In vitro evaluation of tooth discoloration induced by regenerative endodontic therapy and the effectiveness of the walking bleach technique

Background: The present study evaluated the coronal discoloration induced by different materials or blood as well as the effect of internal bleaching on discoloration. Methods: After tooth color measurement at baseline with a sphere spectrophotometer (CIE L*a*b*), the root canals of molars were partially filled with white mineral trioxide aggregate (MTA), triple antibiotic paste (TAP), or a cotton pellet with bovine blood (control) was placed into the pulp chamber. The color changes were assessed at 30, 60, and 180 days after the procedure. Following the discoloration, internal bleaching was performed with a mixture of sodium perborate and hydrogen peroxide inserted into the pulp chamber, and this mixture was replaced weekly for 3 weeks. At baseline, after staining and after bleaching, the data of each color parameter were individually analyzed by one-way ANOVA, while differences in pooled color changes (∆E00) were assessed by two-way repeated measures ANOVA (α = 0.05). Results: After the staining period, the TAP-stained specimens were darker and greener than the other specimens, and no difference was observed between the teeth stained with blood and those stained with MTA. The walking bleach technique resulted in an improved tooth color without a difference in the color changes among the different groups. Conclusion: The TAP-stained specimens had the greatest tooth discoloration, and the discoloration remained the highest after the walking bleach technique. Practical implications: This in vitro study demonstrated that TAP yielded higher tooth discoloration, and this color might hinder a satisfactory tooth color from being obtained with the walking bleach technique.