GB2164858A - Orthodontic appliance - Google Patents

Abstract

De-rotation spring for use in de- rotating a tooth in orthodontic treatment comprising an attachment part 36 to connect the de-rotation spring to the tooth either directly or indirectly as by welding to an orthodontic band surrounding the tooth, a flexible part 40 acircular in cross-section such that its width dimension parallel to the plane of the tooth when fitted is greater than its thickness dimension forwardly perpendicular thereof whereby to inhibit flexure parallel to the plane of the tooth, and a guide part 14 slidable along an orthodontic bar of a fixed or removable orthodontic appliance. <IMAGE>

Description

SPECIFICATION De-rotation springs This invention relates to de-rotation springs for use in de-rotating a tooth in orthodontic treatment.

Many of the prior proposals for tooth derotation springs are complicated to fit, and subsequently to adjust after partial de-rotation has occured, and are not therefore suited to the requirements of the general dental practitioner. Certain of the prior proposed springs are of a shape and size uncomfortable for the patient, particularly since such springs may have to remain fitted in the mouth for extended periods whilst the treatment continues.

Yet others of the prior proposed springs comprise separable parts for ease of adjustment during the treatment, but in which the parts can inadvertently separate, as when the patient bites into an apple or the like, and injure the inside of the mouth. Certain springs in current use are effective in tooth de-rotation but often result in unwanted side-effects such as tooth shortening.

Thus there have been a number of previous proposals for tooth de-rotation springs, particularly for the de-rotation of a single tooth.

One presently used apparatus applies a couple to the tooth, using a pair of springs exerting pressure in opposite directions on the mesial and distal corners of an incisor tooth; use of this apparatus frequently results in shortening of the tooth, and is not applicable to canines which are of unsuitable shape. This known apparatus requires a high degree of skill to fit, and acceptable results cannot be achieved consistently. Another known apparatus uses a long "whip" or "capstan" spring of 0.35mm diameter hard stainless steel wire.One end of the spring is mounted on the tooth to be rotated, as by a standard twin wire channel or "W-lock", which is itself for instance carried by a band of soft stainless steel tape encircling the tooth to be de-rotated and of 3.0mm by 0.1 mum, or of white gold tape of 3.0mm by 0.15mm, the steel tape being welded and the gold tape being soldered. The free end of the spring projects, as made, from the mouth, but in use is restrained by a projection carried by a base plate.It is the practice to kink the spring outwards, after initial rotation of the tooth, so that the spring remains out of contact with the user's intervening teeth and so that the selected tooth can continue its movement and over de-rotate, to reduce the time the apparatus has to be retained in the patient's mouth; but this over de-rotation often results in labial displacement of the tooth, and if this is expected, then in an alternative arrangement a labial arch may be used with the retaining spur welded or soldered to the arch, the spur and arch being of 0.7mm stainless steel wire with the spur usually of softer material than the arch.

In yet a further arrangement currently practiced, the free end of a de-rotation spring of 0.35mm stainless steel wire is formed with a three-quarter collar which fits behind and around a labial orthodontic bow or arch, of 0.8mm stainless steel wire. Part of the spring extends forwardly of the labial orthodontic bow, which can be irritating for the wearer and the relatively large gap between the bow and that portion of the spring can trap food particles which may dislodge the collar upon continued eating.

Contrary to the teaching of the known apparatus and arrangements, it is a feature of my invention that I provide a de-rotation spring which has a flexible part which is a circular, being wider than it is thick, such that its dimension, when fitted, parallel to the plane of a tooth is greater than its dimension forwardly perpendicular thereof. I also propose a lengthened collar in the form of a clasp; preferably the clasp is a snap fit around the bow. Further, the flexible part and clasp are located behind the bow, in use being between the bow and one or more of the patient's teeth.

Thus according to one feature of my invention I provide a de-rotation spring for use in de-rotating a tooth in orthodontic treatment comprising an attachment part, a flexible part and a guide part,the attachment part being adapted to connect the de-rotation spring to a tooth to be de-rotated,the flexible part being acircular, the guide part being slidable along an orthodontic bow.

