John R. Lukacs

Sex differences in dental caries experience: clinical evidence, complex etiology.

A sex difference in oral health has been widely documented through time and across cultures. Womens oral health declines more rapidly than mens with the onset of agriculture and the associated rise in fertility. The magnitude of this disparity in oral health by sex increases during ontogeny: from childhood, to adolescence, and through the reproductive years. Representative studies of sex differences in caries, tooth loss, and periodontal disease are critically reviewed. Surveys conducted in Hungary, India, and in an isolated traditional Brazilian sample provide additional support for a significant sex bias in dental caries, especially in mature adults. Compounding hormonal and reproductive factors, the sex difference in oral health in India appears to involve social and religious causes such as son preference, ritual fasting, and dietary restrictions during pregnancy. Like the sex difference in caries, tooth loss in women is greater than in men and has been linked to caries and parity. Results of genome wide association studies have found caries susceptible and caries protective loci that influence variation in taste, saliva, and enamel proteins, affecting the oral environment and the micro-structure of enamel. Genetic variation, some of which is X-linked, may partly explain how sex differences in oral health originate. A primary, but neglected, factor in explaining the sex differential in oral health is the complex and synergistic changes associated with female sex hormones, pregnancy, and womens reproductive life history. Caries etiology is complex and impacts understanding of the sex difference in oral health. Both biological (genetics, hormones, and reproductive history) and anthropological (behavioral) factors such culture-based division of labor and gender-based dietary preferences play a role.

Interpreting Sex Differences in Enamel Hypoplasia in Human and Non-Human Primates: Developmental, Environmental, and Cultural Considerations

The purpose of this review is to provide a synoptic, critical evaluation of the evidence of, and potential etiological factors contributing to, sex differences in the expression of enamel hypoplasia (EH). Specifically, this review considers theoretical expectations and empirical evidence bearing on two central issues. The first of these is the impact of a theorized inherent male vulnerability to physiological stress on sex differences in EH. The second issue is the potential contribution to sex differences in EH of intrinsic differences in male and female enamel composition and development. To address this first issue, EH frequencies by sex are examined in samples subject to a high degree of physiological stress. Based on the concept of inherent male vulnerability (or female buffering), males in stressful environments would be expected to exhibit higher EH frequencies than females. This expectation is evaluated in light of cultural practices of sex-biased investment that mediate the relationship between environmental stress and EH expression. Defects forming prenatally afford an opportunity to study this relationship without the confounding effects of sex-biased postnatal investment. Data bearing on this issue derive from previously conducted studies of EH in permanent and deciduous teeth in both modern and archaeological samples as well as from new data on Indian schoolchildren. To address the second issue, fundamental male-female enamel differences are evaluated for their potential impact on EH expression. A large sex difference in the duration of canine crown formation in non-human primates suggests that male canines may have greater opportunity to record stress events than those of females. This expectation is examined in great apes, whose canines often record multiple episodes of stress and are sexually dimorphic in crown formation times. With respect to the first issue, in most studies, sex differences in EH prevalence are statistically nonsignificant. However, when sex differences are significant, there is a slight trend for them to be greater in males than in females, suggesting a weak influence of greater male vulnerability. Cultural practices of sex-biased investment in children appear to have greater impact on EH expression than does male vulnerability/female buffering. With respect to the second issue, sex differences in the composition and development of enamel were reviewed and determined to have limited or unknown impact on EH expression. Of these factors, only the duration of crown formation was expected to affect EH expression by sex within the great apes. The data support an association between higher defect counts in the canines of great ape males relative to those of females that may be the result of longer crown formation times in the canines of great ape males. This review concludes with an assessment of the nature of the evidence currently available to examine these issues and suggests future avenues for research focused on elucidating them.

Dates, caries, and early tooth loss during the Iron Age of Oman.

