Performance in vitro of apex locators in determining root length in primary molars Desempenho in vitro de localizadores apicais na determinação de comprimento radicular em molares decíduos

Objective The aim of the study was to evaluate performance of digital radiographic and two electronic apex locators, Propex II and Root ZX in root canal length determination in primary molars. Methods 25 primary molars were divided into two groups, G1 without root resorption and G2 with root resorption. The exams were performed using all methods by two experienced examiners, with 1-week interval. The gold standard was determined by visual examination. The methods were statistically analyzed regarding the values of reproducibility and correlated with the gold standard by Pearson ́s correlation coefficient. Results The root canal length determination coincided with gold standard in 22.7% for Root ZX, 17.5% for Propex II and 12.5% for digital radiography. Correlation values were higher in G1, the Root ZX presented the highest values. In G2 the digital radiography showed the lowest correlation. In G1, the intra-examiner reproducibility values ranged from 0.925 to 0.523, and interexaminer 0.863 to 0.670. In G2, the values of intraexaminer reproducibility ranges from 0.864 to 0.097, and inter was 0.774 to 0.379. Conclusion It was concluded that the methods performance varying according to examiner’s experience. The Root ZX presented the highest reproducibility and accuracy. Indexing terms: Apex locator. Digital radiography. Endodontics. Primary teeth. Root ZX.