Introduction to the Masticatory System and Dental Occlusion E-Book

Dinesh Rokaya

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 299

Veröffentlichungsjahr: 2024

Beschreibung

A comprehensive introduction to the masticatory system and its relation to dental occlusion

Introduction to the Masticatory System and Dental Occlusion meets the need for a rigorous guide to the masticatory system and how it relates to dental occlusion to aid interventions. The text offers a sound understanding of functioning dental anatomy and the biomechanics that are essential to understanding dental occlusion. It covers all structures required for chewing: jaws and jaw muscles, teeth, joints, and tongue as well as other significant areas including the vascular and nervous systems that supply these structures with blood and stimulation. Beginning with the understanding of these concepts, the author provides further guidance on oral function, esthetics, and alerting patients to potential issues.

Introduction to the Masticatory System and Dental Occlusion readers will also find:

• A thorough introduction to the basic structure and function of the masticatory system
• Detailed coverage of subjects including TMJ, mastication muscles, occlusal therapy, and more
• Images to illustrate key concepts and systems
• Advice on choosing the correct medical intervention in each case

Introduction to the Masticatory System and Dental Occlusion is ideal for undergraduate and postgraduate dental students for subjects such as masticatory systems, dental anatomy, restorative dentistry, and prosthodontics, as well as for practicing dentists and medical professionals in related fields.

Leseprobe

Introduction to the Masticatory System and Dental Occlusion

Dinesh Rokaya, PhD

Clinical Sciences DepartmentCollege of DentistryAjman UniversityAjman, United Arab Emirates

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Library of Congress Cataloging‐in‐Publication DataNames: Rokaya, Dinesh, author.Title: Introduction to the masticatory system and dental occlusion / Dinesh  Rokaya.Description: Hoboken, NJ : Wiley Blackwell, 2025. | Includes  bibliographical references and index.Identifiers: LCCN 2023043797 (print) | LCCN 2023043798 (ebook) | ISBN  9781119884187 (paperback) | ISBN 9781119884194 (adobe pdf) | ISBN  9781119884200 (epub)Subjects: MESH: Stomatognathic System–anatomy & histology | Dental  Occlusion | Stomatognathic DiseasesClassification: LCC RK523 (print) | LCC RK523 (ebook) | NLM WU 101 | DDC  617.6/43–dc23/eng/20231106LC record available at https://lccn.loc.gov/2023043797LC ebook record available at https://lccn.loc.gov/2023043798

Cover Design: WileyCover Images: © Dinesh Rokaya

Dedication

This text is personally dedicated to the memory of my grandfather Mr. Singh Bir Rokaya, my father Mr. Jaya Bahadur Rokaya, my aunt Mrs. Laxmi Sharma and my brother‐in‐law Mr. Aadhi Kathayat and dedicated to all my family members, advisors, and friends for their help, support, and encouragement.

About the Author

Dinesh Rokaya received a Bachelor of Dental Surgery from People’s Dental College and Hospital affiliated with Tribhuvan University, Nepal in 2009 and Master of Science in Dentistry in Maxillofacial Prosthetics from the Faculty of Dentistry, Mahidol University, Thailand in 2015, and Doctor of Philosophy in Dental Biomaterials Science from Faculty of Dentistry, Chulalongkorn University, Thailand in 2019. He then did a one‐year Postdoctoral Fellowship in Dental Biomaterials from the Faculty of Dentistry, Chulalongkorn University, Thailand (2019–2020). He is a registered prosthodontist and dental biomaterials specialist in Nepal Medical Council. He has also received a Diploma of Membership of the Faculty of Dental Surgery (MFDS) from the Royal College of Surgeons of England and the Royal College of Physicians and Surgeons of Glasgow. He is also a Fellow of the Higher Education Academy (FHEA), UK and an Affiliate Fellow of the American Academy of Maxillofacial Prosthetics (AAMP), USA. He has co‐authored over 115 articles in international peer‐reviewed journals and 15 book chapters (H‐index 28). He is an Assistant Professor at the Clinical Sciences Department, College of Dentistry, Ajman University, Ajman, United Arab Emirates. He is also a Visiting Professor at the Department of Prosthodontics, Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand. His research areas include prosthetic dentistry, digital dentistry, esthetic dentistry, and dental biomaterials. He is a member of the American Dental Association, British Society of Prosthodontics, International College of Prosthodontics, International Association of Dental Research, International Society of Maxillofacial Rehabilitation, and International Association of Dental Research. He is a life member of the Nepal Dental Association and Nepal Medical Association.

