Working Length Determination and Apex Locators

Following the completion of adequate coronal access and canal exploration, the most critical act in ensuring the success of root canal therapy is the accurate determination of the length of the tooth before radicular preparation. Working length is the distance from the coronal reference plane to the apical construction.

The apical constriction, also referred to as cementodentinal junction (CDJ), represents the transition between the pulpal and the periodontal tissues. Accurate working length (AWL) establishes the apical extent of instrumentation and the ultimate apical level of root canal filling. One of the main concerns in root canal treatment is to determine how far working instruments should be advanced within the root canal, and at what point the preparation and obturation should be located.

The significance of the apical constriction in the root canal treatment is well recognised. It is generally accepted that root canal treatment procedures should be confined within the root canal system. To achieve this objective the canal terminus must be detected accurately during canal preparation and precise control of working length during the process must be maintained. In this tutorial, you will learn about the various methods for determination of this critical position during endodontic treatment. You will also read more about the use of electronic apex locators in determining the working length.