The role of food stiffness in dental microwear feature formation.

OBJECTIVE: The etiology of dental microwear is incompletely understood, despite copious documentation of wear patterns from wild and captive specimens across numerous vertebrate taxa. Among the contested issues with respect to microwear formation is the question of whether materials softer than enamel (specifically, foods themselves) can produce wear features.
DESIGN: We examine the creation of enamel microwear features in vitro from foods that vary in hardness and toughness on a sample of mammalian lower molars (pig, bear, deer, and primate). These experiments involved applying loads at a constant displacement rate perpendicular to an occlusal enamel surface. Changes in surface microwear textures were assessed after 10 loads.
RESULTS: Our experiments demonstrate that even relatively soft foods free of exogenous abrasives modify surface texture to produce distinctive microwear fabrics. Consequently, these data provide clear evidence that materials softer than enamel are capable of indenting and abrading enamel surfaces. Foods with a relatively high elastic modulus are associated with larger and more extensive microwear features, although the relationship between food stiffness and rate of microwear formation does not appear to be a simple one.
CONCLUSIONS: These observations refute recent arguments that food material is an insignificant agent in the formation and accumulation of enamel microwear. Relative hardness of ingested materials is only one factor in the etiology of microwear formation.