Effect of light activation on tooth whitening efficacy and hydrogen peroxide penetration: an in vitro study.

OBJECTIVES: To determine the effect of light activation on tooth whitening efficacy and hydrogen peroxide penetration into the pulp cavity and correlate tooth color change with penetration levels. METHODS: Extracted human canines (40) were randomized into four groups, Group A: placebo gel, Group B, placebo gel with light activation, Group C: 40% hydrogen peroxide gel, and Group D: 40% hydrogen peroxide gel with light activation. Treatment was performed three times, at 1-week intervals. Hydrogen peroxide penetration (HPP) was estimated spectrophotometrically and specimen color measured using the Vita Easy Shade Compact at baseline, after whitening, 1-h, 1-day, 1-, 4-, 8-, 12-, 16-, 20-, and 24-week post-whitening. Color change was measured per Commission Internationale de l'Eclairage methodology. ANCOVA was performed to compare color change and HPP level among the four groups. Partial nonparametric correlations between color change and HPP levels were performed with rank transformations. Tests of hypotheses were two-sided with alpha level of 0.05. RESULTS: Greater HPP was observed in Groups C and D compared to Groups A and B (p<0.001). Highest overall color change (ΔE*ab) values after treatment were observed in Group D and remained higher than Groups A-C (p<0.01). Changes in lightness and in the yellow-blue dimension (ΔL* and Δb*) were higher in Groups C and D compared to Groups A and B from post-whitening until 24 weeks (p<0.05). HPP levels were not correlated to color change (p>0.05). CONCLUSIONS: Light activation enhanced whitening efficacy without affecting hydrogen peroxide penetration levels.

Evaluation of bleaching efficacy and erosion potential of four different over-the-counter bleaching products.

PURPOSE: To evaluate the bleaching efficacy and erosion potential of various over-the-counter bleaching products following a test method specified in ISO 28399. METHODS: Specimens were prepared from bovine molars, stained in tea solution, embedded and randomly assigned to six groups of 10 enamel and dentin specimens each. Color was assessed at baseline, 1 day and 1 month post-bleaching with the Vita Bleachedguide 3D Master shade guide. Surface roughness changes (deltaRa), determined by baseline and post-treatment values were measured with a profilometer. The negative (NC) and positive control (PC) was treated with grade 3 water and 1.0% citric acid, respectively. Over-the-counter products were used according to manufacturer's instructions. Brite Teeth Pro (BT), Natural White 5-Minute Whitening (NW), Luster Premium White (LP), and Crest 3D Whitestrips (WS) represented a brush-on-paint system, tray system, light-activated system and adhesive-strip system, respectively. Kruskal-Wallis procedure was used to compare surface roughness changes among groups. Color change was assessed with Friedman-test and stratified by hard tissue type with alpha= 0.05. RESULTS: WS was the only group demonstrating color changes in enamel and dentin (P< 0.05). There were no differences in deltaRa for enamel and dentin among NC, BT, LP, and WS. NW showed increase in deltaRa in dentin (P< 0.05), while PC demonstrated an increase in deltaRa regardless of hard tissue type (P< 0.05).