Anomalies of tooth numbers including peg-shaping

The congenital defects of hypodontia, peg-shaped teeth and hyperdontia appear to have a genetic basis. Peg-shaping is a modified expression of the same genotype as hypodontia. The defect is inherited as a dominant autosomal trait with variable expressivity. Third molars are the most frequently missing teeth. Both hypodontia and hyperdontia are found in a number of well-defined genetic syndromes and in most instances are common characteristics of the disease.