Results of the in vivo experiments performed to study of the ratio method used in EFLs. A constant electrical current amplitude of 10 μARMS was used in the experiments. Vertical axis: Ratio between the impedances or components amplitudes. Horizontal axis: distances of -3.0, -2.5,-2.0, -1.5, -1.0, -0.5 and zero millimeters from the AF. (a) Ratio between the impedances at 8 kHz (Z1) and those at: 4 (Z2), 2 (Z3), 1 (Z4), 0.5 (Z5) and 0.25 kHz (Z6). (b) To make possible a comparison between the ratios, all curves were divided by their maximum values in graphic (a) that occur at 250 Hz. (c) to (g) are the same curves shown in (b) but with the bar standard deviation and maximum and minimum values included (I). The positive value distance corresponds to the one reading taken with the file tip positioned further the AF.