Symmetry and combinations of hypodontia in non-cleft and cleft palate children.

Symmetry and combinations of hypodontia was studied and compared in non-cleft (NONC) and cleft palate (CP) groups with different prevalences of hypodontia. The NONC group included 300 children with one or more congenitally absent permanent teeth, excluding the third molars, and 79 children with isolated cleft palate without accessory anomalies. There were no significant differences between the groups in distribution of children with agenesis of 1 to 11 teeth. Bilateral agenesis increased with increasing number of absent teeth per child, and it was more frequent in the maxillary teeth of the NONC group and in the mandibular teeth of the CP group. Concomitant agenesis was observed in one to four different dental fields per child, and the distribution of the subjects was similar in both groups. We conclude that the symmetry of agenesis may be dependent on the population frequency of hypodontia and on the number of absent teeth per child. The agenesis in the CP group may have a common genetic basis, but the substantially higher incidence of hypodontia in the maxilla is likely caused by factors similar to those causing the cleft itself.