EP3102148A1

EP3102148A1 - Magnetic drive for contra-angle in dentistry

Info

Publication number: EP3102148A1
Application number: EP15704045.2A
Authority: EP
Inventors: Guy Levy; Claude CASTELLI; françois Levy; Philippe Levy
Original assignee: Micro Mega International Manufactures SA
Current assignee: CASTELLI, CLAUDE; LEVY, FRANCOIS; LEVY, GUY; LEVY, PHILIPPE
Priority date: 2014-01-13
Filing date: 2015-01-13
Publication date: 2016-12-14
Also published as: FR3016283B1; WO2015104519A1; FR3016283A1

Abstract

The invention relates to a contra-angle having a magnetic actuator engaging a transmission system in order to drive, with an alternating motion, a tool-holding head (12) arranged so as to slide inside a housing placed at the end (24) of the handle (9) of the contra-angle. The magnetic actuator comprises at least one coil powered by an AC current with variable frequency and intensity, at least one portion of said coil being subjected to a magnetic field which generates electromagnetic forces therein that tend to impart an alternating motion thereto when the current changes direction, the transmission system transforming the alternating motion of a mounting of the coil into an alternating motion of the tool-holding head (12).

Description

MAGNETIC TRAINING AGAINST ANGLE IN DENTISTRY

The present invention relates to a contra-angle with magnetic operation, provided for this purpose with a magnetic actuator for the automation of endodontic technique, which is common practice in dentistry today.

This automation is currently carried out by various mechanical drive means giving the endodontic files a movement allowing them the penetration of the channel and its shaping.

In a first existing solution, the movement imposed on the file is a cutting movement of the canal walls in alternating rotation. In this case, the friction of the files on the walls of the canal imposes on the limes an alternating twist in both directions, which can lead to their fracture.

More recently, the appearance of nickel titanium alloys, which are more resistant to torsion and flexibility, has allowed slower rotation, or alternating rotation of the limes, for the cutting of canal dentin. as described for example in US 2012 / 0107766Al. The slowing of the speed of rotation is limited by the resistance of these metals to torsion on the one hand and by the cutting effect of the blades on the dentine on the other hand. The possible operating values are difficult to specify, however, because the canal dentin may have a variable hardness - possibly in the same channel - and the torsional resistance depends on the part of the file engaged in the channel, more precisely the volume of the canal. metal in the section in tension.

To avoid the disadvantages resulting from the rotation of the frictional root canal instruments, Lévy (EP0161196 A1) proposed a drive head giving the file an alternating longitudinal movement of variable amplitude. According to this invention, the amplitude of the longitudinal reciprocating movements becomes largely a function of the friction encountered by the file moving in the canal during the cutting of the dentine. The amplitude of the longitudinal movements is supposed to vary from 0.35 mm to 1.5 mm: with a strong friction of the file on the walls, the amplitude would be 0.35 mm whereas with a weak friction, it would be 1.5 mm, both on the rise and the descent of the instrument in the channel.

In addition, the endodontic instrument holder, or tool head, is free to rotate in this solution, which allows the file to rotate on its axis as well during the ascent or descent, because of the oblicity of the blades of the instrument. However, during strong friction during the descent, the file coming into forced contact with the walls may no longer advance, which has the effect of causing the patient an unpleasant sensation of percussion.

Another disadvantage results from the fact that the energy developed during the movements of descent or rise of the file can not be dissociated, and that it is therefore not possible to differentiate the efficiency of the file during the ascent or descent. However, it is important to promote, for example, the cutting effect in tension once the file is engaged smoothly in the channel.

The object of the present invention is first of all to avoid the use of mechanical energy in forced rotation as is the case when the energy is produced by an electric motor for the setting in motion of the counter-rotation. angle and therefore the instrument attached to it. Transformation of rotation into reciprocating longitudinal movement, as for example implemented in the aforementioned Levy patent EP0161196, requires a minimum mandatory displacement. In the Levy patent, this minimum displacement is 0.35mm.

The second objective is to regulate the force developed for moving the file independently both uphill and downhill, and to inform the practitioner of the position of the file in relation to a required minimum of the vibration.

To these effects, the contra-angle of the invention is provided with a magnetic actuator cooperating with a system of transmission for driving in a reciprocating manner a tool head or instrument holder, arranged to slide in a housing placed at the end of the handle of the contra-angle. According to the invention, the magnetic actuator comprises at least one coil fed by an alternating current of variable frequency and intensity, at least a portion of said coil being subjected to a magnetic field which generates electromagnetic forces tending to communicate therewith reciprocating when the current changes direction, the transmission system transforming the reciprocating motion of a coil support into an alternating movement of the tool head.

