Abstract:
Systems and methods for moving teeth to desired positions within a patient&#39;s mouth. A method starts with a step of installing orthodontic appliances, such as brackets, on the teeth to be involved in an orthodontic treatment Then, the gingival tissue is incised along a curve that substantially extends in parallel to the gum line of the gingival tissue at a predetermined distance. Subsequently, the incised gingival tissue is reflected to form a gingival flap and thereby to expose an alveolar bone underlying the gingival flap. A portion of the exposed alveolar bone adjacent the roots of the teeth is moved, preferably in the form of a groove. Then, the orthodontic appliances are adjusted to move the teeth and thereby to realign the teeth as intended.

Description:
FIELD OF INVENTION  
       [0001]    The present invention relates to a method of performing dental procedures, and more particularly, to a method of performing orthodontic procedures and a device for performing some of the procedures. 
       BACKGROUND OF INVENTION  
       [0002]    A fundamental objective in orthodontics is to realign a patient&#39;s teeth to positions where the teeth function optimally and aesthetically. In general, appliances, such as brackets, are applied to the teeth of the patient. The brackets have slots for receiving an archwire. The bracket-archwire interaction governs forces applied to the teeth and defines the desired direction of tooth movement. Typically, orthodontic treatments are divided into two approaches according to the direction in which the major tooth movements are made to realign the teeth. The first approach may be referred to as expansion method. In this method, the crooked and/or crowded teeth are moved facial or peripheral side of the jaw bone to make space for them.  FIG. 1  illustrates an upper arch  10  with crowded/crooked teeth  12  prior to the expansion, wherein arrows  14  show the direction of expansion.  FIG. 2  illustrates the upper arch  10   a  with straightened teeth  12   a  after expansion and a suitable orthodontic treatment using the brackets. The second approach may be referred to as retraction method. In the retraction method, one or more teeth, typically first bicuspid teeth, are removed to create more space in the jaw for the teeth that remain, wherein the remaining teeth are moved in the space to be aligned as intended.  FIG. 3  illustrates an upper arch  20  with crowded/crooked teeth  22  including the first bicuspid teeth  24 .  FIG. 4  is a schematic diagram of the upper arch  20   a  after extraction of the first bicuspid teeth  24 . Typically, a proper orthodontic treatment using the brackets may be followed to move the remaining upper anterior teeth  26  with respect to the posterior teeth  28 , thereby dosing the space  30  previously occupied by the first bicuspid teeth  24  and realigning the remaining teeth. There are other variations of these two approaches. For instance, each of the crowded teeth may be ground to provide room for them. For another instance, both approaches may be applied, i.e., the dentist may retract one or more teeth prior to the expansion of remaining teeth. 
         [0003]      FIG. 5  is a frontal view of anterior teeth  52  and brackets respectively attached, either fixedly or removably, to the teeth. As illustrated, the teeth  52  are covered partially by gingival tissue or gum  54 .  FIG. 6  is a cross section view of an upper anterior tooth  52  that includes central incisor  64 . A portion of the central incisor  64  near the root of the tooth  52  is surrounded by periodontal ligament  58 , which in turn is covered by cortical bone or plate  60 . The gingival tissue  54  also covers the outer surface of the cortical bone  60 . The root of the tooth  52  is surrounded by medullary bone  62  that supplies blood to the tooth  52 . The term alveolar bone collectively refers to a portion of the medullary bone  62  and the cortical bone  60 . The alveolar bone remodels around the tooth  52  being moved in response to pressure from one side of the tooth  52 . 
         [0004]    One of the typical orthodontic treatments is disclosed the U.S. Pat. No. 6,109,916 to Wilcko and illustrated in  FIGS. 7-10 . As illustrated in  FIG. 7 , a set of brackets  74  are attached to crooked/crowded anterior teeth  72 . The dotted lines represent portions of the teeth  72  surrounded by the cortical bone  80 . In the Wilcko &#39;916 patent, surgery is performed under intravenous sedation approximately two to seven days following activation of the brackets  74 . The surgery begins with the step of reflecting the gingival tissue or gum  76 . The gingival tissue  76  is reflected both facially and lingually around all of the teeth  72  in the dental arch by intracrevicular incision, which is an incision in the space between the teeth  72  and the gum  76 . The resulting full thickness gingival flaps, referred to as full thickness mucoperiosteal flaps,  76  and  82  are shown in  FIG. 8 . 
