J Jan1, D Krizaj. 1. Department of Endodontics, Medical Faculty, University of Ljubljana, Ljubljana, Slovenia. janja.jan@mf.uni-lj.si
Abstract
AIM: To provide insight into the principles of operation of electronic apex locators, determine optimal measuring parameters of the impedance ratio method, and to evaluate its accuracy. METHODOLOGY: Electrical impedance was measured ex vivo on 14 extracted human teeth using a QuadTech 1920 precision impedance analyzer. A file electrode was inserted into the root canal; the second electrode was placed in the saline solution surrounding the tooth. Measurements were performed in a frequency range from 20 Hz to 1 MHz, and repeated with different distances of the file tip from the major apical foramen. The measured impedances were analysed as a function of distance of the file tip to the major apical foramen. Parameters (e.g. measurement frequencies, impedance ratio value) that would result in optimal working length determination were evaluated. RESULTS: The optimal determination of the major apical foramen position was obtained at frequencies of 5 kHz and 0.5 kHz, 10 kHz and 0.5 kHz, and 5 kHz and 1 kHz, for the impedance ratios 0.73 (95% CI: -0.33 to 1.74 mm), 0.66 (95% CI: -0.34 to 1.81 mm) and 0.79 (95% CI: -0.33 to 1.58 mm) respectively. The limit of +/-0.5 mm was attained in 86% of all measurements. Standard deviations decreased as the average measured distance approached and extended beyond the major apical foramen. CONCLUSIONS: With the obtained optimal measuring parameters, the impedance ratio method determined position of the major foramen within +/-0.5 mm. Accuracy varied depending on the set of frequencies used for evaluation as well as on the selected impedance ratio.
AIM: To provide insight into the principles of operation of electronic apex locators, determine optimal measuring parameters of the impedance ratio method, and to evaluate its accuracy. METHODOLOGY: Electrical impedance was measured ex vivo on 14 extracted human teeth using a QuadTech 1920 precision impedance analyzer. A file electrode was inserted into the root canal; the second electrode was placed in the saline solution surrounding the tooth. Measurements were performed in a frequency range from 20 Hz to 1 MHz, and repeated with different distances of the file tip from the major apical foramen. The measured impedances were analysed as a function of distance of the file tip to the major apical foramen. Parameters (e.g. measurement frequencies, impedance ratio value) that would result in optimal working length determination were evaluated. RESULTS: The optimal determination of the major apical foramen position was obtained at frequencies of 5 kHz and 0.5 kHz, 10 kHz and 0.5 kHz, and 5 kHz and 1 kHz, for the impedance ratios 0.73 (95% CI: -0.33 to 1.74 mm), 0.66 (95% CI: -0.34 to 1.81 mm) and 0.79 (95% CI: -0.33 to 1.58 mm) respectively. The limit of +/-0.5 mm was attained in 86% of all measurements. Standard deviations decreased as the average measured distance approached and extended beyond the major apical foramen. CONCLUSIONS: With the obtained optimal measuring parameters, the impedance ratio method determined position of the major foramen within +/-0.5 mm. Accuracy varied depending on the set of frequencies used for evaluation as well as on the selected impedance ratio.
Authors: Marcos V H Rambo; Humberto R Gamba; Gustavo B Borba; Joaquim M Maia; Carlos A S Ramos Journal: Biomed Eng Online Date: 2010-09-06 Impact factor: 2.819