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.     

Additional human remains from Blombos Cave, South Africa: (1999-2000 excavations)

The uppermost Middle Stone Age (MSA) layers at Blombos Cave contain high densities of Still Bay bifacial points. Information from other regional sites places the Still Bay prior to the Howiesons Poort industry, which has been dated at 65-70 ka. The Blombos Cave MSA strata have yielded nine human teeth or dental fragments. Four that were recovered during the 1997-1998 excavations have been published elsewhere. The remaining five were discovered during the 1999-2000 field seasons; these are described here. Three of the new specimens are deciduous teeth, and two are permanent premolar and molar crown fragments. The entire dental sample probably represents at least five and as many as seven individuals. The deciduous teeth from the upper MSA levels are likely to have been exfoliated in the cave. One deciduous tooth and the permanent tooth fragments from the lower MSA levels probably represent three individuals who died in or near the cave. The Blombos Cave premolars preserve horizontal circum-cervical striae suggestive of palliative tooth pick use. Approximately half of the permanent and deciduous crown diameters exceed those of recent Africans; for the remainder, the fossil values fall among modern African sample means. The Blombos Cave tooth crowns tend to be smaller than the majority of penecontemporaneous Neandertal teeth. The morphology of the Blombos Cave di is comparable to MSA homologues from the nearby, and presumably somewhat younger site of Die Kelders Cave 1.     

Tissue contributions to sex and race: differences in tooth crown size of deciduous molars.

This study describes size of constituent deciduous tooth crown components (enamel, dentine, and pulp) to address the manner in which males characteristically have larger teeth than females, and the observation that teeth of American blacks are larger than those of American whites. Measurements were collected (n = 333 individuals) from bitewing radiographs using computer-aided image analysis. Tissue thicknesses (enamel, dentine, pulp) were measured at the crown's mesial and distal heights of contour. Deciduous mesiodistal molar crown length is composed of about 1/7 enamel, 1/3 dentine, and 1/2 pulp. Details differ by tooth type, but males typically have significantly larger dentine and pulp dimensions than females; there is no sexual dimorphism in marginal enamel thickness. Males scale isometrically with females for all variables tested here. Blacks significantly exceed whites in size of all tissues, but tissue types scale isometrically with blacks and whites with one exception: enamel thickness is disproportionately thick in blacks. While the absolute difference is small (5.56 mm of enamel in blacks summed over all four deciduous molar tooth types vs. 5.04 mm in whites), the statistical difference is considerable (P < 0.001). Aside from enamel, crown size in blacks is increased proportionately vis-à-vis whites. Principal components analysis confirmed these univariate relationships and emphasizes the statistical independence of crown component thicknesses, which is in keeping with the sequential growth and separate embryonic origins of the tissues contributing to a tooth crown. Results direct attention to the rates of enamel and dentine deposition (of which little is known), since the literature suggests that blacks (with larger crowns and thicker enamel) spend less time in tooth formation than whites.     

The effect of prenatal factors on crown dimensions

As shown in 870 white participants in the National Collaborative Perinatal Project (NCPP), maternal health status during pregnancy and birth size are systematically related to mesiodistal and buccolingual crown dimensions of I1, I2, dc, dm1, dm2 and M1. Maternal diabetes, maternal hypothyroidism and large size at birth are associated with larger maxillary and mandibular teeth in white children. Conversely, deciduous and permanent crown diameters are diminished in maternal hypertension, and in low birthweight and small birth-length conditions. These findings suggest that maternal and fetal (or gestational) determinants of both deciduous and permanent tooth crown dimensions may account for as much as half of crown-size variability with major implications to population comparisons and historical odontometric differences and trends.     

Reduced tooth size in 45,X (Turner syndrome) females

Mean values and variances of deciduous and permanent tooth dimensions were compared between 121 45,X (Turner syndrome) females and 171 control subjects to clarify the role of the X chromosome on dental development. Although deciduous molars tended to be smaller than normal in 45,X females, there was no evidence of a reduction in tooth size for deciduous anterior teeth. In the permanent dentition, all mesiodistal dimensions were significantly smaller in 45,X females but only some of the buccolingual dimensions were smaller. The findings for deciduous tooth-size may reflect a sampling effect related to the extremely high frequency of spontaneous abortion in 45,X individuals. Results for permanent teeth are consistent with the concept of a decrease in enamel thickness in 45,X females.     

