Oral appliance

CA 02583560 2011-03-10

ORAL APPLIANCE

Field of the Invention

This invention relates to an oral appliance that is an orthodontic appliance.

Definitions

In this specification the term “engaging shall bear a broad meaning and shall not be limited to mean retaining or latching engagement.

In the specification the term “comprising shall be understood to have a broad meaning similar to the term including” and will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. This definition also applies to variations on the term comprising” such as “comprise” and comprises.

Background to the Invention

Various types of orthodontic appliances are known. One such type of orthodontic appliance is custom made after taking impressions of a patient’s mouth. The impressions are used to make moulds which in turn are used to make an appliance that is specifically dimensioned and configured to suit that patient's mouth. Not surprising these appliances fit snugly into a user’s mouth and they are efficacious in operation. However the limitation of custom made appliances is the high cost of producing such an appliance and this has reduced their uptake in the market place.

There is therefore a clear need for an appliance that can be manufactured in large quantities in a manufacturing process and that can also be fitted to a variety of patients each having different arch forms and dentition with a snug fit.

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One known orthodontic trainer is produced by Myofunctional Research Pty Ltd, of Helensvale Plaza, Sir John Overall Drive, Helensvale, in the state of Queensland, Australia. The trainer has a shape resembling that of an arch and defines upper and lower teeth channels for receiving respectively the teeth of the upper and lower arches of a user. The trainer , is made of rubber and has a single homogeneous form and consistency throughout which is generally soft and flexible. For example it is easy to bend and twist the member. The walls of the trainer that define the teeth channels for the upper and lower teeth are soft and therefore comfortable against the teeth and gums of a user.

The trainer described above has been used to try and improve the oral habits of users, in particular children. The tongue tab assists in correctly positioning the tongue and reducing tongue thrusting. It also correctly positions the lower jaw with respect to the upper jaw. The trainer has also been found to have some positive influence on the alignment of teeth. However the softness of the silicone rubber material limits the ability of the trainer to apply a force effective to reposition a user's teeth.

Clearly it would be extremely useful if an orthodontic appliance could be devised that was soft and comfortable to wear and which also generated a strong repositioning force. This could exert a strong influence on the development of a user's arch, e.g. an underdeveloped arch of a user, and also help to align a user's teeth.

Summary of the Invention

According to one aspect of this invention there is provided an oral appliance that is an orthodontic trainer, comprising:

a base member having a generally arch shaped form having left and right arms, the base member being made of a polymeric material that is resilient and is capable of some bending when opposing arms of the base member are pulled towards and away from each other; and

CA 02583560 2011-03-10 a continuous teeth engaging member made of another material that is softer than the material of the base member that encloses and encases at least part of the base member and defines at least one of upper and lower teeth channels within which the associated arch and teeth of the user can be received, wherein the base member is designed with a wide arch so that when the appliance is fitted to a user having a narrow arch, the arch is urged to expand by the resilient force of the deformed base member.

The teeth engaging member may include an upper teeth channel and the base member may be designed with a wide arch so that when the appliance is fitted over the upper arch of a user the upper arch is urged to expand out into a wide arch position.

The teeth engaging member may be made of a polymeric material.

The polymeric material may be a polymeric material containing silicon as a repeating unit within the polymer. This may be a synthetic elastomer which is a cross linked polymer reinforced with silica.

The polymeric material may be a siloxane polymer or a silane polymer. In one form of the invention the polymer containing silicon is silicone rubber, e.g. medical grade silicone which has already found acceptance in the field of orthodontic trainers. The silicone material will be particularly soft and comfortable against the gums, and other mouth tissues of a user and has some ability to deform and bend around the teeth and gums.

Alternatively the polymeric material of the teeth engaging member may be an addition polymer. The addition polymer may be polyvinylchloride (PVC). Polyvinyl chloride has a melting point that is lower than that for silicone. As a result the temperature to which the base member is exposed during manufacture, when the polyvinyl chloride teeth engaging member is moulded onto it, is lower than when silicone rubber is moulded onto it.

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The polymeric material from which the base member is formed may be categorised as a hard material. The material from which the base member is made may not deform easily when local pressure or point pressure is applied thereto. The base member may also be regarded as being stiff and may resist being deformed when a force is applied thereto. However at the same time it is resilient and is capable of some bending when opposing sides of the member are twisted or pulled towards and away from each other. The resilience causes it to return to its original shape when the force is removed. Further the polymeric material from which the base member is made may have thermoplastic properties provided it can maintain its form and does not soften when it is exposed to a temperature of 160 degrees Celsius or below. In some embodiments it may maintain its form and not soften when exposed to a temperature of up to 300’c.

The polymeric material from which the base member is made may be a polyamide material. The polyamide material may be formed either by a condensation polymerisation of amide monomers or a ring opening polymerisation of caprolactam. The polyamide material may be a polyamide polymer that is sold under the trade mark NYLON which is the trade mark of the Du Pont Chemical Company, Wilmington, Delaware, U.S.A. (hereinafter referred to simply as nylon). Nylon, is particularly suitable because it has a balance between resilience and stiffness. It does permit some flexing of the arms of the base member. However it has a good memory when subjected to bending or twisting forces and tends to return to its original form when the forces are removed. This helps the base member to maintain the desired arch form while the appliance still maintains a reasonable degree of wearer comfort.

