Accuracy of Root ZX Electronic Apex Locator in Relation to Two Different Employment Protocols: An In Vitro Study.

Objective The aim of this study is to determine the apical level of the root canal, whether it is the apical foramen or a level coronal to it, that Root ZX (J. Morita Co., Kyoto, Japan) targets and to identify its employment protocol that provides better accuracy. Methods Actual lengths (ALs) of 75 extracted single-rooted teeth were obtained by inserting a K-file size 8 until its tip was in level with the most coronal border of the apical foramen. Reference length (RL) was calculated by deducting 0.5 mm from AL. Roots were placed in porous sponge block soaked with Ringer's solution, and canals were irrigated with 2 mL of 5% sodium hypochlorite. The blinded operator used Root ZX to measure lengths with K-file size 8. In the first tested employment protocol, the file was advanced to the "APEX mark" of the digital display, and the length was obtained. The second employment protocol followed the manufacturer's recommendations by inserting the file until the "APEX mark" followed by its withdrawal to the "0.5 mark." Stability of the digital meter for 5 seconds was mandatory before recording the lengths. All measurements were repeated one week later and then both measurements were averaged to represent "APEX mark" and "0.5 mark," respectively. Data were analyzed using