Patent Publication Number: US-2005136374-A1

Title: Implant positioning device and method

Description:
This application is a divisional of U.S. application Ser. No. 10/086,859 filed Mar. 4, 2002. 
    
    
     FIELD OF THE INVENTION  
      This invention relates to the field of dentistry. In particular, the invention relates to the positioning of dental implants.  
     BACKGROUND OF THE INVENTION  
      Dental implants are commonly use in dental procedures. Often when a tooth has been removed, an implant is placed in the jaw bone and a dental prosthesis is then positioned using the implant. The implant is incorporated in the bone material and provides a suitable anchor for various types of dental prostheses.  
      Typically, when a dental implant is to be installed, a dentist prepares a cast of the patient&#39;s dental arch. That cast is then forwarded to a dental lab for creation of a suitable template. When the lab has determined the appropriate implant location to be used given the conditions of the patient&#39;s dental arch, the lab forwards a suitable template to the dentist. The dentist, guided by the template, installs the implant.  
      One of the problems that can arise in this situation is that the template provides only a rough or imprecise guide as to where the dentist should place the implant. Practically speaking, the dentist is allowed considerable leeway in selecting the final position of the implant when using a template. Thus, because the dentist is given some leeway in deciding where the implant is to be placed, the location of the implant is not controlled and may not reflect the position intended by the laboratory. The error in location may be in several different directions. The implant may be positioned either left or right or forward or aft of the location expected by the lab. Also the location of the axis of the implant may be at an angle to that originally considered by the lab. Finally, the depth of the implant in the bone is also controlled by the dentist. All of these locations may vary from that originally intended by the lab. Accordingly, the design of the prosthesis may be non ideal in terms of strength, esthetic appearance or the biological response it provokes.  
      Accordingly, it would be advantageous to provide a system which would provide better correlation between the intended location of a dental implant and the location at which the dental implant is installed by the dentist.  
     SUMMARY OF THE INVENTION  
      In accordance with one aspect of the invention, the invention includes a kit of parts. The kit of parts is used for aligning a drill axis of a dental drill head at a desired location in a selected patient&#39;s dental arch. The kit includes the drill alignment arm for attaching to a dental drill head at a specified drill head location. The drill alignment arm has a drill alignment arm pin and the drill alignment arm pin has a drill alignment arm pin axis. The kit further includes a stent which is adapted to fit the dental arch of a selected patient. The stent includes a locating barrel. The locating barrel has a bore adapted to receive and locate the drill alignment arm pin.  
      In a preferred embodiment, the locating barrel includes a depth control surface. In a further preferred embodiment of the invention, the kit includes at least one drill and the drill may have a length which is correlated with the depth control surface so that the drill may be used to drill a bore hole to a desired depth. Advantageously, the kit includes a plurality of drills having different diameters so a progressively larger hole may be drilled.  
      Additionally the kit may include a stent alignment arm. The stent alignment arm has a stent alignment arm pin and the stent alignment arm pin has a stent alignment arm pin axis. The stent alignment arm pin is adapted to be received within the bore of the locating barrel.  
      In a further preferred embodiment of the invention, the kit additionally includes proxy implant and the proxy implant has a central bore with a proxy axis.  
      In a further preferred embodiment the stent alignment arm includes an alignment coping and the alignment coping has an alignment coping bore with an alignment coping bore axis.  
      In a further preferred embodiment of the invention, the kit further includes a retainer screw for fixedly aligning the alignment coping of the stent alignment arm relative to the proxy implant with the alignment coping bore axis aligned with the proxy axis.  
