Mouthpiece for distribution of a liquid in a user's mouth

Abstract

A mouthpiece 10 for distribution of a liquid in a user’s mouth, the mouthpiece 10 being configured to be positioned within a superior vestibule of the user’s mouth apical to a gingival margin, the m

Description

Xerostomia is a dry mouth symptom, possible due to insufficient production of saliva. As saliva has a plurality of functions in the mouth, xerostomia may lead to many connected symptoms, for example dental caries, acid erosion of the teeth, difficulties with swallowing food, etc. Xerostomia can have different causes, and treatment of the underlying cause is often difficult. Thus, treatment is mostly concerned with alleviating the symptom rather than curing the cause. A known treatment for xerostomia is to deliver fluids orally in a continuous manner, or when desired by the patient, with the help of a device placed in the user’s mouth through which fluid from an external source is pumped. For example, PCT / EP2020 / 075546 discloses a liquid distribution system comprising a thin and flexible mouthpiece for distribution of a liquid in a user’s mouth. The present invention aims to further improve upon the devices / mouthpieces of the prior art. SUMMARY According to a first aspect there is provided a mouthpiece for distribution of a liquid in a user’s mouth, the mouthpiece being configured to be positioned within a superior vestibule of the user’s mouth apical to a gingival margin, the mouthpiece comprising: an inlet configured to receive a fluid supply, at least two fluid outlets, and an internal channel fluidly connecting the inlet to the fluid outlets; and a flange portion at least partially surrounding the channel for adhering to a user’s gum; wherein a thickness of the channel is greater than a thickness of the flange portion. It will be well appreciated that where the terms “thick” and “thin” and “thickness” are used here, they are referring to the depth of the mouthpiece, i.e. from front to back when the mouthpiece is being worn. By providing a mouthpiece wherein a thickness of the channel portion is greater than a thickness of the flange portion, the mouthpiece may have a large surface area to volume ratio (so that it may better adhere to the mucous membrane of the user, ensuring that the mouthpiece will stay in the correct position once placed in the mouth), at the same time as the internal channel in the mouthpiece being able to accommodate a large volume flow rate of liquid. In other words, the large thickness of the internal channel relative to the thickness of the mouthpiece and / or the flange enables sufficient fluid flow without the mouthpiece being too bulky and bothersome. It also reduces the material required to form the mouthpiece than if the flange portion was the same thickness as the internal channel, providing clear benefits in terms of lower material cost and environmental impact. For instance, the approx, average flow for unstimulated saliva is 0.3-0.4ml / min, and the flow rate when sleeping is about 0.1ml / min. However, when a person is stimulated e.g. eating food / chewing gum, the saliva from a healthy person may rise to 4.0-5.0ml / min. Accordingly, the cross-sectional area of the internal channel may be adapted / selected (e.g. the internal channel may be sized) to allow fluid flow of up to 4.0-5.0 ml / min. It should be appreciated that a mouthpiece that is thin (whilst at the same time being able to accommodate a large volume flow rate of liquid) provides improved comfort. Since the mouthpiece is typically worn by the user for many hours a day, comfortability is an important aspect. A thin mouthpiece may be very flexible, whereby it may be able to follow the contour of the mucous membrane of the mouth. In this way the mouthpiece may also be considered to be organically shaped. The flange portion defines / provides a surface / contact area to be attached to the gum of the user. Accordingly, the flange portion at least partially surrounds the channel portion and extends outwardly from the channel portion in a direction parallel to the surface of the gum. The term ‘at least partially surrounds’ should be taken to mean that, when viewed from the front (or back), the majority (e.g. nearly all) of the channel is surrounded by the flange portion - except for where the channel is adjacent / fluidly connects to the inlet. In a side (cross-sectional) view of the arms of the mouthpiece, the flange portion appears to have an upper part extending outwardly from the channel and a lower part extending outwardly from the channel. Thus the flange portion establishes a border / surface area that extends nearly all the way around the channel (when viewed from the front). The size of the flange portion may be selected to provide as large a contact area for attachment to the mucous membrane of the superior gingiva (gum) of the user as possible whilst ensuring that, when the entire mouthpiece is positioned apical to the gingival margin, the mouthpiece will be positioned outside of the oral cavity proper and will not be in contact with the teeth. The ‘size’ of the flange portion referred to is the distance the flange portion extends outwardly from the channel, and will be referred to further herein as the ‘height’ of the flange portion (‘height’ being measured e.g. in a direction parallel to the surface of the superior gingiva, e.g. a dimension from the top to the bottom of the mouthpiece, e.g. the vertical dimension substantially perpendicular to the thickness), because the majority of the flange portion generally extends along the ‘height’ dimension. In other words, when viewed from the front (or back), the flange portion generally either extends above or below the channel (discounting the curvature of the arms). For example, when viewed from the side and in cross-section through one of the arms, the total ‘height’ of the arm of the mouthpiece is comprised of the ‘height’ (e.g. diameter) of the channel and twice the ‘height’ (e.g. extension) of the flange portion. The positioning of the mouthpiece (apical to the gingival margin) may make eating with the mouthpiece in place easier, since neither the teeth nor the oral cavity proper is affected. This may be a major advantage, as people suffering from xerostomia may have trouble swallowing dry food due to the lack of naturally moistening saliva. The mouthpiece may be adapted