LINGUAL ORTHODONTIC APPLIANCE

Abstract

A lingual orthodontic appliance contains a lingual bracket for an anterior tooth and an archwire. The orthodontic appliance is defined in a three-dimensional Cartesian coordinate system. The archwire extends in a first and a second dimension of the coordinate system generally U-shaped. In the third dimension the archwire is generally flat. The archwire has a rectangular cross-section with a height defined by the longer side of the rectangular cross-section. The height is oriented along the third dimension. The bracket further has a bracket pad and a bracket body. The bracket body forms a slot for receiving the archwire. The slot is formed by at least two opposing parallel slot side faces and a slot ground face arranged perpendicular thereto. The slot has a width defined by the distance between the slot side faces. The width matches with the height of the archwire. The invention is advantageous for an orthodontic treatment of teeth requiring good tip and rotation control.

Claims

1. A lingual orthodontic appliance comprising a lingual bracket for an anterior tooth and an archwire, the lingual orthodontic appliance extending through an axis W, an axis I, and an axis C, wherein the axis W and the axis I are perpendicular to each other, and wherein axis C is perpendicular to both axis W and axis I, wherein the archwire has a rectangular cross-section having a height defined by the longer side of the rectangular cross-section, the height being oriented along the axis C, wherein the lingual bracket has a bracket pad and a bracket body with the bracket body forming a slot for receiving the archwire, the slot being formed by at least two opposing parallel slot side faces defining a slot insertion axis, and a slot ground face arranged perpendicular thereto and defining a slot ground face plane, wherein the slot has a width defined by the distance between the slot side faces, and wherein the width corresponds to the height of the archwire, wherein the lingual bracket has at least one archwire support structure that forms a support surface that resides in the slot ground face plane, and wherein the archwire support structure is uncoupled from the bracket body and spaced at a pre-determined distance from the bracket body along axis W such that an open channel extends between the bracket body and the archwire support structure.

2. The lingual orthodontic appliance of claim 1, wherein the lingual bracket and the archwire are arranged relative to each other such that the slot side faces are parallel to a plane defined by axis I and axis W.

3. The lingual orthodontic appliance of claim 1, having a plurality of brackets for anterior teeth and a plurality of brackets for posterior teeth, wherein the width of each slot matches with the height of the archwire.

4. The lingual orthodontic appliance of claim 3, wherein the plurality of brackets are arranged relative to each other such that each bracket is fitted with the slot to the archwire and oriented with the pads forming an outer periphery of the orthodontic appliance.

5. The lingual orthodontic appliance of claim 3, and having a plurality of ligatures for retaining the archwire and the bracket with each other.

6. The lingual orthodontic appliance of claim 1, wherein the shape of the support surface is pre-determined independent from the shape of the bracket pad.

7. The lingual orthodontic appliance of claim 1, wherein at least one archwire support structure forms a flat and protrudes parallel to the third dimension.

8. The lingual orthodontic appliance of claim 1, wherein the archwire support structure protrudes from the bracket body.

9. The lingual orthodontic appliance of claim 1, having two archwire support structures symmetrically arranged on opposite sides of the slot, wherein each archwire support structure is discrete and spaced at a pre-determined distance from the bracket body along axis W such that a channel extends between the bracket body and each archwire support structure.

10. The lingual orthodontic appliance of claim 1, wherein the bracket pad has a tooth facing surface and an opposite tissue facing surface, wherein the tooth facing surface and the tissue facing surface conform in shape to each other, tapering toward each other at the periphery of the bracket pad.

11. The lingual orthodontic appliance of claim 10, wherein the slot ground face is oriented at an acute angle relative to an occlusal region of the tissue facing surface of the bracket pad.

12. The lingual orthodontic appliance of claim 1, wherein the brackets are made of a metal.

13. The lingual orthodontic appliance of claim 12, wherein the metal is selected from the group consisting of gold and steel.

14. The lingual orthodontic appliance of claim 1, wherein, when the lingual bracket is seated on a tooth having a tooth axis, the slot insertion axis extends perpendicular to the tooth axis.

