Micro-CT Study of the In Vivo Accuracy of a Wireless Electronic Apex Locator

Introduction: This study aimed to compare the in vivo accuracy of Wirele-X and RootZX II electronic apex locators (EALs) in determining the position of the major foramen using micro–computed tomography (micro-CT) as the analytical tool. Methods: Eleven vital teeth planned for extraction from 5 patients were used. After conventional access cavity preparation, root canals were flared and negotiated up to the apical third with sizes 08 and 10 K-files followed by irrigation with 2.5% NaOCl. K-type files were used to determine the working length of the selected canals using Root ZX II and Wirele-X apex locators until their numeric displays read “0.0.” After fixing the silicon stop to the file, teeth were extracted and imaged in a micro-CT device using a double-scan protocol. Image stacks, with and without the file in the root canal, were then co-registered and the measurement error calculated as the absolute difference between the tip of the file and the major foramen. Positive and negative values were recorded when the file tip was detected beyond or short of the major foramen, respectively. Accuracy was determined on stable measurements within ± 0.5 mm when the file tip did not extend beyond the major foramen. The χ² test was applied to compare the ability of the EALs to detect the position of the major foramen, and the t test for dependent variables was used to verify differences in the 2 measurements obtained in each tooth. Significance level was set at 5%. Results: Within a tolerance level of ± 0.5 mm, no significant differences were observed between the tested EALs regarding the absolute distance values (P = .82) or in their ability to detect the position of the major foramen (χ² = 0.2588; P = .6109). The accuracy of the Root ZX II and the Wirele-X apex locators within ± 0.5 mm were 81.8% and 90.9%, respectively. Conclusions: Root ZX II and Wirele-X performed similarly regarding the in vivo detection of the major foramen. Using strict criteria, the accuracy of the Root ZX II and the Wirele-X apex locators were 81.8% and 90.9%, respectively.