AU2012241192B2

AU2012241192B2 - An orthodontic appliance

Info

Publication number: AU2012241192B2
Application number: AU2012241192A
Authority: AU
Inventors: Christopher John Farrell
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-10-14
Filing date: 2012-10-18
Publication date: 2014-09-11
Anticipated expiration: 2025-10-14
Also published as: AU2012241192A1

Abstract

An orthodontic appliance 1 for promoting development of a dental arch form in a patient who has an underdeveloped dental arch form is disclosed. The appliance 1 includes an arch-shaped base member 2 that is made of a resiliently flexible 5 material, and a teeth engaging member 5 that encloses at least part of the base member 2. The teeth engaging member 5 defines upper and/or lower dental arch receiving channels 46, 47 and is made of a resiliently flexible material that is softer than the base member and is deformable. The appliance 1 has a resting form in which the resilient materials of the base member 2 and the teeth engaging 10 member 5 are in their resting condition. The appliance 1 can be flexed or deformed out of the resting form to fit the underdeveloped dental arch form into the dental arch receiving channel 46, 47. When deformed the appliance 1 exerts a return force that is directed to returning it to its resting form which in use urges the underdeveloped dental arch to expand into a developed dental arch form. 15 FIG 9 FOR PUBLICATION

Description

AN ORTHODONTIC APPLIANCE FIELD The disclosure relates to an orthodontic appliance for use in orthodontic treatment for developing an underdeveloped arch into a developed arch form. 5 This disclosure relates particularly but not exclusively to an orthodontic appliance for use in treating a Class 2 malocclusion by promoting expansion of an underdeveloped upper dental arch, It will therefore be convenient to hereinafter describe the invention with reference to this example application. However it is to be clearly understood that the disclosure is capable of broader application. For 10 example it can find application in orthodontic treatments other than those seeking to expand the patient's arch form. It can also find application in the treatment of malocclusions other than class 2 malocclusions. DEFINITIONS In this specification the term "engaging" shall bear a broad meaning and shall not 15 be limited to a retaining or latching engagement. Similarly the term "flange" shall bear a broad meaning and shall not be limited to a radially extending wall at the end of a cylindrical section. It shall be understood to include a wall or wall like formation that extends transversely away from another surface, e.g. a web surface. 20 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". 25 In this specification the term "correct dental occlusion" shall bear a broad meaning and shall refer to an occlusion where the dentition of the upper and the lower arches come together in a correct positioning relative to each other along the length of the arch. Similarly the term "dental arch and associated dental structures" shall include the bone of the dental arch, the surrounding bony gum tissues, the soft gum tissues and also the dentition on the arch. Further in this specification the terms "frame", "frame structure" and open frame structure" shall be interpreted broadly and shall include all frames. Further the 5 terms may be used interchangeably in this specification. BACKGROUND One type of orthodontic appliance that is known is a custom made retainer or plate appliance that is made in a dental laboratory and is moulded from bite impressions of the dental arches and associated dental structures of that 10 particular patient. The bite impressions are used to make laboratory models of that particular patient's arches and associated dental structures. These models are then used to mould a customised retainer appliance including a plate that is shaped and configured to be complementary to that particular user's dental arch and thereby closely fit that user's dental arch and arch structures. A limitation of 15 the retainer appliances is that the cost of producing them is high because they are individually made for each patient in a dental laboratory based on a dental model of the patient and a bite impression of the patient. Orthodontic systems using fixed appliances that are commonly called orthodontic braces are also used for orthodontic treatment. Orthodontic braces comprise a 20 plurality of brackets or bands each of which is mounted over an individual tooth and bonded thereto so that it is permanently mounted on the tooth. The brackets are linked together by means of a wire that passes through wire apertures formed in each of the brackets. The wire applies a force to the brackets that can then be used to reposition and align the teeth on the dental arch. In particular these fixed 25 appliances can be used to bring the anterior teeth on the upper and lower arches in the correct relative position to each other. The wire can progressively be drawn in to retract the incisor teeth on the anterior region of the upper dental arch to "close" an "open" bite. The fixed appliances can achieve some degree of arch expansion together with alignment of the teeth but the extent of the expansion is 30 limited. The fixed appliances use brackets to move teeth on a dental arch, and in particular to align the teeth. For example they can be used to retract protruding 3 teeth, in particular protruding incisors on the upper arch of a user, and they can also be used to advance retruded teeth. The fixed braces described above have their drawbacks. Firstly Applicant's experience is that most orthodontic patients would choose not to wear braces if an 5 alternative treatment was available. The brackets of the braces are generally unsightly and detract from the patient's looks while the braces are being worn, e.g. for the duration of the treatment, Secondly the braces can be uncomfortable to wear and can cause trauma, such as cuts and bruises to the intraoral soft tissues of a user. The soft buccal mucosa is particularly susceptible to injury from 10 projections on the buccal surface of the brackets. Thirdly the brackets and wire are permanently attached to the dentition and thus cannot be temporarily removed by a patient in the way that a removable appliance can be removed. If the braces are particularly uncomfortable at any time they cannot be temporarily removed to afford the patient some respite from the discomfort. 15 Fourthly another shortcoming that has plagued the use of braces is patient relapse. By this is meant that the teeth tend to move back to their original positions once the brackets are removed. The braces are permanent appliances so that when they are removed they cease to have any influence on teeth positioning. They cannot be used on an intermittent basis to provide a retaining 20 function after the braces have been removed in the way that a removable appliance can be used. The braces do not offer a realistic or practical option as a retainer appliance once its use as an active appliance to achieve teeth repositioning is completed. Aside from the traditional orthodontic treatments described above, in more recent 25 times some treatments have focused on encouraging and promoting improved myofunctional habits as a way of developing an intraoral environment that is less likely to develop severe class 2 and class 3 malocciusions. For example some orthodontic practitioners have recognised that poor oral habits such as tongue thrusting, incorrect swallowing, and mouth breathing create the conditions in which 30 a malocclusion is likely to develop in a growing child.

4 The applicant has developed an arch shaped appliance having a front region and two arm regions to train a patient's or user's myofunctional habits so that the environment in which arch development and teeth positioning takes place is improved. in particular the appliance can train a patient to position certain key 5 intraoral structures such as the tongue in the correct position and thereby resist the development of malocclusions that are caused by poor oral habits. One such feature is a tongue tab that assists in positioning the tongue at the correct height and to reduce tongue thrusting. The appliance also correctly positions the lower jaw or mandible of the patient relative to the upper jaw or maxillae and thereby 10 encourages the patient to maintain their lips in a closed position and not to breathe through their mouth. These appliances are integrally formed of a soft and resilient material such as PVC or silicon rubber which enables the appliance to be comfortably worn by a patient, The soft and resilient material enables the appliance to be comfortably worn when 15 it bears against the dental arch and arch structures such as the teeth and gums of a patient. The primary orthodontic influence conferred by the appliance is to train the patient to adopt improved myofunctional habits which promotes the intra-oral conditions that are more likely to promote the correct arch development which improves dental occlusion. 20 It would be advantageous if an orthodontic appliance could be devised that at least ameliorated one or more of the shortcomings of the appliances and treatments described above. SUMMARY OF THE DISCLOSURE According to one aspect of the disclosure there is provided an orthodontic 25 appliance for developing a dental arch form of a patient who has an underdeveloped dental arch form, the appliance comprising: a deformable teeth engaging member that includes an arch-shaped web that defines upper and lower occlusal bite surfaces, the teeth engaging member includes inner and outer flanges that project transversely away from the upper 30 surface of the web, the web and the inner and outer flanges defining an upper D arch receiving channel within which an upper dental arch and associated dentition of a patient can be received; and an arch-shaped base member that is constructed from a resilient flexible material that is substantially enclosed by the teeth engaging member, the base 5 member extending through the web and including an outer teeth repositioning formation received within the outer flange of the teeth engaging member, wherein the appliance has a resting form and can be deformed out of the resting form when fitted to a patient to receive a patient's underdeveloped dental arch form in a dental arch receiving channel, and exert a return force against the 10 received dental arch form to develop the arch form. The teeth engaging member may include a tongue tab formed on the inner flange of the teeth engaging member for encouraging a patient to correctly position their tongue within their mouth. The base member may include a frame extending parallel to the web, and the 15 outer teeth repositioning formation may project substantially orthogonally up the frame, In particular the frame may be a flat frame that lies in a plane that passes through the web. The outer teeth repositioning formation may be in the form of an outer flange that extends along the base member, 20 The outer flange may comprise a continuous wall extending lengthwise along the base member. The outer flange of the base member may extend along substantially the full length of the base member and the height thereof may vary along its length. The base member may further include an inner teeth repositioning formation 25 projecting substantially orthogonally up from the frame and being received within the inner flange of the teeth engaging member.

The inner teeth repositioning formation may comprise an inner flange that extends along the base member. The inner and outer flanges of the teeth engaging member may also project transversely downward away from the upper and the lower surfaces of the web 5 and define a lower arch receiving channel (in addition to the upper arch receiving channel) for receiving a lower dental arch and dentition of a patient. The base member may include a further outer teeth repositioning formation which projects substantially orthogonally downward away from the web and is received within the outer flange of the teeth engaging member. 10 The base member may include a further inner teeth repositioning formation which projects substantially orthogonally downward away from the web and is received within the inner flange of the teeth engaging member. The appliance may comprise a front region that merges with two opposing arm regions that project away from either side of the front region. The web may 15 decrease in transverse width in a direction from the arm regions towards the front region so as to correspond with the decrease in width of the occlusal surfaces of a dental arch from a molar region towards an incisor region, The upper dental arch receiving channel may be dimensioned so that the dental arch and dentition are received within the channel with a tight fit where the 20 dentition bears against the inner and outer flanges. The frame may include an arch-shaped outer frame member and an arch-shaped inner frame member that are spaced apart from each other, and the transverse spacing between the inner and outer frame members may decrease a direction from the arm regions to the front region of the appliance. 25 The frame may further include a plurality of transverse frame members that extend substantially linearly between the outer frame member and the inner frame member. The base member may extend along the front region and also the arm regions.

