METHOD FOR MANUFACTURING A PRESSURE CHAMBER OF A DENTAL GUARD, METHOD FOR MANUFACTURING A DENTAL GUARD, PRESSURE CHAMBER AND GUARD MANUFACTURED BY THESE METHODS, PROVIDED BY THESE METHODS, J / U-SHAPED DENTAL GUARD, AND SYSTEMS COMPRISING SAID GUARDS.

Abstract

The present invention relates to the manufacture of a bristle pad for a mouthpiece toothbrush, a bristle pad, the manufacture of a mouthpiece toothbrush with such a bristle pad, and a mouthpiece toothbrush. The bristle pad is manufactured from a prefabricated sheet and prefabricated bristles. The prefabricated bristles are attached to the flexible prefabricated sheet, which is at most 700 µm thick, by fusing the fixed ends of the bristles to the sheet. In the method of manufacturing the mouthpiece, the bristle pad is attached to the body of the mouthpiece. (Figure 10a).

Description

The invention relates to the field of dental cleaning devices having a mouthpiece for simultaneously brushing a plurality of tooth positions, in particular to dental cleaning devices where the mouthpiece is of the type comprising a body having a cavity and at least one bristle carrier covered with bristles, where the cavity has a longitudinal direction in the shape of a J or a U and a cross-section in the shape of a U transverse to the longitudinal direction and configured to encompass a dental arch of multiple tooth positions, and where the at least one bristle carrier delimits the cavity.Such a dental cleaning device is used to simultaneously clean multiple teeth and / or tooth positions, preferably all, (in case one or more teeth may be missing) of a dental arch or both dental arches in case the body has two such cavities having the longitudinal directions in a J or U shape of both cavities that extend parallel and having the cross sections in a U shape of both cavities open in mutually opposite directions. BACKGROUND OF THE INVENTION Cleaning the teeth of humans and animals is a prerequisite for oral health and the health of internal organs. Various dental cleaning devices are available, such as manual and electric toothbrushes. With these typical toothbrushes, it is advised to brush teeth using a prescribed method for at least two minutes per day to effectively remove plaque. However, the average person does not spend the prescribed amount of time cleaning their teeth and does not always brush according to an effective method. Furthermore, for people with disabilities, the elderly, or children, brushing teeth with a toothbrush can be difficult, as typical toothbrushes require precise placement of the bristles on various tooth surfaces. In the event that teeth are missing in some or all of the dental positions, as is often the case with older people, cleaning the gums in these dental positions remains a prerequisite for oral health and the health of internal organs. It is necessary to automatically brush the teeth and / or gums in the designated positions to clean them effectively, thus reducing the time and effort required for thorough brushing. Furthermore, it is necessary to avoid carefully maneuvering the brush. Dental cleaning devices are known to comprise mouthpieces that cover the maxillary and / or mandibular dental arch. These mouthpieces may be of the type comprising a body provided with at least one cavity bounded by a cavity wall covered with a plurality of bristles extending from the cavity wall into the cavity. The cavity wall defines a U-shaped longitudinal axis and, from a view transverse to the longitudinal axis, a U-shaped cross-sectional shape. The mouthpiece is configured to encompass a plurality of tooth positions along a dental arch. The tooth positions, such as the teeth and / or gums, to be brushed are inserted into the at least one cavity, and the bristle-covered cavity wall is operated to brush the teeth and / or gums with the bristles against the cavity wall.Depending on the length of the cavity, several or all of the teeth in the maxillary and / or mandibular dental arches can be brushed simultaneously. An example of such a mouthpiece can be found in WO-2018 / 199760. Part of such a mouthpiece is the bristle-lined cavity wall. This cavity is U-shaped lengthwise and has a U-shaped cross-section perpendicular to this direction, with the bristles located on the inner side of the cavity. The small internal space of the U-shaped cross-section and its arc-shaped length make the fabrication of such a bristle-lined cavity wall quite difficult. Of course, such a bristle-lined cavity wall can be made manually by attaching the bristles or tufts of bristles one by one to the cavity wall. However, this is labor-intensive and not efficient in terms of time and cost.Such a cavity wall with a U-shaped cross-section and bristles on the inner side of the cavity can also be made by injection molding the cavity wall and bristles simultaneously, but, due to the small internal width of the U-shape, it is not possible or very difficult to deal with the discharge of the molded cavity wall and bristles from the mold without damaging the molded product. Other problems with such mouthpieces of the type according to WO-2018 / 199760 or according to other designs such as, for example, those shown in WO-2009 / 150559, US8,359,692, US-4,224,710, are among others: Because the mouthpiece must be fully inserted into the mouth, its dimensions must be small to avoid discomfort during use and gag reflex. Maintaining small dimensions is more challenging when a motor is to be incorporated into the mouthpiece to power the bristles' cleaning motion. The mouthpiece must fit snugly around the teeth. All of this means that it is important to keep the bristle connection (i.e., where the bristles join the rest of the mouthpiece) as small as possible. onna Ln / zznz / e / Ywi On the other hand, to prevent the bristles from separating from the mouthpiece (and the user from swallowing them), it is important that the bristles maintain a certain retention force. 15-20 Newtons per tuft is currently a common standard for retention force. This retention force is at odds with keeping the bristle connection as small as possible. The requirements used for bristle material often differ from those used for the rest of the mouthpiece, resulting in difficulties in attaching the bristles to the rest of the mouthpiece. - The bristle lining inside the cavity must be able to follow the U-shaped dental arch, as well as the much smaller U-shaped cross-section of the cavity. Therefore, there is a need for a method to manufacture a mouthpiece for simultaneously brushing a plurality of tooth positions, wherein the mouthpiece is of the type comprising a body having a cavity lined with bristles, said cavity having a longitudinal direction in the shape of a J or a U and a cross-section in the shape of a U transverse to the longitudinal direction and configured to encompass a dental arch of multiple tooth positions, and wherein at least one bristle carrier delimits the cavity. BRIEF DESCRIPTION OF THE INVENTION It is an objective of the invention to provide an alternative method for manufacturing a mouthpiece for simultaneously brushing a plurality of tooth positions, wherein the mouthpiece is of the type comprising a body having a cavity lined with bristles, said cavity having a longitudinal direction in the form of a J or a U and a cross-section at least partially U-shaped transverse to the longitudinal direction and configured to encompass a dental arch of multiple tooth positions, and wherein at least one bristle carrier delimits the cavity. Another objective of the invention is to provide a method that overcomes one or more of the above problems associated with the manufacture of such mouthpieces. According to a first aspect of the invention, one or more of the above objects are achieved by providing a method of manufacturing a mouthpiece for simultaneously brushing a plurality of tooth positions, the mouthpiece being of the type comprising a body defining a cavity that is covered with bristles and has a longitudinal direction in the shape of a J or a U and a cross-section at least partially in the shape of an L transverse to the longitudinal direction (the cross-section may be partially U-shaped, because, for example, in incisors, the lower part of the U-shape may be open or V-shaped); wherein the method comprises a pad manufacturing step in which at least one pad with bristles is manufactured; the pad comprises a flexible sheet, such as a plastic sheet, and bristles, such as plastic bristles, projecting from a front surface of the sheet; the sheet has a rear surface opposite the front surface; and the pad manufacturing step comprises: - provide bristles with one fixed end and one free end, provide a prefabricated sheet with a thickness of 700 pm at most, and - fuse the fixed ends of the bristles with the prefabricated sheet, which would cause the pad to be made with bristles; wherein the method further comprises a body-making step in which a mouthpiece body to be manufactured is provided; the body-making step comprises providing a body with a cavity and at least one bristle carrier; the cavity has a longitudinal direction in the form of a J or a U and a cross-section at least partially in the form of a U transverse to the longitudinal direction and is configured to encompass a dental arch of multiple tooth positions; the at least one bristle carrier delimits the cavity; and wherein the method further comprises a pad-attachment step in which, during or after the body-making step, one or more bristle pads obtained in the pad-making step are attached to the at least one bristle carrier to cover the bristle carrier;The side of the posterior surface of the sheet faces the bristle carrier, and the side of the front surface of the sheet faces away from the bristle carrier, into the cavity. The method according to the invention basically comprises three main steps. Each main step may comprise further sub-steps, some of which will be discussed later. The main stages are the manufacture of a pad with bristles, referred to as the “pad manufacturing stage,” a body manufacturing stage in which the body is provided, and a pad attachment stage in which the pad with bristles is attached to the body. According to a further embodiment of the invention, the prefabricated sheet can be manufactured in the pad manufacturing stage, such as approximately simultaneously with the fusion of the bristles to the prefabricated sheet. This can be done, for example, by extruding or injection molding the sheet onto the fixed ends of the bristles, making use of the sheet while it is still hot, which allows it to fuse with the fixed ends of the bristles. According to a further alternative or complementary embodiment of the invention, the body can be manufactured in the manufacturing stage. The bristle pad may have already been manufactured before the body manufacturing stage. The bristle pad can be attached to the body after the body manufacturing stage. If the body is manufactured during the body manufacturing stage, the bristle pad can also be attached to the body during the body manufacturing stage. The bristle portion can, for example, be adhered to the bristle carrier with an adhesive. Attaching the bristle pad to the body during the body manufacturing stage, according to a specific embodiment of the invention, can considerably facilitate the integration of the pad as an integral part of the body. An example of attaching the bristle pad during the body manufacturing stage is integrating the pad into the body during the injection molding of the body or a body part.The pad can be a prefabricated insert and can be placed in the mold before the injection molding material is injected to form (at least part of) the body, so that after the injection molding material hardens, the pad is integrated with or within the injection molding material. The bristle pad can also be manufactured during, such as simultaneously with, or after the body forming stage. When the bristle pad is manufactured after the body forming stage, the pad assembly stage will also take place after the body forming stage. In this case, the pad assembly stage can be a stage in which two prefabricated parts (the bristle pad and the body or part of the body) are