Morphology and histology


Published on

Morphology and Histology of Primary and Permanent tooth, Dept of Pedodotnics and Preventive Dentistry

Published in: Health & Medicine, Technology
  • Be the first to comment

No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

Morphology and histology

  1. 1. Morphology And Histology of Primary And Permanent teeth R.Hemalatha st 1 Yr
  2. 2. Introduction and Nomenclature The teeth are arranged in upper and lower arches. Those teeth in the upper arch are termed maxillary, because they are set in the upper jaw, which is the maxilla (Plural - maxillae). The teeth in the lower arch are termed mandibular, because they are located in the lower jaw, which is the mandible. The mandible is the movable member of the two jaws, while the maxilla is stationary. • B. The imaginary vertical line which divides each arch, as well as the body, into two approximately equal halves, is the midline. Strictly speaking, this vertical division is not a one-dimensional line at all, but rather a two-dimensional plane, termed the mid-sagittal lane.
  3. 3. • The two approximately equal portions of each arch divided by the midline are termed g&rants, since there are four in the entire mouth. They are termed: • maxillary (upper) right. • maxillary (upper) left. • mandibular (lower) right. • mandibular (lower) left • The manner in which the mandibular teeth contact the maxillary teeth is called occlusion. The term for the process of biting or chewing of food is mastication midline
  4. 4. Classification of Dentitions: • • A. The human dentition is termed heterodont, which means it is comprised of different types, or classes, of teeth to perform different functions in the mastication process. In comparison, a homodont dentition is one in which all of the teeth are the same in form and type. This sort of dentition is found in some of the lower vertebrates. B. Furthermore, man has two separate sets of teeth, or dentitions. This is termed diphyodonta as opposed to monophyodont when there is only one set of teeth, and polyphyodont, when more than two. or continuous, sets of teeth are developed throughout life.
  5. 5. • In man, the two dentitions are termed deciduous and permanent, while the transitional phase when both deciduous and permanent teeth are present is called the mixed dentition period. • 1. Deciduous dentition - The teeth of the first, or primary dentition. They are so named because they are shed like the leaves of deciduous trees in autumn. They erupt into the mouth from about six months to two years of age. Normally there are 20 total deciduous teeth. Other non-scientific names for the deciduous teeth include "milk" teeth, " baby" teeth, and "temporary" teeth. • 2. Permanent dentition -The teeth of the second, or adult dentition. Normally, there are 32 permanent teeth and they erupt from 6-21 years of age.
  6. 6. Classification of Teeth A. Permanent Dentition: As was pointed out, man is a heterodont, which means that more than one type of tooth is found in the human dentitions. Each complete quadrant of the permanent dentition contains eight teeth of differing type and function, as follows: • 1. Incisors (2) - The incisors are the two teeth of each quadrant which are closest to the midline. They are named central and lateral incisors. There functions in mastication are biting, cutting, incising and shearing. There are four permanent incisors per arch, and a total of eight in the mouth. • 2. Canine (1) - The canine is the third tooth from the midline in each quadrant. Its function in mastication is cutting, tearing, piercing, and holding. It also is called a cuspid. There are two permanent canines per arch, and a total of four in the mouth.
  7. 7. • • • 3. Premolars (2) - The premolars are the fourth and fifth teeth from the midline. They are termed first and second premolars. Their masticatory role is tearing, holding, and grinding. They are also called bicuspids. As with the incisors, there are four per arch, and eight total premolars. 4. Molars (3) - The molars are the sixth, seventh, and eighth teeth from the midline. They are termed first, second, and third molars. They are also called six year’s molar, twelve year &, and wisdom tooth, in that order. Their masticatory function is grinding. There are six permanent molars per arch, and twelve total permanent molars. It can thus be seen that there are 16 permanent teeth in a complete arch, and a total of 32 teeth in the permanent dentition.
  8. 8. B. Deciduous Dentition: • Each quadrant of man's deciduous dentition contains the following types of teeth, all of which have a function similar to their permanent complements: • 1. Incisors (2), which are named central and lateral incisors. • 2. Canine (I), or cuspid. • 3. Molars (2), which are named first and second molars. • Therefore, there are five deciduous teeth per quadrant. ten per arch. and a total of twenty in the primary dentition. When compared to the permanent teeth, the primary dentition contains an identical number of incisors and canines, but has no premolars and one less molar per quadrant.
  9. 9. Dentition Periods and Succedaneous Teeth: It has been pointed out that man has two dentitions, but three periods of dentition,since the deciduous and permanent dentitions overlap in time. These periods are summarized in the following manner: 1. Primary dentition period - That period during which only deciduous teeth are present, and occurs from approximately six months to six J ears of age. The primary dentition period ends at about age six, with the eruption of the first permanent tooth. normally the mandibular first molar. 2. Mixed dentition period - That period during which both deciduous and permanent teeth are present. and lasts from approximately 6years to 12 years of age. The mixed dentition period ends and the permanent dentition period begins at round age twelve. with the exfoliation of the last deciduous tooth, normally the maxillary second molar.
  10. 10. 3. Permanent dentition period- That period when only permanent teeth are present, and which begins at approximately twelve years of age and continues through the rest of life.
  11. 11. B. In order for a permanent tooth to erupt into a space where a deciduous tooth is located, the deciduous tooth must first be shed, or exfoliated. The natural process by which deciduous roots are "melted away" to allow for exfoliation is termed resorption. C. Permanent teeth that replace exfoliated deciduous teeth are called succedaneous teeth, which simply means "succeeding" deciduous teeth. Since there are twenty deciduous teeth to be replaced, there must be twenty succedaneous teeth. The permanent teeth that are also succedaneous teeth include the incisors and canines, which replace their deciduous counterparts, and the premolars, which replace the deciduous molars. Therefore, the only permanent teeth which are not succedaneous are the molars. It may be said, then, that all succedaneous teeth are permanent teeth, but all I permanent teeth are not succedaneous teeth.
  12. 12. • Dental Formulae: • A. Dental formula - A number and letter designation of the various types of teeth found in a dentition. The dental formula indicates the dentition of only one side of the mouth, but includes both the upper and lower quadrants, and so must be multiplied by a factor of two to provide the number of teeth in the entire dentition. • B. Thus, the dental formula for man's permanent dentition is as follows: I-2 : C – 1 : P-2 : M-3 2 1 2 3
  13. 13. • The deciduous dentition of man has the following dental formula: I-2 : C – 1 : M-2 2 1 2 • It should be kept in mind that animals other than man may have differing dental formulae
  14. 14. General Eruption Pattern: Both the deciduous and permanent dentitions have a general order, or pattern, of eruption. For the deciduous dentition, this pattern normally is as follows: A. Deciduous Dentition: Eruption Sequence • 1. Mandibular central incisor • 2. Mandibular lateral incisor • 3. Maxillary central incisor • 4. Maxillary lateral incisor • 5. Mandibular first molar • 6. Maxillary first molar • 7. Mandibular canine • 8. Maxillary canine • 9. Mandibular second molar • 10. Maxillary second molar
  15. 15. • As a general rule, mandibular deciduous teeth normally precede their maxillary counterparts in eruption. It can also be said that the deciduous teeth normally erupt in order from the front of the mouth toward the back, even though the canines in each quadrant normally erupt after the first molars.
  16. 16. Deciduous Dentition: Normal Eruption Time Erruption Age • Mandible Order Maxilla • Central Incisor 6 1 7 'I2 • Lateral Incisor 7 2 9 • Canine 16 4 19 • First Molar 12 3 14 • Second Molar 20 5 24 Order 1 2 4 3 5
  17. 17. • • • • • • • • • • • • • Permanent Dentition: Normal Eruption Sequence 1. Mandibular first molar 2. Maxillary first molar 3. Mandibular central incisor 4. Mandibular lateral incisor 5. Maxillary central incisor 6. Maxillary lateral incisor 7. Mandibular canine 8. Mandibular first premolar 9. Maxillary first premolar 10. Mandibular second premolar 11. Maxillary second premolar 12. Maxillary canine
  18. 18. • • • • 13. Mandibular second molar 14. Maxillary second molar 15. Mandibular third molar 16. Maxillary third molar As can be seen. the permanent mandibular teeth normally precede their maxillary counterparts in eruption. as was also the pattern with the deciduous teeth. If the first molar's eruption sequence is ignored, the permanent mandibular teeth exhibit a perfect anterior to poterior order. However, in the maxillary arch not only is the firstmolar out of order the canine normally follows both premolars.
  19. 19. • • • • • • • • • Eruption Age Mandible Order Central Incisor 6-7 2 Lateral Incisor 7-8 3 Canine 9-10 4 First Pre-molar 10-11 5 Second Pre- Molar 11-12 6 First Molar 6-7 1 Second Molar 11-13 7 Third Molar 17-21 8 Maxilla Order 7-8 2 8-9 3 11-12 6 10-11 4 11-12 5 6-7 1 12-13 7 17-21 8
  20. 20. • It should be noted that the eruption sequences and dates presented here are based on the only studies available, which were conducted a number of years ago. More contemporary data has suggested that, in some cases, these figures may not be entirely correct. It has also been suggested that there really may not be a "normal“ eruption pattern which is true for both sexes, and across all racial groups. In other words, the most common eruption sequences may occur in only a relatively small percentage of the total population. However, until the results of longitudinal studies for North American populations are available, "old sequences and dates will be used.
