Electronic Apex Locator

Working length determination during root canal therapy is an important step to determine the success of root canal treatment. This has been greatly aided by Electronic apex locators (EALs) in our clinic. Root ZX by JMorita, Japan is the gold standared in accuracy as confirmed by various studies. 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. With over the years of practise, we are confident to access a correct WL with the help of this apex locator. (Inaccurate readings sometimes occur when a periapical lesion is present.)

Apex locators function by using the body to complete an electrical circuit. They measure the difference in electrical impedance (resistance to a current, in ohms) between the lip and the file in the tooth. The EAL is connected by wires to the lower lip and to a file which is placed in the root canal. The impedance between the lip and the periodontal ligament (PDL) is a known value, so as the file tip is advanced toward the PDL, the EAL detects the changing impedance values and indicates the approach to the apex on its screen.

When the PDL is contacted by the file tip, an audio alert is sounded and it is indicated visually on the screen. Since the file is contacting the PDL it is slightly past the apical constriction. This information can then be used in length determination.