One of two teeth located between the maxillary central incisors and the canines in the permanent dentition. The crown has a very similar morphology to the upper central incisor but is significantly smaller with a narrower mesio-distal width. The disto-incisal angle is more rounded than the upper central incisor, and below the cingulum there is a well-defined fossa or pit. The root is a similar shape to that of the upper central incisor and of almost equal length. The pulp chamber is triangular in cross-section, with two pulp horns directed towards the mesial and distal incisal corners. There is usually only one root canal but it may be subject to considerable variation. The upper lateral incisor is the most common incisor tooth to be congenitally absent or show some degree of deformity, usually being conical or peg-shaped. Calcification of the tooth begins at about 10–12 months after birth and the crown is normally complete by 4–5 years of age. The tooth erupts at about 8–9 years and the calcification of the root is complete at about 11 years.