Patent application title: APPROACH TO IDENTIFYING DEVICE FOR MEASURING CONCENTRATION OF IRRIGATION SOLUTION IN THE APICAL REGION OF A ROOT CANAL

Abstract

To provide a device capable of knowing in a practical and reliable manner a concentration of an irrigation solution in a root canal during an endodontic treatment.SOLUTION: A device 10 for electronically locating an apex in a root canal CR of a tooth T is able to be electrically connected to an endodontic instrument 20 engaged in the root canal and a labial electrode 30, and includes a display screen 15 to display progression of the endodontic instrument in the root canal relative to a critical point of reference such as a cement-dentinal junction JCD. The device is further able to measure, in the vicinity of the critical point of reference and by conductimetry, a concentration of an electrolyte irrigation solution injected into the root canal.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to the general technical field of endodontics, in particular to devices for determining the root apex position, commonly referred to as (electronic) root canal locators, and more specifically to a root canal locator capable of measuring the concentration of an irrigation solution injected into the root canal just before the cemento-dentin junction.

[0002] Such an canal locator is used, for example, during the canal preparation stage of endodontic treatment. [Background technology]

[0003] It is advisable to first briefly review the anatomy of the root in the apical region. The root canal system, and more specifically the apical structure, can be described according to Kuttler's apical concept, which results in a representative model shown, for example, in FIG.

[0004] FIG. 1 is a partial longitudinal section of the root RT, showing that the root canal CR passes through the center of the root RT and ends in a foramen FA, the so-called apical foramen, which is present at the end of the root and through which the vascular and nerve bundles pass. This foramen FA generally has a bottleneck shape due to the narrowing and widening of the root canal CR, which defines a minimum aperture called the apical constriction CA. This apical constriction CA constitutes the narrowest passage for the neurovascular bundles irrigating the dental pulp. The root canal CR generally has a convergent and widening shape between the coronal part and the periapical part, resulting in a two-cone shape relative to the apex of the apical constriction CA. More precisely, this root canal CR defines a dentin cone and a shorter cementum cone. The interface between these two is called the cemento-dentin junction JCD. As shown in detail A of FIG. 1, this apical constriction CA and the cemento-dentin junction JCD are not necessarily confused, but they can be. The specialist literature indicates that the apical constriction CA usually coincides with or is close to the cemento-dentin junction JCD.

[0005] During endodontic therapy, the practitioner (dentist) tries to remove all material, debris and organic fluids that are embedded in the root canal up to the bottom, i.e., the apical foramen, in order to prevent the re-development of a dental abscess in the root canal. However, the practitioner's aim is in particular to avoid drilling the cavity below the root beyond the apex, where an abscess could occur, while avoiding pain for the patient, by avoiding passing the apex or root apex as much as possible.

[0006] It is therefore essential for the practitioner to locate the apical foramen and the root apex very precisely, especially during the procedure of cleaning and shaping the root canal (canal preparation), in order to avoid going beyond the apical foramen. This brings us back to the main subject of determining the "working length", the exact distance from the crown reference point to a previously fixed and selected apical limit, usually located at the apical constriction. This working length can be determined using radiography (which gives a less precise radiographic apex RA) and / or electronic canal locator (which gives a more precise anatomical apex AA).

[0007] Apical localization allows for precise irrigation, which is a critical step in canal preparation.

[0008] The purpose of irrigation is to remove various microorganisms, lubricate the endodontic instruments that are inserted into the root canal, and dissolve organic and inorganic debris. Irrigation is performed by liberally injecting an irrigating solution, such as sodium hypochlorite (NaOCl), into the root canal.

[0009] Sodium hypochlorite has antibacterial and cell lytic properties, the effectiveness of which increases with concentration, but at high concentrations there is a risk of toxicity, particularly cytotoxicity.

[0010] "Medical" concentrations of NaOCl, ranging from 0.5% to 5.25%, are widely used in clinical practice. Less concentrated solutions have been found to have certain antibacterial efficacy, but the aforementioned concentrations, while providing a faster and more effective bactericidal effect, should generally not be exceeded.

[0011] Excessively high concentrations of sodium hypochlorite are extremely toxic to living tissue and act as caustic agents. Large amounts of high concentrations of sodium hypochlorite delivered periapically can cause hemolysis, skin ulceration, necrosis, and even facial nerve weakness in the affected area. In addition, sodium hypochlorite affects the hardness of dentin. Prolonged exposure to high concentrations can decrease the elastic modulus (in curvature) of dentin.