I The teeth engaging member may be formed of a resilient flexible material that is softer than the material from which the base member is formed and which provides a soft cushion for forming a cushion for bearing against the dental arch and dental structures of the patient. 5 The base member may be made of a resiliently deformable material having a greater hardness and rigidity than the teeth engaging member, and the base member may contribute to generating the resting form return force for driving expansion of the patient's arch. The teeth engaging member may fully encase the base member and the materials 10 of the base member and the teeth engaging member respectively may be selected such that they flex in unison with each other and resist being delaminated from each other when they are deformed out of their resting conditions. According to another aspect of this invention there is provided a pre-manufactured orthodontic appliance for developing a developed dental arch form in a patient 15 who has an underdeveloped dental arch form, comprising a front region that merges with two opposing arm regions that project away from either side of the front region, the appliance including: a deformable teeth engaging member that includes an arch-shaped web that defines upper and lower occlusal bite surfaces, and the teeth engaging 20 member has inner and outer flanges that project transversely away from the upper and the lower surfaces of the web, the web and the inner and outer flanges defining an upper arch receiving channel within which an upper dental arch and associated dentition of a patient can be received, the web decreases in transverse width in a direction from the arm regions towards the front region so as to 25 correspond with the decrease in width of the occlusal surfaces of a dental arch so that the dental arch and dentition are received within the dental arch receiving channel with a tight fit, and the teeth engaging member includes a tongue tab formed on the inner flange of the teeth engaging member for encouraging a patient to correctly position their tongue within their mouth; and an arch-shaped base member that is constructed from a resilient flexible material that is substantially enclosed by the teeth engaging member, the base member including a frame extending substantially through the web substantially parallel to the web, the frame includes an arch-shaped outer frame member and 5 an arch-shaped inner frame member that are spaced apart from each other, and the transverse spacing between the inner and outer frame members decreases a direction from the arm regions to the front region of the appliance, and the base member includes an outer teeth repositioning formation projecting substantially orthogonally up from the frame that is received within the outer flange of the teeth 10 engaging member, wherein the appliance has a resting form and can be deformed out of the resting form when fitted to a patient to receive a patient's underdeveloped dental arch form in a dental arch receiving channel, and exert a return force in the direction of the plane against the received dental arch form to develop the arch 15 form. The appliance may include any one or more of the optional or preferred features of the appliance defined in the preceding aspect of the invention. According to another aspect of the disclosure there is provided a method for treating a class 2 malocclusion in a patient, the method including: 20 providing a plurality of orthodontic appliances that have been pre manufactured on a commercial scale in a plurality of sizes, each orthodontic appliance including: a deformable teeth engaging member that includes an arch-shaped web that defines upper and lower occlusal bite surfaces, the teeth engaging 25 member includes inner and outer flanges that project transversely away from the upper surface of the web, the web and the inner and outer flanges defining an upper arch receiving channel within which an upper dental arch and associated dentition of a patient can be received, and an arch-shaped base member that is constructed from a resilient 30 flexible material that is substantially enclosed by the teeth engaging member, the base member extending through the web and including an outer teeth repositioning formation received within the outer flange of the teeth engaging member; and fitting a suitably sized appliance to the patient by mounting the appliance over an 5 upper arch of the patient to receive the patients' underdeveloped dental arch form within the arch receiving channel thereby deforming the appliance out of its resting form and exerting a return force against the received dental arch form to develop the arch form. The method may include wearing the appliance on a regular basis. The method 10 may further include selecting a suitably sized appliance. The method may include the patient mounting the appliance within the patient's mouth in a removable fashion during the course of treatment. Thus the appliance can be removed by the patient when this is required. Wearing the appliance on a regular basis may include wearing the appliance for at least eight hours in each 24 15 hour day. The system may further include monitoring the class 2 malocclusion at regular intervals over a treatment period that is 12 to 24 months. The appliance in the system may include any one or more of the optional or preferred features of the appliance defined in the preceding aspects of the 20 disclosure. According to yet another aspect of the disclosure there is provided an orthodontic appliance for developing a developed dental arch form in a patient who has an underdeveloped dental arch form, the appliance comprising: an arch-shaped base member that is constructed from a resilient, flexible 25 material; and a deformable teeth engaging member that substantially encloses at least part of the base member and that defines at least one of an upper or a lower dental arch receiving channel, the teeth engaging member being constructed from -l U a resilient, flexible material that is softer than the resilient, flexible material of the base member, wherein the appliance has a resting form in which the base member and the teeth engaging member are in their resting condition, and the appliance can be 5 manipulated from the resting form when fitted to a patient to receive the patient's underdeveloped dental arch form in the at least one dental arch receiving channel, and wherein the appliance exerts a resting form return force urging the underdeveloped dental arch form to develop into the developed dental arch form. The at least one dental arch receiving channel has a shape corresponding to the 10 developed dental arch form when the appliance is in the resting form. The dental arch receiving channel may have a caternary shape representing correct dental occlusion when the appliance is in the resting form. The appliance may have a resilient flexibility that permits the appliance to be manually flexed or deformed out of the resting form to fit the underdeveloped 15 dental arch into the dental arch receiving channel without excessive effort being required. The appliance may include a front region that merges with two opposing arm regions that project away from either side of the front region. The front region of the appliance may be less flexible than the arm regions whereby a flexure may be 20 formed at either side of the front region when the arm regions are flexed towards each other. The material of the base member and the material of the teeth engaging member may be selected so that they flex in unison with each other when they are deformed out of their resting conditions, and also so that the base member and 25 the teeth engaging member resist being delaminated from each other when they are flexed out of their resting conditions. The teeth engaging member may include an arch-shaped web that defines upper and lower occlusal bite surfaces, and the teeth engaging member may have inner and outer flanges that project transversely away from at least one of an upper or a lower surface of the web, whereby the at least one dental arch receiving channel is defined between the web and the inner and outer flanges, The web may decrease in transverse width in a direction from the arm regions toward the front region of the appliance so as to correspond with the decrease in 5 width of the occlusal surfaces of a dental arch in a direction from a molar region towards an incisor region, whereby the inner and outer flanges of the teeth engaging member may bear against a patient's dental arch and dental arch structures. The inner and outer flanges may project away from both the upper and lower 10 surfaces of the web defining both upper and lower dental arch receiving channels within which respective upper and lower dental arches of a patient can be received, The teeth engaging member may substantially fully enclose the base member. In particular the teeth engaging member may fully encase an outer surface of the 15 base member. The teeth engaging member may be made from a resiliently elastic material that is selected to be softer than intra-oral soft tissue, whereby to form a soft cushion for bearing against the dental arch and dental structures of a patient. The resilient, flexible material of the teeth engaging member may be silicone rubber, e.g. a 20 medical grade silicone rubber, The silicone rubber cushions the appliance against the dental arch and associated dental structures including teeth, gums and other intra-oral tissues of a user, Instead the resilient, flexible material of the teeth engaging member may be made of a polyvinyl chloride (PVC). The base member may comprise an open frame structure including an arch 25 shaped outer frame member and an arch-shaped inner frame member that are spaced apart from each other. The base member may include a plurality of spaced apart transverse frame members connecting the outer frame member and the inner frame member.

