the effect of two remineralizing agents and natural saliva on bleached enamel hardness

background: in order to compensate the adverse consequences of bleaching agents, the use of fl uoride-containing remineralizing agents has been suggested by many researchers. the aim of this study was to compare the effect of applying two remineralizing materials on bleached enamel hardness and in comparison to natural saliva. materials and methods: in this experimental study, 30 enamel samples of sound human permanent molars were prepared for this study. microhardness (mh) of all specimens was measured and 35% hydrogen peroxide was applied 3 times to the specimens. after completion of the bleaching process, mh of samples was measured and then enamel specimens were divided into three groups each of 10, specimens of groups 1 and 2 were subjected to daily application of hydroxyl apatite (remin pro) and casein phosphopeptide amorphous calcium phosphate fl uoride (cpp-acpf) (mi paste plus) pastes, respectively, for 15 days. in group 3, the specimens were stored in the operators’ natural saliva at room temperature in this period of time. final mh of all groups was measured. the data were analyzed using repeated measures anova (α = 0.05). results: the hardness signifi cantly decreased in all groups following bleaching. application of either remin pro, cpp-acpf or natural saliva increased the hardness signifi cantly. the hardness of the three test groups after 15 days were statistically similar to each other. conclusion: the hardness of enamel increases eventually after exposure to either mi paste plus, remin pro or natural saliva. key words: bleaching agents, casein phosphopeptide-amorphous calcium phosphate nanocomplex, enamel, hardness, surface properties, tooth remineralization