WO2023089253A1

WO2023089253A1 - Depth gauge for endodontics

Info

Publication number: WO2023089253A1
Application number: PCT/FR2022/051822
Authority: WO
Inventors: Walid NEHME; Stéphane Claude
Original assignee: Micro-Mega International
Priority date: 2021-11-18
Filing date: 2022-09-27
Publication date: 2023-05-25

Abstract

The invention relates to a handpiece (10) for endodontic practice, comprising a control unit (30) that executes a computer program, and designed to drive a root canal instrument (20). According to the invention, the handpiece (10) comprises means (11) for detecting the distance (Le) between a reference point (12) and a portion (41) of a tooth (40) in order for the computer program to determine the depth (Lp) at which the instrument (20) is located during work, based on a known length (Lt) of the instrument (20).

Description

Title of the invention: depth gauge for endodontics

Technical area

The invention relates to the technical field of endodontics.

Prior art

[0002] The endodontic treatment of a root canal consists in evacuating the tissues of this canal. To carry out this operation, the practitioner uses canal instruments, such as files, in order to locate the trajectory of the canal, precisely determine the length of the canal, then evacuate the tissues using a file before shaping the canal by view of its closure.

[0003] Among the parameters of success of the treatment intervenes the precise localization of the apex, that is to say the end of the root canal, as well as the complete removal of the tissues up to the apex.

[0004] Indeed, if all the tissues are not removed from the canal, there is a risk of infection which can lead to an abscess or loss of the tooth. If the root canal goes beyond the apex, then an abscess may form in the gum or bone.

[0005] Referring to Figures 3 and 4, it is known from the prior art to use an apex locator, in order to know, by means of the measurement of an electrical resistance, when an instrument has reached the apex of the canal. The practitioner then places an elastomeric stop (25) in contact with a part (41) of the tooth, typically a cusp, so that the instrument becomes a depth gauge. The practitioner then removes the instrument, and can measure on it the length of the canal to be treated, known as the working length. In practice, the distance (Lb) between the end (23) and the underside (26) of the stop (25) is equal to the working length (Lt).

[0006] This length to be treated is then transferred to the other instruments to be used during the endodontic treatment sequence, so that with each instrument used, the practitioner knows that:

- as long as the stop is not in contact with the cusp, the instrument is at a certain depth in the canal, but the end of the instrument has not reached the apex: the whole channel length is not processed; - when the stop comes into contact with the cusp, then the depth is equal to the working length: do not go any further at the risk of drilling the tooth.

[0007] However, the postponement of the working length by means of an elastomeric stop on each instrument of the sequence is difficult. In addition, since this report is manual, there is a risk of error.

[0008] Furthermore, if the size of the opening made in the enamel in order to have access to the pulp chamber is large, or even if it is a reprocessing, the contact between the abutment and a cusp can be complicated. The measurement or detection of the contact between the abutment and the part of the tooth is then less precise.

[0009] Finally, if the practitioner makes a wrong move, he can press too hard on the elastomeric stop and move it, so that the instrument machines the canal beyond the apex.

Disclosure of Invention

One of the aims of the invention is to overcome the drawbacks of the prior art, in particular by designing an improved handpiece as regards the management of the working depth of the root canal instrument.

[0011] For this purpose, a handpiece has been developed for endodontic practice, comprising a control unit executing a computer program, and designed to drive a root canal instrument.

According to the invention, the handpiece comprises means for detecting the distance between a reference point and part of a tooth, and the computer program is programmed to determine the depth at which the instrument being worked according to a known length of the instrument.

[0013] In this way, it is no longer necessary to adjust the position of the stop by hand, which limits the operations to be carried out. The risk of positioning error of the stop from one instrument to another is also eliminated.

[0014] Above all, the computer program is configured to know in real time the depth at which the instrument is located, instead of being a simple “all or nothing” piece of information as in the prior art. [0015] In particular embodiments, the detection means comprise a distance sensor by laser and/or by infrared and/or by ultrasound and/or by vision system. This type of material is proven, and can be of sufficiently small volume to be used in dentistry.

[0016] Preferably, the detection means are arranged on a contra-angle of the handpiece, in order to be as close as possible to the part of the tooth to be detected.

[0017] In order to guarantee the safety of the treatment by preventing any overshooting of the apex, the computer program is configured to stop the driving of the instrument if the determined depth reaches a value predefined by the practitioner, preferably the working length.

[0018] Advantageously, the handpiece includes a display of the depth value. The practitioner therefore has real-time information on the distance remaining to be covered until reaching the apex.

