Permanent Mandibular Incisors

Morphology of Mandibular Incisors

General of Mandibular Incisors: Description They are generally the first permanent teeth appear in the oral cavity. C.I. Usually erupts during the seventh year of life and followed within 1 year by the lateral incisors. Mandibular incisors might be referred to as the “moving cutting blades” of the dentition, thereby providing the cutting function of masticatory apparatus.

Morphology of Central Incisors

Labial Aspect * The narrowest mesiodistally (5.3 mm) [type trait] a. Crown shape and size (8.8 mm) * The narrowest mesiodistally (5.3 mm) [type trait] * Bilaterally symmetrical [type trait] * Shallow developmental depression. * Mamelon on newly emerged teeth.

b. Incisal Proximal Angles Labial Aspect b. Incisal Proximal Angles * Mesioincisal Angles  sharp form 900 angles * Distoincisal angle  sharp

c. Contact Area * Mesial  in the incisal third Type trait Labial Aspect c. Contact Area * Mesial  in the incisal third Type trait * Distal  in the incisal third

d. Root (12.5 mm) * Narrow M.D., wide F.L. * Tapers uniformly from cervical line to the apex. * Apex curve slightly to the distal. Root to crown ratio is larger than maxillary central incisor. [Arch Trait]

Lingual Aspect * Crown outline is symmetrical a. Lingual fossa - shallow depression. b. Cingulum - convex, small and centered. c. M & D marginal ridge - less prominent. [Arch Trait]. * Root  is narrower from the lingual than labial.  M & D longitudinal depression.

Proximal Aspects * Labial surface  incisal to the cervical line. * Mesially - deep curvature * Distally - less curvature than M.  Crest of curvature * Labial surface  incisal to the cervical line. * Lingual surface  in the cervical third, on the cingulum.

 Root  Broad and flat  Tapers in the apical third  Blunt apex Proximal Aspects  Root  Broad and flat  Tapers in the apical third  Blunt apex  Shallow depression on M & D

Incisal Aspect * Crown proportions  wide labiolingually [Arch trait]. * Crown outline  triangular Cingulum  centered, narrow convex outline.

Morphology of Mandibular Lateral Incisors

Labial Aspect  Crown (9.4 mm.)  Asymmetric [Type trait]  Wider than C.I. (5.7 mm) * Mesioincisal angle  slightly round * Distoincisal angle  more rounded.

third, near the incisal edge. * Distal contact area  in the incisal * Mesial contact area  in the incisal third, near the incisal edge. * Distal contact area  in the incisal third but cervical to the mesial contact area.  Root (13.5 mm) * Narrow M.D. * Tapers from cervical line toward the apex. * Apex curve slightly to the distal

Lingual Aspect  Crown - not bilaterally symmetrical  Cingulum small distally located  Mesial marginal ridge is longer than D.M.R.  Marginal ridges and lingual fossa are not conspicious.

 Root   Narrower than labial Lingual Aspect  Root   Narrower than labial  Longitudinal depressions on the proximal surfaces can be seen.

Proximal Aspects  Incisal edge - twisted disto - lingually  Cervical line - less curved than C.I., M. more curved than D.  Crest of Curvature: * Labially - near the cervical in the cervical third. * Lingually - on the cingulum.

Proximal Aspects  Root * Its outline is straight from the cervical line to the middle third; then it tapers. * Longitudinal depression mesially and distally, but less distinct on the distal.

Incisal Aspect  Crown is broader labiolingually than MD.  Crown outline is not bilaterally symmetrical.  Incisal ridge contour has a distolingual twist.  Cingulum is slightly off center to the distal.  Labial outline is slightly convex.

PULP The pulp cavity is flattened mesio-distally in confirmity with the root shape In the coronal portion similar to its maxillary counterpart The pulp cavity of mandibular lateral incisor is identical to central incisor

Comparison

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