Avaliação da glutationa como dessensibilizante após clareamento dentário com peróxido de hidrogênio: estudos in vitro e clínico randomizado

Abstract

Dental bleaching can trigger a process of tooth sensitivity caused by the drastic decrease of intracellular glutathione. This study was presented in two chapters, whose objectives were: Chapter 1) To evaluate in vitro the effect of glutathione after at-home dental bleaching with 7.5% hydrogen peroxide on the enamel and dentin surfaces properties, as well as to assess the tooth bleaching effectiveness; and Chapter 2) To evaluate absolute risk, intensity of tooth sensitivity, color change, and degree of participant satisfaction after at-home bleaching performed associated with glutathione as a desensitizer. In the Chapter 1, the specimens were obtained from sixty-six human teeth and randomly divided into six groups: CONTROL (without treatment), BLEACH (only dental bleaching), KF2 (Desensibilize KF 2%®, FGM, Joinville, Santa Catarina), CONT-EXP (no desensitizing), GLUTA5 (5% glutathione), and GLUTA10 (10% glutathione). Specimens were bleached for 14-21 days, depending on the test, with a 7.5% hydrogen peroxide-based experimental bleaching gel for 1 h, and a desensitizing agent was applied on the dental substrate per day for 10 min. Specimens surfaces properties were determined by Knoop microhardness (n=5), and analyzed the mineral composition of the substrates (Raman spectroscopy) (n=1). Color change (n=5) was evaluated with a portable spectrophotometer before and after treatments. For statistical analysis of microhardness and color change was performed the two-way repeated measures ANOVA and Holm-Sidak test (α=0.05), while the Raman data was analyzed by qualitative estimation. All bleached groups showed a significant reduction of microhardness in relation to the control. In the commercial group, it was not possible to perform indentation measurement. The mineral composition of GLUTA5 and GLUTA10 groups demonstrated a reduction in the intensity of the phosphate peak and an increase of the carbonate when compared to the control. The bleached groups showed a significantly higher ΔE than did the control group (p<0.05) and had the color stabilized after two months of follow-up. The conclusion was that the use of glutathione after at-home tooth bleaching altered phosphate and carbonate peaks, there was no change neither in the microhardness, nor in the bleaching efficacy or in the color stability. In the Chapter 2, sixty participants with right maxillary canine of color C2 or darker were selected and randomly distributed in three groups (n=20): PLACEBO (no desensitizing), KF2 (5% potassium nitrate and 2% sodium fluoride), and GLUTA10 (10% glutathione). Teeth were bleached for 14-21 days, depending on the degree of satisfaction, for 1h with a 7.5% hydrogen peroxide-based experimental bleaching gel, and a desensitizing agent was applied on teeth per day for 10 min.Tooth sensitivity was recorded for 14 days of bleaching with a four-point numeric rating scale (NRS) and a 0-10 visual analog scale (VAS). The color change was evaluated in the teeth 11 and 13 by objective method (Vita Easyshade Spectrophotometer) at baseline and follow-up evaluations (after 1 day, 15 days, and 2 months of the bleaching procedure completion). The degree of satisfaction was questioned after 14 days of bleaching according to a 0-3 scale. For statistical analysis, the absolute risk of tooth sensitivity was compared using the G-test of independence. Intensity of tooth sensitivity and degree of participant satisfaction were analyzed using Kruskal-Wallis. The color change was tested using the two-way repeated measures ANOVA and the Holm-Sidak test (α=0.05). No significant difference was observed in the risks (p=0.5703) and intensity of tooth sensitivity between groups (p>0.05). The groups showed a color stability up to the end of the study, except the incisors in placebo and 10% glutathione groups (p<0.05), that had not stabilized after two months of follow-up. Also, the degree of satisfaction was not significantly different between the groups (p=0.4101). Clinically, the glutathione was not efficient to reduce tooth sensitivity after at-home dental bleaching with 7.5% hydrogen peroxide; however, glutathione did not interfere in the color change and the degree of participant satisfaction.