[0019] In a particular embodiment, the handpiece comprises means for reading an identification of the instrument, and the computer program is configured to find the length of the instrument within a database instrument length data. The use of the handpiece is thereby facilitated.

In this mode, the reading means are of the RFID type, or a visual code such as a bar code or a QR code. These means allow easy implementation of the reading means.

The invention also relates to a method for determining a working depth of an endodontic instrument driven by a handpiece, noteworthy in that it comprises the following steps:

- obtaining the length of an endodontic instrument;

- measurement of the distance between a reference point of the handpiece and part of a tooth;

- subtracting the distance from the length of the instrument to determine the depth at which the instrument is located. This process makes it possible to know in real time the depth at which the instrument is located.

In a first embodiment, obtaining the length of the instrument is performed by manual entry of the length on an interface of a handpiece control unit. This embodiment makes it possible to limit the additional cost induced on the handpiece.

[0023] In addition or as an alternative, obtaining the length of the instrument is carried out by reading the identification means of the instrument, and by searching for the length of the instrument within a instrument length database. In this way, the manipulations to be carried out by the practitioner are further reduced, the same goes for the risk of error, because the practitioner cannot make an erroneous entry.

[0024] In order to verify that the mechanical stresses undergone by the instrument are well distributed over its length, and in particular with the aim of preventing instrumental ruptures of the fatigue rupture type and/or creep ruptures, the program of computer is programmed to check for a variation in distance over time, and if the variation is less than a predefined threshold for a predefined period:

- to activate handpiece warning means; and or

- to stop driving the instrument.

Brief description of the drawings

[0025] [Fig.1] is a diagram of a tooth to be treated.

[0026] [Fig.2] is a diagram of a root canal instrument.

[0027] [Fig.3] is a diagram of a treatment according to the prior art.

[0028] [Fig.4] is another diagram of a treatment according to the prior art.

[0029] [Fig.5] is an illustration of a handpiece according to the invention.

[0030] [Fig.6] is a diagram of a treatment according to the invention.

[0031] [Fig.7] is another diagram of a treatment according to the invention.

Detailed description of the invention

[0032] With reference to Figures 1, 2 and 5 to 7, the invention relates to an improved handpiece (10) intended for the treatment of root canals. [0033] Figure 1 is an illustration of a tooth (40), one root canal (42) of which is to be treated. For the treatment to be effective, damaged tissue must be removed from the canal (42) to the apex (43).

[0034] In order to be able to measure whether an instrument (20) used during the treatment has indeed reached the apex (43), that is to say whether one end (23) of the instrument (20) is well located at the apex (43), it is common to determine the working length (Lt) between the apex (43) and a part (41) of the tooth (40) to be treated. For practical reasons, the part (41) is generally a cusp of the tooth (40).

Figure 2 is an illustration of a root canal instrument (20). In particular, the instrument (20) is a file comprising a useful part (21) having helical cutting lips, intended to machine the tissues to be removed and/or to shape the channel (42).

The instrument (20) comprises a handle (24) allowing it to be connected and driven by the handpiece (10), generally by means of a contra-angle (13).

The useful length (Lu) of the instrument (20) is defined by the distance between the end (23) of the instrument (20) and a reference point (22) of the instrument (20) , which is generally the underside of the handle (24).

[0038] In the practice of the prior art, the practitioner must place an abutment (25) made of elastomeric material on the useful part (21), so that the distance (Lb) between the end (23) and the underside (26) of the abutment (25) is equal to the working length (Lt).

The instrument (20) used with the handpiece (10) according to the invention is similar, except that the stopper (25) is superfluous.

[0040] Figure 3 is an illustration of the progress of a root canal care of the prior art. At this moment of the treatment, the practitioner notices that the abutment (25) is not yet in contact with the part (41) of the tooth (40), so that he knows that the instrument (20) is not has not yet reached the apex (43). However, the practitioner does not have precise information as to the depth at which the end (23) is located, the depth (Lp) not being available.

[0041] Figure 4 is another illustration of the progress of a root canal care of the prior art, where the end (23) has reached the apex (43). The underside (26) of the stop (25) is then in contact with the part (41) of the tooth (40). However, if the abutment (25) has been incorrectly placed by the practitioner, then the end (23) may actually be either below or beyond the apex (43), which may in both cases lead to postoperative complications.

