R.C. Griffin

Tooth size patterns in patients with hypodontia and supernumerary teeth

AIMS Anomalies of tooth number may not be isolated conditions but may have wider associations in the development of the dentition including tooth size. This study aimed to examine links between hypodontia, supernumerary teeth and crown size, considering the effect on the development of the whole dentition and so increase understanding of the aetiology of these conditions. METHODS AND RESULTS The patients, who were all of European ancestry, were 60 young adults (30 males and 30 females) with hypodontia and 60 age and sex matched controls together with 60 young adults (39 males and 21 females) with supernumerary teeth and 60 age and sex matched controls. Hand measurements of mesiodistal and buccolingual dimensions were made of the teeth on dental study models using Mitutoyo electric callipers. The mean value of two measurements was used and intra-operator and inter-operator reliability determined. Patients with hypodontia had smaller teeth than the control group and this difference was statistically significant (p<0.05) for all teeth except the MD dimensions of 13, 23, 24 and 44. The difference in size was greatest for the BL dimensions in hypodontia patients. Further, the greater the number of missing teeth the smaller the tooth size. The hypodontia patients also showed higher variability in tooth dimensions than the control group. Patients with supernumerary teeth had larger teeth than the controls, with the greatest differences in the MD dimensions. In both hypodontia and supernumerary patients the differences in tooth size were generalised throughout the dentition. CONCLUSIONS In anomalies of tooth number the size of teeth is also involved. In patients with hypodontia and supernumerary teeth the crown size of the whole dentition is affected. These findings are compatible with a multifactorial aetiology of these conditions.

Variability and patterning in permanent tooth size of four human ethnic groups

AIMS Dental dimensions vary between different ethnic groups, providing insights into the factors controlling human dental development. This paper compares permanent mesiodistal crown diameters between four ethnic groups highlighting patterns of tooth size between these groups and considers the findings in relation to genetic and environmental influences. METHODS AND RESULTS Mesiodistal crown dimensions were recorded using standardised manual measurements on dental casts derived from four different human populations: Southern Chinese, North Americans of European ancestry, Modern British of European ancestry and Romano-British. Analyses based on double determinations showed that measurements in all study samples were reliable to an accuracy of 0.1mm. The Southern Chinese sample was found to have the largest teeth overall, whereas the Romano-British sample generally displayed the smallest mesiodistal crown dimensions (p<0.001). However, the Modern British sample had the largest maxillary central incisors, mandibular central and lateral incisors, and mandibular canines, while the North American sample had the largest maxillary first and second molars. Comparisons of coefficients of variation for teeth within each class showed that the later-forming teeth displayed greater variation in mesiodistal size than the earlier-forming teeth. CONCLUSION The different patterns of tooth size observed between the study samples are thought to reflect differences in the relative contributions of genetic, and environmental influences to dental development between the four populations. For example, it is proposed that major environmental insults during the early life of Romano-Britons, including recurrent illnesses, poor nutrition and excessive lead ingestion, contributed to the reduction in size and greater variability of their later-forming teeth. Using a standardised methodology, significant differences in mesiodistal crown diameters have been demonstrated between four human ethnic groups. There were also distinct differences in the patterns of crown size between the groups, with the later-forming teeth in each type generally showing greater size variation.

The aetiology of hypodontia: The prevalence, severity and location of hypodontia within families

AIMS Previous studies have indicated that hypodontia has a significantly higher prevalence in the relatives of affected individuals than in the general population. This study aims to examine further the roles of genetic and environmental factors in the aetiology of hypodontia by investigating the relationship between the severity and distribution of hypodontia between family members, and any discernable effect of maternal health during pregnancy and birth weight. METHODS AND RESULTS 117 first degree relatives of 41 index patients were examined clinically and radiographically to identify the presence, severity and location of hypodontia. Both siblings and parents of index patients had a higher prevalence of hypodontia than the general population. The number and location of missing teeth was not related to the number and location of missing teeth in parents or siblings. The expression of hypodontia within a family was not affected by maternal health during pregnancy. CONCLUSIONS The variation found in the expression of hypodontia within families suggests that its occurrence is not solely determined by genetic factors, but epigenetic and environmental factors probably also are important. This finding is consistent with a multifactorial aetiology for this condition.

Age estimation of archaeological remains using amino acid racemization in dental enamel: a comparison of morphological, biochemical, and known ages-at-death.

