ABSTRACT
Objective: Root canal anatomy significantly impacts the working length determination. This study aimed to
investigate the effect of the preflaring technique on the accuracy of four electronic apex locators. Methods:
Forty-five single-canal central maxillary teeth were selected. The working length was measured before and after
the coronal preparation by four types of electronic apex locators in the range of ±0.5 and ±1 mm matched for the
apical constriction. The actual working length was calculated under a microscope. Data were analyzed using ICC
and paired t-tests in SPSS16. A p < 0.05 was considered significant. Results: The accuracies of Root ZX, DTE,
Denjoy, and Coxo apex locators in the range of ± 0.05 mm were 71.1, 93.3, 84.4, and 75.6% before preflaring, and
82.2, 93.3, 97.8, and 100% after that. The corresponding values in the range of ±1 mm were 86.7, 97.8, 93.3, and
100% before and 97.8, 100, 100, and 100% after preflaring. Significant differences were found between the working
lengths measured by the four devices and the actual working lengths before and after preflaring. Conclusion: The
preflaring technique could impact the performance of apex locators in determining the working length and may
be advocated for better outcomes