Comparison of Surface Microhardness of Enamel after Bleaching with Two Commercially Available Hydrogen Peroxide-based Bleaching Agents -An In-vitro Study

Objective: This in-vitro study aimed to compare the surface microhardness of enamel after bleaching with two commercially available hydrogen peroxide-based bleaching agents. Materials and Methods: Twenty-four extracted human maxillary central incisors were polished, sectioned, and allotted into two groups. Group A was treated with 35% hydrogen peroxide (Mani Bleach N Shine), and Group B with 37.5% hydrogen peroxide (SDI Pola Office Plus). Each tooth was bleached for 10 minutes per session across three sessions. Surface microhardness was measured before and after bleaching using a Vickers indenter. The obtained values were analyzed for statistical significance using paired and unpaired T-test. Results: There was no statistically significant reduction in surface microhardness observed between the two groups after bleaching. The mean surface microhardness for Group A decreased from 358.40 ± 47.19 to 320 ± 34.58, while Group B decreased from 389.20 ± 21.90 to 361 ± 18.09. The percentage reduction in surface microhardness was calculated, resulting in no statistically significant difference between the groups (p=0.05). Conclusion: Both hydrogen peroxide-based bleaching agents evaluated did not result in a statistically significant reduction of enamel surface microhardness. These findings suggest that, when used appropriately, these bleaching agents are safe and effective for tooth whitening with minimal effect on the surface integrity of the tooth enamel. Further research is needed to investigate the long-term effects of these bleaching treatments on enamel.