Abstract
A survey was conducted on the occurrence of conical and dwarf teeth, Carabelli's tubercle and consanguineous marriage in a total of 11830 subjects of both sexes, aged 6 to 18 years and residing in the districts of Northern Kyushu, Kumamoto, Saga, Ohita and Yamaguchi. At the same time the frequency in the appearance of the recessive genes was also calculated following Weinberg and Dahlbelg's principle. The results were summarized as follows. 1) The rate of consanguineous marriage was higher in the rural than in the urban communities among the present districts, the total occurrence being 8.6% of which that of Yunoura, Yamaguchi Prefecture constituted the largest with 15%, Shimonoseki, Yamaguchi Prefecture the smallest with 5%. 2) The occurrence of conical teeth in the lateral incisors of upper jaw amounted to 2.0% in the offspring of consanguineous marriage and to 2.8% in that of heterogeneous marriage, suggesting no remarkable difference present there. 3) The occurrence of dwarf and conical teeth in the lateral incisors of upper jaw was much frequently observed in the female than in the male subjects. It was slightly more often observed in the consanguineous than in the heterogeneous marriage cases with values 5.7% and 5.2% respectively. The total occurrence was 5.3%. 4) The occurrence of Carabelli's tubercle was slightly frequent in the male than in the female. Its appearance in the consanguineous marriage cases was 14.6% and in the heterogeneous marriage cases 17.6%. 5) The gene frequency for the occurrence of conical and dwarf teeth ranged from 0.0495 to 0.0746 and for Carabelli's tubercle from 0.0539 to 0.1452, agreeing approximately to the values obtained by the present study.
