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Permanent Mandibular Incisors

Permanent Mandibular Incisors. Introduction. Simplest, least variable teeth Centrals slightly smaller than laterals Crowns are narrower M-D relative to the I-C length. Permanent Mandibular Central Incisor. Arch position: adjacent to midline Universal #24 and #25

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Permanent Mandibular Incisors

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  1. Permanent Mandibular Incisors

  2. Introduction • Simplest, least variable teeth • Centrals slightly smaller than laterals • Crowns are narrower M-D relative to the I-C length

  3. Permanent Mandibular Central Incisor • Arch position: adjacent to midline • Universal #24 and #25 • Narrowest M-D width and smallest crown size* • Very symmetrical crown

  4. Development Timeline: • Initial calcification: 3 - 4 months • Enamel completed: 4 - 5 years • Eruption: 6 - 7 years • Root completion: 9 years

  5. Labial View • Incisal 2/3 generally flat to slightly convex • Height of contour at cervical third • Geometric form: trapezoidal

  6. Labial View - mesial outline: • Even straight taper towards cervical • MI angle angular • Mesial HOC at the incisal third

  7. Labial View - distal outline: • Almost a mirror image of mesial outline • Difficult to distinguish M from D

  8. Labial View - incisal outline: • Perpendicular to long axis • One wear facet - only anterior tooth that opposes one tooth*

  9. Lingual View • Surface relatively smooth • Marginal ridges indistinct • Lingual fossa shallow • No pits or grooves

  10. Lingual view: • Diminished cingulum • Height of contour at cervical third

  11. Mesial View • Labial outline fairly straight at incisal 2/3 • Facial and lingual heights of contour at cervical third

  12. Mesial view: • Incisal edge lingual to long axis of tooth* • Incisal edge slopes facially • HOC at incisal third

  13. Distal View • Similar to mesial • CE line curvature slightly less than mesial • HOC also at incisal third (unique)

  14. Incisal View • Wider F-L than M-D • Diamond-shaped outline • See more of facial than lingual • M and D halves symmetrical • Incisal edge is perpendicular to F-L bisector*

  15. Root • Normally single and straight, occasional bifurcated • Gradual taper to sharp apex

  16. Root: • Wider F-L, narrower M-D • Slight root concavities M and D • Cross-section at cervical: rounded rectangle

  17. Permanent Mandibular Lateral Incisor

  18. General Characteristics • Arch position: 2nd tooth from midline • Universal #23 and #26 • Very similar in form to mandibular central

  19. Development Timeline: • Initial calcification: 3 - 4 months • Enamel completed: 4 - 5 years • Eruption: 7 - 8 years • Root completion: 10 years

  20. Labial View • Very similar to mandibular central except DI angle slightly more rounded • M and D heights of contour at incisal third, D slightly more cervical

  21. Lingual View • Similar to mandibular central • Cingulum slightly offset to distal

  22. Mesial and Distal Views • Similar to mandibular central except: • Distal incisal corner visible from mesial*

  23. M and D views: • Mesial CE line curvature slightly more than distal

  24. Incisal View • Incisal edge curves towards lingual in distal portion* • Distal HOC more lingual than mesial • Cingulum appears offset to distal • Crown appears twisted on root • Two facets of wear

  25. Root • Similar to mandibular central except slightly wider, thicker • Root concavities present with distal more pronounced • Occasional bifurcated root

  26. How To Tell Mandibular Central from Lateral: • Distal corner of incisal edge twisted lingually on lateral* • One wear facet on central, two facets on lateral

  27. Lateral vs central: • DI corner of lateral very slightly more rounded • Cingulum slightly offset to distal

  28. How to tell right from left: • Very difficult with mandibular centrals

  29. Right from left: • Laterals: • lingual twist of distal incisal edge* • DI slightly more rounded • Cingulum offset distally

  30. Wax Quiz

  31. Dimensions: • 10: 0 - 0.1 mm off • 9: 0.2 - 0.4 mm off • 8: 0.5 - 0.9 mm off • 7: 1.0 - 1.5 mm off • 6: greater than 1.5 mm off

  32. Axial Contours: • Surface contours as compared to the original • Facial, lingual, mesial, distal, incisal, occlusal • Line angles, point angles

  33. Occlusal surface: • Only posterior teeth! • Cusps, marginal ridges, cusp ridges, grooves, etc as compared with original

  34. CE Line: • Position, contour, smoothness, transition from root to crown

  35. Surface Texture: • Smoothness, without visible scratches or irregular surfaces • Wax additions should be seamless

  36. Surface Polish: • Degree of surface shine • No foreign coating on the surface, e.g. Speedshine, die lube, etc.

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