Foreword

As a prosthodontist at Chulalongkorn University, Thailand, I am delighted to see the book “Masticatory System and Dental Occlusion” written by Dr. Dinesh Rokaya which is published by Wiley Publications. The masticatory system and occlusion in dentistry are important subjects for both undergraduate and postgraduate dental students. Although masticatory system and occlusion can sometimes seem to be difficult to understand, the contents in this book clarify them and make them easier to understand. This book describes the anatomic features that are fundamental to comprehending the dental anatomy, masticatory system, temporomandibular joint, muscles of mastication, and dental occlusion. This also covers the problems in occlusion and treatment options. Lastly, I would like to congratulate Dr. Dinesh Rokaya for his hard work in contributing such a valuable book. This book will not only be a benefit to dental students but also to anyone who wants to learn masticatory system and occlusion.

Associate Prof. Viritpon Srimaneepong

Department of ProsthodonticsFaculty of Dentistry, Chulalongkorn UniversityBangkok 10400, Thailand

Foreword 2

Masticatory science and dental occlusion are important topics in dentistry. Understanding the functional anatomy in dentistry is essential to the study of dental occlusion. The knowledge of the masticatory system and dental occlusion is used in various aspects of clinical dentistry such as restorative dentistry, prosthodontics, orthodontics, oral and maxillofacial surgery. I believe that the book “Masticatory System and Dental Occlusion” written by Dr. Dinesh Rokaya is useful for undergraduate dental students.

Finally, I would like to congratulate Dr. Dinesh Rokaya for his contribution and hard work in making this book successful.

Associate Prof. Ahmad Al Jaghsi

Clinical Sciences Department, College of DentistryCenter of Medical and Bio‐Allied Health Sciences ResearchHead, Continuing Education Office and Staff DevelopmentHead of Cellular and Material Sciences Research GroupAjman University, Ajman, United Arab Emirates

Visiting Associate Professor

Department of Prosthodontics, Gerodontology, and Dental MaterialsGreifswald University Medicine, 17489 Greifswald, Germany

Foreword 3

The topic of masticatory science and dental occlusion is always confusing to dental students. Understanding the functional anatomy and biomechanics in dentistry is essential to the study of dental occlusion. The knowledge of the masticatory system and dental occlusion can be applied in restorative dentistry, prosthodontics, periodontics, and oral and maxillofacial surgery. I believe that this book is very useful for undergraduates in dentistry. This book describes the anatomic features that are basic to an understanding of the masticatory system and dental occlusion. The contents of this book include basic dental anatomy, temporomandibular joints, muscles of mastication, and dental occlusion.

Finally, I would like to congratulate Dr. Dinesh Rokaya for his continuous effort in making this book project successful.

Prof. Sittichai Koontonkaew

Dean, Walailak University International College of DentistryWalailak UniversityBangkok 10400, Thailand

Preface

Although the dentistry field is advancing and progressing, a sound understanding of functional dental anatomy and biomechanics is essential in every aspect of dentistry. This book describes the anatomic features that are basic to an understanding of the masticatory system and dental occlusion.

This book gathers and provides an introductory guide to the masticatory system and dental occlusion. This book has 11 chapters ranging from the anatomy of the masticatory system, tooth alignments, functions of the masticatory system, bruxism and clenching, nervous system regulating masticatory system, age changes of the masticatory system, occlusal concept and its application in various aspects of dentistry, and problems in dental occlusion and their treatments.

