The present invention relates to a ligating clip for a self-ligating orthodontic bracket, with the features disclosed herein and a self-ligating orthodontic bracket having at least one such ligating clip and an orthodontic bracket with the features disclosed herein.
A ligating clip and a self-ligating orthodontic bracket having such a clip is shown in EP 3 419 553 B1.
The ligating clip, made of superelastic material, is approximately U-shaped with a labial arm, a lingual arm and a connecting arm connecting the labial arm and the lingual arm and has three fingers (which, in the present disclosure, are also called protrusions or protruding elements) on a free end of its labial arm.
A locking element in form of a hook is provided at a free end of the lingual arm, the hook protruding in a lingual-labial direction. The hook is manufactured by stamping with bending down or up the free end of the lingual arm such that the hook has three cut sides (two of them running in a gingival-occlusal direction and one of them running in a mesial-distal direction) and is connected to the material of the lingual arm by a single side (running in a mesial-distal direction). Due to the stamping, the hook extends generally in a lingual-labial direction. The hole produced as a consequence of the stamping is completely surrounded by material of the lingual arm (in other words, it is not open at any side of the lingual arm). In a view along the lingual-labial direction, the hook is only minimally distanced from the three sides.
In an inserted state in which the ligating clip is inserted in a self-ligating bracket, the lingual arm runs through an occlusal-gingival channel which has two sections of different clearance and separated from each other by a step. The section at the occlusal side has a higher clearance and allows the hook to slide freely and the other section has a lower clearance to stop the hook in a position in which the archwire slot is open such that an archwire can be inserted into or removed from the archwire slot. In this way, a loss of the clip in the open position can be avoided. In the closed position the clip is locked by its elastic force only, not by a dedicated locking element.
During use the archwire will apply varying forces on the ligating clip.
A different concept of a ligating clip in which cutouts are used to provide locking elements in a closed position of the clip is shown in U.S. Pat. No. 9,345,558 B2 and U.S. Pat. No. 10,555,793 B2.
Self-ligating orthodontic brackets were developed to eliminate the need to secure the arch wire to the bracket with external ligation, usually either elastic or metal-wire ties. These brackets have a slot to receive the arch wire, and a clip is then snapped into place over the slot to keep the arch wire attached.
U.S. Pat. No. 3,772,787 to Hanson discloses an early design of a passive self-ligating bracket based on a flexible clip. The disclosed orthodontic bracket comprises a body slotted for the reception of an arch wire and a U-shaped clip for retaining the arch wire in the slot. The clip is designed of flat metal conforming to the shape of the body and is movable between two positions in which the labial opening is respectively open and closed. A big drawback of this original design is there is nothing to secure the free end of the clip's labial side and therefore the arch wire can easily be displaced from the arch wire slot.
U.S. Pat. No. 4,492,573 to Hanson improved upon the original design with an active self-ligating bracket by 1) adding a mesial-distal retainer slot to the gingival side of the arch wire slot, 2) bending the free end of the retainer member's labial side so that it can be inserted into the retainer slot of the arch wire slot and 3) forming a saddle ridge at the labial side of the body. The first two modifications help to hold the free end of the clip's labial side at a closed position and prevent the clip from moving beyond its elastic limit when subjected to a force in the labial direction. The third secures the clip's labial side at the open position. However, there is still insufficient restraint on the free end of the clip's labial side when it is subjected to a force in the mesial-distal direction.
U.S. Pat. No. 5,586,882 to Hanson documented the use of a Ni—Ti based shape-memory alloy as the clip material. The disclosed self-ligating orthodontic bracket comprises a U-shape spring clip with converging arms, movable on the bracket body between slot open and closed positions; in the latter position the spring retains an arch wire in the slot and urges the bracket and wire to their optimum relative positions. The clip is of a superelastic shape recovery metal alloy, preferably of thickness from 0.20 mm (0.008 in) to 0.25 mm (0.010 in), with rounded edges.
