AIM: To evaluate the accumulation of hard-tissue debris when using the Self-adjusting File (SAF) system in mesial roots of mandibular molars with isthmuses and to compare it with that occurring when the ProTaper file system was used.
METHODOLOGY: Forty extracted human mandibular molars with joining mesial root canals and an isthmus between the two canals were randomly assigned to two experimental groups and scanned using micro-computed tomography. Root canals in the control group (N = 20) were instrumented using the ProTaper rotary system until F3. Irrigation with 1 mL of 3% NaOCl solution was applied after each instrument. Root canals in the experimental group (N = 20) were prepared using the SAF for 4 min, with continuous irrigation (3% NaOCl, 4 mL min(-1)). After rescanning, canals in both groups were further irrigated with 5 mL of 17% EDTA for 2 min. After final scanning, the per cent value of total canal system volume filled with hard-tissue debris was calculated. Statistical analysis was performed using Mann-Whitney U-test; the alpha-type error was set at 1%.
RESULTS: Instrumentation of the root canals with ProTaper left 10.1% (IQR 5.2) of the total canal system volume filled with hard-tissue debris while preparation with the SAF left 1.7% (IQR 1.6). This difference was highly significant (P < 0.0001). After subsequent EDTA irrigation, these values were significantly reduced (P < 0.01) to 7.9% (IQR 4.1) and 1.3% (IQR 0.8) in the ProTaper and SAF groups, respectively.
CONCLUSION: Preparation with the SAF system resulted in less hard-tissue debris accumulation in isthmus-containing root canal systems compared with instrumentation with ProTaper rotary files.