Diets high in fermentable carbohydrates are known to be highly cariogenic, particularly when contained in very sticky food such as dates. This medium allows food to remain in contact with the teeth, thereby resisting the normal flushing action of the saliva. When comprising a large portion of the diet, food such as this can lead to high caries incidence and accelerated tooth loss. This appears to be the situation found in a skeletal series from the late Iron Age in the Sultanate of Oman (100 BC-AD 893). Dental remains from 37 individuals were used in this study. Antemortem tooth loss (AMTL), caries, and dental attrition data were compiled from the 32 adult and juvenile specimens. In this sample, the caries rate is 35.5% of individuals (39.4% corrected), and 18.4% of teeth (32.4% corrected), while AMTL occurs in 100% (ten of ten) of preserved mandibles. Caries onset in permanent molars begins soon after eruption, with tooth loss and remodeling of the alveolus frequently complete by the time of third molar occlusion.

Gender differences in oral health in South Asia: metadata imply multifactorial biological and cultural causes.

This study was designed to examine the magnitude and etiology of gender differences in oral health. South Asia was selected for study because sex differences in caries rates exist in prehistory here, great cultural diversity provides context, and clinical reports document caries by gender.

Enamel hypoplasia in deciduous teeth of great apes: Do differences in defect prevalence imply differential levels of physiological stress?

This paper presents new data on enamel hypoplasia in the deciduous canine teeth of great apes. The enamel defect under consideration is known as localized hypoplasia of primary canines (LHPC), and is characterized by an area of thin or missing enamel on the labial surface of deciduous canine teeth (Skinner [1986a] Am. J. Phys. Anthropol. 69:59-69). Goals of this study are: 1) to determine if significant differences in the frequency of LHPC occur among three genera of great apes, and 2) to evaluate variation in LHPC prevalence among great apes as evidence of differential physiological stress. Infant and juvenile apes with deciduous teeth were examined at the Cleveland Museum of Natural History (n = 100) and at the Smithsonian Institution, National Museum of Natural History (n = 36). Deciduous teeth were observed under oblique incandescent light, with the naked eye and with a 10x hand lens. Enamel hypoplasia was scored using Federation Dentaire International (FDI)-Defects of Dental Enamel (DDE) standards. Hypoplasias were recorded by drawing defect location and size on a dental chart, and by measuring defect size and location with Helios needlepoint dial calipers. The prevalence of LHPC is reported by genus and sex, using two approaches: 1) the frequency of affected individuals-those having one or more deciduous canine teeth scored positive for LHPC; and 2) the number of canine teeth scored positive for LHPC as a percentage of all canine teeth observed. Variation in defect size and location will be described elsewhere. Localized hypoplasia of primary canine teeth was found in 62.5% of 128 individual apes, and in 45.5% of 398 great ape deciduous canines. As in humans, LHPC is the most common form of enamel hypoplasia in deciduous teeth of great apes, while LEH is rare or absent. The distribution and pattern of expression of LHPC in great apes is similar to that described in humans: side differences are not significant, but mandibular canines exhibit the defect two to five times more often than maxillary canine teeth. Differences in LHPC prevalence by sex are small and not significant. Intergeneric differences are large and non-random: chimpanzees (Pan) exhibit a significantly lower frequency of LHPC (22%, n = 50) by individual count, than either the orangutan (Pongo, 88.0%, n = 25) or the gorilla (Gorilla, 88.7%, n = 53). Tooth count prevalences exhibit a similar pattern of variation and are also statistically significant. These findings suggest that large bodied great apes (gorilla and orangutan) may be under greater physiological stress during perinatal and early postnatal development than the chimpanzee. The size, position, and timing of LHPC lesions are currently under analysis and may yield more insight into the etiological origin of this enamel defect.

Sex/Gender Differences in Tooth Loss and Edentulism: Historical Perspectives, Biological Factors, and Sociologic Reasons

This review highlights what is known regarding differences in tooth loss by sex/gender, and describes: gender-related tooth ablation (the deliberate removal of anterior teeth during life) found in skulls from history and prehistory; potential mediators of the relationship between sex/gender and tooth loss; the current epidemiology of gender differences in tooth loss (limited to North America); and risk factors for tooth loss in the general population and in women.

