Accuracy of electronic apex locators in comparison to actual length—an in vivo study

Objectives The measurement precision of four electronic apex locators (Root ZX, Morita, Tokyo, Japan; Endy, Loser, Leverkusen, Germany; Justy II, Hager–Werken, Duisburg, Germany; Endox Lysis, Milan, Italy) was examined in the present in vivo study. Methods The root canal length of 40 single-rooted and multi-rooted teeth was determined with the four devices prior to tooth extraction. To determine the actual root canal length, the apical third was longitudinally sectioned, the root canal instrument was positioned and the apex was examined using a microscope. Results The average measurement deviation (±SD) in relation to the apical constriction was 0.3 mm (±0.6) for the Root ZX, 0.7 mm (±1.0) for the Endy, 0.2 mm (±0.7) for the Justy II and 1.3 mm (±1.7) for the Endox. The limit of ±0.5 mm from the apical constriction was attained by the Root ZX in 78%, by the Endy in 67%, by the Justy II in 80% and by Endox in 31% of all measurements. Conclusions The latest generation of apex locaters provide the clinician with an accurate and useful adjunct for the determination of root canal length.