joined together.As will be clear to the expert, it is also conceivable that the pad coupling stage is a stage in which two prefabricated pieces are assembled if the bristle piece is manufactured before or during the manufacture of the body. According to the invention, the pad is a bristle pad consisting of a sheet and bristles projecting from a front surface of the sheet. The back surface of the sheet, opposite the front surface, is essentially flat. In fact, according to a further embodiment of the invention, the pad is manufactured by assembling only two components: a prefabricated sheet and prefabricated bristles, such as tufts of bristles / fibers. The sheet is folded, i.e., bent, so that it can easily follow the curvatures of the cavity, the curvature due to the longitudinal J- or U-shaped direction of the cavity and / or the curvature due to the U-shaped cross-section of the cavity, and therefore has a thickness of at most 700 µm. This thickness also does not use much space in the mouthpiece.Furthermore, the fixed ends of the bristles—that is, the ends opposite the free bristle ends that project into the cavity of the mouthpiece to be fabricated—are fused to the foil. In other words, they are joined to the foil by fusing the fixed ends of the bristles and the foil. This results in a bristle pad made from the assembly of a foil and bristles. Due to the fusion connection, the bond between the bristles and the foil is strong. Because of the foil's flexibility, it is easy to fit the pad into the cavity, and the back surface of the foil conforms to the shape of the surface of the bristle carrier to which it is attached. Due to the foil's small thickness, a significant increase in the mouthpiece's dimensions is avoided. onna Ln / zznz / e / γΐΛΐ According to a further embodiment of the first aspect of the invention, the thickness of the prefabricated sheet is at most 400 µm, or at most 250 µm, or at most 150 µm. According to another further embodiment of the first aspect of the invention, the prefabricated sheet has a thickness of at least 50 µm to ensure that the sheet is sufficiently strong. Considering currently available fusion techniques, it appears that the prefabricated sheet can have a thickness in the range of 50–250 µm, or in the range of 50–150 µm, while still providing sufficient holding strength to prevent, on the one hand, the bristles from separating from the sheet and, on the other hand, the bristle-bearing portions of the sheet from separating from the rest of the sheet due to local tearing or breakage of the sheet. When the bristles are fused to (oa) the prefabricated sheet, the thickness of the sheet may increase because the fusion originates from the fixed ends of the bristles. Bearing this in mind, the invention may be further or alternatively defined in terms of the thickness of the bristle pad sheet, i.e., the sheet after fusion with the bristles: • Therefore, according to a further embodiment of the first aspect of the invention, the bristle sheet can be further defined as having a thickness of at most 1.5 mm, such as 1 mm at most or 750 µm at most. This thickness of the bristle sheet is the thickness of the sheet in the resulting pad, excluding the length of the bristles. In other words, the bristles themselves are not part of the thickness. • Therefore, according to an alternative to claim 1, the first aspect of the invention can be defined as “Method of manufacturing a mouthpiece for simultaneously brushing a plurality of tooth positions, the mouthpiece being of the type comprising a body defining a cavity that is covered with bristles and has a longitudinal direction in the shape of a J or a U and a cross-section at least partially in the shape of a U transverse to the longitudinal direction; wherein the method comprises a pad manufacturing step in which at least one pad with bristles is manufactured; the pad consists of a flexible plastic sheet and plastic bristles projecting from a front surface of the sheet; the sheet has a back surface opposite the front surface; and the pad manufacturing step comprises - provide bristles with one fixed end and one free end, - provide a prefabricated sheet, and - fuse the fixed ends of the bristles with the prefabricated foil, resulting in a bristle pad with a foil that is at least 1.5 mm thick, such as at least 1 mm or at least 750 pm; wherein the method further comprises a body-making step in which a mouthpiece body to be manufactured is provided; the body-making step comprises providing a body with a cavity and at least one bristle carrier; the cavity having a longitudinal direction in the form of a J or a U and a cross-section at least partially in the form of a U transverse to the longitudinal direction and configured to encompass a dental arch of multiple tooth positions; the at least one bristle carrier delimits the cavity; and wherein the method further comprises a pad-attachment step in which, during or after the body-making step, one or more bristle pads are attached to the at least one bristle carrier to cover the bristle carrier;The side of the posterior surface of the sheet faces the bristle carrier, and the side of the front surface of the sheet faces away from the bristle carrier, into the cavity.”; The values ​​of the thickness of the prefabricated sheet as mentioned in claim 14 may, apart from the other features of claims 1-4, be additional embodiments of this alternative for claim 1. According to another embodiment of the first aspect of the invention, the flexible sheet of the bristle pad has a bending strength of less than 2 Newtons, such as less than 1.3 Newtons or less than 0.5 Newtons. Bending strength is defined as the force F required to bend a strip of sheet having a width W of 10 mm and a length L of 20 mm over a distance Q of 10 mm. The force F is directed in the opposite direction to the orientation of the free ends of the bristles. Consequently, due to this low bending strength, the sheet will easily conform to the surface of the bristle carrier to which it is attached. This facilitates not only the pad attachment stage but also the adaptation of the sheet to the shape of the user's teeth. According to another further embodiment of the first aspect of the invention, wherein the mouthpiece to be manufactured has two of said cavities, the longitudinal directions of both cavities being J-shaped or U-shaped and extending in parallel, and the cross-sections of both cavities being U-shaped and opening in mutually opposite directions, the body-making step comprises providing a body with two of said cavities, the longitudinal directions of both cavities being J-shaped or U-shaped and extending in parallel, and the cross-sections of both cavities being U-shaped and opening in mutually opposite directions, each of said cavities having at least one bristle carrier delimiting the respective cavity; and the pad-coupling step comprises coupling one or more of said pads to the at least one bristle carrier of each of said cavities.A mouthpiece with two such cavities allows simultaneous cleaning of the dental positions (with or without teeth) of the maxillary dental arch and the mandibular dental arch. The bristles, according to the first aspect of the invention, may be made of materials frequently used for toothbrush bristles due to their stiffness, flexural strength, chemical resistance, and abrasion resistance. These materials, which according to the invention may be used for bristles, include the following plastics: polyamide (PA), such as all types of nylon, including PA6, PA66, PA610, PA612, PA11, and PA12; polyethylene terephthalate (PBT); polypropylene (PP); polyester (PE); polystyrene (and styrene copolymers) (PS); polyurethane (PU), including TPU; polyvinylidene chloride (PVC); and TPE. According to a specific embodiment of the first aspect of the invention, the bristles comprise fibers of polybutylene terephthalate (PBT) or polyamide (PA), such as nylon fibers. Bristles made of these materials have properties that provide effective cleaning action when brushing teeth.The bristles are rigid (they have a relatively large resistance to bending), which contributes to the scraping action of the free ends of the bristles. According to another further embodiment of the invention, the bristles comprise fibers of a first material, and the front surface side of the sheet, also called the bristle side of the sheet, comprises a second material fusible with the first material. The second material, according to a further embodiment of the first aspect of the invention, may be similar to, but not necessarily identical to, the first material. The second material, according to a further embodiment, may be polybutylene terephthalate (PBT) or polyamide (PA), such as nylon. As an example of the first material being similar to, but not identical to, the second material, nylon may be mentioned as the first material for the bristles and polyamide for the second material of at least the front surface of the sheet. The sheet may be made of one material or multiple materials.The sheet may comprise, for example, two or three layers of different materials. According to another embodiment of the first aspect of the invention, the pad sheet is fused to the bristle carrier during the pad coupling stage. The bristle carrier and the pad, more precisely the pad sheet, then become an integral part, further enhancing the retention force that prevents the bristles from separating from the body. According to another embodiment of the first aspect of the invention, the bristle carrier is made of a third material that is not fusible with the bristles and / or the front surface of the sheet, wherein the sheet comprises a first outer layer of a material that is fusible with the bristles and a second outer layer of a fourth material that is fusible with the third material. In the embodiment where the bristles are made of a first material and the front surface of the sheet, also called the bristle-bearing side of the sheet, comprises a second material that is fusible with the first material, this means that the bristle carrier is made of a third material that is not fusible with the first and / or second material, and that the sheet comprises a first outer layer of the second material and a second outer layer of a fourth material that is fusible with the third material.In these additional embodiments, the foil is multilayered, with the first outer layer on the front surface and the second outer layer on the back. The first and second outer layers may be bonded directly to each other, or one or more intermediate layers may be provided between them. The foil, with the first outer layer configured to be fusible with the bristles and the second outer layer configured to be fusible with the bristle carrier, enables the bristles to be coupled to the carrier by fusing the materials together. This is particularly relevant when the bristles and carrier are made of materials that do not fuse together or, when fused together, do not provide a reliable coupling. The fourth material, according to a further embodiment of the first aspect of the invention, may be similar, but not necessarily identical, to the third material. According to another additional embodiment of the first aspect of the invention, the fourth material is a polypropylene (PP), a polyethylene (PE), a thermoplastic elastomer (TPE), or a thermoplastic polyurethane (TPU). According to another additional embodiment of the invention, the third material is a polypropylene (PP), a polyethylene (PE), a thermoplastic elastomer (TPE), or a thermoplastic polyurethane (TPLI). As an example of the fourth material being similar, but not identical, to the third material, TPE can be mentioned as the material for the carrier and PP can be mentioned as the material for the second outer layer of the sheet. According to another additional embodiment of the first aspect of the invention, the bristle carrier comprises a polypropylene (PP), a thermoplastic elastomer (TPE), or a thermoplastic polyurethane (TPU). According to another additional embodiment of the first aspect of the invention, the sheet is made of a non-elastic material and / or an essentially inextensible material. According to another additional