A complete melting type cordless filling instrument for endodontic treatment is disclosed which uses a switching circuit, to be operable using a miniature dry battery for supplying DC power. The filling instrument includes a body with a battery for supplying DC power, a heater at a front end of the body to heat and melt gutta-percha, an injector mounted to the body in front of the heater to discharge the melted gutta-percha, a charging part provided at the body to charge the gutta-percha in the body, a feeding member which feeds the gutta-percha charged in the body, a filling switch which turns on the heater, and a control circuit installed in the body, to control a temperature of the heating core and an operation of the heating core. The control circuit includes the filling switch, and a switching circuit adapted to efficiently maintain electrical energy supplied from the battery.
