Needle assembly for root canal treatment, device for delivering fluid into a root canal, and method of forming a dental needle

Abstract

The present disclosure relates to a delivery device for endodontic procedures. The invention also relates to a dental device and method. In one aspect, a delivery system for delivering a fluid into a root canal is provided. The system includes a syringe (10) containing the fluid and a needle assembly (50) including a needle (55) extending axially from a proximal end at a body portion to a distal tip. The tip has at least one opening, the needle having an inner lumen extending through the needle to define a fluid passageway from an inlet at the proximal end to the at least one opening. The tip has an outer diameter no greater than 300 µm and a wall thickness less than 50 µm. The needle is formed of a material having a tensile modulus of at least 1 GPa. The fluid can be a high viscosity fluid.

Description

Technical Field

[0001] This invention relates to a delivery device for endodontic surgery. It also relates to a dental device and method. Background Technology

[0002] The applicant has already proposed a dental pulp device and method in its co-pending international patent application PCT / EP2022 / 061638 (the contents of which are incorporated herein by reference). This co-pending application discloses a system and method that seeks to ensure inertial cavitation within the root canal by providing a system with sufficient length and a sufficiently small outer diameter to access at least the coronal portion of the root canal (in contrast to many prior art devices in which the needle is only inserted into the pulp chamber). This method and system enable the formation of an inertial cavitation cloud within the irrigating fluid in a confined space using relatively low system pressure and fluid backflow.

[0003] To achieve the methods and apparatus described in PCT / EP2022 / 061638, the applicant has also developed novel needle assemblies and methods for manufacturing needles to overcome the limitations of currently commercially available needles. Some embodiments of the applicant's needle assembly are proposed in the applicant's co-pending European patent application EP22209102.7 (the contents of which are incorporated herein by reference). The needles and manufacturing methods according to EP22209102.7 can advantageously provide embodiments with very fine needle thread gauges (particularly at the needle tip) while also being suitable for high-pressure and / or high-speed fluid flow. Furthermore, the needles according to EP22209102.7 also possess a beneficial degree of flexibility. Such needle height is suitable for use in endodontic procedures, allowing the needle to be positioned within the root canal of the tooth.

[0004] The applicant has now recognized the further advantages and uses of needles similar to those in EP22209102.7. Therefore, embodiments of the present invention seek to provide further improvements and advantages in terms of methods and apparatus for dental procedures and in methods of manufacturing dental needles. Summary of the Invention

[0005] According to a first aspect of the invention, a delivery system for delivering fluid into a root canal is provided. The system includes a syringe and a needle assembly, the syringe containing the fluid, and the needle assembly including a needle extending axially from a proximal end of a body portion to a distal end. The distal end has at least one opening, and the needle has an internal lumen extending through the needle to define a fluid passage from an inlet at the proximal end to the at least one opening. The distal end has an outer diameter of no more than 300 µm and a wall thickness of less than 50 µm. The needle is formed of a material having a tensile modulus of at least 1 GPa. The fluid may be a high-viscosity fluid.

[0006] In this embodiment, the needle may be formed of a material having a tensile modulus of less than 10 GPa. Needles with a tensile modulus greater than 1 GPa may be particularly useful for use under operating pressures. Needles with a tensile modulus of less than 10 GPa can more easily conform to the shape of the root canal.

[0007] The syringe in the embodiments can be manually activated. The applicant has discovered that embodiments of the invention are capable of delivering fluid with a much lower delivery force than conventional needles of similar diameter via a needle with an extremely fine tip. Therefore, the embodiments enable the delivery of fluid to a precise location within the root canal via the fine needle tip, which would be impossible in other cases using a manually activated syringe.

[0008] According to another aspect of the invention, a delivery device for delivering fluid into a root canal is provided. The device includes a container for the fluid and a handheld device for delivering the fluid under manual pressure via a needle assembly. The device also includes a needle assembly having a needle extending from a rearward end near the container to a forward end away from the container. The needle has an opening at its tip for delivering fluid received from the needle into the dental canal. The needle has a length of at least 20 mm extending from its rearward end to its tip. The needle has an outer diameter of no more than 200 µm at its tip and a wall thickness of less than 40 µm at its tip. Thus, the needle tip can be positioned within a portion of the root canal. The fluid may be a high-viscosity fluid. In embodiments, the delivery device may include a pre-filled container for the fluid. In some embodiments, the container and handheld device may include a manual syringe.

[0009] According to another aspect of the invention, a method for delivering fluid into a root canal is provided. The method includes an syringe for providing the fluid. The method also includes providing a needle coupled to the syringe, the needle having a tip having an outer diameter of no more than 300 µm and a wall thickness of less than 50 µm. The needle is formed of a material having a tensile modulus of at least 1 GPa. The method further includes positioning the needle tip in the root canal; and applying manual pressure to the syringe to deliver fluid from the needle tip into the root canal. The fluid may be of high viscosity. The fluid may be provided in a pre-filled syringe.

[0010] The applicant has found that existing commercially available needles may be particularly inadequate for delivering high-viscosity fluids at acceptable flow rates, especially under manually actuated delivery pressures. In embodiments, the delivery system may include a pre-filled syringe containing the fluid to be delivered. The device and method according to the embodiments may also be advantageous for using lower-viscosity materials because they can provide higher flow rates at a given pressure while still allowing access to narrow root canals (such as those minimally instrumented) that other needles cannot reach.

[0011] Furthermore, it should be understood that the methods and apparatus of the embodiments can be used to aspirate or extract material from the root canal as an equivalent of material delivery.

[0012] In the context of this invention, a high-viscosity fluid can be understood as a fluid with a viscosity higher than that of water. For example, the fluid may have a viscosity greater than 5 mPa*s. A high-viscosity fluid may be one that cannot be delivered manually under pressure through a standard 34G needle at a flow rate greater than 500 mg / mm (and particularly not greater than 250 mg / mm). A high-viscosity fluid may be a flowable high-viscosity fluid to ensure that it can be delivered via a syringe or other manual device. Examples may also be used for ultra-high-viscosity fluids, including, for example, pastes. Ultra-high-viscosity fluids may, for example, be fluids with a viscosity greater than 50 mPa*s and up to 100 Pa*s.