embodiment of the first aspect of the invention, the bristle carrier is made of a flexible and elastic material. According to another embodiment of the first aspect of the invention, the body further comprises at least part of a drive system configured to move, such as alternately move, the bristles provided in the cavity relative to the rest of the body. The alternate movement helps to clean the teeth. According to another additional embodiment of the first aspect of the invention, the body comprises a pressure chamber or chain of pressure chambers extending along the length of the cavity, such as along the entire length of the cavity, wherein the wall of the pressure chamber on the side of the cavity defines the bristle carrier, wherein the pressure chamber is configured to contain a fluid under pressure; and wherein the body is configured to move the bristle carriers from one side to the other with respect to the cavity by alternately increasing and decreasing a pressure in the pressure chamber or chain of pressure chambers between a decreased pressure condition and an increased pressure condition.A pressure chamber chain is understood to be a chain extending along the longitudinal direction in a J or U shape; the chain comprises multiple aligned pressure chambers, viewed in said longitudinal direction in a J or U shape. According to another embodiment of the first aspect of the invention, the pad manufacturing stage comprises the following stages: a) provide the bristles; b) provide said prefabricated sheet; c) put the fixed ends of the bristles in contact with the sheet; d) heat the sheet and / or the fixed ends of the bristles; e) fuse the fixed ends of the bristles with the sheet, obtaining the pad. According to an additional embodiment, the heating in step d) can be achieved by plastic welding, such as hot gas welding, heat sealing, hot plate welding, infrared welding, high-frequency welding, induction welding, ultrasonic welding, friction welding, rotary welding, laser welding, or a combination of one or more of these plastic welding techniques. In hot plate welding, a heat seal is used, which is a heated or hot body that is pressed against the bristles and / or foil to melt them. According to another additional embodiment, step d) can occur after or before step c). According to another embodiment of the first aspect of the invention, step a) may comprise the steps of: - providing a bristle-holding tool having a sheet support surface and a plurality of holes extending from the sheet support surface into the tool, the holes being configured to receive bristles; and inserting the bristles into the holes so that their fixed ends are on the sheet support surface; wherein step c) comprises placing the sheet onto the sheet support surface; and wherein, after step e), the tool is separated from the pad. In the prior art, bristles are known to be attached to a carrier by inserting the bristles through perforations in the carrier and by fusing the projecting portions of the so-called fixed bristle ends together using a heat seal, so that a fusion layer is formed on the carrier and fixed to it. The perforated support is thick and rigid and forms part of the toothbrush construction. This perforated support is not a removable tool, and the fusion layer is not a prefabricated sheet to which the bristles are attached, but rather a fusion layer formed from fused bristle ends. According to a second aspect of the invention, one or more of the objectives of the invention are achieved by providing a mouthpiece obtained by the method according to the first aspect of the invention. According to a third aspect of the invention, one or more of the objects of the invention are achieved by providing a method for manufacturing a bristle pad consisting of a flexible sheet, such as a plastic sheet, and bristles, such as plastic bristles, projecting from a front surface of the sheet, and the sheet having a rear surface opposite the front surface; where the method comprises the following stages: a) provide bristles with one fixed end and one free end; b) provide a prefabricated sheet with a thickness of no more than 700 µm, such as 400 pm maximum or 250 pm maximum or 150 pm maximum; c) put the fixed ends of the bristles in contact with the sheet; d) heat the sheet and / or the fixed ends of the bristles; e) fuse the fixed ends of the bristles with the sheet, obtaining the pad with bristles. According to a further embodiment of the third aspect of the invention, the bristle sheet can have a thickness of at most 1.5 mm, such as 1 mm at most or 750 pm at most. According to a further embodiment of the third aspect of the invention, step a) may comprise the steps of: providing a bristle-holding tool having a sheet support surface and a plurality of holes extending from the sheet support surface into the tool, the holes being configured to receive bristles; and inserting the bristles into the holes so that their fixed ends are on the sheet support surface; wherein step c) comprises placing the sheet on the sheet support surface; and wherein after step e) the tool is separated from the pad. According to a further embodiment of the third aspect of the invention, the heating of step d) can be by means of plastic welding, such as hot gas welding, heat sealing, hot plate welding, infrared welding, high frequency welding, induction welding, ultrasonic welding, friction welding, rotary welding, laser welding, or a combination of one or more of these plastic welding techniques. onna Ln / zznz / e / YiAi According to another additional embodiment of the third aspect of the invention, step d) can occur after or before step c). According to yet another embodiment of the third aspect of the invention, the flexible sheet of the bristle pad has a bending resistance of less than 2 Newtons, such as less than 1.3 Newtons or less than 0.5 Newtons. The bending resistance is defined as the force F required to bend a strip of sheet having a width W of 10 mm and a length L of 20 mm over a distance Q of 10 mm. The force F is directed in the opposite direction to the direction in which the free ends of the bristles are oriented. According to a fourth aspect of the invention, one or more of the objectives of the invention are achieved by providing a bristle pad obtained by the method according to the third aspect of the invention. According to a further embodiment of the fourth aspect of the invention, the mouthpiece has two of said cavities, the longitudinal directions of both cavities being J-shaped or U-shaped and extending in parallel, and the cross-sections of both cavities being U-shaped and opening in mutually opposite directions. According to yet another embodiment of the fourth aspect of the invention, the body comprises a pressure chamber or chain of pressure chambers extending along the length of the cavity, wherein the wall of the pressure chamber on the side of the cavity defines the bristle carrier, wherein the pressure chamber is configured to contain a fluid under pressure; and wherein the body is configured to move the bristle carriers from one side to the other with respect to the cavity by alternately increasing and decreasing a pressure in the pressure chamber or chain of pressure chambers between a decreased pressure condition and an increased pressure condition. According to a fifth aspect of the invention, one or more of the objects of the invention are achieved by providing a dental cleaning device comprising a mouthpiece according to the fourth aspect of the invention and a pressure and / or suction device configured to be in fluid communication with the pressure chamber or chain of pressure chambers and configured to alternately increase and decrease the pressure in the pressure chamber. In this application, the term “flexible” in relation to the sheet is used to mean flexible in such a way that it can be bent freely and repeatedly without breaking. For example, it may be a sheet, such as the sheet of a sandwich bag, that already bends or even, when held horizontally, tends to assume a vertical position under the influence of its own weight. It may also be a sheet that has sufficient rigidity to allow it to remain horizontal, but which can bend under the influence of small forces. onna Ln / zznz / e / γΐΛΐ In this application, the term “with bristles” used as an adjective before a noun such as piece, pad, sheet, or carrier means a piece, pad, sheet, or carrier, respectively, furnished with bristles. In this application, the term “bristle” or “bristle” is used to indicate a single bristle or fiber, as well as to indicate tufts of bristles or fibers. In this application, the term “fixed end” of a bristle (or tuft or bristle fiber) is used to indicate one of the bristle ends, meaning that, depending on the stage in the manufacture of the bristle pad, it (still) needs to be fixed or (already) is fixed to the flexible sheet. The term “fixed end” does not imply that, in the case of, for example, a tuft, these ends of the bristle fibers in the tuft are fixed to each other. The fixed ends of the bristle fibers in a tuft may or may not be fixed to each other. For example, after the bristle pad is manufactured, the fixed ends of the bristle fibers in a tuft may generally be fixed to each other due to fusion, but at the stage before fusing the fixed ends to the sheet, the fixed ends of the bristle fibers in a tuft, although combined into a tuft, may not yet be joined together.However, according to the invention it is conceivable that the so-called fixed ends of the bristle fibers in a tuft have already been joined together at the stage before fusing the fixed ends to the sheet. In summary, the present invention relates to the manufacture of a bristle pad for a mouthpiece toothbrush, a bristle pad, the manufacture of a mouthpiece toothbrush with such a bristle pad, and a mouthpiece toothbrush. The bristle pad is manufactured from a prefabricated sheet and prefabricated bristles. The prefabricated bristles are attached to the flexible prefabricated sheet (maximum 700 µm) by fusing the fixed ends of the bristles to the sheet, resulting in a flexible bristle pad. In the method of manufacturing the mouthpiece, the flexible bristle pad is attached to the mouthpiece body. BRIEF DESCRIPTION OF THE FIGURES The invention will be explained in greater detail with reference to the drawings. In these drawings: Figure 1 shows a lower dental arch with tooth positions and a system of three orthogonal axes that define a dental arch. Figures 2a, 2b, and 2c show an example of a complete U-shaped mouthpiece with a bristle pad manufactured by the method according to the invention, wherein Figure 2a shows a perspective view, Figure 2b shows a cross-sectional view according to arrows llb in Figure 2a, and Figure 2c shows a cross-sectional view according to arrows llb in Figure 2a. Figures 3a and 3b show an example of a J-shaped half-mouthpiece with a bristle pad manufactured by the method according to the invention, wherein the Figure onna Ln / zznz / e / γΐΛΐ Figure 3a shows a perspective view, and Figure 3b shows a cross-sectional view according to arrows llb in Figure 2a. Figures 4a and 4b show, as a variant of Figures 2a-2b, an example of a complete U-shaped mouthpiece with a bristle pad manufactured by the method according to the invention, wherein Figure 4a shows a cross-sectional view according to arrows llb in Figure 2a, and Figure 4b shows a cross-sectional view according to arrows llb in Figure 2a. Figure 5 schematically shows a modality of a dental cleaning device according to the invention; Figure 6 clarifies the definition of the term “flexural strength” as used in this application, as well as the claims. Figure 7 shows two bristle pads according to the invention, one in a flat state and one in a folded state. Figures 8a-8b show two bristle pads according to the invention in the form of bristle strips, Figure 8a shows the strips in the flat state and Figure 8b shows the strips in the folded state. Figures 9a-9b show two sets of bristle strips according to the invention, Figure 9a shows the sets in a flat state and Figure 9b shows the sets in a folded state. Figures 10a-16e show schematic examples of different ways to manufacture a bristle pad