Abstract:
Orthodontic devices including brackets for being attached to a tooth and each having particularly designed slots formed therein for receiving particularly shaped wire arches for avoiding loss of torque.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     It is known that orthodontics deal with the diagnosis, prevention and treatment of the morphological and functional malformation of teeth. One task of orthodontics is to move teeth by applying mechanical forces, using orthodontic appliances, in the in the bones of the maxilla and/or mandible. Movable appliances and fixed appliances, i.e., so-called multi-band devices, are both known for the purpose. The basic components, or attachments, of these fixed, multi-band devices are so-called attachments and include bands, brackets, arches, ligatures, elastics and springs, known, as follows: 
        a. Bands: usually consist of preformed, generally 0.1 millimeter (mm) thick metal rings made of stainless, nickle-chromium steel, and having a lock either soldered or welded from the outside and adapted to be cemented on the molar teeth.     b. Brackets: usually consist of stainless, nickel-chromium steel, but can also be made of plastics and ceramics. Numerous bracket designs are available, usually with an 0.018″ wide slot, or with an 0.02″ wide slot. Principally, it is reasonable to differentiate between “edgewise” brackets and “Begg” brackets. The “Begg” bracket features a narrow mesiodistal slot in which the exclusively used round arch, i.e., of round wire, lies loosely secured by a pin. “Edgewise” brackets feature a slot with rectangular cross-section which has its wider extension in the horizontal plane. The bracket may be embodied as a single bracket or as a twin bracket. Round wire arches or square wire arches may be used. Standardized brackets and programmed edgewise brackets are available. In standard edgewise brackets, the slot is always embodied centrally and at a fixed distance to the bracket base, and information about movement must be incorporated in the arch. The slot position and its distance to the bracket base of programmed edgewise brackets is different for each tooth, and information is incorporated in the bracket.     c. Arch: is the wire which runs through the bracket slot. The arch may be made of stainless steel, or special alloys, and is available in different cross-sections, types and dimensions.     d. Ligatures: are devices that are available as wire or elastic ligatures. These are used to fix the arch in the brackets.     e. Elastics: are rubber rings of different size and thickness. The rubber rings may be suspended either intramaxillary, i.e., between teeth of one and the same jawbone, or intermaxillary, i.e., between teeth of maxilla and mandible.        
 
         [0007]     In the course of further progress in the dental field brought about by the use of composite materials, the brackets were no longer welded on the bands but now may be glued directly on the tooth surface with composite cement. The rigidly cemented brackets provide for a point of application of force in the region of the crown of the tooth, which ensures that the intentional tooth movement by means of continuous or segmented, round and/or square arches of different diameters, wire quality and auxiliary means, is executed until the desired tooth position is achieved. Prior to its insertion into the bracket, the elastic wire arch is bent and/or twisted, which produces in the wire arch a restoring force which acts on the corresponding tooth and shifts, turns and inclines it in any desired direction, depending on the type of wire arch and positioning of the bracket slot.  
         [0008]     Conventional orthodontics brackets and wire arches do not provide for a 100% fill-out of the bracket slots; as a result, the wire arches may twist in the bracket slots causing a loss in torque, usually referred to as the so-called “torque play.” Torque is a force momentum about a neutral axis, in the present environment a movement of the root of a tooth, with a center of resistance in the upper third of the root of the tooth, about a point of rotation in the region of the crown of the tooth. Information about the torque is programmed into the base of each bracket, or by the tilt in the bracket slots. Different torque values are required for different teeth; depending upon the system; they are in the order between +22° and −30°.  
         [0009]     Because of the torque loss and/or torque play, a great part of information about the torque. i.e., nominal torque, embodied in the brackets is lost, and the result is a difference between nominal and effective torques. The torque loss/torque play renders ineffective part of the torque incorporated in the bracket. The effective torque of conventional brackets is calculated according to the following formulae:
 
 T   eff   =T−Φ 
 
Φ=arc cos( h− 2 R )/ D− arc cos( B− 2 R )/ D 
 
 D= ( b− 2 R ) 2 +( h− 2 R ) 2  
 
 where T eff =effective torque, T=nominal torque; Φ=theoretical torque play; 
        h=height of square wire; b=width of square wire; B=slot width;     R=radius of edge rounding; D=diagonal measure minus edge rounding;     (angles in degrees, distances in millimeters)        
 
