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ENDODONTIC INSTRUMENT

20210330424 · 2021-10-28

    Inventors

    Cpc classification

    International classification

    Abstract

    An endodontic instrument for anatomically shaping a root canal of a human tooth, having a base portion, which can be mounted on a holding device and can be rotated around a reference axis A. The endodontic instrument has a working part with an abrasive surface, at least a part of which extends from the base member and has an axis which is arranged angular with respect to a reference axis. The central axis of the base portion and the central axis of working portion enclose an angle a greater than zero, and/or wherein the central axis of the working portion is offset in parallel to the reference axis of the base member by a distance r. The working part is made of a flexible material having a yield strength of less than 200 MPa.

    Claims

    1-6. (canceled)

    7. A endodontic instrument for anatomically shaping a root canal of a human tooth, having a base portion, which can be mounted on a holding device and can be rotated around a reference axis, having a working part with an abrasive surface, which extends from the base portion and has an axis, at least a part of which is arranged angular with respect to a reference axis, wherein the central axis of the base portion and the central axis of working portion enclose an angle α, and/or is offset in parallel to the reference axis of the base portion by a distance r; wherein the working part is made of a flexible material having an upper yield strength of less than 200 MPa, measured according to EN ISO 6892-1.

    8. The endodontic instrument according to claim 7, wherein the working part is made of a flexible material having an upper yield strength of 70 to 180 MPa, measured according to EN ISO 6892-1.

    9. The endodontic instrument according to claim 7, wherein the flexible material is a metallic material.

    10. The endodontic instrument according to claim 7, wherein the flexible material is an alloy of stainless steel.

    11. The endodontic instrument according to claim 7, wherein the flexible material is a nickel titanium alloy.

    12. The endodontic instrument according to claim 7, wherein the distance r is between 0.1 and 1.2 mm.

    13. The endodontic instrument according to claim 7, wherein the distance r is between 0.3 and 0.9 mm.

    14. The endodontic instrument according to claim 7, wherein the distance r is between 0.4 and 0.7 mm.

    15. The endodontic instrument according to claim 7, wherein the angle a enclosed by the central axis of the base portion and the central axis of the working portion is between 0.01° and 20°.

    16. The endodontic instrument according to claim 7, wherein the angle a enclosed by the central axis of the base portion and the central axis of the working portion is between 0.1 and 15°.

    17. The endodontic instrument according to claim 7, wherein the angle a enclosed by the central axis of the base portion and the central axis of the working portion is between 1° and 10°.

    18. The endodontic instrument according to claim 7, wherein the working part has a tip diameter of 0.15 to 0.60 mm.

    19. The endodontic instrument according to claim 7, wherein the working part has a tip diameter of 0.25 to 0.40 mm.

    20. The endodontic instrument according to claim 7, wherein the working part has a taper of 0.01 to 0.08.

    21. The endodontic instrument according to claim 7, wherein the working part has a taper of 0.02 to 0.06.

    22. The endodontic instrument according to claim 7, wherein the holding device comprises a handle or a drive engine.

    Description

    EXAMPLE

    [0035] A set of 12 eccentric instruments having a working part offset in parallel to the main axis of the base portion by 0.5 mm, having a tip diameter of 0.25 mm and a continuous taper of 0.02, were prepared.

    [0036] Three files were made of the same alloy each, chosen from the group of: [0037] austenitic steel, containing shares of ≥0.07 C, 0.80 Si, 0.80 Mn, 19.0 Cr and 10.0 Ni , the balance being composed of iron, having an upper yield strength of 175 MPa (Grp 1); [0038] martensitic steel, containing shares of 0.07 C, 0.40 Si, 0.80 Mn, 12.5 Cr, 1.80 Ni and 0.30 Mo, the balance being composed of iron, having an upper yield strength of 440 MPa (Grp 2); [0039] NiTi alloy consisting of 50.0% Ni and 50.0% Ti having undergone heat treatment at 450° C. for 30 min, having an upper yield strength of 95 MPa (Grp 3); [0040] untreated NiTi alloy consisting of 56.02% Ni and 43.98% Ti having an upper yield strength of 380 MPa (Grp 4).

    [0041] Three files of each material were tested on 12 intact—though extracted—human teeth which had not previously been treated with an endodontic instrument. The teeth were cleaned and scanned using micro-computed tomography. The teeth were randomly divided into groups of 3 and assigned to treatment by endodontic instruments of one of the above groups. Perapical radiographs were created in order to evaluate the preoperative shape of the pulp chambers. The root canal was accessed by providing suitable cavities and afterwards treated by means of a file of the assigned group. The teeth were scanned again and changes introduced by the shaping activity of the file were assessed using micro-computed tomography. The variations in volume, surface and cross-sectional shape were evaluated qualitatively on a scale ranging from low, moderate and substantial to critical. The results are displayed the following table:

    TABLE-US-00001 Variation in Variation in Variation in cross-sectional volume surface shape Grp 1 low moderate moderate Grp 2 substantial substantial critical Grp 3 low low low Grp 4 substantial moderate substantial

    [0042] As an overall result, the files of Grp 1 and 3 showed only little pronounced variation in volume, surface and cross-sectional shape in comparison to the preoperative status of the root canal. This result is desirable in the view of preserving the natural healthy dentine to a high extent. The files pertaining to Grp 4 showed only satisfactory results, while unsatisfactory results were observed in the postoperative root canals treated with files made of martensitic steel (Grp 2).

    [0043] In FIG. 1, an endodontic instrument according the invention is shown. The base portion 1 has a central axis A and can be mounted on a holding device. Preferably, the holding device is engine driven and rotates the mounted base portion 1 concentrically around reference axis A. The endodontic instrument further has a working part 2 with an abrasive surface which extends from the base portion 1 and has an axis which is offset in parallel to the reference axis A of the base portion 1 by a distance r.

    [0044] In FIG. 2, an endodontic instrument is shown. The base portion 1 has a central axis A and can be mounted on a holding device. Preferably, the holding device is engine driven and rotates the mounted base portion 1 concentrically around reference axis A. The endodontic instrument further has a working part 2 with an abrasive surface which extends from the base portion 1 and has an axis which is arranged angular with respect to a reference axis A. The central axis A of the base portion 1 and the central axis of working portion 2 describe an angle α.

    [0045] FIG. 3 shows an alternative embodiment of the invention where a major portion of the working part is offset in parallel to the reference axis of the base portion. In this embodiment, working part 2 is mounted concentrically to the base portion and only partially deflected from reference axis A due to a curved shape of the working part.