Abstract:
A novel dental implant comprising an implant fixture assembly for attachment to a jaw bone at a first end thereof, the fixture assembly having a longitudinal axis; an abutment for mounting on a second end of the fixture assembly, the abutment having a longitudinal axis; and a fastener for connecting the abutment to the second end of the implant fixture assembly such that the abutment is movable on the second end of the implant fixture assembly and, upon disposition of the abutment axis at a selected angle to the implant fixture assembly axis, for connecting the abutment to the second end of the implant fixture assembly such that the abutment is fixed on the implant fixture assembly at the selected angle. A novel tool for deploying the novel dental implant is also disclosed. And a novel method for effecting a dental restoration is also disclosed.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates to dental apparatus and procedures in general, and more particularly to dental implants and tools and methods for effecting dental restorations using the same.  
       BACKGROUND OF THE INVENTION  
       [0002]     In many individuals, disease and/or injury may result in the loss of one or more natural teeth. As a result, various techniques have been developed to replace such lost natural teeth with prosthetic appliances.  
         [0003]     For example, where sufficient natural teeth remain adjacent to the location where a prosthetic tooth is to be positioned, a bridge may be fabricated.  
         [0004]     Alternatively, if insufficient natural teeth remain to support and stabilize a bridge, a denture may be fabricated, with the denture seating against the patient&#39;s gingiva.  
         [0005]     In still other situations, a dental implant may be used. With such a dental implant, a hole is generally first made in the upper or lower jaw bone, as appropriate, and then the distal end of the implant is fixed in the recipient bone, e.g., by screwing the implant into the bone. The dental implant is generally sized and positioned so that the proximal end of the implant protrudes at least partially into the space where the prosthetic tooth is to be positioned. Then the prosthetic tooth is fixed to the proximal end of the implant, such that the prosthetic tooth generally occupies the space of the lost tooth.  
         [0006]     While such dental implants can be effective, they also tend to suffer from a number of problems. Among other things, with current dental implants, the longitudinal axis of the prosthetic tooth must generally follow the longitudinal axis of the implant which is seated in the bone. Unfortunately, the optimal axial alignment for the implant seated in the bone may not necessarily be the same as the optimal axial alignment for the prosthetic tooth extending into the mouth. In particular, it has been found that the optimal axial alignment for the implant tends to be dictated by the specific anatomy of the patient&#39;s recipient jaw bone, while the optimal axial alignment of the prosthetic tooth tends to be dictated by the geometry of the patient&#39;s bite, lip support, phonetics and aesthetics. Thus, with current dental implants, the dental practitioner typically faces a choice of optimizing the orientation of the restoration for either (1) the implant seated in the bone, or (2) the prosthetic tooth extending into the mouth, or (3) some compromise in between. In any case, the result is generally a compromise of some sort.  
       OBJECTS OF THE INVENTION  
       [0007]     Accordingly, one object of the present invention is to provide a novel dental implant which avoids the problems associated with the prior art.  
         [0008]     Another object of the present invention is to provide a novel tool for use in deploying the novel dental implant of the present invention.  
         [0009]     And another object of the present invention is to provide a novel method for effecting a dental restoration.  
       SUMMARY OF THE INVENTION  
       [0010]     These and other objects are addressed by the present invention, which comprises a novel dental implant, a novel tool for deploying the same, and a novel method for effecting a dental restoration.  
         [0011]     The novel dental implant comprises an implant fixture assembly adapted for attachment to a jaw bone at a first end thereof, the implant fixture assembly having a longitudinal axis; an abutment for mounting on a second end of the implant fixture assembly, the abutment having a longitudinal axis; and a fastener for connecting the abutment to the second end of the implant fixture assembly such that the abutment is adjustably movable on the second end of the implant fixture assembly and, upon disposition of the abutment axis at a selected angle to the implant fixture assembly axis, for fixedly connecting the abutment to the second end of the implant fixture assembly such that the abutment is fixed on the implant fixture assembly at the selected angle.  
         [0012]     In one form of the invention, a novel tool is provided for setting the abutment on the second end of the implant fixture assembly by way of a screw interconnecting the abutment and the implant fixture assembly, the tool comprising a first elongated handle having a first hole therethrough; a first driver fixed proximate a distal end of the first handle, the first driver having a hole extending centrally therethrough and in alignment with the first handle hole; a second elongated handle; a second driver fixed proximate a distal end of the second handle and extendible through the first handle hole and the first driver hole and distally beyond the first driver; the first driver being engageable with an interior portion of the abutment and the second driver being engageable with an interior portion of a head portion of the screw.  
