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

Abstract

The present disclosure relates to a delivery apparatus for endodontic procedures. The invention also relates to a dental apparatus and methods. In one aspect there is provided a delivery system for delivery of a fluid into a root canal. The system comprises a syringe (10) containing the fluid and a needle assembly (50) comprising 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 has a 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 external diameter of no more than 300µm and a wall thickness of less than 50 µm. The needle is formed from a material having a tensile modulus of at least 1GPa. The fluid may be a high viscosity fluid.

Description

[0001] ENDODONTIC DELIVERY APPARATUS AND SYSTEM

[0002] Field of Invention

[0003] The present invention relates to a delivery apparatus for endodontic procedures. The invention also relates to a dental apparatus and methods.

[0004] Background

[0005] The applicant has proposed endodontic apparatus and methods in their co-pending international patent application PCT / EP2022 / 061638 (the contents of which are hereby incorporated by reference). This co-pending application discloses a system and method which seeks to ensure that inertial cavitation occurs within the root canal by providing a system which is of sufficient length and small enough external diameter to enter at least the coronal part of the root canal (in contrast to many prior art devices where the needle is merely inserted into the pulp chamber). This method and system results in a cloud of inertial cavitation being formed within the irrigant fluid in narrow spaces using a relatively low system pressure and a backflow of fluid.

[0006] To implement the method and apparatus of PCT / EP2022 / 061638 the applicant has also developed novel needle assemblies, and a method of manufacturing needles, to overcome limitations of current commercially available needles. Some embodiments of the applicant's needle assemblies are proposed in their co-pending European patent application EP22209102.7 (the contents of which are hereby incorporated by reference). The needles and manufacturing methods in accordance with EP22209102.7 may, advantageously, provide embodiments with very fine needle gauges (particularly at the needle tip) whilst also being suitable for use with high pressure and / or high velocity fluid flows. Further, the needles according to EP22209102.7 also have a beneficial degree of flexibility. Such needles are highly suitable for use in endodontic procedures enabling the needle to be positioned in the tooth's root canal.

[0007] The applicant has now identified further advantages and uses for needles similar to those of EP22209102.7. Thus, embodiments of the present invention seek to provide further improvements and advantages in methods and apparatus for dental procedures and in methods of manufacturing dental needles.

[0008] Summary of Invention

[0009] According to a first aspect of the invention, there is provided a delivery system for delivery of a fluid into a root canal. The system comprises a syringe containing the fluid and a needle assembly comprising a needle extending axially from a proximal end at a body portion to a distal tip. The tip has at least one opening, the needle has a 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 external diameter of no more than 300pm and a wall thickness of less than 50 pm. The needle is formed from a material having a tensile modulus of at least lGPa. The fluid may be a high viscosity fluid.

[0010] In embodiments, the needle may be formed of a material having a tensile modulus of less than lOGPa. A needle having a tensile modulus of more than lGPa may be particularly useful for use at operational pressures. A needle having a tensile modulus of less than lOGPa may more easily conform to the shape of a root canal.

[0011] The syringe in embodiments may be manually activated. The applicant has found that embodiments of the invention are able to deliver fluids through a needle with an extremely fine needle tip at much lower delivery force than conventional needles of similar diameter. Thus, embodiments may enable the delivery of fluids to a precise location within a root canal via a fine needle tip which would otherwise not be possible using a manually activated syringe. According to another aspect of the invention, there is provided a delivery apparatus for delivery of a fluid into a root canal. The apparatus comprises a container of fluid and a hand-held device for delivering the fluid under manual pressure through a needle assembly. The apparatus also comprises a needle assembly having a needle extending from a rearward end proximal to the container to a forward tip distal from the container. The needle has an opening at the tip to deliver fluid received from the needle into a tooth canal. The needle has a length, extending from its rearward end to its tip, of at least 20mm. The needle has an external diameter at the tip of no more than 200 pm and a wall thickness at the tip of less than 40 pm. As such, the needle tip is positionable within a portion of the root canal. The fluid may be a high viscosity fluid. In embodiments the delivery apparatus may comprise a pre-filled container of fluid. The container and hand-held device may, in some embodiments, comprise a manual syringe.

[0012] According to a further aspect of the invention there is provided a method of delivering a fluid to a root canal. The method comprises providing a syringe of fluid. The method further comprises providing a needle coupled to the syringe, the needle having a tip with an external diameter of no more than 300pm and a wall thickness of less than 50 pm. The needle being formed from a material having a tensile modulus of at least lGPa. The method further comprises positioning the needle tip in a root canal; and applying manual pressure to the syringe to deliver the fluid from the needle tip into the root canal. The fluid may be a high viscosity. The fluid may be provided in a prefilled syringe.

[0013] The applicant has found that existing commercially available needles may have particular difficulty in delivering high viscosity fluids at acceptable flow rates, particularly under hand actuated delivery pressures. In embodiments the delivery system may comprise a pre-filled syringe containing the fluid to be delivered. Apparatus and methods in accordance with embodiments may also be beneficial for use with lower viscosity materials by providing higher flow rates for a given pressure whilst also being able to access narrow root canals (such as minimally instrumented root canals) which other needles cannot enter. Further, it will be appreciated that methods and apparatus of embodiments may be used for suction or extraction of material from root canals as an equivalent application to the delivery of substances.

[0014] In the context of the invention a high viscosity fluid may be understood to be a fluid which is of higher viscosity than water. For example the fluid may have a viscosity of more than 5mPa*s. A high viscosity fluid may be a fluid that cannot be delivered at a flow rate of more than 500mg / mm (and particularly at not more than 250mg / mm) under manual pressure through a standard 34G needle. The high viscosity fluid may be a flowable high viscosity fluid to ensure it is deliverable via a syringe or other manual device. Embodiments may also be useful for use with ultra-high viscosity fluids, including for example pastes. Ultra-high viscosity fluids may for example be fluids with viscosities above 50 mPa*s and up to 100Pa*s.

