dignify their gift. To these six, our deepest thanks.

Contents Dedication  viii Contributors  x Preface  xi Acknowledgments  xii

[1] 

 rteries, Veins, and Innervation of the Maxilla and the A Mandible  1



External Carotid Artery  2



Maxillary Artery  4



Pterygopalatine Fossa  6



Veins of the Head  12



Trigeminal Nerve  14

[2] 

Muscles of Facial Expression and Mastication  21



Muscles of Facial Expression  22



Muscles of Mastication  28

[3] 

Posterior Maxilla  35



Greater and Lesser Palatine Foramina  36



Greater Palatine Artery and Nerve  38



The Maxillary Sinus  42



The Buccal Fat Pad  80



Inadequate Bony Structure in the Posterior Maxilla  90

[4] 

Anterior Maxilla  97



The Nasal Cavity  98



Infraorbital Foramen  112



Maxillary Incisive Foramen and Canal  114



Inadequate Bony Structure in the Anterior Maxilla  118

[5] 

Posterior Mandible  125



Mandibular Ramus  126



Lingual Nerve  138



Inferior Alveolar Canal/Nerve  144



Submandibular Fossa  147

Inadequate Bony Structure in the Posterior Mandible  152 Clinical Management of Mandibular Alveolar Bone Deficiency  153

[6] 

Anterior Mandible  169



Mental Foramen/Nerve and Its Anterior Loop  170



Mandibular Incisive Canal  178



Accessory Lingual Foramina of the Mandible  184

Harvesting a Block Graft from the Anterior Mandible  192 Inadequate Bony Structure in the Anterior Mandible  193

[7] 

Bone Density and Adjacent Teeth  203



Bone Density  204



Adjacent Teeth/Roots  210

Conclusion  212

[8] 

Anatomy for Surgical Emergencies  215



Intrasurgical Bleeding  216



Hemorrhage of the Floor of the Mouth  222

Cricothyrotomy  228

[9] Topographic Anatomy of the Maxilla and the Mandible  233

[10] Venipuncture 

239



Anatomy of the Systemic Circulation  240



Arteries and Veins of the Upper Limb  243



Venous Physiology  248

Dedication This book is dedicated to Ala-al-din abu Al-Hassan Ali ibn Abi-Hazm al-Qarshi alDimashqi, known as Ibn al-Nafis. Ibn al-Nafis was an Arab physician who is mostly famous for being the first to describe the pulmonary circulation of the blood. He was born in 1213 in Damascus. He attended the Medical College Hospital (Bimaristan Al-Noori) in Damascus. Apart from medicine, Ibn al-Nafis learned jurisprudence, literature, and theology. He became an expert on the Shafi’i school of jurisprudence and an expert physician. In 1236, Al-Nafis moved to Egypt. He worked at the Al-Nassri Hospital and subsequently at the Al-Mansouri Hospital as a chief physician. When he died in 1288, he donated his house, library, and clinic to the Mansuriya Hospital.

Discovery of pulmonary circulation The theory that was accepted prior to Al-Nafis was that of Galen from the 2nd century. Galen had theorized that the blood reaching the right side of the heart went through invisible pores in the cardiac septum, to the left side of the heart, where it mixed with air to create spirit and was then distributed to the body. According to Galen, the venous system was quite separate from the arterial system, except when they came in contact through the unseen pores. Based on his anatomical knowledge, Al-Nafis stated that: The blood from the right chamber of the heart must arrive at the left chamber but there is no direct pathway between them. The thick septum of the heart is not perforated and does not have visible pores as some people thought or invisible pores as Galen thought. The blood from the right chamber must flow through the vena arteriosa [pulmonary artery] to the lungs, spread through its substances, be mingled there with air, pass through the arteria venosa [pulmonary vein] to reach the left chamber of the heart and there form the vital spirit.

Elsewhere in his book, he said that: The heart has only two ventricles…and between these two there is absolutely no opening. Also dissection gives this lie to what they said, as the septum between these two cavities is much thicker than elsewhere. The benefit of this blood [that is in the right cavity] is to go up to the lungs, mix with what is in the lungs of air, then pass through the arteria venosa to the left cavity of the two cavities of the heart and of that mixture is created the animal spirit.

In describing the anatomy of the lungs, Al-Nafis stated: The lungs are composed of parts, one of which is the bronchi; the second, the branches of the arteria venosa; and the third, the branches of the vena arteriosa, all of them connected by loose porous flesh.

He then added that: The need of the lungs for the vena arteriosa is to transport to it the blood that has been thinned and warmed in the heart, so that what seeps through the pores of the branches of this vessel into the alveoli of the lungs may mix with what there is of air therein and combine with it, the resultant composite becoming fit to be spirit, when this mixing takes place in the left cavity of the heart. The mixture is carried to the left cavity by the arteria venosa.

Al-Nafis also postulated that nutrients for the heart are extracted from the coronary arteries: Again, his [Avicenna’s] statement that the blood that is in the right side is to nourish the heart is not true at all, for the nourishment to the heart is from the blood that goes through the vessels that permeate the body of the heart.

viii

Writings The most voluminous of his books is Al-Shamil fi al-Tibb, which was planned to be an encyclopedia comprising 300 volumes but was never completed because of his death. The manuscript is available in Damascus. His book on ophthalmology is largely an original contribution. His most famous book is The Summary of Law (Mujaz al-Qanun). Another famous book embodying his original contribution was on the effects of diet on health, entitled Kitab al-Mukhtar fi al-Aghdhiya.

Left lung

Right lung

Bronchus

Arteria venosus

Left auricle Venous arteriosus

Right auricle

Aorta, blood vital spirit

Left ventricle Vena cava

Right ventricle

  The pulmonary circulation of the blood according to Ibn al-Nafis.

  A page from the book on ophthalmology by Ibn al-Nafis.

ix

Contributors Christopher Church, md

Director Loma Linda Sinus and Allergy Center Associate Professor Department of Otolaryngology–Head and Neck Surgery Loma Linda University School of Medicine Loma Linda, California

Arthur Rathburn, lfd

Clinical Director Department of BioMedical Sciences International Biological Inc Grosse Pointe Park, Michigan

x

Preface There are a number of excellent anatomical atlases and textbooks available to dental clinicians, but often these atlases fail to meet the clinical demands of defining intraoperative structures for oral implantologists because of the overwhelmingly detailed minutia. The aim of this book is to present an adequate amount of anatomical material in a readable and interesting format. I have relied on my own clinical and teaching experience to determine what is adequate. No major omissions have been made intentionally, but the primary focus is the clinical relevance to oral implantology. Every effort has been made to sequence the information in a logical manner. The illustrations in this book are the result of very hard work and cooperation between the illustrators and me. Nonetheless, certain anatomical landmarks are difficult to illustrate in a diagram format, which leads to confusion when students and professionals are confronted with actual specimens in the dissecting room or in the operatory. Therefore, photographs of some clinical cases and of dissected structures of the maxilla, the mandible, and the nasal cavity are provided in this book that show structures as they actually exist in the dissected or live body. I hope that they will bridge the gap that occasionally exists between books and the “real thing.” On another note, today’s oral implantologists have the advantage of cone beam computed tomography (CBCT) volumetric imaging. This book provides several CBCT images of those anatomical landmarks that usually do not appear on two-dimensional imaging (eg, panoramic, intraoral, and cephalometric radiographs). I encourage the use of CBCT imaging for every dental implant surgery. The CBCT scan technology allows us to visualize the patient’s anatomy and pathology like never before. With these images, we can measure the exact distance available for implant placement under or above certain anatomical landmarks, measure the exact bone density and the precise width of the available alveolar ridge, and select the most suitable locations for the planned implants. This will lead to improved treatment planning and reduced morbidity and will also reduce our liability. It is my hope that these illustrations, CBCT images, photographs, and text will simplify the learning and the execution of implant-related surgical procedures in a region of the body that presents special topographic and anatomical difficulties.

xi

Acknowledgments To God, the creator of the perfect human body, who has made all my projects possible through his guidance and gracious love. To my parents, Omar Al-Faraje and Nadia Al-Rifai, whose guidance and nurturing instilled in me a quest for perfection. To my wife, Rana, who gave up many date nights and social events and supported me to the fullest throughout this project. I will make up the time, I promise. To my children, Nadia, Omar, and Tim. Your smiles and inspiration provide the fortitude and drive in my life. I am very blessed. My special thanks go to Dr Christopher Church for his contribution to the nasal and sinus anatomy sections of the book and to Arthur Rathburn, who provided the anatomical dissections and skull preparations used in this book. It is a privilege to have friends like you. It is my pleasure to recognize the help of Mr Kim Jin Cheol, on behalf of DIO Implant, who facilitated the use of the company’s resources for this project. My deepest thanks to Lisa Bywaters from Quintessence Publishing for the opportunity to educate my colleagues on the special anatomical considerations for surgical oral implantology. I am very fortunate to have such a highly skilled and professional editor (I still do not believe that she is not a dentist). To my patients, without whom I would not have been able to compile the clinical photographs I have. You make my profession so enjoyable and rewarding. To all of my students at the California Implant Institute. It is always a pleasure and an honor to share with you my knowledge and expertise in implant dentistry. For the last few years, my greatest professional joy has been interacting with you and my colleagues at the California Implant Institute. I am also particularly grateful to Jason Rohack and Qualis Media for delivering the illustrations used in this text at a high level and in a timely manner. Many hours were spent and countless emails were exchanged to produce these specific illustrations.

xii

1

Arteries, Veins, and Innervation of the Maxilla and the Mandible This chapter describes the following anatomical landmarks and their relevance to implant-related oral surgical procedures: the external carotid artery, the maxillary artery, the pterygopalatine fossa, the veins of the head, and the trigeminal nerve.

Arteries, Veins, and Innervation of the Maxilla and the Mandible

1

External Carotid Artery The arteries that supply blood to the face, the maxilla, and the mandible arise largely from the external carotid artery. However, branches of the ophthalmic artery (a branch of the internal carotid artery) supply the forehead, scalp, upper eyelid, and nose. The external and internal carotid arteries (Figs 1-1 and 1-2) branch off the common carotid artery at the level of the superior border of the thyroid cartilage. The external carotid artery has eight branches: •  Three anterior branches: the superior thyroid artery, the lingual artery, and the facial artery •  Two terminal branches: the maxillary artery and the superficial temporal artery •  Two posterior branches: the occipital auricular artery and the posterior auricular artery •  One medial branch: the ascending pharyngeal artery

Right common carotid artery

Left common carotid artery

Vertebral artery

Left subclavian artery

Right subclavian artery Thyrocervical trunk

Vertebral artery

Innominate artery Aortic arch

Fig 1-1  The main branches of the aortic arch.

2

External Carotid Artery

Ophthalmic artery

Posterior auricular artery

Angular artery

Superficial temporal artery Ascending pharyngeal artery

Maxillary artery

Occipital artery

Internal carotid artery

Facial artery

External carotid artery

Lingual artery

Superior thyroid artery

Vertebral artery Common carotid artery

Subclavian artery

Fig 1-2  The main branches of the external carotid artery.

3

Arteries, Veins, and Innervation of the Maxilla and the Mandible

1

Maxillary Artery The maxillary artery (Fig 1-3) arises in the parotid gland as a terminal branch of the external carotid artery. The branches of the maxillary artery can be divided into three parts: •  Part I or the mandibular part (located within the substance of the parotid gland and anterior to the external acoustic meatus): In this part, the maxillary artery gives branches to the ear, the dura, the temporomandibular joint, the mandibular teeth, and the mylohyoid muscle. •  Part II or the pterygoid part (located in the infratemporal fossa): The branches here are mainly to the muscles of mastication, the buccal mucosa and skin, and the buccinator muscles through the buccal artery. •  Part III or the pterygopalatine part (the branches in the pterygopalatine fossa after entry through the pterygomaxillary fissure): The branches here are mainly to the hard and soft palate through the branches of the descending palatine artery, to the maxillary molars and premolars through the posterior superior alveolar artery, to the upper pharynx and tympanic cavity through the artery of the pterygoid canal, to the nasopharynx and sphenoidal sinus through the pharyngeal artery, and to the maxillary anterior teeth through the infraorbital artery.

Middle meningeal a. entering foramen spinosum

Deep temporal aa.

Posterior superior alveolar a.

Infraorbital a.

Deep auricular and anterior tympanic aa. Maxillary a. Mylohyoid a. Buccal a.

External carotid a. Internal carotid a.

Inferior alveolar a.

Common carotid a.

Fig 1-3  The course of the maxillary artery. a.—artery; aa.—arteries.

4

Maxillary Artery

The maxillary artery terminates as the sphenopalatine artery on the nasal septum after splitting into nasal branches. Figure 1-4 demonstrates in detail the branches of all three parts of the maxillary artery.

Sphenopalatine a. Artery of pterygoid canal

Posterior superior alveolar a. Pharyngeal a.

Infraorbital a.

Anterior tympanic a.

1st

rt

nd

Anterior superior alveolar artery branches

pa

Buccal a.

Posterior superior alveolar a.

2

rt

pa

Accessory meningeal a.

Infraorbital foramen

Descending palatine a.

Foramen ovale

Deep auricular a.

Anterior deep temporal a.

3rd

Posterior deep temporal a.

Middle meningeal a.

Superficial temporal a.

Lateral pterygoid a.

par t

Foramen spinosum

Anterior branch of middle meningeal a.

Masseteric a. Medial pterygoid a.

Lingual foramen of the mandible

External carotid a.

Inferior alveolar a. Mylohyoid a. Mental a.

Mental foramen

Incisive a.

Fig 1-4  The distribution of all three parts of the maxillary artery. a.—artery.

5

Arteries, Veins, and Innervation of the Maxilla and the Mandible

1

Pterygopalatine Fossa The pterygopalatine fossa, also called the sphenopalatine fossa, is a narrow, pyramid‐shaped fossa on the lateral aspect of the skull. The fossa is a crossroads between the orbit, nasal cavity, oral cavity, nasopharynx, and middle cranial fossa (Figs 1-5 to 1-7). The pterygopalatine ganglion and the terminal branches of the maxillary artery are situated in its superior part. The pterygopalatine fossa along with the infratemporal and pterygoid fossae are referred to as the retromaxillary space.

Zygomatic bone

Greater wing of sphenoid bone Sphenopalatine foramen

Margin of infraorbital fissure

Infraorbital groove

Pterygomaxillary fissure

Palatine canal ANTERIOR WALL (maxilla)

Superior orbital fissure

Orbital surface

Sphenopalatine notch (foramen)

Posterior margin of infraorbital fissure Area covered by maxilla

Foramen rotundum POSTERIOR WALL (sphenoid bone)

Palatine canal MEDIAL WALL (palatine bone)

Pyramidal process

Pterygoid canal

Lateral pterygoid plate

Fig 1-5  The anterior, medial, and posterior bony walls of the left pterygopalatine fossa.

6

Pterygopalatine Fossa

Frontal bone Sphenoid bone Optic canal Hypophyseal fossa Dorsum sellae

Ethmoid bone, orbital plate (lamina papyracea)

Canalis rotundus Sphenoid bone, greater wing (cut)

Orbital process (palatine bone)

Sphenoid canaliculi

Sphenopalatine foramen Pterygoid canal Pterygopalatine fossa

Palatine bone Lateral pterygoid plate

Pterygoid hamulus Pyramidal process (palatine bone)

Fig 1-6 The pterygopalatine fossa after removal of the zygomatic bone, greater ala of the sphenoid bone, zygomatic arch, and temporal squama.

7

Arteries, Veins, and Innervation of the Maxilla and the Mandible

1

Hard palate

Infraorbital canal

Maxillary sinus

Zygomatic arch

Infratemporal fossa

Palatine bone Pterygopalatine fossa Projection of the pterygoid canal Lateral pterygoid process (sphenoid bone) The sphenoid sinus can extend into the pterygoid process in cases of excessive pneumatization

Medial pterygoid process (sphenoid bone)

Fig 1-7  Horizontal section of the pterygopalatine fossa at the level of the infraorbital foramen.

8

Pterygopalatine Fossa Boundaries and communications of the pterygopalatine fossa1–3 The anterior boundary comprises the superomedial part of the infratemporal surface of the maxilla. The posterior boundary comprises the root of the pterygoid process of the sphenoid bone. Through this posterior wall, the fossa communicates with the middle cranial fossa via the foramen rotundum and the pterygoid canal (also called the vidian canal). The foramen rotundum lies lateral and superior to the pterygoid canal at the base of the pterygoid process. The vidian canal is located medial and superior to the pterygopalatine ganglion, and thus its nerve lies medial to the major vessels of the pterygopalatine fossa, which allows the surgeon to avoid excessive bleeding during vidian neurectomy (Fig 1-8).

Optic canal Superior orbital fissure Nasal bone Lacrimal bone Lacrimal groove

Inferior orbital fissure

Infraorbital groove Maxillary artery Infraorbital foramen

a

Pterygoid artery and nerve Pharyngeal artery and nerve Pterygopalatine ganglion Posterior superior nasal nerve

CN V2 Infraorbital artery and nerve

Sphenopalatine artery Nasopalatine nerve Descending palatine artery (might branch off into the greater palatine artery and lesser palatine artery while in the fossa) Greater and lesser palatine nerves

b

Lesser palatine artery

Posterior superior alveolar nerve Posterior superior alveolar artery (may arise from the infraorbital artery) Greater palatine artery

Fig 1-8  (a and b) The branching pattern of the maxillary artery in its relationship to the pterygopalatine ganglion in the pterygopalatine fossa. Some variation in the branching pattern does exist. CN V2—maxillary nerve.

9

Arteries, Veins, and Innervation of the Maxilla and the Mandible

1 Also, at the posterior wall and in an inferoposterior direction, the fossa communicates with the nasopharynx through the palatovaginal (pharyngeal) canal. The palatovaginal canal is located between the vaginal process of the vomer bone and the sphenoid process of the palatine bone, and it passes into the floor of the sphenoid sinus between the pterygoid canal and the vomerine crest of the sphenoid. The opening to the palatovaginal (pharyngeal) canal in the nasal cavity is located near the lateral margin of the ala of the vomer, at the roots of the pterygoid process. The medial boundary comprises part of the perpendicular plate of the palatine bone and its orbital sphenoidal processes. The pterygopalatine fossa communicates with the nasal cavity at this wall through the sphenopalatine foramen. The sphenopalatine foramen is bounded in front, below, and behind by the palatine bone (and the sphenopalatine incisure) and above by the body of sphenoid bone. Laterally, the pterygopalatine fossa communicates with the infratemporal fossa through the pterygomaxillary fissure. The superior border of the pterygopalatine fossa comprises a small part of the orbital plate of the palatine bone and part of the maxillary surface of the greater wing of the sphenoid bone and junction with the inferior orbital fissure. The inferior border of the pterygopalatine fossa is formed by the pyramidal process of the palatine bone; the pterygopalatine (greater palatine) canal is located at this inferior border. The pterygopalatine canal is a continuation of the pterygopalatine fossa and is formed when the maxillary surface of the perpendicular plate of the palatine bone articulates with the maxilla. It leads to the greater and lesser palatine foramina in the roof of the oral cavity. Table 1-1 provides a detailed description of the contents of the pterygopalatine fossa.

Surgical importance of the anatomy of the pterygopalatine fossa The anatomy of the pterygopalatine fossa is especially important for the following surgeries: •  Vidian neurectomy (the surgical sectioning of the pterygoid nerve for the treatment of vasomotor rhinitis, Sluder’s neuralgia of the pterygopalatine ganglion, crocodile tears syndrome, allergic rhinitis [hay fever], and nasal polyposis) •  Transmaxillary ligature of the maxillary artery (in cases of severe nasal bleeding that cannot be controlled by anterior and/or posterior tamponades) •  Craniofacial surgery •  Surgery of the base of the skull or nasopharynx •  Lateral approaches to the orbit •  Traumatology Vasomotor rhinitis is a condition that results from a relative imbalance of parasympathetic to sympathetic stimulation of the blood vessels and glands of the nasal mucosa. It is characterized by symptoms of clear rhinorrhea and nasal congestion. Sluder’s neuralgia of the pterygopalatine ganglion is a rare disorder characterized by unilateral, severe, burning, boring, or nagging headache, starting around the eye and the bridge of the nose and radiating to the maxilla and maxillary teeth, zygoma, mastoidal area and occiput, or even as far down as the shoulder and arm. Crocodile tears syndrome (gustatory lacrimation; tearing on eating) is a rare complication of a facial nerve lesion proximal to the geniculate ganglion, whereby regenerating preganglionic salivary fibers intended for the chorda tympani nerve are misdirected to the sphenopalatine ganglion, which project to the lacrimal gland.

10

Pterygopalatine Fossa

Table 1-1

Contents of the pterygopalatine fossa

Opening

Communication

Location

Transmitted structures

Foramen rotundum

Middle cranial fossa

Posterior wall

• CN V2

Pterygoid canal

Middle cranial fossa

Posterior wall

• Nerve of the pterygoid canal (vidian nerve) (formed from the greater petrosal and deep petrosal nerves) • Artery of pterygoid canal • Veins of pterygoid canal

Palatovaginal (pharyngeal) canal

Nasopharynx

Posterior wall

• Pharyngeal branches of the pterygopalatine ganglion of CN V2 (the ganglion is located in the pterygopalatine fossa) • Pharyngeal artery (maxillary artery) • Pharyngeal vein

Sphenopalatine foramen

Nasal cavity

Medial wall

• Nasopalatine nerve and posterior superior nasal nerve (both are pterygopalatine ganglionic branches of CN V2) • Sphenopalatine artery (maxillary artery) • Sphenopalatine vein

Pterygomaxillary suture

Infratemporal fossa

Lateral wall

• Posterior superior alveolar nerve • Pterygoid part of the maxillary artery (after branching off into the posterior superior alveolar artery, its only branch outside the fossa) • Posterior superior alveolar vein

Inferior orbital fissure

Orbit

Superior wall

• Infraorbital and zygomatic nerves (CN V2) • Infraorbital artery (maxillary artery) • Infraorbital vein

Pterygopalatine (greater palatine) canal

Oral cavity

Inferior wall

• Descending palatine nerve (CN V2) (splits into the greater and lesser palatine within the canal) • Descending palatine artery (maxillary artery) (splits into the greater and lesser palatine within the canal) • Descending palatine vein

Yellow bullet—nerve; red bullet­—artery; blue bullet—vein.

11

Arteries, Veins, and Innervation of the Maxilla and the Mandible

1

Veins of the Head The principal veins of the head and neck are the internal jugular vein, the external jugular vein, and the anterior jugular vein. The internal jugular vein collects blood from the interior of the skull, the anterior and lateral face, and the oral cavity and the neck via the sigmoid sinus, the inferior petrosal sinuses, and the facial, lingual, superior, and middle thyroid and retromandibular (anterior division) veins. The external jugular vein collects blood from the lateral skull and the occiput via the posterior auricular and the retromandibular (posterior division) veins. The anterior jugular vein collects blood from the anterior neck region.

Pterygoid venous plexus The pterygoid venous plexus is situated on the medial side of the mandibular ramus within the pterygoid muscles. It is linked to the facial vein via the deep facial vein, to the retromandibular vein via the maxillary vein, and to the cavernous sinus via the sphenoidal emissary vein. The pterygoid plexus drains into the jugular veins. This plexus is of a special importance to dentists because if the needle is overinserted during posterosuperior alveolar block, it may penetrate the pterygoid plexus of the vein and the maxillary artery in the infratemporal fossa (Fig 1-9), thus causing hematoma. This results in extraoral swelling a few minutes after the injection. The hematoma will cause tissue tenderness and discoloration, which will last until the blood is broken down by the body, and possible spread of infection to the cavernous venous sinus if the needle is contaminated. A hematoma can also result during other blocks, such as infraorbital and inferior alveolar blocks. To avoid injection into blood vessels, aspiration should always be attempted for all injections.

12

Veins of the Head

Supraorbital vein

Deep temporal veins

Cavernous sinus

Superficial temporal vein

Supratrochlear vein

Superior ophthalmic vein

Superior and inferior petrosal sinuses

Angular vein

Sigmoid sinus

Deep facial vein Pterygoid plexus Maxillary vein Retromandibular vein

Internal jugular vein

Common facial vein Facial vein

External palatine vein

Lingual vein

Fig 1-9  Pterygoid venous plexus.

13

Arteries, Veins, and Innervation of the Maxilla and the Mandible

1

Trigeminal Nerve The 12 cranial nerves control motor and sensory functions of the head and neck. Table 1-2 and Fig 1-10 summarize the skull base foramina from which these nerves exit the skull and their functions.

Table 1-2

Exit foramina and functions of the cranial nerves

Nerve

Name

Skull base foramina

Functions

I

Olfactory

Cribriform plate

Sensory for smell

II

Optic

Optic canal

Sensory for vision

III

Oculomotor

Superior orbital fissure

Motor for six eye muscles

IV

Trachlear

Superior orbital fissure

Motor for one eye muscle

V1

Trigeminal/ophthalmic Superior orbital division fissure

Sensory for lacrimal gland, nearby air sinuses, scalp, forehead, upper eyelid, and nose

V2

Trigeminal/maxillary division

Sensory for parts of the nasal and oral cavities and the skin of the cheek and upper lip

V3

Trigeminal/mandibular Foramen ovale division

Foramen rotundum

Sensory for the skin over the mandible, lower lip, temporal region, and much of the oral cavity Motor for muscles of mastication as well as the anterior belly of the digastric muscle, mylohyoid muscle, tensor tympani, and tensor veli palatine muscles

VI

Abducens

Superior orbital fissure

Motor for one eye muscle

VII

Facial

Internal auditory meatus

Motor for muscles of facial expression, stapidius, and posterior belly of the digastric muscle; also motor for the lacrimal glands, oral and nasal mucosa, and submandibular and sublingual glands Sensory for the external auditory meatus; lateral pinna; mastoid; mucosa of the pharynx, nose, and palate; as well as sensory for taste for the anterior two-thirds of the tongue via the chorda tympani

VIII

Vestibulocochlear

Internal auditory meatus

Sensory for balance and hearing

IX

Glossopharyngeal

Jugular foramen

Motor for the stylopharyngeus muscle and parotid gland Sensory for the posterior external ear, tragus, posterior third of the tongue, soft palate, nasopharynx, tympanic membrane, Eustachian tube, and mastoid region and sensory for taste for the posterior third of the tongue

X

Vagus

Jugular foramen

Motor for the pharyngeal and laryngeal muscles, including the palatoglossus muscle; also motor to the smooth muscles and glands of the pharynx, larynx, heart, esophagus, and stomach Sensory for the ear, external auditory meatus, external surface of the tympanic membrane, dura of posterior cranial fossa, larynx, lungs, heart, esophagus, and stomach

14

XI

Spinal accessory

Jugular foramen

Motor for the sternocleidomastoid and trapezius muscles

XII

Hypoglossal

Hypoglossal canal

Motor for all intrinsic tongue muscles and all extrinsic tongue muscles except the palatoglossus muscle (innervated by CN X)

Trigeminal Nerve

Olfactory bulb I

Olfactory nerves leave the bulb and the tract and enter the nasal cavity through the cribriform plate

Olfactory tract Optic n. II

Optic canal

Oculomotor n. III

Superior orbital fissure

Trochlear n. IV

Superior orbital fissure

Trigeminal n. V

V1 Superior orbital fissure V2 Foramen rotundum V3 Foramen ovale

Nerve intermedius

Abducens n. VI

Superior orbital fissure

Facial n. VII

Internal auditory meatus

Vestibulocochlear n. VIII Internal auditory meatus

Glossopharyngeal n. IX Jugular foramen

Pyramid

Spinal accessory n. XI Jugular foramen

Olive Spinal accessory n. XI Jugular foramen

Ventral rootlets of first cervical n.

Hypoglossal n. XII Hypoglossal canal

Fig 1-10  The origin of the cranial nerves as seen from an inferior aspect of the brain. n.—nerve.

15

Arteries, Veins, and Innervation of the Maxilla and the Mandible

1 Maxillary nerve (CN V2) The maxillary nerve (Fig 1-11a) is the second branch of the fifth cranial nerve (trigeminal nerve). Its function is the transmission of sensory fibers from the maxillary teeth, the nasal cavity, the sinuses, and the skin between the palpebral fissure and the mouth (Figs 1-11b and 1-11c). In the cranium, the maxillary nerve branches off into the middle meningeal nerve, then passes through the foramen rotundum into the pterygopalatine fossa, where it divides into the zygomatic nerve, the ganglionic branches (pterygopalatine branches), and the infraorbital nerve. •  The zygomatic nerve passes through the inferior orbital fissure and gives branches of sensory fibers to the lacrimal nerve, then divides into the zygomaticotemporal branch (temple) and the zygomaticofacial branch (for the skin over the zygomatic arch). •  The ganglionic branches are nasal branches (nasopalatine branches) that pass through the sphenopalatine foramen into the nasal cavity, the palatine nerves (greater and lesser) for the soft and hard palates, and the pharyngeal nerve, which provides sensory supply to the upper pharynx. •  The infraorbital nerve enters the orbit through the inferior orbital fissure (after branching off into the posterior superior alveolar nerves to the molars and the medial superior alveolar nerves); it traverses the infraorbital groove and canal in the floor of the orbit, where it branches off into the anterior superior alveolar nerve, and appears on the face at the infraorbital foramen. Here it is referred to as the infraorbital nerve, a terminal branch. At its termination, the nerve lies beneath the quadratus labii superioris and divides into several branches that innervate the side of the nose, the lower eyelid (inferior palpebral nerve), and the upper lip (the superior labial nerve), joining with filaments of the facial nerve.

Communicating branch with CN V1 Zygomaticotemporal n.

Zygomaticofacial n.

Foramen rotundum

Infraorbital n.

Maxillary n. (CN V2)

Trigeminal ganglion

CN V1

Zygomatic n.

Infraorbital foramen

Middle meningeal n.

Infraorbital n.

Anterior superior alveolar n. CN V3 Ganglionic n. Pterygopalatine ganglion Posterior superior alveolar nerves

a

16

Medial superior alveolar n.

Trigeminal Nerve

b Nasopalatine nerve Nasopalatine block

Infraorbital nerve Infraorbital block

Incisive foramen Middle superior alveolar nerve MSA block

Greater palatine nerve GP block

Greater palatine foramen

Posterior superior alveolar nerve PSA block

c

Buccal nerve Buccal block

Fig 1-11  (a) The maxillary nerve. n.—nerve; CN V1—ophthalmic nerve; CN V3—mandibular nerve. (b) Region of skin supplied by the maxillary nerve. (c) Innervation of the maxilla along the recommended anesthesia technique per area.

