Accuracy of electronic apex locater-controlled handpieces

An in vitro model was used to test a hypothesis that the manual (apex locator) and motor-driven (apex locator-controlled handpiece) operating modes of 3 newly developed apex-locator-controlled handpiece devices (Dentaport ZX, Endomaster, XSmart Dual) give the same working length. The depth of penetration of the file into the root canal was measured using a digital micrometer and the distance of the tip of the file relative to the major root foramen was determined by scanning electron microscopy (SEM). In the manual mode, the XSmart Dual device reported significantly shorter working lengths than the Dentaport ZX or the Endomaster devices. In the motor-driven mode, the XSmart Dual device reported significantly longer working lengths than the Dentaport ZX but not the Endomaster. Most instruments driven by the handpieces were confined within the root canal and differences in working lengths between manual and motor-driven modes were small for all devices (tenths of millimeters). We concluded that although the motor-driven mode of these devices appeared to be clinically safe, measurements obtained in manual and motor-driven operating modes are not equivalent.