Patent Publication Number: US-2023157861-A1

Title: Mouthpiece

Description:
TECHNICAL FIELD 
     The present invention relates to an oral appliance. 
     BACKGROUND ART 
     It is said that obstructive sleep apnea syndrome is mainly caused with a lower jaw sagging and obstructing an airway. In consideration of the above point, various oral appliances have been proposed to remedy the obstructive sleep apnea syndrome. Those oral appliances are intended to cure apnea or snoring by restricting rearward displacement of the lower jaw of a user and keeping the airway wide. 
     For example, Patent Literature (hereinafter, abbreviated as PTL) 1 proposes an oral appliance including a pair of oral appliance body portions corresponding to an upper jaw and a lower jaw, and a metal-made coupling member coupling the oral appliance body portions to each other. According to the proposed oral appliance, the coupling member adjusts the relative positions of an upper-jaw oral appliance body portion and a lower-jaw oral appliance body portion and displaces the lower jaw of a user wearing the oral appliance forward. In the proposed oral appliance, the coupling member is fixed to the oral appliance body portions made of resin by using, for example, metal fittings. 
     Furthermore, PTL 2 discloses an oral appliance in which a pair of oral appliance body portions corresponding to an upper jaw and a lower jaw are connected to each other by using a flexible band. According to the oral appliance disclosed in PTL 2, the flexible band adjusts the relative positions of an upper-jaw oral appliance body portion and a lower-jaw oral appliance body portion and restricts rearward displacement of the lower jaw of a user. In the oral appliance disclosed in PTL 2, the flexible band is fixed to the oral appliance body portions made of a hard material, such as polycarbonate resin or acrylic resin, by using an adhesive. 
     CITATION LIST 
     Patent Literatures 
     PTL 1 
     
         
         U.S. Unexamined Patent Application Laid-Open No. 2007/0224567 
       
    
     PTL 2 
     
         
         WO 2008/023799 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     In each of the oral appliances disclosed in PTL 1 and PTL 2, the oral appliance body portions are made of materials with high hardness. The oral appliance body portions with high hardness tend to make the user wearing the oral appliance feel uncomfortable. On the other hand, if the oral appliance body portions are entirely made of soft materials to improve wearing feel, there may occur such a problem that the oral appliance body portions are damaged or deformed near the coupling member, and that the rearward displacement of the lower jaw is not sufficiently restricted. 
     The present invention has been accomplished in consideration of the above-described problem. Specifically, an object of the present invention is to provide an oral appliance that gives good wearing feel and that is less susceptible to damage and deformation. 
     Solution to Problem 
     To solve the above-described problem, the present invention provides an oral appliance configured as follows. 
     The oral appliance includes a pair of oral appliance body portions constituted by an upper-jaw oral appliance body portion fitted to an upper jaw and a lower-jaw oral appliance body portion fitted to a lower jaw, a positioning member that restricts rearward displacement of the lower-jaw oral appliance body portion, and a support portion that is disposed between the positioning member and at least one of the oral appliance body portions to cover part of a surface of at least one of the upper-jaw oral appliance body portion and the lower-jaw oral appliance body portion, the surface being opposite to another surface fitted to a tooth row, and that supports the positioning member, wherein the support portion includes a material with a different flexural modulus from the oral appliance body portions. 
     Advantageous Effects of Invention 
     According to the present invention, the oral appliance giving good wearing feel and being less susceptible to damage and deformation is provided. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a schematic front view of an oral appliance according to Embodiment 1 of the present invention; 
         FIG.  2 A  is a schematic side view of the oral appliance, illustrated in  FIG.  1   , in a mouth closed state, and  FIG.  2 B  is a schematic side view of the oral appliance, illustrated in  FIG.  1   , in a mouth open state; 
         FIG.  3 A  is a schematic perspective view illustrating an upper jaw side of an oral appliance according to Embodiment 2 of the present invention, and  FIG.  3 B  is a schematic perspective view illustrating a lower jaw side of the oral appliance according to Embodiment 2 of the present invention; 
         FIG.  4    is a schematic side view of the oral appliance, illustrated in  FIGS.  3 A and  3 B , in a mouth closed state; 
         FIG.  5    is a schematic perspective view of an oral appliance according to Embodiment 3 of the present invention; 
         FIG.  6    is a schematic side view of the oral appliance, illustrated in  FIG.  5   , in a mouth closed state; 
         FIG.  7    is a schematic perspective view of a positioning member of the oral appliance illustrated in  FIG.  5   ; and 
         FIG.  8    is a schematic exploded perspective view of the positioning member illustrated in  FIG.  7   . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     An oral appliance according to the present invention will be described below in connection with several embodiments. In the following description, the words “front” and “rear” indicate, respectively, a direction toward the front of a user wearing the oral appliance (namely, a direction toward a lip side within an oral cavity when viewed from a tongue body) and a direction toward the rear of the user wearing the oral appliance (namely, a direction toward a throat side within the oral cavity when viewed from the tongue body). The word “downward” indicates a direction toward a lower side of the user wearing the oral appliance (namely, a direction from the top of a head toward a foot when the user is upright). The word “left-right direction” indicates leftward and rightward directions with an exact middle of an upper jaw of the user wearing the oral appliance being a reference when viewing forward of the user (specifically, directions toward cheeks on both sides when viewed from the exact middle of the upper jaw). The words “outer side” and “inner side” indicate, respectively, a side closer to a body surface of the user wearing the oral appliance and a side away from the body surface. 
     Furthermore, in the following description, when a mouth of the user wearing the oral appliance is closed, this situation is referred to as a “mouth closed state”, and when the mouth of the user wearing the oral appliance is opened, this situation is referred to as a “mouth open state”. In the mouth closed state, an upper-jaw oral appliance and a lower-jaw oral appliance are arranged such that their surfaces facing each other are substantially parallel. In the mouth open state, because the lower-jaw oral appliance is moved along an arc-shaped path when the mouth is opened, the upper-jaw oral appliance and the lower-jaw oral appliance are arranged such that their surfaces facing each other are non-parallel with an angle of about 45° at maximum formed between both the surfaces. 
     1. Embodiment 1 
       FIG.  1    is a schematic front view of oral appliance  1100  according to Embodiment 1 of the present invention,  FIG.  2 A  is a schematic side view of oral appliance  1100  in the mouth closed state, and  FIG.  2 B  is a schematic side view of oral appliance  1100   n  the mouth open state. As illustrated in  FIGS.  1 ,  2 A, and  2 B , oral appliance  1100  according to this embodiment includes a pair of oral appliance body portions  1110  constituted by upper-jaw oral appliance body portion  1111  and lower-jaw oral appliance body portion  1112 , a pair of left and right positioning members  1160  that restrict rearward displacement of lower-jaw oral appliance body portion  1112 , and support portions  1170  constituted by a pair of left and right upper support portions  1171  that cover parts of upper-jaw oral appliance body portion  1111  and that support positioning members  1160 , and by a pair of left and right lower support portions  1172  that cover parts of lower-jaw oral appliance body portion  1112  and that support positioning members  1160 . 
     In oral appliance  1100  according to this embodiment, the positions of upper-jaw oral appliance body portion  1111  and lower-jaw oral appliance body portion  1112  are determined by positioning members  1160 , and the position of a lower jaw relative to an upper jaw of the user is properly adjusted. As a result, during sleep of the user, an airway is kept wide, and apnea or snoring is cured. 
     In oral appliance  1100  according to this embodiment, the pair of oral appliance body portions  1110  and support portions  1170  have different flexural moduli. Furthermore, support portions  1170  are arranged to cover only parts of oral appliance body portions  1110 . In this embodiment, for example, when the flexural modulus of a material contained in support portions  1170  is set to be higher than that of oral appliance body portions  1110 , oral appliance body portions  1110  are easier to come into close contact with tooth rows of the user and are also deformable appropriately following the shapes of the tooth rows. This improves wearing feel of oral appliance  1100 . On the other hand, support portions  1170  have a higher flexural modulus than oral appliance body portions  1110  and are less susceptible to deformation. Accordingly, positioning members  1160  can be supported at the desired position by support portions  1170 , and support portions  1170  are less susceptible to damage and deformation even when load is applied to support portions  1170 . As a result, oral appliance  1100  according to this embodiment can be stably used for a long period. In another case, the flexural modulus of the material contained in support portions  1170  may be set to be lower than that of oral appliance body portions  1110 . This case can also improve the wearing feel by relieving force applied to oral appliance  1100  while damage and bending are suppressed. 
     Components of this embodiment will be described below. 
     (Oral Appliance Body Portions) 
     As described above, oral appliance body portions  1110  is constituted by upper-jaw oral appliance body portion  1111  and lower-jaw oral appliance body portion  1112 . Upper-jaw oral appliance body portion  1111  is fitted to the upper jaw of the user, and lower-jaw oral appliance body portion  1112  is fitted to the lower jaw of the user. 
     Each of oral appliance body portions  1110  includes a recess capable of receiving the tooth row. Although, in oral appliance body portions  1110  illustrated in  FIGS.  1 ,  2 A , and  2 B, upper-jaw oral appliance body portion  1111  and lower-jaw oral appliance body portion  1112  include respectively tooth row mold portions  1111   a  and  1112   a  corresponding to the tooth rows of the user, the recesses are not always required to correspond to the shapes of the tooth rows. Oral appliance body portion  1110  may cover only part of the tooth row and is not always required to cover incisor teeth, for example. In such a case, structures covering left and right molar teeth are preferably coupled to each other by using, for example, a wire that is arranged along the tooth row. From the viewpoint of increasing strength of oral appliance body portion  1110  and improving the wearing feel, oral appliance body portion  1110  preferably has a structure covering the entire tooth row as illustrated in  FIGS.  1 ,  2 A, and  2 B . 
     A thickness of each of oral appliance body portions  1110  is selected appropriately in accordance with the desired strength, the shape of the tooth row of the user, and so on. The thickness of oral appliance body portion  1110  may be substantially uniform in its entirety or may be changed as required. For example, a region of oral appliance body portion  1110  covered with support portion  1170  (later described) may have a smaller thickness than a region of oral appliance body portion  1110  not covered with support portion  1170 . In that case, the region of oral appliance body portion  1110  covered with support portion  1170  is less likely to become too thick, and the wearing feel is improved. 
     Oral appliance body portions  1110  according to this embodiment are each preferably mainly made of a thermoplastic resin composition. The thermoplastic resin composition is just required to contain thermoplastic resin and may further contain, for example, a filler and/or an additive in addition to the thermoplastic resin insofar as the object and the advantageous effects of the present invention are not impeded. Moreover, for example, a metal wire or plate for increasing the strength may be buried in a product of the thermoplastic resin composition. 
     An amount of the thermoplastic resin composition to a total mass of oral appliance body portion  1110  is preferably 50 mass % to 100 mass %, more preferably 60 mass % to 100 mass %, and particularly preferably 80 mass % to 100 mass %. When the amount of the thermoplastic resin composition is within the above-mentioned range, the total mass of oral appliance  1100  is reduced, and the wearing feel can be easily improved. Furthermore, it is easier to give oral appliance body portions  1110  with proper hardness and to improve the wearing feel. 
     A flexural modulus of the thermoplastic resin composition contained in oral appliance body portion  1110  is preferably 50 to 3000 MPa, more preferably 50 to 2000 MPa, and even more preferably 200 to 1800 MPa. The flexural modulus is measured in conformity with JIS T6501. When the flexural modulus of the thermoplastic resin composition is lower than or equal to 500 MPa, oral appliance body portion  1110  is especially easier to follow the shape of the tooth row. On the other hand, when the flexural modulus of the thermoplastic resin composition is higher than or equal to 1000 MPa, the strength of oral appliance body portion  1110  is especially increased. 
     Tensile strength of oral appliance body portion  1110  is preferably higher than or equal to 10 N and lower than or equal to 1000N and more preferably 100 to 800 N. When the tensile strength is within the above-mentioned range, oral appliance body portion  1110  is easier to increase followability to the shape of the tooth row. The tensile strength indicates strength at which the upper-jaw oral appliance body portion tears when a hole of ϕ1.5 mm is formed in a tooth No. 6 in a tooth row of the upper-jaw oral appliance body portion of the oral appliance (thickness of 3 mm) fabricated using a Nission dental model and a tensile test is performed by applying force in a direction toward the molar teeth (rearward). 
     Here, examples of the thermoplastic resin contained in the thermoplastic resin composition include polyester resin, polycarbonate resin, polyamide resin, (meth)acrylic resin, and so on. However, types of the thermoplastic resin are not limited to those examples. In this Description, “(meth)acrylic” indicates acrylic, methacrylic, or both of them, and “(meth)acrylate” indicates acrylatc, methacrylate, or both of them. 
     The polyester resin is a polycondensation product of polycarboxylic acid such as dicarboxylic acid, for example, and polyalcohol such as diol, for example. Examples of the polyester resin include polyethylene terephthalate (PET), polypropylene terephthalate, polybutylene terephthalate, and so on.
         The polycarbonate resin can be given as known resin.       