         [0005]    After the flaps  76  and  82  have been reflected, the exposed cortical bone or plate  80  adjacent each of the teeth  72  to be moved is partially decorticated. FIG.  9  shows that decortication takes place through the use of grooves  84  shown in the exposed facial cortical bone  80  between the roots of the teeth  72 . If there is sufficient thickness of bone, perforations  86  are also made in the cortical bone  80  overlying the roots of the teeth  72  as illustrated in  FIG. 9 . The grooves  84  and perforations  86  extend slightly into the underlying medullar bone  81 . A grafting material may be overlaid on the cortical bone  80  (nor shown in  FIG. 9 ) and thence the flapped gum  76 ,  82  are sutured as shown in  FIG. 10 . The use of either or both of groove and perforations may cause bleeding points from the cortical bone  80  and medullary bone  83  to create capillary pathways through which pluripotential cells migrate into an overlaying grating material, and thereby to trigger the regional accelerated phenomenon. 
         [0006]    One of the difficulties of the Wilcko&#39;s method is that the flapped gum  76  and  82  may not be replaced in their original positions after orthodontic treatment As depicted in  FIG. 10 , the gum line  90  recedes from its original location  92  formed on the teeth  72 , i.e., gum recession may take place upon completion of the surgery and orthodontic treatment. Hereinafter, the term gum line refers to a curve at the boundary between the gingival tissue and teeth. Another difficulty may be that the curved groove  84  is not suitable for patients who do not have sufficient alveolar bone thickness. As such, there is a strong need for alternative methods and systems for repositioning teeth without gum recession and applicable for a wide range of the alveolar bone thickness. 
       SUMMARY OF INVENTION  
       [0007]    In one aspect of the invention, a method for moving teeth to desired positions within a patient&#39;s mouth includes steps of: installing orthodontic appliances on the teeth to be involved in an orthodontic treatment; incising gingival tissue along a curve that substantially extends in parallel to the gum line of the gingival tissue at a predetermined distance; reflecting the incised gingival tissue to form at least one gingival flap and thereby to expose an alveolar bone underlying the gingival tissue; partially decorticating the exposed alveolar bone adjacent the roots of the teeth to be moved; and adjusting the orthodontic appliances to move the teeth and thereby to realign the teeth as intended. 
         [0008]    In another aspect of the invention, a retraction device for applying orthodontic forces between anterior teeth and posterior teeth that separated from the anterior teeth by at least one edentulous area in the dental arch of a patient, each of the anterior and posterior teeth having a bracket installed thereon and coupled to an archwire via the bracket, includes: an anchoring device secured to an alveolar bone of the patient; at least one hooking mechanism forming a branch of the archwire and located between two neighboring ones of the anterior teeth; and a retraction unit for coupling the anchoring device to the hooking mechanism and for applying a force therebetween. The force is directed to move the anterior teeth toward the posterior teeth across the edentulous area. 
         [0009]    In still another aspect of the invention, a retraction device for applying orthodontic forces between anterior teeth and posterior teeth that separated from the anterior teeth by at least one edentulous area in the dental arch of a patient, each of the anterior and posterior teeth having a bracket installed thereon and coupled to an archwire via the bracket, includes: an anchoring device secured to a palatal bone of the patient; at least one arm for securing at least one of the posterior teeth to the anchoring device, the arm including a first hooking mechanism; at least one second hooking mechanism forming a branch of the archwire and located between two neighboring ones of the anterior teeth; and a retraction unit for coupling the first hooking mechanism to the second hooking mechanism and for applying a force therebetween. The force is directed to move the anterior teeth toward the posterior teeth across the edentulous area. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0010]    These and other features of the invention will now be described with reference to the drawings summarized below. These drawings and the associated description are provided to illustrate preferred embodiments of the invention and are not intended to limit the scope of the invention. 
           [0011]      FIG. 1  is a schematic diagram of an upper dental arch having overlapped and crowded teeth. 
