Comparative odontometry of the permanent post-canine dentition of American Whites and Negroes

The permanent post-canine teeth of American Whites and American Negroes of the New York City area were studied odontometrically. The mesio-distal and bucco-lingual dimensions of the crowns were measured, as was the total tooth height and crown height. The individual root lengths of these teeth were also measured, in several ways, as was root width. The mean total root volumes of these teeth was measured by a unique mercury displacement method. In another aspect of this study the mean angular divergence of the roots from a mid-coronal vertical plane was determined, while the robustness of these roots was described as a ratio between root width and length. Finally, an extensive comparison was made between our data and those in the literature on a number of African Negro populations. American Negro tooth crown and root dimensions and volumes were significantly different from those of American Whites only sporadically, although the Negro teeth usually tended to be larger. Our comparative data gave some indication that the size of both the maxillary and mandibular American negro teeth, as well as the shape of the mandibular (but not the maxillary) American Negro teeth are roughly intermediate between those of American Whites and South African Negroes. This suggestion that a “hybrid” population may possess intermediate values of crown index and of crown module is supported by our analysis of Hottentot-South African Negro hybrids with their presumptive parental stocks.     

Longitudinal analysis of deciduous tooth emergence: IV. Covariate effects in Japanese children

Emergence of the deciduous teeth is generally considered to be robust to moderate environmental insults, malnutrition, and disease. Consequently, deciduous tooth emergence has been used to assess growth and development and for age estimation in children. In this paper, we examine the way in which nutritional status and other covariates affect deciduous tooth emergence in a sample of 114 Japanese children born in Tokyo in 1914 and 1924. Parametric survival analysis was used to quantify the effects of nutritional status, breastfeeding behavior, and sex on the hazard of deciduous tooth emergence. Children of poor nutritional status exhibited significantly delayed emergence of all deciduous teeth, with effects that ranged from 14-29% increases in mean emergence times. Children of medium nutritional status exhibited increases in mean emergence times of 5-9% for the canines and lower molars, and 13-17% for the incisors. Partial breastfeeding had no effect on tooth emergence, but children who were not breastfed at all showed delayed emergence of the upper incisors. No significant sex differences in emergence were found. The findings contradict the idea that moderate malnutrition has little effect on deciduous tooth emergence. Furthermore, nutritional differences may account for some of the observed differences among populations in the timing of tooth emergence.     

Evolution of dentition in prehistoric Ohio Valley Native Americans III. Metrics of deciduous dentition

Deciduous tooth size in Native Americans of the Ohio Valley area is fairly stable from the terminal Late Archaic (3200 BP) through the Late Prehistoric (350 BP) periods. Some fluctuation in average size did occur during this time. These fluctuations most likely reflect random changes due to gene drift. However, no difference in the pattern of interactions among the sizes of teeth (covariance structures) can be demonstrated during this period. Principal components analysis of the buccolingual and mesiodistal dimensions in the total sample indicate that the major axis of deciduous tooth size in the Ohio Valley population shows an allometric relationship, with the dimensions of the anterior teeth increasing (or decreasing) as the 1.33 power of the dimension of m1(1) and as the 2.0 power of the dimension of m2(2). Comparison of the Ohio Valley samples with other samples from the Eastern Woodlands suggests that geography may have played a minor role in structuring deciduous tooth size variation. For the most part, however, widely separated Eastern Woodlands populations appear to have been evolving independently with respect to deciduous tooth size.     

The taming of the shrew milk teeth

SUMMARY A characteristic feature of mammalian dentition is the evolutionary reduction of tooth number and replacement. Because mice do not replace teeth, here we used Sorex araneus , the common shrew, as a model to investigate the loss of tooth replacement. Historically, shrews have been reported to initiate the development of several, milk or deciduous teeth but these soon become rudimentary and only the replacement teeth erupt. Shrews thus offer a living example of a derived mammalian pattern where the deciduous tooth development is being suppressed. Based on histological and gene expression analyses of serial sections, we suggest that S. araneus has discernible tooth replacement only in the premolar 4 (P4) position. Both generations of teeth express Shh in the enamel knot and in the inner enamel epithelium. Nevertheless, the deciduous P4 (dP4) is reduced in size during embryogenesis and is eventually lost without becoming functional. Analysis of growth shows that P4 replaces the dP4 in a "double-wedge" pattern indicative of competitive replacement where the suppression of the deciduous tooth coincides with the initiation of its replacement. Because activator–inhibitor mechanisms have been implicated in adjacent mouse molars and in transgenic mice with continuous tooth budding, we suggest that evolutionary suppression of deciduous teeth may involve early activation of replacement teeth, which in turn begin to suppress their deciduous predecessors.     