         [0013]     In another form of the invention, a novel tool is provided for setting the abutment on the second end of the implant fixture assembly, the implant fixture assembly being fixed at the first end thereof in a jaw bone, and the abutment being adapted to receive and retain a prosthetic tooth, the abutment having an axial cavity therein and extending therethrough, and the implant fixture assembly having a recess in the second end thereof in communication with a threaded bore in the implant fixture assembly, the abutment&#39;s axial cavity being shaped to receive the head portion of a screw and a first shank portion of that screw, and the implant fixture assembly being adapted to receive a second shank portion of the screw, the tool comprising a first elongated handle and a driver fixed on an end of the first handle, the driver and the first handle having a hole extending therethrough centrally of the driver, the driver being engageable with the abutment&#39;s axial cavity so as to hold the abutment in a non-rotative manner, and a second elongated handle and a second driver fixed on an end of the second handle, the second driver being extendible in the hole through the first handle and through the first driver so as to engage an internal recess in the head portion of the screw, wherein movement of the two handles together serves to tilt the abutment on the implant fixture assembly to a desired position, and holding the first handle stationary while rotating the second handle serves to advance the screw in the implant fixture assembly so as to lock the abutment in the desired position on the implant fixture assembly.  
         [0014]     The novel method for effecting a dental restoration comprises the steps of attaching an implant fixture assembly to a jaw bone; attaching an abutment to the implant fixture assembly by a retaining screw so as to permit tilting movement of the abutment on the implant fixture assembly; tilting the abutment on the implant fixture assembly so as to place a longitudinal axis of the abutment at a selected angle relative to a longitudinal axis of the implant fixture assembly; and fixing the abutment on the implant fixture assembly at the selected angle. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     These and other objects and features of the present invention will be more fully disclosed or rendered obvious by the following detailed description of the preferred embodiments of the invention, which is to be considered together with the accompanying drawings wherein:  
         [0016]      FIG. 1  is a side view in elevation of one form of dental implant formed in accordance with the present invention;  
         [0017]      FIGS. 2-8  show various aspects of the implant fixture assembly shown in  FIG. 1 ;  
         [0018]      FIGS. 9 and 10  show various aspects of the floating nut shown in  FIG. 1 ;  
         [0019]      FIGS. 11 and 12  show various aspects of the plug shown in  FIG. 1 ;  
         [0020]      FIGS. 13 and 14  show various aspects of the abutment shown in  FIG. 1 ;  
         [0021]      FIGS. 15-17  show different dispositions of the dental implant shown in  FIG. 1 ;  
         [0022]      FIGS. 18 and 19  show various aspects of the fixation screw shown in  FIG. 1 ;  
         [0023]      FIGS. 20-24  are side elevational views showing various steps in effecting a dental restoration using the dental implant shown in  FIG. 1 ;  
         [0024]      FIGS. 25-29  are various views illustrating a tool which may be used to set the abutment shown in  FIG. 1 ;  
         [0025]      FIGS. 30-32  show various aspects of a cover screw which may be used in conjunction with the dental implant shown in  FIG. 1 , with  FIG. 32  showing the cover screw mounted to the implant fixture assembly;  
         [0026]      FIGS. 33-35  show various aspects of an alternative form of cover screw which may be used in conjunction with the dental implant shown in  FIG. 1 , with  FIG. 35  showing the alternative form of cover screw mounted to the implant fixture assembly;  
         [0027]      FIG. 36  is a side view in elevation of an alternative form of a dental implant formed in accordance with the present invention;  
         [0028]      FIGS. 37-40  show various aspects of the implant fixture assembly shown in  FIG. 36 ;  
         [0029]      FIGS. 41-43  show various aspects of the abutment shown in  FIG. 36 ;  
         [0030]      FIGS. 43A, 43B  and  43 C show various aspects of an alternative form of the abutment shown in  FIG. 36 ;  
         [0031]      FIGS. 44 and 45  show various aspects of the fixation screw shown in  FIG. 36 ; and  
         [0032]      FIG. 46  illustrates a different disposition of the dental implant shown in  FIG. 36 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0033]     Looking first at  FIG. 1 , there is shown a dental implant  5  formed in accordance with the present invention. Dental implant  5  generally comprises an implant fixture assembly  100  and an abutment  200 .  
         [0034]     Implant fixture assembly  100  is adapted to be mounted to the patient&#39;s jaw bone. Implant fixture assembly  100  generally comprises a housing  105  ( FIGS. 1-8 ), a floating nut  110  ( FIGS. 1, 9 ,  10 ,  25 ,  32  and  35 ) and a plug  115  ( FIGS. 1, 11  and  12 ).  
         [0035]     Housing  105  ( FIGS. 1-8 ) comprises a hollow, sleeve-like structure having a distal end  120  ( FIG. 3 ) terminating in an opening  125  ( FIG. 3 ), and a proximal end  130  ( FIGS. 4, 5 ,  7 ,  8 ,  32  and  35 ) terminating in an opening  135  ( FIGS. 4, 6 ,  8  and  32 ). Screw threads  140  ( FIG. 3 ) are formed on the outer surface of housing  105  and extend from distal end  120  toward proximal end  130 , stopping just short of proximal end  130  (see  FIG. 4 ).  
