Color change, diffusion of hydrogen peroxide, and enamel morphology after in-office bleaching with violet light or nonthermal atmospheric plasma: An in vitro study

Objective The aim is to evaluate the effect of violet light (VL) and nonthermal atmospheric plasma (NTAP) combined with or without 35% hydrogen peroxide (HP) and 37% carbamide peroxide (CP). Methods Bovine crowns were divided into (n = 10) VL, VL/HP, VL/CP, NTAP, NTAP/HP, NTAP/CP, HP, CP, and C (control) groups. Color and whiteness change (CIELAB-Delta E-ab,E- CIEDE2000-Delta E-00, whiteness index-Delta WID), color parameters (Delta L, Delta a, and Delta b), and intrapulpal concentration (mu L/mL) of HP were assessed by spectrophotometry. Scanning electron microscopy evaluated the morphology of enamel surface. Data were analyzed by two-way analysis of variance and Tukey (Delta E-ab, Delta E-00, Delta WID, Delta L, and mu L/mL) and Kruskal-Wallis and Mann-Whitney tests (Delta a and Delta b, alpha = 5%). Results VL increased Delta E-ab and Delta WID of CP (P < .05). VL and NTAP alone resulted in perceptible color and whiteness change, but lower than those in the gel-treated groups (P < .05). Activation modes increased Delta L compared with that of C, but only VL enhanced Delta b when applied alone or combined with CP. VL and NTAP did not increase HP diffusion (P > .05) or cause alterations in enamel morphology. However, HP and CP promoted topographical changes. Conclusion VL and NTAP changed color to a lesser extent than bleaching gels. VL produced supplementary effectiveness only for CP (Delta E-ab and Delta WID), without increasing HP diffusion or changing enamel morphology. Clinical Significance Although violet LED light and nonthermal atmospheric plasma (NTAP) promoted in vitro perceptible bleaching without compromising enamel morphology, bleaching gels (hydrogen peroxide and carbamide peroxide) were more effective than VL or NTAP. VL or NTAP did not increase intrapulpal diffusion of peroxide.