Alternatively the polymeric material of the base member may be an addition polymer or a condensation polymer. The addition polymer may include polyethylene or polypropylene. The condensation polymer may include polyurethane or polycarbonate. The polymeric material may also include a thermoplastic elastomer such as santoprene.

In one embodiment of the invention the base member is made of polyamide material and the teeth engaging member is made of silicone rubber.

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With this combination the base member is moulded in a first step during the manufacture of the trainer. Thereafter the silicone teeth engaging member is moulded onto the base member in a second step. The nylon base member has the property that it does not soften and melt when it is exposed to molten silicone rubber when the silicone rubber is injected into the mould and encases the base member.

Thus the orthodontic appliance essentially comprises a base member that is 10 formed from a material that provides an underlying skeletal strength to the appliance, that is encased in a teeth engaging member, of silicone rubber or PVC, that is considerably softer and more formabie than the base member. By having an underlying base member the appliance is able to exert a considerably stronger influence on the alignment of a patient's teeth than if the appliance were made solely of soft silicone rubber. In addition it is able to influence the general shape and the width of the arch.

Urging the arch to expand typically includes widening the arch utilising by the resilient force of the deformed base member, e.g. particularly in an anterior region thereof. The base member may be designed with a wide arch in which case the trainer will tend to force the arch and teeth out into a wide arch position. This way the trainer can be used to expand narrow arches into more aesthetically pleasing and desirable wide arches.

The base member may be in the form of an open frame structure, e.g. a flat open frame structure, with curved inner and outer longitudinal frame members that are interconnected at spaced intervals by transverse frame members. The open frame structure may lie broadly in a plane and in particular the transverse frame members may lie broadly in a plane that extends in a substantially horizontally extending direction.

The base member may further include an outer teeth repositioning formation on the outer longitudinal frame member.

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The outer teeth repositioning formation may comprise an outer flange projecting up from the outer frame member above the height of the transverse frame members and/or depending down from the outer frame member below the level of the transverse frame members.

The base member may further include an inner teeth repositioning formation on the inner longitudinal frame member.

The inner teeth repositioning formation may comprise an inner flange projecting up from the inner frame member above the height of the transverse frame members and/or depending down from the inner frame member below the level of the transverse frame members.

The base member may have a central front region and left and right arms extending rearward from the central front region to left and right rear ends.

The outer flange may project up above the transverse frame members along at least said central front region of the base member extending across the upper incisor teeth of a user.

For example the central front region may project above an upper surface of the transverse frame members that lie broadly in a plane by 2-10mm, e.g. 4-8mm, e.g. about 6mm. Thus the outer flange may have some height, particularly in the central front region.

In some forms the outer flange may also project upwardly above the transverse frame members along the left and right arms of the base member.

For example the left and right arms may project above an upper surface of the transverse frame members that lie broadly in a planeby 2-6mm, e.g. 3-5mm, e.g. about 4mm. Thus the outer flange in the central front region is higher than the flange on the left and right arms, e.g. which extend over at least part of the molars of the user.

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Further the outer flange may be interrupted, or be of reduced height, at positions on the left and right hand sides of the base member, intermediate the left and right arms of the outer flange and the central front region of the outer flange. These positions on the left and right sides correspond to the positions of the canine teeth of a user. The height of the outer flange is reduced at these points because the canine teeth sometimes project out relative to the other teeth and may not easily fit behind the flange if the outer flange is the same height as it is in the central front region.

The outer flange may be formed integrally with the curved outer longitudinal frame member, e.g. in an injection moulding operation.

The inner flange on the curved inner longitudinal frame member may project up above the transverse frame members that lie in the same plane. For example the inner flange may project up a distance of about 1-3mm, e.g. about 2mm above the upper surface of the transverse frame members that lie broadly in a plane.

The inner flange may project up from the transverse frame members along at least the central front region of the inner longitudinal frame member. In some forms the inner flange may project up from the transverse frame members along the full length of the inner longitudinal frame member and the inner flange may have substantially the same height along its full length.

The inner flange may also be formed integrally with the curved inner longitudinal frame member, e.g. in an injection moulding process.

In some forms of the invention, the outer flange on the curved outer longitudinal frame member does not extend or depend downwardly below the plane of the open frame to any appreciable extent. Similarly the flange on the curved inner longitudinal frame member does not extend or depend downwardly below the plane of the open frame to any appreciable extent

However it needs to be appreciated that an appliance with one or more downwardly depending flanges falls within the scope of the invention. Applicant

CA 02583560 2011-03-10 has found that a satisfactory stiffness, i.e. rigidity, and strength can be obtained with outer and inner flanges that only project up from the open frame and not down from the open frame. However if greater stiffness or strength was required from the outer longitudinal frame member, the flange could depend downwardly as well as projecting upwardly. A downwardly depending inner flange could also be provided for the same purpose.

In a further alternative form of the invention, the inner and outer flanges described above could also project down from the plane of the open frame or the transverse frame members instead of projecting up from the transverse frame members.

