The inheritance of bilateral rotation of maxillary central incisors

Abstract

Abstract Wing‐like appearance is a term identifying mesiopalatal torsion of upper permanent central incisors. Previous studies have shown that the trait is more frequent in Amerind populations than in Caucasoids and pointed to a genetic cause. The purpose of this study is to establish the hereditary mechanism involved in the transmission of this trait. The population studied is an Indian community (Queckchi) of the municipality of St. Maria Cahabon, Guatemala. The group examined consists of 1,080 individuals, 752 (69.63%) classified as Indians and 328 (30.37%) as non‐Indians. From this sample 37 index cases were identified and their families studied in detail. Six phenotypic variants were observed (left, right and bilateral mesiolabial and mesiolingual torsion). Sex ratio among affecteds is 45% female, 55% male, Pedigree study supports an autosomal dominant mode of inheritance with 84% penetrance and variable expressivity . Segregation analysis using the maximum likelihood method of Morton yields an estimate of p (the segregation frequency) of 0.42 which rules out recessive inheritance. To rule out a sex‐linked gene, a χ 2 test on offspring of normal females married to affected males is not significant (χ 2 = 0.008). The gene frequency in the Indian and non‐Indian groups is pi = 0.1 and pn = 0.08 respectively. The lack of racial differences is thought to be due to racial admixture.