Abstract

--- - "Background: : The association of low concentration hydrogen peroxide (HP) and a light source has been widely used to achieve efficient bleaching. We investigated the colorimetric and microstructural changes of bovine enamel bleached with 6% HP associated or not with a hybrid light source system of violet light and laser (LED/ laser)." - "Methods: : Twenty bovine crowns were used to obtain specimens of 7 x 7 x 2 mm. Then, they were randomized in two groups (n=10): 6% HP and 6% HP + LED/laser. After staining with dark tea solution, three bleaching sessions were performed. Colorimetric evaluation (Delta L*, Delta a*, Delta b*, Delta E-00 [CIEDE2000] and WID) after 24 hours of each session and 7 days after the final bleaching session was performed. Enamel Vickers microhardness at baseline, 24 hours and 7 days after the last bleaching session were also evaluated. Two-way repeated measures ANOVA and Bonferroni post-test was used at a significance level of 5%." - "Results: : 6% HP and 6% + HP LED/laser showed satisfactory bleaching results. The group photoactivated showed higher WID values (p<0.05). Differences between groups were observed for Delta E-00, Delta L* and Delta a* (p<0.05), except for.b* (p>0.05). Intra-group differences were also found (p<0.05). Regarding microhardness, no inter or intragroup differences were observed (p>0.05)." - "Conclusions: : The photoactivation with LED/laser enhanced the whitening efficacy of 6% HP compared to the group without photoactivation. Thus, the LED/laser activation appears to be a good option when using low concentration HP-based agents. In addition, both bleaching protocols did not cause changes on enamel microhardness."