Abstract:
A convertible orthodontic bracket is disclosed, wherein an archwire slot therein has a removable slot covering, thereby allowing the bracket to serve as a buccal tube during a first stage of treatment and an edgewise bracket during a subsequent phase of treatment. The slot covering is removable by detaching the slot covering from the bracket body along one or more predetermined extents of weakness, wherein each such extent of weakness includes perforations or voids providing a passage between an exterior of the bracket and an interior of the first archwire slot.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     The present application claims the benefit of U.S. Provisional Patent Application No. 60/795,611 filed on Apr. 26, 2006, and entitled “ORTHODONTIC BRACKET WITH CONVERTIBLE BUCCAL TUBE”, the entire content of which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present disclosure is directed to an orthodontic bracket, and in particular, a convertible bracket with a cover that can be removed or otherwise modified in shape.  
       BACKGROUND  
       [0003]     Orthodontic brackets are widely used to align teeth through the application of forces selectively provided by interconnected archwires and accessories. Brackets are typically of metal, ceramic or composite construction and comprise a base interconnecting with a tooth, and a bracket main portion providing a slot and optionally, e.g., tie wings for use in realigning the tooth.  
         [0004]     A convertible bracket is an appliance used by orthodontists to correct malpositioned teeth. In a convertible bracket, the buccal or cheek-facing side of the archwire slot is enclosed by a structure, such as a plate or cap, to form a tubular opening that is typically rectangular or trapezoidal in cross section. The plate or cap can be brazed, laser welded or spot-welded in place. Alternatively, the bracket body may have an integrally formed cover plate with lines of weakness formed by elongated frangible webs extending along the length of the archwire slot as disclosed in U.S. Pat. No. 4,927,362, the contents of which are incorporated herein by reference. In this way, the plate or cap can be removed to convert the tube to a conventional bracket during later stages of treatment. These perforations can also be fabricated by the use of water or other liquids via, e.g., jets for removing material in the same manner as when forming the original part. Such a cap may also be made from a different material than the material of the bracket body. Some possible bracket body and cap combinations may include combinations of one or more of: metal, ceramic, plastic, composite, or other precious metals. For example such a combination may include a metal bracket body with a plastic cap or a ceramic bracket body with a composite cap.  
         [0005]     In orthodontic brackets, an archwire passes through a labially-opening, horizontal slot between, e.g., by one or more pair of opposing tie wings. Reference is made to U.S. Pat. No. 5,470,228 for further background information, with the content of U.S. Pat. No. 5,470,228 incorporated herein by reference. The archwire is preshaped and sized to provide the desired forces. Each bracket typically includes at least one tie wing pair having a gingivally extending tie wing and an occlusally extending tie wing. Once placed in the slot of one or more pair of tie wings, an archwire is typically restricted therein by a ligating device, such as a steel or elastomeric ligature.  
         [0006]     Orthodontic treatment objectives and techniques continue to evolve, and the present disclosure represents significant advances in relation to the above-noted convertible orthodontic bracket while maintaining the utility and structural integrity of a buccal tube and an edgewise bracket.  
