Abstract:
A method of installing a dental implant includes positioning a drill guide tube adjacent to a jawbone and taking a tomographical scan of the two. Based on the scan, a computer-generated image is created and analyzed to confirm whether the drill guide tube is properly aligned. If the drill guide tube is in the correct position, that same tube to used to guide a drill bit into the jawbone. In some cases, the tube also helps guide a biopsy punch in cutting just a small, round opening into the gum tissue, which minimizes the time needed for healing.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The subject invention generally pertains to dental implants and more specifically to a method of installing them.  
         DESCRIPTION OF RELATED ART  
         [0002]    Various dental implant methods and devices have been developed for replacing one or more missing teeth in a person&#39;s jaw with prosthetic teeth. For many prosthetic teeth, a final product comprises three basic components: an implant, an abutment, and a crown. The crown is the exposed portion of the prosthesis that resembles one or more teeth. The implant is an anchor that becomes attached to the jawbone, and the abutment couples the crown to the implant.  
           [0003]    Typical implant methods involve a series of procedures extending over several months. In some cases, for instance, the process involves first, cutting the gum tissue in the area of the missing tooth and pulling the tissue back to expose the jawbone; second, drilling a hole into the bone; third, installing an anchoring member or implant into the hole; fourth, attaching a cover screw to the implant and stitching the gum tissue back together; fifth, waiting up to several months to allow the gum tissue to heal over the cover screw and to allow the bone to grow onto the implant; sixth, cutting a small round hole in the gum tissue to remove the cover screw and expose the implant; seventh, attaching a healing cap to the implant; waiting another extended period to allow the gum tissue to heal around the healing cap; eighth, replacing the healing cap with an abutment; and ninth, attaching a crown (e.g., an individual prosthetic tooth, bridge, denture, etc.) to the abutment.  
           [0004]    An implant process can be improved with the aid of drill guide bushings and tomography as disclosed in PCT Publication WO 99/26540 by Klein et al. (specifically incorporated by reference herein). The Klein method involves taking a CT scan (computed tomography scan) of a patient wearing a surgical template that overlays the patient&#39;s teeth. The surgical template preferably has three fiducial markers that are detected by the CT scan. After taking the tomographical scan, the surgical template is removed from the patient&#39;s mouth and placed over a model of the patient&#39;s jaw. The model jaw with the surgical template is loaded onto a computer-driven milling machine. With the aid of the CT scan data and the three fiducial markers, the milling machine accurately drills a hole into the surgical template. The template, now with an accurately drilled hole, is returned to the patient&#39;s mouth, so the hole in the template can then be used as a drill guide when drilling into the patient&#39;s actual jawbone. Drawbacks of such a method include its overall complexity and the expense of the computer-driven milling machine.  
           [0005]    Another implant method and related device is disclosed by Fenick in U.S. Pat. Nos. 5,015,183 and 5,133,660, which are specifically incorporated by reference herein. Fenick uses X-rays to help identify a drill bit trajectory and uses drill guide bushings to help guide the drill bit. The Fenick system creates a radiology stent that includes a radially opaque grid. The stent, without any drill bushings, is X-rayed while in the patient&#39;s mouth. The stent is then placed over a model of the patient&#39;s jaw where the grid provides a frame of reference that helps in manually positioning a drill bit relative to the model jaw. A hole is drilled into the model, and the resulting hole helps align a drill bushing relative to the model. Next, a cast is created over the model to capture the drill bushing. The cast, with the drill bushing, is then placed in the patient&#39;s mouth to help guide the drill bit that drills a hole into the patient&#39;s jawbone. With the Fenick system, some positional accuracy may be sacrificed because the drill bushing is aligned to a model rather than being aligned directly to the patient&#39;s actual jaw.  
           [0006]    Various other examples of dental implant methods and devices are disclosed in U.S. Pat. Nos. 6,283,753; 5,718,579; 5,613,852; 5,064,374; 5,015,186; RE37,646; 3,748,739; 5,350,297; 6,488,502; 4,998,881; all of which are specifically incorporated by reference herein. Additional examples of dental implant methods and devices are disclosed in U.S. Patent Application Publication US 2002/0182567 and European Patent Application 0437031A1; both of which are specifically incorporated by reference herein.  
