WO2012038437A1

WO2012038437A1 - Endodontic instrument having, along a cutting portion, a supporting core extending along a helical path

Info

Publication number: WO2012038437A1
Application number: PCT/EP2011/066341
Authority: WO
Inventors: Hubert Euvrard; Jacques Pernot; Jean-Marie Vulcain; Pierre Colon
Original assignee: Neolix
Priority date: 2010-09-21
Filing date: 2011-09-20
Publication date: 2012-03-29
Also published as: FR2964852A1; FR2964852B1

Abstract

The invention relates to an endodontic instrument used for working on a tooth canal, having a base from which an active portion for working on the canal extends longitudinally, said active portion being supported by a supporting core. Said instrument is characterized in that said supporting core extends along a helical path.

Description

An endodontic instrument having, along a cutting portion, a carrier core extending along a helical path.

The field of the invention is that of the design and manufacture of instruments for practicing dental care. More specifically, the invention relates to endodontic instruments used to make a canal in a root of a tooth (or root canal).

When a tooth is affected by deep decay, it is sometimes necessary to devitalize the tooth. To do this, remove from the tooth and the root of the tooth infected tissue, and form a channel intended to be closed by a constituent material of Gutta or other pastes drains channel area.

To perform these operations, we use endodontic instruments that are similar to small diameter drills, and that allow to ream and / or cut the tooth of the tooth root to shape the channel to receive the Gutta or other canal filling pastes.

This treatment is therefore mechanized and the endodontic instruments are, at their design, designed to have sufficient hardness to pass through the dentin which is a medium-hard material, while having a certain degree of flexibility to be able to take shape. internal root of the tooth. To this end, it has been proposed for several years endodontic instruments made of an alloy of nickel and titanium, in place of instruments made from steel son.

In general, the current endodontic instruments are made from a cylindrical rod on which one or more helical cuts are cut, traditionally by a grinding process. The cutting surfaces generate at their intersection a cutting edge.

With conventional means of milling or grinding, the cuts produced result from the simultaneous combination of movements of the rotation and the advance of the wire (workpiece) in front of the grinding wheel or the milling cutter. The instruments thus machined have in their section perpendicular to the axis of the wire a known geometry predetermined by the machining cycle (circle, square, polygon ...). The centers of all these cross sections together define the carrier core of the cutting edge along the cutting portion of the instrument. It results from the use of conventional machining means (milling or grinding) that the carrier core extends rectilinearly and coincidentally with the axis of the wire constituting the initial workpiece.

Current instruments require great vigilance and precise dexterity on the part of the practitioner. Indeed, with known endodontic instruments, two opposite phenomena can occur:

either the ridge of the endodontic instrument slides over the material of the dentine;

either the edge of the endodontic instrument engages too quickly in the material of the dentine, which leads to a phenomenon referred to as the "weathering", at the end of which the instrument gets stuck in the material.

In both cases, the machining of the channel does not operate correctly, or even not at all.

It should be noted that in the case where the endodontic instrument gets stuck in the material, it is frequent that it comes to break. However, the endodontic instrument breakage inside the canal results in a significant operating cost for the practitioner and a risk for the health of the patient. The invention particularly aims to overcome these disadvantages of the prior art.

More specifically, the invention aims to provide an endodontic instrument that is more effective than those of the prior art, and which is simpler to use for the practitioner.

The invention also aims to provide such an endodontic instrument that allows the practitioner to consider operating profits.

These objectives, as well as others which will appear later, are achieved thanks to the invention which relates to an endodontic instrument used to work a canal in a tooth, having a base from which extends longitudinally an active working portion of the channel carried by a carrier, characterized in that said carrier core extends along a helical path along at least a portion of said active portion.

In particular, these objectives are achieved by an instrument used to bore a channel in a tooth, having a base from which extends at least one cutting edge, said cutting edge extending longitudinally along a cutting portion having a tip opposite said base, said cutting edge being carried along said cutting portion by a carrier core, characterized in that said carrier core extends in a helical path, along at least a part of said active part.

Thus, thanks to the invention, we obtain an endodontic instrument capable of volumetric variations in its active part.

Indeed, the carrier core being a helix, the instrument in its cutting portion, is likely to know different deformations: lengthening or reduction of the length, extension and radial reduction, curvature ...

