Abstract:
A set of orthodontic brackets is constructed according to preferred parameters of a Deviation Index in order to provide an orthodontic brace that facilitates movement of teeth to ideal positions. The brace also helps eliminate the need to manually bend the archwire during the final stages of treatment such that chair time is reduced.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     This invention broadly relates to a brace used in orthodontic treatment for correcting malocclusions. More particularly, the present invention relates to an orthodontic brace that includes a set of brackets having certain dimensional characteristics that are coordinated with one another to move the patient&#39;s teeth to optimal positions without the need for bending an archwire.  
         [0003]     2. Description of the Related Art  
         [0004]     Orthodontic treatment is often recommended for dental patients having teeth that are improperly positioned. Orthodontic treatment can greatly improve the aesthetic appearance of the patient, especially in regions near the front of the oral cavity. Orthodontic treatment can also enhance the function of the teeth by enabling opposing teeth to better interact with each other during mastication.  
         [0005]     One type of common orthodontic treatment involves the use of a set of tiny appliances commonly known as brackets. Each of the brackets is secured to a corresponding tooth and has a slot to receive a resilient archwire. The slot forms a track to guide movement of the teeth to desired positions. Ends of the archwire are commonly placed in slots or channels of buccal tube appliances that are mounted on the patient&#39;s molar teeth. Molar teeth have relatively large roots and consequently provide good anchorage for various forces that may be exerted on the dental arch during orthodontic treatment.  
         [0006]     In the past, orthodontic treatment was often carried out by forming bends, twists and loops in the archwire as needed for each tooth. The practitioner would then rely on the inherent resiliency of the archwire to urge the teeth to desired locations and proper angular orientations. However, the practice of custom-forming an archwire according to the particular malocclusion of the patient represents a significant expenditure of the practitioner&#39;s time. Moreover, considerable skill is needed to bend an archwire to an exact configuration sufficient to guide the teeth to desired positions.  
         [0007]     In more recent times, the use of pre-adjusted orthodontic appliances has enjoyed widespread popularity. Pre-adjusted appliances are constructed with archwire slots or passages that extend at a certain, pre-selected orientation relative to the base of the appliance. This orientation varies from tooth to tooth, and is selected to help ensure that each tooth is in the desired orientation when the archwire slots or passages of all of the appliances extend in a common plane that is parallel to the occlusal plane at the conclusion of treatment. As a result, fewer custom-made bends are needed to be placed in the archwire by the practitioner.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention relates to an orthodontic brace that comprises a set of brackets constructed for optimizing the positions of the teeth at the conclusion of treatment. The dimensional characteristics of the brackets are, in particular, the “in-out” dimensions of the brackets are selected to help move the patient&#39;s teeth toward optimal positions and eliminate the need for placing custom bends, twists or loops in the archwire. As a result, the present invention provides a significant savings of time for both the practitioner and the patient.  
         [0009]     In more detail, the present invention in one aspect relates to an orthodontic brace for a dental arch comprising a set of brackets. The set includes a lateral anterior bracket, a cuspid bracket and a first bicuspid bracket. Each of the brackets of the set has an archwire slot for receiving an archwire. The Deviation Index for the set of brackets is in the range of about 2 mm 2  to about 10 mm 2 .  
         [0010]     Another aspect of the invention is directed toward an orthodontic brace for an upper dental arch that comprises a set of brackets. The set includes an upper lateral anterior bracket, an upper first cuspid bracket and an upper first bicuspid bracket. Each of the brackets of the set has an archwire slot for receiving an archwire. The Deviation Index for the set of brackets is in the range of about 1 mm 2  to about 10 mm 2 .  
         [0011]     These and other aspects of the invention will be described in the paragraphs that follow and are illustrated in the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a front elevational view of an exemplary upper and lower dental arch of a patient undergoing orthodontic treatment with an upper and lower brace of the present invention;  
         [0013]      FIG. 2  is a top view of the lower dental arch and lower brace illustrated in  FIG. 1 ;  
         [0014]      FIG. 3  is an enlarged side elevational view of an exemplary orthodontic bracket of the upper brace shown in  FIG. 1 ;  