       SUMMARY  
       [0007]     A novel orthodontic bracket and method of use is disclosed herein, wherein the novel bracket has varying utilities both at the start of an orthodontic treatment and during later orthodontic treatment stages. The novel bracket includes a removable cover for an archwire slot of the bracket. During early stages of orthodontic treatment when the cover is in place, the cover creates a tube in the bracket which can assist in maintaining a desired relationship between the archwire and the slot, wherein the archwire is less prone to bind in or around the slot, and thus the archwire moves more freely therein (compared to a non-covered slot with a mechanism to hold the archwire in the slot). Subsequently, during a later stage of orthodontic treatment, the cover can be removed causing the convertible orthodontic bracket to function as a traditional edgewise bracket. Thus, in accordance with embodiments of the present disclosure, a novel convertible orthodontic bracket is provided, wherein the bracket provides structure to accommodate different modes of operation during different phases of patient treatment. In particular, the novel bracket includes perforations extending entirely through (or substantially so) a thickness of the cover so that the cover is attached to the remainder of the bracket by connecting portions that may be considered as “bridges” for attaching the cover to the bracket. Thus, such bridges provide predetermined lines or extents of weakness between the cover and the remainder of the bracket (referred to herein as the “bracket body”) for easy and predictable separation of the cover from the bracket body, wherein the following advantages are obtained over the prior art: 
        (a) The cover separates from the bracket body leaving a reduced extent of irregular surfaces and edges since only portions of the bridges may remain with the bracket body having such irregularities;     (b) Since the cover detaches predictably along the bridges (or at the ends of the bridges abutting the bracket body), the strength of the bracket without the cover is not compromised by the cover being detached from the bracket body whereby an undesired portion of the bracket body is also detached with the cover; and     (c) Since the cover detaches predictably along the bridges (or at the ends of the bridges abutting the bracket body), the entire cover is predictably removed. Thus, no or little additional extra work need be performed by an orthodontist to remove a portion of the cover that did not separate from the bracket body.        
 
         [0011]     An embodiment of the novel convertible orthodontic bracket disclosed herein may include an integrally molded, cast, sintered or machined product comprising an orthodontic bracket body defining an archwire slot that is covered on the buccal side by a detachable which may be integral with the bracket body or attached thereto by brazing, gluing, etc. The bracket body opposite the buccal cover may comprise torque built into the bracket body or slot or both. Angulation and offset may also be built into one or both of the slot and base.  
         [0012]     The occlusal and gingival sides of the cover may be, in one embodiment, joined to the bracket body by connecting portions interleaved with perforations, voids or otherwise weak material forming predetermined separation extents (generally, in the mesial-distal directions) along which the cover can be detached from the bracket body by, e.g., fracturing or breaking the connecting portions. In one embodiment, the thickness of the cover (in the direction of the slot depth) and the thickness of the connecting portions are substantially the same. In another embodiment, the cover plate may have variations in thickness, and/or the connecting portions may have variations in thickness or a thickness different from that of the cover.  
         [0013]     The connection portions may include members or bridges that attach along the mesial and distal sides of the bracket slot. Such members may extend generally in the gingival-occlusal directions of the bracket and may be positioned on the cheek-facing surface of the bracket body. There may be any number of such members at any location along the mesial and distal direction. There may also be a small or large number of perforations (e.g., voids or cutouts) within the interface between the cover and the bracket body, such perforations interleaved with these members. For example, there may be as few as two perforations within the interface, or as many as, e.g., seven or more.  
         [0014]     In accordance with at least one embodiment in the present disclosure, a novel orthodontic bracket is provided, the bracket comprising: (i) bracket body having a base adapted for direct or indirect attachment to a tooth, and a body portion extending from the base and providing an elongated archwire slot, and (ii) slot covering having a cover and connections for connecting the cover to the bracket body, wherein the cover extends across and closes or covers a buccal side of said archwire slot, such a cover being joined to the bracket body along opposite sides of the slot by the connections having perforations therebetween for forming one or more lines or extents of weakness (e.g., two lines or extents of weakness), whereby the cover can be removed from the bracket body along the perforated extents of weakness to uncover the slot. The connections forming the one or more extents of weakness preferably comprise metal alternating with the perforations. The metal may be preferably substantially of the same thickness as the cover and each perforation is preferably oblong, in the mesial-distal direction, and defining a passage from the exterior of the bracket to the interior of the slot. However, such perforations may also be any other shape such as circles, squares, rectangles, etc. Additionally, note that the body of the bracket may have at least one occlusally extending tie wing and at least one gingivally extending tie wing. Alternatively, the bracket body need not include any tie wings, or any other orthodontic structure extending away from the slot. Examples of such structures include a hook, tube, circular boss, etc. as one of ordinary skill in the art will understand.  
