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Influence of Apical Patency, Coronal Preflaring and Calcium Hydroxide on the Accuracy of Root ZX Apex Locator for Working Length Determination: An In Vitro Study

Aim: One of the main steps in a successful endodontic treatment is determining the correct working length (WL) of the root canal. In this regard, electronic apex locators (EAL) have been widely used for measuring the WL. The accuracy of EALs in determining the WL may be influenced by various factors. This study is aimed to evaluate the effects of apical patency, coronal preflaring, and calcium hydroxide on the accuracy of the EAL. Materials and Methods: In this in vitro study, 20 central incisor single-rooted human teeth with fully formed apex were considered. Then, samples were randomly divided into two study groups, ten samples in each group. The WL was determined and recorded at 0.5 mm distance to the apex using Root ZX apex locator before and after creating patency, coronal preflaring, and calcium hydroxide administration. All WLs were measured separately for each tooth and reviewed independently by two experienced operators with extensive experience in using EALs. Paired t test and Wilcoxon signed-rank test were applied and the significant level was at .05. Results: Statistical analysis of the obtained data showed a significant decline in the WL after apical patency and coronal preflaring (P < .05). Moreover, WL exhibited a significant enhancement after calcium hydroxide application (P < .05). Conclusion: Apical patency and coronal preflaring increased the accuracy of apex locators in determining the WL of the teeth. Besides, calcium hydroxide residues in the root canal reduced the accuracy of the apex locator.