Although this book is useful for undergraduates in dentistry, such as BDS, DDS, DMD, DDent, BDent, BDSc, or BScD. Similarly, this book is also useful for students in dental hygiene, dental technology, and dental assistants. In addition, this book will be useful for recent graduates who want to keep updated in the field of dental occlusion and masticatory system. This book can be useful for graduates who are appearing in competitive dental exams for further dental education or dental license.

Dinesh Rokaya

Acknowledgments

I would never accomplish it on my own but rather represent the accumulation of many people. A lot of people have supported me for this book. First and foremost are Prof. Sittichai Koontonkaew and Prof. Natthamet Wongsirichat for their support and inspiration in writing this book. I would like to thank Dr. Dipendra K.C. for his encouragement for this book. I am grateful to Assoc. Prof. Dr. Viritpon Srimaneepong for his continued support and encouragement for this book. I would like to thank my uncle Mr. Anga Lal Rokaya for his encouragement. Finally, I am highly grateful to my brother Dr. Nabin Rokaya, and my wife Dr. Goma Kathayat, who helped me a lot in the editing of the chapters. I would also like to thank Dr. Sonica Khanal for the drawings and editing. I also thank Dr. Bishwa Prakash Bhattarai for his suggestions.

I am deeply grateful to the WILEY publication for accepting my proposal and publishing this book. I am deeply grateful to Mr. Selvakumar Gunakundru and Mr. Raj Oliver at Wiley for their guidance, coordination, and production of this book. I also want to express my appreciation to Mr. Atul Ignatius David and Ms. Susan Engelken and Mrs. Loan Nguyen for their support, guidance, and coordination of this book. I will also like to thank to many others at Wiley for their behind‐the‐scene works and contributions to this book.

Lastly, I am grateful to my family, advisors, colleagues, and friends who supported me. It does take a community for the completion of this textbook and I thank you all.

Dinesh Rokaya

1Structures and Functions of Masticatory System

1.1 Introduction

The masticatory system consists of teeth, muscles, ligaments, bones, and joints, which are responsible for functions of the masticatory system, i.e. mastication, speech, swallowing, and speaking. The system also assists in breathing. It is regulated and coordinated by the neurologic controlling system. The musculature aids in specific motion of the mandible and effective teeth movement during function. To study occlusion, explicit knowledge of biomechanics and functional anatomy of mastication is crucial.

1.2 Structures and Functions of Temporomandibular Joint

The temporomandibular joints (TMJs) are synovial joints and movable articulations in the skull [1, 2]. The muscles of mastication along with the suprahyoid and infrahyoid move the TMJ and play a crucial part in jaw movements. The basic components of the TMJ include (Figures 1.1 and 1.2) the mandible (head of the condyle), disc, temporal bone (glenoid fossa and articular eminence), and the capsule surrounding the TMJs.

1.2.1 Articular Surfaces

Each TMJ is formed by the mandible's condylar head and squamous temporal bone's articular surfaces. Mostly, the synovial joints are shielded by the hyaline cartilage; however, the articular surfaces of TMJs are shielded by fibrocartilage (predominantly collagen accompanied by few chondrocytes), which makes them atypical [3, 4]. During jaw movements, the condyles translate forward onto the convex articular eminence.

1.2.2 Ligaments

The ligaments are mainly built from collagenous connective tissue fibers of distinct lengths. Normally, they are nonstretchable, but they can be elongated if extensive forces are applied. Ligaments control the movements of the border. The three major functional ligaments of the TMJ are the collateral, capsular, and temporomandibular ligaments (TMLs) [1, 5]. The accessory ligaments are two in number: sphenomandibular and stylomandibular.

Figure 1.1 Left temporomandibular joint (TMJ) showing the condyle, disc, glenoid fossa, and articular eminence of the temporal bone. Image taken from the Anatomage Table (Anatomage Inc., California, USA).