[0012] Therefore, precise knowledge of the concentration of the irrigation solution, here NaOCl, in the root canal, especially in the apical region, is crucial to ensure effective treatment and limit toxicity risks.

[0013] To the applicant's knowledge, there are no root canal locators or the like that are capable of determining this concentration in the apical region, particularly at the cemento-dentin junction. Summary of the Invention [Problem to be solved by the invention]

[0014] The present invention aims to address the need of practitioners to know the concentration of irrigation solution in the root canal during endodontic treatment in a practical and reliable manner. [Means for solving the problem]

[0015] To that end, it is an object of the present invention to provide an electronic device for determining the location of the apex in a root canal, said electronic device being electrically connectable to an endodontic instrument inserted in the root canal and to a labial electrode, and comprising a display screen for displaying the progress of the endodontic instrument in the root canal relative to a critical reference point of the apex, such as the cement-dentin junction, said device being distinguished by the additional possibility of measuring the concentration of an electrolyte irrigation solution injected into the root canal by conductometric measurements, in the vicinity of said critical reference point.

[0016] According to a particularly advantageous embodiment of the invention, a measurement of the concentration of the irrigation solution is made in a region one millimeter immediately preceding the cemento-dentin junction in the direction of the insertion of the endodontic instrument into the root canal.

[0017] According to one embodiment, the measured level of concentration, relative to a medical concentration range, is displayed by a visual indicator on the display screen of the device.

[0018] For example, the visual indicator is a bar graph.

[0019] Additionally, the device includes a connection cord that is electrically connectable to the endodontic instrument and the labial electrode, or the like.

[0020] Advantageously, the processing and calculation means of the device are adapted to calculate the conductivity for at least one irrigation solution, sodium hypochlorite NaOCl, and are capable of displaying the measured concentration levels on a scale with at least one value substantially equal to 0.5%, 2.5% or 5.25%, the concentrations most recommended and utilized in endodontic therapy, in particular for canal preparation.

[0021] According to one embodiment, the display screen displays a confirmation message such as "OK" as long as the measured concentration of the irrigation solution is substantially equal to the concentration of the irrigation solution at the time of injection.

[0022] An object of the invention is also a method for measuring the concentration of an irrigation solution in a root canal of a tooth by implementing the device described above.

[0023] Advantageously, the method includes a step of storing the concentration information, which can facilitate the practitioner's work by allowing him to read the irrigation solution concentration value even when he removes the instrument from the patient's root canal.

[0024] The basic concept of the invention in its most basic form has been disclosed above, while other details and characteristics will become clearer on reading the following description, on referring to the accompanying drawings, and on considering, by way of non-limiting example, an embodiment of a device according to the principles of the invention.

[0025] The drawings are for illustrative purposes only, for the understanding of the invention, and are not intended to limit the scope of the invention. Different components are shown diagrammatically and are not necessarily to the same scale. [Brief description of the drawings]

[0026] [Figure 1] This is a longitudinal section of a tooth root in the apical region according to Kuttler's apical concept (mentioned above). [Diagram 2] 1 is an example of the use of the apex locating device according to the invention on a tooth to measure the concentration of an irrigation solution. [Diagram 3] This is the principle of conductivity measurement of the concentration of irrigation solution near the cement-dentin junction. [Figure 4] 1 is a simplified electrical assembly enabling concentration measurement by conductivity according to the present invention. [Figure 5a] FIG. 13 is an example of a graphical interface for monitoring the progress of the instrument and irrigation solution concentration in the root canal as the canal preparation progresses, where the instrument is outside the measurement area near the critical reference point at the apex. [Figure 5b] Graphical interface as the instrument passes one millimeter just before the cemento-dentin junction. [Figure 5c] 13 is a graphical interface when the instrument has reached the apex. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] In order to avoid deficiencies or obscurity in understanding the present invention, it is noted that certain devices and techniques well known to those skilled in the art are described herein.

[0028] In the embodiment described below, an improved apex location device is described for measuring the concentration of irrigation solutions in the root canals of teeth, mainly intended for measuring said concentration just before the cemento-dentin junction during canal preparation. This example is not limiting and is given for a better understanding of the invention, without excluding the use of other devices. For example, the device can be applied to measuring the concentration of irrigation solutions or physiological fluids in other anatomical regions where the treatment is similar to that of endodontic treatment, at least with regard to the injection of ionic solutions into the root canals terminating at the tip (apex).

