Endotherapy device

Abstract

A dental apparatus (1) and method, such as an endodontic apparatus and method, is disclosed. The apparatus includes a source (12) of fluid, a pump (14) for delivering fluid from the source (12) under pressure, and a handpiece (20) in fluid communication with the pump (14). The handpiece (20) includes a needle (30) extending from a proximal rear end of the handpiece to a distal forward tip from the handpiece, the needle lumen extending to an opening in the tip for delivering fluid received from the pump to a tooth. The needle dimensions and fluid delivery pressure are selected such that a cloud of inertial cavitation is formed in front of the tip of the needle by the flow of fluid through the needle.

Description

[Technical Field]

[0001] FIELD OF THE INVENTION The present invention relates to dental devices and methods, and more particularly to endodontic devices and methods for endodontic debridement, cleaning, and / or disinfection. [Background technology]

[0002] Root canal therapy is used to save teeth when severe infection occurs. A typical root canal therapy procedure involves the following steps: (i) opening the cavity to access the pulp and root canals; (ii) enlargement with mechanical instruments and files; (iii) chemical irrigation (using a syringe) with sodium hypochlorite (bleach, NaOCl), EDTA, and / or other chemicals, usually repeated several times; (iv) optional activation of the NaOCl / chemicals with an ultrasonic cleaning device; and (iv) obturation (or filling) of the root canal and closure of the tooth. This multi-step procedure is very laborious and can take approximately 60 minutes to complete.

[0003] Although such procedures are common (approximately 55 million procedures performed annually worldwide), they are laborious, time-consuming, and have a relatively high failure rate (approximately 30% of cases), resulting in costly and complicated retreatment, tooth extraction, or expensive implant placement. The primary causes of these failures are incomplete bacterial removal or weakening of the tooth structure due to mechanical filing. The former is a result of the limitations of the combined mechanical filing and syringe irrigation technique, which cannot access all of the very small (e.g., less than 300 or 100 μm) complex canal structures of the tooth, leaving bacteria behind and causing later reinfection. The latter results from the dilation of the canals to improve access to NaOCl, which weakens the dentin structure and makes the root more susceptible to cracking.

[0004] Some of the common problems dentists face when performing root canal procedures include one or more of the following: the considerable time and effort required to dilate the canals; the risk of weakening the tooth structure by filing the canals; the risk of bacteria in the smallest canals not being detected or not reaching the canals if they are not removed to avoid reinfection through the small canals; the occurrence and / or detection of vapor lock within the canal (when air is trapped and cannot escape and pass through the fluid above, preventing the irrigant from disinfecting the apical third of the canal); the risk of NaOCl being forced beyond the apex into the soft and hard tissues; and / or blood ingress from outside the tooth.

[0005] Several systems are commercially available that aim to improve root canal cleaning and address or mitigate at least some of the problems mentioned above. These systems aim to enhance the hydrodynamic action of the irrigant to improve cleaning, debridement, and / or disinfection.

[0006] One such system uses negative pressure suction to prevent vapor lock from occurring; one example is the EndoVac system (available from Discus Dental, Culver City, California, USA). Such systems use continuous apical negative pressure irrigation, in which fresh irrigant is slowly injected into the pulp chamber from the top with a large needle. This is aspirated into a cannula at the bottom of the canal. The problem with such systems is that significant equipment is required to expand the canal sufficiently to accommodate the two detergent needles.

[0007] Another type of system is the sonic or ultrasonic system, which uses a vibrating plastic or metal tip inserted into the root canal. The vibration frequency is typically between 100 Hz and 20 kHz. The vibration prevents airlock formation and may improve debridement and / or disinfection performance, especially in larger canals. Examples of such systems include the EDDY system (available from VDW, Munich, Germany), the Endoactivator system (available from Dentsply Sirona, York, Pennsylvania, USA), and the Irrisafe system (available from Acteon Group, Norwich, UK). However, such systems generally function only to a very limited extent without prior extensive instrumentation and canal filing.

