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07 CAIRO UNIVERSITY 53 FACULTY OF DENTISTRY Oral Biology Department ESSENTIAL BASICS 9 OF DENTAL ANATOMY AND PHYSIOLOGY 56 2 Edited By Staff Members, 91 Department of Oral Biology 91 256 953 07 ...

07 CAIRO UNIVERSITY 53 FACULTY OF DENTISTRY Oral Biology Department ESSENTIAL BASICS 9 OF DENTAL ANATOMY AND PHYSIOLOGY 56 2 Edited By Staff Members, 91 Department of Oral Biology 91 256 953 07  Contents 07 1 CHAPTER (1) INTRODUCTION AND LIFE HISTORY OF THE TEETH 29 CHAPTER (2) SURFACE ANATOMY OF PERMANENT TEETH. 53 INCISORS CANINES PREMOLARS MOLARS 97 CHAPTER (3) SURFACE ANATOMY OF DECIDUOUS TEETH. 115 CHAPTER (4) 9 CONDITION OF THE TEETH AT DIFFERENT AGES. 121 CHAPTER (5) 56 MANDIBLE AT DIFFERENT AGES. 125 CHAPTER (6) SIGNIFICANCE OF GEOMETRIC OUTLINE OF THE CROWN. 129 CHAPTER (7) 2 THE PHYSIOLOGIC TOOTH FORM PROTECTING THE PERIODONTIUM. 139 CHAPTER (8) 91 ARRANGEMENT OF THE TEETH AND OCCLUSION. 153 REFERENCES 91 256 953 07  Objectives 07 a- Knowledge and Upon successful completion of this course the students will Understanding: be able to: a1- Define the different parts of the oral cavity. a2- Describe macro- and micro-anatomy of the teeth. a3- Select the appropriate tooth identification system needed in any dental practice. 53 a4- Describe the morphological feature of different type of teeth and their pulp cavities. a5- Identify deciduous and permanent teeth and their chronology. a6- Describe the anatomical changes induced in the mandible by age. 9 a7- State the significance of physiologic tooth form in protecting the periodontium. a8- Describe the different curves to which the arrange- ment of teeth conform to. 56 a9- Describe the relation between maxillary and man- dibular teeth in normal centric occlusion as well as during different mandibular movements. b- Intellectual Skills: Upon successful completion of this course the students will be able to: b1- Differentiate between the different types of human 2 teeth. b2- Predict the approximate age of a human being ac- cording to the condition of his teeth and mandible. 91 b3- Distinguish any abnormalities in human teeth as well as in their occluding relations.  c- Professional and Upon successful completion of this course the students will Practical Skills: be able to: 07 c1- Draw the anatomical landmarks in a blank frame of different types of human teeth. c2- Construct the normal shape and size of some per- manent human teeth by carving. c3-Rebuild variable destructed surfaces of permanent human teeth on stone cast models of natural oral 53 size. c4-Differentiate between different types of human teeth and the number of their root canals. d- General and Transfer- Upon successful completion of this course the students will able Skills: be able to: d1- Communicate effectively with colleagues, staff 9 members and helping personnel. d2- Demonstrate appropriate professional attitude and behavior in different situations. 2 56 91  CH. 56 9 INTRODUCTION AND 1 LIFE HISTORY OF THE TEETH 2 53 07 91 Essential ba s i c s o f d e n ta l a nato m y a n d p h y s i o l o g y  (2) Essential basics of dental anatomy and physiology 07 INTRODUCTION Dental anatomy includes: Surface anatomy of teeth; externally and internally, their arrangement in the dental arches, their relationship to each other and to the skull bone. 53 Upon looking into the lower facial third and the oral cavity you can see: 1- Lips 2- Gingiva 3- Cheek 4- Tongue 5- Floor of the mouth 6- Roof of the mouth 7- Teeth 1) Lips : (Fig.1) 9 There are two lips upper and lower. 56 The corner of the mouth where they meet is called commissure. a. Nasolabial groove: run di- agonally downward on each side of the nostril toward the corner of the lip. Fig. 1: Upper and lower lips with the related grooves. 2 b. Labiomental groove: run horizontally under the lower lip and emphasize the chin. 91 2- Gingiva It is that part of the masticatory tissue that surrounds the cervical part of teeth. It is firmly attached to the teeth and their surrounding bone.  Chapter 1— Introduction and life history of the teeth (3) 07 3- Cheek The lining of the inside of the cheeks is shiny with a white line called linea alba buccalis running posteriorly on each side at the level where the upper and lower teeth come together. 53 The parotid papilla: it is a round elevation of tissue observed on the cheek between first and second mo- lar at just above the occlusal plane. It covers the opening of the parotid duct (stensenʼs duct). Fig. 2: Structures in the oral cavity. 9 4- Tongue: (Fig. 2) It is broad flat organ composed of muscle fibers and glands. It rests in the floor of the mouth and manipulates food for mastication. It is the 56 principle organ of taste. 5- Floor of the mouth It is shiny and some large blood vessels may be seen near the surface. Beneath the tongue there are two bilateral bulges caused by the presence of 2 large salivary glands. 6- Roof of the mouth (palate): (Fig. 2) Its anterior part is named as hard palate. The end of hard palate is opposite 91 to third molar. The soft palate is sometimes redder than the hard palate. The junction between hard and soft palate is called vibrating line. Uvula is a small flesh structure hanging from the center of posterior border of soft palate.  (4) Essential basics of dental anatomy and physiology 07 7- Teeth Human teeth are arranged in the oral cavity in two arches called dental arches one upper and one lower. The upper arch is attached to the maxilla. The teeth of upper 53 dental arch are called upper or maxillary teeth. The lower dental arch is at- Fig. 3: Upper and lower jaws and related teeth. tached to a movable bone called the mandible which joins the skull at the temporo-mandibular joint. The teeth of lower dental arch are called lower or mandibular teeth. 9 Each dental arch can be divided into nearly equal halves by an imaginary vertical line called the midline. The right and left halves in each arch are 56 called quadrant (Fig. 3). There are four quadrants in the entire oral cav- ity which includes: a. Maxillary (upper) right quadrant. b. Mandibular (lower) right quadrant. c. Maxillary (upper) left quadrant. d. Mandibular (lower) left quadrant. 2 In the oral cavity there are four types of teeth that includes (Fig.3): 91 I- Incisors: They are the two front teeth in each quadrant. The central incisor is the first tooth next to the midline. The lateral incisor is the second.  Chapter 1— Introduction and life history of the teeth (5) 07 II-Canine (cuspid): There is one canine in each quadrant. It is the third tooth from the midline in each quadrant. III- Premolars (bicuspids): There are 2 premolars in each quadrant. They are the fourth and fifth teeth from the midline. 53 The fourth tooth is the first premolar. The fifth tooth is the second pre- molar. IV. Molars: There are three molars in each quadrant. They are the sixth, seventh and eighth from the midline. The sixth is the first molar. The seventh is the second molar. The eighth is the third molar. 9 »» The incisors and canines are considered anterior teeth since they are closer to the midline. »» Molars and premolars are considered posterior teeth since they are 56 farther from the midline. 2 91  (6) Essential basics of dental anatomy and physiology 07 Overview of The Human Dentitions The word dentition means all of the upper and lower teeth considered collectively. Humans have two dentitions; the primary and the permanent. There is a transitional phase when both dentitions are present in the oral cavity is called mixed dentition. 53 1- The primary dentition: (Fig.4) This is called the deciduous dentition or the one that is shed or exfoliate. This begins at 6 months and ends at 6 years. The eruption of primary teeth 9 begins at 6 months (for lower central incisor) and ends at 2 years (for the upper second deciduous molar). These teeth 56 are also called milk teeth, baby teeth, or temporary teeth. They are 20 in number, 10 Fig. 4: The primary dentition. maxillary and 10 mandibular, 5 in each quadrant. Each quadrant contains 3 types of deciduous teeth which are: 2 1- Two incisors. 2- One canine. 3-Two molars. 2- Mixed dentition: 91 This period begins with the eruption of the first permanent molar at about 6 years. It ends around the age of 12. At this period the deciduous teeth exfoliate or shed and the permanent teeth erupt into their places. Shedding; it is the physiological loss of the deciduous teeth and their subsequent replacement by permanent teeth  Chapter 1— Introduction and life history of the teeth (7) 07 3- The permanent dentition: (Fig.5) It is also called the secondary, adult or succedaneous dentition since many of these permanent teeth succeed deciduous teeth. This dentition begins at approximately 12 years and 53 persists throughout the life span of the teeth. There are 32 permanent teeth, 16 maxillary and 16 mandibular. In each quadrant 8 teeth are present 2 incisors, 1 canine, 2 premolars and 3 molars. Fig. 5: The permanent dentition. 