17

Arteries, Veins, and Innervation of the Maxilla and the Mandible

1 Mandibular nerve (CN V3) The mandibular nerve (Fig 1-12a) is the third branch of the trigeminal nerve, arising from the trigeminal ganglion. Unlike the other two branches (the maxillary and the ophthalmic nerves, both entirely sensory), the mandibular nerve has both sensory and motor divisions. After passing through the foramen ovale and branching off into a meningeal branch in the infratemporal fossa, the nerve divides into the sensory branches—the auriculotemporal, lingual, inferior alveolar, and buccal nerves to the skin over the mandible, lower lip, temporal region, and much of the oral cavity (Fig 1-12b)—and the motor branches that innervate the muscles of mastication (masseteric, deep temporal, and pterygoid nerves). The inferior alveolar nerve carries motor fibers for the mylohyoid muscle and the anterior belly of the digastric muscle and sensory fibers that enter the canal through the mandibular foramen; it gives branches to the mandibular teeth and exits through the mental foramen under the mental nerve (see chapter 6). Damaging the inferior alveolar nerve will alter the sensation to areas supplied by it and by the mental nerve. Branches of the trigeminal nerve are also frequently used to distribute fibers derived from other cranial nerves.

18

Trigeminal Nerve Lateral pterygoid muscle

Pterygoid nerves

Deep temporal nerve

Meningeal branch

Auriculotemporal nerve Lingual nerve Inferior alveolar nerve Masseteric nerve Medial pterygoid muscle Masseter muscle Buccal nerve Buccinator muscle

a

Mental foramen

Inferior dental branches

b

Fig 1-12  (a) The mandibular nerve. (b) Region of skin supplied by the mandibular nerve.

19

Arteries, Veins, and Innervation of the Maxilla and the Mandible

1

References 1. Choi J, Park HS. The clinical anatomy of the maxillary artery in the pterygopalatine fossa. J Oral Maxillofac Surg 2003;61:72– 78. 2. Li J, Xu X, Wang J, Jing X, Guo Q, Qiu Y. Endoscopic study for the pterygopalatine fossa anatomy: Via the middle nasal meatus-sphenopalatine foramen approach. J Craniofac Surg 2009;20:944–947.

20

3. Osawa S, Rhoton AL Jr, Seker A, Shimizu S, Fujii K, Kassam AB. Microsurgical and endoscopic anatomy of the vidian canal. Neurosurgery 2009;64(5 suppl 2):385–411.

2 Muscles of Facial Expression and Mastication This chapter describes the muscles of facial expression and the muscles of mastication and their relevance to implant-related oral surgical procedures.

Muscles of Facial Expression and Mastication

2

Muscles of Facial Expression The muscles of facial expression are paired muscles in the superficial fascia of the facial tissues (Table 2-1 and Figs 2-1 to 2-4). Almost all of them originate from bone (rarely the fascia) and insert on skin tissue, and all of them are innervated by the facial nerve (CN VII).

Table 2-1

Muscles of facial expression

Muscle(s)

Origin

Insertion

Main action(s)

Innervation

Occipitofrontalis/ epicranial (frontal belly)

Epicranial aponeurosis near the coronal suture

Skin and subcutaneous tissue of the eyebrows and forehead

Elevates the eyebrows; wrinkles the skin of the forehead

Temporal branch of the facial nerve

Occipitofrontalis/ epicranial (occipital belly)

Occipital bone and temporal bone

Epicranial aponeurosis near the coronal suture

Pulls the scalp backward

Posterior auricular branch of the facial nerve

Auricularis

Anterior: temporal fascia

Helix of the ear

Pulls the ear superiorly and anteriorly

Temporal branch of the facial nerve

Superior: temporal fascia Helix of the ear

Pulls the ear superiorly and posteriorly

Posterior: epicranial aponeurosis

Upper portion of the auricle

Elevates the ear

Orbicularis oculi

Medial orbital margin, medial palpebral ligament, and lacrimal crest

Adjacent muscles (occipitofrontalis, corrugator supercilii, etc) and eyelids

Closes the eyelid

Temporal and zygomatic branches of the facial nerve

Corrugator supercilii

Bone above the superciliary arch

Skin above the superorbital margin (eyebrow)

Along with orbicularis oculi, pulls the eyebrows medially and inferiorly (during squinting)

Temporal branch of the facial nerve

Procerus

Facial aponeurosis of the lower nasal bone

Skin between the eyebrows

Pulls the eyebrows medially and inferiorly (during frowning)

Temporal and zygomatic branches of the facial nerve

Nasalis

Transverse part: maxilla

Aponeurosis at the bridge of the nose Ala nasi

Compresses the nasal aperture Widens the nasal aperture (flares the nostrils)

Buccal and zygomatic branches of the facial nerve

Greater alar cartilage and upper lip muscles (levator labii superioris and orbicularis oris)

Elevates the upper lip and dilates the nostrils

Buccal and zygomatic branches of the facial nerve

Alar part: maxilla

Levator labii superioris alaeque nasi

22

Frontal process of the maxilla

Muscles of Facial Expression

Table 2-1 (cont)

Muscles of facial expression

Muscle(s)

Origin

Insertion

Main action(s)

Innervation

Levator labii superioris

Frontal process of the maxilla and the infraorbital margin

Skin of the upper lip

Elevates the upper lip

Buccal and zygomatic branches of the facial nerve

Zygomaticus major

Zygomatic bone (lateral and posterior surfaces)

Muscles of the angle of the mouth

Pulls the corner of the mouth laterally and superiorly

Zygomatic branch of the facial nerve

Zygomaticus minor

Zygomatic bone (lateral and posterior surfaces)

Corner of the upper lip

Pulls the upper lip superiorly

Zygomatic branch of the facial nerve

Depressor labii inferioris

Mandible (anterior area of the oblique line)

Middle of the lower lip

Pulls the lower lip inferiorly and laterally

Mandibular branch of the facial nerve

Depressor anguli oris

Mandible (below the canines, premolars, and first molars)

Skin of the corner of the mouth and orbicularis oris

Pulls the angle of the mouth inferiorly and laterally

Buccal and mandibular branches of the facial nerve

Buccinator

Molar areas of the alveolar processes of the maxilla and mandible

Lips, orbicularis oris, and submucosa of the lips and cheek

Helps infants suckle, keeps food out of the oral vestibule during chewing, and expels air from the oral cavity

Buccal branch of the facial nerve

Orbicularis oris

Deep surface of the skin of the maxilla and mandible

Mucous membrane of the lips

Closes or purses the lips (during whistling, sucking, or kissing)

Buccal and mandibular branches of the facial nerve

Risorius

Fascia superficial to the masseter muscle

Skin of the angle of the mouth

Retracts the corners of the mouth during smiling widely and laughing

Buccal branch of the facial nerve

Mentalis

Frenulum of the lower lip Skin of the chin

Elevates and protrudes the lower lip (during drinking)

Mandibular branch of the facial nerve

Platysma

Skin over the lower neck Inferior border of the and upper lateral thorax mandible, skin over the lower face, and angle of the mouth

Wrinkles skin of the lower face and mouth (during grimacing)

Cervical branch of the facial nerve

23

Muscles of Facial Expression and Mastication

2

Galea aponeurotica

Occipitofrontalis, occipital belly

Temporalis Procerus Depressor supercilii Orbicularis oculi

Levator labii superioris alaeque nasi muscle Zygomatic bone, zygomatic arch

Nasalis Zygomaticus minor

Maxilla

Levator labii superioris

Parotid gland

Levator anguli oris

Parotid duct

Zygomaticus major

Buccal fat pad (of Bichat)

Orbicularis oris Masseter

Depressor anguli oris

Orbicularis oris

Depressor labii inferioris

Mental foramen

Mandible

Mentalis

Fig 2-1  Anterior view of the muscles of facial expression.

24

Muscles of Facial Expression

3 13

4

1

5

6

15 14 Skull muscle attachments

6

7

16 17

2

18 8 19 10

2

9

11

19

10

12

20 21 22

1 Temporalis 2 Masseter 3  Corrugator supercilii 4  Orbicularis oculi, orbital part 5  Orbicularis oculi, palpebral part 6  Orbicularis oculi, lacrimal part 7  Levator labii superioris 8  Nasalis, transversal part 9  Nasalis, alar part 10  Orbicularis oris 11  Depressor septi nasi 12 Mentalis 13  Depressor supercilii 14  Levator labii superioris alaeque nasi 15 Procerus 16  Zygomaticus major 17  Zygomaticus minor 18  Levator anguli oris 19 Buccinator 20  Depressor labii inferioris 21  Depressor anguli oris 22 Platysma

Fig 2-2  Anterior view of insertion of the muscles of facial expression (in red) and muscles of mastication (in blue).

25

Muscles of Facial Expression and Mastication

2

Occipitofrontalis, frontal belly

Galea aponeurotica

Orbicularis oculi

Superior auricularis

Procerus Levator labii superioris alaeque nasi muscle

Temporoparietal

Nasalis Anterior auricularis

Dilator naris, anterior muscle Compressor narium minor muscle

Occipitofrontalis, occipital belly

Posterior auricularis Articular capsule

Alar nasalis muscle Levator nasalis muscle

Parotid gland

Orbicularis oris

Accessory parotid gland

Zygomaticus major and minor

Parotid duct

Depressor labii inferioris

Masseter

Mentalis Risorius Buccinator Platysma

Fig 2-3  Lateral view of the muscles of facial expression.

26

Depressor anguli oris

Muscles of Facial Expression

13 3 6

1

4 5 6

16

2

14 15

7

17 1 19

18

10

9 11

Skull muscle attachments 1 Temporalis 2 Masseter 3  Corrugator supercilii 4  Orbicularis oculi, orbital part 5  Orbicularis oculi, palpebral part 6  Orbicularis oculi, lacrimal part 7  Levator labii superioris 8  Nasalis, transversal part 9  Nasalis, alar part 10  Orbicularis oris 11  Depressor septi nasi 12 Mentalis 13  Depressor supercilii 14  Levator labii superioris alaeque nasi 15 Procerus 16  Zygomaticus major 17  Zygomaticus minor 18  Levator anguli oris 19 Buccinator 20  Depressor labii inferioris 21  Depressor anguli oris 22 Platysma

8

2 19

22

21

10 20

12

Fig 2-4  Lateral view of insertion of the muscles of facial expression (in red) and muscles of mastication (in blue).

27

Muscles of Facial Expression and Mastication

2

Muscles of Mastication The muscles of mastication are located in the parotid and infratemporal regions of the face (Table 2-2 and Figs 2-5 to 2-10; see also Figs 2-2 and 2-4). All of them receive innervation from the mandibular division of the trigeminal nerve.

Table 2-2

28

Muscles of mastication

Muscle

Origin

Insertion

Main action(s)

Innervation

Masseter (superficial part)

Maxillary process of the zygomatic bone and the lateral aspect of the anterior zygomatic arch

Inferior lateral surface of the ramus

Elevates the mandible and assists in protraction, retraction, and side-to-side motion

Masseteric nerve (CN V3)

Masseter (middle part)

Medial aspect of the anterior zygomatic arch

Central lateral surface of the ramus

Masseter (deep part)

Deep aspect of the posterior zygomatic arch

Superior lateral surface of the ramus and inferior coronoid process

Temporalis (superficial head)

Temporal fascia

Coronoid process of the Anterior fibers elevate mandible the mandible, posterior fibers retract the mandible; unilaterally causes lateral movement of the mandible (during chewing)

Deep temporal nerve (CN V3)

Temporalis (deep head)

Temporal fossa

Lateral pterygoid (superior head)

Infratemporal crest of the greater wing of the sphenoid bone

Mandible (pterygoid fovea) and temporomandibular joint (articular disc)

Unilaterally causes lateral movement of the mandible (during chewing); bilaterally protrudes the mandible

Lateral pterygoid nerve (CN V3)

Lateral pterygoid (inferior head)

Lateral surface of the lateral pterygoid plate of the sphenoid bone

Mandible (pterygoid fovea and condylar process)

Medial pterygoid (superficial head)

Maxillary tuberosity and pyramidal process of the palatine bone

Pterygoid rugosity on the medial surface of the mandibular angle

Elevates the mandible

Medial pterygoid nerve (CN V3)

Medial pterygoid (deep head)

Medial surface of the lateral pterygoid plate and the pterygoid fossa

Muscles of Mastication

Zygomatic arch Masseter, deep part

Temporalis Joint capsule

Masseter, superficial part

Lateral ligament

Fig 2-5  Lateral view of insertion of the masseter muscle.

Temporalis

Zygomatic arch Joint capsule Lateral ligament

Coronoid process

Masseter

Lateral pterygoid

Fig 2-6  Lateral view of insertion of the temporalis muscle.

29

Muscles of Facial Expression and Mastication

2

Temporalis

Lateral pterygoid

Medial pterygoid

Masseter

Fig 2-7  Lateral view of insertion of the lateral pterygoid muscle.

30

Muscles of Mastication

Lateral pterygoid, superior part

Articular disc

Lateral pterygoid, inferior part

Medial pterygoid

Lateral plate, pterygoid process

Fig 2-8  Lateral view of insertion of the medial pterygoid muscle.

31

Muscles of Facial Expression and Mastication

2

Temporal bone

Vomer

Occipital bone, basilar part

Upper joint cavity Sphenoid, greater wing

Temporalis

Articular disc Lateral pterygoid, superior head

Lower joint cavity

Lateral pterygoid, inferior head

Lateral pterygoid

Masseter

Medial nasal concha

Medial pterygoid

Inferior nasal concha

Teeth Mylohyoid Digastric, anterior belly Genioglossus

Geniohyoid

Fig 2-9  Posterior view of insertion of the lateral and medial pterygoid muscles.

32

Muscles of Mastication

1 3

Sublingual fossa

Lingula 10

Mandibular foramen

5 6 4 2 9 8

7

Mylohyoid (internal oblique) line

Mylohyoid groove Submandibular fossa

Mandibular muscle attachments (posterolateral view) 1 Temporalis 2 Masseter 3  Lateral pterygoid 4  Medial pterygoid 5 Pterygomandibular raphe and superior constrictor 6 Mylohyoid 7  Anterior belly of digastric muscle 8 Geniohyoid 9 Genioglossus 10  Sphenomandibular ligament

Fig 2-10  Muscle insertion on the internal surface of the mandible. The dotted line indicates the limit of attachment of oral mucosa.

33

3 Posterior Maxilla The anatomical landmarks that are relevant to implant placement in the posterior maxilla are the greater and lesser palatine foramina, the greater palatine artery and nerve, the maxillary sinus, and the buccal fat pad. This chapter also discusses the anatomical manifestation of different bone resorption patterns in the posterior maxilla and the proper treatment planning for each.

Posterior Maxilla

3

Greater and Lesser Palatine Foramina The maxillary artery and nerve enter the pterygomaxillary fissure to reach the pterygopalatine fossa approximately 16.6 mm superior to the nasal floor, branching off (while in the fossa) into the posterior superior alveolar artery, the infraorbital artery, and the descending palatine artery. The infraorbital artery branches off into the anterior superior alveolar arteries after exiting the infraorbital foramen. The descending palatine artery travels a short distance within the pterygopalatine fossa and then enters the greater palatine canal. It travels approximately 10 mm within the canal in an inferior, anterior, and slightly medial direction to exit the greater palatine foramen in an anterior direction immediately opposite or even distal to the maxillary third molar or in the region between the second and third molars. While in the greater palatine canal, it branches off into lesser palatine arteries to supply the soft palate and tonsils (Fig 3-1).

Nasopalatine artery and nerve

Greater palatine artery and nerve

Palatine uvula

Lesser palatine artery and nerve

Palatine tonsil

Palatoglossal arch (“anterior pillar”) Palatoglossal muscle

Fig 3-1  The muscles of the soft palate under the thin mucosa that are supplied by the lesser palatine arteries and nerves.

36

Palatopharyngeus muscle (“posterior pillar”)

Greater and Lesser Palatine Foramina

Bilateral symmetry usually exists between the sides of the skull. Many studies1–4 reported the mean distance from the greater palatine foramen to the midsagittal suture or to the posterior palatal border; however, these numbers might still be inaccurate for a particular patient because of variation in the location of the greater palatine foramina. Thus, examination of a three-dimensional (3D) computed tomography (CT) scan of the patient will render a definitive location of the foramen before surgery for the purpose of anesthesia or flap reflection in this region (Fig 3-2).

13.78 12.7

+

+

Fig 3-2  3D CT scan showing the location of the greater palatine foramina/nerves and the distance between each of them and the midline of the palate as well as their relationships with the molars.

37

Posterior Maxilla

3

Greater Palatine Artery and Nerve After exiting from the greater palatine foramen, the greater palatine artery and nerve run across the hard palate to the incisive foramen and enter the nasal cavity to anastomose on the septum with the sphenopalatine artery (Fig 3-3). The maxillary artery terminates as the sphenopalatine artery, which passes through the sphenopalatine foramen to contribute to the blood supply of the lateral wall of the nose and the septum (see chapter 4). It reaches these areas through the posterior lateral nasal arteries and septal branches (after crossing over the roof of the cavity).

Incisive foramen Nasopalatine nerve Greater palatine artery and nerve (hard palate)

Palatine bone (horizontal plate)

Greater palatine foramen

Lesser palatine artery and nerve (soft palate) Lesser palatine foramina Posterior nasal spine Pterygoid process (lateral plate)

Vomer

Choanae

Pterygoid process (medial plate)

Fig 3-3  The course of the greater palatine artery and nerve on the surface of the hard palate.

38

Greater Palatine Artery and Nerve Surgical importance in oral surgery When opening and reflecting a flap in close proximity to the greater palatine artery (as in connective tissue graft harvest5–7 and closure of an oroantral fistula), a safe distance from the artery should be maintained, and the tip of the periosteal elevator should be kept on bone at all times to prevent injury to the artery and thereby prevent soft tissue necrosis. The anatomy of the palatal vault in terms of size and shape may affect the maximum dimensions of the graft that can be safely harvested from it. A study by Reiser et al8 showed that the location of the greater palatine neurovascular bundle is 17 mm from the gingival margin in patients with a high palatal vault, 12 mm from the gingival margin in patients with a medium palatal vault, and 7 mm from the gingival margin in patients with a low palatal vault (Fig 3-4). Furthermore, the greater palatine neurovascular bundle is localized at the junction of the vertical and horizontal palatal walls of the vault. In most patients without periodontal disease, it is possible to harvest a connective tissue graft up to 8 mm in height.9 Vomer Palatine process of maxilla

Inferior meatus 17 mm

Inferior concha

a

Maxillary sinus

Greater palatine bundle (greater palatine artery, nerve, and vein)

12 mm

b

7 mm

c

Fig 3-4  (a to c) The distance of the greater palatine artery and nerve from the surface of the hard palate to the free gingival level as described.

39

Posterior Maxilla

3 Figure 3-5 describes the procedure for harvesting a connective tissue graft from the palate. The recommended donor site for a connective tissue graft is the region found between the distal aspect of the canine and the distal aspect of the first molar. Before the procedure, verification of sufficient thickness (3 to 4 mm) is important to ensure the prevention of necrosis after the harvest (Fig 3-5a). First, a primary straight, partial‐thickness incision with a 15c blade is made about 5 mm from the gingival margin (to ensure proper healing, the thickness of the primary flap should not be less than 1.5 mm). The secondary incision is then made to the bone 1 to 2 mm coronal to the primary incision (Fig 3-5b). Vertical incisions 5 to 10 mm in length are made mesiodistally. The length of the horizontal and vertical incisions is determined by the length and width of the required graft and the size of the donor area (see Fig 3-4). The edge of the primary flap is then held with tissue pliers to expose the palatal connective tissue layer. The blade is advanced toward the center of the palate, parallel to the palatal soft tissue, without penetrating the flap (Fig 3-5c). A small periosteal elevator is then used to gently reflect a full‐thickness periosteal connective tissue graft from the bone (Fig 3-5d), after which a 15c blade is used to incise the connective tissue graft at its base and separate it from the bone surface (Fig 3-5e). The 1 to 2 mm of epithelium is left on the edge of the graft, and its shape is corrected per the recipient site (Fig 3-5f). The donor and recipient sites are then sutured.

40

Greater Palatine Artery Running andANerve Head

a

b

c

d

e

f

Fig 3-5  Procedure for harvesting a connective tissue graft from the palate. (a) A decision is made on the location of the donor area for harvesting the connective tissue graft per the size required for the recipient site. (b) A straight, partial-thickness incision is made 5 mm from the gingival margin, followed by an incision to the bone 1 to 2 mm coronal to the primary incision. (c) The primary flap is held with tissue pliers while a blade is advanced toward the center of the palate, parallel to the palatal soft tissue. (d) A full-thickness periosteal connective tissue graft is reflected from the bone. (e) The connective tissue graft is incised at its base and separated from the bone. (f) After shaping, the graft is ready for placement.

41

3 Posterior Maxilla

The Maxillary Sinus Development There are four pairs of paranasal sinuses: frontal sinuses, ethmoid sinuses, sphenoid sinuses, and maxillary sinuses (Fig 3-6). Of these, only the maxillary sinus is of significant interest to the implant surgeon. The maxillary sinus is the first sinus to develop embryologically, beginning at about the 10th week of gestation.10 The cavity expands into the maxilla by the 5th month of gestation and pneumatizes at birth. The infant’s maxillary sinus is approximately 8 × 4 × 4 mm in size, and it expands rapidly throughout the first year of life, generally extending laterally to the infraorbital nerve by 12 months of age. The sinus continues to grow throughout childhood, reaching adult size by approximately 12 to 14 years of age.11 Periods of more rapid expansion correspond to eruption of the primary and permanent teeth and the corresponding growth of the alveolar process.12

Frontal sinus

Ethmoid sinus

Sphenoid sinus

Maxillary sinus

Fig 3-6a  The four pairs of paranasal sinuses, lateral view.

42

The Maxillary Sinus

Frontal sinus

Sphenoid sinus Ethmoid sinus

Maxillary sinus

Fig 3-6b  The four pairs of paranasal sinuses, frontal view.

43

Posterior Maxilla

3 In children, there is considerable distance between the floor of the sinus and the apices of the maxillary teeth. By the age of 12 years, the floor of the sinus is usually about level with the floor of the nose. There is often continued inferior expansion of the sinus13 (Fig 3-7), frequently associated with other dental events, such as eruption of the third molars and extraction or loss of maxillary molars.

Developmental

Maxillary sinus

Intermediate growth

Adult

Expansion after tooth loss

Fig 3-7  Development of the maxillary sinus.

44

The Maxillary Sinus Continued pneumatization of the sinus inferiorly can eventually result in extreme thinning of the alveolar bone, leaving inadequate support for dental implants11 (Fig 3-8). The roots of the incisors typically are not in close proximity to the sinus. The roots of the maxillary premolars and molars, however, are consistently beneath the maxillary floor. Of these, the roots of the second molar are in closest proximity to the sinus cavity, followed by those of the first and third molars.14

Fig 3-8  Endoscopic photograph of a dental implant penetrating into the maxillary sinus.

45

Posterior Maxilla

3 Bony structure The adult maxillary sinus is roughly a laterally directed pyramid, averaging 3.75 cm high × 2.5 cm deep × 3 cm wide.15 The average volume is about 15 to 20 mL.16 The sinus usually has a single communication to the nose, found in the medial wall of the sinus (which is also the lateral wall of the nose). This wall (Fig 3-9) often contains several areas of incomplete bone formation, which may lead to extra communications between the nose and the sinus called accessory ostia, which are of questionable physiologic significance. The natural ostium of the maxillary sinus (Fig 3-10) averages 2.4 mm in diameter but can range from 1 to 17 mm.15 Considered from an intranasal perspective, this opening is found in the middle meatus, the space above the inferior concha (turbinate) and under the middle concha. Considered from within the sinus, the opening is high on the medial wall. The posterior wall separates the sinus from the structures of the infratemporal and pterygomaxillary fossae. The lateral wall is formed by the zygoma. The anterior wall includes

Orbital lamina

Lacrimal fossa

Middle concha

Pyriform aperture

Projection of the sphenopalatine fossa

Anterior nasal spine

Uncinate process (ethmoid bone)

Maxillary process of the palatine bone

Maxillary process of the inferior concha

Hiatus semilunaris Projection of the maxillary sinus

Inferior concha

Fig 3-9  The bony structures that form the medial wall of the sinus. In a dry skull, there are two large, irregular openings from the nasal cavity into the maxillary sinus cavity, which are separated by a flake of bone called the uncinate process. In a living body, these openings are covered by soft tissue (except the natural ostium of the sinus, through which the sinus drains).

46

The Maxillary Sinus the canine fossa and the infraorbital foramen (through which the second branch of cranial nerve V exits into the soft tissues of the face). The roof of the sinus is also the floor of the orbit, and it contains the infraorbital canal, through which the maxillary nerve (V2) runs in a posterior‐to‐anterior direction before exiting through the infraorbital foramen. In up to 14% of sinuses, this nerve may be on a bony mesentery or may even be dehiscent.17 Because of its superior location, this rarely presents a concern for the implant surgeon. The floor of the sinus is comprised of the hard palate, alveolus, and dental portion of the maxilla and may be anywhere from 1 to 10 mm below the level of the floor of the nose. A rare but significant anatomical variation of the maxillary sinus is called maxillary sinus hypoplasia. The hypoplastic sinus cavity is much smaller than normal and frequently features considerable bony thickening of the inferior and lateral walls. The etiology of a hypoplastic sinus is uncertain, but it is theorized to be related to deficient bone absorption or to the inability to adequately aerate the sinus cavity.18 A history of childhood facial trauma is not uncommon.

Frontal sinus

Nasal cavity

Ethmoid air cells Middle concha

Nasal septum

Maxillary sinus Inferior concha

Fig 3-10  The maxillary sinus ostium into the nasal cavity.

47

Posterior Maxilla

3 Drainage There are three spaces created in the nasal cavity by the inferior, middle, and superior conchae (Fig 3-11). Each of these spaces is known as a meatus. The nasolacrimal duct is the only structure that drains into the inferior meatus under the inferior concha (Fig 3-12).

Frontal sinus Cribriform plate Superior concha Nasal spine of frontal bone

Nasal bone

Sphenoethmoidal recess

Hypophyseal fossa (sella turcica)

Agger nasi Dorsum sellae Frontal process of maxilla

Sphenoid sinus

Middle concha Bulla ethmoidalis Uncinate process Fontanelle Inferior concha Sphenopalatine foramen Palatine bone Pterygoid process

Palatine process of maxilla

Sphenoid sinus Frontal sinus Ethmoid sinus Maxillary sinus Nasolacrimal canal

Fig 3-11 The bony structures that form the medial wall of the sinus. The superior concha and part of the middle concha have been removed to show the drainage patterns of the posterior ethmoidal air cells into the superior meatus and the opening of the maxillary sinus into the middle meatus.

48

The Maxillary Sinus The ostia of the frontal and maxillary sinuses drain into a groove located in the middle meatus known as the infundibulum. The anterior and middle ethmoid cells open into the middle meatus as well. The posterior ethmoid cells drain into the superior meatus, which is a space between the middle and superior conchae. The sphenoid sinus drains into the sphenoethmoidal recess located just posterior to the superior concha.

Orbital and palpebral parts of lacrimal gland Conjunctival sac

Canaliculi

Nasalocrimal duct

Inferior concha

Inferior meatus

Fig 3-12  Relation of the lacrimal structures to the lateral wall of the nose.

49

Posterior Maxilla

3 Innervation and blood supply Sensory innervation to the maxillary sinus is via branches of V2 (the posterior, middle, and anterior superior alveolar branches as well as the infraorbital nerve), while autonomic innervation is via branches of the sphenopalatine nerve. The maxillary sinus derives its blood supply predominately from the external carotid circulation via branches of the maxillary artery (mainly the infraorbital and the posterior superior alveolar arteries but also from branches of the posterior lateral nasal and sphenopalatine arteries, which supply the middle portion of the sinus membrane). It is important to mention the possibility of an extraosseous anastomosis between the posterior superior alveolar artery and a terminal branch of the infraorbital artery. When it occurs, this anastomosis courses at a height of 23 to 26 mm from the alveolar margin and might cause hemorrhage during flap elevation during sinus graft surgery (Figs 3-13 and 3-14). An intraosseous anastomosis, on the other hand, always occurs and courses at a distance of 19 to 20 mm from the alveolar margin (Fig 3-15). This anastomosis would be impossible to avoid if it were within the lateral window outline; however, it is not significant and should not be treated with an electrosurgical unit but rather either ignored or managed by applying a hemostatic agent with light pressure. The venous drainage from the maxillary sinus is by the facial vein, the sphenopalatine vein, and the pterygoid plexus of veins. Gasserian ganglion

Vidian nerve

Maxillary nerve (V2)

Infraorbital artery and nerve Medial superior alveolar nerve (V2) Posterior superior alveolar nerve (V2)

Maxillary sinus

Auriculotemporal nerve (V3)

Inferior alveolar Lingual nerve nerve Maxillary artery Posterior superior Extraosseous alveolar artery anastomosis

Palatine nerve

Intraosseous anastomosis

Fig 3-13  Extraosseous and intraosseous anastomoses between the posterior superior alveolar artery and the infraorbital artery.

50

The Maxillary Sinus

Fig 3-14  Hemorrhage due to damaged extraosseous anastomosis between the posterior superior alveolar artery and the infraorbital artery.

51

Posterior Maxilla

3 Sinus membrane The physiology of the maxillary sinus is closely related to its microanatomy. The mucosal lining of the maxillary sinus (also known as the Schneiderian membrane) is made of respiratory mucosa: a multilayered cylindric epithelium that consists of a surface layer of ciliated and unciliated cylindric cells, basal cells, muciparous beaker (goblet) cells, an underlying basal membrane, and thick lamina propria containing vascular and glandular layers and the periosteum (Fig 3-16). Beaker (goblet) cells produce mucus that traps dust and particles, keeps the membrane moist, and also helps to humidify inhaled air. The ciliated columnar epithelium transports the secretions produced in the maxillary sinus to the maxillary opening. From there, the ciliated columnar epithelium in the nose beat toward the pharynx. In health, the sinus lining is 0.2 to 0.8 mm thick (and thus invisible on CT scans unless chronically inflamed), with a relatively thin basement membrane. Coating the sinus lining is a bilayered secretory blanket. The inner layer (called the sol) is thin, serous, and rich in proteins, immunoglobulins, and complement. The surface layer (called the gel) is a viscous mucus that floats on the thinner sol layer. The cilia of the cells lining the sinus reach up through the sol layer and sweep the gel layer along so that any surface materials are swept toward the sinus ostium at a rate anywhere from 3 to 25 mm per minute.20 This transportation capacity is limited to secretions and extremely small foreign‐body particles, such as dust. The cilia cannot remove larger particles, such as root residues. The mucus flow is in a predictable, stellate pattern beginning from the inferior and lateral portion of the sinus floor and ending at the superior and medial sinus opening (Fig 3-17). Because of this system, the normally functioning sinus is very nearly sterile.

a

b

c

Fig 3-15  (a) Hemorrhage due to damaged intraosseous anastomosis between the posterior superior alveolar artery and the infraorbital artery. (b) Intraosseous anastomosis between the posterior superior alveolar artery and the infraorbital artery in a cadaver specimen. (c) CT scan of an intraosseous anastomosis between the posterior superior alveolar artery and the infraorbital artery. (Figures 3-15b and 3-15c reprinted from Testori et al19 with permission.)

