Dental pulp needle assembly

Abstract

A needle assembly for an endodontic surgical device and a method of forming an endodontic needle are disclosed. The needle assembly includes a connector for removably coupling the needle assembly to the handpiece; a body portion extending from the connector and providing a fluid conduit; and a polymeric needle axially extending from a proximal end at the body portion to a distal tip. The tip has at least one opening, and the needle has a lumen extending through the needle to define a fluid passage from a fluid conduit of the body to the at least one opening. The needle may have a conical shape. The method may include providing a cylindrical preform having a first length and a first diameter, and forming the cylindrical preform into a conical needle that tapers inwardly along its length.

Description

Technical Field

[0001] The present invention relates to a needle assembly for endodontic surgery and to a method of forming an endodontic needle assembly. The present invention also relates to dental devices and methods, and more particularly to endodontic devices and methods for endodontic debridement, irrigation, and / or disinfection. Background Art

[0002] Root canal treatment is used to preserve a tooth in cases of severe infection. A typical root canal treatment procedure involves the following steps: (i) opening the cavity and accessing the pulp and root canal; (ii) enlarging using mechanical instruments and files; (iii) chemically irrigating with sodium hypochlorite (bleach, NaOCl), EDTA, and / or other chemical reagents (using a syringe), typically repeated several times; (iv) optionally activating the NaOCl / chemical reagent with an ultrasonic cleaning device, and (iv) filling (or obturating) the root canal and sealing the tooth. This multi-step procedure is very laborious and may take approximately 60 minutes or longer to complete.

[0003] Some of the common problems faced by dentists during root canal surgery include one or more of the following: the need for a significant amount of time and labor to enlarge the canal; the risk of weakening the tooth structure by filing the canal; the risk of a file breaking inside the root canal and being unable to be removed; the risk of failure to remove bacteria in the smallest canals, either because the smallest canals are not detected and / or because the irrigant does not reach the canals, to avoid re-infection through the small canals; the occurrence and / or detection of vapor lock inside the canal (where air is trapped and unable to escape and pass over the liquid, blocking the disinfection of the apical third of the canal by the irrigant); the risk of NaOCl extruding through the tip into soft and hard tissues; and / or blood flowing in from outside the tooth.

[0004] A variety of systems seeking to provide improved root canal irrigation and to address or mitigate at least some of the above problems are commercially available. Such systems are designed to provide an enhanced hydrodynamic action of the irrigant to provide improved cleaning, debridement, and / or disinfection. While many root canal activation systems claim to produce "cavitation" to ensure effective root canal disinfection, the applicant has found that this is insufficient in practice. For example, in many systems, the cavitation produced is limited and manifests as non-inertial cavitation, where the bubbles in the fluid only oscillate in size and / or shape. Non-inertial cavitation does not cause bubble collapse, which produces a powerful shock wave, as seen in inertial cavitation. In addition, the applicant has also found that many of the existing solutions are unable to produce cavitation within the thin canal sections of the tooth (sizes less than 500 μm and even less than 100 μm), which is required for providing effective cleaning, debridement, and / or disinfection. Another disadvantage of existing systems is that, due to their limited effectiveness or large size, they require the use of NaOCl or other reagents to clean the narrow canals or small adjacent volumes, thereby exposing the patient to risk due to potential leakage of NaOCl through the apical foramen, for example into the sinus tract.

[0005] Accordingly, the applicant has proposed an improved endodontic device and method in its co-pending international patent application PCT / EP2022 / 061638

[0006] (the content of which is incorporated herein by reference). The co-pending application discloses a system and method that aims to ensure inertial cavitation within the root canal by providing a system that is long enough and has a small enough outer diameter to at least enter the coronal portion of the root canal (unlike many prior art devices where the needle is only inserted into the pulp chamber). The method and system use relatively low system pressure and fluid reflux to form an inertial cavitation cloud within the irrigant fluid in a narrow space.

[0007] The applicant has now determined that while the systems and methods in PCT / EP2022 / 061638 are highly advantageous, currently available needles have limitations in providing commercially attractive embodiments. For example, the needle size selection must be a compromise between a larger needle diameter (which cannot enter the smallest root canal areas or root canals not reached by the instrument) and a smaller needle, which may require a higher operating pressure to initiate cavitation. While such pressure may still be significantly lower than that of prior art systems, any need to increase the operating pressure directly affects the system cost (e.g., due to the need for a more expensive, higher-rated pressure pump), and is thus commercially disadvantageous. In addition, since all the needles used in the embodiments are small (e.g., between 30G and 34G according to the Birmingham wire gauge system), care must be taken to ensure that the selected needle has sufficient pressure resistance for safe and effective operation.

[0008] Accordingly, embodiments of the present invention are directed to providing further improvements and advantages to methods and devices for endodontic surgery. In particular, some embodiments are directed to providing a needle assembly adapted for and / or specifically optimized for endodontic devices and methods. SUMMARY OF THE INVENTION

[0009] According to a first aspect of the present invention, there is provided a needle assembly for an endodontic surgical device. The needle assembly includes: a connector for removably coupling the needle assembly to a handpiece; a body portion extending from the connector and providing a fluid conduit; and a polymeric needle axially extending from a proximal end at the body portion to a distal tip. The tip has at least one opening, and the needle has a lumen extending therethrough to define a fluid passage from the fluid conduit of the body to the at least one opening. The outer diameter of the distal tip does not exceed 300 μm, and the wall thickness of the distal tip is 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 made of a material (such as a polymer) having a tensile modulus of less than 10 GPa. The needle can be made of a material having an ultimate tensile strength of at least 15 MPa. The length of the needle can be at least 20 mm.

[0010] Advantageously, the needles of the embodiments are made of a polymer. The advantage of using a polymer is that it provides a flexible needle in use and generally also provides high ductility (e.g., compared to metals used for many conventional needles). The applicant has found that the ductility of the polymer enables the manufacturing process of the needle to form particularly small and thin-walled needle tips (e.g., by using the stretching process described below).

[0011] It should be understood that the 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 can be made of a polymer having an ultimate tensile elongation of at least 5%. In some embodiments, the needle can be made of a polymer having an ultimate tensile elongation of at least 50% (e.g., 100% or higher).