Incremental enamel development in modern human deciduous anterior teeth

This study reconstructs incremental enamel development for a sample of modern human deciduous mandibular (n = 42) and maxillary (n = 42) anterior (incisors and canines) teeth. Results are compared between anterior teeth, and with previous research for deciduous molars (Mahoney: Am J Phys Anthropol 144 (2011) 204-214) to identify developmental differences along the tooth row. Two hypotheses are tested: Retzius line periodicity will remain constant in teeth from the same jaw and range from 6 to 12 days among individuals, as in human permanent teeth; daily enamel secretion rates (DSRs) will not vary between deciduous teeth, as in some human permanent tooth types. A further aim is to search for links between deciduous incremental enamel development and the previously reported eruptionsequence. Retzius line periodicity in anterior teeth ranged between 5 and 6 days, but did not differ between an incisor and molar of one individual. Intradian line periodicity was 12 h. Mean cuspal DSRs varied slightly between equivalent regions along the tooth row. Mandibular incisors initiated enamel formation first, had the fastest mean DSRs, the greatest prenatal formation time, and based upon prior studies are the first deciduous tooth to erupt. Relatively rapid development in mandibular incisors in advance of early eruption may explain some of the variation in DSRs along the tooth row that cannot be explained by birth. Links between DSRs, enamel initiation times, and the deciduous eruption sequence are proposed. Anterior crown formation times presented here can contribute toward human infant age-at-death estimates. Regression equations for reconstructing formation time in worn incisors are given.     

Development and size of the teeth of Macaca mulatta.

A cross-sectional sample of 151 skulls from Macaca mulatta of known age and similar rearing in U.S. Primate Centers was analyzed to determine age-related "norms" of stages of development and size of teeth. The stages of development from the follicle of a deciduous incisor in the fetus to completion of the root with apex closed of the permanent third molar were related to age. The age range observed for eruption of each tooth was noted and related to its stage of development. The crown of each erupted tooth was found to be completely developed, but growth of its root continued for a longer, indeterminate period. When a deciduous tooth was exfoliated, the crown of the permanent successor was found to be completed and root growth had begun. Measurements of both mesiodistal and faciolingual diameters and of crown length of the teeth in situ and of total length and root length on roentgenograms were examined for sexual dimorphism. The faciolingual diameter of the deciduous mandibular second incisor and of both second molars showed the greatest sexual dimorphism among both diameters of all deciduous teeth. The mesiodistal and faciolingual diameters of the mandibular premolars were found to be the best dimensions in discriminant functions for identifying sex in the absence of permanent canines.     

Patterns of dental enamel defects at ancient Mendes, Egypt.

The dental remains of 88 individuals from Old Kingdom, First Intermediate, and Greco-Roman periods at the ancient Egyptian site of Mendes (Tell er-Rub(c)a) were examined for dental enamel hypoplasia, and the results reported here provide some of the first comparative data on enamel defects in ancient Egypt. Overall, 48% of the individuals in the sample have one or more teeth with hypoplasia, with 17% of permanent teeth and 8% of deciduous teeth affected. The permanent teeth account for 87% of the total number of affected teeth, a prevalence over deciduous teeth that is significant at alpha = 0.05. Permanent and deciduous teeth display different patterns of hypoplasia, with the former exhibiting both discrete pitting and linear furrowing, and the latter exhibiting only pits. Teeth with linear defects significantly outnumber those with pits by a factor of more than three to one. Only permanent canines display more than one lesion on a tooth, with a mean of 1.4 defects per affected tooth. Although calculation of the age of insult from lesion position is imprecise, it appears that stress episodes occurred most commonly between approximately 3-5 years of age. The presence of pits in the deciduous dentition, however, suggests that physiological stresses began in utero. There is no statistically significant difference in the frequency of enamel defects between males and females. An observed decrease in the frequency of defects from the Old Kingdom period to the subsequent First Intermediate and Greco-Roman periods is not significant at alpha = 0.05, although such a decrease is expected given epigraphic and other data that refer to prolonged drought and malnutrition in the late Old Kingdom. The calculated chi(2) value of 3.83 is significant at the 0.10 level, however, and since our sample is rather small and the magnitude of the chi-square statistic is a function of sample size, we recommend that future research investigate further the relationship between the frequency of enamel defects and the time period in which they occur.     

