Aim: To evaluate the accuracy of three apex locators using four different irrigant solutions for determining the working length of root canals.

Material and methods: Thirty single rooted teeth were used. Teeth were randomly divided into three groups, in order to establish the working length, using different apex locators: Root ZX mini, Propex Pixi and Ipex Four different irrigant solutions were used combined with the apex locators: saline solution (0.9% sodium chloride), 40% citric acid, 17% EDTA and 5.25% NaOCL. Actual working length (AWL) was determined using a #15 K-file in each specimen until the end of the file was visualized in stereoscopic microscopy. Scores (%) were attributed to each difference found between the working length gave by the apex locators and the AWL.

Results: There was a significant difference between the RWL and that one found with the apex locators Propex Pixi and Ipex; however, Root ZX mini did not show statistical differences. The four different irrigant solutions did not show statistically differences between then.

Conclusions: The precision to estimate the working length with Ipex and Propex Pixi was affected by the different irrigant solutions in the root canal. Root ZX mini was the most accurate apex locator to estimate the AWL.