[0012] It can also be understood that the needles of the embodiments are made of a material having a tensile modulus greater than that of many polymer materials. The applicant has determined that this relatively high tensile modulus enables the needle to have a sufficiently small tip (and a sufficiently thin wall diameter) while also being able to withstand the pressure required to generate an inertial cavitation cloud in front of the needle tip in the root canal during endodontic irrigation surgery. This combination of wall thickness and tensile modulus has been found to provide a needle that has sufficient stiffness to be inserted into the root canal, can withstand the necessary pressure, and also has sufficient flexibility to be inserted into a curved canal. In contrast, needles of the prior art, which are typically made of steel, do not have sufficient flexibility to reach the curved portions of the root canal.

[0013] In some embodiments, the needle is made of a material having a tensile modulus between 1.5 GPa and 10 GPa. For example, the tensile modulus can be greater than 2 GPa. For example, the tensile modulus can be less than 7.5 GPa, such as less than 5 GPa. In some embodiments, the needle is made of a material having an ultimate tensile strength between 40 MPa and 150 MPa. For example, the ultimate tensile strength can be greater than 50 MPa. For example, the tensile modulus can be less than 100 MPa. For example, the ultimate tensile strength can be between 60 MPa and 80 MPa.

[0014] The needle can have a tapered profile. The outer diameter of the needle portion can converge towards the distal end. For example, the needle can be generally conical and can have a frustoconical profile. It has been found that, compared to a conventional cylindrical needle profile, a conical needle can achieve cavitation at lower pressures and / or at a lower pressure difference between the device and the end. The applicant has also found that due to the tendency of the conical needle to position the end of the needle at the center of the tube, the conical needle is less likely to get stuck on the uneven wall structure of the root canal.

[0015] The conical needle also allows the end diameter to be significantly reduced to ensure that the end can be positioned in complex or thin geometries and tubes. For example, the outer diameter of the end can be less than 50% of the diameter of the proximal end of the needle. In some embodiments, the outer diameter of the end is between 10% and 30% of the diameter of the proximal end of the needle. In an embodiment, the end diameter of the conical needle is less than a 32G needle (e.g., less than 320 μm), and in some embodiments less than a 33G needle (e.g., less than 200 μm). The diameter of the proximal end of the conical needle (which is at least 20 mm from the end) can be at least 500 μm, such as at least 700 μm in some embodiments. In some embodiments, the rate of change of the diameter can vary along the length of the needle. For example, at the distal end of the needle, the diameter change can be less than 0.02 mm / mm, while at the proximal end it can be up to 0.05 mm / mm.

[0016] The applicant surprisingly found that current commercial needle manufacturing methods cannot produce conical needles with extremely small tip diameters (e.g., commercially available injection-molded plastic irrigation tools have cannulas with tip sizes of 30G, and the plastic irrigation tools are made of polymers that cannot withstand the pressure required to initiate cavitation). In an embodiment, 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 a tube or extruding a tube), and then subsequently formed into a conical shape (e.g., by extrusion or stretching). The applicant found that this two-stage process provides a highly efficient needle for use in endodontic procedures. It should be understood that the two-stage process may also include additional manufacturing steps, such as a finishing process applied to the conical needle, or an initial step of manufacturing a plurality of cylindrical segments of the desired length from a larger tube segment. The cylindrical needle may be a non-extruded needle, such as an injection-molded needle. The cylindrical needle may be made of 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 materials may also be combined in the form of copolymers, blends, or composites.

[0017] The applicant found that the high flexibility of the needle according to the embodiment is advantageous. For example, the needle of the embodiment may be laterally bendable / deflectable within a tube. The needle of the embodiment, for example, can enter curved and / or un-instrumented sections of the root canal. This enables the needle of the embodiment to enter the entire root canal at a location where existing needles can only enter the upper portion. The applicant recognized that it is advantageous to have a needle with a tip that can be deflected by a relatively low load. Thus, in an embodiment, for a given tip load, the lateral deflection of the needle may be a key criterion for determining whether the needle can be easily inserted into the smallest instrumented root canal. Those skilled in the art will understand that the lateral tip deflection of the needle can be easily determined by fixing the proximal end of the needle (e.g., the applicant found that a point 20 mm from the tip is useful for measurement), applying a load at the tip (or near the tip), and measuring the resulting lateral deflection.

[0018] Therefore, the applicant determined that the needle assembly of the embodiment may have a tip that is laterally deflectable by more than 2 mm under a tip load of 0.01 N. In particular, the tip may be laterally deflectable by more than 4 mm (e.g., 5 mm or more) under a tip load of 0.01 N. Additionally or alternatively, the tip may be laterally deflectable by more than 8 mm (e.g., the tip may deflect at least 10 mm) under a load of 0.05 N. 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 (e.g., the needle may be fixed at a point 20 mm axially from the tip).

[0019] The needle of the embodiment may include a main axial guiding outlet at the end. The axial guiding outlet ensures that the flow from the needle can generate an inertial cavitation cloud in front of the needle end (which is in direct contrast to the prior art arrangement that may include an impact surface blocking the axial flow from the end). In some embodiments, the needle may additionally or alternatively include at least one side discharge hole located in the wall portion of the needle between the proximal end and the distal end at the body portion. One or more side discharge holes may enable at least a portion of the flow from the needle to directly point to the wall portion of the root canal. It should be understood that in various embodiments, the laterally discharging needle may be used with or without a main axial guiding outlet.

[0020] According to another aspect of the present invention, a method of forming an endodontic needle is provided. The method includes providing a cylindrical preform having a first length and a first diameter, and includes forming the cylindrical preform into a conical needle that tapers inwardly along the length of the conical needle, the length of the conical needle being greater than the first length, and the diameter of the conical needle at the end portion being less than the first diameter.

[0021] The preform may be provided by injection molding or extrusion molding. Forming the conical needle may be performed by extrusion or stretching.

[0022] In an embodiment, the method may further include forming a needle assembly that includes a body and a needle according to the embodiment. The method may include molding the needle assembly with the cylindrical preform.

[0023] The method includes: molding a needle assembly that includes a body portion and a cylindrical preform; and forming the cylindrical preform into a conical form that tapers inwardly along the length to provide an end with an outer diameter not exceeding 300 μm (e.g., not exceeding 200 μm).

