Method: 117 polished, 10mm diameter human anterior enamel surfaces were obtained and randomly divided into nine groups(n=13). After recording initial(T0) enamel-color, chemical-analysis and microhardness, the bleaching treatments were performed as G1:Signal Professional White Now POWDER&LIQUID FAST 38% Hydrogenperoxide (S), G2:S&Flor Opal 0.5% fluoride ion (F), G3:S&GC Tooth Mousse CPP-ACP paste (TM), G4:S&UltraEZ 3% potassium nitrate (U), G5:S&Signal Professional SENSITIVE PHASE 1 30% Nano Hydroxyapatite suspension (SP), G6:S-F mixture, G7:S-TM mixture, G8:S-U mixture, G9:S-SP mixture. After 24h(T1) and 14 days(T2), color, chemical-analysis, and microhardness measurements were repeated. Data were analyzed with ANOVA(p<0,001), Tukey(p<0,001) and Dunnett T3(p<0,001) tests using SPSS PASW, 15.0 software.
Result: There were no significant differences in L*, a* and b* values among the nine groups at T0(p>0,001). ΔE value of G7 was significantly higher than G3, G5, G6 and G9 at T1(p<0.001). ΔE value of G8 between T1-T2 was higher than G1, G4 and G5, while ΔE value of G9 was higher than G1, G2, G4, G5 and G6(p<0,001). Microhardness of all groups were similar at T0. There was no significant percentage microhardness loss(PML) between T0-T1 except G3(p>0,001). G1 showed higher PML than G2, G5 and G7(p<0,001) at T2. G6 presented less PML than G1, G2 and G5 between T1-T2(p<0,001). PML G6, G7 and G9 decreased in T1(p<0,001). No significant difference was found between T0-T1(p>0,001) in Ca/P ratios. However Ca/P ratio of G3 was observed higher than G8(p<0,001). F mass increased in G2 and G6 at T1 (p<0,001) but there were no differences among the groups at T2(p>0,001).
Conclusion: Use of desensitizing agents did not affect the success of the bleaching. Furthermore, adding fluoride, potassium nitrate or nano hydroxyapatite could recover microhardness of enamel immediately after office-bleaching.