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Morphology of Permanent Incisors
- 1. MORPHOLOGY OF PERMANENT INCISORS Dental Anatomy & Occlusion Dent 202
- 2. The permanent incisors ▪ Eruption sequence • 41/31, 11/21, 42/32, 12/22 ▪ Functions • Cutting • Esthetics • Speech ▪ Class traits • Incisal 2/3 flattened MD & compressed LL • Long horizontal MD biting edge • 2 or more mamelons • Marginal ridges parallel to long axis
- 3. The permanent maxillary incisors ▪ Arch traits • Crown • Wider MD • Smaller height / width proportion • Greater MD / LL proportion • Root • Greater MD / LL proportion • Conical root in central incisors ▪ Type traits • Size • Height / width proportion in crown • MD / LL proportion in crown and root
- 4. The permanent maxillary central incisors ▪ Labial aspect • The widest MD of all incisors – type trait • 3 mamelons • Middle is the smallest in width • Mesial has a raised shoulder • Distal has a low shoulder • 2 labial lobe grooves • 90º mesioincisal line angle – type trait • Rounded distoincisal line angle • Mesial contour straight, distal is somewhat rounded and both converge cervically • Mesial height of contour (contact point) within incisal third • Distal HOC at junction between incisal & middle thirds • CEJ convex cervically • Root is conical & inclined distally
- 5. The permanent maxillary central incisors ▪ Lingual aspect • Scoop-like surface • Lingual fossa bordered by (all more prominent in max.) • Mesial & distal marginal ridges • Cingulum • CEJ more convex than labial& summit toward distal • Root is narrower seen from lingual ▪ Mesial aspect • Chisel-shaped • Labial HOC in the cervical third • CEJ curved incisally (the most pronounced) – type trait • Incisal edge coincides with long axis • Root is conical
- 6. The permanent maxillary central incisors ▪ Distal aspect • CEJ is less curved than seen from mesial ▪ Incisal aspect • Triangular outline • Labial outline is slightly convex • Meets M+L outlines at sharp line angles • Mesial outline is longer than distal • Labial lobe grooves ▪ Pulp • Mirrors the external configuration • Widest LL diameter at CEJ • Line of division between pulp chamber & canal is not marked • Most incisally, pulp chamber is thin LL with 2 horns • Pulp canal is conical
- 8. The permanent maxillary lateral incisors ▪ Labial aspect • Narrower MD & shorter IC – type trait • Root is of same length • More rounded in general • MI angle • DI angle more rounded • M & D outlines • HOCs are farther from incisal edge • Mesial HOC is between middle & incisal thrids • Distal HOC is at the center of middle third • Root is conical and slightly inclined distally ▪ Lingual aspect • Marginal ridges & cingulum are more pronounced • Lingual fossa is deeper • Developmental groove and pit?
- 9. The permanent maxillary lateral incisors ▪ Mesial aspect • Cingulum more convex • CEJ less curved ▪ Distal aspect ▪ Incisal aspect • Ovoid outline • Smaller MD than central • Labial outline is rounded • ML & DL line angles are more rounded ▪ Pulp • Similar to central
- 11. The permanent mandibular incisors ▪ Arch traits • Crown • Narrower MD • Greater height / width proportion • Smaller MD / LL proportion • Root • Smaller MD / LL proportion • Generally oblong in x-section ▪ Type traits (arch trait) • Nearly equal in size & dimensions
- 12. The permanent mandibular central incisors ▪ Labial aspect • The narrowest MD of all incisors • Bilaterally symmetrical (type trait) • 3 mamelons • Mesail and distal mamelons are of equal prominence • 90 º MI & DI angles and are at same level IC (type traits) • Both HOCs are within the incisal third • M & D outlines are almost straight lines • CEJ convex cervically • Root is narrow but not conical ▪ Lingual aspect • Shallow fossa & less prominent cingulum & marginal ridges • CEJ summit in the center
- 13. The permanent mandibular central incisors ▪ Mesial aspect • Labial HOC within cervical third • From HOC toward incisal edge labial outline is straight • Root • Broad & flat • A shallow depression in the midportion • Ovoid in x-section ▪ Distal aspect • CEJ is less curved ▪ Incisal aspect • Triangular • Labial surface is flat compared to max. incisors • Seldom labial lobe groove • Long axis of incisal edge is perpendicular to LL line (type trait) • Mesial outline = distal outline in length ▪ Pulp • Broad LL and narrow MD
- 15. The permanent mandibular lateral incisors ▪ Labial surface • Slightly wider than central • Lack of bilateral symmetry • MI angle is sharp while DI angle is rounded & more cervically situated ▪ Lingual & mesial aspects • Nearly identical to that of central ▪ Distal aspect • More of the incisal edge is visible • CEJ is less pronounced ▪ Incisal aspect • Incisal edge is not perpendicular to LL line • DI angle is more toward lingual ▪ Pulp • Similar to that of central
- 17. Incisal relationship ▪ Class I ▪ Class II ▪ Class III ▪ Overjet ▪ Reverse overjet ▪ Overbite