      In accordance with another aspect of the invention, the invention includes a method of creating an alignment device for guiding a dental drill head for drilling a bore having a desired axis in a desired location with respect to a selected patient&#39;s dental arch. The method includes the steps of taking an impression of the selected patient&#39;s dental arch, forming a cast dental arch from the impression, determining the desired location of the desired axis and placing a proxy implant having a proxy axis in the desired dental arch so that the proxy axis is coincident with the desired location of the desired axis. The method further includes forming a stent of the selected patient&#39;s tooth crowns from the cast dental arch. The method further includes incorporating into the stent a locating barrel which has a locating barrel axis so that the locating barrel axis is spaced from the proxy axis by a first selected distance. The method also includes providing a drill alignment arm with the drill alignment arm having fixing means for fixing the drill alignment arm to the dental drill head at a predetermined location. The dental drill head has a drill axis. The drill alignment arm has a drill alignment arm pin having a drill alignment arm pin axis. The method further includes providing such parts wherein the drill alignment arm pin is spaced from the drill axis by a second selected distance and the first and second distances are equal. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  illustrates the kit of parts which form a preferred embodiment of the invention and which may be used to practise a preferred embodiment of the method of the invention;  
       FIG. 2 . 1  is an enlarged version of a first component of the kit of  FIG. 1 ;  
       FIG. 2 . 2  is a view similar to  FIG. 2 . 1  but illustrating the placement of a second component of  FIG. 1 ;  
       FIG. 2 . 3  illustrates the incorporation of the component shown in  FIG. 2 . 2  in the component of  FIG. 2 . 1 ;  
       FIG. 3 . 1  is an enlarged view of a third component of the kit of  FIG. 1 ;  
       FIG. 3 . 2  is an enlarged view of a fourth component of the kit of  FIG. 1 ;  
       FIG. 3 . 3  is an elevational view of a fifth component of the kit of  FIG. 1 ;  
       FIG. 3 . 4  is a plan view of an assembly of the components of  FIGS. 3 . 2  and  3 . 3 ;  
       FIG. 4 . 1  is an elevational view illustrating the assembly of the components of  FIGS. 3 . 2  and  3 . 3  with the assembly as shown in  FIG. 3 . 4 ;  
       FIG. 4 . 2  is a plan view of the completed assembly of the components illustrated in  FIG. 4 . 1 ;  
       FIG. 4 . 3  is an elevational view of the assembly of  FIG. 4 . 2 ;  
       FIG. 5 . 1  is a plan view of the assembly of  FIG. 4 . 3  together with a sixth component of the kit of  FIG. 1 ;  
       FIG. 5 . 2  is an elevational view of the assembly of components illustrated in  FIG. 5 . 1 ;  
       FIG. 6  is an exploded elevational view showing the disassembly of components of  FIG. 5 . 2 ;  
       FIG. 7 . 1  is an elevational view illustrating the alignment of one of the components of  FIG. 1  on a patient;  
       FIG. 7 . 2  is an elevational view similar to  FIG. 2 . 1  illustrating the completed placing of components illustrated in  FIG. 7 . 1 ;  
       FIG. 8 . 1  is an elevational view illustrating a seventh component of  FIG. 1  attached to a dental drill hand piece;  
       FIG. 8 . 2  is a plan view of the assembly of  FIG. 8 . 1 ;  
       FIG. 9  is an elevational view illustrating the use of the components shown in  FIG. 8 . 1  for drilling in a patient&#39;s mouth;  
       FIG. 10  is an elevational view illustrating the installation of a dental implant. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       FIG. 1  illustrates a kit of parts that is useful in carrying out the method in accordance with a preferred embodiment of the invention. The kit of parts is indicated generally at  10 . The kit includes a cast dental arch  12 , a proxy implant  14 , a retainer screw  16 , a stent alignment arm  18 , a locating barrel  20 , a stent  22 , a drill alignment arm  24  and a plurality of drills  26 . The kit is used with a custom drill head  110  which may be part of the kit or dealt with separately.  
      The kit of part  10  includes all the pieces required to use the invention described herein in accordance with the preferred embodiment. The persons involved in using the invention include the dental professional, the support staff in the dental professionals&#39; office, dental laboratory professionals and support staff and manufacturers of the components of the kit of parts. Not all parts need be formed, manufactured or used by all persons involved. However, the kit illustrates all components which are used as explained below to establish installation of a dental implant in the place in the patient&#39;s jaw where intended by everyone involved in the patient&#39;s dental care.  
