LAUSR

INTRODUCTION The aim of this study was to evaluate the accuracy of 5 electronic apex locators (EALs): Root ZX II (RZX; J Morita, Tokyo, Japan), Raypex 6 (RAY; VDW GmbH, Munich, Germany), Apex ID (AID; SybronEndo, Orange, CA), Propex II (PRO; Dentsply Maillefer, Ballaigues, Switzerland), and Propex Pixi (PIXI, Dentsply Maillefer) when used in the following protocols: (1) -1.0, insertion up to 1.0 mm below the apical foramen (AF); (2) 0.0/-1.0, insertion until the AF and withdrawn 1.0 mm short of the AF; (3) 0.0, insertion until the AF; and (4) over/0.0, insertion until "over" and withdrawal to AF. METHODS Thirty human lower premolars had coronary accesses and cervical and middle thirds preparations performed, allowing AF standardization (200 μm). Using an alginate experimental model, root canal length (RCL) measurements were performed sequentially with EALs following each of the protocols. RESULTS Considering the suggested protocols, the lowest mean error values were observed in 0.0, 0.10 mm (RZX), 0.13 mm (RAY), 0.16 mm (AID), 0.23 mm (PRO), and 0.10 mm (PIXI), without a significant difference for over/0.0 (P > .05). Comparing the results obtained in 0.0 with those found in -1.0 and 0.0/-1.0, significant differences were observed for most EALs (P < .05). For the comparison between EALs, significant differences were observed only in protocols -1.0 and over/0.0 (P < .05). CONCLUSIONS Under the conditions of the study, it was concluded that, regardless of the mechanism of the device, the best results were found when electronic RCL measurement was performed at the AF; furthermore, the electronic withdrawal did not offer any additional advantage over the reach of the AF.