Abnormalities of tooth size and form associated with familial hypodontia
Background: reduction in tooth size and form associated with hypodontia was well established and in population studies the relationship has been shown to be statistically significant. Mutations in Pax9 gene have been described in families in which inherited hypodontia associated with reduction of tooth size involved permanent molars (posterior teeth).
Objectives: our study analyzed 5 unrelated families with dominantly inherited hypodontia of maxillary lateral incisors (anterior teeth) and characterized the clinical phenotypes, inheritance pattern and molecular diagnosis of associated dental anomalies.
Methods: a group of 76 Caucasian patients with hypodontia undergoing orthodontic treatment were evaluate clinically and radio graphically; nine of them were selected based on their clinical phenotype; we collected information about family medical history; for DNA analysis, blood samples were collected from patients, their affected parents and sibs and unaffected first-degree relatives. DNA samples were analyzed by PCR.
Results: dental abnormalities affected permanent dentition of the patients and two clinical phenotypes were found: congenitally missing lateral incisor on one side of the upper arch and small lateral incisor on the other and congenitally missing lateral incisor on one side of the upper arch and peg-shaped lateral incisor on the other. Both left side and right side of the arch were involved. Associated dental anomalies showed an autosomal dominant inheritance pattern but complete absence in mother or father was followed by small or peg-shaped upper lateral incisor in children. The correlations between clinical phenotypes and molecular results did not confirm the Pax9 phenotypes previously reported.
Conclusions: our results suggest that abnormalities of tooth size and shape associated with familial hypodontia are caused by mutation in a single gene which affects normal development of upper lateral incisors.