         [0015]     The present disclosure describes a novel convertible orthodontic bracket, the bracket comprising: 
        (a) a base adapted for interconnecting with a tooth;     (b) a body portion extending from the base and defining a mesial-distal extending archwire slot, the body portion may have at least one pair of tie wings, wherein the archwire slot is between a gingival wing and an occlusal wing of the at least one pair, or may have one or no tie wings with or without another orthodontic structure (e.g., a hook); and     (c) a removable cover extending across at least a portion of the archwire slot and buccally closing at least a portion of the archwire slot.        
 
         [0019]     In accordance with embodiments of the present disclosure, the bracket body may include three pairs of tie wings, wherein for each pair, there is a tie wing on an occlusal side of the bracket body, and one on the gingival side. More generally, embodiments of the novel convertible bracket may include cantilevered portions extending outward from an occlusal-gingival center line through the bracket, wherein such cantilevered portions may be tie wings, hooks, or other orthodontic bracket extensions. An embodiment of the novel bracket may further comprise at least one sloped surface at a mesial or distal opening of the archwire slot. Additionally, the archwire slot comprises three substantially planar surfaces within the width of the cover. Another embodiment of the present disclosure may include a bracket body portion with one or more archwire slots. The body portion may also contain notches, channels, grooves, or holes along the occlusal, gingival, mesial, and distal sides. The base of the novel convertible bracket may include a dovetail, wire mesh, or integral one piece base as disclosed in U.S. Pat. No. 6,846,178 incorporated herein fully by reference. Note that the base may also include flanges which may be used for welding the bracket upon an orthodontic band. In addition to various tie wing designs, the novel convertible bracket may also include any combination of hook designs, hook locations, and hook orientations.  
         [0020]     In addition, a novel method of use is disclosed herein which includes a method of converting a bracket from a buccal tube to an edgewise bracket. Such a method may include the steps of: 
        (a) Attaching the bracket to a tooth during an orthodontic treatment, the bracket comprising: (i) a body portion extending from a tooth attaching base, the body portion comprising, e.g., one or more tie wings having an archwire slot thereinbetween, or no tie wings, or one or more other orthodontic structures such as a hook, etc, and (ii) a removable cover plate;     (b) Inserting an archwire into the archwire slot;     (c) Removing the cover plate at some time during a series of orthodontic treatments; and     (d) Ligating the archwire by attaching a ligating device to the bracket after inserting the archwire into the archwire slot after the removing step.        
 
         [0025]     In accordance with embodiments of the novel method of use, the ligating device may be formed into a figure “8” as viewed in a mesial-distal direction along a width of the bracket. The ligating device may be alternatively placed around a center pair of tie wings only, or conventionally around all of the tie wings, or on one side of the outer most tie wings with respect to the mesial and distal sides, or around the outer most and middle wings together. Ligation of the archwire may also be performed by ligating around any other suitable structure of the bracket body including a hook.  
         [0026]     In other embodiments of the present disclosure, the connections having perforations therebetween for forming one or more extents of weakness may be composed of ceramic or a composite (a composite such as a polymer plastic) alternating with holes formed in the ceramic or composite. The ceramic or composite may be substantially of the same thickness as the cover plate and the perforations may be oblong slots extending through the cover. The bracket body and cover can also be made out of plastic, ceramic, metal, or a precious metal or any combination thereof. For example, the bracket body may be composed of a metal bracket with a plastic cover or a ceramic bracket body with a composite cover. The fabrication of one or more of these parts can be made by Metal Injection Mold (MIM), Plastic Injection Mold (PIM), Ceramic Injection Mold (CIM), casting, laser welding, brazed, water jet, adhesives, etc.  
         [0027]     In one embodiment of the novel convertible bracket, a second or auxiliary slot is provided parallel to a first archwire slot, such a second slot may be covered by a cover that is not designed to be removed. In another embodiment the second slot may be in any orientation (e.g., non-parallel) with respect to the first slot and may have a removable cover as well, Note that additional auxiliary slots may be included in the bracket which may also be have parallel and/or non-parallel orientations to the first archwire slot. One or more arch-wire/auxiliary slots in any combination of removable/non-removable covers can be provided, and such slots can be angled to one another.  
