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Background: Markers of exposure to environmental toxicants are urgently needed. Tooth enamel, with its unique properties, is able to record certain environmental conditions during its formation. Enamel formation and quality are dependent on hormonal regulation and environmental conditions, including exposure to endocrine disrupting chemicals (EDCs). Among EDCs, phthalates such as di-(2-ethylhexyl) phthalate (DEHP) raise concerns about their contribution to various pathologies, including those of mineralized tissues. Objectives: The effects of exposure to low-doses of DEHP on the continually growing incisors were analyzed in mouse males and females. Methods: Adult male and female C57BL/6J mice were exposed daily to 0.5, 5, and 50 [micro]g/kg per day DEHP for 12 wk and their incisors clinically examined. Incisors of males were further analyzed by scanning electron microscopy (SEM), micro X-ray computed tomography (micro-computed tomography; [micro]CT), and nanoindentation for the enamel, histology and real-time quantitative polymerase chain reaction (RT-qPCR) for the dental epithelium. Results: Clinical macroscopic observations of incisors showed various dose-dependent dental lesions such as opacities, scratches, and enamel breakdown in 30.5% of males (10 of 34 total incisors across three independent experiments), and 15.6% of females (7 of 46 incisors) at the highest dose, among which 18.1% (6 of 34 total incisors across three independent experiments) and 8.9% (4 of 46 incisors), respectively, had broken incisors. SEM showed an altered enamel surface and ultrastructure in DEHP-exposed male mice. Further characterization of the enamel defects in males by [micro]CT showed a lower mineral density than controls, and nanoindentation showed a lower enamel hardness during all stages of enamel mineralization, with more pronounced alterations in the external part of the enamel. A delay in enamel mineralization was shown by several approaches ([micro]CT, histology, and RT-qPCR). Discussion: We conclude that DEHP disrupted enamel development in mice by directly acting on dental cells with higher prevalence and severity in males than in females. The time window of DEHP effects on mouse tooth development led to typical alterations of structural, biochemical, and mechanical properties of enamel comparable to other EDCs, such as bisphenol A. The future characterization of dental defects in humans and animals due to environmental toxicants might be helpful in proposing them as early markers of exposure to such molecules. https://doi.org/10.1289/EHP10208, Introduction The environment is continually evolving, with considerable changes in recent decades that have had an impact on human health and well-being, as well as all living organisms. (1-4) Markers [...]

This paper extends observations by Lukacs ([1999] Am. J. Phys. Anthropol. 110:351-363; [2001] Am. J. Phys. Anthropol. 116:199-208) of localized hypoplasia of the primary canine (LHPC) among large apes to gibbons, bonobos, and orangutans. LHPC is a roughly circular area of deficient enamel on the labial surface of primary canine teeth which, on current evidence from humans, forms several months after birth due to malnutrition-induced craniofacial osteopenia, leading to crypt fenestration that exposes the dental follicle and more deep-sited ameloblasts to minor physical traumata during normal motor infant development. Our goal was to determine the prevalence of LHPC among a variety of apes which differ in body mass and socioecology, with a view to elucidating the etiology of the defect. We examined juvenile dentitions from 122 animals from three taxa: 8 Hylobates lar, 75 Pongo pygmaeus from Borneo and Sumatra, and 39 Pan paniscus from central Africa. Reported variables include taxon, sex, arcade, side, and tooth size. Presence/absence and ordinal severity of defect expression were recorded by description, microphotography, and scanning electron microscopy. Molds were taken in high-resolution dental impression materials and cast in epoxy resin. There are clear taxonomic, but no sex, differences. Prevalence ranged from 0.0% in gibbons to 61.5% in bonobos and 85.3% in orangutans. The result for orangutans is similar to that reported by Lukacs ([1999] Am. J. Phys. Anthropol. 110:351-363), while bonobos are much more affected than were the common chimpanzees (22%) described by Lukacs ([1999] Am. J. Phys. Anthropol. 110: 351-363). There are no significant antimeric differences, but the lower canine is much more affected than the upper by LHPC. We show that larger teeth are more affected by LHPC and have more severe defects. Also, we encountered several instances of patent or healing canine crypt fenestrations, occasionally in direct association with LHPC. Location of the defect indicates that LHPC may occur perinatally but more usually several months postnatally. Histological examination showing the neonatal line and LHPC is required to resolve the issue of timing. We concur with Lukacs ([1999] Am. J. Phys. Anthropol. 110:351-363) that taxonomic, anatomical, and environmental variables combine to determine the occurrence and appearance of LHPC. Nevertheless, we conclude that LHPC probably reflects deficient growth of the arcades in infant apes and humans. Am J Phys Anthropol 120:61-72, 2003. KEY WORDS enamel defects; deciduous dentition; Asian apes; African apes; gibbon; orangutan; bonobos; osteopenia

A significant correlation between childhood stature and prevalence of enamel hypoplasia in deciduous canines has been found in a study of seven groups of school children in western Maharashtra, India. A comparative analysis of hypoplasia prevalence covers living vs prehistoric study groups, urban vs rural groups, and associations with height, weight and SES.

