The present invention relates to a handpiece for dental use, and more particularly, to a handpiece to be used by a dentist for cutting or drilling a root canal of a tooth.
In forming a root canal of a tooth, a dental reamer or a dental file (hereinafter referred to as “cutting tool”) is generally used. The cutting tool may be operated manually or with use of a handpiece with a drive mechanism. With these cutting tools, a spiral cutting edge is inserted into a root canal, and the back and forth movements or rotational movements of the cutting tools by changing the cutting tools corresponding to the shape of the root canal allows the root canal to be tapered. To cut a root canal, a handle of a cutting tool is held for manual operation, or a cutting tool is connected to a dental handpiece for using rotationally driving force of motor or the like.
Since a dental reamer has a large lead, that is, a relatively gentle spiral cutting edge, it is mainly used for cutting by rotational movements. In contrast, a dental file has a spiral cutting edge having a lead smaller than that of the dental reamer, therefore, it is mainly used for cutting through back and forth movements like a file. Further, the dental file is often used by incorporating the back and forth movements as well as some rotational movements at the same time, which allows a root canal to be cut by the back movement and debris generated by the cutting to be carried away to outside of the root canal through spiral channels of the edge portion.
A dental handpiece heretofore in use for operating these cutting tools is sometimes capable of driving the tools like ultrasonic scaler both by the back and forth movements and by the rotational movement. “The back and forth movements” means the movements of the cutting tools for cutting by the back and forth movements, that is, reciprocating movement in a longitudinal direction of the cutting tools.
In a dental handpiece in the past, when an edge portion of a cutting tool is caught by a curved portion of a root canal or the like, the cutting tool does not progress further from the caught portion and stays there, therefore, only a head of the dental handpiece relatively goes up and down, which causes the root canal not to be cut at all.