[0015] Lower viscosity fluids which may be used in embodiments may have a viscosity between 0.5 and 5 mPa*s. Such lower viscosity fluids may include irrigant or disinfectants (such as e.g. saline solution, sodium hypochlorite (NaOCI), hydrogen peroxide (H2O2)), chlorhexidine) used prior to the application of dental materials into teeth.

[0016] The applicant has found that all known prior art needles have limited flow rates for fluid with a water-like or higher viscosity. This is a particular limitation to the use of manual injection devices since the operation of the device must be useable within the range of an average strength user. Current needles (which may have a typical diameter of 300 pm) are incapable of injecting substances (for example NaOCI) into smaller canals (e.g. opened to a size of 150 or 200pm). Further, due to the "vapor lock" effect, the liquid delivered from the needle cannot be injected beyond around 1mm from the tip. This means that in current methods the tooth root canals have to be machined to at least 300 pm in size. This results in up to several times more material (e.g. 2.25x (= PI*300umA3 / (PI*200umA2) needs to be removed if a canal has to be enlarged from 200 to 300 num). Which risks substantially more weakening of the tooth during an endodontic procedure.

[0017] In embodiments, the high viscosity fluid may be a root canal filler material. For example the high viscosity fluid may be a radiopaque paste for the permanent obturation of a root canal. The high viscosity fluid may be a bio ceramic sealer. The fluid may have a viscosity of more than 5 mPa*s. depending upon the environmental conditions the fluid may have a viscosity of between 5 and 50 mPa*s.

[0018] Embodiments of the invention may advantageously enable manual delivery of a high viscosity material into a root canal. Manual delivery may for example by through the use of a syringe and be at a force appropriate for delivery by hand. Such hand force may typically be around 50N.

[0019] To suitable delivery pressure embodiments of the invention may use a syringe (which in the context of the invention may include other equivalent piston arrangements) with a small piston size. For example, the syringe may have a piston of less than 8mm in diameter, and in some embodiments may have a piston size of less than 4mm.

[0020] When using such a syringe at a hand force of at least 10N the delivery pressure in embodiments may for example be at least 1.125MPa (for 10N at 8mm2, corresponding to approximately 3.2 mm in diameter or may for example be greater than 6.25MPa (for 50N at 8mm2) or lower than 0,05MPa (for 10N at 200mm2).

[0021] The needle assembly may comprise a connector for removably coupling the needle assembly to 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 the delivery device such as the syringe.

[0022] The body may further comprise an external gripable portion. The gripable portion may include a moulded profile to aid engagement, for example the moulded profile may comprise a plurality of outwardly extending ridges (with grooves defined between adjacent ridges). The connector may be configured to resist an internal pressure of at least 2 to 3MPa, and in some embodiments may resist an internal pressure of up to lOMPa. The internal pressure may be the pressure along the internal fluid path of the connection. The connector may sealingly engage to provide a leakproof coupling to the needle.

[0023] The body of the needle may comprise a male connector portion which is received into, and engages, a complementary female coupling. The delivery device (for example the syringe) may comprise the complementary female coupling. The male connector portion may comprise an axially extending collar. The collar may comprise at least one circumferentially extending groove. In embodiments the male connector portion may be co-moulded as part of the body of the needle.

[0024] In embodiments the collar may comprise a pair of axially spaced apart grooves. The pair of axially spaced apart grooves may have dissimilar cross-sectional profiles. One of the pair of axially spaced apart grooves may have a greater radial depth (as such the minimum diameter of the pair of spaced apart grooves may be different). In embodiments the rearward of the pair of axially spaced apart grooves may have a lesser depth. The rearward of the pair of axially spaced apart grooves is the groove which is closest to the proximal end of the needle assembly. In one embodiment, the one grove has a rectangular profile and the second pair a conical profile. In a preferred embodiment, the conical profile is distal to the rectangular profile enabling the axial lock-in.

[0025] A sealing element, which may optionally be an engagement member, may be received in the at least one circumferentially extending groove. The complementary female coupling may comprise a single circumferentially extending sealing member. The sealing element may for example be a spring supported seal. The sealing element may be permanently retained in the complementary female coupling. When the complementary male and female coupling members are brought into engagement, the sealing element may initially engage the rearward of the pair of axially spaced apart grooves. When the coupling is fully coupled the sealing element may be seated in the forward of the pair of axially spaced apart grooves.

[0026] In embodiments the connector may allow relative rotary movement between the needle and the delivery device (for example the syringe) enabling unlimited 360° (or more) rotations. The connector may resist axial movement such that the sealing element remains aligned and sealingly engaged. The body may comprise a shoulder adjacent to the male connector portion, for example a shoulder may be provided immediately forward of the axially extending collar. The shoulder may abut a corresponding portion of the female connector when the connector is fully coupled.

[0027] In one embodiment, the tip includes a male (or female) screw connector mechanism that is locked by rotation and not axial movement, or by a clipping mechanism wherein mechanical ledge (or similar) clicks into a grove on the opposite connector thus blocking the axial movement.

[0028] In one embodiment, the connectors resist to a fluid pressure of at least 2 or 3 MPa, or up to 10 MPa.

[0029] The needle may extend axially from a proximal end at the body portion to a distal tip. The tip has at least one opening, the needle has a lumen extending therethrough to define a fluid passageway from the fluid conduit of the body to the at least one opening. The distal tip has an external diameter of no more than 300pm and a wall thickness of less than 50 pm (for example the wall thickness may be between 10 and 50 pm, particularly between 20 and 40 pm). The needle may be formed from a material (for example a polymer) having a tensile modulus of less than 10 GPa. The needle may be formed of a material having an ultimate tensile strength of at least 15MPa. The needle may have a length of at least 20mm. Advantageously the needle of embodiments is formed from a polymer. The use of a polymer is advantageous in providing a flexible needle in use and also generally provides a high ductility (for example in comparison to metal used for many conventional needles) enabling the placement of the needle into curved canals (45°, 90° or more angles, radius of 1 to 5mm) or S-shaped canals. The applicant has found that the ductility of polymers enables the needle manufacturing process to form a particularly small and thin-walled needle tip (for example by using a drawing process as will be described below).

