Evaluation of bleaching with carbamide peroxide on microhardness, mineral content, and color change of white spot lesions

Tooth bleaching changes the microhardness and mineral content and color of the tooth. The present study aimed to evaluate the effect of carbamide peroxide on microhardness, mineral content and color change in white spot lesions.

Thirty-two samples were selected without caries, cracks and stains, and immersed in 0.5% chloramine-T for one week. Then the tooth crowns were separated. The teeth were artificially decayed by pH cycling. For bleaching on the enamel, a coating of 10% carbamide peroxide gel with a thickness of 1 mm was used for 8 hours. Samples were stored in artificial saliva for 16 hours. Bleaching process lasted for 14 days. Microhardness, color changes, calcium and phosphorus levels were measured before and after bleaching. Paired t-test and one-sample test were used to analyze the data.

The microhardness test results were 338.02± 90.15 and 320.94±87.41 before and after bleaching, respectively. microhardness of the samples significantly decreased after bleaching compared to before bleaching (P<0.001). Calcium and phosphorus content in samples after bleaching was not significantly different from before bleaching (P>0.05). The mean color change coefficient (∆E) after bleaching was 6.82±3.96. ∆E in the studied samples was significantly higher than the standard (∆E =3.3).

Bleaching with 10% carbamide peroxide significantly reduced microhardness. There was no change in the mineral content of the enamel and color change was proper. It can be concluded from this study that bleaching with carbamide peroxide can be successful.