|
An electronic apex locator is an electronic device used in endodontics 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. ==History and uses== The original electronic apex locators operated on the direct current principle. A problem with these devices was that conductive fluids such as hemorrhage, exudate, or irrigant in the canal would permit current flow and therefore a false reading. Newer devices are impedance-based, using alternating current of two frequencies;these measure and compare two electrical impedances that change as the file moves apically. The benefit is that these devices are much less affected by fluid conductive media in the canal. The impedance type apex locators have been demonstrated to be 80 to 95% accurate in identifying the apical foramen. Therefore after obtaining a reading, 1 to 2 mm is subtracted as the corrected working length. Electronic apex locators have been shown to be more accurate than radiography when determining the position of the apical foramen. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「electronic apex locator」の詳細全文を読む スポンサード リンク
|