Orthodontic ligature

Abstract

A ligature formed from a superelastic material and configured to fit around an orthodontic bracket, the ligature being configured to form a closed loop and to fit and be held around the orthodontic bracket based on the superelastic effect of the ligature material, the ligature may be configured such that in the unworn state, the perimeter of the loop is the same as the perimeter of the loop in the worn state, and the distance between the occlusal and gingival portions and / or the distance between the mesial and distal portions is different in the unworn state than in the worn state.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of European Patent Application No. 22382218.0, filed March 9, 2022.

[0002] The present disclosure relates to orthodontic appliances, and more particularly to orthodontic ligatures for attachment around orthodontic brackets. Additionally, the present disclosure relates to kits and methods for orthodontic treatment. [Background technology]

[0003] Correcting irregularities and misalignments of teeth by applying a controlled force to the teeth is becoming more common. For example, the use of orthodontic brackets is well known. Orthodontic brackets are typically bonded directly to the front of each tooth and come in a variety of styles and sizes, including self-ligating, lingual, and titanium. The brackets act like handles that hold an archwire that moves the teeth. A single elastic or ligature is placed around the bracket that secures the archwire. As the teeth continue to move, the bands need to be changed or adjusted, usually at monthly appointments.

[0004] The ligatures are typically made of elastic O-rings, for example made of silicone rubber, that are attached to the brackets to secure the archwire. Typically, the orthodontist sees the patient once a month or once every few weeks. At each visit, the orthodontist adjusts the brackets as needed for treatment. Similarly, the ligatures and / or archwires may be replaced during such visits.

[0005] Silicone rubber is used in many medical applications and is therefore biocompatible. Silicone rubber also has good elastic properties. However, silicone rubber also has many drawbacks. First, under the influence of constant stress, saliva, and humidity, the ligature loses its activity or effectiveness fairly quickly, for example within a few days. Furthermore, rubber may absorb and trap water or food, which may lead to tooth demineralization (enamel breakdown) or gingival inflammation. Furthermore, the friction between silicone rubber and metal archwires is relatively high, thereby affecting the effectiveness of orthodontic treatment to resolve the patient's dentition misalignment.

[0006] Instead of elastic O-rings as ligatures, stainless steel ligatures are also known. In such cases, the orthodontist uses a stainless steel wire and wraps it around the bracket. The wire is then wrapped around itself several times to close the ligature loop. The remaining part of the wire is then cut off and discarded. Thus, the use of stainless steel ligatures is very time-consuming and labor-intensive for the orthodontist. Generally, stainless steel ligatures are used to increase archwire retention and provide a relatively high level of friction between the archwire and the ligature.

[0007] Patent Document 1 discloses a self-ligating orthodontic bracket consisting of a ligating member including a coil spring segment for extending the ligating member over the archwire or retainer wire and over one or more tie wings to secure the archwire or retainer wire to the bottom of the bracket slot while avoiding the use of ligatures. The ligating member including the coil spring may have ends engaged with holes extending on opposite mesial-distal sides of one side of the bracket body, and the ligating member is engaged with one or more tie wings on the opposite side of the bracket body. Alternatively, the ligating member may be engaged under both the occlusally projecting and gingivally projecting tie wings, or may form a closed loop with the ligating member engaged under one or more tie wings on one side of the bracket body and passing through holes extending on the mesial-distal sides of the opposite side of the bracket body.

[0008] US Patent No. 5,399,633 discloses a nitinol ligature that follows a rectangular profile similar to an "O" style, which is notable in that the free end can be deflected to meet the needs of attaching the archwire to the bracket, resulting in variable friction. Nitinol ligatures can reduce friction with the archwire, thereby making orthodontic treatment more effective. Furthermore, Nitinol does not suffer from the aforementioned disadvantages associated with silicone rubber.

[0009] However, the structures proposed in this prior art document may not always meet the high safety or security standards required by some orthodontic practitioners. There is a risk of swallowing if the ligature becomes detached from the bracket. Furthermore, applying the ligature of this prior art document may be more complicated than applying a classic rubber band.

