1. Overview of the Dentitions Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 1

2. Introduction Dentition is the term used to describe the natural teeth in the jawbones. The dental assistant must know the names, locations and functions of the teeth. The dental assistant must also understand the various systems of numbering the teeth, as well as the patterns of tooth eruption and occlusion. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 2

3. Dentition Periods Although there are only two sets of teeth, there are three dentition periods. Primary Mixed Permanent Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 3

4. Primary Dentition The first set of 20 primary teeth is called the primary dentition. This dentition is commonly referred to as the “baby teeth.” You may also hear the term deciduous dentition. This is an older and less frequently used dental term to describe the primary dentition. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 4

5. Fig. 11-1B Example of the complete primary dentition. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 5

6. Mixed Dentition Mixed dentition generally occurs between the ages of 6 and 12 years. Both primary and permanent teeth are present during this transitional period. The mixed-dentition period begins with the eruption of the first permanent tooth, which is a permanent mandibular first molar. This period ends with shedding of the last primary tooth. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 6

7. Fig. 11-2 An example of the oral cavity during the mixed dentition period. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 7

8. Permanent Dentition The permanent dentition is the final, or adult dentition. This period begins with shedding of the last primary tooth. Growth of the jawbones slows and eventually stops. There is very little growth of the jaw overall during this period because puberty has passed. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 8

9. Fig. 11-3 Facial and buccal view of a permanent dentition. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 9

10. Dental Arches The maxillary arch (upper), which is actually part of the skull, is fixed and not capable of movement. The teeth are set in the maxilla bone. The mandibular arch (lower) is capable of movement through the action of the temporomandibular joint. The mandible is the bone that supports the lower arch of teeth, hence the name “mandibular arch.” Occlusion is the natural contact between the maxillary and mandibular teeth in all positions. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 10

11. Quadrants Dividing the maxillary and mandibular arches into halves yields four sections, which are called quadrants. Each quadrant of permanent dentition contains eight permanent teeth and a quadrant of primary dentition contains five teeth. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 11

12. Fig. 11-4 A, Primary dentition separated into quadrants. B, Permanent dentition separated into quadrants. (From Finkbeiner B, Johnson C: Comprehensive dental assisting, St Louis, 1995, Mosby.) Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 12

13. Fig. 11-5 Permanent dentition separated into sextants. (From Finkbeiner B, Johnson C: Comprehensive dental assisting, St Louis, 1995, Mosby.) Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 13

14. Sextants Sometimes it is necessary to divide the dentition into six parts, each called a sextant. Maxillary right posterior Maxillary anterior Maxillary left posterior Mandibular right posterior Mandibular anterior Mandibular left posterior Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 14

15. Anterior and Posterior Teeth The anterior teeth are the incisors and canines. They are usually visible when people smile. These teeth are aligned to form a smooth, curving arc from the distal (back of the) canine on one side of the arch to the distal canine on the opposite side. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 15

16. Anterior and Posterior Teeth The posterior teeth are the premolars and molars. The posterior teeth are aligned with little or no curvature. These teeth appear to be in an almost straight line. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 16

17. Types and Functions of Teeth Human beings eat both meat and plants. To accommodate this variety in diet, teeth are designed for the cutting, tearing, and grinding of different types of food. The permanent dentition is divided into four types of teeth: Incisors Canines Premolars Molars Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 17

18. Types and Functions of Teeth The primary dentition has: Incisors Canines Molars There are no premolars in the primary dentition. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 18

19. Fig. 11-6 A, Occlusal view of the permanent dentition. Types of teeth are identified through the Universal/National System. (From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.) Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 19

20. Fig. 11-6 B, Occlusal view of the primary dentition. (From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.) Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 20

21. Incisors Incisors are single-rooted teeth with relatively sharp, thin edges. Located at the front of the mouth, the incisors are designed to cut food without the application of heavy force. Incisor means “that which makes an incision or cut.” The tongue side, or lingual surface of the incisor is shaped like a shovel to help guide food into the mouth. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 21

22. Canines Canine teeth are also known as cuspids. They are located at the “corners” of the arch. The canines are designed for cutting and tearing food. They are the longest teeth in the human dentition. Canine teeth have the longest roots of all teeth and are usually the last teeth to be lost. Because of its sturdy crown, long root, and location in the arch, the canine is referred to as the cornerstone of the dental arch. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 22

23. Premolars There are four maxillary and four mandibular premolars. The premolars, also known as bicuspids, are a cross between canines and molars. The pointed buccal cusps hold the food while the lingual cusps grind it. The premolars are not as long as canines and also have a broader surface made for chewing food. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 23

24. Molars Molars are much larger than premolars and usually have four or more cusps. The function of the 12 molars is to chew or grind food. The molars have more cusps than do the other teeth. There are four or five cusps on the occlusal (biting) surface of each molar, depending on the tooth’s location. Maxillary and mandibular molars differ greatly from each other in shape, size, and numbers of cusps and roots. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 24

25. Tooth Surfaces Occlusal surfaces: posterior teeth Incisal surfaces: anterior teeth Lingual surfaces Buccal or facial surfaces Mesial surfaces Distal surfaces Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 25

26. Fig. 11-7 Surfaces of the teeth and their relationships to other oral cavity structures, to the midline, and to other teeth. (From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.) Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 26

27. Anatomic Features of Teeth Anatomic features of the teeth help maintain their positions in the arch and protect the tissues during mastication. Contours Contacts Embrasures Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 27

28. Contours All teeth have a curved surface except when the tooth is fractured or worn. Some surfaces are convex; others are concave. The general principle that the crown of the tooth narrows toward the cervical line is true for all types of teeth. Facial and lingual contours The normal contour of a tooth provides the gingiva with adequate stimulation for health, while protecting it from damage that may be caused by food. Mesial and distal contours These contours provide normal contact and embrasure form. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 28

