Abstract:
A two-piece dental abutment having a cuff portion that is removable from a upper portion. The upper portion engages and retains the cuff portion during abutment placement.

Description:
This is a continuation-in-part of U.S. application Ser. No. 09/126,511, filed on Jul. 30, 1998, now U.S. Pat. No. 6,012, 923 by Jeffrey A. Bassett, Peter S. Armstrong, Carl W. Pettersen, and Philip S. Lyren, entitled TWO-PIECE DENTAL ABUTMENT WITH REMOVABLE CUFF. 
    
    
     BACKGROUND OF THE INVENTION 
     During a typical dental implantation procedure, the tissue surrounding the jawbone is cut to expose the implantation site. A hole is drilled into the bone, and a dental implant is positioned into this hole. The tissue is then sutured, and the implant is left in the bone for several months as healing and osseointegration occur. During this healing period, a prosthesis or artificial tooth is custom made to fit in the patient&#39;s mouth. During a second surgical procedure, the tissue surrounding the implantation site is again cut. The prosthesis is then connected to the end of the implant. 
     Typically, a dental abutment is located between the implant and prosthesis. The abutment serves several functions but generally provides a structure for extending the implant above the gum-line. One end of the abutment connects to the implant while a second end of the abutment connects to the prosthesis. Typically, a screw holds the abutment to the implant, and either another screw or cement holds the abutment to the prosthesis. 
     Abutments may have numerous configurations, but generally they have a straight or angled cylindrical configuration. U.S. Pat. No. 5,069,622 entitled “Spacer” to Rangert et al. illustrates an angled abutment, shown in FIG. 1 (prior art). 
     FIG. 1 shows a one-piece angled abutment at  10 . This abutment includes a conical base portion  12  and a conical upper portion  14 . These two portions are not removable from one another and are formed together to make a unitary member. 
     A first bore  16  extends downwardly through both the base and upper portions, and a second threaded bore  18  extends through the upper portion. The base portion  12  has a conical shape and includes a bottom surface  20  that abuts against the end of an implant (not shown). An interior portion of the bottom of bore  16  has a non-cylindrical shape  22  to provide anti-rotational engagement between the abutment and implant. A screw (not shown) passes into bore  16 , abuts against a ledge  24 , and holds the abutment to the implant. 
     The upper portion  14  tapers away from the base portion at a preselected angle, preferably between 25° and 40°. The prosthesis fits around the upper portion and abuts against a ledge  26  at the top of the base portion. A screw (not shown) passes into a threaded bore  18  to hold the prosthesis to the abutment. 
     One important disadvantage with prior straight and angled abutments is that the base portion cannot be removed from the upper portion. In some instances, however, the base portion needs to be removed or replaced. For example, the tissue surrounding the base of the abutment tends to recede over time. As this tissue recedes, more and more of the abutment is visible in the patient&#39;s mouth. The abutment, usually made of the metal titanium, has an unappealing appearance and disrupts the aesthetic quality of the prosthesis. 
     As another disadvantage, prior abutments have base and upper portions made from the same material. Generally, the abutments are formed as a solid piece of titanium or other suitable material. Numerous advantages could be realized if the base portion were formed from one material while the upper portion were formed from another material. 
     As another disadvantage, prior abutments are not well suited to have the base portion colored or coated while leaving the upper portion uncolored or uncoated. 
     The present invention solves the problems discussed above with prior dental abutments and provides further advantages. 
     SUMMARY OF THE INVENTION 
     The present invention is directed toward a multi-piece abutment having a cuff portion that can be removed from an upper portion. The cuff and the upper portion are two separate pieces that connect together to form the abutment. The upper portion has a base that connects to the top of the cuff. Once the upper portion and cuff are connected, the abutment is used in a conventional fashion with the cuff attaching to the implant and the upper portion attaching to the prosthesis. 
     The present invention has numerous advantages. For instance, after the prosthesis is connected to the abutment and placed in the mouth of the patient, the abutment may be disassembled into two separate pieces. In some circumstances, the cuff of the abutment may need to be replaced with a new or different cuff. This replacement cuff, for example, may be shorter or wider than the original cuff to compensate for receding tissue around the prosthesis. 