The reciprocating linear movement of the tool holder is thus created by a coil subjected to a magnetic field, the coil being fed by a current generated at very low voltage at a selected frequency and intensity and variables.

According to a first alternative, the coil is of planar appearance and comprises two sections each passing between two opposite magnetic poles of at least one permanent magnet, creating for each section an electromagnetic force tending to move the coil in the same direction when it is traversed by a current.

More precisely, according to one possible configuration, the coil is of rectangular shape or delimits an annular sector, said sections passing between the magnetic poles of two permanent magnets being in fact a pair of opposite sides of the rectangle or the radial sides of the annular sector. .

In other words, the plane coil is hollowed out in the center (without conductor), and its two lateral beams are sandwiched in magnetic fluxes constituted by two powerful magnets whose magnetic effects are added. In practice, the current flowing through the coil flows in opposite directions in the lateral sections, and the Laplace electromagnetic forces generated by the simultaneous existence of the magnetic flux and the current go in the same direction when the poles of the magnets permanent are inverted, creating opposite magnetic fluxes. Each magnet acts only on the conductor beam of a single side concerned by its flow.

To transmit its movements, the support of the coil comprises a parallel arm on the one hand on the plane of the coil and on the other side on said sides, pivotable relative to the housing of the actuator and having at its free end a rotational connection with a shaft, or a connection to a semi-rigid cable followed by a shaft, said shaft being guided axially by the handle.

The pivot axis is placed in the arm between the connection with the transmission system, of which the shaft and possibly the cable are part, and a part of the support located directly under the coil, said arm projecting from the latter. The reciprocating movement of the reel is then transformed into a reciprocating movement of the free end of the arm carrying the connection with the transmission system, which moves in the opposite direction to the displacement of the reel.

According to a second alternative, the coil may be a solenoid wound on the one hand around a support able to slide axially on a central core forming one of the poles of a permanent magnet and surrounded on the other by a cylindrical envelope forming the opposite pole of the magnet, the central core and the support having means for axial guidance and rotational locking of one with respect to the other.

It is a symmetry of revolution configuration, volumiquement less flattened than the previous configuration. More specifically, the axial guide means may comprise at least one rod secured to the inner face of a sleeve constituting the support of the coil, said rod being able to slide in a groove made axially in the central core and being connected to the system. of transmission.

Alternatively, these means may have two rods cooperating with two grooves arranged opposite one another in the central core, each rod being then connected to a shaft guided axially by the handle.

In the various alternatives, the transmission system preferably comprises a shaft extending in the handle of the contra-angle, and which plays an important role in the transmission of the movement generated by the magnetic actuator to the tool head. .

The end near the tool head of said shaft then comprises means for transforming the displacement of the shaft in a first direction substantially parallel to the axis of the handle in a movement of the tool head in a second direction.

According to one possible configuration, said transformation means consist of a pivotable tilting gear in the handle in the vicinity of the tool head along an axis perpendicular to a plane containing the two directions, one end of the tilting gear being slidable in a ring ending the shaft, the other end being equipped with a fork-type end portion cooperating with a cavity in the tool head to drive along the axis of the housing.

The rocking motion of the magnetic actuator is in fact transmitted, at the end of the shaft, to one of the ends of the gearbox, which transmits it at its other end beyond the pivot axis, which is connected to the tool head according to a conventional forked connection inserted into a recess, for example annular of the head. This connection has a degree of freedom in a direction substantially perpendicular to the axis of sliding. The ring at the end of the shaft is dimensioned and oriented to provide mechanical flexibility to the connection, also in the form of a degree of freedom since a sliding of reduced amplitude is possible for the corresponding end of the gearbox.

According to one variant, these transformation means may be provided for connecting the shaft of the transmission system to the periphery of the tool head in order to drive it further in rotation, the connection at this point then being of the type to eccentric pivot relative to the axis of sliding of the tool head.

Furthermore, the handle is preferably equipped with sensors capable of detecting the amplitude of the displacements of the transmission system, so as to optimize the control and control of the tool head, in particular for the purpose of evaluating in real time. some internal variables of displacement and positioning. These sensors make it possible in particular to ensure one of the objectives assigned to the invention, namely to inform the practitioner of the position of the file during the use of the contra-angle.

For the same overall objectives of control and control, in a more external perspective, the contra-angle of the invention is provided with means for adjusting the frequency and intensity of the current flowing through the coil. These external control and control means are preferably able to differentiate the adjustment values according to the direction of the current, that is to say that the setting of the parameters can be dissociated according to the flow direction of the current. It becomes possible, for example, to impose a displacement of the carriage which is not identical in both directions of the current, which amounts to allowing asymmetrical operation of the magnetic actuator and consequently of the contra-angle.