[0010] The present disclosure in various examples provides methods and devices for use in orthodontic treatment that at least partially address some of the problems discussed above. Summary of the Invention

[0011] In a first aspect, a ligature is provided that is formed from a superelastic material and configured to fit around an orthodontic bracket. The ligature forms a closed loop and includes an occlusal portion configured to be positioned on the occlusal side of the bracket, a gingival portion configured to be positioned on the gingival side of the bracket, a mesial portion configured to be positioned on the mesial side of the bracket, and a distal portion configured to be positioned on the distal side of the bracket in a worn state. The ligature is configured such that in the pre-worn state, the perimeter of the loop is the same as the perimeter of the loop in the worn state, and that in the pre-worn state, the distance between the occlusal and gingival portions and / or the distance between the mesial and distal portions is different than in the worn state.

[0012] Ligatures according to this aspect can reduce friction as compared to ligatures formed from silicone rubber or elastic bands. The reduction in friction between the ligature and the archwire can make orthodontic treatment more effective. Furthermore, ligatures do not necessarily suffer from the drawbacks of discoloration, brittleness, and loss of effectiveness associated with rubber bands.

[0013] The ligature according to this embodiment has a closed loop. Compared to the prior art system with an open ligature, the ligature according to the present disclosure is mechanically more durable and can be more firmly and easily placed around the bracket. The ligature is kept in place due to the superelastic effect. The ligature may be deformed to fit around the bracket, and therefore the ligature has a tendency to return to its original shape. However, the bracket and / or archwire prevents the ligature from returning to its original shape, and therefore the ligature is firmly fixed. The ligature loop does not actually change its overall circumference between the pre-installed state and the installed state, so in the pre-installed state, the size of the loop is adjusted to allow the ligature to fit around the bracket.

[0014] Compared to prior art stainless steel ligatures that are made in situ, the ligatures proposed herein are easier to use and easier to fit around orthodontic brackets.

[0015] A superelastic material may be considered herein as a material that exhibits a superelastic or "pseudoelastic" effect. The pseudoelastic effect is an elastic (reversible) response to an applied stress caused by a phase transformation between the austenite and martensite phases of the crystal. Examples of materials that exhibit this type of behavior include Nitinol (nickel-titanium alloy), copper-zinc-aluminum, and copper-aluminum-nickel, for example.

[0016] A "pre-loaded" state, as used throughout this disclosure, may refer to the "as delivered" or "default" state of a ligature. That is, prior to manipulation by the orthodontist, the shape of the ligature will correspond to its pre-loaded state. A "loaded" state, as used throughout this disclosure, may refer to a ligature after it has been loaded around a bracket. That is, the ligature has been deformed from its pre-loaded state to another shape. Once loaded, the ligature cannot return to its pre-loaded state due to some of the brackets and / or archwires.

[0017] The term "closed loop" is used herein to refer to a structure that is bent or curved and whose end is connected to its beginning, i.e., the loop closes on itself.

[0018] The term "perimeter" is used herein to refer to the length of the contour of a shape. While the term "perimeter" is often used to refer to only two-dimensional objects, in this disclosure it is used to refer to the total length of the contour of a ligature, which is a three-dimensional object.

[0019] In some examples, the material may be a superelastic metallic material. In particular, the superelastic metallic material may be Nitinol. Nickel titanium, also known as Nitinol, is a metallic alloy of nickel and titanium, with the two elements present in approximately equal atomic percentages. Different alloys are named according to the weight percentage of nickel, for example Nitinol 55 and Nitinol 60. Nitinol 50 has 50% nickel and 50% titanium by weight. Nitinol 50 exhibits shape memory effect and superelasticity at different temperatures. At body temperature, near 37°C, Nitinol typically exhibits superelastic behavior. Furthermore, Nitinol is known to be a biocompatible material.

