Influence of the Type of Topical Fluoride Delivery at Various Restoration Time Points on the Micro-Shear Bond Strength of a Resin-Based Composite on Bleached Tooth Enamel

Background This study aimed to evaluate the micro-shear bond strength (mSBS) of an adhesive applied to bleached enamel to determine the effects of fluoride supply and restoration time on the mSBS. Methodology In this study, we bleached 130 samples of enamel and split them into the following three groups of 40 each: group MI: McInnes bleaching solution; group MIF: McInnes bleaching solution + topical acidulated phosphate fluoride gel; group FMI: 2% fluoridated McInnes bleaching solution. Non-bleaching or fluoridation was performed on a group of 10. Subgroups were created for each group (except for the control) to be restored for seven, 14, or 21 days. The mSBS test was performed on a universal testing machine after Tygon tubes were filled with composite resin and put on enamel surfaces. Tukey’s post-hoc test (p = 0.05) and two-way analysis of variance were employed to analyze the data. Results The mSBS values obtained for all groups immediately and after seven days were lower, while at 14 and 21 days were similar to the control group. According to the data, group FMI had greater mSBS levels than groups MI and MIF, both immediately and seven days later. Conclusions When in-office bleaching was employed, only the fluoride McInnes solution was successful in quickly correcting the adverse effects of low mSBS.