Authors: Freccia WF, Peters DD, Lorton L, Bernier WE.
Title: An in vitro comparison of nonvital bleaching techniques in the discolored tooth.
Journal: J Endod
Date: Feb 1982
Citation: 8(2):70-7
Category: Bleaching/Tooth Whitening
Evidence-based Ranking: 5
Purpose/Objective: To compare and evaluate the results of the 3 commonly used nonvital bleaching techniques, the thermocatalytic, the walking bleach and the combination.

Materials and methods: 39 extracted anterior teeth were immersed in 5.25% NaOCl to loosen extrinsic surface debris. Each tooth was arranged from lightest to darkest. The lightest, the darkest and the median teeth served as controls. The remaining 36 teeth were the experimental teeth; sets of three from the arranged sequence were taken and a tooth (from each set of three) was randomly assigned to a particular bleaching technique. A layer of 2mm of IRM was placed 2mm below the CEJ. The 3 different bleaching techniques were performed as follows. Thermocatalytic technique: an electric bleaching instrument was used as a heat source. A dry cotton pellet was placed in the pulp chamber and was saturated with 35% hydrogen peroxide. Heat was applied (4 minutes) and the cotton pellet was replaced for 3 repetitions for a total of 12 minute heating. The procedure was then repeated after 7 days and the time of actual bleaching was recorded. Evaluations were done at 1 week and 4 weeks, recording color change using the shade guide. Walking bleach technique: a mixture of Superoxol and powdered sodium perborate were combined to make a thick paste. This was carried to the pulp chamber until the lingual access was filled. The paste was blotted dry with a cotton pellet and temporized. The procedure was then repeated after 7 days. Shade changes were also recorded. Combination technique: thermocatalytic technique then walking bleach technique was performed on the specimens. The process was repeated after 7 days. The time and the shade changes were also recorded. The efficiency of each bleaching technique was based on the degree to which the experimentally stained teeth were returned to their original shade.

Results: There were no differences among the three techniques in their ability to bleach the crowns of the experimental teeth. The crowns of 34 teeth were bleached lighter than their original shades, 2 teeth were bleached back to their original shades.

AuthorÂ’s Conclusions: The 3 techniques were equally effective in bleaching crowns in which pulpal hemorrhage was the primary cause of discoloration. The walking bleach technique used significantly less time.

ReviewerÂ’s comments: If there is no significant difference in the 3 techniques, the most efficient technique should be used, which is the walking bleach technique. Also, the study showed that the techniques that used heat caused diffusion of the agent through the dentinal tubules. The article implies then that the walking bleach is the best bleaching technique.