Endodontic instrument for determining an anatomical datum

Abstract

The present invention relates to a device for the endodontic treatment of a root canal (11), comprising: - an endodontic instrument (20) comprising a passive zone (22) and an active zone (21), wherein the active zone (21) is configured to provide position data via electromagnetic or optical radiation; - acquisition means (30) comprising a sensor (31), and configured to acquire the position data within a system defined by the root canal (11) and the acquisition means (30); and - a processing unit (40) connected to the acquisition means (30), wherein the processing unit (40) is configured to process the position data from the active zone (21) within the system, in order to determine an anatomical datum of the root canal (11).

Description

ENDODONTIC INSTRUMENT FOR DETERMINING ANATOMICAL DATA FIELD OF THE INVENTION

[0001] The present invention relates to the technical field of endodontics. STATE OF THE ART

[0002] In the field of endodontics, a common complication is instrument breakage within a root canal during treatment.

[0003] This may be an elasto-plastic rupture due to a defect in the material from which the instrument is made, a fatigue rupture due to use of the instrument beyond its intended lifespan, or a ductile rupture due to over-stressing of the instrument.

[0004] This over-stressing is particularly likely to occur when the root canal has a bent geometry, or a sudden narrowing of the section: at the level of these “risk zones”, the instrument is put under stress.

[0005] If the practitioner has not previously identified the risk areas of the canal to be treated, he may approach these areas without taking the necessary precautions, such as reducing the rotation speed of the instrument, or even manually applying less force.

[0006] It is observed that the majority of instrumental breakages result from a poorly understood canal geometry by the practitioner, who consequently did not take adequate precautions when treating a risk area.

[0007] Various solutions exist, but they are not entirely satisfactory.

[0008] A first solution lies in handpieces equipped with force sensors. If over-stress is applied to the endodontic instrument, the sensor detects it and automatically adapts the instrumental dynamics, or issues an alert to the attention of the practitioner. However, significant stress is already applied to the endodontic instrument, so breakage prevention is not optimal.

[0009] A second solution is apex locators, which are devices that measure an electrical signal applied between an endodontic instrument and the patient's body, such as a lip. When the instrument reaches the apex of the canal, the electrical signal changes dramatically, so monitoring the electrical signal can detect whether the instrument has reached the apex of the canal.

[0010] An apex locator is used: - either before treatment, in order to measure the distance separating an occlusal face of the tooth and the apex, called “working length”; - either during treatment, in order to assess the working depth, i.e. the position of the tip of the instrument within the canal.

[0011] Knowing the working depth allows the practitioner to adapt his or her action as the endodontic instrument descends into the root canal.

[0012] However, use during treatment is hampered by the presence of tissue within the canal, or by the presence of fluids such as pus or irrigation solutions such as sodium hypochlorite. Indeed, tissues and fluids alter the conduction of the electrical signal, compared to use within a dry root canal. Detection of changes in the electrical signal value is less efficient.

[0013] It follows that monitoring the electrical signal provides reliable information when the instrument is located at the apex, but not when the instrument is located below the apex. An apex locator used during treatment is therefore inaccurate.

[0014] A third solution lies in imaging means such as X-rays.

[0015] A diagnostic radiograph, as illustrated in Figure 1, is a two-dimensional radiograph of the tooth (10) to be treated, making it possible to visualize the general trajectory (D) of the root including the root canal (11) to be treated.

[0016] Diagnostic radiography is primarily intended to illustrate the presence of inflammation or necrosis that requires endodontic treatment. Since it is only a single, two-dimensional image, diagnostic radiography cannot detect: - a curvature of the root canal (11), and which would be in a plane parallel to an axis of the X-ray; - the section (S) of the root canal (11), which is not necessarily circular.

[0017] Two-dimensional X-rays can also be taken during treatment to check the progress of the treatment and in particular to inspect whether the tip of the instrument is indeed at the apex.

[0018] Another radiographic technique is cone beam computed tomography (CBCT). This technique provides a three-dimensional reconstruction of the canal to be treated, as well as several projections along each of these three dimensions, by digitally assembling several hundred individual radiographic images.

[0019] A non-circular section of a canal is detectable using CBCT, as shown in Figure 2.

[0020] On the other hand, although a CBCT provides a three-dimensional reconstruction, it is only an assembly of the individual radiographic images, so the geometry of the root canal as such is not accessible: it is necessary to navigate, by means of a graphical interface, between the different radiographs acquired in order to try to visualize the desired anatomical data of the root canal.

[0021] Another disadvantage of X-rays is the amount of ionizing radiation inflicted: - to the patient, and which is important in the case of a CBCT; - to the practitioner, and which is reasonable in the case of X-rays taken during treatment but which is inflicted repeatedly. SUMMARY

[0022] There is therefore a need to improve devices allowing a practitioner to obtain anatomical data of the canal before processing without using ionizing rays.

[0023] There is also a need during processing to achieve the working depth reliably, and without using ionizing rays.

