Purpose:This in vitro study evaluated the effect of bleaching products and the effect of subsequent applications of CCP–ACP and fluorides on the hardness of enamel during and after tooth bleaching.Methods: The crowns of 30 extracted intact human molars were decoronated and sectioned longitudinally; the buccal part was embedded in acrylic resin, the occlusal part was ground flat, exposing enamel and dentin, and then polished. Baseline Vickers microhardness (VHN) of enamel was determined. The specimens were randomly divided into 6 groups of 5 specimens. Group 1 – Deoblanc;Group 2 – Zoom DayWhite;Group 3 – Deoblanc + CPP–ACP;Group 4 – Deoblanc + APF;Group 5 – Zoom DayWhite + CPP–ACP;Group 6 – Zoom DayWhite + APF. The teeth were bleached for 21 consecutive days.After each day of bleaching, the tooth specimens are treated with CPP– ACP(Tooth Mouse) for 3 minutes using an applicator brush. VHN was measured for 1,2,3 and 5 groups(21st day).Immediately after 21st day, group 4 and 6 received APF 1.23% for five minutes.14 days post fluoridation(35th day), again VHN values were measured for the 6 groups.The results obtained were statistically analysed by Kruskal Wallis test and Wilcoxon Signed Ranks Test. Results:Groups 3 and 5 showed significant increases in enamel microhardness following treatment with no statistically significant difference with the baseline value(p>.05) followed by Group 4 and group 6(p<.05).Conclusion:The results of the current study indicated that the use of CPP–ACP following bleaching improved enamel microhardness than fluoride gel.