Effect of Light Irradiation on Tooth Whitening: Enamel Microhardness and Color Change

ABSTRACT The aim of this study was to evaluate the influence of light exposure associated with 35% hydrogen peroxide (Pola Office, SDI, Melbourne, Vic., Australia) or 15% hydrogen peroxide (BriteSmile, Discus, Culver City, CA, USA) on the microhardness and color changes of bovine enamel. Experimental groups were Britesmile + Light (BL) (15% hydrogen peroxide + plasm arc; 4 × 20 minutes), Britesmile + No Light (BN) (BL, no light), Pola office + Light (PL) (35% hydrogen peroxide + LED; 4 × 8 minutes), and Pola office + No light (PN) (PL, no light). Color changes (ΔE) and the CIELAB (Commission Internationale de l' Eclairage, L*a*b* color system) parameters (L*, a*, and b*) were assessed with a spectrophotometer before (B), immediately (A), 1 day and 7 days after bleaching. The microhardness was measured before (B) and after (A), the obtained data were submitted to a two‐way analysis of variance, and ΔE were submitted to t‐test for each period. Only Pola Office, in which the peroxide is associated with the light, improved ΔE when evaluated immediately after bleaching (p