52

The Maxillary Sinus

Pseudostratified ciliated columnar epithelium

Beaker (goblet) cells

Mucus

Basement membrane

Fig 3-16 Composition of the sinus membrane.

Fig 3-17 Direction of mucus flow in the maxillary sinus.

53

Posterior Maxilla

3 Sinus septa The presence of bony septa, which can partially divide the sinus into two or more compartments, is common. The formation of septa might be promoted by the different phases of sinus pneumatization. Increased antral pneumatization starting after tooth loss seems to result from basal bone loss caused by the osteoclastic activity of the sinus membrane. Septa were first described by the anatomist Underwood21 in 1910. The shape of septa has been described as resembling an inverted gothic arch arising from the inferior and lateral walls of the sinus and coming to a sharp edge along its most apical border22; however, variations in shape, size, and location do exist. More variations of the maxillary sinus septa are described in the literature, such as the partial perpendicular septa, the partial horizontal septa, and the complete septation of the maxillary sinus by a complete vertical septum. Incidence of maxillary septa In an analysis of 312 sinuses in 156 patients, Velasquez‐Plata et al23 noted an incidence of septa in 24% of sinuses and 33% of patients. Kim et al24 reported on 200 sinuses in 100 patients and found 53 sinuses (26.5%) to contain one or more septa. Ulm et al25 noted that in an edentulous population, the incidence of septa may be as high as 32%. Maxillary septa may arise from the anterior, middle, or posterior portions of the sinus floor but most commonly are found in the middle third.23,24 Surgical importance in oral implantology The presence of septa can complicate the creation of the bony window in the lateral wall and increase the risk of tearing the sinus membrane during its elevation. Thus, it is important to analyze these septa on CT scans prior to surgery. Regular radiographs (panoramic or Waters’ view) might not show septa or might falsely suggest that these formations are a pathologic condition. During sinus graft surgery, septa can be left intact by making two windows separated by the septum, or they can be removed with a thin curved hemostat or Kerrison forceps. Underwood’s septa Underwood’s septa are osseous ridges delimiting the root compartments of the premolars and molars (Fig 3-18). They are encountered in 31% to 48% of cases23–25 and appear to develop in one of two ways, either primarily (ie, from the development of the maxilla) or secondarily (ie, as a result of tooth loss and remnant interseptal bone).26 Tooth loss and pneumatization adjacent to either a primary or secondary septum may also exaggerate the height or size of a septum. During sinus grafting procedures, these septa might have to be removed because they can impede the view of the sinus floor and may limit placement of autogenous bone grafts or bone substitutes, thus preventing adequate filling of the sinus floor. In a study by Ulm et al,25 no correlation was found between the six residual ridge classes described by Cawood and Howell27 and the incidence of Underwood’s septa.

54

The Maxillary Sinus

Maxillary process of the inferior concha

Fontanelle

Underwood’s septa

Fig 3-18  Underwood’s septa.

55

Posterior Maxilla

3 Partial perpendicular septa The punctum convergii is an area immediately posterior to the maxillary sinus ostium. Rarely, beginning at this location, a partial perpendicular septum can develop into the maxillary sinus, dividing it into two incomplete compartments (Fig 3-19).

Anterior margin sinus ostium

Posterior margin, hiatus semilunaris

Uncinate process

Punctum convergii

Groove for lacrimal sac

Partial perpendicular sinus septum Anterior nasal spine Incisive canal Palatine process

Fig 3-19  Partial perpendicular septum.

56

The Maxillary Sinus Partial horizontal septa This septum is a horizontally located maxillary process arising from the palatine bone and the inferior concha. If this type of septum occurs, neither process will follow the normal development of the sinus in an inferior‐medial direction. They will maintain their primary horizontal positions while the level of the floor of the sinus is gradually lowered as it develops. This type of septum can be ignored if it is positioned much higher than the area to be grafted. Otherwise, such horizontal septa will impede sinus drainage and lead to sinus graft failure (Fig 3-20). Middle concha Uncinate process

Maxillary sinus

Maxillary process of the inferior concha

Inferior concha

a Middle concha

Middle concha

Uncinate process

Uncinate process

Maxillary process of the inferior concha Maxillary process of the inferior concha

c

b

Fig 3-20  Partial horizontal septum. (a) Normal development of the maxillary process of the inferior concha. (b) Possible horizontal position of the maxillary process of the inferior concha that might occur during development. In patients requiring sinus bone augmentation (c), the distance between the horizontally positioned maxillary process of the inferior concha and the floor of the sinus will dictate the course of action. A short distance between the horizontal septum and the floor of the sinus might represent a contraindication for sinus bone augmentation because of subsequent compromise in the drainage of the sinus membrane secretions.

57

Posterior Maxilla

3 Complete septation of the maxillary sinus A complete vertical septum (Fig 3-21) usually divides the sinus into a big anterior and a smaller (accessory) posterior sinus. The anterior sinus drains into the middle meatus, while the posterior sinus opens into the superior or nasal meatus through a bony hiatus delimited by structures similar to those of the normal hiatus semilunaris (ie, the maxillary process of the middle concha and the posterior maxillary process of the palatine bone). Each of these sinuses can show isolated signs of pathology and thus must be treated separately from one another. The accessory sinus develops in the cartilaginous nasal capsule at the same time as does the normal sinus, or it results from excessive pneumatization of the posterior part of the maxilla by a large ethmoid air cell. In this case, a pathology involving the ethmoid bone will also involve the accessory sinus.

Greater wing (sphenoid bone)

Optic canal

Fossa for the lacrimal sac Orbital surface, maxillary bone

Maxillary sinus

Partial intersinus septum

Sphenopalatine fossa

Pterygoid process

Maxillary process of the inferior concha Pterygoid hamulus Accessory maxillary sinus Fig 3-21  Complete septation of the maxillary sinus.

58

The Maxillary Sinus The author has developed a classification of possible variations of maxillary sinus septa (Box 3-1 and Fig 3-22).

Box 3-1

Al-Faraje classification of maxillary sinus septa for assessment prior to sinus bone graft surgery

Class I

Single basal perpendicular septum (Fig 3-22a)

Class II

Multiple (two or more) basal perpendicular septa (Fig 3-22b)

Class III

Single partial perpendicular septum (Fig 3-22c)

Class IV

Multiple (two or more) partial perpendicular septa (Fig 3-22d)

Class V

Partial horizontal septa (Fig 3-22e)

Class VI

Complete perpendicular septa (complete septation of the maxillary sinus) (Fig 3-22f)

59

Posterior Maxilla

3

a

Class I: Single basal perpendicular septum

b

Class II: Multiple basal perpendicular septa

c

Class III: Single partial perpendicular septum

d

Class IV: Multiple partial perpendicular septa

e

Class V: Partial horizontal septum

f

Class VI: Complete septation of the maxillary sinus

Fig 3-22  (a to f) Al-Faraje classification of maxillary sinus septa.

60

The Maxillary Sinus Clinical management of maxillary septa The following are basic principles for the management of maxillary septa during sinus elevation: •  Complete removal of the bony window, rather than pushing it inside the sinus cavity, is recommended in most situations. •  Identification of the exact location, extent, and size of the septa before sinus graft surgery is critically important. •  Class I or Class II septa (Al‐Faraje classification) do not complicate the sinus elevation procedure; the surgeon should simply take the septa into consideration during reflection of the membrane off the floor of the sinus. •  In Class III septa, the surgeon can make two windows separated by the septum; then, after the elevation of the sinus membrane off the septum, Kerrison forceps or a hemostat can be used to remove the septum. The exact location and size of the septum should be identified on CT scans before surgery (Fig 3-23). •  Class IV septa significantly increase the risk of membrane perforation and may contraindicate surgery. •  In the case of Class V septa, the height of the septum dictates the course of action. If the horizontal septum is located significantly superior to the floor of the sinus, then the procedure can be performed. Otherwise, the close proximity of the horizontal septum to the floor of the sinus might be a contraindication for the sinus graft surgery. •  Class VI septa usually do not interfere with sinus graft surgery, which can still be performed in the anterior compartment for future implant placement.

a

b

c

d

Fig 3-23  A case of a single partial perpendicular septum (Al-Faraje Class I). The recommended management is the creation of two separate windows (a), followed by the elevation of the maxillary sinus membrane off each side of the septum (b), and then the removal of the septum using a Kerrison rongeur (c) before the introduction of the bone graft material into the sinus cavity (d). (Reprinted from Al-Faraje28 with permission.)

61

Posterior Maxilla

3 Figures 3-24 and 3-25 show the sinus septa from various sections of a human cadaver skull.

B

C

D

Cut A: Made between the maxilla and the mandible to separate the mandible from the rest of the skull Cut B: M  ade immediately distal to the posterior wall of the maxilla Cut C: R  uns in the area between the first and second molars Cut D: R  uns through the frontal sinuses (immediately distal to the nasal bone)

A

2

1

3

4 5,6 7

A

B

C

Plates 1 and 2 show the posterior and anterior views, respectively, of slice A after cuts A, B, and C were made. Plate 3 shows the posterior side of Slice B before cut D was made, while plate 4 shows the same slice after cut D was made. Plates 5 and 6 show the anterior view of slice B. Plate 7 shows the posterior view of slice C.

Fig 3-24

62

The Maxillary Sinus

2

1

1 3

3

5

5 4 6

6 7

Plate 1 1. Middle cranial fossa 2. Anterior cranial fossa 3. Sphenoid sinus (anterior face) 4. Posterior nasal septum 5. Middle nasal concha 6. Inferior nasal concha 7. Hard palate

In 1988, Arthur Rathburn created the resin arterial forced infusion method for fresh dissectable anatomical materials. This highly visual hands-on infusion technique provides a hallmark approach to the embodiment and clarity that one expects in natural coloration of real-life illustrations. The principle components of the arterial colorization is a nondissipating latex medium infused into the vessels at different intervals at a high rate of flow in conjunction with a gradual increase in psi flux. This task is accomplished by canalizing the major arteries and veins with a Luer-Lock system, preclamping any severed vessels and presetting the injection procedural rate at 3 to 5 psi (dual-tronic embalmers). As the injection process fills the arteries, a back pressure formulates, reducing the rate of arterial flow and/or formulating an increased incidence of arterial acceptance. Firming action is usually achieved within 1 to 2 hours at room temperature. This application process takes 5 to 10 minutes for every 60 mL of solution.

63

Posterior Maxilla

3

4

5

5

9

2 6

3 6 3 7

7 10

1

8

8

12

1

11

12

Plate 2 1. Posterior maxillary sinus wall 2. Right orbit (empty) 3. Left orbit (with contents) 4. Anterior cranial fossa 5. Posterior ethmoid sinuses 6. Superior nasal concha 7. Middle nasal concha 8. Inferior nasal concha 9. Nasal septum (perpendicular plate of ethmoid) 10. Nasal septum (vomer) 11. Hard palate (palatine bone) 12. Alveolar process

64

The Maxillary Sinus

1 3

1

2

2

9

3

4

4

5

9

5

8

8 7

6

6

11 10

10

Plate 3 1. Ethmoid roof 2. Ethmoid sinuses 3. Orbit (with soft tissues) 4. Superior nasal concha 5. Middle nasal concha 6. Inferior nasal concha 7. Nasal septum 8. Lateral nasal wall / medial maxillary sinus wall 9. Superior maxillary sinus wall / orbital floor 10. Maxillary sinus floor / alveolar process 11. Hard palate

65

Posterior Maxilla

3

1

1 2

3

4

4 3

9

5

5 6 9

7 7 10

10

8

8

12

11

11

Plate 4 1. Anterior cranial fossa 2. Falx cerebri 3. Orbit 4. Ethmoid sinuses 5. Superior nasal concha 6. Nasal septum 7. Middle nasal concha 8. Inferior nasal concha 9. Superior maxillary sinus wall / orbital floor 10. Lateral nasal wall / medial maxillary sinus wall 11. Maxillary sinus floor / alveolar process 12. Hard palate

66

The Maxillary Sinus

2

8

2

8

3

7

1

7

1

4 5

5 10

10

9

9

6 11

12

6 11

12

Plate 5 1. Orbit 2. Anterior cranial fossa 3. Crista galli 4. Nasal septum (deviated to the left) 5. Middle nasal concha 6. Inferior nasal concha 7. Ethmoid sinus 8. Frontal sinus 9. Zygoma 10. Superior maxillary sinus wall / orbital floor 11. Lateral nasal wall / medial maxillary sinus wall 12. Maxillary sinus floor / alveolar process

67

Posterior Maxilla

3

2

8

2

8 3

1

7

1

7

4 5

5

10

10

9

6

Plate 6 1. Orbit 2. Anterior cranial fossa 3. Crista galli 4. Nasal septum 5. Middle nasal concha 6. Inferior nasal concha 7. Ethmoid sinuses 8. Frontal sinus 9. Maxillary sinus 10. Drainage pathway of maxillary sinus

68

6

9

The Maxillary Sinus

1

1

16

16 17

17 2

3

13

14

3

15

15

14 13

L

5 11

11

4 12

R

5

6

12

6

9

9

10

10

8

8 7

Plate 7 1. Anterior cranial fossa 2. Crista galli 3. Cribriform plate 4. Nasal septum 5. Middle nasal concha 6. Inferior nasal concha 7. Hard palate 8. Maxillary sinus floor / alveolar process 9. Lateral nasal wall / medial maxillary sinus wall 10. Lateral maxillary sinus wall 11. Superior maxillary sinus wall / orbital floor 12. Zygoma 13. Globe (remnant) 14. Orbital fat and extraocular muscles 15. Ethmoid sinuses 16. Frontal sinus 17. Ethmoid roof

69

Posterior Maxilla

3

Cut A: Made under the maxilla to separate the mandible from the rest of the skull Cut B: M  ade approximately 15 mm above the crestal bone level

C B

Cut C: M  ade approximately 20 mm above cut B (around the middle of the zygoma bone)

A

2,3,4 5,6,7

1

Plate 1 shows the superior view of slice A, and it shows the sinus floor.

C

B

A

Plate 2 shows the occlusal view of slice B before cut C was made. Plates 3 and 4 show the right and the left maxillary sinuses, respectively, at the level of cut B. Plate 5 shows the occlusal view of slice C. Plates 6 and 7 show the right and the left maxillary sinuses, respectively, at the level of cut C.

Fig 3-25

70

The Maxillary Sinus

10

9

8

2

1

9

8

2

3

4

4 5

3

1

7 7

6

Plate 1 1. Maxillary sinus floor 2. Septum 3. Medial maxillary sinus wall 4. Nasal floor 5. Nasal septum 6. Maxilla 7. Anterior maxillary sinus wall 8. Pterygopalatine fossa 9. Infratemporal fossa 10. Nasal surface of soft palate

71

Posterior Maxilla

3

12

10 10

11

11 7

9

7

9 1

4

5

5

1 8

6

6

8 2

2 3

3

Plate 2 1. Infratemporal fossa 2. Pterygopalatine fossa 3. Choana 4. Nasal septum 5. Inferior nasal concha 6. Middle nasal concha 7. Lateral nasal wall / medial maxillary sinus wall 8. Posterior maxillary sinus wall 9. Lateral maxillary sinus wall 10. Anterior maxillary sinus wall 11. Natural ostium of the maxillary sinus 12. Maxilla

72

The Maxillary Sinus

10

8

9

3

2

1

7

6

4 5

Plate 3 1. Nasal septum 2. Inferior nasal concha 3. Lateral nasal wall / medial maxillary sinus wall 4. Posterior maxillary sinus wall 5. Pterygopalatine fossa 6. Infratemporal fossa 7. Lateral maxillary sinus wall 8. Anterior maxillary sinus wall 9. Natural ostium of the maxillary sinus 10. Maxilla

73

Posterior Maxilla

3

4

5

8 1 2 7

3

6

Plate 4 1. Inferior nasal concha (contralateral) 2. Nasal septum 3. Lateral nasal wall / medial maxillary sinus wall 4. Maxilla 5. Anterior maxillary sinus wall 6. Lateral maxillary sinus wall 7. Mucosal cyst on the medial maxillary sinus wall 8. Natural ostium of the maxillary sinus

74

The Maxillary Sinus

13

13

8

8

10

7

9

7

9 10

1

1 15 6

6 12

2

2

11 5

11

3

5 3

4

14

14

4

Plate 5 1. Zygoma 2. Posterior maxillary sinus wall 3. Infratemporal fossa 4. Pterygopalatine fossa 5. Lateral nasal wall / medial maxillary sinus wall 6. Natural ostium of the maxillary sinus 7. Infraorbital nerve (V2) canal 8. Infraorbital foramen 9. Inferior nasal concha 10. Inferior meatus 11. Middle nasal concha 12. Nasal septum 13. Nasal bone 14. Sphenoid face 15. Mucosal cyst on the medial maxillary sinus wall

75

Posterior Maxilla

3

7

9

8

2 3

1 10

4 6

5

Plate 6 1. Nasal septum 2. Inferior nasal concha 3. Inferior meatus 4. Lateral nasal wall / medial maxillary sinus wall 5. Middle nasal concha 6. Posterior maxillary sinus wall 7. Anterior maxillary sinus wall 8. Infraorbital nerve (V2) canal 9. Infraorbital foramen 10. Natural ostium of the maxillary sinus (middle meatus)

76

The Maxillary Sinus

10

9

1

2

3 11 5

4

6

8

7

Plate 7 1. Nasal septum 2. Inferior nasal concha 3. Inferior meatus 4. Lateral nasal wall / medial maxillary sinus wall 5. Mucosal cyst 6. Posterior maxillary sinus wall 7. Pterygopalatine fossa 8. Infratemporal fossa 9. Infraorbital nerve (V2) canal 10. Anterior maxillary wall 11. Natural ostium of the maxillary sinus

77

Posterior Maxilla

3 Evaluation of the maxillary sinus on CT scans CT scans provide a clear way of evaluating the maxillary sinus. Before the sinus bone augmentation procedure, it is important to evaluate the exact amount of alveolar bone available under the sinus floor and the width of the sinus buccopalatally. The evaluation of the sinus for the existence of septa or soft tissue pathologies is also important because these can complicate the sinus bone augmentation procedure or might even represent a contraindication in certain situations (eg, presence of multiple partial perpendicular septa). Figures 3-26 to 3-34 depict various situations involving the maxillary sinus.

78

Fig 3-26  Wide maxillary sinus.

Fig 3-27  Wide maxillary sinus with compromised alveolar height underneath it.

Fig 3-28 Narrow maxillary sinus with a very thin floor.

Fig 3-29  On this image, the ostium of the sinus can be evaluated.

Fig 3-30 Soft tissue pathology of the maxillary sinus (acute sinusitis).

Fig 3-31 Soft tissue pathology of the maxillary sinus (chronic sinusitis).

The Maxillary Sinus

Fig 3-32  Compromised bony height under the sinus floor. After measuring the bony height under the sinus floor, a decision can be made as to the technique of the sinus augmentation. Sinus augmentation through the osteotomy should be performed when there is at least 5 mm of available bone; the lateral window technique should be used when these is less than 5 mm of bone available.

Fig 3-34  Compromised bony height under the sinus floor with basal perpendicular septa in both sinuses.

79

Posterior Maxilla

3

The Buccal Fat Pad The buccal fat pad (corpus adiposum buccae), first described by Bichat in 1802, is a trigone‐shaped adipose tissue located in the cheek, wedged between the masseter and buccinator muscles. This tissue assumes numerous functional and esthetic clinical uses29; its easy access allows it to cover a variety of oral defects and neoplastic lesions. However, it can undergo pathologies such as lipoma, herniation, and pseudoherniation. It has great importance in facial contour. In properly selected individuals, judicious harvesting of buccal fat can produce dramatic changes in facial appearance by reducing the fullness of the cheek and highlighting the malar eminences.

Development and anatomy Adipose tissue differentiates during the second trimester of gestation (between 14 and 16 weeks). The cheek is the first place on the face where adipose tissue develops. An increase in the number of fat lobules occurs in the period between the 14th and 23rd week, while the increase in the size of these lobules continues until the 29th week.30 The buccal fat pad is confined in the masticatory space between the masseter muscle laterally and the buccinator muscle (and sometimes the periosteum of the posterior wall of the maxilla) medially, with its main body resting on the buccopharyngeal fascia, which

Skin and subcutaneous fat

Parotid duct

Superficial muscular aponeurotic system

Masseter

Branches of facial nerve

Buccal fat pad

Buccinator Mucosa

Fig 3-35  Cross section in the cheek at the location of the parotid gland duct, showing the buccal fat pad.

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The Buccal Fat Pad covers the external surface of the buccinator muscles. Its anterior border goes beyond the anterior wall of the masseter muscle and posterior to the site where the parotid duct pierces the buccinator muscles; thus, it is covered externally in this area by the parotid duct, zygomaticus major, zygomaticus minor, and superficial fascia of the face. The posterior limit is the retromolar area of the mandible. The buccal fat pad is wrapped within a thin fascial envelope.

Structures in the buccal fat pad The structures in the buccal fat pad include the parotid duct, accessory parotid salivary glands, the facial artery, veins (tributaries of the pterygoid venous plexus), the buccal artery (one of the pterygoid branches of the maxillary artery31), lymphatic channels, and branches of the facial (CN VII) and mandibular (CN V3) nerves (Figs 3-35 and 3-36). The blood supply to the buccal fat pad arises from the anterior deep temporal, buccal, and posterior superior alveolar arteries (all are branches of the maxillary artery), from the transverse facial artery (a branch of the superficial temporal artery), and from some little branches of the facial artery.32,33

Superficial temporal artery CN V (trigeminal nerve) Parotid gland Transverse facial artery Pterygoid plexus of veins Maxillary artery Accessory parotid gland Parotid duct Buccal fat pad Masseter (a portion of the anterior wall is removed for better BFP visualization) CN VII (facial nerve) Buccinator Fig 3-36 The buccal fat pad and its surrounding structures. BFP—buccal fat pad.

Facial artery Zygomaticus major

Zygomaticus minor

81

Posterior Maxilla

3 The buccal fat pad can be divided into three lobes (anterior, intermediate, and posterior) and has four extensions (buccal, pterygoid, pterygopalatine or superficial temporal, and temporal or deep temporal) (Fig 3-37). It is fixed by six ligaments to the maxilla, posterior zygoma, inner and outer rims of the infraorbital fissure, temporalis tendon, and buccinator membrane. The mean volume in males is 10.2 mL (range, 7.8 to 11.2 mL), while in females the mean volume is 8.9 mL (range, 7.2 to 10.8 mL). Additionally, the mean thickness is 6 mm, with a mean weight of 9.7 g.34 There is a great variety in the size of the buccal fat pad both among different individuals and between one side and the contralateral side, and the volume of the buccal fat pad may change throughout a person’s life.

Temporalis

Deep temporal extension

Corpus of buccal fat pad

Zygomaticus minor Zygomaticus major

Superficial temporal extension Pterygoid extension

Buccinator

Masseter (cut) Buccal extension

Fig 3-37  Lateral view of the buccal fat pad, showing its lobes and extensions.

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The Buccal Fat Pad Function At birth, the sucking muscles of the lips, orbicularis oris, and cheeks (principally the buccinator muscle) are relatively better developed than the muscles of mastication. In well‐ nourished babies, the fat pad pushes the buccinator muscle inward and forms a prominent elevation on the external surface of the face. It is believed by some that the sucking capabilities of the buccinator muscle are enhanced by the fat pad, which may prevent collapse of the cheeks during suction by counteracting negative pressure.35 The buccal fat pad also functions to fill the deep tissue spaces, acting as gliding pads when masticatory and mimetic muscles contract (as it represents a specialized type of fat also known as syssarcosis, fat that enhances intermuscular motion36,37). Similarly, it cushions important structures from the extrusion of muscle contraction or outer force impulsion (external trauma that may injure the facial neurovascular bundle).38 In addition, as a rich, venous net with valvelike structures, the buccal fat pad is possibly involved in exoendocranial blood flow through the pterygoid plexus.32 Several investigators have noted the persistence of the buccal fat pad during periods of starvation or extreme weight loss, though the chemical composition is similar to that of adipose tissue elsewhere.38

Pathology of the buccal fat pad •  The buccal fat pad may give rise to a lipoma of the cheek, which may simulate a parotid tumor. •  A tumor of the fat pad was described in a patient with a large salivary duct stone. The study suggested that irritation caused by calculus caused overnutrition of the fat pad and hence its hypertrophy.39 •  Facial trauma exposing surrounding adipose tissue can lead to an infection that may extend to various spaces in the head (such as the infratemporal fossa).40

Clinical uses Esthetic surgery The buccal fat pad can modify facial contours and the malar prominence. It can be resected to reduce cheek thickness, thus increasing the projection of the malar prominence, or a buccal fat pad flap can be used to increase the submalar and lateral cheek projection.41–43 Reconstructive surgery The buccal fat pad can be harvested as a free or pedicled buccal fat pad graft for closure of oroantral and oronasal communications, palatal clefts, surgical defects following tumor excision, and more.44–46 In addition, El Haddad et al47 described the use of a buccal fat pad flap for posterior maxillary root coverage of a Miller Class IV recession defect to increase the dimensions of the keratinized mucosa; the epithelium of local mucosa regenerated on the surface of the buccal fat pad, forming a new mucosa that restored the missing part. As described earlier, the buccal fat pad has a rich plexus of blood vessels that ensures survival of the flap after relocation37 and contributes to its resistance to infection, with little necrosis and absorption. Oral implantology The buccal fat pad has been used in oral implantology for the coverage of maxillary and mandibular bone grafts. Zhong et al48 described the use of the buccal fat pad in reconstruction of the maxilla with bone grafts. In addition, the buccal fat pad has been used in sinus augmentation procedures as a means of closing large perforations of the sinus membrane49,50 or as an additional source of blood supply to the graft when perforations are not present.51,52

83

Posterior Maxilla

3 Use of the buccal fat pad during sinus augmentation Membrane perforation is probably the most commonly reported complication during sinus augmentation. If the perforation is small, it can be easily repaired by the placement of a resorbable collagen membrane; however, when the perforation is large (15 mm or more in diameter), the options available include the use of putty bone graft material instead of particulate graft, the Loma Linda pouch technique,53 or abandonment of the procedure.54 The use of the buccal fat pad as a membrane has been reported in the literature with good results and is also a viable option. Successful osseous reconstruction depends not only on the physical protection of the graft from trauma and micromotion but also on the establishment of an adequate blood supply to the graft that will aid in the neovascularization of the graft mass. In sinus augmentation procedures, the buccal fat pad can provide the flap with this important additional blood supply. Wong51,52 found that by using the buccal fat pad for additional and immediate blood and nutrition supply and protection of the graft, the quality of bone could be improved for other parts as well, because adult subcutaneous fat tissue is an abundant source of multipotent cells. Recently, several publications have reported that adipose tissue contains a population of cells able to differentiate into different cell types, including adipocytes, osteoblasts, myoblasts, and chondroblasts55; thus, by placing the buccal fat pad between fast‐growing fibrous tissue and the defect itself, slow‐growing osseoprogenitor cells can migrate into the bone defect and lead to the reossification of this area. Technique Following sinus access and elevation of the sinus membrane, a small incision (15 to 20 mm) is made on the periosteum of the mucosal flap into the buccinator muscle (at the level of the zygomatic/maxillary buttress and extending distally to the area of the second molar) and into the buccopharyngeal membrane. Blunt dissection is then performed into the buccal fat pad’s loose surrounding fascia, allowing its content to herniate into the mouth. Pressure on the cheek helps to express the buccal fat pad into the mouth. Then vascular atraumatic forceps are used to gently tease out the buccal fat pad contents, drape them into the sinus (preserving as wide a base as possible), and fix them with sutures into the palatal mucosa (through holes made in the maxillary bone through the sinus window with a fissure bur). The graft material is packed gently into the sinus against the fat pad until all the space is filled, and the procedure is concluded by closing the access window by normal flap closure (Fig 3-38). The patient is given prophylactic antibiotics and chlorhexidine (0.12%) mouthrinse and is instructed to eat a soft diet. Usually there is a decrease in the vestibular depth immediately after the surgery, but this decrease gradually improves and is restored within about 2 months of surgery. Mild trismus might also occur in the first few days after surgery, but this too should gradually improve with mandibular movement.

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The Buccal Fat Pad

Zygomatic arch

Sinus membrane

Skin

Buccal fat pad

Mucosa

Masseter

Buccinator

a

Capsule

Buccal fat pad

Bony window

Bone graft mix Open flap

Closed flap Mucosa

Mucosa

b

c

Fig 3-38  (a to c) The use of the buccal fat pad flap technique in patching big perforations in the sinus membrane during sinus bone augmentation.

85

Posterior Maxilla

3 Contraindications Contraindications to the use of the buccal fat pad include any presence of pathology (eg, lipodystrophy, angioneurotic edema, sarcoidosis) or history of cosmetic surgery in the region by which liposuction may have reduced the volume of the buccal fat pad. More limitations are described in Box 3-2.

Box 3-2

Advantages and disadvantages of using the buccal fat pad flap in oral reconstruction

Advantages

Disadvantages

Easy mobilization because of its location Limited stretching when used as a pedicled flap (to preserve vascularity)

86

Minimal donor site morbidity

Cannot be used in the mandible as a pedicled flap

Low rate of complications

Cannot be used for adding bulk

Quick surgical technique (one incision)

Small depression may result56

Minimal patient discomfort

Possibility of partial necrosis

No visible scars

Some shrinkage and distortion may occur

Can be done under local anesthesia

Temporary paresthesia of the buccal nerve (leading to temporary weakness in the orbicularis oris and buccinator muscles) (reported in 1% of cases43,52)

The Buccal Fat Pad Trauma Traumatic herniation (pseudolipoma) Traumatic herniation of the buccal fat pad can occur as a result of external or internal trauma. This occurs more often in children because their buccal fat pad is more prominent than that of adults and because they tend to place foreign objects into their mouths that may allow for rupture of the buccal mucosa. Clinically, traumatic herniation of the buccal fat pad appears as a grayish‐yellow, soft, and irregular swelling on the inner aspect of the cheek; this is sometimes misdiagnosed as a lipoma because of its possible delayed appearance after the insult, hence the term pseudolipoma.57 The surgical intervention to treat traumatic herniation involves blunt dissection of the adipose tissue or maneuvering it back through the wound and suturing it closed. The differential diagnosis includes lipoma, hemangioma, inflammatory hyperplasia, and salivary gland neoplasms. Pseudoherniation Pseudoherniation, described by Matarasso,58 is a condition in which a walnut‐sized mass of the lower half of the buccal fat pad is abnormally displaced outward. This outward displacement is what differentiates pseudoherniation from pseudolipoma (ie, intraoral herniation requires the piercing of both the buccinator muscles and the mucosa). The causes of pseudoherniation include natural weakness of the parotidomasseteric fascia or a discontinuation of the fascia covering the muscles of facial expression. Treatment involves excision and replacement of the displaced fat. Traumatic herniation into the maxillary sinus Traumatic assaults on the zygomaticomaxillary complex might lead to a displaced fracture as well as possible herniation of the body of the buccal fat pad into the maxillary antrum. Herniation occurs secondary to the fracture of the lateral wall of the maxillary sinus because, anatomically, the body of the buccal fat pad is adjacent to the lateral wall of the maxillary sinus and forms the leading edge of the herniated portions of the buccal fat pad. Upon displacement, the herniated portions of the displaced buccal fat pad will become gangrenous (ischemic necrosis) and should be removed. The use of magnetic resonance imaging (MRI) and CT imaging to preoperatively investigate the trauma will aid in proper planning for the reduction of complex facial fractures and management of the herniation.59,60 Figure 3-39 shows an intact lateral wall of the maxillary sinus on a CT scan, and Fig 3-40 shows a broken lateral wall of the sinus with buccal fat pad content invading the sinus space.

