Characteristics of incisor-premolar hypodontia in families.

Nonsyndromic tooth agenesis is a genetically and phenotypically heterogenous condition. It is generally assumed that different phenotypic forms are caused by different mutated genes. We analyzed inheritance and phenotype of hypodontia and dental anomalies in 214 family members in three generations of 11 probands collected for genetic linkage study on incisor-premolar hypodontia (IPH). Our analysis confirms the autosomal-dominant transmission with reduced penetrance of IPH. The prevalence of hypodontia and/or peg-shaped teeth was over 40% in first- and second-degree relatives and 18% in first cousins of the probands. Four of nine noted obligate carriers of hypodontia gene had dental anomalies, including small upper lateral incisors, ectopic canines, taurodontism, and rotated premolars. These anomalies were also observed at higher than normal frequency in relatives affected with hypodontia. We conclude that incisor-premolar hypodontia is a genetic condition with autosomal-dominant transmission and that it is associated with several other dental abnormalities.