The invention will now be described with reference to the appended figures, which represent two examples of embodiments, and for which:

Figure 1 shows schematically the planar coil magnetic actuator according to the first alternative;

- Figure 2 shows, in sectional view, the transmission system at the end of the handle of the contra-angle at the connection with the tool head;

Figure 3 is a longitudinal sectional view of the second alternative of the invention; and

- Figure 4 shows a cross section.

With reference to FIG. 1, the magnetic actuator shown generates a reciprocating linear movement by means of a planar-shaped coil (2), in this case in the form of an annular sector consequently comprising, on the lateral sides, coil sections (2) constituting bundles of conductors respectively left (5) and right (6). Each of these beams (5, 6) passes through a magnetic flux produced by a permanent magnet (1). When the coil (2) is fed with a current via the conductors (3, 4), said beams (5, 6) are traversed by a current flowing in opposite directions from each other due to the geometrical structure. of the coil (2). By subjecting them each to a magnetic flux inverse to that to which the other is subjected, the Laplace forces generated are of substantially identical direction and direction, exerting in any case cumulative actions which tend to move the coil (2) in a direction. one and the same meaning:

When the direction of the current in the coil is reversed, the displacement of the coil is reversed also under the cumulative action of the resultants of the Laplace forces also reversed which are generated in the two lateral beams (5, 6). The nature of this displacement depends in practice on the configuration of the support of the coil (2) and the housing (20) of the actuator, and their mechanical connection. In this case, the displacement is in the plane of the coil and is perpendicular to the active beams (5,6). The coil (2) is integral with a flat support having an arm (7) pivoting on an axis (23).

The housing (20) comprises a compartment (21) of substantially identical shape to that of the spool (2), having an opening (22) for the passage of the arm (7) which in practice connects the support to the transmission system . Note that the high and low beams of the coil are without action because out of the magnetic flux of the permanent magnets (1).

Inverse magnetic fields are for example generated by permanent magnets with neodymium of adequate dimensions (for example 12mmx6mmx2mm). These magnets allow a linear alternative movement whose amplitude can go up to 20mm. The optimum frequency of inversion is for example between 20 Hz and 40 Hz. The total linear stroke can be adjusted by a race reducer in both directions, if necessary. The supply of the coil (2) is obtained by a current from a supply of TBT (very low voltage) of 5 to 12 volts, these values being indicative, preferred but not limiting.

The frequency of the inversions can be controlled by potentiometer or by any other suitable digital or analog adjustment means allowing the control of the period of the current supplying the coil (2). The frequency of the changes of direction of the current determines the frequency of "beat" of the coil (2). At the rank of the adjustable parameters, the intensity of the current determines the intensity of the force generated in the magnetic actuator, in the two directions of movement and, according to the control and control means of the invention, independently one from the other.

The displacement of the spool (2) is transmitted by the arm (7) to a transmission shaft (8), which is rotatably connected at its free end. This shaft (8) is deployed in the handle (9) of the contra-angle towards the end (24) provided with the head (12) tool holder equipped with its tool or instrument (25) for treating the tooth .

The travel of the travel of the reel (2), and the amplitude of the resulting movement communicated to the shaft (8), can be indicated to the operator via sensors (30) located in the vicinity of the transmission shaft. (8) for example, at a minimum travel in both directions, the information provided by these sensors (30) is likely to indicate a significant friction, preventing the correct movement of the instrument (25) attached to the against -angle.

Schematically, the horizontal reciprocating linear movement is transmitted by a rigid shaft (8) to the head (12) of the contra-angle, and converted into a vertical reciprocating motion by means of a particular mechanical device, in this case a toggle gear (11), as it appears clearly in Figure 2.

The arm (8) terminates in an orientable ring (26) housing a first end of the tilting gear (11), which slides there smoothly. This rocker gear (11) has at its other end a fork (13) which is inserted into a suitable cavity, for example an annular recess (26) formed in the tool head (12). This fork (13) makes an angle of about 40 ° with the rest of the gear (11) and leaves the tool head (12) free to rotate within the end (24) of the contra-angle. The pivot (14) of the rocker (11) reduces the amplitude of the reciprocating movements of the fork (13), therefore the tool head (12).