According to a further feature of my invention I provide a de-rotation spring for use in de-rotating a tooth in orthodontic treatment comprising an attachment part, a flexible part and a guide part, the attachment part being adapted to connect the apparatus to a tooth to be de-rotated, the flexible part being between the attachment part and the guide part, the flexible part being of greater length than width and of greater width than thickness, the guide part including a base connected to the flexible part and a pair of spaced sidewalls, one edge of each sidewall being connected to the base, and the respective opposed free edges of the sidewalls being spaced apart to form a longitudinally-extending slot, whereby the said free edges can permit the passage therebetween of an orthodontic bow which is to be located between the sidewalls and the base.Preferably the free edges are spaced apart less than the sidewalls with the said one edge of each sidewall connected to the base in such manner that the free edges can be resiliently separated to permit the passage therebetween of the said orthodontic bow.

Conveniently the width of the flexible part decreases from between 1.5mm and 4.0mm adjacent to the tooth to be de-rotated to between 1 .0mum and 3.0mm at the clasp, the maximum and minimum spring widths being selected according to the size of the band to which the flexible part is to be fitted and the required lateral stiffness, the flexible part having a constant thickness of 0.5mm maximum,preferably 0.15mm or 0.1 mum. Thus the flexible part is constructed to have less freedom of movement, when fitted, in a plane parallel to the foreward face of a tooth than in a plane forwardly perpendicular thereof.

The flexible part is further constrained against movement in the plane parallel to the foreward face of a tooth by my clasp being of greater length than its diameter. Preferably the clasp length to diameter ratio is in the range 1.5:1 to 4.0:1. I have found a clasp of length 4.0mm and external diameter 2.0mm decreasing to 1.5mm at the free end suitable for many applications. Conveniently the clasp is shaped to form a three-quarter collar around the labial orthodontic arch, as in the above described prior art device, but the modified construction and greater length of my clasp greatly inhibits accidental disengagement of the clasp from the arch, to avoid the probable resultant patient injury as a sprung clasp moves foreward against the user's lip.

I also propose a modified construction in which the flexible part is longitudinally slotted.

After a predetermined de-rotation of the tooth, with the clasp sliding along the orthodontic bow, for some tooth shapes the flexible part might engage the bow and be pressed against one or more of the intermediate teeth, so preventing further de-rotation of the tooth undergoing treatment. With my modified construction of a flexible part having a slot with longitudinal edges which can locate to either side of the bow, further relative sliding movement is possible, so perhaps avoiding the need to inspect and possibly kink the flexible part prior to completion of the treatment.

Preferably the attachment part, flexible part and guide part are integrally formed from a single material, usually stainless steel, the material being of T-form when flat so that the flexible part and the attachment part are provided by the stem, and the guide part by the cross-pieces which are upturned out of the plane of the sheet. The flexible part when of stainless steel will act as a spring and be adapted to bias the guide part against the orthodontic bow. Conveniently the cross-pieces are turned to form a part-circular channel having a longitudinal slot through which the bow can pass to be retained within the channel, the edges of the slot being inturned to embrace partially the retained bow.

The invention will be further described by way of example with reference to the accompanying drawings, in which Figure 1 is a part perspective view of a first known arrangement, showing a retaining projection carried by a removable appliance; Figure 2 is a part perspective view of a second known arrangement, showing a retaining projection mounted on a labial bow or arch; Figure 3 is a schematic view of a known arrangement with the spring being secured to an upper tooth and engaging the labial bow of a removable appliance; Figure 4 is an enlarged view of part of the appliance of Figure 3; Figure 5 is a view of one embodiment of de-rotation spring of the present invention; Figure 6 is a view of a second embodiment of de-rotation spring of the present invention; and Figure 7 is a part perspective view of the de-rotation spring of Figure 6 fitted to an upper tooth, and clasping a labial orthodontic bow.

Projection 10 is mounted in a base (not shown) which fits the upper palate and lower lingual area. As usual, this base is conveniently of clear acrylic denture material, the nonvisible ends of the projection 10 being within the material so that they cannot contact either the upper or lower mouth tissue. Projection 10 is specially shaped and positioned at 12 to emerge from between two teeth, this position and shaping varying from patient to patient in accordance with the disposition of the individual teeth. The height and shape of the projection 10 is also individually tailored for each patient.

Projection 10 retains the free end 14 of a round wire spring 16. The other or or fixable end 18 of spring 16 is attached to steel tape 22 tightly affixed around tooth 20; thus spring 16 in the position shown effects a de-rotational couple on tooth 20 by way of the steel tape 22.

In the arrangement of Figure 2, the base mounts a labial arch or bow 24, with a projection 10 of a shape and size to suit the individual patient being secured to the bow.

