Effect of fluoride treatment on remineralization of bleached enamel

The objective of the study was to evaluate the remineralizing capacity of different fluoride treatments on dental enamel bleached with carbamide peroxide (Opalescence(R)). Sixty bovine enamel slabs were subjected to four cycles comprising bleaching (12 h) and remineralization in artificial saliva (8 h). The samples were evenly distributed among four groups (A-D). During the first hour of the remineralization period the specimens in group A were covered with a fluoride varnish (Duraphat(R); 2.23% F-). In group B the enamel slabs were stored in a fluoride solution (0.2% F- as NaF) for 1 min prior to remineralization. Group C did not receive a fluoride treatment, and group D (control) was stored in distilled water instead of bleaching. Microhardness (VHN) was evaluated before the experiments and after the second and fourth cycle, respectively. Final hardness was calculated as percentage of the initial hardness. Analysis of variance was applied to the data followed by pairwise comparisons with corrected level of significance (P < 0.01). Hardness decreased significantly in groups A-C compared to the control group (D). The bleached and unfluoridated specimens (group C) showed a significantly higher hardness loss compared to the fluoridated specimens, whereas no significant difference was observed between the two fluoridated groups. It is concluded that remineralization of bleached enamel is improved by application of highly concentrated fluorides.