Figure 1.2 Diagram of the right temporomandibular joint (TMJ) sagittal section showing the various components.

1.2.2.1 Collateral (Discal) Ligaments

The other name for collateral ligaments is discal ligaments. These are the true ligaments that comprise fibers of collagenous connective tissue and are nonelastic. These ligaments divide the joint mediolaterally into the inferior and superior joint cavities. The articular disc (lateral and medial borders) is linked to the condyle by the collateral ligaments. The medial discal ligament connects the medial pole of the condyle from the medial edge of the disc, and the lateral discal ligament connects the lateral pole of the condyle from the lateral edge of the disc (Figure 1.3) [1]. During glides of the condyle anteriorly and posteriorly, passive movement with the condyle is permitted by them. Moreover, the anterior and posterior disc rotation on the condyle's articular surface is allowed by them. Hence, they are beneficial for the hinge motion of the TMJ that happens between the articular disc and the condyle.

Figure 1.3 Anterior view of the temporomandibular joint (TMJ).

Adapted from Reference [1]; chapter published in Management of Temporomandibular Disorders and Occlusion, 7th edition, Okeson J.P., Functional Anatomy and Biomechanics of the Masticatory System, page 10, Copyright Elsevier (2013).

1.2.2.2 Capsular Ligament

The capsular ligament incorporates the entire TMJ (Figure 1.4) [1]. Superiorly, the capsular ligament's fibers are connected to the temporal bone through the mandibular fossa's articular surfaces and the articular eminence. Inferiorly, the capsular ligament's fibers are connected to the condylar neck. The function of this ligament is to withstand all the forces arising medially, laterally, or inferiorly, which might result in the separation or dislocation of the articular surfaces. This ligament also helps retain the synovial fluid.

1.2.2.3 Temporomandibular Ligament

The strengthened capsular ligament builds the temporomandibular (TM) or the lateral ligament with the help of strong tight fibers. The TML consists of an inner horizontal portion and an outer oblique portion (Figure 1.4A) [1]. The inner horizontal portion stretches from the zygomatic process and articular tubercle horizontally to the condyle's lateral pole and the articular disc's posterior part. The outer oblique portion stretches from the articular tubercle and zygomatic process to the neck of the condyle.

Figure 1.4 Ligaments of the temporomandibular joint. A, Temporomandibular ligament showing the outer oblique portion and the inner horizontal portion. B, Stylomandibular ligament and sphenomandibular ligament.

Adapted from Reference [1]; chapter published in Management of Temporomandibular Disorders and Occlusion, 7th edition, Okeson J.P., Functional Anatomy and Biomechanics of the Masticatory System, page 10–11, Copyright Elsevier (2013).

1.2.2.4 Sphenomandibular Ligament

The sphenomandibular ligament is one of the accessory ligaments of the TMJ (Figure 1.4B) [1], which emerges from the sphenoid bone's spine and descends to the mandibular ramus’ lingula [6]. This ligament has no crucial function in mandibular movement limitation.

1.2.2.5 Stylomandibular Ligament

The stylomandibular ligament is another accessory ligament of the TMJ (Figure 1.4B) [1], which emerges from the styloid process and descends downward and forward to the mandibular angle and posterior border of the ramus. The uncontrolled protrusive mandibular motions are limited by the stylomandibular ligament. This ligament becomes tense while protruding the mandible and relaxes while opening the mandible.

1.2.3 Nerve Innervation of the Temporomandibular Joint

The trigeminal nerve innervates the TMJ and supplies sensory and motor innervation to the muscles that regulate it. The afferent innervation is supplied by the mandibular nerve branches. Most of the innervation is supplied through the auriculotemporal nerve while it branches off the mandibular nerve. Masseteric and deep temporal nerves provide supplemental innervation [7].

