The present invention relates to a device for injecting filling of liquid material into a root canal recess, comprising a main body (nozzle adaptor), an automatic mixer, and an injection nozzle. The automatic mixer is connected to the nozzle adaptor. The injection nozzle is set at a tip of the nozzle adaptor and the injection nozzle is connected at an end thereof to a tube having an outside diameter smaller than or equal to 1.5 mm and a length greater than or equal to 8 mm. The tube is made of a shape memory material for shaping purposes when desired. The injection nozzle is provided with marks to allow a dentist to measure the depth of the root canal recess. The marks are formed on an outer layer of the injection nozzle between a circular radial rib and the nozzle tip so as to allow the injection nozzle to be prepared in a length corresponding to the root canal.
