An analysis of the Carabelli trait in the mixed deciduous and permanent human dentition

Permanent first and deciduous second maxillary molars were examined on dental casts of 240 persons. A high degree of equivalence of Carabelli-trait expression between deciduous and permanent molars was demonstrated using the Wilcoxon matched-pairs signed-rank test and chi-square tests. Kolmogorov-Smirnov two-sample tests confirmed a lack of sex dimorphism of trait incidence and expression in permanent and deciduous molars. It is hypothesized that the high degree of within-individual equivalence suggests a low epigenetic and high genetic influence on Carabelli-trait expression and that the findings support the clonal rather than the field theory of tooth morphogenesis.     

Fitting genetic models to Carabelli trait data in South Australian twins.

This study aimed to clarify genetic and environmental contributions to Carabelli trait variation on permanent first molar teeth in a large sample of South Australian twins. Estimates of polychoric correlations were obtained between pairs of monozygous (MZ) and dizygous (DZ) twins for Carabelli data and various gene-environment models fitted by a weighted least-squares approach. The favored model included additive genetic effects together with both a general environmental component and an environmental effect specific to each side. An estimate of heritability around 90% indicated a very strong genetic contribution to observed variation. The pattern of correlations for MZ and DZ data suggested that further studies involving other types of relatives would be worthwhile for detection of possible non-additive genetic effects of dominance or epistasis.     

Classificatory reliability of the Carabelli trait in man

Classificatory reliability of the Carabelli trait was evaluated using randomly-selected study models and 52 unbiased observers. Benzécri's correspondence analysis showed Dahlberg's classification to be the most confidently applied. Observers showed less confidence in the application of individual class boundaries described by Goose and Lee; the methods of Alvesalo and Shapiro were the least confidently applied. Pair-wise Yates' chi-square tests on differences in left and right counts for each of the above methods indicated a significantly higher degree of antimeric classificatory consistency for the Dahlberg method.     

Prevalence of the Carabelli trait in Saudi Arabian children.

This study was carried out to evaluate the prevalence of trait of Carabelli in Saudi Arabian children. 250 children, aged 7 to 10 years were examined. The criterion of inclusion was caries free maxillary second deciduous and first permanent molars. The prevalence of the trait was 58.7% with almost similar distribution between males and females. The tubercular variety was the commonest type, which was significantly more in males than females. The frequency of the trait was similar to that of Malaysians but less than for other population groups.     

Australian Aboriginal studies

Investigations carried out on 6--14 year-old Aboriginal children resident at Bathurst Island and Groote Eylandt showed that the Groote Eylandt children had a higher prevalence of dental caries at statistically significant levels. This difference in prevalence was attributed to the greater financial affluence at Groote Eylandt.     

The Carabelli trait in the mixed deciduous and permanent dentitions of five South African populations

The Carabelli trait in South African negroids, caucasoids, Coloured (Peninsula and Namaqualand) and Indians, classified according to Alvesalo, Nuutila and Portin (1975; Acta odont. scand. 33, 191-197) showed generally peak frequency of expression for dm2 falling into class 3 and for M1 into class 4, that dm2 displays more negative expression (class 2 and 3) and M1 more positive expression (class 4 and 5) and that overall expression in dm2 is higher than in M1. The Indian group was an exception with peak frequencies in class 2 for dm2 and class 1 (right) and class 2 (left) for M1. There was no sex dimorphism and there was a tendency for concordance of expression between sides but not within sides.     

The cusp of Carabelli in Malaysians.

The maxillary casts of 320 Malaysian children were examined for the occurrence of the Carabelli trait on the maxillary first permanent molars. The total trait frequency was observed to be 52.2 per cent. Statistical analysis showed no sex dimorphism in the occurrence of the trait. Bilateral occurrence with a tendency towards concordance of expression between sides was also observed.     

The influence of crown size dimorphism on sex differences in the Carabelli trait and the canine distal accessory ridge in man

When the two sexes were contrasted, Pima Indian males showed larger crown dimensions and more pronounced expressions of two morphologic variables, the Carabelli trait and the lower canine distal accessory ridge. In addition, a significant positive relationship was found between crown size and degree of expression of the morphologic traits. When regression analysis was utilized to control for male-female tooth size differences, the moderate dimorphism shown by Carabelli trait was reduced by about half. The more dimorphic distal accessory ridge, related primarily to mesio-distal diameter, also showed a lesser sex difference when crown size effects were held constant. While size dimorphism does contribute to morphologic dimorphism, factors unrelated to crown size still contribute the majority of variance present in trait expression both within and between sexes.     

