Effect of maintaining apical patency with a CM instrument on apical transportation and centering ability

The aim of this study was to assess the impact of the apical patency technique on apical transportation and centering ability of a controlled memory (CM) instrument in the apical region using cone-beam computed tomography (CBCT). Sixty distobuccal canals of extracted maxillary molars were assigned to three groups (n = 20) based on the patency length achieved using the Easy ProDesign Logic (EPL) 25.01 file: Group A - 1 mm beyond the apical foramen; Group B - at the apical foramen; and Group C - 1 mm short of the apical foramen (no patency). Each group was then subdivided into two subgroups (n = 10) according to the working length used for root canal preparation with the EPL 25.05 file: A1, B1, C1-I, and C1-II - 1 mm short of the apical foramen and A2, B2 - at the apical foramen. CBCT images were acquired at three time points: pre-patency, post-patency, and post-instrumentation. The scanned images were analyzed using the E-VOL DX software. No statistically significant difference in apical transportation was found between the groups after patency or after instrumentation (p < 0.05), irrespective of the measurement levels (0.5, 1, and 2 mm short of the apical foramen). A significant difference in the centering ability of the patency instrument was observed only at 2 mm short of the foramen (p < 0.05). The B2 group exhibited a higher centering ability, with a statistically significant difference compared to the A2 group (p < 0.05), observed only at 0.5 mm short of the foramen. In conclusion, maintenance of apical patency using the EPL instrument had no influence on apical transportation; however, it may slightly affect the centering ability of the root canal.