Abstract: Objective: To evaluate the effects of tooth whitening with different auxiliary light sources on color, microhardness and surface dissolution amount of dental hard tissues. Material and Methods: A total of 30 human premolars, 60 bovine enamel and 30 bovine dentin specimens were prepared for whitening, surface microhardness and erosive tissue loss assessments, respectively. Human teeth were divided into 3 groups and treated with 35% hydrogen peroxide gel combined with halogen and LED lights for 3×10 minutes (HAL group), with LED alone (LED group) for 3×12 minutes, or with no light for 3×10 minutes (NLC group). Tooth color changes were assessed with a dental spectrophotometer using CIEDE2000 and visual analysis using the Vitapan shade guide. Bovine enamel and dentin surfaces were treated with the same protocols to assess the effects of whitening on enamel surface microhardness and enamel and dentin surface tissue loss. Enamel and dentin tissue losses were also compared to a positive (1% citric acid) and a negative control (distilled water). Analysis of variance (ANOVA) with Tukey tests were used to compare findings among the study groups. Results: Whitening outcomes were significantly better in the HAL and LED groups than in the NLC group in color improvements as shown by∆E00 values (3.4±1.3, 3.1±0.8, 1.9±0.6 respectively, P<0.05). The mean shade improved 3.5±0.53, 3.5±0.97 and 1.7±1.16 respectively according visual analysis. Slight decreases in enamel surface microhardness occurred in all 3 groups (6.4±2.5%, 4.0±1.8%, 4.2±2.4% respectively, P>0.05). Significant enamel or dentin tissue loss occurred only in the positive control (4.3±0.7µm in enamel, 6.7±1.0µm in dentin) but not the negative control and the 3 whitening groups (range 0.01-0.18µm). Conclusions: Tooth whitening with either type of light sources improved the whitening outcomes compared to no light, though the LED light alone needed a slightly longer treatment duration to reach the same whitening outcomes. Whitening treatments with 35% H₂O₂ with or without lights did not cause significant surface changes of dental hard tissues.

Key words: bleaching, effects, microhardness, surface dissolution amount, light activate