[0020] In some cases, copper may be added to Nitinol, which can change the temperature at which the shape memory transition occurs as well as the temperature transition range.

[0021] In another aspect, the present disclosure provides a ligature formed from a superelastic material and configured to fit around an orthodontic bracket, the ligature forming a closed loop configured to fit around and be retained around the orthodontic bracket based on the superelastic effect of the ligature material.

[0022] According to this embodiment, the ligature is given a shape that allows it to fit around the bracket. The ligature forms a closed loop (before being placed around the bracket), but due to the superelastic effect, its shape can be changed by applying stress to the loop. The superelastic effect is based on the fact that stress induces a martensitic transformation, resulting in a strain. When the stress is removed, the strain is restored and the ligature tends to return to its original shape. Since the ligature cannot return to its original shape (because the bracket prevents this), the ligature is held in place based on this superelastic effect.

[0023] In some instances, the ligature wire includes a curvature along an occlusal-gingival direction prior to fitting around the orthodontic bracket. In some instances, additionally or alternatively, the ligature wire includes one or more wavy segments prior to fitting around the orthodontic bracket.

[0024] In some instances, the ligature may further be configured such that the mesial and distal portions have a greater curvature in the pre-installed state than in the installed state. "Curvature" should be understood herein as a deviation from an imaginary plane extending along the occlusal-gingival direction (i.e., substantially parallel). A greater curvature may therefore be understood as a more pronounced deviation from the imaginary plane. In other words, the radius of curvature between the occlusal and gingival portions is smaller in the pre-installed state. The curvature relative to this plane allows the ligature to extend, for example, in the occlusal-gingival plane and / or in the mesial-distal plane in order to install the ligature around the bracket.

[0025] In some instances, the distance between the occlusal and gingival portions in the pre-loaded state is less than in the loaded state. In other words, the ligature is "too narrow" to fit around the orthodontic bracket. To fit the ligature around the bracket, tension is applied to the ligature, which causes it to expand. The overall circumference of the loop cannot change due to the material used (i.e., the material does not stretch or expand like a rubber material), so the remaining portion of the loop changes shape as well. In these instances, the ligature has a tendency to return to its original shape in the loaded state. The bracket may be shaped such that the ligature is forced to maintain its loaded state holding the archwire. In some of these instances, the ligature may be further configured such that the distance between the mesial and distal portions is substantially the same in the pre-loaded and loaded states. In these instances, the ligature becomes more versatile and can be held around the bracket in a more predictable manner, regardless of the shape or size of the bracket.

[0026] In a further example, the ligature may be configured such that in the pre-installed state, the distance between the mesial and distal portions is greater than in the installed state, or the ligature may be configured such that in the pre-installed state, the distance between the mesial and distal portions is less than in the installed state.

[0027] In examples, the loop may be substantially circular in top view in the pre-loaded state. In other examples, the loop may be oval in top view in the pre-loaded state. In yet other examples, the loop may have a polygonal shape, such as a triangle or a rectangle, in top view.

[0028] In examples, the ligature may be made from wire that is welded at its ends to form a closed loop. In some examples, the ligature may be made from woven or braided wires or wire bundles.

[0029] In a further example, the ligature may be formed by a stamping process and optionally a subsequent deformation process.

[0030] The ligatures provided throughout this disclosure are generally configured to fit around orthodontic brackets of different shapes, configurations and different sizes. The ligatures provided are not intended to be attached to or fixed to the brackets or to form part of the brackets.

[0031] The ligatures provided throughout the figures of this disclosure have a maximum vertical extension (extension in the lingual-labial direction) along each portion of the loop that corresponds to the local cross-sectional thickness of the loop, i.e., the ligatures provided herein do not include spiral or helical structures, or portions of the loop that are folded over one another, or that are disposed vertically above other portions.