     Examples of the polyamide resin include aliphatic polyamide resin (including alicyclic polyamide resin), semiaromatic polyamide resin, and aromatic polyamide resin. The aliphatic polyamide resin is resin including, as a main component, a structural unit containing an amide bond and not containing an aromatic ring (namely, an amide-bond-containing structural unit not containing the aromatic ring). The wording “including, as a main component, an amide-bond-containing structural unit not containing the aromatic ring” indicates that the resin includes 80 mol % or more and preferably 90 to 100 mol % of the amide-bond-containing structural unit not containing the aromatic ring to a total number of moles of the amide-bond containing structural unit. 
     Examples of the aliphatic polyamide resin (including the alicyclic polyamide resin) include resins resulting from polycondensation reaction of aliphatic dicarboxylic acids with carbon atomic numbers 2 to 14 and aliphatic diamines with carbon atomic numbers 4 to 12; resins resulting from polycondensation reaction of aliphatic amino carboxylic acids with carbon atomic numbers 6 to 12; resins resulting from ring-opening polymerization reaction of lactam with carbon atomic numbers 6 to 12; resins resulting from polycondensation reaction of aliphatic dicarboxylic acids with carbon atomic numbers 2 to 14 and diamines including one or more alicyclic structures; resins resulting from polycondensation reaction of aliphatic dicarboxylic acids including one or more alicyclic structures and aliphatic diamines with carbon atomic numbers 4 to 12; resins resulting from polycondensation reaction of dicarboxylic acids including one or more alicyclic structures and diamines including one or more alicyclic structures, and so on. 
     Specific examples of the above-mentioned aliphatic polyamide resins include polyamide 6, polyamide 6⋅6, polyamide 4⋅6, polyamide 6⋅10, polyamide 6⋅12, polyamide 6⋅14, polyamide 6⋅13, polyamide 6⋅15, polyamide 6⋅16, polyamide 9⋅2, polyamide 9⋅10, polyamide 9⋅12, polyamide 9⋅13, polyamide 9⋅14, polyamide 9⋅15, polyamide 6⋅16, polyamide 9⋅36, polyamide 10⋅10, polyamide 10⋅12, polyamide 10⋅13, polyamide 10⋅14, polyamide 11, polyamide 12, polyamide 12⋅10, polyamide 12⋅12, polyamide 12⋅13, polyamide 12⋅14, and copolymers of the above-mentioned polyamides. The aliphatic polyamide resins may be commercially available ones. Examples of the commercially available aliphatic polyamide resins include Torogamid CX7323 made by Daicel-Degussa Ltd., and so on. Among the above-mentioned examples, polyamide 11, polyamide 12, and the copolymers of aliphatic dicarboxylic acids and diamines including the alicyclic structures are especially preferable. 
     The semiaromatic polyamide resin is polyamide resin resulting from polycondensation of a dicarboxylic acid component and a diamine component and including the aromatic ring and the aliphatic structure. 
     A dicarboxylic acid structural unit constituting the semiaromatic polyamide resin preferably includes a terephthalic acid structural unit. An amount of the terephthalic acid structural unit to total 100 mol % of the dicarboxylic acid structural unit constituting the semiaromatic polyamide resin is preferably 35 to 100 mol % and more preferably 40 to 100 mol %. 
     Furthermore, the dicarboxylic acid structural unit constituting the semiaromatic polyamide resin preferably includes the terephthalic acid structural unit, an isophthalic acid structural unit, and/or an aliphatic dicarboxylic acid structural unit with any of carbon atomic numbers 4 to 10. 
     Assuming that a total of the terephthalic acid structural unit, the isophthalic acid structural unit, and the aliphatic dicarboxylic acid structural unit with any of carbon atomic numbers 4 to 10 is 100 mol %, the content of the terephthalic acid structural unit is preferably 35 to 50 mol % and more preferably 40 to 50 mol %. The content of the isophthalic acid structural unit is preferably 25 to 40 mol % and more preferably 30 to 40 mol %. The content of the aliphatic dicarboxylic acid structural unit with any of carbon atomic numbers 4 to 10 is preferably 15 to 35 mol % and more preferably 20 to 30 mol %. 
     A molar ratio of the terephthalic acid structural unit to the isophthalic acid structural unit is preferably 65/35 to 50/50. A molar ratio of the aliphatic dicarboxylic acid structural unit to the isophthalic acid structural unit is preferably 30/70 to 50/50. When the semiaromatic polyamide resin includes the aliphatic dicarboxylic acid structural unit within the above-mentioned range, the semiaromatic polyamide resin becomes amorphous, and formability is improved. On the other hand, the isophthalic acid structural unit acts to improve the formability while heat resistance of the semiaromatic polyamide resin is maintained. 
     The dicarboxylic acid structural unit constituting the semiaromatic polyamide resin may further include, as required, a structural unit derived from different dicarboxylic acid from the above-mentioned examples of the dicarboxylic acid. Examples of the different dicarboxylic acid include other aromatic dicarboxylic acids such as 2-methyl terephthalic acid or naphthalene dicarboxylic acid; furandicarboxylic acid such as 2,5-furandicarboxylic acid; alicyclic dicarboxylic acids such as 1,4-cyclohexane dicarboxylic acid and 1,3-cyclohexane dicarboxylic acid, and so on. 
     A diamine structural unit constituting the semiaromatic polyamide resin preferably includes an aliphatic diamine structural unit with any of carbon atomic numbers 4 to 12. The aliphatic diamine may be a linear aliphatic diamine or a chain aliphatic diamine with a side chain. Examples of the aliphatic diamine includes linear aliphatic diamines such as 1,4-diaminobutane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, and 1,12-diaminododecane; and chain aliphatic diamines with side chains, such as 2-methyl-1,5-diaminopetane, 2-methyl-1,6-diaminohexane, 2-methyl-1,7-diaminoheptane, 2-methyl-1,8-diaminooctane, 2-methyl-1,9-diaminononane, 2-methyl-1,10-diaminodecane, and 2-methyl-1,11-diaminundecane. The aliphatic diamine is preferably diamine with any of carbon atomic numbers 6 to 9 and more preferably hexamethylenediamine or nonanediamine. 
     An amount of the aliphatic diamine structural unit to total 100 mol % of the diamine structural unit constituting the semiaromatic polyamide resin is preferably 60 to 100 mol % and more preferably 80 to 100 mol %. 
     The diamine structural unit constituting the semiaromatic polyamide resin may further include, as required, a structural unit derived from different diamine from the above-mentioned aliphatic diamine Examples of the different diamine include aromatic diamines such as metaxylenediamine; and alicyclic diamines such as 1,4-cyclohexanediamine and 1,3-cyclohexanediamine. 
     Examples of the aromatic polyamide resin include para and meta amides, and so on. 
     Examples of the (meth)acrylic resin includes a (meth)acrylic thermoplastic elastomer. The (meth)acrylic thermoplastic elastomer is particularly preferably a block copolymer including a hard block and a soft block that are different in glass transition temperature (Tg). 
     In the block copolymer, Tg of the hard block is preferably higher than Tg of the soft block. Tg of the hard block is preferably 30° C. to 200° C., more preferably 60° C. to 140° C., and particularly preferably 60° C. to 120° C. Tg of the soft block is preferably −100° C. to 0° C., more preferably −80° C. to −20° C., and particularly preferably −40° C. to −50° C. 
     In the above-mentioned block copolymer, each of the hard block and the soft block preferably includes a unit derived from alkyl (meth)acrylate (also referred to as an “alkyl (meth)acrylate unit”. In this case, the carbon number of an alkyl group contained in the alkyl (meth)acrylate unit of the hard block (also referred to as the “carbon number C1” hereinafter) is preferably smaller than the carbon number of an alkyl group contained in the alkyl (meth)acrylate unit of the soft block (also referred to as the “carbon number C2” hereinafter). 
     The carbon number of an alkyl portion contained in the alkyl (meth)acrylate unit of the hard block (the “carbon number C1”) is preferably 1 to 6, more preferably 1 to 3, even more preferably 1 or 2, and particularly preferably 1. Furthermore, a (meth)acrylate portion is preferably methacrylate. In other words, the hard block particularly preferably includes a methyl methacrylate unit. 
     The carbon number of an alkyl portion contained in the alkyl (meth)acrylate unit of the soft block (the “carbon number C2”) is just required to be greater than the carbon number C1. A difference between the carbon number C1 and the carbon number C2 is preferably greater than or equal to 1, more preferably 1 to 6, even more preferably 2 to 5, and particularly preferably 2 to 4. 
     Furthermore, a (meth)acrylate portion is preferably acrylate. The soft block particularly preferably includes a butyl acrylate unit. 
     In the above-mentioned block copolymer, a mass ratio of the hard block to total mass of the hard block and the soft block is selected such that the flexural modulus of the (meth)acrylic thermoplastic elastomer falls within the above-mentioned range. Thus, the above-mentioned mass ratio is preferably 5 to 95 mass %, more preferably 10 to 90 mass %, and particularly preferably 15 to 85 mass %. 
     The block copolymer includes preferably 80 to 100 mass % t and more preferably 90 to 100 mass % of the above-mentioned hard block and soft block in total. 
     Mass average molecular weight (Mw) of the (meth)acrylic resin (the above-mentioned block copolymer) is selected as appropriate depending on the flexural modulus and is preferably 10000 to 1000000, more preferably 20000 to 800000, and particularly preferably 50000 to 500000. Mass average molecular weight (Mw) of the hard block is preferably 10000 to 1000000, more preferably 20000 to 800000, and particularly preferably 50000 to 500000. Mass average molecular weight (Mw) of the soft block is preferably 10000 to 1000000, more preferably 20000 to 800000, and particularly preferably 50000 to 500000. The above-mentioned mass average molecular weight (Mw) is a value measured with gel permeation chromatography (GPC) and is given as a value in terms of polymethyl methacrylate. 
     (Support Portions) 
     Support portions  1170  of oral appliance  1100  according to this embodiment are constituted by a pair of left and right upper support portions  1171  and a pair of left and right lower support portions  1172 . Upper support portions  1171  are arranged to cover upper-jaw oral appliance body portion  1111  on left and right molar tooth sides, namely to cover surfaces of upper-jaw oral appliance body portion  1111 , the surfaces being opposite to other surfaces fitted to molar teeth. On the other hand, lower support portions  1172  are arranged to cover lower-jaw oral appliance body portion  1112  on left and right molar tooth sides, namely to cover surfaces of lower-jaw oral appliance body portion  1112 , the surfaces being opposite to other surfaces fitted to molar teeth. 