It follows from this aptitude for volumetric variation that an instrument according to the invention notably provides the following advantages:

- An instrument according to the invention avoids the jamming phenomena, and allows the natural disengagement of the tool by a longitudinal retraction in case of high stress on the proximal portion (base side of the tool);

this retraction effect is accompanied by an enlargement of the upper part and is obtained by a retraction of the external shape with the trajectory of the carrying core of the tool (example: in the case of a tool with a ridge right helical cut, the curve of the carrier core will have its helical direction on the left); the relative variation (axial and radial) of the instrument improves the evacuation of dentinal debris and increases the efficiency of the irrigant fluid;

the effect of the instrument is more like a "scraping" or a milling, compared to the action of traditional endodontic instruments that are similar to a simple cut;

the tool adapts to the morphology of the canal, variable and often complex (ovoid, dissymmetrical, irregular, with narrowing or enlargement, curvature ...); thus, the contact zone is always maximum between the cutting edge (s) of the instrument and the wall of the channel thanks to a natural permanent adjustment of the envelope drawn by the rotating instrument under the effect of the constraints which exercise on the instrument;

the instrument according to the invention performs a more selective curettage of the necrosed tissues, softer, thanks to a reduced stress opposite the instrument in comparison to the healthy, harder tissues, which preserves in an optimized way the shape of the treated channel;

the possible presence of two propellers (an inner helix coinciding with the carrier core and an outer helix corresponding to the cutting edge), in the same or opposite directions, in the direction of rotation of the instrument or in the direction opposite, allows to act on the flow of fluids, in an incoming or outgoing direction (bore, evacuation of debris, irrigation, compaction ...). According to a first variant embodiment, said cutting portion has a plurality of non-contiguous turns. According to a second variant embodiment, said cutting portion has a plurality of contiguous turns.

In either case, said cutting portion may advantageously have a central recess.

Such a feature contributes to further increase the positive effect of the instrument on the flow of fluids, in an incoming or outgoing direction.

According to an advantageous solution, the carrying core has a cross section whose geometric shape is a shape belonging to the following group: triangular, square, rectangular, polygonal, oval, or a combination of these forms.

Advantageously, said turns have a cross section decreasing going from said base to said tip.

According to a first embodiment, said helical path extends around a curvilinear central axis.

According to a second embodiment, said helical path extends around a rectilinear median axis.

According to an advantageous solution, said cutting portion has a constant outer diameter.

It is noted that said cutting portion may have an evolving outer diameter according to another advantageous solution.

According to a particular embodiment, said cutting portion has a conical or frustoconical shape.

According to another particular embodiment, said cutting portion has a diameter increasing from said base to said tip.

However, said cutting portion may have a decreasing diameter from said base to said tip according to another possible embodiment.

According to an advantageous characteristic, said helical trajectory extends around a median axis, said base having an axis of rotation offset with respect to said median axis or said carrier core. This embodiment makes it possible to confer volumetric variability on the endodontic instrument from which the advantages listed above result.

Other features and advantages of the invention will emerge more clearly on reading the following description of various embodiments and variants of the invention, given by way of simple illustrative and non-limiting examples, and the appended drawings in which:

Figures 1 to 3 are schematic views of an endodontic instrument according to a first embodiment of the invention, respectively seen from the side, seen in perspective and seen in a cross section;

Figures 4 and 5 are schematic views of a second embodiment of an endodontic instrument according to the invention, respectively seen from the side and seen in perspective; Figures 6 and 7 are views of a third embodiment of an endodontic instrument according to the invention, respectively seen from the side and seen in perspective;

Figures 8 and 9 are views of a fourth embodiment of an endodontic instrument according to the invention, respectively seen from the side and seen in perspective;

- Figures 10 to 12 are views of a fifth embodiment of an endodontic instrument according to the invention, respectively seen in perspective, seen from the side and seen in a cross section;

Figures 13 and 14 are views of a sixth embodiment of an endodontic instrument according to the invention, respectively seen from the side and seen in perspective;

Figures 15 to 26 are each a schematic representation of the trajectory of the carrier web of the cutting portion of an endodontic instrument according to the invention. As indicated above, the principle of the invention lies in the fact of proposing an endodontic instrument whose cutting edge is carried by a carrier core extending along a helical path.

Of course, the helical trajectory of the carrier core can be alternated by a rectilinear, oblique, curved trajectory, thus generating rectilinear, oblique, curved edges (if there is no conjugation with the axis of rotation), helical (if presence of conjugation with the axis of rotation).