         [0028]     In still other embodiments of the present disclosure, the cover can have a lesser mesial/distal length than the bracket&#39;s base and/or a corresponding covered archwire slot. In particular, the mesial/distal length of the cover may extend over at least 50% of the length of the slot  106  and less than 90%, and more preferably between 60% and 90% of the slot&#39;s length.  
         [0029]     Additionally, the novel bracket disclosed herein may also include the features of U.S. patent application Ser. No. 11/695,555 filed Apr. 2, 2007 incorporated fully herein by reference, wherein the covered slot have a lining of an archwire friction reducing metal (e.g., gold) together with expanded or fluted slot ends for further reducing the friction between an archwire and the slot (in particular, an archwire binding friction).  
         [0030]     Embodiments of the novel bracket disclosed herein may also be considered as improvements on the convertible buccal tube disclosed in U.S. Pat. No. 6,428,314 filed Apr. 20, 2001 which is fully incorporated herein by reference.  
         [0031]     Embodiments of the novel bracket disclosed herein may also be considered to have various forms of indicia and/or patterns in the interface of the base surface that faces the tooth to which the bracket is to be attached. Disclosure of this aspect is disclosed in U.S. Pat. No. 6,846,178 entitled “Orthodontic Bracket Base Apparatus and Method of Manufacture” is incorporated herein by reference in its entirety. In addition, the content of U.S. Patent Application Publication No. 2005/0003320 A1 entitled “Edgewise Orthodontic Bracket with Character Base” is incorporated herein by reference in its entirety.  
         [0032]     In yet other embodiments of the novel bracket, the mesial and distal ends of the archwire slot can be configured in an angled, sloped, or funnel shape to facilitate easier insertion of an archwire.  
         [0033]     Another embodiment of the present disclosure may include a bracket or bracket body that can measure force exerted through an archwire.  
         [0034]     Additional notable aspects of the novel convertible bracket are: 
        (a) The novel convertible bracket may include: 
            a bracket body including: a base adapted for interconnecting to a tooth and a bracket portion extending from the base and defining an archwire slot having a length and having a width extending in an occlusal-gingival direction, said bracket portion further comprising at least one occlusally extending cantilevered portion and at least one gingivally extending cantilevered portion; and     a slot covering attached to the bracket body, wherein the slot covering extends across the slot width for maintaining an archwire in the slot, the slot covering having a first plurality of connecting portions for attaching the slot covering to an occlusal bracket side of the slot, and a second plurality of connecting portions for attaching the slot covering to a gingival bracket side of the slot;     wherein at least one of the first and second pluralities of connecting portions include at least two connecting portions having a perforation therebetween for forming a predetermined extent of weakness adjacent a side of the slot, wherein for disconnecting from the bracket body at least a part of the slot covering extending along the length of the slot, the at least two connecting portions are caused to cease to connect the part of the slot covering from the bracket body.    
            (b) The predetermined extent of weakness includes at least two perforations.     (c) The predetermined extent of weakness extends a majority of the length of the slot but may extend less than 90% of the length of the slot, and a majority of the predetermined extent of weakness is voids, wherein each void provides a passage between an exterior of the bracket and an interior of the slot.        
 
         [0041]     Various embodiments of the present disclosure are set forth in the attached figures and in the detailed description provided hereinbelow and as embodied by the accompanying claims. It should be understood, however, that the present Summary section may not contain all of the novel aspects and novel embodiments claimed herein. Accordingly, the present Summary is not meant to be limiting or restrictive in any manner, and the disclosure herein is and will be understood by those of ordinary skill in the art to encompass obvious improvements and modifications thereto.  
         [0042]     Other embodiments within the scope of the present disclosure will be clear to those of ordinary skill in the art after a review of the detailed description hereinbelow together with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0043]      FIG. 1  shows a top perspective view of a convertible orthodontic bracket  100  in accordance with the present disclosure, wherein the cover  110  is connected to the bracket body  102 . Note that the sidewalls  107  and/or the floor  108  may be covered with an archwire friction reducing material such as gold.  