[0024] For this purpose, a device has been developed for endodontic treatment of a root canal of a patient's tooth root, comprising: - an endodontic instrument comprising a passive zone and an active zone, the active zone being configured to provide position data by electromagnetic or optical radiation, - acquisition means comprising a sensor, and configured to acquire position data within a system defined by the root canal and the acquisition means, and - a processing unit connected to the acquisition means.

[0025] According to the invention, the processing unit is configured to process the position data of the active zone within the system, in order to determine an anatomical data of the root canal. The anatomical data of the root canal can be for example a trajectory of the root canal, or the fact that an apex of the root canal is reached by a tip of the endodontic instrument.

[0026] Since position data is transmitted by electromagnetic or optical radiation: - we avoid using ionizing rays, which is safer for both the patient than for the practitioner - position data is not impacted by the presence of fluids as can be the electrical signal of an apex locator.

[0027] The device according to the invention is therefore reliable, and can be used during treatment without being impacted by the presence, for example, of irrigation solution.

[0028] In an embodiment for checking during treatment whether the tip of the endodontic instrument is located at the apex, the active zone has a magnetism different from that of the passive zone, the sensor is a magnetic sensor, and the sensor is configured to be placed in a vestibule of the patient, at the apex of the root canal. Preferably the magnetism of the active zone is greater than that of the passive zone, in particular when the endodontic instrument is made of a material with low magnetic susceptibility.

[0029] Since a general trajectory of the root is already known by means of a diagnostic radiograph, the acquisition means preferably comprise several sensors arranged along an axis configured to be arranged substantially parallel to the general trajectory of the root of the tooth, from a pulp chamber of the tooth to the apex of the root canal. It is thus possible to place the sensors in the vestibule of the patient, without needing to precisely adjust the position of a single sensor with respect to the apex of the canal. Since the working length is known, it is possible to identify the sensor which is closest to the apex. In addition, it is possible to know the working depth by identifying with respect to which sensor the tip of the endodontic instrument is located.

[0030] Advantageously, the endodontic instrument comprises several active zones, i.e. several zones with high magnetism, in order to make the position data obtained more reliable, through redundancy.

[0031] In order to simplify the implementation of the acquisition means, they include a sensor matrix, defining a plane in which the sensors are distributed according to a two-dimensional system.

[0032] The planar distribution of the sensors ensures that, regardless of the channel trajectory, several magnetic sensors will be in front of it and will be able to detect the passage of magnetic active zones within it.

[0033] Such a sensor array provides a two-dimensional canal trajectory, with each sensor in the array providing information on the passage of an active area opposite it when the endodontic instrument is inserted into the canal. The use of magnetic sensors configured to measure magnetic field strength, such as magnetoresistance sensors, further provides a three-dimensional trajectory. Indeed, an increase in the signal means that the canal is moving closer to the matrix, while a decrease in the signal means that the canal is moving away from the matrix.

[0034] To ensure that the distance between each of the matrix sensors and the root canal is as uniform as possible, the matrix is ​​arranged substantially parallel to the general trajectory of the root, and extending from a pulp chamber of the tooth to an apex of the canal. A uniform distance is advantageous for measuring the magnetic field intensity.

[0035] In a preferred embodiment, the device comprises two sensor matrices according to the aforementioned characteristics, and the two matrices are configured to be arranged in two non-parallel planes. This embodiment makes it possible to obtain, by intersection between the data obtained by each of the matrices, the three-dimensional trajectory of the channel. In addition, this embodiment avoids the additional cost of magnetic sensors configured to measure an intensity of the magnetic field.

[0036] In the preferred embodiment, the processing unit may be programmed to: - acquire multiple position data when the endodontic instrument is manipulated within the root canal, at a given depth within the root canal, - from the several position data of a given depth, determine a section of the root canal at this depth.

[0037] This embodiment makes it possible to obtain the geometry of the root canal, by interpolating the geometry from several sections obtained.

[0038] In a second embodiment, an active zone comprises a first end of an optical fiber which opens at the tip of the endodontic instrument, and a second end of the optical fiber is connected to the sensor which is an optical sensor. This feature allows: - to carry out image recognition, for example to obtain the section of the canal at a given depth, or - to carry out a visual observation of the canal, in order to detect a bifurcation where the canal separates into two secondary canals.

[0039] In this second embodiment, the optical sensor is preferably a laser remote sensing transceiver (“LIDAR” for light detection and ranging). A LIDAR acquisition makes it possible to determine the geometry of an internal surface of the canal, opposite the first end of the optical fiber. A reconstruction of the geometry is then possible, by continuity of the surfaces obtained when the endodontic instrument is introduced into the canal.

[0040] A third embodiment combines the first embodiment and the second embodiment, that is to say that it comprises at least one active zone having a magnetism different from that of the passive zone, as well as an active zone comprising a first end of an optical fiber which opens at the tip of the endodontic instrument, and a second end of the optical fiber connected to an optical sensor of the acquisition means.