The base member may have a front said transverse frame member in the central front region of the base member, and two rear transverse frame members at the rear of the left and right arms of the base member.

The base member may also have a plurality of intermediate said transverse frame members in between the rear transverse frame members at the rear of the arm regions and the front transverse frame member.

The transverse frame member in the central front region of the base member may have a width of 5-15mm, preferably 8-12mm, and most preferably about 9-11mm. The rear transverse frame members may have a width of 2-1 Omm, preferably 38mm, and most preferably 4-6mm. The intermediate transverse frame members may have a width of 1-4mm, e.g. 2-3mm.

Thus the transverse frame member disposed in the front region of the base member, e.g. substantially centrally, has a greater width than the rear and intermediate transverse frame members. The transverse frame members or cross elements perform important structural functions and strengthen the appliance in key areas such as the front region thereof. In particular they stiffen the front region of the base member.

The teeth engaging member may comprise a central web having upper and lower surfaces that extends parallel to the plane formed by the transverse frame

CA 02583560 2011-03-10 members of the open frame structure, and also inner and outer flanges that project transversely away from at least one of the upper and lower surfaces of the web. The inner and outer flanges and the web may form at least one teeth channel within which the teeth of a user can be received.

The flanges of the teeth engaging member may project away from both the upper and lower surfaces of the web and define upper and lower teeth channels. The teeth engaging member may comprise a front region and left and right arms extending away from the front region much like the base member.

The teeth engaging member may fully encase the open frame structure of the base member. Thus the teeth engaging member extends around and over the base member and defines the surfaces of the trainer that come into contact with and engage the teeth and gums of the user. The teeth engaging member may cover an outer surface of the outer flange with a relatively thin layer of material. The advantage of the teeth engaging member encasing the base member is that it assists in holding the teeth engaging member onto the base member. The base member and the teeth engaging member are made of different materials and the encasement of the base member within the teeth engaging member assists in holding the two members together and the appliance resists being delaminated in use.

The teeth engaging member may further include one or more teeth positioning formations projecting into said at least one of the upper and lower teeth channels for assisting in positioning individual teeth of a user that engage or bear against the positioning formation. The teeth positioning formations may be arranged in pairs that are aligned with each other along the length of the inner and outer flanges and that project away from the inner and outer flanges respectively.

Each teeth positioning formation on the teeth engaging member may comprise a wedge shaped protrusion extending inwardly from one of the inner and outer flanges into one of the upper and lower teeth channels. Each teeth positioning formation may be broadly shaped to be complementary to a tooth surface and may extend into the associated channel only a small distance.

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The teeth positioning formations may be positioned so as to encourage the teeth to move towards a certain position on the arch.

The teeth positioning formations may be integrally moulded with the teeth engaging member, e.g. by injection moulding, when the teeth engaging member is moulded onto the base member.

The orthodontic trainer may include holes passing through the teeth engaging member and base member and opening to both the outer surfaces of the teeth engaging member and the inner surface thereof.

The orthodontic trainer may also include a tongue tab for encouraging a user to correctly position their tongue.

The orthodontic trainer may also include a cutaway, or recess defined thereof in the front region of the teeth engaging member, e.g. the curved inner flange, for facilitating adjustment of the width of the trainer when it is being fitted to a user, e.g. particularly the left and right arms of the teeth engaging and base member,. Conveniently this may be provided by the spaces on each side of the tongue tab on the curved inner flange.

The orthodontic trainer may also include a cut away on the midline of the curved outer flange, e.g. both above and below the web to enhance user comfort when the appliance is worn.

The orthodontic appliance may also have some thickening of the web of the teeth engaging member in the left and right arms thereof. The thickness of the teeth engaging member may increase in a direction rearward from a central front region towards the rear of the left and right arms. This thickening may terminate at a point spaced forwardly of the rear of the left and right arms of the teeth engaging member. The teeth engaging member may then thin again from this point to the rear of the left and right arms.

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The thickening of the teeth engaging member may resemble an inverted aerofoil, e.g. with a curved lower surface and a substantially planar upper surface, when viewed in cross section. This shape of the web region of the teeth engaging member correctly positions the teeth of the upper and lower jaw relative to each other so as to encourage relaxation of the muscles and also the temporomandibular joint (TMJ).

Applicant envisages that the orthodontic appliance will be made in several sizes and that a suitable size of trainer could be selected for a given user. Applicant envisages that the appliance will be made in two different arch sizes and each arch size will have about six different arrangements of teeth positioning formations. The different teeth positioning formations will accommodate the different teeth sizes and teeth positions of different users.

The invention also extends to the use of an orthodontic trainer as defined in the preceding aspect of the invention for expanding the upper arch of a patient.

This invention can be used in a method of orthodontic treatment of a patient including treating a patient to encourage improved oral habits and encouraging an and the steps of fitting an appliance as described in the first or second aspects of the invention above to a user, and getting the user to wear the appliance on a regular basis.

Wearing the appliance on a regular basis may comprise wearing the appliance for at least a few hours in each 24 hour day. Preferably the user wears the appliance at least a few hours during the day time and a few hours in the night time on each day.