[0024] The method may further include an initial step of forming a cylindrical needle, for example, by injection molding or extrusion molding. The cylindrical needle may be made of, for example, polycarbonate.

[0025] The step of stretching / traction the cylindrical needle into a conical form that tapers inwardly along the length may also elongate the needle to a length of at least 20 mm. It should be understood that the step of forming the conical needle may enable the length and diameter of the final needle to be customized according to specific requirements.

[0026] The steps of molding a needle assembly can include providing a needle and molding a body portion to secure the needle into an integral needle assembly. For example, the body portion can be secured to the needle by overmolding. The molding of the needle assembly to secure the needle can be performed before stretching / drawing the cylindrical needle into a conical form. In other embodiments, the needle can be attached to the body portion by bonding, gluing, interlocking, or laser welding. Alternatively, the conical needle can be glued to the body, which can be a plastic or metal needle holder.

[0027] Advantageously, the methods according to embodiments can reduce the number of components and manufacturing steps for forming the needle assembly. Additionally, these methods can enable the needle assembly to be specifically shaped for accessing root canals (e.g., having a specifically angled portion). Embodiments also advantageously provide a needle assembly in which sub-components are reliably sealed and pressure-resistant.

[0028] While the needle assemblies of the embodiments are specifically designed for use in endodontic debridement, irrigation, and disinfection devices (endodontic debridement, irrigation, and disinfection devices of the type disclosed in the applicant's co-pending application PCT / EP2022 / 061638), those skilled in the art will understand that since the needle increases the access to narrow canal regions, the needle can also be used in other root canal procedures. For example, the needle according to an embodiment can be used to inject / place a material such as a filling material into a root canal. In such a procedure, the needle assembly of the embodiment can enable a syringe to inject a high-viscosity material in regions where manual injection is not possible (e.g., because the pressure is too high). Additionally, the needle according to an embodiment can be used for manually irrigating a root canal, in which case the needles are connected to a syringe and used to deliver an irrigant fluid. In such a procedure, the needle assembly of the embodiment can provide better performance due to its increased flexibility and conical shape. Other uses can for example include the treatment of carious infections or other dental or medical procedures that require disinfection or delivery of fluid reagents (e.g., periodontitis, cleaning dental implants, wound disinfection, etc.).

[0029] According to another aspect of the present invention, there is provided an endodontic device comprising: a supply of irrigant fluid; a pump for delivering the irrigant fluid from the supply under pressure; a handpiece in fluid communication with the pump and the handpiece comprising a needle assembly having a needle extending from a rearward end portion near the handpiece to a forward tip remote from the handpiece, the needle having an opening at the tip for delivering fluid received from the pump into the tooth cavity; and wherein the length of the needle extending from the rearward end portion of the needle to the tip of the needle is at least 20 mm, the outer diameter of the needle does not exceed 200 μm, and the wall thickness of the needle is less than 50 μm (e.g., between 40 μm and 20 μm) such that the tip of the needle can be positioned within a portion of the root canal; and the pump delivers the irrigant at a delivery pressure less than 80 bar and exceeding the threshold cavitation pressure such that the flow of the irrigant through the needle causes an inertial cavitation cloud to form in the irrigant fluid within the root canal in front of the tip of the needle.

[0030] Once the needle is positioned (in a manner that allows for the establishment of a backflow) within the root canal, the specific pressure required to generate the inertial cavitation cloud can be selected based on the specific geometry of the needle and the canal. For example, such a threshold pressure can be determined for various needle sizes.

[0031] The delivery pressure can be selected such that the minimum exit velocity of the irrigant at the tip of the needle is at least 20 m / s (and for example at least 30 m / s, in particular, the velocity can be between 20 m / s and 60 m / s, for example between 30 m / s and 50 m / s, and in a particular embodiment, the threshold cavitation point can be approximately 38 m / s). The flow rate of the irrigant through the needle is less than 175 ml / min (and for example less than 50 ml / min, for example between 10 ml / min and 50 ml / min, for example between 20 ml / min and 40 ml / min, and in a particular embodiment, the flow rate at the minimum threshold cavitation point can be approximately 30 ml / min). In contrast, prior art systems have been proposed that use irrigant flow rates of up to 50 ml / s (3000 ml / min), which, compared to embodiments of the present invention, would result in a greater risk of causing pain or damage to periapical structures.

[0032] Since embodiments of the present invention use the hydrodynamic effects of cavitation clouds to provide debridement and / or disinfection, it may not be necessary to use chemical disinfectants such as NaOCl for debridement, irrigation, and / or disinfection. Thus, advantageously, embodiments of the present invention can use water or a saline solution as the irrigant fluid. Saline solutions, particularly physiological saline solutions (e.g., 0.9% NaCl), generally have better human tolerance in the event of extrusion beyond the tip compared to chemical disinfectants such as NaOCl and are less likely to cause significant pain, discomfort, or serious adverse events such as "hypochlorite accidents" to the patient.

[0033] In an embodiment, the size of the cavitation cloud extends beyond the distal end of the needle by 0.5 mm, 1 mm, 3 mm, 5 mm, 7 mm, 10 mm, 15 mm, or 20 mm, and the position and size of the cavitation cloud are adjusted by changing the needle size, the exit velocity, and / or the flow rate.

[0034] The irrigant fluid, such as saline, may include one or more additives. For example, the irrigant fluid may also include a disinfectant or an antibacterial agent. These disinfectants or antibacterial agents include, for example, alcohol, chlorine, iodine, or reactive oxygen-based disinfectants or quaternary ammonium compounds (QACs) commonly used to disinfect skin, surfaces, or devices. These agents may be liquid, dissolved in the irrigant, or suspended in the irrigant, such as in the form of nanoparticles. The disinfectant or antibacterial agent may enhance the bactericidal effect of the irrigant. The irrigant may be a low surface tension liquid such that cavitation occurs more readily at lower pressures and / or temperatures. For example, ethanol may be used as a low surface tension liquid, and ethanol is also a disinfectant. The viscosity of the liquid is also a variable in the cavitation conditions of the irrigant, and thus a low viscosity fluid may be selected as the irrigant. The low surface tension fluid and / or the low viscosity fluid may be an irrigant that is selected to have such properties or an irrigant that has additives that reduce these properties of the irrigant. The irrigant fluid may include a dye, for example, to better detect the fluid or to stain soft tissue or bacterial biofilms.