           [0012]      FIG. 2  is a schematic diagram of the upper dental arch in  FIG. 1  after realignment. 
           [0013]      FIG. 3  is a schematic diagram of an upper dental arch having overlapped and crowded teeth. 
           [0014]      FIG. 4  is a schematic diagram of the upper dental arch in  FIG. 3  after extraction of the first bicuspid. 
           [0015]      FIG. 5  is a schematic diagram of upper anterior teeth after bracketing. 
           [0016]      FIG. 6  is a cross sectional diagram of an upper anterior tooth after bracketing. 
           [0017]      FIG. 7  shows upper anterior teeth with full thickness gingival flaps reflected by use of an existing technique. 
           [0018]      FIG. 8  is a cross sectional diagram of an upper anterior tooth with full thickness gingival flaps reflected by use of the existing technique. 
           [0019]      FIG. 9  shows upper anterior teeth with full thickness gingival flaps reflected and the exposed cortical plate partially decorticated by use of the existing technique. 
           [0020]      FIG. 10  shows upper anterior teeth with gingival flaps sutured by use of the existing technique, illustrating gingival tissue recession from the original gum line. 
           [0021]      FIG. 11  shows upper anterior teeth with gingival flaps reflected in accordance with one embodiment of the present invention. 
           [0022]      FIG. 12  is a cross sectional diagram of an upper anterior tooth taken along the direction  12 - 12  in  FIG. 11 . 
           [0023]      FIG. 13  is a partial side view of a dental arch, illustrating an edentulous area where the alveolar bone is partially removed after extraction of the first bicuspid in accordance with another embodiment of the present invention. 
           [0024]      FIG. 14  is a cross sectional diagram of the edentulous area depicted in  FIG. 13 . 
           [0025]      FIG. 15  is a cross sectional diagram of the edentulous area depicted in  FIG. 13 , illustrating a plug used for preventing the gingival tissue from collapsing and for controlling bleeding problem due to the removal of buccal and lingual plates. 
           [0026]      FIG. 16  is an upper dental arch with edentulous areas and a pair of retraction devices in accordance with still another embodiment of the present invention. 
           [0027]      FIG. 17  is a partial buccal or facial side view of the upper dental arch in  FIG. 16 , illustrating the pair of retraction devices for moving the anterior teeth toward the posterior teeth. 
           [0028]      FIG. 18  is a schematic diagram of the retraction unit depicted in  FIG. 17 . 
           [0029]      FIG. 19  is an upper dental arch with edentulous areas and a pair of retraction devices in accordance with yet another embodiment of the present invention. 
           [0030]      FIG. 20  is a partial lingual side view of the upper dental arch in  FIG. 19 , illustrating the pair of retraction devices for moving the anterior teeth toward the posterior teeth. 
           [0031]      FIG. 21  is an upper dental arch with edentulous areas and an anchoring device in accordance with further another embodiment of the present invention. 
           [0032]      FIGS. 22 and 23  are enlarged views of portions of the retraction device depicted in  FIG. 21 . 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0033]    Although this invention will be described in terms of certain preferred embodiments, other embodiments that are apparent to those of ordinary skill in the art, including embodiments that do not provide all of the benefits and features set forth herein, are also within the scope of this invention. Accordingly, the scope of the invention is defined only by reference to the appended claims. 
         [0034]    Now referring to  FIG. 11 ,  FIG. 11  shows upper anterior teeth  102  with gingival flaps  104  reflected in accordance with one embodiment of the present invention. As depicted, brackets  106  are installed to realign the crowded anterior teeth  102 . The brackets  106 , or other suitable types of orthodontic appliances, may be installed on the teeth  102  to be moved to exert force on the teeth  102  toward the desired positions. The brackets  106  may be installed at anytime prior to the surgery or subsequent to it as desired by the dentists performing the surgical and orthodontic procedures. 
