The Endocater (Hygenic Corp., Akron, OH, USA) was developed in 1979 by Hasegawa (Fouad & Krell 1989, Fouad et al. 1990, Pallares & Faus 1994) that used a high frequency (400 kHz) reference circuit (McDonald & Hovland 1990). To further decrease the influence of the variable capacitive characteristics on measurements insulated files were also used (Keller et al. 1991). As explained earlier (equation 3), the value of a capacitor is directly proportional to the area of its plates. Here, the insulator covers most of the surface of the file to decrease its capacitance value. Unfortunately, the coated file cannot be used in narrow canals,because the coating is easily abraded thus disturbing the measurement (Keller et al. 1991). In addition, Himel & Schott (1993) showed that the quality of the seal provided against electrical conductivity was decreased after autoclaving.