Wheeler's Dental Anatomy, Physiology and Occlusion, 10th Ed PDF
Preview Wheeler's Dental Anatomy, Physiology and Occlusion, 10th Ed
WHEELER’S Dental Anatomy, Physiology, and Occlusion This page intentionally left blank TENTH EDITION WHEELER’S Dental Anatomy, Physiology, and Occlusion STANLEY J. NELSON, DDS, MS Professor School of Dental Medicine University of Nevada Las Vegas, Nevada 3251 Riverport Lane St. Louis, Missouri 63043 WHEELER’S DENTAL ANATOMY, PHYSIOLOGY, AND OCCLUSION, TENTH EDITION ISBN: 978-0-323-26323-8 Copyright © 2015, 2010, 2003, 1993, 1984, 1974, 1965, 1958, 1950, 1940, by Saunders, an imprint of Elsevier Inc. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions. This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein). Notices Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary. Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility. With respect to any drug or pharmaceutical products identified, readers are advised to check the most current information provided (i) on procedures featured or (ii) by the manufacturer of each product to be administered, to verify the recommended dose or formula, the method and duration of administration, and contraindications. It is the responsibility of practitioners, relying on their own experience and knowledge of their patients, to make diagnoses, to determine dosages and the best treatment for each individual patient, and to take all appropriate safety precautions. To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. Library of Congress Cataloging-in-Publication Data Nelson, Stanley J., author. Wheeler's dental anatomy, physiology, and occlusion / Stanley J. Nelson. – Tenth edition. p. ; cm. Dental anatomy, physiology, and occlusion Includes bibliographical references and index. ISBN 978-0-323-26323-8 (paperback) I. Title. II. Title: Dental anatomy, physiology, and occlusion. [DNLM: 1. Tooth–anatomy & histology. 2. Dental Occlusion. 3. Tooth–physiology. WU 101] RK280 611'.314–dc23 2014022015 Executive Content Strategist: Kathy Falk Senior Content Development Specialist: Brian Loehr Publishing Services Manager: Hemamalini Rajendrababu Project Manager: Kiruthiga Kasthuriswamy Designer: Amy Buxton Printed in China Last digit is the print number: 9 8 7 6 5 4 3 2 1 This edition is dedicated to Professor Doctor Major McKinley Ash. This page intentionally left blank Preface It is with my great amazement that this work becomes part of the 75-year history of Wheeler’s Dental Anatomy, Physiology, and Occlusion. The first edition was titled Textbook of Dental Anat- omy and Physiology, published in 1940 by Dr. Russell C. Wheeler and remained under this title until the fifth edition, published in 1974, when it became Dental Anatomy, Physiology, and Occlu- sion. The fifth edition of this book holds a very special place in my personal development because this was the text I studied as a freshman dental student. The sixth edition was published by Dr. Major M. Ash Jr. in 1984 under the title of Wheeler’s Dental Anatomy, Physiology, and Occlusion, which continues through this latest edition. I joined Dr. Ash as a co-author in the eighth edition, which was first published in 2003. Looking back over the long history of this textbook, it is very apparent that this, now the 10th edition of Wheeler’s Dental Anatomy, Physiology, and Occlusion, is the result of the collective work of a great many people. As this edition reflects a change in authorship, I believe it is appropriate that the past and present contributors be remembered and once again recognized. What follows is my attempt to include the names of all contributors as published by edition. My apolo- gies if I have overlooked anyone. First Edition: Dr. G. V. Black, Dr. Martin Dewey, Dr. Moses Diamond, Dr Edgar H. Keys, Dr. Jesse D. White, Dr. Clarence O. Simpson, Dr. George B.W. Winter, Ms. Catherine McKenzie, Dean Thomas Purcell and the faculty of the St. Louis University School of Dentistry, Dr. William Bauer, Dr. Ross Bleiker, Dr. Ruth Martin, Dr. Geneve Riefling, Dr. Thomas Knox, Mr. Yandell Johnson, Mr. J. Wade McCarty, Lucille Wengler Wheeler. Second Edition: Dr. John T. Bird with acknowledgment to those others who