         [0036]     Proximal end  130  comprises a generally semi-spherical geometry ( FIGS. 4, 5 ,  7 ,  8 ,  32  and  35 ), and includes a plurality of sharp facets  145  ( FIGS. 1, 4  and  5 - 8 ) formed thereon. Facets  145  are preferably formed on the housing&#39;s proximal end  130  so as to form a concentric pattern about the housing&#39;s semi-spherical dome ( FIGS. 5-8 ). However, facets  145  may also be formed on the housing&#39;s proximal end  130  in other configuration as well, e.g., they may be disposed in a matrix-like configuration, or some other ordered pattern (such as the concentric ribs  145 A shown in  FIGS. 6A and 8A ), or they may be disposed in a substantially random pattern (for example, by roughening the outer surface of housing proximal end  130 ). In any case, facets  145  are created so as to form relatively sharp, substantially clearly-delineated surfaces extending about the generally semi-spherical surface of the housing&#39;s proximal end  130  for engagement with circular rim  250  of abutment  200  as discussed in further detail below.  
         [0037]     The interior of housing  105  is formed so that a passageway  150  ( FIGS. 1, 3 ,  4  and  4 A) of constant diameter extends from distal opening  125  toward proximal end  130 . At the proximal end  130  of housing  105 , the housing defines a substantially hexagonal chamber  155  ( FIG. 4 ), which hexagonal chamber is defined by six planar surfaces  155 A,  155 B,  155 C,  155 D,  155 E and  155 F ( FIGS. 2 and 4 A). Preferably hexagonal chamber  155  is sized so that its six corner apexes are aligned with the wall of passageway  150 , and so that its three pairs of opposing surfaces (i.e., surfaces  155 A and  155 D, surfaces  155 B and  155 E, and surfaces  155 C and  155 F) have a narrower diameter than passageway  150 , as seen in  FIG. 4A . In this way, six lands or stops  158 A,  158 B,  158 C,  158 D,  158 E and  158 F are formed at the intersection of passageway  150  and hexagonal chamber  155  ( FIGS. 4 and 4 A). At the proximal end of hexagonal chamber  155 , housing  105  is undercut so as to form an inclined surface  160  ( FIG. 4 ) which narrows hexagonal chamber  155  to the size of proximal opening  135 . Surface  160  can be planar or arcuate when viewed in cross-section, as desired.  
         [0038]     Thus it will be seen that hexagonal chamber  155  and inclined surface  160  connect the housing&#39;s interior passageway  150  with proximal opening  135  ( FIG. 4 ). It is to be appreciated that the housing&#39;s central lumen narrows as it passes from interior passageway  150  to proximal opening  135 , due to the fact that the six surfaces  155 A- 155 F (making up hexagonal chamber  150 ) have a generally smaller diameter than central passageway  150 , and due to the fact that surface  160  is inclined proximally and distally in the manner shown in  FIG. 4 .  
         [0039]     Floating nut  110  ( FIGS. 1, 9 ,  10 ,  25 ,  32  and  35 ) comprises a substantially hexagonal outer wall  165  ( FIG. 9 ) made up of six semi-spherical surfaces  165 A,  165 B,  165 C,  165 D,  165 E and  165 F ( FIG. 10 ). Floating nut  110  terminates in a pair of end surfaces  170 ,  175  ( FIG. 9 ). A threaded bore  180  ( FIG. 10 ) extends through floating nut  110 , from end surface  170  to end surface  175 . Floating nut  110  is sized and shaped so that its six semi-spherical surfaces  165 A- 165 F will make a close sliding fit with the housing&#39;s six planar surfaces  155 A- 155 F when floating nut  110  is disposed in hexagonal chamber  155  ( FIG. 1 ), as will hereinafter be discussed.  
         [0040]     Plug  115  ( FIGS. 1, 11  and  12 ) comprises a generally cylindrical structure. Plug  115  is sized so that it can be press fit within interior passageway  150  ( FIG. 1 ) of housing  105 .  
         [0041]     Implant fixture assembly  100  is intended to be assembled by first loading floating nut  110  into the open distal end  125  ( FIG. 3 ) of housing  105 , with the floating nut&#39;s threaded bore  180  being generally axially aligned with the longitudinal axis of housing  105 , and then moving floating nut  110  down housing  105  until the nut is located within hexagonal chamber  155 , with the nut&#39;s semi-spherical surfaces  165 A- 165 F ( FIGS. 9 and 10 ) slidingly engaging the six planar surfaces  155 A- 155 F of hexagonal chamber  155  ( FIGS. 2 and 4 ). Then plug  115  is press fit into the distal end  125  of housing  105  and advanced proximally until the proximal end of plug  115  engages stops  158 A- 158 F located at the distal end of hexagonal chamber  155  ( FIG. 1 ). In this way, floating nut  110  is movably captured in hexagonal chamber  155 , between the housing&#39;s inclined surface  160  and the proximal end of plug  115 .  