Preferential expression of linear enamel hypoplasia on the sectorial premolars of rhesus monkeys (Macaca mulatta)

Three hundred and sixty rhesus macaque specimens at the Caribbean Primate Research Center were examined for evidence of linear enamel hypoplasia (LEH). A previously unreported intertooth pattern in LEH was observed. Defects occur preferentially on the sectorial premolar of both males and females. Relative to other teeth, the sectorial premolar exhibits more prominent defects and is more likely to exhibit multiple defects. This pattern is unlike the human intertooth LEH pattern and unlike patterns previously reported for monkeys and apes. These observations are discussed in the context of factors thought to influence the intertooth distribution of LEH in humans and in nonhuman primates. The authors reject crown height, the timing of crown development, and the duration of crown formation as factors contributing to the observed pattern and favor an explanation involving enamel thickness, perikymata spacing, and/or prism orientation.

Interproximal contact hypoplasia in primary teeth: A new enamel defect with anthropological and clinical relevance.

This study reports the prevalence, distribution, and expression of enamel defects in a sample of primary teeth (n = 225) from a prehistoric site in western India (1400–700 BC). Five enamel surfaces of individual, isolated primary teeth were observed for surface defects using a binocular stereomicroscope with variable power of magnification (8–20×). Standards for evaluating dental enamel defects (DDE) recommended by the Fédération Dentaire International (FDI) were employed. Details of defect expression were also recorded, including size, shape, and surface of tooth crown affected. Hypoplastic enamel defects were observed in 28% of teeth, but the distribution and expression of defects was not random. More than 50% of canine teeth had hypoplastic defects (HD); incisors and molar teeth exhibited far fewer HD. The buccal surface of canines was the most commonly affected crown surface. Areas of missing enamel were also common on the mesial and distal surfaces of canines and incisors and on the mesial surface of molar teeth. The high frequency of enamel defects found on interproximal crown surfaces warrants a label, and the name interproximal contact hypoplasia (IPCH) is proposed. Linear enamel hypoplasia (LEH) was absent from this primary dental sample. IPCH is more frequent in mandibular than in maxillary teeth, but no side preference was detected. In canine teeth, buccal hypoplasias (localized hypoplasia of primary canines; LHPC) were not positively correlated with interproximal hypoplastic defects. The etiology of IPCH may involve mesial compaction of developing teeth due to slow longitudinal growth of the jaws. Episodic bone remodeling results in ephemeral fenestrae in the mesial and distal walls of the dental crypt permitting tooth–tooth contact and disruption of amelogenesis. IPCH prevalence decreases across the subsistence transition from sedentary Early Jorwe agriculturalists to seminomadic Late Jorwe hunters and foragers, but the difference is not statistically significant. This may be due to underrepresentation of mandibular teeth in the sample. Am. J. Hum. Biol. 11:718–734, 1999.

Dental Anthropology of South Asian Populations: A Review

Morphological and metrical variations of the human dentition have not been utilized to their full potential by anthropologists concerned with patterns of human biological variation in South Asia. While dental anthropology has contributed major insights into the evolution and migration of many of the world’s populations, physical anthropology in South Asia consists primarily of traditional descriptions of the anthropometric, dermatoglyphic, and immunogenetic characteristics of the subcontinent’s diverse populations.

Cementum annulations, age estimation, and demographic dynamics in Mid-Holocene foragers of North India

One of the principal problems facing palaeodemography is age estimation in adult skeletons and the centrist tendency that affects many age estimation methods by artificially increasing the proportion of individuals in the 30-45-year age category. Several recent publications have indicated that cementum annulations are significantly correlated with known age of extraction or death. This study addresses the question of how demographic dynamics are altered for an archaeological sample when cementum-based age estimates are used as opposed to those obtained via conventional macroscopic methods. Age pyramids were constructed and demographic profiles were compared for the early Holocene skeletal population from Damdama (India). The results demonstrate that the use of cementum annulations for age estimation in only a subset of the skeletal sample has a significant impact on the demographic profile with regard to specific parameters such as mean age at death and life expectancy at birth. This confirms the importance of using cementum annulations to refine age estimates in archaeological samples, which, when combined with a fertility-centred approach to demography, can provide new insights into population dynamics in the past.