12 The transverse spacing between the inner and outer frame members may decrease in a direction from the arm regions to the front region of the appliance, whereby an outline of the base member corresponds substantially with that of the web of the teeth engaging member. 5 The base member may include a first pair of transverse frame members including one transverse frame member towards one side edge of the front region of the appliance and a further transverse frame member towards the other side edge of the front region, wherein the left and right transverse frame members are substantially aligned with respective left and right outer incisors of a patient. 10 The base member may include a front transverse frame member intermediate the first pair of transverse frame members. The front transverse frame member may be positioned substantially centrally with respect to the base member and may have a centre point midway along its length that is aligned with a midline of the base member. The front transverse frame member may extend across at least 15 part of the two central incisors of a patient when the appliance is fitted to a patient. The one and further transverse frame members of the first pair may have a width of I to 4 mm, e.g. 2 to 3 mm. The front transverse frame member may have a width of 5 to 15 mm (when measured extending from one side edge to the other. For example the front transverse frame member may have a width of 8 to 12 mm. 20 The base member may further include a second pair of transverse frame members towards the free ends of the base members comprising a left rear transverse frame member towards a free end of an arm region and a right rear transverse frame member towards a free end of the other arm region. Each of the left and right rear transverse frame members may have a width of 2-10mm, e.g. 25 about 5mm. The base member may further include a third pair of transverse frame members positioned intermediate the first and second pairs of transverse frame members. The third pair of transverse frame members may comprise a left transverse frame member positioned intermediate said transverse frame member of the first pair 30 and the left rear transverse frame member, and a right transverse frame member positioned intermediate said right transverse frame member of the first pair and the right rear transverse frame member. The third pair of intermediate transverse frame members may be positioned adjacent to the first premolars on the dental arch when the appliance is fitted to the patient, which are the fourth teeth on the 5 arch located in the first and second quadrants. The third pair of intermediate transverse frame members may be positioned closer to the left and right rear transverse frame members than said left and right transverse frame members of the first pair on the front region of the base member. Each pair of intermediate transverse frame members may be symmetrically arranged on each side of a 10 midline of the base member, e.g. the arrangement of transverse frame members on the base member may be bilaterally symmetrical. The base member may further include an outer teeth row repositioning formation that projects away from the outer frame member. The outer teeth row repositioning formation may comprise an outer flange that projects up above the 15 open frame structure and extends along the central front region of the appliance and across a patients upper arch incisor teeth. The outer flange may extend up to a height of 2 to 10 mm above the transverse frame members, e.g. an upper surface of the adjacent or proximate transverse frame members, along the front region of the appliance. 20 The outer flange may also extend along at least part of the left and right arm regions of the appliance across a patient's molar teeth. The left and right flange arm regions may extend up to a height of 2 to 6 mm above the transverse frame members, e.g. an upper surface of the adjacent or proximate transverse frame members, along the arm regions of the appliance. Optionally the outer flange may 25 comprise a continuous wall that extends in a substantially uninterrupted fashion along the base member and the height of the continuous wall may vary along the length of the wail The base member may further include an inner teeth row repositioning formation projecting away from the inner frame member. The inner teeth row repositioning 30 formation may comprise an inner flange that projects up above the open frame structure. The inner flange on the inner frame member may project up to a height 14 of about 1-3mm, e g. about 2mm up from the transverse frame members, e.g. on the upper surface of the adjacent or proximate transverse frame members. The inner flange may project up above the transverse frame members along at least the front region of the appliance. The inner flange may also project up from 5 the transverse frame members along the arm regions of the appliance. Further the inner flange may have substantially the same height along its full length. The outer and the inner flanges may be formed integrally with the open frame structure, eg. in an injection moulding operation. In one form of the disclosure neither the outer flange on the outer frame member 10 nor the inner flange on the inner frame member extends or depends downwardly below the plane of the open frame to any appreciable extent. However an appliance with one or more downwardly depending flanges is contemplated to be within the scope of the disclosure. Applicant has found that with the base member materials that he has used, a satisfactory stiffness and strength can be obtained 15 with outer and inner flanges that project up from the open frame but not down from the open frame. However if a greater rigidity is required to be conferred by the base member for the appliance to perform its orthodontic function, then the inner and/or outer flanges could depend downwardly from the open frame as well as projecting upwardly. 20 In a further alternative the inner and outer flanges described above may project down from the plane of the open frame or the transverse frame members instead of projecting up from the transverse frame members. The resiliently flexible material of the base member may be a polymeric material that is a polyamide material, for example nylon, or an addition polymer, for 25 example polyethylene or polypropylene, or a condensation polymer, for example polyurethane, or a polycarbonate, or a thermoplastic elastomer, for example santoprene. The teeth engaging member may include at least one pair of adjacent teeth positioning formations for assisting with the positioning of specific teeth of a patient that are located adjacent to said at least one pair of adjacent teeth positioning formations. Each teeth positioning formation of said at least one pair of adjacent teeth positioning formations may be aligned with each other along the length of the 5 teeth engaging member and may be located on respectively the inner and outer flanges of the teeth engaging member facing into the associated arch receiving channel, being either the upper arch receiving channel or the lower arch receiving channel. Each adjacent teeth positioning formation of said at least one pair of adjacent 10 teeth positioning formations may comprise a wedge shaped protrusion having a wedge point facing into the channel away from the flange on which it is located, Further the adjacent teeth positioning formations of each pair may be integrally formed with the flange on which it is located, e.g. by being moulded integrally with the remainder of the teeth engaging member. 15 The teeth engaging member may include a first pair of said adjacent teeth positioning formations that are arranged on the midline of the appliance for positioning between the two inner incisors when mounted on a patient. The teeth engaging member may include a second and third pair of adjacent teeth positioning formations that are arranged to be positioned between the inner and 20 outer incisors on the left side, and between the inner and outer incisors on the right side, The teeth engaging member may include fourth and fifth pairs of adjacent teeth positioning formations that are arranged to be positioned between the outermost incisor and the canine on the left side, and the outermost incisor and the canine 25 on the right side of the arch of a patient. The teeth engaging member may include sixth and seventh pairs of adjacent teeth positioning formations that are arranged to be positioned between the canine and the first pre-molar on the left side, and the canine and the first pre-molar on the right side of the arch of a patient. The teeth engaging member may include yet 'b further pairs of adjacent teeth positioning formations for positioning further teeth on the arch of a user. In those forms of the disclosure where the teeth engaging member defines both upper and lower channels for receiving the upper and lower dental arches and 5 associated dental structures of a patient, the teeth engaging member may have pairs of adjacent teeth positioning formations in both said upper and lower channels for positioning specific teeth on both the upper and lower arch of the patient. The orthodontic appliance may also include a tongue tab for encouraging a patient 10 to correctly position their tongue. The tongue tab may be formed on the inner flange of the teeth engaging member and may be positioned above the web. The teeth engaging member may include at least one cutaway or recess above the web on the inner flange of the teeth engaging member. Conveniently the inner flange may define two cutaways above the web on the inner flange, namely one 15 on either side of the tongue tab. The teeth engaging member may include at least one further cutaway or recess below the web on the inner flange of the teeth engaging member. The further cutaway may be defined on the midline of the appliance. The one and further cutaways enable the teeth engaging member provide space 20 when the left and arm regions of the appliance are moved towards each other when the appliance is manually flexed out of its resting form and thereby assist with manipulation of the appliance. The teeth engaging member may include a cut away on the outer flange above the web, and another cutaway on the outer flange below the web. These 25 cutaways are formed in the outer flange so that an underlying region of the soft gum on the associated dental arch of a patient does not make contact with the teeth engaging member when the appliance is mounted on the patient in use. The web of the teeth engaging member appliance may be formed of varying thickness along its length. In particular the thickness of the web may increase l I progressively in a direction rearward from the central front region of the appliance up to respective points of maximum thickness that are positioned forward of the free end of the arm regions. The thickness of the web increases up to the respective points of maximum thickness on each arm region, and thereafter the 5 thickness of the teeth engaging member progressively decreases towards the respective free ends of the arm regions. 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. By shaping the web region in this way, the teeth engaging member supports the dentition on the 10 upper and lower arches when the upper and lower jaws are brought together. This encourages relaxation of the muscles, particularly where the user has a malocclusion and there is a space between the occlusal surfaces of the dentition on the upper and lower arches. It also supports the temporomandibular joint (TMJ joint). 15 In one example form of the disclosure the base member may be constructed from nylon and the teeth engaging member from silicon rubber, Applicant envisages that the orthodontic appliance will be made in several sizes and a suitable size of appliance will be selected for a patient based on the size of their dental arches and associated dental structures. Applicant envisages that the 20 appliance will be manufactured in three or more different arch sizes to accommodate relatively larger arch sizes in patients and relatively smaller arch sizes. Each arch size will be manufactured with six or more variations in the arrangements of the adjacent teeth positioning formations. The different arrangements of the adjacent teeth positioning formations are intended to cater for 25 different teeth sizes and different individual teeth positions in different patients. According to another aspect of this disclosure there is provided an orthodontic appliance for developing a dental arch form in a patient who has an underdeveloped arch form, the appliance comprising: an arch-shaped base member that is constructed from a resilient, flexible 30 material having a shape that corresponds generally to a dental arch form; and a deformable teeth engaging member that substantially encloses at least part of the base member and that defines at least one of an upper or a lower dental arch receiving channel, the teeth engaging member being constructed of a resilient, flexible material that is more flexible than the resilient, flexible material of the base 5 member, wherein the appliance comprises a front region that merges with two opposing arm regions that project away from either side of the front region, and the front region is constructed with a greater stiffness than the arm regions, and the appliance has a resting form in which the base member and the teeth 10 engaging member are in their resting condition, and wherein the appliance can be manipulated out of the resting form when fitted to a patient to receive the patient's underdeveloped dental arch form in the at least one dental arch receiving channel, and wherein the front region, due to said greater stiffness, exerts a greater resting form return force against the patient's underdeveloped dental arch form than the 15 arm regions, urging the underdeveloped dental arch form to develop into the developed dental arch form. The greater resting form return force applied by the front region against the corresponding region of the patient's arch form in particular encourages this region of the arch form to develop, i.e. it encourages expansion of an anterior 20 region of the patient's arch form. The base member may be in the form of an open frame structure comprising an arch-shaped outer frame member and an arch-shaped inner frame member, and the front region of the appliance may be formed with a greater stiffness that the left and right arm regions thereof by having at least one transverse frame member 25 extending between the inner and outer frame members in said front region. The at least one transverse frame member in the front region may include a first pair of transverse frame members including one transverse frame member towards a side edge of the front region and a further transverse frame member towards another side edge of the front region.

