Abstract:
A self-ligating orthodontic bracket has a sliding archwire cover that has a top surface congruent with the top surface of an upper body portion having an archwire slot. The cover has a resilient locking tab that slides across the slot, bending upward as it encounters a ridge on the other side of the slot, and latching to the ridge to secure the cover in a closed position. The cover has a modified dovetail shape with flared bottom portions that slideably engage guides for reciprocal opening and closing sliding motion. A groove in the slide support track engages the locking tab in the open position preventing it from disengaging from the upper body portion.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation-in-part application of pending U.S. patent application Ser. No. 13/679,019 filed Nov. 16, 2012. This application also claims priority based upon U.S. provisional application Ser. No. 61/779,630 filed Mar. 13, 2013. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable. 
       NAMES OF PARTIES TO A JOINT RESEARCH AGREEMENT 
       [0003]    Not applicable. 
       REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISC APPENDIX 
       [0004]    Not applicable. 
       BACKGROUND OF THE INVENTION 
       [0005]    1. Field of the Invention 
         [0006]    This disclosure relates to improved self-locking or ligatureless orthodontic brackets. 
         [0007]    2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98. 
         [0008]    Several self-locking or self-ligating (ligatureless) orthodontic brackets have been designed. However, most of those have complex designs, incorporating features requiring prohibitively expensive machining operations or comprising multiple separate parts, which in turn increases the number of failure modes for such brackets. Other designs have been rejected in the marketplace due to poor quality or poor design, a lack of available features, difficulty of use, or other factors. 
         [0009]    One such bracket is disclosed in U.S. Pat. No. 7,621,743 entitled Orthodontic Bracket. That device is a self-ligating bracket that includes a locking slide cover that entrains an archwire. However, like many sliding covers, the top surface is not smooth, which is important for patient comfort. Moreover, this device is difficult to manufacturer requiring small interlocking extensions mating in the plane of the slide and guide members on either side having sharp edges that protrude outwardly which have a tendency to irritate the mouth of the user. 
         [0010]    Another construction is shown in U.S. Pat. No. 8,414,292. In this patent, a keyhole-shaped clip slides across an archwire slot and two wings on the clip engage stops to lock the clip in place. The locking clip is tiny, and because it is flat, it is rather flimsy and prone to failure. 
       BRIEF SUMMARY OF THE INVENTION 
       [0011]    A self-ligating orthodontic bracket has an archwire cover that slides in a guide channel across an archwire slot. A flexible locking tab at the cover&#39;s leading edge engages a ridge on the other side of the archwire slot. It flexes up and over a ridge and a spring restoring force locks it in place once it has cleared the ridge. 
         [0012]    The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL DRAWINGS 
         [0013]      FIG. 1  is a perspective view of a self-ligating orthodontic bracket with a sliding archwire slot cover in a closed position. 
           [0014]      FIG. 2  is a perspective view of the orthodontic bracket of  FIG. 1  with the sliding cover in the open position. 
           [0015]      FIG. 3  is a top view of the orthodontic bracket of  FIG. 1 . 
           [0016]      FIG. 4  is a sectional view taken along line  4 - 4  of  FIG. 3 . 
           [0017]      FIG. 5  is a sectional view taken along line  5 - 5  of  FIG. 3 . 
           [0018]      FIG. 6  is a top view of the orthodontic bracket of  FIG. 2 . 
           [0019]      FIG. 7  is a sectional view taken along line  7 - 7  of  FIG. 6 . 
           [0020]      FIG. 8  is a side elevation view of another embodiment of a self-ligating orthodontic bracket in an open position. 
           [0021]      FIG. 8A  is a side elevation view of the bracket of  FIG. 8  in the closed position. 
           [0022]      FIG. 9  is a top view of an alternate embodiment of an orthodontic bracket in the open position. 
           [0023]      FIG. 10  is a top view of the bracket of  FIG. 9  in the closed position. 
           [0024]      FIG. 11  is a side cutaway view taken along line  11 - 11  in  FIG. 9 . 
           [0025]      FIG. 12  is a side cutaway view taken along line  12 - 12  in  FIG. 10 . 
           [0026]      FIG. 13  is a side cutaway view taken along line  13 - 13  in  FIG. 9 . 
           [0027]      FIG. 14  is a cutaway view taken along line  14 - 14  in  FIG. 10 . 
           [0028]      FIG. 15  is a top view of an alternate construction of a sliding archwire cover used in the embodiment of  FIG. 9 . 
           [0029]      FIG. 16  is a cutaway view taken along line  16 - 16  in  FIG. 15 . 
           [0030]      FIG. 17  is a cutaway view taken along line  17 - 17  in  FIG. 15 . 
