WO2010105069A1

WO2010105069A1 - Convertible twin orthodontic brackets

Info

Publication number: WO2010105069A1
Application number: PCT/US2010/027005
Authority: WO
Inventors: Dwight P. Schnaitter; Paul E. Lewis
Original assignee: Ultradent Products Inc
Current assignee: Ultradent Products Inc
Priority date: 2009-03-13
Filing date: 2010-03-11
Publication date: 2010-09-16
Anticipated expiration: 2011-09-13
Also published as: US20100229280A1

Abstract

Convertible orthodontic brackets (100) of the present invention include a bracket base (102) with an arch wire slot (106) formed therein, a first pair of tie wings (108a, 108b) extending occlusally and gingivally away from the slot, a second pair of tie wings (110a, 110b) extending occlusally and gingivally away from the slot (106), a first labial web cover (114a) integrally formed with and extending between the first pair of tie wings (108a, 108b), and a second and separate labial web cover (114b) integrally formed with and extending between the second pair of tie wings (110a, 110b). The bracket (100) may advantageously be formed by a machining process, in which the web covers (114a, 114b) and tie wings (110a, 110b and 108a, 108b) are formed from a single integral piece of metal. Manufacture by machining allows stronger more dense metals to be employed than when manufacturing by metal injection molding.

Description

CONVERTIBLE TWIN ORTHODONTIC BRACKETS

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The present invention relates to orthodontic brackets. More specifically, the invention relates to convertible orthodontic brackets having a plurality of selectively removable cover portions that initially cover the arch wire slot.

2. The Relevant Technology

Orthodontics is a specialized field of dentistry that involves the application of mechanical forces to urge poorly positioned or crooked teeth into correct alignment and orientation. Orthodontic procedures can be used for cosmetic enhancement of teeth, as well as medically necessary movement of teeth to correct underbites or overbites. For example, orthodontic treatment can improve the patient's occlusion and/or enhanced spatial matching of corresponding teeth.

The most common form of orthodontic treatment involves the use of orthodontic brackets and wires, which together are commonly referred to as "braces." Orthodontic brackets, more particularly the orthodontic bracket bases, are small slotted bodies configured for direct attachment to the patient's teeth or, alternatively, for attachment to bands which are, in turn, cemented or otherwise secured around the teeth. Once the brackets are affixed to the patient's teeth, such as by means of glue or cement, a curved arch wire is inserted into the bracket slots. The arch wire acts as a template or track to guide movement of the teeth into proper alignment. End sections of the arch wire are typically captured within tiny appliances known as tube brackets or terminal brackets, which are affixed to the patient's bicuspids and/or molars. The remaining brackets typically include open arch wire slots and apply orthodontic forces by means of ligatures attached to the brackets and arch wire (e.g., by means of tie wings on the brackets).

It would be an improvement in the art to provide orthodontic brackets combining improved properties and functionality currently not provided by conventional brackets.

BRIEF SUMMARY OF THE INVENTION The orthodontic brackets according to the present invention include a bracket base that includes an arch wire slot formed within the base, a first pair of tie wings extending occlusally and gingivally away from the arch wire slot, and a second pair of tie wings extending occlusally and gingivally away from the arch wire slot. The bracket base further includes a first labial web cover that is integrally formed with the first pair of tie wings. The first web cover extends between the first pair of tie wings, covering a first labial portion of the arch wire slot. A second labial web cover is integrally formed with the second pair of tie wings, extending between the second tie wings so as to cover a second labial portion of the arch wire slot.