Model for the examination of evolutionary trends in tooth development

Through the use of serial computerized tomography (C-t) scans, two distinct developmental stages can be identified in mature teeth. C-t scans thus provide a non-destructive method for assessing growth within individual teeth, as well as for comparison of the development of modern and fossil teeth. The second deciduous molar (DM2) and first permanent molar (M1) resemble one another morphologically, despite differences in size and developmental rates. Thus, they provide an excellent model for studying variation in growth within an individual. To test the C-t method, we first examined a recent archaeological sample and then examined teeth from Skhul I. Serial C-t scans were used to compare two distinct developmental stages represented by the dentine-enamel junction (DEJ) and outer enamel surface (OES), respectively, in mandibular DM2 and M1 of 31 archaeological specimens. The difference in form and size between these two surfaces in and between teeth was calculated from intercusp distances measured at the DEJ and OES using the form distance matrix. Intercusp distances at the DEJ and OES of these teeth were then compared to their counterparts in the DM2 and M1 of Skhul I, taken here as representative of early anatomically modern Homo sapiens sapiens. Form differences between paired DM2 and M1 at the DEJ were smaller than those at the OES, supporting the hypothesis that differences between the two teeth increase throughout development. The increase in intercusp distances from the DEJ to OES was found to reflect the angulation of cusps relative to one another, rather than enamel thickness. Form differences between the Skhul DM2 and M1 were smaller than those observed in the recent series, and the recent M1 differed more than the DM2 from its fossil counterpart. The similarities found between the Skhul permanent and deciduous teeth and the recent DM2, may reflect a similar growth pattern. This would contribute to earlier crown completion in the fossil M1. Am. J. Phys. Anthropol. 102:283–294, 1997 © 1997 Wiley-Liss, Inc.     

Generalized microdontia probably associated with intrauterine growth retardation in a medieval skeleton

True generalized microdontia in a subadult skeleton is described. The bones, dating from the Middle Ages, were excavated at Alborg, Denmark. True generalized microdontia is an extremely rare condition characterized by well-formed teeth with crowns smaller than two times the standard deviation from the population means. Both the deciduous and permanent teeth are involved. The dimensions of the few fragmentary bones were compared with those of medieval Danish and Norwegian samples and the measurements of the teeth with a number of medieval and modern samples. The gracile skull was of normal size except for the low symphyseal mandibular height. The clavicle and the scapular fragment were of very small dimensions suggesting an extremely slender figure. No long bones were found. The dentition was characterized by congenital absence of nine teeth (4 M³₃, 3 P²₂, 1 P₁, 1 I²) with retained deciduous teeth and by microdontia. With few exceptions the shape of the teeth was within the normal range of variation. The lengths of the roots were normal. The relationship between partial anodontia and tooth size is discussed. The establishment of the crown-size of deciduous molars during intrauterine life is documented. Possible causes for generalized microdontia is reviewed and it is concluded that in the present case, the evidence indicates an intrauterine growth retardation (IU.G.R.) which was partly outgrown during childhood. The nature of IU.G.R. and its incidence are briefly mentioned.     

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.     

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.     

Deciduous tooth dimensions in fetal rhesus monkeys from mothers with induced diabetes

Thirty-four measurements of the deciduous dentition in 21 fetal rhesus monkeys from diabetic mothers (FDM) and 36 nondiabetic fetuses were compared in order to assess the effects of induced maternal diabetes on the teeth of third-trimester fetuses. After exclusion of 14 variates due to significant age-related variation, univariate statistical analysis suggested a trend toward smaller teeth in the FDMs. Multivariate discriminant function analysis indicated not only a clear separation between the two groups, with molar breadths and some incisor lengths and breadths serving as the best discriminators, but also that the deciduous dental dimensions in FDMs are smaller than in nondiabetic fetuses.     

Sexual dimorphism in the tooth-crown diameters of the deciduous teeth

Mesiodistal and buccolingual crown dimensions of the right deciduous teeth of 133 white children were analyzed for information on sexual dimorphism and sex discrimination using discriminant analysis. Even though consistent differences were found for only 15 out of 20 paired measurements, five of them significant at p = 0.05 or better, discriminant analysis showed the possibility of correctly sexing up to 75% of the juvenile sample, using a maximum of seven deciduous teeth.     

