Tooth Calcification

Abstract: DURING the years of growth and development, girls are advanced over boys in a great many respects. They are earlier, on the average, in appearance of ossification centers; they are ahead in epiphysial union and the appearance of secondary sexual characteristics. While the direction of sexual dimorphism in the deciduous dentition may be somewhat questionable,' the fact that girls tend to be earlier in eruption of the permanent teeth is not. For white children of European ancestry, the average sex difference in the time of eruption is 0.45 year (or nearly 5 per cent) with a maximum of 0.93 year (9 per cent) for the mandibular canine tooth.2 Whether comparable or equivalent sex differences exist in tooth calcification is open to question. The most commonly used standards fail to provide an answer. The norms of Logan and Kronfeld,3' based on histologic examinations of jaw sections of 30 children, make no distinction between the sexes; Broadbent's roentgenographic standards similarly lump male and female data.5 While the roentgenographic investigations of Gleiser and Hunt on the mandibular first molar6 and Demisch and Wartmann on the mandibular third molar7 both suggest advancement of girls over boys, generalization cannot be made from their studies. It is entirely possible that dental advancement of girls over boys is largely limited to eruption, so that the permanent teeth of girls emerge into the mouth with a lesser degree of calcification. Since, in the course of the Fels Longitudinal investigations, we have amassed serial roentgenograms on a sizable sample of children, exceeding in number the sum of previous studies combined, it seemed pertinent to investigate in detail the question of sex differences in those stages of tooth development not easily accessible to visual examination. The matter of a sex difference and the magnitude of this difference were the problems of primary interest in this investigation.