9 It is important to keep in mind that: 1. Deciduous molars are succeeded by a group of teeth named as premolars, which are not present in deciduous dentition. 56 2. All permanent molars are not preceded with deciduous teeth. So they may be termed non-succedaneous teeth. They represent an extra number of permanent teeth to that of the deciduous teeth. 3. Total number of permanent teeth will exceed that of the deciduous teeth with 12 (3 molars in each quadrant). Dental Formula For Mammalian Teeth 2 The type and number of all mammalian teeth are expressed by formula that is used to differentiate human dentition from that of other experimental animals. The dental formula includes deciduous and permanent dentition. Also it 91 indicates the dentition of one side of the mouth only (upper and lower). Human dental formula for deciduous teeth is: 2 1 0 2 I C PM M = 10 2 1 0 2  (8) Essential basics of dental anatomy and physiology 07 This Dental formula can be read as: Incisors (I): 2 maxillary and 2 mandibular. Canines (C): 1 maxillary and 1 mandibular. Premolar (PM): Absence of these teeth. Molars(M): 2 maxillary and 2 mandibular. * The total number of the human deciduous teeth is 10 teeth for one side 53 upper and lower dental arch. Human dental formula for permanent teeth is: 2 1 2 3 I C PM M = 16 2 1 2 3 9 Dental formula can be read as: Incisors (I): 2 maxillary and 2 mandibular. 56 Canines (C): 1 maxillary and 1 mandibular. Premolars (PM): 2 maxillary and 2 mandibular. Molars (M): 3 maxillary and 3 mandibular. * The total number of the human permanent teeth is 16 teeth for one side upper and lower dental arch. In biological research the most used model of experimental animals are rats, guina pigs and dogs. 2 The rat dental formula: 91 The rat has permanent set only. 1 0 0 3 I C PM M =8 1 0 0 3  Chapter 1— Introduction and life history of the teeth (9) 07 The dog dental formula: 3 1 3 0 For deciduous is: I C PM M = 14 3 1 3 0 3 1 4 2 For permanent is: I C PM M = 21 3 1 4 3 Tooth Anatomy 53 Macro-anatomy of the tooth: (Fig.6) Each tooth consists of three anatomical parts; the crown, root(s) and neck. 1. Crown The crown terminates either with: * Horizontal cutting end termed the incisal ridge as in incisors. 9 * Tapered sharply pointed end termed the cusp as in canines, premolars and molars. Anatomical crown: It is that part 56 of the tooth covered by enamel. It remains mostly constant throughout the life span of the tooth except for attrition which is the physiological loss of hard dental structure by Fig. 6: Macro and micro-anatomy of the tooth mastication Clinical crown: It is the part of the anatomical crown which is visible in the oral cavity and not covered by 2 gingiva. It may be shorter, longer or equal to anatomical crown according to the level of gingiva. Clinical crown may be: 91 1) Shorter than the anatomical crown: in case of newly erupted tooth (Fig. 7 a). 2) Longer than the anatomical crown: in case of gingival Fig. 7: The clinical crown is shorter than the anatomical recession (Fig. 7 b). crown (a) while it is longer due to gingival recession (b).  (10) Essential basics of dental anatomy and physiology 07 2. Root Anatomical root: It is that part of the tooth which is covered by cementum. Clinical root: It is that part of the tooth which is under the gingiva, not exposed to the oral cavity. It is embedded in the jaw bone. Teeth may have one or more roots. Teeth may be divided according to the number of roots into: single rooted teeth and multiple rooted teeth. 53 Multiple roots may be two roots (by bi-furcation) or three roots by tri- furcation. Multiple roots have undivided part called the root trunk. 3- Neck It is the junction between the anatomic crown and the anatomic root. It is named cervical line. It is located at the cervical border of the anatomic crown where the enamel 9 and the cementum meet so it is also named as cemento-enamel junction (CEJ). 56 Micro-anatomy (structure) of tooth: (Fig. 6) The main part of tooth is made up of dentin covered by enamel on the crown and cementum on the root. The central part of the tooth is formed of soft tissue called the pulp. 1. Enamel: It covers the anatomical crown. It is the hardest and the most mineralized tissue in the body which can resist masticatory force. 2 2. Cementum: It is a dull yellow hard tissue covering the anatomical root. It provides a medium of attachment the periodontal ligament. 3. Dentin: It is a hard yellowish tissue which forms the main bulk of the tooth. It is found under enamel coronally and under cementum in the 91 root. It surrounds the pulp. 4. Pulp: It is the only soft tissue of the tooth. It supplies the tooth with blood and lymph vessels and nerves. It occupies the central part of the tooth which is called the pulp cavity.  Chapter 1— Introduction and life history of the teeth (11) 07 Anatomically the pulp cavity is formed of two parts: (Fig. 8) a- The pulp chamber: which lies mostly in the center of the anatomical crown of the tooth. It is the enlarged portion of the pulp. Its outline roughly conforms to crown outline. The pulp chamber roof prolongates into the 53 cusps or mamelons of the crown forming pulp horns. Pulp horns are prominent in young age and disappear by age. b- Root canal: It is located in the root. Root canal ends at the apex of the root by an apical foramen. Apical fo- ramen transmits the neuro-vascular 9 and lymphatic bundles to enter the pulp tissue. The shape of root canal Fig. 8: Anatomy of the pulp cavity. usually follows that of the root. Occasionally, root canals send some branches, which open along the 56 lateral surface of the root termed the accessory canals. Some roots may have more than one canal which may end by common foramen or separate foramina. The periodontium (Fig. 1, chapter 7) It is the investing and supporting attachment system of teeth. It consists of: 2 a) Two soft tissues: gingiva and periodontal ligament. b) Two hard tissues: cementum and alveolar bone. -Terminology 91 * Alveolar process: it is that portion of the jaw which surrounds and supports the teeth. * The root is firmly attached to the socket by a ligament known as the periodontal ligament. * The alveolar process is covered by pale pink tissue called the gingiva or gum which surrounds the necks of teeth.  (12) Essential basics of dental anatomy and physiology 07 Junctions of the tooth tissues: 1. Cemento-enamel junction: (see cervical line) 2. Dentino-enamel junction: it is the junction between enamel and dentin in the crown. 3. Dentino-cemental junction: it is the junction between dentin and cementum in the root. Functions of teeth: 53 1. Mastication: This is the most important function of teeth. Teeth are designed to perform their function:- * Incisors: The form of the incisors is nearly similar to a chisel. This form is suitable for cutting or incising food. 9 * Canine: It is wedge shape suitable mainly for piercing or tearing food, also for lesser extent for cutting. * Premolars: They have intermediate form and location between canine 56 and molars. So, they have the function of tearing and grinding of food. The first premolar function is mainly tearing, while the second premolar is for grinding mainly. * Molars: They have wide surface with multiple elevations (or cusps) and thus they are suitable for grinding food. 2. Appearance: well-arranged clean teeth with proper alignment give nice 2 appearance to the face and also support facial expressions. The facial appearance is altered by extraction of teeth especially the anterior one. 3. Speech: Teeth are important for clear pronunciation and for production of sounds. 91 4. Growth of jaws: teeth have a role in growth of jaws in some periods. If the child eats on one side the facial growth will be unilateral.  Chapter 1— Introduction and life history of the teeth (13) 07 Surfaces of the teeth: (Fig. 9) Each tooth have five surfaces: facial, lingual, mesial, distal and masticatory (functioning surface). 1. The facial surface: 53 It is the surface of a tooth facing the lips or cheeks. It can be also known as: a. Labial surface: the surface of an anterior tooth facing the lips. Fig. 9: The surfaces of the teeth. b. Buccal surface: the surface 9 of a posterior tooth facing the cheeks. 2. The lingual surface 56 a. Lingual surface: the surface of lower anterior and posterior teeth facing the tongue. b. Palatal surface: the surface of upper anterior and posterior teeth facing the palate. 3. The mesial surface: it is the surface of tooth close to the midline. 2 4. The distal surface: it is the surface of tooth away from the midline. Together mesial and distal surfaces are called proximal surfaces, i.e. surfaces between adjacent teeth. 91 5. The masticatory surface a. Incisal ridge or edge: it is the biting edge of anterior teeth. b. Occlusal surface: it is the chewing surface of posterior teeth.  (14) Essential basics of dental anatomy and physiology 07 - Division of tooth surfaces: (Fig.10) For descriptive purposes, each tooth surface is divided into thirds to facilitate description and location of anatomic landmarks. These thirds are 53 named according to the area they are near to. The crown can be divided both vertically or horizontally into three thirds: 9 a. Horizontally Iniso - (occluso) - cervically: the crown is divided into incisal 56 (occlusal), middle and cervical Fig. 10: Division of the teeth into thirds. thirds. b. Vertically 1. Labio - (bucco) - lingually: the crown is divided into labial (buccal), 2 middle and lingual thirds. 2. Mesio-distally: the crown is divided into mesial, middle and distal thirds. The root surface is divided horizontally into cervical, middle and 91 apical thirds and vertically into two halves.  Chapter 1— Introduction and life history of the teeth (15) 07 Line and Point Angles -Line angles: (Fig.11 a&b) It is formed by the junction of two surfaces of the crown and its name is derived from combining the names of the 53 two surfaces. Line angles aid in identification of certain areas of the tooth crown. Line angles of anterior teeth: The anterior teeth have fewer line angles because the meeting of the mesial 9 and distal line surfaces with incisal ridge are rounded, so the mesio-incisal and disto-incisal line angles are practically not exist. 56 There are 6 line angles: 1. Linguo-incisal 2. Labio-incisal 3. Disto-lingual 4. Mesio-lingual Fig. 11: Line angles. a, anterior tooth. b, posterior tooth 5. Disto-labial 6. Mesio-labial 2 Line angles of posterior teeth: There are 8 line angles: 91 1. Mesio-occlusal 2. Disto-occlusal 3. Linguo-occlusal 4. Bucco-occlusal 5. Mesio-lingual 6. Disto-lingual 7. Mesio-buccal 8. Disto-buccal  (16) Essential basics of dental anatomy and physiology 07 Point angles : (Fig. 12 a&b) Point angle is formed by the junction of three surfaces and is named by combining their 3 names. There are 4 point angles for 53 both anterior and posterior teeth. Point angles of anterior teeth: 1. Mesio-labio-incisal 2. Disto-labio-incisal. 3. 9 Mesio-lingo-incisal 4. Dist-lingo-incisal. Point angles of posterior 56 teeth: 1. Mesio-bucco-occlusal Fig. 12: Point angles. a, anterior tooth. b, posterior tooth. 2. Disto-bucco -occlusal 3. Mesio-lingo-occlusal 4. Disto-lingo-occlusal Tooth identification system 2 To identifying a specific tooth, the following items should be mentioned: a- Type of dentition (deciduous or permanent). 91 b- The arch (upper or lower). c- The quadrant (right or left). d- The name of the tooth. There are different systems for numbering or naming teeth. The most popular are:  Chapter 1— Introduction and life history of the teeth (17) 07 1-Palmer notation system: This system utilizes simple brackets to represent the four quadrants of the dentition as if you facing the patient. MAXILLARY RIGHT MAXILLARY LEFT 2. Lateral incisor MANDIBULAR RIGHT 3. Canine 4. First premolar 53 MANDIBULAR LEFT The permanent teeth are numbered from 1-8 on each side from the midline as follows: 9 1. Central incisor 5. Second premolar 6. First molar 7. Second molar 8. Third molar 56 Upper Right Upper Left 8 7 6 5 4 3 2 1 1 2 3 4 5 6 7 8 8 7 6 5 4 3 2 1 1 2 3 4 5 6 7 8 Lower Right Lower Left 2 Example: 91 4 Lower left first premolar 1 Upper right permanent central incisor  (18) Essential basics of dental anatomy and physiology 07 The deciduous teeth are lettered from A-E on each side from the midline as follows: A Central incisor B Lateral incisor C Canine D First molar E Second molar 53 Upper Right Upper Left e d c b a a b c d e e d c b a a b c d e Lower Right Lower Left Examples: 9 A Deciduous lower right central incisor. 56 E Deciduous upper left second molar 2- The international numbering system (the two digit system) Within this system the teeth are designed by two digits: a) The first digit Located at the left side It indicates the quadrant 2 For permanent dentition the quadrants are given the numbers 1 to 4 starting from the upper right quadrant in a clockwise manner. For deciduous dentition, digits from 5 to 8 is used. 91 In the permanent dentition. U.R. 1 2 U.L. L.R. 4 3 L. L.  Chapter 1— Introduction and life history of the teeth (19) 07 In the deciduous dentition. U.R. 5 6 U.L. L.R. 8 7 L. L. 53 b) The second digit Located at the right side of the number. It indicates the number of the tooth in the quadrant. For permanent teeth in each quadrant are the numbers from 1 to 8 while for deciduous teeth are from 1 to 5. This is designed from the midline in a 9 distal direction. The two digits should be pronounced separately. example: 11 (one one) = upper right permanent central incisor. 56 Permanent teeth Upper Right Upper Left 18 17 16 15 14 13 12 11 21 22 23 24 25 26 27 28 48 47 46 45 44 43 42 41 31 32 33 34 35 36 37 38 Lower Right Lower Left 2 Deciduous teeth Upper Right Upper Left 91 55 54 53 52 51 61 62 63 64 65 85 84 83 82 81 71 72 73 74 75 Lower Right Lower Left  (20) Essential basics of dental anatomy and physiology 07 3- The universal numbering system (American numbering system): The numbers in this system is always preceded by the sign # to designate that the system is used for universal system. a) For permanent teeth Numbers from 1—32 are used starting from upper right third molar as # 1 to upper left third molar as # 16 descending down to the lower left third molar as # 17 to ends at lower right third molar as # 32 (going around the 53 two arches in a clock wise from upper right to upper left to lower left to lower right at the end). Permanent teeth (1 – 32) 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 9 b)For deciduous teeth Numbers from 1 to 20 are used with adding a small (d) as a suffix to 56 each number to designate deciduous from permanent e. g. deciduous upper right second molar = # d 1. Another common system for deciduous teeth using alphabet from A to T instead of numbers along with the same sequence without using the small (d). Example: lower right deciduous canine would be # R. Deciduous teeth (1 – 20) 2 1 2 3 4 5 6 7 8 9 10 20 19 18 17 16 15 14 13 12 11 91 Deciduous teeth (A - T) A B C D E F G H I J T S T Q P O N M L K  Chapter 1— Introduction and life history of the teeth (21) 07 Anatomical Landmarks of The Tooth Crown There are certain terms that are frequently used to describe the surface anatomy of tooth. These include elevations and depressions. Crown elevations include: Crown depressions include: A) Lobe A) Developmental groove B) Tubercle B) Supplemental groove 53 C) Ridge C) Fissure D) Fossa E) Pits F) Sulcus Crown Elevations 9 A) Lobe : (Fig. 13) It is one of the primary centers of calcification and growth formed dur- 56 ing the crown develop- ment. Each tooth begins to develop from four lobes or more as follows: * Anteriors: have four Fig. 13: Lobes distribution on teeth. lobes (3 labial and 1 lingual). 2 * Upper first and second premolars: have four lobes (3 buccal and 1 lingual) * Lower first premolars and second premolars (2 cusp type) : have four lobes (3 buccal and 1 lingual) 91 * Lower second premolars (3 cusp type): have five lobes (3 buccal and 2 lingual) * Upper first molars: have four lobes (2 buccal and 2 lingual) * Lower first molars: have five lobes (3 buccal and 2 lingual) * Upper and lower second and third molars: have four lobes (2 buccal and 2 lingual)  (22) Essential basics of dental anatomy and physiology 07 Important note: Only some maxillary third molars have as few as 3 lobes. Peg-shaped maxillary lateral incisors and some supernumerary teeth have less than three lobes. The mature forms of lobes are: 1-Mamelons: (Fig.14) These are 3 small rounded projections 53 of enamel present in the incisal third of newly erupted incisors. The pulp chamber of the maxillary incisors has three pulp horns corresponding to these three labial lobes (mamelons). Mamelons wear down due to normal Fig. 14: Mamelons. use into flat incisal edge. 9 2-Cusp: (Fig.15) It is an elevation nearly pyramidal in shape found on the occlusal surface of posterior teeth and the incisal part of canines. It is formed of enamel, 56 dentin and pulp horn. Fig. 15: Cusps. 3-Cingulum :(Fig.16) It is a rounded prominence or bulge on the cervical third of the lingual surface of the crown of anterior teeth. It is also known as the lingual cervical ridge. Fig. 16: Cingulum. 2 B)Tubercle :(Fig.17) It is a small elevation found on some portion of the crown. It is produced 91 by excessive localized formation of enamel. It is commonly found on the palatal surface of upper 6 and upper E (cusp of Carabelli) and sometimes at the lingual surface of incisors over cingulum. Fig. 17: Tubercle.  Chapter 1— Introduction and life history of the teeth (23) 07 C) Ridge: It is a linear elevation on the different surfaces of the crown. Its name is according to location or shape as follows: I) Ridges on the facial surface (Labial and Buccal) 1. Labial ridge: It is found on the labial surface of canine. It represents a highly developed middle labial lobe (Fig.18 a). 