Antibacterial efficacy of octenidine, sodium hypochlorite, and their combination against multispecies endodontic biofilms: an in vitro CLSM study

The current study used confocal laser scanning microscopy (CLSM) to assess the antibacterial activity of octenidine hydrochloride (OCT) both by itself and in combination with sodium hypochlorite (NaOCl) on the eradication of biofilms. Forty dentin blocks were inoculated with a biofilm consisting of Enterococcus faecalis , Staphylococcus aureus , Pseudomonas aeruginosa , and Streptococcus mutans . After a 3-week incubation period, the resulting diverse biofilm was imaged using a scanning electron microscope (SEM). Five groups were formed: Saline solution (SS), 2% chlorhexidine (CHX), 5% NaOCl, undiluted OCT (containing 0.1% octenidine), and a 5% NaOCl / undiluted OCT mixture (90:10 ratio). Samples were subjected to the relevant agent for 5 min. The percentage of dead cell bacteria was evaluated using the Live/Dead BacLight Viability Kit dye under CLSM. Image analysis was performed with Image J software. The Kruskal-Wallis and Dunn’s tests were used to statistically assess the data, with a significance threshold of p < 0.05. CLSM images showed that the NaOCl alone eliminated the amount of bacteria similar to NaOCl/OCT mixture group ( p > 0.05) and significantly more bacteria compared to other solutions ( p < 0.05). NaOCl/OCT mixture group was also similar to the OCT alone group ( p > 0.05), while CHX and SS groups represented the least amount of dead bacteria than other groups ( p < 0.05). Under the experimental conditions, the NaOCl/OCT combination demonstrated antibacterial activity comparable to NaOCl alone. While 5% NaOCl remained the most effective agent, the addition of OCT did not provide a statistically significant increase in antibacterial efficacy. SS and CHX exhibited significantly lower antibacterial effects.