The original design by Hanson did not have a restraint to prevent the clip moving in the mesial-distal direction. U.S. Pat. No. 5,906,486 to Hanson added a cut-out in the gingival side of the arch wire slot wall to retain the clip and prevent it from moving in the mesial-distal direction. The free end part of the labial arm portion extends into the recess to protect the spring member against excessive movement in the labial direction. Brackets based on the design concepts disclosed in the above patents have been marketed by Speed System and still available today. Only metal brackets have been produced and no aesthetic version is available by Speed System.
A hybrid between a conventional twin bracket and a flexible clip active self-ligating bracket, known as the In-Ovation bracket, was developed by Voudouris in 1997 and is described in U.S. Pat. No. 5,857,850. An improved design has been available since 2002, marketed as In-Ovation R (See U.S. Pat. Nos. 6,368,105 and 6,776,613). An important feature of the design is a slot blocker to prevent the clip's movement in the mesial-distal direction. An aesthetic version of this system (In-Ovation C) was introduced in 2007 in the form of a ceramic bracket, in which the metal clip has been plated with Rh so that it is matte in appearance and thus does not reflect light as much as a polished surface would. The clip is made of a Co—Cr—Mo alloy and tends to lose its modulus after use during treatment. However, the coating tends to wear off in the early stage of treatment and lose its aesthetics.
U.S. Pat. No. 9,770,310 to Hirsch discloses a bracket that has a wall portion extending upward along one side of the arch wire slot. This wall portion has three indentations in a line parallel to the mesiodistal direction. There is a channel running entirely through the bracket element underneath the arch wire slot and in a gingival-occlusal direction of the bracket. The clip is substantially U-shaped and has a first end with three parallel protrusions (which, in this disclosure, are also called fingers) shaped to fit within the three indentations of the wall portion, and a second end having a locking element. The clip is securable to the bracket by placing the second end through the channel and engaging the locking element onto the bracket element and placing the protrusions into the indentations of the bracket element. The protrusions are held in the indentations by friction due to the downward spring force of the clip on the floor of the indentation. The clip is releasable by sliding the protrusions out of the indentations to expose the arch wire slot. While this device is suitable for most purposes, it would be desirable to improve upon this construction and provide a clip that has an even more secure fit to the bracket, to avoid any inadvertent release during use.
It is an object of the invention to develop a ligating clip and a self-ligating orthodontic bracket that are easy to fabricate, easy to assemble and securely fastened. It is another object of the invention to develop a self-ligating orthodontic bracket that is easy to use, even more securely fastened and aesthetically pleasing.
This object is accomplished by a clip for a self-ligating orthodontic bracket having the features disclosed herein and a self-ligating orthodontic bracket having at least one such ligating clip and/or an orthodontic bracket having the features disclosed herein. Preferred embodiments of the invention are defined in the dependent claims.
Embodiments of the invention refer to an orthodontic bracket comprising a base configured for attachment to a tooth surface, a bracket element with an arch wire slot attached to one side of the base, and a clip for securing the arch wire in the slot. The arch wire slot is formed in the labial side of the bracket element and runs along a mesiodistal direction of the bracket element.
In some embodiments, the bracket element has a wall portion extending upward along one side of the arch wire slot. This wall portion has three indentations in a line parallel to the mesiodistal direction. These indentations are bounded on the interior side by two side walls that separate the three indentations. Each of the side walls has a free end on which outwardly extending flanges are formed. Each flange extends toward the respective indentation parallel to the mesiodistal direction and forms a stop surface for the clip elements. There is a channel running entirely through the bracket element underneath the arch wire slot and in a gingival-occlusal direction of the bracket.
In some embodiments, the clip is substantially U-shaped and has a first end with two protruding elements shaped to fit within the outer indentations of the wall portion, and a central element comprising two diverging fingers, that fits within the central indentation. The outer protruding elements have ends that extend inwardly toward the central elements and which are held in place behind the flanges on the side walls. The fingers diverge outwardly and are also held in place behind the flanges on the side walls.