Fig 3-39  CT scan showing an intact lateral wall of the maxillary sinus.

Fig 3-40  CT scan showing a broken lateral wall of the maxillary sinus, with buccal fat pad content invading the sinus space.

87

Posterior Maxilla

3 Surgical complications during oral/implant surgeries The buccal fat pad is sometimes encountered in surgical procedures in the region of the posterior maxilla, and thus traumatic herniation is a possibility. Rupture of the thin buccal fat pad fascia can make the buccal extension drop or prolapse to the mouth or subcutaneous layer.37 Also, if the lymphatic drainage is disturbed, facial swelling will occur.54 Figure 3-41 shows a case in which the buccal fat pad space was inadvertently exposed during a surgical procedure in the left posterior maxilla (no procedure was performed on the right side). This complication went unnoticed during the procedure; however, within 3 months of the surgery, the patient developed a depression in the cheek (Fig 3-41a). The patient was referred to an MRI lab for evaluation of the soft tissue. The MRI study revealed significant atrophic changes in the buccal fat pad. The volume of the buccal fat pad per the radiology report was 7.5 × 1.0 × 6.1 cm (45.8 cm3) on the right side and 7.5 × 0.4 × 6.1 cm (18.3 cm3) on the left side (Figs 3-41b and 3-41c). The cheek contour was restored by a cosmetic surgeon via fat transfer for cheek augmentation (Fig 3-41d), and the patient was satisfied with the results.

a

c

b

d

Fig 3-41  Patient whose buccal fat pad space in the left posterior maxilla was exposed during a surgical procedure. (a) Depression in the cheek 3 months postoperatively. (b and c) CT scans of the buccal fat pad. (d) Cheek contour after cheek augmentation by a cosmetic surgeon.

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The Buccal Fat Pad Figures 3-42a to 3-42c show three views of the same cadaver specimen. Figure 3-42a shows an anterior view of the buccal fat pad and its buccal extension at the level of the corner of the mouth (midcheek). Figure 3-42b shows a superior view of the buccal extension. Figure 3-42c shows the pterygoid/lingual extension.

a

b

c Fig 3-42  Buccal fat pad from a cadaver specimen. (a) Anterior view of the buccal fat pad and its buccal extension at the level of the corner of the mouth (midcheek). (b) Superior view of the buccal extension. (c) Pterygoid/lingual extension.

89

Posterior Maxilla

3

Inadequate Bony Structure in the Posterior Maxilla The judgment of the clinician in treatment planning for the posterior maxilla (and other areas of the mouth) is paramount because each clinical case is unique; however, guidelines are always helpful for keeping practitioners on a path that will most likely be successful. The author has developed a classification for the available bone in the posterior maxilla to help practitioners with the treatment planning for this region (Box 3-3 and Fig 3-43).

Box 3-3

90

Al‐Faraje classification of the available bone in the posterior maxilla

Class I

 mm or more of height with adequate width for implant placement (Fig 3-43a). The treat8 ment plan for this category is the placement of an implant with 7 mm or more in height, maintaining at least a 1-mm distance between the apex of the implant and the sinus floor.

Class II

 to 7 mm of height with adequate width for implant placement (Fig 3-43b). The treatment 5 plan for this category is the placement of an implant with a simultaneous socket elevation procedure (sinus elevation using sinus osteotomes/crestal ridge approach). (The Al-Faraje technique for sinus elevation using the crestal ridge approach is demonstrated in Fig 3-44.)

Class III

 to 4 mm of height with adequate width for implant placement (Fig 3-43c). The treatment 1 plan for this category is the lateral window sinus grafting procedure with delayed implant placement.

Class IV

 to 4 mm of height with inadequate width for implant placement (Fig 3-43d). The treatment 1 plan for this category is the lateral window sinus grafting procedure, with delayed implant placement in a crossbite position or delayed ridge augmentation (using veneer block grafting or guided bone regeneration technique) after the healing period of the sinus graft.

Inadequate Bony Structure in the Posterior Maxilla

Simultaneous crestal sinus elevation with implant placement

≥ 8 mm

5–7 mm

a

b Class I

Class II

Bone graft Block graft(s) (first stage) (second stage)

Bone graft (first stage)

< 5 mm (1–4 mm)

c Implant placement (second stage)

d Class III

< 5 mm (1–4 mm) plus width deficiency

Implant placement (third stage)

Class IV

Fig 3-43  (a to d) Al-Faraje classification of the available bone in the posterior maxilla.

91

Posterior Maxilla

3 Al‐Faraje technique for sinus elevation using the crestal approach This technique is indicated when there is at least 5 mm of alveolar bony height available under the sinus floor (Fig 3-44a). The procedure starts by accessing the bone via a fullthickness flap or flaplessly using a tissue punch. The osteotomy is then formed completely using drills or a combination of drills and implant osteotomes, stopping short of the sinus floor by 0.5 to 1.0 mm (Figs 3-44b and 3-44c). The next step is to use a sinus osteotome with a stopper; the selected osteotome must have a diameter close in size to the diameter of the apical portion of the intended implant, and the stopper must be placed at a distance 3 to 4 mm longer than the available bony height under the sinus floor (Fig 3-44d). The sinus osteotome is then tapped with a mallet to greenstick fracture the floor of the sinus until the stopper reaches the crestal bone (or the soft tissue in cases of flapless insertion) (Fig 3-44e). A small piece of collagen dressing is introduced to patch any possible tear in the sinus membrane, followed by a small amount of bone graft material (Fig 3-44f). Finally, the implant is placed with a cover screw or healing abutment depending on the initial stability reached and the bone quality surrounding the osteotomy site (Fig 3-44g).

92

Inadequate Bony Structure in the Posterior Maxilla

b

a

c < 1 mm

d 2–3 mm

e f

Collagen tape

g

Bone graft mix

Fig 3-44  Al-Faraje technique for sinus elevation using the crestal ridge approach. (a) At least 5 mm of bone must be available under the sinus floor. (b and c) After the bone is accessed via a full-thickness flap or tissue punch, the osteotomy is formed, stopping 0.5 to 1.0 mm short of the sinus floor. (d) An osteotome with a stopper is used. (e) The stopper reaches the soft tissue after greenstick fracture of the sinus floor. (f) A collagen dressing and bone graft material are placed. (g) The implant is placed with either a cover screw or a healing abutment.

93

Posterior Maxilla

3

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28. Al-Faraje L. Surgical Complications in Oral Implantology: Etiology, Prevention, and Management. Chicago: Quintessence, 2011:158. 29. Yousuf S, Tubbs RS, Wartmann CT, Kapos T, Cohen-Gadol AA, Loukas M. A review of the gross anatomy, functions, pathology, and clinical uses of buccal fat pad. Surg Radiol Anat 2010;32:427–436. 30. Poissonet CM, Burdi AR, Bookstein FL. Growth and development of human adipose tissue during early gestation. Early Hum Dev 1983;8:1–11. 31. Baker EW (ed). Head and Neck Anatomy for Dental Medicine. New York: Thieme, 2010:44,312. 32. Racz L, Maros TN, Seres-Sturm L. Structural characteristics and functional significance of the buccal fat pad. Morphol Embryol 1989;35:73–77. 33. Tideman H, Bosanquet A, Scott J. Use of the buccal fat pad as a pedicled graft. J Oral Maxillofac Surg 1986;44:435–440. 34. Loukas M, Kapos T, Louis RG Jr, Wartmann C, Jones A, Hallner B. Gross anatomical, CT and MRI analyses of the buccal fat pad with special emphasis on volumetric variations. Surg Radiol Anat 2006;28:254–260. 35. Vuillemin T, Raveh J, Ramon Y. Reconstruction of the maxilla with bone grafts supported by the buccal fat pad. J Oral Maxillofac Surg 1988;83:257–264. 36. Dubin B, Jackson IT, Halim A, Triplett WW, Ferreira M. Anatomy of the buccal fat pad and its clinical significance. Plast Reconstr Surg 1988;83:257–264. 37. Tuli P, Parashar A, Nanda V, Sharma RK. Delayed buccal fat pad herniation: An unusual complication of buccal flap in cleft surgery. Indian J Plast Surg 2009;42:104–105. 38. Zhang HM, Yan YP, Qi KM, Wang JQ, Liu ZF. Anatomical structure of the buccal fat pad and its clinical adaptations. Plast Reconstr Surg 2002;109:2509–2518. 39. Tostevin PM, Ellis H. The buccal fat pad: A review. Clin Anat 1995;8:403–406. 40. Kahn JL, Wolfram-Gabel R, Bourjat P. Anatomy and imaging of the deep fat of the face. Clin Anat 2000;13:373–382. 41. Stuzin JM, Wagstrom L, Kawamoto HK, Baker TJ, Wolfe A. The anatomy and clinical applications of the buccal fat pad. Plast Reconstr Surg 1990;85:29–37. 42. Jackson IT. Anatomy of the buccal fat pad and its clinical significance. Plast Reconstr Surg 1999;103:2059–2060. 43. Ramirez OM. Buccal fat pad pedicle flap for midface augmentation. Ann Plast Surg 1999;43:109–118. 44. Neder A. Use of buccal fat pad for grafts. Oral Surg Oral Med Oral Pathol 1983;55:349–350. 45. Egyedi P. Utilization of the buccal fat pad for closure of oroantral and/or oro-nasal communications. J Maxillofac Surg 1977;5:241–244. 46. Adeyemo WL, Ladeinde AL, Ogunlewe MO, Bamgbose BO. The use of buccal fat pad in oral reconstruction: A review. Niger Postgrad Med J 2004;11:207–211. 47. El Haddad SA, Abd El Razzak MY, El Shall M. Use of pedicled buccal fat pad in root coverage of severe gingival recession defect. J Periodontol 2008;78:1271–1279. 48. Zhong LP, Chen GF, Fan LJ, Zhao SF. Immediate reconstruction of maxilla with bone grafts supported by pedicled buccal fat pad graft. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2004;97:147–154. 49. Kim YK, Hwang JW, Yun PY. Closure of large perforation of sinus membrane using pedicled buccal fat pad graft: A case report. Int J Oral Maxillofac Implants 2008;23:1139–1142. 50. Hassani A, Khojasteh A, Alikhasi M. Repair of the perforated sinus membrane with buccal fat pad during sinus augmentation. J Oral Implantol 2008;34:330–333. 51. Wong K. Laser Doppler flowmetry for clinical detection of blood flow as a measure of vitality in sinus bone grafts. Implant Dent 2000;9:133–142. 52. Liversedge RL, Wong K. Use of the buccal fat pad in maxillary and sinus grafting of the severely atrophic maxilla preparatory to implant reconstruction of the partially or completely edentulous patient: Technical note. Int J Oral Maxillofac Implants 2002;17:424–428. 53. Proussaefs P, Lozada J. The “Loma Linda pouch”: A technique for repairing the perforated sinus membrane. Int J Periodontics Restorative Dent 2003;23:593–597. 54. Aimetti M, Romagnoli R, Ricci G, Massei G. Maxillary sinus elevation: The effect of macrolacerations and microlacerations of the sinus membrane as determined by endoscopy. Int J Periodontics Restorative Dent 2001;21:581–589.

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58. Matarasso A. Pseudoherniation of the buccal fat pad: A new clinical syndrome. Plast Reconstr Surg 1997;100:723–730. 59. Hines N, Lantos G. Herniation of the buccal fat pad into the maxillary antrum: CT findings in three cases. AJNR Am J Neuroradiol 2006;27:936–937. 60. Marano PD, Smart EA, Kolodny SC. Traumatic herniation of buccal fat pad into maxillary sinus: Report of case. J Oral Surg 1970;28:531–532.

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4 Anterior Maxilla

The anatomical landmarks that are relevant to implant placement in the anterior maxilla are the nasal cavity, the infraorbital foramen, and the maxillary incisive foramen and canal. This chapter also discusses maxillary alveolar bone deficiency and its clinical management.

Anterior Maxilla

4

The Nasal Cavity Bony structure of the nose The bony structure of the external nose is largely formed by the maxilla. Inferiorly, this includes the alveolar process and the anterior nasal spine. Superiorly, this includes the frontal process of the maxilla, which contributes strength to the bony sidewalls of the external nose. The paired nasal bones laterally and the frontal bone superiorly create the bony bridge of the nose. The internal nasal cavity bony structure is illustrated in Figs 4-1 and 4-2. Internally, the superior nasal cavity’s bony structure is formed by the inferior surface of the nasal bones, behind which are the frontal bones, containing the frontal sinuses. The largest portion of the roof of the sinonasal cavity is formed by the ethmoid bone, which is very thin medially (at the cribriform plate, through which the olfactory nerves penetrate) and thicker laterally. The ethmoid bone also gives rise to the superior and middle nasal conchae, which extend down from the roof of the nasal cavity. Most posteriorly in the nose is the sphenoid bone, which encloses its namesake sinus as well as the sella turcica (which surrounds the pituitary gland).

Superior nasal concha

Nasal spine of frontal bone

Sphenoid sinus Nasal bone

Agger nasi (an occasional air cell; agger nasi concha)

Pterygoid process

Sphenopalatine fossa

Middle nasal concha Incisive canal

Inferior nasal concha

Fig 4-1  The bony structure of the lateral wall of the nasal cavity.

98

The Nasal Cavity

Cribriform plate

Crista galli

Frontal sinus

Ethmoid bone, orbital plate Ethmoid bone, perpendicular plate

Superior meatus and concha

Middle meatus and concha Ostium of maxillary sinus

Uncinate process Middle ethmoid air cells

Maxillary sinus

Inferior meatus

Palatine process of maxilla

Inferior concha Vomer

Fig 4-2  Anterior view of the nasal bony structure.

99

Anterior Maxilla

4

The lateral bony wall of the nasal cavity is created anteriorly by the maxilla, which gives rise to the inferior nasal concha. Posterior to maxilla and superior to the inferior concha is the thin lacrimal bone, overlying the lacrimal apparatus. Continuing posteriorly, the lateral nasal wall is created by the perpendicular plate of the palatine bone, which abuts the sphenopalatine foramen anteriorly. Posterior to this is the sphenoid bone, including the plates of the pterygoid process. Inferiorly, the nasal cavity is created in large part by the alveolar and palatine processes of the maxilla. Behind this, the remaining hard palate is created by the horizontal plate of the palatine bone. The bony and cartilaginous structure of the nasal septum is illustrated in Fig 4-3. The midline support of the nasal cavity is created by the septal (or quadrangular) cartilage anteriorly, which meets the bony perpendicular plate of the ethmoid bone about 2 to 3 cm away from its anterior portion. The perpendicular plate forms the superior portion of the bony septum and extends all the way back to the sphenoid face. Beneath this is the vomer, which also extends to the sphenoid face. Making smaller contributions to the most inferior portions of the septum are the nasal crests of the maxilla and palatine bone.

Crista galli

Cribriform plate

Nasal bone

Perpendicular plate, ethmoid bone

Septal cartilage

Vomer

Incisive canal

Fig 4-3  The bony and cartilaginous structure of the nasal septum.

100

The Nasal Cavity

Lining of the nose The soft tissue lining of the nasal cavity and sinuses is designed to optimally carry out the functions of air modulation and immune protection. Most areas of the nose and sinuses are lined with a superficial layer of epithelium, comprised predominately of columnar ciliated cells and a lesser number of goblet cells. Beneath this layer is an acellular basement membrane that overlies a thick lamina propria, containing vascular and glandular layers. Under all of this lies the periosteum. Different areas of the nose display variations in this pattern to carry out specialized functions. The most anterior portion of the nasal cavity is lined with squamous cell epithelium and is suited for protection. The nasal conchae (sometimes referred to as turbinates) and portions of the nasal septal mucosa have considerable venous capacitance vessels, which can lead to considerable congestion in the nasal lining when needed for moisturization of inspired air. The inferior concha is particularly suited for this purpose. The lining of the paranasal sinuses tends to be thinner than that of the nasal cavity and demonstrates fewer goblet cells. Consequently, approximately half a liter of mucus is created by the nasal mucosa each day. The ciliated cells of the nose and sinuses sweep mucus in a coordinated and predictable fashion out of the sinuses and into the posterior nose, from whence it is swallowed. The mucus forms a bilayer over the nasal lining, with a sticky, mucinous gel layer floating on top of a serous sol layer, which contains innate immunity proteins. The cilia extend up through the sol layer and sweep the gel layer along at a rate from 3 to 25 mm per minute. When aerosolized pathogens and debris land on the sticky mucus, they are trapped and swept out of the nose.

101

Anterior Maxilla

4 Blood supply of the nasal cavity The nasal cavity and sinuses are exceptionally well vascularized. Figures 4-4 and 4-5 illustrate the arterial supply of the nose. The largest contribution comes from the sphenopalatine artery, a branch of the internal maxillary artery (which is a branch of the external carotid artery). The sphenopalatine artery enters the nasal cavity through the pterygomaxillary fossa and the sphenopalatine foramen, immediately posterior to the posterior wall of the maxillary sinus. Upon entering the nose, the sphenopalatine artery sends branches anteriorly to supply the lateral nasal wall and the conchae. It also sends a large branch posteriorly and medially across the sphenoid face to provide blood supply to the nasal septum. It is estimated that the sphenopalatine artery accounts for more than 80% of the nasal blood supply.

Anterior ethmoid artery

Posterior ethmoid artery Sphenopalatine artery

Anastomosis with greater palatine artery

Greater palatine artery

Fig 4-4  Vascularization of the nasal septum.

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The Nasal Cavity

Anterior and posterior ethmoid arteries

Sphenopalatine artery

Maxillary artery

Palatine artery

Descending palatine artery

External carotid artery

Internal carotid artery

Fig 4-5  Vascularization of the lateral wall of the nose.

103

Anterior Maxilla

4 A second artery from the internal maxillary circulation contributes to the nasal cavity. The descending palatine artery becomes the greater palatine artery, which exits through the greater palatine foramen into the oral cavity. It then runs anteriorly along the palate and reenters the nasal cavity via the incisive canal, where it anastomoses with branches of the sphenopalatine artery on the anterior septum. The internal carotid artery also contributes arterial branches to the nasal cavity and sinuses. As the ophthalmic artery runs anteriorly through the orbit, it branches off into the posterior and anterior ethmoid arteries, which enter the nasal cavity high along the skull base, cross the ethmoid roof, and reenter the intracranial cavity via the cribriform plate (Fig 4-6). Branches of these vessels supply the lateral nasal wall, sinuses, and superior nasal septum. The venous drainage of the nasal cavity closely follows the arterial pathways. Dorsal nasal artery

Medial palpebral artery

Frontal artery

Supraorbital artery

Anterior ethmoid artery

Arteria centralis retinae

Zygomatic branches of lacrimal artery Posterior ethmoid artery

Anastomotic branch through lacrimal foramen (sphenoid bone)

Lacrimal artery Muscular branches Ophthalmic artery

Optic nerve

Internal carotid artery

Superior orbital fissure

Middle meningeal artery

Fig 4-6  Origin of the ethmoid arteries.

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The Nasal Cavity Innervation of the nasal cavity The nasal cavity and sinuses have sensory, autonomic, and special sensory innervation. The innervation of the nasal cavity is illustrated in Fig 4-7. Nerve branches typically follow vascular patterns of distribution as previously described. While the majority of sensory innervation is via the second division of the trigeminal nerve (V2), there is some contribution from V1 as well. The pterygopalatine ganglion supplies branches, including the nasopalatine nerve, that closely follow the arterial branches of the sphenopalatine artery. The anterior and posterior ethmoidal nerves innervate the superior portions of the nasal cavity and sinuses and arise from the nasociliary nerve, which is a branch of the ophthalmic division of the trigeminal nerve (V1). The olfactory epithelium is found on the upper surfaces of the superior concha, cribriform plate, and nasal septum. Within this special mucosa are found olfactory receptor neurons, which send dendrites to the mucosal surface to detect odors. The axons of these neurons extend through the cribriform plate to the olfactory bulb, which in turn transmits signals to the olfactory cortex. Figure 4-8 shows the nasal cavity from various sections of a human cadaver skull.

Olfactory nerves (fila olfactoria)

Nasopalatine nerve Anterior ethmoid nerve

Incisive (nasopalatine) canal

Fig 4-7  Innervation of the nasal cavity.

105

Anterior Maxilla

4

B

C

Cut A: Made around the middle of the zygoma bone. Cut B: M  ade immediately to the right of the septum of the nose (when looking at the specimen from the anterior). Cut C: M  ade immediately to the left of the lateral wall of the nose (medial wall of the sinus).

A

1

2

3 4

A

B

C

Plate 1 shows the left side of the septum of the nose after cut B is made. Plate 2 shows the left lateral wall of the nose before cut C is made. Plate 3 shows slice B (looking from the left sinus side). Plate 4 shows slice C.

Fig 4-8 

106

The Nasal Cavity

1

4

3

9

2

10 8

6

7

5

Plate 1 1. Anterior table of frontal sinus 2. Frontal sinus 3. Posterior table of frontal sinus 4. Falx cerebri 5. Nasal septum (cartilage) 6. Nasal septum (perpendicular plate of ethmoid and vomer) 7. Sphenoid sinus 8. Sella turcica and pituitary gland 9. Anterior cranial fossa 10. Nasal bone

107

Anterior Maxilla

4

4

10

3

2

6

9

1

7 8 5

11

12

Plate 2 1. Nasal bone 2. Anterior table of frontal sinus 3. Frontal sinus 4. Posterior table of frontal sinus 5. Middle nasal concha 6. Cribriform plate 7. Superior nasal concha 8. Anterior face of sphenoid sinus 9. Sphenoid sinus 10. Anterior cranial fossa 11. Lateral nasal wall 12. Septal branch of sphenopalatine artery

108

The Nasal Cavity

1

3 4 2

6 9 7

5

8

10 11

Plate 3 1. Anterior table of frontal sinus 2. Frontal sinus 3. Posterior table of frontal sinus 4. Anterior cranial fossa 5. Agger nasi cells 6. Anterior ethmoid sinuses 7. Posterior ethmoid sinuses 8. Sphenoid sinus 9. Sella turcica and contents 10. Attachment of inferior nasal concha 11. Inferior meatus

109

Anterior Maxilla

4

4 3

2 1

6

11

5 7

8

9

10

Plate 4 1. Anterior table of frontal sinus 2. Frontal sinus 3. Posterior table of frontal sinus 4. Anterior cranial fossa 5. Agger nasi cells 6. Anterior ethmoid sinuses 7. Posterior ethmoid sinuses 8. Sphenoid sinus 9. Lateral nasal wall 10. Maxillary sinus 11. Sella turcica and contents

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The Nasal Cavity This plate shows the lateral wall of the nose of a separate specimen than the previous plates.

12 11

14

13

6

10 5 1 9 2

4

7

8

3

1. Torus tubarius 2. Opening of Eustachian tube 3. Soft palate 4. Hard palate 5. Inferior nasal concha 6. Middle nasal concha 7. Incisive canal 8. Alveolar process of maxilla 9. Inferior meatus 10. Middle meatus 11. Anterior ethmoid sinuses 12. Posterior ethmoid sinuses 13. Sphenoid sinus 14. Carotid artery

111

Anterior Maxilla

4

Infraorbital Foramen The infraorbital foramen is located just below the inferior border of the orbit. It contains the infraorbital nerve and artery. It is variable in shape and position and may have two or three external openings. Its position is independent of the shape of the facial skeleton. It opens in a medial direction, with its opening inclined caudally so that it is not readily identified through the skin. The infraorbital sulcus is completely enclosed, forming a canal (Fig 4-9). The infraorbital nerve is a branch of the maxillary nerve, which is the second branch of the trigeminal nerve arising from the trigeminal ganglion. After giving off a meningeal branch, the infraorbital nerve passes through the foramen rotundum into the pterygopalatine fossa, where it divides into the zygomatic nerve, pterygopalatine/nasopalatine nerves (ganglionic branches), and the infraorbital nerve. The infraorbital nerve enters the orbit through the inferior orbital fissure (after branching off into the posterior superior alveolar nerves to the molars and the medial superior alveolar nerves). It traverses the infraorbital groove and canal in the floor of the orbit, where it branches off into the anterior superior alveolar nerve, and appears on the face at the infraorbital foramen. Here it is referred to as the infraorbital nerve, a terminal branch. At its termination, the nerve lies beneath the quadratus labii superioris and divides into several branches that innervate the side of the nose (external and internal nasal nerves), the lower eyelid (inferior palpebral nerve), and the upper lip (the superior labial branches), joining with filaments of the facial nerve (Fig 4-10). The facial artery lies in a bony groove along the frontal process of the maxilla. It anastomoses with the dorsal artery of the nose and with the infraorbital artery, which supplies the upper lip, the nose, and the lower eyelid (Fig 4-11).

Fig 4-9 Computed tomography scan of the infraorbital canal.

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Fig 4-10  Area supplied by the maxillary nerve through the infraorbital nerve.

Infraorbital Foramen

Surgical importance in oral implantology The infraorbital nerve can be damaged during flap reflection in lateral window sinus augmentation procedures and during flap reflection for implant placement in the anterior maxilla with extensive resorption, possibly resulting in paresthesia of the upper lip. Injury to the infraorbital nerve can be minimized by determining the exact location of the nerve prior to surgery through computed tomography (CT) scanning, by terminating flap reflection at a level well below the infraorbital foramen, by gentle soft tissue management, and by keeping the retractors a safe distance away from the nerve during surgery.

Supratrochlear artery (medial frontal branch)

Supraorbital artery (lateral frontal branch)

Anterior ethmoid artery

Posterior ethmoid artery Ophthalmic artery

Lacrimal artery Dorsalis nasi artery Sphenoid bone

Zygomatic bone

Angular artery

Superior orbital fissure

Infraorbital sulcus

Maxilla

Contour of the maxillary sinus

Infraorbital artery and nerve

Facial artery

Fig 4-11  Facial artery anastomoses with the infraorbital artery.

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Anterior Maxilla

4

Maxillary Incisive Foramen and Canal The incisive canal is normally located at the midline of the maxilla, posterior to the central trough of routine panoramic radiographs; therefore, it is poorly visualized on these films.1 On regular radiographs, some pathologies, such as the incisive canal cyst, can be misdiagnosed as endodontic lesions.2 The incisive canal contains the nasopalatine nerve and the anterior branch of the greater palatine artery. There are at least two bundles in the canal (Fig 4-12), because the nerves and the arteries in the canal originate from a bilateral source.3

Frontal sinus

Ethmoid cell

Median lamina, ethmoid bone Nasal septum Nasolacrimal duct

Maxillary sinus Pyriform aperture

Nasal floor

Nasal septum Stensen foramen

Nasal cavity 1/

5

Anterior nasal spine Hard palate

4/

5

Oral roof Incisive/nasopalatine canal

Fig 4-12  Anatomy of the maxillary incisive canal.

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Main trunks of nasopalatine nerve and greater palatine artery transverse posteriorly while minor branches supply gingiva/mucosa of anterior palate

Maxillary Incisive Foramen and Canal

•  Nasopalatine nerve: A branch of the posterior superior nasal nerves that arise from the pterygopalatine ganglionic branches of the maxillary nerve. It runs inferiorly and anteriorly to pass through the incisive foramen, supplying the anterior part of the palate and communicating with the greater palatine nerve. Therefore, anesthesia for surgeries involving the anterior maxilla, maxillary central incisors, nasal septum, or nasal floor can be achieved by injection into the incisive foramen. •  Anterior branch of the greater palatine artery: The greater palatine artery emerges from its canal through the greater palatine foramen and runs across the hard palate to the incisive foramen, through which it enters the nasal cavity and anastomoses with the sphenopalatine artery on the nasal septum and sometimes in the canal itself.

Morphology The nasopalatine canal typically appears as a canal with a mean length of 8.1 mm. Its palatal opening is the incisive foramen, with a mean inner diameter of 4.6 mm. Often two openings can be observed just below the level of the nasal floor, although sometimes there is only one or even three or four. The average maximum width of the nasopalatine canal structure at the level of the nasal floor is 4.9 mm. The width of the jaw, anterior to the canal, is 7.4 mm. However, the nasopalatine canal may show important anatomical variations with regard to both morphology and dimensions.4 In a study of 254 human skulls, Iordanishvili5 found that the incisor opening is situated on the inferior surface of the maxillary palatal process, along the median line, at a distance of 9.8 mm ± 0.2 mm from the point formed by the medial angles of the central incisor crowns, irrespective of the subject’s sex. The distance between the incisor opening and the central incisor roots in adults is 3.5 mm ± 0.1 mm. It is important to note that, in individuals with a resorbed anterior maxilla, the distance between the anterior portion of the canal and the buccal plate of the anterior maxilla is compromised and may be much smaller than that in individuals with a dentate anterior maxilla. Bone resorption together with an enlarged incisive foramen can challenge proper implant placement.

115

Anterior Maxilla

4 Evaluation of maxillary incisive foramen and canal on CT scans CT scans provide a clear way of evaluating the location and size of the incisive foramen, the exact topography of its canal, and the distance between the canal and the buccal plate of the midline of the maxilla. Figures 4-13 and 4-14 show different sizes of incisive foramina and canals and various locations relative to the crestal ridge.

Surgical importance in oral implantology To avoid any potential complications during surgical procedures, such as implant placement into the canal, a careful preoperative observation using cross‐sectional imaging is recommended to determine canal morphology and dimensions and to assess anterior bone width for potential implant placement buccally to the canal.

a

b

c

Fig 4-13  (a to c) Various locations of the incisive foramen relative to the crestal ridge level.

a

b

c

Fig 4-14  (a) Unusually narrow maxillary incisive canal. (b and c) The close proximity between the incisive foramen and the crestal ridge, with c being more severe.