  21. 21. Numbering Systems: • Numbering systems in dentistry serve as abbreviations. Instead of writing out the entire name of a tooth, such as permanent maxillary right central incisor, it is much simpler to assign it a number, letter, or symbol, such as #8 for the universal numbering system. Of the many systems, the three most commonly used will be described. • A. Universal Numbering System: The numbering system which enjoys the widest use today is the universal system. It employs a different number (1-32) in a consecutive arrangement for all permanent teeth, and a number-letter (ld-20d) for each of the deciduous teeth. 1. Permanent Teeth - The universal numbering system assigns a specific number to each permanent tooth. The upper right third molar is #I, the upper right second molar #2, and so forth around the entire maxillary arch to the upper left third molar, which is #16. Since there are no more permanent teeth in the maxillary arch, the succession drops to the lower left third molar which is #17, and continues around the entire mandibular arch where the lower right third molar is #32. For example, tooth #11 is the permanent maxillary left canine.
  22. 22. 2. Deciduous Teeth - The twenty teeth of the deciduous dentition are numbered in the same manner as are the permanent teeth (1-20), except that a small (d) is added as a suffix to each number to designate deciduous. The deciduous upper right second molar is thus #Id, while the upper left second molar is #10d. The lower right canine, for example, is #18d. The most common system in use today for designating deciduous teeth uses the capital letters A through T. The maxillary right deciduous second molar is tooth A and the order progresses in the manner used with the 1-32 system for permanent teeth, so that the mandibular right deciduous second molar is tooth T. • B. Palmer Notation Method: Another commonly used numerical and letter notation scheme for identifying an individual tooth utilizes a simple symbol, which differs for each of the four quadrants. In addition, the numbers 1 through 8 are used to identify permanent central • incisor through third molar in the specified quadrant. Letters A through E, with the quadrant symbol, are used for the deciduous dentition
  23. 23. FDI System: The Federation Dentaire Internationale (FDI), the international dental organization, has introduced a new numbering system, which is an attempt at standardization throughout the world. Although presently not in worldwide use, it may be in the future. It is a simple binomial system, which includes both permanent and deciduous teeth. The first of the two numbers identifies the quadrant, and whether the tooth is permanent or deciduous, as follows: • 1 - Permanent maxillary right quadrant • 2 - Permanent maxillary left quadrant • 3 - Permanent mandibular left quadrant • 4 - Permanent mandibular right quadrant • 5 - Deciduous maxillary right quadrant • 6 - Deciduous maxillary left quadrant • 7 - Deciduous mandibular left quadrant • 8 - Deciduous mandibular right quadrant
  24. 24. • • • • • • • • • • The second number identifies the particular tooth in the quadrant, exactly like the Palmer notation method for permanent teeth (1-8). The deciduous teeth in each quadrant are numbered (1-5), the number increasing in size from the midline posteriorly. Examples in notation utilizing the FDI system are as follows: 18 - Permanent maxillary right third molar 27 - Permanent maxillary left second molar 36 - Permanent mandibular left first molar 45 - Permanent mandibular right second premolar 54 - Deciduous maxillary right first molar 63 - Deciduous maxillary left canine 72 - Deciduous mandibular left lateral incisor 81 - Dbciduous mandibular right central incisor
  25. 25. • • • • • As review, the first designation in the above list (18) can be analyzed as follows: 1-The first number indicates that the tooth is located in the permanent maxillary right quadrant. 8-The second number indicates that the tooth is eighth from the midline, and thus is a third molar.
  26. 26. General Oral and Dental Anatomy: brief definition and description of the various anatomical features of a normal tooth, and its supporting structures, include the following: A. Dental Structures: • 1. Anatomical crown - That portion of the tooth which is covered by enamel. • 2. Clinical crown - That portion of the tooth which is visible in the mouth. The clinical crown may, or may not, correspond to the anatomical crown, depending on the level of the tooth's investing soft tissue, and so may also include a portion of the anatomical root. As can be seen from this description, the clinical crown may be an ever changing entity throughout life, while the anatomical crown is a constant entity.
  27. 27. • 3. Anatomical root - That portion of the tooth which is covered with cementum. • 4. Clinical root - That portion of the tooth which is not visible in the mouth. Again, the clinical root is an ever changing entity, and may, or may not, correspond to the anatomical root. Note: In the dental literature, the modifying terms "clinical" and "anatomical“ are not often used with crown or root, but the intended meaning is most often "anatomical" and so will be used in this manner hereafter. • 5. Enamel - The hard, mineralized tissue which covers the dentin of the anatomical crown of a tooth. It is the hardest living body tissue, but is brittle, especially when not supported by sound underlying dentin. • 6. Dentin - The hard tissue which forms the main body of the tooth. It surrounds the pulp cavity, and is covered by the enamel in the anatomical crown, and by the cementum in the anatomical root. The dentin constitutes the bulk, or majority, of the total tooth tissues, but because of its internal location, is not directly visible in a normal tooth.
  28. 28. • 7. Cementum - The layer of hard, bonelike tissue which covers the dentin of the anatomical root of a tooth. • 8. Cervical line - The identifiable line around the external surface of a tooth where the enamel and cementum meet. It is also called the cemento-enamel junction or CEJ. The cervical line separates the anatomical crown and the anatomical root, and is a constant entity. Its location is in the general area of the tooth spoken of as the neck or cervix • 9. Dentino-enamel junction or DEJ - The internal line of meeting of the dentin and enamel in the anatomical crown of a tooth. • 10.Pulp - The living soft tissue which occupies the pulp cavity of a vital tooth. It contains the tooth's nutrient supply in the form of blood vessels, as well as the nerve supply.
  29. 29. Pulp Cavity - The entire internal cavity of a tooth which contains the pulp. It consists of the following entities: • a. Pulp canal(s) - That portion of the pulp cavity which is located in the root(s) of the tooth. and may also be called the root canal(s). • b. Pulp chamber - The enlarged portion of the pulp cavity which is found mostly in the anatomical crown of the tooth. • c. Pulp horns - The usually pointed incisal or occlusal elongations of the • pulp chamber which often correspond to the cusps, or lobes of the teeth
  30. 30. 1 1. Pulp Cavity - The entire internal cavity of a tooth which contains the pulp. It consists of the following entities: • a. Pulp canal(s) - That portion of the pulp cavity which is located in the root(s) of the tooth. and may also be called the root canal(s). • b. Pulp chamber - The enlarged portion of the pulp cavity which is found mostly in the anatomical crown of the tooth. • c. Pulp horns - The usually pointed incisal or occlusal elongations of the pulp chamber which often correspond to the cusps, or lobes of the teeth.
  31. 31. • B. Supporting Structures: • 1. Alveolar process - The entire bony entity which surrounds and supports all the teeth in each jaw member. • 2. Alveolus (Plural - alveoli) - The bony socket, or portion of the alveolar process, into which an individual tooth is set. • 3. Periodontal ligament (membrane) - The fibrous attachment of the tooth cementum to the alveolar bone. • 4. Gingiva (Plural - gingivae) - The "gum" or "gums", or the fibrous tissue enclosed by mucous membrane that covers the alveolar processes and surrounds the necks of the teeth.
  32. 32. Dimensions (Deciduous teeth) Maxillary(in millimeters)
  33. 33. Primary Maxillary Central Incisor Primary Maxillary Central Incisor • Labial Aspect • Smooth labial surface. • The M-D diameter is greater than the cervicoincisal length. • Incisal edge is nearly straight • Developmental lines are usually not seen. • The root is cone-shaped with even, tapered sides. • The root length is greater than crown length than that of the permanent central incisor.
  34. 34. • • • • • Lingual Aspect Well-developed marginal ridges ,highly developed cingulum seen The cingulum extends up toward the incisal ridge ,practically dividing into a mesial and distal fossa. The root narrows lingually ,whereas its flat surface labially..
  35. 35. Mesial and Distal Aspects Similar - The measurement of the crown at the cervical third shows the crown to be wide in relation to its total length. • The curvature of the cervical line is curving towards the incisal ridge • The cervical curvature distally is less than the curvature mesially • The root is cone-shaped with even, tapered sides, apex is blunt • Usually Mesial has a developmental groove and distal is generally Convex
  36. 36. The Pulp Cavity • • • • • Consist of 3 slight projections on incisal border i.e. 3pulp horns Chamber tapers in M-D diameter cervically, widest at cervical region Labiolingually Pulp chamber and Canal are larger than permanent ones. No distinct demarcation between canal &chamber Pulp canal tapers evenly until ending in apical foramen
  37. 37. Incisal Aspect • • • The incisal edge is centered over the main bulk of the crown and is relatively straight. The labial surface is much broader and also smoother than the lingual surface. The lingual surface tapers towards the cingulum.
  38. 38. Primary Maxillary Lateral Incisor • • Similar to the central incisor from all aspects, but its dimensions differ width. The disto-incisal angles of the crown are more rounded than those of the central incisor.
  39. 39. Primary Maxillary Lateral Incisor • • The pulp chamber follows the contour of the tooth, as does the canal The root has similar shape, but is longer, thinner and tapering
  40. 40. PRIMARY MANDIBULAR CENTRAL INCISOR • • • • • • Labial Aspect Flat face ,No developmental grooves Mesial and distal sides of the crown are tapered evenly from the contact areas, with the measurement being less at the cervix Crown is wide in proportion to its length The heavy root trunk permanent maxillary lateral incisor. The root is long and evenly tapered down to the apex, which is pointed. The root is almost twice the length of the crown
  41. 41. Lingual Aspect • • The marginal ridges, cingulum - located easily Middle third may hay a flattened surface/ incisal third slight concavity lingual fossa. • Lingual Convergence of the crown and root is seen
  42. 42. Mesial Aspect • • • • • The incisal ridge is centered over the center of the root The convexity of the cervical contours labially and lingually at the cervical third is Most pronounced More pronounced by far than the prominences found on a permanent mandibular central incisor. These cervical bulges are important. The mesial surface of the root is nearly flat and evenly tapered; the apex blunt.
