The invention relates to a dental bracket according to the preamble of the independent claim 1, the dental bracket comprising a body part with a surface being against a tooth and surface facing away from a tooth and comprising: at least one horizontal groove, which is an arc-wire groove, for inserting the arc-wire, and additional tensioners, and at least one wing for binder material.

Reference is made to Fig. 1. Fixed and loose orthodontic instruments are used for orthodontic dentistry. Fixed instruments are composed of brackets, which are fastened to s tooth surface by an adhesive so that a body of the bottom of the bracket is against the tooth, and of an arc- wire, which is fastened to the brackets and into an arc-wire groove. The arc-wire applies force onto the dental bracket and at the same onto the tooth, which force moves the tooth to the desired position. The arc-wires are generally of metal and have a shape which they seek to recover when they are in a state of tension. Traditionally the arc-wire is fastened in to the arc- wire groove by using wings in the upper and lower portions of the bracket as support parts. For example, metallic or rubber ligature yearns or rubber ligatures can be used for the binder material. Reference is made to Figure Fig. 2. Also known are the brackets, where the arc-wire locks in place by locking mechanism that can be slid or be turned over the arc-wire groove. Also, these brackets usually comprise wings for setting tensioners.

It is possible to fasten brackets to all teeth. Each tooth is required to have its own type of bracket, because torsion angle of the arc-wire groove of the bracket changes from tooth to tooth depending on which positions the teeth are wanted to be after ending the orthodontic treatment. Similarly, width and thickness of the brackets, as well as the shape of the bottom, vary according to the shape of the tooth surface. The brackets can also be fixed to the front or back surfaces of the teeth, whereby design and other values of the body of the dental bracket are different.

The brackets are divided into two groups depending on the direction in which the arc thread is. The groove is horizontal when the side walls of the arc-wire groove are essentially horizontally in the occlusal direction. The groove is vertical when the sidewalls are essentially vertically, mostly perpendicular against occlusal. The ability of these brackets to control the tooth movement in different directions is different. The horizontal groove can control the position of the root and the crown regarding the movements, which are perpendicular against occlusal, regarding so-called tooth angulation j a torque. On the other hand, regarding tooth rotation, the control is poor without special arrangements. Vertical groove controls well tooth movements regarding rotation and torque, but regarding angulation the bracket requires special arrangements to success. The manufacturer and designer of the bracket are forced to make choses between the horizontal and vertical grooves basing to the characteristics and weightings thereof.

Reference is made to Figure Fig. 3. A special challenge for brackets on the back surfaces of teeth is that the brackets should be as low as possible so that they would fit in the front area between upper and lower thighs and so that they would interfere as little as possible tongue and thus speech. Additionally, the insertion of the arc-wire and tensioners should be as simple as possible because working on the back surface of the teeth is difficult. The requirement for the shallowness of the bracket favors the horizontal arc-wire groove.

Reference is made to Figure Fig. 4. Regarding the result of orthodontic treatment, essential is the ability of the device to repair tooth rotations. The special problem, which relates to the conventional brackets having an arc-wire 401 which is secured in place into the horizontal groove by the binder material 402, and especially when using the same on the back surfaces of the teeth, is the inability to rotate the tooth to a straight position because pull direction of the binder material is disadvantageous due to the shape of the tooth surface. Even a slight stretching or other looseness of the binder material causes that the control with respect to the tooth rotation is lost completely. Efforts have been made to remove the problem by tightening the binder material as tightly as possible, however, any substantial improvement has not achieved with respect to the control of the tooth transfer. Tensioning also causes unnecessary friction, which prevents sliding of the arc-wire in the arch-wire groove. A frictionless sliding of the arc-wire in the groove, as far as possible, is essential to the progress of the treatment. In addition, the wing 403, which is from the arc-wire groove on the side of the tip of the tooth, makes the bracket remarkably high in the most critical area, and regarding the fit between the front lower and upper teeth. These problems have led to the development of numerous different mechanical lock systems, cf. Figure Fig.2. The lock systems hold the ac-wire well in place, whereby the tooth control is good. So far, for a very low structure regarding the height of the bracket has not been reached, since the lock structure and the occult wing for additional tensioner require their own space. In addition, the lock systems increase the manufacturing cost of the bracket and the small size of the locks makes them difficult to use.

The prior art is described above referring to the figures Fig. 1 to Fig.4 of drawings, wherein Fig. l shows a bracket, in which an arc-wire is secured into a groove by the binder material using wings at the upper and lower portions of the bracket as supporting members for the binder material. Metal- or rubber-ligature-yarns or rubber-ligatures can be used as a bonder material, as in Fig.1

Fig.2 shows a bracket, in which the arch-wire locks in place by a locking arrangement sliding onto the arc-wire groove. The brackets also comprise wings for setting tensioners.

