In vitro comparison between apex locators, direct and radiographic techniques for determining the root canal length in primary teeth.

AIM: To compare the accuracy of three electronic apex locators in the measurement of the root length of primary teeth with the radiographic and direct visual techniques. METHODS: The sample of the in vitro study was 102 root canals of primary molars. For the direct visual technique, the root canal file was introduced into the canal until its tip passed the apical foramen, then it was moved back to the limit of the foramen or root resorption and the measurement was made with a millimetre ruler. For the radiographic measurement, a calibrated and blinded researcher (kappa > 0.87) measured the root canals using the same rule. Measurements with apex locators were performed by inserting the file into the canal until the word "Apex" or audible warning to indicate the foramen or resorption. For data analysis, one-way ANOVA for repeated measurements and the Sidak post hoc tests were performed. RESULTS: The direct measurement (micro = 8.57) did not present statistical difference when compared to the Root ZX II measurement (micro = 8.45), as opposed to the radiographic measurements (micro = 8.12), the Endus (micro = 8.24) and iPex II (micro = 8.29). CONCLUSION: The use of apex locators was superior to the radiographic method and the Root ZX II was the most effective.