One of two teeth located between the maxillary lateral incisors either side of the midline in the permanent dentition. They replace the maxillary primary central incisor teeth. The crown has a convex labial surface slightly flattened incisally, usually with two slight vertical grooves close to the incisal edge. The labial surface merges more gradually with the distal than the mesial surface. The lingual surface is concave except for a pronounced convexity (cingulum) towards the cervical margin. The lingual surface is triangular, bounded by mesial and distal marginal ridges extending from the incisal edge to the cingulum. Between the marginal ridges and the cingulum lies a lingual pit which may be partly divided by a central ridge. The mesial and distal surfaces are triangular in shape and are both inclined lingually. The angle formed by the incisal edge and the distal surface is much more rounded than the angle formed by the incisal edge and the mesial surface. The tooth has a single root, triangular in cross-section, tapering gradually towards the apex. 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. Calcification of the tooth begins at about 3–4 months after birth and the crown is normally complete by 4–5 years of age. The tooth erupts at about 7–8 years and the calcification of the root is complete at about 10 years.