Non-syndromic concomitant hypodontia and supernumerary teeth in an orthodontic population.

The simultaneous occurrence of hypodontia and supernumerary teeth in the same individual is termed 'concomitant hypo-hyperodontia' (CHH). There appears to be a correlation between CHH and some syndromes, but this anomaly is very rare in the general population. The aim of this study was to investigate the frequency of CHH in a large sample of non-syndromic orthodontic patients. The records of 2108 consecutive non-syndromic orthodontic patients aged from 7 to 16 years were examined retrospectively. Every patient had at least one panoramic radiograph. When the diagnosis of hypodontia and/or hyperodontia was made in a child under 10 years of age, a second panoramic film was taken 2-4 years later. Statistical analysis of the data was undertaken using a chi-square test. Single or multiple hypodontia was diagnosed in 137 patients (6.5 per cent), 62 males and 75 females. One or more supernumerary teeth were found in 42 patients (2 per cent), 22 males and 20 females. CHH was diagnosed in seven subjects (0.33 per cent), four males and three females. In the CHH subpopulation, the total number of absent and supernumerary teeth was nine and eight, respectively. Hypodontia always occurred in the permanent dentition and was more frequent in the mandible than in the maxilla (four versus three teeth). Supernumerary teeth were more frequent in the permanent than in the primary dentition (six versus two teeth). Five supernumeraries were located in the maxilla and three in the mandible.