     As another advantage, the upper portion and the cuff may be made from different materials. Various combinations of materials may be used to meet particular needs of the patient. For example, the cuff may be formed from a material having good aesthetic qualities, especially where the abutment is likely to be exposed, and the upper portion may be formed from a material having a high strength, especially where the abutment requires added strength. The upper portion, for instance, could be made from titanium while the cuff is made from a gold alloy, polymer, or ceramic. 
     As another advantage, the cuff may be colored or have a coating, such as porcelain. This coloring or coating could be separate from the upper portion and would enhance the aesthetics of the abutment. 
     The invention, accordingly, comprises the apparatus and method possessing the construction, combination of elements, and arrangement of parts that are exemplified in the following detailed description. For a fuller understanding of the nature and objects of the invention, reference should be made to the following detailed description taken in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an angled dental abutment known in the prior art; 
     FIG. 2 is an exploded view of a dental implant and a two-piece dental abutment according to the present invention; 
     FIG. 3 is a side-view of the abutment and implant of FIG. 2 connected together; 
     FIG. 4A is a cross sectional view of the abutment having a straight upper portion; 
     FIG. 4B is a cross sectional view of the abutment having a conical upper portion; 
     FIG. 5 is an exploded view of an alternate two-piece dental abutment; 
     FIG. 6 is a partial view of a completely restored dental prosthesis; 
     FIG. 7 is an exploded view of the prosthesis and abutment of FIG. 6; 
     FIG. 8 is an exploded view of a dental implant and an alternate two-piece dental abutment according to the present invention; 
     FIG. 9 is an exploded view of a dental implant and an another alternate two-piece dental abutment according to the present invention; 
     FIG. 10A is an exploded view of a dental implant and yet another alternate two-piece dental abutment according to the present invention; 
     FIG. 10B is an exploded view of a dental implant and yet another alternate two-piece dental abutment according to the present invention; 
     FIG. 11 is a partial cross sectional view of yet another alternate two-piece dental abutment according to the present invention; 
     FIG. 12A is an exploded view of another alternate two-piece abutment; 
     FIG. 12B is an exploded view of another alternate two-piece abutment; 
     FIG. 12C is an exploded view of another alternate two-piece abutment; and 
     FIG. 13 is a top view of the upper portion of FIG.  12 A. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 2 and 3 show a multi-piece dental abutment  100  connecting to an implant  102 . The abutment consists of two separate pieces, a cuff  104  and an upper portion  106 . The cuff and upper portion may be connected together and attached to the implant. 
     Implant  102  has a coronal end  108  with a threaded bore  110  and a plurality of upwardly extending tines  112 . A distal end  114  of the implant shows a bore  116  for aiding integration between the implant and bone. The implant may be any one of various dental implants known to those skilled in the art, such as a TWIST™ implant manufactured by Sulzer Calcitek, Inc. of Carlsbad, Calif. 
     Turning also FIGS. 4A and 4B, two different embodiments for the abutment  100  are shown in greater detail. Cuff  104  has a conical cross section that tapers from a support surface  120  to a top portion  122 . This cross section could also have a more straight cylindrical configuration. Surface  120  abuts against a ledge  124  at the coronal end of the implant. Top portion  122  includes a tapered shoulder  126  that abuts against the bottom end of a prosthesis (not shown). The top portion also includes a threaded section  128 . These threads extend along the interior wall formed from a cylindrical bore  130  that extends through the cuff. 
     The upper portion  106  has a base portion generally denoted at  140 . This base includes a lip  142  with an adjacent threaded section  144 . A plurality of tines  146  extend downwardly to the end of the base. Threads  144  on the upper portion engage threads  128  on the cuff to connect the upper portion and cuff and form an assembled abutment. When the abutment is assembled, the tines  146  on the base extend into bore  130 . These tines then engage with the tines  112  at the coronal end of the implant. Together, these two sets of tines provide anti-rotational engagement between the implant and the abutment. 
