Genetic variance and heritability were estimated for 16 dental occlusal variables, based on a sample of 23 MZ and 35 DZ twin pairs from Chandigarh, India. Results of the t-test for equality of means showed association of zygosity with only one of the 16 variables (posterior teeth displacement), thus showing bias in the trait's genetic variance analysis. Heterogeneity of variance among zygosities was demonstrated for seven traits suggesting considerable amount of hidden environmental influence. There was evidence of stronger environmental covariance for monozygotic than for dizygotic twins. In contrast to other such studies, Indian MZ twins indicated higher variance than the DZ twins for a number of traits. These observations demonstrate some complex environmental determinism for occlusal traits, while significant genetic variance obtains for arch and palate measurements.

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