19 The transverse frame members of the first pair may be positioned so that they align with respectively the left and right outer incisors of a patient, The first pair of transverse frame members may each have a width of 1-4mm, e.g. 2-3mm. The base member may include a further transverse frame member extending 5 between the inner and outer frame members in the front region of the appliance, to further stiffen the front region of the appliance, and the further transverse frame member being positioned between said two transverse frame members making up the first pair. The further transverse frame member in the front region of the appliance may 10 have a width of 5 to 15 mm, e.g. 8 to 12 mm. The transverse frame arrangement may further include a second pair of transverse frame members comprising a left rear transverse frame member towards a free end of one arm region, and a right rear transverse frame member towards a free end of the right arm region. 15 The transverse frame arrangement may further include a third pair of transverse frame members positioned intermediate the first and second pairs of transverse frame members. This disclosure also extends to a method of treating a patient to develop an underdeveloped arch form in a patient into a developed arch form, the method 20 comprising the steps of fitting an appliance as described in the first or second aspects of the disclosure above to a patient, and having the patient wear the appliance on a regular basis. The method may include encouraging development of the upper arch of a patient by expanding the upper arch form to treat a Class 2 malocclusion. 25 The method may include aligning the dentition on the underdeveloped dental arch of the patient that is being developed into a developed arch form. Having the patient wear the appliance may include having the patient wear the appliance for at least 12 hours in each 24 hour day. Preferably the patient wears 2 the appliance at least 2 hours during the day time and during the night while the patient is sleeping. DETAILED DESCRIPTION An orthodontic appliance in accordance with this disclosure may manifest itself in 5 a variety of forms. It will be convenient to hereinafter provide a detailed description of at least one embodiment of the disclosure with reference to the accompanying drawings. The purpose of providing this detailed description is to instruct persons having an interest in the subject matter of the disclosure how to put the disclosure into practice, It is to be clearly understood however that the 10 specific nature of this detailed description does not supersede the generality of the preceding statements, In the drawings: Fig 1 is an upper three dimensional view of an orthodontic appliance that is an orthodontic appliance in accordance with one embodiment of the disclosure, viewed from the front; 15 Fig 2 is an upper rear three dimensional view of the appliance of Fig 1, viewed from the rear; 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; 20 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 a teeth engaging member thereof removed to expose an underlying 25 base member; 21 Fig 10 is an upper three dimensional view of the base member of the appliance of Fig 9 viewed from the front; Fig 11 is an upper three dimensional view of the base member of Fig 10 when viewed from the rear; 5 Fig 12 is a top plan view of the base member of Fig 10; Fig 13 is a three dimensional view of the appliance of Fig 1 in its resting or original condition prior to use; Fig 14 is a schematic three dimensional view of the appliance of Fig 13 showing how left and right arm regions can be moved towards each other by hand 10 pressure being applied by a patient or a dental practitioner; Fig 15 is a schematic three dimensional view of the appliance of Fig 13 showing a dental practitioner fitting the appliance to a patient having an underdeveloped arch with the dentist squeezing the left and right arm regions towards each other to fit the appliance over the underdeveloped dental arch of the 15 patient; Fig 16 is a schematic top plan view of the appliance of Fig 13 in a resting state positioned next to a dental arch of a patient having an underdeveloped arch that is typical of a class 2 malocclusion; Fig 17 is a schematic sectional side view of the appliance fitted to the upper 20 arch of a patient along a dental midline; Fig 18 shows the arch shown in Fig 16 after the orthodontic treatment of the patient has progressed to the point where the patient's arch has undergone some development Fig 19 shows two schematic profiles of a patient prior to treatment 25 illustrating the effect of incorrect swallowing and mouth breathing on the profile of the patient, and a third schematic profile of a patient after treatment showing the correct positioning of the arches and lips; and 22 Fig 20 is a schematic drawing showing a plan view of the appliance in its resting form and also showing the appliance in a deformed condition when it is fitted to an underdeveloped arch of a patient, In Figs 1 to 9 a reference numeral I refers generally to an appliance that is an 5 orthodontic appliance in accordance with the disclosure for promoting development of a dental arch form in a patient who has an underdeveloped arch. The appliance 1 comprises broadly a base member 2 having a shape that corresponds generally to a dental arch form representing correct dental occlusion, i.e. a correct dental bite, and a teeth engaging member 5. The teeth engaging 10 member 5 encloses at least part of the base member 2 and defines upper and lower dental arch receiving channels. The base member 2 is made of a resiliently flexible material, and the teeth engaging member 5 is made of a resiliently flexible material that is deformable and is softer than the resiliently flexible material of the base member 2. 15 The appliance 1 has a resting form in which the resilient materials of the base member 2 and the teeth engaging member 5 are in their resting condition, and the appliance 1 can be flexed or deformed out of its resting form to fit the underdeveloped dental arch form into the dental arch receiving channel. The appliance 1 when deformed in this way exerts a resting form return force that is 20 directed to returning it to its resting form which drives expansion of the underdeveloped arch into a developed arch form, The teeth engagement member 5 is made of silicone rubber and occupies a substantially greater volume than the base member 2 and forms the body and shape of the appliance 1. It also defines the contacting surfaces that make 25 contact with and engage the arch and associated dental structures including the dentition and gum tissues of a patient. The base member 2 is shown in hidden detail lines in Figs 1 to 9 and will now be described in more detail with reference to Figs 10 to 12 in which it is shown separate from the teeth engaging member 5.

23 The base member 2 comprises a front region or central frontal portion that is indicated generally by numeral 17. It also includes a left arm region 18 extending away from a left side edge of the front region 17, and a right arm region 19 that extends away from a right side edge of the front region 17. In this specification 5 the terms left and right shall be considered from the point of view of the side of a patient's body that the feature is located on, when the appliance I is mounted on a dental arch of the patient. Thus the left arm region 18 will extend along the left side of a patient's arch and the right arm region 19 will extend along the right side of the patient's arch. The front region and the left and right arm regions of the 10 base member correspond broadly to a front region and left and right arm regions of the teeth engaging member and also the appliance 1 as a whole. The base member 2 is in the form of an open frame structure 7 extending in an occlusal plane comprising an arch-shaped outer longitudinal frame member 10 and an arch-shaped inner longitudinal frame member 12. The inner frame 15 member 12 broadly follows the arch form on the outer longitudinal frame member 10 but is spaced inward of the outer longitudinal frame member 12. The open frame structure 7 includes a transverse frame member arrangement indicated generally by numeral 15 comprising a plurality of transverse frame members interconnecting the outer and inner longitudinal frame members 10, 12 20 to form the structure. The transverse frame member arrangement 15 is designed to stiffen the front region 17 of the base member 2 so that it requires a greater force to resiliently flex the front region 17 than to flex left and right arm regions 18, 19 of the base member 2 to a similar extent. The front region 17 also exerts a correspondingly greater return force when it is flexed out of its resting position 25 than when the left and right arm regions 18, 19 of the base member 2 are flexed out of their resting position. The result is that when the front region 17 of the appliance I is deformed to fit the appliance to dental arch having a narrowed anterior region with protruding incisors, the front region 17 of the base member 2 and also the appliance 1 as a 30 whole exerts a correspondingly greater return force on the anterior region of the arch than the force applied to other regions of the arch.

24 The transverse frame arrangement 15 includes a first pair of transverse frame members 26 including one transverse frame member towards one side edge of the front region 17 and a further transverse frame member towards the other side edge of the front region 17. The left and right transverse frame members 26 of 5 the first pair are aligned with respectively the left and right outer incisors of a patient (i.e. the second teeth in the first and second quadrants) when the appliance 1 is fitted thereto as is shown in the drawings. The first pair of intermediate transverse frame members 26 have a width of 1-4mm, e~g. about 2mm. 10 The transverse frame member arrangement 15 also includes a front transverse frame member 27 extending between the inner and the outer longitudinal frame members 12, 10 in the front region 17 of the base member 2. The front transverse frame member 27 is positioned substantially centrally with respect to the base member 2 and extends across part of the two central incisors of a 15 patient, The front transverse frame member 27 has a centre point midway along its length that is aligned with a midline of the appliance as a whole. The front transverse frame member 27 has a width of about 8 to 12 mm measured from one side edge thereof to the other side edge thereof and is considerably wider than the first pair of transverse frame members 26 of the transverse frame 20 arrangement 15. The additional width serves to confer additional strength and rigidity in the front region 17 of the base member 2. The first pair of transverse frame members 26 together with the front transverse frame member 27 stiffens the open frame structure 7 of the base member 2 in the front region 17. Consequently a greater force is required to deform the front 25 region out of its resting form than is required to move the arm regions 18, 19 towards or away from each other. The transverse frame arrangement 15 further includes a second pair of transverse frame members 29 comprising a left rear transverse frame member located at the rear end of the left arm region 18, and a right rear transverse frame member at the 30 rear end of the right arm region 19. Each of the left and right rear transverse frame members 29 has a width of 3 to 6mm.