     Shapes of support portions  1170  are not limited to particular ones insofar as the support portions  1170  can support positioning members  1160  described later. The shapes of the support portions may be vertically and horizontally symmetric or not symmetric. Support portions  1170  (upper support portions  1171  and lower support portions  1172 ) may be arranged only between oral appliance body portions  1110  and positioning members  1160 , namely on surfaces of oral appliance body portions  1110  only on outer lateral sides of the molar teeth. More preferably, however, both upper support portions  1171  and lower support portions  1172  have arch-shaped structures covering inner lateral surfaces, bottom or upper surfaces, and outer lateral surfaces of the molar teeth. When support portions  1170  have arch shapes, it is easier to distribute the load and to firmly support the positioning members  1160 . Widths of support portions  1170  are not limited to particular values and may be selected as appropriate in accordance with widths of upper holding portion  1130  and lower holding portion  1140  of positioning members  1160 . 
     A thickness of each of support portions  1170  is not limited to a particular value, but it is preferably set such that, in a state of the user wearing oral appliance  1100 , support portion  1170  does not excessively protrude toward a cheek side, a tongue side, and a lower or upper jaw side facing support portion  1170 . As illustrated in  FIGS.  1 ,  2 A, and  2 B , it is preferable that a level difference or a gap will not be generated between a region where support portion  1170  is arranged and a region where support portion  1170  is not arranged. 
     Support portions  1170  contain a material with a different flexural modulus from upper-jaw oral appliance body portion  1111  and lower-jaw oral appliance body portion  1112 . For example, support portions  1170  may contain a material with a higher flexural modulus or a material with a lower flexural modulus than the thermoplastic resin composition contained in upper-jaw oral appliance body portion  1111  and lower-jaw oral appliance body portion  1112 . 
     A difference between the flexural modulus of oral appliance body portions  1110  and the flexural modulus of support portions  1170  is preferably greater than or equal to 100 MPa and smaller than or equal to 1600 MPa. The difference between both the flexural moduli is more preferably smaller than or equal to 1200 MPa, even more preferably smaller than or equal to 800 MPa, and still even more preferably smaller than or equal to 600 MPa. On the other hand, the difference between both the flexural moduli is more preferably greater than or equal to 50 MPa. 
     The flexural moduli of oral appliance body portions  1110  and support portions  1170  are measured in conformity with JIS T6501. With the flexural modulus of oral appliance body portions  1110  and the flexural modulus of support portions  1170  being different from each other, even if load is applied to oral appliance body portions  1110  from positioning members  1160  when oral appliance  1100  is put on, force exerted on oral appliance  1100  is relieved by support portions  1170  or oral appliance body portions  1110 , and the wearing feel can be improved while damage and bending are suppressed. In addition, the rearward displacement of lower-jaw oral appliance body portion  1112  can also be suppressed. 
     Each of support portions  1170  may contain, for example, various types of fillers and/or additives together with a high elastic material and a low elastic material insofar as the object and the advantageous effects of the present invention are not impeded. However, an amount of the high elastic material and the low elastic material to total mass of support portion  1170  is preferably 50 mass % to 100 mass %, more preferably 60 mass % to 100 mass %, and particularly preferably 80 mass % to 100 mass %. When the amount of the high elastic material and the low elastic material is within the above-mentioned range, support portion  1170  is sufficiently hardened and can more easily support positioning members  1160 . 
     The high elastic material and the low elastic material are not limited to particular ones insofar as those materials can realize the above-mentioned difference in the flexural modulus between oral appliance body portions  1110  and support portions  1170 . Examples of the high elastic material include metal and (meth)acrylic resin. Materials of support portions  1170  are not limited to the above-mentioned examples. 
     The metal contained in support portions  1170  is just required not to substantially affect the human body. Examples of the metal include titanium, iron (such as steel containing stainless), gold, silver, platinum, cobalt, chromium, etc. and alloys of those metals. Corrosion resistance of the metal may be increased with a chemically formed coating, for example. 
     The (meth)acrylic resin is just required to be resin that mainly includes a unit derived from (meth)acrylate (also referred to as a “(meth)acrylatc unit” hereinafter). The (meth)acrylic resin contains preferably 50 mass % to 100 mass %, more preferably 60 mass % to 100 mass %, and particularly preferably 80 mass % to 100 mass % of the (meth)acrylate unit to total mass of structural units of the (meth)acrylic resin. The (meth)acrylic resin may be, for example, a homopolymer of acrylate, a homopolymer of methacrylate, or a copolymer of acrylate and methacrylate. 
     The (meth)acrylate unit is preferably an alkyl (meth)acrylate unit. The carbon number of an alkyl portion of the alkyl (meth)acrylate unit is preferably 1 to 6, more preferably 1 to 3, even more preferably 1 or 2, and particularly preferably 1. 
     A (meth)acrylate portion of the alkyl (meth)acrylate unit is preferably methacrylate and includes preferably 50 mass % to 100 mass %, more preferably 60 mass % to 100 mass %, and particularly preferably 80 mass % to 100 mass % to total mass of the structural units of the (meth)acrylic resin. 
     The (meth)acrylic resin may contain a structural unit other than the (meth)acrylate unit insofar as the object and the advantageous effects of the present invention are not impeded. Examples of the structural unit other than the (meth)acrylate unit includes a structural unit derived from (meth)acrylic acid (preferably, methacrylic acid) and a structural unit derived from α-olefin (preferably, ethylene, propylene, or butylene). 
     The (meth)acrylic resin is preferably polymethyl methacrylate (PMMA) or a methyl methacrylate-methacrylic acid copolymer (MMA-MAA copolymer) and is particularly preferably PMMA. 
     Mass average molecular weight (Mw) of the (meth)acrylic resin is preferably 10000 to 1000000, more preferably 20000 to 800000, and particularly preferably 50000 to 500000. The mass average molecular weight (Mw) is a value measured with gel permeation chromatography (GPC) and is given as a value in terms of polymethyl methacrylate. 
     A density of the material of support portions  1170  is preferably smaller than 1.5 kg/m 3 , more preferably 0.8 to 1.4 kg/m 3 , and even more preferably smaller than 0.8 to 1.3 kg/m 3 . When the density of the material of support portions  1170  is smaller than 1.5 kg/m 3 , the weight of oral appliance  1100  can be reduced, and feel in use can be easily improved. 
     (Positioning Members) 
     Positioning members  1160  are members for adjusting the relative positions of upper-jaw oral appliance body portion  1111  and lower-jaw oral appliance body portion  1112 , and for suppressing the rearward displacement of lower-jaw oral appliance body portion  1112 . In this embodiment, each of positioning members  1160  includes upper holding portion  1130  attached to an outer lateral surface of upper-jaw oral appliance body portion  1111  with upper support portion  1171  interposed therebetween, lower holding portion  1140  attached to an outer lateral surface of lower-jaw oral appliance body portion  1112  with lower support portion  1172  interposed therebetween, and coupling portion  1150  coupling upper holding portion  1130  and lower holding portion  1140 . 
     A structure of upper holding portion  1130  is not limited to a particular one insofar as upper holding portion  1130  can be joined to upper support portion  1171  and can hold coupling portion  1150  described later. As illustrated in  FIG.  1   , for example, upper holding portion  1130  may have a structure including upper shaft  1132  extending outward from upper support portion  1171  and upper flange portion  1134  positioned further outward of upper shaft  1132 . One end of upper shaft  1132  in the form of a column is supported by upper support portion  1171 . A method of joining upper support portion  1171  and upper shaft  1132  is not limited to a particular one. For example, upper shaft  1132  may be supported by being inserted into a through-hole that is formed in upper support portion  1171 , or may be buried in upper support portion  1171 . 
     A structure of lower holding portion  1140  is also not limited to a particular one insofar as lower holding portion  1140  can be joined to lower support portion  1172  and can hold coupling portion  1150  described later. As illustrated in  FIG.  1   , for example, lower holding portion  1140  may have a structure including lower shaft  1142  extending outward from lower support portion  1172  and lower flange portion  1144  positioned further outward of lower shaft  1142 . One end of lower shaft  1142  in the form of a column is supported by lower support portion  1172 . A method of joining lower support portion  1172  and lower shaft  1142  is similar to the method of joining upper support portion  1171  and upper shaft  1132 . 
     A structure of coupling portion  1150  is not limited to a particular one insofar as coupling portion  1150  can couple upper holding portion  1130  and lower holding portion  1140  and can hold upper holding portion  1130  and lower holding portion  1140  while keeping a certain distance therebetween. In positioning member  1160  illustrated in  FIG.  1   , coupling portion  1150  includes cylindrical outer  1152  with one end supported by upper shaft  1132  of upper holding portion  1130 , inner  1154  with one end supported by lower shaft  1142  of lower holding portion  1140  and the other end slidably received in outer  1152 , and a stopper (not illustrated) that is arranged inside outer  1152  and determines an extension/contraction stroke of inner  1154 . Coupling portion  1150  has such a structure that the inner  1154  is slidably received in the outer  1152  to be capable of extending and contracting. Furthermore, the distance between upper holding portion  1130  and lower holding portion  1140  and hence a positional relation between upper-jaw oral appliance body portion  1111  and lower-jaw oral appliance body portion  1112  can be adjusted in accordance with the position of the stopper. 
