Effect of violet LED light on in-office bleaching protocols: a randomized controlled clinical trial

Objective: This study evaluated the clinical effect of violet LED light on in-office bleaching used alone or combined with 37% carbamide peroxide (CP) or 35% hydrogen peroxide (HP). Methodology: A total of 100 patients were divided into five groups (n=20): LED, LED/CP, CP, LED/HP and HP. Colorimetric evaluation was performed using a spectrophotometer (Delta E, Delta L, Delta a, Delta b) and a visual shade guide (Delta SGU). Calcium (Ca)/phosphorous (P) ratio was quantified in the enamel microbiopsies. Measurements were performed at baseline (T-0), after bleaching (T-B) and in the 14-day follow-up (T-14). At each bleaching session, a visual scale determined the absolute risk (AR) and intensity of tooth sensitivity (TS). Data were evaluated by one-way (Delta E, Delta a, Delta L, Delta b), two-way repeated measures ANOVA (Ca/P ratio), and Tukey post-hoc tests. Delta SGU and TS were evaluated by Kruskal-Wallis and Mann-Whitney, and AR by Chi-Squared tests (alpha=5%). Results: LED produced the lowest Delta E (p<0.05), but LED/HP promoted greater Delta E, Delta SGU and Delta b (T-14) than HP (p<0.05). No differences were observed in Delta E and Delta SGU for LED/CP and HP groups (p>0.05). Delta L and Delta a were not influenced by LED activation. After bleaching, LED/CP exhibited greater Delta b than CP (p>0.05), but no differences were found between these groups at T-14 (p>0.05). LED treatment promoted the lowest risk of TS (16%), while HP promoted the highest (94.4%) (p<0.05). No statistical differences of risk of TS were found for CP (44%), LED/CP (61%) and LED/HP (88%) groups (p>0.05). No differences were found in enamel Ca/P ratio among treatments, regardless of evaluation times. Conclusions: Violet LED alone produced the lowest bleaching effect, but enhanced HP bleaching results. Patients treated with LED/CP reached the same efficacy of HP, with reduced risk and intensity of tooth sensitivity and none of the bleaching protocols adversely affected enamel mineral content.