Micro-CT evaluation of canal shaping extent with apex locator–integrated endodontic motors: An in vitro study

INTRODUCTION: This in vitro study evaluated the extent accuracy of canal shaping to apical constriction (AC) with electronic apex locator (EAL)-integrated endodontic motors using micro-computed tomography (MicroCT). MATERIALS AND METHODS: Sixty single-canalled teeth were decoronated, scanned using microCT, and distributed into three groups: Rooter Universal, Tri Auto ZX II, and control group (n = 20 each). The working length (WL) was determined simultaneously during canal shaping using the auto-reverse function set at the 0.5 mark in the RU and TA groups. In the control group, the WL was measured before the shaping using Root ZX (J. Morita, Tokyo, Japan). In the three groups, canals were shaped using ProTaper Gold files (Dentsply Sirona, Ballaigues, Switzerland) until the preset mark was reached in the two experimental groups and to the measured WL in the control group. Afterwards, post-shaping microCT scans were taken. Scan superimposition was conducted to assess the absolute distance between the final shaping endpoint and AC. Negative and positive data were recorded when the measurements were found short or beyond the AC, respectively. Analysis of variance (ANOVA) and post-hoc Tukey tests were used to analyze the distance. The chi-square test was applied to analyze the accuracy of the measurements with respect to the AC. The significance level was set at 5%. RESULTS: No over-shaping beyond the apical foramen was found in any sample, and all systems showed similar accuracy when a tolerance of 0.5 mm was set ((V = 0.263, P = 0.126). However, the shaping extent to AC was closer in the control group than the RU (P = 0.001) and TA (P < 0.001), while RU and TA were similar (P = 0.588). CONCLUSIONS: The accuracy of WL determination was not affected by the tested EAL. However, the standalone EAL was more reliable at maintaining AC integrity.