Accumulated hard tissue debris levels in mesial roots of mandibular molars after sequential irrigation steps.

AIM To investigate the impact of sequential irrigation procedures on accumulated hard tissue debris (AHTD) levels in canal systems in mesial roots of human mandibular molars after instrumentation. METHODOLOGY Based on pre-scans in a micro-computed tomography (μCT) system, 20 extracted human mandibular molars with joining mesial root canals and an isthmus between these were selected. Canals were instrumented using the ProTaper rotary system until the F3 instrument reached working length. A 1% NaOCl solution was applied during instrumentation, followed by a final 5-mL flush to working length. Subsequently, canals were irrigated with 5 mL of 17% EDTA. Thereafter, passive ultrasonic irrigation (PUI) was performed using 1% NaOCl on three occasions each for 20 s. Percent values of total canal system volume filled with AHTD were calculated based on high-resolution scans after each irrigation step. Data was compared using repeated measure anova followed by paired t-test for individual comparisons. Bonferroni's correction was applied for multiple testing; the alpha-type error was set at 1%. RESULTS Instrumentation of the root canals in conjunction with 1% NaOCl irrigation left 6.9 ± 4.2 vol.% of the total canal system volume filled with AHTD. This value was significantly (P < 0.01) reduced to 4.9 ± 3.6 vol.% after EDTA irrigation. Subsequent PUI resulted in a further significant (P < 0.01) reduction to 3.7 ± 2.8 vol.%. CONCLUSIONS In this quantitative study on AHTD reduction, a significant effect of EDTA and PUI was shown. However, approximately half of the debris that accumulated during instrumentation remained in the canal system.