Correlates of permanent tooth development in prenatal time.

Although calcification of the permanent teeth is not radiologically discernible until the first month after birth (GARN, LEWIs, and POLACHECK, J Dent Res 38: 135, 1959) developmental stages of I1, 12, Ml, and often C may be demonstrated in histological sections of jaws well before the 39to 41-week age horizon. It is of interest, therefore, to determine whether intra-uterine development of these permanent teeth is simply and linearly related to the conventional measures of fetal size, namely, crown-rump length (CRL) and weight. It is also interesting to ascertain whether the correlation between fetal size and the overall measure of permanent tooth development obtained by summing individual tooth stages is sufficient to make dental development a reference parameter in prenatal stu(dies. To do this, we have related the stage of development of Il, 12, and Ml in the maxilla and mandible separately to (1) crown-rump length, (2) weight, and (3) the base-10 logarithm of body weight in 34 grossly and histologically normal humani fetuscs. We have uised a simple system of "staging" as previously described by us (GARN and BURDI, J Dent Res 50: 1407, 1971; BURDI, GARN, and BABLER, Arch Oral Biol 19: in press, 1974). Data on permanent canines were excluded because the small number of fetuses providing definitive developmental information was insufficient to compute valid correlations involving C. Linearity of relationship,