A set of hypotheses on tribology of mammalian herbivore teeth

Abstract

Once erupted, mammal cheek teeth molars are continuously worn. Contact of molar surfaces with ingesta and with other teeth contribute to this wear. Microscopic wear features (dental surface texture) change continuously as new wear overprints old texture features. These features have been debated to indicate diet. The general assumption in relating occlusal textures to diet is that they are independent of masticatory movements and forces. If this assumption is not accepted, one needs to propose that occlusal textures comprise signals not only from the 'last supper' but also from masticatory events that represent ecological, species-or taxon-specific adaptations, and that occlusal textures therefore give a rather unspecific, somehow diet-related signal that is functionally inadequately understood. In order to test for mechanical mechanisms of wear, we created a hypothesis matrix that related sampled individuals with six tribological variables. Three variables represent mechanically relevant ingesta properties, and three represent animal-specific characteristics of the masticatory system. Three groups of mammal species (free ranging Cetartiodactyla and Perissodactyla, free ranging primates, and artificially fed rabbits) were investigated in terms of their 3D dental surface textures, which were quantified employing ten ISO 25178 surface texture parameters. We first formulated a set of specific predictions based on theoretical reflections on the effects of diet properties and animal characteristics, and subsequently performed discriminant analysis to test which parameters actually followed these predictions. We found that parameters Vvc, Vmc, Sp, Sq allowed the prediction of both, ingesta properties and properties of the masticatory system, if combined with other parameters. Sha, Sda and S5v had little predictive power in our dataset. Spd seemed rather unrelated to ingesta properties and made this parameter a suitable indicator of masticatory system properties.

Dust affects chewing efficiency and tooth wear in forest dwelling Western chimpanzees (Pan troglodytesverus)

“…Our surface texture findings are in agreement with the description of the dental wear mechanism as proposed by Lucas, Constantino, Wood, and Lawn () as well as with ingesta related hypotheses as proposed by Kaiser et al (). Specifically, the latter suggested that a higher amount of dust particles increase the likelihood of abrasive contacts.…”

“…Larger intrinsic abrasive particles increase the likelihood of large and deep texture valleys. These are detectable using a combination of several specific parameters (see Supporting Information Supplement 6 for exact parameters), including area ( Sda ISO25178 and mea motif ), height ( Sp ISO25178 , Sq ISO25178 , Sz ISO25178 , S5v ISO25178 , metf furrow , and madf furrow ), volume (e.g., mev , Vm ISO25178 , Vmc ISO25178 , Vmp ISO25178 , Vv ISO25178 , and Vvc ISO25178 ), and plateau size ( FLTp ISO12781 , Smr ISO25178 , and Smc ISO25178 ; Calandra et al, ; Kaiser, Clauss, & Schulz‐Kornas, ; Schulz, Calandra, et al, ; Schulz, Piotrowski, et al, ). Smaller intrinsic abrasive particles are associated with smaller and shallower texture valleys.…”

“…Smaller intrinsic abrasive particles are associated with smaller and shallower texture valleys. High homogeneity in occlusal movement pattern is detectable with large values of anisotropy ( Is texture direction , IS2R texture direction , and Str ISO25178 ) and density ( Spd ISO25178 ) parameters (Kaiser et al, ).…”

Ontogenetic Dietary Shifts and Microscopic Tooth Wear in Western Chimpanzees

“…In addition to the higher level of isotropy in adults, indicating less phytoliths in the diet, we found shallower texture hills (smaller Sp, Figure 3C facet 3) than in infants as well as an indication for larger hill areas (larger Sha, Figure 3D facet 3) than in the other age groups. This is in line with the wear theory proposed by Kaiser et al (2015), suggesting that a reduced concentration of abrasives results, among other things, in flatter 3DSTs.…”

“…An increase in the amount of such hard objects in the diet has been shown to correlate with an increase in surface texture complexity , surface texture height and volume, and a decrease in feature area (Calandra et al, 2012;Schulz-Kornas et al, 2019). Kaiser et al (2015) proposed that soft diets, i.e., those with low matrix resistance, allow for a closer contact of the occluding teeth during mastication and therefore result in smooth and less complex wear facets with shallow pits/dales and scratches/valleys. Consequently, if juveniles fed mainly on soft ripe fruits and young leaves, we expect to observe less complex, voluminous and isotropic wear facet surfaces combined with shallower dales or valleys.…”