29. Contacts The contact area is the area of the mesial or distal surface of a tooth that touches the adjacent tooth in the same arch. A proper contact serves the following purposes: Prevents food from being trapped between the teeth. Stabilizes the dental arches by holding the teeth in either arch in positive contact with each other. Protects the interproximal gingival tissue from trauma during mastication. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 29

30. Height of Contour The “bulge” or widest point, on a specific surface of the crown. Contact areas on the mesial and distal surfaces are usually considered the height of contour on the proximal surfaces. Facial and lingual surfaces also have a height of contour. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 30

31. Fig. 11-8 Tooth contours. A, Normal contour. B, Inadequate contour. C, Overcontouring. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 31

32. Fig. 11-9 Example of a permanent anterior tooth with the contact area and height of contour identified. (From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.) Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 32

33. Embrasures When two teeth in the same arch touch, their curvatures next to the contact areas form spaces called embrasures. An embrasure is a triangular space in a gingival direction between the proximal surfaces of two adjoining teeth in contact. Embrasures are continuous with the interproximal spaces between the teeth. All tooth contours, including contact areas and embrasures, are important in the function and health of the oral tissues. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 33

34. Fig. 11-10 Embrasures may diverge facially, lingually, occlusally, or apically. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 34

35. Angles and Divisions of Teeth The crowns and roots of the teeth have been divided into thirds, and junctions of the crown surfaces are described as line angles and point angles. Actually, there are no angles or points on the teeth. Line and point angles are used only as descriptive terms to indicate specific locations. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 35

36. Line and Point Angles An angle is the junction of two or more surfaces of a tooth. A line angle is that angle formed by the junction of two surfaces of a tooth crown along an imaginary line. A point angle is that angle formed by the junction of three surfaces at one point. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 36

37. Fig. 11-11 Line and point angles. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 37

38. Division into Thirds The root of the tooth is divided crosswise into thirds: Apical (nearest the tip of the root) Middle Cervical (nearest the neck of the tooth) The crown of the tooth is divided into thirds in three divisions Occlusocervical division Mesiodistal division Buccolingual division Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 38

39. Fig. 11-12 An anterior tooth and a posterior tooth, with designations for crown and root thirds. (From Bath-Balogh M, Fehrenbach MJ, Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.) Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 39

40. Occlusion and Malocclusion Occlusion is the relationship of the maxillary and mandibular teeth when the jaws are in a fully closed position. Occlusion develops in a child as the primary teeth erupt. Habits such as thumb sucking and improper swallowing habits can affect the occlusion. Proper occlusion of the erupting permanent teeth depends on the occlusion of the primary teeth as they are shed. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 40

41. Occlusion and Malocclusion In centric occlusion, the jaws are closed in a position that produces maximal stable contact between the occluding surfaces of the maxillary and mandibular teeth. Functional occlusion is the contact of the teeth during biting and chewing movements. Malocclusion is an abnormal or malpositioned relationship of the teeth. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 41

42. Fig. 11-13 Lingual view of the teeth in centric occlusion. (From Ash M, Nelson S: Wheeler’s dental anatomy, physiology, and occlusion, ed 9, St Louis, 2010, Saunders.) Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 42

43. Fig. 11-14 Radiograph shows the mesial drift of the mandibular second molar after the first molar has been lost. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 43

44. Angle’s Classification Class I (neutroclusion) Class II (distoclusion) Class II, Division 1 Class II, Division 2 Class III (mesioclusion) Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 44

45. Stabilization of the Arches The dental arch is designed to be stable and efficient as long as its normal arrangement is maintained. Malocclusion or the loss of one or more teeth may greatly reduce the function and stability of the dentition. Closure The stronger posterior teeth come together first Curve of Spee The curvature formed by the maxillary and mandibular arches in occlusion. Curve of Wilson Cross-arch curvature of the posterior occlusal plane. Defined by a line drawn across the occlusal surface of the left mandibular first molar, across the arch, and through the occlusal surface of the right mandibular first molar. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 45

46. Fig. 11-15 A, Curve of Spee. (From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.) Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 46

47. Fig. 11-15 B, Curve of Wilson. (From Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 3, St Louis, 2011, Saunders.) Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 47

48. Tooth-Numbering Systems Universal/National System Palmer Notation System Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 48

49. The Universal/National System Approved by the American Dental Association in 1968. Most commonly used throughout the United States. The permanent teeth are numbered from 1 through 32. Numbering begins with the upper right third molar, works around to the upper left third molar, drops to the lower left third molar, and works around to the lower right third molar. In the Universal Numbering System, the primary teeth are lettered with capital letters from A through T. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 49

50. International Standards Organization System The ISO/FDI system is a two-digit tooth-recording system. The first digit indicates the quadrant, and the second indicates the tooth within the quadrant. The numbering proceeds from the midline toward the posterior. The permanent teeth are numbered as follows: The maxillary right quadrant is 1. The maxillary left quadrant is 2. The mandibular left quadrant is 3. The mandibular right quadrant is 4. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 50

51. The Palmer Notation System Each of the four quadrants is given its own tooth bracket consisting of a vertical line and a horizontal line. This system is a shorthand diagram of the teeth as if the patient’s teeth were being viewed from the outside. The teeth in the right quadrant have the vertical midline bracket to the right of the tooth numbers or letters, just as when you are looking at the patient—the midline is to the right of the teeth in the right quadrant. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 51

52. Fig. 11-16 Palmer notation system. Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved. 52