# Effect of two in-office bleaching agents-35% hydrogen peroxide and 37% carbamide peroxide-on enamel microhardness: An in vitro study

## TL;DR

This study found that two common in-office teeth whitening treatments both reduce enamel hardness, suggesting the need for protective measures after bleaching.

## Contribution

The study compares the enamel microhardness effects of two high-concentration in-office bleaching agents for the first time in an in vitro setting.

## Key findings

- Both 35% hydrogen peroxide and 37% carbamide peroxide significantly reduced enamel microhardness.
- No significant difference in enamel hardness reduction was found between the two bleaching agents.
- The results highlight the need for remineralization strategies after bleaching to protect enamel.

## Abstract

Tooth discoloration frequently drives patients to seek in-office bleaching procedures, which commonly use high-concentration peroxide
agents. This in vitro study evaluated the effect of two chairside bleaching formulations-35% hydrogen peroxide and 37%
carbamide peroxide-on enamel microhardness. Hence, thirty premolars were assigned to control, hydrogen peroxide, or carbamide peroxide
groups, and microhardness was measured before and after bleaching. Both bleaching agents caused significant reductions in enamel
microhardness compared with the control group, although no significant difference was observed between the two peroxide systems. These
findings indicate that in-office bleaching agents can adversely affect enamel hardness, highlighting the importance of post-bleaching
remineralization strategies for clinical safety.