           [0031]      FIG. 18  is a side cutaway view taken along line  18 - 18  in  FIG. 15 . 
           [0032]      FIG. 19  is a top view of another embodiment of a self ligating bracket with a sliding cover in an open position. 
           [0033]      FIG. 20  is a top view of the embodiment of the self ligating bracket of  FIG. 19  with the sliding cover in a closed position. 
           [0034]      FIG. 21  is a cutaway view taken along line  21 - 21  in  FIG. 19 . 
           [0035]      FIG. 22  is a cutaway view taken along line  22 - 22  in  FIG. 20 . 
           [0036]      FIG. 23  is a top view of a sliding cover used in the embodiment of  FIG. 19 . 
           [0037]      FIG. 24  is a cutaway view taken along line  24 - 24  in  FIG. 23 . 
           [0038]      FIG. 25  is a cutaway view taken along line  25 - 25  in  FIG. 23 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0039]    Orthodontic treatment generally comprises dental work to correct irregularities of the teeth or of the relation of the teeth to surrounding anatomy. The irregularities may involve malocclusions with varying degrees of severity. Class 1 malocclusions, for example, may involve spacing irregularities such as excessive crowding or diastema (a gap between two adjacent teeth). Class 2 malocclusions may involve overbite conditions where the upper anterior teeth project labially over the lower anterior teeth. Class 3 malocclusions, in contrast, may involve underbite conditions where the upper anterior teeth close within the lingual side of the lower anterior teeth. For these and other observed irregularities, treatment typically involves installation of braces or mechanical aids for repositioning the teeth into correct orthodontic alignment. 
         [0040]    Braces generally include orthodontic brackets configured for attachment to the labial or lingual surfaces of the teeth or for attachment to metallic bands secured around the teeth. The brackets typically include archwire slots within which a flexible yet resilient archwire may be engaged. Typically, each bracket is bonded to the tooth surface so that the bracket&#39;s archwire slot is oriented for engagement with the archwire. Various techniques are used for orienting the brackets. For example, an edgewise appliance comprises braces whereby each bracket is oriented and bonded to the tooth so that the archwire slot is perpendicular to the long axis of the root of the tooth. Alternatively, a straight-wire appliance includes braces whereby each bracket is oriented and bonded to the tooth so that the archwire slot is parallel to the occlusal plane (the biting surfaces of the teeth). 
         [0041]    The archwire is typically a curved metallic wire having a rectangular or circular cross section that is bent or twisted prior to engagement with the brackets. The memory or restoring force exerted by the archwire upon the brackets serves to move the teeth into the desired alignment. Throughout the duration of orthodontic treatment, the orthodontist periodically adjusts the shape of the archwire (as well as the configuration of other attachments such as elastic bands and so forth) to achieve the correct orthodontic alignment. 
         [0042]    Most brackets in current use incorporate tie wings or extensions that project upwardly and downwardly in a gingival-occlusal orientation and require the use of ligatures or ligating modules to hold the archwire within the archwire slots. The ligatures or ligating modules are typically donut-shaped elastomeric rings or wires that are stretched around or twisted around the tie wings. 
         [0043]    The use of such ligatures or ligating modules presents a number of inherent disadvantages, some of which are mentioned herein. The small size of the ligatures or ligating modules requires substantial time for installation of the archwire. Because the orthodontist will typically make numerous adjustments to the archwire throughout orthodontic treatment, the orthodontist will likely remove and replace the ligatures or ligating modules numerous times. Hygiene is another problem since the use of ligatures or ligating modules increases the areas where food particles may be trapped. Further, with movement due to chewing or other activities, the ligatures or ligating modules may become detached altogether, allowing the archwire to disengage from the archwire slots. 
         [0044]    Ligatures or ligating modules also present other limitations in terms of the forces exerted upon the brackets. For example, the labial or outward force that may be applied to a tooth having a bracket bonded to its labial surface is limited to the strength of the ligature or ligating module in the labial direction. On the same tooth, the force that may be applied in the lingual direction is not so constrained (because the force is applied against the bracket structure rather than the ligature or ligation module). Similarly, the longitudinal (or mesial-distal) forces, which may be applied along the direction of the archwire, may be limited or defined by the friction between the ligature or ligation module and the archwire. By contrast, a means for locking the archwire within the archwire slot would enhance the forces that may be exerted along the direction of the archwire. Likewise, a means for slideably retaining the archwire within the archwire slot would allow greater flexibility than available from brackets requiring the use of ligatures or ligation modules. 
