External Morphology Maxillary Central Incisor

Facial view

Crests of Curvature

The mesial and distal crests of curvatures are at different levels as the mesial surface contacts the adjacent central incisor and the distal surface is in contact with the lateral incisor. The mesial crest of curvature is in the the incisal third of the crown and the distal crest of curvature is located at the junction of the middle and incisal third of the crown. The outline of the crown is a series of curves. The mesial crown outline is slightly convex while the distal outline of the crown is more convex. The crown has an incisal ridge which is slightly convex from mesial to distal. Two basic crown shapes exist; one is wide M-D at the cervix (square crown form) and the other is narrow M-D at the cervix (tapered crown form). In the facial view, the cervical line is convex.

Incisal Ridge

There is evidence of three mamelons visible in the unworn (newly erupted) tooth (see arrows). With wear, the incisal ridge becomes an incisal edge. The incisal ridge is slightly curved mesiodistally so that the crown has its greatest length in the centre of the incisal ridge of the tooth.

Labial Surface of Crown

Three convexities are visible on the labial surface that demarcate the three labial lobes. 

Root

The root is cone-shaped and convex on its labial surface. There is a conical shape to the root which has greater taper in the apical half compared to the cervical half of the root. Overall the root is usually about 2 or 3mm longer than the crown. There is often a curvature of the apex to the mesial or distal and this curvature is variable. The apex is usually slightly blunt.