Summary
Highlights
The permanent maxillary lateral incisor is the second tooth from the midline. Its tooth numbers are 12 and 22 in FDI, 7 and 10 in Universal, and 2 in Zsygmondy Palmar system. Its primary function is cutting. The tooth develops from four lobes: mesial, labial, distal, and lingual, with the lingual lobe forming the cingulum. New teeth often show three mamelons. These teeth are the second most common to exhibit developmental anomalies after third molars, like peg-shaped laterals. Eruption occurs between 8 to 9 years of age.
The cervico-incisal length (crown length) is 9 millimeters, and the root length is 13 millimeters. The mesio-distal diameter of the crown is 6.5 millimeters, narrowing to 5 millimeters at the cervix. The labio-lingual diameter of the crown is 6 millimeters, also 5 millimeters at the cervix. The cervical line curvature on the mesial side is 3 millimeters, and on the distal side, it is 2 millimeters.
From the labial aspect, the crown has a trapezoidal outline, with the longer side towards the incisal ridge. The incisal surface is slightly rounded, and both mesio-incisal and disto-incisal angles are rounded, with the disto-incisal being more rounded. The mesial contact area is at the junction of the incisal and middle thirds, while the distal contact area is in the middle third. Both mesial and distal outlines are convex, and the cervical line is convex towards the root. The labial surface is smooth and convex, and the root is smooth, conical, tapering, often with a distal tilt at the apex.
The lingual aspect is narrower than the labial, retaining the same outline form but with a different surface. It features three ridges: incisal, mesial marginal, and distal marginal, all converging towards the cingulum. The cingulum is a circular convexity in the cervical third. Between these ridges and the cingulum is a V-shaped lingual fossa. The root morphology is similar to the labial aspect. Random grooves and pits, and sometimes a palato-gingival groove, can be found in the lingual fossa, making the tooth susceptible to caries and periodontal problems.
From the mesial aspect, the crown outline is triangular or wedge-shaped, with its base at the cervix and the incisal ridge at the midline. The labial outline is convex with its crest at the cervical third. The lingual outline is convex in the cervical third, concave in the middle, and convex in the incisal third. The cervical line is convex towards the crown. The root is smooth, convex, and tapering. The distal aspect shares all the features of the mesial aspect.
From the incisal aspect, no part of the root is visible. The mesio-distal diameter is greater than the labio-lingual diameter. The labial outline is convex, and the lingual outline shows lingual convergence. The incisal ridge runs horizontally.