[0041] The invention also relates to an endodontic instrument configured to cooperate with the device according to the aforementioned characteristics. BRIEF DESCRIPTION OF THE FIGURES

[0042] [Fig.l] is an illustration of a two-dimensional radiograph of a tooth to be treated, illustrating the incomplete nature of this technology alone.

[0043] [Fig.2] is an illustration of a graphical interface of a software program for exploiting cone beam volumetric imaging (or "CBCT"), illustrating the limitations of this technology.

[0044] [Fig.3] is a diagram illustrating a root canal within a tooth root whose pulp chamber has been opened for endodontic treatment.

[0045] [Fig.4] is a diagram illustrating a first embodiment of the invention, in which two magnetic sensor matrices detect the position of several magnetic active zones.

[0046] [Fig.5] is a diagram illustrating an anatomical data obtained, in the form of a root canal trajectory.

[0047] [Fig.6] is a diagram illustrating an anatomical data obtained, in the form of geometry calculated from a root canal trajectory and sections of the root canal at different depths.

[0048] [Fig.7] is a diagram illustrating a third embodiment comprising several magnetic active zones having a magnetism different from that of the passive zone, as well as an optical active zone comprising a first end of an optical fiber. DETAILED DESCRIPTION

[0049] Figure 1 illustrates a two-dimensional radiograph, of the type used as a diagnostic radiograph. A diagnostic radiograph allows the practitioner to check for the presence of inflammation or tissue necrosis within a root canal (11) of a tooth (10), which indicates the need for endodontic treatment.

[0050] Such an X-ray also makes it possible to identify the general direction (D) of the root of the tooth (10), as well as the general direction (D) of the root canal (11) to be treated.

[0051] A working length (Lt), defined by the distance between an occlusal face (12) of the tooth (10) and the apex (13) of the root canal (11), can be measured on a diagnostic radiograph. However, more precise systems are preferred, such as an apex locator (13) cooperating with an exploratory file.

[0052] Figure 2 illustrates a graphical interface for exploiting images obtained by cone beam volumetric imaging (or "CBCT"). Several hundred radiographs are acquired, in different directions, so that a three-dimensional reconstruction can be proposed to the practitioner.

[0053] Three quadrants (I, II, III) of the graphical interface illustrate two-dimensional radiographs in the three anatomical directions: frontal, sagittal and transverse. A fourth quadrant (IV) illustrates a three-dimensional reconstruction.

[0054] The section (S) of the root canal (11) can be seen on the third quadrant (III), which illustrates the section along a transverse plane. The practitioner must navigate between several successive transverse sections in order to correctly grasp the section (S) of the root canal (11) along its entire length.

[0055] The reconstruction illustrated on the fourth quadrant (IV) has a more figurative than clinical utility, since the reconstruction includes all the tissues of the radiographed jaw, and the bone, dentin and cementum hinder observation of the root canal (11).

[0056] Figure 3 shows a diagram of a tooth (10) whose pulp chamber (14) has been opened for endodontic treatment. The root canal (11) here has two curvatures (C), which are risk areas during treatment.

[0057] Risk areas may be a sudden reduction in the section (S) of the root canal (11), a significant curvature (C) of the root canal (11), or even a bifurcation of the root canal (11) into several secondary canals.

[0058] The more information the practitioner has on the geometry (G) of the root canal (11) to be treated, the more the risks of failure and instrumental breakage are reduced.

[0059] Figure 4 illustrates a first embodiment of the invention in which an endodontic file (20) comprises several active zones (21), the magnetism of which is different from that of a passive zone (22) of the file (20). The active zones (21) are distributed uniformly along a blade of the file (20), which extends from a proximal end connected to a handle (23) of the file (20), up to a distal end, called the tip (24) of the file (20).

[0060] The different magnetism of an active zone (21) is understood as a magnetism greater or less than that of the passive zone (22).

[0061] In practice, the files (20) are generally made from a nickel and titanium alloy ("nitinol" or "Niti"), which has a low magnetic susceptibility when at rest. In this case, the active zone (21) preferably comprises a material with high magnetic susceptibility when at rest.

[0062] Magnetic susceptibility when the material is at rest means that the magnetic susceptibility is considered when the material does not receive energy excitation, such as power supply by electric current. The invention is designed to operate without the endodontic instrument (20) being powered by electric current.

[0063] Materials with low magnetic susceptibility include, for example, nickel and titanium alloys, or plastic.

[0064] Materials with high magnetic susceptibility are, for example, steel or permanent magnets. An active zone (21) may be a pad made of such materials, fixed to the endodontic instrument (20) by any suitable means such as welding, gluing, or even shrinking.

[0065] The position of the active zones (21) is detected by means of an acquisition device (30) comprising a plurality of magnetic sensors (31), configured to detect the active zones (21), in contrast to the different magnetism of the passive zone (22).

[0066] In this embodiment, it is therefore by electromagnetic radiation that the active zones (21) provide position data, and more particularly by magnetism. The position data are not provided by the measurement of an electrical signal within the file (20).