according to the invention. Figures 10a-10c show a first example of manufacturing a bristle pad; Figure 10a shows a first state, Figure 10b shows a second state, and Figure 10c shows a third state. Figures 11a-11b show a second example of manufacturing a bristle pad; Figure 11a shows a first state, and Figure 11b shows a second state. Figure 12 shows a third example of manufacturing a bristle pad. Figures 13a-13c show a fourth example of manufacturing a bristle pad; Figure 13a shows a first state, Figure 13b shows a second state, and Figure 13c shows a third state. Figure 14 shows a fifth example of manufacturing a bristle pad. Figure 15 shows the bristle pad according to the invention, which has a multi-layered sheet. Figures 16a-16e show a sixth example of manufacturing a bristle pad; Figure 16a shows a first state, Figure 16b shows a second state, the onna Ln / zznz / e / γΐΛΐ onna Ln / zznz / e / γΐΛΐ Figure 16c shows a third state, and Figures 16d and 16e each show a fourth state with results from pads with slightly different bristles. DETAILED DESCRIPTION OF THE MODALITIES Figure 1 shows a schematic perspective view of a portion of an upper dental arch 1 with tooth positions 2-14. Each tooth position is indicated by a vertical dashed line. Each tooth position generally comprises one tooth, which is named according to a nomenclature familiar to every dentist. Using this nomenclature: Dental position 2 is the position of the left “second molar”, shown in figure 1; Dental position 3 is the position of the left “first molar”, which is missing in figure 1; Dental position 4 is the position of the left “second premolar”, shown in figure 1; Dental position 5 is the position of the left “first premolar”, shown in figure 1; Dental position 6 is the position of the left “canine”, shown in figure 1; Dental position 7 is the position of the left “lateral incisor”, which is missing in figure 1; Dental position 8 is the position of the left “central incisor”, shown in figure 1; Dental position 9 is the position of the right “central incisor”, shown in figure 1; Dental position 10 is the position of the right “lateral incisor”, shown in Figure 1; Dental position 11 is the position of the right “canine”, shown in figure 1; Tooth position 12 is the position of the right “first premolar”, shown in Figure 1; Tooth position 13 is the position of the right “second premolar”, shown in Figure 1; Dental position 14 is the position of the right “first molar”, shown in figure 1; Figure 1 does not show the position of the right second molar, nor the positions of the right and left third molars, also called wisdom teeth. Similarly, the lower jaw has a similar number of dental positions, which are referred to using the same terminology. Reference number 15 indicates the lingual side of the dental arch. Lingual side 15 is the inner side of the dental arch, facing the tongue. Reference number 16 indicates the facial side of the dental arch. Facial side 16 is the outer side of the dental arch, facing the face, such as the cheeks and lips. Figure 1 further shows a system of three mutually orthogonal axes, comprising an X-axis, a Y-axis, and a Z-axis. The Z-axis is a curved axis that follows the contour of dental arch 1. The X-axis and Y-axis are perpendicular to each other and define an xy-plane that is essentially flat and perpendicular to dental arch 1; that is, every xy-plane that intersects a location on the z-axis is, at that location, perpendicular to the curved Z-axis. The Z-axis defines a curved longitudinal direction. The Z-axis and Y-axis define a curved zy-plane, which, viewed along the z-axis, forms an arch similar to the shape of the dental arch. Furthermore, the Z- and X-axes define a zx-plane, and the X- and Y-axes define an xy-plane. With reference to the terms “J-shaped or U-shaped longitudinal direction” and “U-shaped cross-section” as used in the claims, the “J-shaped or U-shaped longitudinal direction” is associated with the U-shaped Z-axis in Figure 1 and the “U-shaped cross-section” is associated with the xy-plane in Figure 1. Figure 2a schematically shows a perspective view of an example of a complete mouthpiece 20 made using the method according to the invention. Figure 2b schematically shows a cross-section of the mouthpiece of Figure 2a, viewed as indicated by arrows 11b in Figure 2a. The complete mouthpiece 20 comprises a body 21 provided with a first cavity 22a. This first cavity 22a has, when viewed along the z-axis of Figure 1, a U-shaped longitudinal direction and, when viewed in the xy-plane of Figure 1, a U-shaped cross-section. The first cavity 22a is bounded by a cavity wall 23, which is U-shaped in the xy-plane. The cavity wall 23 is lined with a plurality of bristles 24. The bristles shown in Figures 2a-2c are tufts 29 of bristle fibers 24. The bristle fibers may be, for example, PA fibers, such as nylon fibers, or PBT fibers, or a mixture of these fibers. However, fibers of other materials or mixtures of fibers of other materials with or without PA fibers, such as nylon and / or PBT, are also conceivable.Each bristle, like the tuft of fibers, has one end, called the fixed end 19, attached to the cavity wall 23 and extending from the cavity wall 23 into the first cavity 22a. Reference 26 indicates a nozzle configured to connect the mouthpiece to a pumping and / or suction device. The mouthpiece 20 further has a right half 27 and a left half 28, which are joined at the nozzle 26. Reference 25 indicates an imaginary curved dividing line, which defines a mirror plane parallel to the xz plane, as defined in Figure 1. The mouthpiece as shown in Figures 2a–2c is approximately mirror-symmetric with respect to this mirror plane, meaning that there is a second cavity 22b (not visible in Figure 2a but visible in Figure 2b) opposite the first cavity 22a, which second cavity 22b is also lined with bristles. Note that the first cavity 22a may have a different shape than the second cavity 22b because the upper and lower arches (their teeth) of the dental positions have different shapes. The term “mirror-symmetric” above, therefore, is not used in a strict mathematical sense, but only in the sense that there are two cavities, each on one side of the mirror plane. onna Ln / zznz / e / Ywi Cavities 22a and 22b are configured to span an entire dental arch, from the position of the second or first right molar to the position of the second left molar or first first molar, respectively. Cavities 22a and 22b can also be configured to span a larger or smaller portion of an arch of dental positions. Figure 2b shows a cross-section according to arrows llb in Figure 2a of a right portion of mouthpiece 20. As can be seen more clearly in Figure 2b, the bristles can be provided as tufts 29 of relatively thin bristle fibers 24. In addition, it can be seen in Figure 2b that the bristles are provided in bristle pads consisting of a sheet 36a, 36b and bristles fused to the sheet 36a, 36b. The sheet in the example of Figures 2a-2c is a multilayered sheet with a first outer layer 36a and a second outer layer 36b. As can be seen in Figure 2b, the mouthpiece 20 has a body 21 that has a first cavity 22a on its upper side and a second cavity 22b on its lower side. Both cavities 22a and 22b are bounded by a flexible cavity wall 23. In the cross-section parallel to the xy plane as defined in Figure 1, the cavity walls 23 are U-shaped and have a lower cavity wall portion 34 and two cavity wall legs 33 extending from the lower cavity wall. The cavity wall 23 is covered with tufts 29 of bristle fibers 24 on the legs 33 and / or the lower portion 34 of the cavity wall 23. A pressure chamber 35 is provided within the body, which can be filled with a fluid via the nozzle 26 (Figure 2a). The fluid can be a gas, such as air, or a liquid, such as water. In the embodiment shown in Figures 2a-2c, the mouthpiece has one pressure chamber. However, it is noted that the mouthpiece can comprise a plurality of pressure chambers, such as five pressure chambers, or any other number of pressure chambers. WO-2018 / 199760 shows examples of other numbers of pressure chambers in Figures 4a-4b, 5, 7, 9a-9b, and 10a-10c. In the case of multiple pressure chambers, all pressure chambers or groups of pressure chambers can, according to the invention, be in fluid communication with each other, similar to that described in WO-2018 / 199760. Viewed in the longitudinal direction in a U-shape (i.e., along the z-axis of Figure 1), a chain of aligned pressure chambers can also be provided.As can be seen in Figure 2b, the mouthpiece may comprise an internal support structure made of a material that is rigid relative to the cavity wall material 23. This support structure may comprise a lingual plate 30 and a facial plate 32, both of which extend essentially parallel to the curved zy plane defined in Figure 1 and, consequently, are viewed along the z-axis, which is U-shaped. To maintain the lingual plate 30 and the facial plate 32 spaced apart from each other, the support structure may comprise one or more spacers 31. These one or more spacers 31 may be, for example, multiple bars or cables or a single plate that extends essentially parallel to the zx plane as defined in Figure 1. In the case of a single plate as a spacer, this plate may divide the pressure chamber 35 into two pressure chambers, an upper and a lower one.These two pressure chambers can be in fluid communication with each other through one or more through-holes in the plate. In the case of large through-holes and / or a large number of through-holes, the two pressure chambers can effectively function as a single pressure chamber. The mouthpiece, as shown in Figures 2a-2c, is configured for simultaneous brushing of multiple tooth positions. If a tooth is present, the tooth in that position will be brushed. Debris in a tooth position, such as the gum, can be brushed if a tooth is missing, and the teeth adjacent to the missing tooth can be additionally brushed using bristles designed for that location. The single pressure chamber 35 comprises a first flexible cavity wall 23 that delimits the first cavity 22 (the upper portion in Figure 2b) and a second flexible cavity wall 23 that delimits the second cavity 22 (the lower portion in Figure 2b). The first and second cavity walls are deformable, particularly when the pressure in the pressure chamber 23 increases or decreases. The flexible cavity walls 23 can be made from an elastic material, such as a rubber-like material. The flexible cavity walls 23 can also be made from a non-elastic material. Examples of suitable cavity wall materials are PP, PE, TPE, and TPU. The material of the flexible cavity walls 23 can maintain a predetermined shape when there is substantially no pressure difference or a very low pressure difference along an inner and an outer side of the flexible cavity walls 23. The mouthpiece 20 is configured so that the tufts 29 touch the tooth surface of the teeth in a dental arch or, in the event that a tooth is missing in one or more tooth positions, so that they touch the gum in the respective tooth position(s) at least when the pressure in the pressure chamber 35 is increased. In the event that a tooth is missing in a tooth position, especially the tufts 29 at the free ends of the cavity wall legs 33 will touch the gum in the empty tooth position. Viewed in the longitudinal Z direction of the dental arch, as defined in Figure 1, the tufts 29 of bristle fibers 24 can be arranged at approximately the same density as seen in the cross-sections shown in Figure 2b. Figure 2c shows that in the incisor dental location, the lower portion of the U-shaped cavity 22a and 22b can indeed be open (or V-shaped, which is not shown). In this “open configuration,” the first cavity 22a and the second cavity 22b are in open connection with each other. To prevent the lingual side 30 of the body and the facial side 32 of the body from widening against each other, a separator 31 can be provided in the incisor dental position, but this separator 31 may also be omitted. When the pressure in pressure chamber 35 increases to an increased pressure condition, for example, by feeding fluid into pressure chamber 35, or by increasing the amount of fluid in pressure