[0013] The low-viscosity fluids that can be used in the embodiments may have a viscosity between 0.5 mPa*s and 5 mPa*s. Such low-viscosity fluids may include rinsing agents or disinfectants (such as, for example, saline solution, sodium hypochlorite (NaOCl), hydrogen peroxide (H2O2)), or chlorhexidine) used before applying dental materials to teeth.

[0014] The applicant has found that all known prior art needles have limited flow rates for fluids with aqueous or higher viscosity. This is a particular limitation for the use of manual injection devices, as operation must be usable within the range of a user with average strength. Current needles (which can typically have a diameter of 300µm) cannot inject substances (e.g., NaOCl) into smaller tubes (e.g., those opened to a size of 150µm or 200µm). Furthermore, due to the "airlock" effect, the fluid delivered from the needle cannot be injected more than about 1mm from the tip. This means that in current methods, the root canal must be machined to a size of at least 300µm. This results in the need to remove up to several times more material (e.g., if the tube must be enlarged from 200µm to 300µm, then 2.25x (=PI*300µm^3 / (PI*200µm^2)) needs to be removed). This carries the risk of significantly weakening the tooth during endodontic procedures.

[0015] In this embodiment, the high-viscosity fluid can be a root canal filling material. For example, the high-viscosity fluid can be a radiopaque sealant for permanent occlusion of root canals. The high-viscosity fluid can be a bioceramic sealant. The fluid can have a viscosity greater than 5 mPa*s. Depending on environmental conditions, the fluid can have a viscosity between 5 mPa*s and 50 mPa*s.

[0016] Embodiments of the present invention can advantageously enable the manual delivery of high-viscosity materials into the root canal. Manual delivery can be performed, for example, using a syringe and applying a force suitable for hand delivery. This force is typically about 50 N.

[0017] For suitable delivery pressure, embodiments of the invention can use a syringe with a small piston size (which may include other equivalent piston arrangements in the context of the invention). For example, the syringe may have a piston with a diameter of less than 8 mm, and in some embodiments may have a piston size of less than 4 mm.

[0018] When such a syringe is used with a hand force of at least 10N, the delivery pressure in the examples may be, for example, at least 1.125MPa (for 8mm). 2 The following is a reference value: 10 N (corresponding to a diameter of approximately 3.2 mm), or, for example, greater than 6.25 MPa (for an 8 mm diameter). 2 Below 50N) or below 0.05MPa (for 200mm) 2 (10N below).

[0019] The needle assembly may include a connector for removably coupling the needle assembly to a syringe. The needle may have a body portion extending from the connector and providing a fluid conduit. The connector may be configured to axially removably engage with a complementary portion of a delivery device such as a syringe.

[0020] The body may further include an external grippable portion. This grippable portion may include a shaped profile to aid engagement; for example, the shaped profile may include a plurality of outwardly extending ridges (wherein a groove is defined between adjacent ridges). The connector may be configured to withstand internal pressures of at least 2 MPa to 3 MPa, and in some embodiments, up to 10 MPa. The internal pressure may be pressure along an internal fluid path along the connection. The connector may engage hermetically to provide a leak-proof connection with the needle.

[0021] The needle body may include a convex connector portion that is received into and engages with a complementary concave connector. A delivery device (e.g., a syringe) may include the complementary concave connector. The convex connector portion may include an axially extending collar. The collar may include at least one circumferentially extending groove. In embodiments, the convex connector portion may be co-formed as part of the needle body.

[0022] In an embodiment, the collar may include a pair of axially spaced grooves. The pair of axially spaced grooves may have different cross-sectional profiles. One of the pair of axially spaced grooves may have a greater radial depth (therefore the minimum diameters of the pair of spaced grooves may be different). In an embodiment, the rearmost groove of the pair of axially spaced grooves may have a smaller depth. The rearmost groove of the pair of axially spaced grooves is the one closest to the proximal end of the needle assembly. In one embodiment, one groove has a rectangular profile, and the second of the pair has a conical profile. In a preferred embodiment, the conical profile is located distal to the rectangular profile, thereby enabling axial locking.

[0023] Optionally, the sealing element of the mating member can be received in at least one circumferentially extending recess. The complementary concave coupling may include a single circumferentially extending sealing member. The sealing element may, for example, be a resiliently supported seal. The sealing element may be permanently retained in the complementary concave coupling.

[0024] When the complementary convex and concave connecting members are engaged, the sealing element may first engage the latter of a pair of axially spaced grooves. When the connecting members are fully engaged, the sealing element may be positioned in the former of a pair of axially spaced grooves.

[0025] In embodiments, the connector may allow relative rotational movement between the needle and the delivery device (e.g., a syringe), enabling unrestricted 360° (or more) rotation. The connector may resist axial movement, ensuring the sealing elements remain aligned and sealed. The body may include a shoulder adjacent to the convex connector portion; for example, the shoulder may be positioned directly in front of an axially extending collar. When the connector is fully engaged, the shoulder may abut the corresponding portion of the concave connector.

[0026] In one embodiment, the end includes a convex (or concave) threaded connector mechanism that is locked by rotation rather than axial movement, or by a snap-fit ​​mechanism in which a mechanical lug (or similar) engages with a groove on the opposite connector to prevent axial movement.

[0027] In one embodiment, the connector resists fluid pressure of at least 2 MPa or 3 MPa, or up to 10 MPa.

[0028] The needle can extend axially from a proximal end to a distal end at the body portion. The distal end has at least one opening, and the needle has an internal lumen extending through the needle to define a fluid conduit from the body to the at least one opening. The distal end has an outer diameter not greater than 300 µm and a wall thickness less than 50 µm (e.g., the wall thickness can be between 10 µm and 50 µm, particularly between 20 µm and 40 µm). The needle can be formed of a material (e.g., a polymer) having a tensile modulus less than 10 GPa. The needle can be formed of a material having an ultimate tensile strength of at least 15 MPa. The needle can have a length of at least 20 mm.

[0029] Advantageously, the needles in the embodiments are formed from polymers. The use of polymers facilitates the provision of flexible needles in use and generally also provides high ductility (e.g., compared to metals used in many conventional needles), allowing the needles to be placed in curved tubes (45°, 90° or greater angles, radii of 1 mm to 5 mm) or S-shaped tubes. The applicant has discovered that the ductility of polymers allows the needle manufacturing process to form particularly small and thin-walled needle tips (e.g., by using a stretching process described below).