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Maxillary Incisive The Foramen Maxillary and Canal Sinus Grafting the incisive canal (incisive canal deflation) In some cases, the location of the incisive canal may prevent the placement of dental implants to replace missing maxillary central incisors (Fig 4-15). When it is indicated for ideal prosthetic planning, excision of the nerves and the blood vessels of the incisive canal and the subsequent placement of bone graft material for immediate or delayed implant placement is a viable technique that can be done without detriment to the patient.6–8 The nerve and the artery of the incisive canal anastomose with the greater palatine artery and nerve, permitting immediate revascularization and a gradual reinnervation of the region within 3 to 6 months. Nonetheless, loss of sensation in the anterior palate is a possibility, and patients should be warned about it; however, this is rarely a cause of patient complaint. The procedure can be carried out under local anesthesia. It starts with the reflection of a full-thickness flap; then curettes and a round bur with copious irrigation are used to completely remove the contents of the canal, and the bone inside the canal is scored to ensure sufficient bleeding. Bone graft material (autogenous or a mixture of xenograft and allograft) are then placed for simultaneous or delayed implant insertion.

a

b

c

d

e

f

Fig 4-15  Case in which resorption in the area of the central incisors (a to c) prevented the placement of implants in central incisor sites without incisive canal deflation and grafting. In this particular case, it was possible to avoid this procedure by placing implants in the lateral incisor area (d to h) for a four-unit implant-supported fixed prosthesis. Note: If only one lateral incisor had been missing instead of both, then grafting of the incisive canal would have been necessary for a fixed implant-supported prosthesis. Therefore, maxillary incisive canal grafting may be required not only in advanced resorption cases involving the complete arch but also for patients missing only anterior teeth.

g

h

117

Anterior Maxilla

4

Inadequate Bony Structure in the Anterior Maxilla The author has developed a classification for natural resorption patterns of the alveolar bone (Fig 4-16). Current classifications state that after tooth loss, the alveolar bone gradually loses width until the loss is severe, and then height loss begins, but the author rather argues that after the initial width loss, the resorption pattern takes on one of two different formats: severe width loss along the entire alveolar bone or severe width loss only in the crestal half of the alveolar bone with a good amount of alveolar bone width remaining in the apical half. It is important to be aware of these two different patterns and be able to distinguish between them on a CT scan during the CT evaluation and treatment planning stage because the resorption pattern will dictate the bone grafting procedures required to augment the ridge.

Maxillary Class I: Minimal width loss

Maxillary Class II: Moderate width loss

Maxillary Class IIIA: Severe width loss at the crestal half with minimal height loss

Maxillary Class IIIB: Severe width loss affecting the entire alveolar ridge with minimal height loss Maxillary Class IV: Severe height and width loss

Fig 4-16  Al-Faraje classification of bone loss resorption patterns in the anterior maxilla.

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Inadequate Bony Structure in the Anterior Maxilla

Clinical management of maxillary alveolar bone deficiency The following are basic principles for the management of maxillary alveolar bone deficiency: •  Identification of the exact bone loss pattern on the CT scan. •  For Class I bone resorption (Al-Faraje classification), implants with regular or even wide platform diameters may be placed, because the bone loss is minimal in width and height (recent tooth loss). •  For Class II bone resorption, implants can still be placed without any simultaneous bone grafting procedures; however, the operator should select a narrow platform–diameter implant to ensure adequate thickness of bone on the buccal and palatal sides of the implants. •  For Class IIIA bone resorption, the operator should perform alveoloplasty and then ridge augmentation via the split‐ cortical technique before the placement of implants, place implants with simultaneous guided bone regeneration, or perform block grafting with delayed implant placement. Although three techniques are available, the ridge splitting is the easiest and the most reliable in this type of maxillary bone loss. Figure 4-17 illustrates the steps of this procedure, and Fig 4-18 shows a clinical example. •  For Class IIIB bone resorption, the splitting technique is not possible, and the block grafting technique is challenging because of minimal host bone thickness; therefore, the recommended procedure is guided bone regeneration using titanium mesh and recombinant human bone morphogenetic protein 2 (rhBMP‐2)/absorbable collagen sponge (ACS) grafting material. •  For Class IV bone resorption, three techniques are available for vertical ridge augmentation: block grafting, distraction osteogenesis, and interpositional grafting. Nasal floor elevation may also be indicated with certain height in the anterior region. The operator should choose one of these techniques based on the severity of the resorption and the location of the resorbed ridge (anterior versus posterior).

119

Anterior Maxilla

4

a

b

c

d

e

f

Fig 4-17  Alveolar ridge expansion via the split-cortical technique. (a) The procedure starts by evaluating the CT scan to ensure that, based on the patient’s resorption pattern, the patient is a candidate for this procedure. (b) After a full-thickness flap is elevated and the crestal bony ridge is leveled (if needed), a piezotome is used to create a longitudinal cut in the middle of the available alveolar bone. (c) Ridge-splitting chisels are then used as needed to widen the ridge. (d) One or two drills are used to create the osteotomy for implant placement. (e) The implants are placed for a two-stage protocol, and a bone grafting material is used to fill the gaps between the implants before the area is covered with a resorbable membrane. (f) The surgical site is sutured.

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Inadequate Bony Structure in The the Anterior Maxillary Maxilla Sinus

a

b

c

d

e

f

g

h

Fig 4-18  Clinical example of alveolar ridge expansion via the split-cortical technique. (a) A CT scan is taken. (b) The site is clinically evaluated. (c and d) A full-thickness flap is reflected to visualize the alveolar bone width, shape, and trajectory. (e) The alveolar ridge is flattened and leveled using an alveoloplasty bur. (f and g) A piezotome is used to create a longitudinal cut in the middle of the available alveolar bone. (h) An expansion chisel is used to further widen the ridge.

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Anterior Maxilla

4

i

j

k

l

m

n

o

p

Fig 4-18 (cont)  (i) The ridge after piezotome and chisel use. (j and k) The osteotomies are prepped short of the final drills needed for the intended implant diameter, and tapered implants are inserted (DIO Implant system). (l) Bone grafting material is used to fill the gaps between implants (Bio-Oss, Geistlich). (m) A collagen dressing (OraTape, Salvin) is placed. (n) The incision is primarily closed using Gore-Tex suture materials (Gore Medical). (o and p) Postoperative CT scans are taken.

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References 1. Kraut RA, Boyden DK. Location of incisive canal in relation to central incisor implants. Implant Dent 1998;7:221–225. 2. Terry BR, Bolanos OR. A diagnostic case involving an incisive canal cyst. J Endod 1989;15:559–562. 3. Song WC, Jo DI, Lee JY, et al. Microanatomy of the incisive canal using three‐dimensional reconstruction of microCT images: An ex vivo study. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009;108:583–590. 4. Mraiwa N, Jacobs R, Van Cleynenbreugel J, et al. The nasopalatine canal revisited using 2D and 3D CT imaging. Dentomaxillofac Radiol 2004;33:396–402.

5. Iordanishvili AK. Age‐related characteristics and sex differences in the anatomical structure of the incisive canal [in Russian]. Sovetskaia Stomatologiia (Mosk) 1991;(4):25–27. 6. Rosenquist JB, Nyström E. Occlusion of the incisal canal with bone chips. A procedure to facilitate insertion of implants in the anterior maxilla. Int J Oral Maxillofac Surg 1992;21:210–211. 7. Marcantonio E Jr. Incisive canal deflation for correct implant placement: Case report. Implant Dent 2009;18:473–479. 8. Scher EL. Use of the incisive canal as a recipient site for root form implants: Preliminary clinical reports. Implant Dent 1994;3:38–41.

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5 Posterior Mandible The anatomical landmarks that are relevant to surgical oral implantology in the posterior mandible are the mandibular ramus, the inferior alveolar canal/nerve, the lingual nerve, and the submandibular fossa. This chapter also describes the anatomical manifestations of different bone resorption patterns in the posterior mandible and the proper treatment planning for each, as well as the anatomical considerations for harvesting a block graft from the ramus buccal shelf area.

Posterior Mandible

5

Mandibular Ramus The mean anteroposterior width of the ramus is 30.5 mm, with the mandibular foramen located about two‐thirds from the anterior border (Fig 5-1).

Sublingual fossa

Lingula Mandibular foramen

Mylohyoid groove Mylohyoid (internal oblique) line

Submandibular fossa

Fig 5-1  The lingual side of the posterior mandible, showing the location and size of the mandibular foramen. The dotted line indicates the limit of attachment of the oral mucosa.

126

Mandibular Ramus

Block graft harvesting from the ramus buccal shelf1–6 As the cheek (a combination of buccinator and masseter muscles) is pulled laterally, the tissue is stretched over the posterior mandible osseous donor site. The harvest site will include the external oblique ridge, the retromolar triangle, the body of the mandible, and the ascending ramus (Fig 5-2). Note the position of the facial notch and its contents of the facial nerve, artery, and vein. This is found at the angle of the mandible at the anterior border of the masseter muscle.

Masseteric n. (CN V3)

Maxillary a.

Temporalis

Superior posterior alveolar branches

Superior medial alveolar branches

Auriculotemporal n. Posterior superior alveolar aa.

Superficial temporal a.

Buccal a.

Posterior masseteric a. Facial n. (CN VII)

Medial pterygoid n.

Retromandibular v. Buccal n. (CN V2)

Inferior alveolar a.

Medial pterygoid

Inferior alveolar n. (CN V3) Lingual n. (CN V3)

Masseter (anterior portion removed for better viewing of the ramus)

Facial v.

Facial a.

Fig 5-2 The anatomy of the anterior ramus region. n.—nerve; a.—artery; aa.—arteries; v.—vein.

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Posterior Mandible

5 When evaluating the patient’s computed tomography (CT) scan preoperatively, at least 5 mm must exist between the superior border of the inferior alveolar canal and the superior oblique ridge of the mandible. Although the buccolingual position of the inferior alveolar canal in the alveolar bone is variable, the distance from the canal to the medial aspect of the buccal cortical plate (ie, the medullary bone thickness) was found to be greatest at the distal half of the first molar (mean, 4.05 mm) (Fig 5-3). Therefore, when larger grafts are planned, the anterior vertical cut should be made in this area (Fig 5-4). The mean vertical distance between the superior border of the canal and the cortical surface along the external oblique ridge is 7 mm in the second molar region, 11 mm in the third molar region, and 14 mm at the base of the coronoid process. Therefore, when a smaller graft size is required, the harvest may be made higher on the ramus, which usually decreases the proximity to the canal.

External oblique ridge

Buccal cortex 3.5 mm

4 mm

Fig 5-3  A cross section of the mandible at the level of the first molar, showing the distance between the inferior alveolar canal and the medial aspect of the buccal cortical plate.

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Mandibular Ramus

Temporalis muscle

Superior ramus cut

External oblique cut

Masseter muscle

Buccal notch

Inferior ramus cut

Anterior body cut

Fig 5-4 Lateral view of the mandible, showing the proper locations of the four cuts needed to harvest a block graft from the ramus buccal shelf.

129

Posterior Mandible

5 Figure 5-5 shows a clinical example of a block graft harvested from the ramus buccal shelf.

a

b

c

d

e

f

Fig 5-5  Clinical example of a block graft harvested from a ramus buccal shelf. (a) A full-thickness flap is reflected, and the anterior inferior area of the ramus is exposed. The attachment of the temporalis muscle at the inferior border of the mandible is noted, and the partially bony impacted third molar can be seen. (b) Immediate removal of the bone lateral to the third molar will outline the thickness of the ramus block. (c) Ramus area after removal of the third molar. (d) The medial wall of the block is extended toward the anterior slightly (per the required size of the recipient site). (e and f) After the other three cuts are made, the block graft is harvested.

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The Mandibular MaxillaryRamus Sinus Figures 5-6 and 5-7 show four mandible specimens selected by the author to represent the four different stages of bone resorption: 1. Minimal or almost no resorption (dentate jaw bone) (Figs 5-6a and 5-7a) 2. Mild resorption (recent tooth loss) (Figs 5-6b and 5-7b) 3. Moderate to advanced resorption, usually with gross alveolar bone loss in width and moderate bone loss in height (long history of tooth loss) (Figs 5-6c and 5-7c) 4. Severe bone loss, with gross alveolar bone loss in both height and width (extensive history of tooth loss) (Figs 5-6d and 5-7d)

a

b

c

d

Fig 5-6  Four stages of bone resorption. (a) Minimal or almost no resorption. (b) Mild resorption (recent tooth loss). (c) Moderate to advanced resorption, usually with gross alveolar bone loss in width and moderate bone loss in height (prolonged history of tooth loss). (d) Severe bone loss, with gross alveolar bone loss in both height and width (extensive history of tooth loss).

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Posterior Mandible

5

a

b

c

d

Fig 5-7  Anterior view of mandible specimens shown in Fig 5-6. Note the disappearance of the mandibular superior oblique ridge in the mandibles shown in c and d, which exhibit advanced resorption. (a) Minimal or almost no resorption. (b) Mild resorption (recent tooth loss). (c) Moderate to advanced resorption, usually with gross alveolar bone loss in width and moderate bone loss in height (prolonged history of tooth loss). (d) Severe bone loss, with gross alveolar bone loss in both height and width (extensive history of tooth loss).

132

The Mandibular MaxillaryRamus Sinus These mandibles demonstrate the anatomical manifestations of alveolar bone loss and their impact on dental implant placement, as demonstrated by illustrations in this chapter and in chapter 6. Figures 5-8 to 5-12 show three-dimensional CT scans of mandibles (selected from the author’s pool of patients) that exhibit bone loss patterns similar to those demonstrated in the specimens in Figs 5-6 and 5-7. Note the distances between the inferior alveolar nerve (IAN) and the lateral border of the buccal plate in Figs 5-9 to 5-12. The site of the ramus block osteotomy should always be selected based on the actual CT scan measurements of the patient.

a

b

c

d

Fig 5-8  CT scans of the different stages of bone resorption. (a) Minimal or almost no resorption. (b) Mild resorption (recent tooth loss). (c) Moderate to advanced resorption, usually with gross alveolar bone loss in width and moderate bone loss in height (prolonged history of tooth loss). (d) Severe bone loss, with gross alveolar bone loss in both height and width (extensive history of tooth loss).

133

Posterior Mandible

5

a

b

Fig 5-9  Cross sections at the base of the ramus (a) and at the area distal to the first molar (b) in mandibles with minimal bone resorption, showing the distance between the IAN and the lateral border of the buccal plate.

134

Mandibular Ramus

a

b

Fig 5-10  Cross sections at the base of the ramus (a) and at the area distal to the first molar (b) in a mandible with mild bone resorption, showing the distance between the IAN and the lateral border of the buccal plate.

135

Posterior Mandible

5

a

b

Fig 5-11  Cross sections at the base of the ramus (a) and at the area distal to the first molar (b) in a mandible with moderate to advanced bone resorption, showing the distance between the IAN and the lateral border of the buccal plate.

136

Mandibular Ramus

a

b

Fig 5-12  Cross sections at the base of the ramus (a) and at the area distal to the first molar (b) in a mandible with severe bone resorption, showing the distance between the IAN and the lateral border of the buccal plate.

137

Posterior Mandible

5

Lingual Nerve The lingual nerve is a branch of the mandibular nerve. It descends to the base of the tongue just anterior and slightly medial to the IAN7,8 (Fig 5-13) and is thus anesthetized by an IAN block. The lingual nerve supplies the sensory innervation to the anterior two-thirds of the tongue (Figs 5-14 and 5-15) and receives taste fibers from the chorda tympani (facial nerve).9 It is usually located immediately medial to the lingual cortical plate of the mandible below the crest of the ridge and posterior to the third molar roots (Fig 5-16). It is covered in this area by a thin layer of oral mucous membrane and thus is sometimes visible clinically (and therefore often endangered by dental procedures in this region).

Mandibular n. (CN V3)

Medial pterygoid n. Articular capsule

Lateral pterygoid n.

Auriculotemporal n.

Sphenomandibular ligament

Lingual n.

Stylomandibular ligament

Inferior alveolar n. Mylohyoid n.

Possible path of the lingual nerve

Medial pterygoid

Usual path of the lingual nerve

Fig 5-13  The usual lingual nerve path and a possible variation relative to the mandibular ramus. n.—nerve.

138

Lingual Nerve

Lingual nerve and submandibular ganglion Deep lingual artery and vein Sublingual gland Submandibular duct

N. XII Anterior lingual gland

Sublingual fold Sublingual papilla

Fig 5-14  Topography of the lingual nerve passage. The lingual nerve crosses underneath the submandibular duct and passes from dorsolateral to ventromedial toward the tip of the tongue. The nerve and the submandibular ganglion lie near the mandible at the level of the posterior molars. As a result, both structures can be injured in extraction of the distalmost molar. The accessory ducts of the sublingual glands open along the sublingual folds. The main sublingual duct and submandibular duct drain into the anterior floor of the mouth and the sublingual papilla. N.—cranial nerve.

Fig 5-15  Sensory supply to the anterior two-thirds of the tongue (somatic sensation only). Taste to the highlighted area is provided by the facial nerve (CN VII) via the chorda tympani.

139

Posterior Mandible

5 Preventing injury to the lingual nerve10–14 • To avoid cutting the lingual nerve, the distal releasing incision in the retromolar (triangle) pad area should be 30 degrees toward the buccal (not straight), because the nerve might lie on the retromolar pad (see Fig 5-19a). • The lingual side of the flap in the posterior mandibular region should be reflected carefully and gently. • Lingual releasing incisions should be avoided.

Condyle

Angle of flare Lingula

Coronoid process Lingual nerve External oblique ridge

Retromolar pad Angle of mandible

Curvature of the arch (bone level)

Curvature of the arch (tooth level)

a

b

b

Fig 5-16 (a) Superior view of the mandible, showing the angle of flare that starts immediately posterior to the third molar, the two different arches formed by the teeth and the bony structure of the mandible, and the possible location of the lingual nerve on the crestal ridge distal to the third molar toward the lingual plate. (b) Superior view of a mandible specimen, with the angle of flare, arch forms, and lingual nerve location superimposed.

140

Lingual Nerve Figure 5-17 shows the proper location for midcrestal incision to avoid damaging the lingual nerve during third molar extraction or block harvesting in this area.

a

b Fig 5-17  (a) The proper location for midcrestal incision to expose the crestal ridge during third molar extraction or ramus bone block harvesting. (b) The incision exposes an adequate area of the ramus for harvesting ramus buccal shelf block without nearing the lingual half of the crestal ridge, thus eliminating the possibility of damaging the lingual nerve during these procedures.

141

Posterior Mandible

5 In a magnetic resonance study, Miloro et al15 found that the nerve actually coursed over the retromolar pad in 10% of patients (Fig 5-18). In these cases, the nerve is at higher risk for traumatization by flap elevation and retraction or even during suturing. Figure 5-19 shows the proper technique for exposing the lingual nerve. Cutting the lingual nerve will anesthetize the tongue, decrease salivary flow from the submandibular gland, and affect the patient’s sense of taste.

Maxillary a.

Masseteric n. (CN V3)

Superior posterior alveolar branches

Superior medial alveolar branches

Auriculotemporal n. Posterior superior alveolar aa.

Superficial temporal a.

Buccal a.

Posterior masseteric a. Facial n. (CN VII)

Medial pterygoid n.

Retromandibular v. Buccal n. (CN V2)

Inferior alveolar a.

Medial pterygoid

Inferior alveolar n. (CN V3) Lingual n. (CN V3)

Masseter

Facial v. Inferior alveolar n. (CN V3)

Facial a.

Fig 5-18  Anterior view of the mandibular posterior region, showing the possible location of the lingual nerve relative to the retromolar area. a.—artery; aa.—arteries; n.—nerve; v.—vein.

142

Lingual Nerve

a

b

c

d

Fig 5-19  The proper technique for exposing the lingual nerve on a human specimen. (a) The releasing incision to expose the posterior mandibular region is made at the midcrest immediately distal to the second molar, and it is brought 30 degrees toward the buccal as it extends distally. (b and c) The nerve is dissected. Special care must be taken so that the nerve is never pressed against bony structure. (d) Exposed intact lingual nerve.

143

Posterior Mandible

5

Inferior Alveolar Canal/Nerve The mandibular nerve is the third branch of the trigeminal nerve arising from the trigeminal ganglion (the other two are the maxillary and the ophthalmic nerves). Unlike the maxillary and the ophthalmic nerves (both entirely sensory), the mandibular nerve has both sensory and motor divisions.16 After passing through the foramen ovale and giving off a meningeal branch, the nerve divides in the infratemporal fossa into the sensory branches (auriculotemporal, lingual, inferior alveolar, and buccal nerves) and the motor branches that innervate the muscles of mastication (masseteric, deep temporal, and the pterygoid nerves) (Fig 5-20).

Auriculotemporal n. Deep temporal nn.

Nerve to the lateral pterygoid m.

Buccal n.

Lingual n. Masseteric n.

Inferior alveolar n.

Mylohyoid n. Mental n.

Fig 5-20  The main branches of the IAN. n.—nerve; nn.—nerves; m.—muscle.

144

Inferior Alveolar Canal/Nerve

The IAN carries motor fibers for the mylohyoid muscle and the anterior belly of the digastric muscle and sensory fibers that enter the canal through the mandibular foramen, giving inferior dental branches to the mandibular teeth (Fig 5-21) and exiting through the mental foramen as the mental nerve (see later discussion). Damaging the IAN will alter the sensation to areas supplied by it and by the mental nerve.

Lateral pterygoid muscle

Pterygoid nerves

Deep temporal nerve

Meningeal branch

Auriculotemporal nerve Lingual nerve Inferior alveolar nerve Masseteric nerve Medial pterygoid muscle Masseter muscle Buccal nerve Buccinator muscle Mental foramen

Inferior dental branches

Fig 5-21  The dental branches of the IAN.

145

Posterior Mandible

5 Surgical importance in oral implantology It is imperative that a CT scan above the IAN is obtained before implant placement. The IAN enters the body of the mandible on the lingual side of the ramus and exits on the buccal at the mental foramen, and in most mandibles, the IAN is located in the lower half or close to the inferior border of the mandible17,18; however, a review of the literature19 dealing with the intraosseous course of the IAN revealed that the buccolingual and superior‐ inferior positions of the IAN are not consistent among mandibles. Moreover, a bony canal was not always observed between the mandibular and mental foramina; therefore, the feeling of denser bone while drilling does not necessarily equate with getting closer to the IAN, because the canal frequently lacks definite walls, especially near the mental foramen. Therefore, it is imperative to obtain a CT scan before any implant surgery planned above the IAN. It is also worth mentioning that bilateral symmetry of the canal (ie, the location of the canal in each half of the mandible) was common, while duplications of the canal were rare.19 Nutrient canals and other branches of the mandibular nerve have been observed within the mandible. These may have been confused with the IAN or may contribute to the plexus of nerves. Nerve injury can occur during local anesthesia (needle penetration), incision (by scalpel), flap reflection (by stretching), osteotomy preparation (by drills), and implant insertion (by compression). Dental specialists and general practitioners who place implants must discuss the possibility of nerve injury with their patients and include this possibility in the consent forms. Detailed knowledge of the related anatomy, careful planning using CT scans and diagnostic wax‐ups, the use of all available tools to perform the surgery accurately (eg, drill stoppers, computer‐generated surgical guides), and careful manipulation of the soft tissues can help to minimize the incidence of nerve injury.

Preventing injury to the IAN The following guidelines should be followed to eliminate the possibility of injury to the IAN: •  The implant surgeon should obtain a CT scan and determine the exact distance between the superior border of the inferior alveolar canal and the crestal bone. •  A safety margin of 2 mm or more should be maintained between the apical end of the implant and the superior aspect of the inferior alveolar canal.20 •  Whenever possible, drill stoppers should be used to prevent overpenetration of the drill. •  Computer-generated surgical guides (eg, Surgiguide, SimPlant) can make the surgical procedure safer and more accurate. •  The drills for most implant systems are approximately 0.5 to 1.0 mm longer than the implant being placed. The implant surgeon must allow for this additional length when drilling near vital anatomical structures.

146

Submandibular Fossa Posterior region of the mandible In the posterior region of the mandible, the submandibular fossa is located under the mylohyoid muscle in the area of the second and third molars (see Fig 5-1). These fossae should be considered and carefully examined prior to implant treatment, because they are severely pronounced in about one-third of patients, forming concavities that can be easily perforated during drilling.21,22 The anatomy of the lingual aspect of the mandible cannot be observed on panoramic radiographs23 (Fig 5-22), nor can it be visualized because the mylohyoid muscle is located above it. Palpation can be helpful for evaluation of the lingual aspect anatomy; however, a CT scan is the best modality to reveal the shape of the mandible on its lingual aspect. It is crucial that the lingual plate of the posterior mandible is not perforated, because the floor of the mouth is a highly vascularized region. Perforation of the lingual cortical plate of the posterior mandible in the region of the submandibular fossa by instrumentation (eg, a drill) may cause an arterial trauma, resulting in a hemorrhage that may commence immediately or with some delay after the vascular insult. The progressively expanding lingual, sublingual, submandibular, and submental hematomas have a tendency to displace the tongue and the floor of the mouth, thereby obstructing the airway (see also chapter 8). This is a rare but potentially fatal complication of implant surgery. Detailed knowledge of the regional arterial anatomy is therefore imperative for the implant surgeon to avoid this type of complication (see chapter 8).

147

Posterior Mandible

5

Buccinator m. Lingual nerve Vena comitans of hypoglossal nerve (to lingual vein)

A

Hyoglossus muscle

Hypoglossal nerve (XII) Genioglossus muscle

Nerve to mylohyoid

Facial artery

a

Submandibular salivary gland Mylohyoid m.

Lingual artery

Buccinator m. Lingual nerve Vena comitans of hypoglossal nerve (to lingual vein)

B A

Hypoglossus muscle

Hypoglossal nerve (XII) Genioglossus muscle

Nerve to mylohyoid

Facial artery

b

Submandibular salivary gland Mylohyoid m.

Lingual artery

Fig 5-22  Anterior views of the frontal section behind the first molar. The available distance shown on the panoramic radiograph might differ significantly from what is actually available for implant placement. m.—muscle. (a) Because of the lack of submandibular fossa, the available distance shown on the panoramic radiograph (A) matches the actual vertical distance available. (b) The available distance shown on the panoramic radiograph (A) is greater than the actual vertical distance available (B). Distance B is shorter because of a pronounced submandibular fossa; thus, going ahead with the surgery without a CT scan might lead to perforation of the lingual plate and possible significant hematoma, which could be life-threatening.

148

Submandibular Fossa Figures 5-23 and 5-24, respectively, show the lingual aspect and cross section of the submandibular fossa in the four mandible specimens shown in Figs 5-6 and 5-7. Figure 5-25 shows the exact distances available above the IAN, keeping a 2-mm safety margin from the submandibular fossa, in four mandibles with different levels of bone resorption.

a

b

c

d

Fig 5-23  The submandibular fossa as seen from the lingual side of the posterior mandible in four specimens with different levels of bone resorption. (a) Mandible with minimal bone resorption (see Figs 5-6a and 5-7a). (b) Mandible with mild bone resorption (see Figs 5-6b and 5-7b). (c) Mandible with moderate to advanced bone resorption (see Figs 5-6c and 5-7c). (d) Mandible with severe bone resorption (see Figs 5-6d and 5-7d).

149

Posterior Mandible

5

a

b

c d

Fig 5-24  The inferior alveolar canal and the submandibular fossa as seen in cross sections of the distal area of four mandible specimens. (a) Mandible with minimal bone resorption (see Figs 5-6a and 5-7a). (b) Mandible with mild bone resorption (see Figs 5-6b and 5-7b). (c) Mandible with moderate to advanced bone resorption (see Figs 5-6c and 5-7c). (d) Mandible with severe bone resorption (see Figs 5-6d and 5-7d).

150

Submandibular Fossa

a

b

c

d

Fig 5-25  The exact distances available above the IAN, with a safety margin of 2 mm from the submandibular fossa. (a) Mandible with minimal bone resorption. (b) Mandible with mild bone resorption. (c) Mandible with moderate to advanced bone resorption. (d) Mandible with severe bone resorption in which there is less than 1 mm of bone above the inferior IAN, so implant placement is not possible.

151

Posterior Mandible

5

Inadequate Bony Structure in the Posterior Mandible Resorption pattern and treatment planning The author developed a classification for natural resorption patterns of the alveolar bone (Fig 5-26). Current classifications state that, after tooth loss, the alveolar bone gradually loses width until loss is severe, and then height loss begins; the author rather argues that after the initial width loss, the resorption pattern takes on one of two forms: (1) severe width loss along the entire alveolar bone or (2) severe width loss only in the crestal half of the alveolar bone with a good amount of alveolar bone width remaining in the apical half. It is important that implant surgeons are aware of these two patterns and can distinguish between them on a CT scan during the CT evaluation and treatment-planning stage, because the resorption pattern will dictate the bone grafting procedures required to augment the ridge.

Mandibular Class IIIA: Severe width loss at the crestal half with minimal height loss

Mandibular Class I: Minimal width loss

Maxillary Class II: Moderate width loss

Mandibular Class IV: Severe height and width loss

Mandibular Class IIIB: Severe width loss affecting the entire alveolar ridge with minimal height loss

Fig 5-26  Al-Faraje classification of bone loss resorption patterns in the posterior mandible.

152

Clinical Management of Mandibular Alveolar Bone Deficiency Before treatment, the bone loss pattern must be identified on the CT scan. For Class I bone resorption, implants of regular or even wide platform diameter may be placed, because the bone loss is minimal in both width and height (recent tooth loss). For Class II bone resorption, implants can still be placed without any simultaneous bone grafting procedures; however, the operator should select a narrow platform–diameter implant to ensure adequate thickness of bone on the buccal and lingual sides of the implants. (It is vital for the long­-term success of an implant to have 1.0 to 1.5 mm of bone thickness on all sides.) For Class IIIA bone resorption, the operator should perform minimal alveoloplasty, needed only if the crestal ridge is too thin, and then ridge augmentation by pedicled sandwich plasty before the delayed placement of implants (see Figs 5-27 to 5-30). He or she might also consider implant placement with simultaneous guided bone regeneration (if the available ridge can accommodate implant placement in conjunction with bone grafting procedures) or veneer block grafting with delayed implant placement (see Figs 5-31 and 5-32). The selection of one over the other of these three techniques depends on the severity of the Class IIIA resorption, the location (anterior versus posterior zone), and the experience level of the operator. Detailed description of these procedures is beyond the scope of this book, but a brief overview of each of these techniques is provided in the following sections so that the reader can become familiar with the options available for alveolar ridge augmentation in areas of compromised anatomy. For Class IIIB bone resorption, the splitting technique is not possible because of the extensive loss in alveolar ridge width, and the block grafting technique is challenging also because of minimal host bone thickness. The author therefore recommends guided bone regeneration using titanium mesh and recombinant human bone morphogenetic protein 2/ absorbable collagen sponge (rhBMP-2/ACS) grafting material. For Class IV bone resorption, five techniques are available for vertical ridge augmentation: (1) guided bone regeneration using a bone graft material and membrane, (2) nerve repositioning (see Figs 5-33 and 5-34), (3) block grafting, (4) distraction osteogenesis, and (5) grafting by interpositional osteotomy (see Fig 5-35). The selection of one over the other of these five techniques depends on the severity of the Class IV resorption, the location (anterior versus posterior zone), and the experience level of the operator.

153

Posterior Mandible

5 Bone augmentation procedures for Class IIIA mandibular alveolar ridge deficiency Alveolar ridge splitting using pedicled sandwich plasty Unlike in the maxilla, the bone in the mandible is dense, with a thick cortex. Therefore, the split-cortical technique for ridge augmentation is not recommended, because this technique will cause a fracture of the buccal plate (Fig 5-27). Instead, a modified procedure called the two-stage horizontal alveolar bone splitting using pedicled sandwich plasty technique is recommended.24,25

a

b

c

Fig 5-27  (a to c) The fracture that the mandible will incur if the splitting technique with expansion chisels used for the elastic maxillary bone is followed for the denser mandibular bone.

