Taurodontism in 47,XXY males: an effect of the extra X chromosome on root development.

Effects of an extra X chromosome on root development were studied in males with a 47,XXY chromosome constitution. Occurrence of taurodontism in the permanent molars of the lower jaw was noted from orthopantomograms of 30 Finnish 47,XXY males, 16 of their first-degree relatives, and a sample of 157 normal males and females. Nine, or 30%, or the 47,XXY males had at least one mandibular molar which was classified as taurodont. Only hypotaurodont teeth were found, and the teeth affected were all either second or third molars. None of the control relatives showed taurodontism. In the population sample, four individuals, or 2.5%, had taurodont teeth. A change in the mitotic activity of the cells of the developing teeth is one possible factor that can affect root formation leading to the development of taurodontism.