Dental wear proxy correlation in a long-term feeding experiment on sheep ( Ovis aries )

Abstract

Dietary reconstruction in vertebrates often relies on dental wear-based proxies. Although these proxies are widely applied, the contributions of physical and mechanical processes leading to meso- and microwear are still unclear. We tested their correlation using sheep ( Ovis aries , n = 39) fed diets of varying abrasiveness for 17 months as a model. Volumetric crown tissue loss, mesowear change and dental microwear texture analysis (DMTA) were all applied to the same teeth. We hereby correlate: (i) 46 DMTA parameters with each other, for the maxillary molars (M1, M2, M3), and the second mandibular molar (m2); (ii) 10 mesowear variables to each other and to DMTA for M1, M2, M3 and m2; and (iii) volumetric crown tissue loss to mesowear and DMTA for M2. As expected, many DMTA parameters correlated strongly with each other, supporting the application of reduced parameter sets in future studies. Correlation results showed only few DMTA parameters correlated with volumetric tissue change and even less so with mesowear variables, with no correlation between mesowear and volumetric tissue change. These findings caution against interpreting DMTA and mesowear patterns in terms of actual tissue removal until these dental wear processes can be better understood at microscopic and macroscopic levels.

What about the buccal surfaces? Dental microwear texture analysis of buccal and occlusal surfaces refines paleodietary reconstructions

“…Another complicating factor of buccal surface DMTA is the presence of perikymata (Figure 3D), which affect the quantification of complexity and anisotropy and cannot be removed with the MountainsMap software since they are distributed in the entire studied area. In line with Krueger et al (2021) concerning occlusal surfaces, we suggest that more experimental studies on the characterization of buccal surface DMTA will improve our understanding of buccal microwear formation, turnover, and interpretation of DMTA variables for dietary reconstruction. Likewise, the combination of paired surface data would be an advantage for refining the diet reconstruction interpretation when both surfaces are available for same tooth.…”

“…The same sampling bias may apply to buccal surfaces: in traditional SEM methodology, the image acquired at 100× magnification covers a broad patch of enamel (0.56 mm 2 ), whereas we used the same area as occlusal DMTA (242 x 182 μm) in this study. Future investigations of correlations among microwear variables measured on occlusal and buccal surfaces should consider the potential effect of intra‐surface variation by measuring several loci per surface (e.g., Ackermans et al, 2021).…”

“…For example, enamel surfaces dominated by pits of various sizes and striations overlying each other demonstrate high levels of complexity. This is generally attributed to abrasive diets that include the mastication of hard particles (El‐Zaatari, 2010) or erosion from dietary acids (Hara et al, 2016; Ranjitkar et al, 2017; Krueger et al, 2021). In contrast, lower complexity values indicate simpler surfaces, generally thought to be from softer, more processed, or less grit‐laden diets (Scott et al, 2005).…”

“…Dental microwear is generally analyzed on either the buccal or occlusal surfaces, and both surfaces are rarely examined in the same study (García‐González et al, 2015; Hernando et al, 2021; Hernando, Willman, et al, 2020). This may be explained by a difference in imaging technology and associated difficulties of data comparison.…”

Species-specific enamel differences in hardness and abrasion resistance between the permanent incisors of cattle (Bos primigenius taurus) and the ever-growing incisors of nutria (Myocastor coypus)

“…There is a debate whether measures of tooth wear can be considered taxon-free proxies of triggers for wear and hence environmental conditions, in particular in a paleobiological context, or whether the same conditions will lead to different wear patterns in different animal species [ 1 – 4 ] or even in different individuals within a species [ 5 ]. Among the many possible factors by which teeth of different species can vary, enamel hardness appears intuitively relevant for the effect of abrasives on dental wear.…”