contributed material throughout this book. ThirdEdition:Contributorsfromeditions1and2,Ms.Dorothy Permar, Dr. Carmen M. Nolla, Dean Leroy R Boling. Fourth Edition: None listed in the preface. Fifth Edition: Mr. Spencer T. Olin. Sixth Edition: Dr. George M. Ash, Dr. Jeffrey L. Ash, Dr. Christian S. Stohler, Ms. Sally Holden, Dr. Richard E. Charlick, Dr. Richard A. Reed, Dr. Jose dos Santos, Ms. Marian Brockie, Ms. Donna Schimelfening, Per Kjeldon, Kaery Campbell, Thomas Oliver, Ellen Quinn, Carol Robins Wolf, Robert W. Reinhardt, Ms. Sue Seger, Ms. Ruth Cressmann, Dr. J . Henry Clarke, Professor William Brudon. Seventh Edition: Dr. George M. Ash, Dr. Jeffrey L. Ash, Dr. Carolyn M. Ash, Ms. Sally Holden, Dr. Hans Graf, Dr. Jose dos Santos, Dr. Stanley J. Nelson, Dr. E.M. Wilkins, Professor William Brudon, Per Kjeldsen, Kaery Campbell, Joanne Kazlauskas. Eighth Edition: Dr. Jeffrey L. Ash, Dr. Carolyn M. Ash, Dr. George M. Ash, Pat Anderson, Dr. Jose dos Santos, Dr. Tom Nowlin, Professor William Brudon, David Baker, Travis Lippert, Lester Rosebrock, Fayola Ash, Kym Nelson. Ninth Edition: Dr. Edward Herschaft, Dr. David Ord, Dr. Bill Dahlke, David Baker, Sam Newman, Lee Bennack, Dr. George Ash and the Ash family, University of Los Vegas School of Dental Medicine dental students, Mary Sarah Brady, Dr. Charles S. Nelson. And finally, to acknowledge the contributors for this new 10th edition of Wheeler’s Dental Anatomy, Physiology, and Occlusion. I thank my colleague Dr. Wendy Woodall for taking the lead in the development of Chapter 17, clinical application of dental anatomy, physiology, and occlusion. This chapter is new to this edition and represents our attempt to help the stu- dent understand the importance of developing a strong foun- dation in this topic. To Dr. Edward Herschaft for his revisions to Chapter 4 inForensic Odontology.To Dr.Bill Dalhke, Dr. CodyC. Hughes, Dr. Matthew Herring, Dr. Jarod Johnson, Dr. Amy Rusi- noski, Dr. Levi Sorenson, Dr. Emily Whipple, Dr. Vikram Tiku of the University of Nevada Las Vegas program in Pediatric Den- tistry for their review and revisions in Chapter 2, Development and Eruption of the Teeth, and Chapter 3, The Primary (Decid- uous) Teeth. To Dr. Elena Farfel for her documentation of mamelons on primary teeth. To Dr. Lawrence Zoller for his helpful review and edits of the head and neck anatomy mate- rial. To the students of the University of Nevada School of Den- tal Medicine for their suggestions and feedback, with special thanks extended to student doctors Sarah Liu and Colleen Schook. To Kathy Falk, Brian Loehr, and the staff of Elsevier Sci- ence; and lastly, to my wife Mary Sarah Brady for all her help and support. To quote Dr. Wheeler from the first edition preface: “No successful practitioner fails to recognize the importance of the fundamental form of the teeth, their alignment and their occlusion, as a basic subject serving as a background for all phases of dental practice.” Thanks to all who contributed to this textbook. Thanks to all for helping improve dentistry. SJN vii This page intentionally left blank Contents 1 Introduction to Dental Anatomy, 1 Formation of the Dentitions (Overview), 1 Nomenclature, 2 Formulae for Mammalian Teeth, 2 Tooth Numbering Systems, 2 Division into Thirds, Line Angles, and Point Angles, 9 Tooth Drawing and Carving, 10 Measurement of Teeth, 11 Summary, 19 References, 19 2 Development and Eruption of the Teeth, 21 Clinical Considerations, 21 Variability, 22 Malformations, 22 Chronology of Primary Dentition, 23 Development and Eruption/Emergence of the Teeth, 23 The Dentitions, 26 Neuromuscular Development, 27 Transitional (Mixed) Dentition Period, 28 Loss of Primary Teeth, 29 Permanent Dentition, 30 Size of Teeth, 31 Dental Pulp, 31 Cementoenamel Junction, 32 Dental Age, 33 Tooth Formation Standards, 35 Chronologies of Human Dentition, 35 Types of Chronologies, 35 Stages of Tooth Formation, 35 Age of Attainment, 35 Age Prediction, 36 Maturity Assessment, 37 Duration of Root and Crown Formation, 37 Summary of Chronologies, 37 Sequence of Eruption, 40 Estimating Time of Enamel Hypoplasia, 41 References, 41 3 The Primary (Deciduous) Teeth, 43 Life Cycle, 43 