An apex locator is an advanced tool used in endodontic treatments (root canal therapy) to accurately determine the position of the apex (the tip of the tooth root). This device measures the electrical resistance between the tooth root and the surrounding tissues, helping dentists precisely identify the working length of the root canal. Using an apex locator not only enhances accuracy and sensitivity during treatment but also reduces the risk of errors in determining canal length and subsequent complications, such as underfilling or overfilling. It is particularly valuable in cases where visualizing the apex through radiographs is challenging.