[0067] The magnetic sensors (31) are of any suitable type, and may be of the small-scale microelectromechanical systems (“MEMS” according to the English Microelectromechanical systems) magnetic field sensors type, or even Hall effect sensors.

[0068] The magnetic sensors (31) are arranged in a plane and according to a matrix (32), so as to define a two-dimensional system. Within this matrix (32): - when a magnetic sensor (31) is in view of an active zone (21), it detects it and switches to an active state; - when a magnetic sensor (31) is not in view of an active zone (21), that is to say when it is in view of a passive zone (22) or when it is not in view of the endodontic instrument (20), then the magnetic sensor (31) is in an inactive state.

[0069] To simplify Figure 4, only a few magnetic sensors (31) are shown. The distribution of magnetic sensors (31) defines pixels. The matrix (32) shown is square because the distribution of magnetic sensors (31) is regular in two orthogonal directions, but other types of distributions can be considered, such as a hexagonal distribution.

[0070] The magnetic sensors (31) in the active state define active pixels (PI), shown in black. Conversely, the sensors in the inactive state define inactive pixels (PO), shown in white.

[0071] Within a system defined by the root canal (11) and the acquisition means (30) of the position of the active zones (21), the position data is in this case the identification of the magnetic sensors (31) with respect to which there is a magnetic active zone (21m). The anatomical data is a profile (P) defined by the active pixels (PI), corresponding to a planar projection of the trajectory (T) of the root canal (11) on the matrix (32).

[0072] If the magnetic sensors (31) used are configured to measure the intensity of the magnetic field, then a single matrix (32) of magnetic sensors (31) is sufficient to obtain the trajectory (T) of the root canal (11) in three dimensions: - the trajectory (T) along the first two directions (x, z) are directly obtained by active pixels (IP); - the trajectory (T) along the third direction (y) is obtained by the intensity of the signal provided by each magnetic sensor (31): - a strong signal is equivalent to a short distance between the magnetic sensor (31) and the active zone (21); - a weak signal is equivalent to a high distance between the magnetic sensor (31) and the active zone (21).

[0073] Although this embodiment does not directly provide the position of the root canal (11) within the root, since the third dimension is measured relatively, this may be sufficient to characterize the presence of curvatures (C) that define risk areas.

[0074] Another technique is to measure, by means of a matrix (32), the distance separating two active magnetic zones (21m): - if the distance measured between two active zones (21m) within the root canal (11) is equal to the distance separating these two magnetic active zones (21m) from the endodontic instrument (20) at rest, then the endodontic instrument (20) within the root canal (11) is rectilinear over a portion of the root canal (11) separating these two magnetic active zones (21m). - if the distance measured between two active zones (21m) within the root canal (11) is less than the distance separating two magnetic active zones (21m) of the endodontic instrument (20) at rest, then the endodontic instrument (20) within the root canal (11) is curved on the portion of the root canal (11) separating these two magnetic active zones (21m).

[0075] Although this method does not allow the direction of the curvature (C) of the root canal (11) to be identified, it nevertheless allows this curvature (C) to be detected and quantified, which is already important information for the practitioner regarding the difficulty of the procedure to be performed.

[0076] The determination of the curvature of the endodontic instrument (20) based on the measurement of the distance between active zones (21m) can be applied to two zones successive active zones (21m), or preferably be applied simultaneously to several active zones (21m), or even take into account the distances separating several successive pairs of active zones (21m), in order to define the curvature (C) by calculating the profile (P) comprising several points.

[0077] Magnetoresistance and the measurement of the distance separating two magnetic active zones (21m) can be used as an alternative. They are preferably used in addition, in order to perfect the results obtained by means of a single matrix (32) of magnetic sensors (31). The placement of a single matrix (32) within the patient's mouth is less troublesome.

[0078] It is understood that it is not necessary for one of the directions of the distribution of the magnetic sensors (31) to be parallel to the general direction (D) of the root: it is sufficient for the matrix (32) to define pixels whose distribution and resolution make it possible to determine a profile (P) of the root canal (11).

[0079] In the preferred embodiment illustrated, the acquisition means (30) comprise two matrices (32), arranged non-parallel to each other, in order to define a three-dimensional system.

[0080] In practice, the matrices (32) are arranged in the vestibule of the patient's mouth, on either side of the tooth (10) to be treated with an inclination of between 10° and 20° relative to each other, along an axis substantially parallel to the general direction (D) of the root of the tooth (10). The general direction (D) of the root of the tooth (10) is substantially orthogonal to the transverse plane of the patient.

[0081] In the illustrated example, the two matrices (32) are square, and are arranged so that: - a first matrix (32) defines an x ​​axis substantially parallel to the transverse plane and a z axis substantially orthogonal to the transverse plane, - a second matrix (32) defines a y axis substantially parallel to the transverse plane and forming an angle between 10° and 20° relative to the x axis, and the second dimension of the second matrix (32) is the z axis.