Advantageously, each labial web cover is configured to be selectively removable (e.g., by peeling), exposing the initially covered labial side of the arch wire slot. Either or both removable covers can be selectively removed as desired to provide desired functionality. The bracket base and web covers are advantageously formed as a single integral piece. In one embodiment they are manufactured by machining a suitable metal material, rather than by metal injection molding as is typically used in the manufacture of orthodontic brackets. In metal injection molding, a metal powder mixed with a binder material is injection molded, followed by sintering to drive off the binder, which causes the metal particles to hold together. Machining the brackets rather than metal injection molding allows the use of stronger more dense metal materials, provides for a stronger and/or smaller finished product, and allows for greater precision and tighter tolerances with regard to bracket dimensions. The use of stronger metals and more precise dimensional tolerances allows the brackets to have sufficient strength with less metal, allowing the brackets to be significantly smaller than existing brackets formed by metal injection molding. For example, the inventive brackets may preferably be formed of 17-4 and/or 17-7 class stainless steels, which exhibit greater strength and density than classes of stainless steel suitable for use in conventional metal injection molded orthodontic brackets. Furthermore, the strength and density of metal objects formed by metal injection molding is further compromised as a result of micro air pockets present within the finished metal body after sintering.

With regards to the inventive brackets, providing two separate labial web covers allows the practitioner to selectively remove only one labial web cover while leaving the other intact. Such a configuration may be useful, for example, when applying corrective forces to correct a severely rotated tooth. It also permits the practitioner to remove both web covers as desired, either initially or following treatment with one web cover removed and one intact.

These and other features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

To further clarify the above and other advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

Figure 1 is a perspective view of an exemplary convertible orthodontic bracket; Figure 2A is a cross-sectional cut-away view through a first plane on a first side of the bracket of Figure 1 ;

Figure 2B is a cross-sectional cut-away view through a second plane on the first side of the bracket of Figure 1 ;

Figure 3 is a perspective view of an alternative exemplary convertible orthodontic bracket;

Figure 4 is a perspective view showing an exemplary convertible orthodontic bracket in use, bonded to a second bicuspid and with both web covers intact;

Figure 5A is a perspective view of the exemplary convertible orthodontic bracket of Figure 4, but with one of the labial web covers having been removed and one remaining intact; and

Figure 5B is a perspective view of the exemplary convertible orthodontic bracket of Figure 5A, but with the remaining labial web cover having been removed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS I. Introduction The convertible orthodontic brackets of the present invention include a bracket base with an arch wire slot formed therein, a first pair of tie wings extending occlusally and gingivally away from the slot, a second pair of tie wings extending occlusally and gingivally away from the slot, a first labial web cover integrally formed with and extending between the first pair of tie wings, and a second and separate labial web cover integrally formed with and extending between the second pair of tie wings. The bracket base may advantageously be formed by a machining process, in which the web covers and tie wings are formed by machining a single integral piece of metal. Manufacture by machining allows stronger, more dense metals to be employed than when manufacturing brackets by metal injection molding. II. Exemplary Orthodontic Brackets

Figure 1 illustrates an exemplary convertible orthodontic bracket 100 formed by a machining process. Bracket 100 includes a bracket base 102 with bonding pad 104 on the lingual surface of base 102. Bonding pad 104 may be formed integral with the other structures of bracket 100, or may be formed separately and then attached to bracket base 102 (e.g., by welding, brazing, or use of an adhesive). Bracket base 102 includes an arch wire slot 106 formed within base 102 (i.e., first slot portion 106a and second slot portion 106b). Bracket base 102 further includes a first pair of tie wings 108a, 108b and a second pair of tie wings HOa, HOb. Tie wings 108a and HOa extend occlusally away from slot 106, while tie wings 108b and 110b, as well as optional auxiliary hook 112, extend gingivally away from slot 106.