[0008] Another type of system is the closed hydrodynamic activation system, including the Gentlewave system (available from Sonendo, Inc., Laguna Hills, California, USA) and the system disclosed in U.S. Pat. No. 4,993,947. In closed systems, a component such as a coronal head is placed within the pulp chamber and securely attached to form a closed system with the tooth. The requirement for a fluid-tight connection between the tooth and the system requires additional work as part of the dental procedure. A pump delivers alternating flows into the root canal, gradually removing debris. To enhance the hydrodynamic action of the irrigant within the canal, U.S. Pat. No. 4,993,947 passes the fluid through a Venturi nozzle that generates cavitation before delivery to the tooth, irrigating the entire volume of the root canal (including narrow canals) and increasing penetration into the root tissue. In the Gentlewave system (available from Sonendo, Inc., Laguna Hills, California, USA), enhanced hydrodynamic action is achieved through the interaction of a water jet impinging on a platform formed as part of the coronal head. However, besides the major drawback of being cumbersome and rigid to fix on the tooth, alternating flow systems have a significant problem with negative pressure (or insufficient height) at the apex, which leads to blood inflow and inefficient disinfection and debridement of the apical area.

[0009] Open hydrodynamic activation systems have also been proposed, such as the RinsEndo system (available from Duerr-Dental, Wittigheim-Bissingen, Germany) and the systems shown in U.S. Patents 4,247,288 and 6,224,378. For example, the RinsEndo system uses a special disposable cannula designed to deliver irrigant deeper into the root canal. U.S. Patent 6,224,378 uses a high-pressure, high-velocity hydrojet of water or other liquids designed to remove soft tissue within the tooth, but has limited ability to cut or erode hard, calcified dental tissue.

[0010] Finally, laser-activated systems such as Photon Induced Photoacoustic Streaming (PIPS) or SWEEPS (Shock Wave Enhanced Emission Photoacoustic Streaming) (available from Fotona, Ljubljana, Slovenia) can enhance cleaning by inserting a fiber optic system into the pulp chamber. In such systems, a laser is used to superheat water and create cavitation.

[0011] While many root canal activation systems claim to generate "cavitation" to ensure efficient root canal disinfection, Applicant has found that this is insufficient in practice. For example, in many systems, the cavitation generated is limited and appears to be non-inertial cavitation, in which bubbles in the fluid simply oscillate in size and / or shape. Non-inertial cavitation does not result in the bubble collapse that generates the powerful shock waves seen in inertial cavitation. Furthermore, Applicant has found that many existing solutions are unable to generate cavitation within the narrow (less than 1 mm, less than 500 μm, or even less than 300 or 100 μm) canal segments of teeth required for effective cleaning, debridement, and / or disinfection. Finally, none of the existing devices can be used to eliminate or reduce the need for mechanical filing, a major cause of root fractures. These devices only function as irrigant activation devices to improve the disinfecting power of irrigants.

[0012] Thus, there remains a need for improved devices and methods for quickly and reliably cleaning root canals of necrotic tissue, debris, and bacterial biofilm. In particular, there is a need for devices and methods that can eliminate or reduce the need for mechanical rasping, e.g., significantly shortening the required treatment time. Embodiments of the present invention address these needs and overcome at least some of the known problems of root canal treatment procedures. Summary of the Invention

[0013] According to a first aspect of the present invention, there is provided an endodontic treatment apparatus (e.g., an endodontic debridement, irrigation, and disinfection apparatus) comprising: a source of irrigation fluid; a pump for delivering irrigation fluid from the source under pressure; and a handpiece in fluid communication with the pump and having a needle, the needle extending from a proximal rear end of the handpiece to a distal forward tip thereof, the needle having a lumen extending to an opening in the tip for delivering irrigation fluid received from the pump into a tooth cavity, the needle having a length extending from its rear end to its tip and an outer diameter at the tip of no more than 520 μm so that the tip of the needle can be positioned within a portion of a root canal, the diameter of the tip of the lumen being at least 50 μm so that flow of irrigant through the needle forms an inertial cavitation cloud in the irrigation fluid in the root canal forward of the needle, and the pump delivers irrigant at a delivery pressure above a threshold cavitation pressure.

[0014] Applicant has recognized that in order to achieve effective debridement and / or disinfection, it is important that inertial cavitation occur within the root canal. For such cavitation to occur, the needle tip must be sufficiently long and have a sufficiently large inner diameter. Needles with an outer diameter of less than 520 μm are small enough to enter at least the coronal portion of the root canal, in contrast to many prior art devices in which the needle is simply inserted into the pulp chamber.