[0030] It should be understood that ultimate tensile elongation is a commonly used measure of ductility (and can be measured, for example, using established ISO or ASTM procedures). In embodiments, the needle may be formed of a polymer having an ultimate tensile elongation of at least 5%. In some embodiments, the needle may be formed of a polymer having an ultimate tensile elongation of at least 50% (e.g., 100% or more).

[0031] It is also understood that the needles in the embodiments are formed of a material with a tensile modulus greater than that of many polymer materials. The applicant has recognized that such a relatively high tensile modulus allows the needle to have a sufficiently small tip (and thin wall diameter) while still withstanding the pressure required to deliver material from the tip during endodontic procedures in the root canal. It has been found that the combination of wall thickness and tensile modulus provides a needle that is stiff enough to be inserted into the root canal while withstanding the necessary pressure, and also flexible enough to be inserted into curved sections of the canal. In contrast, prior art needles, typically made of steel, do not possess sufficient flexibility to reach the curved portions of the root canal.

[0032] In some embodiments, the needle is formed of a material having a tensile modulus between 1.5 GPa and 10 GPa. For example, the tensile modulus may be greater than 2 GPa. For example, the tensile modulus may be less than 7.5 GPa, for example, less than 5 GPa. In some embodiments, the needle is formed of a material having an ultimate tensile strength between 40 MPa and 150 MPa. For example, the ultimate tensile strength may be greater than 50 MPa. For example, the tensile modulus may be less than 100 MPa. For example, the ultimate tensile strength may be between 60 MPa and 80 MPa.

[0033] The needle may have a tapered profile. The outer diameter of the needle portion may converge toward the distal end. The needle may, for example, be generally conical and may have a truncated conical profile. It has been found that conical needles can achieve cavitation at lower pressures and / or lower pressure differentials between the device and the tip compared to conventional cylindrical needle profiles. The applicant has also found that conical needles are less likely to become stuck on the non-uniform wall structure of the root canal because they tend to position the tip of the needle at the center of the canal.

[0034] The conical needle can also significantly reduce the tip diameter to ensure that the tip can be positioned in complex or thin geometries and tubes. For example, the outer diameter of the tip can be less than 50% of the diameter of the proximal end of the needle. In some embodiments, the outer diameter of the tip is between 10% and 30% of the diameter of the proximal end of the needle. In embodiments, the tip diameter of the conical needle is less than that of a 32G needle (e.g., less than 320 μm), and in some embodiments, the tip diameter of the conical needle is less than that of a 33G needle (e.g., less than 200 μm). The proximal end of the conical needle (at least 20 mm from the tip) can have a diameter of at least 500 µm, for example, at least 700 µm in some embodiments. In some embodiments, the rate of change of diameter can vary along the length of the needle. For example, at the distal end of the needle, the change in diameter can be less than 0.02 mm / mm, and at the proximal end, the change in diameter can be as high as 0.05 mm / mm.

[0035] The applicant has unexpectedly discovered that current commercial needle manufacturing methods cannot produce conical needles with extremely small end diameters (e.g., commercially available injection-molded plastic irrigation tools have cannulas with end dimensions of 30G and are formed from polymers that cannot withstand the pressures required by many procedures). In some embodiments, the needle comprises a needle formed in a two-stage process. The needle is first manufactured in a cylindrical form (e.g., by injection molding or as an extruded tube) and then formed into a conical shape (e.g., by extrusion or stretching). The applicant has found that this two-stage process provides highly efficient needles for endodontic procedures. It should be understood that the two-stage process may also include additional manufacturing steps, such as finishing processes applied to the conical needle, or initial steps for manufacturing multiple cylindrical segments of the desired length from a larger tubular section. The cylindrical needle may be a non-extruded needle, such as an injection-molded needle. The cylindrical needle may be polycarbonate. The cylindrical needle may be a biocompatible polymer. In other embodiments, the needle may be one of polyethylene, polypropylene, polyurethane, polyvinyl chloride, polysulfone, polymethyl methacrylate, polystyrene, polyamide, and other polymers that meet the mechanical properties. These may also be combined in the form of copolymers, blends, or composites.

[0036] The applicant has found that the high flexibility of the needle according to the embodiments is advantageous. For example, the needle of the embodiments can bend / deflect laterally within the canal. For example, the needle of the embodiments can approach curved and / or uninstrumented sections of the root canal. This allows the needle of the embodiments to access the entire root canal, while conventional needles can only access the upper portion. The applicant has recognized that it is advantageous to have a tip of the needle that can be deflected by relatively low loads. Therefore, in the embodiments, for a given tip load, the amount of lateral tip deflection of the needle can be a key criterion for determining whether the needle can be easily inserted into a root canal with minimal instrumentation. Those skilled in the art will understand that the amount of lateral tip deflection of the needle can be easily determined by fixing the proximal end of the needle (e.g., the applicant has found that a point 20 mm from the tip can be used for measurement), applying a load at (or near) the tip, and measuring the resulting amount of lateral tip deflection.

[0037] Therefore, the applicant has recognized that the needle assembly of the embodiments can have an end that can laterally deflect greater than 2 mm under an end load of 0.01 N. In particular, the end can laterally deflect greater than 4 mm (e.g., 5 mm or more) under an end load of 0.01 N. Alternatively, the end can laterally deflect greater than 8 mm (e.g., at least 10 mm) under a load of 0.05 N. The amount of end deflection can be measured perpendicular to the axis of the undeflected needle. The amount of end deflection under load can be determined with the proximal end of the needle fixed (e.g., the needle can be fixed at a point 20 mm axially from the end).

[0038] In some embodiments, the needle may include an axially guided main outlet at its tip. In some embodiments, the needle may additionally or alternatively include at least one lateral outlet in the wall of the needle, between the proximal and distal ends of the body portion. One or more lateral outlets allow at least a portion of the flow from the needle to be directed directly into the wall of the root canal. It should be understood that, in various embodiments, a needle with a side opening may or may not have an axially guided main outlet.