25 The transverse frame arrangement 15 further includes a third pair of transverse frame members 31 comprising a left transverse frame member positioned intermediate the left member 26 of the first pair and the left rear member 29, and a right transverse frame member positioned intermediate the right member 26 of 5 the first pair and the right rear member 29. The third pair of intermediate transverse frame members 31 is typically of similar thickness to the first pair of intermediate transverse frame members 26. Each pair of transverse frame members 26, 29, and 31 is arranged in a bilaterally symmetrical fashion about the midline of the appliance as is shown in the drawings. 10 The third pair of intermediate transverse frame members 31 is positioned adjacent to the first premolars on the dental arch when the appliance is fitted to a patient (e.g. the fourth teeth in the first and second quadrants when viewed in plan view). The third pair of intermediate transverse frame members 31 is thus positioned quite a bit closer to the rear frame members 29 than the first pair of frame 15 members 26 on the front region 17 of the base member 2. This predisposes the section of the base member 2 intermediate the frame members 26 and the frame members 31 to undergo flexing when the appliance 1 is deformed in use, The appliance forms a flexure at either side of the front region when the arm regions are flexed towards each other. 20 The base member 2 also includes a teeth row repositioning formation that is an outer flange 25 in the form of a continuous outer wall extending along the outer frame member 10, The outer flange 25 defines an upper edge that projects up above the plane defined by the outer and inner members 10 and 12 and the transverse frame members of the transverse frame member arrangement 15. The 25 outer flange 25 contributes to the rigidity, including torsional rigidity, and stiffness of the base member 2. The outer flange 25 extends across the front region 17 of the base member 2 and across left and right arm regions 18, 19 thereof. The outer flange 25 extends up to a height of 6-8mm above the transverse frame members 15 in the front region, 30 The outer flange extends up to a height of 5-7mm above the transverse frame members along the left and right arm regions which is not as high as that along the front region. The height is measured from the upper surface of a proximate 26 transverse frame member 25 to the upper edge of the inner flange 30. The outer flange 25 forms a continuous wall along the length of the arch and promotes alignment of the dentition of the upper arch of a patient in a row or line along the arch. 5 The outer flange 25 also defines canine gaps shown by numeral 28 on each side thereof. Each canine gap 28 is formed by having the upper edge of the outer flange 25 descending to a low point intermediate the central front portion 17 and the left and right portions and then ascending upwards again. The canine gaps 28 on the upper edge of the outer flange 25 are located in the 10 position where the eye teeth or canine teeth of a patient would be located. The canine gaps 28 expose more of the canine teeth when the appliance I is being worn so that the outer flange 25 does not need to fit around the canine teeth. Applicant has observed that the canine teeth of a patient are sometimes positioned laterally outward of the other teeth prior to treatment, and the canine 15 gaps 28 permit the canine teeth to project through the gaps and thereby enable the appliance to be fitted to a patient with considerable misalignment of the canines when that would not be the case if the canine gaps were not present, In the illustrated embodiment the base member 2 also includes a curved inner flange 30 in the form of a continuous wall projecting up from the inner frame 20 member 12. The inner flange 30 defines an upper edge projecting up to a height that is 1-3mm, e.g. about 2mm, above the transverse frane members and is less prominent than the outer flange 25. The height is measured from an upper surface of a proximate transverse frame member 25 to the upper edge of the inner flange 30. The inner flange 30 also contributes to the rigidity and stiffness the 25 base member 2 and can also assist with aligning teeth in a row along the arch. The base member 2 in the drawings does not have a flange depending or extending down below either the outer frame member 10 or the inner frame member 12 of the base member 2 to any appreciable extent. Applicant has found that having an outer flange 25 that projects up from the open frame structure 7 but 30 not down there from provides the base member 2 with the necessary level of stiffness. However a flange that also projects downwardly away from the curved 27 outer frame member 10 would further increase the strength of the base member and falls within the scope of this disclosure. In another embodiment of the disclosure that has not been illustrated the orthodontic appliance and specifically the base member thereof does not have an 5 inner flange 30 projecting away from the inner frame member 12, The base member 2 defines a pair of openings 38, 39 in its central front region 17 that relate to the moulding process that is used to manufacture the appliance 1. The openings 38, 39 are integrally formed in both the inner and outer curved frame members 12, 10 on left and right sides of the front region 17. The openings 10 38, 39 are aligned with corresponding openings in the teeth engaging member 5 as is shown in the drawings. The teeth engaging member 5 that surrounds and encases the base member 2 will now be described in greater detail. Broadly the member 5 comprises a central web 40 and an inner flange 44 and an 15 outer flange 45 (inner and outer walls 44, and 45) that project both upwardly and downwardly away from the web 40. The flanges 44, 45 together with the web 40 form an upper arch receiving channel 46 and a lower arch receiving channel 47 within which the upper and lower dental arches and associated dentition of a patient are received. The web 40 forms occlusal bite surfaces with the channels 20 against which the bite surfaces of the dentition of the upper and lower dental arches bears. The teeth engaging member 5 comprises a front region 51, and left and right arm regions 48 and 49 corresponding to the front region 17 and left and right arm regions 18 and 19 of the base member 2. The front region 51 of the teeth 25 engaging member 5 is mounted over and encloses the front region 17 of the base member 2 and has the same extent as the front region 17 of the base member 2. That is the side edges of the front regions 17, 51 of respectively the base member 2 and the teeth engaging member 5 broadly coincide. The left and right arm regions 48, 49 have a greater longitudinal extent than the 30 left and right arm regions of the base member 2 as shown in the drawings and 28 particularly in Figs 2, 5 and 6. That is the rear edges of the teeth engaging member 5 are spaced rearward of the rear edges of the base member 2. The front region of the appliance is basically the same as the front region of the teeth engaging member 5 and the left and right arm regions of the appliance are 5 basically the same as the left and right arm regions of the teeth engaging member 5. The teeth engaging member 5 fills in the space between the inner and outer longitudinal frame members 12, 10 and the transverse frame members 26, 27, 29 and 31 also forms a layer having some thickness above and below the inner and 10 outer frame members 12, 10. The appliance I also includes an adjacent teeth positioning arrangement shown generally by reference numeral 50 on the inner and outer flanges 44, 45 of the teeth engaging member 5 for assisting in positioning specific teeth in certain positions along the line of the arch. 15 Specifically the adjacent teeth positioning arrangement 50 comprises a plurality of pairs of adjacent teeth positioning formations. Each pair of positioning formations comprises a first positioning formation on the outer flange 45 of the member 5 projecting from the channel surface thereof into the upper dental arch channel, and a second positioning formation on the inner flange 44 of the member 5 20 projecting from the channel surface thereof into the upper arch channel. The first and second positioning formations in each pair are aligned with each other in a lengthwise direction along the channel. Each teeth positioning formation within each pair comprises a protrusion that extends away from the surface of the flange on which it is located to a terminal 25 free end that is spaced away from the channel surface. The positioning formations are wedge shaped when the appliance is viewed in plan view tapering inwardly from both sides on the surface of the flange to a wedge point, The wedge point extends in a line broadly transverse to the plane of the web of the member 5 as is shown in the drawings. That is the terminal free end is broadly 30 vertically extending when the appliance is fitted to a patient and is designed to fit 29 into the interproximal space between two adjacent teeth on a patient's arch in use. The first and second positioning formations of each pair are integrally formed with the flange on which they are located when the member is moulded during its manufacture. 5 In the illustrated embodiment the adjacent teeth positioning arrangement 50 has nine pairs of adjacent teeth positioning formations on the upper channel for interacting with the upper dental arch structures of a patient. The adjacent teeth positioning arrangement 50 includes a first pair of said adjacent teeth positioning formations that are arranged on the midline of the 10 appliance for positioning between the two central incisors when mounted on a patient. It also includes a second and third pair of adjacent teeth positioning formations that are arranged to be positioned between the central and outer incisors on the left side, and between the central and outer incisors on the right side. It also includes fourth and fifth pairs of adjacent teeth positioning formations 15 are arranged to be positioned between the outermost incisor and the canine on the left side, and the outermost incisor and the canine on the right side of the arch of a patient, It also includes sixth and seventh pairs of adjacent teeth positioning formations that are arranged to be positioned between the canine and the first pre-molar on the left side, and the canine and the first pre-molar on the right side 20 of the arch of a patient. It also includes eighth and ninth pairs of adjacent teeth positioning formations that are arranged to be positioned between the first pre molar and the second molar on the left side, and the first pre-molar and the second molar on the right side of the arch of a patient. In the illustrated form of the disclosure where the teeth engaging member 5 25 defines both upper and lower channels for receiving the upper and lower dental arches and associated dental structures of a patient, the teeth engaging member 5 includes a similar arrangement of pairs of adjacent teeth positioning formations projecting into the lower arch receiving channel for receiving the lower dental arch and associated dental arch structures of a patient. 30 The adjacent teeth positioning formations 50 assist with the positioning of specific teeth on the dental arch of the patient. The pairs of adjacent teeth positioning 30 formations are positioned so that they insert between adjacent teeth on the dental arch where the wedge shape tends to urge teeth apart from each other and to form a space between adjacent teeth The pairs of teeth positioning formations urge the adjacent teeth apart from each other and thereby form a space between 5 the adjacent teeth. The adjacent teeth positioning formations are located in the anterior region of the arch and thus they work to form spaces between adjacent teeth in the anterior region of the dental arch. As the teeth on the dental arch are generally in end to end contact when the treatment commences, the arch needs to expand to create additional space for 10 spaces between the adjacent teeth to be formed. The teeth positioning formations project into the space between adjacent teeth and push them apart which in turn urge them apart from each other and encourages the arch to expand to provide more space. The teeth positioning arrangement thereby also subtly encourages the arch to expand in addition to the arch developing force of the deformed 15 appliance fitted to a patient as described above. The teeth positioning formations also help to position individual teeth on the dental arch, In the illustrated example the orthodontic appliance also includes a notch or cut out 55 in the midline of the upper surface of the outer flange 45. It also includes a smaller midline notch or cut-out 57 in the lower surface of the outer flange 45. 20 The notches 55, 57 form a recess or gap on the appliance midline so that the member 5 does not come into contact with soft tissue in the area of the dental midlife, There is a tendon that extends across the dental midline and the appliance 1 can be more comfortably worn by a patient if the teeth engaging member 5 does not come into contact with this tendon. The recesses 55, 57 25 avoid contact with this tendon. The orthodontic appliance 1 also has a tongue tab 60 for positioning the tongue of a patient in an exact central position. The tongue tab is formed in the inner flange 44 of the member 5 upwardly of the web 40. This trains a patient to correctly position their tongue to improve their oral habits and particular to avoid tongue 30 thrusting. The inner flange 44 defines gaps on either side of the tongue tab 60 as shown in Fig 4. The inner flange also defines a small notch or cutaway 57 formed in the lower edge of the inner flange as shown in Fig 4. These spaces help to 31 facilitate inward and outward adjustment of the arm regions 48, 49 of the teeth engaging member 5 of the appliance 1 to enable it to be fitted to an underdeveloped arch, Further the occlusal surfaces of the web 40 of the teeth engaging member 5, e.g. 5 upper and lower faces thereof, taper outwardly from the front region 51 of the member 5 in a rear direction to the left and right trailing arm regions 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 of maximum thickness along the left and right trailing arm regions 48, 49 that is 10 spaced forward of the rear ends of the arm regions. Thereafter the upper and lower faces of the engaging member 5 taper inwardly towards each other so as to progressively thin from said point of maximum thickness to the rear of the teeth engaging member 5. In summary each arm region 48, 49 can be described as having an inverted asymmetric aerofoil shape having a curved lower surface. 15 This aerofoil shape of the web 40 fills in any space that exists between the upper and lower teeth of a patient as a result of malocclusion and supports the dentition in cases where the occlusal surfaces of the dentition of the upper and the lower arches are spaced from each other. This enables the lower jaw to assume its anatomically correct position in relation to the upper jaw. This confers muscular 20 benefits on the patient including helping the patient to relax so that they do not clench their jaw. It also confers other muscular benefits on the patient and supports the TMJ joint. 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 25 continuous and open at both ends. The openings 38 and 39 defined in the base member 2 increase the surface area of the teeth engaging member 5 in contact with the base member 2 to assist in moulding the teeth engaging member 5 onto the base member 2. During manufacture of the orthodontic appliance the base member 2 is injection 30 moulded in a first injection moulding step, and the teeth engaging member 5 is then moulded around the base member 2 in a second moulding step.

