Superalkaline reductive solution versus sodium hypochlorite for root canal irrigation: a comparative in vitro study

To evaluate the effectiveness of a Superalkaline reductive solution (SRS) as a root canal irrigant in terms of smear layer removal, antibacterial activity, cytotoxicity, and dentinal tubule permeability. Forty-five single-rooted teeth were instrumented and irrigated with 3% NaOCl, SRS, or 0.9% NaCl. All protocols included EDTA gel, followed by PUI activation of the assigned irrigant for final irrigation. Smear layer removal was assessed using Scanning electron microscopy (SEM) with scoring and ImageJ. Antibacterial efficacy against Enterococcus faecalis was evaluated in sixty-two single-rooted teeth using colony-forming units (CFU) analysis and SEM. Cytotoxicity was tested on L929 cells. Dentinal tubule permeability was assessed in thirty-six single-rooted teeth using confocal laser scanning microscopy (CLSM) and ImageJ. Based on scoring system evaluation, SRS group was superior to 3% NaOCl and 0.9% NaCl groups in smear layer removal across all root thirds ( P < 0.05). In the middle and apical thirds, the SRS group exhibited the highest the percentage of open dentinal tubules among the three groups, followed by the 3% NaOCl group( P < 0.05).For dentinal tubule area percentage, the SRS group showed superiority in the apical third( P < 0.05). SRS showed slightly lower efficacy against Enterococcus faecalis than 3% NaOCl. 3% NaOCl exhibited severe cytotoxicity, whereas SRS showed no toxicity. For dentinal tubule permeability at 3 mm, the SRS group showed superior ( P < 0.05). Under identical conditions, SRS group was superior to 3% NaOCl group in smear layer removal and dentinal tubule permeability, with no cytotoxicity, but its antibacterial efficacy was inferior to 3% NaOCl. Evaluating the smear layer removal, antibacterial activity, cytotoxicity, and dentinal tubule permeability of SRS is essential to ensure its efficacy and safety for clinical application.