[0015] Without being bound by any particular theory, Applicant believes that to generate a cavitation cloud that effectively cleans the root canal and avoid substantial outflow at the apex, reverse flow within the root canal is desirable—such reverse flow requires sufficient clearance within the root canal to allow the outflow to pass between the sides of the needle and the sides of the root canal. The reverse flow creates a large shear layer within the irrigant within the root canal. The shear layer generates a strong vortex at the interface between the inward and outward flow within the root canal. Within the vortex, a significant drop in (dynamic) pressure occurs, and this pressure drop makes cavitation more likely. Furthermore, not only does cavitation debride, clean, and disinfect the canal, but the flow also serves as a highly efficient mechanism for removing debris or bacteria.

[0016] Once the needle is placed in the root canal (in a manner that causes reflux), the specific pressure required to generate the inertial cavitation cloud can be selected based on the specific needle and root canal geometry. Such threshold pressures can be determined, for example, for various needle sizes.

[0017] Applicant has also determined that providing a lumen at the tip with a diameter of at least 50 μm helps ensure sufficient flow at the tip of the needle without being limited by frictional pressure losses as the irrigant passes through the needle lumen. Selection of a delivery pressure above a threshold cavitation pressure (e.g., based on a particular needle and root geometry) can ensure that the irrigant flow exiting the needle has a velocity that causes a cloud of inertial cavitation to form in the irrigation fluid ahead of the nozzle tip.

[0018] The pump may be a mechanical pump or a compressed gas pressure system. The pump may provide a delivery pressure of 5 to 300 bar. For example, the delivery pressure may be between 5 and 100 bar. Applicant has discovered that the threshold cavitation pressure in embodiments may be between 5 and 80 bar, depending on the needle size and length selected.

[0019] The needle length may be at least 5 mm. The length may be, for example, between 10 mm and 30 mm (e.g., the needle length may be between 10 mm and 20 mm). Selecting the appropriate needle length may balance the requirements of ensuring proper tip placement in the root canal and acceptable frictional flow loss within the needle.

[0020] The delivery pressure may be selected to provide a minimum exit velocity of irrigant at the tip of the needle of at least 20 m / s (e.g., at least 40 m / s, 60 m / s, 80 m / s, 100 m / s, 150 m / s, 200 m / s, or 300 m / s). The flow rate of irrigant through the needle is less than 175 ml / min (e.g., less than 75 ml / min, 50 ml / min, 25 ml / min, 10 ml / min, or 5 ml / min). In contrast, prior art systems may irrigate ducts using NaOCl flows at flow rates as high as 1 ml / s, posing a much greater risk of inducing pain or injury than embodiments of the present invention.

[0021] The needle may have a needle gauge of between 25G and 34G (e.g., between 30G and 34G) according to the Birmingham Gauge System. The needle gauge may be specified and measured at the tip of the needle so that the needle gauge at the distal end of the needle is between 30G and 34G.

[0022] It will be appreciated that needle dimensions (i.e., outer diameter and / or lumen diameter) are generally defined based on the characteristics of the needle tip (as they may not be constant along the length of the needle).

[0023] Because embodiments of the present invention utilize the hydrodynamic action of the cavitation cloud to provide debridement and / or disinfection, the use of chemical disinfectants such as NaOCl for irrigation is not necessary. Therefore, embodiments of the present invention advantageously use water or saline as the irrigation fluid. Saline, particularly saline (e.g., 0.9% NaCl), is generally well tolerated by the body even when pushed beyond the apex and is less likely to cause significant pain or discomfort to the patient than chemical disinfectants such as NaOCl.

[0024] In embodiments, the size of the cavitation cloud extends up to 1 mm, 3 mm, 5 mm, 7 mm, 10 mm, 15 mm, or 20 mm from the distal end of the needle, and its location and size are adapted by altering the needle size, outflow rate, and / or flow rate.

[0025] In embodiments, the needle needs to be flexible and able to bend laterally in order to navigate the complex ducts.