         SUMMARY OF THE INVENTION  
         [0007]    To provide a better method of installing a dental implant, it is an object of some embodiments of the invention to take a tomographical scan of a drill guide tube adjacent to a jawbone and to use that same tube for guiding a drill bit into the jawbone.  
           [0008]    In some embodiments, the implant placement direction and angulation are determined by first establishing the occlusal scheme of the proposed final restoration. The process ensures that the implant placement will properly align the implant to the center of the final occlusal table. The occlusal forces then applied to that implant will be in as a direct line as possible, thereby reducing off-axis inappropriate loading final occlusion dictated placement and angulation of the implant.  
           [0009]    Another object of some embodiments is to minimize the cutting of gum tissue in the area where a dental implant is to be installed.  
           [0010]    Another object of some embodiments is to reposition a drill guide tube by referring to a computer-generated image created from a tomographical scan of the tube&#39;s original position relative to a jawbone.  
           [0011]    Another object of some embodiments is to reposition a drill guide tube by rotation, wherein the center of rotation is near the occlusal plane rather than near the gum line.  
           [0012]    Another object of some embodiments is to take a second tomographical scan of the tube and the jawbone to confirm that the tube is properly aligned after the tube is repositioned.  
           [0013]    Another object of some embodiment is to accurately position a circular cutter so that, prior to drilling into the bone, a relatively small, round hole can be cut into the gum tissue rather making a more evasive cut and pulling back the tissue to expose the bone for drilling.  
           [0014]    Another object of some embodiments is to use a tube to guide a circular cutter as the cutter cuts a generally round opening into the gum tissue.  
           [0015]    Another object of some embodiments is to cut a generally round opening into the gum tissue using a biopsy punch, whereby the biopsy punch can be further used to remove a round plug of tissue after the round opening has been cut.  
           [0016]    Another object of some embodiments is to use a model jaw for creating a stent that can hold a guide tube adjacent to a jawbone while a tomographical scan is taken of the tube and the jawbone.  
           [0017]    Another object of some embodiments is to cement a drill guide tube to a stent prior to a tomographical scan indicating that the tube is properly aligned.  
           [0018]    Another object of some embodiments is to cement a drill guide tube to a stent after a tomographical scan indicates that the tube is improperly aligned.  
           [0019]    Another object of some embodiments is to enlarge a hole in a jawbone by first removing a stent that holds a guide tube adjacent to the jawbone.  
           [0020]    Another object of some embodiments is to skip the use of a cover screw by cutting a properly sized round opening in the gum tissue, drilling a hole into the jawbone, inserting an implant into the hole, and installing a healing cap instead of a cover screw, whereby the healing cap prevents the tissue from completely healing over the opening.  
           [0021]    One or more of these and other objects of the invention are provided by positioning a drill guide tube adjacent to a jawbone, taking a tomographical scan of the tube and the jawbone simultaneously, analyzing a computer-generated image that is based on the tomographical scan, repositioning the tube if necessary, and using the tube to guide a drill bit into the jawbone. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0022]    [0022]FIG. 1 is a perspective view illustrating the step of creating a model jaw, wherein the jaw shows the area of at least one missing tooth.  
         [0023]    [0023]FIG. 2 is a perspective view of the model of FIG. 1, but the drawing also shows a drill guide tube in the area of the missing tooth.  
         [0024]    [0024]FIG. 3 is a perspective view illustrating the step of creating a stent that overlays the model jaw.  
         [0025]    [0025]FIG. 4 is a perspective view illustrating the step of taking a tomographical scan of a tube in relation to a bone and creating a plurality of images therefrom.  
         [0026]    [0026]FIG. 5 illustrates the step of creating a first image of a tube at a first position relative to a bone.  
         [0027]    [0027]FIG. 6 illustrates the step of creating a second image of a tube at a second position relative to a bone.  
         [0028]    [0028]FIG. 7 is a cross-sectional view taken along a longitudinal centerline of a drill guide tube, wherein the drawing illustrates the step of inserting a circular cutter through the drill guide tube.  
         [0029]    [0029]FIG. 8 is a cross-sectional view similar to FIG. 7 but showing the step of cutting a substantially round opening in the gum tissue that overlays a jawbone.  
