Push-Out Bond Strength of Calcium Silicate-Based Sealer to Root Canal Walls After Three Retreatment Techniques

Objective: To compare the push-out bond strength of calcium silicate-based sealer to root canal walls after three retreatment techniques in teeth with initial treatment with gutta-percha/AH plus. Materials and methods: Forty human single-rooted maxillary anterior teeth were decoronated to standardize with a root length of 16 mm. The roots were randomly divided into four groups of 10 roots each. The control group was performed without retreatment. The experimental groups were obturated with AH Plus® followed by retreatment using three retreatment techniques as follows; Mtwo R®, Mtwo R® with GuttaClear, and Mtwo R® with Xylene after 7 days of initial treatment. All samples were re-obturated with iRoot SP®and were stored for 7 days. Sections of 2 mm thickness was performed perpendicularly to the long axis to obtain 3 slices per root, and then loaded by a Universal Testing Machine until dislodgement. The maximum load was recorded in MPa and specimens were inspected for failure mode. The data were analyzed by One-way ANOVA and Tukey’s Test with a significance level of 0.05. Results: The highest bond strength was expressed in non-retreatment group followed by retreatment groups. From statistical analysis, at the coronal and middle levels, the bond strength between control group and Mtwo R group did not show significant differences, however, the Mtwo R group was superior to Mtwo R with both gutta-percha solvents. At the apical level, no statistically significant difference was noticed. The pattern of filling dislodgement as cohesive failures was predominantly observed. Conclusion: The use of rotary instrument to remove gutta-percha/AH plus is appropriate for retreatment gutta-percha/calcium silicate in term of push-out bond strength.