     The upper portion  106  also includes a top portion  150  that extends from lip  142  to an end surface  152 . A cylindrical bore  154  extends from end  152  through the base  140 . This bore aligns with the bore  130  in the cuff when the abutment is assembled. The bore  154  in the upper portion includes a shoulder  156 . 
     As best shown in FIG. 2, a screw  160  passes into bore  154  in the upper portion until the head  162  of the screw abuts against shoulder  156 . A threaded portion  164  of the screw fits into the coronal end of the implant to engage corresponding threads in bore  110 . As shown in FIG. 3, the screw holds the assembled abutment to the implant. 
     FIGS. 4A and 4B show two different upper portions. In FIG. 4A, the upper portion  104  connects to the cuff to form a straight abutment. Typically, straight abutments have either a slightly tapering conical configuration (as shown in FIG. 4A) or a non-tapered or straight cylindrical configuration (not shown). 
     In FIG. 4B, the upper portion connects to the cuff to form an angled abutment. Typically, these abutments have either a tapering conical configuration (as shown in FIG. 4B) that angles with respect to the base or a non-tapered or straight cylindrical configuration (not shown) that angles with respect to the base. The angled abutments are available with angles ranging from about 5° to about 40°. 
     Abutments usually connect to the prosthesis with cement or a screw. FIG. 4A illustrates a cement retained connection. The prosthesis fits around the conical top portion  150 , and cement is used to attach the prosthesis to the upper portion. FIG. 4B illustrates a screw retained connection. Here, the prosthesis also fits around the conical top portion  150 , but a screw (not shown) passes through a bore in the prosthesis and into a threaded opening  170 . This threaded opening is formed as a cylindrical bore that passes through the backside of the upper portion. This type of screw connection is known as a lingual screw connection. 
     The threaded opening, however, does not have to be located through the side of the upper portion as shown in FIG.  4 B. Alternatively, this opening may be located through the top of the upper portion and extend through end  152 . 
     The two piece abutment of the present invention has numerous advantages over prior abutments. First, even after the prosthesis has been placed on the abutment and in a patient&#39;s mouth, the cuff on the abutment may be easily and readily replaced with a new or even different cuff. In some instances, for example, the tissue surrounding the implant and prosthesis may recede over time. As this tissue recedes, the cuff portion of the abutment may become exposed. Since abutments are typically made of metal, such as titanium, the exposed portion of the cuff has an unwanted and unsightly aesthetic appearance in the mouth. With the present invention, however, the old cuff can be replaced with a new or different cuff to minimize the visible portions of the cuff. The new cuff, for example, may have a different size or be shaped differently such that no portion of the cuff is exposed. Alternatively, the old cuff may be replaced with one that is coated, colored, or painted to camouflage the abutment in the mouth. 
     Another important advantage of the present invention is that the cuff and upper portion of the abutment may be made of different materials. In the preferred embodiment, the upper portion is made from titanium, such as any one of various titanium alloys known to those skilled in the art. Making the upper portion from titanium provides the abutment with strength and biocompatibility. 
     The cuff may be made from several different possible materials, apart from titanium. The cuff, for example, may be made from steel or a precious metal alloy, such as gold, silver, or iridium. A cuff made from a gold alloy, for example, would have several advantages. Certain gold alloys enable the cuff to easily receive a porcelain coating favorable for aesthetic reasons. A gold cuff coated with porcelain also is less prone to scratch or otherwise show surface marks, as opposed to a titanium cuff. As another advantage, a gold cuff may be used with gold casting procedures, such as a casting procedure to create a custom geometry or anatomical profile around the cuff. 
     The cuff may be made from other materials suited for dental applications. Some of these materials include ceramics (such as aluminum oxide), polymers, composites, or materials having a coating that promotes tissue growth. 