53 2. Buccal ridge: It is found on the buccal surface of premolars. It represents highly developed middle buccal lobe (Fig 18 b). 3. Cervical ridge: It is found in the cervical third of labial or buccal surfaces of all teeth. But it is well developed in the deciduous first molar (D) followed by deciduous second molar (E) (Fig.18 c). 9 56 Fig. 18: Ridges on labial & buccal surfaces. 2 II) Ridges on the lingual surface :(Fig 19 a&b) 1. Incisal ridge: It is found on the lingual surface of newly erupted incisors 91 at its incisal margin. The ridge is transformed into edge as the attrition removes some of the incisal enamel. 2. Lingual ridge: It is found in the lingual surface of canines extending from the cusp tip to the cingulum dividing the lingual surface into two fossae.  (24) Essential basics of dental anatomy and physiology 07 Fig. 19 a: (lingual aspect). CL, Cervical line; CI, 53 Maxillary right lateral incisor cingulum; MR, marginal ridge; IR, incisal 9 ridge; LF, lingual fossa. Fig. 19 b: Maxillary Canine (lingual aspect). CL, Cervical line; C, cingulum; MMR, me- sial marginal ridge; DMR, distal marginal ridge LR, lingual ridge; DLF, distolingual fossa ; MLF, mesiolingual fossa; MCR, me- sial cusp ridge; DCR, distal cusp ridge 56 3. Cusp ridge: They are ridges forming an angle at the tip of the cusp from facial and lingual sides. They also are called cusp slopes or arms. (Usually distal cusp slope is longer than mesial cusp slope in all teeth except upper C & 4 where the mesial cusp slope is longer than the distal one) 4. Marginal ridge: It is a linear elevation found on the mesial and distal margins of the lingual surface of anterior teeth. 2 III) Ridges on the occlusal surface of posterior teeth 1. Marginal ridge: It is linear elevation found on the mesial and distal 91 margins in occlusal surface of posterior (Fig. 20 a). 1. Triangular ridge: It is triangular in shape. It is found in posterior teeth. It descends from the cusp tip to the center of the occlusal surface (Fig. 20 b). All posterior teeth cusps have a triangular ridge except the mesiolingual cusp on maxillary molars which has two triangular ridges.  Chapter 1— Introduction and life history of the teeth (25) 07 2. Transverse ridge: It is formed by union of two triangular ridges of two cusps facing each other c rossing the occlusal surface transversely in a buccolingual direction. It is usually found in lower premolars (Fig. 20 c). 3. Oblique ridge: It is formed by union of two triangular ridges of two cusps not facing each other. It crosses the occlusal surface of upper mo- lars obliquely from the mesiolingual cusp to the distobuccal cusp. It is 53 found on occlusal surface of maxillary molars (E,6,7 also may be D,8) (Fig. 20 d). 9 Fig. 20: Ridges on occlusal surfaces. 56 Crown Depressions: 1- Developmental groove: (Fig. 21a) It is shallow linear depression represents the site of union of primary lobes. Grooves are found on the occlusal surface of posterior teeth and may extend to the buccal or lingual surfaces. They are named according to location. 2 Grooves act as spill ways for cusps during lateral and protrusive jaw motions. 2- Supplemental grooves: (Fig. 21a) 91 They are short, irregular linear depressions found usually on the occlusal surface and do not represent union lobes. They are auxillary grooves radiating from the developmental groove. They can be named according to the parts of the tooth on which they are found (mesiobuccal , distolingual supplemental grooves). The third followed by the second permanent molars are characterized by high number of supplemental grooves.  (26) Essential basics of dental anatomy and physiology 07 3- Fissure: (Fig. 21b) It is a linear depression found in the bottom of developmental groove as a result of incomplete union of the primary lobes. It is a fault in enamel. Dental caries often begins in a deep fissure. 4- Fossa: It is small depression found in both anterior teeth and posterior teeth. 53 It is named according to location or shape: a- Lingual fossa: found on the lingual surfaces of anterior teeth (Fig. 19a&b). b- Central fossa: found on the occlusal surface of molars (Fig. 21a). c- Mesial and distal triangular fossa: found on the occlusal surfaces of posterior teeth mesial and distal to marginal ridges of posterior teeth (Fig. 21a). 9 5- Sulcus: (Fig. 21b) It is a broad depression or valley found between the inclined planes of triangular ridges on occlusal surface of posterior teeth. Its inclines meet in a developmental groove and extend to the cusp tips. 56 6- Pit: It is a small pinpoint depression present at the junction or at the end of the developmental grooves. They may be found at the bottom of the central fossa (central pit) or at the bottom of mesial and distal triangular fossae (mesial and distal pits). * A fault pit usually develops as a result of incomplete formation of enamel. They may be found at the end of buccal developmental grooves of lower 2 molars or palatal developmental grooves of the upper molars (Fig. 21c). 91 Fig. 21: Crown depressions.  Chapter 1— Introduction and life history of the teeth (27) 07 Other terms: Self cleansing surfaces: These are the surfaces of teeth which are cleaned by normal functional action of the tongue and cheeks and mouth fluids; facial, lingual and incisal surfaces are considered self cleaning. 53 Crypt: it is bony space in the alveolar bone containing the developing unerupted tooth (Fig. 22). Fig. 22: Crypts and sockets Socket: it is bony space in the alveolar bone containing the roots of erupted tooth (Fig. 22). LIFE HISTORY OF THE TOOTH 9 1- Soft growth stage: (Fig. 23) The deciduous teeth start their development 56 inside the jaw before birth. From 6 weeks in- tra-uterine (wiu) the oral epithelium begins to form the germ of 10 deciduous teeth in each jaw. Most of the permanent teeth start also their development inside the jaw before birth. Fig. 23: Soft tooth germ. The tooth germ is formed of soft tissue and does not appear in the x-ray films. 2 2- Calcification: (Fig. 24 ) Calcification of the hard dental tissues (enamel, dentin and cementum) occurred by 91 specialized cells. The mineralized salts , mostly calcium , from blood will deposited in the soft tissue in form of small spherical bodies, then they will en- Fig. 24: Calcifying tooth germ. large to form primary lobes which fuse to- gether to form the calcified dental tissues.  (28) Essential basics of dental anatomy and physiology 07 3- Eruption: (Fig. 25) Rules Concerning Eruption The eruption of the mandibular teeth precedes the maxillary teeth. The teeth in both sides of the jaw erupt at the same time. 53 Teeth erupt in girls earlier than boys The tooth erupts in the oral cavity when its crown is completely formed as well Fig. 25: Erupted tooth. as third of the root. 4 - Attrition: It is the physiological loss of the hard dental structure due to the con- tinuous friction of the teeth with each other during mastication 9 The attrition is clearly seen in incisal and occlusal surfaces also at the contact point By attrition, the incisal ridges and cusp tips are lost. 56 The contact point is lost and becomes contact area 5- Shedding of the deciduous teeth: (Fig. 26) Shedding: Is the physiological loss of the deciduous teeth and are replaced by their permanent successors. Before shedding of the deciduous 2 teeth by 3 years, their roots begin resorption apically till reach their whole length then their crowns are exfoliated. 91 Fig. 26: Shedding of deciduous anterior teeth. Loss of the permanent or decidu- ous teeth before their shedding time is considered pathological loss of teeth.  CH. 2 56 9 SURFACE ANATOMY OF PERMANENT TEETH 2 53 07 INCISORS CANINES PREMOLAR MOLARS 91 Essential ba s i c s o f d e n ta l a nato m y a n d p h y s i o l o g y  (30) Essential basics of dental anatomy and physiology 07 SURFACE ANATOMY OF PERMANENT TEETH INCISORS MAXILLARY INCISORS 53 General Characteristics: There are four maxillary incisors (two cen- trals and two laterals). The two central incisors are centered in the maxilla, contact each other at the midline. 9 The lateral incisors are distal to the central Fig. 1: The maxillary permanent incisors. incisors (Fig. 1). In some individuals the two upper central 56 incisors are separated by a space called diastema (Fig. 2). The major function of the incisors is incis- ing or cutting the food. Fig. 2: The diastema between the two upper central incisors. The newly erupted incisors or none func- tioning have three small mamelons form- 2 ing the incisal ridge (Fig. 3). These mamelons soon worn away with mas- 91 tication changing the incisal ridge into an in- cisal edge. Fig. 3: Mamelons  Chpater 2 — Surface Anatomy of permanent Teeth (31) 07 Maxillary Central Incisor (Fig. 4) It is the widest of any of the ante- rior teeth. It is the most prominent in the mouth. 