Chemical Activation Versus Light activation on Bleaching Efficacy

Objectives: The aim of this study was to evaluate the efficacy of different types and concentrations of chemical activators on bleaching efficiency of 35% hydrogen peroxide gel in relation to light activation (LA).

Methods: 540 enamel-dentin disks were obtained from bovine incisors using a 3mm diameter trephine mill. The initial colors of specimens were measured with a spectrophotometer (CM2600d – Konica Minolta) using the CIELab system. An experimental 35% hydrogen peroxide gel was used. A positive (without activator) and a negative (no bleached) control groups were prepared (n=20). Each one of the five chemical activators groups (n= 60) received a different substance: MG - Manganese Gluconate; MC - Manganese Chlorite, FG - Ferrous Gluconate, FC – Ferric Chlorite, FS – Ferrous Sulphate. Each activator group was divided into 3 different subgroups (n=20), according to the concentrations tested (1 - 0.01%, 2 - 0.02% e 3 - 0.03%). In the LA group, the gel was activated with blue light from a LED device (Bright Max II - MM Optics). Three applications of 10 min were performed for each gel, being repeated after 7 days. In intermediate periods, the specimens were stored in artificial saliva. The final color was measured one week after the final bleaching. The data were analyzed using one-way ANOVA and Tukey´s tests (a=5%).

Results: Significant differences were observed among the groups (p=0.0035 for ANOVA). The results of Tukey´s test for Delta E were: MC1-4.48(±1.10)a; MG3-4.69(±1.22)a; PC-4.70(±1.02)a; FC3-4.82(±1.01)ab; FG1-4.88(±1.39)ab; FG3-4.89(±1.25)ab; FS1-4.99(±1.30)ab; MG2-5.04(±1.19)ab; MC3-5.12(±1.29)ab; FG2-5.13(±1.13)ab; FS2-5.18(±1.42)ab; FS3-5.20(±1.13)ab; FC2-5.23(±1.00)ab; MG1-5.31(±1.41)ab; FC1-5.35(±1.18)ab; MC2-5.47(±1.32)ab; LA-5,83(±1,36)b. The groups followed by the same letter did not show significant differences.

Conclusions: Only light activation increased significantly the color change. Significant differences were obtained for all bleached groups in relation to the negative control group.