Brief Description of the Drawings

An oral appliance that is an orthodontic trainer in accordance with this invention may manifest itself in a variety of forms. It will be convenient to hereinafter provide a detailed description of some embodiments of the invention with reference to the accompanying drawings. The purpose of providing this detailed description is to

CA 02583560 2011-03-10 ¹² instruct persons having an interest in the subject matter of the invention how to put the invention into practice. It is to be clearly understood however that the specific nature of this detailed description does not supersede the generality of the preceding statements. In the drawings:

Fig 1 is an upper front three dimensional view of an appliance that is an orthodontic trainer in accordance with the invention;

Fig 2 is an upper rear three dimensional view of the appliance of Fig 1 ;

Fig 3 is a front view of the appliance of Fig 1 ;

Fig 4 is a rear view of the appliance of Fig 1 ;

Fig 5 is a top plan view of the appliance of Fig 1 ;

Fig 6 is a bottom plan view of the appliance of Fig 1 ;

Fig 7 is a side view of the appliance of Fig 1 from one side;

Fig 8 is a side view of the appliance of Fig 1 from the other side;

Fig 9 is an upper three dimensional view of part of the appliance of Fig 1 with part of the teeth engaging member removed to expose an underlying base member;

Fig 10 is an upper three dimensional view of the base member shown in Fig 9 for the appliance of Fig 1 ; and

Fig 11 is a lower three dimensional view of the base member of Fig 10.

Detailed Description of the Preferred Embodiments

In Figs 1 to 9 the reference numeral 1 refers generally to an appliance that is an orthodontic trainer in accordance with the invention.

The orthodontic trainer 1 comprises a base member 2 having a generally Ushaped or arch-shaped form corresponding to the outline of the arch of the jaw of a user. The base member 2 which is shown in Figs 10 and 11 on its own is indicated by hidden detail lines in Figs 1 to 9. The orthodontic trainer 1 further includes a teeth engagement member 5 made of silicone rubber that encloses and encases the base member 2. The teeth engaging member 5 occupies a substantially greater volume than the base member 2 and forms the body and shape of the trainer 1. It also defines the operative surfaces that interact with and

CA 02583560 2011-03-10 engage or bear against the intra-oral structures including teeth and gum tissues of a user. The base member 2 is shown particularly clearly in Figs 9 to 11 and is in the form of an open frame structure with curved outer and inner longitudinal frame members 10 and 12 joined at spaced intervals by transverse frame members 15.

The base member 2 comprises a frontal portion or central front region indicated generally by numeral 17, and left and right arm regions or arms indicated generally by numerals 18 and 19.

In the illustrated embodiment the base member 2 has several transverse frame members 15. One of these is located proximate to the front central region 17 of the circular elements 10, 12. This transverse frame member 15 has a width of about 812mm and is considerably thicker than the other transverse frame members. The additional width serves to confer additional strength and rigidity on this transverse frame member 15. Thus it requires a greater force to deform the central front region 17 of the base member 2. Two further transverse frame members 15 are located adjacent the rear of the left and right trailing arm regions 18, 19 of the base member 2. These rear transverse frame members 15 have a width of 36mm. While the rear transverse frame members 15 are thinner than the front transverse frame member they are thicker than the remaining transverse frame members. The remaining transverse frame members 15 are known as intermediate transverse frame members. In the illustrated embodiment there are two said transverse frame members on each arm region 18, 19. The transverse frame members have a width of 1-4mm, e.g. about 2mm. The transverse frame members 15 are arranged so that they all lie broadly in the same plane. That is the upper surface of each transverse frame members 15 lies in the same plane and the lower surface of each transverse frame member 15 also lies in the same plane.

Further the base member 2 also includes an outer flange 25 projecting up from the curved outer frame member 10 and extending along the full length of the curved outer frame member 10. The outer flange 25 projects up above the plane defined by the transverse frame members 15 . In particular, the outer flange 25 projects

CA 02583560 2011-03-10 up above the plane defined by an upper surface of each transverse frame member 15.

The portion of the outer flange 25 in the central front region 17 of the outer curved frame member 10 projects up further than that portion of the outer flange 25 projecting up from the left and right arm regions 18 and 19. The flange portion in the central front region 17 has a maximum height of 6-8mm. The flange portions on the left and right arm regions of the outer frame member 10 have a maximum height of 5-7mm. The outer flange 25 also defines a low point 28 on each side thereof that is intermediate the central front portion 17 and the left and right hand arm regions 18,19. The low point is positioned at the point where the eye teeth or canine teeth of a user are located. The reason for this is that the canine teeth are sometimes positioned laterally outward of the other teeth and if the flange was higher in this area the trainer might not easily fit over some user's teeth. Applicant has found that by reducing the height of the outer flange 25 at this point on each side thereof, the trainer 1 can be fitted to most users or patients.

The curved inner frame member 12 of the base member 2 also has an inner flange 30 extending up therefrom. The inner flange 30 projects up above a plane formed by the transverse frame members 15. In particular, the inner flange 30 projects up above an upper surface of each transverse frame member 15 by a distance of 13mm, e.g. about 2mm. It is less upstanding than the outer flange 25.

