Effect of resin infiltration on the color and microhardness of bleached white-spot lesions in bovine enamel (an in vitro study)

Objectives: The aim of this study was to investigate both the effect of resin infiltration on the color and microhardness of white spot lesions (WSLs) that treated with bleaching and to analyze the penetration of the infiltrant. Materials and Methods: In each of 135 bovine enamel specimens, WSLs were produced. The samples were then randomly divided into three groups (n = 45): group I, bleached; group II, resin-infiltrated; group III, bleached and resin-infiltrated. The specimens were subjected to a pH-cycling regime for four weeks. The color and microhardness were measured at the baseline, after production of WSLs, after the treatments. The color alteration (Delta E*) and the percentage of surface microhardness recovery (SMHR) were calculated. The penetration of the infiltrant was evaluated by scanning electron microscopy. Results were analyzed with analysis of variance, Shapiro-Wilk, Tukey's, Kruskal-Wallis and Conover-Dunn tests (P = .05). Results: The SMHR% in resin infiltration groups was significantly higher than that of the bleached group only (P < .05). Bleaching treatment prior to resin infiltration produced no significant change in the microhardness (P > .05). Using a bleaching treatment prior to resin infiltration produced significant color alteration (P < .05). The penetration of the resin infiltrant was deepest in-group II. Conclusions: The resin infiltration enhanced the microhardness of the WSLs regardless of whether or not a bleaching treatment was used. Using a bleaching treatment before resin infiltration resulted in color alteration, and it was also found to negatively influence the penetration of the infiltrant.