Patent Publication Number: US-7214062-B2

Title: Method and apparatus for replicating the position of intra-osseous implants and abutments relative to analogs thereof

Description:
RELATED APPLICATIONS 
   Benefit is claimed of provisional application No. 60/274,498 filed Mar. 9, 2001. 
   FIELD OF THE INVENTION 
   This invention relates generally to medical and dental implant devices and more particularly to a method for transferring the relative position of an intra-osseous implant relative to a laboratory replicated position, as in a dental abutment, and for determining the appropriate height of a dental abutment received in an implant for an aesthetic submucosal prosthetic margin placement. 
   BACKGROUND OF THE INVENTION 
   Implant systems comprising an implant having a tapered bore adapted to receive therein an abutment post or the like formed with a matching taper for retention of the post in the implant are known. See for example U.S. Pat. No. 4,738,623, assigned to the assignee of the present invention, the disclosure of which is incorporated herein by this reference. It is also known to provide such posts, which are intended to be used as impression posts or temporary abutment posts, with a longitudinally extending slot in the end thereof in order to more easily remove the posts. Generally, such posts are made of titanium or titanium alloy due to their biocompatibility characteristics. However, titanium has a major limitation relating to the phenomenon of memory. It is possible for the diameter of the slotted post to either widen or narrow over time making the nature of the fit of the post in an abutment unpredictable. The property of memory can cause an abutment to become loose in clinical function and result in an unpredictable degree of retention. 
   There is a need to be able to replicate the position that an abutment would have in an implant in a system using abutment analogs, impression posts and the like made of the same or different materials which accurately and reliably correspond to the locked position of a permanent abutment in an intra-osseous implant. Among the factors which need to be dealt with in doing this is the existence of hydraulic pressure resisting the seating of a post as well as the need for having the post retain its seated position whether gravity is adding a force against seating or toward seating, as in the use in upper teeth versus lower teeth. There is also a need to be able to determine the appropriate height of an abutment which will provide an aesthetic submucosal prosthetic margin placement. 
   SUMMARY OF THE INVENTION 
   It is an object of the invention to overcome the prior art limitations noted above. Another object of the invention is the provision of an impression post and any other post, such as a temporary abutment post, wherein a clinician will want to remove the post with minimal, predictable effort. 
   Briefly, in accordance with one embodiment of the invention, the post of a member, such as an abutment analog, impression post, implant transport handler, healing plug and the like, is formed with a radially outwardly extending stop surface such as a shelf having a diameter larger than the diameter of the bore in a permanent implant and an implant analog and located at a distance from the longitudinal axial position of a reference location of a head formed on the post essentially equal to the distance from the top end surface of a permanent implant to a corresponding reference location of a head of an abutment with the abutment in a clinically locked position as a result of being tapped into the implant. 
   According to another embodiment, an implant analog is formed with a shelf in the bore of the implant analog located at a distance from the mouth of the bore, i.e., the top surface of the implant analog, essentially equal to the distance between the bottom end face of the tapered post of a permanent abutment and the longitudinal axial position on the tapered post at the top face surface of the permanent implant with the permanent abutment in the locked position upon receiving clinical tapping insertion force. The shelf prevents a tapered permanent abutment post from over-seating in an implant analog, which is particularly important when the implant analog is composed of plastic material. According to a feature of the invention, the cylindrical bore of the implant analog can be provided with one or more flats to increase the retention resistance of a cylindrical post, with or without a taper, received therein as well as to provide an axially extending air passage to relieve or prevent the build up of hydraulic pressure in the closed end of the bore. 
   According to a feature of the invention, retentive resistance of the post of the abutment analog, impression post, implant transport handler, healing plug and the like can be increased by forming one or more circumferential rings about the posts, at least one of the rings having an outer diameter larger than the diameter of an implant bore to form an interference fit and preferably, the at least one ring being flexible and having a feathered, or otherwise shaped configuration so that upon being inserted into the bore of the implant the outer peripheral portion of that ring will bend in a direction opposite to the direction of insertion so that upon removal of the post the outer peripheral portion of the ring will have to bend back on itself thereby requiring a greater removal force than insertion force. 
