Accuracy of different electronic apex locators for working length determination in simulated apical root resorption: an in vitro study

This in vitro study aimed to evaluate the effect of simulated apical root resorption (ARR) on the accuracy of working length (WL) determination using the Root ZX mini, Woodpex III Gold Plus, and X-Smart Pro+ electronic apex locators (EALs), and to compare the measurement performance of different devices in the presence of resorption. The study included 40 extracted mandibular premolars with straight canal morphology, a single root, and a single canal. Actual WL was determined using a #15 K-file under ×6 magnification. Simulated ARR was created by preparing a 1-mm-diameter circular cavity centered on the apical foramen, and electronic WL was measured before and after simulated ARR using the three EALs. Measurements were repeated three times, and the mean value was used in the analyses. Measurement error was calculated as the difference between electronic WL and actual WL. Accuracy rates were calculated within tolerance intervals of ± 0.5 mm and ± 1.0 mm from the actual WL. Data were analyzed using Robust ANOVA, Robust t-test with Holm correction, and Fisher’s exact test with Monte Carlo correction ( p < 0.05). The type of EAL ( p = 0.031), ARR ( p < 0.001), and the interaction between these two factors ( p = 0.004) significantly affected WL measurements. ARR resulted in increased WL measurements for all devices. After simulated ARR, the accuracy rates within ± 0.5 mm were 57.5% for the Root ZX mini, 45.0% for the Woodpex III Gold Plus, and 92.5% for the X-Smart Pro+. The X-Smart Pro+ showed the highest measurement accuracy and largely maintained this accuracy after ARR. Furthermore, the presence of resorption did not have a significant effect on measurement accuracy ( p = 0.246). In contrast, the Root ZX mini and Woodpex III Gold Plus showed a significant decrease in measurement accuracy in the presence of resorption ( p < 0.001). Overall, the lowest measurement accuracy was observed with the Woodpex III Gold Plus. Within the limitations of this in vitro study, simulated ARR negatively affected the accuracy of WL determination using EALs. However, this effect varied depending on the EAL used. Among the evaluated devices, X-Smart Pro+ best maintained WL measurement accuracy after simulated ARR.