Permanent Teeth During the Human Fetal Period

ALPHONSE R. BURDI and JEROME SUPERSTINE Department of Anatomy (Medical School) and School of Dentistry, University of Michzgan, Ann Arbor, Michigan 48109, USA J Dent Res 56(12): 1468, December 1977. deciduous and permanent dental arches, raw order Early prenatal development of human dentitions correlations indicate a moderate association (r = through the classical stages of tooth development can 0.68) between like deciduous and permanent teeth be variable. Recognizing that there are patterns of during this time period. However, partial correlations typical and polymorphic tooth germ maturation for show no significant association (rCRL = 0.23) between the deciduous and permanent dental arches during the dentitions. the human embryonic and fetal periods, this investiA demonstrable correlation was shown in developgation was undertaken to examine correlations betment of opponent, adjacent, and even corresponding ween the deciduous and permanent teeth and their teeth in and between the deciduous and permanent histogenesis during the critical morphogenic periods dental arches during prenatal months 3 to 7. Partial before birth. correlation procedures show, however, that without Twenty-six human abortuses representing tooth dethe effects of increasing age and/or crown-rump velopment from dental bud through early apposition length on tooth development there is asynchronous or stages were used. The sample. ranging from 12-28 independent maturation of those deciduous and perweeks fertilization age (75280 mm crown -rump manent teeth monitored in the same individual. Prolength) was selected on the bases of being typical for cedurally, the different messages provided by use of age, no gross signs of abnormal development, and no raw order and partial correlations argues for this kind remarkable clinical histories. Each specimen was serof statistical model when analyzing morphologic traits ially sectioned in the sagittal plane and prepared for with or without reference to increasing age. light microscopy (trichrome connective tissue stain). The finding of developmental independence beThe developmental statusofeach available deciduous tween deciduous and permanent tooth development and permanent tooth of each specimen was assessed. then raises several queries, including to what degree Maturational data were grouped and correlated can the development of prenatal deciduous teeth be statistically on the bases of tooth type, tooth positions, altered, e.g., through teratogens, without a concurand jaw locati, on de onstrating (1) the relationship rent alteration in the typical maturation pattern of of any two dental variables over the crown-rump the permanent teeth? Similarly, since there have genlength range, and (2) the actual relationship of any erally been strong correlations between maxillary and two dental variables that might be expected when mandibular teeth of both deciduous and permanent crown-rump length is constant. tooth types during this prenatal period, to what exSeveral patterns are discernible in deciduous and tent does altered embryonic development of teeth in permanent tooth germ prenatal maturation. There is one jaw affect teeth in the opponent jaw? a significant correlation (0.01 level) in the progressive maturation of each tooth of an opponent pair (Fig 1). Holding age or crown-rump length constant through DECIDUOUS TEETH partial correlations (rCRL), this correlation holds true between opponent tooth germs in both deciduous and permanent dentitions. The high correlations in tooth Maxillary Ia C M M2 development also are shown by pooling data from all available deciduous (r = 0.97; rCRL = 0.89) and perrCRL = 91 .92 .91 91 71 manent (r = 0.91; rCRL = 0.80) tooth germs. A difCRL ferent pattern can be shown for the correlative devel(r) = (97) (97) (98) (.97) (92) opment of adjacent teeth in the deciduous arch (central incisor through second molar) and the two teeth Mandibular ( 1 C M, M) of the permanent arch (central and lateral incisors) which were monitored for adjacency. Raw order correlations (r) indicate that adjacent teeth of either arch (deciduous 0.93; permanent 0.66) are significantly PERMANENT TEETH correlated in their development over the three to seven month period. With the exception of adjacent permanent incisors (rCRL = 0.23), there is still a high Maxillary correlation between adjacent deciduous teeth (rCRL