   According to yet another embodiment of the invention, an elongated probe member having a size to be freely insertable in the bore of an implant is formed with a plurality of axially positioned index configurations, such as circumferential grooves, located in the probe member at selected distances from the free distal end of the probe member corresponding to the position of given reference locations of a clinically seated abutment in the implant. The index configurations indicate the axial position of a given geometry of the implant bore as a reference point so that the appropriate height of an abutment shoulder can be determined to achieve an aesthetic submucosal prosthetic margin placement. 
   Additional objects and features of the invention will be set forth in part in the description which follows and in part will be obvious from the description and drawings. The objects and advantages of the invention may be realized and attained by means of the instrumentalities, combinations and methods particularly pointed out in the appended claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention and, together with the description, serve to explain the objects, advantages and principles of the invention. In the drawings: 
       FIGS. 1   a ,  1   b  are cross sectional views which show a prior art arrangement of an abutment received in the bore of an implant using a first level of pressure, such as finger pressure and a second level of pressure, such as by clinically applied tapping, to a locked position in the bore, respectively;  FIGS. 1   c ,  1   d  are similar cross sectional views which show an impression post made in accordance with a first embodiment of the invention, partially received in the bore of an implant and fully seated therein, respectively;  FIGS. 1   e ,  1   f  are similar cross sectional views which show an impression post partially received in the bore of an implant analog made in accordance with another embodiment of the invention and fully seated therein; and  FIGS. 1   g ,  1   h  are similar cross sectional views which show an abutment partially received in the bore of the implant analog of  FIGS. 1   e ,  1   f  and fully seated therein, respectively; 
       FIG. 2  is an elevational view of an impression post made in accordance with another embodiment of the invention and  FIG. 2   a  is an enlarged, broken away portion of  FIG. 2 ; and 
       FIG. 3   a  is a cross section view taken through an intra-osseous mounted implant with an indicator probe made in accordance with the invention received in the bore of the implant, and  FIG. 3   b  is a view similar to  FIG. 3   a  but showing an abutment received in the bore of the implant at an apical position related to index configurations of the indicator probe. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   With reference to  FIGS. 1   a ,  1   b , a conventional implant  10  is shown having a well or bore  10   a  formed with a female locking taper as disclosed in detail in U.S. Pat. No. 4,738,623 referenced above. Dashed line  2  extends through the top end surface  10   b  of the implant shown in  FIGS. 1   a – 1   d  and the top end surface  16   b  of the implant analogs shown in  FIGS. 1   e – 1   h  to be discussed. Dashed lines  4  and  6  show the same reference distances from dashed line  2  in the respective figures. The post  12   a  of an abutment  12 , also provided with a male locking taper, is received in bore  10   a  at a first apical position relative to the top end surface  10   b  of the implant when a first lower pressure level is used to place the implant, as by finger pressure. Dashed line  2  aligned with the top end surface  10   b  denotes the axial position of post  12   a  in the first, partially seated position at a distance d1 measured along the longitudinal axis of post  12   a  and bore  10   a  from a reference point of the abutment, e.g., the lower end of basal portion  12   c  of head  12   b . Abutment  12  is shown with a head  12   b  including curved basal portion  12   c  and shoulder  12   d  for receiving thereon a suitable crown or the like, not shown.  FIG. 1   b  includes the same implant and abutment but is shown with the abutment post after being seated in a second locked position as by tapping the abutment with a clinically applied tapping force. In the fully seated second position the axially measured distance between dashed line  2  and the same reference point is d2. The change in the apical positions of  FIGS. 1   a  and  1   b  has been shown to be 0.006 inch for 0.0785 inch diameter post and 0.010 inch for 0.1185 inch diameter post systems having a locking taper of 1.5 degrees and received in respective bores of 0.0785 inch and 0.1185 inch having a matching locking taper. The distance d2 is the average distance which was determined by taking a group of abutments for each diameter post and measuring the individual d2 distance for each abutment upon clinical seating thereof. The distance is essentially equal from one abutment to another of a group within manufacturing tolerances and with little or no difference noted for any variations of clinical insertion force used. 