A diachronic decline in stress markers was found in a study of predynastic remains from the Naqada region of Upper Egypt. Dental hypoplasias and porotic hyperostosis were examined in samples representing a period when population density and social complexity were increasing and Nile flooding was decreasing.

One hundred and fifteen unworn anterior teeth were sectioned longitudinally with a diamond saw and prepared for histological examination by polarized light microscopy. Incremental markings in the enamel of each tooth were used to estimate the average total crown formation times of each tooth type. The total time taken to form the crowns of each tooth type was apportioned by 1) cuspal enamel formation and 2) each tenth percentile of total tooth height. Based on these data, and on histological estimates for the time of initiation of mineralization in each anterior tooth, the following conclusions can be drawn. Little if any visible surface enamel is likely to form before the end of the first year after birth in any anterior tooth type. No relation exists between tooth crown height and the total time taken to form enamel. Anterior crown formation is nonlinear and slows towards the cervix in all teeth. The estimated mean chronological age at crown completion ranged in this study from between around 4 years for lower central incisors to around 6 years for lower canines. We suggest that these combined findings will be useful for devising more reliable ways to estimate the timing of linear enamel hypoplasias than some methods currently in use. Keywords: enamel hypoplasia; incremental markings; cross striations

This study describes the expression of linear enamel hypoplasia (LEH), a sensitive dental indicator of physiological stress, in Thailand gibbons (Hylobates lar carpenteri). Previous studies of enamel hypoplasia in hominoids have focused on great apes, with little attention given to the expression of this stress indicator in gibbons. In that gibbons differ from both monkeys and great apes in numerous life history features, LEH expression in gibbons might be expected to show significant differences from both. In this study, 92 gibbon specimens from two sites in Thailand were compared with several samples of monkeys and great apes in their expression of LEH. The intertooth distribution of LEH in gibbons was compared to that of chimpanzees and rhesus monkeys. Gibbon populations from both sites exhibit LEH frequencies intermediate between those of the monkey samples, in which LEH prevalence is usually low, and those of the great ape samples, in which LEH prevalence is high. Gibbons differ significantly from monkeys, but not great apes, in the number of individuals whose teeth record multiple stress events. Multiple episodes of stress are rarely recorded in the teeth of monkeys, while multiple stress events occur with higher frequency in gibbons and great apes. Taxonomic variation in the duration of crown formation, the prominence and spacing of perikymata on dental crowns, life history features, and/or experience of physiological stress may explain these patterns. The intertooth distribution of LEH in gibbons is, for different reasons, unlike that of either chimpanzees or rhesus monkeys. The mandibular canines of gibbons have significantly more LEH than any of their other teeth. Aspects of crown morphology, perikymata prominence/spacing, enamel thickness, and crown formation spans are potential causes of taxonomic variation in the intertooth distribution of LEH. Keywords: primate dentition; enamel hypoplasia; developmental stress; great apes; monkeys

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 modem 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. Keywords: enamel hypoplasia; sex differences; physiological stress; linear enamel hypoplasia; localized hypoplasia; environmental buffering

Interproximal contact hypoplasia has been observed as a common form of enamel defect, occurring in 15.1% of the teeth, in a sample of 225 primary teeth from a prehistoric site in western India, dated from 1400-700 BC. The prevalence, distribution and expression of enamel defects in the sample are discussed.

Results of a study of enamel hypoplasia in a Canadian historic sample do not support the hypothesis that peak ages of hypoplastic devect occurrence are associated with cessation of breastfeeding or the weaning process in general. Calculations of peak ages of occurrence are within the commonly observed 2-4- year range. They are not consistent with other studies of complementary foods and weaning. The study used analyses of skeletal samples from 253 adults of a mid-to-high socioenomic 19th-century community.