to be positioned at the highest point within the superior vestibule of the user’s mouth e.g. the mouthpiece may be sized and shaped to be worn between the user’s superior (upper) lip and superior gingivae (upper gums), and may be configured to be worn higher than the user’s teeth (i.e. above the gingival margin) so as not to obstruct the teeth. In other words, the mouthpiece may be configured to be positioned within the superior vestibule spaced apart from or distal to the gingival margin and / or the teeth. The entire mouthpiece may be adapted to be positioned at the highest point within the superior vestibule of the user’s mouth. By positioning the mouthpiece in the uppermost part of the superior vestibule, the mouthpiece may be worn for long periods of time without interfering with normal mouth operations. This makes it suitable for wearing during such normal mouth operations, e.g. eating and talking. The mouthpiece may be anatomically complementary to the superior vestibule to be firmly positioned within said superior vestibule. The shape of the mouthpiece may thus be bent, for example like a C or a II. The mouthpiece may be curved along its length e.g. so that when worn it wraps around the outside of the user’s upper gums from one side of the mouth to the other. The mouthpiece may be flexible so that it will adjust to fit the user’s mouth, whereby a standard shape may fit a range of users. This has the advantage that only a few different standard sizes are required to fit all users, which may reduce the production costs of the mouthpiece. The mouthpiece may for example comprise any suitable material that is produced from high consistency rubber (e.g. a silicone material) and has the necessary properties to meet the requirements for food contact, health and medical usage (e.g., RoHS, REACH, FDA, ISO 13485, etc.). A suitable material, for example, is EI_ASTOSIL® R401 High Consistency Silicone Rubber. The internal channel of the mouthpiece may be a single internal channel, configured to fluidly connect the inlet of the mouthpiece to the at least two outlets. The single channel may fluidly connect the two outlets e.g. fluidly connecting a first outlet on a first side of the mouthpiece (e.g. the right side) with a second outlet on a second, opposite side of the mouthpiece (e.g. the left side). The mouthpiece may comprise only a single internal channel. At least one outlet may be provided in either side of the mouthpiece e.g. at least one on the left and at least one on the right of the user’s mouth. The single channel may therefore provide liquid to both sides (left and right) of the mouth, specifically the left and right sides of the superior vestibule. The distribution of the liquid to the outlets may thus be determined by the pressure in the internal channel. The single channel may therefore help to self-regulate the distribution of the liquid to ensure it is even, as well as to reduce the likelihood of the mouthpiece failing or breaking e.g. in the event that one of the outlets becomes blocked, for example by food. The internal channel may have a substantially circular cross-section, e.g. the shape of the cross-section of the internal channel may be an ellipse. In a preferred embodiment, the shape of the cross-section may be a circle (e.g. an ellipse with a constant diameter). It will be recognised that the cross-section of the internal channel referred to is the section through the channel perpendicular to the length of the channel (e.g. perpendicular to the (tangential) longitudinal direction of the channel). This may have the effect that the pressure in the channel is more evenly distributed (e.g. than a cross-sectional channel shape without rotational symmetry), reducing the risk of the channel / mouthpiece bursting. The internal channel (e.g. as a result of having a substantially circular crosssection) may provide a resilient structure, and may act as a spine / support for the mouthpiece. This helps the mouthpiece keep its shape, for example preventing it from folding up when a user is inserting it, thus making it easier to insert. Thus, the mouthpiece may not need to comprise any additional structural support components, such as a wire or rib, since the internal channel provides this function. Since the thickness (i.e. the dimension from front to back) of the internal channel is greater than the thickness of the flange portion, the internal channel slightly protrudes from the surrounding material (i.e. the flange portion) of the mouthpiece. The thickness of the channel may be between 1.0 and 3.5 times greater than the thickness of the flange portion. Optionally, the thickness of the channel may be between 1.0 and 2.5 times greater; optionally, between 1.5 and 2.5 times greater. The internal ‘thickness’ (e.g. internal diameter) of the channel may be around 1mm +1- 0.1mm. The thickness of the (mouthpiece at the) channel (e.g. external diameter) may be around 1,2mm (+0.2mm / -0.6mm). The thickness of the channel may be a maximum thickness of the mouthpiece (excluding the inlet). The thickness of the flange portion may be less than 1.0mm. The thickness of the flange portion may be less than 0.8mm. The thickness of the flange portion may be between 0.5mm and 0.8mm. Optionally, it may be 0.6mm. The thickness of the flange portion may vary, e.g. the thickness may be different at different parts of the flange portion. However, the thickness of the flange portion may also be consistent, or substantially consistent, across the flange portion. This may provide improved comfortability and manufacturing advantages. These advantageous proportions of the mouthpiece have been carefully selected and identified by the inventors of the present invention as providing a mouthpiece that has an optimal balance of fluid flow, rigidity, and “wearability” (both in terms of comfort and security of the attachment / fit). The mouthpiece may include a central region. The mouthpiece may include two elongate portions, e.g. “arms”, one on each side of the central region. The channel may extend along these arms, e.g. from an arm on the left of the mouthpiece to an arm on the right of the mouthpiece. The “arms” may alternatively be termed “wings”. A / the height of the flange portion of or in the elongate arms may be between 1.0 and 3.5 times greater than a height (e.g. an inner diameter) of the channel. Optionally, a / the height