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

Tooth bleaching decreases enamel microhardness. The aim of this study was to evaluate the changes in microhardness of bleached enamel after applying fluoride and CPP-ACP (casein phosphopeptide –amorphous calcium phosphate). In this experimental study, sixty extracted human molars were divided into six groups (ten each). The flatted occlusal surface was covered with nail varnish. In the second, third and fourth groups, tooth bleaching was performed. The first and second groups were positive and negative control groups. In the third and fifth groups, the specimens were covered with sodium fluoride varnish and the fourth and sixth groups underwent CPP-ACP therapy. Subsurface enamel microhardness was determined 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. Microhardness of bleached enamel was significantly lower than the other groups. The teeth treated by fluoride agent or CPP-ACP after bleaching had a significant increase in their microhardness in contrast with the bleached enamel. CPP-ACP and fluoride treatment had no significant effect on sound enamel microhardness. Although using CPP-ACP and fluoride increases the enamel microhardness, there was no significant differences between them. Fluoride and CPP-ACP components increase bleached enamel microhardness.