[0082] When two matrices (32) are used to define a three-dimensional system, it is not imperative that each of the matrices (32) be parallel to the general direction (D) of the root, since it is sufficient that the root canal (11) is included in a volume defined by the intersection between: - a first volume whose base is defined by the first matrix (32) and the height is defined by the detection depth of the magnetic sensors (31), and - a second volume is defined in a similar manner, by the second matrix (32).

[0083] To facilitate the positioning of the matrices (32), they are placed on a clamp made of non-magnetic material. The clamps are commonly used in endodontics, and can be directly fixed on the tooth (10) to be treated. The matrices (32) are thus located in the immediate vicinity of the root canal (11).

[0084] Arranging the matrix(es) (32) parallel to the general direction (D) of the root allows the sensors to be placed as close as possible to the tooth (10), which can allow better detection of the active zones (21) (better signal quality).

[0085] In the preferred embodiment with two matrices (32), the trajectory (T) of the root canal (11) in three dimensions is obtained by calculating the intersection, in volume, of the two profiles (P) each obtained by a matrix (32).

[0086] Within a system defined by the root canal (11) and the acquisition means (30), the position data is in this case the identification of the magnetic sensors (31) with respect to which there is a magnetic active zone (21m). The anatomical data is the trajectory (T) of the root canal (11), in three dimensions.

[0087] The resolution of the matrix (32) can be adapted depending on the size of the magnetic sensors (31) used. Miniaturized sensors allowing the resolution of the matrix (32) to be increased are preferred.

[0088] Figure 5 illustrates a trajectory (T) of the root canal (11), obtained by implementing the preferred embodiment. Although the section (S) of the root canal (11) is not provided, the presence of the curves (C) is detected, and the practitioner can prepare his intervention with full knowledge of the facts.

[0089] A method of implementing the preferred embodiment of Figure 4 may also include manipulating the endodontic instrument (20) within the root canal (11) such that the endodontic instrument (20) occupies different positions within the canal.

[0090] Indeed, when the endodontic instrument (20) has an external diameter which is smaller than the internal dimensions of the root canal (11), it is possible to insert it, preferably at the working length (Lt), then to manipulate it so that each active zone (21), at its depth, sweeps the entire section (S) of the root canal (H).

[0091] For each of the depths of each of the active zones (21), the acquisition device (30) acquires the several positions occupied by the active zone (21). From these several positions, the processing unit (40) is programmed to determine what is the section (S) of the root canal (11) at each of the depths of each of the active zones (21).

[0092] From each of the sections (S) obtained, the processing unit (40) is programmed to determine the geometry (G) of the root canal (11).

[0093] The method implemented is based on the principle of continuity of the internal surface of the root canal (11), between two successive sections (S).

[0094] The above method can also work when the endodontic instrument (20) comprises only one magnetic active zone (21m). In this case, the endodontic instrument (20) must be manipulated at different depths, so that the active zone (21) can provide position data of sections (S) at different depths of the canal. Advantageously, the single magnetic active zone is placed on the tip (24), or in its vicinity.

[0095] In a second embodiment, not shown, the endodontic instrument (20) comprises an optical fiber (25), and no magnetic active zones (21m). in this case, the active zone (21) comprises a first end (25i) of the optical fiber (25) which opens at the tip (24) of the endodontic instrument (20). A second end (25o) of the optical fiber (25) is connected to an optical sensor of the acquisition means (30).

[0096] In this embodiment, it is therefore by optical radiation that the active zone (21) provides position data.

[0097] The optical fiber (25) is preferably used as a transmission-reception means, that is to say that the same optical fiber (25) conveys light towards the first end (25i) in order to illuminate the interior of the root canal (11), then conveys light reflected by the internal surface of the root canal (11) towards the acquisition means (30).

[0098] The acquisition means (30) acquire images, which are then analyzed by the processing unit (40) to determine the geometry (G) of the root canal (11), according to the same aforementioned principle of surface continuity. In this case, the acquisition of the geometry (G) of the internal surface of the root canal (11) is done progressively, when the endodontic instrument (20) circulates within the root canal (11).

[0099] The acquisition of position data is preferably carried out within a dry root canal (11), so that the acquisition is as undisturbed as possible, but this is not imperative.

[0100] Within an untreated root canal (11), the tissues are soft and very aqueous: although the aqueous medium slightly distorts the optical signal, acquisition of position data by the optical fiber (25) is possible within the untreated root canal (11).

[0101] Indeed, the distance separating the optical active zone (21o) and the internal wall of the root canal (11) is very short, of the order of a few hundredths of a millimeter to a few tenths of a millimeter. The distortion of the signal is minimal, and therefore does not prevent its use for determining the geometry (G) of the canal.

[0102] The optical acquisition begins when the endodontic instrument (20) is inserted into the root canal (11), and the processing unit (40) determines the geometry (G) of a first portion of the root canal (11) with respect to the first end (25i) of the optical fiber (25).

[0103] The endodontic instrument (20) is then inserted deeper into the canal so that a next portion of the root canal (11), contiguous to the first portion, is opposite the first end (25i) of the optical fiber (25).