[0039] The applicant also recognizes that, for some applications, it may be advantageous to provide a polymer needle having a closed end and at least one side opening, the closed end having an outer diameter of no more than 300 μm and a wall thickness of less than 50 μm.

[0040] For example, in another aspect of the invention, a dental irrigation needle assembly can be provided. The needle assembly includes a body portion comprising a connector for removably coupling the needle assembly to a delivery device (e.g., a handheld device, syringe, or tubing end) and a fluid conduit. A tapered polymer needle extends axially from a proximal end to a distal end at the body portion. The diameter of the tapered polymer needle tapers inward from the proximal end to the distal end. The needle has an inner lumen extending through the needle to define a fluid passage from the fluid conduit in the body to at least one opening at the distal end. The distal end includes a closed distal wall, and at least one opening is disposed in the sidewall of the distal end. The needle assembly of the embodiments may be particularly suitable for delivering irrigants or disinfectants (such as, for example, saline solution, sodium hypochlorite (NaOCl), hydrogen peroxide (H2O2)). For example, the needle assembly can be used with a manual syringe to provide precise, manually activated irrigation directly into the root canal.

[0041] According to another aspect of the invention, a method for forming a dental needle is provided. The method includes providing a cylindrical preform having a first length and a first diameter, and forming the cylindrical preform into a conical needle tapering inward along its length, the conical needle having a length greater than the first length and a diameter at its end smaller than the first diameter. The method may include fusing the end of the needle. The end of the needle may be fused during the step of forming the cylindrical preform into the conical needle. For example, the end of the needle may be fused when it is stretched to a diameter of less than 150 μm—for example, when the diameter is less than about 100 μm.

[0042] The method may further include cutting at least one orifice near the end of a conical needle. This orifice may be cut into the sidewall of the needle. The step of forming the at least one orifice can be performed by laser cutting.

[0043] Laser cutting can be performed using a pulsed laser, such as a 50Hz pulsed laser. For example, a 9.3-micron CO2 laser can be used with a power of 50W, an irradiation duration of 10ms, and a focal length of 37mm (using a 50.8mm lens). The invention can also be extended to methods of dental treatment using or implemented with the needles of the embodiments.

[0044] In one aspect, a method for delivering a dental irrigator (e.g., NaOCl) is provided, the method comprising: providing a delivery device; attaching a flexible polymer needle having a tapered body to the delivery device; and delivering the irrigator through the polymer needle to an outlet at the tip of the needle. The method may further include positioning the tip of the flexible polymer needle into a root canal, particularly into an uninstrumented root canal. The step of delivering the irrigator may include manually activating the delivery device to deliver the irrigator under pressure.

[0045] In another aspect, a method for delivering dental filling material is provided, the method comprising: providing a delivery device; attaching a flexible polymer needle having a tapered body to the delivery device; and delivering an irrigator through the polymer needle to an outlet at the tip of the needle. The method may further include positioning the tip of the flexible polymer needle into a root canal, particularly an uninstrumented root canal. The step of delivering the filling material may include manually activating the delivery device to deliver the irrigator under pressure.

[0046] According to another aspect of the invention, a method for periodontal treatment is provided, the method comprising: providing a handpiece; attaching a flexible polymer needle having a tapered body to the handpiece, the needle having a distal outer diameter of not more than 300 µm; inserting the distal end of the needle into a periodontal pocket; and delivering an irrigating agent through the needle under pressure.

[0047] According to another aspect of the invention, a method for treating peri-implantitis is provided, the method comprising: providing a handpiece; attaching a flexible polymer needle having a tapered body to the handpiece, the needle having a distal outer diameter of not more than 300 µm; inserting the distal end of the needle into a pouch adjacent to the implant; and delivering an irrigation fluid through the needle under pressure.

[0048] As will be understood by those skilled in the art, unless otherwise stated, each of the described elements may be used in combination with any other element. Furthermore, while all aspects of the invention preferably “comprise” the features described with respect to that aspect, it is particularly contemplated that they may “consist of” or “substantially consist of” those features outlined in the claims. Moreover, unless specifically defined herein, all terms are intended to be given their meaning as commonly understood in the art.

[0049] Furthermore, in the discussion of this invention, unless otherwise stated, the disclosure of alternative values ​​for the upper or lower limits of the permissible range of a parameter should be interpreted as an implicit statement that each intermediate value of the parameter between the smaller and larger of these alternative values ​​is itself disclosed as a possible value of the parameter.

[0050] Furthermore, unless otherwise stated, all numerical values ​​appearing in this application should be understood to be modified by the term “about”.

[0051] While the invention has been described above, it extends to any inventive combination of the features set forth in the above or below description or drawings. Attached Figure Description

[0052] Embodiments of the invention can be carried out in various ways, and will now be described by way of example only with reference to the accompanying drawings, in which: Figure 1 This is a schematic diagram of a needle assembly according to an embodiment of the present invention; Figure 2 This is a flowchart illustrating a method for forming a needle assembly according to an embodiment; Figure 3A and Figure 3B An example of the stages in forming the needle assembly according to an embodiment is shown; Figure 4 It is a graph showing the pressure required to induce inertial cavitation for various needles; Figure 5 It is a graph showing the deflection of different pulp needles under load; Figure 6 This is a schematic diagram of a delivery device according to an embodiment; Figure 7A A comparison of water flow rates for various needles is provided; Figure 7B A comparison of flow rates for high-viscosity bioceramic materials used in various needles is provided; Figure 8A and Figure 8B A comparison was drawn between the outer diameter of the needle tip and the water flow velocity; Figure 9 The end is shown for testing the flow rate through the needle assembly; Figure 10 A side view and cross-section of a needle according to an embodiment are shown; and Figure 11 The diagram shows fluid flow from a needle around the tip of a root canal, where the needle has an axial opening and a lateral opening. Detailed Implementation

[0053] It may be noted that the terms proximal and distal are used herein for convenience in referring to the typical orientation of the device during use. Therefore, it should be understood that proximal will generally refer to a surface, component, or orientation close to the operator's hand during use, and distal may be used to generally refer to a surface, component, or orientation away from the operator's hand (and thus, that surface, component, or orientation will be close to the root canal). Similarly, forward will be understood as used relative to a direction away from the proximal and towards the distal (and backward as the opposite direction). However, it should be understood that such references are not intended to be restrictive, and the device may be oriented in any manner during use.