         [0042]     It is to be appreciated that when floating nut  110  is movably captured in this position, the nut&#39;s threaded bore  180  will communicate with the opening  135  ( FIG. 4 ) formed in proximal end  130  of housing  105 , whereby the nut&#39;s threaded bore  180  can be engaged by an appropriate screw extending into the open proximal end of housing  105 , as will hereinafter be discussed.  
         [0043]     It is also to be appreciated that, due to the corresponding geometries of hexagonal chamber  155  and nut wall  165 , floating nut  110  can pivot in hexagonal chamber  155  about the longitudinal axis of the nut&#39;s threaded bore  180  (i.e., clockwise and counterclockwise, as viewed in  FIG. 9 ; see also  FIGS. 15-17 ), but will be held against rotation about the same axis (i.e., it will be held against rotation in a clockwise and counterclockwise sense, as viewed in  FIG. 10 ). As a result of this construction, floating nut  110  will be able to receive the nose of a screw set at a variety of different axial alignments relative to housing  105 , but will be held against rotation as that screw is screwed into and out of the floating nut.  
         [0044]     It should be appreciated that it is important to set the degree of pivot permitted floating nut  110  about the longitudinal axis of its threaded bore  180  (i.e., clockwise and counterclockwise, as viewed in  FIG. 9 ; see also  FIGS. 15-17 ). On the one hand, if floating nut  110  is permitted to pivot too far about this axis, its threaded bore  180  may not be easily accessible through the housing&#39;s proximal opening  135 . On the other hand, if floating nut  110  is not permitted to pivot far enough about this axis, it may unduly limit the axial alignment of abutment  200 , as will hereinafter be made clear. In the present design, the degree of pivot permitted floating nut  110  in hexagonal chamber  155  is established by the engagement of the floating nut&#39;s end surface  175  with the proximal end of plug  115 ; and this point of engagement is in turn determined by the position of the proximal end of plug  115  within housing  105 . As noted above, plug  115  is positioned so that its proximal end contacts stops  158 A- 158 F.  
         [0045]     Abutment  200  (FIGS.  1 ,  13 - 17  and  22 - 25 ) comprises a body  205  ( FIG. 13 ) having a distal end  210  and a proximal end  215 . A multi-stage bore  220  extends axially through abutment  200 , from proximal end  215  to distal end  210 . Multi-stage bore  220  comprise a first, hexagonally-shaped portion  225 ; second, cylindrically-shaped portion  230 ; a third, frustoconically-shaped portion  235 ; a fourth, cylindrically-shaped portion  240 ; and a fifth, hemispherically-shaped portion  245 . The portion of body  205  located adjacent to fifth, hemispherically-shaped bore portion  245  defines a relatively sharp, circular end rim  250  ( FIG. 13 ).  
         [0046]     Abutment  200  is sized so that its distal end  210  can fit over proximal end  130  of implant fixture assembly  100  ( FIG. 1 ), with the abutment&#39;s hemispherically-shaped bore portion  245  mating with the correspondingly-shaped proximal end  130  of implant fixture assembly  100 , and with the abutment&#39;s circular rim  250  engaging selected ones of facets  145  ( FIGS. 1, 4  and  6 - 8 ) or facets  145 A ( FIGS. 6A and 8A ). It will be appreciated that, due to the semi-spherical nature of the surfaces involved, implant fixture assembly  100  and abutment  200  can mate solidly with each other in a wide variety of different axial angles (see, for example,  FIGS. 1 and 15 - 17 ).  
         [0047]     A fixation screw  300  ( FIGS. 1, 18 ,  19 ,  22 ,  23 ,  24  and  25 ) is used to attach abutment  200  to implant fixture assembly  100 . Fixation screw  300  generally comprises a threaded distal portion  305  ( FIG. 18 ), a frustoconical intermediate portion  310 , and a cylindrical proximal portion  315 . Threaded distal portion  305  is sized so that it can pass through the abutment&#39;s multi-stage bore  220  ( FIG. 13 ) and threadedly engage threaded bore  180  of floating nut  110  ( FIGS. 1 and 15 - 17 ). At the same time, the fixation screw&#39;s frustoconical intermediate portion  310  is sized and shaped so that it will mate with the third, frustoconically shaped portion  235  ( FIG. 13 ) of the abutment&#39;s multi-stage bore  220  ( FIGS. 1 and 15 - 17 ). In addition, the screw&#39;s cylindrical proximal portion  315  ( FIG. 18 ) is sized so that it will slidingly fit within the second, cylindrically-shaped portion  230  ( FIG. 13 ) of the abutment&#39;s multi-stage bore  220 . A hexagonally-shaped recess  320  ( FIG. 18, 19  and  25 ) is formed in the fixation screw&#39;s cylindrical proximal portion  315 , whereby the fixation screw may be rotated, e.g., by a driver.  
