Abstract:
An orthodontic bone anchor includes a bone plate, a narrow extension extending from one end of the bone plate, a cap enveloping the extension, and a pair of arms extending outwardly from the cap.

Description:
[0001]     The benefits under 35 U.S.C. 119 are claimed of U.S. provisional patent application 60/534,467 filed Jan. 6, 2004. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     In orthodontics, one type of malocclusion is encountered in which an anterior openbite is caused by occlusal contacts only occurring posteriorly. The standard method to correct this kind of malocclusion is with surgical intervention whereby a wedge of bone is removed from the maxilla apical to the maxillary root tips. After removal of the wedge of bone, autorotation of the mandible will occur thereby correcting the anterior openbite. It is the intent of this invention to eliminate this surgical procedure and provide a device which selectively intrudes the posterior teeth of both the maxilla and mandible and thereby facilitates the closure of anterior openbite malocclusions by autorotation.  
         [0003]     Umemori et al, (Am J Orthod Dentofacial Orthop, 115:166, 1999), in 1999, first described a bone anchor system to intrude posterior teeth and facilitate correction of an anterior openbite without surgery. Several years later, Sherwood, in 2002, (Sherwood, K H et al., Am J Orthod Dentofacial Orthop, 122:593, 2002) and 2003, (Sherwood, KH et al., (Angle Orthod, 73:597, 2003), described similar mechanisms to facilitate anterior rotation and closure of an anterior openbite. Additional descriptions of similar approaches were described by Erverdi, (Erverdi, N et al., World J. Orthod, 3:147, 2002) in 2002 and by Miyawaki, S et al., (Am J Orthod Dentofacial Orthop, 124:84, 2002) in 2003. An overall review of orthodontic anchorage in general, including specific references to bone plates, was completed by Favero, (Favero, L et al., Am J Orthod Dentofacial Orthop 122:84, 2002) in 2002.  
         [0004]     In all of these systems, the bone plate has an extension into the vestibule from which materials or springs are attached to facilitate intrusion of the posterior teeth. The disadvantage to all of the previous methods is that the point of force application cannot be changed during treatment nor can the bone anchor be modified or adjusted prior to insertion or during treatment. A change in the location of force application to the dentition is often required and without a corresponding change on the anchor a different and generally undesirable change in the vector of this force occurs. This change in vector can limit the extent of correction of anterior openbites. If the centroid of the maxillary arch varies from the point of force application, a moment occurs and the resultant rotation around the centroid could actually open the bite thus making the malocclusion worse.  
         [0005]     In practice, the surgeon often encounters difficulty in placing the bone plate as distally as desired. Additionally, the clinician attaching the elastomeric materials or springs from the bone plate to the dentition experiences difficulty when the bone plates are placed too far posteriorly. Often, the surgeon has difficulty placing the anchors in the correct location to achieve the desired point of emergence of the bone plate into the vestibule. This variation in height and location of the bone plate for subsequent tooth movement presents significant difficulties to the clinician attempting to intrude the posterior teeth.  
         [0006]     An adjustable and/or removable cap on the bone plate permits the surgeon to place the bone plate in a more accessible region of the mouth while extensions from the cap can be used to move the point of force application to the dentition in the most desirable location, i.e., the centroid. By utilizing different configurations for the cap, the point of emergence of the bone plate from the vestibule becomes less critical thus facilitating a more clinically acceptable method of intruding the posterior teeth.  
