| 摘要 |
A dental instrument is described by which a tooth file is automatically driven by a driver for producing alternating movement forces in the axial direction of a tool support bearing the file to a predetermined axial limit position in each direction, the distance between these limit positions being such that the instrument tool support is able to take an axial position in which it is unaffected by those movement forces. The movement forces affect the tool support only when it is moved from the unaffected axial position by an external force exerted on it and then by only the one of the forces acting in the axial direction opposite to the external force. External forces in each direction are able to move the tool support up to a predetermined maximum amplitude of action. Each movement force, besides having a first force component in the axial direction of the tool support, has also a second force component in an angular direction in order to impress also a rotational movement on the tool support when it is moved from that unaffected axial position.
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