Tertiary Dentine Frequencies in Extant Great Apes and Fossil Hominins

Abstract

Tertiary dentine forms when an odontoblast is directly affected by stimuli, commonly through occlusal wear and caries. In this study the presence of tertiary dentine was recorded in three South African fossil hominin species (Australopithecus africanus, Homo naledi and Paranthropus robustus), and two extant great ape species (Gorilla gorilla gorilla and Pan troglodytes). Frequencies of tertiary dentine were calculated for each species based on macroscopic observations of teeth with dentine exposed through occlusal wear. Overall, the three hominin species have similar tertiary dentine frequencies ranging from 12% to 16.13%. In contrast, over 90% of permanent gorilla teeth with dentine visible show tertiary dentine. Chimpanzees fall between these extremes, with 47.21% of permanent teeth affected. Deciduous teeth follow the same pattern. Species variances are not related to differences in occlusal wear. Instead, some species appear predisposed to produce tertiary dentine earlier/faster, or more often, than other species. Therefore, tertiary dentine formation has the potential to provide useful information on fossil specimens. For example, the uniformly low frequency of tertiary dentine formation in hominins may relate to diet, or be due to thick enamel having a similar role in preventing loss of function of teeth, i.e., extending the life of a tooth. In contrast, tertiary dentine is clearly an important mechanism for normal dental function in gorillas, and may have evolved to help maintain shearing function.

Dental caries in human evolution: frequency of carious lesions in South African fossil hominins

“…That said, all carious lesions ultimately share an etiology that is based on the presence of certain cariogenic bacteria and fermentable carbohydrates (Clarkson et al, 1987). Clearly, therefore, given the results of this and other recent studies (Grine et al, 1990;Trinkaus et al, 2000;Lanfranco & Eggers, 2012;Lacy et al, 2012;Humphrey et al, 2014;Lacy, 2014;Liu et al, 2015;Arnaud et al, 2016;Margvelashvili et al, 2016;Towle, 2019), cariogenic bacteria were prevalent in many, if not all, hominin species.…”

“…Micro-CT scans can differentiate between normal enamel and dentine, and areas affected by caries, due to the lower density of areas affected with this pathology (Swain & Xue, 2009;Neves et al, 2010;Boca et al, 2017). Tertiary dentine formation can also be associated with carious lesions, and can be observed on Micro-CT scans (Towle, 2019;. Using such techniques can clearly make visible the extent of a lesion, even if the cavity on the surface is ambiguous (Rossi et al, 2004;McErlain et al, 2004)…”

Technical note: Micro‐computed tomography calibration using dental tissue for bone mineral research

“…In our current study, all specimens were positioned in the center of the chamber and with the same vertical orientation. New dentine formation gradually occurs throughout an individual's life (as secondary dentine) or in response to factors such as caries or extensive tooth wear (as tertiary dentine (Dean, 2017;Ricucci et al, 2014;Rutherford et al, 1995;Towle, 2019)). Enamel properties also vary during an individual's lifetime (e.g., Park et al, 2008).…”

Dentin regeneration based on tooth tissue engineering: A review

“…In contrast, the reparative dentine process makes newly differentiated odontoblast-like cells after the death of the post odontoblasts cell in response to intense lesions (Figure 2). 20,[22][23][24]…”