[0104] The processing unit (40) determines what the geometry (G) of this following portion is, and reconstructs the geometry (G) of the root canal (11) by continuity of the surfaces between the first portion and the following portion.

[0105] This operation is repeated as many times as necessary until the entire geometry (G) of the root canal (11) is determined.

[0106] Within a system defined by the root canal (11) and the acquisition means (30), the position data is in this case the distance of points on the internal wall of the root canal (11) relative to the optical active zone (21o). The anatomical data is the geometry (G) of the root canal (11).

[0107] A high-performance transmission-reception technology for implementing surface geometry (G) acquisition methods is “LIDAR” technology, meaning “light detection and ranging”.

[0108] The endodontic instrument (20) may comprise several optical fibers (25), so that several active zones (21) are arranged on a periphery of the endodontic instrument (20) and make it possible to observe an angular sector of the root canal (11).

[0109] For example, three optical fibers can all emerge at the same distance from the tip (24) of the endodontic instrument (20), each first end of each optical fiber being arranged at 120° from each other.

[0110] In this way, a greater number of images are acquired at the same time, at a given depth. [OR I] Preferably, the number of optical fibers (25) is sufficient to simultaneously acquire the entirety of a portion of the root canal (11), that is to say the entire perimeter of the root canal (11), at a given depth.

[0112] However, current optical fibers (25) have an external diameter of the order of 0.15mm, so that an optical fiber (25) can obtain the geometry (G) of the majority of root canals, but is not suitable for the finest root canals. The optical active zone (21o) is placed as close as possible to the tip (24) of the endodontic instrument (20), in order to allow the acquisition of images as far as possible within the root canal (11).

[0113] To overcome this disadvantage of excessive size, a third embodiment, illustrated in figure 7, combines the first and second embodiments: the endodontic instrument (20) comprises both magnetic active zones (21m) with different magnetism, as well as an optical fiber (25) whose first end (25i) opens at an optical active zone (21o).

[0114] The optical fiber (25) is used for a proximal portion of the root canal (11) whose diameter is sufficiently large, and the magnetic active zones (21m) are used for at least a distal portion of the root canal (11), located between the proximal portion and the apex (13), and are preferably used for the entire root canal (11).

[0115] In this embodiment, it is therefore by electromagnetic radiation as well as by optical radiation that the active zones (21) provide position data.

[0116] Advantageously, the processing unit (40) combines the position data: - acquired by electromagnetic radiation, using magnetic active zones (21m), and - acquired by optical radiation, by means of the optical active zone (21o) or optical active zones (21o).

[0117] This complementarity of the position data used makes it possible to improve the precision and reliability of the acquired anatomical data.

[0118] Alternatively, the acquired images can be used only for visual verification by the practitioner, for example checking the presence or absence of bifurcations within the root canal (11).

[0119] The determination of the anatomical data can be done in real time, but it can also be done a posteriori. In this case, the processing unit (40) is configured to determine the anatomical data from previously obtained position data.

[0120] This embodiment can be adapted when the processing unit (40) executes a program whose execution time is long.

[0121] This embodiment is also suitable for improving the computer program that the control unit executes: it may be advisable to save raw, unprocessed position data in order to serve as training data for further improvements to the computer program.

[0122] Such raw data can also serve as training data for artificial intelligence programmed to determine anatomical data of root canals (11).

[0123] The device may be shaped differently from the figures without departing from the scope of the invention, which is defined by the claims.

[0124] In a particular embodiment, the magnetic active zone (21m) of the endodontic instrument (20) is constituted by the entire blade, and the passive zone (22) is constituted by the handle (23) of the endodontic instrument (20). The entire blade can be detected by the magnetic sensors (31). This embodiment is suitable for blades made from steel. It is recalled that the differentiation between the zone active (21) and the passive zone (22) is possible at rest, and does not require, for example, circulating a current within the active zone (21).

[0125] In another particular embodiment, the magnetic active zone (21m) of the endodontic instrument (20) is located on the handle (23), and the passive zone (22) is constituted by the entire blade of the endodontic instrument (20).

[0126] In this way, it is possible to implement the invention on an endodontic instrument (20) already qualified by the health authorities, without making any modifications to the active part of the endodontic instrument (20). Since the active part is not modified, the certification of the modified instrument (20) will be facilitated. This embodiment is suitable for improvements to pre-existing endodontic instruments (20), of all types (files, cannulas, etc.).

[0127] Whatever the embodiment implemented, the device according to the invention can be used during treatment, in order to replace an apex locator (13)

[0128] In particular, an alternative embodiment provides that there is only one magnetic sensor (31), placed by the practitioner with respect to the apex (13) of the root canal (11). The position of the apex (13) is previously determined by means of the diagnostic radiograph, as well as the working length (Lt) obtained by means of an apex locator. A magnetic active zone (21m) is placed at the tip (24) of the endodontic instrument (20).

[0129] This minimalist device makes it possible to know, during treatment, whether the tip (24) of the endodontic instrument (20) has reached the apex (13) or not. This embodiment avoids the risk of exceeding the apex (13) and perforation, which could occur with an apex locator (13) due to the poor quality of the signal it provides during treatment.

