Tooth enamel properties and morphology after microabrasion: an in situ study

AIM This study evaluated the effect of saliva on enamel after microabrasion with different microabrasive compounds under in situ conditions. METHODS Enamel/dentin blocks (16 mm2 ) from bovine incisors were divided into nine groups (n = 19): one control group (no treatment), four groups treated with microabrasion using 35% phosphoric acid (H3 PO4 ) + pumice, and the last four groups treated with microabrasion using 6.6% hydrochloric acid (HCl) + silica. The treated groups were subdivided according to the in situ regimen: without salivary exposure, 1 h, 24 h, or 7 days of saliva exposure. Surface microhardness (SMH) and cross-sectional microhardness (CSMH) were tested. Scanning electron microscopy (SEM) was used to evaluate enamel morphology. Microhardness data were tested by analysis of variance, and Tukey's and Dunnett's tests (α = 0.05). RESULTS The SMH analysis revealed that all the microabrasion-treated groups presented significantly-reduced SMH values when compared to the control group (P < 0.05). Treatment with HCl + silica was more prone to the effect of saliva than H3 PO4 + pumice, even for CSMH analysis, once the superficial layers reached the same microhardness of that of the control group (P > 0.05). These results were confirmed by SEM, which demonstrated the mineral recovery effect over time. CONCLUSION Saliva was effective in promoting the rehardening of enamel after microabrasion, mainly for the surfaces treated with HCl + silica.