chamber 35, the cavity walls 23 compact to narrow cavity 22, so that the bristles 24,29, particularly their free ends, can make firm contact with and / or deform against the tooth surfaces. When the pressure in pressure chamber 35 subsequently decreases, the cavity walls expand to enlarge cavity 22.This narrowing and widening of the cavity walls may be small, but when it is repeated alternately with a certain frequency, for example, from 1 to 50 Hz, this alternating deformation of the cavity wall by means of alternating narrowing and widening causes the bristles to move between a firmer and relatively less firm contact with the tooth surfaces and / or the bristles to alternate between a first and a second deformed condition, which in turn causes a sweeping and / or rubbing of the bristles across the tooth surfaces. By means of a suitable cycle of increasing and decreasing the pressure in the pressure chamber 35, an effective brushing action of the mouthpiece can be achieved. The bristles 24 attached to the underside of the cavity wall 34 generally perform an up-and-down motion during this cycle, and the bristles 24 on the cavity wall legs 33 generally perform a side-to-side motion during this cycle in the x-axis direction as defined in Figure 1. Due to the alternating narrowing and widening of the cavity 22a, 22b when the pressure is alternately increased and decreased, the bristles 24 on the cavity wall legs can also undergo a forward-and-backward rotation about the z-axis as defined in Figure 1, resulting in a sweeping and / or rubbing motion of the bristles in the y-axis direction as defined in Figure 1. With reference to Figure 1, the width of a tooth element in the X direction varies, depending on the tooth position, from approximately 2 to 8 mm. Given the desire to keep the mouthpiece as small as possible, the cavity width in the X direction must be kept as small as possible and can be approximately 0 to 2 mm wider than the respective tooth. The bristles can be 2 to 4 mm long, meaning that between the bristles extending from the opposing cavity wall legs, there is either no gap or a limited amount of gap of approximately 2–4 mm. In Figures 2a–2c, these gaps are shown exaggerated. This limited amount of gap makes it difficult to manufacture a mouthpiece like the one shown in Figures 2a–2c economically.Injection molding, for example, is difficult because the bristles extending from opposite cavity wall legs extend essentially in the X direction, which is transverse to the direction in which injection molding molds can be separated from each other after molding. Figures 3a-3b show half mouthpiece 20. The difference from the mouthpiece in Figure 2a is that the right half of Figure 2a is not included, resulting in a J-shaped half mouthpiece. With a J-shaped half mouthpiece, all the tooth positions on the right half can be cleaned at once. After removing the mouthpiece from the mouth, rotating it, and reinserting it, the left half of the tooth positions can also be cleaned (or vice versa, the right half is cleaned first, then the left half). The half mouthpiece also comprises a body 21 provided with a first cavity 22a and 22b; however, the first cavity 22a and the second cavity 22b have, viewed along the z-axis in Figure 1, a J-shaped longitudinal direction and, viewed in the xy-plane in Figure 1, a U-shaped cross-section. For the remainder, the mouthpiece in Figures 3a-3b is basically the same as the mouthpiece in Figures 2a-2c, except that in Figures 3a-3b the bristle pad lamella 36 is a single-layered lamella, whereas in the embodiment of Figures 2a-2c the lamella has two (or more) layers, a first outer layer 36a and a second outer layer 36b. However, it should be noted that in the embodiment of Figure 2a-2c bristle pads with a single-layered lamella can also be used, and in the embodiment of Figure 3a-3b bristle pads with multi-layered lamellae can also be used. The movement of the bristles from side to side with respect to the cavity or cavities is achieved by means of a drive system, at least part of which is located in the mouthpiece. The drive system can be a mechanical system that causes the bristles to move. Figures 4a-4b show an example of a mechanical drive system. Figure 4b can be considered a variant of Figure 2b, and Figure 4c can be considered a variant of Figure 2c. In this embodiment of the mechanically driven body, the body can be, for example, a solid mass 38 in which a vibrating element 37 is provided as part of the drive system. This vibrating element can be vibrated by means of a handle mounted on 26 with a vibrating interface, which interface is in turn vibrated by a motor provided in the handle. Now, returning to the configuration shown in Figures 2a-2c and 3a-3b, the drive system for moving the bristles from one side to the other with respect to the cavity(ies) is achieved by increasing and decreasing the pressure in pressure chamber 35, which is done by means of a pump unit. Different combinations of pump unit and valve are possible. One possible configuration is explained, by way of example, with reference to Figure 5. Figure 5 schematically illustrates, in a partially cut-through perspective view, a dental cleaning device 200 comprising a handle member 202 and a mouthpiece. 100 coupled to this, e.g., a mouthpiece as described above. The handle member 202 is provided with a handle interface 204, and the mouthpiece 100 is provided with a mouthpiece interface 203 configured to detachably attach to the handle interface 204. The handle member 200 comprises a battery 210 for storing electrical energy, which can be supplied via a battery charging interface 212. The battery 210 provides power to a printed circuit board (PCB) 214, a pump unit comprising a motor 216, a transmission 218, a crankshaft piston 220, and a piston pump 222, and optionally to a mouthwash pump 224. A mouthwash capsule 230 containing mouthwash liquid can be detachably housed in the handle member 200. The piston pump 222 can be a pneumatic pump.Instead of a piston pump, a diaphragm pump, plunger pump, membrane pump, or bellows pump can also be used. The 224 mouthwash pump can be a hydraulic pump. Figure 6 serves to illustrate the definition of the term “flexural strength” as used in the claims and the description of this application. A sample sheet strip with a black border is shown in gray. As shown, this sample strip has a width W and a length L. The sample strip is fixed at its left end A and extends horizontally from A to the right without any support. Therefore, the sample strip represents a “cantilever beam.” When a downward force F is applied to the right end of this sample cantilever strip / beam, the strip / beam will deflect to a deflected condition, which is shown by the dashed line in Figure 6. In the deflected condition, the right end of the strip / beam is a vertical distance Q below the right end of the unloaded strip / beam.The bending strength of the foil, in this application, is defined in terms of the distance Q that a sample foil strip having predetermined dimensions W and L bends when a predetermined force F is applied transversely to the foil. The force F, in this definition, is directed opposite to the direction in which the free ends of the bristles are oriented. This direction of force F means that the foil bends so that the bristles are on the convex side of the bent foil, as shown in this example with the four bristles in Figure 6. Thus, the bending strength of the flexible foil is defined as X Newtons. When a force F of X Newtons is required to bend a strip of such foil having a width of 10 mm and a length of 20 mm over a distance Q of 10 mm, the force F is directed in the direction in which the free ends of the bristles are oriented. The definition illustrated in Figure 6 can be used similarly to define the stiffness of a bristle fiber, for example, as follows: “the fiber that has a stiffness of X onna Ln / zznz / e / Ywi Newton, when a force F of X Newtons is required to bend a bristle fiber that is 1 cm long over a distance Q of 0.2 cm.” Figure 7 shows two bristle pads 50 according to the invention. The pad 50 on the left is in a flat state, and the pad 50 on the right is folded. With reference to the definition of “flexural strength” as elucidated in Figure 6, the folded pad on the right in Figure 7 also has its bristles on the convex side. However, it should be noted that the pad can also be folded in the opposite direction, as shown, for example, in Figures 8b and 9b, see the bristle pads 60 and 70, respectively. As shown in Figure 7, the bristle pad 50 according to the invention consists of a flexible sheet 51 with tufts 52 of bristle fibers. The sheet 51 can have a thickness T of 40-150 µm. Furthermore, the bending strength of the sheet can be, for example, less than 1.3 Newtons or even less than 0.5 Newtons. The sheet 51 has a front surface 53 from which the bristles (tufts) project. Opposite the front surface, the sheet 51 has a back surface 54. Each bristle has a fixed end 55 where the bristle 52 is fused to the sheet 51 and a free end 56 oriented away from the sheet. Figures 8a-8b show two bristle pads 60, 61 which, in cross-section as shown in Figures 8a-8b, may conform to Figure 7. The bristle pads 60, 61 are in this example in the form of elongated bristle strips, a first strip 60 and a second strip 61 which, as can be clearly seen in Figure 8a, is slightly shorter than the first strip 60. Figure 8a shows both bristle strips in a flat condition, and Figure 8b shows both strips in a folded condition as they may be when attached to the body (not shown) of the mouthpiece. The longer strip 60 should be attached to the facial side, i.e., the outer side, of the cavity, and the shorter strip should be attached to the lingual side, i.e., the inner side, of the cavity. With reference to the arrangement in Figures 2a-2c, strips 60 and 61 must be attached to the flexible cavity wall 23, strip 60 to one of the wall legs 33 and strip 61 to the opposite wall leg 33.Strips 60 and 61 can be attached to the cavity wall 23 by fusing the strips along their rear surface 54 to the cavity wall 23. This can be achieved, for example, by inserting strips 60 and 61 as a prefabricated part into an injection mold, molding the cavity wall 23 and possibly other parts of the mouthpiece body. When the cavity wall material is injected into the mold, this material can fuse with the foil or at least with the rear side 54 of the foil. Similarly, a single bristle strip can be provided for the underside of the cavity wall 34 and attached to the underside of the cavity wall 34. Figures 9a-9b show two sets 70, 71 of multiple bristle pads which, in cross-section to Figures 9a-9b, may be in accordance with Figure 7. The sets 70, 71 of bristle pads 60, 61 in this example are in the form of three elongated bristle strips 70a, 70b, 70c and 71a, 71b, 71c. The first set 70 of bristle strips 70a, 70b, 70c is, as can be clearly seen in Figure 9a, slightly shorter than the second set of bristle strips 71a, 71b, 71c. Figure 9a shows both sets of bristle strips in a flat condition, and Figure 9b shows both sets of bristle strips in a folded condition, as they may be when attached to the body (not shown) of the mouthpiece. The longer set 70 should be attached to the facial side, i.e., the outer side, of the cavity, and the shorter set 71 should be attached to the lingual side, i.e., the inner side, of the cavity.With reference to the embodiment in Figures 2a-2c, the bristle strips 70a, 70b, 70c and 71a, 71b, 71c must be attached to the flexible cavity wall 23, strips 70a, 70b, 70c to one of the wall legs 33 and strips 71a, 71b, 71c to the opposite wall leg 33. Strips 70a, 70b, 70c and 71a, 71b, 71c can be attached to the cavity wall 23 by fusing the strips along their back surface 54 to the cavity wall 23. This can be achieved, for example, by inserting strips 70a, 70b, 70c and 71a, 71b, 71c as a prefabricated part into an injection mold, molding the cavity wall 23 and possibly other parts of the mouthpiece body. When the cavity wall material is injected into the mold, this material can fuse with the sheet or at least with the back side 54 of the sheet.Similarly, a set of multiple bristle pads can be provided for