Apical extrusion of intracanal bacteria following use of various instrumentation techniques
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To evaluate the number of bacteria extruded apically from extracted teeth ex vivo after canal instrumentation using a manual technique and three engine-driven techniques utilizing nickel-titanium instruments (K3, RaCe, and FlexMaster). Seventy extracted human mandibular premolar teeth with similar dimensions were used. Access cavities were prepared and root canals were then contaminated with a suspension of Enterococcus faecalis and then dried. The contaminated roots were divided into four experimental groups of 15 teeth each and one control group of 10 teeth. G1. RaCe group: the root canals were instrumented using RaCe instruments. G2. K3 group: the root canals were instrumented using K3 instruments. G3. FlexMaster group: the root canals were instrumented using FlexMaster instruments. G4. Manual technique group: the root canals were instrumented using K-type stainless steel instruments. G5. Control group: no instrumentation was attempted. Bacteria extruded from the apical foramen during instrumentation were collected into vials. The resultant microbiological samples were removed from the vials and then incubated in culture media for 24 h. The number of colony-forming units (CFU) was determined for each sample. The data obtained were analysed using the Kruskal-Wallis one-way analysis of variance and Mann-Whitney U-tests, with alpha = 0.05 as the level for statistical significance. There was a significant difference between experimental-control and engine-driven-manual technique groups (P < 0.05). The manual technique was associated with the greatest extrusion of microorganism. All instrumentation techniques extruded intracanal bacteria apically. No significant difference was found in the number of CFU among the engine-driven techniques; manual techniques extruded significantly more microorganisms.