Table 3: Comparison of microhardness at the enamel surface among the groups

Type of post bleaching surface treatment Enamel Surface
Mean SD Pairwise comparisons
Group 1 (Fluoride) 446.58 53.32 a
Group 2 (Fractional CO2 laser) 429.04 29.04 a
Group 3 (Nanohydroxyapatite) 470.20 53.82 a
Group 4 (Control) 387.70 21.25 b
P-value 0.000*

*Statistically significant difference at P<0.05.
Different letters indicate significant differences at P<0.05.

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