The curved outer and inner frame members 10,12 and the outer and inner flanges 25 and 30 promote correct positioning of the upper teeth. In addition these members and flanges confer further rigidity or stiffness and structural strength on the base member 2 to help it perform its function.

The base member 2 in the drawings does not have a flange depending or extending down below the open frame of the base member 2 to any appreciable extent. Applicant has found that the illustrated outer and inner flanges 25, 30 provide the base member 2 with the necessary level of torsional rigidity and stiffness, and corresponding lower flanges are not necessary. However it Is to be clearly understood that a downwardly depending flange is considered to fall within

CA 02583560 2011-03-10 the scope of this invention. For example, a downwardly depending flange would further increase the strength of the base member 2.

The base member 2 defines a pair of openings 38, 39 in its central front region 17. The openings 38, 39 are formed in both the curved inner and outer frame members 12, 10 of the base member 2. These are located on left and right sides of the front region 17 of the base member 2. The openings are formed by integral bracket or loop formations that depend down below the base member 2, The openings 38, 39 cooperate with corresponding openings in the teeth engaging member 5 as will be described in more detail below.

The base member 2 is made of a polyamide material that is nylon. Nylon is hard and has been found to have an appropriate level of rigidity. At the same time it is resiliently flexible and inter alia permits some movement of the left and right arm regions 18,19 towards and away from each other and some twisting of the left and right arm regions 18, 19 relative to each other.

Nylon is a generic name of any long chain synthetic polymeric amide which has recurring amide groups as an integral part of the main polymer chain. The polymer is linear and as such is suited to being formed into a filament although this need not be the case. One of the properties of nylon that makes it suitable for this application is that it is capable of withstanding particularly high temperatures. As a result it does not soften or deform when it is brought into contact with molten silicon at high temperatures when the trainer is being manufactured. Applicant has obtained nylon from Shinko Chemical Company based in Taipei, Taiwan. The table below indicates the different grades of Nylon 66 supplied by this company.

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<td> TENSILE STRENGTH</td><td> Kg/cm²</td><td> 800</td><td> 900</td><td> 1700</td><td> 1900</td><td> 840</td><td> 1150</td>

<td> ELONGATION</td><td> %</td><td> 55</td><td> 10</td><td> 7.1</td><td> 2</td><td> 4</td><td> 4.5</td>

<td> FLEXURAL STRENGTH</td><td> Kg/cm²</td><td> 1000</td><td> 1350</td><td> 2300</td><td> 2600</td><td> 1200</td><td> 1700</td>

<td> FLEXURAL MODULUS</td><td> Kg/cm²</td><td> 28000</td><td> 35000</td><td> 80000</td><td> 108000</td><td> 31000</td><td> 72000</td>

<td> IZOD IMPACT STRENGTH</td><td> Kg- cm/cm</td><td> 13</td><td> 8.5</td><td> 11</td><td> 9</td><td> 7.3</td><td> 7</td>

<td> ROCKWELL HARDNESS</td><td> R- SCALE</td><td> 118</td><td> 119</td><td> 120</td><td> 120</td><td> 118</td><td> 119</td>

<td> MELTING POINT</td><td> °C</td><td> 260</td><td> 260</td><td> 255</td><td> 260</td><td> 260</td><td> 260</td>

<td> M.D.T (18.6kG/cm2)</td><td> °C</td><td> 66</td><td> 200</td><td> 238</td><td> 240</td><td> 73</td><td> 248</td>

<td> M.D.T (4.6kG/cm2)</td><td> °C</td><td> 230</td><td> 240</td><td> 255</td><td> 255</td><td> 230</td><td> 245</td>

<td> ASH CONTENT</td><td> W1%</td><td></td><td> 13</td><td> 33</td><td> 45</td><td></td><td> 25</td>

<td> MOLD</td><td></td><td> 1.7-1.8</td><td> 0.3-0.5</td><td> 0.2-0.4</td><td> 0.2-0.3</td><td> 1.0-1.3</td><td> 0.3-0.5</td>

<td> SHRINKAGE</td><td></td><td> 1.3-1.4</td><td> 0.8-1.0</td><td> 0.7-1.0</td><td> 0.3-0.5</td><td> 0.7-1.0</td><td> 0.7-1.0</td>

<td> M.F.</td><td> g/10min</td><td> 55</td><td> 20</td><td> 13</td><td> 10</td><td> 43</td><td> 20</td>

<td> SP Gr</td><td> g/cm²</td><td> 1.1</td><td> 1.2</td><td> 1.35</td><td> 1.46</td><td> 1.16</td><td> 1.38</td>

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The Applicant has utilised a grade of Nylon 66 known as Nylon 66 6212GA for the appliances he has made. This material has the following properties:

Tensile strength 900

Flexural Strength 1350

ROCKWELL Hardness 119

Nylon is a staple commodity that could be obtained from a large number of nylon suppliers around the world including Du Pont Nemours Chemical Company (Du Pont) based in Delaware in the USA. Applicant envisages that the invention would be able to be practised equally well no matter which supplier the nylon was sourced from.