the bottom of cavity wall 34 and attached to the bottom of cavity wall 34. With reference to figures 8a-8b and 9a-9b, it is observed that a single bristle strip 60 or 61 according to figure 8 can be combined with a set 71 respectively 70 of bristle strips according to figure 9. The same applies to the single bristle strip at the bottom of the cavity 34 respectively the set of bristle strips for the bottom of the cavity. Figures 10a to 14, and 16a-16e show different examples of manufacturing a bristle pad according to the invention. These examples have in common that a bristle-holding tool 80 with perforations or holes is used, a prefabricated sheet 81 is provided, prefabricated bristles 82 are provided, the prefabricated bristles 82 are inserted into the perforations / holes of the tool, the prefabricated bristles 82 and the prefabricated sheet are joined together by fusing the fixed ends 84 of the prefabricated bristles 82 with the prefabricated sheet 81, and after fusing the fixed ends of the bristles with the sheet, the tool 80 is removed. The difference between the examples lies in the method of heating the fixed ends of the bristles and / or the sheet to fuse them. With reference to Figures 10a-10c, the heat seal 85 is used. A heat seal is a body heated electrically, heated by a fluid, or heated in any other way, for example, by radiation. Figure 10a shows an example of an initial configuration, in which the prefabricated bristles have been inserted into the perforations / holes of the bristle-holding tool, in which the prefabricated foil is a distance above the tool 80 and above the fixed ends 84 of the bristles, and in which the heat seal may already be at its operating temperature. Figure 10b shows a fusion configuration, in which the prefabricated foil 81 has been placed over the fixed ends of the bristles 82, and in which the heat seal 85 is pressed onto the back surface of the foil.The heat from the heat seal causes the fixed ends 84 of the bristles to fuse with the foil, as well as with the foil's front surface. Figure 10c shows the manufactured state of the bristle pad, in which the bristle-holding tool has been removed from the bristle pad. With reference to Figures 10a-10c, it is also conceivable to use a pre-perforated sheet. The perforations in the sheet have the same pattern as the perforations / holes in the tool. In this case, the sheet 81 is placed in the tool so that the fixed ends 84 of the bristles extend into the perforations of the sheet and possibly project above the sheet. The heat seal 85, then, in the condition shown in Figure 10b, will press directly onto the fixed ends 84 of the bristles 82, causing them to melt and fuse with the sheet. With reference to Figures 11a-11b, a heat source 86 (see Figure 11a) is positioned between the prefabricated sheet 81 and the fixed bristle ends 84 to heat the sheet on its front surface 53 and the fixed bristle ends 84. After sufficiently heating the sheet and the fixed bristle ends, the heat source is removed, and the heated sheet is placed over the heated bristle ends to allow them to fuse together (see Figure 11b). This can be facilitated by a seal, which can be heated, that exerts pressure on the back surface of the sheet. When the bristle ends fuse with the sheet, the resulting bristle pad is removed from the tool (not shown in Figures 11a-11b). As with the example in Figures 10a-10c, it is also conceivable to use a prefabricated perforated sheet in the example in Figures 11a-11b.The heat source 86 in Figures 11a-11b can be any type of heat source, such as a heated body, an infrared radiation source, an electric heating element, hot gas, etc. With reference to Figure 12, the prefabricated sheet is placed between the fixed ends 84 of the bristles and a heat source 86, which may be of a type similar to the heat source 86 in Figures 11a-11b. In Figure 12, the sheet is shown at a distance above the fixed ends 84 of the bristles 82, but in practice, the prefabricated sheet will be placed over the fixed ends when the back surface 54 of the sheet is heated by the heat source 86, which is positioned at a distance from the sheet 81 during heating, as shown. Heating will cause the ends 84 of the bristles 82 to fuse with the sheet 81. Fusion can be further facilitated by pressing a seal against the back surface 54 of the sheet at the end of the heating process. As with the example in Figure 10a-10c, it is also conceivable to use a prefabricated perforated sheet in the example in Figure 12.The heat source 86 in Figure 12 can be any type of heat source, such as a heated body, an infrared radiation source, an electric heating element, hot gas, etc. With reference to Figures 13a-13c, the fixed ends 84 of the bristles 82 project from the tool 80, and a heat source 86, such as the heat source in Figures 10a-10c or 12, is used to melt the fixed ends 84 (see Figure 13a). This results in the fixed ends 84 forming mushroom-shaped heads 87 (see Figure 13b). These mushroom-shaped heads 87 prevent the bristles from sliding back into the tool holes when the sheet 81 is placed over the ends 84 / mushroom-shaped heads 87 (see Figure 13b). To establish the fusion, the sheet makes contact with the mushroom-shaped heads and is pressed down by means of a seal not shown. This results in a bristle pad as shown in Figure 13c, in the manufactured state before removing the tool.The heat source 86 in Figure 13 can be any type of heat source, such as a heated body, an infrared radiation source, an electric heating element, hot gas, etc. With reference to Figure 14, the foil is placed over the fixed ends 83 of the bristles located in the holes of the tool 80. Heating is carried out by laser, which can fuse each of the fixed ends individually or in groups with the foil. As with the example in Figures 10a-10c, it is also conceivable to use a prefabricated perforated foil in the example of Figure 14. Figure 15 shows an example of a bristle pad having a multilayer sheet 81. This multilayer sheet may be a prefabricated multilayer sheet. The sheet 81 has a first outer layer 91 on the front surface side 53 of the sheet and a second outer layer 92 on the back side of the sheet. The first and second outer layers 91 and 92 may be of different materials. The first outer layer 91 may be of a second material identical or similar to the first material from which the bristles are manufactured. The second outer layer 92 may be of a fourth material identical to a third material of the bristle carrier body. The third material may be a material that is not fusible with the first and / or second material, but it may also be a material that is fusible with the first and / or second material.Similarly, the fourth material may be non-fusible with the first and / or second materials, but it may also be fusible with them. If the first and second outer layers are in direct contact and fusible, the fusion may be much weaker than the fusion of the bristles with the first outer layer 91, but still strong enough due to the much larger contact surface between the two layers relative to the bristle cross-sections. With reference to Figures 13a-13c, it can be seen that the resulting pad sheet 81 in Figure 13c may indeed be a multi-layered sheet with a first outer layer 91 formed by fusion originating from the fixed ends of the fibers and a second outer layer 92 provided by the initial sheet in Figure 13a. Figures 16a-16e show a fourth example of manufacturing a bristle pad. This example is very similar to the example in Figures 10a-10c, the main difference being that in the example in Figures 16a-16e, the prefabricated sheet 81 is provided with perforations 93 that align with the pattern of holes 89 in the tool. An additional difference is that Figures 16a-e show manufacturing with a multi-layer prefabricated sheet having a first outer layer 91 and a second outer layer 92. However, it should be noted that a single-layer perforated prefabricated sheet, as in Figures 10a-14, can also be used in the example in Figure 16a-16e. Conversely, in the examples in Figures 10a-14, a multi-layer prefabricated sheet, such as the one in Figure 16a-16e, can also be used. Figure 16a shows, in a first state, a tool 80 with holes 89, a sheet 81 having two outer layers 91 and 92, in this example, of mutually dissimilar materials, and a heat seal 85. The heat seal may be replaced by any other heat source 86. The lower outer layer 91 may, in one embodiment, be made of a material with which the bristles do not melt or hardly melt. In the second state of Figure 16b, the sheet 81 is placed in the tool 80 with the perforations 93 aligned with the holes 89 and with the tufts 82 inserted through the holes 89 and the perforations 93 aligned so that the fixed ends 84 of the tufts 82 are approximately aligned with the second outer layer 92 or project above the outer layer 92. In the third state of Figure 16c, the heat seal 85 is pressed onto the fixed ends 84 of the top end of the tufts 82 of the second outer layer 92, and the fixed ends 87 of the tufts fuse with the second outer layer 92. Fusing the tufts with the second outer layer 92 instead of fusing them with the first outer layer 91 results in the first outer layer 91 serving as a retaining layer that prevents the tufts from being pulled out. This is because the fixed ends of the tufts will widen slightly due to the heat seal 85 pressing them. Figure 16d shows a final state in which the top surface of the sheet is etched with bristles. This etching may be due to the fixed ends 84 of the tufts 82 projecting above the sheet as shown in Figure 16b. However, as shown in Figure 16e, it is also possible to obtain a bristle pad with an essentially flat surface of the second outer layer 92. onna Ln / zznz / e / γΐΛΐ With reference to the example in Figures 16a-16e, it should be noted that sheet 81 can also be rotated so that the second outer layer becomes the bottom layer and the first outer layer, which is not fused with the bristles, becomes the top layer. The fixed ends of the bristles will then fuse with the bottom layer instead of the top layer. Therefore, the top layer may not have any perforations. Examples of embodiments of the present invention can be expressed in words as set forth in the following clauses: 1) Method of manufacturing a mouthpiece for simultaneously brushing a plurality of tooth positions, the mouthpiece being of the type comprising a body defining a cavity that is covered with bristles and has a longitudinal direction at least partially J-shaped or U-shaped and a cross-section at least partially U-shaped transverse to the longitudinal direction; wherein the method comprises a pad manufacturing step in which at least one pad with bristles is manufactured; the pad consists of a flexible plastic sheet and plastic bristles projecting from a front surface of the sheet; the sheet has a back surface opposite the front surface; and the pad manufacturing step comprises - provide bristles with one fixed end and one free end, provide a prefabricated sheet with a maximum thickness of 700 µm, and - fuse the fixed ends of the bristles with the prefabricated sheet, which would cause the pad to be made with bristles; wherein the method further comprises a body-making step in which a mouthpiece body to be manufactured is provided; the body-making step comprises providing a body with a cavity and at least one bristle carrier; the cavity has a longitudinal direction in the form of a J or a U and a cross-section at least partially in the form of a U transverse to the longitudinal direction and is configured to encompass a dental arch of multiple tooth positions; the at least one bristle carrier delimits the cavity; and wherein the method further comprises a pad-attachment step in which, during or after the body-making step, one or more bristle pads are attached to the at least one bristle carrier to cover the bristle carrier;The side of the posterior surface of the sheet faces the bristle carrier, and the side of the front surface of the sheet faces away from the bristle carrier, into the cavity. 