         [0030]    [0030]FIG. 9 is a cross-sectional view similar to FIG. 7 but showing a circular cutter being withdrawn from the tube, thereby leaving a substantially round hole in the gum tissue.  
         [0031]    [0031]FIG. 10 is a cross-sectional view similar to FIG. 7 but showing a drill bit drilling a hole into the jawbone.  
         [0032]    [0032]FIG. 11 is a cross-sectional view similar to FIG. 7 but showing the stent being removed and the hole in the jawbone being enlarged.  
         [0033]    [0033]FIG. 12 is a cross-sectional view similar to FIG. 7 but showing an implant being inserted into a hole that was drilled into the jawbone.  
         [0034]    [0034]FIG. 13 is a cross-sectional view similar to FIG. 7 but showing a healing cap being attached to the implant.  
         [0035]    [0035]FIG. 14 is a cross-sectional view similar to FIG. 7 but showing the abutment replacing the healing cap.  
         [0036]    [0036]FIG. 15 is a cross-sectional view similar to FIG. 7 but showing a crown or similar item being attached to the abutment. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0037]    For simplicity and clarity, the invention will be described with reference to replacing a single missing tooth, however, it will be appreciated by those skilled in the art that the method can be readily applied to multiple teeth or even an entire set of teeth. Thus, the term, “crown” broadly encompasses an individual prosthetic tooth, bridge, denture, etc. For the illustrated example, a patient  10  is missing his lower-right cuspid as shown in FIGS. 1-4.  
         [0038]    To replace the missing tooth, the process may begin by creating a cast model  12  (FIG. 1) of the patient&#39;s lower jaw. Arrow  14  indicates the general area of the missing tooth. Model  12  may be a plaster casting; however, the actual structure and method of making such a model may vary. Such models and methods of making them are well known to those skilled in the art.  
         [0039]    In FIG. 2, a drill guide tube  16 , can be placed on model  12  in the area of the missing tooth. Tube  16  is preferably made of metal or some other generally radially opaque material. The tube&#39;s longitudinal centerline  18  should lie generally along the anticipated centerline of the prosthetic tooth and its supporting implant. In some cases, tube  16  is preferably held temporarily to model  12  using some type of clamp or bonding material. Examples of such a clamp include, but are not limited to, a fastener, screw, nail, tack, etc., and examples of a bonding material (see material  20  of FIG. 7) include, but are not limited to wax, adhesive, thermoplastic, etc. In other embodiments of the invention, tube  16  is placed in the area of the missing tooth after a stent is made.  
         [0040]    In FIG. 3, a surgical stent  22  is made by vacuum-forming an acrylic sheet over model  12 ; however, it should be appreciated by those skilled in the art that there are other ways of making a surgical stent that are well within the scope of the invention. In some embodiments of the invention, stent  22  is formed over both model  12  and tube  16 . Once stent  22  is formed, a small hole in the stent can be drilled or cut away so that the stent does not close off the inner bore of tube  16 . In some cases, tube  16  may be repositioned to protrude through the hole. In some embodiments, stent  22  is formed over model  12  without tube  16  in place, and tube  16  is attached to stent  22  afterwards. In the later case, a temporary removable filler member or plug (e.g., cylindrical or tooth shaped) may need to be installed on model  12  in the area of the missing tooth to reserve space for tube  16  within stent  22 . After stent  22  is made, tube  16  can be affixed to the stent in the space left by the filler member. Again, a small hole can be cut away or drilled through stent  22  to open the inner bore of tube  16 .  
         [0041]    Regardless of how the stent is made, stent  22  with the attached tube  16  is placed on the patient&#39;s lower jaw as shown in FIG. 4. This places tube  16  in the actual area of the missing tooth with the tube being in the same relative orientation as it was when the stent and tube were on model  12 . A tomographical scan is taken of the patient&#39;s jaw to record the position of tube  16  relative to a bone  28  (i.e., the patient&#39;s upper or lower jawbone). For illustrative purposes, the patient&#39;s mouth is shown open only to show that stent  22  and tube  16  are in the patient&#39;s mouth. From the tomographical scan, a computer  24  creates a first image  26  that shows tube  16  at a first position in relation to bone  28  as shown in FIG. 5. For reference purposes only, an outline of an adjacent tooth  30  is also shown in image  26 , wherein tooth  30  corresponds to a lower-right first bicuspid  30 ′ of the model in FIG. 1.  