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. Key words: primate dentition; enamel hypoplasia; dental enamel defects; stress indicators; crown height; enamel thickness; perikymata

Diagnosis of the congenital form of syphilis is an important part of the palaeopathology of this disease. In theory, there are clear clinical signs to be found in the long bones and teeth, but it has rarely been possible to recognise the latter with a confidence in archaeological material, partly because the original descriptions of the dental deformities are sometimes contradictory and partly because it is nowadays difficult to find reference specimens in museums. This article describes two such specimens which have recently been rediscovered, and discusses the form of the dental defects which they show (Hutchinson's incisors, Moon's molars, and mulberry molars) in relation to the developmental sequence of the teeth. KEY WORDS enamel hypoplasia; Hutchinson's incisors; Moon's molars; mulberry molars; dental development

A skeletal sample of 44 individuals born and raised in early 18th century frontier settlements of Northeastern United States is examined for the frequency and chronological distribution of linear enamel hypoplasia (LEH) on the maxillary and mandibular incisors and canines. The prevalence of LEH ranged from 31% on the [I.sup.2] to 66% on the mandibular C and the mean number of defects ranged from .59 on the [I.sup.2] to 1.08 on the mandibular C. These frequencies were generally lower than those reported for two later samples; the Monroe County Poorhouse sample and the Hammon-Todd sample. Individuals in these latter two samples were derived from the lowest socioeconomic stratum of their respective populations. Frequency differences are explained within the context of the changing availability of resources that resulted from the rise of industrialization, urbanization, and wage labor which took place during the 18th and 19th centuries. The frequency of LEH was low prior to 1.5 years of age and may result from attrition and/or decreased susceptibility in the relevant area of the crown or from low morbidity or high mortality. Peak frequencies are observed in all age categories ranging from 2.5 to 3.0 years up to 4.0 to 4.5 years and are too late to result from weaning. Instead, they may reflect the susceptibility of nonimmune children to diseases that were common in colonial North America. As the majority of these diseases were not fatal, most victims who survived may have had one or more LEHs as visible proof of their earlier encounter(s). KEY WORDS Anterior dentition, Dental defects, Biological stress, Historical

Chewing hydrochloric acid (HCl) tablets can erode the tooth enamel. HCl tablets are available without prescription at health food stores and are used to treat digestive problems. It is well known that acid in food, drinks, or medicines can erode tooth enamel. A 67-year-old woman came for routine dental treatment who had not seen a dentist for several years. Her teeth were severely acid eroded. The enamel on her front teeth was entirely gone. A cast model of her teeth made about five years earlier showed that her teeth had been normal at that time. She had been taking HCl tablets for the past five years for a digestive problem, and since she could not swallow the pills, she chewed them instead. The directions on the bottle gave no instructions about chewing or swallowing. She reported no other sources of acid coming in contact with her teeth.

Most analyses of dental enamel hypoplasia compare frequencies of disturbed tooth types, which do not account for variability in the area of affected enamel. An alternate methodology, hypoplastic area, is presented here that accounts for this variability by combining acute and continuous enamel hypoplasia into an interval-level variable. The method compares samples based on individuals, by multiple tooth type variables, or by a single value rather than by tooth types. Use of the hypoplastic area method is illustrated by analyzing human skeletal dentitions in three archaeological samples: Meroitic Nubians from Semna South, Sudan; Anasazi from Navajo Reservoir, New Mexico; and Mogollon from Grasshopper Pueblo, Arizona. Both univariate and multivariate statistical tests are employed to assess variation in defects between individuals and samples. By incorporating measurements of continuous defects, the hypoplastic area method provides information beyond that of frequency data in comparing levels of stress. Flexibility of the method is also discussed. KEY WORDS Enamel hypoplasia, Area of affected enamel, Nubia, American Southwest

The dentition of 27 enslaved African Americans from archaeological sites in Maryland and Virginia were examined. All 17 males and 7 of the 10 females in this study exhibited enamel hypoplastic defects indicative of systemic nutritional and disease stresses interfering with amelogenesis. Estimates of the ages of occurrence of these defects show that most occur between 1.5 and 4.5 years of age, 0.5-3.75 years later than historically documented weaning age (9-12 months of age) in similar plantation populations. Comparisons are made with studies of dental enamel hypoplasia in contemporaneous enslaved and free African American populations, including our data on 75 individuals from the First African Baptist Church cemetery in Philadelphia. These populations were highly stressed. While there appears to be a modest effect of early weaning stress, no direct relationship of peak frequencies to weaning age can be shown. These data raise questions about the attribution of peak hypoplasia frequencies to age at weaning or 'post-weaning' stresses in previous paleopathological studies. High hypoplasia frequencies during the middle years of enamel development are more likely the result of a combination of 1) multiple environmental stresses, 2) differences in hypoplastic susceptibility in enamel, and 3) random factors. KEYWORDS: African Americans, Slavery, Hypoplasia, Weaning

A sample representing a population of the Florence district of middle 19th century was studied to determine the age of occurrence of enamel hypoplasias. The age interval most affected was that between 1.5 and 3.5 years. Historical sources on weaning habits of 19th-century Italian populations indicate a weaning period between 12 and 18 months. This is in agreement with the data on enamel defects, showing that children of post-weaning age are more subject to stress. Wide 'grooves', with prolonged duration, are concentrated between 2 and 2.5 years, whereas 'lines' occur primarily between 2.5 and 3 years. We suggest that this distribution could reflect the gradual introduction of dietary supplements until weaning is complete.

