Maxillary Lateral and Mandibular Incisors

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Maxillary Lateral and Mandibular Incisors

  1. 1. Anatomy Of The Maxillary Lateral Incisors And Mandibular Central And Lateral Incisors Howard Chi D.M.D.
  2. 2. Learning Objectives • Anatomy of the maxillary lateral incisors • Anatomy of the mandibular central incisors • Anatomy of the mandibular lateral incisors
  3. 3. Anatomy of the Maxillary Lateral Incisors
  4. 4. Morphology Of The Crown From The Labial • Similar to that of a central incisor • More convex, or less flat mesiodistally
  5. 5. Morphology Of The Crown From The Labial • Appears more oblong cervicoincisally • Mamelons and labial depression less prominent than central
  6. 6. Crown Size And Shape From The Labial • Narrower by about 2mm from that of a central incisor • This yields a long, slender look • Outline is less symmetrical than a central incisor + 2 mm
  7. 7. Crown Incisal Proximal Angles From The Labial • Both the mesio and distoincisal angle are more rounded than central incisor • Mesioincisal angle is more acute than central incisor
  8. 8. Crown Incisal Proximal Angles From The Labial • Distoincisal is wider and more obtuse than maxillary central incisor • Incisal angle slope more cervically towards the distal on a maxillary lateral
  9. 9. Crown Contact Areas From The Labial • Mesial contact is in the incisal near the junction of the incisal and middle thirds • Distal contact is at the junction of the incisal and middle thirds
  10. 10. Tooth Proportions From The Labial • The root is narrower, but can be longer than that of a maxillary central incisor • This makes the root longer in proportion to the crown than a central incisor
  11. 11. Root From The Labial • The root tapers evenly toward the rounded apex • The root commonly curves distally
  12. 12. Lingual Fossa Of The Crown • Is smaller in area than a central incisor • More pronounced than a central incisor • May appear either shallow or deep
  13. 13. Cingulum Of A Maxillary Lateral Incisor • Narrower than a central incisor • Almost centered on the long axis of the root
  14. 14. Marginal Ridges Of A Maxillary Lateral Incisor • Developed to different degrees on different teeth • May be prominent or inconspicuous • Can be worn from attrition
  15. 15. Marginal Ridges Of A Maxillary Lateral Incisor • Mesial marginal ridge outline is nearly straight • Distal marginal ridge is shorter and curved incisocervically • Shortness of the distal marginal ridge is due to slope of the incisal ridge
  16. 16. Lingual Anatomy Of The Crown • May possess lingual accessory ridges near cingulum • Fewer and less common than the central incisor's • A lingual pit is frequently present and often restored to arrest decay
  17. 17. Root From The Lingual • Narrower on the lingual side than the labial • Surface root depression present on the mesial
  18. 18. Incisal Ridge From The Proximal Aspect • Usually 1.0 to 1.5 mm thick and labial to the root axis • Sloped cervically toward the lingual from its most labial portion
  19. 19. Cervical Line From the Proximal Aspect • Curvature is deep on the mesial (2.5mm) • More curved on mesial than on the distalMesial #7 Distal #7 2.5mm
  20. 20. Root Outline From The Mesial • Appears blunt from the proximal • Root ratio is slightly greater than the central incisor Mesial #7
  21. 21. Root Depressions From The Proximal • Similar to the central, found on the mesial mid-root Mesial #7 Distal #7
  22. 22. Root Depressions From The Proximal • Mesial surface is the least convex of the four sides (another way of saying its the flattest) Mesial #7 Distal #7
  23. 23. Crown Proportion From The Incisal Aspect The mesiodistal measurement is greater than the faciolingual • On some this dimension may be the same
  24. 24. Crown Outline From The Incisal • Is less symmetrical, but in general, resembles the central • It is narrower mesiodistally than the central • Cingulum is nearly centered mesiodistally
  25. 25. Incisal Ridge Contour • Incisal ridge straighter mesiodistally than a central incisor
  26. 26. Cingulum From An Incisal Aspect • Centered mesiodistally and noticeably more convex than the central incisor
  27. 27. Labial Contour From The Incisal Aspect • Noticeably more convex than the maxillary central incisor (type trait)
  28. 28. Anatomy Of The Mandibular Central Incisors
  29. 29. Mandibular Central Incisor From The Labial Aspect • The surface of the crown is nearly smooth • Can have two shallow depressions in the incisal third (similar to maxillary, but far less pronounced)
  30. 30. • Mamelons are usually present on newly emerged teeth • Quickly worn off with contact with maxillary teeth (if not, suspect malocclusion) Mandibular Central Incisor From The Labial Aspect
  31. 31. • Crown is five-eighths the width of a maxillary central • Crown is proportionally narrow in comparison to its length Mandibular Central Incisor From The Labial Aspect
  32. 32. • The tooth is so symmetrical it is difficult to tell left from right • Only difference is the mesial cervical line curve more incisally than the distal Mandibular Central Incisor From The Labial Aspect
  33. 33. • The mesial and distal outlines is straight in the incisal third • The crown tapers to the cervical third • Contacts are well within the incisal one third Mandibular Central Incisor From The Labial Aspect
  34. 34. • Labial surface is convex mesiodistally in the cervical third • Mesio and distoincisal angle is nearly 90 degrees Mandibular Central Incisor From The Labial Aspect
  35. 35. • Distoincisal angle may be more rounded (slightly) than the mesioincisal angle Mandibular Central Incisor From The Labial Aspect