         [0042]    The equipment and method for taking a tomographical scan is well known to those skilled in the art. Tomography generally involves creating a computer-generated image (e.g., image  26 ) from a plurality of X-rays as indicated by lines  32  and  34  of FIG. 4. Other terms used for tomography include, but are not limited to, CT scan (computed tomographical scan), EIT (electrical impedance tomography), CAT scan (computerized axial tomography). System  36  of FIG. 4 is schematically illustrated to represent all types tomography systems. Some examples of system  36  include, but are not limited to a CommCAT IS-2000, Panorex CMT, and a Panorex CMT Plus, all of which are products of Imaging Sciences International, Inc., of Hatfield, Pa.  
         [0043]    Image  26  of FIG. 5 shows that drill guide tube  16  is not properly aimed toward bone  28 , so in this particular case, the next step in the process would be to reposition tube  16 . A second image  38  of FIG. 6 illustrates the step of repositioning tube  16  to a second position. Repositioning tube  16  simply involves releasing the clamp or bonding material that holds tube  16  to sent  22 , and reaffixing the tube at the second position shown in FIG. 6. Once tube  16  is fixed at the second position, system  36  takes another tomographical scan of the patient with stent  22  and tube  16  again in the patient&#39;s mouth. The resulting second image of FIG. 6 shows that tube  16  is now properly aligned relative to bone  28 , so tube  16  can now be used as a tool guide.  
         [0044]    In FIG. 7, a circular cutter  40  is inserted through tube  16 . Circular cutter  40  represents any cutter that can cut a substantially round opening into gum tissue  42  that covers bone  28 . One example of cutter  40  is a cylindrical biopsy punch.  
         [0045]    In FIG. 8, cutter  40  is shown cutting a substantially round opening into gum tissue  42 , while tube  16  helps guide the angular position of cutter  40  relative to bone  28 . To help hold tube  16  at its proper position, it should be noted that stent  22  engages the patient&#39;s teeth (e.g., tooth  30 ) and/or the patient&#39;s gums  42  (in the case where a patient has no teeth).  
         [0046]    In FIG. 9, cutter  40  is shown withdrawing a round plug  44  of gum tissue as cutter  40  is withdrawn from tube  16 . This leaves a substantially round opening  46  in gum tissue  42 .  
         [0047]    In FIG. 10, a drill bit  48  is inserted through tube  16 , so tube  16  can help guide the drill bit as the drill bit drills a hole  50  into bone  28 .  
         [0048]    In FIG. 11, stent  22  and tube  16  are entirely removed from the patient&#39;s mouth to allow room for a larger drill bit  52  to enlarge hole  50  in diameter and/or depth, thereby producing an enlarged hole  54 .  
         [0049]    In FIG. 12, a conventional implant  56  is shown being inserted (arrow  58 ) and anchored into hole  50  (enlarged to hole  54 ). The actual structure of implant  56  may vary widely as can be appreciated by those skilled in the art.  
         [0050]    In FIG. 13, a healing cap  60  is attached to implant  56  to allow the gum tissue  42  to heal around the perimeter of opening  46 . Healing cap  60  protrudes sufficiently above gum tissue  42  to inhibit tissue  42  from completely closing opening  46  at any time during a period extending from when opening  46  was first created (FIG. 9) until healing cap  60  is removed from implant  56  (FIG. 14).  
         [0051]    In FIG. 14, healing cap  60  is removed from implant  56 , and a conventional abutment  62  is attached to implant  56 . The actual structure of abutment  62  may vary widely as can be appreciated by those skilled in the art  
         [0052]    In FIG. 15, a crown  64  (e.g., an individual prosthetic tooth, bridge, denture, etc.) is attached to abutment  62 . Crown  64  can be bonded and/or mechanically fastened to abutment  62 . In some cases, for example, a bonding material  66  bonds crown  64  to abutment  62 .  
         [0053]    Although the invention is described with reference to a preferred embodiment, it should be appreciated by those skilled in the art that various modifications are well within the scope of the invention. Therefore, the scope of the invention is to be determined by reference to the claims that follow.