[0035] The irrigant may also be selected or customized to increase the abrasive impact of the irrigant. For example, the density of the irrigant may be increased and / or the irrigant fluid may also include abrasive particles (such as solid particles suspended in the fluid).

[0036] The device may include a regulator for controlling the delivery pressure. This may enable the operator to adjust the delivery pressure, for example, taking into account the different geometries of the teeth or root canals.

[0037] In an embodiment, the device may also include a heater to control the temperature of the irrigant. The heater may be provided as part of the supply unit (such that the heater heats the irrigant in batch or heats the irrigant before it is delivered by the pump). Alternatively, the heater may be provided as part of the handpiece such that the heater heats the irrigant as it flows through the handpiece. The phase boundary of the irrigant depends on both temperature and pressure, and for any given temperature, increasing the temperature of the irrigant will provide more favorable conditions for cavitation. For example, the temperature may be increased to above 20°C. The temperature of the irrigant may also be selected to avoid any pain response, and thus the temperature may be less than 60°C (or less than 50°C).

[0038] In some embodiments, the device may further include a pulse generator to pulse the flow of the irrigant fluid. The pulse generator may be, for example, a single piston pump, a controllable pressure release valve between the pump and the needle, or an on-off valve between the pump and the needle.

[0039] Unless otherwise stated, each integer described may be used in combination with any other integer that would be understood by a person skilled in the art. Further, although all aspects of the invention preferably "comprise" the features described with respect to that aspect, it is specifically contemplated that these aspects of the invention may "consist of" or "consist essentially of" those features outlined in the claims. Additionally, unless specifically defined herein, all terms are intended to be given the meaning that would be commonly understood by a person in the art for that term.

[0040] Further, in the discussion of the present invention, unless otherwise indicated, the disclosure of an alternative value for the upper or lower limit of the allowable range of a parameter shall be construed to implicitly state that each intermediate value of the parameter lying between the smaller and larger alternative values is also disclosed as a possible value of the parameter.

[0041] Additionally, unless otherwise stated, all numerical values appearing in this application should be understood to be modified by the term "about".

[0042] Although the present invention has been described above, the present invention extends to any inventive combination of the features set forth above or in the following description or drawings. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0044] Figure 1 A schematic diagram of a device according to an embodiment of the present invention is shown;

[0045] Figure 2 Shows Figure 1 Details of the schematic diagram of, which shows the position of the needle within the tooth;

[0046] Figures 3(A), 3(B), 3(C) and 3(D) illustrate the working principle behind an embodiment of the present invention;

[0047] Figure 4 is a schematic representation of a needle assembly according to an embodiment of the present invention;

[0048] Figure 5 is a flow chart representing a method of forming a needle assembly according to an embodiment;

[0049] Figure 6A and Figure 6BShows an example of the stages of forming a needle assembly according to an embodiment;

[0050] Figure 7 is a graph showing the pressures required to initiate inertial cavitation for various needles; and

[0051] Figure 8 is a graph showing the deflection of different endodontic needles under load. DETAILED DESCRIPTION

[0052] It can be noted that the terms proximal and distal are used herein to conveniently refer to the device in its normal orientation of use. Thus, it should be understood that proximal generally refers to the surface, component, or direction that is closer to the operator's hand during use, while distal can generally be used to refer to the surface, component, or direction that is away from the operator's hand (and this surface, component, or direction will thus be closer to the root canal). Similarly, forward will be understood to be used with respect to the direction away from the proximal end and towards the distal end (while backward is understood to be the reverse direction). However, it should be understood that such references are not intended to be restrictive, and the device can take any orientation during use.

[0053] Figure 1 An endodontic irrigation device 1 is schematically shown in. The device includes a base unit 10, which includes a reservoir 12 and a pump 14. The reservoir 12 contains a supply of irrigation fluid, and the pump 14 is used to convey the irrigation fluid from the supply under pressure through a flexible conduit 16. The base unit 10 can include a pressure sensor, an overpressure relief valve, and a waste water container, and the pressure sensor is used to monitor and control the pressure. The base unit 10 can also include a user interface 18 (the user interface 18 can be in any convenient form), and can enable the operator to adjust operating parameters, such as the pressure output of the pump 14.

[0054] A handpiece 20 is connected to the distal end of the flexible conduit 16, for example, by a conventional removable connector, such that the handpiece 20 is in fluid communication with the base unit 10 and can receive irrigation fluid from the supply 12 via the pump 14. The handpiece 20 includes a grip portion 22 at the proximal end, and a head 24 connected to the grip portion 22 via a neck 23. The head 24 extends to a needle 30, and the needle 30 can generally be removably mounted in the head 24. It can be understood that the term "needle" as used herein broadly refers to an elongated conduit that has a hole (the "lumen" of the needle), which extends through the elongated conduit and from the proximal end to an opening at the distal end, the proximal end being for receiving a supply of fluid during use, and the distal end being for delivering out fluid during use. As Figure 2Best seen in, the needle extends axially from the proximal end 33 to the distal end 34 and has a length l. The lumen 32 extends through the length of the needle 30 to provide a passage for the irrigant. The end 34 of the needle terminates in a forward-facing axial opening such that the irrigant exits the lumen in a forward axial flow.

[0055] In use, the needle 30 is inserted into the tooth 100 via the cavity 110 (formed in any convenient manner, such as by drilling), which provides an entrance to the pulp chamber 120. According to an embodiment of the invention, the needle has a length of at least 5 mm measured in the direction l and an outer diameter of no more than 300 μm measured in the direction d such that the needle end 34 can be positioned within a portion of the root canal 130. By positioning the needle in this way, the applicant has surprisingly found that, under conditions where the irrigant is supplied in such a way as to create an inertial cavitation cloud in front of the needle end 34, the irrigant will provide effective debridement and / or disinfection without the need for a NaOCl-based irrigant. In contrast, many prior art systems use needles that are too short to reach the root canal by themselves (instead, only positioning the end in the cavity 100 or pulp chamber 120), and / or needles that have too large a diameter to enter the root canal.

