Evaluation of sealing ability of Glass Ionomer, white MTA, and Super EBA as coronal plug in intra coronal bleaching

External resorption of cervical area is one of the worst side effects of bleaching in non vital teeth. One method for inhibition is placing a coronal plug into the canal's entrance. Therefore sealing ability of 3 materials including Super EBA, MTA and Glass Ionomer were examined in this research as coronal plug before bleaching procedure.Methods and Materials: Seventy single canal anterior teeth were chosen by simple randomization. After access cavity preparation, the canals were cleaned and shaped. Five teeth were used as positive control and five as negative control. Other sixty teeth were filled with gutta-percha and sealer using lateral condensation method. In the next step, 3mm of gutta percha was removed from the coronal part and a thickness of 2mm of one of the materials (GI, Super EBA, MTA) was placed as coronal plug. Then the teeth were bleached 3 times with an interval of 72h, using Sodium Perborate and 3% H2O2.Then the access cavities were completely cleaned and filled with 2% methylene blue for 24h. The sample teeth were washed, dried and sectioned and dye penetration was measured using magnifying glass and cullies. Data was analyzed by ANOVA and LSD tests. The average dye penetration was 3.23mm in MTA, 5.42mm in Super EBA and 1.76mm in GI group (p value = 0.018). Based on the results obtained from this study, glass ionomer was the best material for secondary seal before bleaching. Sealing ability of MTA was lower than GI, and of Super EBA was the least.