154

Clinical Management of Mandibular Alveolar Bone Deficiency The protocol is as follows: After full‐thickness flap elevation, four osteotomies are created using a piezotome cutting tip (Fig 5-28a). The ostoetomies should be deep enough to reach the cancellous bone layer and should be well connected. The flap is then sutured back (Fig 5-28b), after which a minimum period of 28 days must be observed before the second procedure (Fig 5-28c). Proceeding with implant placement during stage-one surgery is not recommended, because the full-thickness flap from the first surgery will disrupt the blood supply to the bone that is provided via the periosteum, which might lead to bone segment necrosis when the bone segment is mobilized during implant placement. After 28 days, a full‐thickness flap is opened again, but it is limited to the crestal ridge area only (Figs 5-28d and 5-29a) in order to avoid destroying the restored blood supply to the bone segment about to undergo vertical osteotomy. After initial pilot drill use (Figs 5-28e and 5-29b), the “split” is done via a combination of chisels and rotary osteotomes (Fig 5-29c), and the implants are placed (Fig 5-28f). The gap between implants is filled with allograft or xenograft material (eg, Bio‐Oss, Geistlich) (Fig 5-29d). Primary closure without tension concludes the stage-two surgery. The bone will consolidate, and the implants will be ready to be restored in 4 to 6 months (Fig 5-29e). Figure 5-30 shows a clinical case demonstrating this procedure.

a

b

c

d

e

f

Fig 5-28  Cross-sectional view of mandibular ridge augmentation surgery with the horizontal alveolar bone splitting using pedicled sandwich plasty technique. (a) A full-thickness flap is reflected, and four osteotomies are created with a piezotome cutting tip. (b) The flap is sutured back. (c) The bone is observed for 28 days. (d) The flap is reopened but limited to the crestal ridge area. (e) The pilot drill creates space for the implant. (f) The implant is placed after further enlargement of the osteotomy with chisels and rotary osteotomes.

155

Posterior Mandible

5

a

b

d

c

e

Fig 5-29  (a to e) Superior view of horizontal alveolar bone splitting using pedicled sandwich plasty technique. (a) In stage-one surgery, a full-thickness flap is elevated, four well-connected osteotomies drilled completely through the cortex layer are created, and the flap is sutured. A healing period of at least 28 days is observed for the purpose of reattaching the periosteum layer to the bony surface. (b) In stage-two surgery, a full-thickness flap limited to the crestal ridge area is elevated, and a pilot drill starts the osteotomies for the planned implants. (c) The bone is split with chisels and rotary osteotomes. (d) The implants are placed, and allograft or xenograft is placed to fill the gaps between implants. (e) The implants are ready for restoration after the bone has consolidated (4 to 6 months later).

156

Clinical Management of Mandibular Alveolar Bone Deficiency

a

b

c

d

e

f

g

h

Fig 5-30  (a) Preoperative CT scan. (b) Preoperative clinical evaluation. (c and d) A full-thickness flap is reflected to visualize the alveolar bone width, shape, and trajectory. (e) All four osteotomies are performed. (f) The incision is sutured. (g) Inflammation-free wound healing. (h) Stagetwo surgery starts with a full-thickness flap that is limited to the crestal ridge, especially on the buccal side.

157

Posterior Mandible

5

i

j

k

l

m

n

o

p

Fig 5-30 (cont)  (i) An expanding chisel is used to split the bone. (j) A rotary expanding tool (DIO Implant system) is used to create space for the implants. (k) The implants are placed. (l) The flap is sutured after the gaps between implants are filled with xenograft material (Bio-Oss). (m) Uneventful healing. (n to p) Healing abutments are installed 4 months after stage-two surgery.

158

Clinical Management of Mandibular Alveolar Bone Deficiency

q

r

s

t

u

v

Fig 5-30 (cont)  (q to t) Postoperative CT scans. (u) Cross-sectional image of the mesial implant. (v) Cross-sectional image of the distal implant.

159

Posterior Mandible

5 Block grafting The block grafting technique to augment the alveolar ridge width (Fig 5-31) is a reliable procedure. It is less challenging than using a particulate bone graft and a membrane alone, because there is less chance of collapse due to soft tissue pressure or pressure from removable provisional appliances. However, proper patient selection for this method is important, and primary closure must be achieved, among many other factors, for a successful outcome. Implant’s long axis The direction of occlusal load

Bone grafting mix Block fixation screws

Resorbable membrane

Resorbing bone due to overload (excessive stress) in this region Bleeding points

Block graft material

Buccal

Lingual

Buccal

Lingual

Membrane fixation screw

a

b

Area of new grafted bone

Buccal

c

160

Lingual

Fig 5-31 The surgical steps of ridge augmentation using the block grafting technique. (a) The improper inclination of an implant when it is placed in a compromised alveolar ridge. This angulation will lead to many biomechanics-related complications, including fracture of the restoration, retaining screw, abutment, or implant body; osseous destruction by unfavorable loading; and difficulties with oral hygiene because of the ridge lap pontic design. (b and c) The proper protocol is to delay the implant placement and graft the area to restore its dimensions so it can support an implant in optimum buccolingual angulation.

Clinical Management of Mandibular Alveolar Bone Deficiency The protocol is as follows: After full-thickness flap elevation, the buccal plate of the host site is prepared by decortication with an alveoloplasty bur (Figs 5-32a to 5-32d). Then the block is adjusted to fit as precisely as possible onto the host site and fixated with two screws (Fig 5-32e). The area around the block is augmented, if needed, with additional bone grafting material (allograft or Bio‐Oss particulate material can be used) (Fig 5-32f), and then the area is covered by a resorbable membrane (Bio‐Gide, Geistlich) (Fig 5-32g) and sutured without tension. A healing period of 4 months is observed before implant placement (Fig 5-32h).

161

Posterior Mandible

5

a

b

c

d

e

f

g

h

Fig 5-32  Clinical case demonstrating the use of an allograft block to augment the deficient alveolar ridge in the posterior mandible. (a to d) The host site is prepared by decorticating its buccal plate with an alveoloplasty bur. (e) The block is adjusted to fit as precisely as possible onto the host site and fixated. (f) The area around the block is augmented with additional allograft particulate material. (g) The area is covered by a resorbable membrane (Bio-Gide) and sutured without tension. (h) New bone formation in the grafted site after a healing period of 4 months, with an adequate ridge dimension for implant placement.

162

Clinical Management of Mandibular Alveolar Bone Deficiency Bone augmentation procedures for Class IV mandibular alveolar ridge deficiency IAN and mental nerve repositioning Jensen and Nock26 were the first to describe placement of dental implants in the posterior mandible in conjunction with IAN repositioning. They used a large round bur to create a channel in the lateral mandibular cortical plate distal to the mental foramen to permit IAN repositioning. Several modifications have been described since then.27–31 The protocol is as follows: After thorough CT scan evaluation to ensure that there will be adequate alveolar bone available for proper implant positioning and stability after the IAN repositioning, the surgery starts with a full‐thickness flap to access the buccal plate. Then the osteotomy for the lateral access is performed. The nerve is retracted with a blunt tool (Fig 5-33), the implants are placed, and then bone grafting material and a resorbable membrane are placed to cover the buccal aspect of the implants. A concern has been reported regarding the morbidity of IAN repositioning.32 Davis et al33 surveyed 22 practitioners performing IAN repositioning; 9 of 190 patients experienced a disconcerting level of burning dysesthesia. Friberg et al28 reported a 7‐month evaluation of 10 patients and found hypesthesia or paresthesia in 30% of them. Rosenquist30 noted that 6 of 100 patients had either diminished or complete lack of neurosensation at 18 months postoperatively. Jensen et al31 reported that 10% of the patients in their study had signs of neurosensory disturbance. Haers and Sailer34 reported light paresthesia in 76.5% of their patients at 12 months. Kan et al35 reported a 52.4% incidence of neurosensory disturbance 41.3 months after surgery. Although in the majority of the cases affected sensation appears to be transient,27,35 risks regarding neurosensory disturbance should be considered and explained to the patient during treatment planning. The procedure for mental nerve repositioning is similar to that for IAN repositioning (Fig 5-34); however, there must be no teeth anterior to the mental foramen, because the incisive nerve(s) must be excised with a sharp scalpel before repositioning the mental nerve and its anterior incisive branch(es) (see Fig 5-34i); otherwise, it is impossible to move it. Forcing movement of the mental nerve without first excising these incisive nerves will damage it. However, excising these nerves will permanently eliminate the sensation of the roots anterior to the mental foramen, hence why it is so important that no teeth are present there.

Mental nerve Mandible Gingiva

Fig 5-33  Mental nerve repositioning. The procedure starts by exposing the nerve and carefully removing the bone around it using a piezotome tip.

163

Posterior Mandible

5

a

b

c

d

e

f

g

h

i

j

Fig 5-34  The proper technique for performing IAN and mental nerve repositioning on a human specimen. (a and b) A full-thickness flap is elevated, and the periosteum is carefully incised to expose the mental nerve. (c to f) A piezotome tip is used to cut and remove a block of bone from around the mental foramen to access the mental nerve loop and the incisive nerves and to have room distal to the foramen for working with the IAN. (g and h) Anterior branching of the mental nerve. (i) The incisive nerve is cut, and all small nerve fibers are removed. (j) The area is cleaned and ready for mental nerve and IAN repositioning. If needed, the lateral bony window can be extended posteriorly.

164

Clinical Management of Mandibular Alveolar Bone Deficiency Interpositional osteotomy Vertical ridge augmentation using sandwich osteotomy with interpositional bone grafting is a predictable surgical procedure.36–42 The goal of the procedure is to cut a bone segment, reposition it higher than its original level, fix it with plates, and then fill the interpositional gap with a bone grafting material. The protocol is as follows: After proper CT scan evaluation to ensure a minimum height of 5 mm above the IAN (Fig 5-35a), the procedure starts with a vestibular incision 2 to 3 mm below the crestal ridge (Fig 5-35b). (It is important to maintain the periosteum on the superior aspect of the ridge as well as on the lingual side to maintain intact blood supply to the mobile bone segment; thus, no lingual mucosa should be elevated.) Vertical releasing incisions are then made as necessary, and a full‐thickness flap is elevated. Next, using a piezotome cutting tip, a horizontal osteotomy is made above the inferior alveolar canal, and two vertical cuts are made with minimal periosteum elevation (see Fig 5-35b). The lingual periosteum must not be injured, and thus a finger can be placed over the lingual mucosa to feel the piezotome cutting tip as it exits the bone. Once the segment is completely freed, a plate is secured onto it with screws, the segment is elevated and oriented to minimize bone irregularities on the lingual mucosa, more screws are used to fixate the other side of the plate onto the inferior mandibular intact bone, and the space is grafted using allograft bone material (Fig 5-35c). Primary closure without tension concludes the stage-one surgery (Fig 5-35d). After a healing period of 3 to 4 months, the plate is removed and the implants are placed in a routine manner (Fig 5-35e). Complications with this procedure include risk of sensory nerve damage, failure of the graft to consolidate, and failure to achieve the required vertical dimension.

165

Posterior Mandible

5

a

b

Membrane Membrane Bone graft

Metal fixation plate

c

d

e Fig 5-35  The surgical steps of the interpositional osteotomy for posterior mandibular ridge augmentation. (a) There must be at least 5 mm of bone above the IAN. (b) A full-thickness flap is elevated, and a piezotome cutting tip is used to make a horizontal osteotomy above the inferior alveolar canal and two vertical cuts to free the bone segment. (c) A plate is secured to the freed bone segment, which is then elevated and oriented to minimize irregularity. The segment is then fixated to the inferior intact mandibular bone with more screws, and the site is grafted with allograft bone material. (d) Primary closure. (e) After a healing period of 3 to 4 months, the plate is removed, and an implant is placed.

166

References 1. Leong DJ, Li J, Moreno I, Wang HL. Distance between external cortical bone and mandibular canal for harvesting ramus graft: A human cadaver study. J Periodontol 2010;81:239–243. 2. Hwang KG, Shim KS, Yang SM, Park CJ. Partial-thickness cortical bone graft from the mandibular ramus: A non-invasive harvesting technique. J Periodontol 2008;79:941–944. 3. Misch CM. Distance between external cortical bone and mandibular canal for harvesting ramus graft: A human cadaver study. J Periodontol 2010;81:1103–1104. 4. Aalam AA, Nowzari H. Mandibular cortical bone grafts part 1: Anatomy, healing process, and influencing factors. Compend Contin Educ Dent 2007;28:206–212. 5. Nowzari H, Aalam AA. Mandibular cortical bone graft part 2: Surgical technique, applications, and morbidity. Compend Contin Educ Dent 2007;28:274–280. 6. Clavero J, Lundgren S. Ramus or chin grafts for maxillary sinus inlay and local onlay augmentation: Comparison of donor site morbidity and complications. Clin Implant Dent Relat Res 2003;5:154–160. 7. Fehrenbach M, Herring S. Illustrated Anatomy of the Head and Neck. Philadelphia: W. B. Saunders, 1996:205–206. 8. Balaji T, Sharmila Saran R, Vaithianathan G, Aruna S. Variations in the posterior division branches of the mandibular nerve in human cadavers. Singapore Med J 2013;54:149–151. 9. Hall-Craggs ECB. Anatomy as a Basis for Clinical Medicine. Munich: Urban & Schwarzenberg, 1985:546–547. 10. Greenstein G, Cavallaro J, Romanos G, Tarnow D. Clinical recommendations for avoiding and managing surgical complications associated with implant dentistry: A review. J Periodontol 2008;79:1317–1329. 11. Meyer RA, Bagheri SC. Lingual nerve repair. J Oral Maxillofac Surg 2013;71:830. 12. Elfring TT, Boliek CA, Seikaly H, Harris J, Rieger JM. Sensory outcomes of the anterior tongue after lingual nerve repair in oropharyngeal cancer. J Oral Rehabil 2012;39:170–181. 13. Hillerup S, Hjørting-Hansen E, Reumert T. Repair of the lingual nerve after iatrogenic injury: A follow-up study of return of sensation and taste. J Oral Maxillofac Surg 1994;52:1028–1031. 14. Robinson PP, Smith KG. A study on the efficacy of late lingual nerve repair. Br J Oral Maxillofac Surg 1996;34:96–103. 15. Miloro M, Halkias LE, Slone HW, Chakeres DW. Assessment of the lingual nerve in the third molar region using magnetic resonance imaging. J Oral Maxillofac Surg 1997;55:134–137. 16. Guyton AC. Anatomy & Physiology. New York: CBS College Publishing, 1985:264–266. 17. Anderson LC, Kosinski TF, Mentag PJ. A review of the intraosseous course of the nerves of the mandible. J Oral Implantol 1991;17:394–403. 18. Kieser J, Kieser D, Hauman T. The course and distribution of the inferior alveolar nerve in the edentulous mandible. J Craniofac Surg 2005;16:6–9. 19. Kieser JA, Paulin M, Law B. Intrabony course of the inferior alveolar nerve in the edentulous mandible. Clin Anat 2004;17:107–111. 20. Worthington P. Injury to the inferior alveolar nerve during implant placement: A formula for protection of the patient and clinician. Int J Oral Maxillofac Implants 2004;19:731–734. 21. Parnia F, Fard EM, Mahboub F, Hafezeqoran A, Gavgani FE. Tomographic volume evaluation of submandibular fossa in patients requiring dental implants. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010;109:e32–e36. 22. Chan HL, Benavides E, Yeh CY, Fu JH, Rudek IE, Wang HL. Risk assessment of lingual plate perforation in posterior mandibular region: A virtual implant placement study using cone-beam computed tomography. J Periodontol 2011;82:129–135. 23. Thunthy KH, Yeadon WR, Nasr HF. An illustrative study of the role of tomograms for the placement of dental implants. J Oral Implantol 2003;29:91–95.

24. Ewers R, Fock N, Millesi-Schobel G, Enislidis G. Pedicled sandwich plasty: A variation on alveolar distraction for vertical augmentation of the atrophic mandible. Br J Oral Maxillofac Surg 2004;42:445–447. 25. Garcia AG, Somoza-Martin M, Martins D. Algipore sandwiches or alveolar distraction? Re: Ewers R, Fock N, Millesi-Schobel G, Enislidis G. Pedicled sandwich plasty: A variation on alveolar distraction for vertical augmentation of the atrophic mandible. Br J Oral Maxillofac Surg 2004;42:445–447. Br J Oral Maxillofac Surg 2005;43:438. 26. Jensen O, Nock D. Inferior alveolar nerve repositioning in conjunction with placement of osseointegrated implants. A case report. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1987;63:263–268. 27. Rosenquist B. Fixture placement posterior to the mental foramen with transposing of the inferior alveolar nerve. Int J Oral Maxillofac Implants 1991;7:45–50. 28. Friberg B, Ivanoff CJ, Lekholm U. Inferior alveolar nerve transposing in combination with Brånemark implant treatment. Int J Periodontics Restorative Dent 1992;12:440–449. 29. Smiler DG. Repositioning the inferior alveolar nerve for placement of endosseous implants: Technique note. Int J Oral Maxillofac Implants 1993;8:145–150. 30. Rosenquist B. Implant placement in combination with nerve transposing: Experience with the first 100 cases. Int J Oral Maxillofac Implants 1994;9:522–531. 31. Jensen J, Reiche-Fischel O, Sindet-Petersen S. Nerve transposing and implant placement in the atrophic posterior mandibular alveolar ridge. J Oral Maxillofac Surg 1994;52:662–668. 32. Krough PH, Worthington P, Davis WH, Keller EE. Does the risk of complication make transposing the inferior alveolar nerve in conjunction with implant placement a ‘‘last resort’’ surgical procedure? Int J Oral Maxillofac Implants 1994;9:249–254. 33. Davis H, Rydevik B, Lundborg G, Danielsen N, Hausamen JE, Neukam F. Mobilization of the inferior alveolar nerve to allow placement of osseointegratable fixtures. In: Worthington P, Brånemark P-I (eds). Advanced Osseointegration Surgery: Applications in the Maxillofacial Region. Chicago: Quintessence, 1992:129–144. 34. Haers PE, Sailer HF. Neurosensory function after lateralization of the inferior alveolar nerve and simultaneous insertion of implants. Oral Maxillofac Surg Clin North Am 1994;7:707–716. 35. Kan JYK, Lozada JL, Goodacre CJ, Davis WH, Hanisch O. Endosseous implant placement in conjunction with inferior alveolar nerve transposing: An evaluation of neurosensory disturbance. Int J Oral Maxillofac Implants 1997;12:463–471. 36. Block MS, Haggerty CJ. Interpositional osteotomy for posterior mandible ridge augmentation. J Oral Maxillofac Surg 2009;67(11 suppl):31–39. 37. Moloney F, Tideman H, Stoelinga PJ, de Koomen HA. Interpositional bone-grafting of the atrophic edentulous mandible. A review. Aust Dent J 1985;30:211–219. 38. Moon JW, Choi BJ, Lee WH, An KM, Sohn DS. Reconstruction of atrophic anterior mandible using piezoelectric sandwich osteotomy: A case report. Implant Dent 2009;18:195–202. 39. Sohn DS, Shin HI, Ahn MR, Lee JS. Piezoelectric vertical bone augmentation using the sandwich technique in an atrophic mandible and histomorphometric analysis of mineral allografts: A case report series. Int J Periodontics Restorative Dent 2010;30:383–391. 40. Choi BH, Lee SH, Huh JY, Han SG. Use of the sandwich osteotomy plus an interpositional allograft for vertical augmentation of the alveolar ridge. J Craniomaxillofac Surg 2004;32:51–54. 41. González-García A, Diniz-Freitas M, Somoza-Martín M, GarcíaGarcía A. Piezoelectric and conventional osteotomy in alveolar distraction osteogenesis in a series of 17 patients. Int J Oral Maxillofac Implants 2008;23:891–896. 42. Yeung R. Surgical management of the partially edentulous atrophic mandibular ridge using a modified sandwich osteotomy: A case report. Int J Oral Maxillofac Implants 2005;20:799–803.

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6 Anterior Mandible The anatomical landmarks that are relevant to surgical oral implantology in the anterior mandible are the mental foramen/nerve and its anterior loop, the mandibular incisive canal, and accessory lingual foramina of the mandible. This chapter also describes the anatomical manifestations of different bone resorption patterns in the anterior mandible and the proper treatment planning for each, as well as the anatomical considerations for harvesting a block graft from the chin.

Anterior Mandible

6

Mental Foramen/Nerve and Its Anterior Loop Mental nerve The mental nerve exits the body of the mandible through the mental foramen, which is located usually between the apices of the first and second mandibular premolars. It provides sensory supply to the chin, lower lip, labial mucosa near the mandibular anterior teeth, and the skin over the body of the mandible (Figs 6-1 and 6-2).

Buccal nerve Buccal block

Inferior alveolar nerve IAN block

Mental foramen

Mental nerve Mental block

Incisive nerve

Bilateral IAN block

Fig 6-1 Innervation of the mandible along with the recommended anesthesia technique per area.

Fig 6-2  Region of skin supplied by the mandibular nerve.

170

Mental Foramen/Nerve and Its Anterior Loop

The following factors must be considered to avoid injury to the mental foramen. Location The height of the mental foramen can be used as available bone height without surgical risk because the inferior alveolar nerve (IAN) always rises as it approaches the mental foramen (Fig 6-3). So even if the implant is placed close to the superior border of the mental foramen, it will still be located lingual to it (Figs 6-4 and 6-5).

B

A

Fig 6-3  Distance A is the available alveolar bony height for implant placement above the mental foramen as seen on a panoramic image. There is no need to leave a 2-mm safety distance above distance A because the implant is placed in the middle of the alveolar bone and not in the buccal plate; by using the entire distance A for implant placement, the implant will be still be at least 2 mm from the IAN. Distance B is the actual distance available above the nerve, and it is considerably greater than distance A (usually by 2 to 5 mm).

171

Anterior Mandible Mandible Anterior

6

b

a

d

c

Fig 6-4  Cross sections of four human mandible specimens (same as those in chapter 5) with different bone resorption patterns showing the position of the mental foramen relative to the IAN. In the middle of the alveolar bone, the nerve is considerably lower than the superior border of the foramen. (a) Mandible with minimal bone resorption. (b) Mandible with mild bone resorption. (c) Mandible with moderate to advanced bone resorption. (d) Severely resorbed mandible. On a panoramic radiograph of such a mandible, the mental foramen will be absent.

172

Mental Foramen/Nerve and Its Anterior Loop

a

b

c

d

Fig 6-5  Computed tomography (CT) scans showing the precise locations of the mental foramen in mandibles with different patterns of resorption. (a) Mandible with minimal bone resorption. (b) Mandible with mild bone resorption. (c) Mandible with moderate to advanced bone resorption. (d) Mandible with severe bone resorption in which placement of implants is not possible in the vicinity of the mental foramen area.

173

Anterior Mandible

6 Anterior loop The IAN usually courses anterior to the mental foramen, turning posteriorly and superiorly to exit the mental foramen.1 Because the nerve may be as much as 3 mm anterior to the mental foramen,2 if an implant is to be placed mesial and below the level of the foramen, the most posterior extent of the implant should be a minimum of 5 mm anterior to the mesial aspect of the foramen. To avoid drill penetration though the anterior loop, the pilot drill should penetrate the crestal bone 7 to 8 mm anterior to the most mesial aspect of the mental foramen (3 mm for the loop plus a 2-mm safety zone plus the radius of the implant) (Fig 6-6).

Pilot drill

5 mm + R

Fig 6-6  The three implants on the left side of the mandible are well above the mental foramen and its anterior loop, and thus they can be placed anywhere relative to these landmarks. On the right side of the mandible, however, the desired implant will invade the mental foramen level; therefore, to be at a safe distance from the anterior loop, the pilot drill (ie, the initial osteotomy) should be located 7 mm from the mesial border of the mental foramen. It is important to note that CT scans should not be trusted to identify the mental loop. The initial osteotomy should always be placed 7 mm anterior to the most mesial border of the mental foramen if the implant is to invade the level of the mental foramen apicocoronally.

174

Mental Foramen/Nerve and Its Anterior Loop Flap-releasing incisions in close proximity to the mental nerve Flap-releasing incisions mesial to the mental nerve should terminate just superior to the mucogingival junction to avoid possible injury to major branches of the mental nerve (Fig 6-7).

Fig 6-7  The location and extensiveness of the releasing incision mesial to the mental foramen.

175

Anterior Mandible

6 Resorption In a mandible with extensive resorption, the position of the mental foramen might be on the crest of the ridge (Fig 6-8). In such cases, care should be taken not to harm the mental nerve; this can be accomplished by placing the midcrestal incision slightly toward the lingual and by gently reflecting a full-thickness flap until the foramen is identified. In some situations, it is recommended not to open a flap at all and follow a flapless insertion protocol to avoid damaging the mental nerve or any of its branches by the flap reflection (Fig 6-9).

Mental foramen

Fig 6-8  The location of the mental foramina as depicted on a mandible exhibiting severe resorption.

176

Mental Foramen/Nerve and Its Anterior Loop

a

b

c

d

e

f

g

h

Fig 6-9   (a to h) Clinical case in which the mandible showed extensive resorption. Both the panoramic radiograph and the CT scan failed to identify the exact location of the mental foramina. A decision was made to place the implants using a flapless protocol. It was decided that 12 mm away from the midline was a safe area in which to drill, thus avoiding the risk of damaging the mental nerve by the scalpel. A periodontal probe (f) was used after each drill to verify that the osteotomy was completely within bone. Because the vertical cantilever on the future prosthesis would be extensive, the patient was treatment planned for a Locator overdenture (Zest Anchors). The Locator caps will allow the prosthesis to disengage its attachments before transferring too much stress onto the implants and creating a weak link in the prosthesis-implant interface.

177

Anterior Mandible

6

Mandibular Incisive Canal Typically, the IAN splits3 near the molars into the mental nerve (to supply the skin of the mental foraminal region, the lower lip, the mucous membrane, and the gingiva) and the incisive nerve (to supply the mandibular anterior teeth) (Fig 6-10). However, in some cases the incisive nerve presents as a true canal with large lumen (0.48 to 2.90 mm)4 that extends anteriorly and inferiorly from the mental foramen, located 8 to 10 mm from the inferior border of the mandible (Fig 6-11). The existence of the canal can be problematic; as an extension of the inferior mandibular nerve, it should be considered to contain the same neurovascular elements,5 and thus osteotomies should not be made though this canal.

Pterygoid nerves

Buccal nerve

Mandibular ramus (cut)

Medial pterygoid muscle Masseteric nerve Lingual nerve Masseter muscle Inferior alveolar nerve, artery, and vein Mental foramen

Anterior loop of the mental nerve

Mental nerve

Fig 6-10  The usual innervation of the mandibular anterior teeth.

178

Mandibular Incisive Canal

Inferior alveolar nerve, artery, and vein Mental foramen

Anterior loop of the mental nerve

Mental nerve

Mandibular incisive canal

Fig 6-11  When implants are planned in the anterior mandible, the operator should be aware of the possibility of the existence of a mandibular incisive canal. Although this canal is only 8 to 10 mm above the inferior border of the mandible, it may still lie in the pathway of the osteotomy in a severely resorbed mandible.

179

Anterior Mandible

6 However, the incisive canal cannot be detected clearly on conventional radiography; therefore, computed tomography (CT) scans are recommended for proper assessment. Figure 6-12 shows three-dimensional and panoramic CT images of an incisive canal.

a

b Fig 6-12  The incisive mandibular canal as depicted on a three-dimensional image (a) and on a CT panoramic image (b). A regular panoramic radiograph will not reveal the existence of this canal, hence the importance of obtaining a CT scan prior to every implant surgery.

180

Mandibular Incisive Canal It is important to note that in the resorbed mandible the position of the incisive canal, if present, is expected to be closer to the alveolar crest. No matter the resorption pattern, the incisive canal should always be taken into consideration when planning for implant placement in the intraforaminal region6 (Figs 6-13 and 6-14).

a

b

c

d

e

Fig 6-13  (a to n) Clinical case in which the patient sought treatment to replace failing mandibular anterior teeth. Upon CT scan evaluation, it was noted that the mandible had an incisive mandibular canal on the right side. Cross-sectional images of the right mental foramen (b), mandibular right canine (c), left mental foramen (d), and mandibular left canine (e) are shown. Note that the canal was not evident on the panoramic CT image (a) but can clearly be seen on the cross-sectional image of the mandibular right canine (c). The canine is about 12 mm mesial to the mental foramen, so this canal underneath the canine cannot be the anterior loop of the IAN. On the left side, the mental foramen is located between the first molar and the second premolar, and the cross-sectional image of the canine does not show an incisive mandibular canal. Therefore, the implant selected to replace the mandibular right canine was shorter than the implant selected to replace the mandibular left canine (11 mm versus 13 mm) to maintain a safe distance from the mandibular incisive canal.

181

Anterior Mandible

6

f

g

h

i

j

k

l

m

n

Fig 6-13 (cont)  After extraction and implant placement (f to i), bone graft material was placed (j), and the area was sutured (k). (l and m) Postoperative radiographs show the shorter implant on the right side. (n) Four months later, the case was successfully restored.

182

Mandibular The Maxillary Incisive Canal Sinus

a

b

c

d

e

f

Fig 6-14 (a to h) Clinical case in which the anterior incisors were replaced by two implants (DIO Implant system) in a mandible that did not exhibit an incisive mandibular canal; thus, both implants were 12 mm long.

g

h

183

Anterior Mandible

6

Accessory Lingual Foramina of the Mandible Anatomical structures of the anterior region of the floor of the mouth receive blood supply from both the sublingual artery (a branch of the lingual artery) and the submental artery (a branch of the facial artery) (Figs 6-15 and 6-16).

Dorsal lingual branches

Ascending pharyngeal artery

Incisor Deep lingual artery Genioglossus muscle (lower part along with the geniohyoid muscle are removed to visualize the mylohyoid muscle)

Suprahyoid branch

Incisive artery (a branch of the inferior alveolar artery)

External carotid artery

Accessory lingual foramina Mandible (midline cut)

Superior thyroid artery

Facial artery Lingual artery

Hyoglossus muscle

Sublingual artery

Submental artery

Mylohyoid muscle

Fig 6-15  Lateral view of the anatomy of the lingual artery.

184

Anterior belly of the digastric muscle

Accessory Lingual Foramina of the Mandible

Hyoglossus muscle Submandibular gland (extraoral lobe)

Stylohyoid muscle

Hyoid bone

Submandibular gland (intraoral lobe)

Lingual artery

Mylohyoid muscle

Submandibular duct

Geniohyoid muscle

Sublingual gland Genioglossus muscle

Oral mucosa Sublingual fold Sublingual papilla

Fig 6-16  Superior view of the anatomy of the lingual artery.