This is illustrated by Figures 1 to 3 which show an embodiment of an endodontic instrument according to the invention.

As illustrated by these figures, the endodontic instrument comprises a base 1 that can constitute either a gripping end intended to be manipulated manually by a practitioner, or an assembly member for mounting the endodontic instrument on a tip of a rotary tool.

As an indication, an endodontic instrument according to the invention is made from a metal rod, and more precisely from a rod made of an alloy of nickel and titanium, machined by an electro-erosion technique.

The EDM wire used is moved in a combination of longitudinal and transverse displacements with respect to the longitudinal axis of the endodontic instrument, so as to generate cutting surfaces leading to their intersection, the appearance of a cutting edge extending longitudinally along a cutting portion 2 extending between two ends, one of which is defined by the tip 20 of the instrument and the other by the base 1 of the instrument.

FIG. 3 is a view in a transverse section (that is to say in a plane perpendicular to the longitudinal axis X of the endodontic instrument) of the cutting portion 2, in this case at the plane of C section shown in Figure 1. Figure 3 thus shows a cross section of the cutting portion 2, here taking the form of a triangle; this section has cutting surfaces, the intersection of two cutting surfaces forming a cutting edge 21. This cross section has a central point 22. The carrier core 200 is the path connecting the central points 22 of all the cross sections along the cutting portion, the edge or edges 21 being carried by the carrier core 200 along the cutting portion.

According to the principle of the invention, the carrier core 200 extends along a helical path. Indeed, the carrying core 200 has a spiral shape in Figure 3, the ends correspond to the ends of the cutting portion, one of them corresponding to the tip 20 and the other extending from from base 1.

In this way, the turns 23 formed in the cutting length 2 have a radial elasticity which offers the following advantages:

the cutting portion 2 is adaptable in diameter, which generates a maximum contact area between the edges of the instrument and the wall of the canal, whatever the morphological variability of the channel (narrowing or bulging), finally allowing curettage parietal optimal at all times;

the cutting portion 2 is adaptable to the hardness of the channel: the instrument retracts in length and contracts in width, automatically, which allows the possibly blocked instrument to disengage naturally from the blocking zone, this retractability is conferred by the bearing core which will then turn in the opposite direction of the direction of rotation of the base.

In accordance with the principle of the invention, the carrier core 200 can then take on various possible configurations, among which:

the helical path of the carrier core is constituted by a plurality of turns of the same diameter, with a regular pitch, as illustrated by FIG. 15; the helical path of the carrier core is constituted by turns of the same diameter, with a variable increasing pitch, as shown in Figure 16;

the carrier core is constituted by a plurality of turns of the same diameter, with a decreasing variable pitch, as shown in Figure 17;

the helical path of the carrier core is constituted by a plurality of turns whose diameter decreases towards the tip, this with a regular pitch as shown in Figure 21;

the helical path of the carrier core is defined by a plurality of turns whose diameter decreases towards the tip, this with a variable increasing pitch as shown in Figure 22;

the helical path of the carrier core is constituted by a plurality of turns whose diameter decreases toward the tip, with a decreasing variable pitch as shown in FIG. 23;

the helical path of the carrier core is constituted by a plurality of turns whose diameter increases towards the tip, with a regular pitch as shown in Figure 24;

the helical path of the carrier core is constituted by a plurality of turns whose diameter increases in the direction of the tip, with a variable increasing pitch as shown in Figure 25;

the helical trajectory of the carrying core is constituted by a plurality of turns whose diameter increases towards the tip, with a decreasing variable pitch as shown in FIG. 26. Note that the helical trajectory of the carrier core extends around a median axis M which can be confused with the axis of rotation R of the base 1 of the instrument as illustrated by FIGS. 15 to 17 and 21 to 26.

According to possible variants, the median axis M of the helical trajectory of the carrying core can be shifted, remaining in the illustrated example parallel to the axis of rotation R of the base as illustrated by FIGS. 18, 19 and 20.

Of course, these variants can be combined with the other embodiments illustrated in the other figures, except of course the offset between the axis of rotation R and the central axis M.

The median axis M may not be parallel to the axis of rotation R.

Moreover, the turns 23 of the helical trajectory of the carrier core can be:

non-joined, as illustrated by Figures 1 to 9;

- joined, as illustrated by Figures 10 to 14.

