Abstract:
A system and method for translating teeth along an arch wire which utilizes brackets with larger dimensions and with variable dimensions so that larger lever arms are possible thereby reducing the need for excessive pressure and reducing occasions of excessive tooth rotation which is incidental to tooth translation.

Description:
CLAIM OF PRIORITY 
     The present application is a national stage application under 35 U.S.C. 371 and/or a continuation under 35 U.S.C. §120 of PCT/US2012/020877, filed on Jan. 11, 2012, which claims the benefit of U.S. provisional application 61/452,839, filed on Mar. 15, 2011 and U.S. provisional application 61/431,968, filed on Jan. 12, 2011, all of which are incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to orthodontic methods and appliances, and more particularly relates to the edgewise appliance, and even more particularly relates to methods and systems for bodily movement of teeth along an arch wire at times when excessive rotation of and or forces on a tooth would otherwise be a concern. 
     BACKGROUND OF THE INVENTION 
     Since 1928 and 1929 when Edward H. Angle first publicly described his invention of the edgewise appliance, the single width bracket he invented has been modified to correct tooth rotations in the horizontal plane. Since the 1990s the width of the brackets typically used by orthodontists have decreased over time. Two other dimensions of Angle&#39;s original rectangular edgewise slot, height of 22 mils and depth of 28 mils (one thousandths of an inch) are used by many orthodontists currently. A smaller 18 mil by 25 mil slot was invented and is used by a large number of orthodontists. In some cases, patient comfort and cosmetic appeal have motivated the decrease in width and size of these various components of the edgewise appliance. 
     While these smaller components have been used extensively in the past, they do have some drawbacks. First of all, while not wishing to be bound by theory, the applicant opines that when retracting upper canines in a typodont, using a nickel-titanium spring delivering initially 150 grams of force, the canine with a twin edgewise bracket (22 by 28 mil slot) and bracket width of 4.6 mm moved in a bodily manner along the 20 mil arch wire. In contrast, the canine with a twin edgewise bracket (22 by 28 mil slot) and bracket width of 2.2 mm experienced with the same spring force controlled tipping. Explanation: In the edgewise bracket the tooth is translated by a series of opposite rotations about the center of resistance (CR) in the root and about the center of the bracket. As a bracket is reduced in width and size, the lever arms within the bracket are also reduced in size which requires greater forces to operate them, hence the retraction force rotating the tooth about its CR overpowered the ability of the bracket and arch wire to create a couple to rotate the tooth about the center of the bracket. A wider bracket can more effectively translate a tooth along an arch wire than a narrower bracket. For both wide and narrow brackets, use of heavy forces probably increase the potential for undesirable consequences such as high amounts of root resorption. Narrow brackets are useful in the initial stages of tooth alignment because they have larger inter-bracket distances that allow flexible arch wires to properly align the teeth. 
     Consequently, there may exist a need for improved methods and systems for translating of teeth along an arch wire while minimizing rotation of teeth in an edgewise appliance. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a system and method for controlling rotation of a tooth in an edgewise appliance. 
     It is a feature of the present invention to utilize generally wider brackets. 
     It is an advantage of the present invention to create brackets which provide for longer lever arms for causing translation of the tooth along an arch wire. 
     It is another feature of the present invention to include larger slot depth and slot height dimensions of the brackets. 
     It is another advantage of the present invention to allow use of larger arch wires which also provide for longer lever arms for causing buccal-lingual rotation of the tooth. 
     It may be possible to reduce the magnitude of the rotations that occur in the translation and buccal-lingual movement of the teeth. The present invention may allow better operation of the physical properties in arch wires made of different alloys. 
     It is another object of the present invention to reduce the number of brackets that need to be placed on a given patient&#39;s teeth during the course of an extended treatment. 
     It is another feature of the present invention to use adjustable width brackets. 
     It is an advantage of the present invention to place one bracket on a tooth adjust it to a narrow bracket width to start and then later adjust the bracket width to be wider later on, all without removing the bracket from its position on a tooth. 
     Accordingly, the present invention is a system and method including a collection of larger and variable dimension brackets and a larger arch wire which are capable of having larger lever arms for rotating the tooth. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention may be more fully understood by reading the following description of the preferred embodiments of the invention, in conjunction with the appended drawings wherein: 
         FIG. 1  is a perspective view of a bracket of the present invention, in an open or wide orientation. 
         FIG. 2  is a perspective view of the bracket of  FIG. 1  in a closed or narrow orientation. 
         FIG. 3  is an end view of a bracket of the present invention. 
         FIG. 4  is a top view of the bracket of  FIG. 3  after being manipulated into a closed orientation. 
         FIG. 5  is a top view of the bracket of  FIG. 3  in an open orientation. 