  43. 43. Distal Aspect • • Outline : Opp of mesial • Cervical line is less curved. • Developmental depression is evident on the distal side of the root Pulp Cavity • • • • • Widest mesiodistally at the roof Labiolingually the is widest at the cingulum Oval in appearance, tapers as it reaches apex Definite demarcation between chamber and canal
  44. 44. Incisal Aspect • • • The incisal ridge is straight and bisects the crown labiolingually. A definite taper is evident toward the cingulum on the lingual side. The labial surface from this view presents a flat Mir surface that is slightly convex, whereas the lingual surface presents a flattened surface that is slightly concave.
  45. 45. MANDIBULAR LATERAL INCISOR • • • • • The fundamental outlines are similar to those primary central incisor. These two teeth supplement each other in function. Somewhat larger in all measurements except labiolingually, where the two teeth are practically identical. Cingulum of the lateral incisor may be a little more generous than that of the central incisor Crown root ratio is more in lateral than in central
  46. 46. MANDIBULAR LATERAL INCISOR • • • The lingual surface of the crown between the marginal ridges may be more concave. Incisal ridge tends to slope downward distally. This design lowers the distal contact area apically, so that proper contact may be made with the mesial surface of the primary mandibular canine
  47. 47. Pulp Cavity • Oval in appearance, tapers as it reaches apex • No demarcation between chamber and canal
  48. 48. Primary Maxillary Canine • • • • • • • LABIAL SURFACE • The crown is more constricted at the cervix in relation to its M-D width. The mesial and distal surfaces are more convex. It has a long, well-developed, sharp cusp. • The cusp on the primary canine is much longer and sharper ,than permanent Contact areas are at the same level, which is not the same in permanent The Mesial slope of the cusp is longer than the distal slope The root of the primary canine is long, slender, and tapering and is more than twice the crown length
  49. 49. LINGUAL SURFACE • • • Shows well pronounced enamel ridges that merge with each other This lingual ridge divides the lingual surface into shallow mesiolingual and distolingual fossae The root of this tooth tapers lingually and is usually inclined above the middle third
  50. 50. Mesial Aspect • • • Similar to that of the lateral and central incisors.• Difference in proportion is evident. The measurement labiolingually at the cervical third is much greater. * This permits resistance against forces the tooth must withstand during function. * The function of this tooth is to punch, tear, and apprehend food material. Distal Aspect • • The distal outline of this tooth is the reverse of the mesial aspect. Only difference being, Cervical line towards the cusp ridge is less than on the mesial surface.
  51. 51. Pulp Cavity • • • • There is a little demarcation between pulp chamber and the canal. The canal tapers as it approaches the apex. Pulp chamber follows the external contour of teeth. Central pulpal horn is projecting incisally.
  52. 52. Incisal Aspect • • • diamond-shaped The angles that are found at the contact areas mesially and distally are more pronounced and less rounded than those on permanent canines. Mesial cusp slope is longer than the distal cusp slope, i.e for Intercuspation with the lower
  53. 53. MANDIBULAR CANINE • • • • Little difference in function between the mandibular canine and the maxillary canine. The crown is perhaps 0.5 mm shorter, The root is at least 2 mm shorter . The M-D measurement at the root trunk is greater when compared with its M-D measurement at the contact areas, than is that of the maxillary canine It is "thicker" accordingly at the "neck" of the tooth.
  54. 54. • • • The deciduous maxillary canine is much larger labiolingually The cervical ridges labially and lingually are not quite as pronounced as those found on the maxillary canine. The greatest variation is the distal cusp slope is longer than the mesial slope.
  55. 55. Pulp Cavity • Wide mesiodistally as labiolingually • No cliff between canal &chamber • Ends in marked constriction at the apex
  56. 56. PRIMARY MAXILLARY FIRST MOLAR • Buccal Aspect • • The widest measurement of the crown of the maxillary first molar is at the contact areas mesially and distally From these points, the crown converges toward the cervix, with the mm at the cervix being fully 2 mm less than the mm at the contact areas. * This furnishes a narrower look to the cervical portion of the crown and root, than compared to permanent maxillary first molar.
  57. 57. • • • • • • The occlusal line is slightly scalloped but with no definite cusp form. Smooth buccal surface, little evidence of developmental grooves seen. Relatively smaller than Second molar THE ROOT The roots of the maxillary first molar are slender and long, and they spread widely. All three roots may be seen from this aspect. The distal root is shorter than the mesial one. The bifurcation of the roots begins almost immediately at the site of the cervical line (CEJ). * Actually which includes a trifurcation, and this is a characteristic of all primary molars, whether maxillary or mandibular. Permanent molars do not possess this characteristic. * The root trunk on permanent molars is much heavier, with a greater distance between the cervical lines to the points of bifurcations a
  58. 58. Lingual Aspect • • • The general outline of the lingual aspect of the crown is similar to that of the buccal aspect. The crown converges considerably in a lingual direction, which makes the lingual portion calibrate less mesiodistally than the buccal portion.
  59. 59. • • • • • • The mesiolingual cusp is the most prominent cusp on this tooth. It is the longest and sharpest cusp. The distolingual cusp is poorly defined; it is small and rounded. The distobuccal cusp may be seen, since it is longer and better developed than the distolingual cusp. All three roots also may be seen from this aspect. The lingual root is larger than the others.
  60. 60. Mesial Aspect • • • • The dimension of cervical third is greater than occlusal third The mesiolingual cusp is longer and sharper than the mesiobuccal cusp. A pronounced convexity is evident on the buccal outline of the cervical third *characteristic bulge It actually gives the impression of overdevelopment in this area
  61. 61. • • • • The mesiobuccal and lingual roots are visible The distobuccal root is hidden behind the mesiobuccal root. The lingual root from this aspect looks long and slender and extends lingually to a marked degree. It curves sharply in a buccal direction above the middle third
  62. 62. Distal Aspect • • • From the distal aspect, the crown is narrower distally than mesially; it tapers markedly toward the distal end. The distobuccal cusp is long and sharp, and the distolingual cusp is poorly developed. The prominent bulge seen from the mesial aspect at the cervical third does not continue distally.
  63. 63. • • • The cervical line may curve occlusally, or it may extend straight across from the buccal surface to the lingual surface. All three roots may be seen from this angle, but the distobuccal root is superimposed on the mesiobuccal root so that only the buccal surface and the apex of the latter may be seen. The point of bifurcation of the distobuccal root and the lingual root is near the CEJ and, as described earlier, is typical.
  64. 64. Occlusal Aspect • • • • • • The crown outline converges lingually. The crown also converges distally. Outline however is rectangular, with the shortest sides of the rectangle represented by the marginal ridges The occlusal surface has a central fossa. A mesial triangular fossa is just inside the mesial marginal ridge, with a mesial pit in this fossa and a sulcus with its central groove connecting the two fossae. A well-defined buccal developmental groove divides the mesiobuccal cusp and the distobuccal cusp occlusally.
  65. 65. • • Supplemental grooves radiate from the pit in the mesial triangular fossa as follows: -one buccally, one lingually, and one toward the marginal ridge,with the last sometimes extending over the marginal ridge mesially. Oblique ridge. The distal marginal ridge is thin and poorly developed in comparison with the mesial marginal ridge
  66. 66. Pulp Cavity • Pulp Cavity Consists of a chamber Straight 3 pulpal canals corresponding to 3 roots • Variations from this basic design may be present as anastomoses & branchings. • 3-4 pulp horns Pulp horn sizes MB>ML>DB
  67. 67. • • • • Mesio-buccal horn is the largest of pulpal horns occupying a prominent portion of pulp chamber. Mesiolingual pulpal horn is second in size,quite angular & sharp. Distobuccal horn is smallest , sharp & occupies distobuccal angle. Occlusal view of the pulp chamber resembles somewhat a triangle with rounded corners
  68. 68. Clinical Significance • • • • Narrow occlusal table Mb pulp horn Distal surface Cervical Constriction
  69. 69. Primary Maxillary Second Molar • Buccal aspect • The characteristics resemble those of first permanent molars , but is smaller. • The buccal view shows two well defined buccal cusps with buccal development grooves between them. • The crown is narrow at the cervix in comparison with its M-D measurement at the contact areas.
  70. 70. • The crown is much larger then that of first primary molar • Roots are slender , are much longer and heavier ten maxillary first molar • The point of bifurcation between buccal roots is close to the cervical line of crown. • The two buccal cusps are more nearly equal in size and development than those of permanent max 1st molar.
  71. 71. • • • • Lingual Aspect 3 cusps seen Mesiolingual cusp- large and well developed Distolingual cusp- well developed more then primary 1st molar • Third supplemental cusp- apical to mesiolongual cusp called the tubercle of carabelli, or fifth cusp • The cusp is poorly developed and merely acts as a buttress or supplement to bulk of mesiolingual cusp.
  72. 72. • If the tubercle if carabelli seems to be missing, some traces of developmental lines or dimples • A well defined developmental grooves separates mesiolingual cusp from distolingual and connects with developmental groove which outlines with fifth cusp • All three roots are visible from this aspect • Lingual root is large and thick in comparison with other two roots • Approx the same length as mesiobuccal root .
