Evaluation of the Accuracy in Four Electronic Apex Locators toward determination of working length of root canal: an in-vitro study

Determination of the exact working length is one of the most important steps in root canal treatment. Various devices and methods, such as electronic apex locators, have been developed for the determination of the working length. The present study aimed to compare the accuracy of four electronic apex locators, DTE, Denjoy, Woodpecker and Coxo, in determining the actual working length.

In this descriptive study, fourty mandibular premolar teeth that fulfilled the inclusion criteria were selected and examined. First, each tooth was measured with four apex locators. The electronic measurements were performed following the manufacturers’ instructions within ±0.5 mm, ±1 mm and exactly at apical constriction. To calculate the actual working length, 4 mm of the root end was buccolingually cut from buccal side of the canal, and the distance between the coronal reference point and apical constriction was measured under a microscope. Then, data were analysed with Paired T test.

. Within ±0.5 mm from the apical constriction and at the apical constriction, the accuracy of apex locators DTE, Woodpecker, Coxo and Denjoy were 87% and 45%, 85% and 37%, 85% and 45% and 82% and 42%, respectively. All specimens measured with four types of apex locators were within the range of -1 to +1 mm to the apex with an accuracy of 97.5%.

 None of the four apex locators reported an accuracy of 100% at apical constriction. There was no statistically significant difference between the working length measured by four apex locators and the actual working length.