The effect of root canal preparation on microleakage within endodonticallytreated teeth: an in vitro study

Aim The purpose of this study was to evaluate the effects of smear layer an d canal instrumentation on leakage in root-filled teeth. Methodology Six groups (n = 12) of freshly extracted human canines and prem olars with closed apices and single roots were used. Groups A, B, C, and D were instrumented with engine-driven rotary nickel-titanium MCXIM files and Groups E and F were instrumented with conventional stainless steel hand fi les. Groups A, C, and E were flushed with 3.0 mL of 17.0% REDTA to remove t he smear layer prior to obturation. All teeth were flushed with 5.25% NaOCl , then obturated with AH-26 sealer and either the lateral condensation (Gro ups C-E) or thermomechanical compaction technique (Groups A and B). Copper wire was placed coronally in contact with the gutta-percha in each tooth an d, after immersion in 0.9% NaCl solution, a 10 volt dc voltage was connecte d between each tooth and a stainless steel electrode. The current flow in t he circuit was observed for 45 days. One way ANOVA and Duncan's Multiple Ra nge Test were used to compare Groups A-F at time intervals of 10, 20, 30 an d 45 days and identify statistically significant differences. Results Significantly less microleakage occurred when the smear layer was r emoved and when the canals were obturated with thermoplasticized gutta-perc ha. Canals instrumented with engine-driven NiTi files exhibited less leakag e than hand-instrumented canals irrespective of obturation method. Conclusions Smear layer removal is beneficial to root canal sealing. Obtura tion with thermoplasticized gutta-percha provides a superior seal whilst ca nal instrumentation with engine-driven NiTi files reduces the extent of mic roleakage in root canals.