         [0015]      FIG. 4  is a diagram showing an outline of the teeth of the upper dental arch depicted in  FIG. 1  along with an embrasure line and the path of an archwire of the brace;  
         [0016]      FIG. 5  is a graph depicting the distance relationship between the bottom of the archwire slot and the embrasure line for the brackets of the lower arch brace depicted in  FIG. 1  as well as for the brackets of lower arch braces previously known in the art;  
         [0017]      FIG. 6  is a graph somewhat similar to  FIG. 5  except that the brackets are for an upper brace for an upper dental arch;  
         [0018]      FIG. 7  is a graph depicting the Deviation Index for an upper dental arch brace of the present invention as well as for various upper arch dental braces known in the art; and  
         [0019]      FIG. 8  is a view somewhat similar to  FIG. 7  except that the braces are for a lower dental arch. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]      FIG. 1  illustrates an example of an oral cavity of an orthodontic patient who is undergoing orthodontic therapy. The patient has an upper orthodontic brace  20  that is connected to the teeth of the patient&#39;s upper dental arch  22  and a lower orthodontic brace  24  that is connected to the teeth of the patient&#39;s lower dental arch  26 . Each brace  20 ,  24  includes a set of orthodontic appliances along with an archwire  27  that is received in slots of the appliances, as will be described in more detail below.  
         [0021]      FIG. 2  is an enlarged view of the lower dental arch  26  along with the lower brace  24 , looking in an downwardly direction toward the outer or occlusal tips of the patient&#39;s teeth. The lower dental arch  26  includes a left dental quadrant  28  and a right dental quadrant  30 . Each of the quadrants  28 ,  30  includes a lower central anterior tooth  32 , a lower lateral anterior tooth  34 , a cuspid tooth  36 , a lower first bicuspid tooth  38  and a lower second bicuspid tooth  40 . In addition, each of the quadrants  28 ,  30  includes a first molar tooth  42  and a second molar tooth  44 .  
         [0022]     The illustration of the lower dental arch  26  shown in  FIGS. 1 and 2  is only one example of dentition, and many variations are possible. For example, the patient may lack one or more of the illustrated teeth, as may occur in adolescent patients when some of the permanent teeth have not yet erupted. Alternatively, one or more teeth may have been removed prior to orthodontic treatment in order to reduce crowding, especially in instances where the overall size of the dental arch is relatively small. Moreover, the lower dental arch  26  may include third molar teeth, also known as wisdom teeth which are not illustrated in the drawings.  
         [0023]     The lower brace  24  includes a set of appliances connected to the teeth of the lower quadrants  28 ,  30 . In particular, the lower brace  24  in each of the quadrants  28 ,  30  includes a lower central bracket  46  that is connected to the lower central tooth  32 , and a lower bracket  48  that is connected to the lower lateral tooth  34 , a lower cuspid bracket  50  that is connected to the lower cuspid tooth  36 , a lower first bicuspid bracket  52  that is connected to the lower first bicuspid tooth  38  and a lower second bicuspid bracket  54  that is connected to the lower second bicuspid tooth  40 . In this example, the lower brace  24  also includes in each of the quadrants  28 ,  30  a lower first molar buccal tube  56  that is connected to the lower first molar tooth  42  and a lower second molar buccal tube  58  that is connected to the lower second molar tooth  44 .  
         [0024]     Optionally, one or more of the brackets or buccal tubes described above may be omitted in accordance with the preferences of the orthodontist. For example, if the second molar teeth  44  have not yet fully erupted, the practitioner may elect to omit the buccal tubes  58 , at least during the early stages of treatment. Optionally, the first molar buccal tubes  56  may be of the “convertible” types that have a cap that can be removed during the course of treatment in order to convert the buccal tube to a bracket.  
         [0025]     The archwire  27  of the lower brace  24  is made of a resilient material. Suitable materials include, for example, metallic materials such as alloys of nitinol and stainless steel. The archwire  27  has a generally overall “U”-shaped configuration and extends along both of the quadrants  28 ,  30 . The archwire  27  is received in slots of the brackets  46 ,  48 ,  50 ,  52  and  54  and in passages of the buccal tubes  56 ,  58 .  
         [0026]     An exemplary orthodontic bracket  80  is shown in  FIG. 3  in side elevational view. In this instance, the bracket  80  is intended for mounting on the enamel surface of an upper central incisor tooth. The bracket  80  includes a base  82  for bonding the bracket  80  directly to the patient&#39;s tooth enamel by use of an adhesive. A body  84  of the bracket  80  extends outwardly from the base  82  in a generally buccolabial direction. The body  84  in this embodiment includes a spaced-apart pair of gingival tiewings  86  and a spaced-apart pair of occlusal tiewings  88 . An archwire slot  90  extends across the body  84  in a generally mesial-distal direction and along the space presented between the gingival tiewings  86  and the occlusal tiewings  88 .  
