Letters to the editor

Health of infants in an Imperial Roman skeletal sample: Perspective from dental microstructure

This study examines general health in the first year of life of a population of 127 subadults from the Imperial Roman necropolis of Isola Sacra (2nd-3rd century ACE). Health status was determined by analyzing 274 deciduous teeth from these children for Wilson bands (also known as accentuated striae), microscopic defects caused by a disruption to normal enamel development arising from some generalized external stressor. While macroscopic enamel defects, or hypoplasias, have long been used as proxies of general population health, we believe that this is the first population-wide study of microscopic defects in deciduous teeth. We used microstructural markers of enamel to attach very precise chronologies to Wilson band formation that allowed us to calculate maximum prevalence (MAP) and smoothed maximum prevalence (SMAP) distributions to portray what we believe to be a realistic risk profile for a past population of children. There appear to be two periods of high prevalence, the first beginning around age 2 months and continuing through month 5, and the second higher period beginning around month 6 and continuing through month 9. These results are discussed in light of historical records of Roman childhood rearing practices.

Enamel hypoplasia in a Canadian historic sample

Analyses of historical skeletal samples provide useful comparisons of the prevalence of skeletal indicators of stress to documentary information on health, diet, and socioeconomic status. A sample of the permanent dentitions of 253 adults from the St. Thomas' Anglican Church 19th-century skeletal sample in Belleville, Ontario, was examined macroscopically for the prevalence of enamel defects on the six anterior maxillary and mandibular teeth. The maximum frequency of hypoplasias on the left mandibular canine is 36.1%. The prevalence of enamel defects is low to moderate compared to almost all other reported frequencies in historical samples, which is consistent with historical descriptions of this developing community of middle to high socioeconomic status Canadians. Hypoplasias are significantly more frequent in males but there are no significant differences in the mean age at death between individuals with hypoplasia and those without. Calculations of the peak ages of occurrence of hypoplasias fall within the commonly observed 2-4-year range. This is not consistent with separate studies, demographic, isotopic and historical, of the introduction of complementary foods to 19th-century Belleville infants and of the weaning process. These results do not support the view that peak ages of occurrence of hypoplastic defects are associated with the cessation of breast-feeding or the weaning process in general. Am. J. Hum. Biol. 11:513-524, 1999. Copyright 1999 Wiley-Liss, Inc.

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.

Biological mechanisms of early childhood caries

The present paper reviews biological issues in early childhood caries (ECC) in light of the current understanding of the field. Despite the general global decline in dental caries in the past decades, ECC has become a significant problem in many developing countries and some minority communities in western industrialized nations. Like other types of caries, ECC is caused by mutans streptococci that ferment dietary carbohydrates to produce acid attacks on susceptible teeth over a period of time. However, while the general etiology of ECC appears similar to that of other types of caries, the predisposing factors are still unclear. The biology of ECC may be modified by several factors unique to young children, related to the implantation of cariogenic bacteria, immaturity of the host defense systems, as well as behavioral patterns associated with feeding and oral hygiene in early childhood.

Subadult stress, morbidity, and longevity in Latte Period populations on Guam, Mariana Islands

The frequency and age distribution of linear enamel hypoplasia (LEH) in the dentition of 293 individuals from Latte Period sites (AD 800-1521) on Guam, Mariana Islands, are examined in this study. Individuals dying as subadults (before age 16) and as young adults (ages 16-21) have more frequent LEHs than those who survived to middle or late adulthood, documenting a relationship between LEH-causing stress events and reduced life expectancy. The age distributions of cribra orbitalia and skeletal infection in children who died by age 10 exhibit striking similarities to the etiological age patterns of LEH in children, and those with skeletal infection have more frequent hypoplasias than children without infection. The comorbidity of systemic stress and infection in children, and their impact on life expectancy, are interpreted in the biocultural context of high population density in the large coastal villages of the late prehistoric period in the Marianas.

Dental caries prevalence and treatment among Navajo preschool children

OBJECTIVES

The purpose of this study was to assess the dental health of Navajo preschool children, a population about whom little dental information is published.

METHODS

Caries data were collected and analyzed for 2,003 Navajo children aged 3-5 years in the Head Start program, and for a convenience sample of 115 children younger than three years old from the Women, Infants and Children (WIC) program.

RESULTS

Each age group had an extremely high mean dmfs; however, as much as 70 percent of this index comprised treated surfaces. Maxillary anterior caries was observed in the WIC children under two years of age and posterior proximal caries was observed as early as two years of age. The prevalence of maxillary anterior caries reached a maximum of 68 percent in the three-year-old Head Start children, and may be associated with the high level of posterior caries in this population.

CONCLUSIONS

Most children in this population may be considered at risk for developing caries. This Navajo preschool population has perhaps the earliest caries onset, among the highest caries prevalence, and among the highest level of treatment of any reported population.

