True grit: A microwear experiment

Abstract

Recently we noted the effects of experimental diets on microscopic dental wear in the American opossum and concluded that it might prove difficult to distinguish the microwear produced by an insectivorous diet from that produced by some kinds of herbivorous ones. We also noted that wear caused by gritty diets and those containing plant opal, although they might be confused with one another, are easily distinguished from other sorts of dietary wear. Our conclusions have been challenged on the basis that possibly we did not allow sufficient time in the experiments for diagnostic wear patterns to emerge. Additional data reported here show that this is not so. Even in our "control" animals, fed a relatively soft unabrasive diet, enough time elapsed to produce significant dental wear. A new technique is described which for the first time allows the study of changing patterns of microscopic wear in a living animal over a period of time, thus allowing each animal to serve as its own control. A solution containing a broad-spectrum proteolytic enzyme when applied to the teeth of an anesthetized animal removes the proteinaceous coat (pellicle) which will otherwise obscure wear scratches. Precision dental impressions can then be made which reveal the details of the pattern of microwear on the teeth.

Controlled feeding trials with ungulates: a new application of in vivo dental molding to assess the abrasive factors of microwear

“…Inadequate molds may have been primarily due to re-growth of the pellicle, the proteinaceous film produced from animal saliva that coats teeth. To improve success rate, a proteolytic enzyme treatment (Kay and Covert, 1983) can be applied to the occlusal surface after teeth cleaning, but before making the second mold. The molding plate should also be held in place, with the mouth held open, as we found that the anesthetized sheep were prone to moving their jaws and distorting the molds if their mouths were closed.…”

“…Kay and Covert (1983) reported the complication of the pellicle, a proteinaceous film on teeth that can obscure dental impressions, in their live feeding trials with opossums. An enzyme can be applied to remove the pellicle; however, abrasives also obliterate the film.…”

“…However, several studies examining the effects of biogenic and abiotic abrasives have cast doubt on the central role of biogenic silica in scratch accumulation (Covert and Kay, 1981;Kay and Covert, 1983;Maas, 1991Maas, , 1994Gügel et al, 2001;Mainland, 2003;Sanson et al, 2007;Lucas et al, 2013;Schulz et al, 2013;Müller et al, 2014). Whereas an early study of material properties showed phytoliths were harder than sheep tooth enamel (Baker et al, 1959), subsequent nanoindentation tests have found phytoliths from four globally widespread species of grass to be softer than enamel (Sanson et al, 2007).…”

“…American opossum (Didelphis viriginianus) fed fine-grained pumice showed a prevalence of scratches (Covert and Kay, 1981;Kay and Covert, 1983). Similarly, rabbits (Oryctolagus cuniculus) fed grass diets of increasing biogenic abrasiveness (i.e.…”

Dental microwear analysis in Gliridae (Rodentia): methodological issues and paleodiet inferences based on "Armantomys" from the Madrid Basin (Spain)

“…Furthermore, they added that species presenting high number of fine scratches occupy open areas as grasslands, where dust is abundant. Other studies also suggested that exogenous particles as dust, are also responsible for the large number of parallel striations, being not exclusively attributed to phytholiths alone (Gordon, 1982;Kay and Covert, 1983;Teaford, 1988;Ungar et al, 1995;Sanson et al, 2007). The dentition of the lineage Armantomys aragonensis-A.…”