Aim:
Comparing the effect of Proanthocyanidin and Sodium thiosulfate solutions as final irrigants on the push-out bond strength of epoxy-resin sealer to sodium-hypochlorite-treated root dentin and studying the physicochemical properties of both solutions for potential routine use.

Methodology:
Thirty-three single-rooted extracted teeth were decoronated and mechanically-prepared using rotary NiTi instruments and irrigated with 2.5% sodium hypochlorite. Samples were randomly allocated into three groups according to the final irrigant: group1(control), Saline; group2, 6.5% proanthocyanidin, and group3, 5% sodium-thiosulfate. All samples were obturated using gutta-percha and AH-plus epoxy-resin sealer and then cross-sectioned and subjected to push-out bond strength test at different root levels.
For physicochemical evaluation, a sample of each experimental irrigant was tested for surface tension using the du-Noüy-ring method via force-tensiometer. Viscosity was tested using a rotational digital viscometer and pH was measured using a benchtop pH-meter.
Statistical analysis was performed using one-way ANOVA test followed by Tukey's post-hoc test for intergroup comparisons. Repeated measures ANOVA followed by Bonferroni post-hoc test were used for intragroup comparisons. The significance level was set at p ≤ 0.05.

Results:
Proanthocyanidin-treated group showed -significantly- the highest mean push-out bond strength values (~1.58 MPa) compared to other groups. Proanthocyanidin solution showed significantly lower mean surface tension (46.71 mN/m) and viscosity (37.43 KU). Sodium-thiosulfate showed a slightly alkaline pH (~8.2), while proanthocyanidin showed a slightly acidic pH (~5.8).

Conclusions:
Proanthocyanidin solution can improve the bond strength of epoxy-resin sealer to sodium-hypochlorite-treated dentin. It also revealed favorable physicochemical properties which make it promising for routine endodontic use.