Effect of Retreatment Protocols on the Push-Out Bond Strength of Hydraulic Calcium Silicate Cement in Open-Apex Teeth.

Abstract

Objectives: During retreatment, complete removal of previous obturation materials is essential, as remnants may compromise adhesion. This study evaluated the effect of four retreatment protocols on the push-out bond strength of RetroMTA (BioMTA, Seoul, Korea), a fast-setting calcium silicate-based material, used as an apical barrier in teeth with open apices that had been previously obturated with gutta-percha and AH26 sealer.

Materials and methods: Sixty extracted single-rooted human teeth were instrumented and obturated using lateral condensation and then stored in phosphate-buffered saline (PBS) at 37°C for 4 weeks. Specimens were randomly assigned to four groups (n = 15): mechanical retreatment, mechanical retreatment with passive ultrasonic irrigation (PUI), chloroform-assisted retreatment, and chloroform-assisted retreatment with PUI. After retreatment, the apical 5 mm of each canal was obturated with RetroMTA and stored for another 4 weeks. Push-out bond strength was measured using a universal testing machine. Data were analyzed using two-way ANOVA. The significance level was set at α = 0.05.

Results: Chloroform use did not significantly affect the push-out bond strength of RetroMTA (p = 0.349). In contrast, PUI significantly increased bond strength regardless of solvent use (p < 0.001). No significant interaction was observed between chloroform and PUI.

Conclusion: Within the limitations of this ex vivo study, PUI significantly enhanced the bond strength of RetroMTA to root dentin, whereas chloroform provided no additional benefit.