53 Labial aspect: (Fig. 5) For proper description of the labial aspect of incisors; First, describe the crown: a. Geometric outline. b. Outline form; proximal (me- 9 sial and distal with reference Fig. 4: Maxillary right permanent central incisor. to the contact areas), cervical and incisal outlines (with reference to the shape of 56 the incisal angles). c. Surface anatomy; elevations and depressions. Second, describe the root: Number, shape and apex (position and shape). 1- The crown: 2 · The geometric outline is trapezoidal with the shortest of the uneven sides is located cervically. Fig. 5: Labial aspect. · The outline form: 91 * The mesial outline: is slightly convex with the maximum convexity (representing the contact area) is in the incisal third near the mesio- incisal angle. * The distal outline: is more convex and the contact area is more cervi- cally, near the junction of the incisal and middle thirds.  (32) Essential basics of dental anatomy and physiology 07 * The incisal outline: newly erupted incisor shows three small mam- elons. These mamelons soon undergo attrition giving a regular and straight incisal edge. The mesioincisal angle is sharp and it nearly forms right angle. The distoincisal angle is rounded. * The cervical outline: convex root-wards. 53 Surface anatomy: * Elevations The labial surface of the crown is smoothly convex with the maxi- mum convexity at the cervical third (cervical ridge). In newly erupted tooth, three mamelons are prominent. * Depressions 9 There are two shallow developmental grooves, which divide the labial surface into three lobes. 2- The root: 56 This tooth has a single root, which is cone-shaped, with blunt centralized apex. Thus this tooth can be extracted by rotational movement. Lingual aspect: (Fig. 6) 1- The crown: The geometric outline and outline form are similar to that 2 of the labial aspect. However, it differs in crown size and surface anatomy. 1- The crown converges lingually to accommodate the U shaped dental arch which has larger size facially 91 than lingually. 2- Surface anatomy: *Elevations The cingulum is a well developed smooth large Fig. 6: convexity occupies the cervical third. Lingual aspect.  Chpater 2 — Surface Anatomy of permanent Teeth (33) 07 The mesial and distal marginal ridges are well developed ridges that extend from the cingulum to the incisal ridge. *Depressions The lingual fossa is a large concavity lies between the marginal ridg- es, the cingulum and the incisal ridge. 2- The root: 53 The lingual surface of the root is convex. It is narrower than the labial sur- face due to lingual convergence. Mesial aspect: (Fig. 7) For proper description of the proximal aspects of incisors; 9 First-Describe the crown: a. Geometric outline. 56 b. Outline form; labial, lingual, cervical and incisal ridge. c. Position of the contact areas. Second-Describe the root: Number, shape and apex (position and shape). 2 1-The crown: · The geometric outline is triangular in shape with the base of the triangle at the cervix and the apex at the 91 incisal ridge. · The outline form: * The labial outline: is convex in the cervical third (cercical ridge) and is slightly convex or nearly Fig. 7: flat, in the middle and incisal thirds. Mesial aspect.  (34) Essential basics of dental anatomy and physiology 07 * The lingual outline: is convex in the cervical third (cingulum), con- cave in the middle third (lingual fossa), and slightly convex at the incisal ridge. * The cervical line: curves incisally to a marked degree. Note; The incisal ridge of the crown is on a line with the center of the root (root axis line). 53 · The contact area: It is centralized (labio-lingually) and in the incisal third near the mesioincisal angle (inciso-cervically). 2-The root: It is cone-shaped. Its apex is centralized and blunt. 9 Distal aspect: (Fig. 8) Geometric outline and outline form are similar to that of the mesial aspect. However, it differs in; 56 1. The crown is somewhat thicker toward the incisal third. 2. The curvature of the cervical line is less distally than on the mesial surface. 3. The distal contact area is still centralized but is located more cervically. 4. The surface of the root is convex and does not have a 2 depression. Fig. 8: Distal aspect. Incisal aspect: (Fig. 9) 91 For proper description of the incisal aspects of incisors; 1. Geometric outline with reference to the type of convergence and the relation between width and thickness. 2. Labial and lingual outlines. Fig. 9: Incisal aspect.  Chpater 2 — Surface Anatomy of permanent Teeth (35) 07 3. Surface Anatomy. The crown outline is triangular, the labial outline forms the base while the apex is lingually (Lingual convergence). * The crown width is larger than its thickness. The labial outline is relatively broad and flat in comparison with the lingual surface. 53 The incisal edge is centrally situated in relation to the thickness. * The lingual fossa is seen as broad concavity between the two marginal ridges and the cingulum. Pulp cavity (Fig. 10) 9 To study the pulp cavity, the teeth should be sectioned both mesiodistally and la- biolingually. Mesiodistally (Fig.10 a); the pulp chamber is trapezoidal in shape and its size is wider in the mesiodistal dimension than in the labioloingual dimension 56 (the pulp cavity follows the general outlines of the crown and the root). In young teeth usually show three pulp horns in the incisal region conforming to the three mamelons present at the incisal border. The pulp chamber tapers in the root to form the root canal that ends at the apical foramen. Labiolingually (Fig.10 b); roughly triangular with pointed incisal edge. 2 91 Fig. 10: Pulp cavity of upper permanent central incisor. a, mesiodistal section. b, labiolingual section.  (36) Essential basics of dental anatomy and physiology 07 Maxillary Lateral Incisors (Fig. 11) The general form of the crown closely resembles that of the upper central. The lateral incisor is smaller in all dimensions than the central incisor except root length. 53. This tooth shows great variations; may show lingual pit, may be cone shaped (peg shaped) due to absence of the middle lobe (Fig. 12) or the tooth may be completely absent. Labial aspect: (Fig.13). 1- The crown: 9 The geometric outline of the Fig. 11: Maxillary right permanent lateral incisor. crown is similar to that of the 56 central incisor. The out line * Mesial and distal outlines resemble that of the central incisor. The mesial contact area is near or at the junction of the incisal and middle thirds while the Fig. 12: Peg shaped lateral incisor. distal is more cervically. 2 * Incisal outline is rounded with distoincisal angle is more rounded than the mesioincisal angle. The mamelones are less pronounced and less common than on the central incisors. 91 * Cervical line is similar to that of central incisor. Surface Anatomy: * The labial surface is similar to that of the upper central incisor, but is more convex. * Labial developmental grooves are less prominent. Fig. 13: Labial aspect.  Chpater 2 — Surface Anatomy of permanent Teeth (37) 07 2- The root: The single root tapers towards a pointed distally curved apex. Lingual aspect: (Fig. 14) The marginal ridges are prominent. Both the cingulum and the incisal ridge are well developed. 53 The lingual fossa is more concave. The palatal pit, if it is found, is enclosed by the cingulum. This pit is prone to decay. Fig. 14: Lingual aspect. Mesial aspect: (Fig. 15) The mesial aspect of the upper lateral 9 incisor is similar to that of a small central incisor except differences in size as mentioned before. The curvature of the cervical line is well marked. 56 Distal aspect: (Fig. 16) The curvature of the cervical line is less in depth than on the mesial side. Fig. 15: Mesial aspect. Fig. 16: Distal aspect. The distal contact area is still centralized but is located more cervically. The distal surface of the root is slightly more convex than mesially. 2 Incisal aspect: (Fig. 17) 91 The incisal aspect of this tooth resembles that of central incisor except in size. The incisal outline is more rounded labially and lingually than that of upper central incisor. When palatal pit is present; it is located in the depth of the lingual fossa. Fig. 17: Incisal aspect.  (38) Essential basics of dental anatomy and physiology 07 Pulp cavity: (Fig. 18) The pulp cavity is similar but smaller than that of central incisor. It consists of a pulp chamber and a single root canal. The pulp chamber does not have three sharp pulp horns as it does in the maxillary central incisor (The mamelones are less pronounced and less common than on the central incisors). 