Colorimetric evaluation was performed using a spectrophotometer (ΔE, ΔL, Δa, Δb) and a visual shade guide (ΔSGU). 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 (ΔE, Δa, ΔL, Δb), two-way repeated measures ANOVA (Ca/P ratio), and Tukey post-hoc tests. ΔSGU and TS were evaluated by Kruskal-Wallis and Mann-Whitney, and AR by Chi-Squared tests (a=5%). Results: LED produced the lowest ΔE (p<0.05), but LED/HP promoted greater ΔE, ΔSGU and Δb (T 14) than HP (p<0.05). No differences were observed in ΔE and ΔSGU for LED/CP and HP groups (p>0.05). ΔL and Δa were not influenced by LED activation. After bleaching, LED/CP exhibited greater Δb 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.

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Objective: This study evaluated the efficacy and tooth sensitivity of bleaching with the novel violet LED light used in different in-office approaches. Clinical Considerations: Three patients were submitted to anamnesis, clinical and radiographic exams and to different bleaching protocols and materials. Case report I: Violet LED light was applied in 20 irradiations of 1 minute at 30-s intervals without the use of peroxide agents. After eight appointments with 4 or 7-day intervals, no tooth sensitivity (TS) was reported and color changed from A2 to A1 and from B3 to A2 in upper central incisor (tooth 11) and upper canine (tooth 13), respectively. Case report II: The same protocol established for violet LED light application was used and associated with 37% carbamide peroxide in three appointments at intervals of 7 days. Color changed from A3,5 to B2 (tooth 13), and provoked TS was reported. Case report III: 35% hydrogen peroxide was associated with the same violet LED regimen and number of sessions. Although spontaneous TS was reported in low levels, color changed from A2 to B1 (tooth 11) and from A3 to B1 (tooth 13). Conclusion: Although the three treatments promoted different bleaching responses, in vitro and in vivo investigations of the violet LED protocols are still necessary. In addition, the fact that the sensitivity levels obtained are compatible with conventional bleaching treatments demonstrated that violet LED light is possibly adequate for clinical use. Clinical Significance: Bleaching of vital teeth with violet LED with or without peroxide agents exhibited acceptable clinical results and low sensitivity responses.

We investigated qualitative characteristics and spatial distribution of subchondral bone pores of the mandibular condyle in adult rats submitted to dental premature contact condition using micro-CT analysis.