  36. 36. • Mesial and distal contact areas are within the incisal third at roughly the same height (type trait) • Root longer than crown proportionally compared to the maxillary incisors Mandibular Central Incisor From The Labial Aspect
  37. 37. • The root is narrow mesiodistally, but wide faciolingually • The root is tapered evenly on both sides from the cervical line to the apex, root tip may curve to the distal Mandibular Central Incisor From The Labial Aspect
  38. 38. Mandibular Central Incisor From The Lingual Aspect • The outline is much more symmetrical than all other incisors • The lingual crown surface is smooth and shallow with a slight concavity in the middle and incisal thirds
  39. 39. • The cingulum is convex, small and centered • The marginal ridges and lingual fossa are scarcely discernible, if at all • No grooves, pits or accessory ridges are present Mandibular Central Incisor From The Lingual Aspect
  40. 40. Mandibular Central Incisor From The Proximal Aspect • The incisal edge is on or lingual to the long axis of the root • Mesial cervical line (CEJ) extends 2mm incisally • Distal cervical line extends .4 mm less than the mesial
  41. 41. • The facial height of contour is located in the cervical third • The lingual height of contour is located on the cingulum, within the cervical third Mandibular Central Incisor From The Proximal Aspect
  42. 42. • The labial contour is so slightly curved that it often appears flat • The lingual contour is convex on the cingulum, concave in the fossa and flat towards the incisal Mandibular Central Incisor From The Proximal Aspect
  43. 43. • The facial and lingual sides of the root are nearly straight from the cervical line to the middle third • The root then tapers to its apex Mandibular Central Incisor From The Proximal Aspect
  44. 44. • Roots are flat mesiodistally compared to their maxillary counterparts • Roots are wider faciolingually than mesiodistally by approximately 2mm Mandibular Central Incisor From The Proximal Aspect
  45. 45. Root depressions can be found on both the mesial and distal aspects in the middle third of the roots Mandibular Central Incisor From The Proximal Aspect #25 Mesial #25 Distal
  46. 46. Mandibular Central Incisor From The Incisal Aspect • The labiolingual measurement of the crown is greater than the mesiodistal measurement (this is quite different from the maxillary counterparts)
  47. 47. • The labial and lingual height of contour is centrally located • The incisal edge runs in a straight line mesiodistally and is roughly 2mm thick Mandibular Central Incisor From The Incisal Aspect
  48. 48. • The cingulum is centered, smooth and has a convex outline • The labial surface is slighly convex in the incisal one third and noticeably convex in the cervical third Mandibular Central Incisor From The Incisal Aspect
  49. 49. Anatomy Of The Mandibular Lateral Incisors
  50. 50. Mandibular Lateral Incisor From The Facial View • Similar to the central, smooth and minimal depressions • Labial surface is convex mesiodistally, more in the cervical third and less in the incisal third
  51. 51. • Crown is tilted distally on the root, giving a bent appearance • This makes the distal outline of the crown shorter than the mesial aspect Mandibular Lateral Incisor From The Facial View
  52. 52. • The distoincisal angle is noticeably more rounded than the mesioincisal angle • This aids in telling left from right Mandibular Lateral Incisor From The Facial View
  53. 53. • The mesial contact is in the incisal third, near the incisal edge • The distal contact is in the incisal third, but cervical to the level of the mesial contact Mandibular Lateral Incisor From The Facial View
  54. 54. • Crown is narrower with respect to its length • Root is narrow mesiodistally, tapering gradually from the cervical line to the apex. It may have a distal curvature Mandibular Lateral Incisor From The Facial View
  55. 55. Mandibular Lateral Incisor From The Lingual View • Similar to the central, but not bilaterally symmetrical • Crown is tilted distally, and tapers lingually in the middle and cervical thirds
  56. 56. • The cingulum is slightly distal to the long axis of the root, similar to the maxillary central • This makes the mesial marginal ridge longer than the distal Mandibular Lateral Incisor From The Lingual View
  57. 57. • Marginal ridges and lingual fossa are not conspicuous and generally smooth • The root is narrower lingually than facially Mandibular Lateral Incisor From The Lingual View
  58. 58. Mandibular Lateral Incisor From The Proximal View • The incisal edge is on or lingual to the long axis of the root • From the mesial a distolingual twist of the incisal edge places the distal portion more lingual Central Lateral
  59. 59. • The C.E.J. curves 2 mm incisally on the mesial aspect • The C.E.J. curve 1.4 mm incisally on the distal aspect Mandibular Lateral Incisor From The Proximal View
  60. 60. • The facial and lingual heights of contour are in the cervical third • The labial outline is nearly flat in the middle and incisal thirds Mandibular Lateral Incisor From The Proximal View
  61. 61. • The root is straight from cervical to middle third • The distal portion of the root contains a depression that is more distinct than the mesial Mandibular Lateral Incisor From The Proximal View
  62. 62. Mandibular Lateral Incisor From The Incisal View • The crown is broader faciolingually than mesiodistally • Not bilaterally symmetrical, distal is twisted
  63. 63. • The cingulum is off center to the distal with a barely dicernible lingual fossa • The labial outline is slightly convex in the incisal one third Mandibular Lateral Incisor From The Incisal View

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