Method of controlling a drive device for preparing a root canal, and rotating handpiece for root canal preparation

1. A method of controlling a drive device for moving a root canal instrument provided with at least one cutting edge for preparing a root canal and a drive shaft connected to a drive motor controlled by a programmed controlled unit, wherein the programmed control unit controls the drive motor to:

move the root canal instrument in at least one reciprocal movement in a first direction of rotation over a predetermined first angle of rotation and subsequently in a second direction of rotation opposite to the first direction of rotation over a predetermined second angle of rotation;

after the at least one reciprocal movement, rotate the root canal instrument over at least one third angle of rotation; and

near an apex of a root of a tooth, begin full rotation of the root canal instrument with a reduced torque as compared to a torque during a preceding angle of rotation.

2. The method according to claim 1 , wherein the third angle of rotation has at least one of an identical or an opposite direction of rotation as the second direction of rotation or an angle of rotation of at least 360°.

3. The method according to claim 2 , wherein the first and the second angles of rotation have different magnitudes.

4. The method according to claim 3 , wherein at least one chosen from the first and the second angles of rotation and the third angle of rotation are randomly selected.

5. The method according to claim 4 , wherein the at least one chosen from the first and the second angle of rotation and the third angle of rotation are randomly selected by at least one of a random generator or in response to a torque acting on the root canal instrument.

6. The method according to claim 2 , wherein the first and the second angles of rotation have identical magnitudes.

7. The method according to claim 1 , wherein the first and the second angles of rotation have a value which is

360

⁢

°

n

,

where n is the number of the cutting edges of the root canal instrument.

8. The method according to claim 1 , wherein any of the angles of rotation can be varied in dependence upon a position of the root canal instrument relative to the apex of the root.

9. The method according to claim 8 , wherein the any of the angles of rotation can be varied in dependence upon the position of the root canal instrument relative to the apex of the root by superposed length measurement.

10. The method according to claim 1 , wherein the at least one of the angles of rotation is changed near the apex of the root to full rotation with the reduced torque by superposed length measurement.

11. The method according to claim 1 , wherein the root canal instrument is moved to and fro in a longitudinal movement along its axis of rotation, and the longitudinal movement is carried out during or after the reciprocal movement or during or after the movement about the third angle of rotation.

12. The method according to claim 1 , wherein the first and the second angles of rotation have different magnitudes.

13. The method according to claim 1 , wherein the first and the second angles of rotation have identical magnitudes.

14. The method according to claim 1 , wherein at least one chosen from the first and the second angles of rotation and the third angle of rotation are randomly selected.

15. The method according to claim 14 , wherein the at least one chosen from the first and the second angle of rotation and the third angle of rotation are randomly selected by at least one of a random generator or in response to a torque acting on the root canal instrument.