Permanent Maxillary Incisors: Detailed Characteristics and Development

1. Permanent Incisors

2. Introduction: • Centrals and laterals • #7, 8, 9, 10 and 23, 24, 25, 26 • Maxillary larger than mandibular • Important in esthetics, mastication, phonetics

4. Terminology: cingulum CEJ lingual fossa mamelons marginal ridge

5. Some common traits: • Incisal edge present = incisor • Mamelons: 2 or 3 • Marginal ridges more parallel to long axis • Presence of lingual fossa and cingulum

7. Permanent Maxillary Central Incisor

8. General characteristics: • Arch position: on either side of midline • Adjacent mesial surfaces • Universal #8 and #9 • M-D almost as wide as I-C dimension* • Wider M-D than F-L* (I-C > M-D > F-L) • Widest M-D of all anterior teeth* *type trait

11. Development timeline* • Beginning calcification: 3 - 4 months • Completion of enamel: 4 - 5 years • Eruption: 7 - 8 years • Root completion: 10 years (2 years later) *Fuller/Denehy

12. Labial View • Basic crown shape is trapezoidal • Surface generally flat, developmental depressions visible • M-D and I-C dimension more nearly equal* (as compared to other incisors) • Cervical line more flat (more than any other anterior teeth)

13. Labial view: • Incisal edge perpendicular to long axis • Facial height of contour in cervical third • Mamelons visible in newly erupted teeth

14. Labial view: mesial outline • Mesial outline nearly straight • MI angle sharp • Mesial contact area (HOC) at incisal third

15. Labial view: distal outline • Outline more convex than mesial • DI angle more rounded • Distal contact area (HOC) near junction of incisal-middle third

16. Lingual View • Slightly narrower M-D than labial • Surface has both convexity and concavity • Marginal ridges, M and D • Cingulum • Lingual fossa • Incisal ridge

17. Lingual view: • M and D outlines similar to labial view • CE curvature greater than labial, slight offset to distal • Lingual height of contour at cervical third • M and D marginal ridges border lingual fossa

18. Mesial View • Crown basically triangular • Mesial CE line curvature is greatest of any tooth* • Incisal edge is in line with long axis • Mesial height of contour (mesial contact area) at incisal third

19. Mesial view: • Labial outline • slightly convex • height of contour at cervical third • incisal 2/3 nearly flat • Lingual outline: S-shape • concave incisally • convex cervically • height of contour at cervical third • Incisal edge slopes lingually

20. Distal View • Generally similar to mesial • Distal surface slightly more convex than mesial • CE line curvature is less than mesial • Distal HOC near junction of incisal-middle third

21. Incisal View • Roughly triangular outline* • Lingual narrower than labial • Wider M-D than F-L* • Incisal edge is midway faciolingually *type trait

22. Root • Single, conical, straight • Cross-section at cervical roughly triangular* • Ratio of crown to root: 2/5 to 3/5

23. How to tell if you have a maxillary central: • Presence of incisal edge, sloping lingually • M-D width broad (8-9 mm) • M-D almost as wide as I-C dimension* • Wider M-D than F-L* • I-C > M-D > F-L • Relatively flat labial surface • M and D incisal corners relatively sharp • Root cross-section more triangular

24. How to distinguish right from left: • Mesial outline straighter than distal* (distal has more convexity than mesial) • MI angle is sharper than DI* • CE line curvature is greater on mesial* • Mesial HOC more incisal than distal* • Lingual cervical line sometimes offset distally

30. Next… Maxillary Lateral Incisor

31. Permanent Maxillary Lateral Incisor

32. General Characteristics • Second tooth from midline • Between maxillary central and maxillary canine • Universal numbers: #7 and #10 • Resembles maxillary central except: • Smaller in all dimensions except root length* • Generally more rounded • Displays more variation in form

36. Development Timeline: • Beginning calcification: 1 year • Completion of enamel: 4 - 5 years • Eruption: 8 - 9 years • Root completion: 11 years

37. Labial View • Mesial outline • More convexity than mesial of central • HOC (contact area) is at incisal third (closer to the junction of the incisal and middle thirds)

38. Labial View • Distal outline • DI corner noticeably more rounded than MI (most rounded incisal corner*) • HOC is at junction of incisal-middle third to the middle of the middle third

39. Labial view: • Incisal outline • More rounded than central esp. DI corner • Greatest rounding of any incisor* • Labial height of contour: cervical third

40. Lingual View • Marginal ridges more prominent • Lingual fossa deeper • Lingual pit often present • Linguogingival fissure sometimes present • Height of contour at cervical third

41. Mesial View • Labial outline is convex • Lingual outline is S-shape • CE line curvature greater than distal • Incisal edge is inline with long axis of tooth • Mesial HOC near junction of incisal and middle 1/3

42. Distal View • Similar to mesial except • HOC more cervical (closer †o middle 1/3) • CE line curvature less than mesial

43. Incisal View • Generally more convexity than central • MD ≥ FL dimension • Incisal edge is midway faciolingually

44. Root • Single rooted • Root wider F-L than M-D • Apical third may be deflected distally* • Cross-section more ovoid than central

45. Variations and anomalies: • Most variations in form besides third molars* • May be congenitally missing • “Peg” lateral: peg-shaped crown

46. How to tell if you have a maxillary lateral: • Smaller in size than max central • More distinct lingual anatomy • Presence of deeper lingual fossa • Presence of lingual pit • Incisal outline more rounded • M and D outlines more rounded

48. How to tell right from left: • MI corner sharper than DI corner* • Mesial CE line curvature greater than distal • Mesial height of contour more incisal than distal’s* • Distal outline more convex* • Apex deflected distally