2) Method in accordance with clause 1, wherein the prefabricated flexible sheet has a thickness of at most 400 pm. qooq Ln / zznz / e / YiAi 3) Method in accordance with one of the above clauses, wherein the prefabricated flexible sheet has a thickness of at most 250 pm, such as 150 pm at most. 4) Method in accordance with one of the above clauses, wherein the flexible sheet has a thickness of at least 50 pm. 5) Method in accordance with one of the above clauses, wherein the bristle sheet has a thickness of at most 1.5 mm, such as 1 mm at most or 750 pm at most. 6) Method of manufacturing a mouthpiece for simultaneously brushing a plurality of tooth positions, the mouthpiece being of the type comprising a body defining a cavity that is covered with bristles and has a longitudinal direction in the shape of a J or a U and a cross-section at least partially in the shape of a U transverse to the longitudinal direction; wherein the method comprises a pad manufacturing step in which at least one pad with bristles is manufactured; the pad consists of a flexible plastic sheet and plastic bristles projecting from a front surface of the sheet; the sheet has a back surface opposite the front surface; and the pad manufacturing step comprises - provide bristles with one fixed end and one free end, - provide a prefabricated sheet, and - fuse the fixed ends of the bristles with the prefabricated foil, resulting in a bristle pad with a foil that is at least 1.5 mm thick, such as at least 1 mm or at least 750 pm; wherein the method further comprises a body-making step in which a mouthpiece body to be manufactured is provided; the body-making step comprises providing a body with a cavity and at least one bristle carrier; the cavity has a longitudinal direction in the form of a J or a U and a cross-section at least partially in the form of a U transverse to the longitudinal direction and is configured to encompass a dental arch of multiple tooth positions; the at least one bristle carrier delimits the cavity; and wherein the method further comprises a pad-attachment step in which, during or after the body-making step, one or more bristle pads are attached to the at least one bristle carrier to cover the bristle carrier;The side of the posterior surface of the sheet faces the bristle carrier, and the side of the front surface of the sheet faces away from the bristle carrier, into the cavity. 7) Method according to one of the above clauses, wherein the flexible sheet of the bristle pad has a bending strength of less than 2 Newtons, such as less than 1.3 Newtons or less than 0.5 Newtons, the bending strength being defined as the force F required to bend a strip of sheet having a width W of 10 mm and a length L of 20 mm over a distance Q of 10 mm, the force F being directed in the opposite direction to the direction in which the free ends of the bristles are oriented. 8) A method according to one of the preceding clauses, wherein the mouthpiece to be manufactured has two of said cavities, the longitudinal J-shaped or U-shaped directions of both cavities extend in parallel and the U-shaped cross-sections of both cavities open in mutually opposite directions, wherein the body-making step comprises providing a body with two of said cavities, the longitudinal J-shaped or U-shaped directions of both cavities extend in parallel and the U-shaped cross-sections of both cavities open in mutually opposite directions, each of said cavities having at least one bristle carrier delimiting the respective cavities; and wherein the pad-fitting step comprises fitting one or more of said pads to the at least one bristle carrier of each of said cavities. 9) Method in accordance with one of the above clauses, wherein the bristles comprise polybutylene terephthalate (PBT) or polyamide (PA) fibers, such as nylon fibers. 10) Method according to one of the preceding clauses, wherein the bristles comprise fibers of a first material and wherein the bristle surface side of the sheet comprises a second material fusible with the first material. 11) Method according to clause 10, wherein the second material is a polybutylene terephthalate (PBT) or polyamide (PA), such as nylon. 12) Method in accordance with one of the above clauses, wherein, in the pad coupling stage, the pad sheet is fused with the bristle carrier. 13) Method in accordance with one of the above clauses, wherein the sheet has a first outer layer configured to be fusible with the bristles and a second outer layer configured to be fusible with the bristle carrier. 14) Method according to one of the preceding clauses, such as according to clause 12 in combination with clause 10, wherein the bristle carrier is made of a third material not fusible with the bristles and / or the front surface of the sheet, such as not fusible with the first material and / or the second material, wherein the sheet comprises a first outer layer of a material fusible with the bristles and a second outer layer of a fourth material fusible with the third material. 15) Method in accordance with clause 14, wherein the fourth material is a polypropylene (PP), a polyethylene (PE), a thermoplastic elastomer (TPE), or a thermoplastic polyurethane (TPU). onno Ln / zznz / e / γΐΛΐ 16) Method according to clause 14 or 15, wherein the third material is polypropylene (PP), polyethylene (PE), thermoplastic elastomer (TPE), or thermoplastic polyurethane (TPU). 17) Method according to one of the preceding clauses, wherein the bristle carrier comprises polypropylene (PP), thermoplastic elastomer (TPE), or thermoplastic polyurethane (TPU). 18) Method in accordance with one of the above clauses, wherein the sheet is made of a non-elastic material. 19) Method in accordance with one of the above clauses, wherein the sheet is made of an essentially non-extensible material. 20) Method in accordance with one of the above clauses, wherein the bristle carrier is made of a flexible and elastic material. 21) Method according to one of the preceding clauses, wherein the body further comprises at least part of a drive system configured to move, such as alternately move, the bristles provided in the cavity with respect to the rest of the body. 22) Method according to one of the preceding clauses, wherein the body comprises a pressure chamber or chain of pressure chambers extending along the length of the cavity, wherein the wall of the pressure chamber on the side of the cavity defines the bristle carrier, wherein the pressure chamber is configured to contain a fluid under pressure; and wherein the body is configured to move the bristle carriers from one side to the other with respect to the cavity by alternately increasing and decreasing a pressure in the pressure chamber or chain of pressure chambers between a decreased pressure condition and an increased pressure condition. 23) Method in accordance with one of the preceding clauses, wherein the pad manufacturing stage comprises the following stages: a) provide the bristles; b) provide said prefabricated sheet; c) put the fixed ends of the bristles in contact with the sheet; d) heat the sheet and / or the fixed ends of the bristles; e) fusing the fixed ends of the bristles with the sheet, obtaining the pad with bristles. 24) Method according to clause 23, wherein the heating of step d) is by means of plastic welding. 25) Method in accordance with one of clauses 23-24, wherein step d) is performed after or before step c). 26) Method in accordance with one of clauses 23-25, wherein stage a) comprises the stages of: onna Ln / zznz / e / Ywi provide a bristle-holding tool having a sheet support surface and a plurality of holes extending from the sheet support surface into the tool, the holes being configured to receive bristles; and insert the bristles into the holes so that their fixed ends are on the sheet support surface; wherein step c) comprises placing the sheet on the sheet support surface; and wherein after step e) the tool is separated from the pad. 27) Oral specimen obtained by the method in accordance with one of clauses 1-26. 28) Method of manufacturing a bristle pad consisting of a flexible plastic sheet and plastic bristles projecting from a front surface of the sheet, the sheet having a back surface opposite the front surface; where the method comprises the following stages: a) provide bristles with one fixed end and one free end; b) provide a prefabricated sheet with a thickness of at most 700 pm, such as a thickness of at most 400 pm or at most 250 pm or at most 150 pm; c) put the fixed ends of the bristles in contact with the sheet; d) heat the sheet and / or the fixed ends of the bristles; e) fusing the fixed ends of the bristles to the sheet, obtaining the bristle pad. 29) Method according to clause 28, wherein the bristle sheet has a thickness of at most 1.5 mm, such as 1 mm at most or 750 pm at most. 30) Method according to clause 28 or 29, wherein step a) comprises the steps of: providing a bristle-holding tool having a sheet support surface and a plurality of holes extending from the sheet support surface into the tool, the holes being configured to receive bristles; and inserting the bristles into the holes so that their fixed ends are on the sheet support surface; wherein step c) comprises placing the sheet on the sheet support surface; and wherein after step e) the tool is separated from the pad. 31) Method in accordance with one of clauses 28-30, wherein the heating of step d) is by means of plastic welding. 32) Method in accordance with one of clauses 28-31, wherein step d) is performed after or before step c). 33) Method in accordance with one of clauses 28-32, wherein the flexible sheet of the bristle pad has a bending strength of less than 2 Newtons, such as less than 1.3 Newtons or less than 0.5 Newtons, the bending strength being defined as the force F required to bend a strip of sheet having a width W of 10 mm and a length L of 20 mm over a distance onna Ln / zznz / e / γΐΛΐ Q of 10 mm, the force F is directed in the opposite direction to the direction in which the free ends of the bristles are oriented. 34) Bristle pad obtained by the method in accordance with one of clauses 28-33. 35) Mouthpiece comprising a body having a cavity and at least one bristle carrier covered with bristles, the cavity having a longitudinal direction in the shape of a J or a U and a cross-section at least partially in the shape of a U transverse to the longitudinal direction and configured to encompass a dental arch of multiple tooth positions, the at least one bristle carrier delimiting the cavity; wherein the mouthpiece comprises one or more pads, such as one or more pads with bristles obtained in accordance with one of clauses 24-26, the pad consists of a flexible sheet and bristles projecting from a front surface of the sheet; the sheet is at most 400 pm thick; the bristles have a fixed end fused to the sheet; the sheet has a rear surface opposite the front surface; and wherein the one or more pads are attached to at least one bristle carrier to cover the bristle carrier with bristles, the rear surface side of the sheet is oriented towards the bristle carrier and the front surface side of the sheet is oriented away from the bristle carrier into the cavity. 36) Mouthpiece according to clause 35, wherein the mouthpiece has two of said cavities, the longitudinal J-shaped or U-shaped directions of both cavities extend in parallel and the at least partially U-shaped cross-sections of both cavities open in mutually opposite directions. 37) Mouthpiece according to clause 35 or 36, wherein the body comprises a pressure chamber or chain of pressure chambers extending along the length of the cavity, wherein the wall of the pressure chamber on the side of the cavity defines the bristle carrier, wherein the pressure chamber is configured to contain a fluid under pressure; and wherein the body is configured to move the bristle carriers from one side to the other with respect to the cavity by alternately increasing and decreasing a pressure in the pressure chamber or chain of pressure chambers between a decreased pressure condition and an increased pressure condition. 38) Dental cleaning device comprising a mouthpiece according to clause 37 and a pressure and / or suction device configured to be in fluid communication with the pressure chamber or chain of pressure chambers and configured to alternately increase and decrease the pressure in the pressure chamber.

