Abstract: Apparatus and method for treating a tooth infected by a pathogen. The apparatus comprises at least one adjustable electric voltage generator for generating an direct current, an applicator device having a first pole and a second pole, the first pole being formed as a needle so as to penetrate into a canal of the infected tooth and the second pole being brought into direct contact with a zone of a body of a patient having the infected tooth and an electric circuit for maintaining the direct current constant while an impedance of the at least one adjustable electric voltage generator varies, the impedance being determined by the zone of the body of the patient where the direct current passes. The method for treating a tooth infected by a pathogen comprises applying an direct current into a canal of the infected tooth and maintaining the direct current constant during a duration of an application of the direct current to the infected tooth.