In some embodiments, a second end of the U-shaped clip has a locking element that engages the underside of the bracket. This second end is curved in the shape of a J, with the short end of the J being bent downward to engage a stop surface in the channel. The clip is securable to the bracket by placing the second end through the channel until the downwardly bent section passes the stop surface, and placing the three protruding clip elements into the indentations of the bracket. The outer protrusions are held in the indentations by friction due to the downward spring force of the clip on the floor of the indentations, as well as by the flanges acting as a stop surface against the protrusions of the outer elements, which engage a rear surface of the flanges as rearward pressure is applied to the clip to remove it from the bracket. The fingers of the central element engage the flanges that extend toward the central indentation, to further lock the clip into the bracket.
In some embodiments, the clip is releasable by sliding the protrusions and central element out of the indentations to expose the arch wire slot. This sliding motion can require additional force, to allow the fingers and the protrusions to bend enough to clear the flanges.
The combination of the two protrusions, central element and three indentations with the locking flanges secures the clip firmly when it is subjected to force in the mesial-distal direction as well as the gingival-occlusal direction, and provides an even distribution of forces on the arch wire during the active ligation stage.
In the present disclosure a coordinate system is used which is attached to a labial tooth surface on the mandible. This is not to be understood in a limiting way. The invention can be practiced irrespective of the position of the tooth and irrespective of the tooth surface. By way of example, a ligating clip and a self-ligating orthodontic bracket according to the invention could also be used with a labial or lingual surface of a tooth of the maxilla.
A ligating clip and a self-ligating orthodontic bracket according to the invention will have the following pairs of direction:
In the present disclosure the term “connected to” is not to be construed as implying that the objects connected to each other would have to be separate physical parts. By way of example, with respect to the ligating clip, although it is stated that the labial arm and the lingual arm are connected to the connecting arm it is possible—even preferred—that the ligating clip is made of a single physical part.
The ligating clip is made of superelastic material and is approximately U-shaped with a labial arm, a lingual arm and a connecting arm connecting the labial arm and the lingual arm and has one, two or three fingers on a free end of its labial arm.
A locking element in form of a hook is provided at a free end of the lingual arm, the hook protruding in a lingual-labial direction. In an inserted state in which the ligating clip is inserted in a self-ligating bracket, the lingual arm runs through an occlusal-gingival channel which has two sections of different clearance and which are separated from each other by a step. The section at the occlusal side has a higher clearance and allows the hook to slide freely and the other section has a lower clearance to stop the hook in a position in which the archwire slot is open such that an archwire can be inserted into or removed from the archwire slot. In this way, a loss of the clip in the open position can be avoided. In the closed position the clip is locked by its elastic force only, not by a dedicated locking element, namely, the fingers are held in the cavities of the occlusal wall of the bracket by friction due to the downward spring force of the clip on the floor of the cavities. Of course, during insertion of the clip, in the gingival section the hook is pressed into the plane of the lingual arm which is possible due to the elasticity of the hook. Once the section having higher clearance is reached, the hook is released back into its state protruding from the plane of the lingual arm.
Due to the cutout the clip is better suited to endure the forces acted upon by the archwire because the cutout increases the elasticity of the clip resulting in a securely fastened clip. Due to the increased elasticity assembly of the clip and the bracket is easier because a hook having a smaller width can be used. The cutout and the hook can easily be produced by stamping with bending down or up.
In some embodiments of the clip the at least one cutout has at least one mesial-distal border and at least one gingival-occlusal border.
In some embodiments of the clip the hook, in a view along the lingual-labial direction, has a length and is distanced from at least one mesial-distal border and from at least one gingival-occlusal border by at least half of its length.