Bracket 100 may be characterized as a twin bracket, as it includes two pairs of tie wings (108a, 108b and HOa, 1 10b). An integral selectively removable labial web cover is provided with each pair of tie wings. First tie wings 108a and 108b are formed integral with a first web cover 114a extending occlusally-gingivally between the first tie wings, covering first slot portion 106a of arch wire slot 106. Similarly, second tie wings 110a and 110b are formed integral with a second web cover 114b extending occlusally-gingivally between the second tie wings, covering the second slot portion 106b of arch wire slot 106. As shown, arch wire slot 106 may be discontinuous, including separated first and second slot portions 106a and 106b. Alternatively, bracket base 102 may be configured so as to initially provide a continuous arch wire slot 106 between first tie wings 108a, 108b and second tie wings 1 10a, 110b (e.g., by means of first and second web covers 114a and 114b converging at the center of the bracket, or closer to one side or the other). Labial web covers 114a and 1 14b are each configured to be selectively removable from bracket 100, for example, by peeling away with pliers or other appropriate tool. In the illustrated embodiment, each labial web cover 114a, 1 14b includes two web regions 116, 118 of reduced cross-sectional thickness interconnecting a thicker central portion between opposite occlusal and gingival tie wing portions. For example, first cover 1 14a includes an occlusal connecting web region 116a of reduced cross-sectional thickness. A gingival connecting web region 118a of reduced cross-sectional thickness is spaced apart from and generally parallel to region 116a. The web regions 116a and 118a are separated by the thickened central portion of labial web cover 114a. Second web cover 114b includes similar connecting web regions 116b and 1 18b defining localized regions of reduced cross- sectional thickness where the labial web cover 114b may be peeled away from bracket 100.

When bracket 100 is formed by machining, it is possible to form the connecting web regions so as to include variable thicknesses that change as one moves from the mesial edge towards the distal edge of the connecting web. Such an embodiment is illustrated in Figures 2A-2B, which illustrate cross-sections at different locations on the mesial side of bracket 100 through tie wings 108a and 108b. As seen in Figure 2A, the extreme mesial edge of connecting web regions 116a and 118a may be machined so as to provide a minimum thickness, facilitating easier removal of the labial web cover from the mesial edge. As seen in Figure 2B, a cross section near the distal edge of connecting web regions 116a and 118a may advantageously be provided with greater thickness, providing an overall level of desired strength to the web cover so as to prevent premature and/or unintentional removal of the web. Providing a variable, tapered thickness as illustrated allows a practitioner to begin peeling at the mesial edge, where web thickness is at a minimum, and continuing towards the thicker distal edge. Such a variable tapered web thickness is difficult, if not a practical impossibility, to form using conventional metal injection molding techniques. For example, such a variable tapered thickness would be impractical with a metal injection molded bracket, as the unpredictable shrinkage associated with the manufacturing process would likely make it difficult or impossible to provide desired dimensional tolerances. By way of example, the amount of peeling force required to remove the web covers is between about 10 and about 30 lbs., more preferably between about 12 and about 28 lbs, and most preferably between about 17 and about 23 lbs. Commercially available metal injection molded brackets are batch tested as a result of the inability to provide tight dimensional tolerances relative to web thickness. For example, such batch testing results in rejection of batches in which the web removal force is less than 10 lbs or greater than 30 lbs. As a result, a significant quantity of the manufactured brackets must be discarded. Any attempt to metal injection mold a bracket including a variable tapered thickness would be impractical, as the rejection rates would likely be even higher. By contrast, manufacture by machining allows for significantly improved dimensional tolerances, which tolerances directly affect the force required for web removal. For example, the machined brackets could easily be price competitive with existing metal injection molded brackets, but include a much narrower range of force required for web removal (e.g., about 17 lbs to about 23 lbs). Such an improvement would be appreciated by practitioners, as the bracket's performance would be significantly more predictable.

As mentioned, the brackets are preferably formed by machining, rather than a metal injection molding process. Machining the brackets rather than metal injection molding allows use of stronger, more dense metal materials, which materials are not suitable for use in metal injection molding. Use of the stronger, more dense metal materials (e.g., 17-4 and/or 17-7 class stainless steels) provides for a stronger, more dense finished product. In addition, 17-4 and 17-7 class stainless steels may be heat treated after machining to further increase strength. Such heat treatments are not possible using classes of stainless steels suitable for use in metal injection molding. By contrast, metal injection molded brackets are formed from stainless steel powder materials (e.g., 303, 304, and/or 316L class stainless steels) which although they are better suited for powderization and sintering, exhibit less strength and lower density. In addition, the strength and density of actual finished brackets formed by metal injection molding is less than the bulk strength and density of the metal materials employed as micro air pockets can form during molding and sintering, and the strength of the finished article may be reduced as the sintering process may result in weak bonding of the metal powder. No such issues occur when machining a bulk metal material.