         [0027]     In this example, the bracket  80  is a self-ligating bracket having a latch  92  for releasably retaining an archwire in the archwire slot  90 . The latch  92  includes a distal clip  94  as well as a mesial clip that is not shown in the drawings. The distal clip  94  has an overall, generally “C”-shaped configuration and is held in place by a support  96  that extends outwardly from the body  84  in a distal direction.  
         [0028]     Further details regarding the exemplary bracket  80  including the latch  92  as well as other aspects are set out in pending U.S. patent application Ser. No. 11/050,615, filed Feb. 2, 2005 and entitled “PRE-TORQUED ORTHODONTIC APPLIANCE WITH ARCHWIRE RETAINING LATCH”. However, other brackets are also possible. For example, the bracket  80  may be replaced by a bracket that is not self-ligating. As yet another option, the bracket may be made of metal (such as alloys of stainless steel or other metallic materials), ceramic materials (including monocrystalline and polycrystalline light-transmitting ceramics) and polymeric materials (such as fiber-reinforced polycarbonate).  
         [0029]     In  FIG. 3 , the in-out dimension of the bracket  80  is designated by the notation “I/O”. The in-out dimension is the distance between the bottom or lingual side of the archwire slot  90  and the exterior surface of the base  82 , measured along a reference axis that is perpendicular to the bottom of the archwire slot  90  and passes through the mesial-distal and occlusal-gingival center of the archwire slot  90 .  
         [0030]      FIG. 4  is a diagram showing an outline of the teeth of the upper dental arch  22 , along with a first curve representing an embrasure line and a second curve representing the path of a lingual side of the upper archwire  27 . The embrasure line is designated by the letter “e” in  FIG. 4  for the exemplary upper dental arch  22 . The embrasure line is an imaginary curve, located at the level of the tooth crown&#39;s midtransverse plane that connects the most facial portions of the contact areas of all of the tooth crowns in the upper dental arch  22  when the teeth are in desired orientations.  
         [0031]     The letter “a” in  FIG. 4  represents the path of the lingual side of the archwire such as archwire  27 . The archwire path “a” illustrates the configuration of the lingual side of the archwire when the teeth are in their ideal or finished positions and when the lingual side of the archwire is seated against the bottom or lingual wall of the archwire slot, such as archwire slot  90 .  
         [0032]      FIG. 4   a  is an enlarged view of a portion of  FIG. 4 , depicting the relationship between the archwire path “a”, the embrasure line “e”, the in-out dimension I/O and the crown prominence (“CP”) for one of the upper teeth. The in-out dimension, or I/O, is described above. The crown prominence “CP” is the distance in a buccolabial direction from the embrasure line “e” to each crown&#39;s most prominent facial point.  
         [0033]     Preferably, each of the brackets of the upper and lower braces  20 ,  24  is pre-adjusted for torque and angulation. Tooth angulation may be defined according to the teachings of Dr. Lawrence F. Andrews as the mesiodistal cant of the facial axis of the clinical crown (“FACC”) relative to a line perpendicular to the occlusal plane (see, e.g.,  Straight Wire, The Concept and Appliance , by Lawrence F. Andrews, (L. A. Wells Co., ©1989)). Bracket angulation may be defined as the particular angular orientation of the archwire slot of the bracket relative to the base of the bracket in order to provide tooth angulation.  
         [0034]     Tooth torque may be defined as the buccolabial-lingual cant of the FACC when measured from a line perpendicular to the occlusal plane. Consequently, bracket torque may be defined as the orientation of the archwire slot relative to the base of the bracket such that the desired tooth torque is attained.  
         [0035]     Table I sets out the crown prominence “CP” as determined by Dr. Andrews for teeth of the upper or maxillary arch along with preferred values according to the present invention for in/out, torque and angulation. Table II is a table similar to Table I except that Table II is directed to the lower or mandibular arch.  
                                                                                   TABLE I                           Maxillary Arch                            1 st     2 nd     1 st     2 nd             Central   Lateral   Cuspid   Bicuspid   Bicuspid   Molar   Molar                        Andrews   2.1   1.65   2.5   2.4   2.5   2.9   2.9       Crown       Prominence,       mm       torque,   17   10   −7, +7 or 0   −7   −7   −14   −14       degrees       angulation,   4   8   8   0   0   0   0       degrees                  
 
