An apex locator (or electronic apex locator – EAL) is an electronic device used in endodontics/root canal therapy to determine the position of the apical foramen and thus determine the length of the root canal space. The apex of the root has a specific resistance to electrical current, and this is measured using a pair of electrodes typically hooked into the lip and attached to an endodontic file. The electronic principle is relatively simple and is based on electrical resistance; when a circuit is complete (tissue is contacted by the tip of the file), resistance decreases markedly and current suddenly begins to flow. According to the device, this event is signaled by a beep, a buzz, a flashing light, digital readouts, or a pointer on a dial. – source from wikipedia
Role of Electronic Apex/ Foramen Locators
Working length determination during root canal therapy has been greatly aided by Electronic apex locators (EALs). They can save time in determining initial working length, save on the number of X rays taken, and can be particularly helpful when the periapex is unclear on radiographs or when there is a question about whether a perforation has occurred.
As the matter of fact, foramen does not coincide with the anatomical apex in most teeth. You can confirm this fact by examining the morphology of extracted teeth. One of the earliest brands was Root ZX by JMorita of Japan which still is the gold standard in accuracy as confirmed by various studies. We have been using it for many years. Intraoral radiographs do not show the apical foramen and are often misleading, leading to compromising results, see below. Picture shows how radiographs can be deceptive in determing correct working length-WL, you will never be able to assess correct WL without a good apex locator.
Root ZX II – Accurate apical foramen measurement
Currently, we are using Root ZX apex locator for our root canal treatments.
Invented in 1992, the J. Morita Root ZX II is currently one of the best selling apex locators. It has proven itself safe and accurate, and was the first unit providing dentists the capability to work in wet canals. Blood and other fluids do not typically affect measurements.
Root ZX II patented technology offers an accuracy rate above 96%. LCD readout is large and easy to read. Action of the meter in the display corresponds to the tactile sensation of using the file.
Other Root ZX II Features:
- slim, lightweight file holder
- no zero-adjustment
- automatic calibration
- battery power indication
- automatic power off function
An in vitro comparison of three apex locators concluded that the Root ZX II was significantly more accurate at finding the apical foramen than competitive models.