  73. 73. • Mesial Aspect • The crown has a typical molar outline that resembles that of the permanent molars very much • • The crown appears short because of its width buccolingually in comparison with its length. • The crown of this tooth is usually only about 0.5 mm longer than the crown of the first deciduous molar, but the buccolingual measurement is 1.5 t 2 mm greater. • In addition, the roots are 1.5 to 2 mm longer.
  74. 74. • The mesiolingual cusp of the crown with its supplementary fifth cusp appears large in comparison with the mesiobuccal cusp. • The mesiobuccal cusp from this angle is relatively short and sharp. • Little curvature to the cervical line is evident. • Usually, it is almost straight across from buccal surface to lingual surface.
  75. 75. • The mesiobuccal root from this aspect is broad and flat. The lingual root has somewhat same curvature as of 1 molar. • The mesiobuccal root extends lingually far out beyond the crown outline. • The point of bifurcation between the mesiobuccal root and the lingual root is 2 or 3 mm apical to the cervical line of the crown
  76. 76. • Distal Aspect • From both the distal and the mesial aspects, the outline of the crown lingually creates a smooth, rounded line, • whereas a line describing the buccal surface is almost straight from the crest of curvature to the tip of the buccal cusp. • The distobuccal cusp and the distolingual cusp are about the same in length. • The cervical line is approximately straight, as was found mesially
  77. 77. • All three roots are seen from this aspect, although only a part of the outline of the mesiobuccal root may be seen, since the distobuccal root is superimposed over it. • The distobuccal root is shorter and narrower than the other roots. • The point of bifurcation between the distobuccal root and the lingual root is more apical in location than any of the other points of bifurcation.
  78. 78. • Occlusal Aspect • From the occlusal aspect, this tooth resembles the permanent first molar • It is somewhat rhomboidal and has four well-developed cusps : mesiobuccal, distobuccal, mesiolingual, distolingual, and fifth supplemental cusp. • The buccal surface is rather flat with the developmental groove between the cusps less marked than that found on the first permanent molar.
  79. 79. Pulp Cavity • The pulp cavity consist of a pulp chamber & 3 pulp canals corresponding to three roots. • These canals leave floor of chamber at the mesiobuccal & distobuccal corners & from lingual area. • Pulp chamber has 4 pulpal horns, a fifth horn projecting from lingual aspect of mesiolingual horn may be present. • The mesiobuccal pulp horn is largest, pointed & extends occlusally
  80. 80. • Mesiolingual pulp horn is second in size, when combined with fifth horn it presents a bulky appearance. • Distobuccal pulp horn is third in size, joining mesiolingual pulp horn as slight elevation. • Distolingual pulp horn is shortest & extends only slightly above occlusal level.
  81. 81. Primary Mandibular First Molar • It appears strange and primitive • Buccal Aspect • The mesial outline of the crown is almost straight from the contact area to the cervix • The distal portion converges toward the cervix more than usual, so that the contact area extends distally to a marked degree. • The distal portion of the crown is shorter than the mesial portion, with the cervical line dipping apically where it joins the mesial root.
  82. 82. • • No developmental groove is evident between them • The mesial cusp is larger than the distal cusp. • A developmental depression dividing them (not a groove) extends over to the buccal surface. THE ROOT • The roots are long and slender, and they spread greatly at the apical third beyond the outline of the crown. • The buccal aspect emphasizes the strange, primitive look of this tooth.
  83. 83. • Lingual Aspect • Mesially, the crown and root converge lingually to a marked degree • • Distally, the opposite is true of both crown & root. • The distolingual cusp is rounded. • The mesiolingual cusp is long and sharp at the tip. • The sharp and prominent mesiolingual cusp is an • outstanding characteristic • Mesial marginal ridge is well developed. • Part of the two buccal cusps may be seen from this
  84. 84. Mesial Aspect • The mesiobuccal cusp and the mesiolingual cusp are in view from this aspect, also the well-developed mesial marginal ridge. • Cervical line slanted upwards buccolingually • The buccal and lingual outlines of the root drop straight down and are approximately parallel for more than half their length, tapering only slightly at the apical third
  85. 85. • The root end is flat and almost square. • A developmental depression usually extends almost the full length of the root on the mesial side.
  86. 86. Distal Aspect • Cervical line does not drop bucally • Cervical line is almost straight • Distobuccal cusp and distolingual cusp are not as long or as sharp as mesial cusps • Distal marginal ridges not as straight and well defined as mesial marginal ridge • Distal root is rounded and shorter and tapers more apically
  87. 87. Occlusal aspect • Crowns outlines converges lingually and also distally • Occlusal surface is more nearly rectangular with shorted sides of the rectange represented by marginal ridges • Occlusal surface has central fossa • Mesial triangular fossa is just inside the mesial marginal ridge , with a mesial pit in this fossa and a sulcus with its central groove connecting the two fossae
  88. 88. • A well defined buccal developmental groove divides mesiobuccal cusp and distobuccal cusp occlusally • Supplemental grooves radiate from the pit in mesial triangular fossa as follows • -one buccally , one lingually and one towards the marginal ridge with last sometimes extending over the marginal ridge mesially
  89. 89. Pulp Cavity • Pup cavity contains a chamber and 3 canals • Mesiobuccal and mesiolingual canals are confluent and leave the chamber in the form of a ribbon • The distal pulp canal projects in ribbon fashion floor of chamber in distal aspects
  90. 90. • Pulp chamber had 4 pulpal horns • Mesiobuccal horn- largest and rounded • Distobuccal pulp horn-is second , but lacks height of mesial horns • Mesiolingual Horn is third in size and second in height , while • Distolingual pulpal horn is smallest • Occlusal view of pulp chamber is rhomboidal
  91. 91. • Clinical significance • Cavity preparation • Mesiobuccal pulp horn
  92. 92. Mandibular second molar • It has characteristics that resembles those of Permanent mandibular first molar, although its dimensions differ • Buccal Aspect • IT has a narrower M-D calibration at the cervical Portion of the crown than at contact level • The mandibular first permanent molar, accordingly is wider at the cervical portion
  93. 93. • The roots are slender and long • Characteristic flare mesioditally at the middle and apical thirds • The point of Bifurcation of the roots starts immediately below the CEJ
  94. 94. Lingual Aspect • Two cusps are almost equal dimensions • Seen , a short , lingual groove is • between them • The cervical line is relatively Straight • The mesial Portion of the crown seems to be a little higher then the distal portion , thus appears tipped distally
  95. 95. Mesial Aspect • Outline resembles permanent mandibular First molar • The crest of contour is more prominent bucally • Marginal ridge is high • The lingual cusp is longer or higher then Buccal cusp • Cervical line is regular • Mesial root is unusually broad and flat with a blunt and apex sometimes serrated
  96. 96. • The cervical line is regular • The distal root is almost as broad as the mesial root and is flattened on distal surface • The distal root tapers more at the apical end than does the mesial root
  97. 97. Distal Aspect • Crown is not as wide distally as it is. • Mesially, therefore mesiobuccal and distobuccal cusps from the distal aspect • The distolingual cusp appears well developed and triangular ridge Is seen over the distal marginal ridge • The distal marginal ridge dips down more • sharply and is shorter buccolingually than mesial marginal ridge
  98. 98. Occlusal Aspect Occlusal outline is some what rectangular Three buccal cusps are similar in Size Two lingual cusps are also equally Matched Well defined triangular ridges seen The distal triangular fossa is not well defined as mesial triangular fossa • The mesial marginal ridge is better developed and more pronounced than the distal marginal ridge • Supplemental grooves are seen on the slopes of triangular ridges and in the mesial and distal triangular fossa • • • • • •
  99. 99. Pulp Cavity • Pulp cavity is made up of chamber and usually 3 pulp canals • Two mesial pulp canals are confluent as they leave floor of pulp chamber through A common orifice • Distal canal is constricted in the centre
  100. 100. • Pulp chamber has 5 pulp horns corresponding to 5 cusps • Mesiobuccal and Mesiolinual Pulp Horns are largest • Distobuccal horn is smaller then mesial horns • The distal horn is shorter and smallest occupying a position distal to distobuccal horn
  101. 101. How it differs from Permanent • In the deciduous molar the M-B,D-B, and the distal cusps are almost equal in size and development • The distal cusp of the permanent molar is smaller than the other two • Because of the small buccal cusps, deciduous tooth crown is narrower bucolingually,in comparison with its mesiodistal measurement, than is the permanent tooth
  102. 102. Permanent Incisors • The permanent incisors are the first and second teeth from the midline, which, • along with the canines, comprise the anterior teeth of each quadrant. The incisor • closest to the midline is termed the central incisor, while the second tooth from the • midline is the lateral incisor. This positions the lateral incisor distal to the central • incisor and mesial to the canine.
  103. 103. • In size, the maxillary • incisor crowns are generally larger than those of the mandibular incisors. In the • maxillary arch, the central incisor crown is normally larger than the crown of the • lateral incisor. However, in the mandibular arch, the lateral incisor crown and root • are generally larger than those of the central incisor, although only very slightly
  104. 104. • The incisors as a group participate in all three of the major functions of the • human dentition and have a greater role in esthetics and phonetics than any other • group of teeth. • 1. Mastication - They function by biting, cutting, incising and shearing, thus • breaking the food particles into smaller pieces suitable for grinding. • .