Enamel microabrasion may be more effective than bur-cut enamel stripping for the removal of superficial tooth discoloration. Enamel microabrasion involves the rotary application of an abrasive compound to form a smooth enamel glaze. A nine-year-old boy had unsightly white spots on his maxillary central incisors. The right central incisor was treated with enamel microabrasion with a 12-fluted carbide finishing bur followed by application of a microabrasion compound. The left central incisor was treated with application of the microabrasion compound alone. No difference in appearance was observed between the right and left central incisors. An 11-year-old girl underwent a similar type of treatment for decalcification of the maxillary permanent incisors. No difference was seen between the two types of treatment. The main disadvantage of enamel microabrasion is that it may be more time consuming.

Hutchinson's incisors and Moon's molars are specific lesions of congenital syphilis. The extensive but fragmentary clinical literature on these conditions describes reduced dimensions and thin enamel in the permanent incisors and first molars, crowding and infolding of the first molar cusps, notching of the upper incisors, and apical hypoplasias of the permanent canines. A Barbados slave cemetery (ca. 1660--1820 AD) includes three individuals with these features, suggesting a frequency at birth of congenital syphilis in the population approaching 10%. These three cases show triple the frequency of all hypoplasias and more than seven times the frequency of pitting hypoplasia present in the remainder of the series. The recognizable congenital syphilis cases account for much of the remarkably high frequency of hypoplasias in the series as a whole. We infer that syphilis contributed substantially to morbidity, infant mortality, and infertility in this population. Presence or absence of congenital syphilis may account for much of the variability in health and mortality seen among nineteenth century African-American populations. [C] 1992 Wiley-Liss, Inc.

Bulimia nervosa is a disorder characterized by distortion of the body image, a preoccupation with weight and food, and eating binges followed by purging (vomiting and enemas). Its effects on the composition and production of saliva were studied in 15 female patients (average age, 25). The condition leads to tooth erosion because stomach contents are very acidic; this, in turn, causes tooth sensitivity and increased cavity formation. An additional complication is the decreased salivary flow in bulimics, which leads to poorer digestion and the loss of the protective effect exerted by saliva on the oral mucosa. Dental examinations were carried out and salivary flow and composition measures completed for the bulimic subjects and for 15 age- and race-matched control subjects. In addition, subjects' olfaction (sense of smell) was evaluated. Results showed that bulimic and normal subjects had saliva of similar composition (potassium chloride, calcium, urea nitrogen and albumin). Differences between the groups in olfactory function were not found. A discussion is presented of the physiologic mechanisms that determine the concentrations of salivary components. The results suggest that the oral tissue abnormalities associated with bulimia are the result of diet and binging-purging, rather than a consequence of salivary changes. (Consumer Summary produced by Reliance Medical Information, Inc.)

A case report is presented of a 10-year-old girl with multiple dental abnormalities, including the loss of enamel (the outer layer of the teeth) on several teeth, extensive calculus (hard substance deposited on the teeth), gum inflammation, severe overbite (eight millimeters), and extreme sensitivity to heat. The diagnosis was made of hypomaturation amelogenesis imperfecta, a type of hereditary enamel defect. The treatment plan is described. It ultimately involved an oral surgeon, a maxillofacial surgeon, an orthodontist, and a prosthodontist. The patient had intense anxiety and had undergone painful dental treatment earlier in life. After the initial extractions and crown placement (19 crowns were used), the patient returned at regular intervals to receive help with oral hygiene. Her fear lessened with time, but as she grew older, the patient became more concerned with her appearance. Consultation among several specialists resulted in a new plan involving orthognathic (jaw-straightening) surgery; this is described. Further cosmetic surgery was also needed. The patient was able to achieve a satisfactory esthetic result through this multidisciplinary approach, essential in disorders such as this one. (Consumer Summary produced by Reliance Medical Information, Inc.)

