effect of different protective bases on ph changes and hydrogen peroxide microleakage during intracoronal bleaching

Objectives: this study aimed to evaluate the ph changes and penetration of hydrogen peroxide into radicular dentin when different protective bases were used with and without a bonding agent.materials and methods: in this in-vitro experimental study, 70 single-rooted bovine teeth were instrumented and obturated with gutta-percha. the gutta-percha was removed 3mm below the cementoenamel junction (cej) and the teeth were divided into seven groups (n=10). in each group, 2mm base (1mm apical to the cej) was applied as follows:  theracal lc, theracal lc plus se bond, lime-lite, lime-lite plus se bond, ionoseal, ionoseal plus se bond, and resin-modified glass ionomer (rmgi). the teeth were placed in vials containing distilled water, and ph values and molar concentration of the medium surrounding the teeth were recorded immediately after internal bleaching with 35% hydrogen peroxide. the ph values were also recorded at 1, 7, and 14 days following renewal of the medium. data were analyzed with t-test, one-way anova, and kruskal-wallis test. results: after bleaching, the medium ph became acidic in all groups. there were no significant differences among groups in the mean ph of the medium after bleaching (p=0.189). moreover, there were no significant differences among the study groups with respect to hydrogen peroxide concentration (p=0.895).conclusion: intra-orifice barriers such as light-cure resin-modified calcium hydroxide, light-cure resin-reinforced glass ionomer, and light-cure calcium silicate can be as effective as rmgi in providing coronal seal during intracoronal bleaching.