of the flange portion of or in the elongate arms may be between 1.5 and 2.5 times greater than a height (e.g. an inner diameter) of the channel. A / the height of the flange portion of or in the elongate arms may be between 1.5mm and 3.5mm. A / the height of the flange portion of or in the elongate arms may be between 2.0mm and 3.0mm. As discussed above, a ‘height’ of the flange portion can be considered as the measured distance / extension of the flange portion outwardly from the internal channel (the term ‘height’ is used simply for ease of reference). Thus, the total ‘height’ of the mouthpiece includes the height (internal diameter) of the channel and twice the height of the flange portion (a height of the flange portion above the channel and a height of the flange portion below the channel, as viewed from the side). Typically, the internal channel will be located substantially in the middle of the (total) height of the mouthpiece, for example substantially in the middle of the elongate arms. In other words, the part of the flange portion in the elongate arms located above the channel, and the part of the flange portion located below the channel, in the height dimension, will be substantially equal. This enables the channel to provide optimum support for the mouthpiece. The mouthpiece may sufficiently attach to the mucous membrane without the need for any additional substance. For example, saliva will be present between the mouthpiece and the membrane, and this may adequately retain the mouthpiece in place, e.g. by cohesion / adhesion. In other words, the mouthpiece may be affixed to the mucous membrane by the presence of moisture in the mouth, without requiring any further substance. Such attachment may be improved by the shape of the (flange portion of the) mouthpiece, e.g. by having a large surface to volume ratio, as mentioned above. However, to further improve the attachment of the mouthpiece to the mucous membrane, the surface of the mouthpiece may comprise an adhesive layer. The material of the adhesive layer must be safe for humans to consume. The adhesive layer may be a dry material that obtains adhesive properties only after being wetted. This will have the advantage that the mouthpiece will not stick to other surfaces before it is to be used. Wetting of the mouthpiece may easily be performed, for example by applying water on the mouthpiece with a finger prior to use. A suitable adhesive material may for example be or be based on gum arabic, which is efficient, and established to be safe for humans. Gum arabic may also be applied on the mouthpiece as a powder. The adhesive material may also be e.g. starch. The surface of the mouthpiece may be rough, for example comprising small indentations or ridges, for the adhesive material to stick better to said surface. As discussed above, the mouthpiece may typically be worn by the user for many hours a day. The material of the adhesive layer may therefore be selected to exhibit strong bonding properties for an extended time period, for example all day, or between 2-10 hours, preferably between 6-10 hours. By firmly securing the mouthpiece in the mouth for extended time periods, the comfort of the mouthpiece during use may be greatly increased. The mouthpiece may be constructed such that, when in use, each outlet is positioned complementary to an opening of a parotid duct. The parotid ducts are where the saliva produced by the parotid glands enters the mouth, so these positions of the outlets are therefore the most natural regions of the mouth to inject liquid such as water or saliva substitutes. The mouthpiece may comprise an upper edge configured (e.g. shaped) to fit comfortably in the user’s mouth. Particularly, the upper edge of the mouthpiece, in particular the upper edge of the central region of the mouthpiece, may be configured to accommodate a labial frenulum of the user, for example: the mouthpiece may comprise two convex curved portions (e.g. flaps), which can fit either side of the labial frenulum, and a central concave portion between the convex portions wherein the labial frenulum may fit. This shape was tuned to fit the majority of the population’s mouth comfortably based on findings from clinical tests on tooth moulds and live patients. Furthermore, it enables the mouthpiece to be positioned at the highest point within the superior vestibule without being displaced downwardly by the labial frenulum. By adapting the mouthpiece to fit at the highest point in the superior vestibule, the mouthpiece is positioned outside of the oral cavity proper and will not be in contact with the teeth, therefore not interfering with chewing, eating or talking. This enables the mouthpiece to be worn for long periods of time. The convex curved portions may extend outwardly from the flange portion by up to 3mm. For example, they may extend outwardly from the flange portion by a distance in the range of 1.0 to 2.5mm. The inlet of the mouthpiece may be positioned in the front (e.g. in the central portion) of the mouthpiece, thus close to the mouth opening. This ensures even distribution of fluid to the at least two outlets in the left and right side of the mouth. Alternatively, the inlet may be positioned at the side of the mouth (e.g. off-centre, in one of the arms of the mouthpiece), so as not to interfere with the insertion of food, for example, into the mouth. This may make eating with the mouthpiece in place easier. The mouthpiece may be formed of two sheets that are bonded / fixed together, apart from in a region that defines the internal channel. At least one of the sheets may have at least two outlets (e.g. at least one hole formed toward the end of each elongate arm) formed therein (e.g. in the region that defines the internal channel). The sheets may be formed by punching / cutting out, e.g. mechanically or by water jet or laser, from a larger sheet of suitable material. Optionally, the at least two outlets may also be formed by punching / cutting them out from the sheets. The sheets may be formed by printing (e.g. 3D printing). The sheets may be formed by injection moulding, e.g. wherein liquid material (i.e. liquid silicone rubber) is injected into a cavity of a closed mould under (very) high pressure. The sheets may be formed by compression moulding, e.g. wherein a ‘shot’ (premeasured amount of uncured material) is placed in a cavity of an open