[0042] Figure 5 is an illustration of a handpiece (10) according to the invention. This comprises a control unit (30) provided with an interface (31), and the control unit (30) executes a computer program in order to drive a motor, not shown. The motor drives a transmission arranged in a contra-angle (13), which receives the instrument (20).

The handpiece (10) comprises detection means (11) between a reference point (12) of the handpiece (10) and a part (41) of a tooth (40).

The detection means (11) can be of any suitable type. It can be a sensor using laser, infrared, ultrasound or even video technology. The particular advantage of the laser is to emit a ray of light, and the practitioner can check that the point of impact of the ray is indeed on the part (41) to be used to perform the measurement.

The part (41) of the tooth (40) is chosen according to the detection modes (11) or the practice of the practitioner. It can for example be a highest point of the tooth (40), i.e. a cusp. It may also be the edge of the hole that has been drilled into the enamel to gain access to the pulp chamber.

The reference point (12) is arranged at will on the handpiece (10), but choosing a reference point (12) close to the instrument (20) makes it possible to reduce parallax errors. Preferably, the reference point (12) is therefore arranged on the contra-angle (13) of the handpiece (10), it is ideally the underside of the contra-angle (13), orthogonal to the instrument (20).

Referring to Figure 6, the detection means (11) measure a distance (Le) between the part (41) of the tooth (40) and the reference point (12). Starting from the useful length (Lu) known to the instrument (20), the computer program is programmed to subtract the distance (Le) from the useful length (Lu), in order to determine the depth (Lp) at which the end (23) is located. In a first embodiment, the useful length (Lu), supplied by the manufacturer of the instrument (20), is entered manually by the practitioner by means of the interface (31).

Since a root canal is rarely straight, the lengths to be considered are obviously curvilinear, in particular for their portion located inside the canal (42). However, the instrument (20) marrying the shape of the channel (42), the simple subtraction described makes it possible to know what is the depth (Lp) of the end (23), without requiring more geometric interpretations.

[0050] Since the depth (Lp) is now known in real time, it is possible to provide this information to the practitioner, for example by means of the interface (31) or a display external to the handpiece (10) .

[0051] Having this information allows the practitioner to know more precisely from when the end (23) approaches the apex (43), in order to slow down the progression of the instrument (20) and thus prevent any protrusion of the apex (43).

[0052] With reference to FIG. 7, the subtraction of the distance (Le) from the useful length (Lu) provides that the depth (Lp) is equal to the previously entered working length (Lt): this means that the extremity (23) has reached the apex (43). In this case, the practitioner stops his gesture and can continue the care sequence, for example by removing the current instrument (20).

The working length (Lt) is preferably entered manually by means of the interface (31). In another mode, the handpiece (10) comprises means of communication with the endodontic installation of the practice, and the working length (Lt) previously determined, for example with an apex locator, is uploaded directly into the control unit memory (30).

[0054] In one embodiment, when the depth (Lp) reaches the working length (Lt), the computer program is programmed to stop driving the instrument (20): this disengagement guarantees that the instrument (20) will not machine the tissues excessively, and that the end (23) will not exceed the apex (43).

[0055] In order to facilitate the use of the handpiece (10), it is possible that each instrument (20) is equipped with a means of identification, such as a bar code, a QR code or even an RFID chip. This means of identification makes it possible to recognizing the reference of the instrument (20) in order to determine its useful length (Lu).

In this case, the handpiece (10) comprises means for reading the identification of the instrument (20), and these reading means are connected to the control unit (30). The computer program is then programmed to search within a database of useful lengths of instruments, the useful length (Lu) of the instrument (20) selected and mounted in the handpiece (10). The database is recorded in the computer program, or is recorded on a remote support and the handpiece (10) is adapted to communicate, in particular by wireless link, with said remote support.

The manipulations to be carried out by the practitioner are reduced, and the risk of input error is eliminated.

Of course, even if the handpiece (10) includes such reading means, it is advantageous that the interface (31) can still be used for manual entry of the useful length (Lu), in the case of an instrument (20) whose means of identification is defective, or else in the case of an instrument (20) without means of identification.

The invention also provides advantageous results in the prevention of instrumental ruptures, and in particular in the case of fatigue and/or creep ruptures. This type of rupture occurs if the instrument (20) rotates in a curvature imposed by the geometry of the channel (42), in a static position: that is to say that the practitioner does not move back and forth in order to varying the depth of the instrument (20). The instrument (20) then undergoes a rotary flexion at a given length, fixed by the depth at which it is, instead of the rotary flexion being distributed along the length of the instrument (20) by the back and forth movement . It follows the rupture of the instrument (20). The practitioner must therefore perform a back and forth movement, the amplitude of which depends on the treatment technique. The amplitude can be short, from 1 to 2mm, or longer, up to 10mm.