     FIG. 5 shows an abutment  180  illustrating some of the advantages of the present invention. In the figure, the upper portion  182  is made of a titanium alloy and has a configuration similar to the upper portion described in FIGS. 2 and 3. The cuff  184  is made from a gold alloy and has a thin porcelain coating  186  along the exterior surface. The cuff tapers from a support surface  188  toward top portion  190 . This top portion, however, has an anatomical profile in the shape of an ellipse. This profile more closely resembles the shape of a natural tooth and, as such, encourages and promotes natural soft tissue growth around the cuff. Proper bio-aesthetics are also enhanced with this cuff. 
     Although FIG. 5 shows a specific embodiment, it will be appreciated that numerous other combinations with a separate cuff and upper portion are also within the scope of this invention. For example, the cuff could be made of a polymer or ceramic with an elliptical profile. Likewise, the geometry of the cuff could be changed to another anatomical profile, such as a tri-lobed configuration. 
     As noted, one important advantage of the present invention is the ability to change cuffs after the prosthesis is attached in the patient&#39;s mouth. The method for changing the cuff is now discussed in more detail. 
     FIG. 6 shows a partial view of a patient&#39;s mouth having a retrievable dental prosthesis  200  embedded in jawbone  202 . As shown in FIG. 7, a dental tool  204  is used to detach the prosthesis (connection of the abutment to the implant is more fully discussed in connection with FIGS.  2  and  3 ). This tool has an end  206  that engages the head  208  of screw  210 . The tool passes into a cavity  212  in the prosthesis to access the screw. After the screw is loosened and removed from cavity  212 , the prosthesis freely detaches from the implant  214 . The implant remains embedded in the bone  216 , and the surrounding soft tissue  218  remains unaffected. 
     FIG. 7 shows that the upper portion  220  remains attached to the prosthesis. The cuff  222 , however, is not permanently attached to the prosthesis or implant. As such, the next step is to separate the cuff from the upper portion. 
     The cuff may be connected to the upper portion in various ways. FIG. 2, for example, shows that the cuff and upper portion are threaded together. Alternatively, the cuff could be press fit to the upper portion or connected in other ways known to those skilled in the art. Regardless of the fit between the cuff and the upper portion, the two pieces preferably can be separated. 
     At this point, the cuff may be replaced. The old cuff may, for example, be damaged or scratched and need to be replaced with a new one. Alternatively, a cuff having a different shape, size, coating, or composition, as discussed herein, may be preferred to the old cuff. For example, a new cuff having a porcelain coating could replace the old cuff. This new cuff would provide aesthetic advantages for the patient. As another example, the new cuff could have a different size to accommodate for receding tissue around the prosthesis. In general, the new cuff should be selected to accommodate the particular needs of the patient and could have any one of various designs discussed herein. 
     The next step is to place the new cuff back on the gingival end  224  of the implant. Thereafter, the prosthesis is placed on the cuff such that the upper portion and cuff connect to form an assembled abutment. The screw  210  is then positioned back into cavity  212  and passed through the abutment to engage the implant. The noted dental tool  204  passes into the cavity to engage and tighten the screw. 
     One advantage of the present invention is that the cuff of the abutment may be changed without altering or affecting the prosthesis. With prior unitary abutments, the cuff cannot be removed from the upper portion. As such, in order to change the cuff, the entire abutment has to be replaced. In this instance, a new prosthesis may also need to be fabricated to the new upper portion of the abutment. Fabricating a second prosthesis would be time consuming and costly. 
     In the present invention, after the prosthesis is removed, a new cuff is placed on the implant and the prosthesis is re-attached. The prosthesis itself though did not have to be modified or replaced. Thus, a second prosthesis does not have to be fabricated. Further, the procedure to replace the cuff is relatively quick and not invasive to the patient. Further yet, no additional costs are necessary to replace the entire abutment since the original upper portion may be used even after a new cuff is placed on the implant. 
     Other variations of the abutment are also within the scope of this invention. FIG. 8 shows one such alternate embodiment. Here, the upper portion  250  has a base  252  that includes a cylindrical extension  254 . This extension tapers from a shoulder  256  to an end  258 . 
