The wire of the interdental treatment part is inserted into a shaft opening of the injection molding tool, preferably into a strip of the injecting molding tool such that said treatment part projects with a mounting section thereof into a cavity connected to the shaft opening. Preferably, a first cavity section is configured is configured on the strip, and a second cavity section is configured on a cavity body, to with the strip abuts at least during the injection molding process. After injection of plastic into the cavity, and after the at least partial curing thereof, the handle part thus formed is moved by a distance in the direction against the cavity along with the interdental treatment part, and the handle part is removed from the opened injection molding tool.