         [0048]     Dental implant  5  is intended to be used as follows.  
         [0049]     First, an opening is formed in the patient&#39;s gingiva  400  ( FIG. 20 ), and then a hole  405  is formed in the patient&#39;s jaw bone  410  ( FIG. 20 ). In accordance with the present invention, hole  405  is formed so as to substantially optimize the safe and secure attachment of implant fixture assembly  100  to jaw bone  410 . Then implant fixture assembly  100 , previously assembled, is screwed, distal end first, into jaw bone  410  ( FIG. 21 ). As this is done, it is preferred, for the sake of subsequent convenience, that floating nut  110  be oriented within housing  105  so that the nut&#39;s threaded bore  180  is substantially aligned with the longitudinal axis of the housing, in the manner shown in  FIG. 21 . This disposition ensures that the nut&#39;s threaded bore  180  may thereafter be easily accessed through the housing&#39;s proximal opening  135  ( FIG. 4 ).  
         [0050]     Next, distal end  210  ( FIG. 13 ) of abutment  200  is brought into engagement with the proximal end  130  ( FIG. 4 ) of implant fixture assembly  100 , and fixation screw  300  is used to loosely secure the two members together ( FIG. 22 ). More particularly, fixation screw  300  is initially only loosely screwed into floating nut  110  of implant fixture assembly  100 , such that abutment  200  will be held to implant fixture assembly  100 , yet still be capable of being moved about relative to implant fixture assembly  100 . The dental practitioner then selects the precise orientation desired for abutment  200  relative to implant fixture assembly  100 . In accordance with the present invention, abutment  200  is intended to be oriented so as to substantially optimize the orientation of a prosthetic tooth which will subsequently be attached to the proximal end  215  ( FIG. 13 ) of abutment  200 .  
         [0051]     Once the proper orientation of abutment  200  has been established, fixation screw  300  is tightened (or torqued) with the proper torque all the way down ( FIG. 23 ), whereupon end rim  250  ( FIGS. 1 and 13 ) of abutment  200  will securely engage selected ones of the housing&#39;s facets  145  or  145 A, whereby subsequent slippage of abutment  200  relative to implant fixture assembly  100  will be prevented. If it is thereafter determined that the alignment of abutment  200  needs to be adjusted, fixation screw  300  may be loosened and the process repeated.  
         [0052]     Thereafter, after the deployment of dental implant  5  has been finalized, a prosthetic tooth  500  ( FIG. 24 ) may be fabricated in ways well known in the art, and then attached onto abutment  200 , also in ways well known in the art. By way of example but not limitation, once the deployment of dental implant  5  has been finalized, an impression of the patient&#39;s mouth may then be made, this impression thereafter used to fabricate prosthetic tooth  500 , and then the prosthetic tooth cemented onto abutment  200 . It should also be appreciated that the cement used to hold the prosthetic tooth onto abutment  200  will fill the multistage bore  220  and help hold fixation screw  300  fast.  
         [0053]     It is to be appreciated that with the dental implant  5  described above, fixation screw  300  follows the orientation of the abutment&#39;s multi-stage bore  220  ( FIGS. 1 and 13 ) and not (necessarily) the orientation of housing  105 , as seen in  FIGS. 23 and 24 .  
         [0054]     If desired, a tool  600  ( FIGS. 25-29 ) may be conveniently used to attach abutment  200  to implant fixture assembly  100 . Tool  600  generally comprises a first element  605  ( FIGS. 25-27 ) and a second element  610  ( FIGS. 25, 28  and  29 ). Second element  610  preferably comprises a torque wrench. First element  605  ( FIGS. 25-27 ) includes a handle  615  and a working end  620 . Working end  620  essentially comprises a driver mounted to the end of handle  615 . A bore  625  extends through handle  615  and working end  620 . Working end  620  is sized and shaped so as to fit within, and securely engage, the first hexagonally-shaped portion  225  ( FIG. 13 ) of the multi-stage bore  220  formed in abutment  200 . Second element  610  ( FIGS. 25, 28  and  29 ) includes a handle  630  and a working end  635 . Working end  635  essentially comprises an elongated second driver mounted to the end of handle  630 . Working end  635  is sized so as to pass through bore  625  formed in first element  605  and then fit within, and drivingly engage, the hexagonally-shaped recess  320  ( FIGS. 18 and 19 ) of fixation screw  300 . As a result of this construction, the tool&#39;s first element  605  permits abutment  200  to be held against rotation ( FIG. 25 ) while the tool&#39;s second element  610  permits fixation screw  300  to be turned down into, or withdrawn from, engagement with floating nut  110 . By fabricating second element  610  in the form of a torque wrench, the dental practitioner is quickly and easily able to set fixation screw  300  with the desired amount of torque.  