[0029] In the following description, the cemento-dentin junction will be referred to as "JCD", its French acronym. "Irrigant" refers to the irrigation solution and "Apex Locator" refers to the electronic Apex Locator. For the anatomical parts of the root in the apical region, please refer to Figure 1 already described.

[0030] FIG. 2 shows a root canal locator 10 conventionally connected to a specimen or root canal model of a tooth T, via an endodontic instrument 20, such as a file, and a labial hook 30, which have conductive parts electrically connected to the root canal locator by connecting cords 12 and 13 to form two measurement electrodes.

[0031] According to known principles, by applying Ohm's law between the terminals defined by the two electrodes, the root canal measuring device 10 is able to determine the position of the apex in the root canal CR of the tooth T using an indirect resistance measurement, or more generally the impedance, as a measurement standard.

[0032] In principle, the Apex Locator utilizes the knowledge that the root canal has a fixed electrical impedance at the apical constriction and operates with a closed circuit alternating current with two currents that delimit the conductive anatomical unit between the root canal and the labium of the patient. Since the voltage applied by the generator of the Apex Locator is known, the Apex Locator calculates the intensity of the current. The intensity of the current varies more than the impedance at the conductive anatomical unit. The impedance value therefore abruptly reaches a value that is practically constant between individuals when the instrument used passes through the apical region and the Apex Locator detects the corresponding intensity of the current.

[0033] As will be explained hereinafter, the root canal length measuring instrument 10 of the present invention utilizes the above principles and the relationship between electrical impedance and conductivity to determine the irrigation solution concentration in the root canal by conductometry.

[0034] According to the illustrated example, the root canal length measuring instrument 10 is provided with a display screen 15 on which various information can be read so as to enable real-time monitoring of the insertion of the endodontic instrument 20 within the root canal CR until the root apex is detected.

[0035] The connecting cords 12 and 13 of the root canal measuring instrument 10 have a clamp 121 or any other connecting means 131 at each free end, to which the conductive parts of the endodontic instrument 20 and the labial hook 30 are attached, respectively.

[0036] According to the illustrated example, the endodontic instrument 20 is a canal forming file including a metal rod 21 having a tip 211. Such a file is preferably flexible to accommodate root canals with different curvatures. The clamp 121 of the connecting cord 12 is fixed to the metal rod 21 of the canal forming file 20.

[0037] On the other hand, the labial hook 30 is configured to provide secure contact with the patient's lips and / or gums G.

[0038] Thus, the endodontic instrument 20 and the labial hook 30 electrically define an anatomical unit through which electrical current flows, indicated by dashed line S in FIG.

[0039] According to a basic aspect of the present invention, the conventional mounting further enables the root canal length measuring device 10 to perform a measurement of the irrigation solution concentration in the root canal CR at the tip 211 of the instrument 20 by electrical conductivity measurement technology.

[0040] In fact, the irrigation solution is an electrolyte solution in which aqueous charge carriers (ions) dissolve, which are generated by the chemical reaction of the root canal medium with the irrigation solution.

[0041] We consider here the case of sodium hypochlorite, NaOCl, which is currently still the most commonly used, and even unavoidable, irrigant in endodontic therapy.

[0042] The bactericidal and lytic effect of NaOCl is achieved by the following sequential reactions:

[0043] [ka]

[0044] First, sodium hypochlorite dissolves in the solution to produce hypochlorous acid HOCl, which, in a basic medium, dissociates in a second reaction to produce hypochlorite ions OCl, known for their antibacterial properties. - In fact, hypochlorite ions are powerful oxidizing agents that inhibit bacterial enzymes and lead to the irreversible oxidation of sulfhydryl groups (SH) that form the bulk of the so-called enzyme membranes, resulting in the destruction of sulfhydryl groups (SH).

[0045] Of course, the ions formed after the second reaction above are aqueous. Due to the presence of electronically charged species, the conductivity σ of the irrigation solution is expressed as follows for NaOCl:

[0046] [ka]

[0047] where λ X is the ionic molar conductivity of ion X and [X] is the concentration of ion X in solution.

[0048] C is the concentration of the solution at chemical equilibrium, and taking into account the charge coefficients of the influencing ions, it can be expressed as follows:

[0049] [ka]

[0050] However, it is known that the conductivity is proportional to the conductivity G which is nothing but the reciprocal of the resistance R according to the following formula:

[0051] [ka]

[0052] The coefficient k depends on the geometry of the measurement cell. Λ is the sum of the molar conductivities of the ions and is constructed as follows:

[0053] [ka]

[0054] Thus, the concentration C is inversely proportional to the resistance R, with the proportionality coefficient k' being a constant that depends essentially on the nature of the ions in the irrigation solution and on the geometry of the measuring cell.