Fig. 3 shows a bracket at the back of the tooth. A special challenge is that the bracket should be as low as possible in view of the fit at the front upper area between the upper and lower front teeth and so that it would interfere as little as possible tongue and hence the speaking. Additionally, the insertion of the arc-wire and tensioners should be so simple as far as possible, because the working on the back surface of the teeth is difficult.

Fig.4 shows a conventional bracket at the back of the tooth where the arc-wire 401 is fixed in place with the binder material 402. The problem is the inability to rotate the tooth directly because the pulling direction of the binder material is disadvantageous due to the shape of the tooth surface. The bolt can slip further away from the back wall of the groove without the binder material being able to apply the force mentioned to prevent slipping. The control of tooth rotation is completely lost. In addition, the wing 403, which is from the arcuate tooth to the tip of the tooth, makes the bracket remarkably high in the most critical area, in view of the fit between the lower and upper front teeth.

It is an object of the invention to improve securing method of the arc-wire at the traditional bracket containing a horizontal groove so that the bracket control of the arc-wire is good so that it allows a correction by an accurate tooth rotation without increasing friction between the arc-wire and the binder material. In addition, the object is to lower the bracket at its most critical points so that it can fit better between the front lower and upper teeth. The objects according to the invention can be achieved by the dental bracket comprising a body part with a surface being against a tooth and surface facing away from a tooth and comprising: at least one horizontal groove, which is an arc-wire groove, for inserting the arc- wire, and additional tensioners, and at least one wing for binder material, generally such that said arc-wire groove includes a side on the side of said surface being against the tooth, and a side on the said of said surface facing away from the tooth, and a side joining these sides, that said arc-wire groove is open to said surface facing away from the tooth through an opening of the arc-wire groove beside said wing, and that a side of said arc-wire groove on the side of said surface facing away from the tooth is shorter than a side of said arc-wire groove on the side of said surface being against the tooth for providing said opening of said arc-wire groove, wherein said arc-wire fits into said arc-wire groove beside said wing through said opening of the arc-wire groove.

Regarding the other preferred embodiments of the invention reference is made to the dependent claims of the set of claims.

The dental bracket can be fixed both to the front and to the back side of the tooth. The size and shape of the dental bracket can be adapted for each tooth and for each tooth surface. The arc-wire groove can be positioned in the body part to various positions for each dental bracket for applying different forces to the tooth. An advantage of the invention is that accurate control of the tooth is obtained during the transfer without increasing the friction of the arc- wire. In addition, the bracket can be made very low. Manufacturing costs remain reasonable due to the simplicity of the structure. For the dentist, the simplicity of the structure makes it easier to mount the bracket.

Preferred embodiment of the present invention is described in the following more detailed with reference to the Figures Fig.5 to Fig.10, wherein

Fig. 5 shows a dental bracket according to the invention, in which the wing on the side of the tooth tip locates in front of the opening of the arc-wire groove at such a distance that the arch- wire can pass between the wall of the arc-wire groove and the wing,

Fig. 6 shows a dental bracket according to the invention comprising a body part having a surface against a tooth and a surface facing away from the tooth,

Fig. 7 shows a dental bracket according to an embodiment of the invention, in which the wing extends upwards from the surface facing away from the tooth, Fig. 8 shows a dental bracket according to another embodiment of the invention, in which the wing extends upwards and to the sides for supporting and refine the binder material,

Fig. 9 shows a dental bracket according to a third embodiment of the invention comprising a second groove; and

Fig.10 shows an arrangement for straightening of teeth, comprising: a dental bracket to be fixed onto the tooth including a surface against the tooth and a surface facing away from the tooth having at least one arc-wire groove for the arc-wire and/or additional tensioners; and an arrangement applying the force of the arc-wire with the binder to the dental brackets and hence to the tooth.

Reference is made is made generally to Figures Fig.5 to Fig. 10. In the dental bracket, according to the present invention, a side of the arc-wire groove 604, 905b, 1005 a, 1005b 905b on the side of the surface 1008 being against the tooth is essentially horizontal and terminates at its both ends to a wall 1005 that is substantially perpendicular to this side, and the side 507 on the side of the side facing away from the tooth 1007 is shorter such that the arch-wire 501, 1001 can fit into the groove between it and the substantially perpendicular wall. When the arc-wire 501, 1001 is in place, the opening 1006 is closed by the binder material 502, 1002 which tightens to this passage preventing the arc-wire 501, 1001 from getting off the arc-wire groove. If the arc-wire tends out of the arc-wire groove, it presses the binder material against the perpendicular wall 1005. Thus, the control weakening, due to strain or loosening of the binder material, has eliminated completely by this structure. Only reduction of the control remains, which is caused of the arc-wire compression against the wing 503, 1003, 1004, which is nonexistent with the metallic binder material and is of no relevance with rubber material from the clinical point of view. Since the pull direction of the binder material is no longer towards the arc-wire, the friction between the arc-wire and the binder material is substantially reduced. Since the wing 503, 1003 on the side of the tooth tip is not necessary the dental bracket is extremely low in profile. Computationally, the height is, at the most critical point, only half as compared to the previous brackets of this type. Figure Fig. 5 shows the bracket according to the invention, in which the side of the arc-wire groove on the side of the surface being against the tooth is essentially horizontal and terminates at its both ends to the wall that is substantially perpendicular to this side, and the side on the side of the side facing away from the tooth is shorter such that the arch-wire 501 can fit into the groove through opening formed by it and the substantially perpendicular wall. When the arc-wire 501 is in place, the opening is closed by the binder material 502 which tightens thereto preventing the arch wire from getting off the arc-wire groove. If the arc-wire 501 tends out of the arc-wire groove, it presses the binder material 502 against the