     The cuff  260  has a top portion  262  with a tapering, cylindrical cavity or recess  264 . This cavity is sized and shaped to fit together with the extension  254 . When the abutment is assembled, the upper portion fits on top of the cuff with the extension within the cavity. A screw  266  passes through a bore  268  in the abutment and into a threaded cavity  269  in the implant  270 . This screw holds the abutment to the implant and also prevents the upper portion from rotating about the cuff. The cuff may be provided with splines (not shown) or another engaging feature to prevent rotation between the cuff and implant. 
     One advantage of the abutment shown in FIG. 8 is that the upper portion and cuff may be rotated to numerous positions relative to each other. Once the cuff is positioned on the gingival end  272  of the implant, the upper portion may be rotated 360° about the longitudinal axis running through the implant and cuff. Once the proper orientation of the upper portion is determined, the screw  266  is tightened to hold the upper portion in place and prevent relative movement between the cuff and the upper portion. 
     FIG. 9 depicts another alternate embodiment. Here, the upper portion  280  has a base  282  that includes an engaging feature  284 . This engaging feature comprises four tines extending downwardly. A cylindrical bore  286  extends through the upper portion  280  and cuff  288 . 
     Two different perspective views of the same cuff  288  are shown. The cuff has a top portion  290  and a support surface  292 . An engaging feature  294  extends along the bore  286  from the top portion  290  to the support surface  292 . This engaging feature is comprised of Spline™ tine receptors. These receptors enable the cuff to engage both the upper portion and implant  296 . The use of tines on the upper and lower engaging portions provides double indexing. 
     The gingival end  298  of the implant includes a plurality of tines  300 . These tines engage the tine receptors when the support surface  292  of the cuff is positioned on the gingival end of the implant. 
     The cuff may be rotated between several positions at various intervals depending on the number of tines. Likewise, when the base  282  of the upper portion is positioned on the top portion  290  of the cuff, the upper portion may be rotated relative to the cuff. Rotation of the cuff relative to the implant and upper portion relative to the cuff provides the noted double indexing. 
     Other engaging features, besides tines, may be used for any of the embodiments shown in the figures. For example, the upper portion and the cuff could include polygonal engaging features. The base portion of the upper portion could have a hexagonal projection, and the engaging feature in the bore of the cuff could be a hexagonal female receptor. Further to this end, the gingival end of the implant could have a polygonal engagement, such as a hexagonal projection. Of course, the male and female engaging features for all embodiments within the scope of this invention may be switched between the upper portion, cuff, and implant. 
     FIGS. 10A and 10B show example embodiments using polygonal engaging features. In FIG. 10A, the upper portion  310  has a base  312  that includes an engaging feature  314 . This engaging feature comprises a hexagonal projection. A bore  316  extends through the upper portion  310  and cuff  318 . 
     The cuff  318  has a top portion  320  and a support surface  322 . An engaging feature  324  extends along the bore  316  from the top portion  320  to the support surface  322 . This engaging feature comprises a hexagonally shaped bore. 
     The gingival end  330  of the implant  332  includes an engaging feature  334  formed as a hexagonal projection. This projection engages the hexagonal bore  324  when the support surface  322  of the cuff is positioned on the gingival end of the implant. 
     In FIG. 10B, the upper portion  340  has a base  342  that includes an engaging feature  344 . This engaging feature comprises an octagonal recess. A bore  346  extends through the upper portion  340  and cuff  348 . 
     The cuff  348  has a top portion  350  and a support surface  352 . An engaging feature  354  projects outwardly from the support surface and from the top portion. This engaging feature comprises an octagonally shaped projection. 
     The gingival end  360  of the implant  362  includes an engaging feature  364  formed as a hexagonal recess. This projection engages the hexagonal projection  354  when the support surface  352  of the cuff is positioned on the gingival end of the implant. 
     In FIGS. 10A and 10B, the cuff may be rotated between several positions with respect to the implant. Likewise, when the base of the upper portion is positioned on the top portion of the cuff, the upper portion may be rotated relative to the cuff. As in FIG. 9, this dual rotation may provide the noted double indexing if the polygons have different geometric configurations. 
