Permanent Incisors Overview

Study Notes

The permanent incisors are the first four teeth in each quadrant of the mouth. They are responsible for biting, incising, and shearing food.
They also contribute to aesthetics and phonetics.
They are anterior teeth and are essential for a person’s appearance, facial profile and speech.

The maxillary central incisors are the two teeth adjacent to the midline in the upper arch.
They share a mesial contact with each other and a distal contact with the lateral incisors.
The crown is trapezoidal in shape when viewed labially or lingually and widest mesiodistally.
It is triangular in shape when viewed proximally.

The labial aspect is generally convex in both mesiodistal and incisogingival directions.
The convexity is greatest in the cervical third and tends to become flatter towards the incisal third.
The mesiolabial aspect is slightly convex and may be nearly straight.
The crest of curvature is located at the contact area in the incisal third.
The mesio-incisal angle is sharp.
The distolabial aspect has a convex outline, but a more rounded disto-incisal angle.
The crest of curvature is associated with the contact area, which is located in the incisal third, very near the junction of the incisal middle third.
The incisal margin may exhibit mamelons and has a generally straight outline, nearly perpendicular to the long axis of the tooth.
The CEJ curves evenly towards the root.
The cervical margin is narrower mesiodistally.

Two straight, shallow depressions, extending from the incisal edge toward the gingival, represent the division of the three labial lobes. These are called mesiolabial and distolabial depressions.
Faint curved lines roughly parallel to the CEJ in the cervical third are called imbrication lines. These are not always present.

The lingual aspect is roughly trapezoidal, slightly narrower mesiodistally.
It exhibits both concavity and convexity.
The concavity is called the lingual fossa and covers the incisal half to two-thirds of the surface.
The convexity is called the cingulum and is located in the cervical portion.
The mesial and distal outlines are similar to their labial counterparts, except that they converge slightly more toward the gingival.
The incisal margin is similar to the labial aspect.
The cervical margin has a greater depth of curvature apically than the labial margin; it is asymmetrical.

The lingual fossa is a shallow concavity located in the incisal half to two-thirds of the crown, including the largest area of the lingual surface.
It is bounded by the mesial and distal marginal ridges, the incisal edge, and the cingulum.
The cingulum is a bulky convexity located in the cervical portion.
The lingual fossa is usually smooth and sometimes poorly defined, creating a W-shaped pattern.

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