     In positioning member  1160  according to this embodiment, lower holding portion  1140  is arranged forward of upper holding portion  1130 . Stated in another way, positioning member  1160  has a structure of pushing lower-jaw oral appliance body portion  1112  forward from a rear side and restricting the rearward displacement of lower-jaw oral appliance body portion  1112 . On the other hand, because inner  1154  can be withdrawn from outer  1152  over a certain range, movement of the lower jaw is hardly impeded, and the wearing feel of the user can be easily made less uncomfortable. A restriction position and a sliding stroke of the lower jaw are adjusted in accordance with the position of the stopper (not illustrated) of coupling portion  1150 . Moreover, the structure of coupling portion  1150  is not limited to the above-described one and may be given as a structure capable of extending and contracting in multiple stages. 
     Positioning member  1160  may be made of the same material in the entirety or made of different materials. Examples of the material(s) of positioning member  1160  include metal materials such as titanium, iron (such as steel containing stainless), gold, silver, platinum, cobalt, chromium, and alloys of those metals, resin materials (such as polycarbonate resin) with the flexural moduli of higher than or equal to 1000 MPa and lower than or equal to 3000 MPa, those flexural moduli being measured in conformity with JIS T6501, and so on. Corrosion resistance of the metal materials may be increased with a chemically formed coating, for example. 
     Method of Manufacturing Oral Appliance According to Embodiment 1 
     A method of manufacturing oral appliance  1100  according to this embodiment is not limited to a particular one. For example, oral appliance body portions  1110  and support portions  1170  may be fabricated by preparing sheets containing the thermoplastic resin composition and sheets containing the above-described high elastic material and low elastic material, and by molding the sheets with heat molding (for example, suction molding, pressure molding, or suction and heat molding). Alternatively, the above-mentioned components may be formed by pouring the thermoplastic resin composition, the high elastic material, etc. into molds, or may be fabricated by laser processing, for example. In this embodiment, the above-mentioned components are particularly preferably fabricated by milling or 3D printing. Those methods enable oral appliance body portions  1110  and support portions  1170  to be fabricated with high accuracy. Furthermore, with the milling or the 3D printing, the machining or the processing can be performed even when a material with high transparency to visible light is used for oral appliance body portions  1110  and so on. Oral appliance body portions  1110  and support portions  1170  may be fabricated by the same method or different methods. 
     For example, when oral appliance body portions  1110  and support portions  1170  are fabricated by the milling, each oral appliance body portion  1110  and each support portions  1170  may be fabricated separately, and individual parts may be joined by fusion bonding or with an adhesive, for example. Alternatively, it is also possible to previously prepare a stacked body in which the thermoplastic resin composition forming oral appliance body portion  1110  and the high elastic material and the low elastic material forming support portion  1170  are stacked one above the other, and to perform the milling on the stacked body. 
     When oral appliance body portions  1110  and support portions  1170  are fabricated by the 3D printing, they may be produced from the thermoplastic resin composition, the high elastic material, etc. by using a known 3D printer. In this case as well, each oral appliance body portions  1110  and each support portion  1170  may be fabricated separately, and individual parts may be joined by fusion bonding or with an adhesive, for example, or may be formed integrally. 
     A method of fabricating each of positioning members  1160  is selected as appropriate depending on the material, and positioning member  1160  can be fabricated by a known metal machining method or a known resin processing method. A method of joining support portion  1170  and positioning member  1160  is not limited to a particular one and is selected as appropriate in conformity with the method of fabricating support portion  1170  and so on. For example, a through-hole may be formed in support portion  1170  that has been fabricated in advance, and upper shaft  1132  or lower shaft  1142  may be inserted into the through-hole. Alternatively, upper shaft  1132  or lower shaft  1142  may be arranged in place and, in such a state, upper shaft  1132  or lower shaft  1142  may be buried in support portion  1170  by 3D printing or heat molding, for example. 
     2. Embodiment 2 
       FIG.  3 A  is a schematic perspective view illustrating an upper-jaw side structure of oral appliance  2100  according to Embodiment 2 of the present invention, and  FIG.  3 B  is a schematic perspective view illustrating a lower-jaw side structure of the oral appliance  2100 .  FIG.  4    is a side view of the oral appliance  2100  in the mouth closed state. As illustrated in  FIGS.  3 A,  3 B, and  4   , oral appliance  2100  according to this embodiment includes a pair of oral appliance body portions  1110  constituted by upper-jaw oral appliance body portion  1111  and lower-jaw oral appliance body portion  1112 , positioning members constituted by a pair of left and right stoppers  2130  arranged on upper-jaw oral appliance body portion  1111  and by a pair of left and right movable wings  2160  arranged on lower-jaw oral appliance body portion  1112 , and support portions constituted by a pair of left and right upper support portions  2171  that cover parts of upper-jaw oral appliance body portion  1111  and that support stoppers  2130 , and by a pair of left and right lower support portions  2172  that cover parts of lower-jaw oral appliance body portion  1112  and that support movable wings  2160 . 
     In oral appliance  2100  according to this embodiment, the rearward displacement of lower-jaw oral appliance body portion  1112  is suppressed by movable wings  2160  (specifically, the wings  2140  described later) and stoppers  2130  of the positioning members abutting on each other. As a result, an airway of the user is kept wide, and apnea or snoring is cured during sleep. 
     In oral appliance  2100  according to this embodiment as well, the support portions (upper support portions  2171  and lower support portions  2172 ) contain a material with a different flexural modulus from the pair of oral appliance body portions  1110 . Furthermore, the support portions (upper support portions  2171  and lower support portions  2172 ) is arranged to cover only parts of oral appliance body portions  1110 . For example, when the flexural modulus of the material of the support portions (upper support portions  2171  and lower support portions  2172 ) is higher than that of oral appliance body portions  1110 , oral appliance body portions  1110  are easier to come into close contact with the tooth rows of the user, and the wearing feel becomes more comfortable. The support portions (upper support portions  2171  and lower support portions  2172 ) are less susceptible to deformation and can support the positioning members (stoppers  2130  and movable wings  2160 ) at the desired positions. In addition, even when load is applied, the support portions are less susceptible to deformation and damage. As a result, oral appliance  2100  according to this embodiment can be stably used for a long period. On the other hand, when the flexural modulus of the material of the support portions (upper support portions  2171  and lower support portions  2172 ) is lower than that of oral appliance body portions  1110 , the support portions relieve force applied to oral appliance  2100 , whereby the wearing feel is improved while damage and bending are suppressed. 
     The pair of oral appliance body portions  1110  (upper-jaw oral appliance body portion  1111  and lower-jaw oral appliance body portion  1112 ) in this embodiment are similar to the pair of oral appliance body portions  1110  in Embodiment 1. Hence those body portions are denoted by the same reference signs as in  FIG.  1    and so on, and description of those body portions is omitted. The support portions and the positioning members of oral appliance  2100  according to this embodiment will be described below. 
     (Support Portions) 
     The support portions of oral appliance  2100  according to this embodiment are constituted by a pair of left and right upper support portions  2171  and a pair of left and right lower support portions  2172 . Upper support portions  2171  are arranged to cover upper-jaw oral appliance body portion  1111  on left and right molar tooth sides, namely to cover surfaces of upper-jaw oral appliance body portion  1111 , the surfaces being opposite to other surfaces fitted to molar teeth. On the other hand, lower support portions  2172  are arranged to cover lower-jaw oral appliance body portion  1112  on left and right molar tooth sides, namely to cover surfaces of lower-jaw oral appliance body portion  1112 , the surfaces being opposite to other surfaces fitted to molar teeth. 
     Shapes of upper support portions  2171  are not limited to particular ones insofar as upper support portions  2171  can support stoppers  2130  of the positioning members described later. The shapes of upper support portions  2171  may be horizontally symmetric or not symmetric. Upper support portions  2171  may be arranged, for example, only between upper-jaw oral appliance body portion  1111  and support stoppers  2130  of the positioning members, namely on surfaces of upper-jaw oral appliance body portion  1111  only on outer lateral sides of the molar teeth. More preferably, upper support portions  2171  have arch-shaped structures covering inner lateral surfaces, bottom surfaces, and outer lateral surfaces of the molar teeth. When upper support portions  2171  have arch shapes, load can be more easily distributed, and upper support portions  2171  are less susceptible to damage even when the load is applied from stoppers  2130 . Widths of upper support portions  2171  are not limited to particular values and may be selected as appropriate in accordance with widths of stoppers  2130  of the positioning members. 
     A thickness of each of upper support portions  2171  is preferably set such that, in a state of the user wearing oral appliance  2100 , upper support portion  2171  does not excessively protrude toward a cheek side, a tongue side, and a lower jaw side facing upper support portions  2171 . As illustrated in  FIG.  3 A , upper support portion  2171  is preferably formed not to generate a level difference or a gap between upper support portion  2171  and upper-jaw oral appliance body portion  1111 . 
