Maxillary Central Incisor - Variation

Variation

Sinodonty, a genetic variation occurring in Native Americans and some East Asian populations, is possibly a trait retained from an indigenous East Asian archaic human ancestor Homo Erectus Pekinensis. Among its features are shovel-shaped incisors that derive their name from the deeper-than-normal lingual fossa and prominent marginal ridges of the teeth. When seen from lingual view, the tooth is said to resemble a shovel and are rotated slightly inward. It is also common to see signs of attrition, which is wear over time from other tooth contact. The lingual of maxillary incisors and the facial of mandibular incisors are the most common places for attrition to occur.

When space exists between the contacts of the maxillary central incisors, the condition is referred to as a diastema or "gap tooth." One frequent cause of the space is the presence of a large labial frenum from the upper lip extending near the teeth. Treatment depends upon the cause and extent of the gap. Periodontal surgery may be required to reduce the frenum. A small space may be corrected with a filling, veneer, or crown. Larger spaces may require orthodontics.

The maxillary incisors, both the central and lateral, are the most likely teeth to have a talon cusp, which is an extra cusp on the lingual surface. Talon cusps have been found in to range in less than 1% to 6% of the population, and 33% of cases occur on the permanent maxillary central incisor. Deciduous teeth are unlikely to have talon cusps. Also, the permanent maxillary incisors are the most likely teeth to have a dilaceration, which is a sharp curve on a tooth.

All incisors have the potential to be affected by a case of congentital syphilis, which can cause a notch to form on the incisal edges of these teeth. These teeth, sometimes described as screwdriver-shaped, are called "Hutchinson's incisors." They serve as part of Hutchinson's triad, which also includes interstitial keratitis and eighth nerve deafness.