      In order to custom configure a dental implant to a patient, an impression is taken of the patient&#39;s dental arch. The dental arch may be either of the upper jaw or the lower jaw as required. The impression taken from the patient&#39;s dental arch will enable a cast dental arch to be made from the impression which duplicates the patient&#39;s dental arch. In most cases the cast dental arch will be made by the dentist from the impression made by the dentist. Either the impression or the cast dental arch, as appropriate, made by the dentist, is shipped to a laboratory facility. The cast dental arch will thus have the location of the patient&#39;s crowns, gums and bone structure. In addition, the cast dental arch made from the impression will duplicate the location of any gaps where teeth are missing and indicate the location where ultimately the implant is to be positioned in order to position a dental prosthesis.  
      Upon receipt of the impression made by the dentist, the lab or other facility can then create a cast dental arch  12  from the impression which duplicates the patient&#39;s dental arch. Such a cast dental arch is illustrated in  FIG. 2 . 1 . From reference to  FIG. 2 . 1 , for convenience, there is illustrated a missing tooth at the maxiallary right central incisor position. The dental adviser to the patient has determined that a dental implant is required at that location. The site has been indicated generally by the arrow  30 . The cast dental arch may be made from any material which is suitably rigid. At the intended site  30  where the implant  28  (see  FIG. 10 ) is to be installed, the laboratory professional at the lab creates an excavated site  32  (see  FIG. 2 . 2 ).  
      The next step in the procedure is to position the proxy implant  14  in a location determined by the dentist and laboratory professional. The proxy implant  14  is a proxy for the dental implant  28 . The proxy implant  14  is located so that the location of the proxy implant will be suitable for integration of the dental implant  28  within the patient&#39;s bone structure so as to provide a suitable basis for a prosthesis. The proxy implant  14  comprises a central threaded bore  40 . The central threaded bore  40  defines a proxy axis  42 . The axis  42  will ultimately determine the location of a similar implant axis  29  in the implant  28 . Thus, when the proxy implant  14  which is a proxy for the implant  28  is positioned in the arch as shown in  FIG. 2 . 3 , the implant axis  29  of the implant will be ultimately determined by the location of the proxy axis  42  of the proxy implant. In addition, as well as locating the proxy axis  42  and thereby the implant axis  29  with respect to the patient&#39;s dental arch, the proximal depth of the dental implant  20  may also be determined by the location of the proxy implant. This depth locating function will be discussed below after discussing the other elements of the kit  10  illustrated in  FIG. 1 . As shown in  FIG. 2 . 3 , when the location of the proxy implant has been determined, the proxy implant  14  is held in that location and a hardenable material such as silicone is used to encase the proxy implant  14 . The hardenable material then cures so that the proxy implant  14  is permanently located with respect to the cast dental arch  12 .  
      If desired, the cast dental arch with the proxy implant could be sent back to the dental professional for checking and vertification that the position of the implant as selected in the laboratory is acceptable to the dental professional. The dental professional may, for example, wish to verify that the implant, if positioned like the proxy implant, will be positioned to meet the patient&#39;s requirement, that is, would not conflict with roots of adjacent teeth or other bony or vital structure within the patient&#39;s mouth.  
      The next step in the procedure is to make use of the stent alignment arm  18  (see  FIG. 3 . 2 ). The stent alignment arm  18  comprises an alignment coping  50  having a central bore  52  and an alignment coping axis  54 . The stent alignment arm  18  also comprises a stent alignment arm pin  56 . The stent alignment arm pin  56  is a substantially cylindrical configuration having a pin axis  58 . The axis  58  is co-planar and parallel to axis  54 .  
      The stent alignment arm  18  may be made from any dimensionally accurate material and may be reusable. Thus, the stent alignment arm  18  may be made from metal or suitable hard plastics having the necessary dimensional accuracy. The stent alignment arm  18  is not intended to be placed in the patient&#39;s mouth and is used only in the lab. Thus, the part need not be sterilizable. The axis  54  of the alignment coping  50  defines the bore  52  passing axially through the alignment coping  50  of the stent alignment arm  18 . The bore  52  of the alignment coping  50  has a diameter to closely receive the shank of the retainer screw  16  illustrated in  FIG. 3 . 1 . The retainer screw  16  has a general axis  60 . The retainer screw has a thread  62  at one end and a head  64  having a socket or slot  66  for turning the head by means of a screwdriver. The length of the retainer screw  16  along the axis  60  is greater than the axial length of the alignment coping  50  along axis  54 . This means that when the retainer screw  16  is placed within the bore  52  of the alignment coping  50 , the threaded end  62  will project beyond the length of the alignment coping  50  when the head  64  bears against the uppermost surface of the alignment coping  50  as illustrated in  FIGS. 3 . 2  and  3 . 1 .  