     Shapes of lower support portions  2172  are not limited to particular ones insofar as lower support portions  2172  can support the positioning members (adjustment portions  2150  of movable wings  2160 ) described later. The shapes of lower support portions  2172  may be horizontally symmetric or not symmetric. Lower support portions  2172  may be arranged on lower-jaw oral appliance body portion  1112  only on outer lateral sides of the molar teeth. However, lower support portions  2172  preferably have arch-shaped structures covering inner lateral surfaces, upper surfaces, and outer lateral surfaces of the molar teeth. When lower support portions  2172  have arch shapes, adjustment portions  2150  of movable wings  2160  can be firmly supported by lower support portions  2172 . Widths of lower support portions  2172  are not limited to particular values and may be selected as appropriate in accordance with widths of adjustment portions  2150  of movable wings  2160  of the positioning members. 
     Each of lower support portions  2172  are preferably formed such that, in the state of the user wearing oral appliance  2100 , lower support portion  2172  does not excessively protrude toward a tongue side and an upper jaw side facing lower support portions  2172 . On the other hand, lower support portion  2172  preferably has, on the outer lateral surface side of the molar teeth (namely, on the cheek side), a thickness allowing part of adjustment portion  2150  of movable wing  2160  of the positioning member to be sufficiently buried in lower support portion  2172 . Furthermore, as illustrated in  FIG.  3 B , lower support portion  2172  is formed such that part of adjustment portion  2150  of movable wing  2160  of the positioning member protrudes rearward of lower support portion  2172 . 
     A flexural modulus of the support portions (upper support portions  2171  and lower support portions  2172 ) in this embodiment is just required to be different from that of upper-jaw oral appliance body portion  1111  and lower-jaw oral appliance body portion  1112 . For example, the support portions (upper support portions  2171  and lower support portions  2172 ) may contain a high elastic material with a higher flexural modulus or a low elastic material with a lower flexural modulus than the thermoplastic resin composition forming upper-jaw oral appliance body portion  1111  and lower-jaw oral appliance body portion  1112 . When the support portions contain the high elastic material, the support portions are sufficiently hardened, and the positioning members (stoppers  2130  and movable wings  2160 ) can be more easily supported at the desired positions. Materials contained in the support portions are similar to those contained in the above-described support portions in Embodiment 1, and hence detailed description of those materials is omitted here. 
     (Positioning Members) 
     The positioning members are members for adjusting the relative positions of upper-jaw oral appliance body portion  1111  and lower-jaw oral appliance body portion  1112 . The positioning members in this embodiment include a pair of left and right stoppers  2130  attached to the outer lateral surface of upper-jaw oral appliance body portion  1111  with upper support portions  2171  interposed therebetween, and movable wings  2160  attached to the outer lateral surface of lower-jaw oral appliance body portion  1112  with lower support portions  2172  interposed therebetween, each of movable wings  2160  including wing  2140  and adjustment portion  2150 . 
     In the positioning members, rear surfaces  2142  of wings  2140  of movable wings  2160  and front surfaces  2132  of stoppers  2130  abut on each other, whereby the position of the lower jaw of the user is adjusted. More specifically, the rearward displacement of lower-jaw oral appliance body portion  1112  is limited in an occlusal state with the wings  2140  and the stoppers  2130  abutting on each other, and the rearward displacement of the lower jaw of the user wearing oral appliance  2100  is limited. 
     A structure of each of stoppers  2130  is not limited to a particular one insofar as the structure enables the stopper to abut on wing  2140  of movable wing  2160  described later. As illustrated in  FIG.  3 A , for example, stoppers  2130  can be formed of a pair of left and right plate-shaped members supported by upper support portions  2171  and protruding toward the low jaw from the upper jaw of the user. However, stoppers  2130  are not always required to protrude downward beyond a bottom surface of upper-jaw oral appliance body portion  1111  in a wearing state of oral appliance  2100 . 
     As illustrated in  FIG.  4   , each of movable wings  2160  includes wing  2140  abutting on stopper  2130  when the user occludes the teeth while wearing upper-jaw oral appliance body portion  1111  and lower-jaw oral appliance body portion  1112 , and adjustment portion  2150  adjusting the position of wing  2140 . As described above, part of adjustment portion  2150  is incorporated in lower support portion  2172 . 
     A structure of wing  2140  is not limited to a particular one insofar as the structure enables a rear surface of the wing  2140  (rear surface  2142  to be abutted on stopper  2130 ) to abut on front surface  2132  of stopper  2130 . Wing  2140  of oral appliance  2100  illustrated in  FIGS.  3 A,  3 B, and  4    is a plate-shaped member protruding above an upper surface of lower-jaw oral appliance body portion  1112  in the occlusal state. 
     Furthermore, the position of wing  2140  is adjusted in a front-rear direction by adjustment portion  2150  that is supported by lower support portion  2172 . When wing  2140  is arranged at a more rear position by adjustment portion  2150 , lower-jaw oral appliance body portion  1112  is moved further forward in the occlusal state. 
     Adjustment portion  2150  includes first screw rod  2154  having one end supported in lower support portion  2172  and including a male screw formed thereon, second screw rod  2152  having one end supported in wing  2140  and including a male screw formed thereon, and turnbuckle  2156  inserted into screw holes with which the other ends of first screw rod  2154  and second screw rod  2152  mesh. With adjustment portion  2150 , the position of wing  2140  fixed to second screw rod  2152  is adjusted by inserting a rotation pin into a pin hole formed in turnbuckle  2156 , rotating turnbuckle  2156 , and by adjusting an amount of meshing between turnbuckle  2156  and each of first screw rod  2154  and second screw rod  2152 . 
     Stopper  2130  and wing  2140  preferably have such shapes that stopper  2130  does not restrict movement of wing  2140  when lower-jaw oral appliance body portion  1112  is moved in a mouth opening direction during the wearing of the oral appliance. More specifically, as illustrated in  FIG.  4   , stopper  2130  may include inclined portion  2136  that enables lower-jaw oral appliance body portion  1112  to be easily moved in the mouth opening direction. Furthermore, as illustrated in  FIG.  3 B , wing  2140  may include inclined portion  2146  that enables lower-jaw oral appliance body portion  1112  to be easily moved in the mouth opening direction. In other words, stopper  2130  may include, in its front end portion, a rearward-extending inclined surface having an upper end positioned on a relatively forward side and a lower end positioned on a relatively rearward side, and wing  2140  may include, in its rear end portion, a rearward-extending inclined surface having an upper end positioned on a relatively forward side and a lower end positioned on a relatively rearward side. Inclined portion  2146  of wing  2140  abuts on stopper  2130  in the occlusal state. 
     Each of stopper  2130  and wing  2140  preferably contains a material with a high flexural modulus, for example, a material similar to the high elastic material forming the support portions. With stopper  2130  and wing  2140  containing the high elastic materials, strength of stopper  2130  and wing  2140  is sufficiently increased. As a result, the positions of the upper jaw and the lower jaw are less likely to shift during use of oral appliance  2100 . On the other hand, adjustment portion  2150  can be made of a material similar to that of the positioning members in Embodiment 1. Thus, adjustment portion  2150  is preferably made of a metal material or a resin material (for example, polycarbonate resin) with the flexural modulus of higher than or equal to 1000 MPa and lower than or equal to 3000 MPa when measured in conformity with the JIS T6501. 
     Although, in the above-described description, stoppers  2130  are arranged on the upper jaw side and movable wings  2160  are arranged on the lower jaw side, movable wings  2160  may be arranged on the upper jaw side and stoppers  2130  may be arranged on the lower jaw side. 
     Method of Manufacturing Oral Appliance According to Embodiment 2 
     A method of manufacturing oral appliance  2100  according to this embodiment is not limited to a particular one. For example, oral appliance body portions  1110 , the support portions, stoppers  2130  and wings  2140  of the positioning members, and so on may be fabricated by preparing sheets containing the thermoplastic resin composition and sheets containing the high elastic material and the low elastic material, and by molding the sheets with heat molding (for example, suction molding, pressure molding, or suction and heat molding). Alternatively, the above-mentioned components may be formed by pouring the thermoplastic resin composition, the high elastic material, etc. into molds, or may be fabricated by laser processing, for example. In this embodiment, the above-mentioned components are particularly preferably fabricated by milling or 3D printing. Those methods enable oral appliance body portions  1110 , the support portions, stoppers  2130  and wings  2140  of the positioning members, and so on to be fabricated with high accuracy. Furthermore, with the milling or the 3D printing, the machining or the processing can be performed even when a material with high transparency to visible light is used for oral appliance body portions  1110  and so on. 
     Oral appliance body portions  1110 , the support portions, and stoppers  2130  and wings  2140  of the positioning members may be fabricated by the same method or different methods. Moreover, oral appliance body portions  1110 , the support portions, stoppers  2130  of the positioning members, and so on may be fabricated separately, and individual parts may be joined by fusion bonding or with an adhesive, for example, or may be molded integrally. 
     A method of fabricating each of adjustment portions  2150  of movable wings  2160  is selected as appropriate depending on the material, and adjustment portion  2150  can be fabricated by a known metal machining method or a known resin processing method. A method of joining lower support portion  2172  and wing  2140  to adjustment portion  2150  is selected as appropriate in conformity with the method of forming the support portions. For example, adjustment portion  2150  may be buried in wing  2140  or lower support portion  2172  by performing the 3D printing or the heat molding, for example, in a state in which adjustment portion  2150  is arranged in place. 