       SUMMARY OF THE INVENTION  
       [0007]     An adjustable bone anchor has a fixed plate attached to bone at a distance from its emergence into the buccal vestibule of a patient. The bone plate is attached by screws or other osseointegrated anchors to the bone. Attached to the protruding portion of the plate is an extension or cap, which can be removed, adjusted or replaced as desired. The supragingival cap has a series of small holes or indentations through which or under which elastomeric material or coil springs can pass or attach for the purpose of applying force to the surrounding dentition. The supragingival cap varies in size and shape and is adjustable before final attachment to the bone plate by a variety of means such as ligature wire, a pin, a spring clip, a tapped screw, etc. Removal of the supragingival cap during orthodontic movement is easily facilitated and adjustments made thereto or the cap replaced with a supragingival cap having a different configuration. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0008]     In the drawings:  
         [0009]      FIG. 1  is a side view showing an anterior openbite;  
         [0010]      FIGS. 2 and 3  are elevational views showing one form of the bone anchor according to this invention;  
         [0011]      FIGS. 4, 5  and  6  depict an orthodontic application of the invention as applied to the mandible;  
         [0012]      FIG. 6  is an elevational view of a modification of the invention;  
         [0013]      FIGS. 7-15  are perspective views of further modifications of the bone anchor attached to the maxilla; and  
         [0014]      FIGS. 16-19  show additional modifications of the bone anchor. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]     With reference to  FIG. 1 , an anterior openbite is shown. Historically, an openbite, which is caused by posterior occlusal contacts, was corrected by removal of bone wedge  1  from the maxilla apical to the maxillary root tips. Following surgery, autorotation results in correction of the openbite.  
         [0016]     In  FIGS. 2 and 3 , titanium bone plate  2  is shown which is attached by means of bone screws inserted through apertures  3  into the bone. Protruding end  4  of bone plate  2  is narrowed and supragingival cap  5  is fitted over it. A small aperture  6  is formed in bone plate  2  and a small diameter ligature wire or pin or screw, if the aperture is tapped, is inserted through apertures  7  and  8  in cap  5  and aperture  6  in protruding end  4  of bone plate  2  to secure cap  5  to bone plate  2 . Arms  9  and  10  extend outwardly from cap  5  and include apertures  11 .  
         [0017]     Supragingival cap  5  comes in a variety of lengths and heights and the appropriate one can be selected to meet the requirements of a particular patient before attachment to bone plate  2  by means of ligature wire, a pin, spring clip or screw if the aperture is tapped.  
         [0018]     A modified version of cap  5  includes neck  12  extending upwardly from bone plate  2  as illustrated in  FIGS. 4 and 5  wherein elastomeric or spring material  13  is threaded through one or more of the apertures  11  formed in arms  9  and  10  and then attached to archwire  14 . By this means, intrusion of the posterior teeth is facilitated in a variety of locations and directions based on the observations of the clinician. Also, small groove  15  helps maintain the ligature wire, which secures cap  5  to bone plate  2 , in place.  
         [0019]     In  FIG. 6 , a modification of the invention is shown wherein cap  16  envelops end  4  of bone plate  2  and includes laterally extending arms  17  and  18 . Multiple indentations  19  are formed along the lower edges of arms  17  and  18  for the purpose of receiving elastomeric or other like spring means  13 .  
         [0020]     Another modification is shown in  FIG. 7  with attachment of the bone plate  40  to the maxilla, wherein bone plate  20  is provided which extends downwardly with the lower end thereof disposed at a right angle thereto with interiorly threaded cap  21  affixed to the end thereof. Angular attachment tube  22  is secured to screw  23  which is screwed into threaded cap  21 . One end of attachment bar  24  is inserted into attachment tube  22  with the opposite end offset therefrom and extending parallel hereto and which includes indentations  25 . Of course, attachment bar  24  may be bent in a variety of directions. Then appropriate spring means is looped over attachment bar  24  and maintained in position by means of indentations  25 .  
         [0021]     A similar configuration to that shown in  FIG. 7  is shown in  FIG. 8  wherein angular attachment tube  22  is secured to attachment square  26 . Attachment square  26  is inserted into square cap  27  which is attached to bone plate  20  and wherein the two are secured together by means of a wire inserted through aperture  28  on the top of attachment square  26  and aperture  29  formed in the top of the square cap  27  and the corresponding apertures formed in the bottoms thereof.  
         [0022]     In  FIG. 9 , square cap  30  is attached to the lower right angle portion of bone plate  20  and is threaded interiorly and is adapted to receive screw  31 . Aperture  32  is formed in attachment block  33 . To complete the assembly, attachment block  33  is simply slipped over square cap  30  and then screw  31  is threaded into square cap  30  to secure the two together. Angular attachment tube  34  is secured to attachment block  33  for the purpose as discussed above in connection with  FIG. 7 .  