Importance of Primary Teeth, 43 Nomenclature, 43 Major Contrasts between Primary and Permanent Teeth, 44 Pulp Chambers and Pulp Canals, 45 Detailed Description of Each Primary Tooth, 46 References, 63 4 Forensics, Comparative Anatomy, Geometries, and Form and Function, 65 Forensic Dentistry, 65 Comparative Dental Anatomy, 68 Facial and Lingual Aspects of All Teeth, 72 Summary of Schematic Outlines, 74 Form and Function of the Permanent Dentition, 74 Alignment, Contacts, and Occlusion, 74 References, 77 5 OrofacialComplex:FormandFunction, 79 Form and Function, 79 Form Follows Function, 79 Articulation of Teeth, 79 Physiological Form of the Teeth and Periodontium, 80 Fundamental Curvatures, 80 Proximal Contact Areas, 80 Interproximal Spaces (Formed by Proximal Surfaces in Contact), 82 Embrasures (Spillways), 84 Contact Areas and Incisal and Occlusal Embrasures from the Labial and Buccal Aspect, 86 Contact Areas and Labial, Buccal, and Lingual Embrasures from the Incisal and Occlusal Aspects, 87 Facial and Lingual Contours at the Cervical Thirds (Cervical Ridges) and Lingual Contours at the Middle Thirds of Crowns, 89 The Height of Epithelial Attachment: Curvatures of the Cervical Lines (Cementoenamel Junction [CEJ]) Mesially and Distally, 92 References, 94 ix 6 The Permanent Maxillary Incisors, 97 Maxillary Central Incisor, 97 Maxillary Lateral Incisor, 104 References, 109 7 The Permanent Mandibular Incisors, 111 Mandibular Central Incisor, 111 Mandibular Lateral Incisor, 117 References, 121 8 The Permanent Canines: Maxillary and Mandibular, 123 Maxillary Canine, 123 Mandibular Canine, 130 References, 136 9 The Permanent Maxillary Premolars, 137 Maxillary First Premolar, 137 Maxillary Second Premolar, 146 10 The Permanent Mandibular Premolars, 151 Mandibular First Premolar, 151 Mandibular Second Premolar, 159 11 The Permanent Maxillary Molars, 165 Maxillary First Molar, 165 Maxillary Second Molar, 174 Maxillary Third Molar, 178 12 The Permanent Mandibular Molars, 183 Mandibular First Molar, 183 Mandibular Second Molar, 193 Mandibular Third Molar, 196 References, 200 13 Pulp Chambers and Canals, 203 Pulp, Chamber, and Canals, 203 Radiographs, 203 Foramen, 205 Demarcation of Pulp Cavity and Canal, 206 Pulp Horns, 206 Clinical Applications, 206 Pulp Cavities of the Maxillary Teeth, 207 Pulp Cavities of the Mandibular Teeth, 215 Radiographs: Pulp Chamber and Canals, 226 Crown and Root Fractures, 227 References, 230 14 Dento-osseous Structures, Blood Vessels, and Nerves, 231 The Maxillae, 231 The Mandible, 236 Arterial Supply to the Teeth, 242 Nerve Supply to the Jaws and Teeth, 248 References, 249 15 The Temporomandibular Joints, Teeth, and Muscles, and Their Functions, 251 Temporomandibular Articulation, 251 Muscles, 257 Mandibular Movements and Muscle Activity, 262 References, 264 16 Occlusion, 267 Concepts of Occlusion, 267 Development of the Dentitions, 268 Primary Dentition, 268 Mixed (Transitional) Dentition, 271 Permanent Dentition, 274 Cusp, Fossa, and Marginal Ridge Relations, 280 Lateral Occlusal Relations, 288 Biomechanics of Chewing Function, 290 Neurobehavioral Aspects of Occlusion, 290 Oral Motor Behavior, 294 Swallowing, 295 Summary, 295 References, 296 17 Clinical Application of Dental Anatomy, Physiology, and Occlusion, 299 Instrument Design/Usage Relating to Dental Anatomy, 299 Oral Surgery, 301 Periodontics, 305 Endodontics, 306 Restorative Dentistry, 307 Esthetics, 309 Variant Anatomy, 309 Occlusion, 310 References, 312 Appendix A Review of Tooth Morphology, 315 Appendix B Tooth Traits of the Permanent Dentition, 333 Index, 341 Flash Cards x Contents 11 Introduction to Dental Anatomy For additional study resources, please visit http://evolve.elsevier.com/Nelson/dentalanatomy Dental anatomy is defined here as, but is not limited to, the study of the development, morphology, function, and identity of each of the teeth in the human dentitions, as well as the way in which the teeth relate in shape, form, structure, color, and function to the other teeth in the same dental arch and to the teeth in the opposing arch. Thus, the study of dental anatomy, physiology, and occlusion provides one of the basic compo- nents of the skills