The teeth engaging member 5 comprises a central web 40 that broadly surrounds and encases the open frame portion of the base member 2. It fills in the space between the transverse frame members 15 and also forms a layer of some thickness around the open frame structure. The teeth engaging member 5 also has inner and outer flanges 44, 45 extending both upwardly and downwardly both sides of the web 40. These flanges 44, 45 together with the web 40 form an upper teeth channel 46 within which the upper arch and teeth of a user are received in use. The flanges 44, 45 and web 40 also form a lower teeth channel 47 within which the lower arch and teeth of a user are received in use. As with the base member 2 the teeth engaging member 5 may comprise a central front region and left and right arm regions or arms 48 and 49 which also form the front region and arms of the appliance as a whole.

In this embodiment the teeth engaging member 5 is made of a polymeric compound containing silicon that is a silicone rubber that is of medical grade. This rubber is a staple commodity and can be bought from a number of well known chemical companies. For example, Applicant is aware that it can also be procured from Du Pont. Applicant has sourced a suitable silicone rubber from a Japanese

CA 02583560 2011-03-10 chemical company by the name of Shin-Etsu Chemical Co Ltd based at 6-1, 2 Chôme, Ohtemachi, Chiyodaku, Tokyo, Japan. The material specification data sheet provided by Shin- Etsu for this material is provided below.

MATERIAL SPECIFICATION DATA SHEET

<td colspan="3"> SHIN-ETSU ® TWO-COMPONENT</td><td colspan="2"> Transparent</td><td></td>

<td colspan="3"> SILICONE RUBBER COMPOUND</td><td colspan="2"> High Strength</td><td></td>

<td> Typical Properties</td><td></td><td> Units</td><td> KE-1950-</td><td> KE-1950-</td><td> KE-1950-</td>

<td></td><td></td><td></td><td> 50</td><td> 60</td><td> 70</td>

<td></td><td></td><td></td><td> (A-B)</td><td> (A-B)</td><td> (A-B)</td>

<td> Viscosity in mPa.s</td><td></td><td></td><td> 680</td><td> 730</td><td> 750</td>

<td colspan="3"> (P) Brookfield-type rotational viscometer</td><td> (6800)</td><td> (7300)</td><td> (7500)</td>

<td colspan="2"> Specific Gravity at 25°C (77°F)</td><td> g/cm³</td><td> 1.13</td><td> 1.14</td><td> 1.15</td>

<td colspan="3"> Mixing Ratio A:B</td><td> 1:1</td><td> 1:1</td><td> 1:1</td>

<td> Hardness</td><td> JIS-A</td><td></td><td> 50</td><td> 58</td><td> 68</td>

<td> Tensile Strength</td><td> JIS-6301</td><td> MPa</td><td> 9.3</td><td> 7.8</td><td> 7.8</td>

<td> Elongation at break</td><td> JIS-6301</td><td> %</td><td> 55</td><td> 380</td><td> 350</td>

<td> Tear Strength</td><td> JIS-6301</td><td> kN/m</td><td> 44.1</td><td> 43.1</td><td> 49</td>

<td> Compression set</td><td> 22h/150°C</td><td> (%)</td><td> 28</td><td> 22</td><td> 50</td>

<td> Linear Shrinkage</td><td> JIS-6301</td><td> (%)</td><td> 2</td><td> 1.9</td><td> 2.1</td>

<td colspan="2"> Volume Resistivity Comments</td><td> Ω-m</td><td> 10T</td><td> 10T</td><td> 10T</td>

The grade of the silicone that the Applicant has used the most frequently for the appliance is KE-1950-70, which is the hardest grade.

Another supplier of silicone rubber is the Bayer Chemical Company based in Leverkusen, Germany. Bayer supplies a liquid silicone rubber LSR 2050 that is non toxic and suitable as a medical grade material. It is a two component rubber with each component packed in a separate container, in use the two components

CA 02583560 2011-03-10 are pumped into a static mixer and mixed thoroughly, and then the mixture is injected into an injection mould die.

The trainer 1 also includes teeth positioning formations 50 formed on each of the inner and outer flanges 44, 45 of the teeth engaging member 5 as shown in the drawings. The teeth positioning formations 50 which project out from the member 5 engage or bear against individual teeth of the user in use and urge them into certain positions on the arch.

Each teeth positioning formation 50 comprises a wedge shaped protrusion projecting out from each of the inner and outer flanges 44, 45 into the upper and lower teeth channels for projecting between the inter-proximal surfaces of adjacent teeth. Each of the wedge shaped protrusions when viewed in cross section tapers inwardly from both sides.

The trainer 1 includes teeth positioning formations 50 projecting into each of the upper and lower teeth channels of the teeth engaging member 5. In the illustrated embodiment the teeth positioning formations 50 are designed for locating the ten teeth of a user nearest the front of the arch on the upper jaw. Similarly the appliance may include similar teeth positioning formations 50 for locating the ten forward teeth on the arch of the lower jaw of a user.

The orthodontic trainer may also include a notch or cut-out 55 in the midline upper surface of the outer flange 45 of the teeth engaging member 5. It also includes a smaller midline notch or cut-out 57 in the lower surface of the outer flange 45. The notches 56, 57 remove material from the teeth engaging member 5 on the midline so that it does not come into contact with soft gum tissue of a user in this area. The gum of a user has a tendon that extends across this area and the appliance will be more comfortable for the user if the teeth engaging member 5 does not come into contact with this tendon.

