Susceptibility of teeth to re-pigmentation after bleaching: An in vitro study

Introduction: Whiter or brighter smile, which is a cornerstone of a beautiful esthetic smile, can be achieved by bleaching. The public concern about appearance has been partly responsible for increased awareness in esthetic dentistry and consequently bleaching techniques. Bleaching solutions have been reported to cause alterations and loss of mineral content in surface enamel after bleaching. These irregularities in enamel surface could result in more susceptibility to re-pigmentation, thereby adversely affecting the whitening treatment. Aim: To evaluate the susceptibility of teeth to re-pigmentation using two different bleaching materials, i.e. 35% hydrogen peroxide (H 2 O 2 ) and 16% carbamide peroxide. Subjects and Methods : In this study, 30 extracted teeth were divided in three groups. Group I was bleached with 35% H 2 O 2 , Group II with 16% carbamide peroxide, and Group III was used as control. They were then stained with silver nitrate stain to evaluate their susceptibility to pigmentation after bleaching. The shade of each tooth was recorded before bleaching, after bleaching, and after pigmentation using a Vita shade guide. Results: Results showed that after staining with silver nitrate, the teeth in all groups became darker but the amount of change in the shade value of the samples was different for the two groups. The change of shade was greater for Group I as compared to Group II after pigmentation. This change in shade between Groups I and II was found to be statistically significant using one-way ANNOVA test (P < 0.05). Conclusions : Thus, we concluded that susceptibility to pigmentation increases after bleaching. Furthermore, pigmentation is greater when H 2 O 2 is used for bleaching.