WO2003045266A1

WO2003045266A1 - Orthodontic bracket

Info

Publication number: WO2003045266A1
Application number: PCT/GB2002/005291
Authority: WO
Inventors: Yann Sofian Taddei
Original assignee: Yann Sofian Taddei
Priority date: 2001-11-26
Filing date: 2002-11-26
Publication date: 2003-06-05
Also published as: AU2002347307A1; GB0128278D0

Abstract

An orthodontic bracket (10), comprising a base (15) with at least one outwardly projecting pair of wings (12) between which is a slot (26) with an inner and outer part (28, 30) of which the sides (32) may vary in distance apart.

Description

ORTHODONTIC BRACKET

The present invention relates to an ^"orthodontic bracket and an arch wire for straightening teeth or correcting a mal- occlusion .

Orthodontic brackets are used to move crooked, alaligned or misaligned teeth and do so by controlling tooth movement in three dimensions namely vertical, horizontal and rotational. A previously proposed orthodontic technique is the Edgewise technique that uses so-called Edgewise brackets. The Edgewise brackets have horizontal arch wire slots that allow good control of tooth movement in the horizontal and rotational direction. Another previously proposed technique is the Begg technique that uses so-called Begg brackets. The Begg brackets have a vertical extending arch wire slot that permits tipping in the mesio-distal direction.

The tipping of teeth requires less force than moving teeth in a bodily fashion and the up righting of tipped teeth requires more force than the initial tipping force. Classical Edgewise brackets express tip and torque by incremental increase of the arch wire until the bracket slot is filled completely. Freedom of tip and torque is allowed only when using undersized arch wire. This degree of freedom or ^Λplay' is determined by the size of the slot and the arch wire dimension. A more recently proposed Edgewise bracket does allow tipping and later the express of tip and torque prescribed to the bracket with the use of accessories. The Edgewise and Begg brackets however are restricted by their not being able to differentiate • anchorage requirements . Furthermore a single arch wire, whether round or rectangular/square in shape, will have the same effect in the tip prescription of the bracket. In the case of a modified Edgewise bracket the use of accessories requires correct orientation and precise positioning into a vertical slot. Incorrect positioning will result in the absence of the desired effect at best and at worst the opposite effect. Furthermore, loss or deformation of the accessories will limit or prevent the desired tooth movement, which leads to prolonged treatment times .

It is an aim of the present invention to provide an orthodontic bracket that overcomes these problems.

The present invention offers versatility not previously available in one bracket with the choice of utilising the inner part of the .slot alone or extending into the outer part . The inner part of the slot allows increased tip tolerance with the option to express torque with a square arch wire and thus manage anchorage predictably. The curved inner slot removes the potential of notching taking place between the arch wire and the slot thereby reducing friction. The outer part of the slot can be used to further manage ^'anchorage by expressing tip and torque automatically without use of accessories apart by using the arch wire according to the second aspect of the present invention.

Examples of brackets and an arch wire made in accordance with the present invention will now be described in relation to the accompanying drawings, in which:

Figure 1 shows a perspective view of a bracket according to the present invention;

Figure 2 shows an end view of the bracket shown in

Figure 1;

Figure 3 shows an elongate cross-sectional view of the bracket slot;

Figure 4 shows cross-section of arch wire for use with the bracket;

Figure 5 shows a perspective view of arch wire according to the present invention;

Figure 6 shows an end sectional view of the bracket with round arch wire within the inner part of the slot;

Figure 7 shows a front view of the bracket shown in

Figure 6 illustrating the arch wire in the inner part of the slot;

Figure 8 shows an end sectional view of the bracket with rectangular arch wire which extends into the outer part of the slot;

Figure 9 shows a front view of the bracket shown in

Figure 8; Figure 10 shows a perspective view of a modified bracket according to the present invention;

Figure 12 shows a perspective view of a modified bracket according to the present invention and;

Figure 13 shows a perspective view of a modified bracket according to the present invention.

Figures 1, 2 and 3 shows a bracket 10 for mounting on the crown of a tooth. It should be noted that the bracket may be of the single, double or triple winged type, the double winged type being illustrated. Furthermore the bracket could be made of metal, ceramic or plastics material. The bracket has pairs of tie wings 12 and a support part 14 integrally formed on a base or pad 15 defining opposed flanges 18. The tie wing 12 includes a rear face 20 and a front bucco-labial face 22 that is in front of the rear face 20. The tie wing 12 is further defined by opposed mesial and distal sides and gingival and occlusal sides. These surfaces are often parallel but this is not necessary for function. At the front face 22 of the tie wing 12, gingival and occlusal tips or hooks 24 are formed for the purpose of receiving a ligature to secure the arch wire on the bracket 10.