Brief communication: The use of alternative dental measurements on deciduous teeth

The present study investigates the utility of cervical measurements in deciduous teeth and how they correlate with traditional measurements of the crown. First, this study establishes definitions by which these measurements could reliably be taken. Next, deciduous cervical and traditional crown diameters were taken on three distinct skeletal samples: a Neolithic assemblage from Central Anatolia (Çatalhöyük, n = 85), a precontact sample from Northern California (CA‐ALA‐329, n = 34), and a group of intrusive burials interred at Çatalhöyük that date between AD 60 and 1650 (n = 38). Across the dentition there are positive correlations between crown and cervical measurements, which tend to be higher in anterior teeth than in posterior teeth. Both measurements show low correlations with age; however, cervical measurements show fewer negative correlations with age. An intraobserver error study found low levels of error for both types of measurements. On a subset of the Çatalhöyük sample (n = 9), a principal components and biological distance analysis were conducted comparing the two types of measurements. Also, all three samples were subject to a canonical discriminant function analysis and the results from cervical and crown measurements were compared. All analyses produced slightly different results for each type of data suggesting that crown and cervical measurements capture different aspects of tooth shape. While cervical and crown measurements provide different statistical results, cervical measurements can provide information relevant to anthropological studies and may allow for larger datasets to be used by allowing the inclusion of teeth with modified crowns. Am J Phys Anthropol 149:299–306, 2012. © 2012 Wiley Periodicals, Inc.     

Japanese oak silkmoth feeding preference for and performance on upper-crown and lower-crown leaves

We quantified differences in leaf traits between upper and lower crowns of a deciduous oak, Quercus acutissima, and examined feeding preference, consumption and performance of the Japanese oak silkmoth, Antheraea yamamai, for those leaves. Upper‐crown leaves had significantly smaller area, larger dry mass per area, greater thickness, lower water content, higher nitrogen content and a higher N/C ratio than lower‐crown leaves. When simultaneously offered upper‐crown and lower‐crown leaves, moth larvae consumed a significantly larger amount of the former. However, when fed with either upper‐crown or lower‐crown leaves (no choice), they consumed a significantly larger amount of the latter. Female larvae reared on upper‐crown leaves had a significantly smaller fresh weight, but attained a significantly larger pupal fresh and dry weight, with a significantly higher relative growth rate than those on lower‐crown leaves. Although, like female larvae, male larvae had a significantly smaller fresh weight when reared on upper‐crown leaves, they had a significantly larger value only for pupal dry weight. These results suggest that: (i) larvae ingest a greater amount of lower‐crown leaves to compensate for the lower nitrogen content of the foliage, resulting in having an excess of water because of the higher water content of the foliage; (ii) feeding preference for upper‐crown leaves accords with better performance (with respect to dry pupal weight and relative growth rate) on the foliage; (iii) better performance is explained by a higher nitrogen content and N/C ratio of the upper‐crown foliage; and (iv) the effects of leaf quality on performance differ between sexes.     

Perikymata spacing and distribution on hominid anterior teeth

We documented the spacing and distribution of perikymata on the buccal enamel surface of fossil hominin anterior teeth with reference to a sample of modern human and modern great ape teeth. A sample of 27 anterior teeth attributed to Australopithecus (5 to A. afarensis, 22 to A. africanus) and of 33 attributed to Paranthropus (6 to P. boisei, and 27 to P. robustus) were replicated and sputter-coated with gold to enable reflected light microscopy of their surface topography. Anterior teeth were then divided into 10 equal divisions of buccal crown height. The total perikymata count in each division of crown height was recorded using a binocular microscope fitted with a vernier micrometer eyepiece. Then the mean number of perikymata per millimeter was calculated for each division. Similar comparative data for a modern sample of 115 unworn human anterior teeth and 30 African great ape anterior teeth were collected from ground sections. Perikymata counts in each taxon (together with either known or presumed periodicities of perikymata) were then used to estimate enamel formation times in each division of crown height, for all anterior tooth types combined. The distributions of these estimates of time taken to form each division of crown height follow the same trends as the actual perikymata counts and differ between taxa in the same basic way. The distinction between modern African great apes and fossil hominins is particularly clear. Finally, we calculated crown formation times for each anterior tooth type by summing cuspal and lateral enamel formation times. Estimates of average crown formation times in australopiths are shorter than those calculated for both modern human and African great ape anterior teeth. The data presented here provide a better basis for exploring differences in perikymata spacing and distribution among fossil hominins, and provide the first opportunity to describe four specimens attributed to Homo in this context. Preliminary data indicate that differences may exist among the species attributed to early Homo, especially between Homo ergaster and Homo rudolfensis on the one hand, and Homo habilis sensu strico on the other.     

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.     