         [0044]      FIG. 2  shows another view of the convertible orthodontic bracket of  FIG. 1 .  
         [0045]      FIG. 3  shows a substantially side view of another embodiment of the bracket  100 .  
         [0046]      FIG. 4  shows a top perspective view of the convertible orthodontic bracket of  FIG. 3 , with the cover  110  removed from the bracket body  102 .  
         [0047]      FIGS. 5 through 15  show additional embodiments of the novel convertible bracket disclosed herein. Note that the sidewalls  107  and/or the floor  108  may be covered with an archwire friction reducing material such as gold.  
         [0048]      FIGS. 16 and 17  show, respectively, perspective and side views of a twin tie wing embodiment of the novel convertible bracket (identified as  100 L). Note that the sidewalls  107  and/or the floor  108  may be covered with an archwire friction reducing material such as gold. Moreover, the floor  108  and the sidewalls  107  may be expanded or fluted at the ends of the slot  106  as described in U.S. patent application Ser. No. 11/695,555 filed Apr. 2, 2007.  
         [0049]      FIGS. 18 and 19  show, respectively, perspective and side views of a twin tie wing embodiment of the novel convertible bracket (identified as  100   m ), wherein the bracket base  104  is flanged for attaching to, e.g., an orthodontic band (not shown). Note that the sidewalls  107  and/or the floor  108  may be covered with an archwire friction reducing material such as gold. Moreover, the floor  108  and the sidewalls  107  may be expanded or fluted at the ends of the slot  106  as described in U.S. patent application Ser. No. 11/695,555 filed Apr. 2, 2007. 
     
    
     DETAILED DESCRIPTION  
       [0050]     As illustrated in  FIGS. 1 and 2 , a convertible orthodontic bracket  100  is shown which includes: 
        (a) a bracket body  102  having a base  104  for interconnecting (either directly or indirectly) with a tooth, and extending from the base, a main portion  105  having an archwire slot  106  therein, the slot having sidewalls  107 , and a floor  108  ( FIG. 2 ), and     (b) a slot covering  109  for retaining an archwire within the slot  106 , wherein the slot covering includes: a cover  110  for the slot  106 , and connecting portions  132  for connecting the cover  110  to the bracket body  102 .        
 
         [0053]     The connecting portions  132  extend along the two outer side edges (in the direction of the slot  106 ) of the cover  110  to form two perforated extents of weakness generally co-linear with the axes  111 , each such extent of weakness having at least one perforation or hole  112  extending entirely through the thickness of the cover  110  so that this cover is only attached to the bracket  100  by the connecting portions  132 . Preferably, each of the perforations  112  is longer in the mesio-distal direction  114  than they are wide in the traverse occluso-gingival direction, and in particular each perforation may have a length approximately at least three times that of its width. However, various sizes and shapes of perforations optionally together with any thin or weakened areas of the connecting portions  132  can be used to address specific manufacturing and/or use requirements, without departing from the scope of the present disclosure. Thus, for example, such perforations may be square, round, or rectangular. However, a preferred shape of such perforation, as discussed below, is trapezoidal.  
         [0054]     In one embodiment, the connecting portions  132  are integrally formed with and made of the same material as the cover  110  and have substantially the same thickness as the cover  110 , wherein “thickness” refers to the linear dimension along the axis  117  ( FIG. 2 ) corresponding with, e.g., the depth of the slot  106 . However, in another embodiment, the connecting portions  132  may be less thick than the thickness of the cover  110 . In one embodiment, such thinness of the connecting portions  132  may be due to the exposed or cheek facing surface  119  of the connection portions being recessed (not shown in  FIGS. 1 and 2 ). Accordingly, in this embodiment, when the cover  110  is detached from the bracket  100  (along the lines of weakness), any irregularly shaped or non-smooth surfaces or edges where the connection portions  132  separated from the bracket  100  will be recessed into the bracket, and therefore less likely to be an irritation or require smoothing. In another embodiment, as shown in  FIG. 3 , the cover  110 , the connecting portions  132 , and the bracket body  102  may be formed as an integral unit, wherein each perforation  112  is formed in the a unitary combination of the bracket body  102  and the cover  110 .  
