In vivo characterization of the electrical impedance between the electrodes of the electronic foramen locators

Purpose Electronic foramen locators are widely used to locate the apical foramen (AF), by measuring the electrical impedance between the electrodes (ZE). There is no in vivo study that completely characterizes ZE as a function of frequency and endodontic file tip position. The results of in vivo stu...
Ausführliche Beschreibung

Purpose Electronic foramen locators are widely used to locate the apical foramen (AF), by measuring the electrical impedance between the electrodes (ZE). There is no in vivo study that completely characterizes ZE as a function of frequency and endodontic file tip position. The results of in vivo studies of the impedance ZE and a coefficient that can be used to locate the AF are presented. Methods An electronic device was specially built to study ZE. Ten root canals were used in the experiment. The spectral attenuation of ZE was in vivo measured with the endodontic file tip placed at −3.0, −2.5, −2.0, −1.5, −1.0, −0.5 and zero millimeters from the root canal AF. At each file position the spectrum attenuation was modeled. Based on the attenuation models an endodontic spectral attenuation coefficient (ESAC) was defined. Results The in vivo results demonstrate that the spectral attenuation of the electrical impedance ZE has an exponential decay in the frequency range of the study. It was verified that ESAC can be correlated to the distance between the endodontic file tip and the apical foramen. The ESAC accuracy was assessed and the results showed that it can locate the AF with accuracy better than 0.5mm. Conclusions The spectral attenuation of ZE has an exponential decay for all file tip distances from the AF. It supports the feasibility of ESAC to accurately locate the root canal AF. Moreover, using frequencies steps of one octave makes the implementation of ESAC in an embedded system easier. Ausführliche Beschreibung