Changes in bleached enamel microhardness after application of fluoride and CPP-ACP

Abstract Background and Aim: Tooth bleaching decreases enamel microhardness. The aim of this study was to evaluate the changes in microhardness of bleached enamel after ap-plying fluoride and CPP-ACP (casein phosphopeptide –amorphous calcium phos-phate). Materials and Methods: In this in vitro experimental study, sixty extracted human molars were divided into six groups. The flatted occlusal surface was covered with nail varnish. Group 1 and 2 served as positive and negative control groups. Group 2, 3 and 4 underwent bleaching procedure. Specimens of group 3 and group 5 were covered with sodium fluoride varnish and group 4 and 6 underwent CPP-ACP therapy. Subsurface enamel microhardness was measured on the occlusal surface with 300 micron distance from the buccal or lingual surface. One way ANOVA and Tukey post hoc were used for statistical analysis. Results: Microhardness of bleached enamel was significantly lower than the other groups. CPP-ACP or fluoride had no significant effect on sound enamel microhard-ness. The bleached specimens treated by fluoride or CPP-ACP had a significant in-crease in their microhardness compared with theuntreated bleached enamel. Although appliance of CPP-ACP and fluoride increases the enamel microhardness, there were no significant differences between them. Conclusion: Fluoride and CPP-ACP components increase bleached enamel micro-hardness. Key Words: Subsurface enamel – Teeth Bleaching – Microhardness – CPP-ACP – Fluoride varnish