An in vivo comparison of working length determination by only root-ZX apex locator versus combining root-ZX apex locator with radiographs using a new impression technique

Objective: The objective of this study was to compare, in vivo, the accuracy of working length determination using only the Root-ZX electronic apex locator versus adjusting Root-ZX measurements after obtaining a working length radiograph. Study design: The working length was determined in 25 premolar root canals using Root-ZX and K-files were fixed at these positions. Radiographs were acquired and interpreted, and the recorded working length measurement was adjusted, if necessary, for a combined measurement. The teeth were then extracted in an effort to determine the position of the file tip to the root canal constriction. On the basis of the position of the file tip to the apical foramen, polyvinylsiloxane impressions of the root apex were taken, or the root was imbedded in acrylic resin and ground in order to measure the position of the file tip to the apical constriction. Results: The Root-ZX alone detected the apical constriction within ± 0.5 mm in 84% of the samples (21 of 25 canals). However, 96% (24 of 25 canals) were within this range when the combination of Root-ZX and radiographs was used. We noted no statistical significance between these 2 methods (P > .05). Conclusion: Using a Root ZX Electronic Apex Locator combined with radiographs is recommended for the determination of working length, although there was no statistical significance between those 2 groups in this study.