     
    
    
     DETAILED DESCRIPTION 
     Now referring to the drawings, wherein like numerals refer to like matter throughout, and more specifically referring to  FIG. 1 , there is shown an increased lever arm bracket of the present invention generally designated  100 , which includes a bracket tooth mounting base  102  which could be made using materials, such as stainless steel, and methods which are well known in the art for making bases of other brackets. Bracket tooth mounting base  102  could have integrally formed therein or attached thereto a first base mounted guide rail  110  and a second base mounted guide rail  112  or other suitable support and translation permitting structure. Disposed upon said first base mounted guide rail  110  and second base mounted guide rail  112  in a movable and longitudinally translateable manner are first end ear structure  120  and second end ear structure  122  which are each structures which are very similar to corresponding portions of existing prior art twin brackets, except that they are detached from their base and are configured with longitudinal voids therein, which are configured to receive therein, the first base mounted guide rail  110  an second base mounted guide rail  112 . The surfaces of first end ear structure  120  and second end ear structure  122 , especially those surfaces which mate with first base mounted guide rail  110  and second base mounted guide rail  112  and those that touch bracket tooth mounting base  102 , are preferable made to reduce and\or manage friction therebetween. First end ear structure  120  and second end ear structure  122  may have a longitudinal threaded channel extending from an exterior face to an interior face for receiving therein and operatively mating with a rotating linear adjusting spreading screw shaft  130  which extends between first end ear structure  120  and second end ear structure  122 . 
     First end ear structure  120  and second end ear structure  122  are shown having two ears coupled to each other. The present invention is not limited to ear structures which have multiple ears per ear structure. The term ear is well known in the art and is used here to refer to that portion of the bracket which in combination with another adjacent ear forms a channel for the arch wire. Additionally, the ears are configured to receive thereon chains or other tooth to tooth connecting structures. Rotating linear adjusting spreading screw shaft  130  is configured with a male right handed threaded segment  132  and a male left handed threaded segment  134  which may mate with female at least partially threaded channels or in the alternative, the channels could be non-threaded and there could be a first threaded shaft receiving plate  140  and second threaded shaft receiving plate  142  coupled to first end ear structure  120  and second end ear structure  122  respectively. Rotating linear adjusting spreading screw shaft  130  and the threaded channels, plates or other structure at each end form a mechanism known as a separating screw or a turnbuckle, whereby rotation of the rotating linear adjusting spreading screw shaft  130  with its oppositely threaded male ends, mates with the female threaded structures and causes the first end ear structure  120  and second end ear structure  122  to either approach each other or separate depending upon the direction of rotation of rotating linear adjusting spreading screw shaft  130 . To facilitate rotation of rotating linear adjusting spreading screw shaft  130  there is a central tool engaging region  136  which could be configured with various tool engaging structures such as a hole for receiving therein a pin or key or a hexagonal or other shaped section for mating with a wrench head, still other structures for facilitating rotation of the rotating linear adjusting spreading screw shaft  130  are envisioned. The ends of rotating linear adjusting spreading screw shaft  130  could be non-threaded hexagonal or similar shaped tips (not shown) which could be used to mate with a wrench. 
       FIG. 1  shows the increased lever arm bracket  100  in a fully extended or open position. When the rotating linear adjusting spreading screw shaft  130  is turned in a direction for closure, See  FIG. 2 , the left hand thread segment end  138  is shown protruding out of the first threaded shaft receiving plate  140 , (without the optional hexagonal end) and the gap shown in  FIG. 1 , between first end ear structure  120  and second end ear structure  122  has been reduced. If it desired to completely close the bracket the optional hexagonal tips at the end of the shaft  130  could be used when access to the center of the shaft is difficult or impossible. 
     In many aspects the brackets of the present invention are similar in many ways to prior art stainless steel twin brackets, however, some key dimension are dramatically different from prior art brackets. 
       FIG. 1  shows the bracket width dimension BW which is preferably wider or capable of being adjusted to be wider than currently popular brackets. A preferred embodiment the present invention includes a system of brackets on various teeth to form an edgewise appliance where the maximum or open BW is approximately 70% to 80% of the tooth width. Ideally, the rotating linear adjusting spreading screw shaft  130  and cooperating elements of first end ear structure  120  and second end ear structure  122  can close enough so that the closed or minimum bracket width dimension BW is approximately 2-3 mm. The slot depth dimension SD is preferably substantially larger than current slot depths. Preferably the SD is 32 mils or between 32 and 39 mils, so a larger arch wire of stainless steel (SS), TMA or NiTi can be used and still provide the necessary forces to torque the tooth about its center of rotation. It should be understood that the current SD and arch wire sizes could be used in some embodiments of the present invention. Similarly, the ear width dimension EW is preferably 1 millimeter, but a range of 1 mm to 2 mm could be helpful. Of course the current and prior art EW could be used in some embodiments of the present invention. In a preferred embodiment the slot height dimension SH is 22 mils or within a range of 22 mils to 28 mils. Of course, current and prior art SH dimensions could be utilized in some embodiments of the present invention. 