15. The lingual orthodontic appliance of claim 2, wherein the width of each slot matches with the height of the archwire.

16. The lingual orthodontic appliance of claim 15, wherein the plurality of brackets being arranged relative to each other such that each bracket is fitted with the slot to the archwire and oriented with the pads forming an outer periphery of the orthodontic appliance.

17. The lingual orthodontic appliance of claim 1, wherein the shape of the support surface is pre-determined independent from the shape of the bracket pad.

18. The lingual orthodontic appliance of claim 1, wherein the archwire support structure is spaced at a pre-determined distance from the bracket body such that a portion of a ligature can run through the channel.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0027] FIG. 1 is a perspective view of a computer model of a bracket pad of a bracket according to an embodiment of the invention;

[0028] FIG. 2 is a perspective view of a computer model of a bracket body of a bracket according to an embodiment of the invention;

[0029] FIG. 3 is a perspective view of a computer model of a bracket according to an embodiment of the invention; and

[0030] FIG. 4 is perspective view of an orthodontic appliance according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0031] FIG. 1 illustrates a portion of a computer model of a patient's dentition 100. A bracket pad 2 is arranged on a tooth 101 of the patient's dentition 100. The dentition model 100 can be scanned directly from a patient's mouth or from a physical model of the patient's teeth. Such physical model is typically prepared from making a dental impression replicating the negative shape of the patient's teeth, and casting a positive plaster model by using the dental impression as a mold. In the example the dentition model 100 represents the malocclusion of the patient's teeth. A physical model may further be provided by 3D printing based on a computer model obtained by scanning.

[0032] The bracket pad 2 has a tissue facing surface 3, which in the example is a tongue facing surface. This is because the bracket pad is arranged on the lingual side of the tooth 101. The bracket pad 2 further has a tooth facing surface (not visible in this view) on the opposite side of the tissue facing surface. The tooth facing surface conforms in shape to the shape of the lingual side of the tooth 101. Further, because in the example the tissue facing surface is derived from the tooth facing surface or the lingual side of the tooth, the tissue facing surface also generally conforms in shape to the shape of the lingual side of the tooth 101. Therefore the bracket pad has a generally uniform thickness, although the bracket pad may be modified in a subsequent step to provide a periphery of the bracket pad with a tapered and/or rounded shape.

[0033] FIG. 2 shows an exemplary computer model of a bracket body 1. Although a computer model of the bracket body is illustrated, it is further referred to simply a bracket body in the following. The bracket body 1 can be obtained from a library which is accessible by the computer that stores the bracket body 1. The bracket body 1 may be otherwise generated and coupled with the bracket 2. The bracket body 1 has a slot 4 for receiving an orthodontic archwire (not shown). The slot 4 extends through the bracket body 1 along an archwire axis W. The slot 4 has a proximal slot side face 4a and an opposing distal side face 4b. The proximal and distal side face 4a, 4b extend parallel to the archwire axis W and further parallel to an archwire insertion axis I. The archwire axis W and the archwire insertion axis I are perpendicular to each other. The slot 4 has further a slot ground face 4c that extends parallel to the archwire axis W and further parallel to a slot cross axis C. The slot cross axis C is perpendicular to the archwire axis W as well as to the archwire insertion axis I.

