Enamel resistance to demineralization after treatment with 10% carbamide-peroxide

Objectives: The aims of this study using fluoride-containing and non-fluoride-containing 10% peroxide gel were: a) to assess the effects of these gels on the surface microhardness of enamel; b) to assess the effects of these gels on enamel resistance to demineralization produced by an S. mutans biofilm in vitro. Methods: Fifty bovine enamel blocks (4x4x2mm) were polished, screened for cracks, evaluated for microhardness using a Knoop indenter (50 g load) and randomly allocated to one of the groups: 1) Artificial Saliva (SC); 2) Acidulated Phosphate Fluoride Topex? gel (APF); 3) Opalescence? (OPA); 4) non-F Whiteness? gel (NFW); 5) F-Whiteness? gel (FW). In phase 1 the APF blocks received a single 4-minutes APF application in the first day; Groups OPA, NFW and FW were treated with the appropriate gel 8 hours/day for 14 days. During this phase all blocks were stored overnight, in artificial saliva at 37ºC, for 14 days. Treatments were done at 37ºC and solutions were changed daily. After this treatment the blocks were re-assessed for microhardness and submitted to demineralization using a S. mutans biofilm for 18 hours (Phase 2). Results: Indentation length changes (µm) after phase 1 were SC (4.63±5.58), OPA (16.3±3.03) and, APF (6.03±1.96) were not significantly different between themselves (ANOVA, Fisher's test, p>0.05). NFW (68.96±32.57) and FW (22.61±2.65) were significantly different from the other groups but not between themselves (ANOVA, Fisher's test). After phase 2 indenter length changes in OPA, (11.23±11.34) APF (15.48±15.25), NFW (11.69±11.44) and FW (10.72± 17.14) were different from control SC (51.54±19.67) (ANOVA, Fisher's test, p<0.05). Conclusions: Whitening treatment with these gels may not reduce enamel resistance to demineralization. Supported by FAPEAL Grant#20031029522-6