WO2010105301A1

WO2010105301A1 - Orthodontic bracket and arch wire

Info

Publication number: WO2010105301A1
Application number: PCT/AU2010/000315
Authority: WO
Inventors: Felix Goldschmied
Original assignee: Goldschmied Pty Ltd
Current assignee: Goldschmied Pty Ltd
Priority date: 2009-03-18
Filing date: 2010-03-18
Publication date: 2010-09-23
Anticipated expiration: 2011-09-18

Abstract

An orthodontic bracket and an orthodontic arch wire are provided. The orthodontic bracket has a bracket base with a bracket base jaw and a slide with a slide jaw. The slide is movable with respect to the bracket base. A closure device prevents movement of the slide with respect to the bracket base. Movement of the slide with respect to the bracket base causes the slide jaw to move with respect to the bracket base jaw. Also provided is an arch wire to be mounted on orthodontic bracket at orthodontic stations. The arch wire has a cross-section at the one or more stations which provides surfaces for an orthodontic bracket to engage to prevent rotation of the bracket relative to an axis transverse to the cross-section. The cross-section of the arch wire at a station has a selected orientation.

Description

ORTHODONTIC BRACKET AND ARCH WIRE

FIELD OF THE INVENTION

The invention relates to an orthodontic appliance. In particular, although not exclusively, the invention relates to an orthodontic appliance having orthodontic brackets and an arch wire.

BACKGROUND TO THE INVENTION

Orthodontic appliances are commonly applied to the teeth of a patient in order to gradually move the teeth to a more desirable position either to improve the patient's bite or for cosmetic purposes. The appliance exerts a force upon the tooth which causes it to move.

A commonly used type of orthodontic appliance involves fixing a bracket to the surface of each tooth and then attaching an arch wire to the brackets. The force applied by the arch wire is transmitted by the bracket to exert force upon the teeth and cause movement. By manipulation of the arch wire and its interaction with the brackets, differing amounts of force may be exerted in differing directions to provide the correct direction and amount of tooth movement.

The forces applied to the teeth by the arch wire and brackets can create a significant level of patient discomfort due to pressure on the periodontium. Additionally the time to complete the tooth movement can be lengthy and require frequent adjustments by an orthodontist.

Previously known brackets are generally attached either directly to the tooth surface using a dental binding agent or to a band which surrounds the tooth. The bracket usually supports an arch wire by way of a horizontal projection from the bracket or a slot formed within the bracket. The arch wire Is usually secured to the bracket by the use of ligatures, pins or other holding devices.

Brackets of the prior art, however, are static and invariable and will only allow the attachment of a particular type and dimension of arch wire. Thus when a different arch wire is required, to obtain different angulations and torques, a different bracket must be used. The current bracket must be removed from the tooth and a different bracket attached. This process causes discomfort for the patient, as well as requiring extra time and costs.

The invariable brackets of the prior art also are unable to accurately fit a designated arch wire into the bracket slot. Due to tolerance discrepancies, either the slot width needs to be overstated or the arch wire dimension understated or both.

As disclosed In AU 2007201756, a bracket was designed with a variable and active slot as a result of a slide inserted into a base. One of the side walls of the slot formed a V-shape which allowed variable slot geometry in more than just the vertical dimension. Thus variable changes to torque and angulations during treatment were possible. However, it was found that the torque variations and angulations were not sufficiently translated to the tooth, and in many instances could not be sustained.

Additionally, it was found that even when arch wire was firmly legated to the prior art bracket, there was a tendency for the legating wire to loosen minutely due to functional forces (applied by a patient, such as biting) being applied to the bracket slide during the final stage of active treatment. Loosening of the legating wire led to less accurate translation of the arch wire prescription via the bracket slot to the tooth.

Aspects of the invention attempt to overcome or at least alleviate one or more of the above problems and/or provide the consumer with a useful or commercial choice,

SUMMARY OF ASPECTS OF THE INVENTION

In on© aspect, although it need not be the only or indeed the broadest aspect, the invention resides in an orthodontic bracket comprising: a bracket base having a bracket base jaw; a slide moveable with respect to the bracket base, said slide having a slide jaw; and a closure device to prevent movement of the slide with respect to the bracket base; wherein movement of the slide with respect to the bracket base causes the slide jaw to move with respect to the bracket base jaw.

