Clinical efficacy of electronic apex locators: systematic review.

Apical constriction has been proposed as the most appropriate apical limit for the endodontic working length. Despite being the most used, some limitations are attributed to the radiographic method of working length determination. It lacks precision because it is based on the average position of the apical constriction. The electronic apex locators have been presented as an alternative to the odontometry performed by radiography. These devices detect the transition of the pulp to the periodontal tissue, which is anatomically very close to the apical constriction and may perform with improved accuracy.