The orthodontic trainer 1 also has a tongue tab 60 for training a user to position their tongue in a certain position. The tongue tab 60 is formed in the inner flange

CA 02583560 2011-03-10 of the member 5 upwardly of the web 40. This assists in improving the oral habits of a user and particularly in avoiding tongue thrusting.

There are spaces on each side of the tongue tab 60. The spaces on either side of the tab 60 facilitate inward adjustment of the arms of the trainer 1 when it is fitted to a user. There is also a small notch formed in the lower edge of the inner flange, e.g. in a central position.

Further the web 40 of the teeth engaging member 5, e.g. the upper and lower faces thereof, taper outward from the front region of the member in a rear direction to the left and right trailing arms 48, 49. The effect of this is to progressively thicken the web 40 in a direction from the front to the rear of the teeth engaging member 5. This continues up to a point in the left and right trailing arms 48,49 that is spaced forward of the rear ends of the arms 48, 49. Thereafter the upper and lower faces of the engaging member 5 taper inwardly towards each other so as to progressively thin from said point to the rear of the teeth engaging member 5. In summary the web 40 can generally be described as having an aerofoil shape on each arm 48, 49 extending back from the front region. The aerofoil shape is asymmetric having a curved surface on its lower side and a more planar upper surface. It thus can be thought of as being an inverted or upside down aerofoil shape. This aerofoil shape of the web 40 fills in the space between the upper and lower teeth of a user and supports the jaw. This enables the bottom jaw to assume its anatomically correct position in relation to the upper jaw and this has relaxation and muscular benefits to the user.

The teeth engaging member 5 also has passages defined therein in the same place as the apertures 38, 39 of the base member 2. These passages are continuous and open at both ends and increase the surface area of the teeth engaging member 5 in contact with the base member 2 thereby to assist in keying the teeth engaging member 5 onto the base member 2.

The orthodontic trainer is manufactured as follows. First the base member 2 is injection moulded from nylon in a first Injection moulding step. The teeth engaging member 5 is then moulded around and over the base member 2 and encases the

CA 02583560 2011-03-10 base member 2 in a second moulding step. The formed orthodontic trainer 1 can then be removed from the die. The cycle times for each of the moulding steps may be about 15 seconds. The cycle time for the silicone rubber moulding will be longer than that for the nylon base member. Generally the moulded pieces are allowed to cool passively. However the silicone rubber can be actively cooled once it has been moulded. Generally the members are removed from the die once the moulded material has had an opportunity to cool sufficiently.

The molten silicone is introduced to the die at a very high temperature and the moulded base member has to be able to withstand this temperature without softening. Nylon is capable of withstanding the temperatures of injection of the silicone and thus has been found to be very suitable for this purpose. Further as described above nylon is particularly suitable because it has a high level of stiffness and local hardness while at the same time permitting some flexing of the arm regions of the trainer towards and away from each other.

The trainer 1 can be moulded in two separate dies with the base member 2 being moulded in a first die in the first injection moulding step, and then being removed and placed in a second die where the teeth engaging member 5 is moulded in the second injection moulding step.

Alternatively the base member 2 and the teeth engaging member 5 can be moulded in the same mould in a co-injection process. That is the base member 2 is moulded in the first moulding step by an injection moulding process and then subsequent thereto the teeth engaging member 5 is moulded onto the base member 2 in the second moulding step. In this alternative form of manufacture the base member 2 does not have to be removed from the mould before the teeth engaging member 5 is moulded onto it. The mould comprises two mould parts, one for each of the base member 2 and the teeth engaging member 5, which are brought in sequence into operative positions in the moulding area.

In use the orthodontic trainer 1 described above is typically initially fitted to a user that is a patient by an orthodontist or a dentist.

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Applicant envisages that a range of trainers 1 will be provided having different sizes of base member 2, Each of the sizes of base member 2 will then have a teeth engaging member 5 having one of at least four different arrangements of teeth positioning formations 50 for catering for the different dentition in different patients.

Accordingly the first step of the dentist is to choose an appropriately sized trainer 1 from the different sizes of trainers and insert it into a patient's mouth. Generally a practitioner will choose a certain size of trainer after inspecting and measuring the arch and teeth of the patient. However a trial and error procedure could also be used whereby the practitioner tried each of the different sizes of appliance and selects the one that fits the patient the best.

Once fitted to the patient's mouth the soft silicone rubber of the teeth engaging member 5 bears against the gum and teeth of the patient. The skeletal base member 2 provides the underlying strength when deformed to urge development of the arch shape and form defined by the trainer 1 in the patient and also to urge the teeth into position.

The inner and outer flanges 44, 45 of the teeth engaging member 5 bear against the arches and the dentition of the patient. The silicone from which the base member 5 is formed, is soft and has some ability to conform to the mouth of the patient. It is also resilient and thus when it is deformed when fitted to the patient it applies a return force against the intra-oral structures including the teeth of the patient. This force tends to align individual teeth so that they do not protrude or retract and also contributes to expansion of the arch form.