     3. Embodiment 3 
       FIG.  5    is a schematic perspective view of oral appliance  3100  according to Embodiment 3 of the present invention, and  FIG.  6    is a schematic side view of the oral appliance  3100  in the mouth closed state. As illustrated in  FIGS.  5  and  6   , oral appliance  3100  includes a pair of oral appliance body portions  1110  constituted by upper-jaw oral appliance body portion  1111  and lower-jaw oral appliance body portion  1112 , a positioning member  3160  that restricts the rearward displacement of lower-jaw oral appliance body portion  1112 , and support portions  3170  constituted by upper support portion  3171  that covers part of upper-jaw oral appliance body portion  1111  and that supports positioning member  3160 , and a lower support portion  3172  that covers part of lower-jaw oral appliance body portion  1112  and that supports positioning member  3160 . 
     In oral appliance  3100  according to this embodiment, the rearward displacement of lower-jaw oral appliance body portion  1112  is restricted by positioning member  3160 , whereby an airway of the user is kept wide and apnea or snoring is cured during sleep. 
     In oral appliance  3100  according to this embodiment as well, support portions  3170  (upper support portion  3171  and lower support portion  3172 ) contain a material with a different flexural modulus from the pair of oral appliance body portions  1110 . Furthermore, the support portions  3170  are arranged to cover only parts of oral appliance body portions  1110 . For example, when support portions  3170  include high elastic material with a higher flexural modulus than oral appliance body portions  1110 , oral appliance body portions  1110  are easier to come into close contact with the tooth rows of the user, and the wearing feel becomes more comfortable. Furthermore, in that case, the support portions  3170  are less susceptible to deformation and can support the positioning member  3160  at the desired position. In addition, even when load is applied to oral appliance  3100 , the support portions  3170  are less susceptible to deformation and damage. As a result, oral appliance  3100  according to this embodiment can be stably used for a long period. On the other hand, when the flexural modulus of the material contained in the support portions  3170  is lower than that of oral appliance body portions  1110 , the support portions  3170  relieve force applied to oral appliance  3100 , whereby the wearing feel is improved while damage and bending are suppressed. 
     The pair of oral appliance body portions (upper-jaw oral appliance body portion  1111  and lower-jaw oral appliance body portion  1112 ) in this embodiment are similar to the pair of oral appliance body portions  1110  in Embodiment 1. Hence those body portions are denoted by the same reference signs as in  FIG.  1    and so on, and description of those body portions is omitted. The support portions  3170  and the positioning member  3160  of oral appliance  3100  according to this embodiment will be described below. 
     (Support Portions) 
     The support portions of oral appliance  3100  according to this embodiment are constituted by upper support portion  3171  and lower support portion  3172 . Upper support portion  3171  is arranged to cover upper-jaw oral appliance body portion  1111  at least on an incisor tooth side, namely to cover a surface of upper-jaw oral appliance body portion  1111 , the surface being opposite to another surface fitted to incisor teeth. On the other hand, lower support portion  3172  is arranged to cover lower-jaw oral appliance body portion  1112  at least on an incisor tooth side, namely to cover a surface of lower-jaw oral appliance body portion  1112 , the surface being opposite to another surface fitted to incisor teeth. 
     Shapes of support portions  3170  (upper support portion  3171  and lower support portion  3172 ) are not limited to particular ones insofar as support portions  3170  can support positioning member  3160  (described later) on a front side of the incisor teeth. Support portions  3170  may be arranged, for example, only between oral appliance body portions  1110  and mounting portions  3216  and  3226  of positioning member  3160  described later. Alternatively, or mounting portions  3216  and  3226  of positioning member  3160  may be buried in support portions  3170 . 
     Support portions  3170  (upper support portion  3171  and lower support portion  3172 ) may be arranged only on the outer lateral surfaces of upper-jaw oral appliance body portion  1111  and lower-jaw oral appliance body portion  1112 . However, support portions  3170  preferably have arch-shaped structures covering not only the outer lateral surfaces, but also bottom surfaces, upper surfaces, and inner lateral surfaces of upper-jaw oral appliance body portion  1111  and lower-jaw oral appliance body portion  1112 . When upper support portion  3171  and lower support portion  3172  have arch shapes, positioning member  3160  can be firmly supported by upper support portion  3171  and lower support portion  3172 . Widths of the support portions (upper support portion  3171  and lower support portion  3172 ) are selected as appropriate in accordance with widths of mounting portions  3216  and  3226  of positioning member  3160 . 
     Support portions  3170  in this embodiment are also just required to have a different flexural modulus from upper-jaw oral appliance body portion  1111  and lower-jaw oral appliance body portion  1112 . Support portions  3170  may contain a high elastic material with a higher flexural modulus or a low elastic material with a lower flexural modulus than upper-jaw oral appliance body portion  1111  and lower-jaw oral appliance body portion  1112 . For example, when support portions  3170  contain the high elastic material, support portions  3170  are sufficiently hardened, and the positioning member  3160  can be more easily supported at the desired position. Materials contained in support portions  3170  are similar to those contained in the above-described support portions in Embodiment 1, and hence detailed description of those materials is omitted here. 
     (Positioning Member) 
     Positioning member  3160  is a member for adjusting the relative positions of upper-jaw oral appliance body portion  1111  and lower-jaw oral appliance body portion  1112 .  FIG.  7    is a schematic perspective view of positioning member  3160 , and  FIG.  8    is a schematic exploded perspective view of positioning member  3160 . 
     As illustrated in  FIGS.  6 ,  7 , and  8   , positioning member  3160  in this embodiment includes at least fixed member  3210  supported by upper support portion  3171 , sliding member  3220  supported by lower support portion  3172 , and male screw  3230  coupling fixed member  3210  and sliding member  3220  such that fixed member  3210  and sliding member  3220  are arranged with a predetermined gap kept therebetween. 
     Fixed member  3210  includes substantially semicylindrical cover portion  3214  of which surface facing sliding member  3220  defines substantially semicylindrical groove portion  3212 , and sliding member  3220  includes substantially semicylindrical cover portion  3224  of which surface facing fixed member  3210  defines substantially semicylindrical groove portion  3222 . When fixed member  3210  and sliding member  3220  are arranged with groove portions  3212  and  3222  facing each other, a substantially cylindrical insertion hole is formed through which male screw  3230  can be inserted. 
     Shapes of cover portion  3214  and cover portion  3224  are not limited to the above-described ones, and a substantially truncated conical cylindrical shape, a substantially elliptic cylindrical shape, or a substantially truncated elliptic conical cylindrical shape, for example, may be formed when both the cover portions are arranged to face each other. Furthermore, an outer shape of cover portion  3214  and an outer shape of cover portion  3224  are not always required to be substantially the same and may be different from each other insofar as the above-mentioned insertion hole can be formed. 
     Fixed member  3210  further includes, in addition to cover portion  3214 , mounting portion  3216  for fixing fixed member  3210  to upper support portion  3171 , and female screw  3240 . 
     Cover portion  3214  may be, for example, a thin plate member formed into a semicylindrical shape. Cover portion  3214  may be formed in substantially the same thickness from a front end to a rear end that is in continuity with mounting portion  3216 , or may be formed to have a greater thickness at the rear end to which stress in the left-right direction tends to be applied during the wearing of oral appliance  3100 . 
     Mounting portion  3216  is a thin plate member extending in the left-right direction continuously from the rear end of cover portion  3214  and is formed in a curved shape following the shape of a front surface of upper-jaw oral appliance body portion  1111 . Mounting portion  3216  is fixed to a front side of upper-jaw oral appliance body portion  1111  with upper support portion  3171  interposed therebetween. Mounting portion  3216  may include multiple through-holes  3216   a  that allow mounting portion  3216  to be deformed for easier mounting to upper support portion  3171 . 
     Female screw  3240  is arranged at a position on an inner circumference of groove portion  3212  rearward of the above-mentioned insertion hole. In this embodiment, female screw  3240  is made of the same material as cover portion  3214  and mounting portion  3216  and is formed integrally with cover portion  3214  and so on. 
     Female screw  3240  may be arranged at a rear end of groove portion  3212 . However, female screw  3240  is preferably arranged with a distance kept from the rear end of groove portion  3212  from the viewpoint of suppressing reduction in the wearing feel of the user, the reduction being attributable to a situation that the male screw  3230  deeply meshed with the female screw  3240  and protruding from a rear end of the above-mentioned insertion hole abuts on the tongue of the user. 
     Sliding member  3220  may include, in addition to cover portion  3224 , mounting portion  3226  for fixing sliding member  3220  to lower support portion  3172 , and U-shaped fastener  3228  that holds male screw  3230 . 
     Cover portion  3224  may be, for example, a thin plate member formed into a semicylindrical shape. Cover portion  3224  may be formed in substantially the same thickness from a front end to a rear end that is in continuity with mounting portion  3226 , or may be formed to have a greater thickness at the rear end to which stress in the left-right direction tends to be applied during the wearing of oral appliance  3100 . Cover portion  3224  further includes through-holes  3224   a  and  3224   b  into which end portions of fastener  3228  can be fitted. 
