Kobayashi C, Suda H
Department of Endodontics, Faculty of Dentistry, Tokyo Medical and Dental University, Japan.
J Endod. 1994 Mar;20(3):111-4. doi: 10.1016/S0099-2399(06)80053-1.
The most striking disadvantage of most apex locators is that if there are electrolytes in the canal the meter shows a reading which is too short or sometimes the measurement itself becomes impossible. To overcome this drawback, a new concept for electrically measuring the root canal length has been developed. The device simultaneously measures two impedances of the canal using current sources with two different frequencies. Then the ratio between the two electric potentials proportional to each impedance is calculated. The quotient is shown on the device's meter and represents the position of a file tip in the canal. The present study found that the quotient was only negligibly influenced by the electrolyte present in the canal and decreased considerably as the file tip approached the apical foramen.
大多数根尖定位仪最显著的缺点是，如果根管内存在电解质，仪器会显示一个过短的读数，或者有时根本无法进行测量。为了克服这一缺点，人们开发了一种用于电测根管长度的新概念。该设备使用具有两种不同频率的电流源同时测量根管的两个阻抗。然后计算与每个阻抗成正比的两个电势之间的比值。该商数显示在设备的仪表上，代表锉尖在根管内的位置。本研究发现，该商数仅受根管内存在的电解质的轻微影响，并且随着锉尖接近根尖孔而显著降低。