needed to practice all phases of dentistry. The application of dental anatomy to clinical practice can be envisioned in Figure 1-1, A, where a disturbance of enamel formation (considered briefly in Chapter 2) has resulted in esthetic, psychological, and periodontal problems that may be corrected by an appropriate restorative dental treatment, such as that illustrated in Figure 1-1, B. The practitioner must have knowledge of the morphology, occlusion, esthetics, phonetics, and functions of these teeth to undertake such treatment. Formation of the Dentitions (Overview) Humans have two sets of teeth in their lifetime. The first set of teeth to be seen in the mouth is the primary or deciduous dentition, which begins to form prenatally at about 14 weeks in utero and is completed postnatally at about 3 years of age. In the absence of congenital disorders, dental disease, or trauma, the first teeth in this dentition begin to appear in the oral cavity at the mean age of 6 months, and the last emerge at a mean age of 28�4 months. The deciduous den- tition remains intact (barring loss from dental caries or trauma) until the child is about 6 years of age. At about that time, the first succedaneous or permanent teeth begin to emerge into the mouth. The emergence of these teeth begins the transition or mixed dentition period, in which there is a mix- ture of deciduous and succedaneous teeth present. The tran- sition period lasts from about 6 to 12 years of age and ends when all the deciduous teeth have been shed. At that time, the permanent dentition period begins. Thus, the transition from the primary dentition to the permanent dentition begins with the emergence of the first permanent molars, shedding of the deciduous incisors, and emergence of the permanent incisors. The mixed dentition period is often a dif- ficult time for the young child because of habits, missing teeth, teeth of different colors and hues, crowding of the teeth, and malposed teeth. The permanent, or succedaneous, teeth replace the exfo- liated deciduous teeth in a sequence of eruption that exhibits some variance, an important topic considered in Chapter 16. After the shedding of the deciduous canines and molars, emergence of the permanent canines and premolars, and emergence of the second permanent molars, the permanent dentition is completed (including the roots) at about 14 to 15 years of age, except for the third molars, which are com- pleted at 18 to 25 years of age. In effect, the duration of the permanent dentition period is 12+ years. The completed per- manent dentition consists of 32 teeth if none is congenitally 1 missing, which may be the case. The development of the teeth, dentitions, and the craniofacial complex are considered in Chapter 2. The development of occlusion for both denti- tions is discussed in Chapter 16. Nomenclature The first step in understanding dental anatomy is to learn the nomenclature, or the system of names, used to describe or classify the material included in the subject. When a signifi- cant term is used for the first time here, it is emphasized in bold. Additional terms are discussed as needed in subsequent chapters. The term mandibular refers to the lower jaw, or mandible. The term maxillary refers to the upper jaw, or maxilla. When more than one name is used in the literature to describe something, the two most commonly used names will be used initially. After that, they may be combined or used separately, as consistent with the literature of a particular specialty of dentistry, for example, primary or deciduous dentition, perma- nent or succedaneous dentition. A good case may be made for the use of both terms. By dictionary definition,1 the term primary can mean “constituting or belonging to the first stage in any process.” The term deciduous can mean “not perma- nent, transitory.” The same unabridged dictionary refers the reader from the definition of deciduous tooth to milk tooth, which is defined as “one of the temporary teeth of a mammal that are replaced by permanent teeth; also called baby tooth, deciduous tooth.” The term primary can indicate a first denti- tion, and the term deciduous can indicate that the first denti- tion