ABSTRACT
Introduction: There are few researches in literature that mention the use of the apex locator in deciduous teeth and working length is obtained through radiographies. Objective: The purpose of this research was to compare the radiographic and the electronic method to obtain the working length in deciduous molars. Material and methods: Twelve molar teeth were used. The specimens in the visual method had their root length measured through the passive insertion of a 10 K-file with a silicone stop within root canal until its tip was seen at the apical foramen. The working length was measured through radiographs or using the apex locator Root ZX II. The mean between the examiners was submitted to the variance analysis (ANOVA). Results: Statistically significant differences were found between the visual method and the radiographic method (p < 0.001). There was no significant difference between the working length measurements in visual method and those obtained with the apex locator (p = 0.1319). Conclusion: The apex locator is indicated as a clinical implementation for endodontic treatment in primary teeth.