Claims

1] Method of manufacturing a mouthpiece for simultaneously brushing a plurality of tooth positions, the mouthpiece being of the type comprising a body defining a cavity that is lined with bristles and has a longitudinal direction in the form of a J or a U and a cross-section at least partially in the form of a U transverse to the longitudinal direction; wherein the method comprises a pad-making step in which at least one pad with bristles is manufactured; the pad consists of a flexible plastic sheet and plastic bristles projecting from a front surface of the sheet; the sheet having a rear surface opposite the front surface;and the pad manufacturing step comprises providing bristles with a fixed end and a free end, - providing a prefabricated sheet with a thickness of 700 µm at most, and - fusing the fixed ends of the bristles to the prefabricated sheet, thereby manufacturing the bristle pad; wherein the method further comprises a body manufacturing step in which a mouthpiece body to be manufactured is provided; the body manufacturing step comprises providing a body with a cavity and at least one bristle carrier; the cavity has a longitudinal direction in the form of a J or a U and a cross-section at least partially U-shaped transverse to the longitudinal direction and is configured to encompass a dental arch of multiple tooth positions; the at least one bristle carrier delimits the cavity;and wherein the method further comprises a pad coupling step in which, during or after the body making step, the sheet of one or more bristle pads is attached to at least one bristle carrier to cover the bristle carrier such that: a) the back surface of the sheet faces the bristle carrier, b) the back surface of the sheet follows the shape of the surface of the bristle carrier to which it is coupled, and c) the front surface of the sheet faces away from the bristle carrier in the cavity. 2] Method according to claim 1, wherein the prefabricated flexible sheet has a thickness of at most 400 pm. onna Ln / zznz / e / γΐΛΐ 3] Method according to one of the preceding claims, wherein the prefabricated flexible sheet has a thickness of at most 250 pm, such as 150 pm at most. 4] Method according to one of the preceding claims, wherein the flexible sheet has a thickness of at least 50 pm. 5] Method according to one of the preceding claims, wherein the bristle sheet has a thickness of at most 1.5 mm, such as 1 mm at most or 750 pm at most. 6] Method of manufacturing a mouthpiece for simultaneously brushing a plurality of tooth positions, the mouthpiece being of the type comprising a body defining a cavity that is lined with bristles and has a longitudinal direction in the form of a J or a U and a cross-section at least partially in the form of a U transverse to the longitudinal direction; wherein the method comprises a pad-making step in which at least one pad with bristles is manufactured; the pad consists of a flexible plastic sheet and plastic bristles projecting from a front surface of the sheet; the sheet has a rear surface opposite the front surface;and the pad manufacturing step comprises providing bristles with a fixed end and a free end, providing a prefabricated sheet, and fusing the fixed ends of the bristles to the prefabricated sheet, resulting in a bristle pad with a sheet having a thickness of at least 1.5 mm, such as at least 1 mm or at least 750 µm; wherein the method further comprises a body manufacturing step in which a mouthpiece body to be manufactured is provided; the body manufacturing step comprises providing a body with a cavity and at least one bristle carrier; the cavity having a longitudinal J-shaped or U-shaped direction and a cross-section at least partially U-shaped transverse to the longitudinal direction and configured to encompass a dental arch of multiple tooth positions; the at least one bristle carrier delimits the cavity;and wherein the method further comprises a pad coupling step in which, during or after the body making step, one or more bristle pads are attached to at least one bristle carrier to cover the bristle carrier with bristles; the back surface side of the pad is oriented towards the bristle carrier and the front surface side of the pad is oriented away from the bristle carrier into the cavity. onno Ln / zznz / e / γΐΛΐ; 7] Method according to one of the preceding claims, wherein the flexible sheet of the bristle pad has a bending strength of less than 2 Newtons, such as less than 1.3 Newtons or less than 0.5 Newtons, the bending strength being defined as the force F required to bend a strip of sheet having a width W of 10 mm and a length L of 20 mm over a distance Q of 10 mm, the force F being directed in the opposite direction to the direction in which the free ends of the bristles are oriented. 8] Method according to any of the preceding claims, wherein the mouthpiece to be manufactured has two of said cavities, the longitudinal J-shaped or U-shaped directions of both cavities extend in parallel and the U-shaped cross-sections of both cavities open in mutually opposite directions, wherein the body-making step comprises providing a body with two of said cavities, the longitudinal J-shaped or U-shaped directions of both cavities extend in parallel and the U-shaped cross-sections of both cavities open in mutually opposite directions, each of said cavities having at least one bristle carrier delimiting the respective cavities; and wherein the pad-fitting step comprises fitting one or more of said pads to the at least one bristle carrier of each of said cavities. 9] Method according to one of the preceding claims, wherein the bristles comprise polybutylene terephthalate (PBT) or polyamide (PA) fibers, such as nylon fibers. 10] Method according to one of the preceding claims, wherein the bristles comprise fibers of a first material and wherein the bristle surface side of the sheet comprises a second material fusible with the first material. 11] Method according to claim 10, wherein the second material is a polybutylene terephthalate (PBT) or polyamide (PA), such as nylon. 12] Method according to one of the preceding claims, wherein, in the pad coupling stage, the pad sheet is fused with the bristle carrier. 13] Method according to one of the preceding claims, wherein the sheet has a first outer layer configured to be fusible with the bristles and a second outer layer configured to be fusible with the bristle carrier. 14] Method according to any one of the preceding claims, as according to claim 12 in combination with claim 10, wherein the bristle carrier is made of a third material that is not fusible with the bristles and / or the front surface of the sheet, such as not fusible with the first and / or second material, wherein the sheet comprises a first outer layer of a material fusible with the bristles and a second outer layer of a fourth material fusible with the third material. onna Ln / zznz / e / Ywi 15] Method according to claim 14, wherein the fourth material is a polypropylene (PP), a polyethylene (PE), a thermoplastic elastomer (TPE), or a thermoplastic polyurethane (TPU). 16] Method according to claim 14 or 15, wherein the third material is a polypropylene (PP), a polyethylene (PE), a thermoplastic elastomer (TPE), or a thermoplastic polyurethane (TPU). 17] Method according to one of the preceding claims, wherein the bristle carrier comprises a polypropylene (PP), a thermoplastic elastomer (TPE), or a thermoplastic polyurethane (TPU). 18] Method according to one of the preceding claims, wherein the sheet is made of a non-elastic material. 19] Method according to one of the preceding claims, wherein the sheet is made of an essentially non-extensible material. 20] Method according to one of the preceding claims, wherein the bristle carrier is made of a flexible and elastic material. 21] Method according to one of the preceding claims, wherein the body further comprises at least part of a drive system configured to move, such as alternately move, the bristles provided in the cavity with respect to the rest of the body. 22] Method according to any one of the preceding claims, wherein the body comprises a pressure chamber or chain of pressure chambers extending along the length of the cavity, wherein the wall of the pressure chamber on the side of the cavity defines the bristle carrier, wherein the pressure chamber is configured to contain a fluid under pressure; and wherein the body is configured to move the bristle carriers from one side to the other with respect to the cavity by alternately increasing and decreasing a pressure in the pressure chamber or chain of pressure chambers between a decreased pressure condition and an increased pressure condition. 23] Method according to any of the preceding claims, wherein the pad manufacturing step comprises the following steps: a) providing the bristles; b) providing said prefabricated sheet; c) putting the fixed ends of the bristles in contact with the sheet; d) heating the sheet and / or the fixed ends of the bristles; e) fusing the fixed ends of the bristles with the sheet, obtaining the bristle pad. 24] Method according to claim 23, wherein the heating of step d) is by means of plastic welding. onna Ln / zznz / e / Ywi 25] Method according to any one of claims 23-24, wherein step d) is performed after or before step c). 26] Method according to any one of claims 23-25, wherein step a) comprises the steps of: providing a bristle-holding tool having a sheet support surface and a plurality of holes extending from the sheet support surface into the tool, the holes being configured to receive bristles; and inserting the bristles into the holes so that their fixed ends are on the sheet support surface; wherein step c) comprises placing the sheet onto the sheet support surface; and wherein after step e) the tool is separated from the pad. 27] Mouthpiece obtained by the method according to one of claims 1-26. 28] Method of manufacturing a bristle pad comprising a flexible plastic sheet and plastic bristles projecting from a front surface of the sheet, the sheet having a back surface opposite the front surface; wherein the method comprises the following steps: a) providing bristles with a fixed end and a free end; b) providing a prefabricated sheet with a thickness of at most 700 µm, such as a thickness of at most 400 µm, or at most 250 µm, or at most 150 µm; c) bringing the fixed ends of the bristles into contact with the sheet; d) heating the sheet and / or the fixed ends of the bristles; e) fusing the fixed ends of the bristles to the sheet, obtaining the bristle pad. 29] Method according to claim 28, wherein the bristle sheet has a thickness of at most 1.5 mm, such as 1 mm at most or 750 pm at most. 30] Method according to claim 28 or 29, wherein step a) comprises the steps of: providing a bristle-holding tool having a sheet support surface and a plurality of holes extending from the sheet support surface into the tool, the holes being configured to receive bristles; and inserting the bristles into the holes so that their fixed ends are on the sheet support surface; wherein step c) comprises placing the sheet onto the sheet support surface; and wherein after step e) the tool is separated from the pad. 31] Method according to any one of claims 28-30, wherein the heating of step d) is by means of plastic welding. onna Ln / zznz / e / Ywi 32] Method according to any one of claims 28-31, wherein step d) is performed after or before step c). 33] Method according to any one of claims 28-32, wherein the flexible sheet of the bristle pad has a bending strength of less than 2 Newtons, such as less than 1.3 Newtons or less than 0.5 Newtons, the bending strength being defined as the force F required to bend a strip of sheet having a width W of 10 mm and a length L of 20 mm over a distance Q of 10 mm, the force F being directed in the opposite direction to the direction in which the free ends of the bristles are oriented. 34] Bristle pad obtained by the method according to one of claims 28-33. 35] Mouthpiece comprising a body having a cavity and at least one bristle carrier covered with bristles, the cavity having a longitudinal J- or U-shaped direction and a cross-section at least partially U-shaped transverse to the longitudinal direction and configured to encompass a dental arch of multiple tooth positions, the at least one bristle carrier delimiting the cavity; wherein the mouthpiece comprises one or more pads, such as one or more bristle pads obtained according to one of claims 24-26, the pad consisting of a flexible sheet and bristles projecting from a front surface of the sheet; the sheet having a thickness of at most 400 µm; the bristles having a fixed end fused with the sheet; the sheet having a rear surface opposite the front surface;and where one or more pads are joined to at least one bristle carrier to cover the bristle carrier with bristles, the side of the back surface of the sheet is oriented towards the bristle carrier and the side of the front surface of the sheet is oriented away from the bristle carrier into the cavity. 36] Mouthpiece according to claim 35, wherein the mouthpiece has two of said cavities, the longitudinal J-shaped or U-shaped directions of both cavities extend in parallel and the at least partially U-shaped cross-sections of both cavities open in mutually opposite directions. 37] Mouthpiece according to claim 35 or 36, wherein the body comprises a pressure chamber or chain of pressure chambers extending along the length of the cavity, wherein the wall of the pressure chamber on the side of the cavity defines the bristle carrier, wherein the pressure chamber is configured to contain a fluid under pressure; and wherein the body is configured to move the bristle carriers from one side to the other with respect to the cavity by alternately increasing and decreasing a pressure in the pressure chamber or chain of pressure chambers between a decreased pressure condition and an increased pressure condition. 38] Dental cleaning device comprising a mouthpiece according to claim 37 and a pressure and / or suction device configured to be in fluid communication with the pressure chamber or chain of pressure chambers and configured to alternately increase and decrease the pressure in the pressure chamber.

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