is not permanent, but not unimportant. The term succedaneous can be used to describe a successor dentition and does not suggest permanence, whereas the term perma- nent suggests a permanent dentition, which may not be the case because of dental caries, periodontal diseases, and trauma. All four of these descriptive terms appear in the pro- fessional literature. Formulae for Mammalian Teeth The denomination and number of all mammalian teeth are expressed by formulae that are used to differentiate the human dentitions from those of other species. The denomi- nation of each tooth is often represented by the initial letter in its name (e.g., I for incisor, C for canine, P for premolar, M for molar). Each letter is followed by a horizontal line and the number of each type of tooth is placed above the line for the maxilla (upper jaw) and below the line for the mandible (lower jaw). The formulae include one side only, with the number of teeth in each jaw being the same for humans. The dental formula for the primary/deciduous teeth in humans is as follows: I2 2C1 1M2 2 ¼ 10 This formula should be read as: incisors, two maxillary and two mandibular; canines, one maxillary and one mandibular; molars, two maxillary and two mandibular—or 10 altogether on one side, right or left (Figure 1-2, A). A dental formula for the permanent human dentition is as follows: I2 2C1 1P2 2M3 3 ¼ 16 Premolars have now been added to the formula, two max- illary and two mandibular, and a third molar has been added, one maxillary and one mandibular (Figure 1-2, B). Systems for scoring key morphological traits of the perma- nent dentition that are used for anthropological studies are not described here. However, a few of the morphological traits that are used in anthropological studies2 are considered in later chapters, (e.g., shoveling, Carabelli’s trait, enamel extensions, peg-shaped incisors). Some anthropologists use di1, di2, dc, dm1, and dm2 notations for the deciduous denti- tion and I1, I2, C, P1, P2, M1, M2, and M3 for the permanent teeth. These notations are generally limited to anthropolog- ical tables because of keyboard incompatibility. Tooth Numbering Systems In clinical practice, some “shorthand” system of tooth nota- tion is necessary for recording data. Several systems are in use around the world, but only a few are considered here. In 1947, a committee of the American Dental Association (ADA) recommended the symbolic system (Zsigmondy/ Palmer) as the numbering method of choice.3 However, because of difficulties with keyboard notation of the symbolic notation system, the ADA in 1968 officially recommended B A FIGURE 1-1 A, Chronological developmental disorder involving all the anterior teeth. B, Illustration of restored teeth just after completion, taking in account esthetics, occlusion, and periodontal health. Note that the gingival response is not yet resolved. (From Ash MM, Ramfjord S: Occlusion, ed 4, Philadelphia, 1995, Saunders.) 2 Tooth Numbering Systems the “universal” numbering system. Because of some limita- tions and lack of widespread use internationally, recommen- dations for a change sometimes are made.4 The universal system of notation for the primary dentition uses uppercase letters for each of the primary teeth: For the maxillary teeth, beginning with the right second molar, let- ters A through J, and for the mandibular teeth, letters K through T, beginning with the left mandibular second molar. The universal system notation for the entire primary denti- tion is as follows: tfe L t h gi R T S R Q P O N M L K A B C D E F G H I J Midsagittal Plane Central incisor (first incisor) Lateral incisor (second incisor) Canine (cuspid) First molar Second molar Second molar First molar A Canine Lateral incisor (second incisor) Central incisor (first incisor) RIGHT LEFT MANDIBULAR MAXILLARY Central incisor (first incisor) Lateral incisor (second incisor) Canine (cuspid) First premolar (first bicuspid) Second premolar (second bicuspid) First premolar (bicuspid) Canine (cuspid) Lateral incisor (second incisor) Central incisor (first incisor) B Second premolar (bicuspid) First molar First molar Second molar Second molar Third molar Third molar RIGHT