To allow a dentist to maintain concentration by reducing fatigue by facilitating cutting operation of a root canal of a tooth concerning a cutting tool used in dental treatment.SOLUTION: To the tip of a handle-side housing 10, there is attached a vibration-side housing 11. The attaching/detaching part 13 of a reamer 3 is assembled in a freely reciprocating manner in the vibration-side housing 11. The reamer 3 that is inserted from a reamer attaching port 16 in the rear end of the attaching/detaching part 13 and fixed with a screwing lid 32 has a needle part 31 protruding from the attaching/detaching part 13 and the front end of the vibration-side housing 11. The rotary axis 20 of a micromotor 2 is connected to a deficiency gear 25 of a gear box 24 which is provided in the tip end part of the handle-side housing 10, with the deficiency gear 25 meshed with a tooth 14 which becomes a lack gear carved and provided in the outer periphery of the attaching/detaching part 13. A coil spring 19 is made to stay by a spring receiver 100 protruding to the outer periphery of the attaching/detaching part 13, and is stored in a groove provided in the inner periphery of the vibration-side housing 11.SELECTED DRAWING: Figure 1【課題】 歯科治療で用いる切削用具に関して、歯の根管の切削作業が容易に行い得るようにすることによって、歯科医師の疲労を少なくして集中力が持続できるようにする。【解決手段】 ハンドル側筐体１０の先に振動側筐体１１を取り付ける。振動側筐体１１の中にリーマ３の着脱部１３を、往復動自在に組み込む。着脱部１３の後端部のリーマ装着口１６から挿着してネジ蓋３２で固定されたリーマ３はその針部３１が着脱部１３および振動側筐体１１の前端部から突出する。マイクロモータ２の回転軸２０をハンドル側筐体１０の先端部分に設けたギヤードボックス２４の欠損歯車２５に連結し、欠損歯車２５を着脱部１３の外周部に刻設したラックギヤとなる歯１４に噛合させる。コイルバネ１９を着脱部１３の外周に突出するバネ受け１００で止めるようにして振動側筐体１１の内周に設けた溝に納める。【選択図】図１