[0054] A pulp irrigation device has been disclosed in the applicant's existing patent application WO 2022 / 243016A1. This pulp irrigation device includes a needle adapted for insertion into a tube at the root of a tooth. The applicant has further developed a needle and a method for using the needle.

[0055] The applicant has acknowledged that there are drawbacks in the use of commercially available needles in the methods and apparatus described in WO 2022 / 243016A1. In particular, because needle size is directly related to the system pressure required for inertial cavitation, the selection of needle size must be weighed against a larger needle diameter that cannot access the smallest root canal areas and a smaller needle that may require higher operating pressures.

[0056] Importantly, the operating pressure required by the system can directly impact operational and equipment costs, and can, for example, hinder the delivery of fluids using manual delivery devices such as syringes. Therefore, a system that provides effective operation at the lowest possible pressure offers both clinical and commercial advantages. Accordingly, the applicant has developed a novel needle assembly, which will be described below.

[0057] Figure 1 A needle assembly 400 according to an embodiment of the present invention is shown. The needle assembly 400 is a single, integrated component, which may be provided, for example, as a single-use, sterile, consumable item. The needle assembly 400 includes a connector 410, a body portion 420, and a needle 430.

[0058] Connector 410 is located at the proximal end of the needle assembly and is configured to be removably coupled to a corresponding coupling portion on the handheld component. It should be understood that connector 410 can be of any convenient form and can be, for example, an existing standardized form to allow interconnection with existing devices and / or provide familiar operation for the user. A particularly suitable connector could be, for example, a Bal Seal (RTM) connector, which may include a retaining device supported by an elastic element (e.g., a connector of the type disclosed in U.S. Patent US8,167,285B2). The body portion 420 of the needle assembly extends forward from the coupling portion and defines a fluid conduit 422 that delivers rinsing agent from the handheld component 20 to the needle 430 during use. In the illustrated embodiment, a flange 425 is disposed around a central portion of the exterior of the body 425 and may be configured, for example, to provide a stop or tactile feature for use when attaching the needle assembly 400 to the handheld component 20.

[0059] The needle 430 extends forward from the distal end of the needle assembly. The proximal end 433 of the needle is in fluid communication with the fluid conduit 422 of the body. The distal end of the needle 430 terminates at a distal end 434. The axial length of the needle from the proximal end 433 to the distal end 434 is at least 20 mm. For ease of use, the axis of the needle 430 is angled relative to the axis of the body portion 420. The applicant has found that providing the needle 430 at an angle between 30 and 90 degrees—for example, approximately 60 degrees—towards the body portion 420 facilitates allowing clinicians to guide the distal end 434 of the needle 430 into the root canal during use. In some embodiments, the needle may include additional angled or curved sections, such as having a swan-neck profile, to aid in distal end positioning during procedure. The distal end 434 includes an axially guided opening, allowing the main irrigant flow to be sprayed in the direction indicated by arrow A. Optionally, at least one side outlet may be provided near the end 434 (but near the rear of the end 434) to provide additional side flow that can be directed toward the sidewall of an adjacent portion of the pipe, as indicated by arrow S.

[0060] Needle 430 is formed from a polycarbonate material (e.g., Macrolon 3258). Before being formed into a conical profile, needle 430 is first injection molded into a cylindrical needle (as described further below). Table 1 below provides the dimensions of a typical needle manufactured according to the embodiments (for ease of reference, this needle is labeled "Needle X"). As shown in the comparison in the table, the tip 434 of needle X has an outer diameter of less than 200 µm, which is finer than that of the 33G needle, while the proximal end 433 has a diameter greater than 750 µm. The thickness of the needle at the tip 434 is between 40 µm, with the embodiment detailed in Table 3 having a wall thickness of 34 µm. It has been found that the polycarbonate needles of the embodiments exhibit significantly improved flexibility compared to metal needles, while being able to withstand the required operating pressures that would hinder the use of many thermoplastic materials. The combination of the needle's flexibility and small tip diameter in the embodiment allows the tip to be positioned in uninstrumentally treated, narrow root canals (e.g., those narrower than 300 μm), especially in those root canals with a high curvature (e.g., greater than 30°) that cannot be accessed by conventional needles.

[0061] Table 1: Comparison of needle size with standard Birmingham gauge cylindrical needles

[0062] Figure 2 A method for manufacturing a needle assembly 400 according to an embodiment is illustrated schematically. In step 510, an injection-molded cylindrical needle preform (of polycarbonate) is provided. The needle preform may be formed as a single cylindrical needle, or it may be a segment cut from a larger extruded or molded cylindrical tube.

[0063] The next step in the process (shown in step 520) involves forming the cylindrical needle preform into a conical needle having the desired length and diameter. This second step is performed in a drawing process (also known as a stretching process), which elongates the needle during forming. By forming the needle directly from the preform, the need to glue or otherwise attach the needle to its proper position is eliminated. This reduces manufacturing steps and provides a robust needle capable of withstanding the required pressure while having a thin wall thickness and a small end diameter. Alternatively, the preform extruded in a conical shape can be drawn into a cylindrical needle shape and then glued to a body, which can be an injection-molded or plastic / metal needle or hub.

[0064] In some embodiments, a monolithic needle assembly comprising a cylindrical preform of the needle can be formed first, prior to the step of drawing the needle into its conical form. For example, in some embodiments (as shown in FIG3 and described below), the cylindrical preform can be integrally formed with the body of the needle assembly first (e.g., in an injection molding process). In other embodiments, the needle preform can be positioned within a mold, and the needle body can be overmolded using an injection molding process to form a monolithic needle assembly comprising both the needle preform and the body. In alternative embodiments, the needle preform can be bonded to the molded needle body (however, it should be understood that this typically requires additional manufacturing steps). After forming the monolithic needle assembly, the next step of the process involves forming the cylindrical preform into a conical needle having the desired length and diameter. This second step is performed in a drawing process that elongates the needle during needle forming. By forming the needle directly from the monolithic needle assembly, the need to glue or otherwise attach the needle to its proper position can be eliminated. This reduces manufacturing steps and provides a robust needle that can withstand the required pressure while having thin walls and a small end diameter.