[0026] The cleaning fluid, e.g., saline, may contain one or more additives. For example, the cleaning fluid may further contain a disinfectant. The disinfectant may enhance the germicidal effect of the cleaning fluid. The cleaning fluid may be a low-surface tension liquid so that cavitation occurs more easily at lower pressures and / or temperatures. For example, ethanol, which is also a disinfectant, may be used as a low-surface tension liquid. Because such low-viscosity fluids may be selected as cleaning fluids, the viscosity of the liquid is also a variable in the cavitation state of the cleaning fluid. The low-surface tension and / or low-viscosity fluid may be a cleaning fluid selected with such properties, or it may be a cleaning fluid containing additives that reduce its properties.

[0027] The cleaning material may also be selected or tailored to enhance its abrasive effect, for example, the density of the cleaning material may be increased and / or the cleaning fluid may further include abrasive particles (e.g., solid particles suspended in the fluid).

[0028] Devices according to embodiments can use needles with forward-facing axial openings. While such forward-facing needles typically produce better forward flow of irrigant, in contrast to embodiments of the present invention, many prior art designs avoid the use of such needles due to the risk of pushing aggressive irrigants, such as NaOCl, beyond the apex of the teeth, causing significant pain and serious complications.

[0029] The device may include a regulator for controlling the delivery pressure, which may allow the operator to adjust the delivery pressure to account for different tooth or root canal geometries, for example.

[0030] In embodiments, the device may further include a heater for controlling the temperature of the irrigant. The heater may be provided as part of the supply (resulting in either bulk heating of the irrigant or heating of the irrigant prior to delivery by the pump). Alternatively, the heater may be provided as part of the handpiece to heat the irrigant as it flows through the handpiece. The phase boundary of the irrigant is dependent on both temperature and pressure, and increasing the temperature of the irrigant for any given temperature provides more favorable conditions for cavitation. For example, the temperature may be increased to above 20°C. The temperature of the irrigant may also be selected to avoid any pain response, so the temperature may be below 60°C (or below 50°C).

[0031] In some embodiments, the device may further comprise a pulse generator for pulsing the flow of irrigation fluid, which may be, for example, a single piston pump, a controllable pressure relief valve between the pump and the needle, or an on / off valve between the pump and the needle.

[0032] According to another aspect of the present invention, there is provided a method of endodontic irrigation, the method comprising: positioning a needle having a length of at least 5 mm and a tip outer diameter of no more than 520 μm within a portion of a root canal; supplying an irrigation fluid under pressure to the needle such that the fluid is expelled from the tip of the needle into the root canal; and selecting a delivery pressure of the irrigation fluid such that the pressure at the tip of the needle exceeds a threshold cavitation pressure such that flow of irrigant through the needle forms an inertial cavitation cloud within the irrigation fluid in the root canal in front of the tip of the needle.

[0033] The delivery pressure may be selected from the range of 5 to 300 bar. In particular, the delivery pressure may be selected from the range of 5 to 100 bar.

[0034] The method may further include heating the cleaning fluid. For example, the cleaning fluid may be heated to between 20 and 57°C.

[0035] The method further includes adjusting the pressure depending on the depth to which the needle is inserted into the vessel.

[0036] Some embodiments may include pulsing the delivery of the irrigation fluid. Pulsing (rather than a continuous flow) provides a burst of flow that recoils upon impact, thereby increasing the impulse (rate of change of momentum) of the irrigant. This increases the erosive potential of the flow, thus further increasing the efficiency of debridement and / or disinfection. A pulsed flow also has the advantage of reducing the total amount of irrigant used.

[0037] According to a further aspect of the present invention, there is provided a dental instrument comprising: a source of fluid; a pump for delivering fluid from the source under pressure; and a handpiece in fluid communication with the pump and having a needle, the needle extending from a proximal rear end of the handpiece to a forward tip distal to the handpiece, the needle lumen extending to an opening in the tip for delivering fluid received from the pump to a tooth, wherein the needle dimensions and fluid delivery pressure are selected such that fluid flow through the needle causes a cloud of inertial cavitation to form in front of the tip of the needle.

[0038] The dimensions of the needle can be selected, for example, depending on the procedure required. For example, the procedure can include one or more of debridement and / or disinfection of a cavity, removal of plaque from the outer or subgingival surface of a tooth, drilling into dental tissue (dentin, enamel), cutting soft tissue, or locating an entrance to a root canal. The length of the needle can be selected to ensure that the tip of the needle is properly positioned during use. The dimensions of the needle can be selected to ensure that sufficient flow is possible through the needle while also ensuring that the tip of the needle can be properly positioned. The dimensions can also be selected to ensure that a backflow of fluid is formed proximal to the fluid flow ejected from the needle.

