Tooth Size Data Research Articles

Deciduous molar sizes and sexual dimorphism: South Indian study

Odontometrics is the biometric science that studies size of tooth. This tooth size data can be used to compare prehistoric and modern populations; to know the heritabilities and to study the development of dental occlusion. Thus the aim of the present study was to obtain crown dimensions of primary molars in a sample of South Indian children. 100 children between the age groups of 4 to 9 years was randomly selected. Molars presenting anomalies of the crowns, caries or restorations were excluded. Measurements were made on dental plaster models, using digital Vernier calipers. The tooth in the right and left quadrant (antimeric teeth) did not show any statistically significance. Males show larger mean measurement than females. The maximum sexual dimorphism was observed with respect to the buccolingual dimension. Primary first molars had less variability than second molars in the measurements studied. The measurement with less variability was mesiodistal dimension, followed by buccolingual dimension. This is an attempt to obtain average dimensions of primary molars in South Indian children thus the data can be utilized for fabrication of preformed crowns and bands and also to study the patterns of occlusal development. The male children had significantly larger primary molars when compared to female children. The primary first molars exhibited relatively less variability when compared to the second molars.

Variation of the intermaxillary tooth-size relationship in normal occlusion

The purpose of this study was to explore the intermaxillary tooth-size relationship that is attributed to normal occlusion using multivariate cluster analysis, while simultaneously incorporating the full dentition as a data set. From the central incisor to the second molar, the tooth sizes of 307 subjects (188 males and 119 females; mean age ± standard deviation, 19.9 ± 3.3 years) with normal occlusion were investigated. Tooth-size data were analysed separately for the maxilla and the mandible. When clustering, the partitioning around medoids (PAM) algorithm was performed with the transformed data based on principal component analysis (PCA). After the subjects were classified into four groups, the cluster memberships were cross-classified, and the distribution pattern and intermaxillary tooth-size relationships were explored. Bolton tooth ratio showed a relatively wide range, and this was indicative of the variability in tooth size in subjects with a normal occlusion. However, the patterns of the intermaxillary tooth-size relationship were similar for males and females, and this result was concordant with the findings of the classic Bolton analysis. Using the multivariate approach to analyse the tooth-size data set of an individual patient and then comparing the results with the normal occlusion cluster has possible clinical applications in determining the amount and location of tooth-size control in orthodontics.

Tooth size in individuals with congenitally missing teeth: a study of Japanese males

There is evidence of a relationship between tooth size and tooth agenesis in human populations, with a tendency for reduced tooth size in individuals with missing teeth. The aim of this study was to analyze the size of remaining teeth (mesiodistal crown diameters) and their variability in individuals with varying degrees of severity of congenitally missing teeth. Tooth crown diameters were recorded from 100 dental plaster casts of Japanese males. Subjects were divided into three agenesis groups: group A had one missing tooth per individual, group B had two missing teeth per individual, and group C had three or more missing teeth per individual. For comparison, tooth size data were used from a previously studied sample of Japanese males who did not have any congenitally missing teeth. Group A displayed the largest mesiodistal crown size dimensions for all maxillary and mandibular teeth, followed by group B, and then group C. In comparison with the reference data, when only one or two teeth were missing, the remaining teeth tended to be larger, but when there were three or more missing teeth, the remaining teeth tended to be significantly smaller throughout the dentition. In terms of tooth size variability, dental dimensions in the agenesis groups were generally more variable compared with those in the reference sample. This tendency was most pronounced in the group with the greatest number of missing teeth. Although there was a tendency for the size of the remaining teeth to be more reduced as the number of missing teeth increased, tooth size in individuals with only one or two teeth missing was generally larger than in a control group with all 32 permanent teeth, suggesting that the relationship between tooth size and dental agenesis may be more complicated than previously thought, perhaps due to local compensatory interactions affecting the size of teeth.

