Improved Root Canal Disinfection through Extended Sodium Hypochlorite Exposure and Renewal after Preparation...

This study evaluated whether extending sodium hypochlorite (NaOCl) contact time with periodic renewal after preparation enhances root canal disinfection compared with a standard continuous-irrigation protocol.

Twenty-eight bovine incisors were contaminated with Enterococcus faecalis (ATCC 29212) for 28 days. Specimens were assigned to 2 experimental groups (n = 10) and 2 controls (positive, n = 4; negative, n = 4). Experimental canals received either standard continuous irrigation (20 mL 1% NaOCl over 4 min) or an extended protocol, in which 5 mL 1% NaOCl was left in situ for 5 min and replenished over 4 cycles, with a total of 20 mL. All canals were subsequently irrigated with 6 mL 17% ethylenediaminetetraacetic acid and 6 mL 1% NaOCl under ultrasonic activation, followed by NaOCl neutralization. Microbiological samples were collected at baseline (S1), after primary irrigation (S2), and after final irrigation/activation (S3) using paper points and Hedström file scrapings. Colony-forming units (CFU) were quantified on Mitis Salivarius agar. Statistics comparison was performed with Kruskal-Wallis and Mann-Whitney U tests (α = 0.05).

Negative controls confirmed asepsis, and positive controls verified bacterial viability. Both irrigation protocols significantly reduced CFU counts at S2 and S3 compared with baseline (P < .05). The extended protocol yielded lower CFU counts than standard irrigation at both postirrigation time points (P < .05). Overall bacterial reduction from baseline to final sampling (S1→S3) was significantly greater for the extended protocol (P = .027), while intermediate reduction (S1→S2) did not differ between groups (P > .05).

The extended protocol resulted in a significantly greater microbial reduction compared with standard continuous irrigation.