         [0045]    A self-ligating orthodontic bracket  10  includes two separate parts, which together comprise a bracket assembly. A bracket body  12  includes a base portion  14  that is secured to a patient&#39;s tooth (not shown) with an adhesive or the like. The base portion  14  supports an upper body  16  that includes a pair of tie wing portions  17 ,  18 , one portion extending in the gingival direction and the other portion oriented in the occlusal direction. It is to be understood that these directions may be reversed depending upon the bracket&#39;s position and the preference of the designer. The upper body  16  has an archwire slot  20  that extends in a mesial-distal direction when the bracket  10  is installed on a patient&#39;s tooth. The archwire slot  20  has a first sidewall  19  and a second sidewall  23 . The second part is a sliding cover  22  that engages the upper body  16  and is selectively opened and closed over the archwire slot  20  so as to retain the archwire (not shown) or to provide access to the archwire slot  20  for installation, removal, and/or adjustment. 
         [0046]    The sliding cover  22  has a lower portion  24  that resembles a semi-dovetail shape. Rounded lower side portions  25 ,  28  flare outwardly beyond the width of the top surface portion. These side portions engage a guide channel  27  in the upper tie wing portion  16  of the bracket  20 . The guide channel  27  overlaps the side portions of the cover  25 ,  28  and retains the cover  22  as it slides forward. A depression  21  in the top surface of the cover permits an orthodontist to use a tool to manipulate the sliding cover from a locked to an unlocked position. On the opposite side of the archwire slot is a receiving space  29  into which a locking tab nests when the slide cover is in a fully closed position. 
         [0047]    The sliding cover  22  has a flexible locking tab  24  on its forward end. The locking tab is joined to the main body of the sliding cover by a narrow neck  26  of reduced height and width. The neck  26  provides elasticity so that the locking tab  24  can flex in an upward (labial) direction relative to the base  14  and spring back into a locked position under the restoring force of the flexible neck  26 . No particular shape is necessary for providing enough flex for the locking tab  24 , and other shapes such as a relief channel or merely making the tab out of a material that permits it to act like a leaf spring are also contemplated. The locking tab  24  has a rounded leading edge  30  in front and a straight undercut surface  32  behind the leading edge so that the front part of the locking tab  24  forms a hook. 
         [0048]    The leading edge of the tab  24  slides across a ridge  34  as the cover  22  is urged across the archwire slot  20 . The ridge  34  is curved or angled so that the rounded leading edge  30  easily slides Op and over it. This forces the tab  24  to flex upwardly. Once the leading edge  30  clears the ridge  34 , it snaps back onto the latch effectively latching the cover  22  in a closed position. The sliding cover  22  has a length dimension such that when the cover is closed, the forward ends  40 ,  42  of the flared side portions  25 ,  28  abut a wall  37  of the tie wing portion  17 , and the back end  39  of the sliding cover  22  is flush with the upper body portion  16  forming essentially a smooth and continuous surface. Thus, there are no sharp protruding parts to irritate the patient&#39;s mouth. 
         [0049]    To open the archwire slot  20 , a tool (not shown) is inserted into the depression  21  in the top of the cover  22  and the cover is pulled back. The locking tab  24  flexes upward as the cover  22  retracts, clearing the ridge  34 . The neck  26  is formed so that the spring action of the tab is not too stiff to resist the ramping action of the tab  24  over the ridge  34  as the cover is retracted. 
         [0050]    In its retracted position, the locking tab  24  rests in a groove  44  on the opposite side of the archwire slot. This prevents the sliding cover from becoming separated from the body of the bracket. It also defines the amount of travel of the sliding cover from open position to closed position. 
         [0051]      FIGS. 8 and 8A  show an alternate version of the sliding cover of  FIGS. 1-7 . The lingual front edges  47   a  and  47   b  of the two side portions  26 ,  28  of the cover  22  each have a chamfered edge  46 . With a chamfered edge as an underside surface, the cover more easily engages the archwire  50  and acts like a sliding inclined plane, pushing the archwire  50  into the slot  20  so that it contacts the bottom surface of the slot. This makes for better coupling of torqueing forces to be transferred to the teeth. 
         [0052]    An alternate bracket construction is shown in  FIG. 9 . Bracket  100  has a base  102  and a body portion  104 . The base  102  and body  104  are a single piece, preferably formed through the process of metal injection molding. A single piece molded bracket is much stronger than a conventional two piece unit in which the base and the upper body are formed separately then attached to each other. A sliding archwire slot cover  106  provides self ligation. The body portion  104  comprises two parts, a gingival portion  108  housing the cover  106  and an occlusal portion  110  which receives the cover when it closes. Labeling these parts as gingival and occlusal portions is for convenience in description only, and in actual practice the orientation of the bracket could be reversed, if desired. 