Figure 3 is of a further known arrangement, in which the free end 14 of the spring 16 is shaped to form a collar 28, this collar being best seen in Figure 4, the collar 28 locating around the bow 24. It will be understood that in this embodiment of the invention and for clarity is not shown); but any other suitable mounting can be used, as can any suitably shaped base provided it can readily be removed for cleaning or for comfort by the patient, or perhaps the supervising dentist. The force of spring 16 acts to apply an anticlockwise de-rotation as seen in Figure 3 to tooth 20.

Though the embodients described above can be effective for tooth de-rotation, they can be complicated for the dentist to make and to fit properly in the surgery. Additionally, for the apparatus of Figures 1 and 2 the free end 14 of the spring 16 can become detached during treatment from behind projection 10 when subject to an upward force, as might occur during eating, and this results in frequent complaints by patients whose inner mouth is thereby injured; this shortcoming makes dentists unwilling to recommend or fit an appliance which otherwise could greatly benefit many patients.Similarly the arrangement of Figure 3 can also inadvertently become detached and spring free, perhaps to puncture the patient's lip; but an additional and frequent problem with the Figure 3 arrangement is premature failure, due usually to metal fatigue as a result of the continual torsionally-induced rotation of the free end 14 of spring 16 about bow 24 during eating. Such torsional rotation of end 14, which occurs about the axis of the spring 16, is resisted by tooth 20, which tooth thereby itself suffers a torsional force active to rotate the tooth 20 outwardly, that is to the right as seen in Figure 3. Increasing the outward and forward prominence of tooth 20 will often be of greater concern to the patient than any improvement the spring may produce in the de-rotating of the tooth about the tooth vertical axis.Thus this apparatus, though arguably of simpler construction than the previously described prior arrangements, has not found general favour.

As seen in Figure 5, the de-rotation spring of the present invention comprises three parts: a flexible part 2, an attachment part 4 and a guide part 6, of unitary construction.

Attachment part 4 is secured to the tooth to be de-rotated, and for this purpose may be treated to provide better adhesion to the tooth, or may be welded to an orthodontic band fitted around the tooth. Guide part 6 has raised and shaped sidewalls 1 adapted to fit around a bow, and slide along the bow as the tooth being treated de-rotates, the bow being a component of'a fixed orthodontic appliance of conventional design or of an appliance fitted for easy and regular removal from the mouth, as for cleaning.

Flexible part 2 is acircular and is wider than it is thick, to ensure that it is flexible only in the required direction, specificaliy to inhibit flexure in its plane; whilst in the embodiment of Fig.5 the flexible part 2 is of constant width w, in an alternative embodiment the part 2 can be tapered in width, being narrower adjacent the guide part 6 than adjacent the attachment part 4. Not only is the length 1 of the flexible part greater than its width w, but the width w is in turn greater than its thickness t.

Sidewalls 1 are each connected to base 3 at edges or edge regions 5, base 3 being connected to flexible part 2 at region 7. The free edges 9 of sidewalls 1 opposed to edges 5 are spaced apart to form a longitudinallyextending slot 11; in a prefered embodiment the free edges 9 are separated less than the normal spacing between sidewalls 1, and the sidewalls 1 are connected to base 3 such that the edges 9 are resiliently separable to permit the passage therebetween of the orthodontic bow, the bow being located between the sidewalls 1 and base 3, with the free edges 9 helping to retain the bow. Together base 3 and sidewalls 1 are of channel form; and in an alternative embodiment form, with the slot 11, a channel of part-circular cross-section.

In this embodiment, the parts are formed from flat metal sheet of T-shape, the stem providing the attachment part and the flexible part, and the cross-pieces the guide part by way of cross-pieces upturned out of the plane of the stem. In a preferred embodiment the sheet and thus the flexible part 2 is of stainless steel, and so able to resist chemical attack from mouth juices and from ingested food and liquids, whilst yet being easily manipulated by tools readily available to the dentist, so that for instance flexible part 2 can have a crank inserted should the tooth be over de-rotated. The flexible part 2 will act as a resilient metal spring, able to bias base 3 resiliently against the bow to help prevent its inadvertent detachment from the bow, in addition to the bow/clasp retention provided by edges 9.However, in alternative embodiments flexible part 2 may be of any suitable flexible material, including tooth-coloured plastics materials such as nylon, if the patient or dentist so prefers and the required treatment so permits; and in such alternative embodiments, one or both of the attachment part 4 and guide part 6 may be of the same or of a different material or materials to that of flexible part 2.