53 Fig. 18: Pulp cavity of upper permanent lateral incisor. a, mesiodistal section. b, labiolingual section. Mandibular Incisors General characteristics: (Fig. 19) There are four mandibular (lower) incisors: 9 two central and two lateral incisors. The lower incisors function with the upper incisors in; cutting of food, speech and maintenance of a good appearance by 56 supporting the lower lip. The lower incisors differ from the upper incisors in the following: 1. They look alike, as their crowns labially Fig. 19: The mandibular permanent incisors. are fan shaped (due to wide incisal measurements and narrow cervix). 2. They are smaller; having smaller mesiodistal dimension than any of 2 the other teeth. The central incisor is somewhat smaller than the lateral incisor, which is the reverse of the situation in the maxilla. 3. Their crowns are wider labiolingally than mesiodistally. 4. Their mamelons worn off soon after eruption. 91 5. Their incisal ridges inclined lingual to the root axis. 6. Their anatomical landmarks are less prominent compared with those of upper incisors. 7. Their mesial and distal contact areas exist near the incisal ridges. 8. Their roots are flattened labiolingually and are longer in proportion to the crown.  Chpater 2 — Surface Anatomy of permanent Teeth (39) 07 Mandibular Central Incisor (Fig. 20 ) It is the smallest tooth in the permanent dentition. The central incisor is the most symmetrical tooth in the permanent dentition. 53 Labial aspect: (Fig. 21) 1- The crown: · The geometric outline of the crown is trapezoidal with the shortest uneven sides is located cervically. · The outline form: 9 * The mesial and distal outlines: are straight and taper evenly to the narrow neck giving the crown fan 56 shaped appearance. Fig. 20: Mandibular left permanent central incisor. The mesial and distal contact areas exist in the incisal third near the incisal angles and nearly at the same level. * The incisal outline: the incisal ridge is straight and is at nearly a right angle to the long axis of the tooth. »» Mamelons are usually present on newly erupted 2 teeth. »» The mesio and distoincisal angles are sharp. * The cervical outline: convex root-wards. 91 Surface anatomy: Fig. 21: Labial aspect. * Elevations »» The labial surface of the crown is smoothly convex with the maximum convexity at the cervical third (cervical ridge). »» In newly erupted tooth, three mamelons are prominent.  (40) Essential basics of dental anatomy and physiology 07 * Depressions There are two shallow developmental grooves that are well demarcated in newly erupted teeth. 2- The root: This tooth has a single root. The labial surface is narrow and convex. The apex is pointed and curved distally. 53 Lingual aspect: (Fig. 22) Both crown and root surfaces are narrower lingually than labially (lingual convergence). The marginal ridges and cingulum are less well developed compared with upper incisors. The incisal ridge is narrow and rounded or flat. The lingual fossa is shallow. 9 Mesial aspect: (Fig. 23) Fig. 22: 1- The crown: Lingual aspect. 56 · The geometric outline is triangular in shape with the base of the triangle at the cervix and the apex at the incisal ridge. · The outline form: * The labial outline: is convex in the cervical third (cervical ridge) and is nearly straight in the middle and incisal thirds. 2 * The lingual outline: is convex in the cervical third (cingulum), concave in the middle third (lingual fossa) and slightly convex at the incisal ridge. * The cervical outline: curves incisally to a marked de- Fig. 23: gree. Approximately one third the length of the crown. 91 Mesial aspect. Note: The incisal ridge is lingual to the root axis (lingual inclination). · The contact area: It is centralized (labiolingually) and in the incisal third near the mesioincisal angle (incisocervically).  Chpater 2 — Surface Anatomy of permanent Teeth (41) 07 2- The root: The labial and lingual outlines of the root are nearly straight from the cervical line to the middle third; then tapers to the rounded apex. The mesial surface of the root is flat with a deep developmental depression. Distal aspect: (Fig. 24) 53 Geometric outline and outlines form are similar to that mesially except; The curvature of the cervical line which is shallower. The root shows a deeper developmental depression and groove at its center. Incisal Aspect: (Fig. 25) 9 The crown outline is diamond. Fig. 24: Distal aspect. * The crown converges lingually. * The crown thickness is larger than its width. 56 The labial and lingual outlines are convex. The incisal edge is lingually situated (lingual inclination) and almost at right angles to a line bisecting the crown labiolingually, which is a characteristic feature of lower Fig. 24: Incisal aspect. central incisor. * The lingual fossa is seen as a shallow concavity between the two marginal ridges and the cingulum. 2 Note, This aspect shows the mesial and distal symmetry of the lower central incisor. 91 Pulp cavity: (Fig. 26) It is similar to that of upper incisors as it has a single root canal and three pulp horns (in newly erupted teeth). Fig. 26: Pulp cavity of lower permanent However, the pulp chamber is narrower central incisor. a, mesiodistal section. b, labiolingual section. mesiodistally than labiolingually.  (42) Essential basics of dental anatomy and physiology 07 Mandibular Lateral Incisor (Fig. 27 ) It is very similar to the lower central incisor. It is slightly larger than the lower central incisor. 53 Labial (a) and lingual (b) aspects: (Fig. 28 a and b) 1- The crown: It resembles that of the lower central incisor with some differences: 1- The lateral incisor has a more 9 fan-shaped appearance. 2- The mesial outline of the crown is often longer than the Fig. 27: Mandibular right permanent lateral incisor. 56 distal outline (as the incisal ridge slopes downward in a distal direction), therefore, it is not as bilaterally symmetrical as the lower central incisor. 3- The distal contact area is more cervically than the mesial contact area. 2 4- The distoincisal angle of the lower lateral incisor is more rounded than the sharp mesioincisal angle (both angles of Fig. 28: a, labial aspect. b, lingual aspect. the lower central incisors are relatively 91 sharp). 5- The cingulum, incisal ridge and marginal ridges are ill developed. However, these ridges are more prominent than in lower central incisor. 6- The cingulum shows distal deviation (it is centralized in the central incisor).  Chpater 2 — Surface Anatomy of permanent Teeth (43) 07 2- The root: It is similar to that of the central incisor, but is slightly longer. Mesial (a) and distal (b) aspects: (Fig. 29 a and b) 53 There is no marked difference between mesial and distal surfaces of lower central and lateral incisors, except for the size of the tooth and the location of the contact area incisocervically. Incisal aspect: (Fig. 30 and 31) Fig. 29: a, mesial aspect. b, distal aspect. The most important feature is the appearance 9 of the crown of the lower lateral incisor to be slightly twisted distolingually on its root in order to allow the incisive ridge to follow the curve of the dental arch. This means 56 that the incisal edge is not at a nearly right angles to a line bisecting the crown and root labiolingually, as is found in lower central Fig. 30: Incisal aspect. incisor. Pulp cavity: The pulp cavity for this tooth is very similar 2 to that of lower central incisor. Fig. 31: Comparison between incisal aspects of both lower central and lateral incisors. 91  (44) Essential basics of dental anatomy and physiology 07 CANINES General characteristics: (Fig. 32) There are one canine in each quadraut. 53 Canines have longer and stronger roots than those of other teeth. Over the labial aspect of their roots there is well developed Fig. 32: The upper and lower permanent canines. 9 bone ridge called the canine eminence giving the canine a very important cosmotic value since they ensure facial expression. 56 Canines are formed of four lobes, (3 labial and 1 lingual), the middle labial lobe is highly developed labially (forming the labial ridge), lingually (forming the lingual ridge) and incisally (forming a well developed pointed cusp). Therefore, the canines are called cuspids. The canines are located between the incisors and premolars, so, they support 2 the two groups in function (tearing and partial cutting). 91  Chpater 2 — Surface Anatomy of permanent Teeth (45) 07 Maxillary Canine (Fig. 33) Labial aspect: (Fig. 34) For proper description of the labial aspect of canines; First, describe the crown: a. Geometric outline. 53 b. Outline form; proximal (mesial and distal with reference to the contact areas), cervical and in- cisal outlines (with reference to the cusp slopes, shape and posi- tion of the cusp tip). c. Surface anatomy; elevations 9 and depressions. Second, describe the root: Number, shape and apex (position and 56 shape). Fig. 33: Maxillary left permanent canine. 