In a preferred embodiment, the closure device is a rotational device, which when rotated moves the slide with respect to the bracket base and when stationary prevents movement of the slide with respect to the bracket base. The closure device is preferably mounted on the slide.

Preferably, a channel is located in the bracket base, said channel adapted to receive the slide.

Preferably, a slot is formed between the slide jaw and the bracket base jaw by the slide passing through a portion of the bracket base.

Preferably, the slide jaw includes a slot lip projecting from the slide jaw towards the bracket base jaw. Alternatively; the bracket base jaw includes a slot lip projecting from the bracket base jaw towards the slide jaw.

In another aspect, although it need not be the only or indeed the broadest aspect, the invention resides in an arch wire operable to be mounted on one or more orthodontic brackets at one or more stations along the arch wire, the arch wire having a cross-section at a station which provides one or more surfaces which are engagable by a bracket so as to allow the arch wire to impart torque to the bracket transverse to the cross-section, wherein when the arch wire is not mounted the one Or more surfaces have selected orientations.

In another aspect, although it need not be the only or indeed the broadest aspect, the invention resides in an arch wire operable to be mounted to orthodontic brackets at one or more stations, wherein the arch wire has a cross-section at the one or more stations which provides one or more surfaces for an orthodontic bracket to engage so as to prevent rotation of the bracket relative to an axis transverse to the cross-section, wherein the cross-section of the arch wire at a station has an adjusted orientation. When the arch wire is fitted to a bracket in use, the orientation of the cross-section of the arch wire at the one or more stations will be rotated by the bracket. Resilience, of the arch wire, will cause it to apply a torque to the bracket. The selected orientation of the cross-section of the arch wire will select a torque to be applied to the bracket.

This allows an orthodontist to prescribe different torques for different sets of, or individual, tθθth.

The member may be formed from a resilient material so that torque may be provided by the resilience of the material when the material is deformed by the bracket being forced against a tooth in use.

The cross-section may be configured to provide one or more surfaces suitable for engagement by a selected orthodontic bracket.

The cross-section may be square and given orientations may be provided by given tilt of the cross-section.

The cross-section may be rectangular and given orientations may be provided by given tilt of the cross-section.

Given orientations of the cross-section of the arch wire may be provided by given 1Ht of the cross-section. The crass-section may be rectangular. The cross-section may be square.

In another form, although it need not be the only or indeed the broadest form, the invention resides in a bracket with jaws which are movable relative to each other to engage an arch wire at a section along the arch wire wherein the arch wire iδ configured to apply adjusted torque at a section to a bracket which has engaged the arch wire at the section. Adjusted torque may be determined by the cross- sectional shape or by the orientation of the cross-section of the arch wire. A bracket attached to a tooth may close on the arch wire to engage it and may apply torque to the arch wire and force it out of it's out of it's natural orientation or position. The arch wire may tend to return to it's natural orientation and thereby apply torque to the bracket. The properties of the arch wire may allow selection o( the torque to be applied at sections. The properties may be cross-sectional shape or orientation of cross-sectional shape or may be adjusted resilience.

In another form, although it need not be the only or indeed the broadest form, the invention resides in an arch wire which is configured to apply adjusted torque at a section to a bracket which has engaged the arch wire at the section.

It will be understood that 'arch wire¹ is a term which is intended to broadly refer to the member mounted on brackets which provides force and/or torque for the brackets and the term may not necessarily bθ limited to any particular shape.

Further features of the present invention will become apparent from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

To assist in understanding the Invention and to enable a person skilled in the art to put the invention into practical effect preferred embodiments of the invention will be described by way of example only with reference to the accompanying drawings, wherein:

FlG. 1 shows an orthodontic bracket according to one embodiment of the invention, wherein the closure device is in an open position;

FIG. 2 shows a side view ol the orthodontic bracket of FIG- 1 ; FIG, 3 shows a bottom view of the orthodontic braGket of FIG. 1 ;

FIG. 4 shows the orthodontic bracket of FIG. 1 , wherein the closure device is In a closed position; .

FIG. 5 shows the orthodontic bracket of FIG. 1 with an accompanying arch wire, wherein the closure device is in a closed position;

F)G. 6 shows an expanded view of an interface between a closure device and a slide according to a further embodiment of the orthodontic bracket; and

FlG. 7 shows a side view of a closure device according to a third embodiment of the orthodontic bracket.