[0039] Unless otherwise specified, each of the recited integers can be used in combination with any other integer, as will be understood by those skilled in the art. Furthermore, while all aspects of the present invention preferably "comprise" the features recited in connection with that aspect, it is specifically contemplated that it may "consist" or "consist essentially of" the features outlined in the claims. Furthermore, unless otherwise defined herein, all terms are intended to be given their meanings as commonly understood in the art.

[0040] Furthermore, in the discussion of the present invention, unless otherwise stated, the disclosure of alternative values ​​at the upper or lower limits of an acceptable range of a parameter should be construed as an implicit statement that each intermediate value of said parameter between the lower and upper alternatives is itself also disclosed as a possible value of the parameter.

[0041] Additionally, unless otherwise specified, all numerical values ​​set forth in this application should be understood as modified by the term "about."

[0042] The invention has been described above but extends to any inventive combination of the features set out above or in the following description or drawings. [Brief explanation of the drawings]

[0043] Embodiments of the present invention may be carried out in various ways and embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0044] [Figure 1] 1 shows a schematic diagram of an apparatus according to one embodiment of the present invention. [Figure 2] FIG. 2 shows a detail of the schematic diagram from FIG. 1 showing the position of the needle within the tooth. [Figure 3] 3(A), 3(B), 3(C) and 3(D) illustrate the operating principles behind embodiments of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0045] (Detailed Description of the Invention) It should be noted that the terms proximal and distal are used herein for convenience to refer to the device in its typical orientation during use. It is therefore understood that proximal may generally be used to refer to a surface, component, or direction that is closer to the operator's hand during use, and distal may generally be used to refer to a surface, component, or direction that is distal to the operator's hand (and thus proximal to the root canal). Similarly, anterior is understood to be used in reference to a direction away from the proximal end toward the distal end (and posterior is understood to be the opposite direction). However, it will be understood that such references are not intended to be limiting, and the device may be in any orientation during use.

[0046] An endodontic irrigation device 1 is shown schematically in Figure 1. The device comprises a base unit 10 including a reservoir 12 that contains a source of irrigation fluid and a pump 14 that delivers irrigation fluid under pressure from the source through a flexible conduit 16. The base unit 10 may also include a user interface 18 (which may be in any convenient format) that allows an operator to adjust operating parameters such as the pressure output of the pump 14.

[0047] The handpiece 20 is connected to the distal end of the flexible conduit 16, for example, by a conventional detachable connector, allowing the handpiece 20 to be in fluid communication with the base unit 10 and to receive irrigation fluid from the source 12 via the pump 14. The handpiece 20 includes a grip portion 22 at its proximal end and a head 24 connected to the grip portion 22 via a neck 23. The head 24 typically extends to a needle 30, which may be replaceably mounted within the head 24. As used herein, the term "needle" broadly refers to a thin, elongated conduit having a bore therethrough (the needle's "lumen") extending from the proximal end, where it receives a fluid supply during use, to an opening at the distal end through which the fluid is delivered during use. As best seen in FIG. 2 , the needle extends axially from the proximal end 33 to the distal tip 34 and has a length 1. A lumen 32 extends through the length of the needle 30 and provides a passage for irrigation agent. The tip of the needle 34 terminates in a forward-facing axial opening, allowing the irrigant to exit the lumen in a forward axial flow.

[0048] In use, the needle 30 is inserted into the tooth 100 through a cavity 110 (formed by any convenient method, e.g., by drilling) that provides access to the pulp chamber 120. According to an embodiment of the present invention, the needle has a length measured in direction l of at least 5 mm and an outer diameter measured in direction d of no more than 520 μm, such that the needle tip 34 can be positioned within a portion of the root canal 130. With the needle positioned in this manner, applicant surprisingly discovered that delivering an irrigant in a manner that generates an inertial cavitation cloud in front of the needle tip 34 can provide effective debridement and / or disinfection without the need for an NaOCl-based irrigant. In contrast, many prior art systems use needles that are too short to reach the root canal itself (instead simply positioning the tip within the cavity 100 or pulp chamber 120) and / or that are too large in diameter to enter the root canal.