1- The crown: · The geometric outline of the crown is trapezoidal with the shortest of the uneven sides is located cervically. · The outline form: * The mesial outline: from the cervical line to the con- 2 tact area is convex. The contact area is nearly at the junction of the middle and incisal thirds of the crown. * The distal outline: from the cervical line to the contact area is concave. The contact area is more cervically 91 Fig. 34: Labial aspect. than mesial (in the middle third). * The incisal outline: The mesial cusp slope is concave while the distal cusp slope is convex and longer than the mesial. The cusp tip is pointed and mesial to the midline (long distal slope). * The cervical outline: convex root-wards.  (46) Essential basics of dental anatomy and physiology 07 Surface anatomy: * Elevations The labial surface of the crown is convex with the maximum convex- ity at the cervical third (cervical ridge). Labial ridge is prominent extending from the cusp tip to the cervical ridge. 53 * Depressions There are two shallow developmental grooves mesial and distal to the labial ridge, which divide the labial surface into three lobes. 2- The root: This tooth has a single root. It is long and slender. The apex is pointed and distally curved. 9 Lingual aspect: (Fig. 35) 1- The crown: The geometric outline and outlines form are similar to that 56 of the labial aspect. However it differs in the crown size and surface anatomy. The crown is narrower lingually than labially (lingual convergence). Similar to incisors, cingulum and marginal ridges (me- sial and distal) are characteristics for the lingual sur- Fig. 35: Lingual aspect. faces of anterior teeth. 2 Lingual ridge: a prominent vertical ridge extends from the cusp tip to the cingulum. Canines are the only teeth that have a promi- nent lingual ridge. 91 Lingual fossae: on each side of the lingual ridge a mesial and distal lin- gual fossae are present. The root: The lingual surface of the root is smooth and convex. It is narrower lingually than labially.  Chpater 2 — Surface Anatomy of permanent Teeth (47) 07 Mesial aspect: (Fig. 36) For proper description of the proximal aspects of canines; First-Describe the crown: a. Geometric outline. b. Outline form; labial, lingual (with reference to the po- sition of the cusp tip) and cervical. 53 c. Position of the contact area. Second-Describe the root: Fig. 36: Mesial aspect. Number, shape and apex (position and shape). 1- The crown: · The geometric outline is triangular in shape with the base of the triangle 9 at the cervix and the apex at the cusp tip. · The outline form: * The labial outline: is convex with the maximum convexity is at the 56 cervical third (cercical ridge). * The lingual outline: is convex in the cervical third (cingulum), straight in the middle third (lingual ridge), and convex in the incisal third representing the cusp tip. * The cervical line: curves incisally to a marked degree. Note; The cusp tip is located labially to the root axis. 2 · The contact area: It is centralized (labio-lingually) and nearly at the junction of the mid- dle and incisal thirds of the crown (inciso-cervically). 91 2-The root: The single root is conical. Its apex is blunt and curved labially. The mesial surface is broad with a shallow longitudinal depression.  (48) Essential basics of dental anatomy and physiology 07 Distal aspect: (Fig. 37) The geometric outline and outlines form are similar to that of the mesial aspect, except; The cervical line has less curvature toward the cusp tip. The contact area is still centeralized but is located more cervically. The depression on the distal surface of the root is more pro- nounced than that on the mesial surface. These vertical de- 53 pressions on the heavy root help to anchor the teeth in their socket bone and help to prevent rotation and displacement. Incisal aspect: (Fig. 38) Fig. 37: Distal aspect. For proper description of the incisal aspects of canines; Similar to that of the incisors in addition to the position of the cusp tip The crown outline is diamond. 9 * The crown converges lingually. * The crown thickness is larger than its width. The labial and lingual surfaces are convex, more than ei- Fig. 38: ther incisor. Incisal aspect. 56 The cusp tip is labial and mesial to the centers of the crown. The labial ridge is very noticeable from this aspect. The lingual ridge extends from the cusp tip to the cingulum in between the two lingual fossae. The cingulum and marginal ridges are also seen from this aspect. Pulp cavity: (Fig. 39) * Mesiodistally (Fig.39 a); 2 The pulp cavity is much narrower in the mesiodistal section than in the incisors. The pulp chamber is pointed incisally with a prominent pulp horn 91 corresponding to the cusp. The root canal is narrow along its entire length. * Labiolingually (Fig.39 b); Wide root canal and pulp chamber Fig. 39: Pulp cavity of upper permanent canine. with pointed pulp horn. a, mesiodistal section. b, labiolingual section.  Chpater 2 — Surface Anatomy of permanent Teeth (49) 07 Mandibular Canine (Fig. 40) It closely resembles the upper canine. Its anatomical landmarks are less developed than those of the upper canine. 53 Labial aspect: (Fig. 41) It resembles that of the upper canine with some differences: Its width is narrower than the upper canine but longer. 9 The mesial outline is nearly straight from the cervical line to the mesial 56 contact area. Fig. 40: Mandibular left permanent canine. The mesial contact area is in the incisal third while the distal is at the junction of the middle and incisal thirds, more cervically located than the mesial contact area. 2 Note: The crown of the lower canine appears longer than that of the upper canine. Sometimes it is longer, but the effect of greater length is emphasized by the narrowness of 91 the crown and incisally positioned contact areas. Fig. 41: Labial aspect. The cusp is less pointed than that of upper canine. The anatomical landmarks are less developed than those of the upper canine. The root is shorter than that of the upper canine with more pointed apex.  (50) Essential basics of dental anatomy and physiology 07 Lingual aspect: (Fig. 42) It is similar to that of the upper canine with some differences; * The lingual ridge is restricted to the incisal third leading to presence of one lingual fossa. * The cingulum and marginal ridges are not prominent Mesial aspect: (Fig. 43) 53 The mesial aspect of the lower canine is similar to that of the upper canine with some differences: The convexity of the labial outline is less prominent due to less developed anatomical landmarks. 9 The lingual outline in the middle third is concave due to absence of long prominent lingual ridge of the upper canine. Fig. 42: Lingual aspect. 56 The cusp tip is pointed and located lingual to the root axis line (lingual inclination) or may be centered over it. The contact area is centralized and in the incisal third. Fig. 43: Mesial aspect. The developmental depression on the root mesially is more pronounced than that on the upper canine root. 2 Distal aspect: (Fig. 44) The curvature of the cervical line is less in depth than on 91 the mesial side. The distal contact area is still centralized but is located more cervically. The developmental depression on the distal side of the Fig. 44: root is deeper than the depression on the mesial side. Distal aspect.  Chpater 2 — Surface Anatomy of permanent Teeth (51) 07 Note; The developmental depression on the root in rare cases may be deep that divide the root into two labial and lingual roots (Fig. 45). Incisal aspect: (Fig. 46) The outline of lower canine from the 53 incisal aspect is similar to that of the upper canine with some differences; Fig. 46: Fig. 45: Lower canine The cusp tip inclined lingually or Incisal aspect. with bifurcated root. centeralized. The lingual ridge is restricted to the incisal third. Pulp cavity: 9 The pulp cavity of lower canine resembles that of the upper canine except the possibility of presence of two separate labial and lingual root canals. 56 Chronology of the permanent anterior teeth is summarized in the following table. Beginning of Crown Root Eruption calcification completion Completion 2 7 y. 1 3 y. before eruption date 3-4 m. 3 y. after eruption date 1 6 y. 91 8 y. 2 10-12 m. 2 3-4 m. 7 y. 11 y. 3 4-5 m. 3 9 y.  (52) Essential basics of dental anatomy and physiology 07 PREMOLARS General characteristics: (Fig. 47) The premolars are so named because they are situated me- sial to the permanent molars (Fig 1 in molars). They replace the deciduous molars, so they are succeda- neum teeth. 53 There are two premolars in each quadrant. They have usually two cusps, buccal and lingual, so they are called bicuspid. This term is misleading, since the lower second premolars may have three cusps. Fig. 47: The upper They are developed from four lobes as anterior teeth, three and lower premolars. buccal and one lingual except the lower second premolar three cusp type developed from five lobes. 