The underlying rigidity of the base member develops the shape of the arch so that it forms a smooth curved shape that mimics the appliance as shown in the drawings. In this way a narrow arch on the patient is urged to widen by the resilient biasing force of the deformed base member. This is analogous to active spring energy. The biasing force is applied against the arch and teeth tending to widen out the arch.

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Over time through the application of force the teeth will tend to move towards their desired positions. The application of force to move teeth is standard practice in orthodontics. The physiological mechanism by which tooth movement is accomplished is well understood by the dental and orthodontic community and will not be described further in this specification.

The teeth positioning formations 50 also encourage certain teeth to take up certain positions along the arch.

The orthodontic trainer receives both the upper and lower arches and teeth of a patient and thus is not suitable for use during every day living. For example a patient could not talk or eat while they were wearing the trainer. The trainer will typically be worn by a patient for a few hours each night. It is also advantageous if the trainer is also worn for a few hours in the day time when this is possible.

In another embodiment of the invention that has not been illustrated in the drawings the base member 2 is made out of nylon and the teeth engaging member 5 is made of polyvinylchloride (PVC). PVC resin is a staple commodity in the chemical industry and is available from a large number of chemical manufacturers around the world. Applicant has obtained PVC resin from IMPRODEX which is a division of Pacific Dunlop Limited based at 135 Racecourse Road, Flemington, VIC, Australia. The specification for the product used by the Applicant is HYCO 4016-89 PVC compound. This is a clear extrusion grade PVC compound for applications requiring good clarity and low toxicity and is suitable for food contact use.

The properties of this PVC grade are as follows:

<td colspan="2"> SPECIAL PROPERTIES</td>

<td> Shore A Hardness (ASTM 2240) Instantaneous</td><td> 79</td>

<td> Shore A Hardness (ASTM 2240) 10 second delay</td><td> 71</td>

<td> Specific Gravity</td><td> 1.22</td>

<td> Tensile Strength</td><td> 17.7Mpa</td>

CA 02583560 2011-03-10

<td> Elongation at Break</td><td> 400%</td>

A trainer 1 made of these materials and having the same structural features and form as the silicone rubber trainer described above is manufactured by a similar two step moulding process. The base member 2 is moulded of nylon in a first step. Thereafter the teeth engaging member 5 is manufactured of PVC in a second injection moulding step.

An advantage of using PVC instead of silicone rubber is that it does not require as high an injection temperature as silicon which simplifies the moulding equipment that is used. It also reduces the temperature that the base member is required to withstand when the teeth engaging member is injected onto the base member when being moulded and this makes it possibile to use materials other than nylon for the base member. Applicant envisages that other materials including addition polymers such as polyethylene and polypropylene; condensation polymers such as polyurethane and polycarbonate; and thermoplastic elastomers such as santoprene may be used for forming the base member 2.

In use this trainer is used in the same way as the trainer described above. The PVC has similar properties to silicone and the other polymeric materials if they are used have similar properties in use as the nylon.

An advantage of the appliance described above with reference to the drawings is that it can apply a force that is strong enough to widen the user’s arch and it can also reposition teeth. The force that is applied to the arch and teeth is comparable to that achieved by other orthodontic appliances. The repositioning force is due to the underlying strength of the base member. The trainer does not simply align adjacent teeth with each other so that they do not protrude. Rather it tends to widen the arch if it is narrower than the ideal arch width. In particular if the arch form is narrow, the inner and outer frame members of the base member have a wide arch form and are resilient, and thus urge a widening of the arch form when the appliance is fitted.

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The base member also has the effect of applying a force to misaligned teeth, be it protruding or retruding teeth, and this force tends to return them to the arch form or the arch line.

The nylon of the base member has sufficient resilience and spring force to enable the appliance to be fitted to most users with some degree of comfort. Further the softness of the silicone rubber also assists the appliance to be fitted to a user with a reasonable degree of comfort notwithstanding that it has not been custom moulded for a particular user.

The flange on the outer curved frame member of the base member assists with the realignment of teeth. The inner and outer longitudinal frame members of the base member including the associated flanges, have the effect of pushing teeth that are retruded or misaligned. Similarly if the tooth is rotated, with the distal edge protruding and the mesial edge retruded, then the Inner and outer flanges also apply a force to encourage rotational realignment to the correct position.

A further advantage of the orthodontic trainer described above is that the silicone rubber is a very soft material. It therefore has the ability to conform to the contours of a user's teeth and gums without applying too much local pressure to the teeth and gums. As such the trainer is not unduly harsh on a user’s mouth and can be worn with a reasonable degree of comfort.

Yet further the trainer can be manufactured in a moulding operation in large quantities on a commercial scale. The appliance is injection moulded in a two step moulding operation in a number of different sizes. It does not need to be custom moulded for each individual user. This enables it to be supplied to the market at a reasonable cost.

A further advantage of the orthodontic trainer described above is that it has individual teeth positioning formations projecting out from the outer teeth engaging member for positioning individual teeth of a user in an optimum position along the curved line of the arch.

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It will of course be realised that the above has been given only by way of illustrative example of the invention and that all such modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of the invention as herein set forth.