ENDODONTIC INSTRUMENT, IN PARTICULAR FOR REAMING A ROOT CANAL

Abstract

The present invention relates to an endodontic instrument comprising a working segment (11) having a working section (110) and terminating in a distal portion (12) having a guiding and cutting function. The distal portion comprises a rounded guide head (13) and an angular cutting section (14). The angular cutting section comprises a distal zone (16) adjacent to the guide head and a proximal zone (17) between the distal zone and the working segment. The angular cutting section (14) further comprises cutting edges (15) extending over the full length of the proximal and distal zones. The distal zone comprises a distal section (160) with constant geometry and the proximal zone comprises a proximal section (170) the geometry of which varies between the distal section and the working section (110).

Claims

1. An endodontic instrument notably for reaming a root canal of a tooth of a patient, the instrument comprising a working length having a working section, the 5 working length being terminated by a distal portion having a dual guiding and cutting function; the distal portion comprising a rounded guide head and an angular cutting segment between the guide head and the working length; wherein the angular cutting segment comprises a distal zone adjacent to the guide head and a proximal zone between the distal zone and the working length; the angular cutting segment further comprising cutting edges that extend over the entire length of the proximal zone and the distal zone; the distal zone comprising a distal section of constant geometry and the proximal zone comprising a proximal section, the geometry of which varies between the distal section and the working section.

2. The endodontic instrument as claimed in claim 1, wherein the ratio of the length of the distal zone to the length of the guide head is greater than 1 or is greater than 2.

3. The endodontic instrument as claimed in claim 1, wherein at least one portion of the distal zone and the proximal zone is tapered, respectively forming a distal angle and a proximal angle with the longitudinal axis of the instrument.

4. The endodontic instrument as claimed in claim 1, wherein the diameter of the guide head is greater than the diameter of the circumscribed circle of the distal zone over at least a part of the length of the distal zone.

5. The endodontic instrument as claimed in claim 4, wherein the diameter of the guide head is greater than the diameter of the circumscribed circle of the distal zone at the junction of the guide head and of the distal zone.

6. The endodontic instrument as claimed in claim 1, wherein the ratio of the length of the proximal zone to the length of the distal zone is between 0.1 and 10.

7. The endodontic instrument as claimed in claim 6, wherein the ratio of the length of the proximal zone to the length of the distal zone is between 0.2 and 4.5 or between 0.6 and 1.8.

8. The endodontic instrument as claimed in claim 1, wherein the diameter of the circumscribed circle of the distal zone is constant over the entire length of the distal zone.

9. The endodontic instrument as claimed in claim 1, wherein the diameter of the circumscribed circle of the proximal zone is constant over the entire length of the proximal zone.

10. The endodontic instrument as claimed in claim 1, wherein the distal section has the form of a substantially regular hexagon.

11. The endodontic instrument as claimed in claim 1, wherein the distal section has the form of an “S” with two cutting edges, has a triangular form with three cutting edges, or a quadrilateral form with four cutting edges.

12. The endodontic instrument as claimed in claim 1, wherein the working section is triangular.

13. The endodontic instrument as claimed in claim 1, wherein the working section has the form of an “S” with two cutting edges, has a triangular form with three cutting edges, or a quadrilateral form with four cutting edges.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0014] Examples of implementation of the invention are indicated in the description illustrated by the attached figures in which:

[0015] FIGS. 1a and 1b show a longitudinal view (FIG. 1a) and a transverse cross-sectional view (FIG. 1b) of an end zone of an endodontic instrument;

[0016] FIG. 2 schematically represents the penetration of the instrument of FIGS. 1a and 1b into a rectilinear canal;

[0017] FIG. 3 schematically represents the penetration of the instrument of FIGS. 1a and 1b into a curved canal;

[0018] FIG. 4 illustrates an endodontic instrument comprising a working length that is terminated by a distal portion, according to an embodiment;

[0019] FIG. 5 shows a detail of the distal portion, according to an embodiment;

[0020] FIG. 6a shows planes of cross sections at different positions of the distal portion along the longitudinal axis of the instrument;

[0021] FIG. 6b shows cross sections of the distal zone according to the different transverse planes of FIG. 6a;

[0022] FIG. 7 shows a section of the distal portion along the longitudinal axis of the instrument; and

[0023] FIG. 8 shows a detail of a guide head and of the distal zone according to an embodiment.