A skeletal sample of 296 individuals from a 19th century American poorhouse cemetery is examined for the frequency and chronological distribution of linear enamel hypoplasias on the mandibular canines and maxillary central incisors. Dental enamel hypoplasias may be considered to be indicators of increased exposure to health risk at the time of weaning. The purpose of this study is to examine childhood stress and provide a relative measure of that stress, as evidenced by hypoplasias, ina historic sample that represents an industrializing population. The frequency of enamel hypoplasias per individual by tooth ranged from 70 to 73%, with a peak age at stress of 2.5 to 3 years for the maxillary central incisor and 3.5 to 4 years for the mandibular canine. There were no significant differences in the presence of hypoplasias between males and females. The peak age at stress between 2.5 and 4 years in this 19th century sample transects the ranges reported for prehistoric populations (2-6 years) and for modern groups (0-3 years). These results indicate that the stress associated with weaning probably occurred earlier in incipient industrial societies than in prehistoric hunter/gatherers and agriculturalists, yet not as early as in modern industrial groups. The high level of childhood stress in this skeletal sample compared with that of other samples may indicate a change in health, at least among the lowest class, associated with t he cultural transition from an agricultural to an industrial society.

Clinical studies of the relationship between developmental enamel defects and caries susceptibility have often produce conflicting results. This has been due in part to a failure to distinguish between different types of defects. Studies of this association in prehistoric populations have been rare. The complete deciduous dentitions of 57 subadults from the Libben site, a large Late Woodland cemetery in Ottawa County, Ohio, were selected for analysis. Defects were classified as either hypoplasias (deficiencies in matrix apposition) or hypocalcifications (deficiencies in mineralization) and were graded for severity. The presence or absence of carious lesions was recorded for each tooth. Results indicate a strong positive relationship between hypocalcifications and caries susceptibility. The elevated caries susceptibility of hypocalcified teeth may be related to high levels of magnesium or altered enamel microcystallite orientation within these teeth. Variations in the frequency of hypocalcifications may partially explain differences in caries rates that have been observed in different prehistoric populations.

Dental enamel hypoplasias are deficiencies in enamel thickness resulting from physiological perturbations (stress) during the secretory phase of amelogenesis. The results of a wide variety of experimental, clinical, and epidemiological studies strongly suggest that these defects and their associated histological abnormalities (such as accentuated stria of Retzius and Wilson bands) are relatively sensitive and nonspecific indicators of ring-like nature of their development, these defects can provide an indelible, chronological record of stress during tooth crown formation. For these reasons, along with the ease with which they are studied, enamel hypoplasias have been increasingly employed as indicators of nutritional and disease status in paleopathology, and their study has begun to extend into other subdisciplines of physical anthropology. In order to provide the reader with a better understanding of the current issues in this field, we first review normal enamel development, historical advances in the study of enamel developmental abnormalities, and provide a threshold model to help conceptualize the etiology of enamel developmental defects. Specific attention is then centered on extant, fundamental issues in the use of enamel hypoplasias and histological structures as epidemiological indicators of nonspecific stress. Most enamel hypoplasias are associated with abnormal histological changes (accentuated stria of Retzius or 'Wilson' and 'Cluster' bands). However, the lack of association of some mild surface irregularities, characteristically seen as thin, perikymata-like surface depressions, with abnormal prism morphology suggests that these surface features may not be evidence of physiological perturbation. Methods now exist to reliably identify both histological and enamel surface defects. However, further research is needed on methods for determining the size of defects and the epidemiological significance of defect widths and depths. Similarly, the general relationship between the location of enamel hypoplasias and associated histological structures on the one hand, and an individual's age at the time of their development on the other hand, is also well understood. However, better estimates of intra- and inter-population variation in the timing of enamel matrix formation are needed before these defects can reach their full potential as chronometric measures of stress. Lack of understanding patterns of differential susceptibility of enamel to developmental disruption has likely hindered interpretations of the results of a number of past experiments. The seemingly strong pattern of differential susceptibility of enamel to disruption--within teeth and across tooth classes, dentitions, and taxa--may yield a number of significant clues to understanding basic issues in enamel development. Populations that are exposed to a high degree of undernutrition and disease, from prehistoric to contemporary times, share high rates of linear enamel hypoplasias. While these defects seem to relate to bouts of undernutrition and infection, their specific etiology is still unknown. In the next decade we expect to develop more precise information on the specificity and sensitivity of secretory ameloblasts to disruption. A variety of research directions are suggested for further anthropological study.