      The kit  10  illustrated in  FIG. 1  also includes a locating barrel  20 . The locating barrel  20  comprises a cylindrical portion  70  and a wing portion  72 . The cylindrical portion  70  of the locating barrel  20  has a substantially cylindrical central bore  74  which has substantially the same diameter as the cylindrical portion of the stent alignment arm pin  56  and a locating barrel axis  76 . The wing portion  72  of the locating barrel  20  has a central slot  78  whose width is the same as the width of the stent alignment arm  18  in the direction transverse to the plane including axes  54  and  58 . The slot  78  and the bore  74  do not pass completely through the locating barrel  20 , but rather, end in a surface shown in dotted lines at  80  in  FIG. 3 . 3 .  
      The locating barrel is a single use component and will be incorporated in a stent that will be placed in the patient&#39;s mouth. Thus, the locating barrel  20  may be manufactured from a sterilizable material, but as it is a single use device, it is preferable to make the locating barrel from a sterilizable plastic rather than more expensive materials such as metals.  
      The next step in the method is to assemble various of the parts discussed thus far. The locating barrel  20  is slid on to the stent alignment arm  18 . The stent alignment arm pin  56  is received within the bore  74  of the locating barrel  20 , while a portion of the stent alignment arm  18  is received within the slot  78 . The locating barrel  20  is then pushed onto the stent alignment arm  18  until the stent alignment arm  18  bottoms out against surface  80 . The assembled condition of these two parts is illustrated in  FIG. 3 . 4 .  
      The next step in the procedure is to place the assembly of the stent alignment arm  18  and locating barrel  20  on the proxy implant  14  which has been integrated into the cast dental arch  12 . This is accomplished by aligning the alignment coping  50  so that axis  54  coincides with axis  42  of the encapsulated proxy implant  14 . The retainer screw  16  is then passed downwardly through the alignment coping  50  along the alignment barrel bore  52 . When the threaded end  62  of the retainer screw  16  encounters the threaded bore  40  of the proxy implant  14 , the retainer screw  16  is rotated by means of the socket or slot  66 . The thread  62  is sufficiently long to engage with the threaded central bore  40 . The threaded central bore  40  is deep enough, however, that the screw  16  can be rotated until the head  64  of the screw engages the upper surface of the locating barrel  50  and the lower surface of the locating barrel  50  engages the upper surface of the proxy implant  14  as shown in  FIG. 4 . 3 . The initial alignment stage is shown in  FIG. 4 . 1 . The assembly is shown in  FIG. 4 . 2  in a plan view and  FIG. 4 . 3  in an elevational view.  
      The next procedure then occurs in the dental laboratory facility. A stent  22  is fabricated on the crowns of the cast dental arch  12 . The stent  22  incorporates a plurality of crowns and should include enough of the crowns taken from the cast dental arch  12  so as to determine an accurate location of the stent relative to the assembly of the proxy implant  14 , retainer screw  16 , stent alignment arm  18  and locating barrel  20 . The stent  22  encompasses the cylindrical portion  70  and the wing portion  72  of the locating barrel  20  but does not otherwise engage with or encapsulate the stent alignment arm  18  nor the retainer screw  16 . The stent  22  may be made from any suitable material such as polymethyl methacrylate resin, bearing in mind that the stent needs to be relatively precise and will ultimately be placed within the patient&#39;s mouth. Thus, the material should be sterilizable or at least otherwise suitable for brief placement in the patient&#39;s mouth. The stent  22  is then left to fully set or cure.  
