A functional analysis of Carabelli trait in Australian aboriginal dentition

Abstract

Objectives: Carabelli is a nonmetric dental trait variably expressed as a small pit to a prominent cusp in the maxillary molars of modern humans. Investigations on the occurrence and expression rates of this trait have been conducted extensively, tracing its origin to genetic sources. However, there remains a lack of understanding about its potential role in chewing. In this study, we examine molar macrowear with the aim of reconstructing Carabelli trait occlusal dynamics occurring during chewing. Methods: We have examined 96 deciduous and permanent maxillary molars of children and young adults from Yuendumu, an Australian Aboriginal population that was at an early stage of transition from a nomadic and hunter-gatherer way of life to a more settled existence. We apply a well-established method, called Occlusal Fingerprint Analysis, which is a digital approach for analyzing dental macrowear allowing the reconstruction of jaw movements required to produce wear pattern specific to each tooth. Results: Carabelli trait slightly enlarges the surface functional area, especially in those molars where this feature is expressed in its cuspal form and it is closer to the occlusal plane. Moreover, the highly steep contact planes would also indicate that Carabelli wear areas contribute to increasing the shearing abilities of the occluded teeth, which are particularly important when processing fibrous and tough foods. Conclusions: The macrowear analysis suggests that Carabelli trait in the Aboriginal people from Yuendumu slightly enhanced occlusion and probably played some functional role during mastication. Future biomechanical and microwear analyses could provide additional information on the mechanical adaptation of Carabelli trait in modern human dentition.

Tooth wear development in the Australian Aboriginal dentition from Yuendumu: A longitudinal study

“… Wear contacts have been labelled following the numbering system created by Maier & Schneck [ 30 ] and grouped by chewing cycle phases [ 31 , 32 ]: Buccal phase I (areas 1, 1.1, 2, 2.1, 3 and 4; coloured in blue), Lingual phase I (areas 5, 5.1, 6, 6.1, 7 and 8; coloured in green) and Phase II (areas 10, 11, 12 and 13; coloured in red). CA1 upper ( a ) and lower ( b ) arches, age E 8.07 years; CA4 upper ( c ) and lower ( d ) arches, age E 12.44 years; CA9 upper ( e ) and lower ( f ) arches, age E 17.44 years.…”

“…In addition, we generated high-resolution physical replicas of the digital models via stereolithography, since 3D prints can be more helpful when trying to identify qualitative details, such as cusp morphology, fissure patterns and wear areas than a two-dimensional photograph or a 3D model viewed on a screen [ 30 ]. Furthermore, we tested the presence of tooth-to-tooth occlusal contact in the intercuspal position between upper and lower teeth using an 8 μm Shimstock Foil (Coltene ™ ) [ 31 ] that was inserted between 3D prints of upper and lower dental arches [ 32 ].…”

Dental Anomalies: An Identification Marker in Forensics

“…Around 49.7% of the population who showed shovel and Carabelli features belonged to the Chinese population. The fifth cusp (Carabelli cusp) prevalence in the maxillary molars in 41.7% of school children in Saudi Arabia was observed [17]. According to the well-known paleontologist William King Gregory (1922), there was not much variation in tooth crown shape between the various human groups [5].…”

Quantification of dental macrowear using 3D occlusal surface topographic measurements in deciduous and permanent molars of children

“…These descriptions of the occlusal surface aim to further contribute to paleodietary reconstruction as dental macrowear patterns are known to differ between hunter‐gatherers and agrarian populations (Rose & Ungar, 1998 ; B. H. Smith, 1984 ; Watson & Schmidt, 2020 ). Quantitative methods describing wear patterns such as OFA (occlusal fingerprint analysis) (Kullmer et al, 2009 ), are especially suited to study the biomechanics of both deciduous and permanent teeth (Fiorenza et al, 2020 ; Fung et al, 2021 ); however, such studies are more time consuming are require more specialized equipment. The measurements proposed in this study could likely be adapted to describe dental macrowear patterns, by, for example, dividing the occlusal surface into quadrants or measuring multiple intercusp slope angles and calculating ratios between them, however, it is uncertain how useful such an approach would be given the success of existing methods for describing dental macrowear patterns.…”