  105. 105. • 2. Esthetics - Not only do the size, shape, color, and manner of placement of • incisors directly contribute to a person's appearance, but they provide the support • necessary for the normal profile of the lips and face. • 3. Phonetics - They are necessary for the execution of certain sounds
  106. 106. Labial Aspect • The mesial margin is straight and meets the incisal edge at right angle. The distal margin is shorter and more rounded. • The distoincisal angle is more rounded than the mesioincisal angle. • The labial surface is marked by two developmental groove and has convexity in cervical third. • Maxillary central incisor is the widest anterior tooth mesiodistally
  107. 107. Lingual Aspect • The crown profile is same as that of labial surface except that there is a broad depression in the central portion called the lingual fossa and a well developed cingulum. • The lingual fossa is bordered by mesial and distal marginal ridges on the sides Lingual aspect and the cingulum cervically. • The cervical line on labial and lingual surface is convex apically.
  108. 108. Mesial aspect • From the mesial aspect the labial • margin is convex • The lingual margin is ‘S’ shaped, being convex near cingulum and concave in the middle • Mesial curvature of cervical line (3.5mm) is the most pronounced compared to any other tooth. • The cervical line on the mesial and distal surface is convex incisally
  109. 109. • Distal surface • is very similar to the mesial surface. • This outline is also convex, but more rounded than on the mesial, as is the distoincisal angle. • The crest of curvature is associated with the contact area,which is located • in the incisal third very near the junction of the incisal and middle thirds, and so is farther cervically than it is on the mesial. • Although the cervical half of the mesial and distal outlines is normally convex, either outline can be nearly straight, in comparison to the almost always convex incisal half.
  110. 110. Incisal aspect • The crown and incisal margin are centered over root • Crown profile is almost bilaterally symmetrical • The incisal margin of newly erupted teeth show three elevations called mamelons. They correspond to the developmental lobes
  111. 111. • Root  The root is straight and tapers from the cervical line to the apex giving it a conical shape  The root ends in a blunt apex. Average Dimensions in millimeters Crown Root Length Length 10.5 13.0 Mesiodistal Diameter at Contact Area 8.5 Mesiodistal Diameter at Cervical Line 7.0 Labiolingual Diameter at Crest of Curvature 7.0 Labiolingua l Diameter at Cervical Line 6.0 Curvature of Cervical Line M D 3.5 2.5
  112. 112. Maxillary Lateral Incisor • The general shape is similar to maxillary central incisors except that they are shorter and narrower. • Next to third molars maxillary lateral incisors are the teeth that show most variation in crown size, shape and form
  113. 113. • Labial Aspect • The mesioincisal and distoincisal angles are more rounded than the corresponding angles of the maxillary central incisor Maxillary Lateral Distoincisal angle more rounded Mesioincis al angle more rounded Maxillary Central Incisor Distoincisal angle Mesioincisal angle
  114. 114. • On the lingual aspect the marginal ridges and cingulum are more prominent Prominent marginal ridges Prominent cingulum
  115. 115. Labial aspect Mesial aspect Lingual aspect Distal aspect
  116. 116. CANINES • Canines are very long and stable teeth There are four canines placed at the corner of the mouth and hence called the ‘corner stones’ of the dentition They have a single pointed cusp (also called cuspids) Maxillary canine erupts between 10-12 years and mandibular canine erupts between 9-10 years of age
  117. 117. Maxillary Canine Labial aspect  The crown of maxillary canine is narrower mesiodistally than that of maxillary central incisor. The incisal aspect has a large cusp with a pointed cusp tip It has two slopes (cusp ridges), the mesial slope being shorter than the distal slope • The labial surface is smooth and bulky in the middle because of the labial ridge  • • •
  118. 118. Lingual aspect • The crown and root are narrower lingually • The cingulum is well developed, large and sometimes pointed like a cusp • Occasionally a well developed lingual ridge is seen that divides the lingual fossa into mesial and distal lingual fossae • Heavy marginal ridges are associated with well formed cingulum and fossae
  119. 119. Mesial aspect • From the mesial aspect canine looks similar but bulkier than maxillary central incisor • Maxillary canine is the widest anterior tooth labiolingually • The cervical line curvature is towards the cusp (incisally) • The contact area is near the junction of the incisal and middle third Mesial aspect
  120. 120. Distal aspect • Distal surface is very similar to the mesial surface • The cervical line exhibits less curvature • The contact are is near the middle third
  121. 121. Incisal aspect • The labiolingual dimension is greater than the mesiodistal dimension • The cusp tip is labial to the centre of the crown labiolingually and mesial to the centre mesiodistally • The labial ridge and the cingulum are very noticeable from this aspect
  122. 122. • Root – only one  The root is the longest and strongest of all the teeth in the dentition  The mesial and distal surfaces of the root have developmental depressions. Average Dimensions in millimeters Crown Length Root Length 10.0 17.0 Mesiodistal Diameter at Contact Area 7.5 Mesiodistal Diameter at Cervical Line 5.5 Labiolingual Diameter at Crest of Curvature 8.0 Labiolingual Diameter at Cervical Line 7.0 Curvature of Cervical Line M D 2.5 1.5
  123. 123. Mandibular Canine •    Labial aspect Mandibular canines are similar to maxillary canines except that they are slightly narrower mesiodistally Mesial outline of the crown is straight and inline with the mesial outline of the root The mesial cusp ridge is smaller than the distal cusp ridge
  124. 124. •   •   Lingual aspect The lingual surface of the crown is smooth and flat simulating the surface of mandibular lateral incisor Cingulum is less prominent and marginal ridges are less distinct Mesial and Distal aspects These aspects are very similar and the cervical line curves more on the mesial aspect The contact area on mesial aspect is in the incisal third and a little higher on the distal third
  125. 125. •   •   Incisal aspect Like maxillary canine the labiolingual dimension is more than the mesiodistal dimension The cusp tip appears inclined in a lingual direction Root The root is shorter by 1 or 2 mm The developmental depression is more pronounced on the lower canine
  126. 126. Labial aspect Lingual aspect Incisal aspect Mesial aspect Distal aspect
  127. 127. Maxillary Pre- Molars Introduction • Premolars are so named because they are placed between the anterior teeth and the molars • Premolars assist the canines and the molars in tearing and chewing food • Maxillary premolars have two cusps and sometimes one or two roots • Maxillary 1st premolar erupts between 10-11 years and maxillary 2nd premolar erupts between 10-12 years of age
  128. 128. Maxillary 1st Premolar Maxillary 2nd Premolar
  129. 129. Maxillary 1st Premolar • Buccal aspect • This tooth has two cusps, buccal and lingual cusps. • The buccal cusp is long with a pointed tip • resembling the cusp of a canine • The mesial slope of the buccal cusp is longer than the distal slope, which is the opposite of canine • The buccal surface is convex, showing strong a strong buccal ridge • The crown exhibits little cervical line curvature
  130. 130. Lingual aspect  The crown tapers towards the lingual aspect  The lingual cusp is shorter than the buccal cusp  The lingual cusp is smooth from the cervical portion to the area near the cusp tip  The cusp tip is pointed with mesial and distal slopes meeting at an angle of about 90 degrees  Small portion of the buccal cusp can be seen from this aspect
  131. 131. Mesial aspect  From the mesial and distal aspect both the buccal and lingual cusps are visible  A well developed mesial marginal ridge and a mesial marginal developmental groove is present  In the middle of the mesial surface is the mesial Mesial aspect developmental depression which continues beyond the cervical line  The contact area is near the halfway point (JOM ) 3
  132. 132. Distal aspect There is no developmental depression or groove on this aspect, instead it is convex at almost all points The curvature of the cervical is less on this aspect The contact area is near the junction of occlusal and middle third
  133. 133. Occlusal aspect The occlusal aspect is roughly hexagonal in shape The buccolingual dimension of the crown is much greater than the mesiodistal dimension The occlusal surface is circumscribed by the cusp ridges and marginal ridges
  134. 134.  1. 2. 3. 4. 5. 6. Within the cusp ridges and marginal ridges the following are present Central developmental groove Mesiobuccal and distobuccal developmental groove Mesial marginal developmental groove Mesial and distal developmental pit Mesial and distal triangular fossa Buccal and lingual triangular ridge
  135. 135. Root  Most Maxillary first premolars have 2 roots, but one and three roots can also be seen. Two roots; buccal and lingual  The buccal portion of the root resembles canine • The root when viewed from the proximal side shows a big trunk and bifurcation area from where the buccal and lingual root separate  A developmental depression is seen on the mesial aspect of the trunk.
  136. 136. Average Dimensions in millimeters Crown Length Root Length 8.5 14.0 Mesiodistal Diameter at Contact Area 7.0 Mesiodistal Diameter at Cervical Line 5.0 Labiolingual Diameter at Crest of Curvature 9.0 Labiolingual Diameter at Cervical Line 8.0 Curvature of Cervical Line M D 1.0 0
  137. 137. Maxillary 2nd Premolar Buccal aspect  The maxillary second premolar resembles the maxillary first premolar in form and function  The buccal cusp is not as long as that of maxillary 1st premolar  It is less pointed.  The mesial slope of the buccal cusp ridge is shorter than the distal cusp ridge •
  138. 138. •  •    Lingual aspect The lingual cusp is more or less the same size as the buccal cusp Mesial and Distal aspects There is greater distance between the cusps No developmental depression is present nor any developmental groove crossing the marginal ridge on the mesial aspect On the distal aspect there is a developmental depression which is deeper than the depression on the mesial surface of maxillary 1st premolar
  139. 139. Occlusal aspect  The occlusal aspect is more rounded  The central developmental groove is shorter  There are multiple supplementary grooves radiating from the central groove Root  Maxillary 2nd premolar has one root, which is usually as long or a millimeter longer than the root of maxillary 1st premolar
  140. 140. Buccal aspect Lingual aspect Occlusal aspect Mesial aspect Distal aspect
  141. 141. Maxillary Molars • Maxillary molars are the largest teeth in the maxillary arch. The permanent molars are not succedaneous teeth because they don’t have any predecessors. The deciduous molars are still in place when the first permanent molars erupt at the age of 6. • Maxillary First Molar It has a large crown with four well developed cusps and occasionally a small fifth cusp. In addition to the cusps it has three well formed roots; two buccal and one lingual.