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

[0031] It may also be appreciated that the needle of embodiments is formed from a material with a tensile modulus which is greater than that of many polymer materials. The applicant has identified that such a relatively high tensile modulus enables the needle to have a sufficiently small tip (and thin wall diameter) whilst also withstanding the pressures required to deliver materials from the needle tip during endodontic procedures in root canals. The combination of wall thickness and tensile modulus has been found to provide a needle which is sufficiently stiff for insertion into the root canal as well as withstand the necessary pressures and also flexible enough to be inserted into curved canals. In contrast, prior art needles, which are typically made from steel have insufficient flexibility to reach curved parts of root canals.

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

[0033] The needle may have a tapered profile. The external diameter of the needle portion may converge towards the distal tip. The needle may for example be generally conical and may have a frustoconical profile. It has been found that a conical needle enables cavitation at lower pressure, and / or a lower pressure difference between device and tip, in comparison to a conventional cylindrical needle profile. The applicant has also found that a conical needle is less prone to becoming stuck on the uneven wall structure of the root canal due to the tendency for the conical needle to cause the tip of the needle to be positioned in the centre of the canal.

[0034] A conical needle also enables a significant reduction in the tip diameter to ensure that the tip can be positioned into complex or thin geometries and canals. The external diameter of the tip may, for example, be less than 50% of the diameter of the proximal end of the needle. In some embodiments the external diameter of the tip is between 10 to 30% of the diameter of the proximal end of the needle. In embodiments the conical needle tip diameter is less than a 32G needle (for example less than 320pm) and in some embodiments less than a 33G needle (for example less than 200pm). The proximal end of the conical needle (which would be at least 20mm from the tip) may have a diameter of at least 500pm, for example in some embodiments at least 700pm. In some embodiments the rate of change of diameter may vary along the length of the needle. For example, at the distal end of the needle the change in diameter may be less than 0.02mm / mm and may be up to 0.05mm / mm at the proximal end.

[0035] The applicant has surprisingly found that current commercial needle manufacturing methods are unable to produce conical needles with extremely small tip diameters (for example commercially available injection moulded plastic irrigation tools have a cannula with a tip size of 30G and are formed of polymers which cannot withstand the pressure required for many procedures). In embodiments the needle comprises a needle which is formed in a two-stage process. The needle is initially manufactured in a cylindrical form (for example by injection moulding or an extruded tube) and is then subsequently formed into a conical shape (for example by extrusion or drawing). The applicant has found that this two-stage process provides a highly effective needle for use in endodontic procedures. It will be appreciated that the two-stage process may also include additional manufacturing steps for example finishing processes applied to the conical needle or initial steps to make a plurality of cylindrical sections of a required length from a larger tubing section. The cylindrical needle may be a nonextruded needle, for example an injection moulded needle. The cylindrical needle may be polycarbonate. The cylindrical needle may be a bio-compatible polymer. In other embodiments the needle could be one of polyethylene, polypropylene, polyurethane, polyvinylchloride, polysulfone, polymethylmethacrylate, polystyrene, polyamide and other polymers fulfilling the mechanical properties. These can also be combined in copolymers, blends or composites.

[0036] The applicant has found that the high flexibility of needles in accordance with embodiments is advantageous. For example needles of embodiments may be laterally bendable / deflectable within the canal. The needle of embodiments is, for example, able to access curved and / or non-instrumented sections of root canals. This enables needles of embodiments to access the full root canal where existing needles can only enter the upper portions. The applicant has recognised that it is advantageous to have a needle with a tip which can be deflected by a relatively low load. As such, in embodiments the lateral deflection of the needle for a given tip loading may be a key criterion in determining whether the needle can be easily inserted into a minimal instrumented root canal. The skilled person will appreciate that lateral tip deflection of a needle can be readily determined by fixing the proximal end of the needle (for example the applicant has found a point of 20mm from the tip to be useful for measurement) and applying a load at (or proximal to) the tip and measuring the resultant lateral deflection.

[0037] Thus, the applicant has identified that a needle assembly of embodiments may have a tip which is laterally deflectable by more than 2mm with a tip load of 0.01N. In particular the tip may be laterally deflectable by more than 4mm (for example by 5mm or more) under a tip load of 0.01N. Additionally or alternatively, the tip may be laterally deflectable by more than 8mm under a load of 0.05N (for example the tip may deflect by at least 10mm). The tip deflection may be measured perpendicular to the axis of the undeflected needle. The tip deflection under load may be determined with the proximal end of the needle fixed (for example the needle may be fixed at a point 20mm axially from the tip).

[0038] In some embodiments the needle may comprise a primary axially directed outlet at the tip. In some embodiments the needle may additionally or alternatively comprise at least one side vent in the wall of the needle between proximal end at the body portion and the distal tip. One or more side vents may enable at least a portion of the flow from the needle to be directed directly at the wall of the root canal. It will be appreciated that in various embodiments a side vented needle may be used with or without a primary axially directed outlet.

[0039] The applicant has further identified that for some applications the provision of a polymer having a closed tip with a diameter of less than needle with a closed tip with an external diameter of no more than 300pm and a wall thickness of less than 50 pm and at least one side opening can be beneficial.