         [0036]    
       
         
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE II 
               
             
             
               
                   
               
               
                   
               
               
                 Mandibular Arch 
               
             
          
           
               
                   
                   
                   
                   
                 1 st   
                 2 nd   
                 1 st   
                 2 nd   
               
               
                   
                 Central 
                 Lateral 
                 Cuspid 
                 Bicuspid 
                 Bicuspid 
                 Molar 
                 Molar 
               
               
                   
                   
               
             
          
           
               
                 Andrews 
                 1.2 
                 1.2 
                 1.9 
                 2.35 
                 2.35 
                 2.5 
                 2.5 
               
               
                 Crown 
               
               
                 Prominence, 
               
               
                 mm 
               
               
                 torque, 
                 −6 
                 −6 
                 −6, +6 or 0 
                 −12 
                 −17 
                 −20 
                 −10 
               
               
                 degrees 
               
               
                 angulation, 
                 0 
                 0 
                 3 
                 2 
                 2 
                 0 
                 0 
               
               
                 degrees 
               
               
                   
               
             
          
         
       
     
         [0037]      FIG. 5  is a graph depicting the relationship of the distance between the bottom of the archwire slot and the embrasure line (“S/E”) for the brackets of the brace  24  for the patient&#39;s lower arch  26 . In  FIG. 5 , this relationship for the present invention is designated by the graph identified by the letter “M”. In  FIG. 5 , the designation “L Ant  1 ” refers to the lower central anterior bracket, “L Ant  2 ” refers to the lower lateral anterior bracket, “L Cusp” refers to the lower cuspid bracket, “L Bi  1 ” refers to the lower first bicuspid bracket, and “L Bi  2 ” refers to the lower second bicuspid bracket. For each bracket, the values are identical for the left and right quadrants.  
         [0038]      FIG. 5  also shows the S/E distance for this relationship for several brackets systems known in the art including Victory Series brand bracket systems (“V”) and Clarity brand bracket system (“C”), both from 3M Unitek Corporation.  FIG. 5  also shows the S/E distance for the Damon 3 brand bracket system (“D”) from Ormco Corporation, In-ovation R brand bracket system (“IOR”) from GAC International, Inc., Speed brand bracket system (“S”) from Strite Industries, Inspire Ice brand bracket system (“I”) from Ormco Corporation, Mystic brand bracket systems (“MY”) from GAC International, Inc., and InVu brand bracket systems (“IV”) from TP Orthodontics, Inc. In connection with the latter bracket systems, sample brackets were measured to determine the I/O for calculation of S/E values.  
         [0039]     For purposes of comparison, the values for S/E as proposed by Dr. Andrews are identified in  FIG. 5  by the graph designated with the letter “A”. Additionally, the values for crown prominence as proposed by Dr. Andrews are designated by the graph identified “AC” in  FIG. 5 . Importantly, the distance from the bottom of the archwire slot to the embrasure line S/E) is greater for the lower lateral anterior bracket than the lower cuspid bracket. The S/E value for the lower lateral anterior bracket is preferably greater than 0.1 mm, and more preferably is greater than 0.15 mm, than the S/E value for the lower cuspid bracket. This is in contrast to many known bracket systems wherein the S/E value for the lower lateral anterior bracket is less than the S/E value for the lower cuspid bracket.  
         [0040]     Additionally, the S/E value for the lower first bicuspid bracket is preferably less than the S/E value for the lower second bicuspid bracket. The S/E value for the lower first bicuspid bracket is preferably about 0.15 mm less than the S/E value for the lower second bicuspid bracket.  
         [0041]     Preferably, the in-out dimension or “I/O”, for the lateral anterior bracket is greater than the I/O value for the cuspid bracket. Preferably, the I/O value for the lateral anterior bracket is at least 0.9 mm greater than the I/O value for the lower cuspid bracket.  
         [0042]      FIG. 6  is a graph somewhat similar to  FIG. 5  except that the values are provided for an upper brace of the present invention as well as, for comparative purposes, upper braces of known bracket systems. The designations used in  FIG. 6  are the same as the designations used in  FIG. 5  in addition.  
         [0043]     As shown in  FIG. 6 , the difference in the S/E values for the upper lateral bracket and the upper cuspid bracket of the brace of the present invention is significantly different than the difference of the S/E values for the upper lateral bracket and upper cuspid brackets of known bracket system known in the art. The S/E value for the upper lateral bracket is preferably less than about 0.35 mm, more preferably less than about 0.2 mm and most preferably less than about 0.1 mm than the S/E value for the upper cuspid bracket.  
         [0044]     In addition, the S/E value for the upper lateral anterior bracket of the present invention is less than the S/E value for the upper central anterior bracket of the present invention. The S/E value for the upper cuspid bracket is greater than the S/E value for the lateral anterior bracket. In instances where the brace includes an upper second bicuspid bracket, the S/E value for the upper second bicuspid bracket is equal to or greater than the S/E value for the upper first bicuspid bracket.  
         [0045]      FIG. 7  is a graph depicting the Deviation Index for an upper dental arch brace of the present invention as well as the Deviation Index for various upper arch dental braces known in the art. The Deviation Index “D” is created to evaluate the degree of deviation from a “straight” archwire as follows:  
         D     2   -   4       =     100   ⁢       ∑     i   =   2     4     ⁢       (       c   i     -     c   avg       )     2               
 where c i  is the S/E distance that is equal to the crown prominence (CP, as determined by Dr. Andrews as set out above) plus the in/out (S/E, or slot to crown prominence) for i tooth (2=lateral, 3=cuspid, 4=first bicuspid) and c avg  is the average. 
 