In a particularly advantageous embodiment ,the flexible part is of 0.152mm thick high tensile stainless steel, having a width of 3.2mm at its connection to the attachment part and tapering at 3.5 degrees so that its width at the connection to the guide part is 1.5mm. The attachment part 4 is 3.2mm by 3.2mm square, and has a layer of 0.2mm thick gauze spot welded to the attachment face. The guide part has an inside diameter of 1.Omm, and outside diameter of 1.304mm and a longitudinal slot of gap width .07mm; its length is 1.7mm. The overail length of the de-rotation spring is 18.75mm.

The arrangement of Figure 5 thus overcomes the disadvantages of the Figure 3 arrangement, essentially by using a flexible part of flat plate material resistant to deflection in its own plane; and by providing a lengthened clasp which has a greater resistance to inadvertent detachment from the bow 24 at angles other than directly forward between the jaws of the clasp. This de-rotation spring is easily manufactured, with the clasp being formed in the embodiment shown from side pieces integral with the body of the spring and turned to form three-quarter grips.

In an alternative embodiment as seen in Figure 6 I provide a de-rotation spring which has a longitudinally slotted flexible part 2. Thus the spring is formed from flat stainless steel plate, the flexible part and attachment part each having a greater width than thickness; the flexible part 2 has the longitudinally extending slot 34 intermediate the side edges of the flexible part 2.Slot 34 has side edges 40 which are spaced apart more widely than the width of the bow 24 with which it is to be used and which can therefore fit between these edges; this embodiment allows the supervising dentist to take advantage of one or both of the features that the bow can be mounted closer to the adjacent teeth without affecting the disposition of the de-rotation spring in the mouth and thus the resilient or spring characteristics of flexible part 2; and that during treatment the flexible part is less likely to contact such adjacent teeth when it inches and slides along the bow as the tooth 20 to which the de-rotation spring is attached gradually de-rotates. Clearly however, if the supervising dentist prefers, the bow to tooth relative position can be retained and the flexible part set initially at a larger angle so as to permit greater angular de-rotation of the tooth.

The need to kink a prior art spring such as the spring 16 of Figure i can in some cases be avoided; this is doubly advantageous in that such kinking, which currently is a common practice, can alter the spring characteristics in an arbitrary manner, which necessitates more frequent inspections by the supervising dentist.

The de-rotation spring has a rearward flange 36, which can be welded to a steel tape or band affixed to and encircling tooth 20. Flange 36 is arranged so that the weld will be adjacent a rear surface of the tooth i.e. a surface facing the palate, to permit a greater length of active spring within a given circumferential spring projected length.

Clasp 32 comprises two jaws or sidewalls 39, of part circular form, sized to clasp around the respective bow 24 and to provide a longitudinally-extending opening through which the bow can be inserted and removed, in a preferred embodiment with a positive snap action. Bow 24 and the appliance base on which it is mounted can be simply disengaged, as for cleaning, from clasp 32 (which will be retained in the mouth because of its attachment to the tooth to be de-rotated), by removal of bow 24 through the jaws in a direction generally perpendicular to the plane of flexible part 2; removal at other angles is inhibited by one or other of the jaws or sidewalls 39.

In use, as seen in Figure 7, the de-rotation spring of the present invention lies behind the orthodontic bow rather than to one or other side of it and thus occupies a minimum of space in a plane parallel to the front face of a tooth, behind the lip. In particular, there is no wire lying alongside the patient's gum.

The de-rotation spring I propose thus satisfies a long-felt need for a simple but effective arrangement for the de-rotation of a tooth, which is acceptable both to patients and to their supervising dentists, which can be manufactured ready for fitting to one of a number of patients rather than being individually tailored so greatly simplifying this type of work for the dentist, and rendering it more readily available to a wider range of patients.

The improved de-rotation spring of my invention can be used to de-rotate any upper or lower tooth, molar, premolar, canine, lateral or centre.

Claims (29)

1. De-rotation spring for use in de-rotating a tooth in orthodontic treatment comprising an attachment part, a flexible part and a guide part, the attachment part being adapted to connect the spring to a tooth to be de-rotated, the flexible part being acircular, the guide part being slidable along an orthodontic bow.