[0040] For example, in another aspect of the invention there may be provided a dental irrigation needle assembly. The needle assembly comprises a body portion comprising a connector for removably coupling the needle assembly to a delivery device (for example a handpiece, syringe or hose end) and a fluid conduit. A tapered polymer needle extends axially from a proximal end at the body portion to a distal tip. The diameter of the tapered polymer needle tapers inwardly from the proximal end to the distal tip. The needle has a lumen extending therethrough to define a fluid passageway from the fluid conduit of the body to at least one opening at the distal tip. Wherein the distal tip comprises a closed distal end wall and the at least one opening is provided in a side wall of the tip. The needle assembly of embodiments may be particularly suitable for the delivery of irrigants or disinfectants (such as e.g. saline solution, sodium hypochlorite (NaOCI), hydrogen peroxide (H2O2)) irrigant. The needle assembly may, for example, be usable with a manual syringe to provide precise hand activated irrigation directly to the root canal.

[0041] According to a further aspect of the invention, there is provided a method of forming a dental needle. The method comprises providing a cylindrical preform of a first length and a first diameter and forming the cylindrical preform into a conical needle which tapers inwardly along its length, the conical needle having a length greater than the first length and a diameter at the tip end which is less than the first diameter. The method may comprise fusing the tip end of the needle. The tip of the needle may be fused during the step of forming the cylindrical preform into a conical needle. The tip of the needle may for example fuse when the tip is drawn to a diameter of less than 150pm, for example when less than approximately 100pm.

[0042] The method may further comprise cutting at least one orifice in the conical needle proximal to the tip end. The at least one orifice may be cut into the side wall of the needle. The step of forming at least one orifice may be formed by laser cutting.

[0043] The laser cutting may be carried out with a pulsed laser, for example a 50Hz pulsed laser. A 9.3-micron CO2 laser may, for example, be used with a power of 50W with an illumination duration of 10ms, and a focal distance of 37mm (using a 50.8mm lens).

[0044] Aspects of the invention may also extend to methods of dental treatment using or enabled by the needle of the embodiments.

[0045] In one aspect there is provided a method of delivering dental irrigating (for example NaOCI) the method comprising providing a delivery device, attaching a flexible polymer needle having a tapered body to the delivery device and delivering irrigant through the polymer needle to an outlet at the needle tip. The method may further comprise positioning the tip of the flexible polymer needle into a root canal, particularly an uninstrumented root canal. The step of delivering irrigant ay comprise manually activating the delivery device to deliver the irrigant under pressure. In another aspect there is provided a method of delivering dental filing material, the method comprising providing a delivery device, attaching a flexible polymer needle having a tapered body to the delivery device and delivering irrigant through the polymer needle to an outlet at the needle tip. The method may further comprise positioning the tip of the flexible polymer needle into a root canal, particularly an uninstrumented root canal. The step of delivering filling material may comprise manually activating the delivery device to deliver the irrigant under pressure.

[0046] According to another aspect of the invention there is provided a method of periodontal treatment the method comprising providing a handpiece, attaching a flexible polymer needle having a tapered body to the handpiece the needle having an external tip diameter of no more than 300pm, inserting the tip of the needle into a periodontal pocket and delivering an irrigant through the needle under pressure.

[0047] According to another aspect of the invention there is provided a method of treatment of periimplantitis, the method comprising providing a handpiece, attaching a flexible polymer needle having a tapered body to the handpiece the needle having an external tip diameter of no more than 300pm, inserting the tip of the needle into a pocket adjacent an implant and delivering an irrigant through the needle under pressure.

[0048] Unless otherwise stated, each of the integers described may be used in combination with any other integer as would be understood by the person skilled in the art. Further, although all aspects of the invention preferably "comprise" the features described in relation to that aspect, it is specifically envisaged that they may "consist" or "consist essentially" of those features outlined in the claims. In addition, all terms, unless specifically defined herein, are intended to be given their commonly understood meaning in the art.

[0049] Further, in the discussion of the invention, unless stated to the contrary, the disclosure of alternative values for the upper or lower limit of the permitted range of a parameter, is to be construed as an implied statement that each intermediate value of said parameter, lying between the smaller and greater of the alternatives, is itself also disclosed as a possible value for the parameter.

[0050] In addition, unless otherwise stated, all numerical values appearing in this application are to be understood as being modified by the term "about".

[0051] Whilst the invention has been described above, it extends to any inventive combination of the features set out above or in the following description or drawings.

[0052] Description of the Drawings

[0053] Embodiments of the invention may be performed in various ways, and embodiments thereof will now be described by way of example only, reference being made to the accompanying drawings, in which:

[0054] Figure 1 is a schematic representation of a needle assembly in accordance with an embodiment of the invention;

[0055] Figure 2 is a flow chart representing the method of forming a needle assembly in accordance with embodiments;

[0056] Figure 3A and 3B show an example of the stages of forming a needle assembly in accordance with an embodiment;

[0057] Figure 4 is a graph showing the pressure required to induce inertial cavitation for a variety of needles;

[0058] Figure 5 is a graph showing the deflection of different endodontic needles under load;

[0059] Figure 6 is a schematic representation of a delivery apparatus in accordance with an embodiment;

[0060] Figure 7A provides a comparison of flow rates for water for a variety of needles;

[0061] Figure 7B provides a comparison of flow rates for a high viscosity bio ceramic material for a variety of needles;

[0062] Figure 8A and 8B plots a comparison of needle tip outside diameter to water flow rate; Figure 9 shows the tips used in testing the flow rates through needle assemblies;

[0063] Figure 10 shows a side view and cross section of a needle in accordance with an embodiment; and

[0064] Figure 11 illustrates the flow of fluid from a needle around the apex of a root canal with a needle having an axial and a side opening.

[0065] Detailed Description of Embodiments

[0066] It may be noted that proximal and distal are used herein to conveniently refer to the device in its typical in use orientation. Thus, it will be understood that proximal will generally mean a surface, component or direction which is proximal to the operator's hand during use and distal may be used to generally mean the surface, component, or direction distal to the operator's hand (and which will therefore be proximal to the root canal). Forward will likewise be understood to be used with respect to the directions away from the proximal end and towards the distal end (and rearwards understood to be the reverse direction). However, it will be appreciated that such references are not intended to be limiting and that the device may take any orientation in use.

