Authors: Rotstein I, Zyskind D, Lewinstein I, Bamberger N.
Title: Effect of different protective base materials on hydrogen peroxide leakage during intracoronal bleaching in vitro.
Journal: J Endod
Date: Mar 1992
Citation: 18(3): 114-117
Category: Bleaching/Tooth Whitening
Evidence-based Ranking: 5
Purpose/Objectives: To examine the preventative effect of a protective base placed over the root canal obturation on the radicular penetration of hydrogen peroxide during intracoronal bleaching and to compare the efficacy of different materials used for such purposes.

Materials & Methods: Two tests were done. A first group of 72 bovine teeth were sectioned and canal spaces enlarged. The teeth were divided into 4 experimental groups and based with either IRM, ZOE, Durafill composite, or Fuji II glass ionomer. Radicular 30% H2O2 penetration of each group was measured at 4 different levels (initial, 1mm, 1mm and .5mm reduction of base material). The second test was performed on 20 human teeth. The teeth were prepared and filled by LC w/ AH26 sealer. Cementum preps were done with a #8 round bur to create areas of open dentinal tubules at the level of the CEJ. The experiment was done in 3 stages – no protective base, a uniform layer of IRM over the GP to the level of the CEJ, and IRM removed 0.5mm below the CEJ. Bleaching was performed and radicular 30% H2O2 penetration was assessed.

Results: No materials during the bovine test leaked when the base thickness was 2mm. When reduced to 1mm some leakage occurred, but none was statistically significant for the 4 different materials. At 0.5mm penetration in each group increased and composite proved better than glass ionomer at this level. During the human test when no base was used, 90% of the teeth showed penetration. When a layer of IRM was placed to the CEJ one tooth (5%) showed penetration, but when reduced by 0.5mm 4 teeth (20%) leaked.

Author’s Conclusion: It is recommended that a protective base be placed to the CEJ level before intracoronal bleaching to prevent possible H2O2 leakage and problems.

Validity of Conclusion: The results seem valid

Reviewer’s Comments: The author indicates IRM and ZOE have the potential to reduce the effectiveness of composite resin bonding to natural tooth structure and should be considered when deciding what to use for a base.