         [0055]     It should be appreciated that, by virtue of the fact that abutment  200  is held against rotation while fixation screw  300  is turned down into, or withdrawn from, engagement with floating nut  110 , high torque forces are not applied directly to implant fixture assembly  100 . As a result, abutment  200  may be tightened to implant fixture assembly  100  with the highest possible torque forces, without fear of undermining the osseo-integration of implant fixture assembly  100  to bone  410 .  
         [0056]     It should also be appreciated that, inasmuch as tool  600  comprises two interoperative elements  605  and  610 , with element  605  engaging abutment  200  and element  610  engaging fixation screw  300 , movement of the two elements  605  and  610  together can be used to tilt abutment  200  on implant fixture assembly  100  to the desired position, and movement of second element  610  relative to first element  605  can be used to move fixation screw  300  towards and away from floating nut  110 .  
         [0057]     In some circumstances it may be desirable to permit a period of healing to occur between placement of implant fixture assembly  100  in jaw bone  410  and the subsequent attachment of abutment  200  to implant fixture assembly  100 . In this case, it is generally desirable to temporarily cap off opening  135  of implant fixture assembly  100 .  
         [0058]     To this end, a “healing” cover screw  700  ( FIGS. 30-32 ) is provided. Cover screw  700  comprises a threaded post  705  ( FIGS. 30 and 32 ) for engagement with the threaded bore  180  ( FIG. 10 ) of floating nut  110 , an enlarged head  710  for seating in (and sealing off) opening  135  ( FIG. 4 ) of implant fixture assembly  100 , and a hexagonally-shaped recess  715  for receiving a wrench, by which cover screw  700  may be screwed into, or removed from, implant fixture assembly  100 .  
         [0059]      FIG. 32  shows how cover screw  700  may be screwed into opening  135  of implant fixture assembly  100  so as to close off the open proximal end of the implant fixture assembly.  
         [0060]     In effect, cover screw  700  forms a sort of plug for closing off the opening  135  ( FIGS. 4 and 32 ) formed in the proximal end  130  of implant fixture assembly  100  while the gingiva heals over it.  
         [0061]     In use, implant fixture assembly  100  is deployed in bone  410  in the manner previously described, cover screw  700  is used to close off opening  135  of implant fixture assembly  100 , and then gingiva  400  closed. After an appropriate period of healing, during which implant fixture assembly  100  can osseo-integrate with bone  410 , gingiva  400  is re-opened, cover screw  700  is removed from implant fixture assembly  100 , and then abutment  200  is attached to implant fixture assembly  100  using fixation screw  300  in the manner previously described.  
         [0062]     An alternative cover screw  720  ( FIGS. 33-35 ) is also provided. Cover screw  720  comprises a threaded post  725  ( FIGS. 33 and 35 ) for engagement with the floating nut&#39;s threaded bore  180 , an enlarged head  730  for seating over (and capping off) proximal end  130  of housing  105 , and a hexagonally-shaped recess  735  for receiving a wrench, by which cover screw  720  may be screwed onto, or removed from, implant fixture assembly  100 . Cover screw  720  is used in substantially the same manner as the cover screw  700  previously described, except that the enlarged head  730  of cover screw  720  is adapted to cover a substantial portion of the distal end  130  of implant fixture assembly  100  ( FIG. 35 ). In effect, cover screw  720  forms a sort of top cap for distal end  130  of implant fixture assembly  100 . This can prevent bone from growing over the implant&#39;s facets.  
         [0063]     Looking next at  FIG. 36 , an alternative dental implant  10  is shown. Dental implant  10  generally comprises an implant fixture assembly  800  and an abutment  900 .  
         [0064]     Implant fixture assembly  800  ( FIGS. 36 and 37 ) is adapted to be mounted to the patient&#39;s jaw bone. Implant fixture assembly  800  generally comprises a housing  805  having a distal end  810  and proximal end  815 . Housing  805  is preferably formed with a distal bore  820  extending proximally from distal end  810 , a proximal opening  822  opening on the proximal end of the housing, and an intermediate, threaded bore  825  connecting distal bore  820  with proximal opening  822 . Distal bore  820 , proximal opening  822  and intermediate threaded bore  825  are all aligned with the longitudinal axis of housing  805 . Screw threads  830  are formed on the outer surface of housing  805  and extend from distal end  810  toward proximal end  815 , stopping just short of proximal end  815 .  