Moreover, the median axis M of the helical trajectory of the carrying core may be rectilinear as illustrated by FIGS. 1 to 9, curvilinear, or arbitrary

According to another aspect of the invention, the flutes (or in other words, the cutting surfaces) extending between two cutting edges define, along the cutting portion, a plurality of cross sections all centered on the carrier core, these flutes or cutting surfaces themselves extending along a helical path around the carrier, this with a pitch that may be less than, equal to or greater than the pitch of the helical path of the soul carrier.

In addition, the helicoidal trajectory of the flutes around the helical trajectory of the carrier core may consist of a plurality of turns of a constant or progressive pitch (increasing or decreasing).

According to the embodiment illustrated in FIGS. 1 and 2, the carrier core of the cutting portion has a helical trajectory of conical shape of the tip 20 at the base 1, with turns having a variable pitch increasing from the tip of the instrument, and external flutes (between two cutting edges) have a helical shape with a smaller pitch than that of the carrier, the turns of external flutes having a decreasing diameter.

As an indication, the helical trajectory of the load-bearing core defines six turns, while the helical path of the external flutes (or cutting surfaces) defines twelve turns.

For example, according to the embodiment illustrated in FIGS. 4 and 5, the helical trajectory of the carrier core of the cutting portion is constituted by a plurality of turns whose diameter decreases from the base towards the tip of the tool, with a variable step decreasing towards the tip of the instrument. The external flutes form a helical winding around the bearing core, the helical coils having a decreasing diameter towards the tip of the tool, this with a pitch less than that of the helical trajectory of the carrier core (the trajectory the helical helix defines six turns between the base and the tip of the instrument while the helical path of the outer flutes defines twelve turns from the base to the tip).

For example again, according to the embodiment illustrated in FIGS. 6 and 7, the helical trajectory of the load-bearing core consists of a plurality of turns whose diameter decreases in the direction of the point, with a variable pitch decreasing in going towards the point. The external flutes define a helical winding around the load-bearing core, the turns of which have a variable diameter decreasing towards the tip of the tool, this with a pitch greater than that of the helical trajectory of the load-bearing core (number of turns defined by the helical path of the carrier core is equal to thirteen while the number of turns defined by the helical path of the external flutes is equal to six).

For example again, according to the embodiment illustrated by FIGS. 8 and 9, the helical trajectory of the carrier core is constituted by a plurality of constant diameter turns with a regular pitch. The external flutes define a winding around the carrier core, with turns also of constant diameter and a pitch equal to that of the helical trajectory of the carrier core (number of turns defined by the helical trajectory of the load-bearing core and by the helical path of the external flutes is equal to seventeen).

In addition, as shown in FIGS. 3 and 12, the turns of the cutting portion have a cross section that can have a triangular shape whose center 22 is a point of the carrier core.

However, according to other conceivable embodiments, the cross section of the turns (or more generally of the carrier core) may have any geometrical shape consisting of segments and / or curved sectors, for example a triangular, square shape, rectangular, polygonal, oval, or a combination of these forms.

The shape of this cross section may be composed of rectilinear sectors and / or curves (concave for example) and have a regular shape or not.

The direction of the helical path of the carrier core may be left or right, or mixed left and right, one or more times over all or part of the length of the cutting portion.

In addition, the generatrix of the envelope of the cutting portion can be:

rectilinear, which generates a cylindrical envelope;

rectilinear inclined, which generates a conical or frustoconical envelope;

curve (concave or convex), which generates an envelope whose shape is that of a sphere, an ogive, a diabolo ...

According to another characteristic (combined with the preceding or independent characteristics thereof), the base 1 of the present instrument a notch 11, one end of which opens at the end of the base from which the cutting portion extends.

Such a notch facilitates the circulation of a fluid to or from the channel, for example with regard to the introduction of an irrigant fluid to the channel.

This effect can be optimized in the presence of a central recess 24 delimited by the turns 23 of the instrument in the cutting portion, such a recess also promoting the circulation of fluid inside the channel.

In addition, such a notch solves the possible problem of stiffness that exists on the instrument between the handle (passive part) and the blade (active part).

Note that this notch can be unique or repeatedly present. The shape of this notch may be rectilinear, helical or otherwise, in the direction of width, length, or oblique.

This or these notches and / or the central recess thus allow a vertical circulation of fluids, liquid or semi-liquid, in possibly opposing directions along the cutting portion of the instrument (proximo-di stal or di sto- proximal) inside and / or outside the instrument.