Ramapithecus and Sivapithecus from China: Some implications for higher primate evolution

The pattern of overall dental dimensions in over 900 teeth of ramapithecines from Lufeng in China is examined using frequency distribution histograms and fitted normal curves, and compared with data for extant hominoids. A prior study has demonstrated unequivocally that at least two groups of animals must have existed at Lufeng [Wu and Oxnard, 1983; Oxnard, 1983a]. The present investigation confirms this finding in more detail. In addition it shows that one fossil group possesses smaller teeth with a lesser degree of sexual dimorphism and approximately equal numbers of adult males and females, and the other possesses larger teeth with a rather larger degree of sexual dimorphism and a female-male ratio that may have approximated from as low as 2:1 to as high as 4:1. Comparisons of patterns of difference along the tooth row demonstrate that both these forms differ from modern apes in their sexual dimorphism, the smaller form being more like humans than the larger, which is more like apes, especially orangutans. Comparisons of the areas of the canine teeth with each of the other functional segments of the tooth row again show that the smaller form is basically similar to modern humans and that the larger resembles extant great apes. Comparisons of other functional dental areas seem to relate to dietary and masticatory functions. Thus the cutting areas are large relative to the chewing areas in omnivorous humans, whereas in the essentially vegetarian great apes this ratio is smaller. The smaller fossil resembles the human condition and may have been somewhat omnivorous; the larger one more resembles the apes and may have been somewhat more vegetarian. However, these comparisons also show that the way in which the larger form resembles the apes is associated with special development of the canines, which is different from that in any modern ape. Comparisons show that the canines in the larger form project far beyond the normal line of tooth crowns. Finally, comparisons show that canine sexual dimorphism in height is marked in the larger form. Neither of these last two features is true of the smaller fossil. These findings have implications for our understanding of the evolution of early pongids and hominids, and for the evolution of primate sexual dimorphisms and dental mechanisms.     

Comparison of dental measurement systems for taxonomic assignment of Neanderthal and modern human lower second deciduous molars

Traditional morphometric approaches for taxonomic assignment of Neanderthal and modern human dental remains are mainly characterized by caliper measurements of tooth crowns. Several studies have recently described differences in dental tissue proportions and enamel thickness between Neanderthal and modern human teeth. At least for the lower second deciduous molar (dm₂), a three-dimensional lateral relative enamel thickness index has been proposed for separating the two taxa. This index has the advantage over other measurements of being applicable to worn teeth because it ignores the occlusal aspect of the crown. Nevertheless, a comparative evaluation of traditional crown dimensions and lateral dental tissue proportion measurements for taxonomic assignment of Neanderthal and modern human dm₂s has not yet been performed.In this study, we compare various parameters gathered from the lateral aspects of the crown. These parameters include crown diameters, height of the lateral wall of the crown (lateral crown height = LCH), lateral enamel thickness, and dentine volume of the lateral wall, including the volume of the coronal pulp chamber (lateral dentine plus pulp volume = LDPV), in a 3D digital sample of Neanderthal and modern human dm₂s to evaluate their utility in separating the two taxa.The LDPV and the LCH allow us to discriminate between Neanderthals and modern humans with 88.5% and 92.3% accuracy, respectively. Though our results confirm that Neanderthal dm₂s have lower relative enamel thickness (RET) index compared with modern humans (p = 0.005), only 70% of the specimens were correctly classified on the basis of the RET index. We also emphasize that results of the lateral enamel thickness method depend on the magnitude of the interproximal wear. Accordingly, we suggest using the LCH or the LDPV to discriminate between Neanderthal and modern human dm₂s. These parameters are more independent of interproximal wear and loss of lateral enamel.     

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.     

The dentition of the Indian Knoll skeletal population: odontometrics and cusp number.

Data on the permanent dentition of 153 individuals from the well known Indian Knoll skeletal population are presented. Mesiodistal and buccolingual measurements were taken with a Helios dial caliper. Cusp number of maxillary and mandibular molars are recorded. The Indian Knoll dentition is larger than many modern groups but smaller than Australoid or Mesolithic groups. With the exception of maxillary 12, males have larger teeth than females in both dimensions. The lower canine is the most dimorphic tooth. Through rank order correlation, an association was shown between the sexual dimorphism of the mesiodistal and buccolingual dimensions. Compared to modern groups, the Indian Knoll population displays a moderate degree of sexual dimorphism in tooth size. In general, the coefficients of variation were greater for the more distal teeth within morphological classes. Amounts of size variability did not differ significantly between the sexes; moreover, rank order correlations indicated that patterns of variability in both dimensions were similar for males and females. The predominant cusp number pattern for upper molars is 4-3-3 and for lowers 5-5(4)-5. No sex differences were shown for cusp occurrence or bilateral asymmetry in cusp number.