Although illustrated with thinned connecting web regions, one of skill in the art will readily appreciate that additional and/or alternative structures (e.g., perforations) may also be provided along the separable connecting webs 1 16a, 1 18a and 116b, 118b. Figure 3 illustrates such an embodiment of a bracket 100' including perforations 117.

Figures 4-5B illustrate an exemplary method of using convertible orthodontic brackets according to the disclosure. In Figure 4, bracket 100 is bonded to a patient's tooth (e.g., a bicuspid). Typically, convertible twin brackets will be used on bicuspids and/or cuspids during treatment, although they may also be used on other teeth. For example, convertible twin bracket 100 may be bonded to the second bicuspid 150 while arch wire 152 is terminated in a conventional tube bracket 154 bonded to the first molar 156. In Figure 4, arch wire 152 is shown as having a relatively thin, rounded cross-section. Such an arch wire is typically used in the early phases of treatment for aligning and leveling teeth through application of relatively gentle, small forces.

Once the desired degree of aligning and leveling is accomplished, the round arch wire 152 may be replaced with a somewhat larger rectangular arch wire. Such a later treatment phase is shown in Figure 5A. In addition, as shown in Figure 5A one of the labial web covers (e.g., mesial web cover 114a) has been removed, leaving the other cover (e.g., distal web cover 114b) intact. Treatment with a bracket that includes only one labial web cover, with one cover removed, may be advantageous when attempting to correct a severely rotated tooth, as a twin bracket including unremoved web cover 114b effectively creates a fulcrum about which the tooth may be rotated. As shown, each thinned connecting web region is advantageously formed so as to be substantially in a plane defined by the occlusal or gingival sidewall of the arch wire slot so that when the labial web cover is removed, no remaining portion of the labial web cover occludes labial access to the arch wire slot.

As shown in Figure 5B, once the desired rotation has been achieved, the remaining labial web cover 114b may also be removed, allowing treatment to be completed with larger rectangular arch wire 158. Because machined brackets provide for narrower dimensional tolerances and thus web removal force, intraoral removal of the labial web covers 1 14a and 1 14b is less likely to result in debonding of the bracket from the tooth, as might otherwise occur with metal injection molded convertible brackets where the dimensional tolerances (and thus web removal force) varies within a wider range. As shown in Figure 4, the practitioner may rely on the presence of web covers

114a and 114b for ligating the arch wire 152 within the arch wire slot. As the web covers are removed, ligation of the arch wire 154 may be aided or accomplished by ligatures 160, as seen in Figures 5A-5B.

The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope. What is claimed is:

Claims

1. A convertible orthodontic bracket comprising: a bracket base including an archwire slot formed therein; a first pair of tie wings which extend occlusally and gingival Iy away from said arch wire slot; a first labial web cover integrally formed with said first pair of tie wings, said first web cover extending between the first pair of tie wings over a first portion of said arch wire slot; a second pair of tie wings which extend occlusally and gingivally away from said arch wire slot; and a second labial web cover integrally formed with said second pair of tie wings and separate from said first web cover, said second web cover extending between the second pair of tie wings over a second portion of said arch wire slot, wherein the first and second labial web covers are independently removable so as to permit either or both to be removed as desired.

2. An orthodontic bracket as recited in claim 1, wherein the bracket comprises a single integral piece of metal.

3. An orthodontic bracket as recited in claim 2, wherein the bracket comprises at least one of 17-4 or 17-7 class stainless steel.

4. An orthodontic bracket as recited in claim 2, wherein the bracket is formed by machining.

5. An orthodontic bracket as recited in claim 1, wherein each labial web cover includes: a first connecting web region of reduced cross-sectional thickness bridging between a tie wing on one side of the first connecting web region and a thickened central portion of the labial web cover on an opposite side of the first connecting web region; and a second connecting web region of reduced cross-sectional thickness bridging between a tie wing on one side of the second connecting web region and a thickened central portion of the labial web cover on an opposite side of the second connecting web region.