  142. 142. Buccal aspect  The crown is roughly trapezoidal • Mesiobuccal and distobuccal cusps are the two buccal cusps • Part of mesiolingual and distolingual cusps are seen from this aspect as the distolingual line angle is obtuse • The buccal developmental groove divides the two buccal cusps.
  143. 143. Lingual aspect • General outline of lingual aspect is reverse of buccal aspect • The mesiolingual, distolingual and fifth cusp are the only cusps seen from this aspect • Mesiolingual cusp is largest of all the cusps. Distolingual cusp is small and spheroidal
  144. 144. The lingual developmental groove separates the lingual cusps Sometimes a fifth cusp called the cusp of carebelli may be present. When present it attached to the Lingual aspect mesiolingual surface of the mesiolingual cusp.
  145. 145. Mesial aspect • Mesiobuccal, mesiolingual and fifth cusps are visible from this aspect also • Mesial marginal ridge is confluent • with the mesiobuccal and • mesiolingual cusp ridges and is • curved cervically • The cervical line is irregular, Mesial • Curving occlusally aspect • The contact area is at the junction of the middle and occlusal third, closer to the buccal aspect • A shallow concavity is found just below the contact are.
  146. 146. Distal aspect • Distobuccal and distolingual cusps are seen • The marginal ridge dips sharply cervically • The cervical line is almost straight Distal aspect
  147. 147. Occlusal aspect • The occlusal aspect is roughly rhomboidal in shape • Maxillary first molar crown is wider mesially than distally and wider lingually than buccally • The elevations and depression on this surface are: 1. Cusps • Mesiolingual cusp is the largest followed by mesiobuccal, distolingual, distobuccal, and the smallest being the fifth cusp.
  148. 148. • 2.Ridges  Mesial marginal ridge and distal marginal ridge  Oblique ridge 3. Fossae  Major fossae: central fossa and distal fossa  Minor fossae: mesial triangular and distal triangular fossae
  149. 149. 4 Grooves  Central developmental groove  Buccal developmental groove  Lingual developmental groove  Transverse groove of the oblique ridge  Distal oblique groove  Fifth cusp groove  Supplemental grooves
  150. 150. Pit  Central developmental pit Occlusal aspect
  151. 151. • Root  Maxillary first molar has three roots; two buccal and one lingual  The lingual root is long and slender with bluntly round apex  Mesiobuccal root is broader and curves distally while the distobuccal root is narrower at the base and a lot straighter
  152. 152.  Both the buccal roots are of equal size but smaller than the lingual root  The level of bifurcation area is more closer to the cervical area on the mesial side than on the distal side. Average Dimensions in millimeters Crown Lengt h 7.5 Root Length B L 12 13 Mesiodistal Mesiodistal Labiolingual Labiolingual Curvature of Diameter at Diameter at Diameter at Diameter at Cervical Line D Contact Area Cervical Line Crest of Curvature Cervical Line M 10.0 8.0 11.0 10.0 1.0 0
  153. 153. Maxillary Second Molar  The crown is shorter cervico-occlusally and about the same width buccolingually when compared with maxillary first molar  The distobuccal cusp is not as well developed and the distolingual cusp is also small. The fifth cusp is absent  The roots are as long as, if not somewhat longer than those of the first molar  The elevations and depression on the occlusal surface are similar to that of maxillary first molar.
  154. 154. Buccal aspect Lingual aspect Occlusal aspect Maxillary Second Molar Mesial aspect Distal aspect
  155. 155. Maxillary Third Molar  Maxillary third molar varies considerably in size, shape and position  It often presents itself as a developmental anomaly  Third molar supplements second molar and is also similar in its design  All third molars show more developmental variation than any other teeth in the dentition
  156. 156. Mandibular Incisors • Introduction • Mandibular incisors are four in number • Mandibular central incisor and lateral are similar in anatomy and complement each other in function • They are smaller than the maxillary incisors Mandibular central incisor erupts between the age of 6 and 7 • Mandibular lateral incisor erupts between the age of 6 and 8
  157. 157. 2 1 1 1 : Mandibular Central Incisor 2 : Mandibular Lateral Incisor 2
  158. 158. Mandibular Central Incisor Mandibular Central Incisor is the smallest tooth in the dentition Labial aspect  Labial surface of mandibular central incisor is very small. It is the narrowest tooth mesiodistally of all the permanent teeth  Narrowest tooth in the dentition Labial aspect
  159. 159.   It is bilaterally symmetrical It is the only incisor where both mesioincisal and distoincisal angles are sharp and at right angles Both mesioincisal and distoincisal angles are sharp Labial aspect
  160. 160. Lingual aspect  The lingual aspect is concave from the incisal edge to the cervical line  Cingulum is smooth and barely visible Shallow lingual fossa and smooth cingulum
  161. 161. • The surface is smooth and devoid of any grooves. No other tooth in the mouth, except the mandibular lateral incisor, shows so few developmental lines and grooves
  162. 162. Mesial aspect  The labial outline is almost straight, except near cervical third where it is convex  The labial surface is inclined lingually  The lingual margin is ‘S’ shaped  The cervical line on the mesial and distal surface is convex incisally Mesial aspect
  163. 163. Distal aspect • Distal surface is very similar to the mesial surface. • The cervical line is less curved. Distal aspect
  164. 164. Incisal aspect • This aspect illustrates the bilateral symmetry of this tooth. • The labiolingual diameter is greater than mesiodistal diameter. Labiolingually bigger than mesiodistally Bilaterally symmetrical • Newly erupted teeth show mamelons which wear off upon mastication
  165. 165. • Root  The root is single and straight.  The deflection of the root if present is on the labial or distal side.
  166. 166. Average Dimensions in millimeters Mesiodistal Crown Root Lengt Length Diameter at Contact Area h 9.0 12.5 5.0 Mesiodistal Diameter at Cervical Line Labiolingual Diameter at Crest of Curvature 3.5 6.0 Labiolingual Diameter at Cervical Line 5.3 Curvature of Cervical Line M D 3.0 2.0 CHRONOLOGY Contact Area Man L.I Appearance of enamel organ 5 m.i.u First evidence of calcification 3-4 months Crown completion 4-5 years I3 Eruption 6-8 years I3- Incisal third Root completion 10 years Mesial Distal I3
  167. 167. Mandibular Lateral Incisor   Mandibular lateral incisor is slightly wider mesiodistally The cervical portion of the lingual aspect is narrower while the incisal portion is wider. This gives the crown a more or less a fan shaped appearance Fan shaped appearance Cervical portion narrower
  168. 168.   The concavity in the lingual aspect is slightly more when compared to mandibular central incisor The incisal edge follows the mandibular arch, giving the crown a slightly twisted appearance on its root Lingual fossa more concave
  169. 169. Labial aspect Lingual aspect Incisal aspect Mesial aspect Distal aspect
  170. 170. Mandibular Pre-molars • Mandibular First Premolar • Mandibular 1st premolar has many characteristics of mandibular canine • It functions along with mandibular canine • It has two cusps and one root • Mandibular 1st premolar erupts between 10-12 years of age
  171. 171. • Buccal aspect  From the buccal aspect a large well formed, pointed buccal cusp is seen  The mesial outline is similar to the distal outline  The mesiobuccal cusp ridge is shorter than the distobuccal cusp ridge (similar to canines) Buccal aspect  The mesial and distal slope of the buccal cusp sometimes show concavity
  172. 172. Lingual aspect  The crown tapers and inclines lingually  The lingual cusp is small, pointed and nonfunctional and in some specimens it is no longer than the cingulum of maxillary canine Lingual aspect  Between the mesiobuccal and lingual lobe is the mesiolingual developmental groove
  173. 173. Mesial aspect      The lingual inclination of the crown can be seen from this aspect The lingual cusp is approximately two thirds the size of the buccal cusp The mesial marginal ridge has extreme lingual slope Mesial aspect
  174. 174.   Mesiolingual developmental groove is present between the mesial marginal ridge and the mesiolingual cusp ridge The mesial and distal contact areas are in the middle third, the distal contact area being more wider.
  175. 175. Distal aspect  Distal marginal ridge is higher and does not have the extreme lingual slope  The cervical line curvature is less curved Distal aspect
  176. 176. Occlusal aspect  The crown converges sharply to the centre of the lingual surface  The occlusal surface has two depressions; mesial and distal fossae  Most common form of mandibular 1st premolar shows a mesiolingual depression and mesiolingual developmental groove Occlusal aspect
  177. 177. Root  The mandibular 1st premolar has one root  The root is approximately (3-4mm)shorter than the root of mandibular canine but the outline bears a close resemblance to the canine  A deep developmental groove is seen on the mesial aspect on the root  On the distal aspect there is a shallow depression devoid of any developmental groove.