In some embodiments of the clip the at least one cutout, in a view along the lingual-labial direction, is generally L-shaped. With respect to these embodiments it can be provided that a shape of the lingual arm due to the cutout is given by a gingival section, a protrusion connected to the gingival section, the protrusion running in the gingival-occlusal direction and having a smaller width along the mesial-distal direction than the gingival section, and, preferably, a transversal part running in the mesial-distal direction, the transversal part being connected on one end to the protrusion and on a further end to the hook.
In some embodiments of the clip the labial arm is provided with a mesial finger and a distal finger, only. Alternatively, a single finger or an additional (mesial) finger could be provided.
In some embodiments, the clip can be slid open and closed with the aid of an aperture for a tool.
In some embodiments, the clip is provided with only one cutout such that, in a view along the lingual-labial direction, the clip is of asymmetric design due to the presence of the cutout.
Preferably, the clip is made of superelastic material, e.g., a Ni—Ti alloy.
In some embodiments, the hook protrudes from a lingual surface of the lingual arm. Alternatively, it could be provided that the hook protrudes from a labial surface of the lingual arm (of course, the position of the step in the occlusal-gingival channel has to be adapted accordingly).
Preferably, the clip can be provided with a coating minimizing the amount of Ni leaching from the clip (in case a Ni—Ti alloy is used) and/or improving the aesthetics of the clip.
In some embodiments of the bracket it is provided with an occlusal-gingival channel which has two sections of different clearance and which are separated from each other by a step such that, in a position in which the archwire slot is open, the hook acts together with step to prevent a separation of the clip from the bracket.
Preferably, the bracket is made of ceramics, metals, or polymeric materials.
Optional tie-wings of the bracket can be used to apply bands
With the exception of the provision of a cutout as described in this document, the clip and the bracket can have the features described in EP 3 419 553 B1.
In one embodiment, the clip is made of a Ni—Ti alloy. This alloy exhibits superelasticity, which keeps the elastic modulus of the clip substantially unchanged even with extended use. The clip can also be coated with a coating such Au/Rh, Pt/Rh and Pd/Rh, with Rh being an outermost layer. This coating minimizes the amount of Ni that leaches from the clip, and improves the aesthetics of the bracket when used in conjunction with a ceramic bracket body.
In a preferred embodiment, the arch wire slot is chamfered on its edges to minimize friction when inserting and removing the arch wire from the slot.
Preferably the base is manufactured by embossing protrusions into the base, by stamping the base immediately after molding. This forms undercuts around the protrusions, which enhances the adhesion of the base to the tooth surface.
Other objects and features of the invention will become apparent from the following detailed description considered in connection with the accompanying drawings. It is to be understood, however, that the drawings are designed as an illustration only and not as a definition of the limits of the invention.
In the drawings,
It can be seen, that the at least one cutout 9 has two mesial-distal borders 911, 912 and two gingival-occlusal borders 921, 922.
The hook 7, in a view along the lingual-labial direction, has a length L and is distanced from the mesial-distal borders 911, 912 and from the gingival-occlusal borders 921, 922 by at least half of its length L.
The at least one cutout 9, in a view along the lingual-labial direction, is generally L-shaped and a shape of the lingual arm 4 due to the cutout 9 is given by a gingival section 23, a protrusion 5 connected to the gingival section 23, the protrusion 5 running in the gingival-occlusal direction and having a smaller width along the mesial-distal direction than the gingival section 23, and a transversal part 6 running in the mesial-distal direction, the transversal part 6 being connected on one end to the protrusion 5 and on a further end to the hook 7.
In the embodiment of
In the alternative embodiment of a clip 1 shown in
The bracket 12 is provided with an occlusal-gingival channel 21 which has two sections of different clearance and which are separated from each other by a step 211 (of.
A base 15 of the bracket 12 can be bonded to a tooth enamel by applying adhesives between the base 15 and the enamel as is well known in the art.
The bracket 12 has an archwire slot 22 to accept an archwire (not shown).