[0032] In a further aspect, there is provided an orthodontic kit comprising a ligature according to any of the examples disclosed herein and an orthodontic bracket comprising an archwire slot, one or more wings on a gingival side of the archwire slot and one or more wings on an occlusal side of the archwire slot, one or more of the wings configured to hold a ligature. [Brief description of the drawings]

[0033] Non-limiting examples of the present disclosure will now be described with reference to the accompanying drawings. [Figure 1A] 1 is a schematic diagram of an example of a ligature in a pre-installation state. [Figure 1B] 1 is a schematic diagram of an example of a ligature in a pre-installation state. [Figure 1C] 1 is a schematic diagram of an example of a ligature in a pre-installation state. [Figure 1D] 13A-13C are schematic diagrams illustrating how a ligature according to this embodiment may deform in its installed state. [Figure 1E] 13A-13C are schematic diagrams illustrating how a ligature according to this embodiment may deform in its installed state. [Figure 2A] 10A and 10B are schematic diagrams illustrating an example ligature fitted around an orthodontic bracket. [Figure 2B] 10A and 10B are schematic diagrams illustrating an example ligature fitted around an orthodontic bracket. [Figure 3A] Further examples of ligatures are shown diagrammatically in their pre-applied state. [Figure 3B] Further examples of ligatures are shown diagrammatically in their pre-applied state. [Figure 4A] Further examples of ligatures are shown diagrammatically. [Figure 4B] Further examples of ligatures are shown diagrammatically. [Figure 4C] Further examples of ligatures are shown diagrammatically. [Figure 5A] Further examples of ligatures are shown diagrammatically. [Figure 5B] Further examples of ligatures are shown diagrammatically. [Figure 5C] Further examples of ligatures are shown diagrammatically. [Figure 5D] Further examples of ligatures are shown diagrammatically. [Figure 6] 1 is a schematic diagram of some terminology in the orthodontic field. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] 6 shows a schematic of the arrangement of teeth in the lower jaw (mandible). The front of the mouth 110 may be referred to as the mesial region. The back of the mouth 120 may be referred to as the distal region. In orthodontics, mesial and distal are terms used to refer to the dental arch closer to and further from the central midline, respectively.

[0035] In the distal region of the mouth, the molar zone may be found. The molar zone may include the first molar, the second molar, and possibly the third molar ("wisdom teeth"). The inner portion 130 of the mouth behind the teeth may be referred to as the lingual region (area where the tongue is located). The outer portion 140 of the mouth may be referred to as the labial region (area where the lips are located). The mesial-distal direction 115 for a particular tooth (the first molar) is shown diagrammatically in FIG. 6. Also shown in FIG. 6 is the lingual-labial direction 135 for the same tooth. This terminology will be adhered to in this disclosure.

[0036] The term "gingival" as used throughout this disclosure relates to a direction toward the gingiva (gums), which is synonymous with cervical. Instead, the term "occlusion" refers to the opposite direction, i.e., toward the biting surfaces of the teeth. The term occlusion is usually used in reference to the back teeth, while the term "incisor" is sometimes used in reference to the front teeth. Throughout this disclosure, the term "occlusion" is intended to encompass both "incisor" and "occlusion."

[0037] In this particular illustration the mandible is shown, but it will be apparent that the same terminology applies to the maxilla as well.

[0038] Figure 1A illustrates a schematic representation of a first example of a ligature 10. Figure 1A illustrates an isometric view of the ligature 10 in a pre-applied state. The ligature 10 may be formed from a superelastic material, and in particular, from Nitinol.

[0039] The ligature includes portion 12, which is a gingival portion, and portion 14, which is an occlusal portion, i.e., portion 12, when fitted around an orthodontic bracket, is positioned near the patient's gum line and portion 14 is positioned near the occlusal surface of the tooth.

[0040] Ligature 10 further comprises a mesial portion 16 and a distal portion 18. That is, when worn, portion 16 is disposed on the mesial side of the bracket and portion 18 is disposed on the distal side of the bracket. It is noted that, as used herein, the ligature forms a closed loop and there is not necessarily a clear separation between one portion and another, i.e., the portions identified herein are not separated from one another and the boundary where one portion begins and another portion ends is not necessarily identifiable.

