An in vitro comparison of two modern apex locators.

Two apex locators were compared regarding their ability to accurately locate the apical constriction in the presence of various canal fluids at different meter readings. Forty-one root canals were filled with 1% NaOCl, 3% H2O2, and 0.9% NaCl, respectively. Electronic working length (EWL) measurements were recorded with the apex locators Root ZX (meter readings: "Apex", "0.5", and "1") and Apit (meter readings: "Apex" and "3"). The deviation of the EWL from the apical constriction was determined. The proportion of measurements within +/- 0.5 mm of the apical constriction ranged between 0.76 and 0.85 for Root ZX at the meter readings "Apex" and "0.5," regardless of the canal contents. Apit consistently displayed shorter measurement values than Root ZX and reached the highest proportions at the meter reading "Apex": 0.59 (1% NaOCl), 0.61 (3% H2O2), and 0.68 (0.9% NaCl). In the presence of NaOCl, Root ZX provides the more accurate EWL measurements at the meter reading "0.5" and "Apex."