         [0046]     As shown in  FIG. 7 , the Deviation Index for an upper dental arch brace of the present invention is about 6.2 mm 2 . Preferably, the Deviation Index for the upper dental arch brace is in the range of about 2 mm 2  to about 10 mm 2 , and more preferably is in the range of about 3 mm 2  to about 9 mm 2 , and most preferably is in the range of about 4 mm 2  to about 8 mm 2 .  
         [0047]      FIG. 8  is a graph depicting the Deviation Index for a lower dental arch brace of the present invention as well as the Deviation Index for various lower arch dental braces known in the art. However, for the lower dental arch, the S/E distance for the bracket of the lower cuspid tooth should be about 0.2 mm less than the S/E distance of the lower lateral bracket for the lower lateral tooth. Consequently, in order to calculate the Deviation Index for the lower dental arch, the S/E distance for the lower cuspid bracket is c 3 =c 3,actual +0.2 where c 3,actual  is the actual S/E value.  
         [0048]     As illustrated in  FIG. 8 , the Deviation Index for the lower dental arch brace of the present invention is about 5.8 mm 2 , in contrast to the significantly higher deviation indices of the lower dental arch braces currently known in the art. Preferably, the Deviation Index for the lower arch dental brace is in the range of about 2 mm 2  to about 10 mm 2 , more preferably is in the range of about 3 mm 2  to about 9 mm 2 , and most preferably is in the range of about 4 mm 2  to about 8 mm 2 .  
         [0049]     The bracket sets of the present invention provide a significant improvement over sets of brackets previously known in the art. For example, in connection with the bracket sets proposed by Dr. Andrews, many practitioners believe that the anterior brackets are too “thick”, i.e. have excessive in-out dimensions which lead to patient discomfort and sometimes interfere with the brackets mounted on opposing teeth. However, commercially available brackets are often considered not entirely satisfactory because the final tooth positions are less than ideal. Often, for example, the final position of the cuspid tooth is observed to be out of ideal alignment with adjacent teeth. By contrast, however, the bracket sets of the present invention help ensure that the final position of the cuspid tooth is more satisfactory, while patient discomfort and bracket interference are avoided. Moreover, the bracket sets of the present invention have sufficient thickness in an in-out direction to help avoid fracture during manufacture and use, even when relatively brittle materials such as ceramic materials are employed.  
         [0050]     In some instances, the practitioner may prefer to extract the first bicuspid teeth. In these instances, the second bicuspid teeth shall be considered as first bicuspid teeth, and the values set out above and in the following claims relating to the Deviation Index, the S/E values and the in-out dimensions of brackets for the first bicuspid tooth shall be interpreted to mean values for brackets for the second bicuspid teeth.