[0041] Additionally, it should be noted that the ligature 10 may be substantially symmetrical about an axis 13 disposed along an occlusal-gingival direction. That is, the orthodontist or professional may place the ligature around the bracket as desired, with the occlusal portion becoming the gingival portion, and vice versa.

[0042] Similarly, the ligature 10 may be symmetric about a mesial-distal axis. The ligature may also be rotationally symmetric.

[0043] However, in some instances, the ligature may be provided with markings that indicate which portion of the ligature is configured to be attached to the bracket at a given location. For example, color coding may be used, or small markings such as dots may indicate certain portions of the ligature. In further instances, the location where the ligature should be attached may be apparent from the shape of the ligature itself.

[0044] FIG. 1B shows a schematic top view of the ligature 10. The ligature may be elliptical in top view. In a further example, the ligature may be substantially circular in top view. In FIG. 1B, the gingival portion 12, the occlusal portion 14, the mesial portion 16, and the distal portion 18 are shown schematic.

[0045] 1C shows a schematic side view of ligature 10. Axis 13 is also shown in FIG. 1C. It can be seen that ligature 10 is curved in that direction, i.e., the height of the ligature relative to a plane containing axis 13 varies along axis 13.

[0046] In the pre-worn state, the maximum height of the ligature line between the occlusal and gingival portions is H. When a "normal" force is applied to the ligature line, the height H can be reduced to H', as shown in Figure ID. At the same time, the length L of the ligature line (i.e., the maximum distance between the occlusal and gingival portions) is increased to L'.

[0047] FIG. 1D shows a schematic comparison between the shape of the ligature in a pre-loaded state (top of FIG. 1D) and the shape of the ligature in a pre-loaded state (bottom of FIG. 1D). The ligature can be fitted around the bracket by reducing the curvature. Once fitted around the bracket, the ligature has a tendency to return to its pre-loaded state due to its superelastic properties. That is, the ligature has a tendency to shorten the distance between the occlusal and gingival portions and increase the curvature to its original shape. However, the wings of the brackets and / or archwire may prevent the ligature from returning to its pre-loaded state.

[0048] FIG. 1E shows the same ligature 10 diagrammatically in its fitted state (but without the orthodontic bracket).

[0049] 2A and 2B show schematic diagrams of an example ligature fitted around an orthodontic bracket 20. The bracket 20 includes an archwire slot 27. An archwire 30 may be placed within the slot 27 and may connect multiple brackets attached to multiple teeth. The ligature 10 is configured to hold the archwire 30 within the slot 27.

[0050] The bracket 20 includes occlusal wings 22, 24 and gingival wings 26, 28. The ligature 10 includes an occlusal portion 14 below the wings 22, 24 and a gingival portion 12 below the wings 26, 28.

[0051] 2B shows a side view of the same bracket 20 and the same ligature 10. Also shown is the mounting surface 25 of the bracket 20. The bracket 20 may be attached to a tooth at the mounting surface 25. The mounting surface may include protrusions or roughness to facilitate mounting. Self-curing resin-reinforced glass ionomer cements are known for bonding orthodontic brackets to teeth.

[0052] In these instances, the ligature 10 may exert forces on the wings 22, 24, 26, 28 and / or the archwire due to its tendency to return to its pre-installation shape.

[0053] In contrast to prior art elastic band ligatures, in the unwrapped state, the circumference of the loop formed by the ligature is the same as the circumference of the loop when in the worn state, i.e., the overall length of the ligature is not increased even though the shape is changed.

[0054] In the unworn state, the distance between the occlusal and gingival portions and / or the distance between the mesial and distal portions is different than in the worn state so that a ligature can be fitted around the bracket.