Enamel hypoplasia (EH). is a dental enamel defect that is often used as an indicator of non-specific systemic stress during the early stages of development. There are few reports of this enamel defect in non-human primates and little is known about the prevalence of this defect in the bonobo, Pan paniscus. The frequency and distribution of EH within the bonobo are investigated using skeletal specimens from the Royal Museum for Central Africa in Tervuren, Belgium. All permanent teeth were examined with a 5-20X pocket hand lens in oblique incandescent and natural light. Linear defects were scored as mild, moderate, or severe and defect distances from the cemento-enamel junction were measured with digital calipers. Pit-type hypoplasias were counted and recorded as present or absent. At the level of the individual (N=82), the vast majority of bonobos in this skeletal sample (98.8%) are affected to some degree with linear enamel hypoplasia (LEH) and there is no significant difference in the expression of LEH between the sexes. Pitting is observed in 13.4% of these individuals with no significant difference between the sexes. The anterior teeth are more affected with hypoplasias than the posterior teeth although maxillary and mandibular differences are noted. The incisors express the greatest frequency of enamel hypoplasias, closely followed by the canines. In contrast to previous studies, the mandibular canine does not demonstrate a marked difference in the expression of LEH when compared with the maxillary canine. Comparisons with the common chimpanzee are made and it appears that the bonobo is more developmentally stressed. Etiological factors such as locality and seasonal stress are examined. This macroscopic inventory of EH provides the necessary insight into the prevalence of this defect within the bonobo and serves as a foundation for the current micro-incremental analysis of EH within this endangered species. Research funded by Natural Sciences and Engineering Research Council of Canada (OGP0171168).

The analysis of potential sources of bias in archaeological skeletal samples has received an increasing amount of attention over the last several decades. In addition to the continuing discussions of differential preservation, curation biases, and problems with age and sex estimation, new questions have recently arisen regarding the very nature of skeletal samples as reflections of the populations from which they are derived. Some of the most interesting of these discussions have been instigated by the now famous 'Osteological Paradox' article (Wood et al. 1992). Although this article raises fascinating questions about our ability to reconstruct populations from the remains of their dead, one large potential confounder was apparently overlooked: the effects of temporally specific environmental stressors on a population. Because most cemeteries are aggregate samples, with an accumulation of several generations which are indistinguishable from each other, such effects are usually not measurable. In this study, we take advantage of a unique skeletal collection to begin to address the question of how much lesion frequency can be attributed to secular trends and unique environmental circumstances. In this study, a sample of 64 individuals with relatively complete anterior dentitions from the site of Herculaneum was assessed for enamel hypoplastic defects. The individuals from Herculaneum were all killed simultaneously, on August 24th, 79 A.D. in the documented eruption of Mt. Vesuvius. This unique situation allowed us to determine the approximate year in which each hypoplastic defect was formed, and draw conclusions based on our estimates of the age at death of each individual. The data indicate that there is indeed a secular trend apparent, with younger individuals displaying a much lower frequency of hypoplasias than older ones. Because this is precisely the reverse of the effect usually observed in cemeteries, where individuals with multiple hypoplasias have a lower age at death on average, the results are striking. The implications for the future study of more conventional cemetery samples is clear. A new potentially pervasive source of bias has been identified, and the impact of secular trends and singular historical environmental circumstances must now be more fully addressed in the study of archaeological skeletons.

Previous studies have assessed the prevalence and expression of enamel hypoplasia in samples of gibbons but have not addressed the timing of hypoplastic defects. By analyzing ages at defect formation and the intervals between them, it is possible to gain insight into potential relationships between aspects of life history and physiological stress. This study focuses on estimating the age at which hypoplastic defects form, and the time intervals between them, in a sample of wild-shot specimens of Hylobates lar carpenteri housed at the Museum of Comparative Zoology (MCZ) at Harvard University. Ages at defect formation were determined for defects on 78 lower canines of the MCZ sample using measurements from the CEJ to each defect and information from growth increments in histological sections of canines from two Hylobates lar specimens from the New York University skeletal collections. An estimated age at completion of canine crown formation was determined by combining information from the two specimens. Measurements from the CEJ to each defect were multiplied by the average rate of lateral enamel formation and subtracted from the estimated age at completion of the canine. A minimum, maximum, and mean age of formation were determined for each defect in each specimen. Inter-LEH intervals were determined on a sub-set of the sample restricted to individuals who had two or more matching adjacent defects on a canine antimeric pair. Intervals were calculated by multiplying the distance between defects in mm by the average rate of lateral enamel formation. Based on this analysis, most hypoplasias appear to form at 1.8, 2.3, and 2.5 years of age, with a mode at 2.3 years. The median interval between defects is 0.41 years, just over five 28-day months. These results will be discussed in relation to post-weaning stress and in the context of defect intervals reported in studies of LEH in other non-human primates. Research supported by NSF grants SBR 9615006 and 9700822.