perpendicular wall. Thus, the control weakening, due to strain or loosening of the binder material 502, has eliminated completely by this structure. Only reduction of the control remains, which is caused of the arc-wire 501 compression against the wing, which is nonexistent with the metallic binder material 502 and is of no relevance with rubber material from the clinical point of view. Since the pull direction of the binder material 502 is no longer towards the arc-wire, the friction between the arc-wire 501 and the binder material 502 is substantially reduced. Since the wing 503 on the side of the tooth tip is not necessary the dental bracket is extremely low in profile. Computationally, the height is, at the most critical point, only half as compared to the previous brackets of this type.

Reference is made to Figure Fig.6. The dental bracket according to the invention comprises a body part. The dental bracket has at its body a surface 608 facing the tooth, which that can be designed by additional retentions for gluing and by various formations for different teeth shapes, and the surface 607 facing away from the tooth. The body part has at least one arc- wire groove 604 for the arc-wire on the surface away from the tooth. The body part has a wing or wings 603 for securing the binder material. The side of the arc-wire groove 604 on the side of the surface facing against the tooth is substantially horizontal and ends at both ends to a wall 605 that is substantially perpendicular to this wall, and the side 607 on the side of surface facing away from the tooth is shorter such that the arc-wire can fit into the groove between it and the substantially perpendicular wall. Reference is made to Figure Fig.7. In a dental bracket, according to an example of the invention, the wall and the wing 703 at the dental bracket are oriented so that it rises from the surface only upwards, which holds and supports the binder material in place so that it prevents the arc-wire from coming out from the arc-wire groove. Reference is made to Figure Fig.8. The dental bracket according to the second example has the wings upwards 803a and sidewards 803b. The dental bracket wall is facing upward and the sides of the dental bracket has under-pulls, so that the support of the binder material in place is confirmed and refined on the sides of the dental bracket and in the center of the dental bracket. Reference is made to Figure Fig.9. The third bracket according to the third example has a second groove 905b for securing a second arc-wire or additional tensioners. Reference is made to Figure Fig.10, which shows an arrangement for straightening the teeth. The arrangement includes the dental brackets to be fixed on the teeth comprising a surface 1008 being against the tooth and a surface 1007 facing away from the tooth and one or more arc-wire grooves 1005b for arc-wires 1001 and/or additional tensioners; and an arrangement for applying the force of the arc-wire 1001 with the binder material 1002 to the dental brackets and hence to the tooth. In the arrangement of Fig. 10, the side of the arc- wire groove 1005b, which is on the side of the surface being against the tooth, is substantially horizontal and ends at both ends to wall 1005 that is substantially perpendicular to this side, and the side on the side of the surface 1007 facing away from the tooth is shorter such that the arc-wire 1001 can fit into the groove through opening 1006 formed by it and the substantially perpendicular wall. When the binder material is placed to pass through this opening it blocks the opening of the arc-wire groove so that the arc-wire cannot get out from the arc-wire groove. When the arc-wire 1001 is in place, the opening is closed by the binder material 1002 which is tightens to this passage preventing the arc-wire from getting out the arc-wire groove 1005b. If the arc-wire 1001 tends out of the arc-wire groove 1005b, it presses the binder material 1002 against the perpendicular wall 1005. If the tooth is not in the straight line, the arc-wire tries to push the arc-wire out of the arc-wire groove through another end of the groove. The binder material 1002 prevents this by pressing against the wall 1008 and thereby transmits the force of the arc-wire via the wall to the dental bracket and hence to the tooth, which will move the tooth to the position desired by the arc-wire.

Some preferred embodiments of the invention have been described above. The invention is not limited to the solutions described above, but the inventive idea can be applied in numerous ways within the scope of the protection defined by the claims. Reference numerals

501, 1001 : Arc-wire;

502, 1002: Binder material;

503, 603, 703, 1004: Wing;

604, 1005 a, b: Arc -wire groove;

605 Wall of the arc-wire groove against the tooth surface;

607, 1007: Surface away from the tooth or the side thereof;

608, 1008: Surface against the tooth;

803a: Wing upwards;

803b: Wing to the side;

905b: Another arc- wire groove or groove for additional tensioners;

1003 : Wing on the tooth tip side;

1005: Perpendicular wall for binder material;

1006: Opening of the arc-wire groove.