         [0055]     In at least some embodiments, the cover  110  may have a thickness of about 0.1 mm to about 5 mm. Note that the thickness of the cover  110  may vary according to the desired force to be applied for removing the cover from the bracket body  102 . Additionally, note that the preferable range of forces for removal of the cover  110  is 5 lbs to 30 lbs (equivalently, 22 Newtons to 133 Newtons). Additionally, the cover  110  may extend over at least 50% of the length of the slot  106  and less than 90%, and more preferably between 60% and 90% of the slot&#39;s length. In general, it is preferable for the cover  110  to not extend the full length of the slot  106  since such a full length cover may make it harder for an orthodontist to thread an archwire into the slot. Note, however, that in one embodiment, the thickness of the cover  110  may decrease at least one of its longitudinal ends so that the corresponding slot cross section at the cover end is greater than the cross section of the slot at, e.g., the center of the length of the slot. Accordingly, in this later embodiment, the length of the cover  110  may extend substantially the full length of the slot  106 ; e.g., 90% to 100% of the slot length.  
         [0056]     The base  104  can be employed in connecting the convertible orthodontic bracket  100  to a patient&#39;s tooth. Any suitable means of attachment, whether presently known or developed in the future, can be used to attach the convertible orthodontic bracket  100  to the patient&#39;s tooth (not shown). Accordingly, various methods for attaching the bracket  100  to the tooth may be employed, including direct bonding to a tooth, welding flanges onto a band which is then connected to a tooth, via a mesh base, etc.  
         [0057]     In the embodiment of  FIGS. 1 and 2 , the cover  110  is shown on a bracket body  102  having three tie wings  118  on one side (gingival or occlusal), and two tie wings  124  together with a central extended wing/hook  124  on the other side (gingival or occlusal) of the bracket body  102 . However, the cover  110  or variations thereof may be provided on other types of slotted bracket bodies. For example, the brackets  100   a  through  100   k , respectively shown in  FIGS. 5-15  (and variations thereof) are within the scope of the present disclosure. Additionally, a twin tie wing embodiment of the novel convertible bracket ( 100 L) is shown in  FIGS. 16 and 17 . Also, a further embodiment is shown in  FIGS. 18 and 19 , wherein in this embodiment, a twin tie wing bracket  100   m  is shown having curved flanges  120 . The flanges  120  provide appropriate surface area and contour for attaching the bracket  100   m  to an orthodontic band (not shown) instead of attaching the bracket  100   m  directly to a tooth. Note that the sidewalls  107  and/or the floor  108  of any of the embodiments  100 , and  100   a  through  100   m  may be covered with an archwire friction reducing material such as gold. Moreover, the floor  108  and the sidewalls  107  may be expanded or fluted at the ends of the slot  106  as described in U.S. patent application Ser. No. 11/695,555 filed Apr. 2, 2007.  
         [0058]     In yet another embodiment, the bracket  100  (and/or brackets  100   a - 100   k ) may comprise a built-in torque.  
         [0059]     Referring to  FIG. 2 , this figure more clearly shows the alignment indicia  150  and bracket type identification  154  also shown in  FIG. 1 . Additionally,  FIG. 2  better shows the chamfered or fluted slot openings  200  preferably provided in one or both entrances to the archwire slot  106 . Additionally, note that the floor  108  of the slot  106  may also slope toward the base  104  near a slot opening  200  to further increase one or both openings to the slot  106 . Accordingly, when the archwire is inserted into the slot  106  via such an expanded opening  200 , the threading of the archwire (not shown) through the archwire slot  106  is much easier. More particularly, since the entrance to the archwire slot  106  is larger than the archwire and is somewhat funnel shaped, easier threading of the archwire through the bracket  100  is provided for the orthodontist in much the same manner that a countersink simplifies the placement of a screw in a pre-drilled hole.  