[0049] Furthermore, embodiments of the present invention allow root canal treatment to be performed without the need for mechanical filing (at least in all but the most difficult cases—e.g., elderly patients with calcified and narrowed canals), thereby requiring only initial access to the root canal prior to using the inventive device. To provide such an inertial cavitation cloud, Applicant has discovered that the needle inner diameter (i.e., lumen diameter) and delivery pressure (depending on the geometry of the particular tooth-needle combination) must be selected to exceed a threshold cavitation pressure, such that the flow of irrigant through the needle creates an inertial cavitation cloud within the irrigation fluid in the root canal ahead of the needle tip. For example, the lumen diameter may be at least 25 μm, e.g., at least 50 μm. Without understanding this effect, it might be natural to select a needle with too small an inner diameter (e.g., less than 50 μm to ensure a reliable fit in the root canal), but Applicant recognizes that such a needle introduces significant frictional losses, meaning that even very high delivery pressures will not provide a flow exiting the needle that generates effective cavitation. In contrast, in embodiments of the present invention, cavitation provides powerful debridement, disinfection, and / or removal of debris or bacteria due to the well-known erosive effect resulting from shock waves caused by rapidly collapsing vapor bubbles within the fluid.

[0050] As shown in the 16,000 fps high-speed photograph in Figure 3(A), a glass micropipette (e.g., with an inner diameter of 1.2 or 0.6 mm) can be used to simulate a root canal. When an appropriately sized needle 330 is inserted into the canal 350 and flow is provided at a pressure above the cavitation threshold, a clear cavitation cloud 360 forms downstream of the needle. The flow within the canal 350 is shown schematically in Figure 3(B). Importantly, the size of the needle (520 μm or less) ensures that fluid flow within the canal (or indeed the root canal) includes both inflow from the needle and outflow between the canal wall and the outside of the needle.

[0051] Cavitation occurs under the right conditions, where a liquid rapidly changes to a gas across a phase boundary. Without being bound by any particular theory, the applicant recognized that selecting a needle capable of generating reverse flow within a root canal, as shown in Figure 3(C), creates a strong shear layer effect between the inward and outward flow. This shear layer increases vortices within the flow, significantly increasing the occurrence of cavitation. The resulting conditions mean that very strong vortices can be generated at the interface between the inflow and outflow flows within the root canal. Within the vortex, the (dynamic) pressure drops significantly. This pressure drop makes cavitation more favorable (the onset point approaches the phase boundary). As a result of this effect, cavitation clouds can be generated within passages such as root canals under flow conditions (pressure, velocity, and flow rate) that would not cause cavitation in an open environment. Increasing the velocity at which the liquid exits the needle also helps increase the vortex, and for a given channel, there is a minimum nozzle exit velocity below which cavitation does not occur. If the needle's inner diameter is not excessively narrow, the delivery pressure can be used to control the needle exit velocity.

[0052] To test the performance of the device according to the embodiment, tests were conducted on a transparent plastic tooth (RepliDens Mandibular Molar, Transparent Type 03.2.1, Medicem GmbH, Weinfelden, Switzerland) with a realistic root canal structure filled with colored gelatin used to simulate the internal structure of the tooth. Various devices were tested, and the amount of gelatin removed before and after irrigation was measured using image analysis and pixel counting. The device according to one embodiment used a needle with a length of 20 mm and a gauge of 30G (corresponding to an inner diameter of 0.16 mm and an outer diameter of 0.31 mm). The delivery pressure was set to 60 bar. The irrigant was saline, and the needle was placed and moved up and down the canal for 180 seconds. Results from multiple root canal systems were compared based on the amount of gelatin before and after irrigation, and the percentage of material removed was determined. The same tests were performed using commercially available ultrasonic and laser-based irrigant activation systems. For the ultrasonic (EDDY, VDW GmbH, Munich, Germany), a vibrating tip was inserted into each canal and activated for 120 seconds. For the laser system (LiteTouch Er:YAG Laser, Orcos Medical AG, Küssnacht, Switzerland), a plastic pulp chamber was filled with water, the laser tip was placed in it, and activated for 120 seconds. The results are shown in Table 1 below, and demonstrate that embodiments of the present invention significantly improved debridement of uninstrumented teeth (our invention) over commercially available systems (ultrasonic system (no instrumentation / file), laser system (no instrumentation / file), and instrumented mechanical filing (ProTaper, Dentsply, Vallée, Switzerland), followed by syringe irrigation). Experiments demonstrated that conventional ultrasonic and laser-activated systems cannot adequately remove material from inside the canal. Therefore, they can only be used for activation, are not suitable for treating uninstrumented canals, and cannot reduce the need for mechanical filing. For the ultrasonic system, the narrow root canal prevents the tip from oscillating back and forth, resulting in damped vibrations. For the laser system, gelatin was observed not to emerge from the root canal due to insufficient flow generation.Mechanical sanding combined with flushing using a water-filled syringe provides better performance, but is less effective and significantly more time consuming than embodiments of the present invention.