[0056] Furthermore, embodiments of the present invention enable root canal treatment to be performed without the need for mechanical filing (at least in all cases except the most difficult cases - such as in elderly patients where the canals have become calcified and narrowed), such that only an initial entrance to the root canal needs to be formed prior to using the device of the present invention. To provide such an inertial cavitation cloud, the applicant has found that the inner diameter of the needle (i.e., the diameter of the lumen) and the delivery pressure above the threshold pressure cavitation pressure should be selected (depending on the geometry of the particular tooth and needle combination) such that the flow of the irrigant through the needle causes an inertial cavitation cloud to form in the irrigant fluid within the root canal in front of the needle end. For example, the lumen diameter can be at least 25 μm, such as at least 50 μm. Without knowledge of this effect, it might be natural to select a needle with too small an inner diameter (e.g., less than 50 μm to ensure placement of the needle into the root canal), but the applicant has recognized that it is important that such a needle will create frictional losses, meaning that even very high delivery pressures will not provide a flow that establishes effective cavitation upon exiting the needle. In contrast, in embodiments of the present invention, due to the well-known erosive effect of the cavitation cloud caused by shock waves, cavitation provides powerful debridement, disinfection, and / or removal of debris or bacteria, which are caused by the rapid collapse of vapor bubbles within the fluid.

[0057] As shown in the 16,000 fps high-speed photograph of FIG. 3(A), a glass micropipette (e.g., with an inner diameter of 1.2 mm, 0.6 mm, or 0.29 mm) can be used to simulate a root canal. When a needle 330 of appropriate size is inserted into a conduit 350 and a flow is provided at a pressure exceeding the cavitation threshold, a cavitation cloud 360 is clearly formed downstream of the needle. The flow within the conduit 350 is schematically illustrated in FIG. 3(B). Importantly, the size of the needle (not exceeding 800 μm at 20 mm from the tip) ensures that the flow of fluid in the conduit (or in an actual root canal) includes an inflow from the needle and an outflow passing between the wall of the conduit and the outside of the needle.

[0058] Cavitation occurs under appropriate conditions when a liquid rapidly transforms into a gas across a phase boundary. Without being limited to a particular theory, the applicant recognizes that, as illustrated in FIG. 3(C), selecting a needle that enables a recirculation flow to be generated in the root canal forms a strong shear layer effect between the inward and outward flows. This shear layer increases the vortices in the flow and significantly increases the occurrence of cavitation. The resulting condition means that very strong vortices can be generated at the interface between the inflow and the outflow inside the root canal. Inside the vortices, the (dynamic) pressure is greatly reduced. The reduction in pressure makes cavitation more favorable (bringing the initiation point closer to the phase boundary). As a result of this effect, cavitation clouds are generated in channels such as root canals under flow conditions (pressure, velocity, and flow rate) where cavitation would not be established in an open environment. Increasing the velocity of the liquid present in the needle will also help to increase the vortices, and for a given channel, there will be a minimum nozzle exit velocity below which cavitation will not occur. Under the condition that the inner diameter of the needle is not too narrow, the delivery pressure can be used to control the needle exit velocity.

[0059] To test the performance of the device according to the embodiments, transparent plastic teeth (RepliDens mandibular molars, transparent type 03.2.1, Medcem AG, Weinfelden, Switzerland) were tested, which had a realistic root canal structure filled with colored gelatin to simulate the tissue inside the tooth. Different devices were tested, and the amount of gelatin before and after cleaning was measured using image analysis and pixel counting. The device according to the embodiments used a needle with a length of 20 mm and a 30G gauge (corresponding to an inner diameter of 0.16 mm and an outer diameter of 0.31 mm). The delivery pressure was set to 60 bar. The irrigant was a saline solution, and the needle was positioned and moved up and down in the tube for 180 seconds. The results of multiple root canal systems were compared based on the percentage of material removed determined from the amount of gelatin before and after cleaning. The same tests were performed using a commercial ultrasonic-based irrigant activation system and a laser-based irrigant activation system. In the case of ultrasound (EDDY, VDW GmbH, Munich, Germany), the vibrating tip was inserted into each tube and activated for 120 seconds. For the laser system (LiteTouch Er:YAG Laser, Orcos Medical AG, Küsnacht, Switzerland), the plastic tooth pulp chamber was filled with water, and the laser tip was placed in the water and activated for 120 seconds. The results are shown in Table 1 below, where, compared to commercially available commercial systems (ultrasonic system (without using instruments / without filing), laser system (without using instruments / without filing), and mechanical filing with instruments followed by syringe irrigation (ProTaper, Dentsply, Ballaigues, Switzerland)), the embodiments of the present invention provided significantly improved debridement (our invention) in teeth without using instruments. Experimental findings showed that conventional ultrasonic activation systems and laser activation systems were unable to sufficiently remove material from the inside of the tubes. Therefore, conventional ultrasonic activation systems and laser activation systems can only be used for activation and are not suitable for treating tubes without using instruments (which can be defined, for example, as tubes enlarged only using an ISO 10 hand file), and do not reduce the need for mechanical filing. In the case of the ultrasonic system, due to the narrow root canals, the tip could not vibrate side to side, thus suppressing oscillation. In the case of the laser system, we observed that no gelatin came out of the root canal because insufficient flow was generated. Using a mechanical file and irrigating with a syringe filled with water performed better than other methods but was less effective and significantly more time-consuming than the embodiments of the present invention.

[0060] Table 1: Cleaning effects of different systems in a tooth model without using instruments

[0061] Cleaning area [%] Standard deviation Ultrasonic wave 59.7 10.3 Laser system 80.9 - Mechanical filing 89.8 8.1 The present invention 97.1 1.0

[0062] Importantly, the applicant also compared the situation between the open area and the closed / restricted area (where the tooth root is closed). This has demonstrated unexpected results and illustrated the importance of the geometry of the tooth canal and the needle for cavitation. It can be considered that the existing systems failed to consider the geometry of the tooth canal and the needle as factors, and this reflects why such systems may not be able to provide true effective cavitation.