[0067] An endodontic irrigation apparatus has been disclosed in the applicant's prior patent application WO2022 / 243016A1. Which includes a needle adapted for insertion into the canal of a tooth root. The applicant further developed a needle and a method of needle

[0068] The applicant has identified that commercially available needles present disadvantages to the utilisation of the method and apparatus described in WO2022 / 243016A1. In particular, as needle dimensions and the required system pressure for inertial cavitation are directly related, the needle size selection must compromise between larger needle diameters which cannot enter the smallest root canal regions and smaller needles which may require a higher operational pressure. Importantly, the required operating pressure of the system can directly impact the operating and equipment cost and may, for example, prevent the delivery of fluids using manual delivery devices such as syringes. As such, the provision of systems which operate effectively at the lowest possible pressure provides both clinical and commercial advantages. The applicant has, therefore, developed a novel needle assembly which will be described below.

[0069] Figure 1 shows a needle assembly 400 in accordance with embodiments of the invention. The needle assembly 400 is a single integral component which may for example be provided as a single-use, sterile, consumable item. The needle assembly 400 includes a connector 410, a body portion 420 and a needle 430.

[0070] The connector 410 is at the proximal end of the needle assembly and is configured to removably couple to a corresponding coupling portion on a handpiece. It will be appreciated that the connector 410 may be of any convenient form and may for example be of an existing standardised form to allow interconnection with existing equipment and / or to provide familiar operation for users. One particularly suitable connector may for example be a Bal Seal (RTM) connector which may include a spring supported retaining arrangement (for example a connector of the type disclosed in US Patent US8167285B2). A body portion of the needle assembly 420 extends forwardly from the coupling and defines a fluid conduit 422 which, in use, delivers irrigant from the handpiece 20 to the needle 430. In the illustrated embodiment a flange 425 is provided around a mid-portion of the exterior of the body 425 and may for example be configured to provide a stop or a tactile feature for use when connecting the needle assembly 400 to a handpiece 20.

[0071] The needle 430 extends forwardly from the distal end of the needle assembly. The proximal end of the needle 433 is in fluid communication with the fluid conduit 422 of the body. The distal end of the needle 430 terminates at a tip 434. The axial length of the needle from the proximal end 433 to the tip 434 is at least 20mm. 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 extending at an angle of between 30 to 90 degrees, for example approximately 60 degrees, to the body portion 420 is beneficial in enabling the clinician to direct the tip 434 of the needle 430 into the root canal during use. In some embodiments the needle may include further angled or curved sections, for example having a goose-necked profile to assist in positioning of the tip during procedures. The tip 434 includes an axially directed opening such that a primary flow of irrigant can be ejected in the direction shown by arrow A. Optionally, at least one side vent may also be provided proximal to (but rearward of) the tip 434 to enable an additional side flow to be provided which can be directed towards the side wall of an adjacent portion of the canal as shown by arrow S.

[0072] The needle 430 is formed from a polycarbonate material (for example Macrolon 3258). The needle 430 is initially injection moulded as a cylindrical needle prior to being formed into a conical profile (as described further below). Table 1 below provides the dimensions of a typical needle made in accordance with an embodiment (which is labelled "Needle X" for ease of reference). As shown in the comparison in the table, the tip 434 of the needle X has an external diameter of less than 200pm which is finer than a 33G needle whilst the proximal end 433 has a diameter of greater than 750pm. The thickness of the needle at the tip 434 is between 40pm, with the embodiment detailed in table 3 having a wall thickness of 34pm. The polycarbonate needle of embodiments has been found to have significantly improved flexibility in comparison to metal needles whilst being able to withstand the required operating pressures which would prevent the use of many thermoplastic materials. The combination of the flexibility and small tip diameter of the needle of embodiments enables the tip to be positioned in uninstrumented, thin, root canals (for example those narrower than 300um), especially if those with higher curvature (for example greater than 30°) which cannot be accessed by conventional needles. Table 1: needle dimensions in comparison to standard Birmingham gauge cylindrical needles

[0073] The method of manufacturing a needle assembly 400 in accordance with an embodiment is shown schematically in figure 2. An injection moulded cylindrical needle preform (of polycarbonate) is provided in step 510. The needle preform could be formed as a single cylindrical needle or could be sections cut from a larger extruded or moulded cylindrical tube.

[0074] The next step of the process (shown in step 520) comprises forming the cylindrical needle preform into a conical needle of the required length and diameter. This second step is performed in a towing process (which may also be referred to as a drawing process) which lengthens the needle as it is shaped. By forming the needle directly from the preform, the need to glue or otherwise bond the needle into place is removed. This both reduces the manufacturing steps and provides a robust needle which is capable of withstanding the pressures required whilst having a thin wall thickness and small tip diameter. Alternatively, a conically extruded preform can be towed into the cylindrical needle shape and then glued to a body, which may be injection moulded or a plastic / metal needle or hub.

[0075] In some embodiments an integrated needle assembly may be initially formed including the cylindrical preform of the needle prior to the step of towing of the needle into its conical form. For example, in some embodiments (as shown in Figure 3 and described below) the cylindrical preform may be initially integrally moulded with the body of the needle assembly (for example in an injection moulding process). In other embodiments a needle preform may be positioned within a mould and the needle body overmoulded using an injection moulding process to form the integral needle assembly including both the needle preform and body. In alternate embodiments the needle preform could be bonded to a moulded needle body (but it will be appreciated that this will usually require more manufacturing steps). After forming the integrated needle assembly, the next step of the process comprises forming the cylindrical preform into a conical needle of the required length and diameter. This second step is performed in a towing process which lengthens the needle as it is shaped. By forming the needle directly from the integral needle assembly the need to glue or otherwise bond the needle into place may be removed. This both reduces the manufacturing steps and provides a robust needle which is capable of withstanding the pressures required whilst having a thin wall thickness and small tip diameter.