32 The base member 2 is made of a polymeric material having suitable physical properties of stiffness and resilient flexibility to enable the appliance to perform its orthodontic function. In the illustrated embodiment the base member is made of a polyamide material that is nylon. Nylon is a generic name of any long chain 5 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 it can also be used to form a three dimensional body. Nylon has been found to have an appropriate level of rigidity yet the base member as a whole is resiliently flexible and can be resiliently flexed out of its 10 resting form so that the left and right arm regions of the base member can be moved towards and away from each other. It also permits some twisting of the left and right arm regions relative to each other. Further Nylon has a high melting temperature so that when a material having a high injection temperature, e.g. silicon rubber is used as the material for the teeth 15 engaging member can withstand the injection temperature of silicone when it is injected onto the base member to form the teeth engaging member. 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, TEN SILE --- ------------- ------- - ---- - ---- - --- TENSILE Kg/cm2 800 900 1700 1900 840 1150 STRENOTH Kg/cm----- 800----- - - --- .................. ELONGATION 5 ___ 10 7, 2445 FLEXURAL Kg/ciF 1000 1350 2300 2600 1200 1700 _STRENGTH FLEXURAL Kg/cm 28000 35000 80000 108000 31000 [2000 MODULUS IZOD IMPACT Kg- 13 8.5 11 !9 7.3 7 STRENGTH I cm/cm ROCKWELL R-SCALE 118 '119 120 120 118 119 HARDNESS MELTING PONT "c 260 1260 255 260 260 260 M.D.T 66 200 238 240 73 248 (1 8.6kG/cmr2) M.D.T "C -230 240 255 255 230 245 (4.6kG/cm2) ____ __ __ ATH W1% 13 33 45 - 25 CONTENT MOLD 1718 0.3-0.5 0.2-0.4 0.2-0.3 1.0-1.3 0,3-0 5 SHRINKAGE 1.3-1 4 0.8-1.0 0.7-1 0 0.3-0.5 0.7-1.0 0.7-1 0 MF g/10min 55 1 20 13 10 43 20 57 7 /cm 1.I 1,2 135 1,46 1.16 | 138 33 A grade of Nylon can be used having a tensile strength 800-1000, e.g. about 900, a flexural Strength 1000-1500, e.g, about 1350, and a ROCKWELL Hardness of 90 - 150, e.g. about 119. In particular Applicant has used a grade of nylon known as Nylon 66 6212GA for the manufacture of appliances in accordance with this 5 disclosure. A suitable nylon material can also be obtained from other chemical suppliers such as E I. Du Pont Nemours Chemical Company (Du Pont) based in Delaware in the USA and other suppliers. In the illustrated embodiment the teeth engaging member is formed of a silicone rubber, A medical grade silicon rubber that is a basic commodity that can be 10 obtained from a number of suppliers such Du Pont Chemical Company based in Delaware in the USA. Applicant has sourced a suitable silicone rubber from a Japanese chemical company by the name of Shin-Etsu Chemical Co Ltd based at 6-1, 2 Chome, Ohtemachi, Chiyodaku, Tokyo, Japan. The material specification data sheet provided by Shin-Etsu for this material is provided below. 15 MATERIAL SPECIFICATION DATA SHEET SHIN-ETSU @ TWO-COMPONENT Transparent SILICONE RUBBER COMPOUND High Strength Typical Properties Units KE-1950~ KE-1 950- KE-1 950 50 60 70 A-B) (A-B) _I(A-B) Viscosity in mPa.s 680 730 750 (P) Brookfield-type rotational viscometer (6800) (7300) (7500) Specific Gravity at 25C (770F)gm 3 1.13 1.14 1,15 Mixing Ratio A:B 1:1 1:1 1:1 Hardness JIS-A 50 58 68 Tensile Strength JIS-6301 Mpa 9.3 7.8 7,8 Elongation at break JIS-6301 % 55 380 350 Tear Strength JIS-6301 kN/m 44.1 43,1 49 Compression set 22h1 50_C (%) 28 22 50 Linear Shrinae JIS-6301 (%) 2 19 2.1 Volume Resistivity Comments 0-m 101 l0T 10T The silicone rubber used to make the orthodontic appliance can have the following properties: 34 Hardness of 50-68 according to JIS-A; Tensile strength of 7.8 to 9.3 Mpa according to JIS-6301; Elongation at break 55 to 350% according to JIS-6301; Tear strength of 43.1 to 49 KN/m according to JIS-6301; 5 Applicant has used the hardest grade of silicon extensively, namely KE-1950-70 supplied by Shin-Etsu. 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 10 with each component packed in a separate container. These two components are pumped into a static mixer and mixed thoroughly and then injected into the injection mould die, In the actual moulding of the orthodontic appliance I the base member 2 and the teeth engaging member 5 can be moulded in a co-injection moulding process. 15 The base member 2 is moulded in a first step by an injection moulding process and then the teeth engaging member 5 is moulded directly onto the base member 2 in a second moulding step without it being removed from the mould. The base member 2 does not have to be removed from the mould for the teeth engaging member 5 to be moulded onto it. The mould comprises two mould parts, a first 20 mould part for the base member 2 and a second mould part for the teeth engaging member 5. During the moulding operation in a first moulding step the first mould part is mounted in an operative moulding position in a moulding zone and molten nylon is injected into the first mould part to form the base member 2. Thereafter the first 25 moulding part is withdrawn from the moulding zone, the second moulding part is moved into its operative position in the moulding zone, and thereafter molten silicon rubber is injected into the second mould part in a second moulding step to mould the teeth engaging member onto the already moulded base member. The second moulding part is then withdrawn to reveal the newly moulded appliance 30 with the base member encased within the teeth engaging member. Generally the formed orthodontic appliance 1 can be removed from the die once the moulded 35 silicon rubber material has had an opportunity to cool sufficiently for it to be handled. The cycle times for each of the moulding steps is typically about 15 seconds. The cycle time for the silicone rubber moulding is longer than that for the nylon base 5 member. Generally the moulded pieces are allowed to cool passively, However the silicone rubber can be actively cooled once it has been moulded. Nylon is capable of withstanding the injection temperature of silicone and this property as well as its other physical properties that make it suitable for use in the base member of the appliance. 10 In another form of the disclosure the appliance can be moulded in two separate dies with the base member being moulded in a first die then the base member can be removed and be placed in a second die where the teeth engaging member is moulded onto the base member 1. In use the orthodontic appliance 1 described above will typically be initially fitted 15 by an orthodontist or a dentist. A first step in fitting an appliance 1 is to choose an appropriately sized appliance from the different sizes of appliances. The range of appliances I envisaged by the Applicant will have at least three different sizes of base member defining the basic arch form. Each of these base member sizes will then have at least four 20 different sizes of teeth engaging member some of which have an adjacent teeth positioning arrangement thereon and others which do not have a teeth positioning arrangement. Generally an orthodontist will choose a size of appliance after inspecting and measuring the dental arch and associated dental arch structures of the patient using a suitable measuring device that is supplied to the dental 25 practitioner. This procedure of fitting the appliance to a patient's dental arch is shown schematically in Figs 13 to 15. Where the patient has an under developed arch structure such as that found in a class 2 malocclusion, the dentist will manually flex the appliance to an extent that enables it to be fitted onto the patient's dental 30 arch so that the arches are received within the respective arch receiving channels 36 with a tight fit and a tight grip as shown schematically in Fig 17. This flexing may involve deformation of the arm regions as well as the more stiff front region of the appliance. The arches are received within the respective arch receiving channels with a tight fit and a tight grip as shown schematically in Fig 17. The inner and 5 outer flanges 44 and 45, and the occlusal surfaces of the web 40 of the teeth engaging member 5, bear against the upper and lower dental arches and the associated arch structures. The soft silicone rubber of the teeth engaging member 5 is in contact with and bears against the dental structures including the gums and teeth of the patient. 10 The silicon rubber cushions the underlying force being applied by the deformed base member so that the appliance is reasonably comfortable to wear despite the resting force return force that is being applied to the arch to encourage expansion of the arch, The appliance and particularly the base member 2 thereof generates a force that 15 bears against the dental arch and associated dental structures of the patient that have a physiological influence on the bone development of the dental arch form that drives expansion of the arch form. The dental arch forms are encouraged to develop into an arch form corresponding to the respective arch receiving channels within which they are received which correspond to a developed arch form that is 20 conducive to correct dental occlusion. Applicant regards the resting form return force that is generated by the appliance when fitted to an underdeveloped arch form and which is applied to the dental arch form as being analogous to active spring energy. Fig 16 show an appliance in its original shape next to an underdeveloped dental 25 arch that requires expansion into a more developed arch form, The drawings clearly show how the arch form of the appliance 1 is noticeably wider than the underdeveloped dental arch form of the patient. Consequently the appliance I has to undergo significant deformation to fit the appliance 1 over the underdeveloped arch form of the patient. The deformation causes the appliance 1 30 to exert a buccally directed return force against the dental arch and associated dental structures of the patient, particularly in the narrowed anterior region thereof.