         [0053]    In the embodiment of  FIGS. 9-12 , the cover  106  includes a pair of side wing portions  126  and  124 . These portions fit within guide channels similar to those shown in  FIG. 4  and slide all the way across the archwire slot  112  to a ledge  120  on the gingival side of the upper bracket body, thus firmly locking the archwire in the slot. 
         [0054]    The sliding cover  106  is similar to the cover of  FIG. 1 . A flexible locking tab portion  114  is joined to the main body of the cover  106  by a narrow neck  116 . As  FIG. 11  shows, the neck  116  is thin in the lingual-labial plane as well as narrow in the mesial-distal plane. This permits the tab portion  114  to flex upward (in a labial direction) when the tab encounters a ridge  118  as the cover moves from an open to a closed position. The nose  117  of the locking tab  114  has an inclined planar surface  115  that engages a curved portion  119  of the ridge  118  that is adjacent the archwire slot as the sliding cover  106  is moved from an open toward a closed position. The inclined planar surface  115  meets the curved ridge surface  119 , and as the cover  106  slides over the slot, the locking tab  114  flexes in a labial direction until it clears the ridge  118 . Once this occurs, the tab portion  114 , under the restoring force action of the thin neck  116 , which acts as a spring, snaps down, and locks onto the ridge. A hook portion  111  of the locking tab  114  effectively latches the sliding cover shut by engaging the back surface  121  of the ridge  118 . At the same time the nose  117  of the tab portion  114  contacts a stop  122  thus preventing further forward movement. The interaction of the inclined plane  115  with the curved ridge surface  119  under the force of the forward movement of the sliding cover efficiently latches the sliding cover without requiring an undue amount of force to move the locking tab up and over the ridge. It will be understood that the front of the ridge may assume other shapes that could work equally well such as a slanted or inclined surface. Similarly the nose portion of the locking tab need not be an inclined plane, but could be merely curved. What is important is not the specific form of these surfaces, but that they are formed to slide smoothly against each other and provide some mechanical advantage to overcome the stiffness of the spring effect of the neck  116 . 
         [0055]    When the cover  106  is to be retracted to an open position the process is reversed, and the cover is slid back until the hook  111  is caught by a groove  113  in the slide track  125  of the occlusal portion  108  thus preventing any further rearward movement. 
         [0056]      FIGS. 13-18  show an embodiment of the sliding cover that may be used as an alternative to the sliding cover of  FIGS. 8 and 8A . The cover  106  is in all other respects the same as that illustrated in  FIGS. 9-12 , but instead of using chamfered undersurfaces on the sliding cover, it employs insertable leaf springs to push the archwire into the archwire slot. The side wing portions  126  and  124  of the sliding cover  106  have underside (lingual) pockets that are fitted with insertable leaf springs  128  and  130 . When the cover  106  moves from an open to a closed position, entraining the archwire  50  in the slot  112 , the leaf springs  128 ,  130  apply pressure to the top of the archwire and press it down into the slot. 
         [0057]      FIGS. 19-25  illustrate another alternative embodiment of a self ligating bracket. This bracket is of single piece construction as well and may be made of a clear or translucent material such as a plastic co-polymer. A bracket  200  includes a base  202  and an upper body portion  204  with an occlusal side  206  and a gingival side  208  separated by an archwire slot  210 . Preferably the bracket  200  is of single piece construction formed by a three dimensional printing process. 
         [0058]    A sliding cover  212  slides across the archwire slot  210  to close over and entrain an archwire (not shown) therein. The cover  212  has a leading edge  211  that slides across the slot  210  and in the closed position engages a ledge  214  formed in the gingival side  208  of the upper body portion  204 . The cover&#39;s top surface includes a small depression  209  which may be engaged by a manipulator tool (not shown) to open the cover  212 . A groove  207  in the top surface provides a means for engaging the cover with the tool to slide it into a closed position. 
         [0059]    Referring to  FIGS. 21 and 22 , the sliding cover  212  has a recess  216  formed in its lingual underside. A downwardly (lingually) depending leaf spring  218  is adapted to flex within the recess  216  and engages a rear stop groove  220  in the occlusal side  206  of the bracket when the sliding cover is in an open position. This limits rearward movement of the sliding cover and prevents its dislodging from the upper bracket body  204 . When the cover is moved forward to a closed position, the spring  218  flexes upwardly within the recess as it slides over a curved surface  217  that extends between the rear stop groove  220  and a forward locking groove  222 , and then snaps downwardly into the groove  222  to lock the cover in place over the archwire slot  210 . As in the embodiment of  FIGS. 8 and 8A , the leading edge  211  of the cover  212  may have a chamfered undersurface  224  that aids in pushing the archwire into the slot. 
         [0060]    The terms and expressions which have been employed in the foregoing specification are used therein as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims which follow.