To avoid this type of break, the computer program is programmed to check that the distance (Le) is not fixed for a period greater than a predefined period, for example 2, 4, or 6 seconds. Otherwise, the computer program is programmed to actuate means for alerting the handpiece (10), such as an audible alarm, to alert the practitioner. In addition or as an alternative, the computer program is programmed to stop the motor before the instrument breakage occurs.

The measurement of the distance (Le) is of course carried out according to good measurement and analysis practices in the field of automation, that is to say that the value of the distance (Le) is averaged over a course of time by the computer program, for example between 0.25 and 1 second, and that the variation in the value of the distance (Le) must exceed a predefined threshold, for example between 1 and 10 mm .

Furthermore, the handpiece (10) can be shaped differently without departing from the scope of the invention, which is defined by the claims.

In a variant not shown, the useful length (Lu) is measured in situ by the detection means (11). For example, if the detection means (11) are of the video type, the program is programmed to recognize the instrument (20) on the acquired image, and detect its useful length (Lu), at the same time as it recognizes the part (41) in order to measure the distance (Le).

In a variant not shown, the insertion length of the handle (24) varies depending on the model of the handle (24), and an offset value, "offset" in English, should be added or subtracted from the useful length (Lu). The models of handles (24) being standardized, it is easy, starting from the reference of the instrument (20), to program the computer program so that this offset is taken into account.

[0065] In addition, the technical characteristics of the various embodiments and variants mentioned above may be, in whole or for some of them, combined with each other. Thus, the handpiece (10) can be adapted in terms of cost, functionality and performance.^

Claims

[Claims 1] Handpiece (10) for endodontic practice, comprising a control unit (30) executing a computer program, and designed to drive a root canal instrument (20), characterized in that the handpiece ( 10) comprises means (11) for detecting the distance (Le) between a reference point (12) and a part (41) of a tooth (40), and the computer program is programmed to determine the depth (Lp) at which the instrument (20) is located during work as a function of a known length (Lt) of the instrument (20).

[Claims 2] Handpiece (10) for endodontic practice according to claim 1, characterized in that the detection means (11) comprise a distance sensor by laser and/or infrared and/or ultrasound and/or by system of vision.

[Claims 3] Handpiece (10) for endodontic practice according to one of the preceding claims, characterized in that the detection means (11) are arranged on a contra-angle (13) of the handpiece.

[Claims 4] Handpiece (10) according to one of the preceding claims, characterized in that the computer program is configured to stop the drive of the instrument (20) if the determined depth (Lp) reaches a value predefined by the practitioner, preferably the working length (Lt).

[Claims 5] Handpiece (10) according to one of the preceding claims, characterized in that it comprises a display (31) of the depth value.

[Claims 6] Handpiece (10) according to one of the preceding claims, characterized in that it comprises means for reading an identification of the instrument (20), and in that the computer program is configured to look up the length (Lt) of the instrument (20) within a database of instrument lengths.

[Claims 7] Handpiece (10) according to one of the preceding claims, characterized in that the reading means are of the RFID type, or a visual code such as a bar code or a QR code.

[Claims 8] Method for determining a working depth (Lp) of an endodontic instrument (20) driven by a handpiece (10), characterized in that it comprises the following steps:

- obtaining the length (Lt) of an endodontic instrument;

- measurement of the distance (Le) between a reference point (12) of the handpiece and a part (41) of a tooth (40);

- subtraction of the distance (Le) from the length (Lt) of the instrument (20) in order to determine the depth (Lp) at which the instrument is located.

[Claims 9] Method for determining a working depth (Lp) according to claim 8, characterized in that the length (Lt) of the instrument (20) is obtained by manually entering the length on an interface (32) of a control unit (30) of the handpiece (10).

[Claims 10] Method for determining a working depth (Lp) according to one of Claims 8 or 9, characterized in that the length (Lt) of the instrument (20) is obtained by reading means of identification of the instrument (20), and by searching for the length (Lt) of the instrument (20) within a database of instrument lengths.

[Claims 11] Method for determining a working depth (Lp) according to one of the preceding claims, characterized in that the computer program is programmed to verify a variation in the distance (Le) over time, and in the event that the variation is less than a predefined threshold during a predefined period:

- to actuate alert means of the handpiece (10); and or

- to stop the driving of the instrument (20).