[0055] The simplified formula above is intended to relate the resistance (or impedance) of the anatomical unit through which the current flows to the concentration of the irrigation solution, and using the basic principles of the Apex Locator, the concentration can be determined by conductometric measurements.

[0056] Figure 3 illustrates the principle of measuring irrigant concentration in the apical region of a tooth root, with simplified anatomy for ease of understanding.

[0057] During irrigation, the NaOCl solution fills the root canal CR to the apical foramen FA and penetrates into the smallest gaps in the root canal due to its low surface tension.

[0058] An object of the present invention is to allow the practitioner to know the concentration of irrigant proximate to the JCD, for example, one millimeter immediately before the JCD.

[0059] As a rule, root canal irrigation is performed with NaOCl at concentrations between 0.5%, 2.5% and 5.25%. The root canal locator 10 can therefore be adjusted to display concentration levels measured within this range of so-called "medical" concentrations.

[0060] Among its calculation and processing means, the root canal locator 10 may include a specific electronic module 141 for managing the conductivity calculation, independent of the basic functionality of the root canal locator, i.e. apex detection. Such a module may be in the form of an electronic board that can be easily integrated into known models of root canal locators.

[0061] Preferably, the conductivity calculation is performed directly by the central processing unit of the root canal measuring instrument 10, as will be explained below with reference to FIG.

[0062] Insofar as electronic apex locators work based on the variation of electrical current due to the specific impedance of the root canal, which impedance is directly dependent on the concentration of any electrolyte filling the root canal, such as an irrigant, the present invention applies to different generations and technologies of apex locators.

[0063] In particular, according to this embodiment of FIG. 4, the root canal measuring device 10 comprises a connection interface 11 with electrodes 20 and 30 via connection cords 12 and 13, a microprocessor-based computing unit 14 connected to different services, inter alia a display module 15, an on / off button 16, a power supply battery 17 and an AC regulator 18.

[0064] The microprocessor 14 uses both the apex localization calculations and the conductivity calculations to determine the irrigation solution concentration. Naturally, the Apex Locator has the necessary memory means to store the generated information.

[0065] It is important to take into account that the degree of cleaning of the root canal depends mainly on the concentration of the irrigant (within the medical range mentioned above) and the time it is present in the root canal. Therefore, the practitioner must monitor the irrigant concentration in the root canal when performing root canal cleaning with irrigation. Moreover, knowing the irrigant concentration near the JCD is very important for effective treatment of areas prone to complications and abscesses.

[0066] Thus, the root canal length measuring instrument 10 of the present invention provides quick and intuitive access to information regarding the concentration of irrigant in the apical region of the root canal.

[0067] 5a to 5c show an example of a possible display (graphical interface) of the progression of the endodontic instrument 20 in the root canal CR of a tooth T. This display allows a rough visualization of a partial longitudinal section of the root, with a dashed progression line 151 indicating the progression of the instrument 20 in the root canal CR in the apical region Z. In the illustrated example, the displayed apical region corresponds approximately to the last 3 mm of the root, more precisely the last 3 mm just before the JCD. To allow a better monitoring of this critical region in endodontic therapy, a magnification is preferably applied up to the last millimeter.

[0068] In FIG. 5a, the instrument 20 starts to enter the apical region Z of the root canal CR. The display obtained on the display screen 15 of the apex locator shows that the progress line 151 has not yet entered the last millimeter of the JCD, which corresponds to the critical region where the concentration of the irrigant needs to be known. In fact, the displayed cross-sectional portion of the root canal can be divided into two regions: region Z1 and region Z2, where the latter is not measured because no concentration measurement is necessary, and region Z2 where a concentration measurement is mandatory so that the practitioner does not leave any doubt during the canal preparation. Region Z is located upstream from the last millimeter, whereas region 2 corresponds to the last millimeter of the JCD. Also, whatever the concentration of the irrigant injected, the irrigant fills region Z1 without difficulty and its concentration is approximately constant, so no concentration measurement is necessary in this region. On the other hand, in the region Z2, located near the JCD (and therefore often near the apical constriction), the narrow width of the root canal means that filling with the irrigation solution remains problematic and uncertain, which is why it is necessary to measure the concentration in this critical region.