LEFT MANDIBULAR MAXILLARY FIGURE 1-2 A, Casts of deciduous, or primary, dentition. B, Casts of permanent dentition. (A from Berkovitz BK, Holland GR, Moxham BJ: Oral anatomy, histology and embryology, ed 3, St Louis, 2002, Mosby.) (To view Animations 1 and 2, please go to the Evolve website.) Chapter 1 Introduction to Dental Anatomy 3 The symbolic system for the permanent dentition was introduced by Adolph Zsigmondy of Vienna in 1861 and then modified for the primary dentition in 1874. Independently, Palmer also published the symbolic system in 1870. The sym- bolic system is most often referred to as the Palmer notation system in the United States and less frequently as the Zsigmondy/Palmer notation system. In this system the arches are divided into quadrants, with the entire dentition being notated as follows: E D C B A A B C D E E D C B A A B C D E Thus, for a single tooth such as the maxillary right central incisor, the designation is . For the mandibular left central incisor, the notation is given as . This numbering system presents difficulty when an appropriate font is not available for keyboard recording of Zsigmondy/Palmer symbolic nota- tions. For simplification this symbolic notation is often des- ignated as Palmer’s dental notation rather than Zsigmondy/ Palmer notation. In the universal notation system for the permanent denti- tion, the maxillary teeth are numbered from 1 through 16, beginning with the right third molar. Beginning with the mandibular left third molar, the teeth are numbered 17 through 32. Thus, the right maxillary first molar is designated as 3, the maxillary left central incisor as 9, and the right man- dibular first molar as 30. The following universal notation designates the entire permanent dentition: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 The Zsigmondy/Palmer notation for the permanent den- tition is a four-quadrant symbolic system in which, beginning with the central incisors, the teeth are numbered 1 through 8 (or more) in each arch. For example, the right maxillary first molar is designated as , and the left mandibular central incisor as . The Palmer notation for the entire permanent dentition is as follows: 8 7 6 5 4 3 2 2 3 4 5 6 7 8 8 7 6 5 4 3 2 1 1 1 1 2 3 4 5 6 7 8 Viktor Haderup of Denmark in 1891 devised a variant of the eight-tooth quadrant system in which plus (+) and minus (�) were used to differentiate between upper and lower quad- rants and between right and left quadrants. In other words, +1 indicates the upper left central incisor, and 1� indicates the lower right central incisor. Primary teeth were numbered as follows: upper right, 05+ to 01+; lower left, �01 to �05. This system is still taught in Denmark.5 The universal system is acceptable to computer language, whereas the Palmer notation is generally incompatible with computers and word processing systems. Each tooth in the universal system is designated with a unique number, which leads to less confusion than with the Palmer notation. A two-digit system proposed by Fédération Dentaire Internationale (FDI) for both the primary and permanent dentitions has been adopted by the World Health Organiza- tion and accepted by other organizations, such as the Inter- national Association for Dental Research. The FDI system of tooth notation is as follows. For the primary teeth: Upper Right 55 54 53 52 62 63 64 65 85 84 83 82 51 61 81 72 73 74 75 Lower Right 71 Upper Left Lower Left Numeral 5 indicates the maxillary right side, and 6 indi- cates the maxillary left side. The second number of the two-digit number is the tooth number for each side. The number 8 indicates the mandibular right side, and the num- ber 7 indicates the mandibular left side. The second number of the two-digit system is the tooth number. Thus, for exam- ple, the number 51 refers to the maxillary right central incisor. For the permanent teeth: Upper Right 18 17 16 15 14 13 12 22 23 24 25 26 27 28 48 47 46 45 44 43 42 11 21 41 31 32 33 34 35 36 37 38 Lower Right Upper Left Lower Left Thus, as in the two-digit FDI system for the primary den- tition, the first digit indicates the quadrant: 1 to 4 for the per- manent dentition, and 5 to 8 for the primary