Oral conditions in Australian children of Aboriginal and Caucasian descent

Oral health parameters were examined for 211 schoolchildren (128 Aborigines and 83 Caucasians) representative of the 6–8 and 10–11 year age groups in the Brewarrina and Walgett areas of western New South Wales (fluoride in water ≤ 0.02–0.26 parts/10⁶). Despite similar dietary carbohydrate challenge and tooth eruption patterns, Aboriginal children, most of whom were members of a transitional community within a low socioeconomic stratum, had higher prevalence of caries (DIMFT) and severity rating of carious lesions (SR), poorer oral hygiene (OHI) and more gingivitis (PI) than Caucasian children, in both age groups. Tooth defects were more frequent (2.5 times) and severe in Aborigines than in Caucasians. Outstanding treatment needs were very high in both ethnic groups, but more so in Aborigines.     

Dental caries risk indicators among Australian Aboriginal young adults

Jamieson LM, Roberts‐Thomson KF, Sayers SM. Dental caries risk indicators among Australian Aboriginal young adults. Community Dent Oral Epidemiol 2010; 38: 213–221. © 2009 John Wiley & Sons A/S Abstract – Objectives: To determine dental caries risk indicators among a birth cohort of Australian Aboriginal young adults (n = 442). Methods: Data were from the Aboriginal Birth Cohort study, a prospective longitudinal investigation of Aboriginal individuals born 1987–1990 at an Australian regional hospital. Models representing demographic, socioeconomic, behavioural, dental service utilization and clinical oral health variables were tested using multivariate regression. Results: The percent DT > 0 was 72.9 (95% CI 68.7–77.1), mean DT was 4.19 (95% CI 3.8–4.6), percent DMFT > 0 was 77.4 (95% CI 73.5–81.3) and mean DMFT was 4.84 (95% CI 4.4–5.3). After controlling for other covariates, risk indicators for percent DT > 0 included soft drink consumption every day or a few times a week (PR 1.25, 95% CI 1.08–1.45), not consuming milk every day or a few times a week (PR 1.16, 95% CI 1.04–1.30) and sweet consumption every day or a few times a week (PR 1.18, 95% CI 1.04–1.33). Risk indicators for mean DT included sweet consumption every day or a few times a week (B = 1.14, 95% CI 0.27–2.02), nonownership of a toothbrush (B = 0.91, 95% CI 0.10–1.87) and presence of plaque (B = 2.46, 95% CI 0.96–3.96). Those with 4 + occupants in their house the previous night had 1.2 times the prevalence of having DMFT > 0 than their counterparts with less household occupants (95% CI 1.01–1.49). Percent DMFT > 0 was also associated with consumption of soft drink every day or a few times a week (PR 1.18, 95% CI 1.04–1.34) and consumption of sweets every day or a few times a week (PR 1.23, 95% CI 1.10–1.37). Mean DMFT was higher among those who consumed sweets every day or a few times a week (B = 0.13, 95% CI 0.05–0.22) and who had dental anxiety (B = 0.10, 95% CI 0.01–0.19). Conclusions: In an Australian Aboriginal young adult cohort, risk indicators for dental caries included social determinants such as household size, dietary behaviours such as regular consumption of soft drink and sweets, dental behaviour such as nonownership of a toothbrush and dental anxiety.     

Sex determination of Australian Aboriginal skulls by discriminant function analysis

A bstract — The technique of discriminant function analysis was applied to determine the sex of Australian Aboriginal skulls using data derived from standardized roentgenograms. Even when only a few well-defined landmarks were included, the functions, representing linear combinations of cranial variables, provided good discrimination. This approach proved more reliable in classification than applying previously reported functions derived for other populations.     

Nature and frequency of dental wear facets in an Australian Aboriginal population

The nature and frequency of dental wear facets were studied in a sample of 18-year-old Aborigines, 28 males and 31 females, living at Yuendumu in the Northern Territory of Australia. Facet frequencies were scored indirectly using dental models for all permanent teeth, except third molars, and evidence of non-masticatory tooth grinding in eccentric jaw positions was also recorded. The interplay between attrition and abrasion in an individual over time was assessed by examining facet appearance on serial dental models obtained at approximately yearly intervals from 7 to 25 years of age.
Facetting was found to be a very common feature of the Aboriginal dentitions, with frequencies ranging from around 65% for pre-molars to about 90% for molars. Evidence of extreme mandibular movement was noted in 93% of males and 100% of females. The longitudinal observations indicated that wear facet definition varied over time, apparently due to episodes of tooth grinding superimposed on continually-acting abrasive influences.
These results show that facetting on teeth associated with extreme mandibular positions and, by inference, the related behaviour of tooth grinding or bruxism are very common features in dentitions of Australian Aboriginals living an essentially non-industrial way of life.