   In accordance with a preferred embodiment of the invention, a radial, outwardly extending shoulder  14   c  is formed on post  14   a  of impression post  14  at an axial distance d2 from a reference point  14   f  corresponding to the reference point  12   f  of the abutment shown in  FIGS. 1   a ,  1   b . The outer portion of post  14   a  is preferably formed with no taper and with a diameter to permit full insertion into the tapered bore of implant  10 . The provision of shoulder  14   c , chosen to have an outer diameter greater than the opening of bore  10   a , results in placement of head portion  14   b  in essentially the same position in implant  10  as head  12   b  of abutment  12  in implant  10 . A reference configuration, e.g., circumferential groove  14   g  of post  14  can be used to reflect the position of top end face  12   e  of an abutment as noted by dashed line  6 . Although an impression post member is shown in the drawings, it will be understood that shoulder  14   c  can be provided on the post of other members such as abutment analogs, healing plugs and the like for receipt in the bore of an implant to obtain the same benefits. Further, it should be realized that shoulder  14   c  can be discontinuous or formed as spaced apart stop surfaces, if desired. 
   Referring to  FIGS. 1   e – 1   h , an implant analog  16  made in accordance with another embodiment of the invention comprises a body made of polycarbonate or other suitable plastic such as ultra high molecular weight polyethylene (UHMW-PE), or a composite, ceramic or metal and is shown having a bore  16   a  of generally the same diameter as bore  10   a  of implant  10  however the bore may have a straight bore if desired. Bore  16   a  is formed with a shelf  16   c  formed at a depth or axial distance from the end face surface  16   b  of the implant analog which is essentially the same as the distance between dashed lines  2  and  4 , that is, the axial distance from the top end surface  10   b  of implant  10  and the bottom end face surface  12   g  of abutment  12  when in the second, fully seated locked position of  FIG. 1   b . Placement of shelf  16   c  in this position limits travel of an abutment post when inserted into bore  16   a  as shown in  FIG. 1   h  and prevents over-seating of an abutment having no shoulder on the post thereof for that purpose. Bore  16   a  preferably extends beyond shelf  16  as indicated at  16   d  to minimize the effects of hydraulic pressure build up as a post is inserted in the bore. Preferably the axial distance of post  14   a  of impression post  14  from shoulder  14   c  to end face surface  14   h  of the post is selected to be slightly less than the distance of post  12   a  of abutment  12  from an axial location at dashed line  2  in  FIG. 1   b  indicating a clinically seated abutment and end face surface  12   g  of the abutment to ensure that shoulder  14   c  limits travel as it engages top end surface  16   b  of implant analog  16 . 
   Typically, implants  10  and abutments  12  are composed of titanium or titanium alloys for biocompatibility while the implant analogs and impression posts and the like are composed of plastic such as polycarbonate and ultra high molecular weight polyethylene (UHMW-PE), composites or other suitable materials. This results in a problem in simulating the locking taper of the titanium implants and abutments when using a different material for the abutment analog or impression post and when using them without a locking taper. That is, the problem of achieving the same axial displacement without the same retention and in achieving the same lateral stability of the posts from one female bore to another. According to a modified embodiment of the invention, one or more flat surfaces  16   e  ( FIG. 1   e ) is formed in bore  16   a  of implant analog  16  to form a limited interference with a generally cylindrical post to increase retentive force and stability of a post received therein. Usually, a plurality of flats, preferably symmetrically spaced about the periphery of the bore, are formed to provide consistent placement of a post in the bore of an implant analog relative to the bore of an implant. Such flats also provide an axially extending air passage to allow air to escape as a post is being inserted in the bore and thereby minimize hydraulic pressure build up. 