[0055] In some instances, the distance between the occlusal and gingival portions in the pre-loaded state may be smaller than in the loaded state. Such an example is shown in FIG. 3A, which shows the pre-loaded state of an example ligature. The ligature may be configured to be very wide, i.e., the distance between the mesial and distal portions is greater in the pre-loaded state than in the loaded state. To fit the ligature around the bracket, the ligature may be pulled apart in a gingival-occlusal direction. Once engaged, the ligature has a tendency to return, but this may be impeded by the occlusal or gingival surfaces of the bracket.

[0056] Alternatively or additionally, the ligature may be configured such that in the pre-installed state, the mesial and distal portions have a greater curvature than in the installed state. To fit the ligature around the bracket, the curvature is reduced and the distance between the occlusal and gingival portions is increased. Once fitted, the ligature has a tendency to return, but the base of the wings may be shaped such that the ligature is held in a given position along the base.

[0057] In some instances, the ligature may be configured such that in the pre-worn state, the distance between the mesial and distal portions is smaller than in the worn state. In this case, to fit the ligature around the bracket, the ligature may be expanded to fit around the bracket. Once fitted around the bracket, the ligature has a tendency to return to its original shape. The sides of the orthodontic bracket may prevent the ligature from returning to its original shape. Thus, the ligature is held in its worn state. Such a ligature is shown diagrammatically in top view in FIG. 3B.

[0058] To fit a ligature around the bracket, the distance between the mesial and distal portions is decreased, thereby increasing the distance between the occlusal and gingival portions. Return to the original shape may be hindered by the shape of the base of the wings. In some instances, the base of the wings of the orthodontic bracket may include specific recesses or other retention features to hold the ligature.

[0059] 4A-4C are schematic diagrams illustrating yet another example of a ligature according to the present disclosure. Fig. 4A shows a top view of ligature 10 in a pre-applied state. Fig. 4B shows a top view of ligature 10 in its applied state or in a shape that will result when a user is in the process of fitting the ligature around a bracket.

[0060] In Figure 4A, as before, there is shown a gingival portion 12, an occlusal portion 14, and mesial and distal portions 16 and 18. In the example of Figure 4A, the mesial and distal portions include substantially wavy segments 17 and 19, respectively. The wavy shape may include straight portions to form a zigzag shape, but may also include rounded or curved portions to form a sinusoidal shape.

[0061] The wavy segments 17 and 19 of the mesial and distal portions may be configured to absorb most or all of the increase in distance between the gingival and occlusal portions of the ligature. The zigzag shape may provide hinge points (e.g., shown as 19A, 19B, 19C) at the peaks and valleys of the wavy segments. Specifically, elongation may occur between these hinge points as the segments are rotated about the hinge points to become more aligned with axis 13, which indicates the occlusal-gingival direction. The wavy segments may concentrate elongation in this segment, even though elongation may occur throughout the entire ligature.

[0062] It is clear that the wavy segments may contain more peaks and valleys if desired. The height of the wavy segments (measured substantially perpendicular to the axis 13 with respect to an imaginary straight line or line of continuous curvature extending between the mesial and distal portions) may be adapted as required.

[0063] 4B shows the same ligature 10 after it has been stretched in the occlusal-gingival direction (axis 13). In the fitted state, the distance between the occlusal and gingival portions has been increased as the wave height has been reduced to bring portions of the wavy segments more into alignment with the gingival-occlusal direction, while the distance between the mesial and distal portions remains substantially the same as in the pre-fitted state.

[0064] 4C shows a schematic comparison between a ligature in its pre-installed state and the same ligature in its installed state, where it can be seen that most of the deformation is concentrated in the wavy segments.

[0065] Figures 5A-5D show schematic diagrams of another example of a ligature 10 of the present disclosure. Figure 5A shows an isometric view of the ligature 10. Figures 5B, 5C, and 5D show schematic diagrams of the same ligature 10 in top, side, and front views, respectively.

[0066] Ligature 10 includes portion 12, which is a gingival portion, and portion 14, which is an occlusal portion, i.e., when fitted around an orthodontic bracket, portion 12 is positioned near the patient's gum line and portion 14 is positioned near the occlusal surface of the tooth. As another example, ligature 10 further includes mesial portion 16 and distal portion 18, i.e., when fitted, portion 16 is positioned on the mesial side of the bracket and portion 18 is positioned on the distal side of the bracket.

