The prevalence and mode of inheritance of median diastema in the Sinhalese

Prevalence and mode of inheritance of median diastema has been studied in a population of 1018 Sinhalese (551 males and 467 females, age range 20 to 30 yrs). Median diastema is a visually detectable gap or space of more than 1mm between the upper permanent central incisors 1^1. A metal blade 1 mm thick was used as a measuring gauge. If the gauge passed through without any interference when inserted at right angles to the surface of 1^1, the trait was recorded as present. The prevalence of median diastema in the Sinhalese was compared with that reported for other population groups. Fifteen subjects who had median diastemas with high frenum were randomly selected as probands for construction of pedigrees. The most probable mode of inheritance was determined by using different models of inheritance. The findings were confirmed by assessing the frequency of distribution of the trait among individuals in the pedigrees using the simple counting method. The prevalence of median diastema in the Sinhalese is 9% and the mode of inheritance in the pedigrees studied was autosomal dominant with full penetrance.