| Summary: | The principle aims of this work were two-fold: to investigate the effects of a short duration acid exposure on enamel and to evaluate the suitability of bovine material as a substitute for human enamel at these early stages. The former has largely been overlooked in the literature and has potential for clinical care and remineralisation strategies, while the latter has become an increasing issue manifesting as a lack of human research material neccessitating the substitution of an alternative species. Two models of erosion commonly employed in the literature were evaluated against each other. Greater bulk tissue loss was observed in the model with a repeated exposure of acid to enamel compared to the alternative single immersion model. Quantitative optical profilometry (OP) assessment of bulk tissue loss in both human and bovine enamel using 1 mol.L-1 acetic, citric and phosphoric acid solutions was not significant, a finding supported by alternative quantitative light fluorescence (QLF). This early data provided information regarding the expected shape of subsequent, more commercially applicable experimental data. The next series of experiments mirrored those mentioned previously but using commercially applicable 0.05% solutions. OP assessed bulk tissue loss was significantly different from that of 1 mol.L-1 solutions but direct comparison of the two species at 0.05% remained not significant. Both 1M and 0.05% acid solution datasets revealed a biphasic trend during the early erosion challenge. The erosion rate between 10-60 seconds was significantly different from the later 60-600 seconds, irrespective of acid type or species. Further analysis of the erosion lesions using atomic force microscopy (force vs distance measurements) suggested lesion morphology was more varied than previously thought. This led to an examination of lesion ultrastructure using micro-computed tomography and confocal microscopy. Potential subsurface softening was observed, together with areas of apparent acid resistance standing proud of the lesion base. The latter were probed using EDX, AFM and focussed-ion beam SEM, which confirmed the uneroded nature of these resistant areas. As far as we are aware, this is the first time such erosion trends and morphology have been reported.
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