Premaxillary-maxillary suture asymmetry in a juvenile Gorilla. Implications for understanding dentofacial growth and development

A specimen of juvenile gorilla was found that had the premaxillary-maxillary suture coursing between the lateral deciduous incisor and deciduous canine on one side of the jaw, but between the central and lateral deciduous incisors on the other; in the latter, the suture also separates the alveolus of the lateral deciduous incisor from the crypt of the growing successional lateral incisor. Rather than dismiss this exception to the traditional dictum of tooth identification--which is based on the position to teeth relative to this suture--as some inconsequential anomaly, an attempt is made to understand how this can occur within the confines of present understanding of dentofacial growth and development and developmental theory. An hypothesis relating tooth and tooth class identification is presented in the context of ectomesenchymally predifferentiated stem progenitors and subsequent tooth class proliferation.     

Longitudinal analysis of deciduous tooth emergence: III. Sexual dimorphism in Bangladeshi, Guatemalan, Japanese, and Javanese children

Previous studies, mostly in European populations, found sex differences in the pattern of deciduous tooth emergence. Most studies find that the anterior dentition in males is precocial relative to the female dentition, and the pattern reverses so that females lead males in the emergence of the posterior deciduous dentition. Less is known about sex differences in the dental development and emergence of non-European populations. Here we examine the pattern of sex differences in deciduous tooth emergence in Japanese, Javanese, Guatemalan, and Bangladeshi children. The data come from four longitudinal or mixed longitudinal studies using similar study protocols. Survival analysis was used to estimate parameters of a log-normal distribution of emergence for each of the 10 teeth of the left dentition, and sexual dimorphism was assessed by sex-specific differences in mean emergence times and by Bennett's index. The results support the pattern of developmental cross-over observed in other populations. We conclude that there is little evidence to support the hypothesis of Tanguay et al. ([1984] J. Dent. Res. 63:65-68) that ethnic factors mediate sex differences in the emergence of deciduous teeth.     

Crown dimensions of deciduous teeth from prehistoric India

Mean mesiodistal and buccolingual diameters are presented for deciduous teeth from the important Chalcolithic site of Inamgaon (1400–700 B.C.), a prehistoric farming community on the Deccan Plateau of western India. The deciduous teeth from Inamgaon are consistently larger than deciduous teeth of modern populations of European descent and smaller than the deciduous teeth of modern Australian aboriginals. Comparative data for prehistoric deciduous teeth are rare, especially for populations of southern Asia. The deciduous teeth of Mesolithic Europeans are comparable in size to certain dimensions of the Inamgaon teeth, and a small sample of deciduous teeth from the Iron Age site of Pomparippu (Sri Lanka) exhibits larger anterior teeth and smaller molar teeth than does the sample from Inamgaon.     

Morphology of Liberian Negro deciduous teeth. II. Arch dimensions and occlusion

Liberian Negro deciduous dentitions have arch dimensions which significantly exceed those of a variety of White populations. Winged incisors were present in 14.3% of the Negro population, again exceeding White values. No differences were noted in incisal overbite or overjet. Diastemal spaces were greater in the Negro dentitions than in the White, but the significance of this is as yet unknown. An exceptional finding was the absolute lack of Class II (distocclusion) in the Negro series. A discussion of functional occlusion stressed the necessity for the inclusion of such dynamic factors as dental abrasion, mesial migration and physiological rest position in future studies of comparative dental anthropology.     

Increasing human tooth length between birth and 5.4 years

Most previous studies of tooth development have used fractional stages of tooth formation to construct growth standards suitable for aging juvenile skeletal material. A simple alternative for determining dental age is to measure tooth length throughout development. In this study, data on tooth length development are presented from 63 individuals of known age at death, between birth and 5.4 years, from an archeological population recovered from the crypt of Christ Church, Spitalfields, London. Isolated developing teeth (304 deciduous, 269 permanent) were measured in millimeters and plotted against individual age. Regression equations to estimate age from a given tooth length, are presented for each deciduous maxillary and mandibular tooth type and for permanent maxillary and mandibular incisors, canines, and first permanent molars. Data on the earliest age of root completion of deciduous teeth and initial mineralization and crown completion of some permanent teeth in this sample are given, as well as the average crown height and total tooth length from a small number of unworn teeth. This method provides an easy, quantitative and objective measure of dental formation appropriate for use by archeologists and anthropologists. © 1993 Wiley-Liss, Inc.     