  178. 178. Average Dimensions in millimeters Crown Length Root Length 8.5 14.0 Mesiodistal Diameter at Contact Area 7.0 Mesiodistal Diameter at Cervical Line 5.0 Labiolingual Diameter at Crest of Curvature 7.5 Labiolingual Diameter at Cervical Line 6.5 Curvature of Cervical Line M D 1.0 0
  179. 179. Mandibular Second Premolar • • • Mandibular 2nd premolar resembles the mandibular 1st premolar from the buccal aspect only The crown assumes two common types. The first and more common type is the 3-cusp type and the second is the 2-cusp type The two differ mainly in the occlusal design
  180. 180. Buccal aspect  The buccal cusp is shorter with the cusp slopes presenting less degree of angulations Lingual aspect  There may be one or two lingual cusps – mesiolingual and distolingual cusps  The cusp(s) are more developed than the lingual cusp of lower first premolar  A groove separates the two lingual cusps
  181. 181. •     Mesial and Distal aspects The crown and root are wider buccolingually Unlike mandibular 1st premolar the marginal ridge is at right angle to the long axis of the tooth More of occlusal surface is visible form the distal aspect because the distal marginal ridge is at lower level than the mesial marginal ridge The contact areas both mesial and distal are broad and appear higher because of the short buccal cusp
  182. 182. Occlusal aspect  From the occlusal aspect the 3-cusp type appears square and the 2-cusp type appears rounded. • 3-cusp type:- each cusp is separated by deep developmental grooves forming a “Y” shape in the centre ,the occlusal surface also includes a. central pit b. mesial developmental groove c. mesial triangular fossa d. distal developmental groove e. distal triangular fossa f. lingual developmental groove g. supplemental grooves
  183. 183. • 2-cusp type: - one buccal cusp and one well developed lingual cusp is present - a central groove travels in a mesiodistal direction and end in mesial and distal fossa (forming ‘H’ shape) Root  Mandibular 2nd premolar has a single root which is larger and longer than the root of mandibular 1st premolar  The root is usually wide with a blunt apex
  184. 184. Buccal aspect Lingual aspect Occlusal aspect Mesial aspect Mandibular Second Premolar Distal aspect
  185. 185. Mandibular Molars • The mandibular molars are larger than any other mandibular teeth. • They are three in number on each side of the mandible ,the first, second, and third mandibular molars. • The first molar lies posterior to the second premolar, followed by the second and third molars. • They perform the major portion of the work of the lower jaw in mastication. • Each mandibular molar has two roots, one mesial and one distal. The third and some second molars may show a fusion of these roots.
  186. 186. • • • Decrease in size, crowns & Roots Roots less divergent More distal inclination • Cusp number
  187. 187. Mandibular First Molar • Measurements: Average length 21.5 mm • Crown length (CL) 7.5mm, • Root length 14 mm • Mesiodistal (MD) diameter 11mm • Buccal Aspect: the mandibular first molar is the largest tooth in the mandibular arch. • It has five well-developed cusps: two buccal, two lingual, and a distal cusp. • It has two well-developed roots, one mesial and one distal. These roots are widely separated at the apices.
  188. 188. Buccal Aspect: • All five cusps can be seen; the tips of the lingual cusps can be seen because they are higher than the others. • Two developmental grooves appear on the crown portion; the mesiobuccal developmental groove and the distobuccal developmental groove. • The mesiobuccal, distobuccal, and distal cusps are relatively flat. • The cervical line is commonly regular in outline.
  189. 189. Lingual Aspect: • Three cusps may be seen: two lingual cusps and the distal cusp. • The lingual cusps are high • enough to hide the buccal cusp. The lingual developmental groove is between the lingual cusps, extending on the lingual surface. •
  190. 190. • The mesial outline of the crown is convex. The crest of contour is higher mesially than distally. • The distal outline of the crown is straight. • The cervical line lingually is irregular. The root bifurcation lingually starts at 4mm below the cervical line.
  191. 191. Mesial Aspect: • Two cusps and the mesial root only are to be seen: the mesiobuccal and mesiolingual cusps and the mesial root. • the entire crown has a lingual tilt in relation to the root axis. • The buccal outline of the crown is convex; this curvature outlines the buccal cervical ridge. • The cervical line may assume a straight line. • The surface of the crown is convex. • The mesial root curve lingually.
  192. 192. Distal Aspect: • We see more of the tooth than in the mesial aspect because there is a distal convergence of the tooth. • The distal cusp is in the foreground of the crown portion. • The distal contact area is placed just below the distal cusp. • The distal marginal ridge is short. The surface is convex. • The cervical line is straight.
  193. 193. • Occlusal Aspect: outline is hexagonal. • The MD measurement is greater than BL. The mesiobuccal cusp is larger than either of the two lingual cusps, which are almost equal to each other in size; the distobuccal cusp is smaller than any one of the other three mentioned, and the distal cusp is the smallest. Occlusal aspect
  194. 194. • The land marks to be identified on this surface are: (a) Central fossa. (b) Mesial and distal triangular fossae. (c) Central developmental groove. (d) Mesiobuccal and distobuccal • developmental grooves. • (e) Lingual Developmental groove. (f) Central pit • (g) Mesial and distal marginal ridges.
  195. 195. Mandibular Second Molar • • • • • Measurements: Average length 20 mm Crown length (CL) 7mm, Root length 13mm Mesiodistal (MD) diameter10.5mm Buccal Aspect: The crown is shorter and narrower than the first molar. There is one developmental groove, the buccal developmental groove, between the mesiobuccal and distobuccal cusps. The roots are inclined distally.
  196. 196. Lingual Aspect: • The crown and root converge lingually. • The mesiodistal at the cervix is always greater than that of the first molar. • The contact areas are more noticeable from the lingual aspect; at a lower level, especially in the distal, than those of the first molar.
  197. 197. • Mesial Aspect: • Except for the differences in measurement, there are little differences from the first molar. • The cervical ridge buccally is less pronounced. Distal Aspect: • It is similar to the first molar except for the absence of the distal cusp and a distobuccal groove. • The contact area is centered on the distal surface.
  198. 198. • Occlusal Aspect: There is considerable difference from the first molar. The small distal cusp of the first molar is not present, as well as an absence of the distobuccal developmental groove. Occlusal aspect of Mandibular Second Molar
  199. 199. Mandibular Third Molar • • • • • Measurements: Average length 18 mm Crown length (CL)7mm, Root length11 mm Mesiodistal (MD) diameter10 mm Buccal Aspect: vary in outline buccal cusps are short and rounded. • shows two roots, mesial and distal, shorter than the roots of the first and second molars, and their distal inclination is greater. • The roots may be separated or fused.
  200. 200. Lingual Aspect: The third molar, when well developed, corresponds closely to the form of the second molar except for size and root development.
  201. 201. • Mesial Aspect &Distal Aspect: This tooth resembles the mandibular second molar except in dimension. • Occlusal Aspect: similar to second mandibular molar; with a more rounded outline and a smaller buccolingual measurement
  202. 202. HISTOLOGY Germ layer Formative tissue Tooth structure Ectoderm Dental organ ENAMEL Dental papilla DENTIN PULP Mesoderm Dental sac CEMENTUM PERIODONTAL LIGAMENT
  203. 203. Tooth development Initiation of tooth Odontogenesis-Factors from first arch Ones ability acquired maintained by dental papillary cells
  204. 204. 6 wks In utero • Tooth Buds • Dental Lamina
  205. 205. Life Cycle of the Tooth • • • • • • • • • Growth Initiation Proliferation Histodifferentiation Morphodifferentiation Apposition Calcification Eruption Attrition
  206. 206. Primary Epithelial band/ 6 week th Continuous band of thickened epithelium  Roughly horse shoe shaped  Thickening first seen in ant midline
  207. 207. • Contd thickening of DL in 10 areas of upper/ lower arch • Thickenings correspond to position of future primary dentn
  208. 208. Proliferation • • • • • • Multiplication of the cells of the initiation stage Formation of the tooth germ Cap Stage formation of the Dental Papilla Stellate reticulum – Enamel pulp 9-11 weeks
  209. 209. Histodifferentiation • • • • • Bell Stage Dental papilla Dental Organ Dental Sac Dental Lamina 14th week
  210. 210. Morphodifferentiation • • • • Advanced bell stage. Inner enamel epithelium Formation of Dentin Fate of the Dental Lamina 18th week
  211. 211. Apposition • appositional, additive and regular
  212. 212. Calcification • Begins at the cusp tips or incisal edges and proceeds cervically
  213. 213. Lines of Retzius
  214. 214. Neonatal line
  215. 215. Stages in tooth growth Dental lamina and Bud stage Cap stage Bell stage[ Early] Bell stage {advanced} Formation of enamel and dentin matrix Initiation Proliferation Hiisto defferentiation Morpho defferentitiation Apposition
  216. 216. Formation of Single and Multirooted Teeth
  217. 217. Formation of multirooted teeth
  218. 218. Eruption of teeth • Pre-eruptive phase • Eruptive Phase (Prefunctional) • Eruptive phase functional
  219. 219. Theories of Eruption • • • • • • Root Formation Theory Proliferation of the Hertwig’s Epithelial Root Sheath Proliferation of the connective tissue of the papilla Simultaneous growth of the jaw Pressures from muscular action Apposition and resorption of bone
  220. 220. Exfoliation of the Primary Tooth • Pressure on the roots by the erupting permanent tooth • Development of osteoclasts • Successive resorption of tooth root, cementum, dentin and adjacent bone due to the action of the osteoclasts.
  221. 221. Clinical significance of morphology& histology • Variation of teeth has been an enduring interest to the clinical practitioner and the laboratory scientist. • No two teeth are alike. • The day-to-day variation of teeth that we see is the norm. • It is the odd, peculiar, and strange group of teeth to which we focus our attention here. They are called anomalies.
  222. 222. • These few facts about tooth development will assist us in understanding tooth variation: • (1) Teeth form from the cooperative interaction of two germ layers--ectoderm and ectomesenchyme (a neural crest derivative). • (2) Enamel is formed from the ectodermal components. • (3) Dentin, pulp, cementum, the supporting PDL, and bone are all derived from ectomesenchyme.