mould, and the mould is then closed under hydraulic pressure. The heat and pressure applied during the moulding process cures the material in the desired shape of the mould. The sheets may be formed by transfer moulding, e.g. wherein material from a chamber / pot is placed under pressure, such that it transfers / flows into a cavity of a closed mould via a sprue, and heated to cure the material in the desired shape of the mould. Where the sheets have been (or will be) cut out, e.g. cut to shape, at least one of the sheets may have a groove formed therein such that when the sheets are bonded together the at least one groove provides the internal channel. In other words, at least one of the sheets may be shaped (before or after the cutting out of the sheet(s)) to provide a groove in the sheet. Thus, the groove formed in the sheet acts as / provides the internal channel in the assembled mouthpiece. Both / each sheet may be shaped / moulded with a groove therein. Accordingly, when the two sheets are bonded together, the grooves are aligned to provide / form the internal channel in the mouthpiece. The inlet of the mouthpiece may be formed by an end of a fluid supply tube, placed (e.g. held) between the two sheets prior to the two sheets being fixed / bonded together. Alternatively, the end of a fluid supply tube may be fixed inside the (already formed) inlet provided in the mouthpiece, e.g. by a bonding agent, such as a solvent welding agent or a glue / other adhesive, or it may be removably attached to the inlet e.g. by a screw thread. Alternatively, the mouthpiece may be integrally formed by printing (e.g. 3D printing) or by casting, injection moulding, compression moulding, or transfer moulding. In other words, the mouthpiece may be formed as a single unitary piece (as opposed to being formed from two thin sheets of material). In this case, the inlet may be formed by placing an end of a fluid supply tube within the mould for forming the mouthpiece. Alternatively, the end of a fluid supply tube may be fixed inside the (already formed) inlet provided in the mouthpiece, e.g. by a bonding agent, such as a solvent welding agent or a glue / other adhesive, or it may be removably attached to the inlet e.g. by a screw thread. The at least two outlets may have a diameter of between 0.3mm and 0.8mm, optionally around 0.5mm. According to a second aspect there is provided an assembly comprising a mouthpiece according to the first aspect, optionally including any of the optional features described above, the assembly further comprising a fluid supply tube fluidly connected to the inlet of the mouthpiece. The fluid supply tube may be reversibly or irreversibly connected to the inlet of the mouthpiece. However, preferably, the fluid supply tube is irreversibly connected to, e.g. permanently fixed to, and / or moulded together / integrally formed with, the inlet of the mouthpiece. The tube may have an outer diameter of between 1.0mm and 3.0 mm, and may have an outer diameter of about 2.6mm (and internal diameter of about 2.0mm). The mouthpiece may be provided as a single-use, i.e. disposable, item. The assembly comprising the mouthpiece and the fluid supply tube, optionally including a check valve, may be provided as a single-use, i.e. disposable, item. Typically, the mouthpiece or assembly may be suitable for use for up to 12 hours a day for 14 days. At the end of that time, it would generally be disposed of and replaced with a new mouthpiece or assembly. This will have the benefit that it will not be necessary to clean the mouthpiece to maintain good hygiene. The simple and thin design of the mouthpiece will make it cost-effective to manufacture, whereby single use is feasible for the user. Since the assembly may be disposable, it may not include a check valve and may therefore be sufficiently simple and cost-effective to manufacture. According to a third aspect there is provided a liquid distribution system comprising a mouthpiece according to the first aspect, optionally including any of the optional features described above, wherein the liquid distribution system comprises: a container for containing the liquid to be distributed to the user’s mouth; a fluid supply tube for fluid communication from the container to the mouthpiece; and a mechanism for conducting flow of the liquid from the container to the mouthpiece. The liquid distribution system may comprise a system as described in PCT / EP2023 / 054879 in combination with a mouthpiece according to the first aspect, optionally including any of the optional features described above. According to a fourth aspect there is provided a method of manufacturing a mouthpiece for distribution of a liquid in a user’s mouth, the mouthpiece being configured to be positioned within a superior vestibule of the user’s mouth apical to a gingival margin, the mouthpiece comprising: an inlet for a fluid supply tube, at least two fluid outlets, and an internal channel fluidly connecting the inlet to the fluid outlets; and a flange portion at least partially surrounding the channel for adhering to a user’s gum; wherein a thickness of the channel is greater than a thickness of the flange portion. The method may comprise: providing a first half of the mouthpiece as a first sheet; providing a second half of the mouthpiece as a second sheet. At least one of the sheets may have at least two outlets (e.g. at least one hole formed toward the end of each elongate arm) formed therein (e.g. in the region that defines the internal channel). The method may comprise forming these outlets in the at least one sheet. The method may comprise bonding / fixing the first sheet and second sheet together while keeping a region between the at least two holes unfixed, said region forming the internal channel. The sheets may be formed by punching / cutting out, e.g. mechanically or by water jet or laser, from a larger sheet of suitable material. Optionally, the at least two outlets may also be formed by punching / cutting them out from the sheets. Alternatively, the sheets may be formed by printing (e.g. 3D printing), or formed by injection moulding, compression moulding, or transfer moulding. The method may comprise forming the sheets by punching or cutting out, or 3D printing, or injection moulding, compression moulding, or transfer moulding. Where the sheets have been (or will be) cut out, e.g. cut to shape, at least