The root canal filling with paste has such advantages as continuous germicidal effect, prevention of re-infection of the root canal and promotion of the healing in the apical wound.However, it is not so easy to fill up a root canal with paste perfectly on account of difficulty of the manipulations, though “ Lentulo stopper” has been used as the most excellent instrument.Then the author tried to find out more suitable instruments and devised seven types of spiral filling instruments. The efficiency of them were compared.The types of these instruments were as follows:No.1 File type with square form in the section.No.2 Reamer type with triangle form in the section.No.3 Flat type with rectangle form in the section.No.4 Lens type with convex lens form in the section.No.5 Wood drill type with carved spiral.No.6 and No.7 Lentulo stopper type.From the data of this experiment, No.3 and No.5 among them showed the most favorable results.