[0076] As will be explained further below (with reference to figure 11) in some applications it is desirable to provide a needle which has a side opening at the tip rather than an axial opening. Methods of the invention may, therefore, include the additional steps of fusing the tip of the needle (step 530) and cutting at least one side-vent in the needle wall proximal to the tip. Embodiments of the invention are particularly effective at enabling such a method as the step of fusing of the tip of the needle can be carried out as an integral part of the step of towing the cylindrical needle into a conical form (step 520). In particular, when the needle is towed until the tip has a particularly small external diameter (for example 100pm or less) this will cause the end of the needle tip to fuse. Thus, in such a process the cylindrical needle can be towed until it is formed into a conical needle with a closed tip.

[0077] The subsequent step 540 of forming of a side-vent in the needle wall proximal to the tip can be performed by any suitable means. For example the openings in the side wall may be cut, punched or drilled. To provide openings of a precise form and dimension laser cutting may be used. In one embodiment, a 9.3-micron CO2 laser is used with a power of 50W (for material thicknesses less than 1mm) and pulsed at 50 kHz, with an illumination duration of 10ms, and a focal distance of 37mm (using a 50.8mm lens). It will be appreciated that the specific size, shape, location and number of openings formed in the needle may be tailored for the intended application of any specific needle. For example, the orifices may be circular, oval, elongated or square.

[0078] As shown in figure 11, in some uses, for example when irrigating a root canal it may be advantageous to use a side vented needle tip, particularly when using needles in accordance with embodiments which are able to reach close to the apex of even uninstrumented root canals. An example of an end vented needle 500 positioned with its tip 501 close to the apex of the canal of a tooth root R is shown. In this arrangement there is a risk that the flow F may extrude beyond the apex of the root. In contrast when using a side vented needle 500" with a closed tip 501' and orifices 502' formed in the side walls, the flow F' may be directed outwardly and rearwardly to fully irrigate the tip (as the small size of the needle ensures the tip is proximal to the apex) with a reduced risk of extruding beyond the apex.

[0079] It may be noted that, for clarity, in the simplified representation of figure li the shape and convergence of the needle 500' and the root canal R are substantially identical this would not generally be the case in a real embodiment. Further, in a typical case the tip 501' of the needle 500' will be positioned substantially in the opening of the apex (in a standard case the apex may for example have been machined to 1mm). By positioning the closed tip 501' in or through the apex the needle can effectively close the apex. For example, opposing radial sides of the tip 501' may abut the side walls of the root canal at or proximal to the apex. This reduces or substantially removes the possibility of the flow F' extruding axially forward and beyond the apex. An example of a needle assembly 400' comprising a body 420' and a needle preform 440' is shown in figure 3A. In this example the body 420' and needle preform 440' (which is substantially cylindrical) is a single integral injection moulded component. Figure 3B shows the same example needle assembly 400' after the needle preform has been towed to form a conical needle 430' of the required length and diameter.

[0080] Figure 4 shows testing which was carried out on the conical needle of embodiments in comparison to conventional needles of 25G, 30G and 31G gauge. To simulate the endodontic method of the invention the needles were tested in a free water bath and micropipettes of decreasing size (1.2mm, 0.6mm and 0.29mm diameter) which provide a simulation of dental canals of different sizes. For each needle and environment the threshold pressure required to cause cavitation in the flow of irrigant ahead of the needle tip was measured. The results clearly showed that the conical needle of embodiments significantly reduced the threshold pressure required for cavitation, especially in a closed canal (for example for the medium micropipette to less than 20 bar in comparison to 50 or 60bar for existing needles). The conical needle of embodiments was the only needle which was able to generate cavitation in the smallest micropipette (with a diameter of 0.29mm). The applicant has now identified further uses and advantages for such needles.

[0081] Further testing was carried out to quantify the ability of needles in accordance with embodiments to penetrate a root canal in comparison to prior art, commercially available needles. A needle in accordance with an embodiment (labelled "Needle Y" for ease of reference) was tested alongside standard metal endodontic needles sized 30G and 31G (both needles being Transcodent brand needles from Sulzer Mixpac, Germany) and a flexible "Irriflex" needle (available from Produit Dentaires SA, Switzerland). For the purpose of this testing standard transparent resin endodontic training blocks where used which have a single curved root canal formed therein. For the testing the training blocks used were 0.02 taper 15-30 2A blocks commercially available from Dentsply Sirona. The blocks were shaped prior to testing with ISO files, one with an ISO 15 file (with taper 0.02) and one with an ISO 20 file (with taper 0.02) to provide two different sized canals.

[0082] Each needle was inserted into the two training blocks to the maximum penetration depth. This maximum penetration depth was then measured using an endo stop and an endoscopic ruler. The maximum working length for each canal was also measured using an ISOIO hand file to allow comparison to the penetration depth of each needle. Tables 2 and 3 below provided the results. Table 2: Penetration depth of different needles in an ISO15, 0.02 instrumented dental training block

[0083] Table 3: Penetration depth of different needles in an ISO20, 0.02 instrumented dental training block

[0084] It can be seen from this data that the only needle able to reach the full working length of either the ISO 15 or ISO 20 canal was Needle Y, the needle in accordance with an embodiment. The penetration depth of the needle in accordance with an embodiment significantly exceeded that of both the conventional and "flexible" prior art needles. The needle in accordance an embodiment was the only needle which was able to reach the full working length of a minimal instrumented canal (i.e. a canal which has only which may for example be defined as canals which have only been enlarged with an ISO 20 or even ISO 15 handfile).

