Evaluation of Five Electronic Apex Locators Accuracy in Determining the Major Foramen and Apical Constriction: An in vitro study

The purpose of this study was to compare the diagnostic accuracy of five different electronic apex locators (EAL), including the Root ZX II, Endo-EZE FIND, APEX ID, ProMark, and Parkell Formatron. The evaluation of the EALs were two-fold. One objective was to evaluate the ability of each EAL to detect the major foramen, and the second objective was to evaluate the reliability of each EAL indication of the apical constriction.;Materials and Methods: A total of 100 single-canal extracted human teeth were decoronated and checked for patency. Fifty teeth were evaluated by each electronic apex locator to determine their accuracy for locating the major foramen. The teeth were embedded in alginate. A #15 K-file was advanced in each canal until the major foramen indicator was reached on their screen. The remaining 50 teeth were randomly assigned to five groups (n=10). Each group was assessed by a single EAL. A #15 K-file was advanced until the major foramen was reached and then retreated slowly until the apical constriction indicator was achieved on the EAL's screen. The file was then cemented in place, with the apical 5 mm of the tooth sectioned longitudinally until the file was exposed. The distance from the file tip to the major foramen was measured.;Results: Statistical results showed a significant difference between the five EALs in their ability to accurately identify the major foramen, as found by a repeated-measures ANOVA (p<0.0001). A Tukey's Standardized Range Test found the Apex ID and Root ZX II to have significantly lower mean measurements (mm) from the file tip at the major foramen indicator to the major foramen. However, when analyzing the distances (mm) from the file tip to the "apical constriction" indicator to the major foramen, there was no significant difference found between the respective EAL groups, as determined by Kruskal-Wallis test.;Conclusions: The Apex ID and Root ZX II were more accurate in their location of the major foramen. All five EALs preformed within the same level of consistency in their indication of an apical constriction. The Apex ID location of the apical constriction resulted in no overextension of the file tip beyond the major foramen.