         [0014]     In the prior art, the use of a wire arch which fills the bracket slot almost completely and thus would have a low torque loss and/or torque play is impossible, firstly, because of the strong forces which cause resorption of the root of the tooth and, secondly, because of teeth which are still rotated and tilted. Complete alloying of the wire arch in the bracket slot would be impossible in this phase.  
       SUMMARY OF THE INVENTION  
       [0015]     The invention provides for a solution to the problem of torque loss/torque play.  
         [0016]     It is an object of the invention to reduce the torque loss/torque play to zero even for the use of wire arches which do not fill the slot in the bracket. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]      FIG. 1A  shows the root and crown of a tooth having a bracket affixed to the crown.  
         [0018]      FIG. 1B  shows an enlarged profile of the bracket of  FIG. 1A .  
         [0019]      FIG. 2A  shows the root and crown of a tooth having a modified bracket affixed to the crown.  
         [0020]      FIG. 2B  shows an enlarged profile of the modified bracket of  FIG. 2A .  
         [0021]      FIG. 3  is a fragmentary, perspective view showing a pentagon-shaped, vertical cross-section of a first wire arch.  
         [0022]      FIG. 4  is a fragmentary, perspective view showing a pentagon-shaped, vertical cross-section of a second wire arch.  
         [0023]      FIGS. 5A through 5F , inclusive, show templates typical of brackets having slots 0.028″ in height, and arches with differing dimensions disposed within the slots.  
         [0024]      FIGS. 6A through 6D , inclusive, show templates typical of brackets having slots 0.025″ in height, and arches with differing dimensions disposed within the slots. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0025]     Referring to the drawings in detail,  FIG. 1A  illustrates a tooth, generally indicated by the numeral  10 , having a root  12  and a crown  14 . A bracket  16  is shown as being affixed to the crown  14  such as with composite cement, not shown.  
         [0026]      FIG. 1B  shows an enlarged profile of bracket  16  as including a bracket base  18 , bracket wings  20  and  22  and a bracket slot  24  opening outwardly at the side of the bracket  16  opposite from the base  18 . Slot  24  includes a straight, generally horizontal side  26 , a straight, generally vertical side  28 , a straight, upper horizontal side  30  which is spaced from vertical side  28  by a canted side  32  that is slanted 45° forming a top angle at the inner portion of the slot  24  toward the base  18  facing the tooth  10 .  
         [0027]      FIG. 2A  illustrates a tooth, generally indicated by the numeral  40 , having a root  42  and a crown  44 . A bracket  46  is shown as being affixed to the crown  44  such as with composite cement, not shown.  
         [0028]      FIG. 2B  shows an enlarged profile of bracket  46  as including a bracket base  48 , bracket wings  50  and  52  and a bracket slot  54  opening outwardly at the side of the bracket  46  opposite from the base  48 . Slot  54  includes a straight, generally horizontal, top side  56 , a straight, generally vertical side  58 , a straight, lower horizontal side  60  which is spaced from vertical side  58  by a canted side  62  that is slanted 45° forming a bottom angle at the inner portion of the slot  54  toward the base  48  facing the tooth  40 .  
         [0029]      FIG. 3  shows a fragmentary, perspective view of a lateral cross-section of a first form of wire arch  70  having a bottom edge  72  extending the width of the arch  70 , a top edge  74 , a first vertical edge  76  extending the height of the arch  70 , a short vertical edge  78 , and a canted edge  80  which is slanted at 45° between edges  74  and  78 . The resulting cross-section of wire arch  70  forms an irregular pentagon. It is readily seen that wire arch  70  is to be used in combination with bracket  16  as shown in  FIGS. 1A and 1B .  
         [0030]      FIG. 4  shows a fragmentary, perspective view of a lateral cross-section of a second form of wire arch  82  having a top edge  84  extending the width of the arch  82 , a bottom edge  86 , a first vertical edge  88  extending the height of the arch  82 , a short vertical edge  90 , and a canted edge  92  which is slanted at 45° between edges  86  and  90 . The resulting cross-section of wire arch  82  forms an irregular pentagon. It is readily seen that wire arch  82  is to be used in combination with bracket  46  as shown in  FIGS. 2A and 2B .  
         [0031]      FIGS. 5A through 5F  show a series of identical templates T, representing typical brackets, each having a slot generally indicated by the letter S and having a typical height of 0.022″ and a typical width of 0.028″ for cooperation with a wire arch having a circular cross-section or a pentagon shape typical of arch  70 , as is shown in  FIG. 3 .  FIG. 5A  shows a circular wire arch  101  having a diameter of 0.016″.  FIG. 5B  shows a pentagon shaped wire arch  102  having a height of 0.016″ and a width of 0.022″.  FIG. 5C  shows a pentagon shaped wire arch  103  having a height of 0.019″ and a width of 0.025″.  FIG. 5D  shows a pentagon shaped wire arch  104  having a height of 0.016″ and a width of 0.016″.  FIG. 5E  shows a pentagon shaped wire arch  105  having a height of 0.017″ and a width of 0.025″.  FIG. 5F  shows a pentagon shaped wire arch  106  having a height of 0.021″ and a width of 0.025″.  
         [0032]     Likewise,  FIGS. 6A through 6D  show a series of templates P, representing typical brackets, each having a slot X having a typical height of 0.018″ and a typical width of 0.025″ for cooperation with a wire arch having a circular cross-section or a pentagon shape typical of arch  70  as is shown in  FIG. 3 .  FIG. 6A  shows a circular wire arch  110  having a diameter of 0.012″.  FIG. 6B  shows a pentagon shaped wire arch  112  having a height of 0.016″ and a width of 0.022″.  FIG. 6C  shows a pentagon shaped wire arch  114  having a height of 0.016″ and a width of 0.016″.  FIG. 6D  shows a pentagon shaped wire arch  116  having a height of 0.017″ and a width of 0.025″.  
         [0033]     It will be understood by those of ordinary skill in this art that brackets as shown in  FIGS. 2A and 2B  are to be used with pentagon shaped wire arches as shown in  FIG. 4  in a manner as described above with respect to  FIGS. 5 and 6 .  
         [0034]     From the foregoing description, it will be apparent to those skilled in the art that various forms of the invention minimize or eliminate loss of torque with respect to the improved orthodontic devices, and it is to be understood that the devices, as disclosed, are representative of the inventive features which are set out in the appended claimed subject matter.