The effect of birthweight on tooth-size variability in twins.

Studies indicate that low birthweight (LBW) children display reduced deciduous tooth size but there is little information about permanent tooth size. It has also been shown that dental fluctuating asymmetry (FA) increases in response to various environmental influences, but the relationship between birthweight and FA remains unclear. The aim of this study was to compare tooth size and asymmetry, according to birthweight, in the deciduous and permanent dentitions of a sample of Australian twins. The study sample comprised 436 twins, classified into 2 groups: normal birthweight (NBW > 2500 g) and low birthweight (LBW < or = 2500 g). For each individual it was generally possible to measure maximum mesiodistal crown diameters of both deciduous and permanent central incisors from serial dental models. Correlations were calculated between tooth-size variables and birthweight; subsequently comparisons of tooth size and FA were made between the LBW and NBW samples using Student's t tests. Small positive correlations (around .1) were noted between birthweight and tooth-size variables. There was no evidence of tooth-size reduction in the LBW male sample, but the LBW females displayed tooth-size reduction of approximately 2-3% for both deciduous and permanent incisors, compared to the NBW females. There was no evidence of increased FA in the LBW individuals of either sex. These findings indicate that developing teeth are generally well-protected from developmental disturbances during prenatal and perinatal periods. Further research is needed to clarify the biological basis of an apparently true but weak association between tooth size and birthweight.     

Interspecies difference in placement of developing teeth and its relationship with cross-sectional geometry of the mandibular symphysis in four primate species including modern humans

The form of the anthropoid mandibular symphysis has recently been addressed in association with spatial requirements for the forming anterior teeth. To evaluate potential relationships between the symphyseal shape and teeth further, the growth patterns of the symphyseal region and the positioning of the tooth crypts were examined using CT data, comparing four primate species (modern humans, chimpanzees, Japanese monkeys, and hamadryas baboons) with varied symphyseal curvature and tooth size. First, results showed that interspecies differences in overall mandibular shape including symphyseal inclination and bicanine width are consistently expressed throughout postnatal ontogeny, although local symphyseal configurations related to the superior transverse torus (STT) tended to change considerably during growth in chimpanzees. Second, the four species were found to exhibit differentiated formation positions of the incisor and canine crypts. In particular, I2 developed between I1 and C in humans with a broad bicanine space and small teeth, whereas it was positioned posterior to I1 and above C in the cercopithecines with an extremely narrow bicanine space. In chimpanzees, despite the large bicanine width, I1 and I2 grew with a large antero-posterior overlap owing to their large size. These results indicate that the dental positioning is determined in concert with the size balance of the available mandibular space and forming teeth. Finally, the positions/contours of I2 crypt were shown to correspond strongly with the STT across the taxa. This suggests that interspecies differences in symphyseal shape should be interpreted partially by the species-specific positional relationships of the developing anterior teeth.     

Dental fluctuating asymmetry in the Gullah: tests of hypotheses regarding developmental stability in deciduous vs. permanent and male vs. female teeth

In this investigation, deciduous teeth (canines, c; first molars, m1; second molars, m2) and their permanent successors (canines, C; first premolars, P1; second premolars, P2) were used to test two related hypotheses about fluctuating asymmetry (FA). First, based on the biology of the developing dentition, it was predicted that deciduous teeth would be more developmentally stable and thus exhibit less dimensional FA than their permanent successors. Second, based on sex differences in tooth development, it was predicted that female canines would have greater developmental stability (less FA) than male canines. Bucco-lingual measurements were made on dental casts from a single Gullah population. Using a repeated-measures study design (n = 3 repeated measures), we tested these hypotheses on sample sizes ranging from 63-82 antimeric pairs. Neither hypothesis was supported by our data. In most cases, Gullah deciduous teeth did not exhibit statistically significantly less FA than their permanent successors; indeed, statistically significant differences were found for only 3 of 12 deciduous vs. permanent contrasts, and in two cases, the deciduous tooth had greater FA. Female mandibular canines exhibited statistically significantly greater FA than those of males, while there was no statistically significant sex difference in FA for the maxillary canine. FA in these Gullah samples is high when compared to Archaic and late prehistoric Ohio Valley Native Americans, consistent with historical and archaeological evidence that environmental stress was relatively higher in the Gullah population. We suggest that when environmental stress in a population is high, the impact of differences in tooth formation time spans and developmental buffering upon FA may be minor relative to the effect of developmental noise.     

