Apical Extrusion of Intracanal Bacteria with Single File and Multifile Rotary Instrumentation Systems

Instrumentation techniques may cause extrusion of microorganisms and their products into the periapical region resulting inflammation and treatment failure. The aim of this ex vivo study was comparing the apical bacterial extrusion in canals prepared with single file versus multiple file rotary systems.

Ninety-two human single-rooted mandibular first premolars were used. Endodontic access cavities were prepared, and root canals were contaminated with an Enterococcus faecalis (E. faecalis) suspension. The samples were incubated at 37°C for 30 days; the contaminated teeth were divided into four groups of 20 specimens each (1: Reciproc, 2: Mtwo, 3: Neoniti A1, 4: Safesider). Six teeth were not infected and each were prepared with one of the above instruments were considered as negative and six teeth which had been previously infected, were used as positive control groups. Extruded bacteria from the apical foramen during instrumentation were collected into vials containing 0.9% NaCl. The microbial samples were taken from the vials and incubated in brain heart agar medium for 24 h. The resulting bacterial titer, in colony-forming units per mL, was determined. The data entered into SPSS 18 software and were analyzed by Kruskal-Wallis and Mann-Whitney U-tests at 0.05 significance level.

Mtwo multifile system showed significantly less bacterial extrusion than Safesider (P = 0.015) and Neoniti A1 (P = 0.042) but did not show significant difference with Reciproc system (P = 0.25).

All instrumentation systems extruded bacteria beyond the apical foramen. However, this study showed that Mtwo multifile rotary system extruded fewer bacteria.