[0085] A key characteristic of needles in accordance with embodiments which is considered to be an enabler for increased canal penetration is the high level of flexibility provided by the design and manufacture of the needle (particularly the flexibility transverse to the needle axis). To quantify the flexibility the applicant tested a series of needles alongside a needle according to an embodiment (labelled "Needle Z"). The same set of needles were tested as in the penetration testing, namely the 30G and 31G Transcodent brand needles, a flexible "Irriflex" needle and the needle of an embodiment.

[0086] Each needle was clamped horizontally (in a desk vice) in a cantilever manner at a point 20mm from the tip of the needle. A load point was marked at 1mm from the tip of the needle at which a point load would be applied. Each needle was then deflected under a sequence of loads (lg, 2g, 3g, 5g, 10g and 20g corresponding respectively to loads of 0.01N, 0.02N, 0.03N, 0.05N, 0.10N and 0.20N). Under each load the deflected position of the needle tip was recorded. From the recorded position the deflection in the vertical axis (i.e. perpendicular to the initial axis of the needle) was recorded in millimetres. The results for each needle are shown in Table 4 below and shown graphically in Figure 5.

[0087] Table4: Flexibility test results, needle tip deflection in y-direction under different applied loads.

[0088] It is particularly notable that the needle tip in accordance with an embodiment of the invention deflects by 5 mm under a load of just 0.01N. In contrast all the other needles, including the "flexible" prior art needle, by a maximum of than 1mm at this load. Further a force at least five times higher is required to deflect any of the other needles by the same amount of 5mm. It is clear that the needle of embodiments is more flexible than any of the prior art needles regardless of the load applied. The difference in flexibility between needles of embodiments and the prior art is particularly notable at lower loads. The metal needles (30G and 31G) have deflection behaviour which is close to linear whereas needle Z show logarithmic type behaviour. The applicant has recognised that this is particularly beneficial for an endodontic needle and to access highly curved canals.

[0089] It will be appreciated that in use this will provide a needle which is more readily deflected around curves of a minimally instrumented root canal. This increased flexibility, especially at the distal end of a needle in accordance with embodiments, enables the needle to follow strongly curved canals where other needles would become stuck.

[0090] It will be further appreciated that the conical shape combined with the flexible materials reduces substantially the risk of the needle tip to get stuck in the porous dentin walls (i.e. compared to a conical metal needle).

[0091] The applicant has now identified that the needle of embodiments also provides clear advantages with respect to the flow rates possible through the needle for a given tip size and operating pressure which cannot be achieved with existing needles. Such advantages are particularly notable when seeking to delivery relatively high viscosity (for example having a viscosity greater than water or of greater than 5mPa*s) fluids to root canals. The applicant has found that the needle of embodiments provided the only system which was capable of manually injecting a viscous flowable fluid into a minimally instrumented root canal. It may be appreciated that a minimally instrumented root canal has typical size of less than 300pm, and as little as 150 to 200pm. Conventional needles of greater than 34G gauge cannot enter such fine canals and as will be explained further below narrower needles such as 34G gauge needles cannot deliver high viscosity fluids at acceptable flow rates.

[0092] A schematic of a typical manual delivery device in accordance with an embodiment is shown in Figure 6. The device 1 comprises a syringe 10 having a body 20 containing a high viscosity fluid 25 and a piston 30 at its rear which is activated manually by the user via a plunger 32. A needle assembly 50 is attached to the forward end of the syringe 10 and includes a body portion 52 defining a connector (which may be of a standard form such as a luer lock) for engagement with the syringe. The needle 55 of the needle assembly 50 is of the form described above formed of a plastic material that has been drawn into a tapered or conical form.

[0093] A variety of needles were used to compare the delivery rates of materials of differing viscosity with the results shown below in Table 5 and in Figures 7A and 7B. Each needle was attached to a standard syringe containing the specified material and the flow rate under full force manual activation tested. The distilled water was dispensed using a standard 10ml syringe. The EndoFill filing material (a commercially available radiopaque preparation for permanent root-canal filling) was dispensed using an EndoFill syringe. The BC sealer (a commercially available radiopaque and hydrophilic sealer) was dispensed using a standard BC sealer syringe. The tips were connected to each syringe using a standard removable luer lock connection. The 34G, 32G, 30G and 28G tips are standard gauge cylindrical needles of constant cross section. The Irriflex tip and BC tip are commercially available plastic tip devices. The "EndoFill (EF) Tip" is a needle assembly in accordance with an embodiment of the invention. The tips are shown in Figure 9.

[0094] As can be seen in Figure 7A the flow rate of water for the "EndoFill (EF) Tip" in accordance with an embodiment of the invention was in excess of that of a 30G needle and exceeded only by needle devices (28G and Irriflex) which have a significantly larger outside diameter than the embodiment. Such needles are too large to enter an uninstrumented root canal which has a typical diameter of less than 300pm. Thus, the embodiment of the invention has the highest flow rate fort a needle small enough to enter such uninstrumented canals and has a flow rate of water 4 times that of the 32G needle which is sufficiently small to also enter such canals.

[0095] When delivering high viscosity materials the distinction becomes even more significant. The EndoFill material which has a moderate high viscosity can only be delivered at a very low rate of flow (less than lOOOmg / min) with conventional needles less than 28G and delivery using a 32G or 34G needle suitable for uninstrumented root canals cannot provide a useable rate of flow. Thus, the needle assembly of embodiments was the only needle capable of both being inserted into an uninstrumented root canal and delivering the EndoFill material at an acceptable flow rate.

[0096] BC sealer was used as an example of a very high viscosity flowable material. Delivery of such material was not possible (under manual force) using a needle of less than 28G gauge. A needle in accordance with an embodiment was able to deliver the BC sealer despite having a tip diameter which is less than the 28G and 30G needle. Table5: Material Flow rate for different needles and materials.

[0097] A comparison of the outside diameter of each needle type and the flow rate of water (ml / min) is graphically shown in figure 8A and 8B. It can be seen from these figures that the tip in accordance with an embodiment (circled in the figure) provides a combination of flow rate and small tip size which cannot be achieved with any of the commercially available needle tips.