185

Anterior Mandible

6 Lingual artery The lingual artery is one of eight branches of the external carotid artery arising at the level of the hyoid bone. It gives blood supply to the body and the apex of the tongue through its terminating deep lingual artery and its dorsal lingual branches. The lingual artery gives rise to the sublingual artery at the anterior border of the hyoglossus muscle.

Sublingual artery With a mean diameter of 2 mm, the sublingual artery supplies the sublingual salivary glands; the mylohyoid, geniohyoid, and genioglossus muscles; the mucous membranes of the floor of the mouth; and the lingual gingiva. In addition, it splits off into several alveolar branches for complementary blood supply to the lingual anterior cortical plate of the mandible. These branches enter the cortical plate through various foramina called accessory lingual foramina and form canals reaching the center of the alveolar bone. Rosano et al7 studied 60 dry mandibles from adult human cadavers to evaluate the prevalence, size, location, and content of the foramina and bony canals located on the lingual side of the mandibular midline. Another 20 dry mandibles were injected with red latex and then dissected to view the vascular canal contents associated with these midline lingual foramina and canals. A total of 118 foramina were detected, and each mandible had at least one lingual foramen at the midline above the genial spines (mean height, 12.5 ± 2.1 mm [SD] from the inferior border of the mandible). In 19 of the 20 latex-injected mandibles, macroanatomical dissection showed a clear vascular branch entering the mandibular midline as a single vessel from a sublingual-sublingual anastomosis. Therefore, blood vessels in the floor of the mouth may be in close proximity to the lingual cortical plate of the mandibular midline, which means that bleeding can occur when the mandibular cortical plate is perforated even minimally. Krenkel et al8 described midline interspinal, superspinal, and subspinal lingual foramina containing small branches of the sublingual artery, according to their vertical orientation in relationship to the genial tubercles. In another set of studies by Liang et al,9,10 out of 50 dry mandibles studied, 49 (98%) had at least one midline lingual foramen. Microanatomical dissection of these specimens indicated a clear neurovascular bundle in both superior and inferior genial spinal foramina and canals. The content in the superior canal derived from the lingual artery and the lingual nerve, while that in the inferior canal originated in the submental (a branch of the facial artery) and/or sublingual artery and was innervated by a branch of the mylohyoid nerve. In conclusion, different kinds of lingual foramina have been identified according to their location. The superior and inferior genial spinal foramina have different neurovascular contents, determined by their anatomical location above or below the genial spines. Other studies have described the existence of accessory foramina on the lingual side of the mandible in the premolar region, near the inferior mandibular border,11 and also near the crest of the alveolar ridge between the lateral incisors and the canines.12

Role of the sublingual arteries The inferior alveolar arteries supply the symphysis of the mandible by the incisive arteries; however, an additional blood supply to the intercanine area is derived, as mentioned above, from the alveolar branches of the sublingual artery through the accessory lingual mandibular foramina. This complementary blood supply is especially important in edentulous mandibles, because arteriosclerotic changes of the inferior alveolar artery after tooth loss make the blood circulation in the mandible increasingly dependent on the external blood supply provided by the periosteum and the accessory lingual canals. This fact should be taken into consideration when performing extensive reflection of lingual mucoperiosteal flaps13,14 (Fig 6-17a). Disruption in the blood supply to the anterior mandible can cause a hematoma in the sublingual region; several of the arteries associated with accessory lingual mandibular foramina are of sufficient size to be implicated in severe hemorrhaging episodes during implant placement in this region15 (Fig 6-17b).

186

Accessory Lingual Foramina of the Mandible

a

b Fig 6-17  (a) A case in which an accessory lingual foramen was detected on the CT scan image. The accessory lingual foramen (arrow) was taken in consideration during the full-thickness flap reflection on the lingual side to prevent excessive bleeding into the surgical field. (b) Sublingual hemorrhaging caused by damage to the sublingual artery during implant placement in the anterior region. (Reprinted from Ten Bruggenkate et al16 with permission.)

187

Anterior Mandible

6 Facial artery The facial artery arises from the external carotid artery above the lingual artery. It passes deep to the posterior belly of the digastric muscle and the stylohyoid muscle and then grooves the surface of the submandibular gland, which it supplies, and curls around the mandible onto the face at the anterior border of the masseter muscle. Its branches include the ascending palatine, submandibular, submental, inferior labial, superior labial, and angular arteries.

Submental artery The submental artery branches off from the facial artery before crossing the mandibular border and courses interiorly along the inferior border of the mylohyoid muscle together with the mylohyoid nerve. It supplies the submandibular lymph nodes, the submandibular salivary gland, and the mylohyoid and digastric muscles. It is important to note that the sublingual and submental arteries anastomose17 through their mylohyoid branches (the sublingual artery runs on the superior aspect and the submental artery on the inferior aspect), and, thus, it is a challenge to know whether the source of bleeding in the floor of the mouth is the lingual of the facial artery. Endovascular angiography can help to define and isolate the bleeding source.18 Care must be taken to avoid hemorrhaging during surgeries in the anterior mandible. Therefore, several guidelines should be followed: •  The operator should obtain a CT scan and evaluate carefully the existence of accessory lingual foramina and their locations. •  Placement of implants at the midline is not recommended, especially for patients with advanced resorption, because the lingual accessory foramen will be close to the crestal bone in these patients. •  Flap reflection on the anterior lingual side must kept to the minimum to prevent disruption of the blood supply to the lingual plate and to minimize bleeding. Figures 6-18 to 6-20 show accessory lingual foramina/canals on human cadaver specimens and CT images.

188

Accessory Lingual Foramina The of Maxillary the Mandible Sinus

a

b

c

d Fig 6-18  Lingual view of the anterior mandible in four human mandible specimens (same as those in chapter 5) with different patterns of bone resorption. The arrows indicate accessory lingual foramina. (a) Mandible with minimal bone resorption. (b) Mandible with mild bone resorption. (c) Mandible with moderate to advanced bone resorption. (d) Mandible with severe bone resorption.

189

Anterior Mandible

6

a

b

c

d Fig 6-19  Inferior view of the anterior mandible in four human mandible specimens (same as those in chapter 5) with different patterns of bone resorption. The arrows indicate accessory lingual foramina. (a) Mandible with minimal bone resorption. (b) Mandible with mild bone resorption. (c) Mandible with moderate to advanced bone resorption. (d) Mandible with severe bone resorption. Note that the arrows in a, b, and c indicate the same foramina seen in Figs 6-18a to 6-18c, while the arrows in d indicate three accessory foramina not depicted in the lingual view of the same mandible (see Fig 6-18d).

190

Accessory Lingual Foramina of the Mandible

a

b

c

d

Fig 6-20  The existence of the accessory lingual foramen/canal is depicted in four mandibles with different patterns of bone resorption. All mandibles show two foramina and canals (arrows). In the mandibles with minimal (a) and moderate bone resorption (c), the superior accessory lingual canal is at a safe distance from the crestal ridge for implant midline placement. In the mandible with mild bone resorption (b), there is a risk of damaging the accessory lingual canal if alveoloplasty is to be performed to widen the crestal ridge. In the mandible with severe resorption (d), placement of an implant in the midline area is not possible because of the proximity of the superior canal to the crestal ridge.

191

Anterior Mandible

6

Harvesting a Block Graft from the Anterior Mandible When harvesting chin bone block(s) from the anterior mandible (Fig 6-21), the operator should be aware of the following anatomical landmarks: the mental foramen, the anterior loop of the IAN, the incisive mandibular canal, the accessory lingual foramina, bone density (block graft harvest should not be attempted in D1 bone), and the roots of the teeth adjacent to the block. With the help of CT scan data and the information presented in this chapter, avoidance of these landmarks should not be difficult.

a

5-mm minimum must be left between the superior border of the block and the apices of the roots

5-mm minimum from the mesial border of the mental foramen

3-mm minimum distance from the inferior border of the mandible to the inferior border of the chin block

5-mm minimum from the mesial border of the mental foramen

b 3–5 mm must be left between the crestal ridge and the superior border of the chin block

The midline area should be kept intact to eliminate any possibility of facial contour change postoperatively

3-mm minimum distance must be kept from the inferior border of the mandible to the inferior border of the chin block

Fig 6-21  Recommended location for bone block harvest from the chin area in a dentate mandible (a) and in an edentulous mandible (b).

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Inadequate Bony Structure in the Anterior Mandible Resorption pattern and treatment planning The author has developed a classification for natural resorption patterns of the alveolar bone (Fig 6-22). Current classifications state that after tooth loss, the alveolar bone gradually loses width until the loss is severe, and then height loss begins, but the author rather argues that after the initial width loss, the resorption pattern takes on one of two different formats: severe width loss along the entire alveolar bone or severe width loss only in the crestal half of the alveolar bone with a good amount of alveolar bone width remaining in the apical half. It is important to be aware of these two different patterns and be able to distinguish between them on a CT scan during the CT evaluation and treatment planning stage because the resorption pattern will dictate the bone grafting procedures required to augment the ridge.

Mandibular Class IIIA: Severe width loss at the crestal half with minimal height loss

Mandibular Class I: Minimal width loss

Mandibular Class IV: Severe height and width loss

Mandibular Class II: Moderate width loss Mandibular Class IIIB: Severe width loss affecting the entire alveolar ridge with minimal height loss

Fig 6-22  Al-Faraje classification of bone loss resorption pattern in the anterior mandible.

193

Anterior Mandible

6 Figure 6-23 shows four mandible specimens exhibiting four of the five resorption patterns within the Al-Faraje classification of bone resorption.

a

b

c

d Fig 6-23  Superior view of the anterior region of four human mandible specimens (same as those in chapter 5) with different patterns of bone resorption. (a) Mandible exhibiting a Class I bone resorption pattern (dentate mandible with no or minimal resorption). (b) Mandible exhibiting Class II bone resorption. (c) Mandible exhibiting Class IIIB bone resorption. (d) Mandible exhibiting Class IV bone resorption.

194

Inadequate Bony Structure in the The Anterior Maxillary Mandible Sinus Clinical management of alveolar bone deficiency of the anterior mandible •  Identification of the exact bone loss pattern on the CT scan. •  For Class I bone resorption (Al-Faraje classification), implants with regular or even wide platform diameters may be placed, because the bone loss is minimal in width and height (recent tooth loss or immediate placement after extraction). Dentate alveolar bone is considered Class I; in multiple extractions, alveoloplasty is almost always needed to level the crestal ridge and eliminate sharp bony edges between implants (Fig 6-24).

a

b

c

d

e

f

g

h

Fig 6-24  Clinical case in which alveoloplasty was required after multiple extractions. This procedure is almost always needed before implant placement with multiple or full-arch tooth extractions. After extraction and reflection of a full-thickness flap (a to d), an alveoloplasty bur (e) was used to level the crestal ridge (f). Two implants were then placed (g) to support a Locator overdenture, and the flap was sutured (h).

195

Anterior Mandible

6 •  For Class II bone resorption, implants can still be placed without any simultaneous bone grafting procedures; however, the operator should select a narrow platform–diameter implant to ensure adequate thickness of bone on the buccal and lingual side of the implant. If indicated, alveoloplasty can provide a wider crestal ridge and should be considered. •  For Class IIIA bone resorption, the alveolar ridge can be augmented using ridge augmentation via the pedicled sandwich plasty splitting technique (see chapter 5) before the placement of implants, via implant placement with simultaneous guided bone regeneration (GBR), or via block grafting with delayed implant placement.19,20 As an alternative to these three procedures, narrow-diameter implants or mini-implants can be placed (Fig 6-25).

a

b

c

Fig 6-25  Placement of narrow-platform implants (DIO Implant system) in an alveolar bone with compromised width. After clinical and CT scan evaluation (a to c), the osteotomies were created using one drill and a flapless technique (d and e).

196

Inadequate Bony Structure in the The Anterior Maxillary Mandible Sinus

d

e

f

g

h

i

Fig 6-25 (cont)  (f and g) Five narrow-platform implants (2.5-mm diameter) were placed as symmetrically and equally spaced as possible. Note that when placing narrow-platform/mini-implants, it is preferred to place three implants in the anterior area between the two mental foramina and one implant distal to the mental foramen on each side, if the alveolar bony height above the IAN will permit doing so, in order to distribute the occlusal forces onto all implants. (h) Postoperative CT panoramic image. (i) Cross section of the central implant. Note the safe distance left above the accessory lingual canal in the midline area.

197

Anterior Mandible

6 •  For Class IIIB bone resorption, the splitting technique is not possible and the block grafting technique is challenging because of minimal host bone thickness; therefore, the recommended procedure is GBR using titanium mesh and recombinant human bone morphogenetic protein 2 (rhBMP-2)/absorbable collagen sponge (ACS) grafting material (Fig 6-26). •  For Class IV bone resorption, three techniques are available for vertical ridge augmentation: block grafting, distraction osteogenesis, and interpositional grafting.

a

b

c

d

e

f

Fig 6-26  Clinical case demonstrating Class IIIB bone deficiency along with vertical bone loss (due to a previously failed implant) in the anterior mandible. As can be seen on the three-dimensional CT images (a to d) and clinically (e), the defect presented a challenge for augmentation via block grafting, distraction osteogenesis, or interpositional grafting because of the narrow alveolar ridge and vertical and horizontal bone loss. Therefore, a GBR technique using titanium mesh and rhBMP-2/ACS grafting material was selected. After full-thickness flap elevation, the hopeless mandibular left canine was extracted and replaced with an implant (f and g).

198

Inadequate Bony Structure in the The Anterior Maxillary Mandible Sinus

g

h

i

j

k

l

Fig 6-26 (cont)  The bone grafting material was prepared according to the manufacturer’s protocol (h), and the buccal plate in the area to be grafted was decorticated to create bleeding points and invite osseous blood into the area (i). The bone grafting material was then placed into the area, and the titanium mesh was fixed (j). The area was sutured after ensuring primary closure with no tension (k). (l) Stage-two surgery to remove the titanium mesh after a healing period of 9 months. New bone formation is evident.

199

Anterior Mandible

6

m

n

o

p

Fig 6-26 (cont)  (m and n) CT images taken immediately after the initial surgery, showing a bone density of 168 Hounsfield units (HU). (o and p) CT images taken just before the removal of the titanium mesh, showing a bone density of 1,112 HU.

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References 1. Greenstein G, Tarnow D. The mental foramen and nerve: Clinical and anatomical factors related to dental implant placement. A literature review. J Periodontol 2006;77:1933–1943. 2. Hupp JR, Ellis E, Tucker MR. Contemporary Oral and Maxillofacial Surgery, ed 3. St Louis: Mosby-Yearbook, 1998:378–379. 3. Wadu SG, Penhall B, Townsend GC. Morphological variability of the human inferior nerve. Clin Anat 1997;10:82–87. 4. Mardinger O, Chaushu G, Arensburg B, Taicher S, Kaffe I. Anatomic and radiologic course of the mandibular incisive canal. Surg Radiol Anat 2000;22:157–161. 5. Monsour PA, Dudhia R. Implant radiography and radiology. Aust Dent J 2008;53(1 suppl):S11–S25. 6. Romanos GE, Greenstein G. The incisive canal. Considerations during implant placement: Case report and literature review. Int J Oral Maxillofac Implants 2009;24:740–745. 7. Rosano G, Taschieri S, Gaudy JF, Testori T, Del Fabbro M. Anatomic assessment of the anterior mandible and relative hemorrhage risk in implant dentistry: A cadaveric study. Clin Oral Implants Res 2009;20:791–795. 8. Krenkel C, Holzner K, Poisel S. Hematoma of the mouth floor following oral surgery and its anatomical characteristics [in German]. Dtsch Z Mund Kiefer Gesichtschir 1985;9:448–451. 9. Liang X, Jacobs R, Lambrichts I. An assessment on spiral CT scan of the superior and inferior genial spinal foramina and canals. Surg Radiol Anat 2006;28:98–104. 10. Liang X, Jacobs R, Lambrichts I, Vandewalle G. Lingual foramina on the mandibular midline revisited: A macroanatomical study. Clin Anat 2007;20:246–251. 11. Shiller WR, Wiswell OB. Lingual foramina of the mandible. Anat Rec 1954;119:387–390.

12. McDonnell D, Reza Nouri M, Todd ME. The mandibular lingual foramen: A consistent arterial foramen in the middle of the mandible. J Anat 1994;184:363–369. 13. Bradley JC. The clinical significance of age changes in the vascular supply to the mandible. Int J Oral Surg 1981;10(suppl 1):71–76. 14. Castelli WA, Nasjleti CE, Diaz-Perez R. Interruption of the arterial inferior alveolar flow and its effects on mandibular collateral circulation and dental tissues. J Dent Res 1975;54:708–715. 15. Kalpidis CD, Setayesh RM. Hemorrhaging associated with endosseous implant placement in the anterior mandible: A review of the literature. J Periodontol 2004;75:631–645. 16. Ten Bruggenkate CM, Krenkeler G, Kraaijenhagen HA, Foitzik C, Oosterbeek HS. Hemorrhage of the floor of the mouth resulting from lingual perforation during implant placement: A clinical report. Int J Oral Maxillofacial Implants 1993;8:329–334. 17. Bavitz JB, Harn SD, Homze EJ. Arterial supply to the floor of the mouth and lingual gingiva. Oral Surg Oral Med Oral Pathol 1994;77:232–235. 18. Zimmerman RA, McLean G, Freiman D, Golestaneh Z, Perez M. The diagnosis and therapeutic role of angiography in lingual arterial bleeding. Radiology 1979;133:639–643. 19. Misch CM, Misch CE. The repair of localized severe ridge defects for implant placement using mandibular bone grafts. Implant Dent 1995;4:261–267. 20. Garg AK, Morales MJ, Navarro I, Duarte F. Autogenous mandibular bone grafts in the treatment of the resorbed maxillary anterior alveolar ridge: Rationale and approach. Implant Dent 1998;7:169–176.

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7 Bone Density and Adjacent Teeth In addition to the anatomical landmarks described in chapters 1 to 6, bone density and the position and angulation of roots adjacent to the planned implant sites are important to evaluate. These factors should also be considered anatomical landmarks.

Bone Density and Adjacent Teeth

7

Bone Density Bone density (as well as bone volume and drilling/insertion technique) is directly related to primary stability during implant placement. Primary stability is in turn directly related to osseointegration; thus, the importance of achieving high primary stability during implant insertion cannot be overstressed. An initial torque of about 20 Ncm is usually adequate for achieving osseointegration if all other healing factors are met, including an adequate healing period, a surgical technique with minimal trauma, the lack of micromovement during healing, a precise preparation (no gap between the implant and the walls of the osteotomy), and the absence of implant surface contamination by organic or inorganic materials. However, immediate loading requires an increased initial torque to withstand the micromovement and stress applied to the implant in the critical early stages after immediate placement of the provisional prosthesis.1–3 Most references refer to an optimum insertion torque of about 35 to 45 Ncm, among other conditions for immediate loading.1 However, even if immediate loading is not desired, the operator should try to achieve higher than 20 Ncm of initial torque, because this allows for a shorter healing period and increased chances of successful osseointegration. Therefore, bone density is a critical factor in achieving osseointegration and in the survival of an implant, because when it is high, it is easier to achieve high initial torque/stability.

Bone density types The bone quality classification introduced by Lekholm and Zarb in 1985 subdivides bone into four types4 (Fig 7-1): •  D1 bone: almost the entire jaw bone is composed of compact bone •  D2 bone: a thick layer of cortical bone surrounds dense trabecular bone •  D3 bone: a thin layer of cortical bone surrounds less dense trabecular bone •  D4 bone: a thin layer of cortical bone surrounds low‐density trabecular bone Without a computed tomography (CT) scan, it is not possible to know the type of bone density before surgery; thus, it is highly recommended to obtain a CT scan before surgery to evaluate the bone density in the areas of planned implants. Regular periapical or panoramic radiographs are not helpful because the cortical buccal plate obscures the trabecular density. Each axial image on a CT scan has 260,000 pixels, and each pixel has a CT number (measured in Hounsfield units [HU]) related to the density of the tissues within the pixel. The higher the CT number, the denser the tissue. D1 bone density type starts at around 1,200 HU and higher; D2 bone density type is usually in the range of 800 to 1,200 HU; D3 bone density type is usually in the range of 300 to 800 HU; and D4 bone density type is usually at or below 300 HU. Therefore, measuring the bone density is quick and simple with a CT scan.

204

Bone Density

a

c

b

d

Fig 7-1  Bone quality classification according to Lekholm and Zarb: (a) D1 bone, in which almost the entire jaw bone is composed of compact bone; (b) D2 bone, in which a thick layer of cortical bone surrounds dense trabecular bone; (c) D3 bone, in which a thin layer of cortical bone surrounds less dense trabecular bone; and (d) D4 bone, in which a thin layer of cortical bone surrounds low-density trabecular bone. D1 density is usually in the anterior mandible, D2 density in the posterior mandible, D3 density in the anterior maxilla, and D4 density in the posterior maxilla; however, the operator must obtain a computed tomography scan and actually measure the bone density before planning the number of implants to be placed, the length of the healing period, and other factors based on bone density.

205

Bone Density and Adjacent Teeth

7 Achieving optimum initial stability in various bone density types It is important to follow the proper technique during implant insertion to achieve the optimum initial stability of 35 to 45 Ncm of torque. In denser bone, high initial stability is easy to achieve; however, the implant insertion should be accomplished without compressing the bone beyond its physiologic tolerance, because this may result in ischemia with subsequent necrosis. The crestal region (usually dense cortex) of an implant is the most susceptible to bone necrosis because of its minimal blood supply. Clinically, bone necrosis due to overcompression during insertion will appear within the first month after implant placement (Fig 7-2). Histology of the area of a failed implant due to necrotic compression reveals nonviable bony sequestra with bacterial colonization and subacutely inflamed granulation tissue.5 Special drills such as tapping drills/threadformers are necessary in these types of bone density. When using tapping drills, it is important to form the threads in the osteotomy site in small incremental fashion. If the operator is not careful, he or she can place a loose implant in high‐density bone by performing too many in‐and‐out motions during drilling or by overtapping. On the other hand, if the bone density is low, then placement of an implant with low torque into the bone is a possibility and can be a factor for implant failure. Loose implants are subject to movement during the healing period, which interferes with osseointegration. Implants can become loose during the surgical insertion if: •  The operator overdrilled/overprepared the osteotomy site (ie, too many in-and-out motions during drilling) •  Dense bone drills or tapping drills (threadformers) were used in soft bone •  An elliptical/imprecise osteotomy was created

206

Bone Density

a

b

c

d

Fig 7-2  Bone necrosis caused by overcompression during insertion of an implant after tooth removal (a and b). Symptoms include bone resorption around the overcompressed area, radiolucency on the radiograph (c), and complaint from the patient of continuous discomfort. The solution is to remove the implant and the affected tissues and graft the area (d) for delayed new implant placement.

207

Bone Density and Adjacent Teeth

7 Prevention includes: •  Drilling short of the last drill or two. •  Not using the threadformer/tapping drill. The implant osteotomy should be made conservatively. In D1 bone density, for example, all drills and the threadformer should be used; however, in D2 bone, the threadformer is not needed. In D3 bone, the osteotomy should be a bit narrower than the implant’s diameter for high initial stability. In D4 bone, the osteotomy is created via the use of osteotomes to condense bone laterally rather than removing bone using the drills. •  Use of osteotomes to condense the bone laterally rather than removing bone from the osteotomy site6–10 (Fig 7-3).

Management A loose implant should be removed and: •  Replaced by a wider and/or a longer implant if the recipient site/available bone will allow the placement of a larger-diameter implant. •  The osteotomy site can be aborted and a new one started in another location (this is possible in some cases of fully edentulous arches or in edentulous areas with long span). •  The placement procedure can be aborted and the osteotomy site grafted. Implant placement can be attempted in the same location 3 to 4 months later.

208

The Maxillary Bone Density Sinus

a

b

c

d

e

f

g

h

Fig 7-3  Placement of four implants in poor-quality D4 maxillary bone (HU value around 100 all around the maxilla). After clinical and CT scan evaluation (a and b), a full-thickness flap is retracted (c), and the pilot drill is used to create the initial osteotomies. After a panoramic radiograph is taken with the parallel pins in place (d), osteotomes are used to condense the bone laterally while enlarging the osteotomes to the desired diameter (e). Four implants are then placed (f and g), followed by primary flap closure (h). The implants are left to heal for a period of 6 months.

209

Bone Density and Adjacent Teeth

7

Adjacent Teeth/Roots Incorrect positioning and/or angulation of an implant might result in striking an adjacent tooth, which may lead to the removal of the affected tooth. If the implant is too close to a tooth, it may damage it by impinging on its blood supply or by overheating the bone around it during the osteotomy, causing the tooth to become nonvital due to irreversible pulpal damage.11–13 In this case, the tooth will need endodontic therapy or an apicoectomy or may need to be extracted; the implant also may need to be removed.

Symptoms Patients with teeth damaged during implant placement complain about severe pain, swelling, and fever soon after the implant placement or even up to a month or more later. Once the tooth becomes nonvital, it will react slightly or strongly to percussion but will give no response to thermal and electric pulp testing. A radiograph, however, will reveal a radiolucency at the tip of the tooth within a short period after the damage via implant placement.

Prevention Avoiding damage to adjacent teeth is possible by following these guidelines: •  Careful space assessment of the edentulous area should be done before surgery via CT imaging. CT scans provide the implant surgeon with life‐size images without distortion, enabling very accurate measurements. It is recommended that there be at least 1 mm of bone between an implant and an adjacent tooth. •  It is always highly recommended to take a panoramic radiograph with the parallel pin in the osteotomy site immediately after the pilot drill, because at this point the osteotomy’s diameter is still small (2 mm or less), and adjusting the osteotomy’s angulation will not present any challenges. Figure 7-4 demonstrates a case with an inclined root of the maxillary right lateral incisor. This finding was discovered during the panoramic radiograph examination. The periapical radiograph with the parallel pins shows the proximity of the right-side pin to the root, and thus a shorter implant was selected for the right-side implant to avoid any damage to the right lateral incisor. •  If the space for the implant is too narrow, the implant surgeon should refer the patient to an orthodontist before implant insertion to move teeth or roots to make the space bigger. •  Computer‐generated surgical guides should be used to direct the osteotomies in proper directions when teeth are in close proximity to the planned implants.

Management During implant placement Redirecting the osteotomy after the pilot drill can easily be done by using a side-cutting drill, such as a Lindemann drill. If the osteotomy is enlarged well beyond the pilot drill and its direction is not satisfactory, then the course of action should be to abort the procedure. Bone grafting should be done in the osteotomy site, and implant placement should be attempted at a later time. After implant placement and pulpal damage Administration of systemic antibiotics along with endodontic therapy should be initiated immediately. If the root of the affected tooth is penetrated, the implant should be removed. Serious injury to adjacent teeth may be critical to the fate of the implant as well. Development of an abscess could potentially affect the bone involved in the osseointegration of an implant placed in close proximity to adjacent teeth.

210

Adjacent The Maxillary Teeth/Roots Sinus

a

b

c

d

e

f

g

h

Fig 7-4  A clinical case with an inclined root of the maxillary right lateral incisor. (a) Panoramic radiograph examination shows the inclined root. (b and c) A flap is elevated. (d) A periapical radiograph taken with the parallel pins in place shows the proximity of the right-side pin to the root. Thus, a shorter implant (DIO Implant system) was selected for the right-side implant to avoid any damage to the right lateral incisor. (e and f) The implants are placed. (g and h) Cover screws are placed for stage-two surgery, and the incision line is sutured.

211

Bone Density and Adjacent Teeth

7

Conclusion When planning implants in the maxilla, the operator should evaluate the patient’s CT scan for the following anatomical landmarks: •  Position of the incisive foramen/canal relative to the anterior alveolar crest and central incisors •  Vault shape of the palate (to get an idea about the location of the greater palatine artery and nerve) •  Undercuts (sublabial and subbuccal) •  Topography of the alveolar ridge/bone (including crestal morphology) •  Curvature of the teeth adjacent to the planned osteotomy site(s) •  Possible root remnants at the intended implant sites •  Bone density of the alveolar bone in general and at the planned implant site(s) in particular •  Any pathologies in the bone or the nerve canals •  Alveolar dimensions (in height and width) for single or multiple implant placement •  Distance available for implant placement under the sinus floor •  Distance available for implant placement under the nasal floor •  Presence of septa or soft tissue pathologies in the sinus When planning implants in the mandible, the operator should evaluate the patient’s CT scan for the following anatomical landmarks: •  Position of the IAN (distance from the alveolar crest, path, and diameter) •  Position of the mental foramen/nerve •  Existence and extensiveness of the intraosseous mental nerve loop (always assume that a 3-mm loop does exist even if not clearly seen on the CT imaging) •  Incisive mandibular canal (length and distance from the crestal ridge) •  Possible undercuts (sublabial, subbuccal, submandibular fossa, and subdigastric fossa) •  Topography of the alveolar ridge/bone (including crestal morphology) •  Accessory lingual foramina and their location/distance from the crestal ridge •  Curvature of the teeth adjacent to the planned osteotomy site(s) •  Bone density in general and at the planned implant site(s) in particular •  Any possible pathologies in the bone or the nerve canals •  Possible root remnants at the intended implant sites •  Alveolar dimensions (in height and width) for single or multiple implant placement Please note that soft tissue anatomical structures (eg, lingual nerve, biotype, shape of papillae) cannot be evaluated on the CT scan; however, they are important to the overall success of the surgical phase of the implant treatment.

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References 1. Szmukler‐Moncler S, Salama H, Reingewirtz Y, Dubruille JH. Timing of loading and effect of micromotion on bone‐dental implant interface: Review of experimental literature. J Biomed Mater Res 1998;43:192–203. 2. Brunski JB. In vivo bone response to biomechanical loading at the bone/dental‐implant interface. Adv Dent Res 1999;13:99–119. 3. Worle PS. Single tooth replacement in the esthetic zone with immediate provisionalization: 14 consecutive case reports. Pract Periodontics Aesthet Dent 1998;10:1107–1114. 4. Lekholm U, Zarb GA. Patient selection and preparation. In: Brånemark PI, Zarb G, Albrektsson T (eds). Tissue-Integrated Prostheses: Osseointegration in Clinical Dentistry. Chicago: Quintessence,1985:199–210. 5. Bashutski JD, D’Silva NJ, Wang HL. Implant compression necrosis: Current understanding and case report. J Periodontol 2009;80:700–704. 6. De Vico G, Bonino M, Spinelli D, Pozzi A, Barlattani A. Clinical indications, advantages and limits of the expansion‐condensing osteotomes technique for the creation of implant bed. Oral Implantol (Rome) 2009;2:27–36.

