Efficacy of antimicrobial solutions against polymicrobial root canal biofilm

To evaluate the antibiofilm activity of 2.5% sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX), 2% alexidine (ALX) and 0.2% cetrimide (CTR) alone and in combination on mature polymicrobial root canal biofilms on human dentine using confocal laser scanning microscopy (CLSM).

Twenty-eight human dentine specimens were infected for 21 days with microbial samples collected from infected root canals of three volunteers. Antibiofilm activity of the irrigating solutions was evaluated after 3 min of contact time under CLSM. For quantification purposes, bioimage_L software was used. The variables evaluated were the log₁₀ of total biovolume (μm³ ) and percentage of live cells (green) population. Statistical analysis of both variables was performed using an anova test and a post hoc Duncan test to determine significant clusters amongst groups. The variable green population percentage was previously subjected to the normalized Anscombe transformation.

The NaOCl group had a total biovolume and percentage of live cells significantly lower than the other groups (P ˂ 0.001). The addition of 0.2% CTR significantly increased the antimicrobial effect of 2% CHX (P ˂ 0.001). There were no significant differences between 0.2% CTR, 2% ALX and the combination of both (P ˂ 0.05).

Overall, 2.5% NaOCl dissolved and killed bacteria significantly more efficiently when used against polymicrobial mature biofilm on human dentine. Cetrimide improved the antimicrobial activity of chlorhexidine and alexidine.