9 The middle buccal lobe of the premolars is highly developed. It corresponds to the middle labial lobe of the canine. The cusps of upper and lower first premolars are more sharp than those of the second premolars. 56 The premolars differ from the anterior teeth in the following: a) They have occlusal surfaces with well-developed cusps instead of incisal edges. b) Their marginal ridges are part of the occlusal surface. c) Their crowns are shorter occluso-cervically. d) The contact areas of premolars (and molars) are nearly at the same level, broad and are more cervically than those for anterior teeth. 2 e) Their cervical line is less curved proximally. Function of premolars: —— The premolars assist the canines in tearing of food by the sharp cusps of 91 first premolars and assist the molars in mastication of food by the nearly equal cusps levels of second premolars. —— The premolars function with molars in maintaining the vertical dimen- sion of the face. —— They support the corners of the mouth and cheeks to keep them from sagging.  Chpater 2 — Surface Anatomy of permanent Teeth (53) 07 Maxillary First Premolar (Fig. 48) The maxillary first and second premolars are more alike than the mandibu- lar premolars. It may have two roots (80%). 53 Buccal Aspect : (Fig. 49) For proper description of the buccal aspect of posterior teeth; First, describe the crown: a- Geometric outline. 9 b- Outline form; proximal (mesial and distal with reference to the contact 56 areas), cervical and occlusal out- lines (with reference to the number of cusps (in case of molars),cusp slopes, shape and position of the Fig. 48: Maxillary right first premolar. cusp tip). c- Surface anatomy; elevations and 2 depressions. Second, describe the root: 91 Number, shape and apex (position and shape). 1- The crown: The geometric outline is trapezoidal with the shortest Fig. 49: Buccal aspect. of the uneven side is located cervically.  (54) Essential basics of dental anatomy and physiology 07 The outline form: * The mesial & distal outlines are slightly concave. The mesial con- tact area is localized in the middle third, while the distal one is at the junction of the occlusal & middle thirds. (This is the opposite for all posterior teeth). * The occlusal outline: - The mesial& distal slopes of the buccal cusp are concave and the 53 mesial slope is longer than the distal slope (the opposite of that of canine). - The buccal cusp is long, pointed and its tip is located slightly distal to the center of the tooth (as a result of the long mesial slope). * The cervical line is slightly curved root wise. Surface anatomy: 9 * Elevations: - Buccal ridge extends cervico- occlusally in the middle of the crown. 56 - Cervical ridge at the cervical third. * Depressions: Two shallow vertical developmental grooves mesial and distal to the buccal ridge. 2- The root: it is conical in form with convex surface and pointed distally curved apex. Lingual Aspect: (Fig. 50) 2 1- The crown The lingual surface is narrower than the buccal surface 91 (lingual convergence). The geometric outline is similar to that of the buccal aspect. The outlines form: Fig. 50: * The mesial & distal outlines are slightly convex. Lingual aspect.  Chpater 2 — Surface Anatomy of permanent Teeth (55) 07 * The occlusal outline: The lingual cusp tip is pointed and shorter than the buccal cusp by 1mm (to accommodate the tearing function of the first premolar rather than the grinding function found in the second premolar). * The cervical line is slightly curved root wise. Surface anatomy: 53 The lingual surface is highly convex which is similar to lingual ridge. 2- The roots: - Most of the upper first premolars (80%) have two roots, buccal& lingual roots, 20% have one root or has bifid root at its apical third. The lingual root (if present) is shorter or equal to the buccal root with tapered distally curved apex. 9 56 Mesial aspect: (Fig. 51) For proper description of the proximal aspects of pos- terior teeth; First-Describe the crown: a- Geometric outline. 2 b- Outline form; buccal, lingual, occlusal with reference to the cusps and marginal ridges and cervical. Fig. 51: c- Surface anatomy and position of the contact area. 91 Mesial aspect. Second-Describe the root: Number, shape and apex (position and shape). The geometric outline is trapezoidal with the shortest of the uneven sides is located occlusally.  (56) Essential basics of dental anatomy and physiology 07 The outline form: * The buccal outline is convex with the maximum convexity is at the cervical third. * The lingual outline is convex with the maximum convexity is at the middle third. * The occlusal outline: - The buccal cusp is longer than the lingual cusp by 1 mm, the two 53 cusp tips are sharp. - The buccal cusp tip is in one line with the buccal root apex. - The lingual cusp tip is in one line with the lingual border of the lin- gual root. - The mesial marginal ridge lies in the middle third. * The cervical line slightly curves occlusally. Surface anatomy and position of the contact area: 9 * The mesial marginal ridge is crossed by the mesial marginal develop- mental groove. * Mesial developmental depression (canine fossa) located in the cervical 56 third of the crown and root trunk. * The mesial contact area is localized in the middle third 2- The roots: May be one or two roots but the majority is the bifurcated root at the middle third.There is deep developmental depression along the root trunk. * If one root is present, the root outlines end in a blunt apex above the center of the crown. 2 Distal aspect: (Fig. 52) Is similar to the mesial one except: 91 - No developmental groove crossing the marginal ridge. - The distal marginal ridge is occlusal than the mesial one (the opposite of all other posterior teeth). - No developmental depression on the crown or root. - The contact area is broader and is located more occlus- Fig. 52: ally (this is the opposite for all posterior teeth). Distal aspect.  Chpater 2 — Surface Anatomy of permanent Teeth (57) 07 - The cervical lineis less curved. - The bifurcation is more apical. Occlusal aspect: (Fig. 53) For proper description of the occlusal aspects of posterior teeth; 53 1- Geometric outline with reference to the type of conver- gence and the relation between width and thickness. Fig. 53: Occlusal aspect. 2- Surface anatomy. The geometric outline is roughly hexagonal (two buccal, two proximal and two lingual sides). * The crown converges lingually 9 * The crown thickness is wider than its width. * The mesiobuccal & distobuccal sides are nearly equal in length. * The mesiolingual side is shorter than the distolingual one 56 * The mesial side is shorter than the distal one. Surface anatomy: * Elevations: - Buccal& lingual triangular ridges over the buccal &lingual cusps. - Mesial & distal marginal ridges the distal one is well developed (this 2 is the opposite for all posterior teeth) * Depressions: - Mesial& distal triangular fossae with developmental pits in their bot- 91 toms. - Central developmental groove extends from the two triangular fossae and pass over the mesial marginal ridge as mesial marginal develop- mental groove.  (58) Essential basics of dental anatomy and physiology 07 Maxillary Second Premolar (Fig. 54) Buccal aspect: In comparison to the upper first premolar: - The crown is shorter. 53 - The buccal cusp is less pointed and shorter. - The mesial slope is shorter than the distal slope. - The mesial contact area is in the 9 occlusal third while the distal one is more cervical. Fig. 54: Maxillary right second premolar. 56 - The buccal ridge is less prominent. - The single root (higher percentage) is longer and tapered to an apex that curves distally. Lingual Aspect: - The lingual cusp is nearly equal to the buccal cusp (to accommodate the 2 grinding function of the second premolar rather than the tearing function found in the first premolar). - Has less lingual convergence to accommodate the shape of the dental arch at 91 this region. Mesial & Distal Aspects - The buccal & lingual cusps are equal and are further apart giving wider occlusal surface buccolingual to help for grinding.  Chpater 2 — Surface Anatomy of permanent Teeth (59) 07 - There is absence of the developmental grooves and depressions found on the mesial surface of the first premolar. - The mesial marginal ridge is located more occlusally than the distal one. - The distal surface of the single root has a deeper depression in the middle than mesially. 53 The occlusal aspect - It is less angular and has oval shape. - A shorter central developmental groove due to absence of the mesial marginal developmental groove. - Has multiple supplemental grooves. 9 - The marginal ridges are thicker than those of the first premolar Pulp cavities of upper premolars: (Fig. 55) 56 * Mesiodistally: (Fig. 55 a) - The pulp chamber is pointed occlusally. - The root canal is narrow along its entire length. * Buccolingually: (Fig. 55 b)