[0067] Again, it should be noted that the ligature lines form closed loops and there is not necessarily a clear separation between one portion and another, i.e., the portions identified herein are not separated from one another and the boundaries where one portion begins and another portion ends cannot necessarily be identified.

[0068] The ligature 10 in this example is symmetrical about an axis 13 oriented along an occlusal-gingival direction and about an axis 33 oriented along a mesial-distal direction.

[0069] As in the example of FIG. 1, the ligature 10 is curved along an occlusal-gingival direction 13 which can be seen in FIG. 5C.

[0070] As in the example of Figure 4, wavy segments 17, 19 are disposed along the mesial portion 16 and the distal portion 18. In the example of Figure 4, the occlusal and gingival portions 14, 12 also include wavy segments 37, 39. In this case, the wavy segments 37, 39 form waves with two peaks, while the wavy segments 17, 19 include a single peak.

[0071] The curvature along the occlusal-gingival direction 13 in combination with the wavy segments allows for ligatures to be placed around the bracket.

[0072] In some examples, the cross section of the ligature may not be constant. The cross sectional dimensions may be varied to control which portion deforms the most. For example, in the examples of Figures 4A-4C and 5, the wavy segment may be thinner than other portions of the ligature. This may be particularly useful to allow that segment to deform when placed around the ligature.

[0073] In any of the examples disclosed herein, the wires or bundles of wires forming the ligature may have a variety of cross-sections, for example, substantially circular, hexagonal, rectangular, more polygonal, or other cross-sections.

[0074] The dimensions of the ligature may be determined according to the ligature shape selected. For circular cross sections, wires having diameters of 0.008 to 0.012 inches (0.2032 mm to 0.3048 mm) may be used. For other cross sections, similar thicknesses may be used.

[0075] The distance between the mesial and distal portions and the distance between the occlusal and gingival portions, as well as the curvature (if any) may be adapted to a particular orthodontic bracket, or the ligature dimensions may be selected such that the ligature can be used with (almost) all available orthodontic brackets. The dimensions may vary, particularly depending on the overall shape of the ligature.

[0076] In some instances, the ligature may be made by the process of stamping. Stamping is a manufacturing process in which a flat geometric shape (or "blank") is created by feeding a coil of sheet metal into a press and die. In this process, the blank is stamped out of a larger sheet of metal.

[0077] Thus, a substantially flat metal sheet may be provided and an annular ligation blank may be stamped out of the sheet by a stamping process. Such an annular blank may then be deformed to impart a desired curvature, for example along the occlusal-gingival direction, and / or a suitable corrugation. If necessary, the flat metal sheet and / or the annular blank may be heated to appropriately deform them.

[0078] In the worn state, the ligature may have a curvature along the occlusal-gingival direction as it fits under the bracket wings and over the archwire. The wavy segments may be straightened while fitting around the bracket, i.e., the wave height decreases to provide a greater distance between the occlusal and gingival portions as the ligature fits around and under the bracket wings.

[0079] In a further aspect, the present disclosure provides an orthodontic kit comprising a ligature according to any of the examples set forth herein and one or more orthodontic brackets. The orthodontic brackets and ligature may be adapted to one another such that the ligature can be easily fitted and retained around the brackets. The orthodontic bracket comprises an archwire slot, one or more wings on a gingival side of the archwire slot and one or more wings on an occlusal side of the archwire slot, one or more of the wings configured to retain the ligature.

[0080] In some instances, the distal and / or mesial sides may contact the ligature to hold the ligature. Alternatively or additionally, the underside of the orthodontic bracket's wings may contact and hold the ligature. In some instances, the orthodontic bracket may have specific features, such as protrusions and recesses, specifically intended to hold the ligature in a given position.