Living on Ambergris Caye, off of the northeastern coast of Belize, the Postclassic Maya inhabitants of Marco Gonzalez and San Pedro hosted centers of maritime trade in Central America. Both sites had strong cultural ties to the inland ceremonial center of Lamanai, yet little is known of how coastal living may have affected the health of their occupants. This paper uses evidence of linear enamel hypoplastic (LEH) defects to evaluate whether juvenile health at these coastal sites was experienced differentially compared to other Maya centers located on the mainland. An examination of 81 individuals and 1236 teeth from Marco Gonzalez and San Pedro indicated that juvenile health at these sites was relatively good by ancient Maya standards. Eighty-three per cent of individuals at these sites manifested LEH defects of the permanent dentition, a comparatively low ancient Maya value. The fact that these coastal sites share a lack of sex and age-at-death differences, as well as a similar age of peak LEH formation with mainland sites helps to narrow down the key factors influencing the appearance of better juvenile health along the coast. Evidence regarding the ethnohistory, archaeology, palaeopathology, stature, and diet of these skeletal samples support the LEH data discussed here. As suggested by the LEH data presented, and despite sharing cultural norms with their mainland trading-partners, something unique to the coastal environment benefited childhood health on the . Cayes. Possible factors (e.g. marine diet) influencing juvenile health along the coast will be discussed in the hopes that regional variation and adaptation to coastal environments will be better understood for Maya groups just prior to Spanish contact. Supported in part by SSHRC fellowship #752-2000-1192.

The dental remains of ten adult chimpanzees from Gombe National Park, Tanzania, were examined for enamel attrition, caries, abscesses, periodontal disease, and tooth loss. Age was the underlying factor in the development of dental pathology, in that enamel wear was present to some extent in all ten but was uniformly severe only in the three for whom estimated age at death was 39-43 years. In turn, enamel wear appears to have been the direct cause of abscess development, periodontal disease, and tooth loss. Periodontal disease was commonly expressed as alveolar resorption, particularly around the premolars and molars. This involvement was variable in all except the two youngest. Some interesting wear patterns were evident in the form of deep grooves in the upper incisors and dramatic notching of the lower canines. These patterns, and enamel attrition in general, were attributed to normal mastication and to various stripping activities. Only one carious lesion was observed, in a male with an estimated age of 26 years. An accurate assessment of the actual prevalence of caries was obscured by enamel wear and tooth loss in the older individuals.

Recent studies of teeth from prehistoric children have reported a localized, roughly circular patch of deficient enamel on the labial aspect of the primary canine, which reaches its highest prevalence in the Upper Paleolithic of Europe. This study reports social and biological correlates of 33 affected kindergarten-aged children from Vancouver, Canada (2.4% of 1,350 examined). Affected children can be characterized as coming from low-income families often of East Asian or Chinese origin in which there is a degree of milk avoidance and reduced breastfeeding. The defect appears to be due to minor physical trauma to the face approximately 6 months after birth occasioned by normal motor development, involving handling and mouthing objects, which damages the developing tooth crown through deficient cortical bone over the canine crypt. Reduced cortical bone in the face of the infant is attributed to nutritional factors, involving calcium deficiency, of the mother and/or developing infant.

Genetics determined the arrest of ameloblast activity which resulted in thin tooth enamels among Neanderthals. The degree of prism decussation and the length of prisms are the factors involved in enamel density. Higher degrees of prism decussations connote thin enamels while long prisms indicate thicker enamels. These facts support the theory that thin enamels are characterized by rapid tooth formation prevalent among Neanderthals.

Examinations of the inter-tooth distribution of enamel hypoplasia in humans have provided consistent evidence regarding which teeth are most affected. Goodman and Armelagos (1985), Duray (1992), Mack and Coppa (1992), and Al-Abbasi (1997), among others, found the highest frequency of defects in the maxillary central incisors, followed by the mandibular canines. Following this pattern, recent analyses of linear enamel hypoplasia (LEH) in non-human primates have often focused on the maxillary incisors and mandibular canines (e.g., Eckhardt 1992). The present research examines the suitability of this restricted focus for studies of LEH in non-human primates. Data were collected from the full dentitions of 3,375 wild-caught specimens derived from 117 taxa. LEH frequencies are calculated for each tooth, within each species. To determine inter-tooth frequency differences between taxa, average frequencies are calculated for each tooth in larger taxonomic groups. While these analyses indicate that the tooth classes most often affected by LEH are distinct across nonhuman primate taxa, in contradistinction to humans, canines and premolars have the highest frequencies of LEH for the order. Of equal importance, at all taxonomic levels, mandibular teeth have significantly higher frequencies of LEH than maxillary dentition (p

