Oral Anatomy 2 - The Maxillary First (central) Permanent Incisor
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What do human incisors look like?
Human incisors have thin, blade-like crowns that are adapted for the cutting and shearing of food preparatory to grinding.
Viewed mesially or distally, the crowns of the incisors are roughly triangular in shape, with the apex of the triangular at the incisal margin of the tooth.
This shape is thought to facilitate the penetration and cutting of food.
Viewed buccally or lingually, the incisors are trapezoidal, the shortest of the uneven sides being the base of the crown cervically.
Generally, what is the maxillary first (central) permanent incisor like?
- This tooth is the widest mesiodistally of all the permanent incisors and canines, the crown being almost as wide as it is long.
- Like all incisors, it is basically wedge or chisel shaped and has a single conical root.
How does the maxillary first (central) permanent incisor appear from the incisal view?
- From the incisal view, the crown and incisal margin are centrally positioned over the root of the tooth.
- The incisal margin presents as a narrow, flattened ridge rather than as a fine sharp edge.
- The crown outline is bilaterally symetrical, being triangular - However, the mesial profile may appear slightly larger than the distal profile.
What may the incisal margin be grooved by?
- The incisal margin may be grooved by two troughs, the labial lobe grooves, which correspond to the divisions between three developmental lobes (or mammelons) seen on newly erupted incisors.
- The mammelons are lost by attrition soon after eruption.
How does the maxillary first (central) permanent incisor appear from the labial view?
- From the labial view the crown length can be seen to be almost as great as the root length.
- The crown has a smooth, convex labial surface.
- It may be marked by two faint grooves that run vertically towards the cervical margin and which are extensions of the labial lobe grooves.
- The convexity of the labial surface is especially marked cervically, the labial surface sometimes being flat at its middle and incisal regions.
What are the mesial and distal surfaces of the maxillary first (central) permanent incisor like?
- The mesial surface is straight and approximately at right angles to the incisal margin.
- The distoincisal angle, however, is more rounded and the distal outline more convex.
The mesial and distal views of the crown illustrate the fundamental wedge-shaped or triangular crown form of the incisor.
A line drawn though the axial center of the tooth lies roughly parallel to the mesial outline of the crown and root.
How does the maxillary first (central) permanent incisor appear palatally?
- Viewed palataly, the crown is more irregular, its middle and incisal regions being concave, giving a slightly shovel-shaped appearance to the incisor.
- The palatal surface of the crown is bordered by mesial and distal marginal ridges.
- Near the cervical margin lies a prominent cingulum.
- The cingulum may be single, divided, or replaced by prominent portions of the marginal ridges.
- Ocassionally, a slight ridge of enamel may run towards the incisal margin, dividing the palatal surface into two shallow depressions.
What is the cervical margin like in the maxillary first (central) permanent incisor?
The sinuous cervical margin is concave towards the crown on the palatal and labial surfaces and convex towards the crown on the mesial and distal surfaces, the curvature on the mesial surface being the most pronounced of any tooth in the dentition
What is the root like in the maxillary first (central) permanent incisor?
- The single root of the central incisor tapers towards the apex.
- The root is conical in cross section and apears narrower from the palatal than from the labial aspect.
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