Chairside Sterilization of Endodontic Files and Gutta-Percha Cones Using 8.25% Sodium Hypochlorite

Introduction: Sodium hypochlorite is now available in a higher concentration of 8.25%. No research has been published examining this higher concentrations effectiveness in sterilizing endodontic files and gutta-percha cones. Objective: The purpose of this in-vitro study was twofold: to determine the percentage of bacterial contamination of files and cones taken directly from their packaging and to determine if files and cones inoculated with Staphylococcus epidermidis could be sterilized by immersion in 8.25% sodium hypochlorite. Methods: Part 1: 100 files and 100 cones were transferred from original packaging into individual sterile tubes containing 10 ml of sterile broth, incubated for 72 hours and examined for turbidity. Part 2: 300 files and 300 cones were inoculated with Staphylococcus epidermidis followed by immersion in 8.25% sodium hypochlorite. Files were immersed for 1, 2, or 5 minutes and cones for 30, 45, and 60 seconds. Files and cones were transferred, incubated, and examined as described in part 1. Fishers exact test compared frequencies of turbidity by immersion time and post-hoc comparisons were completed to determine significance in turbidity by brand (alpha<0.05). Results: Three out of 100 files and 3 out of 100 cones produced turbidity when tested directly from the manufacturers packaging. File turbidity ranged from 3.0% after immersion for 2 minutes to 12.0% after immersion for 5 minutes with significant difference by immersion time when combining brands (P=0.046). Cone turbidity ranged from 0% after immersion for 45 sec to 9.0% after immersion for 60 sec with a significant difference in turbidity by immersion times when combining brands (P<0.001). Conclusions: Immersion in 8.25% sodium hypochlorite did not guarantee sterility at any time tested for either files or gutta-percha cones.