Comparison of In Vivo and In Vitro Readings When Testing the Accuracy of the Root ZX Apex Locator

Abstract: Introduction: The purpose of the study was to compare the accuracy of the Root ZX electronic apex locator (J Morita Corp, Tokyo, Japan) between an in vivo and an in vitro model.Methods: The working length (WL) was determined electronically for 46 root canals of human teeth with a 15 K-file using both in vitro (n = 23) and in vivo (n = 23) models. The files were fixed at the WL. The apical 4 mm of each canal was trimmed to expose the file tip. The samples were observed under a scanning electron microscope, and the distance from the file tip to the point 0.5 mm coronal to the major foramen (the final WL) was measured. The data were analyzed using the Student t test, and significance was set at P ≤ .05.Results: The statistical analysis revealed no significant differences between the in vivo group and in vitro group with respect to the accuracy of the Root ZX device in determining the final WL. The mean distance from the final WL to the file tip was 0.23 ± 0.39 mm for the in vivo group and 0.29 ± 0.32 mm for the in vitro group. In determining the final WL, the Root ZX was accurate 78.3% of the time to ±0.5 mm and 100% of the time to ±1 mm in the in vivo group, whereas it was accurate 74% of the time to ±0.5 mm and 100% of the time to ±1 mm in the in vitro group.Conclusions: No statistically significant differences were observed between the in vivo group and the in vitro group.