Dental crown size and sex hormone concentrations: Another look at the development of sexual dimorphism

Previous researchers hypothesized that tooth types forming during early childhood should be less sexually dimorphic than those forming during later childhood, if sex hormone concentration differences between males and females increase progressively throughout childhood and can affect tooth size. Descriptive tooth size data have recently been cited in support of this hypothesis, particularly with respect to differences in sexual dimorphism among the tooth types of tooth classes. The present study tests this hypothesis for the mesiodistal dimension of human permanent teeth using published data for incisor, premolar, and molar tooth classes from seven diverse populations. The sample size for each tooth type per population was at least 50. This study also tests a modification of this hypothesis which takes into account the postnatal testosterone surge in males and the low levels of sex hormones in both sexes prior to puberty. Predictions are developed for both the original and modified hypotheses. The "D" statistic, the total area of nonoverlap between the phenotypic distributions of males and females, is used to quantify sexual dimorphism. Comparison of D values for different tooth types within tooth classes across these seven populations does not strongly support either hypothesis. These results suggest that gross changes in sex hormone concentrations during development are not related to population-wide patterns of sexual dimorphism among the tooth types of human permanent tooth classes, as recent studies indicate. This finding is consistent with other studies which suggest that sex hormones have only a minor role in generating crown size sexual dimorphism.

Chorion Type, Birthweight Discordance and Tooth-Size Variability in Australian Monozygotic Twins

AbstractChorion type is an important variable that can affect the prenatal environment of monozygotic (MZ) twin pairs, leading to differences in growth and development. In particular, vascular anastomoses between monochorionic (MC) MZ twin pairs can lead to an imbalance in nutrition between co-twins. One objective of this study was to determine whether maternal reports, hospital records or birthweight discordances found in MZ co-twins provide reliable indications of monochorionicity. The other objective was to test the hypotheses that in MZ twin pairs of known chorion type, MC twin pairs would show greater birthweight differences and greater within-pair variability in permanent tooth size than dichorionic (DC) twin pairs, reflecting greater differences in intrauterine environment between MC MZ pairs. Birthweights and tooth size data were recorded for 170 pairs of MZ Australian twins enrolled in an ongoing study of dentofacial growth and development. Chorion type based on maternal reports was compared with that based on hospital records for a subsample of 68 pairs of these MZ twins. Maternal reports were found to be unreliable for determining chorion type and hospital records often did not provide enough information to be certain about chorionicity. For 27 twin pairs with confirmed chorion type, associations were tested between birthweight discordances in MZ twin pairs and chorion type, and also between intrapair variances for tooth size and chorion type. A significant association was noted between birthweight discordance and chorion type (p<.05), with greater discordances occurring more often in MC twin pairs. Although significant heterogeneity of intrapair variances for tooth size was found in only 5 of 48 comparisons, intrapair variances for crown dimensions were greater significantly more often in MC pairs than DC pairs (p<.05). Our findings indicated that neither maternal reports nor often hospital records can be relied upon for information on chorion type. However, when analyses were performed on data for MZ twin pairs of known chorion type, we found evidence of a significant association between intrapair birthweight differences and chorion type and also between intrapair variances of dental crown measurements and chorion type. Consistent with our hypotheses, large birthweight discordances were found to occur more often in MC twin pairs than DC twin pairs, and intrapair variances for tooth size in MC twin pairs exceeded those in DC twin pairs more often than expected due to chance.

Chorion Type, Birthweight Discordance and Tooth-Size Variability in Australian Monozygotic Twins

Chorion type is an important variable that can affect the prenatal environment of monozygotic (MZ) twin pairs, leading to differences in growth and development. In particular, vascular anastomoses between monochorionic (MC) MZ twin pairs can lead to an imbalance in nutrition between co-twins. One objective of this study was to determine whether maternal reports, hospital records or birthweight discordances found in MZ co-twins provide reliable indications of monochorionicity. The other objective was to test the hypotheses that in MZ twin pairs of known chorion type, MC twin pairs would show greater birthweight differences and greater within-pair variability in permanent tooth size than dichorionic (DC) twin pairs, reflecting greater differences in intrauterine environment between MC MZ pairs. Birthweights and tooth size data were recorded for 170 pairs of MZ Australian twins enrolled in an ongoing study of dentofacial growth and development. Chorion type based on maternal reports was compared with that based on hospital records for a subsample of 68 pairs of these MZ twins. Maternal reports were found to be unreliable for determining chorion type and hospital records often did not provide enough information to be certain about chorionicity. For 27 twin pairs with confirmed chorion type, associations were tested between birthweight discordances in MZ twin pairs and chorion type, and also between intrapair variances for tooth size and chorion type. A significant association was noted between birthweight discordance and chorion type (p < .05), with greater discordances occurring more often in MC twin pairs. Although significant heterogeneity of intrapair variances for tooth size was found in only 5 of 48 comparisons, intrapair variances for crown dimensions were greater significantly more often in MC pairs than DC pairs (p < .05). Our findings indicated that neither maternal reports nor often hospital records can be relied upon for information on chorion type. However, when analyses were performed on data for MZ twin pairs of known chorion type, we found evidence of a significant association between intrapair birthweight differences and chorion type and also between intrapair variances of dental crown measurements and chorion type. Consistent with our hypotheses, large birthweight discordances were found to occur more often in MC twin pairs than DC twin pairs, and intrapair variances for tooth size in MC twin pairs exceeded those in DC twin pairs more often than expected due to chance.