         [0023]     By the modification shown in  FIG. 10 , attachment tab  35  extends perpendicularly from the lower edge of bone plate  36  and is adapted to receive attachment cap  37 . Then a wire, pin or spring clip is inserted through apertures  38  and  39  and the corresponding aperture in the bottom portion of cap  37  to secure attachment cap  37  onto attachment tab  35 .  
         [0024]     In order to attach attachment bar  24  securely to an angular tube such as shown in  FIGS. 7-10 , attachment bar  24  is inserted into angular tube  40  as shown in  FIG. 11 . Adjustable ring  41  is provided so as to prevent attachment bar  24  from sliding too far into angular tube  40 . Then a small wire or other material  42  is secured on attachment bar  24  to the angular tube  40  by using loop  43 .  
         [0025]     In  FIG. 12 , bone anchor  44  is shown wherein sliding cap  45  is fitted around right angle protrusion  46 . Aperture  47  is formed in protrusion  46  in order to receive a brass pin, ligature wire, spring clip or light cured material which is placed and cured. All of these means serve to secure sliding cap  45  in place.  
         [0026]     In  FIGS. 13 and 14 , shaped attachments  48  and  49  are secured to sliding cap  45 . Of course, elastomeric or spring material is positioned in the indentations  50 , as desired. A further modification of the invention is shown in  FIG. 15  wherein a further modification includes attachment bar  24  which is generally vertically disposed and secured to angular tube  40 .  
         [0027]     A further modification of the invention is shown in  FIG. 16  wherein L-shaped spring clip  51  is attached to cap  5  by means of laser weld  52  with the end opposite from weld  52  being inserted into aperture  7  and, when completely seated, being securely locked in place. Spring clip  51  is manufactured of a highly flexible material such as a titanium alloy. To remove cap  5  from the bone plate  2 , a sharp rectangular instrument is inserted under spring clip  51  and rotated in such a manner that spring clip  51  is moved out of aperture  7  (as viewed in  FIG. 16 ) thereby permitting removal of cap  5  from bone plate  2 . To insert cap  5  onto bone plate  2 , a curved groove in the apical end  53  of bone plate  2  forces spring clip  51  to open as internal edge  54  slides in the groove formed in end  53  when cap  5  is pressed basally.  
         [0028]     Conversely, spring clip  51 , shown in  FIG. 17 , can be welded to bone anchor  2  and inserted into cap  5  by way of aperture  8 . On insertion of cap  5  onto bone plate  2 , groove  53  helps deflect clip  51 , by means of bevel  54 , to aid in the insertion process. Removal of cap is as described in connection with  FIG. 16 .  
         [0029]     In  FIG. 18 , spring clip  51  is attached to angular apical end  27  of bone plate  2  by means of weld  52 . Attachment angular block  26  includes a beveled surface to urge spring clip  51  upwardly from aperture  29  as attachment angular block  26  moves into angular apical end  27  when aperture  28  becomes aligned with aperture  29 , spring clip  51  then snaps into aperture  28  thereby securing angular block  26  to angular apical end  27 .  
         [0030]     The same structure as shown in  FIG. 18  could be utilized in connection with the means shown in  FIG. 10  wherein the spring clip is attached to attachment cap  37  at the buccal surface with aperture  38  as close to the lingual surface of cap  37  as possible. Attachment tab  35  and the end of the spring clip are beveled to facilitate manipulation of the spring clip.  
         [0031]     Finally, in  FIG. 19 , protrusion  46  corresponds generally to that shown in  FIG. 12  wherein spring clip  51  is attached to cap  45  by means of weld  52  and projects through aperture  47 . Spring clip  51  is removed from aperture  47  by insertion of a rectangular instrument under spring clip  51 .  
         [0032]     As orthodontic treatment progresses, resistance to intrusion varies along the dentition depending on a number of factors including surface area to resistance, varying metabolic activity surrounding particular roots, root position relative to cortical verses alveolar bone, etc. By having an adjustable cap, which is also replaceable by other types of caps, if desired, the clinician is able to maintain the optimal force vector for optimum intrusion along the entire posterior occlusal plane.