Fig. 8 shows orthodontic brackets with accompanying arch wire of another embodiment of the present invention, the appliance having a number of orthodontic brackets mounted on an arch wire;

Fig. 9 shows the orthodontic brackets with accompanying arch wire of Fig 8, from another view and shows various orientations of the brackets mounted on the arch wire;

Fig. 10 shows various orientations or torques selected for various stations of the arch wire shown in Fig 8 and Fig 9; Fig. 11 shows an orthodontic bracket and accompanying arch wire of another embodiment, with a first station of the arch wire shown with the arch wire resting freely in the bracket;

Rg. 12 shows an orthodontic bracket and accompanying arch wire of another embodiment, with a second station of the arch wire shown with the arch wire resting freely in the bracket;

Fig. 13 shows an orthodontic bracket and accompanying arch wire of another embodiment, with the arch wire fixed in the bracket.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

FlG. 1 shows an orthodontic bracket 100 for attachment to a tooth. The orthodontic bracket 100 is shown in an open position. The orthodontic bracket 100 has a bracket base 200, a slide 300 and a closure device 400.

The bracket base 200 includes a mounting base 21O₁ a bracket base jaw 220 and a slide channel 230. The mounting base 210 has an attachment surface 211 which is substantially flat, for mounting onto a surface of a tooth. However, the attachment surface 211 may be varied to allow for the shape of a tooth's surface. For example, some curvature or angulation of the attachment surface 211 may be provided. An example of a curved attachment surface 211 is shown in FiG. 2.

The attachment surface 21 1 may additionally include a plurality of raised portions 212 as shown in FIG. 3 to increase the surface area of the attachment surface 211 , such that the adherence of the attachment surface 211 to a tooth is improved. The raised portions 212 may be mushroom shaped in order to provide a greater surface area for adhesion of a bonding material and also to provide a mechanical means of locking the bonding material to the bracket base 200. A raised border 213 at the periphery of the bracket base 200 serves to compress the bonding material between the attachment surface 211 and- the tooth. The bracket base jaw 220 is integrally formed with the mounting base 210. Alternatively, the bracket base jaw 220 may be formed separately and affixed to the mounting base 210. The bracket base jaw 220 Is located towards an end of the mounting base 210 and extends the entire width of the mounting base 210. The bracket base jaw 220 has a bracket base jaw face 221 that Is substantially planar and generally perpendicular to the mounting base 210. The opposite face of the bracket base jaw 220 to the bracket base jaw face 221 has a bracket base ligation lip 222 which projects outwardly from the bracket base jaw 220.

A slide channel 230 is formed in an upper surface of the mounting base 210. The slide channel 230 extends centrally along the length of the mounting base 210 and passes under, or through, the bracket base jaw 220.

The slide 300 consists of a slide base 310 and a slide jaw 320. The slide base 310 is received within the slide channel 230 of the mounting base 210, and is able to move longitudinally within the slide channel 230. The slide base 310 extends outwardly beyond the end of the slide channel 230, such that a portion of the slide base projects from the bracket base 200.

The slide jaw 320 is integrally formed with the slide base 310.

Alternatively, the slide base 310 can be formed separately and affixed to the slide base 310. The slide jaw 320 is located towards an end of the slide base 310 and extends to the width of the mounting base 210. The slide jaw 320 has a slide jaw face 321 that is substantially planar and generally perpendicular to the mounting base 210. The slide jaw 320 also has a slot lip 322 located at the top of the slide jaw face 321. The slot lip 322 projects outwardly from the slide jaw face 321. Alternatively, the slot lip 322 is located at the lop of and projects outwardly from the bracket base jaw face 221. Additionally, the slide ]aw 320 has a slide jaw ligation lip 323 located on the opposite face of the slide jaw 320 from the slide jaw face 321. The slide jaw ligation lip 323 projects outwardly from Ihe slide jaw 320. In this embodiment, the closure device 400 is in the form of a cam 410 which is fixed with a cam pin 420 set off centre at a point midway between the central axis of the cylinder and the circumference of the cylinder. The cam 410 is in the shape of a cylinder, which has had a portion removed such that a horizontal cross-section of the cylinder is a circle with a segment removed. The cam 410 has a sidewall 411 which may include a groove 412 shaped to receive ligation members. The groove 412 may be concave or rectangular in profile or alternatively the sidewall 411 includes a lip projecting outwardly from the sidewall 411.