     FIG. 11 shows an example embodiment of another two-piece abutment  370  according to the invention. The upper portion  372  has a base  374  and a top portion  376 . The base includes a threaded exterior surface  378  and a shaft  380  extending downwardly from the threaded surface  378 . This shaft includes a threaded section  382 . 
     The cuff  384  has a top portion  386  and a bottom portion  388 . A passageway  390  extends through the cuff and has a threaded interior portion  392  that threads with the threaded surface  378  on the upper portion. 
     When the abutment is assembled, the shaft  380  extends through the passageway  390  until a shoulder  394  above the threaded surface  378  abuts with a top end  396  of the top portion  386 . The threads  382  on the shaft  380  engage with a threaded bore at the gingival end of an implant (not shown). A separate screw to connect the abutment to the implant is thus not needed. A prosthesis (not shown) connects around the top portion  376  of the upper portion  372  and a screw (not shown) threads into the recess  398  to hold the prosthesis to the upper portion. 
     Turning now to FIGS. 12A,  12 B, and  12 C, three more embodiments for the present invention are shown. Here, abutments  400 A,  400 B, and  400 C each have an upper portion  402 A,  402 B, and  402 C, respectively, and a cuff  403 . Each upper portion has a top portion  404  and a base  406  that includes an engaging feature  408 . This engaging feature comprises six tines extending downwardly. A bore  410  extends through the top portion  404  and cuff  403 , and upper portion  402 A (FIG. 12A) is shown having a second bore  412  through the side of the top portion for receiving a lingual screw (not shown). As shown, the base may taper slightly outwardly, and the top portion may taper slightly inwardly. 
     A transition region  414  extends between the base  406  and the top portion  404 . This transition region includes a curved, smooth lip or margin  416 . The margin extends circumferentially around the exterior of the upper portion and functions, in part, to support a prosthetic restoration (not shown). 
     One important advantage of this margin is that it has a contour that slopes downwardly from a back side  418  of the upper portion toward a front side  420  of the upper portion. As another advantage, the curvature or the margin around the upper portion more naturally follows the anatomical contour of a natural tooth. Further the slope more closely conforms with the natural, anatomical contour of the gingival tissue. FIG. 13 shows a top view of the upper portion  402 A to better illustrate this curvature. As shown in this figure, margin  416  has a noncircular curvature and may be, for example, elliptical or a tapered rectangular prism with radius corners. 
     Turning now to specific attributes of the engaging feature  408 . In FIG. 12A, the individual tines of upper portion  402 A are tapered. As shown, the thickness of these tines decreases as the tines extend downwardly from a bottom surface  424 . 
     Looking now to FIG. 12B, the thickness of the tines is constant. The tines, however, are bent inwardly toward the center of bore  410 . Preferably, the tines are bent inwardly at an angle of up to about 15°. The distance between adjacent tines will decrease slightly after the tines are bent inwardly. The tines may also be bent outwardly, as shown in FIG.  12 C. Chamfer  430  at the bottom of all bent tines terminates in a shape and size sufficiently small to engage the upper opening in cuff  403 . Preferably, the tines are bent outward at an angle of up to about 15°. 
     The cuff  403  in FIGS. 12A,  12 B, and  12 C is very similar to the cuff  288  described in connection with FIG.  9 . One difference, though, is that cuff  403  has six Spline™ tine receptors to receive the corresponding six tines of the engaging feature  408 . Another difference is that the cuff has a cylindrical configuration that is not tapered. 
     When the engaging feature  408  of each upper portion  402 A,  402 B, and  402 C is placed into the bore of the cuff  403 , the tines of the upper portion engage the six tine receptors. This engagement forms a frictional fit between the upper portion and the cuff. The upper portion and the cuff are thus held together, but they may thereafter be separated if a pulling force is applied between them. 
     FIG. 12A shows an engaging feature  408  that includes tines. Other types of engaging features may be used instead of tines. For example, a polygonal projection (such as a hexagon or octagon) could extend downwardly from surface  424 . The sides of the polygonal feature could be tapered inwardly and engage a corresponding polygonal recess in the cuff  403 .