37 Over time this force will progressively develop of the arch form whereby over time it becomes more and more like the arch form defined by the resting form of the appliance. Fig 18 shows the arch of the patient of Fig 15 after it has undergone treatment with the oral appliance and the anterior region of the arch has widened 5 into a developed arch form, The distance "X" between the inner surface of the left and right canine teeth in Fig 18 is much greater than the corresponding distance of the dental arch in Fig 16. Further the radius of curvature of the line of teeth in the anterior portion of the arch in Fig 18 shown by "R" is much greater than the corresponding radius of the dental 10 arch in Fig 18 thereby showing clearly how the arch and in particular the anterior region thereof is developed. In addition to influencing arch development on the patient the orthodontic appliance I and particularly the teeth engaging member 5 thereof is in contact with the dentition and applies an aligning force to the dentition on the arch. As the 15 appliance 1 has curved arch receiving channels, the appliance 1 will influence the dentition to align along a similar curve. The rigidity of the base member 2, and in particular the continuous outer flange on the base member 2, contributes to alignment of the dentition on the arch by encouraging protruding and retruding teeth to move to their desired position received within the relevant channel. The 20 teeth are moved into a position between the inner and outer walls of the teeth engaging member 5 thereby aligning the teeth with other teeth in the row, Thus the use of the appliance over a period of time also assists with the alignment of teeth in a line along the arch. The application of force to move teeth is standard practice in orthodontics and the physiological mechanism by which tooth 25 movement is accomplished is understood by the dental and orthodontic community and will not be described in this specification. Further the adjacent teeth positioning arrangement 50 on the teeth engaging member 5 also assist in positioning individual teeth on the arch form. The orthodontic appliance is a removable appliance that is worn for a number of 30 hours each day and is not worn by a patient at other times of the day. The appliance should be worn for a few hours during the day and the appliance should 38 also be worn during the night while the patient is sleeping, As the appliance has both upper and lower channels that receive both the upper and lower dental arches of a patient, it is not suitable for being worn while the patient is carrying out certain activities. For example a patient would not be able to talk or eat while they 5 were wearing the appliance. Over time with proper use of the appliance and good patient compliance, the application of force by the base member that has been deformed out of its original shape will cause the arch to develop. Once the arch develops any crowding of teeth that exist on the arch form should diminish and with further treatment the teeth will move towards aligning with each other along 10 the arch form. Fig 19 shows a sequence of schematic profiles of a patient showing how their profile develops with the progression of treatment with the orthodontic appliance. The first two drawings show the effect of incorrect swallowing and mouth breathing on the profile of the patient. This is evident in the relative positioning of 15 the upper and lower arches and the lip profile. The third drawing shows the profile of the patient after treatment has been completed. The upper and lower arches are correctly positioned relative to each other in the third drawing and the lips are together. Fig 20 is a basic schematic drawing showing a plan view of an appliance that is 20 similar but not necessarily the same as that of Fig 1 in a resting condition and also shows how the appliance can be deformed to fit it to an underdeveloped dental arch of a patient. In the schematic drawing the patient has an underdeveloped upper arch that needs to be expanded, particularly in the anterior region thereof. The front region of the appliance in particular is flexed and deformed to fit the 25 appliance to the arch The front region has a greater stiffness than the left and right arm regions of the appliance as has been described above. Consequently when deformed, the front region exerts a return force that is related to the force required to flex it out of its resting condition and this return force is applied to the underdeveloped arch of a user to encourage it to develop. This force is greater 30 than the force appiied by the arm regions when they undergo a corresponding amount of deformation or flexing. The arrows on the schematic drawing indicate schematically the direction and the strength of the return force that is applied by 39 the deformed front region of the appliance. The longer arrows in the front region shown in the drawings show that the return force applied by the deformed front region is greater than the return force applied by the arm regions when flexed. The strong return force applied by the front region of the appliance encourages 5 the anterior region of the dental arch corresponding to the incisors and the canines to develop. It is to be understood that this schematic drawing is provided purely to assist an addressee with an understanding of the disclosure and is not to be regarded as a detailed drawing that is dimensionally exact, In another embodiment of the disclosure that has not been illustrated in the 10 drawings, the base member 2 is made out of nylon and the teeth engaging member is made of polyvinylchloride (PVC). PVC resin is a staple commodity that is supplied by a number of chemical manufacturers including 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 15 4016-89 PVC compound. Applicant has used a clear extrusion grade PVC compound for the appliance which is supplied by IMPRODEX as their HYCO 4016-89 PVC compound. The properties of this PVC grade are as follows: SPECIAL PROPERTIES Shore A Hardness ASTM 2240) Instantaneous 79 Shore A Hardness (ASTM 2240) 10 second delay 71 Specific Graviy 1. _22 __ [Tnile Strength 17.7Mpa ___________ Elongation at Break__ _________ 400% An appliance in which PVC is substituted for silicon is manufactured by a similar two step moulding process to that described above. The base member is 20 moulded of nylon in a first step and then the teeth engaging member is moulded of PVC in a second moulding step. An advantage of using PVC instead of silicone rubber is that it does not require as high an injection temperature as silicon rubber and this reduces the mould temperature that the mould equipment and the material of the base member must be able to withstand when the molten PVC is 25 injected into the mould This opens up the possibility of using other materials including addition polymers, such as polyethylene, and polypropylene for the base 40 member. Applicant also envisages that condensation polymers such as polyurethane and polycarbonate and a thermoplastic elastomer such as santoprene could also be used because they have a suitable amount of stiffness when they are formed into a base member. Further Applicant believes that other 5 thermoplastic materials could also be found to meet these requirements and to be suitable for use in constructing the base member. In use an orthodontic appliance with a member 5 made of PVC is used in the same way as the appliance described above with reference to Fig 1. Further the appliance functions in exactly the same way when fitted to the dental arch and 10 associated arch structures of the patient. Applicant has carried out a series of treatments on patients suffering from a class 2 malocclusion to demonstrate the efficacy of the treatment and some of these treatments are described below. An advantage of the appliance described above with reference to the drawings is 15 that it can direct a force with sufficient strength onto the dental arch of a patient to develop the arch form within a reasonable treatment time. In particular it can apply a force that is capable of developing an underdeveloped arch to develop into a more fully developed arch form with improved dental occlusion. The appliance applies a force that is comparable to that applied by orthodontic braces 20 due to the underlying resilience of the base member through the teeth engaging member to the patient's dental arch. The force urges expansion of an underdeveloped arch in the anterior region thereof when the patient suffers from a class 2 malocclusion, A further advantage of the appliance described above is that it assists in aligning 25 the dentition on both dental arches. The appliance has upper and lower dental arch receiving channels and promotes alignment of the teeth of each arch in a line within their respective arch receiving channels. The flange or continuous wall on the outer curved frame member of the base member in particular promotes alignment of teeth along the arch, 41 The appliance promotes alignment of both protruding and retruding teeth, Further if one or more teeth are rotated, with the distal edge protruding and the mesial edge retruded, then the consequent deformation of the inner and outer flanges defining the respective arch receiving channel applies a rotational force to the 5 rotated teeth to encourage rotational realignment of the rotated teeth into a non rotated position. Thus the appliance promotes both arch widening and dental alignment in a single removable appliance and Applicant believes that this functionality has not previously been obtained in a single orthodontic appliance. The appliance also has a teeth positioning arrangement that can also assist in 10 encouraging an arch form to expand over and above the arch expansion promoted by the return force of the appliance when it is deformed. The adjacent teeth positioning arrangement can also assist with rotational realignment of individual teeth that have been rotated. Another advantage of the appliance described above is that it is removable so that 15 it can be inserted and removed from the patient's mouth during the course of treatment at the patient's discretion. This way the patient can pick the times when they wear the appliance and remove the appliance on important occasions A further advantage of the orthodontic appliance described above is that the silicone rubber is a soft material that has a significant ability to deform. It 20 therefore has the ability to deform significantly to fit the appliance to the dental arch structure of a patient having a shape that is quite different to that of the appliance. It also bears against the dental arch and dental structures of the patient and cushions the appliance against the dental arch and arch structures. As a result the teeth engaging member does not apply excessive local pressure to 25 the teeth and gums, and is comfortable to wear even when the base member has been significantly deformed. This comfort is important as the patient has to be able to sleep and perform other activities when they wear the appliance. Further patient comfort is an important factor in obtaining patient compliance which is crucial to successful treatment outcomes. Further unlike orthodontic braces the 30 appliance does not have sharp surfaces that would tend to injure the soft tissues in a patient's mouth.

