The objectives of the present study were to assess the antibacterial effectiveness of two sodium hypochlorite (NaOCl) concentrations (2.5% and 5.25%) activated by means of two techniques, passive ultrasonic irrigation (PUI) and XP-endo® Finisher (FKG Dentaire SA, La Chaux-de-Fonds, Switzerland) (XPF) against bacteria growth in intracanal mature biofilm. Our aim was to determine if the effect of heating up NaOCl at body temperature (BT) contributed to an improvement of the efficacy of XPF. Sixty-two single-canal human roots previously instrumented were infected with E. faecalis inoculum at 0.5 McFarland and incubated at 37 °C for two weeks. Twelve specimens were randomly selected as positive control, and the remaining fifty were divided into five experimental groups (n = 10). The first two were irrigated with 2.5 vs. 5.25% NaOCl at room temperature (RT), activated with PUI, and the other three were irrigated with XPF. Of these three, two were irrigated using 2.5 vs. 5.25% NaOCl at RT and one was irrigated with 5.25% NaOCl at BT. Our results showed that NaOCl was effective in biofilm removal for all experimental groups (p > 0.05), especially in the groups irrigated with 5.25% NaOCl at room temperature (RT) activated with PUI and the group treated with 5.25% NaOCl at BT with XPF. These groups were the most successful ones (p < 0.001). NaOCl, activated with XPF, was as effective as PUI in biofilm removal from the apical third of the canal when it was used at higher concentration and heated up. This study indicates that XPF only reached the efficacy of PUI when NaOCl was heated up.
Keywords: Enterococcus faecalis biofilm; XP-endo® Finisher (XPF); passive ultrasonic activation (PUI); root canal irrigation; sodium hypochlorite (NaOCl).