THE GENETIC CONTRIBUTION TO DENTAL MATURATION

It has been established in the literature that there is a major geneti c impact on tooth size (Potter et al., 1976; Corruccini and Sharma, 19 85; Sharma et al., 1985), tooth morphology (Kraus and Furr, 1952; Bigg erstaff, 1970), and root formation (Garn et al., 1960; Green and Aszkl er, 1970). None of the studies concerning root formation, however, use d the more advanced method of path analysis and model fitting to estim ate genetic influence. The aim of the present study was to determine t he genetic and environmental influence on dental maturation. Dental ag e scores were determined on panoramic radiographs of 58 pairs of twins -26 monozygotic (MZ) and 32 dizygotic (DZ)-with the method of Demirjia n et al. (1973). No mirror-image effect was found between the sides of the same individual or between twin members, so dental maturation see ms to be symmetrical for both left and right sides of the mandible. Co rrelation coefficients were significantly higher in MZ than in DZ twin s, which suggests a genetic influence. Model fitting showed that the v ariation in dental age was best explained by additive genetic influenc es (A-component) (43%) and by environmental factors common to both twi ns (C-component) (50%). The specific environment (E-component) added o nly 8% to the model. The importance of the common environmental factor can be explained by the fact that twins, being raised together, share the same prenatal, natal, and immediate post-natal conditions that ar e of importance for the formation of the teeth.