2. De-rotation spring for use in de-rotating a tooth in orthodontic treatment comprising an attachment part, a flexible part and a guide part, the attachment part being adapted to connect the spring to a tooth to be de-rotated, the flexible part being between the attachment part and the guide part, the flexible part being of greater length than width and of greater width than thickness, the guide part including a base connected to the flexible part and a pair of spaced sidewalls, one edge of each sidewall being connected to the base, and the respective opposed free edges being spaced apart to form a longitudinally extending slot, whereby the said free edges can permit the passage therebetween of an orthodontic bow which is to be located between the sidewalls and the base.

3. De-rotation spring as claimed in claim 2 in which the said respective opposed free edges are spaced apart less than the sidewalls, and in which each said one edge is connected to the base such that the respective opposed free edges can be resiliently separated.

4. De-rotation spring as claimed in any of claims 1-3 in which the attachment part, the flexible part and the guide part are integrally formed from a single material.

5. De-rotation spring as claimed in claim 4 in which the material is a sheet material.

6. De-rotation spring as claimed in claim 5 in which the material is of T-form when flat, the flexible part and the attachment part being provided by the stem, and the guide part being provided by the cross-pieces, the crosspieces being upturned out of the plane of the sheet.

7. De-rotation spring as claimed in claim 6 in which the upturned cross-pieces form a part-circular channel.

8. De-rotation spring as claimed in claim 6 or claim 7 in which the stem is of uniform width.

9. De-rotation spring as claimed in claim 6 or claim 7 which the stem is tapered in width from adjacent the attachment part to the guide part.

10. De-rotation spring as claimed in any of claims 6-9 in which the attachment part is a flange downwardly turned out of the plane of the sheet and adapted to at least partly encircle the tooth to be de-rotated.

11. De-rotation spring as claimed in any of claims 6-9 in which the attachment part is treated to adhere directly to the tooth to be de-rotated.

12. De-rotation spring as claimed in any of claims 6-9 in which the attachment part is suitable for welding to an orthodontic band.

13. De-rotation spring as claimed in claim 10 which the flange is of a shape and size to grip around a tooth.

14. De-rotation spring as claimed in any of claims 5-13 which the flexible part includes a slot of length greater than its width.

15. De-rotation spring as claimed in any of claims 9-14 in which the width of the flexible part adjacent the attachment part is between 1.5mm and 4.0mm.

16. De-rotation spring as claimed in any of claims 9-15 in which the width of the flexible part adjacent the guide part is between 1.0mum and 3.0mm.

17. De-rotation spring as claimed in any of claims 6-16 in which the flexible part has a thickness no greater than 0.5mm.

18. De-rotation spring as claimed in claim 17 in which the flexible part has a thickness no greater than 0.15mm.

19. De-rotation spring as claimed in any of preceding claim when dependent on claim 7 in which the part-circular channel has a length to diameter ratio in the range 1.5:1 to 4.0:1.

20. De-rotation spring as claimed in claim 1 7 in which the part-circular channel is of length 4.0mm and of external diameter adjacent the flexible part of 2.0mm and of external diameter at its opposite free end of 1.5mum.

21. De-rotation spring as claimed in any preceding claim in which the flexible part is of stainless steel, and both flexible and resilient.

22. De-rotation spring as claimed in any of claims 1-20 in which the flexible part is of a synthetic plastics material self coloured substantially to match the tooth coiour, and both flexible and resilient.

23. De-rotation spring as claimed in claim 22 in which the material is nylon.

24. De-rotation spring for use in de-rotating a tooth in orthodontic treatment constructed and arranged substantially as herein described with reference to Fig 5 of the accompanying drawings.

25. De-rotation spring for use in de-rotating a tooth in orthodontic treatment constructed and arranged substantially as herein described with reference to Figs 6 and 7 of the accompanying drawings.

26. The combination of an orthodontic bow and de-rotation spring as claimed in any of claims 1-25.

27. The combination of a removable orthodontic appliance including a labial bow and derotation spring as claimed in any of claims 125 including a clasp snap-fittable to the bow.

28. The combination of an orthodontic bow, metal tooth-surrounding tape and de-rotation spring as claimed in any of claims 1-25.

29. The combination as claimed in claim 26 or claim 27 in which the orthodontic bow is part of a removable orthodontic appliance and the de-rotation spring is secured to a tooth to be de-rotated.