7. Santagata M, Guariniello L, D’Amato S, Tozzi U, Rauso R, Tartaro G. Augmentation of atrophic posterior maxilla by short implants and osteotome technique. Stomatologija 2012;14:85–88. 8. Toffler M. Treating the atrophic posterior maxilla by combining short implants with minimally invasive osteotome procedures. Pract Proced Aesthet Dent 2006;18:301–308. 9. Davarpanah M, Martinez H, Tecucianu JF, Hage G, Lazzara R. The modified osteotome technique. Int J Periodontics Restorative Dent 2001;21:599–607. 10. Toffler M. Site development in the posterior maxilla using osteocompression and apical alveolar displacement. Compend Contin Educ Dent 2001;22:775–780,782,784. 11. Sussman HI. Tooth devitalization via implant placement: A case report. Periodontal Clin Investig 1998;20:22–24. 12. Kim SG. Implant-related damage to an adjacent tooth: A case report. Implant Dent 2000;9:278–280. 13. Margelos JT, Verdelis KG. Irreversible pulpal damage of teeth adjacent to recently placed osseointegrated implants. J Endod 1995;21:479–482.

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8 Anatomy for Surgical Emergencies

This chapter covers the etiology and subsequent manifestation of a surgeryrelated hemorrhage in the floor of the mouth. It also outlines the steps that can be taken to avoid such a hemorrhage as well as the protocol to manage it should one occur.

Anatomy for Surgical Emergencies

8

Intrasurgical Bleeding Avoiding excessive bleeding starts with a thorough review of the patient’s health history. The following questions are only examples of what must be included in the health history: •  Have there been any bleeding problems in the past? •  Is there a history of a bleeding problem in the family? •  Does the patient have hypertension or a nonalcoholic liver disease? •  Is the patient taking any medication that could interfere with normal coagulation? (eg, aspirin, anticoagulants, broad-spectrum antibiotics, alcohol, anticancer drugs) If the answer to any of the above questions is yes, then the patient should stop taking certain medications 1 to 2 days before surgery, or the patient’s physician should be consulted and/or a prothrombin test requested. During the surgery, the following techniques will help in minimizing the bleeding: •  The crestal incision should be made midcrestal because of the small size of arteries at the crest. •  Releasing incisions should be limited to the mucogingival fold area. •  The flap should be a full-thickness flap, because the bleeding comes mainly from the periosteum layer. •  The incision should be large enough so that the corners of the flap are not torn upon flap reflection, which would cause more bleeding (Fig 8-1).

216

Intrasurgical The Maxillary Bleeding Sinus

a

b

c

d

Fig 8-1  Torn envelope incision resulting from an inadequately sized envelope flap. (a) An envelope flap is reflected to extract a primary molar to be replaced by an implant. (b and c) The envelope flap was inadequate, leading to tears in the mesial corner of the flap. (d) The torn section is sutured for bleeding control.

217

Anatomy for Surgical Emergencies

8 Bleeding sources Bleeding in the oral cavity can have three different sources: soft tissue, bone, and main blood vessels. Soft tissue bleeding Bleeding from the soft tissue (the flap) most likely will not be life-threatening; nonetheless, it should be avoided. In most cases, direct pressure over the soft tissue bleeding area for 5 minutes results in complete control (Fig 8-2). If the small bleeder can be identified, then it can be cauterized with an electrosurgical tip, or it can be clamped with a hemostat and tied off with a suture. Figure 8-3 describes a technique for tying off a small bleeder that cannot be identified (buried bleeder).

Fig 8-2  For most small-size soft tissue bleeding during oral surgical procedures, direct pressure over the bleeding area for 5 minutes results in complete bleeding control.

218

Intrasurgical Bleeding

a

b

Fig 8-3  (a and b) The recommended technique for controlling a small buried bleeder. Using a tapered needle, the suture is passed blindly beneath the vessel. The first pass should be approximately 6 mm from the vessel and aimed to exit about 2 mm from the vessel. A second pass is then made, starting approximately 2 mm from the vessel. This second pass should be aimed to exit about 6 mm from the vessel. Tension is then applied to the free ends to put pressure on the source of bleeding.

219

Anatomy for Surgical Emergencies

8 Bony bleeding Abnormal bony bleeding in the oral cavity can occur during extraction (from extraction sockets), during flap reflection (from nutrient canals at the bony surface), and during implant placement (from the inferior alveolar artery). Controlling the excessive bleeding from a socket can be facilitated by the use of materials such as Gelfoam (absorbable gelatin, Pfizer), Surgicel (oxidized regenerated cellulose, Ethicon), topical thrombin (bovine source), Avitene (microfibrillar collagen, Davol), and OraPlug (highly cross-linked collagen, Salvin). Controlling the excessive bleeding from a small artery on the bony surface can be facilitated by the use of bone wax or by crushing the adjacent bone into the bleeding orifice with an instrument such as an amalgam burnisher or the tip of the periosteal elevator. Also, the tip of an electrode would work effectively in these cases. When bleeding occurs from the inferior alveolar artery, placement of an implant is usually adequate; if no implant is planned, then the following technique can be followed: Place iodoform gauze into the socket and then apply pressure over it with a gauze pad. When bleeding is controlled, suture the soft tissue over the iodoform gauze, thereby applying pressure to it with the flaps. Instruct the patient to continue to use gauze with biting pressure over the socket. Remove the iodoform gauze 5 to 7 days later. Main blood vessel bleeding As mentioned in chapter 5, extra caution needs to be exercised when placing implants in the mandible because the floor of the mouth is a highly vascularized region. Perforation of the lingual cortical plate by instrumentation or a drill may cause an arterial trauma, resulting in a hemorrhage that may commence immediately or with some delay after the vascular insult. The progressively expanding lingual, sublingual, submandibular, and submental hematomas have the tendency of displacing the tongue and the floor of the mouth to obstruct the airway (Fig 8-4). This possibility is a rare but potentially fatal complication of implant surgery. To avoid this possibility, detailed knowledge of the regional arterial anatomy is imperative for the implant surgeon.

220

Intrasurgical Bleeding

Nasopharynx

Airway

Foodway Oropharynx

Laryngopharynx

a

Soft palate

Epiglottic cartilage Esophagus

Oral floor

Hyoid bone Thyroid cartilage Cricoid cartilage

b Fig 8-4  (a) Airways through the oral and nasal cavities. (b) Displaced tongue due to massive hemorrhage in the floor of the mouth, leading to airway obstruction.

221

Anatomy for Surgical Emergencies

8

Hemorrhage of the Floor of the Mouth Etiology As mentioned above, arterial injury of the floor of the mouth is usually induced by perforation of the lingual plate with rotary instruments1; however, severe bleeding during flap elevation of the lingual periosteum, during subsequent flap manipulation, and during surgical manipulation into the deep muscle layer have been described in the literature. The onset of the hemorrhage is usually noticed during the surgical intervention, but it has also been reported to have been noticed shortly after the surgery or delayed for up to 4 to 6 hours after the surgical intervention.2,3

Symptoms Symptoms include swelling; elevation of the floor of the mouth; possible protrusion of the tongue; respiratory distress; formation of extensive sublingual, submandibular, or submental hematomas; inability to swallow; and profuse or pulsating intraoral bleeding.

Management Airway management Securing and maintaining an adequate airway should be given the highest priority. The implant surgeon should be prepared to deal with the possibility of airway obstruction. The clinical signs of airway obstruction include tachypnea, dyspnea, hoarseness, cyanosis, and drooling, all of which can be absent until the obstruction is severe. Persistent intraoral bleeding can cause a mechanical pressure to the pharyngeal lumen and consequent airway obstruction, which poses a serious threat. The airway can be secured by nasotracheal, orotracheal, or emergency tracheostomy or cricothyroidotomy (when the endotracheal intubation is impossible because of extensive hematoma). Manual tongue decompression and tactile intubation have been successful in one report during hemorrhagic swelling of the tongue.4 Bleeding management Many bleeding-control measures have been used and described in the literature, including the use of hemostatic agents, digital compression, and cauterization. Also, bleeding may eventually stop when the pressure of the extravasated blood exceeds the vascular pressure of the feeding bleeder; thus, hematoma drainage might have a reverse effect by lowering the pressure of the adjacent soft tissues and hence promoting further drainage. Hemorrhage self-resolution has been reported in few cases. When conservative measures are ineffective, intraoral or extraoral surgical evacuation and ligation of the bleeding artery are necessary.

Prevention of arterial injury to the floor of the mouth The following guidelines are important for preventing arterial injury to the floor of the mouth. •  The implant surgeon must obtain a detailed examination of the patient’s medical history. •  The implant surgeon must have a good knowledge of the fine regional arterial anatomy of the submandibular and neck regions (Figs 8-5 to 8-7). •  There is an element of risk associated with all clinical procedures; thus, even routine tasks must be carried out with utmost attention. The simplest implant procedure can trigger an extremely serious complication.5 •  The implant surgeon must select the proper diameter and length of the implant per the available alveolar ridge and pay attention to the appropriate angulation of the implant. •  The implant surgeon must strictly follow the appropriate surgical protocols.

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Hemorrhage of the Floor of the Mouth

•  Adequate training in surgical implant dentistry is essential for success. Implant training courses should include a thorough review of the regional anatomy and basic sciences as well as training in medical emergencies. •  The surgical implant room should be equipped with emergency equipment, including emergency airway tools such as a laryngeal mask airway or Guedel airway. •  The lingual side of the mandible, including the submandibular fossa and the accessory lingual foramina, must be thoroughly evaluated. •  Digital palpation of the lingual mandibular surface can help to detect any pronounced concavity in the anterior or posterior areas of the mandible; however, computed tomography (CT) scanning is highly recommended. •  Clinicians should be aware that there may be a latency period after arterial trauma and that hemorrhage can occur several hours later6; therefore, it is important to monitor patients for a sufficient period of time after implant surgery in the anterior mandible. •  Patients should be advised of the warning signs of a hematoma, and clinicians should be readily available to manage this complication should it occur.7 •  Implant therapy is an elective procedure; thus, areas with high potential risk of nerve or arterial injury should be avoided.

Marginal mandibular branch (VII)

Lingual nerve

Digastric muscle

Retromandibular vein

Facial vein

N. XI

Facial artery

N. X Submandibular duct

N. XIII Veins accompanying N. XII

Mylohyoid nerve

Submandibular ganglion

Mylohyoid muscle Pharynx

Lingual artery Ansa cervicalis (hypoglossi) n. Internal jugular vein Common carotid artery Thyroid gland Sternocleidomastoid muscle

Greater horn

Hyoid bone

Superior laryngeal nerve and artery

Superior thyroid artery Thyrohyoid muscle Omohyoid muscle

Sternohyoid muscle

Fig 8-5  Topography of the carotid triangle and the submandibular fossa after removal of the submandibular gland. N.—cranial nerve; n.—nerve.

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Anatomy for Surgical Emergencies

8

Styloid process N. VII Internal branch, superior laryngeal nerve

N. IX N. X

Superior laryngeal artery

N. XI N. XII

Digastric muscle External carotid artery

Superior thyroid artery

Internal jugular vein

External branch, superior laryngeal n.

Phrenic nerve

Cricothyroid muscle

Middle scalene muscle

Thyroid gland Anterior scalene muscle

Inferior laryngeal nerve Thyroid isthmus

Brachial plexus

Inferior thyroid artery

Thoracic duct

Trachea Clavicle Subclavian artery Sternum Subclavian vein

Rib 1

Left brachiocephalic vein Aortic arch

Recurrent laryngeal nerve

Fig 8-6  Lateral view of the neck, showing the thyroid gland, larynx, trachea, and arteries and nerves. N.—cranial nerve; n.—nerve.

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Hemorrhage of the Floor of the Mouth

Thyrohyoid muscle

Hyoid bone Internal carotid artery

External carotid artery

Vagus nerve

Sternohyoid muscle

Internal jugular vein Omohyoid muscle

Cricothyroid ligament

Thyroid cartilage

Trachea Cricoid cartilage Thyroid isthmus Anterior scalene muscle

Ascending cervical artery

Vagus nerve

Thyrocervical trunk

Thyroid gland

Vertebral artery

Brachial plexus Thoracic duct

Subclavian artery

Right lymphatic trunk Subclavian vein

Clavicle

Rib 1

Phrenic nerve Inferior thyroid venous plexus

Sternothyroid muscle Innominate artery

Superior vena cava

Manubrium sterni

Fig 8-7  Anterior view of the neck, showing the thyroid gland and the neck’s vessels and nerves.

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Anatomy for Surgical Emergencies

8 Protocol for management of hemorrhage of the floor of the mouth 1. At the first sign of swelling in the floor of the mouth, call 911. 2. Using both thumbs, press the tongue down to keep the airway open. 3. Calmly explain to the patient the nature of the complication. 4. Insert an emergency airway (ie, laryngeal mask airway or Guedel airway). 5. The tongue can be pulled out to press the lingual artery against the hyoid bone, thus reducing bleeding from the lingual artery and its branches (Fig 8-8). 6. If the injury was made to the facial artery, step #5 will not reduce the bleeding; in this situation, press the common carotid artery against the fourth cervical vertebrae (C4) to help reduce the bleeding (Fig 8-9). [Note that incisions in the floor of the mouth to relieve the hematoma should be avoided and that removal of the already placed implant would not be effective.] 7. If, despite all the steps above, a hematoma of large size develops along with signs of respiratory distress, insertion of a flexible nasal airway should be performed, or emergency tracheostomy or cricothyroidotomy might be necessary (see next section). 8. The patient should be transferred to a nearby hospital for monitoring. Once the bleeding is reduced, it can be stopped by surgical ties, electrocautery, or hemostasis after clot formation.

Facial a.

Internal carotid a.

Lingual a.

Sublingual a. Hyoid bone

Fig 8-8  The relationship between the lingual artery and the hyoid bone. a.—artery.

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Hemorrhage of the Floor of the Mouth

Maxillary Internal carotid artery artery Descending palatine artery

Atlas

C3

C4

N. XII

External carotid artery

Dens axis (odontoid process) Axis

N. IX

Ascending pharyngeal artery

Ascending palatine artery Facial artery

Lingual artery

Fig 8-9  Projections of the first four cervical vertebrae in the facial region. The first two cervical vertebrae are projected into the oral cavity when the mouth is opened. With the mouth closed, the body of the second vertebra corresponds to the level of the lower lip and the first vertebra to the upper lip. The common carotid artery (before splitting into the external and internal carotid arteries) corresponds to the level of the fourth vertebra. N.—cranial nerve.

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Anatomy for Surgical Emergencies

8

228

Cricothyrotomy Procedure (Fig 8-10) 1. Place the patient in a supine position, stabilize the neck region by placing a pillow or piece of cloth under the patient’s shoulders, hyperextend the neck, and then disinfect the neck region with povidone iodine/iodophor swab sticks, if available. 2. Stabilize the larynx with your nondominant hand by grasping the side of the thyroid cartilage with your thumb and middle finger, and palpate the depression over the cricothyroid membrane (just inferior to the laryngeal prominence and superior to the cricoid cartilage) using your index finger (Fig 8-11). 3. Use a no. 15 scalpel blade to make a 3-cm vertical incision through the skin and subcutaneous tissue overlaying the cricothyroid membrane. 4. Palpate the cricothyroid membrane through the membrane using your index finger. 5. Make a stabbing horizontal incision through the lower portion of the cricothyroid membrane (Fig 8-12). 6. Place the Trousseau dilator into the trachea, then spread its blades open to dilate the opening in a vertical direction. Do not insert the dilator too deep. 7.  Insert the airway into the trachea so it is oriented in a plane parallel to the Trousseau dilator (while maintaining control of the Trousseau dilator), then rotate both together 90 degrees while advancing the tube further and remove the Trousseau dilator. The airway should be inserted until the flange of the device rests against the patient’s neck. 8. Remove the obturator. 9. Inflate the cuff with air. 10. Secure the airway with tape. 11. Begin to ventilate the patient using a resuscitation bag or ventilation circuit.

Cricothyrotomy

a

Thyroid cartilage Cricoid cartilage Thyroid gland

b

Fig 8-10  (a) Proper patient positioning for a cricothyrotomy and stabilization of the larynx with the nondominant hand. The cricothyroid membrane is identified by palpating the indentation between the thyroid cartilage and cricoid cartilage. (b) Proper location and horizontal direction of the incision through the lower portion of the cricothyroid membrane. The cricothyroid membrane is opened with a scalpel. The opening may be enlarged by twisting the instrument and patency preserved by inserting rubber tubing.

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Anatomy for Surgical Emergencies

8

Epiglottis Lesser horn

Greater horn

Foramen for superior laryngeal artery and internal laryngeal nerve

Hyoid bone (body)

Thyrohyoid ligament

Superior horn

Laryngeal prominence

Thyroid cartilage

Median cricothyroid ligament

Cricotracheal ligament

Inferior horn

Cricoid cartilage

Tracheal cartilage

Fig 8-10  Anterior view of the thyroid, cricoid, and tracheal cartilages.

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Cricothyrotomy

Lingual tonsil Vallecula

Epiglottis Hyoid bone

Hyoepiglottic ligament

Thyrohyoid ligament

Vestibular fold

Ventricle Vocal fold Cricoid cartilage Median cricothyroid ligament

Cricoid cartilage

Tracheal cartilage

Esophagus

Fig 8-12  Lateral view of the midsagittal section of the larynx. Air enters through the laryngeal inlet formed by the epiglottis and aryepiglottic folds.

231

Anatomy for Surgical Emergencies

8

232

References 1. Del Castillo-Pardo de Vera JL, López-Arcas Calleja JM, BurgueñoGarcía M. Hematoma of the floor of the mouth and airway obstruction during mandibular dental implant placement: A case report. Oral Maxillofac Surg 2008;12:223–226. 2. Kalpidis CD, Setayesh RM. Hemorrhaging associated with endosseous implant placement in the anterior mandible: A review of the literature. J Periodontol 2004;75:631–645. 3. Dubois L, de Lange J, Baas E, Van Ingen J. Excessive bleeding in the floor of the mouth after endosseous implant placement: A report of two cases. Int J Oral Maxillofac Surg 2010;39:412– 415. 4. Piper SN, Maleck WH, Kumle B, Deschner E, Boldt J. Massive postoperative swelling of the tongue: Manual decompression and tactile intubation as a life-saving measure. Resuscitation 2000;43:217–220.

5. Felisati G, Saibene AM, Di Pasquale D, Borloni R. How the simplest dental implant procedure can trigger an extremely serious complication. BMJ Case Rep 2012 Nov 28. 6. Ten Bruggenkate CM, Krenkeler G, Kraaijenhagen HA, Foitzik C, Oosterbeek HS. Hemorrhage of the floor of the mouth resulting from lingual perforation during implant placement: A clinical report. Int J Oral Maxillofacial Implants 1993;8:329–334. 7. Ferneini E, Gady J, Lieblich SE. Floor of the mouth hematoma after posterior mandibular implants placement: A case report. J Oral Maxillofac Surg 2009;67:1552–1554.

Topographic Anatomy of the Maxilla and the Mandible

The illustrations in this chapter are meant to serve as guides for interpreting cone beam computed tomography axial images taken at the same levels and to help dental colleagues understand and correlate structures in the maxillary and mandibular regions.

9

Topographic Anatomy of the Maxilla and the Mandible

9

Condyle

Articular disc

Articular tubercle

Temporalis

Buccal fat pad (of Bichat)

Lateral pterygoid External acoustic meatus

Orbicularis oculi

External carotid a.

Zygomatic bone

Retromandibular v.

Zygomaticus minor

Parotid gland Digastric posterior belly

Masseter

Mandibular n. (CN V3)

Medial pterygoid

Facial v.

Ramus of mandible Platysma

Fig 9-1  Sagittal section through the right temporomandibular joint region. v.—vein; n.—nerve; a.—artery.

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Topographic Anatomy of the Maxilla and the Mandible

Temporal bone

Temporalis

Anterior auricularis Upper joint cavity

Optic n. (CN II) Internal carotid a.

Articular disc Lower joint cavity

Auditory tube

Head of mandible

Lateral pterygoid

Pteryoid plexus (deep temporal vv.)

Masseter

Parotid gland

Fig 9-2 Frontal section through the right temporomandibular joint region. n.—nerve; a.—artery; vv.— veins.

235

Topographic Anatomy of the Maxilla and the Mandible

9

Orbicularis oris

Buccinator

Levator anguli oris

Masseter

Facial a. and v.

Ramus of mandible

Medial pterygoid

Retromandibular v.

Inferior alveolar a., v., and n.

Digastric, posterior belly

Palatine tonsil

Internal carotid a.

Fig 9-3  Horizontal section through the oral cavity region at the level of the maxillary roots/cervical vertebra I (atlas). a.—artery; v.—vein; n.—nerve.

236

Topographic Anatomy of the Maxilla and the Mandible

Orbicularis oris Buccinator Zygomaticus major Mandible

Facial a. and v.

Inferior alveolar a., v., and n.

Masseter

Platysma

Medial pterygoid

Parotid gland

Submandibular gland

Hypoglossal n. Stylopharyngeus Retromandibular v. (CN XIII)

Internal Glossopharyngeal n. External (CN IX) carotid a. carotid a.

Internal jugular v.

Sternocleidomastoid

Fig 9-4  Horizontal section through the oral cavity region at the level of the mandibular roots/cervical vertebra II (axis). a.—artery; v.—vein; n.—nerve.

237

Topographic Anatomy of the Maxilla and the Mandible

9

Facial a. and v.

Sublingual gland

Mentalis Depressor anguli oris

Inferior alveolar n. (CN V3)

Geniohyoid Mandible

Masseter

Depressor labii inferioris

Medial pterygoid

Inferior alveolar a. and v.

Platysma

Mylohyoid Retromandibular v. Submandibular gland Facial n. (CN VIII)

Digastric, posterior belly

Parotid gland

External jugular v.

Sternocleidomastoid

Internal jugular v.

External carotid a.

Internal carotid a.

Glossopharyngeal n. (CN IX)

Vagus n. (CN X)

Fig 9-5  Horizontal section through the oral cavity region at the level of the mandibular roots/cervical vertebra III. a.—artery; v.—vein; n.—nerve.

238

10 Venipuncture This chapter serves as a reminder of the vascular anatomy of the upper limb for implant surgeons interested in obtaining venous blood for the purpose of extracting platelet-rich plasma.

Venipuncture

10

Anatomy of the Systemic Circulation Although the heart pumps all of its blood into a single artery, the aorta, it receives its returning blood from two separate systemic veins: the superior vena cava and the inferior vena cava. The venae cavae then carry the deoxygenated blood to the right side of the heart to be pumped to the lungs. The majority of veins carry deoxygenated (blue) blood, returning it to the heart from the various organs and tissues of the body. There are two exceptions: 1. The pulmonary veins in the chest carry oxygenated blood from the lungs to the left side of the heart (Fig 10-1). 2. The portal vein carries nutrient‐rich blood from the intestines to the liver.

HEAD and UPPER EXTREMITY

Aorta Pulmonary artery

LUNGS

Superior vena cava Pulmonary veins Left atrium Pulmonary valve

Aortic valve Mitral valve

Right atrium

Tricuspid valve

Left ventricle

Inferior vena cava Right ventricle

TRUNK and LOWER EXTREMITY

Fig 10-1 Heart circulation.

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Anatomy of the Systemic Circulation

The major tributaries of the superior vena cava are the following: •  Right and left brachiocephalic veins, each of which is formed by an internal jugular vein and a subclavian vein (Fig 10-2). •  The azygos vein, which enters the superior vena cava posteriorly and collects blood from intercostal, bronchial, esophageal, phrenic, and small segmental veins.

Superior petrosal sinus

Superficial temporal veins

Inferior petrosal sinus

Inferior sagittal sinus

Cavernous sinus

Superior ophthalmic vein

Great cerebral vein

Angular vein

Superior sagittal sinus Straight sinus

Confluence of the sinuses Transverse sinus Pterygoid plexus Sigmoid sinus

Vagus nerve

Facial vein

Retromandibular vein External jugular vein

Superior thyroid vein Internal jugular vein

Scalenus posterior

Anterior jugular vein

Scalenus medialis

Right lymphatic duct

Subclavian artery

Scalenus anterior

Subclavian vein Fig 10-2  Veins of the head and neck.

241

Venipuncture

10 The major tributaries of the inferior vena cava (Fig 10-3) are the following: •  Two hepatic veins (they drain blood from the two sides of the liver; most blood comes into the liver from the gastrointestinal tract through the portal venous system) •  Right and left renal veins •  Right gonadal vein (the left gonadal vein drains into the left renal vein) •  Right and left common iliac veins

Sinuses

Internal jugular Subclavian Brachiocephalic

Superior vena cava

Cephalic Pulmonary

Inferior vena cava

Coronary Brachial

Hepatic

Basilic

Portal

Splenic Renal

Superior mesenteric

Inferior mesenteric Internal iliac

Common iliac

External iliac

Femoral Great saphenous

Posterior tibial Anterior tibial

Fig 10-3  Major tributaries of the inferior vena cava.

242

Arteries and Veins of the Upper Limb Arteries of the upper limb Blood to the right upper limb leaves the aortic arch through the brachiocephalic (innominate) artery, which divides into the right common carotid and right subclavian arteries. The right subclavian artery delivers blood to the upper limb, and its left side is a direct branch of the aorta (Fig 10-4). From this point onward, the arteries of the two sides are symmetric. At the outer border of the first rib, the subclavian artery turns laterally to enter into the axilla through the axillary artery. The axillary artery leaves the axilla to enter the brachium as the brachial artery. One inch below the antecubital fossa, it bifurcates into the radial (lateral) and ulnar (medial) arteries, terminating in the palm as an arterial arch. The radial artery on the ventral surface of the wrist is quite superficial, and at this point the radial pulse and arterial blood for blood gas analysis may be obtained.

Arterial supply

Venous supply

Left ventricle

Venous return

Ascending aorta

Capillaries

Subclavian (brachiocephalic [innominate] on right)

Venules

Superficial and deep volar arches Axillary

Brachial

Ulnar

Radial

Superficial and deep volar arches Digital arteries Arterioles

Superficial veins Dorsal venous network

Cephalic

Basilic Median

Median cephalic

Median basilic

Deep veins

Ulnar

Radial

Brachial

Axillary

Brachial Axillary

Capillaries

Subclavian Brachiocephalic (innominate) Superior vena cava Right atrium of heart Fig 10-4  Arteries and veins of the upper limb.

243

Venipuncture

10 Veins of the upper limb The veins of the upper limb may be divided into deep veins, which accompany arteries within the fascial sleeve, and superficial veins, which lie mostly outside the fascial sleeve (see Fig 10-4). Blood from the digits and palm drains into the dorsal venous network. Cephalic (lateral) and basilic (medial) veins rise from this network and ascend the forearm, where the median vein of the forearm arises. The cephalic vein lies laterally and empties into the axillary vein, which is a direct continuation of the basilic vein and continues centrally as the subclavian and brachiocephalic veins before emptying into the superior vena cava. The basilic vein lies medially and joins the brachial vein. The median cubital vein, which is commonly used for venipuncture, lies over the antecubital fossa and serves as an anastomosis between the cephalic and basilic veins (Fig 10-5).

Subclavian

Axillary a.

Cephalic Brachial a.

Basilic

Median cubital

Ulnar a. Radial a.

Cephalic

Median antebrachial

Basilic

Digital

Fig 10-5  Veins of the upper limb. a.­—artery.

244

Arteries and Veins of the Upper Limb Clinical significance Within the antecubital fossa, the brachial artery is commonly found just medial of the midline, beneath the median basilic vein, the most prominent vein in the antecubital fossa.

Vascular walls Veins and arteries have walls constructed of three coats (Fig 10-6): 1. The inner coat (tunica interna or intima), composed of simple squamous epithelial cells, a connective tissue layer, and elastic fibers called elastin 2. The middle coat (tunica media), composed of smooth muscle 3. The external coat (tunica externa or adventitia), composed mainly of connective tissue

Vein

Valve

Tunica externa (adventitia)

Tunica media

Elastic tissue (elastin)

Connective tissue

Endothelial cells

Artery

Fig 10-6  Vascular wall structure.

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Venipuncture

10 Primary veins for venipuncture The primary veins for venipuncture (Fig 10-7) include the following: •  In the antecubital fossa: °°Cephalic vein °°Basilic vein °°Median vein, which divides into the median basilic vein (the largest and most common vein for phlebotomy) and the median cephalic vein •  In the forearm: °°Basilic (medial) vein °°Cephalic (lateral) vein •  In the dorsum of the hand: °°Dorsal venous network

Brachial a.

Median nerve

Cephalic v.

Basilic v.

Median basilic v.

Median cephalic v.

Median cubital v.

Median antebrachial v.

Median antebrachical cephalic v.

Antebrachial basilic v. Median antebrachial basilic v. Ulnar a.

Radial a.

Fig 10-7  Primary veins for venipuncture. v.—vein; a.—artery.

246

Arteries and Veins of the Upper Limb

Table 10-1 highlights the advantages and disadvantages of the various primary veins for venipuncture.

Table 10-1

Advantages and disadvantages of primary veins for venipuncture

Location

Advantages

Disadvantages

Antecubital fossa

Veins are large

Veins are not as superficial as in other areas

Veins are not as mobile as in other areas

Medial aspect should be avoided

Lateral aspect is anatomically safe Forearm

Veins are large Veins are not superficial (ie, they do not roll)

Lack of superficiality of veins makes it difficult in some patients

Anatomically safe Dorsum of the hand

Veins are quite superficial

Veins are small

Anatomically safe

Veins are mobile

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Venipuncture

10

248

Venous Physiology •  Veins feel like an elastic tube and “give” under pressure. •  Veins do not pulsate. •  The blood pressure in veins is much lower than that in arteries. This blood pressure is determined mainly by the pressure in the right atrium of the heart and is normally zero. This does not mean that the force distending on the walls of the right atrium is zero, because the pressure in the chest cavity surrounding the heart is –4 mm Hg. This partial vacuum in the chest pulls the walls of the atrium outward so that the blood is normally sucked into the atrium from the vein (Fig 10-8). •  Peripheral venous pressure is determined by five factors: (1) right atrial pressure; (2) the resistance to blood flow from the vein to the right atrium; (3) the rate of blood flow along the vein; (4) the pressure caused by the weight of the blood itself (hydrostatic pressure; considerable extra pressure must develop to drive the blood uphill); and (5) the venous pump (or muscle pump), by which the moving tissues compress at least some veins and push blood toward the heart every time a muscle contracts or a limb moves. •  Unlike arteries, veins collapse when they are empty. When they are lower than the heart, they become full of blood and stand out beneath the skin. When the arm is raised, the veins normally collapse at a level approximately 9 cm above the level of the heart (Fig 10-9). Therefore, raising an injured limb above the level of the heart will stop bleeding from veins (though not from arteries). •  Most veins (except those in the in venae cavae and the head) have valves inside them to prevent backflow of blood (Fig 10-10). Failure of these venous valves will permit blood flow back down between movements so that the venous pressure increases and the veins grow large; this condition is known as varicose veins.

Venous Physiology

Sagittal sinus –10 mm Hg

0 mm Hg 0 mm Hg +6 mm Hg +8 mm Hg

+22 mm Hg

+35 mm Hg

+40 mm Hg

+90 mm Hg

Fig 10-8  Venous pressure in various veins of the body.

249

Venipuncture

10

Veins collapsed

Veins collapsing

Veins congested

Fig 10-9  Venous collapse.

Vein

Orifice of small tributary

Venous branch

Cusp

Fig 10-10  Venous valves inside certain veins.

250