[0130] Within a system defined by the root canal (11) and the acquisition means (30), the position data is in this case the presence or absence of the magnetic active zone (21m) with respect to the magnetic sensor (31), and the data anatomical is the presence of the tip (24) of the endodontic instrument (20) at the level of the apex (13) of the root canal (11).

[0131] An improvement to this minimalist device comprises a plurality of magnetic sensors (31) arranged along an axis configured to be arranged substantially parallel to a general direction (D) of the tooth root (10), from the pulp chamber (14) to the apex (13).

[0132] As the endodontic instrument (20) progresses within the root canal (11), the magnetic sensors (31) become active. It is therefore possible to monitor the working depth of the endodontic instrument (20) as it progresses, in order to predict its arrival at the apex (13). The anticipation made possible is preferable, compared to only having information when the tip (24) of the endodontic instrument (20) has reached the apex (13).

[0133] Within a system defined by the root canal (11) and the acquisition means (30), the position data is in this case the identification of the magnetic sensor (31) with respect to which the magnetic active zone (21m) is located. The anatomical data is the position of the tip (24) of the endodontic instrument (20) within the root canal (11), i.e. the working depth.

[0134] A modification of the first embodiment provides that there is only one magnetic active zone (21m) arranged at the tip (24) of the endodontic instrument (20). When inserting the endodontic instrument (20) into the root canal (11), the magnetic active zone (21m) is detected successively by different magnetic sensors (31), which allows the control unit (40) to reconstruct the profile (P) or the trajectory (T) of the canal, depending on whether there are one or two matrices (32) of magnetic sensors (31).

[0135] Whatever the method implemented, it is possible to acquire the geometry (G) of the root canal (11) in several stages, during the treatment: - the practitioner acquires the geometry (G) of a first portion of the root canal (11), then treats the first portion, - then the practitioner acquires the geometry (G) of a second portion of the root canal (11), then treats the second portion, - and so on until the root canal (11) is treated to the working length (Lt).

[0136] It is noted that the invention aims to provide the practitioner with information relating to position data within a system defined by the root canal (11) and the acquisition means (30), regardless of the type of endodontic treatment that the practitioner is carrying out.

[0137] Also, the term "file" should be interpreted in its broadest sense "endodontic instrument", generally of elongated shape. It can for example be an exploratory instrument, without cutting lips, or a canal shaping instrument, equipped with cutting lips.

[0138] The invention also relates to instruments of the type of a cannula of a product injection device, for example an irrigation cannula intended to pour a sodium hypochlorite solution into the canal (11): the invention makes it possible to know whether the cannula is correctly located at the level of the apex (13) in order to irrigate the entire length of the canal (11).

[0139] It may also be an ultrasonic insert intended to remove from the root canal (11) a breakage of a previously broken instrument: the invention makes it possible to know whether the insert is correctly located at the level of the breakage to be recovered, the position of which within the canal (11) was obtained by radiology.

[0140] Finally, the invention also makes it possible to locate a breakage of the endodontic instrument (20) within the canal, in the case where the breakage has an active zone (21). It is therefore possible to locate the breakage without requiring an X-ray.

[0141] In particular, the invention can be implemented with the different instruments of a sequence of endodontic treatment.

[0142] Depending on the type of endodontic instrument (20) on which the invention is implemented, and depending on the embodiment applied to different instruments endodontics (20), the invention can be exploited in different ways. An example of a treatment protocol is provided below.

[0143] First, an exploratory file is configured to provide the canal geometry (G), regardless of the acquisition means technology (30) used (with magnetic or optical sensor). Once the canal geometry (G) is obtained, it becomes a positioning reference within the system defined by the root canal (11) and the acquisition means (30). For example, a clamp carrying a magnetic sensor is located by a curvilinear abscissa within this system.

[0144] The following instruments (20) in the sequence, for example a root canal preparation file, a shaping file or an irrigation cannula, do not need to be configured to acquire the geometry (G) of the root canal (11) since this is already obtained. These instruments (20) only need to be positioned relative to the chosen reference frame.

[0145] That is to say, once the geometry (G) is obtained, the instruments (20) only need one active zone (21), which allows economy and simplification of their design.

[0146] The unique active zone (21) of these instruments (20) is sufficient to position them within the reference system whose geometry (G) is known, and the invention can be implemented to guide the practitioner and inform him when the instruments (20) have arrived at a desired position within the system (for example bifurcation or apex in the case of a file, breakage to be recovered in the case of an ultrasonic insert).

[0147] Another technique of using the invention lies in its combination with radiographic imaging, for example a CBCT, despite the disadvantages that this type of imaging implies.

