Aim: The aim of this study was to analyze ex vivo the sealing properties of the resin-based endodontic sealer AH Plus modified by incorporating chitosan nanoparticles (AHCNp) compared with AH Plus without nanoparticles (AHPs). The materials were tested using a bacterial microleakage test method.

Methods: Twenty-two (n = 22) human-extracted lower premolars were randomly assigned to two experimental groups of 10 teeth (n = 10) each, while the remaining two teeth served as positive (n = 1) and negative (n = 1) controls. The teeth were autoclaved, and the root canals were chemomechanically prepared under sterile conditions. In Group 1, the canals were obturated with AHCNp and matched-taper single gutta-percha cones. In Group 2, the canals were obturated as in Group 1, except that AHPs was used as the sealer. All teeth were subjected to microleakage testing with an E. faecalis culture using a dual-chamber leakage model. The broth in the lower chamber was checked daily for turbidity for up to 90 days. Statistical significance was determined at P < 0.05.

Results: In Group 1, the root canals leaked significantly less (P < 0.001). In this group, three samples exhibited bacterial leakage, whereas in Group 2, eight samples leaked. The median survival time for both groups could not be calculated because it exceeded 90 days.

Conclusions: After 90 days, AHCNp was significantly more effective than AHPs in resisting coronal bacterial leakage. Longterm experimental and clinical studies are recommended to confirm these findings.