Alternatively, the closure device 400 may be a calibrated sleeve fitted over the end of the slide base 310 which may be crimped into place. In a further alternative, the closure device 400 is a spring attachment. In another embodiment a hexagonal member is mounted with an offset axis similar to the cam 410. The hexagonal periphery of the member contacts or abuts a flat surface on the base jaw. The jaws can be closed in stepped, or indexed, positions by turning the hexagonal member to select a flat surface on the periphery which abuts against the flat surface of the base jaw. Suitable alternatives to a hexagon and a flat surface on the base jaw will be apparent. In other embodiments a moon-shaped or rectangular wedge are used.

Suitable alternatives will be apparent which reverse the role of either the base or slide in mounting the cam, hexagonal member or sleeve, for example. For example, the cam 410 may be mounted on an axis fixed relative Io the base father than the slide and the cam 410 may contact a suitable surface provided on the slide jaw 320.

In this embodiment, the closure device 400 is fixed to the slide base 310 where the slide base 310 projects from the bracket base 200. In a preferred embodiment, as shown in FlG. 7, the cam pin 420 passes through the slide base 310. A cap lock 421 is fitted to the cam pin 420 to allow the cam 410 to rotate with respect to the slide base 310 without becoming dislodged. The portion of the slide base 310 in contact with the closure device 400 may be flat, recessed or stand proud. One or more marker points (not shown) may be inscribed or labeled on the top surface of the cam 410 such that the operator can quickly determine the rotation applied to the closure device 400. i The cam 410 rotates about the cam pin 420 in a stepped manner for more precise adjustment of the closure device 400 and to prevent unwanted rotation. Stepping of the rotation of the closure device 400 is achieved by providing a non-flat interface between the cam 410 and the slide base 310. The bottom surface of the cam 410 and the portion of the surface of the slide base 1310 which contacts the cam 410 are provided with corresponding recessed and projecting portions. FIG. 6 shows an embodiment where the bottom surface of the cam 410 is provided with a ball 413 which is freely rotatable in a recess 414. The, surface of the slide base 310 is provided with recesses 415 into which ball 413 fits.

The recessed and projecting portions may alternatively be in the form of one or more sets of grooves and ridges, divots and points or a combination thereof. When the closure device 400 Is rotated, some force is required to move the closure device 400 from a position where the recessed and projecting portions correspond, to the next position where the recessed and projecting portions correspond. Rotation of the cam 410 can be achieved by insertion of a tool, such as a screwdriver, into a female fitting 420 on the closure device 400.

The orthodontic bracket 100 may also include ligation members (not shown), for use when the closure device 400 is not fully closed. Elastic bands, springs or "C-damp" devices, as are well known in the field, may be used. Ligation members may be placed to hook under the bracket base ligation lip 222 and the slide jaw ligation lip 322. Alternatively, ligation members may hook over the closure device 400 into the groove 412 in the sidewall 411 of the cam 410 and under the slide jaw ligation lip 322.

In use, the orthodontic bracket 100 is mounted either directly onto a surface of a tooth using a dental binding agent or mounted onto a band surrounding a tooth. The bracket base jaw 220 and the slide jaw 320 form a slot 500, as shown in FlG. 1. An arch wire 600 is chosen according to a tooth movement prescription and Inserted into the slot 500 beneath the slot lip 322.

The cam 410 contacts the bracket base jaw 220. Rotation of the cam increases the distance between the cam pin 420 and the bracket base jaw 220. Thus the slide base 310 is forced to move within the channel 230 to allow this increase, The movement of the slide base 310 changes the distance between the bracket base jaw 220 and the slide jaw 320 and thus reduces the size of the slot 50O₁ as shown in FlG. 4. The closure device 400 of the orthodontic bracket 100 is rotated by insertion of a tool into the female fitting 420 of the closure device 400. If the closure device 400 is in th© form of a calibrated sleeve, markings on the calibrated sleeve show how far to fit the calibrated sleeve over the end of the slide base 310 to correspond to the size of slot 500. The calibrated sleeve can than be crimped into place.

When the closure device 400 is fully closed, the arch wire 600 within the slot 500 is secured firmly and accurately by the slot lip 322, as shown in FIG. 5, and no ligation members or elastomers are required to prevent dislodgement of the arch wire 600. When the closure device 400 is fully closed, the slot lip 322 may extend from the slide jaw 320 to. abut the bracket base jaw 220. Alternatively, the slot lip 322 may only extend partially from the slide jaw 320 towards the bracket base jaw 220. If the closure device 400 is not fully closed, ligation members may be used to secure the arch wire 600 into the slot 500 of the orthodontic bracket 100, If elastic band ligation members are placed to hook under the bracket base ligation lip 222 and the slide jaw ligation lip 322, this allows for the slot 500 to close due to the elastic properties of the ligation member. However,-as the elastic band may deteriorate in a short time, the slot 500 may partially reopen.