[0148] When a root canal (11) is mineralized, the use of an exploratory file is very difficult: - in the case of severe mineralizations, the practitioner may have to cross up to ten millimeters of solid tissue before emerging into a non- mineralized canal (11). In this case, the risk of perforation of the canal (11) is very high: the practitioner can generate bifurcations, or even take the exploratory file beyond the apex (13). - in the case of lighter mineralizations, for example in the case of a mineralized canal of about 1 mm, the tissues create a plug which can nevertheless hinder the practitioner's exploration. In the case of teeth with several roots, for example a molar, the practitioner may be able to explore a non-mineralized canal (11), but not find another mineralized canal (11).

[0149] Firstly, the invention makes it possible to obtain the geometry (G) of the channel (11) explored only, faithfully and with good resolution.

[0150] The use of CBCT, despite its imperfections in terms of precision, makes it possible to obtain an image (I) of each of the canals (11) of the tooth (10).

[0151] The geometry (G) of the canal (11) explored in combination with the imaging (I) of the tooth (10), by superimposing the geometry (G) on the corresponding part of the imaging (I), allows the imaging (I) to be integrated into the system defined by the root canal (11) explored and the acquisition means (30).

[0152] Displayed on a monitor of a practitioner's installation, the overlay makes it possible to provide the practitioner, even though he has not yet been able to explore them, with an indication of the location and trajectory of the channels (11) remaining to be explored, as well as the position of an instrument (20) according to the invention in relation to this imagery (I).

[0153] The practitioner can therefore finalize his exploration, while being assisted by information on the position of the instrument (20) in relation to the imaging (I) of the canals (II) to explore. The risks of perforation are therefore greatly limited.

[0154] Once the exploration is complete, then the geometry (G) of all channels (11) is obtained and imaging (I) is no longer necessary.

[0155] Furthermore, the technical characteristics of the different embodiments and variants mentioned above may be, in whole or in part, combined with each other. Thus, the device and the endodontic instrument (20) can be adapted in terms of cost, functionality and performance.

[0156] In particular, a characteristic compatible with the embodiments presented above is to add, within the system defined by the root canal (11) explored and the acquisition means (30), an element configured to be detected by the acquisition means (30). This element is intended to serve as a reference within the system, for example to superimpose a geometry (G) of a canal (11) of a tooth with an image (I) of other canals (11) of this tooth. In this case, in addition to being compatible with the acquisition means, the element must be compatible with the imaging device, therefore be radiopaque.

Claims

CLAIMS 1. Device for endodontic treatment of a root canal (11) of a root of a tooth (10) of a patient, comprising: - an endodontic instrument (20) comprising a passive zone (22) and an active zone (21), the active zone (21) being configured to provide position data by electromagnetic or optical radiation, - acquisition means (30) comprising a sensor (31), and configured to acquire the position data within a system defined by the root canal (11) and the acquisition means (30), and - a processing unit (40) connected to the acquisition means (30), characterized in that the processing unit (40) is configured to process the position data of the active zone (21) within the system, in order to determine an anatomical datum of the root canal (11), for example a trajectory (T) of the root canal (11) or that an apex (13) of the root canal (11) is reached by a tip (24) of the endodontic instrument (20).

2. Device according to claim 1, wherein the active zone (21) has a magnetism different from that of the passive zone (22), preferably the magnetism of the active zone (21) is greater than that of the passive zone (22), and the sensor (31) is a magnetic sensor, and the sensor (31) is configured to be placed in a vestibule of the patient, at the apex (13) of the root canal (11).

3. Device according to claim 2, in which the acquisition means (30) comprise several sensors (31) arranged along an axis configured to be arranged substantially parallel to a general direction (D) of the root of the tooth (10), from a pulp chamber (14) of the tooth (10) to the apex (13) of the root canal (11).

4. Device according to claim 3, wherein the endodontic instrument (20) comprises several active zones (21).

5. Device according to claim 2 or 3 or 4, in which the acquisition means (30) comprise a matrix (32) of sensors (31): - the matrix (32) defining a plane in which the sensors (31) are distributed so as to define a two-dimensional system, and - the matrix (32) being configured to be arranged substantially parallel to the general direction (D) of a root of the tooth (10), and extending from a pulp chamber (14) of the tooth (10) to an apex (13) of the canal.

6. Device according to claim 5, in which the acquisition means (30) comprise two matrices (32) of sensors (31) configured to be arranged in two non-parallel planes.

7. Device according to one of claims 5 or 6, in which the processing unit (40) is programmed to: - acquiring multiple position data when the endodontic instrument (20) is manipulated within the root canal (11), at a given depth within the root canal (11), - from the several position data of a given depth, determine a section (S) of the root canal (11) at this depth.

8. Device according to one of the preceding claims, in which an active zone (21) comprises a first end (25i) of an optical fiber (25) which opens at the tip (24) of the endodontic instrument (20), and a second end (25o) of the optical fiber (25) is connected to the sensor (31) which is an optical sensor.

9. Device according to claim 8, in which the optical sensor (31) is a laser remote sensing transceiver.

10. Endodontic instrument (20), configured to cooperate with the device according to one of the preceding claims, the endodontic instrument (20) comprising a passive zone (22) and an active zone (21), the active zone (21) being configured to provide position data by electromagnetic or optical radiation.

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