Estimation of sex assigned at birth using dental crown and cervical measurements in a modern global sample.

Despite developing prior to the appearance of secondary sexual characteristics of the skeleton, the permanent dentition exhibits sexual dimorphism. Therefore, teeth can serve as a means to estimate sex assigned at birth even in young individuals. This project takes a large global sample of maximum dimensions of the crown as well as measurements of the crown at the cervix to explore sexual dimorphism. Dimorphism is noted in teeth throughout the dental arcade, particularly in the canines. We provide sectioning points as well as the probability of correct classification (ranging from 50.9% to 81.3%) for each measurement to aid the practitioner in sex estimation from the dentition. This research provides a method to estimate sex without arbitrary population specifications. We argue for a global approach that incorporates more population variation to remove the need to estimate "ancestry," (which in actuality is translated to a social race category) and therefore does not force sexual dimorphism-related variation into these mutable and ambiguous categories. Further, this paper demonstrates the utility of the dentition as an additional indicator to aid with the estimation of sex assigned at birth in forensic anthropology. The goal of this research is to better understand the expression of sexual dimorphism across the skeleton in a global context.

Evaluating predictions of the patterning cascade model of crown morphogenesis in the human lower mixed and permanent dentition.

OBJECTIVE: The patterning cascade model of crown morphogenesis has been studied extensively in a variety of organisms to elucidate the evolutionary history surrounding postcanine tooth form. The current research is the first to use a large modern human sample to examine whether the crown configuration of lower deciduous and permanent molars aligns with expectations derived from the model. This study has two main goals: 1) to determine if metameric and antimeric pairs significantly differ in size, accessory trait expression, and relative intercusp spacing, and 2) assess whether the relative distance among early-forming cusps accounts for observed variation in accessory cusp expression. METHODS: Tooth size, intercusp distance, and morphological trait expression data were collected from 3D scans of mandibular dental casts representing participants of the Harvard Solomon Islands Project. Paired tests were utilized to compare tooth size, accessory trait expression, and relative intercusp distance between diphyodont metameres and permanent antimeres. Proportional odds logistic regression was implemented to investigate how the odds of greater accessory cusp expression vary as a function of the distance between early-developing cusps. RESULTS/SIGNIFICANCE: Comparing paired molars, significant differences were identified for tooth size and cusp 5 expression. Several relative intercusp distances emerged as important predictors of cusp 6 expression, however, results for cusp 5 and cusp 7 did not match expected patterns. These findings support previous quantitative genetic results and suggest the development of neighboring crown structures represents a zero-sum partitioning of cellular territory and resources. As such, this study contributes to a better understanding of the foundations of deciduous and permanent molar crown variation in humans.

An Anthropological Investigation of the Sociocultural and Economic Forces Shaping Dental Crowding Prevalence.

OBJECTIVE: The aim of the current study is to explore country of origin and social race category differences in dental crowding prevalence through an anthropological approach. DESIGN: Data were collected from individuals within five countries (Australia, China, Japan, South Africa, United States; n = 1008) and seven social race groups in two countries (American Black, American White, Latinx, and Indigenous in the United States, South African Black, South African White, and South African Coloured; n = 654). Statistical significance between groups was assessed with a Kruskal-Wallis test, while a Dunn's post-hoc test identified which groups significantly differed. RESULTS: Results indicate South Africa is characterized by the lowest frequencies of dental crowding, with Coloured South Africans yielding the highest and Black South Africans displaying the lowest frequencies. Individuals in the United States exhibited relatively high levels of minor dental crowding. American Blacks had lower crowding levels, while the Indigenous group had high levels of severe crowding. Individuals within China and Japan exhibited higher relative prevalence of severe crowding. CONCLUSIONS: Overall, significant differences exist in dental crowding prevalence across countries and social race categories using an anthropological grading system to assess crowding. These differences are likely impacted by sociocultural (aesthetic preferences) and economic (access to dental care) factors.