Developmental patterns of human dental morphological traits

Saunders, Shelley R.; Mayhall, John T.

doi:10.1016/0003-9969(82)90175-3

Cited by 59 publications

(51 citation statements)

References 8 publications

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“…Saunders and Mayhall (1982b) also reported a slightly higher frequency of the entoconulid on M1 than dm2 in a Caucasian sample, but again very few individuals displayed the trait. In the present study, we have found a higher frequency of occurrence of the entoconulid on dm2 than M1, although its degree of expression increased distally.…”

Section: Discussionmentioning

confidence: 83%

Expression of the entoconulid (sixth cusp) on mandibular molar teeth of an Australian aboriginal population

Townsend

Yamada

Smith

1990

American J Phys Anthropol

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The expression and genetic basis of the entoconulid (sixth cusp) on mandibular molars were examined in a geographically isolated group of aboriginals from Yuendumu in the Northern Territory of Australia. Four grades of trait expression, ranging from trace to small, medium, and large cusps, were defined on dental casts of 399 subjects. Frequencies of occurrence were among the highest reported in human populations. Approximately 80% of dm2s showed the trait, whereas frequencies in the permanent dentition ranged from around 50% on M2 to 70% on M1 and 80% on M3. The degree of expression increased distally along the molar series, with only 3% of dm2s showing large cusps compared with 25% of M3s. Fluctuating asymmetry was highest for M2 and lowest for dm2. No strong evidence for sexual dimorphism in occurrence or degree of expression was found. Based on a quasi-continuous threshold model, a genetic contribution to entoconulid variability was observed that was strongest for M1. Significant associations were noted between entoconulid expression on mandibular molars and metaconule expression on maxillary molars, indicating that similar developmental mechanisms may influence these traits. The entoconulid and the metaconule both provide additional bulk on the distal occlusal surface of molar teeth, an area subjected to early wear during mastication in aboriginals.

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Section: Discussionmentioning

confidence: 83%

Expression of the entoconulid (sixth cusp) on mandibular molar teeth of an Australian aboriginal population

Townsend

Yamada

Smith

1990

American J Phys Anthropol

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“…Many studies (Alvesalo et al, 1975;Rusmah, 1992;Saunders and Mayhall, 1982;Thomas et al, 1986) failed to show any sex dimorphism in the occurrence of the trait, although some investigators (Kaul and Prakash, 1981;Kieser and Preston, 1981) observed a sex-linked pattern. Therefore, the relationship of sex to the Carabelli trait was not investigated in this study.…”

Section: Discussionmentioning

confidence: 93%

The prevalence of the Carabelli cusp in selected Saudi population

Shethri

2011

King Saud University Journal of Dental Sciences

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The Carabelli cusp is a tubercle or cuspule, or a groove often seen on the palatal surface of the mesiopalatal cusp of maxillary permanent molars and maxillary second deciduous molars. The purpose of this study was to determine the prevalence, degree of expression of the Carabelli structure, and caries prevalence in the Carabelli structure in the permanent first and second maxillary molars in selected Saudi population. Two hundred and seventy six Saudi patients attending the college of dentistry clinics at King Saud University in Riyadh city were selected for examination. The patients' age ranged from 11 to 55 years old. Patients with severely carious, restored or missing upper first or second maxillary molars on any side were excluded. Both the first and the second upper molars were carefully examined for the occurrence of the Carabelli structure and the presence of caries. The prevalence of the Carabelli structure was 57.6% with a bilateralism of 91.2% in the first maxillary molars and 86.4% in the second molars. The Carabelli structure was found to be 29.7% as a groove expression, and 35.5% as a cusp expression. It was concluded that more than half of the Saudi population have a degree of expression of the Carabelli structure and the Carabelli trait is associated with increased caries incidence. Clinical relevance: Prominent pits and grooves can be foci for plaque retention and caries development, a large tubercle can pose some problems with orthodontic bands.

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“…Hlusko and Mahaney (2003) found that cusp-like structures which derived from the lingual cingula of maxillary molars in baboons, similar to features referred to as Carabelli trait in humans, were significantly heritable. However, several studies mentioned that Carabelli trait may be present on the deciduous second molar but not on the permanent first molar of the same individual (Townsend and Brown, 1981;Saunders and Mayhall, 1982;Smith et al, 1987;Pinkerton et al, 1999). Interestingly, the reverse relationship is very rare.…”

Section: Discussionmentioning

confidence: 94%

Associations between Carabelli trait and cusp areas in human permanent maxillary first molars

Kondo

Townsend

2005

American J Phys Anthropol

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Few dental anthropological studies have investigated the associations between tooth crown size and crown traits in humans using quantitative methods. We tested several hypotheses about overall crown size, individual cusp areas, and expression of Carabelli cusps in human permanent first molars by obtaining data from standardized occlusal photographs of 308 Australians of European descent (171 males and 137 females). Specifically, we aimed to calculate the areas of the four main molar cusps, and also Carabelli cusp, and to compare the relative variability of cusp areas in relation to timing of development. We also aimed to compare cusp areas between males and females and to describe how Carabelli cusp interacted with other molar cusps. Measurements included maximum crown diameters (mesiodistal and buccolingual crown diameters), the areas of the four main cusps, and the area of Carabelli cusp. The pattern of relative variability in absolute areas of molar cusps corresponded with their order of formation, the first-forming paracone displaying the least variation, and the last-forming Carabelli cusp showing the greatest. Overall crown size and areas of individual cusps all showed sexual dimorphism, with values in males exceeding those in females. Sexual dimorphism was smallest for paracone area and greatest for Carabelli cusp area. Overall crown size and cusp areas were larger in individuals displaying a Carabelli cusp, especially the hypocone area. Although the combined area of the protocone and a Carabelli cusp was greater in cuspal forms than noncuspal forms, protocone area alone was significantly smaller in the former. Our findings lead us to propose that, in individuals with the genotype for Carabelli trait expression, larger molar crowns are more likely to display Carabelli cusps, whereas molars with smaller crowns are more likely to display reduced forms of expression of the trait. We suggest that the pattern of folding of the internal enamel epithelium in developing molar crowns, particularly in the protocone region, can be modified by a developing Carabelli cusp.

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Developmental patterns of human dental morphological traits

Cited by 59 publications

References 8 publications

Expression of the entoconulid (sixth cusp) on mandibular molar teeth of an Australian aboriginal population

Expression of the entoconulid (sixth cusp) on mandibular molar teeth of an Australian aboriginal population

The prevalence of the Carabelli cusp in selected Saudi population

Associations between Carabelli trait and cusp areas in human permanent maxillary first molars

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