[New investigations on the question of secular acceleration of permanent dentition].

A sample of 1,310 girls, 5 to 13 years of age, drawn from Mainz, Wiesbaden and vicinity was studied to establish the eruption time of the permanent dentition. The data of the median date of eruption of different teeth was determined employing a nonparametric test for the estimation of a survivorship function with doubly censored data (TURNBULL 1974). The method presented shows a marked superiority over other techniques used to verify the median date of eruption. The diachronic comparison of several samples--mainly from the Rhine-Main-Area-encompassing the years 1909 till today, showed no uniform trend towards an earlier eruption date. In some cases, temporal differences were ascertained which can be readily attributed to varied definitions of dental status. Furthermore, a recalculation--using this innovative mathematical approach--of a sample from the Frankfurt area, originally studied by FRANZ (1938) did not show any unambiguous acceleration tendencies-at least not within the past 50 years. These results suggest that the human dentition is predominantly genetically determined and therefore environmental factors play a by far lesser role than in general physical development.