      When the stent  22  has fully set or cured, it is disassembled from the cast dental arch  12 .  FIG. 6  illustrates an exploded elevational view showing the disassembly. The retainer screw  16  is unscrewed so that the threaded end  62  is released from the threaded central bore  40  of the proxy implant  14 . The retainer screw can then be removed by being withdrawn upwardly as shown in  FIG. 6 . The removal of the retainer screw  16  thereby permits the removal of the stent alignment arm  18  from its position registering with the proxy implant  14 . The stent alignment arm  18  can be removed from the stent  22  by sliding the mold alignment arm upwardly relative to the stent  22  as shown in  FIG. 6 . This then leaves an assembly of the stent  22  incorporating the locating barrel  20 . The bore  74  and the locating barrel axis  76  of the locating barrel  20  is now located at a particular location and orientation relative to the proxy axis  42  of the proxy implant  14 . No further use need be made of the cast dental arch  12  and the proxy implant  14  contained therein may be disposed of in due course. Because the proxy implant  14  is intended to be disposed of, that proxy implant may be made from aluminium or similar material.  
      It will also be appreciated that as the locating barrel  20  has a defined depth defined by the depth control surface  80 , the surface  80  of the locating barrel when incorporated in the stent  22 , creates a depth reference.  
      The dental professional who will install the implant  28  thus receives from the dental laboratory the stent  22  which has been processed to fit precisely on the patient&#39;s teeth. One or more drills  26  as necessary are used to create the appropriate site in the patient&#39;s mouth to incorporate the dental implant  28 .  
       FIGS. 2 . 1  through  6 . 1  have all illustrated a cast of the dental arch placed on a flat surface such as a work bench in a position in which the crowns of the teeth face upwardly as displayed on the page and the references to up and down have been used in this description to designate directions relative to these figures. However, it will be recognized that this method and these components are equally useful whether it is the patient&#39;s upper dental arch or the lower dental arch that is to be the site of the dental implant. In  FIGS. 7 . 1 ,  7 . 2 ,  9 . 1  and  10 . 1 , the method and apparatus is illustrated installing a dental implant  28  in the patient&#39;s upper dental arch from whom the cast dental arch  12  illustrated in FIGS.  2  to  6  was made.  
      The first step will be for the dental professional to prepare the site for installation of the implant  28 . The patient&#39;s dental arch is illustrated at  90  in  FIG. 7 . 1 . The site for the implantation of the dental implant  28  is made ready by removing soft tissue and exposing the bone. This is illustrated diagrammatically by a flap of soft tissue illustrated at  92  having been raised thereby exposing the bone  94 . When the site is then ready for drilling a hole to accommodate the implant  28 , the stent  22  is fitted to the patient&#39;s dental arch  90 . Fitting the stent  22  to the patient&#39;s dental arch  90 , positions the incorporated locating barrel  20  with precise reference to the patient&#39;s actual dental arch  90 . The assembly of the stent  22  to the patient&#39;s dental arch  90  is illustrated in  FIG. 7 . 2 .  
       FIG. 8 . 1  illustrates a further component of the kit of  FIG. 1 . The drill alignment arm  24  comprises a drill alignment arm pin  100 . The drill alignment arm pin  100  is a generally cylindrical structure having a drill alignment pin axis  102 . The drill alignment arm  24  also includes an attachment screw  104 . The drill alignment arm  24  is attached to the drill head  110  which is installed on a dentist&#39;s drill hand piece  112 .  
      The drill head  110  accommodates a drill  26   a  illustrated in  FIG. 8 . 1 .  FIG. 8 . 2  illustrates the assembly of the drill alignment arm  24  to the drill head  110  in plan view. The drill alignment arm  24  thus defines the relative location of a drill axis  106  of the drill  26   a  when mounted in the drill head  110  with respect to the axis  102  of the drill alignment arm pin  100 . This relative distance is shown as  130  in  FIG. 8 . 2 . The distance  130  between the axes  102  and  106  is the same as the distance  132  between axes  54  and  58  of the stent alignment arm  18  ( FIG. 3 . 3 ).  