Prevalence and age at development of enamel hypoplasias in Mexican children

Enamel hypoplasias, deficiencies in enamel thickness resulting from disturbances during the secretory phase of enamel development, are generally believed to result from nonspecific metabolic and nutritional disruptions. However, data are scare on the prevalence and chronological distributions. of hypoplasias in populations experiencing mild to moderate malnutrition. The purpose of this article is to present baseline data on the prevalences and chronological distributions of enamel hypoplasias, by sex and for all deciduous and permanent anterior teeth, in 300 5 to 15-year-old rural Mexican children. Identification of hypoplasias was aided by comparison to a published standard (Federation Dentaire Internationale: Int. Dent. J. 32(2):159-167, 1982). The location of defects, by transverse sixths of tooth crowns, was used to construct distributions of defects by age at development. One or more hypoplasias were detected in 46.7% (95% CI = 40.9-52.5%) of children. Among the unworn and completely erupted teeth, the highest prevalence of defects was found on the permanent maxillary central incisors (44.4% with one or more hypoplasias), followed by the permanent maxillary canine (28.0%) and the remaining permanent teeth (26.2 to 22.2%) Only 6.1% of the completely erupted and unworn deciduous teeth were hypoplastic. The prevalence of enamel defects on the permanent teeth was up to tenfold greater than that found in studies of less marginal populations that used the FDI method. The prevalence of defects in transverse zones suggests a peak frequency of hypoplasias during the second and third years for the permanent teeth, corresponding to the age at weaning in this group. In the deciduous teeth, a smaller peak occurs between 30 and 40 weeks post gestation. The frequency of defects after three years of age is slightly higher in females than males, suggesting a sex difference in access to critical resources.

Deciduous enamel defects in prehistoric Americans from Dickson Mounds: prenatal and postnatal stress

The month of onset, duration, and incidence of dental enamel hypoplasia and hypocalcification was determined in sub-adults from the Dickson Mounds (Illinois) skeletal series (A.D. 950-1300). The onset of enamel defects occurred predominantly during the intrauterine period, suggesting maternal stress. There are marked differences in survivorship and the duration of enamel disruption in those affected prenatally and postnatally. The relationship between these data and studies of adult dentition is examined.

The etiology of enamel hypoplasia: a unifying concept

In a study of children with chronic disorders of calcium and phosphate homeostasis, enamel hypoplasia was found in hereditary vitamin D-dependency rickets and in hypoparathyroidism, conditions characterized by hypocalcemia, and was not found in X-linked hypophosphatemic rickets, a condition in which the plasma calcium concentration is normal. The occurrence of enamel hypoplasia bore no relation to the plasma phosphate concentration. Enamel hypoplasia has also been reported in other pediatric disorders in which hypocalcemia is a major sign (for example, vitamin D deficiency, prematurity, and neonatal tetany). The existence of enamel hypoplasia in a hypoparathyroid or rachitic patient, when correlated with the chronology of enamel mineralization, helps to establish the time of onset of hypocalcemia. The observations led us to the hypothesis that a low serum calcium concentration during enamel formation is a specific determinant of enamel hypoplasia. This hypothesis may be relevant to the etiology of linear enamel hypoplasia, an endemic lesion of primary teeth in children of many Third World countries that predisposes the teeth to dental caries. The hypothesis may therefore be relevant also in explaining the prevalence of caries in the primary teeth of children in many underdeveloped countries.

Health and differential survival in prehistoric populations: prenatal dental defects

Linear hypoplasia of the deciduous teeth is rare in most human populations, but common where nutritional status is poor. Deciduous enamel hypoplasia, hypocalcification, and hypoplasia-related caries are described in Middle and Late Woodland skeletal series from the Lower Illinois Valley. Gross enamel defects that can be referred to pre-natal development are found in 83 of 170 children under six years of age at death. Circular caries secondary to hypoplasia is significantly more common in the Late Woodland series, reflecting the apparent higher cariogenicity of Late Woodland diets. There is a significant association between prenatal dental defects and bony evidence for anemia and infectious disease. Children with enamel defects show relatively higher weaning age mortality than those without. These relationships suggest that at least moderate levels of malnutrition existed in Illinois Woodland populations.

A descriptive and comparative study of the deciduous dentition of prehistoric Ohio Valley Amerindians

The deciduous dentition of 58 individuals from groups of prehistoric Ohio Valley Amerindians (2,000 B.C.-1,600 A.D.) was measured for antero-posterior and bucco-lingual dimensions and scored for morphological characteristics and macroscopic pathology. Only five dimensions of the posterior teeth and the frequency of severe linear enamel hypoplasia showed significant differences in the groups. In all cases focal agriculturalists exhibited smaller teeth and a higher frequency of severe linear enamel hypoplasia. These findings are explained as the result of changing diet and food preparation techniques, and/or sampling bias in the earlier burial cult groups where primarily higher status individuals may be the representatives. Comparison of metric and morphological characteristics of the deciduous dentition in the prehistoric Amerindians and roughly contemporaneous European groups indicates morphological characteristics are the better means of discrimination.

Enamel hypoplasia in relation to caries in Guatemalan children

Guatemalan children with anterior linear enamel hypoplasia (LEH) had a significantly greater caries experience in posterior dentition than their peers who did not have anterior LEH. The findings suggest that the synergistic mechanism of undernutrition and infection, which may underlie the occurrence of anterior LEH, may also predispose clinically normal appearing deciduous molars to an excessive caries attack equal to that observed in the grossly hypoplastic anterior teeth. The nutritional implications merit further investigation.

Dental caries experience in the deciduous dentition of rural Guatemalan children ages 6 months to 7 years

A study of 528 Guatemalan children indicated that caries prevalence in the deciduous dentition was twice as great as but in the permanent dentition was similar to that for US white children. This is a repeated observation for children of some preindustrial societies. Caries experience was significantly greater in boys. Until 4 years of age, caries attack was greater in the anterior segment of the oral cavity; linear enamel hypoplasia was a predisposing factor.