     Now referring to  FIG. 3 , there is shown an alternate embodiment of the present invention which utilizes discrete shims in a channel instead of the infinitely adjustable spreading screw and rail structures of  FIG. 1 . More particularly, there is shown a bracket with a guide channel  310  formed thereon or attached thereto. Disposed partially in guide channel  310  is first ear structure  320  which may be slid in from the end during assembly. Preferably an end cover (not shown) is attached to the end of guide channel  310  after insertion of first ear structure  320  so that first ear structure  320  cannot be accidentally separated from guide channel  310 . Also shown is an optional hook  350 . 
     First ear structure  320  is sized and configured to be translated within the guide channel  310 . Bracket tooth mounting base  302 , guide channel  310  and first ear structure  320  may be any suitable material but stainless steel may be preferred. 
     To stop first ear structure  320  from moving around within the guide channel  310 , second spacing shim  364  is used. Now referring to  FIG. 4  there is shown a bracket of  FIG. 3  where the first ear structure  320  has been moved to a central location in guide channel  310  for a closed bracket orientation, and second spacing shim  364  is shown disposed between the first ear structure  320  and the end of the guide channel  310 . Also shown in  FIG. 4  is second ear structure  322  and first spacing shim  362 . This configuration of shims and ear structures results in a closed orientation of the adjustable bracket. 
     Now referring to  FIG. 5 , there is shown an open configuration of the adjustable bracket which includes the first ear structure  320  and the second ear structure  322  separated by a third spacing shim  366 . Note that the spacing shims are preferably made of some resilient non-toxic material with sufficient resilience to allow them to be bent slightly so they can be inserted into and removed from the guide channel  310  from the top and yet provide for minimal compression in a direction parallel with the guide channel  310  so as to hold the first ear structure  320  and second ear structure  322  in a stable arrangement. It should be understood that intermediate separations and even non-centralized locations of first ear structure  320  and second ear structure  322  could be accomplished by using other sized shims or placement of the shims. For example, a configuration of an adjustable bracket could be deployed where first spacing shim  362  of  FIG. 4  is moved from its location shown in  FIG. 4  to a position between first ear structure  320  and second ear structure  322 . Many different sizes and combinations of shims could be provided to an orthodontist as kit for adjusting the width of the bracket. The shims could be coded so that the separation between the first ear structure  320  and structure  322  can be ascertained by reviewing these codes on the shims and their placement within the guide channel  310  and no measurements would be necessary. 
     In operation, the present invention comprises a method of moving teeth in a human mouth which utilized many known orthodontic methods and practices. Preferably, the method of the present invention provides for use of just one twin bracket attached to each tooth during the duration of the orthodontic treatment, which could take several months. For example, it may be preferred that the increased lever arm bracket  100  be deployed in a closed position at the beginning of treatment and as the treatment progresses the width of the various increased lever arm brackets  100  are opened up or made wider. In the alternative, if a version of the increased lever arm bracket  100  is used which is not adjustable, it is desired that the wider range of bracket dimensions mentioned above be used. It is understood that arch wire changes may be made at various points in the treatment. 
     Throughout this description, reference is made to stainless steel central male components and distal female components because it is believed that the beneficial aspects of the present invention would be most readily apparent when used in connection with such configurations, however, it should be understood that the present invention is not intended to be limited to such matter and should be hereby construed to include any suitable mating configuration and material including TMA, NiTi, ceramics, plastics, etc. Throughout this description TMA is used herein to refer to the titanium, molybdenum, zirconium, and tin alloy commonly referred to in the industry as TMA. 
     Throughout this description, reference is made to a “separating screw” this term is herein defined to mean a device which changes amount of separation of structures coupled to it depending up the rotation of a central threaded shaft with opposite threads at each end, which are coupled to female threaded members, which are coupled to objects which will not rotate but are free to translate when the central threaded shaft is rotated. This rotation of the central threaded shaft will thereby cause the female threaded members to either approach each other or separate; i.e., adjust their separation, depending upon the direction of rotation of the central threaded shaft. The term “turnbuckle” is defined herein to mean a device which is similar to the spreading screw except that the central member that is rotated is a not a threaded shaft with opposing threads on male ends, but a pair of separated female threaded members which are fixed with respect to each other and are configured to receive therein threaded male shafts. When the central female members are rotated as a unit the male members are either brought closer to one another or separated, depending upon the direction of rotation of the central female members. 
     It is thought that the method and apparatus of the present invention will be understood from the foregoing description and that it will be apparent that various changes may be made in the form, construct steps, and arrangement of the parts and steps thereof, without departing from the spirit and scope of the invention or sacrificing all of their material advantages. The form herein described is merely a preferred exemplary embodiment thereof.