         [0035]    As discussed above, in the existing approach, the gingival tissue is separated from the teeth along the gum line  92  ( FIG. 10 ), which yields a recession of the gingival tissue from the gum line upon completion of the orthodontic treatment. In contrast to the existing approach, a portion of gingival tissue  112  is separated from the cortical bone or plate  118  ( FIG. 12 ) along a curve  120 , forming a gingival flap  104 . The curve  120  may extend substantially in parallel to the gum line  92  and be approximately separated from a gum line  122  by a distance d, wherein the distance d may range from 4 to 6 mm. Upon completion of the orthodontic treatment, the flap  104  is sutured (not shown in  FIG. 11 ) and thereby the original um line is maintained, i.e., the gum line does not recede from its original location. 
         [0036]    A cortical bone line  116  represents the boundary of the cortical bone or plate  118  on the tip side of the tooth  102 , wherein the distance d is determined such that the cortical bone line  116  is interposed between the curve  120  and the gum line  122 . When the flap  104  is generated to expose a portion of the cortical bone  118 , the exposed portion may be decorticated (not shown in  FIG. 11 ) in the  25  similar manner as depicted in  FIG. 9 , i.e., perforations and/or vertiavscalloped horizontal grooves may be formed to activate the cortical bone  118 . Alternatively, a groove  110  may be formed on the cortical bone  118  (or, alveolar bone) beyond the apices  108  of the teeth  102 . The depth of the groove  110  may be determined to barely extend into the medullary bone under the cortical bone  118  so that nerve tissues, such as anterior loop of the inferior alveolar nerve, is not damaged by the decortication. The perforations and/or groove(s) are formed to access vasculature and pluripotential cells in the medullary bone. It is noted that, for simplicity, only the facial side of the gingival tissue is shown. However, it should be apparent to those of ordinary skill that the same treatment can be applied to the lingual side gingival tissue  114  ( FIG. 12 ) to form another gingival flap  106 . 
         [0037]      FIG. 12  is a cross sectional diagram of an upper anterior tooth taken along the direction  12 - 12  in  FIG. 11 . As depicted, portions of the gingival tissue  104  and  106  on the facial and lingual sides, respectively, are separated from the cortical bone  118  and reflected to gain access to the bone around the teeth to be moved. The reflected gingival tissue may form flaps  104  and  106 . The bracket  106  may be installed on the either labial (or facial) or lingual side of the tooth  102 , which should be apparent to those of ordinary skill. Upon completion of the decortication (perforations and/or groove(s)), the flaps  104  and  106  may be sutured to their original locations. As the portion of the gingival tissue near the original gum line  122  is not separated from the tooth  112  ( FIG. 11 ) in the present invention, the final gum line remains the same as the original gum line, i.e., the gum line does not recede toward the root of the tooth  102  due to the surgery for the decortation process. 
         [0038]    As discussed in connection with  FIG. 4 , one or more bicuspids may be extracted to provide spaces to the remaining teeth.  FIG. 13  is a partial side view of a dental arch, illustrating an edentulous area  132 . As illustrated, the alveolar bone (which collectively refers to buccal and lingual plates or bones surrounding the teeth  130 ) adjacent the edentulous area  132  is partially removed after extraction of the first bicuspid in accordance with another embodiment of the present invention.  FIG. 14  is a cross sectional diagram of the edentulous area  132  depicted in  FIG. 13 . As depicted, a portion  133  of the alveolar bone, which includes buccal (or, equivalently, facial) and lingual plates or bones, is removed to form a socket  135 . The removal of the portion  133  may decrease bony resistance during the subsequent orthodontic treatment, i.e., the realignment of the remaining teeth, and thereby facilitate orthodontic movement. 
         [0039]      FIG. 15  is a cross sectional diagram of the edentulous area  132  depicted in  FIG. 13 , wherein a plug  136  is used for preventing the gingival tissue  134  from collapsing after extraction of the first bicuspid and for controlling bleeding due to the removal of the portion  133  of the alveolar bone (or, equivalently, buccal and lingual plates). The blood supplied into the space  138  via the medullary bone may carry cells that lead to new bone formation in the space  138 , while the plug  136  may be resolved gradually during realignment of the remaining teeth so as to obviate any resistance against the intended movement of the remaining teeth. 
