Method: Thirty-six extracted human anterior teeth with pre-existing attrition, erosion and combined wear were selected (n=12 per group). Only one tooth with attrition had wear extending into dentine, whereas both enamel and dentine were present in other teeth. The worn surfaces were scanned using confocal microscopy to generate three-dimensional models (at an optical resolution of 0.15µm) that were subjected to complex mathematical modelling to calculate microwear complexity (i.e. measurement of peak to valley distances) and anisotropy (i.e. measurement of the degree of scratch orientation in various directions).
Result: Kruskal Wallis one way ANOVA showed an overall effect of wear type on both microwear complexity and anisotropy for enamel. Enamel complexity in both the erosion group (median, IQR; 4.1, 1.8-5.9) and the combined wear group (4.9, 2.0-6.2) was significantly greater than that in the attrition group (0.7, 0.4-2.9) (p<0.05). There was a trend for complexity in the erosion group to be lower in enamel (4.1, 1.8-5.9) than dentine (5.7, 4.0-12.1) (p=0.06). Mann Whitney U test showed that anisotropy was greater in enamel than dentine in both the erosion group (0.0030, 0.0023-0.0037 vs 0.0014, 0.0010-0.0018) (p<0.001) and the combined wear group (0.0025, 0.0018-0.0026 vs 0.0015, 0.0012-0.0018) (p<0.05).
Conclusion: This is the first report on quantitative assessments of attrition, erosion and combined wear in the form of microwear complexity and anisotropy values. Further refinement of this technique has the potential to provide a new sensitive diagnostic clinical tool for longitudinal assessment of tooth wear.