      In order to begin the procedure of boring the hole into which the dental implant  28  will be received, the dental practitioner places the first drill  26   a  in the drill head  110 . The drill  26   a  is then aligned in the correct position by sliding the drill alignment arm pin  100  with its axis  102  into the bore  74  of the locating barrel  20 . This then aligns the axis  102  of the drill alignment arm pin  100  with the axis  76  of the locating barrel  20 . Because the stent  22  accurately located the axis  76  relative to the axis  42  of the proxy implant  14 , the axis  106  of the drill  26  is aligned with the location of the axis  42  of the proxy implant  14 . Thus, the first drill  26   a  will drill a bore in the patient&#39;s bone  94  which is in exactly the same location as the axis  42  of the proxy implant  14 , the intended axis of the installed implant  28 . Depending upon the particular configuration of the implant  28 , several drills  26  may be utilized to make a bore of suitable diameter in the patient&#39;s bone  94 . Some implants have a threaded exterior surface and when that type of implant is desired, the final step in making the site in the bone may include the use of a tap to thread the bone to receive the implant.  
      As referred to above, the proximal height of the implant with respect of the patient&#39;s bone is also a critical component in determining the correct positioning of the implant. The depth of the bore in which the implant is to be installed is thus controlled by controlling the length of the drills provided to the dental practitioner for installing the implant. With drills of a predetermined length, the dentist aligns the drill head  110  by means of the stent  22  and its incorporated locating barrel  20  and advances the drill into the bone. The drill head  110  is then advanced proximally with respect to the host bone until the lower surface of the drill alignment arm  24  (as shown in  FIG. 8 . 1 ) abuts the surface  80  of the locating barrel  20 . Thus, the locating barrel  20  determines the location of the axis of the drill  106  and its angular orientation with reference to the crowns of the patient&#39;s dental arch and the length of the drill together with the surface  80  of the locating barrel determines the depth of the bore drilled into the patient&#39;s bone.  
      As discussed above, the kit preferrably involves the use of a set of drills having the same length but of differing diameters so that the bone may be drilled to the desired size and depth. However, alternatively, to give more freedom of judgement to the dental professional who will be installing the implant, it would be desirable to supply alternate sets of drills. One set would have the length recommended by the dental laboratory; additional sets, however, may have a length greater than intially recommended or a length less than recommended. There may be additional sets with lengths considerably longer or shorter than recommended. This would facilitate the exercise of the skill and judgment of the dental professional. By way of example, the dental professional upon opening the patient&#39;s soft tissue, may find that the quantity of bone present at the desired location is different from what was expected and that the implant should be positioned somewhat higher or lower in the bone than originally planned.  
      In each set of drills, all drills would have the same length. Thus, once the dental professional decides the proper depth, a drill set is selected and then all bores drilled will have the same depth.  
      When the site for receiving the implant has been drilled and tapped as necessary, the dentist may then install the implant using the drill head  110  while the drill alignment arm  24  remains attached to the drill head  110 . As the drill alignment arm pin  100  is passed into the locating barrel  20 , the implant  28  is installed coaxially with the axis of the drills  26  which have been use to make the bore.  
      Once the implant has been installed, to the correct depth, the assembly of the drill head  110  and drill alignment arm  24  is removed from the stent  22 . The stent  22  is then removed from the patient&#39;s teeth and the site of installation of the implant is closed to permit integration of the implant  28 .  
      The above procedure and components thus ensure that the implant  28  is located precisely in the location determined from the patient&#39;s dental cast when studied by the dental professionals in the laboratory as shown in  FIG. 2 . 2 .  
      When the procedure has been completed, the drill alignment arm  24  may be removed from the drill head  110  so that the drill head  110  can be used for other purposes. The drill head  110  is similar to the drill head which a dentist may already possess which is adapted to be driven by the dentist&#39;s drill hand piece  112 . The only adaption which is necessary is the modification which permits the drill alignment arm  24  to be attached to the drill head  110 . Conveniently, the drill alignment arm  24  may be provided with a screw  104 . To modify the drill head  110 , a threaded bore  136  is provided. The bore  136  is threaded to accept the screw  104 .  
      The drill head  110  attaches to the drill hand piece  112 . There are several options for this component of the kit of parts. A standard drill head could be modified as discussed above. Alternatively, a single piece drill head and drill alignment arm can be produced. The principal maintained is the axis  106  of a drill inserted into the drill head is at a known distance from the axis  102  of the drill alignment arm pin.  
      While the terms “up” and “down” have been used in this description of a preferred embodiment, the axis of drilling may not be vertically up or down, but may be located at any orientation as desired to meet the patient&#39;s needs.  
      The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.