General of Mandibular General of Mandibular Incisors: DescriptionIncisors: 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.

Labial AspectLabial Aspect

a. a. Crown shape and size (8.8 Crown shape and size (8.8 mm)mm)

* The narrowest mesiodistally (5.3 mm) [type trait]

* Bilaterally symmetrical [type trait] * Shallow developmental depression. * Mamelon on newly emerged teeth.

Labial AspectLabial Aspect

b. b. Incisal Proximal AnglesIncisal Proximal Angles * Mesioincisal Angles sharp

form 900 angles

* Distoincisal angle sharp

Labial AspectLabial Aspect

c. c. Contact AreaContact 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 AspectLingual Aspect** Crown outline is symmetricalCrown 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 AspectsProximal Aspects 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.

ProximalProximal AspectsAspects

Root

Broad and flatBroad and flat

Tapers in the apical thirdTapers in the apical third

Blunt apexBlunt apex

Shallow depression on Shallow depression on M & DM & D

Incisal AspectIncisal Aspect

* Crown proportions wide labiolingually [Arch trait].

* Crown outline triangular

• Cingulum centered, narrow

• convex outline.

Labial AspectLabial Aspect Crown Crown (9.4 mm.)(9.4 mm.)

Asymmetric [Type trait]Asymmetric [Type trait]

Wider than C.I. Wider than C.I. (5.7 mm)(5.7 mm)

* * Mesioincisal angleMesioincisal angle slightly roundslightly round

* * Distoincisal angleDistoincisal angle more rounded.more rounded.

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

Lingual AspectLingual Aspect CrownCrown - - not bilaterally symmetricalnot bilaterally symmetrical

CingulumCingulum small small

distally locateddistally located

Mesial marginal ridge isMesial marginal ridge is

longer than D.M.R.longer than D.M.R.

Marginal ridges and lingual Marginal ridges and lingual fossa fossa are not conspicious.are not conspicious.

Lingual AspectLingual Aspect

Root Root

Narrower than labialNarrower than labial

Longitudinal depressions Longitudinal depressions on the proximal surfaces on the proximal surfaces

can be seen.can be seen.

Proximal AspectsProximal Aspects Incisal edgeIncisal edge - - twisted disto - twisted disto - lingually lingually

Cervical lineCervical line - less curved than - less curved than C.I., C.I., M. more curved M. more curved than D.than D.

Crest of CurvatureCrest of Curvature::

** Labially Labially - near the cervical in - near the cervical in the cervical third. the cervical third.

** LinguallyLingually - on the cingulum. - on the cingulum.

Proximal AspectsProximal Aspects

RootRoot

* * Its outline is Its outline is straight straight from the from the cervical line to the middle cervical line to the middle

third; third; then it tapers.then it tapers.

* * Longitudinal depression Longitudinal depression mesially mesially and distallyand distally, but less distinct on , but less distinct on

the distal.the distal.

Incisal AspectIncisal Aspect

Crown is Crown is broaderbroader labiolingually labiolingually than MD.than MD.

Crown outline is Crown outline is notnot bilaterally bilaterally symmetrical.symmetrical.

Incisal ridge contour has a Incisal ridge contour has a distolingual twist.distolingual twist. Cingulum is slightly off center to Cingulum is slightly off center to

the distal.the distal. Labial outline is slightly Labial outline is slightly convex.convex.

The pulp cavity is The pulp cavity is flattenedflattened mesio-distally mesio-distally in confirmity with the root shapein confirmity with the root shape

In the coronal portion In the coronal portion similarsimilar to its to its maxillary counterpart maxillary counterpart

The pulp cavity of mandibular lateral The pulp cavity of mandibular lateral incisor is incisor is identicalidentical to central incisor to central incisor