Alternatively, ligation members may hook into a groove in the sidewall 411 of the cam 410 and under the slide jaw ligation lip 322. This placement holds the arch wire 600 in place and does not affect the opening and closing of the slot 500. In this configuration, the slot 500 may open and close depending on forces applied to the slide 200 and the bracket base 300. These forces may include functional forces (biting etc), force exerted by the arch wire 600 or other forces applied to the orthodontic bracket When more than one orthodontic bracket 100 is used with a single arch wire 600, each orthodontic bracket 100 may be locked by operation of the closure device 400 on an individual basis. Thus the arch wire 600 may be locked within some brackets whilst further adjustment of other brackets (s continued.

Alterations to the width of the slot 500 may be made at any time, as the orientation of the tooth changes. Additionally, the arch wire 600 may be exchanged for a different arch wire 600 to alter the forces placed on the tooth.

The bracket of the current invention allows the use of arch wire of any dimension, and thus different arch wires may be utilised without the necessity of changing the brackets. Full or segmented multiple arch wires may also be inserted into the bracket slot. The ability of the bracket of the current invention to self-Hgate the arch wire within the slot by way of the slot lip results in the arch wire being firmly and accurately held within the slot. This contributes Io an accurate transfer of the prescription of torque and angulation formulae from the arch wire to the tooth.

The arch wire may be fitted easily and accurately into the slot regardless of manufacturing tolerance variations, due to the variability of the slot dimensions. Thus a more predictable and more accurate tooth movement outcome may be achieved.

Figures 8 and 9 show part of an orthodontic appliance according to another embodiment of the present invention. The appliance 700 is formed of a member, or arch wire, 701 which forms an arch approximately following an arch formed by an upper or lower set of teeth. Mounted on the arch wire 701 at stations 702A - 702E are brackets 703A -703E. The stations 702 correspond to sections of the arch wire which line up with given teeth when the appliance 700 is fitted. Suitable lengths of sections or positions of stations will bθ apparent to the reader. For clarity, only approximately half of the brackets are shown. In this embodiment, the orientation of the arch wire cross-section at a station 702 is selected and set prior to the appliance being fitted, so the arch wire may be considered to be pre-torqued.

(n thfs embodiment, the brackets are similar to the brackets 200 illustrated with reference to figure 1. The bracket 200 has a base jaw 220 and a slide jaw 320 which engage the surface of the arch wire 701. In this embodfment, the arch wire i has a rectangular or square cross-section which provides flat surfaces (not shown) for the jaws 220 and 320 to engage. By engaging the surface of the arch wire, the brackets are held in given orientations when the appliance is not fitted. When the arch wire is fitted, the brackets are forced against teeth and the arch wire is deformed or twisted. In this embodiment, the arch wire is resilient and imparts forces arid torque to the brackets when it is deformed. By engaging the surface of the arch wire, the brackets receive force and/or torque and impart force and/or torque to the teeth.

Alternative embodiments may have arch wires with various alternative cross- sections which also allow torque to be lmparted to the brackets. Suitable alternative cross-sectional shapes will be apparent to the reader but may be ovals, ellipses, stars, or triangles, although the reader will recognize some of these being more practical for orthodontic application. It will be apparent also that the shape and dimensions of the arch defined by the arch wire will also affect the torque or force imparted to teeth and suitable adjustments, if any, for the of the shape and dimension of an arch wire incorporating this invention will be apparent. In some alternative embodiments the arch wires have a interchangable and detachable portions at the stations where the cross-section with different detachable portions may provide different orientations of surfaces engaged by the base jaws and slide jaws. In use, the detachable portions are interchanged to select the orientation of the surfaces engaged and, thereby, to select the torque to be applied to the bracket by the archwire.

In this embodiment the arch wire 701 is formed from resilient metal. Various suitable types and grades of metal will be apparent. Suitable alternative materials to metals will also be apparent. These include resins, fibres, plastics and composite materials.