[0034] The bracket body 1 further has two archwire support structures 5a, 5b. Each of the archwire support structures 5a, 5b forms a flat 6a, 6b. The flats 6a, 6b are within an (imaginary) plane of or flush with the slot ground face 4c. Further, the flats 6a, 6b each are spaced from the slot ground face 4c. The bracket body 1 has a head portion 7 which in the example has a tie wing 8 and a hook 9 which on the final bracket serve for retaining a ligature. The bracket body 1 has a first end portion 10 and, opposite thereof, a second end portion 11. The first end portion 10 is pre-shaped and in the example has the slot 4, the support structures 5a, 5b, the tie wing 8 and the hook 9. Further, the second end 11 portion extends at a generally uniform cross-section, in the example rectangular. The bracket body 1 is a precursor of the finally shaped bracket body with respect to the length of the second end portion 11. The second end portion 11 is typically shortened in a subsequent step of the bracket design. It is noted that the model of the bracket body 1 may further be a precursor with respect to the first end portion in that the initial presence and/or angulation of the slot 4 is optional. Further, the slot 4 and the support structures 5a, 5b may be adjustable in their angle relative to a dimension in which the second end portion extends. Although in the example the second end portion 11 extends along the slot insertion axis I, in another example the slot insertion axis I may extend at an angle to the dimension along which the second end portion extends. The end portion 11 may extend along the slot insertion axis I, or may extend at an angle to the slot insertion axis I.

[0035] The wire support structures 5a, 5b are arranged at a pre-determined distance from the slot 4, in particular from the slot ground face 4c. Thus, a bracket obtained from this design allows for a predictable rotation control of a tooth in a patient's mouth. Further, the space between the wire support structures 5a, 5b and the slot ground face 4c is preferably dimensioned so that a portion of a ligature can run through without getting compressed or clamped.

[0036] FIG. 3 shows a computer model of a bracket 12 which is obtained by combination of the bracket pad 2 (shown in FIG. 1) and the bracket body 1 (shown in FIG. 2). The combination is typically performed by aid of a computer. Thereby the patient's dentition is typically used to determine the path along which the archwire of the orthodontic appliance should extend, and the path of the archwire is used to align the bracket body 1. Typically, the second end portion of the bracket body 1 is shortened to avoid that it protrudes beyond the tooth facing surface of the bracket pad 2.

[0037] The slot insertion axis I extends generally perpendicular to the tooth axis (not shown). This type of slot, because of the orientation relative to the tooth, is typically referred to as horizontal slot in the field of orthodontics. The horizontal slot as shown features a slot ground face 4c oriented at an acute angle relative to the occlusal tissue facing surface 3 of the bracket pad 2. Likewise, the horizontal slot 4 as shown features a slot side face 4a oriented at an acute angle relative to the gingival portion of tissue facing surface 3 of the bracket pad 2 (the orientation angle is generally obtuse relative to the occlusal tissue facing surface). An orientation of the slot 4 as shown enables for effectively exerting a torque to the tooth in a plane parallel to dimensions of the slot cross axis and the slot insertion axis. This is because the two opposing slot side faces 4a, 4b allow for tightly clamping a rectangular wire by a positive fit so that therefore the archwire can transmit a torsional moment to the bracket 12 for rotating the tooth as desired. In an orthodontic treatment of anterior teeth it is typically desired that the brackets used for the treatment not only provide for good torque control but also good rotation control. Although the horizontal arrangement of the slot is typically less efficient for rotation control (twisting about the tooth axis) it has been found that the rotation control can be performed at relatively low forces that can be provided by a bracket having a horizontal slot. On the other hand, due to the positive fit between the archwire and the bracket with respect to a torsional moment in a plane of the slot cross axis C and the archwire axis W the bracket with the horizontal slot provides for excellent tip control. Accordingly, the bracket according to the invention can be used for posterior teeth as well as for anterior teeth. Further, the bracket according to the invention provides for excellent tip control which is particularly relevant for the anterior teeth.

[0038] FIG. 4 shows a part of an orthodontic appliance comprising a plurality of lingual orthodontic brackets 12 arranged on the front teeth of a patient's dentition 100. The brackets 12 are customized on the respective tooth on which they are arranged. In particular, each bracket 12 has a bracket pad 2 which conforms in shape to the lingual side of the respective tooth. Although the brackets 12 are differently configured they all have a horizontal slot 4. Therefore the orthodontic appliance provides for good rotation, torque and tip control during an orthodontic treatment.

[0039] The orthodontic appliance further has an archwire 20 mounted in the slots of the brackets 12. Further, the orthodontic appliance typically has a plurality of ligatures fixed on the brackets 12 for retaining the archwire in the slots.