[0069] In the example of Figures 5a to 5c, the injection of a sodium hypochlorite NaOCl solution with a concentration of 2.5% is considered.

[0070] FIG. 5b shows that the instrument 20 has passed through the apical region of interest, and thus a result is displayed indicating the presence of a progress line 151 in the concentration measurement zone Z2. The measured concentration level is therefore indicated by a visual indicator, such as a bar graph 152, on the display screen of the canal measuring device. For example, the concentration level display can be automatically and unannounced on the screen as soon as the instrument enters the measurement zone Z2, to provide a visual alert to the practitioner. In this example, the display screen shows a concentration of 2.5% according to the injection concentration. Also, a monitoring message such as "OK" can be displayed when the concentration has reached the required level, so that the practitioner does not get confused by reading complex information. This allows the practitioner to concentrate almost entirely on manipulating the endodontic instrument in the root canal.

[0071] Furthermore, the density values ​​are stored so that they can be easily read even after the root canal treatment instrument has been removed. This information is reset when the instrument is reinserted into the root canal or when the Apex Locator is automatically terminated.

[0072] In FIG. 5c, the instrument 20 has reached the apex or at least approximated it within a tolerance, so the display screen shows a progress line 151 extending to the "zero" reference point in millimeters. The Apex Locator can provide a visual and / or audible notification that the instrument 20 has approximated the apex. In the illustrated example, the concentration of the irrigant is less than 1% and therefore remains lower than required. In this case, the practitioner must re-irrigate the canal by adding a certain amount of solution to increase the concentration of irrigant in this area. Moreover, even if the concentration is insufficient, no negative message is displayed on the screen to avoid confusion and to make the graphical interface as intuitive as possible.

[0073] However, the simplified example of the graphical interface shown above is not limiting and the graphical interface can be modified according to the recommendations of the intended user of the root canal locate device.

[0074] Finally, it will be apparent from this specification that certain elements of the root canal locator can be modified, suppressed or substituted without departing from the scope of the invention as defined in the claims. [Explanation of symbols]

[0075] 10 Root canal length measuring device 11 Connection Interface 12 Connection cord 13 Connection cord 14 Calculation unit / microprocessor 15 Display screen / display module 16 On / Off Button 17 Power Supply Battery 18 AC regulator 20 Endodontic Instruments / Canal Formation Files / Electrodes 21 Metal Rod 30 Labial Electrode / Labial Hook 121 Clamp 131 Any other connection means 141 Electronic Module 151 (Instrument) Progress Line 152 Visual Indicators / Bar Graphs 211 Tip AA anatomical apex APX apical end CA apical stenosis CR root canal FA apical foramen G. Gingiva JCD Cement Ivory Border RA X-ray periapical RT Root S dashed line T tooth Z apical region Z1 (concentration measurement not required) area Z2 (concentration measurement) area

Claims

1. 1. An apparatus (10) for electronically locating an apex position in a root canal (CR) of a tooth (T), comprising a display screen (15) electrically connectable to an endodontic instrument (20) inserted in the root canal (CR) and a labial electrode (30), the display screen (15) displaying progress of the endodontic instrument (151) in the root canal relative to a critical reference point of the apex, such as the cemento-dentin junction (JCD), The device further comprises the capability of measuring the concentration of the electrolyte irrigation solution injected into the root canal by conductometric measurements in the vicinity of the critical reference point.

2. 2. The device of claim 1, wherein the concentration measurement of the irrigation solution is performed in an area 1 millimeter just before the cemento-dentin junction (JCD) in the direction of insertion of the endodontic instrument (20) into the root canal (CR).

3. 3. The apparatus of claim 1 or 2, wherein the measured level of concentration is displayed by a visual indicator (152) on the display screen (15) relative to a range of medical concentrations.

4. The apparatus of claim 3 , wherein the visual indicator (152) is a bar graph.

5. 5. The device according to claim 1, further comprising a connection cord (12, 13) for electrically connecting the endodontic instrument (20) and the labial electrode (30).

6. 6. The device according to any one of claims 1 to 5, wherein the processing and calculation means is configured to calculate the conductivity for at least one irrigation solution, sodium hypochlorite (NaOCl), and is capable of displaying the measured concentration level on a scale having at least one value substantially equal to 0.5%, 2.5% or 5.25%.

7. 7. The device according to claim 1, wherein the display screen (15) displays confirmation information as long as the measured concentration of the irrigation solution is substantially equal to its concentration at the time of injection.

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