         [0060]     Note that  FIGS. 1 and 2  also show a ledge  208  above each of the sidewalls  107 . Each ledge  208  may be used for proper placement of the cover  110  when it is attached to its bracket body  102  above the slot  106 . In particular, the cover  110  and its connecting portions  132  may be attached to the bracket body  102  (i.e., the bracket without the cover) by first positioning the cover and its connecting portions  132  on the ledges  208  and then (or thereby) securing each connecting portion  132  to a corresponding ledge wall  212  ( FIG. 1 ) to which the connecting portion abuts. Alternatively/additionally, the connecting portions  132  may be secured to the ledges  208 . Note that the securing of the cover  110  and its connecting portions  132  may be performed by brazing, using an adhesive, etc. as one of ordinary skill in the art will understand. Moreover, note that since the attachment of the connecting portions  132  to the ledge  208  and/or the ledge walls  212  occurs in only about 5% to 20% of the length of the slot  106 , there is a substantial reduction in irregular surfaces, irregular or sharp edges, and a very reduced likelihood of portions of the bracket body  102  being removed with the cover  110  (and at least some part of the connecting portions  132 ). That is, since the perforations  112  are preferably longer than the connecting metal  132  there between. This aids in the separation of the cover plate  110  from the convertible orthodontic bracket  100 . Accordingly, in at least some embodiments, the perforations  112  are preferably elongated apertures. The number and dimension of such apertures forming the perforations  112  can be varied; however, preferably there are more perforations  112  and/or a greater area of perforations  112  and/or weaknesses along a separation line or path than there is material between such apertures along the same line. In accordance with at least one embodiment of the present disclosure, one or more of the perforations  112  are trapezoidal in shape, with the longest parallel side along the outer distal ends of the connector portions  132 , the shorter parallel edge towards the center of the cover plate  110 , and the two nonparallel edges at the mesial-distal ends of the perforations  112 . Note that such a trapezoidal configuration for each perforation  112  is advantageous in that when separating the cover  110  from the bracket body  102 , it is much more likely that the separation will occur nearer to (or at) each juncture where the distal or free end of each of the connecting portions  132  abuts bracket body  102 .  
         [0061]     Preferably, the convertible orthodontic bracket  100  (or any one of the brackets  100   a - 100   k ) is manufactured by molding and sintering; however, the perforations  112  can alternatively be formed by laser techniques, etc.  
         [0062]     In use, the convertible orthodontic bracket  100  (or any one of the brackets  100   a - 100   k ) is typically secured to a tooth by adhering the bracket  100  to a surface of the tooth. Alternatively, the bracket  100  may be secured to a tooth by connecting the bracket to a tooth band (not shown) that is then attached to a tooth. A terminal end of a conventional archwire is then fitted into the covered slot  106  of the bracket  100  (or any one of the brackets  100   a - 100   k ) for early-stage orthodontic treatment. Subsequently, in a later stage of treatment, the initial archwire is removed, and the cover  110  is removed from convertible orthodontic bracket  100  to convert the bracket  100  to an edgewise bracket wherein the slot  106  is buccally-open.  
         [0063]     A technique for removing the cover plate  110  comprises use of a prying tool inserted in the archwire slot  106  openings  200  for shearing or breaking the cover  110  away from the bracket body  102 . As one of ordinary skill in the art will understand, there are various other ways in which to remove the cover  110  from the convertible orthodontic bracket  100  (or any one of the brackets  100   a - 100   k ), including use of different metals, plastics, ceramics, polymers, etc., which have distinct physical characteristics that would allow for the separation of the cover from the rest of the bracket body  102 . Although not shown, alternative methods to remove cover  110  include the provision of drawstring-like structures (not shown) which, when pulled, will separate one edge of the cover  110  from the rest of the bracket body  102 . Still other techniques that may be employed include chemical dissolution of particular areas of the connecting portions  132  and/or the cover  110  to permit easy removal, laser techniques to separate the cover from the bracket body  102 , etc. All of the above methods and techniques are within the scope of the present disclosure.  