one of, optionally both, sheets may have a groove formed therein such that when the sheets are bonded together the at least one groove provides the internal channel. In other words, at least one of, optionally both, sheets may be shaped (before or after the cutting out of the sheet(s)) to provide a groove in the sheet. Thus, the groove formed in the sheet acts as / provides the internal channel in the assembled mouthpiece. Both / each sheet may be shaped / moulded with a groove therein. Accordingly, when the two sheets are bonded together, the grooves are aligned to provide / form the internal channel in the mouthpiece. The method may comprise shaping / moulding at least one of the sheets to comprise a groove, optionally wherein the groove extends between the at least two holes. The inlet of the mouthpiece may be formed by an end of a fluid supply tube, placed (e.g. held) between the two sheets prior to the two sheets being fixed / bonded together. The method may comprise forming the inlet by placing an end of a fluid supply tube between the two sheets prior to the step of fixing (or bonding) the sheets together. Alternatively, the mouthpiece may be integrally formed by printing (e.g. 3D printing) or by casting, injection moulding, compression moulding, or transfer moulding. In other words, the mouthpiece may be formed as a single unitary piece (as opposed to being formed from two thin sheets of material). Therefore the method may comprise forming the mouthpiece by printing, optionally 3D printing, or by casting, injection moulding, compression moulding, or transfer moulding. In this case, the inlet may be formed by placing an end of a fluid supply tube within the mould for forming the mouthpiece. Alternatively, the end of a fluid supply tube may be fixed inside the (already formed) inlet provided in the mouthpiece, e.g. by a bonding agent, such as a solvent welding agent or a glue / other adhesive. According to a fifth aspect there is provided a method of distributing liquid in a user’s mouth, comprising placing a mouthpiece within a superior vestibule of the user’s mouth apical to a gingival margin, wherein the mouthpiece comprises: an inlet configured to receive a fluid supply, at least two fluid outlets, and an internal channel fluidly connecting the inlet to the fluid outlets; and a flange portion at least partially surrounding the channel for adhering to a user’s gum; wherein a thickness of the channel is greater than a thickness of the flange portion, the method comprising: supplying liquid from a container through a fluid supply tube and into the inlet of the mouthpiece, through the internal channel, and through the outlets. The mouthpiece may be used to alleviate xerostomia by being inserted into the mouth of a person suffering from xerostomia and injecting a liquid through said mouthpiece via the inlet. The liquid may for example comprise water, saliva substitutes, or aqueous solutions comprising pharmaceuticals etc. The saliva substitutes may be e.g. synthetic saliva, and the pharmaceuticals may be e.g. saliva stimulants. BRIEF DESCRIPTION OF THE DRAWINGS Various embodiments will now be described, by way of example only, and with reference to the accompanying drawings in which: Fig. 1 shows a schematic view of a liquid distribution system comprising a mouthpiece; Fig. 2 shows a perspective view of the mouthpiece of Figure 1; Fig. 3 shows a cross-sectional side view of an arm of the mouthpiece of Figure 1; and Fig. 4 shows a cross-sectional front view of the mouthpiece of Figure 1. DETAILED DESCRIPTION Figure 1 shows a schematic view of a liquid distribution system 1 comprising a mouthpiece 10 for distributing liquid in a user’s mouth. The system 1 comprises a source of fluid 2, in the form of a fluid reservoir or container, and a tube 3 which fluidly connects the mouthpiece 10 with the fluid container 2 so that, in use, fluid may flow from the fluid container 2 to the mouthpiece 10. The system 1 also comprises a means 4 for conducting the flow of fluid from the container 2 to the mouthpiece 10 through the tube 3 (e.g. a peristaltic pump, such as that described in PCT / EP2023 / 054879). In the described example, the tube 3 comprises a first tube section 3a and a second tube section 3b. A first end of the first tube section 3a is connected to the mouthpiece 10, and a second end of the first tube section 3a is joined to a first end of the second tube section 3b by a connector 5. The connector 5 may be a simple connector, or may be a check valve configured to inhibit liquid from the mouthpiece 10 flowing back into the second tube section 3b and / or the container 2. The second tube section 3b passes through the means 4 in such a way that the means 4 is able to act upon the fluid in the tube 3b (e.g. in the case of a peristaltic pump, the tube 3b is brought into contact with a roller assembly of the peristaltic pump). Accordingly, the second tube section 3b comprises tubing that is thicker than the tubing of the first tube section 3a. A second (e.g. the other) end of the second tube section 3b is connected to the container 2. The container end of the tube 3 (e.g. the end of the second tube section 3b connected to the container 2) is secured in a seal in a screw top for the container 2. Thus the tube 3 is configured to be easily attachable to and detachable from the container 2. The container 2 may comprise any suitable fluid that it is desired to be administered and distributed within the user’s mouth, e.g. water, saliva substitutes, pharmaceuticals, etc. The mouthpiece end of the tube 3 (e.g. the end of the first tube section 3a connected to the mouthpiece 10) is irreversibly connected to an inlet 12 (e.g. port) of the mouthpiece 10. For example, the mouthpiece end of the tube 3 may be integrally formed with the inlet 12. Alternatively, the end of the tube 3 may be reversibly connected to the inlet 12 (e.g. the inlet 12 and the end of the tube 3 each comprise a screw connector that can be connected to each other). The mouthpiece 10 and the tube 3 together form an assembly which may be provided as a single-use, i.e. disposable, unit. Typically, the mouthpiece 10 and / or assembly may be suitable for use for up to 12 hours a day for 14 days. At the end of that time, it would generally be disposed of and replaced with a new mouthpiece 10 and / or assembly. This will have the benefit that it will not be