Color Alteration and H2O2 Penetration Caused by Different Bleaching Protocols

Objective: : Evaluate the color change and diffusion of hydrogen peroxide (HP) on bovine enamel /dentin specimens subjected to different bleaching protocols.

Method: The specimens were divided into five groups (n = 15): 1- control, no bleaching; 2- bleached for 21 days, 3 hours / day with carbamide peroxide 10% (CP)(Whiteness Perfect- FGM); 3- bleached with 35% HP (Whiteness HP Maxx- FGM), ​​three applications of 15 minutes; 4- bleached   with 35% HP (Whiteness HP Maxx- FGM), an application of 45 minutes, 5- bleached with  20% HP (Whiteness HP blue- FGM) for 50 minutes. The groups 3 to 5 received three bleaching sessions, one per week. To quantify the penetration of the H₂O₂, the specimens were placed in artificial pulp chamber containing acetate buffer solution, which was collected, added to peroxidase and leucocrystal violet to evaluate the optical density by spectrophotometry. The color alteration (bleaching effect) was accomplished by reflection spectrophotometry. Readings were performed after each week of CP bleaching or after each in office session and 7 days after the treatment. 

Result: Data were subjected to statistical analysis by ANOVA and Fisher’s PLSD test at 0.05 significance level. Regarding color alteration, after 21 days, statistical analysis showed that all bleaching groups differed from the control (p<0.05); there were no differences among groups using 35% HP (p>0.05); groups 2, 4 and 5 were equally effective in bleaching effect (p>0.05); after one week post treatment, no color rebound was verified statistically in any of the groups.  The higher HP concentration groups resulted in a higher pulpal peroxide penetration than CP group, and all groups differed from control group (p<0.05). 

Conclusion: Bleaching protocol using CP caused less color alteration than group using 35% HP, ​​three applications of 15 minutes; however the technique with CP caused less H₂O₂ penetration than all other groups.