     Mounting portion  3226  is a thin plate member extending in the left-right direction continuously from the rear end of cover portion  3224  and is formed in a curved shape following the shape of a front surface of lower-jaw oral appliance body portion  1112 . Mounting portion  3226  is supported to the front surface of lower-jaw oral appliance body portion  1112  with lower support portion  3172  interposed therebetween. Mounting portion  3226  may include multiple through-holes  3226   a  that allow mounting portion  3226  to be deformed for easier mounting to lower support portion  3172 . 
     Fastener  3228  is a U-shaped member including a pair of substantially rectangular parallelepiped fitted portions  3228   a  and  3228   b  that form the end portions of fastener  3228 , and curved portion  3228   c  that is curved into a semicircular shape and that couples fitted portions  3228   a  and  3228   b  to each other. Curved portion  3228   c  of fastener  3228  is engaged with an annular constricted portion  3235 , described later, of male screw  3230 . The pair of fitted portions  3228   a  and  3228   b  of fastener  3228  are fitted respectively to through-holes  3224   a  and  3224   b  of cover portion  3224 . Male screw  3230  is rotatably fixed to sliding member  3220  with the aid of fastener  3228 . In a state in which fixed member  3210  and sliding member  3220  are not coupled (namely, in a state in which male screw  3230  and female screw  3240  are not meshed), fastener  3228  can be easily removed from sliding member  3220 . 
     Male screw  3230  includes engagement portion  3232  capable of engaging with screwdriver  3400 , a pair of flange portions  3234  and  3236  arranged to face each other, annular constricted portion  3235  arranged between flange portions  3234  and  3236 , and threaded portion  3238  capable of meshing with female screw  3240 . Engagement portion  3232 , flange portion  3234 , constricted portion  3235 , flange portion  3236 , and threaded portion  3238  are arranged in order mentioned from one end of male screw  3230  to the other end. 
     Engagement portion  3232  is arranged at a front end of male screw  3230 . A shape of engagement portion  3232  is just required to make engagement portion  3232  engageable with screwdriver  3400  and to enable male screw  3230  to be rotated when screwdriver  3400  engaged with engagement portion  3232  is rotated. For example, engagement portion  3232  is in the form of a hexagonal hole, and male screw  3230  can be rotated by inserting a tip end of screwdriver  3400  in the form of a hexagonal prism (namely, a hexagon spanner) that can be fitted to the hexagonal hole. 
     The pair of flange portions  3234  and  3236  are each formed with the radius of its outer circumference being greater than that of an inner circumference of the curved portion  3228   c  of fastener  3228 , and constricted portion  3235  is formed with the radius of its outer circumference being smaller than that of the inner circumference of the curved portion  3228   c  of fastener  3228 . As a result, movement of male screw  3230  in the front-rear direction is restricted to be held within a spacing between the pair of flange portions  3234  and  3236 . 
     Threaded portion  3238  is arranged on a rear end side of male screw  3230 . Threaded portion  3238  is just required to have a thread shape capable of meshing with female screw  3240 . A length of threaded portion  3238  is preferably greater than or equal to a half length of male screw  3230  from the viewpoint of increasing an amount by which sliding member  3220  can be advanced relative to fixed member  3210  and increasing an amount by which lower-jaw oral appliance body portion  1112  can be advanced relative to upper-jaw oral appliance body portion  1111 . 
     With positioning member  3160  in this embodiment, the position of lower-jaw oral appliance body portion  1112  relative to the position of upper-jaw oral appliance body portion  1111  can be adjusted by meshing male screw  3230  held on sliding member  3220  with female screw  3240  held on fixed member  3210 , and by rotating male screw  3230  to adjust an amount of meshing between male screw  3230  and female screw  3240 . For example, by moving lower-jaw oral appliance body portion  1112  forward relative to upper-jaw oral appliance body portion  1111  through a distance in accordance with the jaw shape of the user, the rearward displacement of the lower jaw is restricted, and the airway of the user wearing oral appliance  3100  can be made less likely to narrow. 
     Fixed member  3210 , sliding member  3220 , and male screw  3230  can be each made of, for example, a metal material such as titanium, an alloy containing titanium, iron (such as steel containing stainless), gold, silver, platinum, cobalt, chromium, or any alloy of those metals, or a hard resin material (such as polycarbonate resin) with the flexural modulus of higher than or equal to 1000 MPa and lower than or equal to 3000 MPa, that flexural modulus being measured in conformity with JIS T6501. Corrosion resistance of the metal material may be increased with a chemically formed coating, for example. 
     Method of Manufacturing Oral Appliance According to Embodiment 3 
     A method of manufacturing oral appliance  3100  according to this embodiment is not limited to a particular one. For example, oral appliance body portions  1110  and support portions  3170  may be fabricated by preparing sheets containing the thermoplastic resin composition and sheets containing the high elastic material and the low elastic material, and by molding the sheets with heat molding (for example, suction molding, pressure molding, or suction and heat molding). Alternatively, the above-mentioned components may be formed by pouring the thermoplastic resin composition, the high elastic material, etc. into molds, or may be fabricated by laser processing, for example. In this embodiment, the above-mentioned components are particularly preferably fabricated by milling or 3D printing. Those methods enable oral appliance body portions  1110  and support portions  3170  to be fabricated with high accuracy. Furthermore, with the milling or the 3D printing, the machining or the processing can be performed even when a material with high transparency to visible light is used for oral appliance body portions  1110  and so on. Oral appliance body portions  1110  and support portions  3170  may be fabricated by the same method or different methods. The method(s) of fabricating oral appliance body portions  1110  and support portions  3170  may be selected as in Embodiment 1. 
     A method of fabricating each of the components of positioning member  3160  is selected as appropriate depending on the material, and each component can be fabricated by a known metal machining method or a known resin processing method. For example, female screw  3240  may be molded integrally with the other portions of fixed member  3210  (such as cover portion  3214  and mounting portion  3216 ) by using the same material. Alternatively, female screw  3240 , cover portion  3214 , mounting portion  3216 , and so on m may be fabricated separately, and those components may be joined to each other by a known method. 
     A method of supporting positioning member  3160  on support portions  3170  is selected as appropriate in conformity with the method of fabricating support portions  3170 . Upper support portion  3171  and lower support portion  3172  may be fabricated in advance, and mounting portions  3216  and  3226  of positioning member  3160  may be fixed, res respectively, to surfaces of upper support portion  3171  and lower support portion  3172  with metal fittings, for example. Alternatively, mounting portions  3216  and  3226  may be buried in support portions  3170  by performing 3D printing or heat molding, for example, in a state in which mounting portions  3216  and  3226  of positioning member  3160  are arranged at predetermined positions. 
     (Others) 
     Although any of Embodiments 1 to 3 described above includes the upper support portion covering part of the upper-jaw oral appliance body portion and the lower support portion covering part of the lower-jaw oral appliance body portion, the oral appliance may include only one of the upper support portion and the lower support portion. 
     EXAMPLES 
     Oral appliances fabricated in the following Examples and Comparative Example were evaluated on the wearing feel, damage, and deformation in accordance with the criteria described later. 
     Example 1 
     Nylon 12 (product name: Lucitone, made by DENTSPLY-Sirona K.K., flexural modulus: 1330 MPa, and density: 1.02 kg/m 3 ) was prepared as the material of the support portions. On the other hand, PMMA (polymethyl methacrylate, flexural modulus: 1731 MPa) was prepared as the material of the oral appliance body portions. Then, oral appliance  1100  illustrated in  FIG.  1    was fabricated. The wearing feel of the fabricated oral appliance was good, and neither damage nor deformation was not visually found on the oral appliance taken off after the wearing. 
     Examples 2 and 3 
     As listed in Table 1, oral appliances were fabricated in the same manner as in Example 1 except for using, as the material of the support portions, polycarbonate resin (product name: Reining resin N. made by Toushinyoukou Co., Ltd., flexural modulus: 2004 MPa, and density: 1.2 kg/m 3 ) or polyester resin (product name: Estheshot, made by Nissin Dental Products Inc., flexural modulus: 1490 MPa, and density: 1.2 kg/m 3 ). The wearing feel of each of the fabricated oral appliances was good, and the oral appliances were less susceptible to damage and deformation. 
     Example 4 
     An oral appliance was fabricated in the same manner as in Example 1 except for using, as the material of the support portions, nickel cobalt metal (product name: Wironit. made by Nissin Dental Products Inc., flexural modulus: 221,000 MPa, and density: 8.2 kg/m 3 ). The fabricated oral appliance was less susceptible to damage and deformation, but the wearing feel deteriorated a little. 
     Example 5 
     An oral appliance was fabricated in the same manner as in Example 1 except for using, as the material of the support portions, ethylene-vinyl copolymer (flexural modulus: 100 MPa and density: 1.0 kg/m 3 ). The wearing feel of the fabricated oral appliance was good, but damage and deformation occurred in part of the oral appliance. 
     Comparative Example 1 
     An oral appliance was integrally fabricated using PMMA (polymethyl methacrylate, flexural modulus: 1731 MPa) without distinguishing support portions and oral appliance body portions. The wearing feel of the fabricated oral appliance was not good. 
     