The poor accuracy of most current methods for estimating age-at-death in adult human skeletal remains is among the key problems facing palaeodemography. In forensic science, this problem has been solved for unburnt remains by the development of a chemical method for age estimation, using amino acid racemization in collagen extracted from dentine. Previous application of racemization methods to archaeological material has proven problematic. This study presents the application to archaeological human remains of a new age estimation method utilizing amino acid racemization in a potentially closed system-the dental enamel. The amino acid composition and extent of racemization in enamel from two Medieval cemeteries (Newcastle Blackgate and Grantham, England) and from a documented age-at-death sample from a 19th century cemetery (Spitalfriedhof St Johann, Switzerland) were determined. Alterations in the amino acid composition were detected in all populations, indicating that diagenetic change had taken place. However, in the Medieval populations, these changes did not appear to have substantially affected the relationship between racemization and age-at-death, with a strong relationship being retained between aspartic acid racemization and the morphological age estimates. In contrast, there was a poor relationship between racemization and age in the post-medieval documented age-at-death population from Switzerland. This appears to be due to leaching of amino acids post-mortem, indicating that enamel is not functioning as a perfectly closed system. Isolation of amino acids from a fraction of enamel which is less susceptible to leaching may improve the success of amino acid racemization for archaeological age estimation.

Patterns in dental enamel hypoplasia by sex and age at death in two archaeological populations

AIMS Levels of enamel hypoplasia in past populations are frequently used to study health. However, few studies have looked at patterning in the occurrence of different types of hypoplasia. In this pilot study, skeletal remains from an Iron Age tomb at Pella in Jordan were analysed for the presence of linear and pit enamel hypoplasia, to investigate enamel hypoplasia aetiology by comparison of the results obtained for adults and juveniles, and females and males. METHODS AND RESULTS The proportion of individuals with enamel hypoplasia was determined for males and females and for adults and juveniles using the F.D.I. Developmental Defects of Enamel (DDE) Index. Although males and females had a similar percentage of individuals affected, females had a higher prevalence of enamel hypoplasia per tooth than males. Adults had a higher prevalence of enamel hypoplasia than juveniles. In particular, adults had a higher prevalence of linear enamel hypoplasias and pit enamel hypoplasia arrays, but a similar prevalence of single pit enamel hypoplasia when both the permanent and deciduous dentitions were considered. These differences were largely due to different patterns and frequencies of enamel hypoplasia in deciduous teeth compared to permanent teeth. CONCLUSIONS The different patterns of occurrence of the various forms of hypoplasia observed in this study imply that single pits may have a different aetiology to linear enamel hypoplasias and pit arrays. By investigating similar patterns in other archaeological populations, we may develop a better understanding of the specific causes of particular types of enamel hypoplasia, and may be able to more meaningfully interpret enamel hypoplasia data from past populations.

The impact of random natural variability on aspartic acid racemization ratios in enamel from different types of human teeth.

Previous research has indicated that the extent of amino acid racemization in enamel varies systematically between tooth types within the dentition. This phenomenon was suggested to be due to differences in temperature at various locations within the mouth. This paper presents an analysis of aspartic acid racemization in a fraction of the enamel proteins which should be particularly susceptible to deviations in temperature, in order to assess the impact of temperature on variability in racemization values. The acid soluble fraction of the enamel was analysed from 129 human teeth of different tooth types and from both living individuals and archaeological skeletal remains. Samples were collected by acid etching of the enamel to isolate proteins located a small distance below the enamel surface. For each population, the racemization values for different tooth types were compared to identify any possible systematic variation. Where multiple teeth were analysed from the one individual, the age estimates produced for the different teeth were compared to obtain an indication of the overall level of variability in racemization values. No systematic variation in the extent of racemization between different tooth types was observed in any of the populations analysed. There appeared instead to be a high level of random variability in the extent of racemization, with substantial differences observed between age estimates produced from multiple teeth from the one individual. The results of this study suggest that the differences in racemization values observed here are due to random variations and not the temperature at different locations within the mouth.

INEQUALITY AT LATE ROMAN BALDOCK, UK The Impact of Social Factors on Health and Diet

This study explores the impact of social inequality through a study of health and diet involving the analysis of skeletal remains and grave furnishings from the Roman period cemetery of Baldock, UK. Analysis revealed correlations between the presence of different types of grave furnishing with aspects of childhood health, and consistent differences in diet between individuals with different quantities and types of furnishings. These findings suggest that inequality may have had a considerable impact upon both health and diet at Baldock. The further observation of patterns in diet by sex and in grave furnishings by sex and age-at-death suggests that these factors may have played an important role in determining access to resources within the community at Baldock.

A New Approach to Amino Acid Racemization in Enamel: Testing of a Less Destructive Sampling Methodology.

Abstract:  Aspartic acid racemization has been found to be an accurate measure of age at death for recent forensic material. This paper examines the practicality of using acid etching of the tooth surface to extract amino acids from the enamel for racemization analysis. By serial etching of the tooth and contamination of the teeth with bovine serum albumin prior to etching, the ability of etching to remove contamination was assessed. The destructiveness of the method was visualized and quantified using micro‐computed tomography (micro‐CT). By bleaching the teeth and by deeper etching it was possible to obtain more consistent values. While etching had little effect on the enamel at the macroscale, it did have an impact at the microscale. The quantities of enamel removed varied depending upon the tooth morphology, but were not large. Acid etching of enamel thus appears to be a promising new method for extracting proteins for amino acid racemization age estimation noninvasively.