     FIGS. 2 and 2   a  show an impression post  18  made in accordance with another preferred embodiment of the invention which is formed of suitable material which in thin configurations has a degree of flexibility, such as some plastic materials, e.g., polycarbonate or ultra high molecular weight polyethylene (UHMW-PE), and formed with circumferentially extending rings or rib like formations  18   b ,  18   c  on the portion of post  18   a  receivable in the bore of an implant or implant analog. Post  18   a  is cylindrical and can be formed with or without a taper. At least one of the rings is formed to provide an interference fit. Ring  18   b  is used in cooperation with ring  18   c  to provide enhanced lateral stability in a bore. Ring  18   c  has a slightly larger diameter than ring  18   b  to form an interference fit and is somewhat feathered at its outer periphery or otherwise configured to allow it to be bent in a direction toward or away from the distal free end of the post. When used in a properly sized bore with or without a locking taper, the material of ring  18   c  is bent upon insertion of the post into such a bore in a direction opposite to the direction of insertion with the outer portion of the ring material being closer to the entrance to the bore than the remainder of the ring. When the post is then removed the outer portion bends back in the opposite direction, that is, in effect, it is folded back on itself into an ogee type of configuration, due to the limited space available, with the base of the ring or rib like formation gradually advancing to the position of the outer portions and finally assuming a position with the base portion being closer to the entrance of to the bore than the outer portion. This reverse bending increases the retentive force required for removal, in a manner predictably controlled by the material and dimensions of the rings relative to the bore. As a result of this, the force required to remove the post from such a bore is greater than the force required to insert the post into the bore. It will be understood that ring  18   c  can be used by itself, if desired, to provide a retention resistance greater than an insertion resistance for a post. Likewise, ring  18   b  can be used by itself to provide lateral stability as well as retention resistance with the ring having a tight fit or an interference fit, as desired. It will also be understood that rings as described above can be provided on the posts of other members receivable in the well of an implant abutment, e.g., an abutment analog. 
   Impression posts were made in accordance with the invention having a nominal post diameter of 0.113/0.112 inch for a 0.1185 inch diameter bore and provided with first and second spaced apart, circumferentially extending, rings or rib like formations. The first ring, closest to the free end of the post has an outer diameter of 0.116/0.115 inch and the second ring has an outer diameter of 0.119/0.118 inch. Members having another post size were made having a nominal post diameter of 0.073/0.072 inch for a 0.0785 inch diameter bore, the first ring has a diameter of 0.076/0.077 inch and the second ring has a diameter of 0.079/0.080. 
   With reference to  FIGS. 3   a  and  3   b , a generally elongated indicator probe  20  comprises a head portion  20   a  formed with an outer periphery of a size selected to be freely received in the bore of an implant  10  with the distal free end engaging the bottom wall of the bore. Implant  10  is shown in the drawings implanted in the bone of a patient. Horizontally extending, spaced apart index points or configurations  20   c  are formed on the probe body at locations corresponding to the axial positions of reference points or configurations of an abutment  12  ( FIG. 3   b ) to be clinically seated in the implant. For example, a longitudinal axial distance d3 from the bottom surface of the bore of implant  10 , represented by dashed line  8 , to shoulder  12   d  of abutment  12 , represented by dashed line  9 , clinically seated in the second locked position in the implant as shown and described in  FIG. 1   b , is essentially the same as the axial longitudinal distance d3 from the distal end surface  20   b  to index configuration  20   c  of probe  20  when bottomed out in the bore of implant  10  of  FIG. 3   a . Thus probe  20 , when seated in the bore of an intra-osseous implant will indicate the axial position of various geometries on posts inserted into the implant relative to the height of soft tissues overlying the implant by index configurations  20   c – 20   g.    
   Axial adjustment is essential for the fabrication of integrated abutment crowns, i.e., prefabricated or custom crowns mounted, bonded or fabricated on abutments extra-orally, where the proper anatomical relationships and adjustments needed to obtain them are greatly enhanced and facilitated by means of the above described features of the invention. 
   Although the invention has been described with regard to a certain specific embodiment thereof, variations and modifications will become apparent to those skilled in the art. For example, although the post is described as generally cylindrical, it is within the skill of the art to use any selected outer configuration, such as elliptical, if desired, in conjunction with rib like formations extending around the circumference as taught by the invention. It is, therefore, the intention that the appended claims be interpreted as broadly as possible in view of the prior art to include all such variations and modifications.