Abstract: Objective To compare the efficacy of a novel rotary file system (EZ Pass) with two well-established rotary file systems (ProTaper Gold and ProTaper Next) for removal of Enterococcus faecalis from infected root canals in extracted maxillary central incisors. Methods Models of root canal infection with Enterococcus faecalis were constructed in 51 extracted single-rooted maxillary central incisors. One of the incisor model with infected root canal was demineralized, sectioned, and stained with Brown & Brenn technique for microscopic observation; The remaining 50 models were randomly divided into 5 groups (n=10) for treatment with EZ Pass, ProTaper Gold, ProTaper Next, 0.9% NaCl or 2% NaOCl. Samples were collected from the infected root canals before and after the treatments to assess the percent reduction and logarithmic reduction value of CFU in the root canals. Results The incisors with root canal infection by Enterococcus faecalis showed obvious biofilms on the surface of the root canals and massive bacterial invasion deep into the dentinal tubules, with a maximum invasion depth of about 475 μm. The percent reduction of the CFU did not differ significantly after treatments with EZ Pass, ProTaper Gold, ProTaper Next and 2% NaOCl (P>0.05), but all these treatments resulted in significantly greater reduction than 0.9% NaCl (P<0.01). The logarithmic reduction of CFU were comparable after treatments with EZ Pass (1.47 ± 0.12), ProTaper Gold (1.74 ± 0.14) and ProTaper Next (1.63±0.17; P>0.05). Conclusion EZ Pass can significantly reduce the bacterial load in infected root canals with an equivalent bacterial elimination capacity to ProTaper Gold and ProTaper Next.

Key words: infected root canals; bacterial elimination; EZ Pass; ProTaper Next; ProTaper Gold