necessary to clean the mouthpiece 10 to preserve good hygiene. The mouthpiece 10, as shown in Figures 1 and 2, is thin and flexible and shaped to fit within a superior vestibule of a user’s mouth, apical to a gingival margin. The mouthpiece 10 can generally be defined as comprising a central region 18 and two elongate arms 20, one on each side of the central region 18. When in use, the elongate arms 20 extend around the curvature of the user’s mouth, helping secure the mouthpiece in place in the user’s mouth (e.g. the elongate arms 20 may act as a pair of (flexible) wings for adapting to the shape of the user’s mouth). The thin mouthpiece 10 comprises a (single) internal fluid channel 14 and a flange portion 16. As shown in Figures 1, 2 and 4, the flange portion 16 of the mouthpiece 10 substantially surrounds the internal fluid channel 14 when viewed from the front (or back), except for where the inlet 12 is adjacent the channel, and extends above and below the internal fluid channel 14 in a side (cross-sectional) view. The flange portion 16 is adapted to provide a flat (e.g. thin) projecting edge / surface. This (increased) contact surface / area provided by the flange portion 16 facilitates the fixing (e.g. sticking) of the mouthpiece 10 to the user’s gum, holding the mouthpiece 10 in place during use. The internal fluid channel 14, which is for conveying fluid to the user’s mouth, extends from the port / inlet 12 (through which fluid enters the channel 14 and which is positioned in the central region 18 of the mouthpiece 10) and branches along both elongate arms 20, with each branch terminating at a corresponding outlet 22 positioned at a respective longitudinal end of the elongate arm 20. In one example, the outlets 22 have a diameter of around 0.5mm. As shown in Figure 4, the inlet 12 is at the lower side of the central region 18, which allows a tube 3 connected to the inlet 12 to be passed through / out of a user’s mouth in a comfortable manner. In one example, the inlet 12 has an internal diameter of around 2.0mm (and an external diameter of around 2.6mm). The internal channel 14 conveys the fluid from the inlet 12 to the outlets 22. Each outlet 22 is arranged in the mouthpiece 10 such that, in use, each outlet 22 is complementary to an opening of a parotid duct. The parotid ducts are where the saliva produced by the parotid glands enters the mouth, so these positions of the outlets are therefore the most natural regions of the mouth to inject liquid such as water or saliva substitutes. The central region 18 has an upper edge shaped to accommodate a labial frenulum of the user. In particular, two convex curved portions 26 (which may be considered as “flaps”) can fit either side of the labial frenulum, whilst a central concave portion 28 between the convex portions 26 is provided wherein the labial frenulum may fit. This shape enables the mouthpiece 10 to fit comfortably in the user’s mouth without slipping out of position. Furthermore, it enables the mouthpiece 10 to be positioned at the highest point within the superior vestibule without being displaced downwardly by the labial frenulum. By adapting the mouthpiece 10 to fit at the highest point in the superior vestibule, the mouthpiece 10 is positioned outside of the oral cavity proper and will not be in contact with the teeth, therefore not interfering with chewing, eating or talking. This enables the mouthpiece 10 to be worn for long periods of time. As shown in the cross-sectional side view of Figure 3, the mouthpiece 10 has a substantially elongate cross-section (e.g. a (total) height of the mouthpiece 10 is larger than a (maximum) thickness of the mouthpiece 10). The internal channel 14 has a substantially circular cross-section, and the flange portion 16 extends above and below the channel 14 to provide the surface / area for contact with the user’s gum. As also can be seen in Figure 3, the thickness of the mouthpiece 10 at the channel 14 is greater than a thickness of the mouthpiece 10 at the flange portion 16 (e.g. the thickness of the channel 14 is greater than the thickness of the flange portion 16). In other words, the channel 14 protrudes slightly from the surrounding material (of the mouthpiece 10 in the front to back direction). As such, the internal channel 14 (having a substantially circular cross-section) provides a resilient structure, and it may therefore act as a spine / support for the mouthpiece 10. Accordingly, the described arrangement provides useful structural stiffness which enables the mouthpiece 10 to hold its shape and make it easy to insert, whilst being sufficiently flexible to fit easily and comfortably in the user’s mouth (e.g. an additional structural support such as a wire or rib is not required). The large diameter of the internal channel 14 relative to the thickness of the mouthpiece 10 and / or the flange portion 16 enables sufficient fluid flow without the mouthpiece 10 being too bulky and bothersome. For instance, the approx, average flow for unstimulated saliva is 0.3-0.4ml / min, and the flow rate when sleeping is about 0.1ml / min. However, when a person is stimulated e.g. eating food / chewing gum, the saliva from a healthy person may rise to 4.0-5.0ml / min. Thus the mouthpiece 10 is adapted to allow fluid flow of up to 4.0-5.0ml / min. The internal diameter of the internal channel 14 is around 1mm +1- 0.1mm, resulting in a thickness of the mouthpiece (i.e. the dimension from front to back) where the channel is present of around 1.2mm (+0.2mm / -0.6mm). The flange portion 16 may have a thickness of around 0.6mm +1- 0.1mm. As discussed above, the material of the mouthpiece 10 that surrounds the channel 14 when viewed from the front (the flange portion 16) provides a large surface area for adhering to the user’s gum (whilst also providing additional support to the internal channel 14). However, the height of the flange portion 16 should not be made too large as this can result in the mouthpiece 10 being too flimsy (e.g. it folds / does not hold its shape, making it more difficult for it to be inserted into the user’s mouth), as well as the mouthpiece 10 not being able to fit above, and not interfere with, the user’s teeth. Accordingly, in order to achieve this balance, the present inventors have identified that the desired characteristics of the mouthpiece 10 can be achieved by carefully controlling the