         [0065]     Proximal end  815  comprises a generally semi-spherical geometry ( FIGS. 36 and 37 ) and includes a plurality of sharp facets  835  formed thereon. Facets  835  are preferably formed on the housing&#39;s proximal end  815  so as to form a concentric pattern about the housing&#39;s semi-spherical dome. However, facets  835  may also be formed on the housing&#39;s proximal end  815  in other configurations as well, e.g., they may be disposed in a matrix-like configuration, or some other ordered pattern (such as the concentric ribs  835 A shown in  FIGS. 37A and 37B ), or they may be disposed in a substantially random pattern (for example, by roughening the outer surface of housing proximal end  815 ). In any case, facets  835  are created so as to form a plurality of relatively sharp, substantially clearly-delineated surfaces extending above the generally semi-spherical surface of the housing&#39;s proximal end  815  for engagement with annular end rim  930  of abutment  900 .  
         [0066]     If desired, implant fixture assembly  800  can be fabricated from a single piece of material.  
         [0067]     Alternatively, implant fixture assembly  800  can be formed out of a housing A ( FIGS. 38 and 39 ) and an adapter B ( FIG. 40 ), with the two being joined together so as to form the complete implant fixture assembly  800 . In such a case, housing A might comprise an implant element of the sort well known in the art, where the element has a hex configuration C at its proximal end for turning the element into or out of a bone with a wrench; and adapter B might comprise a counterpart hex-shaped recess D, whereby adapter B can be seated upon housing A so as to form the complete implant fixture assembly  800 . Such a two-part construction can be advantageous in certain situations, such as where the patient might already have had a dental implant involving a housing A, and that housing A is already osseo-integrated into a jaw bone. In such a case, implant fixture assembly  800  can be formed in-situ, simply by mounting adapter B to the osseo-integrated housing A.  
         [0068]     Abutment  900  ( FIGS. 36 and 41 - 43 ) comprises a multi-stage passageway  905  ( FIG. 42 ) comprising a first stage  910 , a second stage  915  and a third stage  920 . First stage  910  widens laterally as it approaches the distal end of abutment  900  ( FIGS. 41 and 42 ). A shoulder  925  ( FIG. 42 ) is formed at the intersection of first stage  910  and second stage  915 . Third stage  920  is substantially identical to the fifth, hemispherically-shaped portion  245  previously described with respect to abutment  200  ( FIG. 13 ), i.e., it has a hemispherical shape which is complimentary to the semi-spherical geometry formed at the proximal end of the implant housing. Third stage  920  terminates in a relatively sharp annular end rim  930  which is substantially identical to the annular end rim  250  ( FIG. 13 ) described above with respect to abutment  200 .  
         [0069]     As a result of this construction, abutment  900  can be movably seated atop implant fixture assembly  800 , with the abutment&#39;s hemispherically-shaped bore portion  920  riding on the implant&#39;s semi-spherically-shaped proximal end  815 , and with the abutment&#39;s end rim  930  engaging selected ones of facets  835 . Thus, abutment  900  can be moved about through a range of different positions atop implant fixture assembly  800  (see  FIGS. 36 and 46 ).  
         [0070]     It is to be understood that the first stage  910  of multi-stage passageway  905  may have any one of several shapes within the scope of the invention in its broadest aspects.  
         [0071]     Thus, first stage  910  might be frusto-conical in shape, with its narrow end adjacent to second stage  915 . This configuration will allow the longitudinal axis of the abutment to be set at a selected angle in any one of multiple planes containing the longitudinal axis of implant fixture assembly  800  in a manner analogous to that discussed above with respect to the embodiment of the invention shown in  FIG. 1 .  
         [0072]     Alternatively, the first stage  910  of the passageway  905  may be formed in the shape of a slot, as shown in  FIGS. 41 and 43 .  
         [0073]     Similarly, the first stage  910  of passageway  905  might also take the form of only a portion of the slot shown in  FIGS. 41 and 43 . Thus, as is shown in  FIGS. 43A, 43B  and  43 C, the first stage  910  of passageway  905  might comprise an axial bore portion  911  having side slot portion  913  extending generally radially outwardly therefrom. If desired, first stage  910  of passageway  905  might extend out the side wall of abutment  900 , as shown in  FIGS. 43A, 43B  and  43 C. Such an arrangement may be desirable inasmuch as it permits the abutment  900  to be oriented at an increased angle relative to the vertical axis of implant fixture assembly  800 .  
         [0074]     Fixation screw  1000  ( FIGS. 36 and 44 - 46 ) is used to attach abutment  900  to implant fixture assembly  800 . Fixation screw  1000  generally comprises a threaded distal portion  1005 , a cylindrical intermediate portion  1010 , and an enlarged cylindrical proximal portion  1015 . A hexagonally-shaped recess  1017  is formed in the fixation screw&#39;s cylindrical proximal portion  1015 , whereby the fixation screw may be rotated, e.g., by a driver. A relatively sharp edge rim  1020  ( FIG. 44 ) is formed at the distal end of proximal portion  1015 . The fixation screw&#39;s edge rim  1020  engages the abutment&#39;s annular shoulder  925  ( FIGS. 42 and 46 ) so as to lock abutment  900  in the desired position relative to implant fixture assembly  800 . In this respect it is to be appreciated that the laterally-widening first stage  910  ( FIG. 42 ) of the abutment&#39;s multi-stage bore  905  accommodates the head of fixation screw  1000  as abutment  900  is moved off axis relative to implant fixture assembly  800 .  
