in vitro evaluation of two techniques to determine working length with an electronic apex locator

Objective: To verify in vitro whether an electronic apical location using a non-foramen by-pass technique influences the accuracy of the procedure. Methods: Fifteen incisors and canines human teeth with complete apical formation were used. Teeth were fixed to a resin-based model and embeded into alginate to serve as a conduction medium for the eletronical readings. Using a K-flexofile #20 coupled to the apical locator device (Root ZX II, J Morita, Kyoto, Japan), root canals were electronically measured at two different time-points. Firstly, it has been registered before passing through the apical foramen (alternative technique) and, thereafter with the file bypassing the apical foramen (recomended technique). On both techniques the readings were performed whenever the display was stabilized at level 0.5. After each electronic determination, the tooth was radiographed with the file in position. To measure the agreement between the two techniques, the interclass correlation statistical procedure was used. Results: The difference between the two techniques at the radiographic evaluation was 0.118 mm (± 0.170) and for the electronic reading 0.086 mm (± 0.398). The two techniques were significantly correlated both for the electronic reading and for the radiographic evaluation (ICC = 0.98; p < 0.001, ICC = 0.97; p < 0.001, respectively). Conclusion: The alternative technique for electronic apical location, without passing the foramen, has shown similar accuracy as the standard technique, sugested by