Note that the surface of the instrument may be more or less granular depending on the setting of the machine's machining machines, including the treatment of any surfaces subsequent to machining to ensure abrasiveness to the instrument.

In addition, the handle and the blade can be machined in one piece to obtain a monobloc instrument, including the base for holding the instrument on an instrument holder.

It should be noted that the invention more generally applies to an endodontic instrument used to work a canal in a tooth, having a base from which extends longitudinally an active portion of working the channel carried by a carrier core, said carrier core extending in a helical path.

Indeed, the principle of the invention applies both to a dental canal boring instrument, as to compaction tools, for example to fill and stuff the dough channel or other sealing products.

Indeed, the combination of two propellers on the instrument (one formed by the bearing core and the other formed by the helical winding of the flutes (cutting surfaces around the carrier core) makes it possible to envisage six families of cases and a wide range of endodontic applications.This is summarized by the table below.

G: flutes

P: carrying core

: direction of rotation in the direction of clockwise

: direction of rotation counterclockwise.

0: no rotation

Moreover, the invention can be applied to instruments having characteristics of various shapes and / or sizes belonging in particular to the following group: the instrument is produced from a blank in the form of a solid rod or a tube, rectilinear or twisted (or of any shape);

in the case of a blank machined externally, the number of flutes on a given section is typically between 1 and 6 (but may exceed 6, especially for a large diameter instrument);

the endodontic instrument may have a conventional taper of between 0 and 15%, up to 30% or more;

the diameter of the instrument is conventionally between 0.06 mm and 1.2 mm, but can reach 4 mm in the case of a veterinary use for example, or even be less than 0.06 mm at the tip;

the instrument has a length conventionally comprised between 15 and 30 mm, but can more generally vary between 5 mm and 200 mm;

the instrument is intended for manual or mechanized use, and may have a means of wrapping;

the instrument may be intended for continuous rotational, alternating rotary, vibratory or even a combination of these uses; the instrument may be metallic (nickel-titanium or other possible alloys, stainless steel, carbide, or any other metals ...), or plastic.

Claims

An endodontic instrument used for working a channel in a tooth, having a base (1) from which extends longitudinally an active working part of the channel, carried by a carrying core (200) characterized in that said carrier core s' extends along a helical path along at least a portion of said active portion.

An endodontic instrument according to claim 1, used for making a channel in a tooth, having a base (1) from which at least one cutting edge (21) extends, said cutting edge (21) extending longitudinally along a cutting portion (2) having a tip (20) opposite said base (1), said cutting edge (21) being carried along said cutting portion (2) by a web carrier (200), characterized in that said carrier core extends in a helical path.

Endodontic instrument according to claim 1, characterized in that said cutting portion has a plurality of non-contiguous turns (23).

Endodontic instrument according to claim 1, characterized in that said cutting portion has a plurality of contiguous turns (23). Endodontic instrument according to any one of claims 1 to 3, characterized in that said cutting portion (2) has a central recess (24).

Endodontic instrument according to claim 1, characterized in that the carrier core (200) has a cross section whose geometric shape is a shape belonging to the following group: triangular, square, rectangular, polygonal, oval, or a combination of these forms .

Endodontic instrument according to one of Claims 2 to 6, characterized in that said turns (23) have a decreasing cross section from said base (1) to said tip (20).

8. endodontic instrument according to any one of claims 1 to 7, characterized in that said helical path extends around a curvilinear central axis.

9. Endodontic instrument according to any one of claims 1 to 7, characterized in that said helical path extends around a rectilinear median axis.

10. endodontic instrument according to any one of claims 1 to 9, characterized in that said cutting portion (2) has a constant outer diameter.

11. Endodontic instrument according to any one of claims 1 to 9, characterized in that said cutting portion (2) has an evolving outer diameter.

12. endodontic instrument according to claim 1 1, characterized in that said cutting portion (2) has a conical or frustoconical shape. 13. endodontic instrument according to claim 1 1, characterized in that said cutting portion (2) has a diameter increasing from said base (1) to said tip (20).

14. endodontic instrument according to claim 1 1, characterized in that said cutting portion (2) has a decreasing diameter from said base (1) to said tip (20).

15. Endodontic instrument according to any one of claims 1 to 14, characterized in that said helical path extends around a median axis, said base having an axis of rotation offset from said median axis of said central core.