[0065] As will be explained further below (see below) Figure 11 In some applications, it is desirable to provide a needle with a side opening at the end rather than an axial opening. Therefore, the method of the present invention may include the additional steps of fusing the end of the needle (step 530) and cutting at least one side outlet in the needle wall near the end. Embodiments of the present invention are particularly effective in implementing this method because the fusion step of the needle end can be performed as an integral part of the step of drawing the cylindrical needle into a conical shape (step 520). Specifically, this results in the end-to-end fusion of the needle end when the needle is drawn until the end has a particularly small outer diameter (e.g., 100 µm or less). Thus, in this process, the cylindrical needle can be drawn until it is formed into a conical needle with a closed end.

[0066] The subsequent step 540, forming a side outlet in the needle wall near the end, can be performed by any suitable method. For example, the opening in the side wall can be cut, punched, or drilled. To provide an opening with precise shape and size, laser cutting can be used. In one embodiment, a 9.3-micron CO2 laser with a power of 50W (suitable for material thicknesses less than 1 mm) is used, pulsed at 50 kHz, with an irradiation duration of 10 ms and a focal length of 37 mm (using a 50.8 mm lens). It should be understood that the specific size, shape, location, and number of openings formed in the needle can be customized for the intended application of any particular needle. For example, the orifice can be circular, elliptical, oblong, or square.

[0067] like Figure 11 As shown, in some applications, such as when irrigating root canals, using a needle tip with a side opening may be advantageous, particularly when using a needle according to an embodiment that can access even the tip of an uninstrumented root canal. An example of a needle 500 with a side opening is shown, positioned with its tip 501 close to the tip of the tube R at the root of the tooth. In this arrangement, there is a risk that the flow F may be squeezed out beyond the root tip. In contrast, when using a needle 500'' with a side opening having a closed tip 501' and an orifice 502' formed in the sidewall, the flow F' can be directed outward and backward to completely irrigate the tip (because the small size of the needle ensures that the tip is close to the tip), while reducing the risk of squeezing out beyond the tip.

[0068] It can be noted that, for clarity, in Figure 11 In the simplified illustration, the needle 500' and the root canal R have essentially the same shape and taper, which is not typically the case in actual implementations. Furthermore, in typical cases, the tip 501' of the needle 500' will be positioned substantially within the opening at the tip (in standard cases, the tip may be machined to, for example, 1 mm). By positioning the closing tip 501' within or through the tip, the needle effectively closes the tip. For example, the opposing radial sides of the tip 501' may abut against the sidewalls of the root canal at or near the tip. This reduces or essentially eliminates the possibility of the flow F' being axially extruded forward and beyond the tip.

[0069] Figure 3A An example of a needle assembly 400' including a body 420' and a needle preform 440' is shown. In this example, the body 420' and the needle preform 440' (which is substantially cylindrical) are a single, integral injection-molded part. Figure 3B A needle assembly 400' of the same example is shown after the needle preform has been drawn to form a conical needle 430' with the desired length and diameter.

[0070] Figure 4 Tests comparing the conical needle of the embodiment with conventional needles of 25G, 30G, and 31G gauges are shown. To simulate the endodontic method of the present invention, the needle was tested in a free water bath and in micropipettes of progressively decreasing sizes (1.2 mm, 0.6 mm, and 0.29 mm diameter), which provide a simulation of different sizes of dental canals. For each needle and environment, the threshold pressure required to induce cavitation in the irrigant flow preceding the needle tip was measured. These results clearly show that the conical needle of the embodiment significantly reduces the threshold pressure required for cavitation, especially in closed tubes (e.g., less than 20 bar for medium-sized micropipettes compared to 50 or 60 bar for conventional needles). The conical needle of the embodiment is the only needle capable of inducing cavitation in the smallest micropipettes (with a diameter of 0.29 mm). The applicant now recognizes further uses and advantages of this needle.

[0071] Further tests were conducted to quantify the root canal penetration capability of the needle according to the embodiment compared to commercially available needles of the prior art. The needle according to the embodiment (labeled "Needle Y" for ease of reference) was tested along with standard metal pulp needles of 30G and 31G sizes (both Transcodent brand needles from Sulzer Mixpac, Germany) and flexible "Irriflex" needles (purchased from Produit Dentaires SA, Switzerland). For this testing purpose, standard clear resin pulp training blocks with a single curved root canal formed therein were used. The training blocks used for testing were 0.02 taper 15-30 2A blocks commercially available from Dentsply Sirona. The blocks were shaped prior to testing using ISO standard files, one block using an ISO 15 file (with a 0.02 taper) and the other using an ISO 20 file (with a 0.02 taper) to provide two different sizes of canals.

[0072] Each needle was inserted into two training blocks to the maximum penetration depth. This maximum penetration depth was then measured using an endoscopic stop and an endoscopic ruler. Additionally, the maximum working length of each tube was measured using an ISO 10 hand file to allow for comparison with the penetration depth of each needle. The results are presented in Tables 2 and 3 below.

[0073] Table 2: Penetration depth of different needles in dental training blocks treated with ISO 15, 0.02 instruments

[0074] Table 3: Penetration depth of different needles in dental training blocks treated with ISO 20, 0.02 instruments

[0075] This data shows that the only needle capable of achieving the full working length of an ISO 15 or ISO 20 tube is needle Y, i.e., the needle according to the embodiment. The penetration depth of the needle according to the embodiment significantly exceeds that of both conventional prior art needles and "flexible" prior art needles. The needle according to the embodiment is the only needle capable of achieving the full working length of even the smallest instrumented tube (i.e., a tube that can be limited, for example, to a tube enlarged only with an ISO 20 hand file or even an ISO 15 hand file).

[0076] A key feature of the needles considered to increase tube penetration according to the embodiments is the high level of flexibility (particularly transverse to the needle axis) provided by the needle's design and manufacture. To quantify this flexibility, the applicant tested a series of needles along with needles according to the embodiments (labeled "Needle Z"). The same set of needles tested as in the penetration test, namely 30G and 31G Transcodent brand needles, flexible "Irriflex" needles, and needles of the embodiments, were used.