[0063] To demonstrate this effect, experiments were conducted using a delivery pressure of 60 bar connected to needles with different shapes, diameters, and lengths. The water coming out of the needle was sprayed into (i) a basin with water, (ii) a glass micropipette with an open end, or (iii) a glass micropipette completely sealed at one end. The needles tested included needles of standard gauge sizes. The threshold pressure was recorded as the point at which a stable cavitation cloud was first visible. Compared to the unconstrained water basin, the threshold for sufficient cavitation to be generated by the upstream pressure is generally much lower inside the narrow tube with a closed end. From the experimental data, it can be noted that 30G (needle gauge) needles with a length of 20 mm or 15 mm only produced cavitation inside the micropipette and not in the open basin, and a higher pressure was required to produce cavitation in the open basin. All other needle sizes including 30G needles with lengths of 10 mm or 5 mm cavitated in the open water. However, using these other sized needles inside the micropipette reduced the upstream pressure required by 15 bar to 40 bar. There was an exception for the 25G needle and the 0.6 mm tube (Table 2; closed-end micropipette d = 0.6 mm, 25G), in which case the needle itself blocked the backflow, and thus the cavitation threshold increased after closing the end of the micropipette (because the outer diameter of the needle was very close to the inner diameter of the pipette). Thus, the applicant has been able to confirm that a backflow within the channel is required to effectively initiate cavitation.

[0064] Table 2: Cavitation Pressures for Various Needle Configurations

[0065]

[0066] The volumetric flow rate through the needle depends largely on the upstream pressure and the needle diameter. Thus, when a lower pressure is required to generate cavitation, the volumetric flow rate decreases. This is advantageous in practice because reducing the flow rate and / or pressure can reduce the risk of any unwanted damage to the teeth caused by the high flow rate. Experimental findings show that the volumetric flow rate is highest for a maximum needle diameter of 25G and lowest for the smallest diameter of 34G. For a 25G needle with a length of 10 mm, the lowest pressure threshold for cavitation occurred, which was 6 bar, accompanied by a volumetric flow rate of 72 ml / min. These results indicate that the threshold for cavitation decreases significantly inside a narrow, end-closed tube. Thus, embodiments of the present invention can generate effective cavitation at a lower upstream pressure accompanied by a lower volumetric flow rate. This flow provides distinct advantages in terms of the reduced pressure and lower volumetric flow rate at the root canal tip, both of which minimize the risk of extrusion at the tip.

[0067] Thus, the results confirm that the properties of the needle, such as diameter and length, have a significant effect on the threshold cavitation pressure. Additionally, experiments have confirmed that the role of the recirculating fluid is very important - increasing the relative velocity and the formation of vortices, thus significantly reducing the pressure required to generate cavitation.

[0068] The effect of needle length on the cavitation threshold is straightforward. A longer needle increases the pressure required for cavitation, which is thought to be consistent with the fact that a shorter needle will provide less flow resistance. However, in practical embodiments, this generally means that the choice of needle length is a compromise between an increase in the threshold pressure and the length sufficient to position the tip within the root canal to deliver cavitation and effectively debride the canal.

[0069] In some embodiments of the present invention, a heater 15 can be included to increase the temperature of the irrigant (thus bringing the temperature closer to the phase boundary at a given pressure and further making cavitation more favorable). The heater 15 can be included as part of the base unit 10 or can be integrated into the handpiece. In some embodiments, the pump 14 or the base unit can include a pressure regulator.

[0070] Additionally, or as an alternative to the user interface 18, the handpiece 20 can include a controller, such as a switch on the handpiece (or a switch associated with the handpiece, such as a switch on a foot pedal). For example, a trigger can be provided to activate the flow through the system.

[0071] Since embodiments of the present invention enable the use of simple irrigants such as water or saline, it can be understood that the embodiments can provide various options in use. For example, the irrigant can be a low surface tension liquid or a high viscosity liquid. The irrigant can also include additives such as abrasive particles.

[0072] In some embodiments, the device may include a tube sensing system. For example, to ensure that liquid does not pass through the tooth tip, embodiments may include a tip locator to measure the distance to the tip and assist the dentist in operating the device.

[0073] While the primary purpose of the endodontic irrigation device of the embodiments may be root canal surgery, it is also understood that the debriding and / or disinfecting effects of the cavitation flow can also be applied to other uses in dental practice. For example, the device can be used for plaque removal from the external surface of the tooth or at the subgingival surface. Embodiments can also be used to drill through dental tissue (dentin, enamel) or for cutting soft tissue. The device can also be used to locate the entrance to the root canal.

[0074] The applicant has now determined that for the use of the above methods and devices, commercially available needles have drawbacks. In particular, since the needle size is directly related to the system pressure required for inertial cavitation, the needle size selection must be a compromise between a larger needle diameter that cannot access the smallest root canal areas and a smaller needle that may require a higher operating pressure to initiate cavitation. Importantly, the operating pressure required by the system can directly affect the operation and equipment costs, for example, due to the need for more expensive high-rated equipment such as pumps. Therefore, a system that operates effectively at the lowest possible pressure provides clinical and commercial advantages.

[0075] Figure 4 A needle assembly 400 according to an embodiment of the present invention is shown. The needle assembly 400 is a single integral part, which can be provided, for example, as a disposable, sterile consumable for use in Figure 1 the irrigation device 1. The needle assembly 400 includes a connector 410, a body portion 420, and a needle 430.

[0076] The connector 410 is located at the proximal end of the needle assembly, and the connector 410 is configured to removably couple to a corresponding coupling portion on the handpiece 20. It should be understood that the connector 410 can be in any convenient form and can be, for example, an existing standardized form to allow interconnection with existing devices and / or to provide a familiar operation for the user. A particularly suitable connector can be, for example, a Bal Seal® connector, which can include a spring-supported retention arrangement (e.g., the type of connector disclosed in U.S. Patent US8167285B2). The body portion of the needle assembly 420 extends forward from the coupling portion and defines a fluid conduit 422, which, in use, conveys the irrigant from the handpiece 20 to the needle 430. In the illustrated embodiment, a flange 425 is provided at an intermediate portion 425 around the exterior of the body, and the flange 425 can be configured, for example, to provide a stop or a tactile feature for use when connecting the needle assembly 400 to the handpiece 20.

[0077] 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 tip 434. The axial length of the needle from the proximal end 433 to the tip 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 setting the needle 430 to extend at an angle between 30 degrees and 90 degrees relative to the body portion 420, for example, extending at approximately 60 degrees, is beneficial for enabling the clinician to guide the tip 434 of the needle 430 into the root canal during use. In some embodiments, the needle may include other angled or curved sections, such as having a gooseneck profile, to assist in positioning the tip during the procedure. The tip 434 includes an axially directed opening such that the main stream of the irrigant can be ejected in the direction shown by arrow A. Optionally, at least one side discharge hole may also be provided near (but behind) the tip 434 to enable an additional side flow that can be directed towards the side wall of the adjacent canal portion, as shown by arrow S.

