Modern electronic apex locators are reliable for determining root canal working length

Abstract

The investigation was carried out by a single operator who was taught to use the different types of electronic apex locators (EAL) according to the operators' manuals. Four EAL were tested: Root ZX (J. Morita Corporation, Tokyo, Japan); Endy (Loser, Leverkusen, Germany); Justy II (Hager-Werken, Duisburg, Germany); and Endox (Lysis, Milan, Italy). Forty root canals were measured prior to tooth extraction for periodontal, endodontic, prosthetic or orthodontic reasons. Canals were rinsed with hydrogen peroxide (3%) and dried with paper points. K-Files (Dentsply-Maillefer, Konstanz, Germany; ISO sized 15, length 28 mm) were used as active electrodes, with the exception of tests with the Endox device, for which special needles are provided by the manufacturer. After extraction and storage in isotonic sodium chloride solution, teeth were sectioned longitudinally until the root canal was longitudinally exposed. Using a stereo microscope, a 15 K-file was inserted into the canal until the tip reached the apical constriction; it was then marked, removed and the length read off a steel rule. Root canal length could be determined for all the teeth using the EAL and the actual root canal length could be determined by microscopic investigation. The Justy II gave the most accurate results, with a mean difference between the actual length of the root canal and the working length of 0.2 mm [standard deviation (SD), ±0.7]. This compared with mean differences between measured and actual lengths from the other devices as follows: Root ZX (mean, 0.3 mm; SD, ±0.6); Endy (mean, 0.7 mm; SD, ±1.1); Endox (mean, 1.3 mm; SD, ±1.7). The numbers of samples are shown in Table 1. The data revealed different accuracy in working length determination of the four EAL evaluated but, overall, modern EAL offered a reliable method for endodontic working length determination.