An occlusal wall of the bracket 12 is provided with a mesial cavity 13 and a distal cavity 14 to cooperate with the fingers 10, 11. Another (medial) cavity 18 is not used in this embodiment but could be used together with a clip 1 having three fingers. Alternatively, it could be provided that the medial cavity 18 is not present.
The clip 1 can be slid open and closed with the aid of an aperture 8 for a tool.
Preferably, the clip 1 is made of superelastic material, e.g, a Ni—Ti alloy.
Preferably, the clip 1 can be provided with a coating minimizing the amount of Ni leaching from the clip (in case a Ni—Ti alloy is used) and/or improving the aesthetics of the clip 1.
Preferably, the bracket 12 is made of ceramics, metals, or polymeric materials.
Optional tie-wings 16, 17, 19, 20 can be used to apply bands.
The clip 320 is made of a superelastic material. The bracket element and base can be made of ceramics, metals, or polymeric materials.
Lingual side 325 of clip 320 is inserted into a gingival-occlusal channel 319 of bracket element 312, as shown in
At the labial side 326, the clip 320 expands to cover the full length of the arch wire slot towards its gingival end. As shown in
Clip 320 can be slid open and closed with the aid of an aperture 335 disposed behind protrusions 321, 322 and fingers 323, 324. A user can slide clip 320 open and closed by inserting a tool through aperture 335 and moving the tool back and forth.
Due to the interaction of the ends of protrusions 321, 322 and fingers 323, 324 with the flanges 317a-317d, the user must exert sufficient force to bend the protrusions and fingers so that they clear flanges 317a-317d to release clip 320 from bracket element 312.
As shown in
The base 311 is bonded to the tooth enamel by applying adhesives between the base and enamel. A structured bottom surface of the base 311 can be formed such as shown in
In a preferred embodiment, the clip 320 is made of Ni—Ti alloy. Due to the superelastic property of the alloy, the elastic modulus of the clip remains unchanged even after extended use in oral cavity. This is a big advantage compared with other spring materials such as Co—Cr—Mo alloys. In addition, the clip can be coated with dual layers of Au/Rh, Pt/Rh or Pd/Rh, all with Rh in the outermost layer. Preferably, the thickness of the Rh is between 0.5 pm and 3 pm to maintain the integrity of the coating during long exposure in oral cavity. This coating can minimize Ni from leaching and improve the esthetics when used along with a ceramic bracket body.
In another preferred embodiment, the bracket body is manufactured by injection molding. The molded green bodies are converted to transparent ceramics through binder burnout, sintering and/or hot isostatic pressing. The materials can be high-purity alumina, zirconia or other compounds that can be densified to full density and high translucency, such as sialon or spinel. Preferably, the body is polished chemically to produce a fine surface finish. The smoothly polished surface, combined with a chamfer 336 at the edge of the arch wire slot (
In a further embodiment, the bracket body can be manufactured by 3D printing, in particular using a DLP (digital light processing) or SLA (stereolithography) printer.
Although only a few embodiments of the present invention have been shown and described, it is to be understood that many changes and modifications may be made thereunto without departing from the spirit and scope of the invention.
Number | Date | Country | Kind |
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16804382 | Feb 2020 | US | national |
20200793.6 | Oct 2020 | EP | regional |
This application is a continuation of and Applicant claims priority under 35 U.S.C. § 120 of International Application No. PCT/EP2021/054521 filed on Feb. 24, 2021, which claims priority under 35 U.S.C. § 119 of U.S. patent application Ser. No. 16/804,382 filed on Feb. 28, 2020, now abandoned, and European Application No. 20200793.6 filed on Oct. 8, 2020. The international application under PCT article 21(2) was published in English. The disclosures of the aforesaid International Application, U.S. patent application, and European application are incorporated by reference.
Number | Date | Country | |
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Parent | PCT/EP2021/054521 | Feb 2021 | US |
Child | 17896226 | US |