height of the flange portion 16 (above and below the internal channel 14) relative to the diameter of the internal channel 14. In one example, the height of the flange 16 in the elongate arms 20 is between 1.0 and 3.5 times greater than the diameter of the channel 14, and optionally between 1.5 and 2.5 times greater. The height of the flange 16 in the elongate arms 20 may be between 1,5mm and 3.5mm, and preferably between 2.0mm and 3.0mm. In the specific example shown in Figure 4, the majority of the height of the elongate arms 20 (i.e. the total height of the upper part of the flange portion 16 and the lower part of the flange portion and the internal diameter of the internal channel 14, as shown in Figure 4) is around 6mm: the upper part of the flange portion 16 and the lower part of the flange portion 16 on either side of the channel 14 each have a height of around 2.5mm, and the channel 14 has a height (diameter) of around 1.0mm. The height of the central region 18 is variable and larger than 6mm due to the curved convex portions 26 and the port 12. As shown, the total height of the mouthpiece 10 at the location of the inlet 12 is around 11.3mm. The thickness of the mouthpiece 10 at the location of the inlet 12 is around 2.6mm which is larger than the rest of the thickness of the mouthpiece 10, due to the internal diameter of the inlet 12 (which is around 2.0mm). A method of manufacturing a (thin) mouthpiece 10 as described above is also provided, and described in further detail below. The method of manufacturing the mouthpiece 10 may comprise providing a first half of the mouthpiece 10 as a first sheet and providing a second half of the mouthpiece as a second sheet. The first and second sheet may be made out of any suitable material that is produced from high consistency rubber (e.g. a silicone material) and has the necessary properties to meet the requirements for food contact, health and medical usage (e.g., RoHS, REACH, FDA, ISO 13485, etc.). A suitable material, for example, is EI_ASTOSIL® R401 High Consistency Silicone Rubber. At least one of the first half / sheet and the second half / sheet has at least two holes formed through it, which form the outlets 22. The sheets may be formed by punching or cutting them out from a (larger) sheet of material. The punching or cutting could be performed mechanically, or performed by a waterjet or laser cutting. The at least two holes / outlets 22 may also be formed by punching or cutting them out from the first half and / or the second half of the mouthpiece. Alternatively, the sheets may be printed, e.g. formed by 3D printing (although the person skilled in the art would recognise that the sheets are essentially 2D given the small relative thickness), or formed by injection moulding, compression moulding, or transfer moulding. The method may comprise fixing the two sheets / halves together, while keeping a region extending between the at least two holes unfixed, with said region forming the internal channel. To fix the two sheets together, any suitable bonding agent could be used, such as a platinum crosslinking agent, a solvent welding agent or glue / other adhesive. Where the method comprises punching or cutting the sheets, the method may comprise shaping at least one of the sheets to form a groove therein. The sheets may be shaped before or after the sheets are cut out. The groove(s) provided in the first sheet / half and / or the second sheet / half thus form the internal channel 14 in the (finished) mouthpiece (when the two sheets are fixed together). The method may comprise placing an end of a fluid supply tube (e.g. an end of first tube section 3a) between the two sheets before fixing the two sheets together, e.g. in order to (irreversibly) secure the tube 3a to the mouthpiece 10. In an alternative embodiment, the mouthpiece 10 may be integrally formed by printing (e.g. 3D printing) or by casting, injection moulding, compression moulding or transfer moulding. In other words, the mouthpiece 10 may be formed as a single unitary piece (as opposed to being formed from two thin sheets of material fixed together). In this case, the inlet 12 may be formed by placing an end of the fluid supply tube 3a within the mould for forming the mouthpiece. Alternatively, the end of the fluid supply tube 3a may be fixed inside the inlet 12 provided in the (already formed) mouthpiece, e.g. by a bonding agent (such as a solvent welding agent or a suitable glue / adhesive). A method of distributing liquid in a user’s mouth may comprise using a mouthpiece 10 as described above. Accordingly, the method may comprise placing a mouthpiece 10 within a superior vestibule of the user’s mouth apical to a gingival margin, wherein the mouthpiece 10 comprises: an inlet 12 for a fluid supply tube 3, at least two fluid outlets 22, and an internal channel 14 fluidly connecting the inlet 12 to the fluid outlets 22; and a flange portion 16 at least partially surrounding the channel 14 for adhering to a user’s gum; wherein a thickness of the channel 14 is greater than a thickness of the flange portion 16. The method may comprise supplying liquid from a container 2 through at least one tube 3, 3a, 3b and into the inlet 12 of the mouthpiece 10 (e.g. via the action of the pumping mechanism 4), through the internal channel 14, and through the outlets 22. The method may comprise wetting the flange portion 16 and / or the outer surface of the channel 14 (which may or may not comprise an adhesive layer) prior to placing the mouthpiece 10 within a superior vestibule of the user’s mouth apical to a gingival margin. The described mouthpiece arrangement has an internal channel that provides the mouthpiece with structural stiffness / rigidity, and a flange that provides an increased surface area (to help ‘stick’ the mouthpiece in place). The described arrangement uses less material compared to known mouthpieces, making it compact and light. This allows the mouthpiece to be more easily positioned and more comfortable for the user. Furthermore, because the mouthpiece is thickest across the channel portion, this enables sufficient fluid flow without the mouthpiece as a whole being too bulky and bothersome. Although the present invention has been described with reference to particular embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the scope of the invention as set forth in the accompanying claims.

