Influence of In-office Bleaching Agent on Root Dentin Surface

—Assessment of TMR and Vickers Hardness Test—

Abstract

 Purpose: Dentin discoloration that appears like a cervical shadow is one of the most serious problems when making aesthetic ceramic prostheses. There are case reports that in-office bleaching can be used for discolored cervical dentin of abutment teeth as a pre-treatment of the crown prosthesis. In this study, the influence of in-office bleaching agent on root dentin was examined.
 Methods: The specimens were divided into four groups: non treatment group (cont), and three bleaching treatment groups (tre-2, tre-4 and tre-6). In the bleaching groups, Shofu HiLite, an in-office bleaching agent containing 35% hydrogen peroxide, was applied to each specimen according to the manufacturer’s instructions. One session consisted of three applications of bleaching agent. This session was repeated 2 times, 4 times and 6 times. The mineral profiles and integrated mineral loss (IML: vol%×μm) of each specimen were obtained with a system that combined transverse microradiography (TMR) with image-analysis software. In addition, Vickers hardness tests were performed on the dentin surfaces of the same groups. Differences in IML and hardness were compared between the groups by one-way ANOVA followed by Tukey’s test. All statistical analyses were performed using SPSS (version 10.1) with p<0.05 defined as statistically significant. Numbers of each group were 6.
 Results: Representative TMR images showed no significant difference in radio-opacity in all groups. Average mineral profiles showed that the surface mineral density of the tre-6 group was slightly decreased compared with the other groups. The mean IML showed a significant difference between cont and tre-6. By the Vickers hardness test, a significant difference was observed between cont and the other groups. Vickers hardness decreased with the increase of treatment time.
 Conclusion: It was concluded that consecutive applications of HiLite as an in-office bleaching to discolored dentin will demineralize its surface.