1.2.4 Blood Supply of the Temporomandibular Joint

The principal arteries of the TMJs are composed of the middle meningeal artery anteriorly, the superficial temporal artery posteriorly, and the internal maxillary artery inferiorly. The deep auricular, ascending pharyngeal, and anterior tympanic arteries are the additional crucial vessels. The “feeder vessels” that by a direct route get into the head of the condyle both anteriorly and posteriorly and the inferior alveolar artery through marrow spaces are the routes through which the condyle acquires its vascular supply [8].

1.2.5 Functions of the Temporomandibular Joint

The function of the TMJ is based on the articular design, neuromuscular control, and integrity of soft tissue elements that comprise the anatomy [9]. The prime function of the TMJ is to facilitate movements of the lower jaw. This joint allows a range of movements of the lower jaw, i.e. translational movements (protrusion, retraction, and lateral deviation) and rotational movements (elevation and depression) [2, 9].

1.2.6 Clinical Evaluation of the Temporomandibular Joint

The clinical evaluation of the TMJ includes the observation of the symmetry of the face and the various movements of TMJ. In patients with TMJ dysfunction, it will result in an asymmetry of the mandibular branch.

Pain and clicking are recorded at specific degrees of articular opening or closing, along with accessory movements. The muscles are palpated (externally and internally) and the presence of enlarged submandibular lymph nodes is also checked by palpation. The jaw is slowly moved to evaluate the TMJ ligament apparatus. The fingers are placed on the joint while the patient opens his mouth to evaluate the TMJ. The maximum opening of the mouth should also be evaluated [10].

1.2.7 Radiographic Examination of the Temporomandibular Joint

Various instruments are used in the assessments of the TMJs, and they play a vital role in the diagnosis. Hence, it is necessary to do a proper assessment using instruments before taking a therapeutic approach to a TMJ in the dysfunction [11]. Various imaging techniques for the TMJ include panoramic radiography, plain radiography (transcranial projection), computed tomography or cone‐beam computed tomography, and magnetic resonance imaging (Figure 1.5) [12–14]. Panoramic radiography (Figure 1.5A) is important in the evaluation of the mandibular condyles to the glenoid fossa relationship. Plain radiography of the TMJs (Figure 1.5B) using transcranial projections is useful in the evaluation of the TMJ. The images can be taken at various angulations (lateral oblique transcranial projections, anterior–posterior projections, submental‐vertex projection, transpharyngeal view) to avoid the superposition of the temporal bone and the opposite TMJ [13]. Computed tomography or cone‐beam computed tomography (Figure 1.5C,D) is done to evaluate the morphology of the components that make up TMJ as well as bone position and pathologies [14]. Magnetic resonance imaging of TMJ (Figure 1.5E) helps observe the condition of the articular disk, anatomy, function, and form.

Figure 1.5 Various imaging techniques for the temporomandibular joint. A, Panoramic radiography. B, Plain radiography (transcranial projection) [(a) and (d) Closed‐mouth, (b) and (c) Open‐mouth]. C, Computed tomography [(a) Saggital plane, (b) Coronal plane]. D, Cone‐beam computed tomography [(a) Coronal plane, (b) Axial plane]. E, Magnetic resonance imaging [(a) Closed‐mouth, (b) Open‐mouth].

Reproduced from [12] / with permission of Kathmandu University Medical Journal (KUMJ) Kathmandu University.

1.2.8 Clinical Considerations of the Temporomandibular Joint

Loss of teeth results in the subsequent loading of the TMJ, and it can lead to histomorphological and pathophysiological changes in the TMJ joint (the articular disc, articular cartilages, the synovium, and the articular bony components) [15]. The severity of the changes increases with increasing age and is aggravated by impaired occlusal stabilization and existing arthritis of the joint.

Various pathologies can affect the TMJ and potentially cause varying degrees of dysfunction [16]. Damage or disease in the joint area adversely affects masticatory function and speaking, affecting the quality of the life of the patient. Common conditions and diseases of the TMJ include joint pain, muscular pain, rheumatoid arthritis, ankylosing spondylitis, psoriatic arthropathy, fibromyalgia syndrome – myalgia, and multiple sclerosis.