Method: Flat, polished enamel surfaces of human third molar teeth (n = 5) were treated with artificial saliva for two hours before being eroded in citric acid at pH 3 for two minutes. Nano-scratches were placed on enamel surfaces at baseline and after erosion using a spherical tip (with a 20μm radius) in a nano-indenter (Ultra-micro Indentation System, UMIS-2000, CSIRO, Australia) at a load of 100mN. Data on scratch depths, 10-point mean surface roughness (R10z) values and coefficients of friction were generated for each specimen after both the baseline stage (control) and the erosion stage.
Results: Paired t-tests showed that nano-scratch depth of eroded enamel (mean ± SE, 0.68 ± 0.14µm) was significantly greater than at baseline (0.55 ± 0.10µm) (p<0.01). There were also trends for the mean R10z value and the mean coefficient of friction to increase after erosion compared with the baseline values (0.15 ± 0.02µm versus 0.12 ± 0.02µm, respectively, for R10z value, and 0.40 ± 0.17µm versus 0.27 ± 0.09µm, respectively, for coefficient of friction).
Conclusions: The finding of greater susceptibility of eroded enamel to mechanical abrasion is consistent with results of other studies conducted over longer durations. Nano-scratch testing is a more sophisticated technique for assessing early erosive tooth wear than traditional approaches, offering greater sensitivity and efficiency in data acquisition. Future studies are recommended to apply this technique in investigating changes in mechanical properties associated with early erosive tooth wear in a larger sample under a variety of experimental conditions.