         [0064]     Referring now to  FIG. 4 , the convertible orthodontic bracket  100  of  FIG. 3  is illustrated, wherein the cover plate  110  has been removed, e.g., by the orthodontic tool for entering the openings  200 . Note that such a tool may break the connecting portions  132 , disengage the connecting portions from the bracket body  102 , or otherwise terminate the connections to the bracket body provided by the connecting portions. With the cover plate  110  removed, the interior of the archwire slot  106  can be seen, and bracket  100  is then utilized as an edgewise bracket.  
         [0065]     The archwire slot  106  can be configured to have reliefs at the end of the sidewalls  107  and slot floor  108  for reducing the surface area contact with an archwire. However, in at least one preferred embodiment of the present disclosure, the gingival and occlusal side walls  107  and slot floor  108  are substantially flat and planar. Moreover, in at least one embodiment of the present disclosure, the gingival and occlusal side walls are substantially parallel between the mesial and distal ends of the cover  110 .  
         [0066]     Referring again to  FIG. 4  and in accordance with embodiments of the present disclosure, after the cover plate  110  has been removed, it is useful to employ one or more ligatures to maintain the archwire (not shown) within the archwire slot  106 . As illustrated, a first of one or more tie wings  118  extend from the gingival-occlusal center line  230  of the convertible orthodontic bracket  100 . A second of one or more tie wings  124  extends in the opposite gingival-occlusal direction from the gingival-occlusal center line  230 . Beneath and between each of the first tie wings  118 , and the second tie wings  124 , there are first and second ligature grooves  400 ,  404 . A ligature can be wrapped about one or more of the tie wings  118  and one or more of the tie wings  124 , wherein the ligature seats in at least one of the ligature grooves  400 ,  404  on each side of the center line  230 , and also extends over the top of the archwire to keep the archwire in place. Thus, various ligature configurations and corresponding variations in the amount of ligature tension on an archwire can be provided as is described hereinbelow.  
         [0067]     With three of tie wings on each of the occlusal and gingival sides of a bracket body  102  (i.e., the bracket  100  without at least the cover  110 ), the bracket body  102  provides a number of ligature configurations, whereby the amount of coupling friction between the archwire and the bracket can be controlled by the orthodontist by using the various possible ligature configurations. For example, by placing a ligature over the center tie wings only, the amount of coupling friction is relatively small. In contrast, by forming a “figure 8” around all of the tie wings, a maximum amount of coupling friction can be applied. Thus, the features of the convertible bracket  100  allow it to be used as a buccal tube in the early stages of treatment, while further offering the synergistic capability of having the bracket function as an edgewise bracket in later stages of treatment, wherein the orthodontist is able to apply minimal ligature pressure on the bracket during early phases of treatment using the convertible bracket  100  as an edgewise bracket, and greater ligature pressure during later phases treatment as an edgewise bracket.  
         [0068]     Another embodiment of the novel convertible bracket includes at least two archwire slots  106 , wherein such slots may be parallel and adjacent to one another, each extending in the mesial-distal direction. One or more of the slots  106  may be have a slot covering  109  as described hereinabove. Note that the material of the bracket body  102  between the two slots is sufficiently wide (between the slots) and strong to accommodate connecting portions  132  attaching to at least one side of the material. In one embodiment, such width may be in the range of 1.0 mm to 3.0 mm. Note that one of the archwire slots  106  may have a non-removable cover.  
         [0069]     Those skilled in the art will appreciate that numerous changes and modifications may be made to the preferred embodiments of the disclosure and that such changes and modifications may be made without departing from the spirit of the disclosure. It is therefore intended that the appended claims cover all such equivalent variations as fall within the true spirit and scope of the disclosure.