  223. 223. Disturbances in Size • Microdontia means teeth that are smaller than normal. Generalized microdontia is a rare condition associated with uncommon conditions such as pituitary dwarfism."Pegshaped" upper lateral incisors and small third molars are seen regularly by the practicing dentist. Occasionally, an upper lateral incisor is missing on one side, peg-shaped on the other side. • -Macrodontia refers to teeth that are larger than normal. Generalized macrodontia is rare, seen infrequently in conditions such as pituitary gigantism. It can be localized involving just one or a few teeth. You may occasionally see the term 'megadontia' used for this condition. • .....
  224. 224. Disturbances in Number. • Anodontia is the congenital absense of all teeth, Anodontia means the failure of teeth to form at all.) In true (or complete) anodontia, all teeth fail to develop. • -True anodontia is an extremely rare occurrence. When this does occur, it is usually part of a more generalized disorder ectodermal dysplasia, an inherited defect of all ectodermally derived structures. • -Partial anodontia is the failure of one or more teeth to develop. It is much more common than complete anodontia. Third molars, lower second premolars, and upper lateral incisors (in that order) are the most common congenitally absent teeth. When a deciduous tooth is absent, its permanent successor is usually missing also.)
  225. 225. • Supernumerary teeth are 'extra' teeth. Most (90%) occur in the maxilla. Their presence in the deciduous dentition is quite rare. Two terms occasionally used to describe are polydontia or hyperdontia. • The most common of all supernumerary teeth is the mesiodens which is a supernumerary that forms in the midline between and lingual to the roots of the maxillary central incisors. • Most supernumerary teeth do not erupt; they often are unknown until detected on X-ray films. Fourth molars, themselves a rare occurrence are infrequently called 'paramolars' or 'distomolars.' Supernumerary teeth occur less often than do missing teeth.
  226. 226. Disturbances in Eruption. • -Premature eruption of all of the teeth, either deciduous or permanent, may suggest an underlying endocrine dysfunction such as hyperthyroidism. • A natal tooth seen at birth may be an aberrant 'tooth' nodule, or it may actually be a deciduous incisor that has erupted early. The etiology is unknown. • -Delayed eruption can be due to local or systemic factors. For one or a few teeth, surgical exposure and--if needed-orthodontic guidance can bring the tooth into its proper place. X-ray films are useful in evaluating early or late eruption of teeth.
  227. 227. • Impacted teeth are those that have failed to erupt and remain buried in the alveolar bone. The third molars and maxillary canine are the most frequently impacted teeth, followed by premolars and supernumerary teeth. • Ectopic eruption is another type of eruption disturbance; this occurs when a tooth cannot complete its eruption because it is blocked by an adjacent tooth or by a misplaced orthodontic band usually on a first molar tooth.
  228. 228. • An iatrogenic disease or condition is one that is 'doctorcaused'. If a second molar is inadvertently impacted by a poorly placed molar band, it is an iatrogenic condition. These things happen to the best of us. We need to make these occurrences as few as possible, and to be on the lookout for them when they do occur.
  229. 229. Disturbances in Shape (The Odd and the Bizarre)• Dilaceration is a severe bend in the long axis of the tooth. The bend it located at the junction between the crown and the root. The bend can be as much as 90 degrees. • Dilaceration usually results from trauma to the unfinished tooth when development is in progress. Such a tooth in the old literature is sometimes called a 'hawk billed tooth'. • -Flexion is a deviation or bend restricted just to the root portion of the tooth. Usually the bend is less than 90 degrees. It may be a result of trauma to the developing tooth.
  230. 230. • -Taurodontism literally means 'bull-like teeth'. Taurodont teeth are usually molars. They have an abnormally long pulpal chamber and shortened roots. The pulp chamber has no constriction near the CEJ as do normal teeth. Clinically these teeth appear normal. Taurodontism was relatively common amongst the European Neandertals. It is also found on occasion in people living today. The implication of its appearance in modern people is unknown. No treatment of the condition is necessary apart from due prudence when doing root canal therapy.
  231. 231. • Dens in dente literally means 'tooth within a tooth'. It is an uncommon developmental abnormality that primarily affects maxillary lateral incisors. It is in fact a deeply invaginated lingual pit with an important clinical implication: these are very susceptible to caries and they ought to be restored promptly. Left unattended, these teeth tend to decay very rapidly. Modern literature will often refer this condition as dens invaginatus. This is a term you should know. • -Supernumerary cusps, or as they are often called, extra cusps are occasionally found on teeth. We review here the common types.
  232. 232. • (1) The most common one is the Carabelli Cusp which is found on the mesiolingual aspect (on the mesiolingual cusp) of maxillary first molars and maxillary second deciduous molars. • -This occlusal landmark can appear with varying degrees of intensity either as a cusp or pit. These conditions are known collectively as the Carabelli trait. It is frequently a site of early dental caries. It is a heritable trait most commonly seen in European populations. The Carabelli trait is best understood as a variation, not an anomaly.
  233. 233. • (2) A talon cusp is an extra cusp that resembles an eagle's talon (a talon is the claw of a bird of prey). A talon cusp appears as a projection from the cingulum of incisor teeth. These can interfere with occlusion; however, grinding them down is a hazardous endeavor. Talon cusps often contain a prominent pulp horn which is very susceptible to exposure in the younger patient. • (3) Very rarely, a similar projection of enamel can occur on the occlusal surface of the premolar teeth. It forms a tubercle called a 'dens evaginatus'. Dens evaginitus can also contain a pulp horn as does the talon cusp mentioned earlier. Fortunately, these conditions are infrequent.
  234. 234. • (4) One other variation of the upper first premolar is the 'Uto-Aztecan' upper premolar. It is a bulge on the buccal cusp that is only found in Native American Indians, with highest frequencies of occurrence in Arizona. The name is not a dental term; it comes from a regional linguistic division of Native American Indian language groups. • (5) Peg-shaped lateral incisors have already been discussed above. • (6) Certain teeth exhibit a variation in the number of roots.
  235. 235. • Incidentally, most root variation is in the distal third of the root. Sometimes roots can be blunted or shortened. It tends to occur without apparent cause. • root resorption and root blunting can be unfortunate consequence of orthodontic treatment with fixed appliances • Extra or fused roots. • (a.) Upper first premolars usually have two roots; however, one root is occasionally found in these teeth. More rarely there are three roots.
  236. 236. • (b.) Lower permanent canines on occasion have a bifurcation near the apex resulting in two short roots. A question about this condition has appeared frequently on Part I National Boards for dental students. • (c.) Sometimes lower first permanent molars have three roots. It is the mesial molar root that is bifurcated. Clinical articles often consider it an anomaly. It is just a variation. Three rooted lower first molars are found in greater frequency amongst North American Indians with origins in Asia. • (d.) In upper third molars, and on occasion with fused roots, second molars, the roots can be fused together. This is a variation, not a pathological condition.
  237. 237. • Shovel shaped incisors display enhanced marginal ridges and present with a distinctive shovel-shaped appearance on the lingual aspect. They appear frequently in many persons of Asian origin, including many Native American Indians. They are especially prominent in Eskimo/Inuit who are descendants of Siberians about 4,000 years ago. •
  238. 238. • This next section might best be called 'joined teeth.' • -Fusion is the union of two teeth by dentin and enamel. The pulp chambers are often shared; however, they can be separate. This condition can be differentiated from gemination (discussed below) by counting the teeth. The diagnosis can be confirmed if there is a reduction in the number of teeth that are present in the dental arch. Can you stand another term? Some authors refer to fusion as 'syndontism'.
  239. 239. • • • • • • • • • • Gemination is the development of two crowns from a single tooth germ. It is an incomplete twinning of the gooth germ. In gemination, there is a shared pulp and root. Unlike fusion, the number of teeth is correct; however, the 'gemination‘ gemination tooth is unusually wide. Some writers refer to gemination as 'schizodontism'.
  240. 240. • -Concrescence is the joining of tooth roots by cementum. It occurs after tooth formation is complete. Usually this condition is 'silent' without clinical significance. When extracting teeth, however, the prudent clinician will carefully examine X-ray films of the patient for this condition. A missed diagnosis can be serious business during an attempted extraction. • -A related occurrence is hypercementosis. It is a consequence excessive cementum deposition. It occurs in older people often when there are greatly increased or decreased occlusal forces.
  241. 241. Disturbances in Formation • • • • • • • • • • Enamel pearls (enamelomas) are small nodules of enamel found on the root of the tooth close to or at the cemento-enamel junction. They are found most often at the bifurcation or trifurcation of molars. They do appear radiographically. While they can be a problem in periodontal disease, they should usually be left alone.
  242. 242. • Their attempted removal can do more harm than good.• Winged incisors are not a disturbance of development, but rather a special case of rotation of the upper central incisors. • It is usually described as a distinctive bilateral rotation to the mesial which is particularly common amongst Native American Indians. • -Enamel hypoplasia can be localized or generalized. Localized enamel hypoplasia is a visible defect that is important in archaeology as an indicator of severe sickness or nutritional deprivation. • When the insult during tooth formation is brief in duration, it can be detected histologically in the enamel as a Wilson line
  243. 243. References • Wheeler's Dental Anatomy, Physiology and Occlusion • Shafer'S Textbook Of Oral Pathology (6Th Edition) • Orban's Oral Histology and Embryology • Woelfel's Dental Anatomy: Its Relevance to Dentistry • Internet