Human biological studies of contact between European and Indigenous populations have focused upon a basic contrast between pre- and post-contact health. This study examines how health transitions are reflected in the pattern of linear enamel hypoplasia (LEH) incidence. These defects of the enamel are commonly used as non-specific indicators of stress in skeletal populations but there have been few well-documented historic sequences. The series of dental casts of Aboriginal people resident at Yuendumu (n = 377), a Government Settlement in Central Australia, were studied in order to see whether changes in LEH incidence are consistent with historical changes in the developmental environments experienced by these people. Members of the University of Adelaide Dental School made the Yuendumu dental casts between 1950 and 1970. The casts are of people born between the 1890s and 1959, and therefore cover the period of establishment of the settlement in 1946. The prevalence of LEH increases markedly through this time from 37.5% of the oldest cohort (growth completed before mission establishment) to more than 89.6% of the cohort born between 1955-1960. The age pattern of defects also changes, with an earlier mode of onset in later cohorts. Possible intervening factors such as severe attrition are taken into account. Nevertheless, the overall pattern demonstrates clearly the increasing impact of morbidity among the Yuendumu population despite increasing government attempts to improve the health of Indigenous inhabitants within the 'total institution' and highlights the value of LEH as a marker of morbidity.

The prevalence of enamel hypoplasia in the deciduous teeth of great apes has the potential to reveal episodes of physiological stress in early stages of ontogenetic development. However, little is known about enamel defects of deciduous teeth in great apes. Unresolved questions addressed in this study are: Do hypoplastic enamel defects occur with equal frequency in different groups of great apes? Are enamel hypoplasias more prevalent in the deciduous teeth of male or female apes? During what phase of dental development do enamel defects tend to form? And, what part of the dental crown is most commonly affected? To answer these questions, infant and juvenile skulls of two sympatric genera of great apes (Gorilla and Pan) were examined for dental enamel hypoplasias. Specimens from the Powell-Cotton Museum (Quex Park, UK; n = 107) are reported here, and compared with prior findings based on my examination of juvenile apes at the Cleveland Museum of Natural History (Hamman-Todd Collection; n = 100) and Smithsonian Institution (National Museum of Natural History; n = 36). All deciduous teeth were examined by the author with a x10 hand lens, in oblique incandescent light. Defects were classified using Federation Dentaire International (FDI)/Defects of Dental Enamel (DDE) standards; defect size and location on the tooth crown were measured and marked on dental outline charts. Enamel defects of ape deciduous teeth are most common on the labial surface of canine teeth. While deciduous incisor and molar teeth consistently exhibit similar defects with prevalences of ~10%, canines average between 70-75%. Position of enamel defects on the canine crown was analyzed by dividing it into three zones (apical, middle, and cervical) and calculating defect prevalence by zone. Among gorillas, enamel hypoplasia prevalence increases progressively from the apical zone (low) to the middle zone to the cervical zone (highest), in both maxillary and mandibular canine teeth. Results from all three study collections reveal that among the great apes, gorillas (87-92%) and orangutans (91%) have a significantly higher prevalence of canine enamel defects than chimpanzees (22-48%). Sex differences in canine enamel hypoplasia are small and not statistically significant in any great ape. Factors influencing intergroup variation in prevalence of enamel defects and their distribution on the canine crown, including physiological stress and interspecific dento-gnathic morphological variation, are evaluated. Am J Phys Anthropol 116: 199-208, 2001. KEY WORDS enamel defects; deciduous denition; growth disruption; African apes; chimpanzee; gorilla

The dental remains of 88 individuals from Old Kingdom, First Intermediate, and Greco-Roman periods at the ancient Egyptian site of Mendes (Tell er-Rubca) 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].sup.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. KEY WORDS dental pathology; systemic stress; malnutrition; enamel hypoplasia

This paper presents an assessment of enamel defects (hypoplasias) in the permanent anterior teeth of three Tupi-Monde-speaking groups from the Brazilian Amazonia: the Gaviao, Surui, and Zoro. These are native societies that experienced the onset of permanent contact with Brazilian national society in different periods of the 20th century. Tupi-Monde dentition is highly hypoplastic, which is possibly related to exposure to adverse health and nutritional conditions. Data for the Gaviao, Surui, and Zoro are in agreement with results from other populations that show that certain teeth, the maxillary central incisors and the mandibular canines in particular, tend to be more hypoplastic. Although all types of teeth show hypoplasia concentrations at some enamel zones, there is substantial intertooth variation in the age at which peaks occur. It is argued that hypoplasia concentrations at certain ages are unlikely to be related to postweaning stresses for the Tupi-Monde. Statistically significant associations between presence of enamel defects and deficits in physical growth (height-for-age) were detected in children 7-11 years of age. Diachronic assessment of enamel defects, which rested upon the potential of enamel as 'memory' of past periods of systemic physiological perturbation, allowed us to unravel aspects related to the dynamics of Tupi-Monde life during the 20th century. Frequencies of enamel zones with defects peaked during the contact years of each of the Tupi-Monde groups, attesting to the extreme social and biological hardships that characterized the contact experiences of these native societies with Brazilian national society. KEY WORDS dental defects; hypoplasia; Indians of Brazil; Amazonia; epidemics