[0098] A further needle in accordance with an embodiment is shown in figure 10. This figure shows an external top view of the needle 400", a longitudinal cross section (through line A-A) and a detailed section of the connector portion. The needle assembly 400" has a needle 430" which has been drawn (as described above) into a tapered, frustoconical profile which extends from the proximal end 433" to the tip 434". The body 420" of the needle includes a connector 410". The connector 410"is a male element which is received into, and engages, a complementary female coupling provided on a syringe or other device to which the needle is being connected. The male element is formed by an axially extending collar portion 412" which extends rearwardly from a shoulder 418" to an end 413. The end 413 may have a chamfered or tapered profile to aid alignment and insertion into the a complementary female connector.

[0099] The collar includes first 414 and second 416 circumferentially extending grooves. The grooves are axially spaced apart. The first groove 414 (which is the rearward most groove) has a stepped profile and extends radially inwardly from the outer surface of the collar portion 412. The second groove 416 has a tapered profile with converging sides which provide 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. The grooves 414 and 416 provide sealing and engagement features for the connector to engage a seal element of a complementary female coupling.

[0100] It may be noted that in addition to having differing profiles the rearward groove 414 and forward groove 416 are of different depths. The forward groove 416 apart grooves may have a greater radial depth. As such the minimum diameter of the pair of spaced apart grooves may be different. For example the rearward groove 414 may have a minimum diameter (i.e. at the deepest point of the groove) which is around 80 to 90% of the diameter of the collar 412". The forward groove may have a minimum diameter which is around 70 to 80% of the diameter of the collar 412". Thus, in one example the rearward groove 414 may have a radial depth of less than 1mm, for example 0.5mm. The forward groove 416 may have a depth of at least 0.5mm, and may for example have a depth of 1mm. The forward groove may have a depth of between 0.5mm and 1.5mm. A sealing and engagement element may be provided as a part of a complementary female member (not shown) which engages and seals with the connector 410". The sealing and engagement member may be mounted in an internal recess of the female connector such that it faces and engages the collar 412" in use. The sealing and engagement element may for example be a spring supported seal. When the complementary male and female coupling members are brought into engagement, the sealing and engagement element may initially engage the rearward groove 414. This may provide an initial locking of the needle and delivery device together and may help to orientate sealing and engagement element When the coupling is fully coupled the sealing and engagement element may be seated in the forward groove 416.

[0101] It may be noted that immediately forward of shoulder 418 the body 420" has a section 428" with an increased cross-sectional area which provides a graspable region for the user when connecting or removing the needle. The graspable region 428" provides an intuitive and ergonomic configuration for the user. The graspable region may be formed by a series of radially extending ridges or fins with grooves therebetween. The radial direction of the ridges and separating grooves are beneficial when the connector is axially decouplable to provide increased friction when a user is applying an axial force to the outside of the connector.

[0102] Although the invention has been described above with reference to preferred embodiments, it will be appreciated that various changes or modification may be made without departing from the scope of the invention as defined in the appended claims.

Claims

CLAIMS1. A needle assembly for root canal treatment, the needle assembly comprising: a body portion extending from a proximal end to a distal end, the body portion being configured to provide a fluid conduit; and a conical needle extending axially from a rearward end proximal to the distal end of the body portion to a distal tip, wherein the distal tip has a closed axial tip and comprises at least one side opening, and a lumen extending through the needle defines a fluid passageway from the fluid conduit of the body portion to the at least one side opening.

2. The needle assembly of claim 1, wherein the distal tip has an external diameter of no more than 300pm and a wall thickness of less than 50 pm.

3. The needle assembly of claim 1 or 2, the needle is formed from a material having a tensile modulus of at least lGPa.

4. The needle assembly of any preceding claim, further comprising a connector at or near the proximal end of the body portion, the connector configured to removably couple the needle assembly to a device for delivering a fluid through the needle assembly.

5. The needle assembly of claim 4, wherein the connector is configured to resist an internal pressure of up to lOMPa.

6. The needle assembly of claim 4 or 5, wherein the connector comprises a male connector for engaging a complementary female coupling, the connector comprising an axially extending collar.

7. The needle assembly of claim 6, wherein the collar comprises at least one circumferentially extending groove.

8. The needle assembly of claim 7, wherein the circumferentially extending groove receives a spring supported sealing element.

9. The needle assembly of any preceding claim, wherein the needle is so dimensioned such that the distal tip is positionable within a portion of the root canal.

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

11. An apparatus for delivery of a fluid into a root canal, the apparatus comprising: a container of fluid; the needle assembly of any preceding claim; and a hand-held device for delivering the fluid under manual pressure through the needle assembly.

12. The apparatus of claim 11, wherein the fluid is a high-viscosity fluid.

13. The apparatus of claim 12, wherein the fluid has a viscosity of more than 5mPa*s.

14. The apparatus of any preceding claim, wherein the container is a syringe.

15. The apparatus of claim 15, wherein the syringe has a piston diameter of less than8mm.

16. A method of forming a dental needle comprising: providing a cylindrical preform of a first length and a first diameter; forming a conical needle from the cylindrical preform tapering from a rearward end to a distal tip, the conical needle having a second length greater than the first length and a second diameter at the distal tip less than the first diameter; fusing an axial opening of the distal tip of the conical needle; and cutting at least one side opening in the conical needle proximal to the distal tip.

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

18. The method of claim 17, wherein the step of fusing an axial opening of the distal tip of the conical needle comprises drawing the preform during the step of forming a conical needle until the tip is closed.

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

20. The method of any of claims 16 to 19, wherein the cylindrical preform is one of a polycarbonate, a bio-compatible polymer, polyethylene, polypropylene, polyurethane, polyvinylchloride, polysulfone, polymethylmethacrylate, polystyrene, polyamide, or any combination thereof.

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