         [0040]    The plug  136  may be formed of collagen material, such as Collaplug®, manufactured by Integra LifeScience Corporation, Plainsboro, N.J. The remaining teeth  130  ( FIG. 13 ) may be rearranged by use of any suitable devices, such as brackets. As such, detailed description of the orthodontic treatment for realigning the remaining teeth is not given in the present document. 
         [0041]      FIG. 16  is an upper dental arch with edentulous areas  160  and a pair of retraction devices  166  in accordance with another embodiment of the present invention. The alveolar bones adjacent the edentulous areas  160  may be removed by use of the technique described with reference to  FIGS. 13-14 , and each edentulous area  160  may be covered by a plug as depicted in  FIG. 15 . In  FIG. 16 , brackets  168  are installed on anterior teeth  162  and posterior teeth  164  to realign them. To move the anterior teeth  162  toward the posterior teeth  164 , a pair of retraction devices  166  may be used.  FIG. 17  is a partial buccal or facial side view of the upper dental arch in  FIG. 16 , illustrating the retraction device  166 .  FIG. 18  is a schematic diagram of a retraction unit  177  included in the retraction device in  FIG. 17 . As depicted, the retraction device  166  may include: an orthodontic microimplant screw  170 , such as micro-screw manufactured by Dentaurum, Inc, Newton, Pa., installed in the alveolar bone through the gingival tissue and operating as an anchorage device; a pair of rings  176 ; and an elastic member, such as coil spring,  178  having two ends attached to the pair of rings  176 ; and a hooking mechanism  174  branched from the archwire  172 . As depicted in  FIG. 18 , the retractive unit  177  includes the pair of rings  176  and elastic member  178 . The length of the elastic member  178  may be determined to provide a predetermined retractive force between the ring members  176  during orthodontic treatment. It is noted that, in many retraction cases, the remaining teeth may be expanded as well. But, for simplicity, the detailed description of orthodontic realignment process of the remaining teeth  162  and  164  are not given in the present document. 
         [0042]      FIG. 19  is an upper dental arch with edentulous areas  196  and a pair of retraction devices  194  in accordance with still another embodiment of the present invention. As depicted, the brackets  192  and the pair of retraction devices  194  are installed on the lingual side.  FIG. 20  is a partial lingual side view of the upper dental arch in  FIG. 19 , illustrating the pair of retraction devices  194  for moving the anterior teeth toward the posterior teeth. The structure and functions of the devices  194  are similar to those of the device  166  in  FIG. 17 . For instance, a microimplant screw  191  may be used as an anchoring device. It is noted that the alveolar bones adjacent the edentulous areas  196  may be removed and each edentulous area may be covered by a plug as described in connection with  FIGS. 13-15 . 
         [0043]      FIG. 21  is an upper dental arch with edentulous areas  202  and a retraction device  210  in accordance with further another embodiment of the present invention. The retraction device  210  may include: a orthodontic microimplant screw  212  mounted on a palatal bone (not shown in  FIG. 21 ) and operating as an anchoring device; and a pair of arms  214  for connecting the screw  212  to the brackets  204  installed on the first molars  206 , each arm containing a hooking mechanism  222  ( FIG. 22 ); a pair of retraction unit  177  ( FIG. 18 ) coupled to hooking mechanisms  222  and a branch  224  ( FIG. 23 ) of the archwire  226 . The alveolar bone adjacent the edentulous areas  202  may be removed and a plug may be used for each edentulous area  202  as illustrated in connection with  FIGS. 13-15 . 
         [0044]      FIGS. 22 and 23  are respectively enlarged views of portions  220  and  250  in  FIG. 21 . As depicted in  FIG. 22 , each arm  214  may include a hooking mechanism  222  that are coupled to the retraction unit  177 . Likewise, the branch  224  of the archwire  226  may be coupled to the retraction unit  177  as depicted in  FIG. 23 . It is noted that several variations of the hooking mechanism can be used without deviation from the spirit of the present invention. For example, an elastic member may be used in place of the retraction unit  177 . 
         [0045]    Those skilled in the art will appreciate that the methods and designs described above have additional applications and that the relevant applications are not limited to those specifically recited above. Also, the present invention may be embodied in other specific forms without departing from the essential characteristics as described herein. The embodiments described above are to be considered in all respects as illustrative only and not restrictive in any manner.