[0078] The needle 430 is made of a polycarbonate material (such as Macrolon 3258). The needle 430 is first injection molded into a cylindrical needle and then formed into a conical profile (as described further below). Table 3 below provides the dimensions of a typical needle (labeled "Needle X" for ease of reference) manufactured according to an embodiment. As shown by the comparison in the table, the outer diameter of the tip 434 of Needle X is less than 200 μm, which is thinner than a 33G needle, while the diameter of the proximal end 433 is greater than 750 μm. The thickness of the needle at the tip 434 is between 40 μm and the dimensions of the embodiment with a wall thickness of 34 μm detailed in Table 3. Compared to metal needles, it has been found that the polycarbonate needles of the embodiments have significantly improved flexibility while being able to withstand the required operating pressure that would prevent the use of many thermoplastic materials. The combination of the flexibility of the needles of the embodiments and the small tip diameter enables the tip to be positioned in fine root canals that have not been instrumented (such as those narrower than 300 μm), especially for those with a high curvature (such as greater than 30°) that are inaccessible by conventional needles.

[0079] Table 3: Needle dimensions compared to standard Birmingham wire gauge cylindrical needles

[0080] Distance from the end [mm] 0 5 10 15 20 Needle X 0.19 0.27 0.38 0.54 0.76 30G 0.312 0.312 0.312 0.312 0.312 32G 0.325 0.325 0.325 0.325 0.325 33G 0.21 0.21 0.21 0.21 0.21 34G 0.159 0.159 0.159 0.159 0.159

[0081] In Figure 5FIG. schematically shows a method of manufacturing a needle assembly 400 according to an embodiment. In step 510, an injection molded cylindrical needle preform (made of polycarbonate) is provided. The needle preform can be formed as a single cylindrical needle, or can also be a section cut from a larger extruded cylindrical tube or molded cylindrical tube.

[0082] The next step of the process (shown in step 520) includes forming the cylindrical needle preform into a conical needle having a desired length and diameter. This second step is performed by a draw process (the draw process can also be referred to as a stretching process), which elongates the needle while forming the needle. By forming the needle directly from the preform, the need to glue the needle in place or otherwise attach the needle in place is eliminated. This both reduces the manufacturing steps and provides a robust needle that can withstand the required pressure while having a thin wall thickness and a small tip diameter. Alternatively, a conically extruded preform can be drawn into a cylindrical needle shape and then glued to a body, which can be injection molded or a plastic / metal needle hub.

[0083] In some embodiments, before the step of drawing the needle into its conical form, an integrated needle assembly can be first formed, which includes the cylindrical preform of the needle. For example, in some embodiments (shown in FIG. 6 and described below), the cylindrical preform can be first integrally molded with the body of the needle assembly (e.g., by an injection molding process). In other embodiments, the needle preform can be placed in a mold and the needle body is overmolded using an injection molding process to form an integrated needle assembly including the needle preform and the body. In alternative embodiments, the needle preform can be joined to a molded needle body (but it should be understood that this generally requires more manufacturing steps). After forming the integrated needle assembly, the next step of the process includes forming the cylindrical preform into a conical needle having a desired length and diameter. This second step is performed by a draw process, which elongates the needle while forming the needle. By forming the needle directly from the integrated needle assembly, the need to glue the needle in place or otherwise attach the needle in place is eliminated. This both reduces the manufacturing steps and provides a robust needle that can withstand the required pressure while having a thin wall thickness and a small tip diameter.

[0084] In Figure 6A 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' (the needle preform 440' is substantially cylindrical) are a single integrally injection molded part. Figure 6B The needle assembly 400' of the same example is shown after the needle preform has been drawn to form a conical needle 430' having a desired length and diameter.

[0085] Figure 7 Tests were performed comparing the conical needle of the embodiment with conventional needles of 25G, 30G, and 31G gauges. To simulate the endodontic method of the present invention, the needles were tested in an unconstrained water basin and in micropipettes of gradually decreasing size (1.2 mm, 0.6 mm, and 0.29 mm in diameter), which simulated dental canals of different sizes. For each needle and environment, the threshold pressure required to cause cavitation in the irrigant flow in front of the needle tip was measured. The results clearly showed that the conical needle of the embodiment significantly reduced the threshold pressure required for cavitation, especially in a closed tube (e.g., for the medium-sized micropipette, the threshold pressure was reduced to less than 20 bar compared to 50 bar or 60 bar for the existing needles). The conical needle of the embodiment was the only needle capable of producing cavitation in the smallest micropipette (0.29 mm in diameter).

[0086] Other tests were performed to quantify the ability of the needles according to the embodiment to penetrate the root canal compared to needles of the prior art that are commercially available. The needles according to the embodiment (labeled "Needle Y" for ease of reference) were tested together with standard metal endodontic needles of 30G and 31G sizes (both needles are of the Transcodent brand from Sulzer Mixpac, Germany) and a flexible "Irriflex" needle (obtainable from Produit Dentaires SA, Switzerland). For this test, a standard transparent resin endodontic training block was used, which had a single curved root canal formed therein. For this test, the training block used was a 0.02 taper 15 - 30 2A block commercially available from Dentsply Sirona. Before the test, the block was shaped using ISO files, one block using an ISO 15 file (taper 0.02) and one block using an ISO 20 file (taper 0.02) to provide two different-sized tubes.

[0087] Each needle was inserted into two training blocks to the maximum penetration depth. The maximum penetration depth was then measured using an internal stop and an endoscopic ruler. The maximum working length of each tube was also measured using an ISO 10 hand file to compare with the penetration depth of each needle. Tables 4 and 5 below provide the results.