[0077] Each needle was held horizontally (in a bench vise) in a cantilever configuration at a point 20 mm from the needle tip. The load point was marked 1 mm from the needle tip, where a point load was applied. Each needle was then deflected under a series of loads (1 g, 2 g, 3 g, 5 g, 10 g, and 20 g, corresponding to loads of 0.01 N, 0.02 N, 0.03 N, 0.05 N, 0.10 N, and 0.20 N, respectively). The deflection position of the needle tip under each load was recorded. From the recorded position, the amount of deflection on the vertical axis (i.e., perpendicular to the initial axis of the needle) was recorded in millimeters. This is shown in Table 4 below and graphically presented in... Figure 5 The results for each needle are shown in the image.

[0078] Table 4: Flexibility test results, deflection of the needle tip in the y direction under different applied loads.

[0079]

[0080] Of particular note is that the tip of the needle according to an embodiment of the invention deflects 5 mm under a load of only 0.01 N. In contrast, all other needles, including "flexible" prior art needles, deflect a maximum of 1 mm under the same load. Furthermore, at least five times the force is required to deflect any other needle by the same amount of 5 mm. Clearly, the needle of the embodiment is more flexible than any prior art needle, regardless of the applied load. The difference in flexibility between the needle of the embodiment and prior art needles is particularly significant under lower loads. Metal needles (30G and 31G) exhibit near-linear deflection behavior, while needle Z shows logarithmic behavior. The applicant has recognized that this is particularly advantageous for dental endodontic needles and tubes with near-high curvature.

[0081] It should be understood that, in use, this will provide a needle that can be more easily deflected around the bends of root canals that have been minimally instrumented. This increased flexibility, particularly at the distal end of the needle according to the embodiment, allows the needle to follow highly curved canals in which other needles would be stuck.

[0082] It should be further understood that the combination of the conical shape and the flexible material significantly reduces the risk of the needle tip getting stuck in the porous dentin wall (i.e., compared to a conical metal needle).

[0083] The applicant now recognizes that, for a given end-size and operating pressure, the needle of the embodiments also offers significant advantages regarding the possible flow rate through the needle, advantages that cannot be achieved with existing needles. Such advantages are particularly pronounced when seeking to deliver relatively high-viscosity fluids (e.g., with viscosities greater than water or greater than 5 mPa*s) into the root canal. The applicant has found that the needle of the embodiments provides the only system capable of manually injecting viscous, flowable fluids into root canals with minimal instrumentation. It is understood that root canals with minimal instrumentation typically have dimensions less than 300 µm and as low as 150 µm to 200 µm. Conventional needles larger than 34G gauges cannot access such narrow canals, and, as will be further explained below, narrower needles such as 34G gauge needles cannot deliver high-viscosity fluids at acceptable flow rates.

[0084] Figure 6 A schematic diagram of a typical manual delivery device according to an embodiment is shown. Device 1 includes a syringe 10 having a body 20 containing a high-viscosity fluid 25 and a piston 30 at the rear of the high-viscosity fluid 25, the piston 30 being manually activated by a user via a plunger 32. A needle assembly 50 is attached to the front end of the syringe 10 and includes a body portion 52 defining a connector for engagement with the syringe (this connector may have a standard form, such as a Luer lock). The needle 55 of the needle assembly 50 is of the form described above, formed from a plastic material that has been stretched into a conical or tapered shape.

[0085] Various needles were used to compare the delivery rates of materials with different viscosities, as shown in Table 5 below. Figure 7A and Figure 7B The results are shown below. Each needle was attached to a standard syringe containing the specific material, and the flow rate was tested under full manual activation. Distilled water was dispensed using a standard 10 ml syringe. EndoFill filling material (a commercially available radiopaque preparation for permanent root canal fillings) was dispensed using an EndoFill syringe. BC sealant (a commercially available radiopaque and hydrophilic sealant) was dispensed using a standard BC sealant syringe.

[0086] The tips are attached to each syringe using a standard removable Luer lock connection. 34G, 32G, 30G, and 28G tips are standard wire gauge cylindrical needles with a constant cross-section. Irriflex and BC tips are commercially available plastic tip devices. The “EndoFill (EF) tip” is a needle assembly according to an embodiment of the invention. The tip is in... Figure 9 As shown in the image.

[0087] As in Figure 7A As can be seen, the water flow rate at the "EndoFill (EF) tip" according to an embodiment of the invention exceeds that of a 30G needle and is only exceeded by needle devices (28G and Irriflex) with significantly larger outer diameters than those in the embodiments. Such needles are too large to enter uninstrumented root canals with a typical diameter of less than 300µm. Therefore, the embodiments of the invention have the highest flow rates for needles small enough to enter such uninstrumented canals, and their water flow rates are four times that of a 32G needle that is also small enough to enter such canals.

[0088] The difference becomes even more pronounced when delivering high-viscosity materials. EndoFill materials with moderately high viscosity can only be delivered at very low flow rates (less than 1000 mg / min) using conventional needles smaller than 28 G, and delivery with 32 G or 34 G needles suitable for uninstrumented root canals does not provide a usable flow rate. Therefore, the needle assembly of this embodiment is the only needle capable of being inserted into uninstrumented root canals and delivering EndoFill material at an acceptable flow rate.

[0089] BC sealant is used as an example of a very high-viscosity, flowable material. It is impossible to deliver such a material using a needle with a wire gauge smaller than 28G (under manual force). Although the tip diameter of the needle according to the embodiment is smaller than that of 28G and 30G needles, the needle according to the embodiment is capable of delivering BC sealant.

[0090] Table 5: Material flow rates for different needles and materials.

[0091]

[0092] exist Figure 8A and Figure 8B The figures show a comparison of the outer diameter of each needle type with the water flow rate (ml / min). As can be seen from these figures, the tip according to the embodiment (circled in the figures) provides a combination of flow rate and small tip size that cannot be achieved with any commercially available needle tip.

[0093] Figure 10Another needle according to an embodiment is shown. The figure shows an external top view of needle 400'', a longitudinal section (through line AA), and detailed sections of the connector portion. Needle assembly 400'' has needle 430'', which has been stretched (as described above) into a tapered truncated conical profile extending from proximal end 433'' to distal end 434''.