42 Another advantage of the appliance described above with reference to the drawings is that it positions the upper arch in the correct position relative to the lower arch to achieve correct dental occlusion. It trains the upper and lower jaws to adopt the correct position relative to each other which is something that is not 5 achieved with prior art braces and retainers. Further this supports the TMJ joint. Another advantage of the appliance described above with reference to the drawings is that it incorporates certain other features that have been shown to improve the myofunctional environment in the patient's mouth by improving the patient's oral habits, These myofunctional features include a tongue tab for 10 correctly positioning the tongue of the patient. They also include features for inhibiting mouth breathing, incorrect swallowing and tongue thrusting. A yet further advantage of the orthodontic appliance described above is that it is pre-formed or manufactured in a number of sizes in a moulding operation and these sizes can then be fitted to a significant cross-section of the population. 15 Thus the appliance can be manufactured in a commercial scale manufacturing operation in large quantities and is not custom made for each patient. In particular the appliance can be injection moulded in a two step moulding operation in a number of sizes which enables it to be manufactured on a large scale and be supplied to the market at a lower cost than existing orthodontic treatments 20 including braces. This opens up the possibility of orthodontic treatment becoming accessible to a broader cross section of the population including people in developing countries. It will of course be realised that the above has been given only by way of illustrative example of the disclosure and that all such modifications and variations 25 thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of the disclosure as herein set forth.

Claims

1. An orthodontic appliance for developing a dental arch form of a patient who has an underdeveloped dental arch form, the appliance comprising: a deformable teeth engaging member that includes an arch-shaped web 5 that defines upper and lower occlusal bite surfaces, the teeth engaging member includes inner and outer flanges that project transversely away from the upper surface of the web, the web and the inner and outer flanges defining an upper arch receiving channel within which an upper dental arch and associated dentition of a patient can be received; and 10 an arch-shaped base member that is constructed from a resilient flexible material that is substantially enclosed by the teeth engaging member, the base member extending through the web and including an outer teeth repositioning formation received within the outer flange of the teeth engaging member, wherein the appliance has a resting form and can be deformed out of the 15 resting form when fitted to a patient to receive a patient's underdeveloped dental arch form in a dental arch receiving channel, and exert a return force against the received dental arch form to develop the arch form.

2. An orthodontic appliance for developing a dental arch form according to claim 1, wherein the teeth engaging member includes a tongue tab formed on the 20 inner flange of the teeth engaging member for encouraging a patient to correctly position their tongue within their mouth,

3. An orthodontic appliance for developing a dental arch form according to claim 1 or claim 2, wherein the base member includes a frame extending parallel to the web through the web, and the outer teeth repositioning formation projects 25 substantially orthogonally up the frame.

4. An orthodontic appliance for developing a dental arch form according to any one of claims I to 3, wherein the outer teeth repositioning formation is in the form of an outer flange that extends along the base member. 44

5. An orthodontic appliance for developing a dental arch form according to claim 4, wherein the outer flange comprises a continuous wall extending lengthwise along the base member.

6. An orthodontic appliance for developing a dental arch form of a patient 5 according to claim 4 or claim 5, wherein the outer flange of the base member extends along substantially the full length of the base member and the height thereof varies along its length.

7. An orthodontic appliance for developing a dental arch form according to any one of claims 1 to 6, wherein the base member further includes an inner teeth 10 repositioning formation which projects substantially orthogonally up from the frame and is received within the inner flange of the teeth engaging member,

8. An orthodontic appliance for developing a dental arch form according to claim 7, wherein the inner teeth repositioning formation comprises an inner flange that extends along the base member. 15

9. An orthodontic appliance for developing a dental arch form according to any one of claims I to 8, wherein the inner and outer flanges of the teeth engaging member also project transversely downward away from the upper and the lower surfaces of the web and define a lower arch receiving channel for receiving a lower dental arch and dentition of a patient. 20

10. An orthodontic appliance for developing a dental arch form according to claim 9, wherein the base member includes a further outer teeth repositioning formation which projects substantially orthogonally downward away from the web and is received within the outer flange of the teeth engaging member.

11. An orthodontic appliance for developing a dental arch form according to 25 claim 10, wherein the base member includes a further inner teeth repositioning formation which projects substantially orthogonally downward away from the web and is received within the inner flange of the teeth engaging member.

12. An orthodontic appliance for developing a dental arch form according to claim 3, wherein the appliance comprises a front region that merges with two 4:3 opposing arm regions that project away from either side of the front region, and the web decreases in transverse width in a direction from the arm regions towards the front region so as to correspond with the decrease in width of the occlusal surfaces of a dental arch from a molar region towards an incisor region. 5

13. An orthodontic appliance for developing a dental arch form according to claim 12, wherein the upper dental arch receiving channel is dimensioned so that the dental arch and dentition are received within the channel with a tight fit where the dentition bears against the inner and outer flanges.

14, An orthodontic appliance for developing a dental arch form according to 10 claim 12 or claim 13, wherein the frame includes an arch-shaped outer frame member and an arch-shaped inner frame member that are spaced apart from each other, and the transverse spacing between the inner and outer frame members decreases a direction from the arm regions to the front region of the appliance.

15 15. An orthodontic appliance for developing a dental arch form according to claim 14, wherein the frame further includes a plurality of transverse frame members that extend substantially linearly between the outer frame member and the inner frame member.

16. An orthodontic appliance for developing a dental arch form according to 20 any one of claims 12 to 15, wherein the base member extends along the front region and also the arm regions,

17, An orthodontic appliance for developing a dental arch form according to any one of claims 1 to 16, wherein the teeth engaging member is formed of a resilient flexible material which provides a soft cushion for forming a cushion for 25 bearing against the dental arch and dental structures of the patient, and the base member is formed of a resiliently deformable material having a greater hardness and rigidity than the teeth engaging member for contributing to the return force when the appliance is deformed out of its resting form.

18. An orthodontic appliance for developing a dental arch form according to 30 claim 17, wherein the teeth engaging member fully encases the base member and 4t the materials of the base member and the teeth engaging member respectively, are selected to flex with each other and resist being delaminated when deformed out of their resting conditions.

19. A pre-manufactured orthodontic appliance for developing a dental arch 5 form in a patient who has an underdeveloped dental arch form, comprising a front region that merges with two opposing arm regions that project away from either side of the front region, the appliance including: a deformable teeth engaging member that includes an arch-shaped web that defines upper and lower occlusal bite surfaces, and the teeth engaging 10 member has inner and outer flanges that project transversely away from the upper and the lower surfaces of the web, the web and the inner and outer flanges defining an upper arch receiving channel within which an upper dental arch and associated dentition of a patient can be received, the web decreases in transverse width in a direction from the arm regions towards the front region so as to 15 correspond with the decrease in width of the occlusal surfaces of a dental arch so that the dental arch and dentition are received within the dental arch receiving channel with a tight fit, and the teeth engaging member includes a tongue tab formed on the inner flange of the teeth engaging member for encouraging a patient to correctly position their tongue within their mouth: and 20 an arch-shaped base member that is constructed from a resilient flexible material that is substantially enclosed by the teeth engaging member, the base member including a frame extending substantially through the web substantially parallel to the web, the frame includes an arch-shaped outer frame member and an arch-shaped inner frame member that are spaced apart from each other, and 25 the transverse spacing between the inner and outer frame members decreases a direction from the arm regions to the front region of the appliance, and the base member includes an outer teeth repositioning formation projecting substantially orthogonally up from the frame that is received within the outer flange of the teeth engaging member, 30 wherein the appliance has a resting form and can be deformed out of the resting form when fitted to a patient to receive a patient's underdeveloped dental 4/ arch form in a dental arch receiving channel, and exert a return force in the direction of the plane against the received dental arch form to develop the arch form.

20, A method for treating a class 2 malocclusion in a patient, the method 5 including: providing a plurality of orthodontic appliances that have been pre manufactured on a commercial scale in a plurality of sizes, each orthodontic appliance including: a deformable teeth engaging member that includes an arch shaped web that defines upper and lower occlusal bite surfaces, the teeth 10 engaging member includes inner and outer flanges that project transversely away from the upper surface of the web, the web and the inner and outer flanges defining an upper arch receiving channel within which an upper dental arch and associated dentition of a patient can be received, and an arch-shaped base member that is constructed from a resilient flexible material that is substantially 15 enclosed by the teeth engaging member, the base member extending through the web and including an outer teeth repositioning formation received within the outer flange of the teeth engaging member; and fitting a suitably sized appliance to the patient by mounting the appliance over an upper arch of the patient to receive the patients' underdeveloped dental 20 arch form within the arch receiving channel thereby deforming the appliance out of its resting form and exerting a return force against the received dental arch form to develop the arch form.