EXEMPLARY EMBODIMENT(S)

[0024] FIG. 4 shows an endodontic instrument 10 intended notably for the reaming of a root canal of a tooth of a patient. The instrument comprises a working length 11 having a working section 110. The working length 11 is terminated by a distal portion 12 that has a dual guiding and cutting function. FIG. 5 shows a detail of the distal portion 12. The distal portion 12 comprises a guide head 13 and an angular cutting segment 14 between the guide head 13 and the working length 11. The angular cutting segment 14 comprises cutting edges 15 forming an angle with respect to the longitudinal axis 20 of the instrument 10. The angular cutting segment 14 comprises a distal zone 16 adjacent to the guide head 13 and a proximal zone 17 between the distal zone 16 and the working length 11. It will be noted that the cutting edges 15 extend over the entire length of the proximal zone 17 and over the entire length of the distal zone 16, to the junction of the guide head 13 and the distal zone 16, indicated by the plane 161 in FIG. 5.

[0025] FIGS. 6a and 6b show cross sections A-A, B-B, C-C, D-D, E-E, F-F and G-G, at different positions (FIG. 6a) of the distal portion 12 along the longitudinal axis 20 of the instrument, respectively of the guide head 13 working toward the working length 11. As illustrated in FIG. 6b, the distal zone 16 comprises a distal section 160 of hexagonal geometry forming six cutting edges 15 (cross sections A-A and B-B). The proximal zone 17 comprises a proximal section 170, the geometry of which changes between the hexagonal section 160 of the distal zone 16 and the working section 110 (cross sections C-C, D-D, E-E, F-F and G-G).

[0026] The distal section 160 of hexagonal geometry and the distribution of the cutting over the six cutting edges 15 ensure an optimized distribution of the mechanical stresses, minimizing the risk of breakage of the instrument.

[0027] For the use of this type of instrument, the following quantities are decisive. The nominal diameters D1 and D2 are the diameters of the circumscribed circle, that is to say the circle in which a cross section of the instrument at the working length 11 (see FIG. 4) is inscribed. The guide head diameter D3 corresponds to the diameter of the proximal base 130 of the guide head, that is to say at the plane 161.

[0028] According to one form of execution, the dimension of the distal section 160 of the distal zone 16 is constant. In other words, the circumscribed circle (the circle in which a cross section of the distal zone 16 is inscribed) is of constant diameter. FIG. 6a shows such an example of the distal portion 12 of which the distal zone 16, extending between the cross sections A-A and B-B, has a distal section 160 of constant dimension.

[0029] FIG. 7 shows a section of the distal portion 12 along the longitudinal axis 20 of the instrument. According to FIG. 8, the diameter D.sub.17 of the proximal zone 17 increases progressively over at least a part of its length L.sub.17, between the distal zone 16 toward the working length 11 of the instrument 10. The diameter D.sub.16 of the distal zone 16 also increases progressively over at least a part of its length L.sub.16, between the guide head 13 and the proximal zone 17. In other words, at least a portion of the distal zone 16 and the proximal zone 17 is tapered and forms, respectively, a distal angle α.sub.16 and a proximal angle α.sub.17 with the longitudinal axis 20 of the instrument.

[0030] According to another form of execution, the distal section 160 of the distal zone 16 and the proximal section 170 of the proximal zone 17 increase progressively over at least a part of the length of the proximal zone 17 and of the distal zone 16, between the guide head 13 toward the working length 11 of the instrument 10.

[0031] In one embodiment, the guide head 13 is rounded. As illustrated in FIGS. 5, 6a and 7, the guide head 13 is of substantially hemispherical form (or in dome form).

[0032] In yet another embodiment illustrated in FIG. 8, the diameter D3 of the guide head 13 is greater than the diameter D.sub.16 of the circumscribed circle of the distal zone 16 over at least a part of the length of the distal zone 16. According to one form of execution, the diameter D3 of the guide head 13 is greater than the diameter D.sub.16 of the circumscribed circle of the distal zone 16 at the plane 161.

