Blood factors and morphology of the Negroes of James Island, Charleston, S. C.

The tempo of tooth mineralization is under significant genetic control, and the orderly progression of morphological changes-in concert with the long span during growth in which teeth form-makes "dental age" a useful measure of a person's degree of biological maturity. The third molar is of particular interest because (1) it is the last and most variable tooth to form and (2) it is the only tooth to complete formation after puberty, which has made it attractive in forensic and legal circles as an estimator of adulthood. Age standards are described here for mandibular third molar formation stages in a cross-sectional sample of 4,010 persons (age range: 3-25 years), with proportionate sample sizes of American blacks and whites and males and females. Formation was scored against the 15-grade ordinal scheme of Moorrees, and descriptive statistics were computed using proportional hazards survival analysis. Blacks achieved each formation stage significantly ahead of whites, but not in a uniform manner. Instead, there was an enhanced advancement in blacks during crown formation and during late stages of root formation. In both races formation proceeded faster in males, which is unique for the third molar, as prior studies suggest. Sample variance increases with the stage of formation, such that 95% confidence limits span 8 or more years for root formation stages. Consequently, the third molar provides a rough gauge of an individual's chronological age, but the considerable variability precludes any precise estimate, particularly in late adolescence where most forensic interest has focused.

Section: Methodsmentioning

confidence: 95%

Mineralization of the mandibular third molar: A study of American blacks and whites

Harris

2006

“…Admixture estimates of whites with American blacks are on the order of 20 -30% for Northern and Western samples (e.g., Glass and Li, 1953;Glass, 1955;Roberts, 1955;Roberts and Hiorns, 1962), but are generally below 10% for Southeastern samples (e.g., Pollitzer, 1958;Workman et al, 1963;Pollitzer et al, 1964Pollitzer et al, , 1970Blumberg and Hesser, 1971). Children in the present study were born in western Tennessee, northern Mississippi, and eastern Arkansas.…”

Section: Methodsmentioning

confidence: 98%

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

Harris

Hicks

Barcroft

2001

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.

“…Previous studies using the reconstructed genealogies suggest minimal impact of recording errors (Stojanowski et al, , ), although there is the potential for adoptions and other fictive kin relationships (and half sibships) that were not captured in the genealogical recording (Twining & Baird, ). Further details on the Gullah sample can be found in Stojanowski et al (, ), which summarize the relevant details from initial work among the population (Menegaz‐Bock, ; Pollitzer, , , ; Pollitzer, Menegaz‐Bock, Ceppellini, & Dunn, ), including prior dental anthropological analyses (Edgar, ; Edgar & Sciulli, ; Guatelli‐Steinberg et al, ) and assessments of genetic variation (McClean Jr. et al, 2003, 2005; Parra et al, ; Sale et al, ). All research presented in this article was conducted under the approval of The Ohio State University IRB (2012B0529).…”

Section: Methodsmentioning

confidence: 99%

Quantitative genetic analyses of postcanine morphological crown variation

Stojanowski

Paul

Seidel

et al. 2019

Objectives: This article presents estimates of narrow-sense heritability and bivariate genetic correlation for 14 tooth crown morphological variants scored on permanent premolars, first molars, and second molars. The objective is to inform data collection and analytical practices in dental biodistance and to provide insights on the development of molar crowns as integrated structures.Materials and Methods: African American dental casts from the Menegaz-Bock collection were recorded for the Arizona State University Dental Anthropology System. Estimates of narrowsense heritability and genetic correlation were generated using SOLAR v.8.1.1, which included assessment of age, sex, and birth year as covariates. Both continuous scale and dichotomized estimates are provided.Results: Heritability estimates were nonsignificant for the majority of variables; however, for variables yielding significant estimates, values were moderate to high in magnitude and comparable to previous studies. Comparing left and right-side heritability estimates suggests directional asymmetry in the expression of environmental variance, something not seen in anterior tooth traits. Genetic correlations were moderate among antimeres and metameres and low for different traits scored on the same tooth crown. Although several negative correlations were noted, few reached statistical significance. Results affirm some of the current data cleaning and analytical practices in dental biodistance, but others are called into question. These include the pooling of males and females and combining left and right-side data into a single dataset.Conclusions: In comparison to anterior tooth crown traits, postcanine heritabilities were more often non-significant; however, those traits with significant heritability also tended to produce higher estimates. Genetic correlations were unremarkable, in part, because they were underpowered. However, M1 results may provide insight into the complex relationship between genes, environment, and development in determining ultimate crown form. K E Y W O R D Sbiodistance, dental morphology, heritability, pleiotropy, quantitative genetics