Differential wear resistance as a function of tooth enamel structure in the koala Phascolarctos cinereus
Young, W.G., Douglas, W.B., and Robson, S.K. (1990) Differential wear resistance as a function of tooth enamel structure in the koala Phascolarctos cinereus. In: Biology of the koala. Surrey Beatty & Sons, Sydney, pp. 145-150.
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The crests on the molar teeth of the koala are an ideal model for studying the interaction between an invariable diet, a unidirectional jaw movement and an enamel with regional variations in its ultrastructure. Three zones exist within this enamel; leading, intermediate, and trailing. In leading and trailing enamel, the prisms are aligned so that they oppose the predominantly labial to lingual chewing stroke, but those in the intermediate zone are random. Twenty-seven crests from six koala molars were viewed under the scanning electron microscope. Qualitatively, microwear on worn surfaces varied between the three zones. The number of striae per mm of crest length and width of striae in μm in each zone was measured on enlarged electron micrographs using a digital image analysis system. The indentation hardness (Knoop) of each zone was also measured. The number and the width of striae varied significantly (P < 0.01) between zones and individuals. Further, analysis of striae which spanned all three zones showed they were narrower in the leading zone, broader in the intermediate and narrower again in the trailing zone. No significant difference in Knoop hardness was found between the zones. These findings show that the natural scratch hardness of the leading and trailing zones is approximately equal and greater than that of the intermediate zone. Thus enamel ultrastructure appears to influence the microwear facets of the koala, despite no measureable difference in indentation hardness.
|Item Type:||Book Chapter (Research - B1)|
|Keywords:||tooth enamel hardness; tooth wear; microwear; enamel ultrastructure; phascolarctos|
|FoR Codes:||06 BIOLOGICAL SCIENCES > 0602 Ecology > 060201 Behavioural Ecology @ 100%|
|SEO Codes:||97 EXPANDING KNOWLEDGE > 970106 Expanding Knowledge in the Biological Sciences @ 100%|
|Deposited On:||22 Aug 2012 11:17|
|Last Modified:||22 Aug 2012 18:06|
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