Sealing capacity of a flowable composite, as a protective base, with different conditioning methods in nonvital bleaching.

Objective: The purpose of this in vitro study was to determine the microleakage of a nano-flowable composite used as a protective base, applied with different conditioning methods in nonvital bleaching.
Materials and Methods: Forty root-filled teeth were divided into four treatment groups (n = 10 per group): group 1--Er:YAG laser etching + Adper Single Bond 2; group 2-37% phosphoric acid + Adper Single Bond 2; group 3--Adper Prompt L-Pop; and group 4--No treatment. A nano-flowable composite (Filtek Supreme Flow) base was used in each group. For a 24-h period, 40% hydrogen peroxide solution was applied to the pulp chambers, and they were subsequently subjected to a dye (silver nitrate) challenge for 4 h. After the dye was washed out with water, each tooth was cut in half and both halves were exposed to sunlight for 2 h to promote oxidation of the dye, turning it black. Finally the sections were examined under 4x magnification to determine the degree of leakage as assessed with a four-point scale. Statistical analysis was performed with the Mann-Whitney U test.
Results: There were no significant differences between groups 1, 2, and 3 (p > 0.05), but the teeth in group 4 had significantly higher microleakage scores than the teeth in the other groups (p < 0.05).
Conclusion: Self-etching adhesive application, Er:YAG laser etching, and phosphoric acid etching combined with an adhesive system all showed similar microleakge scores when a nano-flowable composite was applied as a protective base in nonvital bleaching.