The walking bleach procedure: An in vitro study to measure microleakage offive temporary sealing agents

The purpose of this study was to compare the in vitro sealing capacity of f ive materials, each used as a temporary sealing agent for the walking bleac h technique. All teeth received traditional biomechanical root canal instru mentation, after which the walking bleach agent was placed in the pulp cham ber space. The occlusal access was sealed with one of five temporary materi als: two hydraulic filling materials, a photoactivated resin composite, a z inc oxide-eugenol cement, and a zinc oxide phosphate cement with/without th e placement of a piece of rubber sheet that was placed as a barrier to isol ate filling material from the bleaching agent. All teeth were stored in a 1 % solution of Alcian blue with thermal cycling stress. After 1 wk, they wer e sectioned longitudinally, and ranked by graded scores of 0 to 3, accordin g to the degree of the dye penetration. Significantly less dye microleakage was observed in the two hydraulic materials than in the photoactivated res in. Both zinc oxide-eugenol and zinc phosphate cements showed a considerabl e amount of microleakage. There were no significant differences between the groups with and without a rubber sheet. Our data demonstrate that hydrauli c filling materials provide the most favorable cavosurface seal when they a re firmly packed into the cavity space to prevent microleakage.