Figure 9 specifically, shows the orthodontic appliance 700 from an angle which shows the brackets 703 in different orientations when the appliance is not fitted. This allows prescribed degrees of force and/or torque to be applied at different stations 702 to given rackets attached to given teeth (not shown).

Figure 10 shows different orientations for the cross-section of the one example of an arch wire 701 at different stations 702A to 702E when the appliance is not fitted. The different orientations illustrate how the orientation might be selected for a given patient to provide adjusted torques for given teeth. At station 702A of this example the arch wire cross-section is tilted by +14 degrees. At station 702B the cross-section is tilted by +7 degrees. At station 7O2C the cross-section is tilted by 0 degrees. At.station 702D the cross-section is tilted by -7 degrees. At station 702E the cross-section is tilted by -14 degrees. When the appliance is fitted the orientations illustrated correspond to various levels, or Newton-metres, of torque applied to various teeth. In this example, the orientations follow a moπotonic progression from +14 degrees to -14 degrees. It will be apparent that in other examples the there may be no such progression and the orientation at each station is simply prescribed for each tooth at each station. Therefore, the orientations may be entirely arbitrary, or given, for each station. It will be apparent also that the maximum tilt or minimum tilt illustrated may be different for other examples. Suitable maximum or minimum tilt will be apparent to to the reader based on the materials used and the method of manufacturing or adjusting the archwires. It will also be apparent that the different orientations are not limited to different tilts of the same shape and that the cross-sectional shape may be adjusted or selected for each station.

Figures 11 , 12 and 13 show a bracket in relation to a pre-torqued arch wire 801 of an embodiment similar to that of figures 8, 9 and 10. This embodiment differs only in the scale of dimensions of the bracket relative to the cross-section of the arch wire. The embodiment has brackets 1100 similar to the bracket 100 of the embodiment of Figure 1. The bracket 1100 of this embodiment has a mounting base 1210 with a bracket base jaw 1220 and a slide 1300 with a slide jaw 1320. The bracket 1100 also has a closure device 1400 with a cam 1410 which is capable of forcing the slide jaw 1300 in the direction denoted by the arrow G to close the base jaw 1220 and slide jaw 1320 on the arch wire 701. The flat surfaces (shown vertical) of the square cross-section of the arch wire are engaged by the jaws of the bracket to prevent rotation of the arch wire relative to the brackets and to allow the arch wire to apply torque to the bracket. The base jaw 1220 and slide jaw 1320 are dimensioned to be larger that the cross-section of the arch wire so that the tilted cross-sections are positively engaged by the base jaw 1220 and slide jaw 1320. The relatively large scale of the bracket to the archwire provides better engagement of the archwire which will often not be perfectly oriented, or aligned, with the jaws, due to orientations being prescribed for given stations.

Figure 11 shows the pre-torqued arch wire sitting loosely in the bracket 1100A prior an orthodontic appliance formed of the arch wire 801 and brackets 1100A to N, for example, being fitted. Figure 11 illustrates a station 802A₁ similar to station 702A at which the arch wire cross-section has positive tilt to apply 'positive torque¹ to the arch wire 801.

Figure 12 shows the pre-torqued arch wire at a station 802B similar to station 702B with the arch wire 801 sitting loosely in the bracket 1100B. At station 802B the arch wire has a cross-section with negative tilt to apply 'negative torque' to the arch wire. Figure 13 shows the pre-torqued arch wire 801 at a given station 8OE.. The cam 1410 has been rotated relative to the cams 1410A and 1410B to force the slide jaw 1300 in direction G. To lock the arch wire 801 in place. As shown in Figure 13 the bracket is aligned with the cross-section of the arch wire 801. Therefore, the pre-torqued arch wire may apply a torque in positive or negative directions of rotation denoted by the curved arrow H depending on whether the positive or negative torque is applied to the arch wire at the given station. It will be appreciated that at some stations, similar to station 702C, may apply zero torque to the bracket 1100.

In use orthodontic brackets 1100 is mounted to a tooth, directly or with a dental binding agent. An arch wire 801 is chosen according to tooth movement prescription. The arch wire chosen also has selected orientations, or tilt, of the cross-section at one or more of the stations 802. The arch wire 801 is then mounted to the bracket 1200 by inserting the arch wire in a slot formed by the bracket base jaw 1200 and the slide jaw 1300 and turning the cam 1410 to close the jaws to engage the flat surfaces of the square cross-section of the arch wire 801 at the station 802. Initially, prior to completion of mounting, the cross-section of the arch wire 801 Is tilted to provide a selected orientation the flat surfaces of- the square shape of the cross-section. In this embodiment the degree of tilt is selected at manufacture, or in a post-manufacture adjustment, according to a tooth movement prescription. Once the mounting is completed, the bracket forces the arch wire cross-section into an orientation determined by the bracket and a tooth. The arch wire applies a torque to the bracket and therefore the tooth due to the resilient nature of the material, or alternatively to resilience In the bracket.