[0088] Table 4: Penetration depths of different needles in a dental training block using an ISO 15, 0.02 instrument

[0089]

[0090] Table 5: Penetration depths of different needles in a dental training block using an ISO 20, 0.02 instrument

[0091]

[0092] As can be seen from this data, the only needle that can reach the full working length of an ISO 15 tube or an 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 conventional prior art needles and "flexible" prior art needles. The needle according to the embodiment is the only needle that can reach the full working length of the smallest tube of the instrument to be used (i.e., the tube of the smallest instrument to be used can be defined, for example, as a tube that is enlarged only using an ISO 20 or even an ISO 15 hand file).

[0093] A key feature of the needle according to the embodiment, which is considered to be a contributing technology to increased tube penetration, is the high level of flexibility (especially flexibility transverse to the needle axis) provided by the design and manufacture of the needle. To quantify the flexibility, the applicant tested a series of needles together with the needle according to the embodiment (labeled "needle Z"). The same set of needles as in the penetration test was tested, i.e., 30G and 31G Transcodent brand needles, the flexible "Irriflex" needle, and the needle of the embodiment.

[0094] Each needle was horizontally clamped in a cantilever manner (in a vise) at a point 20 mm from the end of the needle. A load point was marked 1 mm from the end of the needle, and a point load was applied at this load point. Then each needle was 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 end under each load was recorded. The deflection in the vertical axis (i.e., perpendicular to the initial axis of the needle) was recorded in millimeters from the recorded positions. Table 6 below shows the results for each needle and is shown graphically in Figure 8 as follows.

[0095] Table 6: Flexibility test results, needle end deflection in the y direction under different applied loads

[0096]

[0097]

[0098] Of particular note is that the needle tip according to an embodiment of the present invention deflects 5 mm under a load of only 0.01 N. In contrast, all other needles, including the "flexible" prior art needles, deflect a maximum of 1 mm under this load. Additionally, at least five times more force is required to deflect any of the other needles by the same amount of 5 mm. Clearly, regardless of the load applied, the needles of the embodiment are more flexible than any of the needles of the prior art. The difference in flexibility between the needles of the embodiment and the needles of the prior art is particularly evident at lower loads. The deflection behavior of the metal needles (30G and 31G) is nearly linear, while needle Z exhibits a logarithmic behavior. The applicant recognizes that this is particularly advantageous for endodontic needles and for entering highly curved canals with endodontic needles.

[0099] It should be understood that in use, this will provide a needle that is more easily deflected around the curvature of the root canal of the smallest instrumentation. The increased flexibility of the needle according to the embodiment, particularly the increased flexibility at the distal end of the needle, enables the needle to follow a strongly curved canal where other needles would become stuck.

[0100] It should also be understood that the combination of the conical shape with the flexible material significantly reduces the risk of the needle tip becoming stuck in the porous dentin wall (i.e., compared to a conical metal needle).

[0101] Although the present invention has been described above with reference to preferred embodiments, it should be understood that various changes or modifications can be made without departing from the scope of the present invention as defined in the appended claims.

Claims

1. A needle assembly for an endodontic surgical device, the needle assembly comprising: A connector for removably coupling the needle assembly to a handpiece; A body portion extending from the connector and providing a fluid conduit; And A needle axially extending from a proximal end at the body portion to a distal tip, the tip having at least one opening, the needle having a lumen extending therethrough to define a fluid passage from the fluid conduit of the body to the at least one opening; Wherein, The outer diameter of the tip does not exceed 300 μm and the wall thickness of the tip is less than 50 μm, and The needle is made of a material having a tensile modulus of at least 1 GPa.

2. The needle assembly according to claim 1, wherein, The needle is made of a material having an ultimate tensile strength between 15 MPa and 150 MPa.

3. The needle assembly according to claim 1 or 2, wherein, The needle has a tapered profile, wherein the outer diameter of the needle portion converges towards the distal tip.

4. The needle assembly according to claim 3, wherein, The needle has a frustoconical profile.

5. The needle assembly according to claim 3 or 4, wherein, The outer diameter of the tip is less than 50% of the diameter of the proximal end of the needle, and preferably, the outer diameter of the tip is between 10% and 30% of the diameter of the proximal end of the needle.

6. The needle assembly according to any one of claims 3 to 5, wherein, The needle comprises a cylindrical needle machined into a conical form.

7. The needle assembly according to any one of the preceding claims, wherein, The needle assembly comprises a needle having the following flexibility: the needle tip laterally deflects more than 2 mm under a tip load of 0.01 N, and additionally or alternatively, laterally deflects more than 8 mm under a tip load of 0.05 N.

8. The needle assembly according to any one of the preceding claims, wherein, The needle is made of polycarbonate.

9. The needle assembly according to any one of the preceding claims, the needle assembly further comprising at least one side discharge hole located in the wall portion of the needle between the proximal end and the distal tip at the body portion.

10. An endodontic device, the device comprising: A supply of irrigant fluid; A pump for delivering the irrigant fluid from the supply under pressure; A handpiece in fluid communication with the pump, and the handpiece comprises a needle assembly having a needle extending from a rearward end near the handpiece to a forward tip away from the handpiece, the needle having an opening at the tip for delivering the fluid received from the pump into the tooth cavity; and wherein, The length of the needle extending from the rearward end of the needle to the tip of the needle is at least 20 mm, the outer diameter of the needle does not exceed 200 μm, and the wall thickness of the needle is less than 40 μm, such that the needle tip can be positioned within a portion of the root canal; and The pump delivers the irrigant at a delivery pressure less than 80 bar and above the threshold cavitation pressure, such that the flow of the irrigant through the needle forms an inertial cavitation cloud in front of the needle tip, within the irrigant fluid in the root canal.

11. A method of forming an endodontic needle, the method comprising: Providing a cylindrical preform having a first length and a first diameter; And Form the cylindrical preform into a conical needle that tapers inwardly along the length of the conical needle, the length of the conical needle being greater than the first length and the diameter of the conical needle at the distal end being less than the first diameter.

12. The method according to claim 11, wherein, Provide the preform by injection molding.

13. The method according to claim 11 or 12, wherein, Forming the conical needle includes extruding or stretching the cylindrical preform.

14. A method of forming an endodontic needle assembly, the needle assembly including a body and a needle formed by the method of claim 11, 12, or 13, the method including molding a body portion and securing the conical needle to the body portion.

15. The method according to claim 14, wherein, Securing the conical needle to the body portion includes securing a proximal end of the cylindrical preform to the body portion prior to forming the cylindrical preform into a conical needle.

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