Thus, according to the invention, the alternately energized coil (2) ultimately causes a vertical reciprocating linear movement of an endodontic instrument (25) or an instrument (25) for scaling or root planing inserted in the head-holder. tools (12). The alternating current supply frequency of the coil (2) conditions the frequency of the reciprocating movement of the instrument, and the intensity of the force exerted by the instrument can be adjusted by adjusting the intensity of the current which feeds the driving coil (2). This adjustment must be able to be obtained independently for both directions of movement of the coil (2). The adjustment of at least one of these 2 parameters is obtained for example by action on at least one potentiometer located at the power supply of the coil (2).

These settings being established, they constitute a safety because the use of a magnetic actuator, providing a kind of "magnetic link" in the chain of actuation of the instrument, acts as a force limiter and removes, by simple magnetic damping, the effect "jackhammer" resulting from the structure disclosed in the previous document EP 0 161 196 in the name of Lévy.

The variant of FIG. 1, and more generally the device of the invention, preferably comprises a housing of control and control comprising 1 supply electronics, with possibility of adjusting the intensity and frequency of the current, and a visual control screen associated with a hearing alarm. The supply electronics is moreover connected to the sensors (30) located in the vicinity of the shaft (8) of the transmission system.

A first "alarm" signal is obtained when, for example, a file can not reach, on descent, a minimum distance of vibration chosen by the practitioner, because prevented by excessive friction, for example on the canal dentin, when the forces of friction are greater than the displacement force of the instrument. The skilled practitioner can then choose to increase the displacement force by increasing the intensity of the current supplying the coil (2), or to change the instrument for a smaller diameter, or to increase the cutting force in traction. to allow for example an enlargement of the diameter of the channel in its upper coronary, following the well-known principle of the "crown down technique".

A second signal occurs when, for example, the file can not reach an established cutting distance (for example 2/3 of the maximum cutting distance in tension): in this case, the practitioner can choose to increase the intensity of the current feeding the coil, and / or increasing the frequency of the AC power supply.

These alarm signals are generated by the microsensors (30) connected to the audible and / or visual alarm systems of the control box. The control and control unit also comprises, as part of the power electronics, circuits for the transformation of electrical signals of the sector into very low voltage supply (TBT).

It may be advantageous to integrate the power supply electronics, control and control on the one hand, and the coil (2) and the magnets (1) on the other hand, in the same housing. The displacement of the coil (2) is then transmitted by semi-rigid cable to the transmission shaft (8) and then to the tilting gear (11) connected to the tool head (12). The longitudinal displacement of the cable is transmitted in the handle (9) of the contra-angle, to the reducing scale (11) having the fork (13) inserted into the instrument core (12) to give it a vertical vibration.

It may also be advantageous to convert this longitudinal displacement of the coil (2) into an alternating rotation of the tool head (12) installed in the end of a specific contra-angle. This is obtained by connecting the transmission shaft (8) laterally to the cylindrical instrument-holder head (12), which will rotate alternately in its housing, depending on the displacement of the rigid cable driven by the coil (2).

According to an alternative version appearing in FIGS. 3 and 4, the invention may comprise a coil / magnet assembly adopting a geometry of revolution, replacing the magnetic actuator of planar appearance of the first version illustrated in FIG.

This assembly comprises, as a coil, a solenoid

(15) wound on the one hand around a support (27) capable of sliding axially on a central core (19) forming one of the poles of a permanent magnet. The solenoid is further surrounded by a cylindrical envelope (17) forming the opposite pole of the magnet. The two poles are connected by a pole piece (18) which can act as a stop when moving the sliding support (27). The central core (19) and the support (27) comprise axial guide means and, in this case, rotational locking relative to each other, in the form of longitudinal grooves (28) arranged on both sides of the core axis (19). These two grooves (28) are intended to receive two guide rods (16) for guiding the support (27) during its sliding movement.

The support (27) of the coil (15) is a hollow cylinder with a circular section housing in its internal face the two guide rods (16), which are fixed thereto, and on its outer part one or more layers of copper wire fed with alternating current in TBT from a control and control box of the same type as that mentioned above, which in particular manages the intensity and frequency of the current power.

The movement management of the mobile element, in this second version of the magnetic actuator, is carried on one side by the pole piece (18) effecting the magnetic connection between the poles, and on the other side by the head of the counter angle. The two supply wires (3, 4) of the coil (15) pass into said pole piece (18). The two guide rods (16) are secured, at the output of this assembly, to be connected to the shaft (8) of the transmission system, continuing for example by a rocker device (11) like the The solution shown in Figure 2. In this option, a single power cord is sufficient to connect the control and control box to the contra-angle.