[0094] The needle body 420'' includes a connector 410''. The connector 410'' is a convex element that is received into and engages with a complementary concave connector disposed on the syringe or other device to which the needle is attached. The convex element is formed by an axially extending collar portion 412'' that extends rearward from a shoulder 418'' to an end portion 413. The end portion 413 may have a beveled or tapered profile to aid in alignment and insertion into the complementary concave connector.

[0095] The collar includes a first groove 414 and a second groove 416 extending circumferentially. The grooves are axially spaced apart. The first groove 414 (which is the rearmost groove) has a stepped profile and extends radially inward from the outer surface of the collar portion 412. The second groove 416 has a tapered profile with converging sides providing a generally V-shaped cross-sectional profile. The sides of the second groove may, for example, be arranged at an angle of approximately 45 degrees to the axial direction. Grooves 414 and 416 provide sealing and engagement features for the connector to engage the sealing elements of complementary concave couplings.

[0096] It can be noted that, in addition to having different profiles, the rearward groove 414 and the forward groove 416 have different depths. The forward groove 416 in the separating grooves can have a greater radial depth. Therefore, the minimum diameters of a pair of spaced-apart grooves can be different. For example, the rearward groove 414 can have a minimum diameter of approximately 80% to 90% of the diameter of the collar 412'' (i.e., at the deepest point of the groove). The forward groove can have a minimum diameter of approximately 70% to 80% of the diameter of the collar 412''. Thus, in one example, the rearward groove 414 can have a radial depth of less than 1 mm, for example, a radial depth of 0.5 mm. The forward groove 416 can have a depth of at least 0.5 mm, and for example, can have a depth of 1 mm. The forward groove can have a depth between 0.5 mm and 1.5 mm.

[0097] The sealing and engaging element can be configured as part of a complementary concave member (not shown) that engages and seals with connector 410''. The sealing and engaging member can be mounted in an inner recess of the concave connector such that it faces and engages collar 412'' during use. The sealing and engaging element can be, for example, a resiliently supported seal. When the complementary convex and concave connecting members engage, the sealing and engaging element can initially engage the rearward recess 414. This can be used to initially lock the needle and delivery device together and can help orient the sealing and engaging element. When the connecting members are fully engaged, the sealing and engaging element can be positioned in the forward recess 416.

[0098] It can be noted that directly in front of the shoulder 418, the body 420'' has a segment 428'' with an increased cross-sectional area, which provides a gripping area for the user when connecting or removing the pins. The gripping area 428'' provides the user with an intuitive and ergonomic construction. The gripping area may be formed by a series of radially extending ridges or fins with grooves between them. The radial orientation of the ridges and the separated grooves are advantageous when the connector is axially disengaged, providing increased friction when the user applies an axial force to the outside of the connector.

[0099] Although the invention has been described above with reference to preferred embodiments, it should be understood that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.

Claims

1. A needle assembly for root canal treatment, the needle assembly comprising: A main body portion extending from a proximal end to a distal end, the main body portion being configured to provide a fluid conduit; as well as A conical needle, the conical needle extending axially from a rearward end near the distal end of the body portion to a distal end, wherein the distal end has a closed axial end and includes at least one side opening, and extends through the lumen of the needle to define a fluid passage from the fluid conduit of the body portion to the at least one side opening.

2. The needle assembly according to claim 1, wherein, The distal end has an outer diameter of no more than 300 μm and a wall thickness of less than 50 μm.

3. The needle assembly according to claim 1 or 2, wherein the needle is formed of a material having a tensile modulus of at least 1 GPa.

4. The needle assembly according to any of the preceding claims, the needle assembly further comprising a connector at or near the proximal end of the body portion, the connector being configured to removably connect the needle assembly to a means for delivering fluid through the needle assembly.

5. The needle assembly according to claim 4, wherein, The connector is configured to withstand internal pressures up to 10 MPa.

6. The needle assembly according to claim 4 or 5, wherein, The connector includes a convex connector for engaging complementary concave couplings, the connector including an axially extending collar.

7. The needle assembly according to claim 6, wherein, The collar includes at least one circumferentially extending groove.

8. The needle assembly according to claim 7, wherein, The circumferentially extending groove receives a sealing element supported by an elastic element.

9. The needle assembly according to any of the preceding claims, wherein, The needle is sized such that the distal end can be positioned within a portion of the root canal.

10. The needle assembly according to claim 9, wherein, The needle has a length of at least 20 mm extending from the rearward end to the distal end, an outer diameter of no more than 200 μm, and a wall thickness of less than 40 μm.

11. A device for delivering fluid into a root canal, the device comprising: A container for fluids; The needle assembly according to any of the preceding claims; as well as A handheld device for delivering the fluid through the needle assembly under manual pressure.

12. The device according to claim 11, wherein, The fluid is a high-viscosity fluid.

13. The device according to claim 12, wherein, The fluid has a viscosity greater than 5 mPa*s.

14. The device according to any of the preceding claims, wherein, The container is a syringe.

15. The device according to claim 15, wherein, The syringe has a piston diameter of less than 8 mm.

16. A method for forming a dental needle, the method comprising: Provide a cylindrical preform having a first length and a first diameter; A conical needle is formed from the cylindrical preform, tapering from the rear end to the distal end, the conical needle having a second length greater than the first length and a second diameter smaller than the first diameter at the distal end; The axial opening at the distal end of the conical needle is fused together; as well as At least one side opening is cut in the conical needle near the distal end.

17. The method according to claim 16, wherein, The step of forming a conical needle from the cylindrical preform includes stretching the cylindrical preform to the second length and the second diameter.

18. The method according to claim 17, wherein, The step of fusing the axial opening at the distal end of the conical needle includes stretching the preform during the step of forming the conical needle until the end is closed.

19. The method according to claim 16, 17 or 18, wherein, The step of cutting at least one side opening includes laser cutting the sidewall of the needle.

20. The method according to any one of claims 16 to 19, wherein, The cylindrical preform is one of polycarbonate, biocompatible polymer, polyethylene, polypropylene, polyurethane, polyvinyl chloride, polysulfone, polymethyl methacrylate, polystyrene, polyamide, or any combination of the above materials.

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