dentition. The second digit indicates the tooth within a quadrant: 1 to 8 for the permanent teeth, and 1 to 5 for the primary teeth. For example, the permanent upper right central incisor is 11 (pro- nounced “one one,” not “eleven”). THE CROWN AND ROOT Each tooth has a crown and root portion. The crown is cov- ered with enamel, and the root portion is covered with cementum. The crown and root join at the cementoenamel junction (CEJ). This junction, also called the cervical line (Figure 1-3), is plainly visible on a specimen tooth. The main bulk of the tooth is composed of dentin, which is clear in a cross section of the tooth. This cross section displays a pulp chamber and a pulp canal, which normally contain the pulp tissue. The pulp chamber is in the crown portion mainly, and the pulp canal is in the root (Figure 1-4).The spaces are continuous with each other and are spoken of collectively as the pulp cavity. The four tooth tissues are enamel, cementum, dentin, and pulp. The first three are known as hard tissues, the last as soft tissue. The pulp tissue furnishes the blood and nerve supply to the tooth. The tissues of the teeth must be considered in relation to the other tissues of the orofacial structures (Figures 1-5 and 1-6) if the physiology of the teeth is to be understood. The crown of an incisor tooth may have an incisal ridge or edge, as in the central and lateral incisors; a single cusp, as in 4 Tooth Numbering Systems the canines; or two or more cusps, as on premolars and molars. Incisal ridges and cusps form the cutting surfaces on tooth crowns. The root portion of the tooth may be single, with one apex or terminal end, as usually found in anterior teeth and some of the premolars; or multiple, with a bifurcation or trifurcation dividing the root portion into two or more exten- sions or roots with their apices or terminal ends, as found on all molars and in some premolars. The root portion of the tooth is firmly fixed in the bony process of the jaw, so that each tooth is held in its position relative to the others in the dental arch. That portion of the jaw serving as support for the tooth is called the alveolar process. The bone of the tooth socket is called the alveolus (plural alveoli) (Figure 1-7). The crown portion is never covered by bone tissue after it is fully erupted, but it is partly covered at the cervical third in young adults by soft tissue of the mouth known as the gingiva or gingival tissue, or “gums.” In some persons, all the enamel and frequently some cervical cementum may not be covered by the gingiva. SURFACES AND RIDGES The crowns of the incisors and canines have four surfaces and a ridge, and the crowns of the premolars and molars have five surfaces. The surfaces are named according to their positions and uses (Figure 1-8). In the incisors and canines, the surfaces toward the lips are called labial surfaces; in the premolars and molars, those facing the cheek are the buccal surfaces. When labial and buccal surfaces are referred to collectively, they are called facial surfaces. All surfaces facing toward the tongue are called lingual surfaces. The surfaces of the premolars and molars that come in contact (occlusion) with those in the opposite jaw during the act of closure are called occlusal sur- faces. These are called incisal surfaces with respect to incisors and canines. A R CL C IE FIGURE 1-3 Maxillary central incisor (facial aspect). A, Apex of root; R, root; CL, cervical line; C, crown; IE, incisal edge. (To view Animations 3 and 4, please go to the Evolve website.) A B CR A B A BI CEJ CU F PH PCH PC A AF SC B C PM B PC G GC GM PCH D E A FIGURE 1-4 Schematic drawings of longitudinal sections of an anterior and a posterior tooth. A, Anterior tooth. A, Apex; AF, apical foramen; SC, supplementary canal; B, bone; C, cementum; PM, periodontal ligament; PC, pulp canal; G, gingiva; GC, gingival crevice; GM, gingival margin; PCH, pulp chamber; D, dentin; E, enamel; CR, crown. B, Posterior tooth. A, Apices; PC, pulp canal; PCH, pulp chamber; PH, pulp horn; F, fissure; CU, cusp; CEJ, cementoenamel junction; BI, bifurcation of roots. Chapter 1 Introduction to Dental Anatomy 5
The list of books you might like