Crown size variability in the deciduous dentition of South Australian children.

Although many studies of the permanent dentition have been published, there are still relatively few reports relating to variability within the deciduous dentition. The aim of this study was to provide a detailed description of crown size variability in the deciduous dentition of South Australian children. Dental impressions were obtained of 160 children, 3-6 years of age, and stone models constructed. Mesiodistal and buccolingual crown diameters were recorded from the dental models using a computerized data acquisition system. Several aspects of deciduous tooth size were studied, including variation within and between dental arches, sexual dimorphism, and correlations within and between crown diameters. Principal components analysis was used to summarize the inter-correlated tooth size data and to facilitate the biological interpretation of common variability. The magnitude and pattern of mean values for deciduous tooth size were similar in South Australian children to published data for other Caucasian populations. Although mean values for tooth size were generally larger in boys than in girls, sexual dimorphism in deciduous tooth size was low. Correlation analyses indicated low to moderate associations for size between teeth in the same arch, with highest values between the molars. In both sexes there was a tendency for correlations between buccolingual dimensions to exceed those between mesiodistal dimensions. Although distinct morphogenetic fields have not been defined in the deciduous dentition, there appeared to be a gradient of decreasing size variability from anterior to posterior, with the second deciduous molar being particularly stable. The observed pattern of phenotypic variation appeared to be directly related to the relative length of the developmental period that tooth crowns spent in the soft tissue stage prior to calcification. Multivariate analyses confirmed some overall coordination for crown size of deciduous teeth, but also highlighted specific size patterning related to incisor, canine, and molar regions. © 1993 Wiley-Liss, Inc.

Dental reduction in post-pleistocene Nubia.

Tooth size changes among Nubian archaeological populations dating from the Mesolithic through the Christian era, a period of approximately 12,000 years, are analyzed. Standard length and breadth dimensions of all permanent teeth from several cultural horizons are combined to form three large samples: Mesolithic, 10000-70000 B.C.; Agriculturalist, 3300-1100 B.C. (A-group, C-group, Pharaonic); and Intensive Agriculturalist, A.D. 0-1400 (Meroitic, X-Group, Christian). Such information not only fills a void in the knowledge of Nubian skeletal biology, but also provides a much needed African reference point for the comparison of tooth size data among anatomically modern Homo sapiens from various regions of the world. Changes in mean tooth size and associated t-tests reveal strong and significant reduction in dental size between the Mesolithic and Agriculturalist samples, followed by a continued although diminished trend of reduction for only the molar teeth between the two Agriculturalist groups. These patterns are best observed by examining tooth breadths, which are considered as the most reliable indicator of tooth size. Previously published odontometrics of the Nubian Mesolithic are briefly compared to the findings of this diachronic analysis of Nubian dental change.

Heritability of permanent tooth size.

The aim of this investigation was to quantify the relative contributions of genetic and environmental influences to the observed variability of permanent tooth size in a group of Australian Aboriginals. Tooth size data were obtained from dental casts of Aboriginals living at Yuendumu in the Northern Territory of Australia. The custom of polygyny practised by these people enabled the analysis of associations between full-siblings and half-siblings. Phenotypic variability of tooth size was partitioned into four variance components; between sides, between fathers, between mothers and between offspring. From these components, the relative genetic and environmental contributions were quantified and heritability estimates for tooth size derived. Additional estimates of heritability were obtained by regression analysis from a small sample of parent-offspring data. Results of the analyses suggested that about 64% of the total variability of permanent tooth size could be attributed to genetic factors, while a further 6% was due to common environment. Although the findings confirm a relatively strong genetic component, they emphasise the importance of non-genetic influences in the determination of tooth size variability.