6. An orthodontic bracket as recited in claim 5, wherein the first connecting web region is substantially parallel to the second connecting web region.

7. An orthodontic bracket as recited in claim 5, wherein the first connecting web region is formed so as to be substantially in a plane defined by an occlusal edge of the arch wire slot and the second connecting web region is formed so as to be substantially in a plane defined by a gingival edge of the arch wire slot such that, when removed, no remaining portion of the labial web cover occludes labial access to the arch wire slot.

8. An orthodontic bracket as recited in claim 5, wherein the cross- sectional thickness of each connecting web region is tapered so as to be thinner at a mesial edge and thicker at a distal edge of each labial web cover.

9. An orthodontic bracket as recited in claim 5, further comprising perforations formed through each connecting web region.

10. A convertible orthodontic bracket formed by machining a metal material, the orthodontic bracket comprising: a bracket base including an archwire slot formed therein; first and second pairs of tie wings, each pair of tie wings including a tie wing extending occlusally away from the arch wire slot and a tie wing extending gingivally away from the arch wire slot; a first labial web cover integrally formed with said first pair of tie wings, said first web cover extending between the first pair of tie wings over a first portion of said arch wire slot, a second labial web cover integrally formed with said second pair of tie wings and separate from said first web cover, said second web cover extending between the second pair of tie wings over a second portion of said arch wire slot; wherein each labial web cover includes: a tapered occlusal connecting web of reduced cross-sectional thickness bridging between the respective occlusally extending tie wing and a thickened central portion of the respective labial web cover, the connecting web having a thickness that is tapered so as to be thinner at a mesial edge and thicker at a distal edge of each labial web cover; and a tapered gingival connecting web of reduced cross-sectional thickness bridging between the respective gingival Iy extending tie wing and a thickened central portion of the respective labial web cover, the connecting web having a thickness that is tapered so as to be thinner at a mesial edge and thicker at a distal edge of each labial web cover.

1 1. An orthodontic bracket as recited in claim 10, wherein the bracket is machined from at least one of 17-4 or 17-7 class stainless steel.

12. An orthodontic bracket as recited in claim 10, wherein the occlusal connecting web is substantially parallel to the gingival connecting web.

13. An orthodontic bracket as recited in claim 10, wherein the occlusal connecting web is formed so as to be substantially in a plane defined by an occlusal edge of the arch wire slot and the gingival connecting web is formed so as to be substantially in a plane defined by a gingival edge of the arch wire slot such that when removed, no remaining portion of the labial web cover occludes labial access to the arch wire slot.

14. A method of using a convertible twin orthodontic bracket comprising: providing a convertible twin orthodontic bracket comprising: a bracket base including an archwire slot formed therein; a first pair of tie wings which extend occlusally and gingivally away from said arch wire slot; a first labial web cover integrally formed with said first pair of tie wings, said first web cover extending between the first pair of tie wings over a first portion of said arch wire slot; a second pair of tie wings which extend occlusally and gingivally away from said arch wire slot; and a second labial web cover integrally formed with said second pair of tie wings and separate from said first web cover, said second web cover extending between the second pair of tie wings over a second portion of said arch wire slot; bonding the convertible twin orthodontic bracket to a patient's tooth; inserting an arch wire into the arch wire slot of the convertible twin orthodontic bracket; and selectively removing a first one of the labial web covers, leaving a second labial web cover intact.

15. A method as recited in claim 14, further comprising selectively removing the second labial web cover after first performing an orthodontic treatment involving the second labial web cover.

16. A method as recited in claim 15, wherein removal of the remaining labial web cover is performed intraorally, with the convertible twin orthodontic bracket remaining bonded to the patient's tooth.

17. A method as recited in claim 14, wherein the convertible twin orthodontic bracket is bonded to at least one of a bicuspid or a cuspid in need of rotational correction.

18. A method as recited in claim 14, further comprising attaching a ligature to the orthodontic bracket and arch wire after removing the first one of the labial web covers.

19. A method as recited in claim 18, further comprising removing the ligature and replacing it after removal of the second labial web cover.