[0053] [Table 1]

[0054] Importantly, applicant also compared conditions between open-ended and closed / confined regions (where the root is closed). This showed unexpected results, demonstrating the importance of the shape of the tooth tube and needle on cavitation. It is believed that previous systems failed to consider this as a factor, which may reflect why such systems fail to provide truly effective cavitation.

[0055] To demonstrate this effect, experiments were performed using a 60 bar delivery pressure connected to needles of various shapes, diameters, and lengths. Water exiting the needles was discharged into either (i) a water bath, (ii) an open-ended glass micropipette, or (iii) a glass micropipette with one end completely sealed. The needles tested included standard gauge needles. The threshold pressure was recorded as the point at which a stable cloud of cavitation was first visible. The upstream pressure threshold for generating developed cavitation was generally much lower in closed-ended narrow tubes compared to open water baths. Experimental data confirmed that 20 mm or 15 mm 30 Gauge (needle gauge) needles generated cavitation only in micropipettes, not in open baths, and that higher pressures were required to generate cavitation in open baths. All other needle sizes, including 10 mm or 5 mm 30 Gauge needles, generated cavitation in open water. However, their use in micropipettes reduces the required upstream pressure by 15 to 40 bar. An exception was found for 25G needles and 0.6 mm tubing (Table 2; closed-end micropipette d=0.6 mm, 25G)—in this case, the needle itself blocked backflow, and therefore the cavitation threshold increased after closing the end of the micropipette (because the outer diameter of the needle was very close to the inner diameter of the pipette tubing). Therefore, Applicant was able to confirm that backflow in the flow channel is necessary to efficiently induce cavitation.

[0056] [Table 2]

[0057] The volumetric flow rate through a needle is highly dependent on the upstream pressure and needle diameter. Therefore, if lower pressure is required to generate cavitation, the flow volume decreases. This is actually advantageous because lowering the flow rate and / or pressure reduces the risk of a high flow rate causing the jet to cause undesired damage to the tooth. Experiments have shown that the maximum flow rate occurs with a needle with a maximum diameter of 25G and the minimum flow rate occurs with a needle with a minimum diameter of 34G. The lowest pressure threshold for cavitation occurred with a 25G needle with a length of 10 mm—72 ml / min at 6 bar. These results indicate that the cavitation threshold is significantly lowered within narrow, closed-end canals. Therefore, embodiments of the present invention can generate effective cavitation at lower flow rates and lower upstream pressures. Such flow offers the significant benefits of reduced pressure at the apex of the root canal and lower flow rate, both of which minimize the risk of apical extrusion.

[0058] Therefore, the results confirmed that the needle characteristics (diameter, length, etc.) have a significant impact on the threshold cavitation pressure. Furthermore, the experiments confirmed that the effect of backflowing fluid is very important - increasing the relative velocity and vortex formation, thereby significantly reducing the pressure required for cavitation onset.

[0059] The effect of needle length on cavitation threshold is straightforward: longer needles increase the pressure required for cavitation, which is thought to be consistent with the fact that shorter needles provide less flow resistance. However, in practical embodiments, this generally means that the choice of needle length is a compromise between increasing the threshold pressure and the length required to position the tip sufficiently within the root canal to deliver cavitation and effectively debride the canal.

[0060] Although the invention has been described with reference to preferred embodiments, it will be appreciated that various changes or modifications can be made thereto without departing from the scope of the invention as defined in the appended claims.