[0081] In all examples disclosed herein, the ligature loop in the pre-applied state is substantially rounded, i.e., circular or elliptical, although it will be apparent that in other examples straight edges may be used as well, including, for example, rectangular shapes.

[0082] In any of the examples disclosed herein, a suitable tool may be used to apply the ligatures around the orthodontic brackets. For example, a mosquito forceps may be used by the orthodontist for application.

[0083] Although only a few examples have been disclosed herein, other alternatives, modifications, applications, and / or equivalents may be envisioned. Moreover, all conceivable combinations of the described examples are covered. Thus, the scope of the disclosure should not be limited by the specific examples, but should be determined solely by a fair reading of the following claims. [Prior art documents] [Patent documents]

[0084] [Patent Document 1] U.S. Patent No. 6,042,374 [Patent Document 2] US Patent Application Publication No. 2013 / 0266907

Claims

1. 1. A ligature formed from a superelastic material and configured to fit around an orthodontic bracket, comprising: the ligature forms a closed loop configured to fit around and be retained around an orthodontic bracket based on a superelastic effect of the ligature material. ligature line.

2. The ligature of claim 1 , including a curvature along an occlusal-gingival direction prior to fitting around the orthodontic bracket.

3. The ligature of claim 1 , comprising one or more wavy segments prior to fitting around the orthodontic bracket.

4. 10. The ligature of claim 1, comprising an occlusal portion configured to be positioned on an occlusal side of the bracket, a gingival portion configured to be positioned on a gingival side of the bracket, a mesial portion configured to be positioned on a mesial side of the bracket, and a distal portion configured to be positioned as a distal side of the bracket.

5. The ligature of claim 4 , wherein the occlusal portion and / or the gingival portion comprises wavy segments.

6. The ligature of claim 4 , wherein the mesial portion and / or the distal portion comprises wavy segments.

7. The ligature comprises: In the pre-attached state, the circumferential length of the loop is the same as the circumferential length of the loop in the attached state; 5. The ligature according to claim 4, wherein in the pre-attached state, the distance between the occlusal portion and the gingival portion and / or the distance between the mesial portion and the distal portion is configured to be different from that in the attached state.

8. The ligature of claim 7 , wherein the ligature is configured such that the mesial and distal portions have a greater curvature in the pre-installed state than in the installed state.

9. The ligature of claim 7 , wherein the distance between the occlusal portion and the gingival portion in the pre-installed state is smaller than in the installed state.

10. 10. The ligature of claim 9, wherein the distance between the mesial portion and the distal portion in the pre-installed state is substantially the same as in the installed state.

11. The ligature of claim 7 , wherein the ligature is configured such that in the pre-installed state, the distance between the mesial portion and the distal portion is greater than in the installed state.

12. The ligature of claim 7 , wherein the ligature is configured such that in the pre-installed state, the distance between the mesial portion and the distal portion is smaller than in the installed state.

13. 8. The ligature of claim 7, wherein said loop in said pre-installed state is substantially circular in top view.

14. The ligature of claim 1 wherein said material is a superelastic metallic material.

15. The ligature of claim 14, wherein the superelastic metallic material is nitinol.

16. The ligature of claim 1 , wherein the ligature is formed from wires welded at their ends to form the closed loop.

17. 17. The ligature of claim 16, wherein the ligature has a diameter of 0.008 to 0.012 inches.

18. 10. The ligature of claim 1, wherein the ligature is formed by woven or braided wires or a wire bundle.

19. 10. The ligature of claim 1, wherein the ligature is formed by stamping from a flat metal sheet.

20. 10. The ligature of claim 1, comprising markings indicating orientation for attachment around an orthodontic bracket.

21. 21. An orthodontic kit comprising a ligature according to any one of claims 1 to 20 and an orthodontic bracket, the orthodontic bracket comprising an archwire slot, one or more wings on a gingival side of the archwire slot, and one or more wings on an occlusal side of the archwire slot, one or more of the wings configured to hold the ligature.

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