Aluminum concentrations in human deciduous enamel and dentin related to dental caries

The aluminum (Al) concentrations in the enamel and dentin of 314 human deciduous teeth were determined in order to examine the relationship between Al and dental caries. The sample teeth were divided into three groups: the sound tooth group, carious tooth group and filled tooth group. The teeth of the carious tooth group were further classified into three groups depending on the stage of caries. The Al content was determined using graphite furnace atomic absorption spectrometry. In both the enamel and dentin, the Al concentrations were unaffected by sex, but did depend on tooth type. In enamel, the Al concentration was significantly higher in the sound tooth group (42.8 +/- 37.3 microg/g) than in the three carious groups (20.7 +/- 17.1-24.9 +/- 22.0 microg/g) and the filled tooth group (27.3 +/- 25.5 microg/g). As for dentin, the Al concentration was also significantly higher in the sound tooth group (36.2 +/- 35.1 microg/g) than in the three carious groups (15.1 +/- 13.3-24.5 +/- 23.4 microg/g) and the filled tooth group (17.2 +/- 20.6 microg/g). Even when analyzing incisors alone, the Al concentrations were significantly higher in the sound tooth group than in the other groups, for both enamel and dentin. Furthermore, the Al levels in carious enamel and dentin did not decrease with the advance of caries. These findings indicated that the deciduous teeth containing higher Al concentrations on average had less caries than the teeth with lower Al concentrations, and suggest that Al acts as a possible cariostatic agent by itself.     

Incidence and patterning of dental enamel hypoplasia among the Neandertals

Dental enamel hypoplasia (DEH), as an indicator of nonspecific stress during development, provides an assessment of the relative morbidity of past human populations. An investigation of 669 Neandertal dental crowns yielded an overall DEH frequency of 36.0% by tooth (41.9% for permanent teeth; 3.9% for deciduous teeth) and about 75% by individual. These incidences place the Neandertals at the top of recent human ranges of variation in DEH frequencies, indicating high levels of stress during development. The paucity of deciduous tooth DEH and M1 DEH, combined with generally increasing levels of DEH through later calcifying teeth, suggests that the stress was primarily nutritional, beginning at weaning and continuing through adolescence. This supports paleontological and archeological interpretations implying significantly lower effectiveness for Neandertal foraging compared to that of modern humans.     

The size and morphology of the Nasioi dentition

Dental impressions were obtained on 240 Nasioi, a Melanesian population living on the island of Bougainville. Odontometric data are presented for both the permanent and deciduous teeth, and the former teeth are also examined morphologically. The results show that the Nasioi have large permanent teeth like other Australoid populations whereas the deciduous teeth are only of moderate size. The coefficients of variation are large in the permanent teeth compared to other populations but the sexual dimorphism in tooth size and variability is not remarkable. Morphologically, the permanent teeth of the Nasioi are characterized by a cusp number pattern, a high frequency of the Dryopithecus + pattern on the first mandibular molar, few individuals with a Cusp of Carabelli, and a moderate expression of shovelled-shaped anterior teeth.     

The tooth of perfection: functional and spatial constraints on mammalian tooth shape

This paper addresses the question of how close mammalian teeth are to ideal functional forms. An 'ideal' form is a morphology predicted to be the best functional shape according to information of the relationships between shape and function. Deviations from an ideal form are likely to indicate the presence of developmental or genetic constraints on form. Model tools were constructed to conform to functional principles from engineering and dental studies. The final model shapes are very similar to several mammalian tooth forms (carnassial teeth and tribosphenic-like cusps), suggesting that these tooth forms very closely approach ideal functional forms. Further evidence that these tooth forms are close to ideal comes from the conservation over 140 million years, the independent derivation and/or the occurrence over a size range of several orders of magnitude of these basic tooth forms. One of the main functional shapes derived here is the 'protoconoid', a fundamental design for double-bladed tools that fits a large number of functional parameters. This shape occurs in tooth forms such as tribosphenic, dilambdodont and zalambdodont. This study extends our understanding of constraints on tooth shape in terms of geometry (how space influences tooth shape) and function (how teeth divide food).  © 2003 The Linnean Society of London . Biological Journal of the Linnean Society , 2003, 78 , 173–191.