[0061] For example, some embodiments of the present invention may include a heater 15 that increases the temperature of the irrigant (thereby bringing the irrigant closer to the phase boundary at a given pressure, further favoring cavitation). The heater 15 may be included as part of the base unit 10 or may be integrated into the handpiece. In some embodiments, the pump 14 or the base unit may include a pressure regulator.

[0062] In addition to, or as an alternative to, the user interface 18, the handpiece 20 may include controls such as switches on the handpiece (or associated with the handpiece, e.g., on a foot pedal). For example, a trigger may be provided to activate flow through the system.

[0063] Because embodiments of the present invention allow for the use of simple cleaning agents such as water or saline, it can be appreciated that embodiments can provide a variety of options during use. For example, the cleaning agent can be a low surface tension liquid or a high viscosity liquid. The cleaning agent can also include additives such as abrasive particles.

[0064] In some embodiments, the device may include a canal sensing system. For example, to ensure that fluid does not pass through the apex, embodiments may include an apex locator to measure the distance to the apex and assist the dentist in manipulating the device.

[0065] While the primary purpose of the endodontic cleaning device of the embodiments may be root canal treatment procedures, it can also be appreciated that the debridement and / or disinfection effects of the cavitational flow can be applied to other uses within dental practice. For example, the device can be used to remove plaque from the outer or subgingival surfaces of teeth. Embodiments can also be used to perforate dental tissue (dentin, enamel) or cut soft tissue. The device can also be utilized to find an entrance to a root canal.

Claims

1. 1. An endodontic treatment device, the endodontic treatment device comprising: a source of cleaning fluid; a pump for delivering cleaning fluid from said source under pressure; a handpiece in fluid communication with the pump and including a needle, the needle extending from a proximal rear end of the handpiece to a forward tip distal from the handpiece, a lumen of the needle extending to an opening in the forward tip for delivering irrigation fluid received from the pump into a tooth cavity, the opening in the forward tip of the needle being a forward-facing axial opening, and the irrigation fluid being discharged from the lumen in a forward axial flow; the needle has a length extending from its rear end to its tip of at least 5 mm, and an outer diameter at the front tip of no more than 520 μm so that the tip of the needle can be positioned within a portion of the root canal and reflux can occur between the root canal and the needle; an endodontic treatment device, wherein the diameter of the tip of the lumen is at least 50 μm, and the pump delivers irrigation fluid at a delivery pressure above a threshold cavitation pressure, such that flow of irrigation fluid through the needle and into the root canal forms an inertial cavitation cloud in the irrigation fluid in the root canal in front of the tip of the needle.

2. 10. The endodontic treatment device of claim 1, wherein the needle is sized to allow reflux to pass between the root canal and the needle, the occurrence of reflux in the root canal increasing cavitation.

3. The endodontic treatment device of claim 1, wherein the threshold cavitation pressure is between 3 and 80 bar.

4. The endodontic treatment device according to claim 1 or 2, wherein the needle has a length of 10 to 20 mm.

5. An endodontic treatment device according to any one of claims 1 to 3, wherein the threshold cavitation pressure is based on a minimum exit velocity of the irrigation fluid at the tip of the needle being at least 20 m / sec.

6. An endodontic treatment device according to any one of claims 1 to 3, wherein the flow rate of irrigation fluid through the needle is greater than 37 ml / min and less than 75 ml / min.

7. An endodontic treatment device according to any one of claims 1 to 3, wherein at least the distal end of the needle has a needle gauge size of between 30G and 34G.

8. An endodontic treatment device according to any one of claims 1 to 3, wherein the needle comprises a distal portion including the open front tip and a proximal portion connected to the proximal end of the distal portion, the proximal portion having an increased diameter.

9. An endodontic treatment device according to any one of claims 1 to 3, wherein the irrigation fluid is saline.

10. An endodontic treatment device according to any one of claims 1 to 3, wherein the cleaning fluid further comprises a disinfectant.

11. An endodontic device according to any one of claims 1 to 3, wherein the irrigation fluid further comprises abrasive particles.

12. An endodontic treatment device according to any one of claims 1 to 3, wherein the endodontic treatment device comprises a regulator for controlling the delivery pressure.

13. The endodontic treatment device of any one of claims 1 to 3, further comprising a heater for controlling the temperature of the irrigation fluid.

14. An endodontic treatment device according to any one of claims 1 to 3, further comprising a pulse generator for pulsing the supply of irrigation fluid.

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