As for the previous version, the operating possibilities open to the operator, by varying the control parameters, are for example:

adjusting the frequency of the alternating current supplying the coil (15) by means of potentiometers or any other analog or digital control and adjustment device, causing in this case the reciprocating sliding of the coil (15) and consequently the tool head (12);

the adjustment of the amplitude of the sliding of the reel (15) in its outward and return movements, for example by action on the intensity of the current or on the TBT, independently for the outward and return races of the instrument (25).

In the two alternatives described, in short, the reciprocating displacements of the coil (2, 15) are transmitted to a shaft (8) and then for example to a rocking gear (11) - together constituting the transmission system - transmitting the movements alternating said coil (2, 15) to a tool head (12), that is to say in fine endodontic instruments (25) or root planing used for the Periodontology.

The alternatives described with reference to the figures should not be considered as exhaustive of the invention, which on the contrary covers variants of shapes and configurations within the reach of those skilled in the art.

Claims

1. A magnetically actuated contra-angle cooperating with a transmission system for reciprocatingly driving a tool head (12) arranged to slide in a housing at the end (24) of the handle (12). 9) of the contra-angle, characterized in that the magnetic actuator comprises at least one coil (2, 15) fed by an alternating current of variable frequency and intensity, at least a portion of said coil (2, 15) being subjected to a magnetic field which generates electromagnetic forces tending to impart to it an alternating movement when the current changes direction, the transmission system transforming the reciprocating displacement of a support (27) of the coil (2, 15) into a reciprocating movement of the tool head (12).

2. Contra-angle with magnetic actuator according to the preceding claim, characterized in that the coil (2) is planar and has two sections (5, 6) passing each between two opposite magnetic poles of at least one magnet per - Manent (1), creating for each section (5, 6) an electromagnetic force tending to move the coil (2) in the same direction when it is traversed by a current.

3. Contra-angle magnetic actuator according to the preceding claim, characterized in that the coil (2) is of rectangular shape or defines an annular sector, said sections (5, 6) passing between the magnetic poles of two magnets permanent members (1) being a pair of opposite sides of the rectangle or the radial sides of the annular sector.

4. Magnetic actuator contra-angle according to the preceding claim, characterized in that the support of the coil

(2) comprises an arm (7) of parallel shape on the one hand on the plane of the coil (2) and on the other side on said sides, pivotable relative to a housing (20) of the actuator and having on its free end a rotational connection with a shaft (8), or a connection to a semi-rigid cable followed by a shaft (8), said shaft (8) being guided axially by the handle (9).

Magnetic actuator contra-angle according to claim 1, characterized in that the coil is a solenoid (15) wound on the one hand around a support (27) able to slide axially on a central core (19) forming one of the poles of a permanent magnet and surrounded on the other by a cylindrical envelope (17) forming the opposite pole of the magnet, the central core (19) and the support (27) comprising axial guiding means from one to the other.

6. Contra-angle magnetic actuator according to the preceding claim, characterized in that said means comprise at least one rod (16) secured to the inner face of a sleeve (27) constituting the support of the coil (15) said rod (16) being slidable in a groove (28) formed axially in the central core (19) and connected to the transmission system.

7. Contra-angle magnetic actuator according to one of claims 5 and 6, characterized in that it comprises two rods (16) cooperating with two grooves (28) arranged opposite one another in the central core (19), each rod (16) being connected to a shaft (8) axially guided by the handle (9).

8. contra angle with magnetic actuator according to one of claims 4 and 7, characterized in that the end near the tool holder head (12) of said shaft (8) comprises means for transforming the displacement of the shaft in a first direction substantially parallel to the axis of the handle (9) in a movement of the tool head (12) in a second direction.

Magnetic actuator contra-angle according to the preceding claim, characterized in that the transformation means consist of a tilting gear (11) pivotable in the handle (9) in the vicinity of the tool head (12). along an axis perpendicular to a plane containing the two directions, one of the ends of the tilting gear (11) being slidable in a ring (26) terminating the shaft (8), the other end being equipped with a fork type end portion (13) cooperating with a cavity in the tool head (12) to drive it along the axis of the housing.

Magnetic actuator contra-angle according to claim 8, characterized in that the transformation means connect the shaft (8) to the periphery of the tool head (12) in order to drive it in rotation.

Magnetic actuator contra-angle according to any one of the preceding claims, characterized in that the handle (9) is equipped with sensors (30) able to detect the amplitude of the displacements of the transmission system.

Magnetic actuator contra-angle according to one of the preceding claims, characterized in that it is provided with means for adjusting the frequency and intensity of the current flowing through the coil (2, 15), preferably able to differentiate their setting values according to the direction of the current.