Technical note: An in vitro study of dental microwear formation using the BITE Master II chewing machine

Abstract

Dental microwear has been used for decades to reconstruct the diets of fossil hominins and bioarchaeological populations. The basic theory has been that hard-brittle foods (e.g., nuts, bone) require crushing and leave pits as they are pressed between opposing cheek-tooth surfaces, whereas soft-tough foods (e.g., grass blades, meat) require shearing and leave scratches as they are dragged along opposing surfaces that slide past one another. However, recent studies have called into question the efficacy of microwear as an indicator of diet. One issue has been the limited number of in vitro studies providing empirical evidence for associations between microwear pattern and chewing behavior. We here describe a new study using a chewing simulator, the BITE Master II, to examine the effects of angle of approach between opposing teeth and food consistency on microwear surface texture. Results indicate that opposing teeth that approach one another: 1) perpendicular to the occlusal plane (crushing) result in pits; 2) parallel to the occlusal plane (shearing) result in striations in the direction of movement; and 3) oblique to the occlusal plane (45°) result in both striations and pits. Results further suggest that different food types and abrasive loads affect the propensity to accumulate microwear features independent of feature shapes.

The role of food stiffness in dental microwear feature formation

“…Initial contact areas and local stresses likely differed among experiments, even on the same food items over different loading runs. These considerations, plus the variability of enamel microstructure within and between individuals and species, as well variation in angle of approach between opposing teeth (Hua, Brandt, Meullenet, Zhou, & Ungar, 2015), caution against seeking a singular food-based predictor variable for explaining dental microwear.…”

Mechanical modelling of tooth wear

“…Exposing rabbits and guinea pigs (Cavia porcellus) to diets designed to reflect different proportions of internal and external abrasives (sand), and measuring the resulting effects manually and by computed tomography, differences in wear and in the responding tooth growth could be demonstrated [11,12]. Most recently, the effects of external grit on the microwear signature were demonstrated in live sheep [13] and angles of approach in chewing were shown to affect microwear [14].…”

Seeds, browse, and tooth wear: a sheep perspective

“…2013), the root causes for the formation of microwear patterns remain to be characterized in a controlled setting (Hua et al. 2015; Xia et al. 2015).…”