At the front face 22 of the tie wing 12, a mesio-distally extending and bucco-labial opening arch wire slot 26 is formed. The bracket slot 26 comprises an inner part 28 and an outer part 30. The inner part 28 comprises two non-parallel sides 32. The inner part 28 as illustrated in the Figure 1 comprises two predominantly curved sides 32 that are symmetrical. The inner part 28 of the slot 26 is formed with a curvature of the curved sides 32- that ^■ allows increased tip tolerance in the mesio-distal direction as shown in Figures 6 and 7, where the arch wire 50 sits entirely in the inner part 28 of the slot 26. At the mid-point between the mesio-distal ends of the bracket slot 26, the curve is replaced by a flat surface 34. The flat surface 34 enables the inner part 28 of the slot 26 to express torque with a perpendicular four-sided arch wire. The inner part 28 of the slot 26 is symmetrical with the flat surfaces 34 of the slot 16 directly opposed to each other. The characteristics of the inner part 28 of the slot 16 allow for increased freedom of movement in the mesio/distal and bucco/lingual directions when using a round arch wire as shown in Figure 6 and 7. When using a square arch wire the increased freedom of movement in the mesio/distal movement is maintained while the prescribed value of torque in the bucco/lingual is expressed. The increased tip tolerance exists in both clockwise and anti-clockwise sense. The curved surface 32 can be varied such that tip tolerance is expressed in only one direction. This is achieved by having the curved surface 32 diagonally opposed. The same characteristic movement of the inner part 28 of the slot 26 can be achieved by the flat or inversely curved surface 32, 34. The curved surface 32 is used to reduce the notching of sharp edges on the arch wire 50 thus reducing friction. The -outer part 30 of the slot 26 has flat, opposed, sides 36. The flat surface 36 extends from the flat surface 32 of the inner part 28 of the slot 26 as illustrated in Figure 3. These are also parallel to the occlusal and gingival side of the bracket 10. At the bottom of the walls of the slot 26, a slot base wall 38 extends perpendicular to the opposed walls. In Figure 8 and 9 a rectangular arch wire 50 is placed in the slot 26 which allows greater torque to be imparted by the bracket 10 than using square arch wire which will only make contact on surfaces 34 as opposed to surface 34 and 36. Thus giving the bracket 10 increased torque in the bucco/lingual direction.

While the edges of the bracket 10 are shown in the Figures sharply formed, they will be smoothed or rounded in practice. The bracket 10 may be made by investment casting and the edges and sides may be rounded. For example, while mesial and distal sides are shown to be -flat, they may be easily shaped somewhat rounded when cast, although they will still have a parallel appearance with the opposite sides or surfaces as mirror images.

Arch wire 50 according to the present invention, shown in Figure 5 for the bracket 10 is a combination of the round and rectangular cross-section wire shown in Figure 4. The round cross sectional part 52 of the arch wire is set inwards towards (arrow a) the centre of the arch form. These cross-sectional variations can be anywhere along the arch wire 50. The most common combination would be to have the round part 52 of the arch wire between the distal aspects of the canine bracket slot. Distal to this round aspect, the arch wire 50 will have a rectangular part 54. Alternatively, this arrangement can be reversed. This has the effect of utilising the biological resistance offered when tip and torque is expressed as opposed that when only torque is expressed.

The prescriptions for tip and torque will depend upon the specific tooth for which the bracket 10 is designed. The tip prescribed is created by the slot orientation in the mesiodistal direction. The torque prescription can be created in the bracket 10 by either using the bracket slot 26 or the base pad.

It will be understood that modifications and variations may be affected without departing from the scope of the present invention. It may be modified to a single or triple wing. While it is preferred that the bracket is made of metal, it will be appreciated that it could be made of ceramic or plastic with a metal lined slot. The body could also be separately formed and mounted on a bonding pad or a band, or in any suitable manner otherwise mounted on a tooth surface. As shown in Figure 10, the slot 26 may be modified to have walls of the inner part 28 that are rounded 40, shown in Figure 10, to accommodate a round arch wire. The walls of the inner part 28 of the slot 26 may be cut away in only one direction 42a outwardly from the middle and the opposing wall cut away in the opposite direction 42b from the middle resulting in a bracket that expresses rotation in one direction only. The slot 26 may also be modified by the absence of the outer and inner slot wall connecting the tie wings 12 as shown in Figure 12. Figure 13 shows a bracket 10 adapted for use with trapezoidal arch wire 50. The walls of the outer slot 30 are varied in cross-sectional angle with one opposing wall being biased 31 to accommodate a rhombic or trapezoidal arch wire 56.

Claims

1. An orthodontic bracket comprising -a base with at least one outwardly projecting pair of wings between which is a slot with an inner and outer part of which the sides may vary in distance apart.

2. An orthodontic bracket according to claim 1, in which the walls of the outer part of the slot are of equal distance apart to the distance apart of the walls of the central portion of the inner part of the slot.

3. An orthodontic bracket according to claim 1 or claim 2, in which the distance apart of the sides of the inner part are such that the inner part of the slot is waisted.

4. An orthodontic bracket according to claim 3, in which the walls of the inner part of the slot are convex in shape.

5. An orthodontic bracket according to any preceding claim, in which the walls of the inner part of the slot are angled such that rotational tip is applied to the bracket by the arch wire in one sense and not the other.

6. An orthodontic bracket according to claim 4 and claim 5, read appendant thereto, in which the convex sides of the inner part are mirror images of each other.

7. An arch wire having parts with rhombic or trapezoidal and round cross-sections. Preferably the rhombic or trapezoidal parts are rectangular.

8. An arch wire according to claim 7, in which the arch wire has the part with the round cross-section set inwards towards the centre of the arch form and a rectangular cross-section that extends outwards .