INTRACANAL ISOLATING BARRIERS AS THEY RELATE TO BLEACHING

Four restorative materials were evaluated for effectiveness as intraca nal isolating barriers to prevent leakage of bleaching agents into the coronal part of the root canal. Fifty-five teeth were stained in vitr o, instrumented, and filled with gutta-percha. In the experimental gro ups, gutta-percha was removed 2 mm apical to the labial cementoenamel junction, and an intracanal isolating barrier (zinc oxide-eugenol, IRM , Ketac-Cem, or Scotchbond Multipurpose) was placed even with the faci al and proximal cementoenamel junction areas in a sloped manner. All w ere bleached with a thermocatalytic and walking bleach technique until the crown was one shade lighter than the original shade. The roots we re then examined for the occurrence of bleaching. The results indicate that none of the materials used was a totally effective intracanal is olating barrier. Although a significant difference was found when IRM was compared with Ketac-Cem or Scotch-bond Multipurpose (p < 0.05), al l restorative materials evaluated showed a high incidence of leakage a s demonstrated by bleached roots. There was no significant difference between zinc oxide-eugenol and IRM.