Mandibular Incisors PDF

“ MORPHOLOGY OF PERMANENT MANDIBULAR INCISORS ”  MANDIBULAR CENTRAL INCISOR The mandibular central incisors are characterized by having a smaller mesiodistal dimension than any other tooth. IT is even smaller than the lateral incisor....

“ MORPHOLOGY OF PERMANENT MANDIBULAR INCISORS ”  MANDIBULAR CENTRAL INCISOR The mandibular central incisors are characterized by having a smaller mesiodistal dimension than any other tooth. IT is even smaller than the lateral incisor. Each tooth occludes with 2 teeth of the opposing arch except the mandibular central incisor and the maxillary last molar. ❑1st Evidence of Calcification 3 to 4 Months ❑Enamel Completed 4 to 5 Years ❑Eruption 6 to 7 Years ❑Root Completed 9 Years  5 ASPECTS Labial Lingual Mesial Distal Incisal Labial Aspect The labial aspect of the mandibular central incisor is symmetrical The tooth tapers evenly from the incisal Angle to the root apex.  Labial aspect The Crown outline: - The mesial and distal outlines of the crown are straight D M - The contact areas at the incisal third, are near the incisal ridges mesially and distally. - The incisal ridge is smooth and straight, as mamelons are worn off soon after eruption. - Incisal outline is regular and at right angle to the long axis of the tooth.  Disto- Mesio- Labial aspect incisal incisal angle angle -The mesial and distal incisal angle are sharp. ❖The cervical line is convex root wise. D M The root: - The mesial and distal outlines of the root are tapered from the cervix to the pointed apex. - The apical third curves distally in most cases, but sometimes straight.  Labial Aspect Lingual Aspect The outline is a mirror image of that of the labial  Lingual aspect 1 The crown and root tapers lingually. M D 2 ✓ Poorly developed cingulum (present at cervical 1/3). ✓ Indistinct marginal ridges and incisal ridge. ✓ In the middle and incisal thirds shallow lingual fossa. 3 ✓ The cervical line is placed ½ mm apically, making the crown longer on the lingual side. PROXIMAL ASPECTS Mesial Distal  Mesial aspect The Geometric outline of the crown: Wedge in shape or triangular; the base cervically and the apex incisally. The incisal ridge is lingual to the long axis of the tooth. The outline: - The labial outline is convex in the cervical third then straight. - The lingual outline is convex at cervical 1/3. - Then concave at the lingual fossa. - Then slightly convex for the incisal ridge. ❑ The labial crest of curvature is at center of cervical third and at the same level on the lingual. ❑ The mesial cervical line is concave root wise reaching about 1/3 of the crown. The root: The root outlines are straight and parallel in the cervical and middle thirds keeping the root broad, the root then tapers in the apical third to a rounded or pointed apex. The mesial surface of the root is broad with a developmental depression.  Distal aspect Is a mirror image of the mesial one --The cervical line curvature is shallower than mesial. - The developmental depression is more marked with a developmental groove in its center.  Incisal aspect -The dimensions of the crown are greater labiolingually than mesiodistally - The labial surface is broader than the lingual. - This aspect demonstrates bilateral symmetry. - The incisal ridge is at right angle to the line bisecting the crown labiolingually. -The incisal ridge tend to be inclined lingually, so much of the labial surface is see than on the lingual surface.  MANDIBULAR LATERAL INCISOR ❑1st Evidence of Calcification 3 to 4 Months ❑Enamel Completed 4 to 5 Years ❑Eruption 7 to 8 Years ❑Root Completed 10 Years  MANDIBULAR LATERAL INCISOR The mandibular lateral incisor is slightly larger than the mandibular central incisor.  DIFFERENCES FROM LABIAL AND LINGUAL ASPECTS Mesial and distal contact areas not at the same level. The mesial contact area is near the mesio-incisal angle and the distal slightly apical. The mesial side is longer than the distal and the incisal edge is slopping distally.  INCISAL ASPECT The incisal ridge follows the curvature of the mandibular arch giving the crown the appearance of being slightly twisted over the root base.  Any Questions ?