[0033] Once again referring to FIG. 6b (cross sections A-A and B-B), the distal section 160 has the form of a substantially regular hexagon, that is to say whose six sides all have substantially the same length. However, it is also possible to consider the distal section 160 having the form of an irregular hexagon without departing from the scope of the invention.

[0034] The proximal section 170 of the proximal zone 17 has a geometry which changes gradually from the hexagonal geometry of the distal section 160 to the geometry corresponding to that of the working section 110, working from the guide head 13 to the working length 11.

[0035] For example, and as illustrated in FIG. 6b (cross sections B-B, C-C, D-D, E-E, F-F and G-G), the working section 110 is triangular (cross section G-G) and the proximal section 170 is transformed from a regular hexagonal geometry (cross section B-B) into a triangular geometry (cross sections F-F and G-G), in going through an irregular geometry (cross sections C-C, D-D and E-E).

[0036] It goes without saying that the present invention is not limited to the embodiment which has just been described and that various modifications and simple variants can be envisaged by the person skilled in the art without departing from the scope of the present invention.

[0037] For example, the working section 110 can have a form other than triangular with three cutting edges. Likewise, the distal zone 16 can comprise a distal section 160 having a geometry which differs from the hexagonal geometry illustrated in FIG. 6b. In particular, at least the working section 110 and/or the distal section 160 can have a section in the form of an “S” with two cutting edges, a triangular section with three cutting edges, a quadrilateral section with four cutting edges, or even a section of more complex form with more than four cutting edges 15.

[0038] According to a preferred form of the invention, the ratio L.sub.16/L.sub.G of the length L.sub.16 of the distal zone 16 to the length L.sub.G of the guide head 13 is greater than 1. The ratio L.sub.16/L.sub.G can also be greater than 2, even than 3 or than 5. A high ratio L.sub.16/L.sub.G means that the guiding edges 15 of the distal zone 16 come right to the end of the angular cutting segment 14, facilitating the apical machining of the canal by the angular cutting segment 14.

[0039] The ratio of the length L.sub.17 of the proximal zone 17 to the length L.sub.16 of the distal zone 16 can be expressed as a function of the distal angle α.sub.16, of the proximal angle α.sub.17, of the diameter D.sub.17 of the proximal zone 17 and the diameter D.sub.16 of the distal zone 16. More particularly, the ratio of the length L.sub.17 to the length L.sub.16 can be expressed by the equation 1:

[00001]$\begin{array}{cc}\frac{L_{17}}{L_{16}}=\frac{\left(D_{17}-D_{16}\right)}{\left(D_{16}-D_3\right)}\times \frac{\tan {\alpha }_{16}}{\tan {\alpha }_{17}}& \left(1\right)\end{array}$

[0040] According to one form of execution, the ratio of the length L.sub.17 of the proximal zone 17 to the length L.sub.16 of the distal zone 16 is between 0.1 and 10. The ratio of the length of the proximal zone 17 to the length of the distal zone 16 can be between 0.2 and 4.5 or between 0.6 and 1.8.

[0041] According to one form of execution, the diameter D.sub.16 of the circumscribed circle of the distal zone 16 is constant over the entire length L.sub.16 of the distal zone 16. In other words, the distal angle (α.sub.16) is substantially 0°.

[0042] Similarly, the diameter D.sub.17 of the circumscribed circle of the proximal zone 17 can be constant over the entire length L.sub.17 of the proximal zone 17.

REFERENCE NUMBERS EMPLOYED IN THE FIGURES

[0043] 10 instrument [0044] 11 working length [0045] 110 working section [0046] 12 distal portion, end zone [0047] 13 guide head, guiding segment [0048] 130 proximal base [0049] 14 angular cutting segment [0050] 15 cutting edge [0051] 16 distal zone, tip [0052] 160 distal section [0053] 161 plane at the junction of the guide head and the distal zone [0054] 17 proximal zone [0055] 170 proximal section [0056] 20 longitudinal axis [0057] 30 canal [0058] α.sub.16 distal angle [0059] α.sub.17 proximal angle [0060] D1, D2 nominal diameter [0061] D3 guide head diameter [0062] D.sub.16 diameter of the distal zone [0063] D.sub.17 diameter of the proximal zone [0064] L.sub.16 length of the distal zone [0065] L.sub.17 length of the proximal zone [0066] L.sub.G length of the guide head