Manufacture of pre-torqued arch wires with different cross-section orientations at different stations will be apparent. In one embodiment trie manufacture involves deforming a resilient wire by twisting, rolling, peening or hammering to a degree sufficient to permanently deform the material. In another embodiment, It may involve forming a material in a predefined shape which has surfaces at different orientations. In some embodiments the manufacture may involve applying heat treatment to various sections of the arch wire 701 corresponding to various stations 702. In other embodiments the manufacture may involve machining the cross-sectional shape of the arch wire. Other embodiments may involve adjusting the resilience of the arch wire at a station, by thermal treatment or machining, mechanical force or chemical treatment for example.

Throughout the specification, the aim has been to describe the invention without limiting the invention to any one embodiment or specific collection of features. Persons skilled In the relevant art may realize variations from the specific embodiments that will nonetheless fall within the scope of the invention. For example, a projecting lip could be located on both the first and the second sidewall such that when the closure device is closed the projecting lips come together and secure an arch wire within the slot of the bracket. Additionally, further embodiments may be formed of suitable combinations of features described herein.

It will be appreciated that various other changes and modifications may be made to the embodiments described without departing from the spirit and scope of the invention.

Claims

Claims:

1. An orthodontic bracket comprising: a bracket base having a bracket base jaw; a slide moveabfe with respect to the bracket base, said slide having a slide jaw; and a closure device to prevent movement of the slide with respect to the bracket base; wherein movement of the slide with respect to the bracket base causes the slide jaw to move with respect to the bracket base Jaw.

2. The bracket of claim 1 , wherein the closure device is a rotational device, which when rotated moves the slide with respect to the bracket base and when stationary prevents movement of the slide with respect to the bracket base.

3. The bracket of claim 2, wherein the closure device is preferably mounted on the slide,

4. The bracket of any one of claims 1 to 3, wherein the bracket base includes a channel, said channel adapted to receive the slide.

5. The bracket of any one of claims 1 to 4, comprising a slot formed between the slide jaw and the bracket base jaw by the slide passing through a portion of the bracket base.

6. The bracket of any one of claims 1 to 5, wherein the slide jaw includes a slot lip projecting from the slide jaw towards the bracket base jaw.

7. The bracket of any one of claims 1 to 6, wherein the bracket base jaw includes a slot lip projecting from the bracket base Jaw towards the slide jaw.

8. The bracket of any one of claims 1 to 7, wherein the closure device includes a rotational element which is pivotally mounted to the slide at an axis of the rotational element which is selected such that a periphery of the rotational element in contact with the base changes the distance between the periphery and the axis as the rotational element is rotated.

9. The bracket of claim 8 wherein the cam and the slide are provided with non flat profiles operable to engage each other to provide stepped locking of the rotational element relative to the slide.

10. The bracket of any one of claims 1 to 7, wherein the closure device includes a crimp.

11.- An arch wire operable to be mounted on one or more orthodontic brackets at one or more stations along the arch wire, the arch wire having a cross- section at a station which provides one or more surfaces which are engagable by a bracket so as to allow the arch wire to impart torque to the bracket transverse to the cross-section, the wherein when the arch wire is not mounted the one or more surfaces have selected orientations.

12. The arch wire of claim 11 wherein the arch wire includes a resilient material so that torque may be provided by the resilience of the material when the material is deformed by the bracket being forced against a tooth in use.

13. The arch wire of any one of claims 11 to 12, wherein selected orientation is provided by selected tilt of the cross-section.

14. The arch wire of any one of claims 11 to 13, wherein the cross-section Is rectangular.

15. An orthodontic appliance including the bracket of any one of claims 1 to 10 and the arch wire of any one of claims 11 to 14.

16. An orthodontic bracket substantially as herein described and illustrated with reference to figures 1 to figures 1 to 7.

17. An arch wire substantially as herein described and illustrated with reference to figures 8 to 10 or 11 to 13.