Claims

1. A mouthpiece (10) for distribution of a liquid in a user’s mouth, the mouthpiece (10) being configured to be positioned within a superior vestibule of the user’s mouth apical to a gingival margin, the mouthpiece (10) comprising:an inlet (12) configured to receive a fluid supply, at least two fluid outlets (22), and an internal channel (14) fluidly connecting the inlet (12) to the fluid outlets (22); anda flange portion (16) at least partially surrounding the channel (14) for adhering to a user’s gum;wherein a thickness of the channel (14) is greater than a thickness of the flange portion (16).

2. The mouthpiece (10) according to claim 1, wherein the internal channel (14) has a substantially circular cross-section.

3. The mouthpiece (10) according to any preceding claim, wherein the thickness of the channel (14) is between 1.0 and 3.5 times greater than the thickness of the flange portion (16).

4. The mouthpiece (10) according to any preceding claim, wherein the flange portion (16) has a thickness of less than 1.0mm, optionally less than 0.8mm.

5. The mouthpiece (10) according to any preceding claim, wherein the mouthpiece comprises a central region (18) and two elongate arms (20), one on each side of the central region (18); andwherein a height of the flange portion (16) in the elongate arms (20) is between 1.0 and 3.5 times greater than a height of the channel (14), optionally between 1.5 and 2.5 times greater.

6. The mouthpiece (10) according to any preceding claim, wherein a height of the flange portion (16) in the elongate arms (20) of the mouthpiece is between 1.5mm and 3.5mm, optionally between 2.0mm and 3.0mm.

7. The mouthpiece (10) according to any preceding claim, wherein the mouthpiece is formed of two sheets that are bonded together, apart from in a region that defines the internal channel, optionally wherein at least one of the sheets has at least two holes formed therein.

8. The mouthpiece (10) according to claim 7, wherein at least one of the sheets is formed to comprise a groove within the sheet such that, when the sheets are bonded together, the at least one groove forms the internal channel (14).

9. The mouthpiece (10) according to claim 7 or claim 8, wherein the inlet (12) is formed by placing an end of a fluid supply tube (3) between the two sheets before fixing the two sheets together.

10. An assembly comprising a mouthpiece according to any preceding claim, further comprising a fluid supply tube (3) fluidly connected to the inlet (12) of the mouthpiece (10).

11. A liquid distribution system (1) comprising a mouthpiece (10) according to any one of claims 1 to 9, wherein the liquid distribution system comprises:a container (2) for containing the liquid to be distributed to the user’s mouth;a fluid supply tube (3) for fluid communication from the container (2) to the mouthpiece (10); anda mechanism (4) for conducting flow of the liquid from the container (2) to the mouthpiece (10).

12. A method of manufacturing a mouthpiece (10) for distribution of a liquid in a user’s mouth, the mouthpiece (10) being configured to be positioned within a superior vestibule of the user’s mouth apical to a gingival margin, the mouthpiece (10) comprising: an inlet (12) configured to receive a fluid supply, at least two fluid outlets (22), and an internal channel (14) fluidly connecting the inlet (12) to the fluid outlets (22); and a flange portion (16) at least partially surrounding the channel (14) for adhering to a user’s gum; wherein a thickness of the channel (14) is greater than a thickness of the flange portion (16);the method comprising:providing a first half of the mouthpiece (10) as a first sheet;providing a second half of the mouthpiece (10) as a second sheet, wherein at least one of the first half and the second half comprises at least two holes; andfixing the first and second sheets together while keeping a region between the at least two holes unfixed to create the internal channel.

13. The method according to claim 12, wherein:providing a first half of the mouthpiece as a first sheet comprises pre-forming the first sheet to create a groove in the first half of the mouthpiece; and / orwherein providing a second half of the mouthpiece as a second sheet comprises pre-forming the second sheet to create a groove in the second half of the mouthpiece.

14. The method according to claim 12 or claim 13, comprising placing a fluid supply tube (3) between the two sheets before fixing the two sheets together to form the inlet (12) of the mouthpiece (10).

15. A method of distributing liquid in a user’s mouth, comprising placing a mouthpiece within a superior vestibule of the user’s mouth apical to a gingival margin, wherein the mouthpiece comprises: an inlet (12) configured to receive a fluid supply, at least two fluid outlets (22), and an internal channel (14) fluidly connecting the inlet (12) to the fluid outlets(22); and a flange portion (16) at least partially surrounding the channel (14) for adhering to a user’s gum; wherein a thickness of the channel (14) is greater than a thickness of the flange portion (16), the method comprising:supplying liquid from a container (2) through a fluid supply tube (3) and into an inlet 5 (12) of the mouthpiece (10), through the internal channel (14), and through the outlets (22).s

Images