       
         
           
               
               
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                   
                   
                   
                   
                   
                 Comparative 
               
               
                   
                   
                 Example 1 
                 Example 2 
                 Example 3 
                 Example 4 
                 Example 5 
                 Example 1 
               
               
                   
               
             
            
               
                 Support 
                 Type 
                 Nylon12 
                 Polycarbonate 
                 Polyester 
                 Nickel 
                 EVA 
                 PMMA 
               
               
                 Portions 
                   
                   
                 Resin 
                   
                 Cobalt 
                   
                   
               
               
                   
                 Flexural 
                 1330 
                 2004 
                 1490 
                 221000 
                 100 
                 1731 
               
               
                   
                 Modulus A 
                   
                   
                   
                   
                   
                   
               
               
                   
                 (MPa) 
                   
                   
                   
                   
                   
                   
               
               
                   
                 Density 
                 1.02 
                 1.2 
                 1.2 
                 8.2 
                 1.0 
                 0.95 
               
               
                   
                 (kg/m 3 ) 
                   
                   
                   
                   
                   
                   
               
               
                 Oral 
                 Type 
                 PMMA 
                 PMMA 
                 PMMA 
                 PMMA 
                 PMMA 
                 PMMA 
               
               
                 Appliance 
                 Flexural 
                 1731 
                 1731 
                 1731 
                 1731 
                 1731 
                 1731 
               
               
                 Body 
                 Modulus B 
                   
                   
                   
                   
                   
                   
               
               
                 Portions 
                 (MPa) 
                   
                   
                   
                   
                   
                   
               
               
                 Difference in 
                 B-A (MPa) 
                 −401 
                 273 
                 −241 
                 219269 
                 −1631 
                 0 
               
               
                 Flexural 
                   
                   
                   
                   
                   
                   
                   
               
               
                 Modulus 
                   
                   
                   
                   
                   
                   
                   
               
               
                 Evaluation 
                 Presence of 
                 A 
                 A 
                 A 
                 A 
                 B 
                 A 
               
               
                   
                 Damage 
                   
                   
                   
                   
                   
                   
               
               
                   
                 Wearing Feel 
                 A 
                 A 
                 A 
                 B 
                 A 
                 D 
               
               
                   
               
            
           
         
       
     
     In the above Table, the presence of damage was evaluated in accordance with the following criteria. Grades A and B fall in the range where there is no problem in practical use.
         A: the oral appliance is not damaged when put on and fitted to a toot row model   B: the oral appliance is partly damaged (flaking is found in parts of the support portions and the oral appliance body portions) when fitted to the tooth row model   C: the oral appliance is damaged when fitted to the tooth row model   D: the oral appliance is damaged before being fitted to the tooth row model       

     The wearing feel was evaluated in accordance with the following criteria. Grades A and B fall in the range where there is no problem in practical use.
         A: the tooth row model does not drop when the oral appliance is held after fitting the oral appliance to the tooth row model   B: the tooth row model is partly damaged when the oral appliance is fitted to the tooth row model   C: the tooth row model is damaged when the oral appliance is fitted to the tooth row model   D: the oral appliance cannot be fitted to the tooth row model or/and the tooth row model drops when, after fitting the oral appliance to the tooth row model, the oral appliance is held while it is kept fitted to the tooth row model       

     As seen from above Table 1, the oral appliance fabricated using one material could not be fitted to the tooth row model, and the wearing feel was not good (Comparative Example 1). By contrast, the wearing feel of the oral appliances each fabricated using materials different in level of flexural modulus for the support portions and the oral appliance body portions was good, and the oral appliances were less susceptible to damage (Examples 1 to 5). Particularly, when an absolute value of the difference in flexural modulus between the support portions and the oral appliance body portions was higher than or equal to 100 MPa and lower than or equal to 1600 MPa (Examples 1 to 3), no damage occurred, and the wearing feel was very good. 
     This application claims priority based on Japanese Patent Application No. 2019-170696 filed Sep. 19, 2019. The contents disclosed in Specification of the cited Japanese Patent Application and the attached drawings are all incorporated in Description of this application by reference. 
     INDUSTRIAL APPLICABILITY 
     According to the oral appliance of the present invention, since the rearward displacement of the lower jaw of the user can be restricted, the oral appliance is very effective in prevention and treatment of the sleep apnea syndrome. Furthermore, the oral appliance of the present invention gives more comfortable wearing feel than the related art and is less susceptible to damage and deformation. Hence the oral appliance of the present invention can be applied to not only prevention and treatment of the sleep apnea syndrome, but also prevention and treatment of temporomandibular disorders, suppression of bruxism, and so on. 
     REFERENCE SIGNS LIST 
     
         
           1100 ,  2100 ,  3100  Oral appliance 
           1110  Oral appliance body portion 
           1111  Upper-jaw oral appliance body portion 
           1111   a ,  1112   a  Tooth row mold portion 
           1112  Lower-jaw oral appliance body portion 
           1130  Upper holding portion 
           1132  Upper shaft 
           1134  Upper flange portion 
           1140  Lower holding portion 
           1142  Lower shaft 
           1144  Lower flange portion 
           1150  Coupling portion 
           1152  Outer 
           1154  Inner 
           1160 ,  3160  Positioning member 
           1170 ,  3170  Support portion 
           1171 ,  2171 ,  3171  Upper support portion 
           1172 ,  2172 ,  3172  Lower support portion 
           2130  Stopper 
           2132  Front surface of stopper 
           2136  Inclined portion of stopper 
           2140  Wing 
           2142  Rear surface of wing 
           2146  Inclined portion of wing 
           2150  Adjustment portion 
           2152  Second screw rod 
           2154  First screw rod 
           2156  Turnbuckle 
           2160  Movable wing 
           3210  Fixed member 
           3212  Groove portion of fixed member 
           3214  Cover portion of fixed member 
           3216 ,  3226  Mounting portion 
           3216   a ,  3226   a  Through-hole 
           3220  Sliding member 
           3222  Groove portion of sliding member 
           3224  Cover portion of sliding member 
           3224   a ,  3224   b  Through-hole 
           3228  Fastener 
           3228   a ,  3228   b  Fitted portion 
           3228   c  Curved portion 
           3230  Male screw 
           3232  Engagement portion 
           3234 ,  3236  Flange portion 
           3235  Constricted portion 
           3238  Threaded portion 
           3240  Female screw 
           3400  Screwdriver