         [0075]     Dental implant  10  is intended to be used in substantially the same way as the dental implant  5  described above. More particularly, an opening is first formed in the patient&#39;s gingiva, and then a hole is formed in the patient&#39;s jaw bone. In accordance with the present invention, the hole is formed in the patient&#39;s jaw bone so as to substantially optimize the safe and secure attachment of implant fixture assembly  800  to the jaw bone. Then implant fixture assembly  800  is screwed, distal end first, into the jaw bone. Next, the distal end of abutment  900  is brought into engagement with the proximal end  815  of implant fixture assembly  800 , and fixation screw  1000  is used to loosely secure the two members together. More particularly, fixation screw  1000  is initially only loosely threaded into threaded bore  825  of implant fixture assembly  800 , such that abutment  900  will be held to implant fixture assembly  800 , yet still be capable of being moved about relative to implant fixture assembly  800 . In this respect it will be appreciated that the laterally-widening first stage  910  ( FIG. 42 ) of the abutment&#39;s multi-stage bore  905  will accommodate the head of fixation screw  1000  as abutment  900  is moved off axis relative to implant fixture assembly  800 . The dental practitioner then selects the precise orientation desired for abutment  900  relative to implant fixture assembly  800 . In accordance with the present invention, abutment  900  is intended to be oriented so as to substantially optimize the orientation of a prosthetic tooth which will be attached to the proximal end of abutment  900 . Once the proper orientation of abutment  900  has been established, fixation screw  1000  is tightened all the way down, whereupon the fixation screw&#39;s annular rim  1020  will engage the abutment&#39;s shoulder  925  and thereby force the abutment&#39;s annular rim  930  into secure engagement with selected ones of the housing&#39;s facets  835 , whereby subsequent slippage of abutment  900  relative to implant fixture assembly  800  will be prevented. If it is thereafter determined that the alignment of abutment  900  needs to be adjusted, fixation screw  1000  is loosened and the process repeated. Thereafter, after the deployment of dental implant  10  has been finalized, a prosthetic tooth may be fabricated in ways well known in the art, and then attached onto abutment  900 , also in ways well known in the art. It should be appreciated that the cement used to hold the prosthetic tooth onto abutment  200  will fill the multistage bore  905  and help hold fixation screw  1000  fast. In this respect it should also be appreciated that the abutment and screw are preferably formed so that the cement will be able to fill around the head of the screw, in the manner shown in  FIGS. 36, 46  and  43 C.  
         [0076]     It is to be appreciated that with the dental implant  10  described above, fixation screw  1000  follows the orientation of housing  805  and not (necessarily) the orientation of abutment  900 , as seen in  FIG. 46 .  
         [0077]     It should also be appreciated that, if desired, tool  600  may be used to set abutment  900  on implant fixture assembly  800 .  
         [0078]     And it should be appreciated that cover screw  700 , or cover screw  720 , may be used in conjunction with dental implant  10 , if it is desired to seal off the open proximal end of implant fixture assembly  800  during a period of healing.  
         [0079]     In addition, it should also be appreciated that the outer surface  200 A of abutment  200  ( FIG. 1 ), and the outer surface  900 A of abutment  900  ( FIG. 36 ), are preferably formed with a profile which is tapered in the manner shown. More particularly, the profile preferably comprises a hollow ground profile which provides a concave geometry. This taper is advantageous in that it (1) provides a good path of insertion, (2) provides a good mechanical interlock with the dental prosthesis which will be mounted on the abutment, (3) permits the prosthesis to be set with the desired disposition on the abutment, i.e., it permits the prosthesis to be set at the desired angle on the abutment, and (4) provides a space for receiving a substantial quantity of luting material. In one preferred form of the invention, the outer surface  200 A of abutment  200 , and the outer surface  900 A of abutment  900 , is set at an angle of 6-12 degrees off the longitudinal axis of the prosthesis.  
         [0080]     Furthermore, dental implant  5  might have its implant fixture assembly  100  formed without screw threads  140  formed thereon. More particularly, implant fixture assembly  100  might have some other external geometry to facilitate its fixation in the patient&#39;s jaw bone  410 , e.g., it might be formed with a generally cylindrical external geometry, with an external surface configured to promote osseointegration, or carrying an external surface coating adapted to promote osseointegration. Correspondingly, dental implant  10  might have its implant fixture assembly  800  similarly formed.  
         [0081]     It is to be understood that the present invention is by no means limited to the particular constructions herein disclosed and/or shown in the drawings, but also comprises any modifications or equivalents within the scope of the claims.