Patent Publication Number: US-2015079542-A1

Title: Dental implant abutment

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and is a continuation application of U.S. application Ser. No. 13/736,496, filed Jan. 8, 2013, which claims priority to and is a continuation application of U.S. application Ser. No. 12/027,657, filed Feb. 7, 2008, now U.S. Pat. No. 8,371,851, which claims priority to and is a continuation-in-part application of U.S. application Ser. No. 10/799,513, filed Mar. 12, 2004, all of which are hereby incorporated by reference. 
    
    
     BACKGROUND 
     The present invention relates generally to restorative dentistry. More specifically, the invention relates to an implant abutment for dental restorations. 
     Restorative dentistry has made significant advances in the use of dental implants to support dental restorations intended to permanently replace natural teeth. Dental implants provide an alternative to removable dentures, fixed partial dentures, and single-tooth restorations. 
     In a jawbone anchored dental restoration, an implant of known design is surgically implanted into a patient&#39;s jawbone, leaving a gingival surface exposed. A support post, commonly referred to as an abutment, is then firmly fixed to the exposed surface of the implant. A dental prosthesis is secured to the abutment by means of a screw extending through a bore in the prosthesis and into a threaded bore in the abutment (screw retained) or via conventional cementation techniques (cement retained). 
     As described, for example, in U.S. Pat. No. 4,988,298 to Lazzara et al., the entire content of which is incorporated herein by reference, and as shown in  FIG. 1 , a dental implant restoration system  10  generally includes a dental implant  14 , a support post or abutment  16 , and a prosthesis  12 . The implant is typically made from a biocompatible material such as titanium or titanium alloy, and is embedded into the jawbone leaving a gingival surface  22  flush or nearly flush with the gingival surface A-A of the jawbone. This gingival end includes an internally-threaded recess  24  and a multi-sided male projection for abutting with the abutment  16 . The abutment  16  is securely attached to the lower or gingival end of the prosthesis  12  and functions to provide a rigid interconnection between the implant  14  and the prosthesis  12 . 
     A passageway extends through the abutment  16  and provides a recess at the transgingival portion for engaging the projection of the implant. A screw  26  abuts against a shoulder  28  of the abutment and engages the threaded recess  24  of the implant to force a precision formed abutment surface  29  into seated contact with the gingival surface of the implant. The prosthesis  12  is fabricated around the upper portion of the abutment and may be connected to the abutment via screw  26  or cement. The prosthesis is colored to match the surrounding dentition. 
     Typically, the abutment is made of metal, such as titanium, and the prosthesis is fabricated from ceramic, a ceramic-based material such as porcelain, or a polymeric resin material. An entirely metallic abutment however, can be visible through the prosthesis, resulting in a dark, central rod-like shadow, particularly when exposed to bright light, which makes the prosthesis somewhat unattractive since it is distinguishable from a natural tooth. Various methods for preventing or masking the appearance of the shadow are known in the art. 
     One attempt to solve the attractiveness problem involves making a support post entirely of tooth-colored ceramic material. This approach allows direct surface bonding by interaction of a porcelain coping and/or prosthesis to the support post, resulting in a secure and almost seamless bond between the prosthesis and support post. While presenting an attractive alternative to the use of a titanium support post, the proposed solution presents a number of problems. 
     Ceramic materials generally have a much greater hardness than titanium. When an all-ceramic support post is used, inevitable rocking of the support post due to, for example, chewing, causes a high stress interaction between the metal implant and the ceramic material of the post. Since a ceramic support post is of greater hardness than a titanium implant, it can and does cause damage to the implant. If sufficient damage is caused, eventual surgical intervention is required to remove and replace the titanium implant. In addition, ceramic material is typically not radiopaque, and when using conventional x-ray imaging to examine the juncture between the abutment and the titanium implant, the interface between the two elements is not readily viewable and adequate examination cannot be conducted. Moreover, fracture of the all-ceramic post is also a consideration. 
     Recognizing the benefits of a metallic support, U.S. Pat. No. 5,685,714 to Beaty et al. describes an abutment having two distinct sections. As seen in  FIG. 2 , abutment  12  includes an inner section, or core  36 , made from titanium or a titanium alloy and an outer section, or cuff  34 , made from ceramic, typically aluminum oxide. The metallic core  36  provides the necessary strength to the abutment and provides a framework for connecting prosthesis  38  to implant  40 . The ceramic cuff  34  preferably surrounds the entire exterior surface of the core  36 , and shields the shadow of the metallic core  36  through the prosthesis  38 . PureForm™ (Centerpulse Dental Inc., Carlsbad, Calif.), for example, is a tooth-shaped abutment composed of a titanium core and a ceramic cuff made of an alumina/zirconia blend. Screw-retained alumina or zirconia/alumina based abutments are available under the trademarks Bio-Cera™ (Bio-Lok International, Inc., Deerfield Beach, Fla.), CerAdapt™ (Nobel Biocare™ AB, Goteborg, SE) and ZiReal™ Post (Implant Innovations, Inc., Wilmington, Del.). 
     U.S. Pat. No. 6,497,573 to Wagner et al. describes a three part dental abutment that includes a shield between a metallic core and a polymeric cuff. The shield is preferably formed of an opaque material, such as a mixture of several mono and dimethacrylates, and may include various pigments to provide a variety of colors to best shield or mask any grayish or metallic color of the core. 
     U.S. Pat. No. 7,179,089 is directed to a two-part abutment having an upper section fabricated of a metal, zirconia or alumina cylinder and a shoulder attached to the cylinder and fabricated of a hybrid ceramic material, whereby a pigment may be added to the hybrid ceramic material to match the color of the patient&#39;s gum tissue. 
     Each of the aforementioned devices however, have certain drawbacks. The three part system is inherently more costly, both in time and materials. The two-part system of U.S. Pat. No. 7,179,089 requires the attachment of the cylinder to the shoulder component. Moreover, the two part systems, while effectively masking the shadow of the metallic core, result in the requirement for additional time and expertise in the fabrication of the prosthesis. When utilizing an entirely metallic abutment, the technician simply acknowledged the resulting appearance of the shadow and fabricated a prosthesis that matched the surrounding dentition. With the addition of a cuff component, however, the color of the cuff and the color of the prosthesis combine to create the color of the final restoration, and the technician must therefore take the color of the abutment into consideration when fabricating the prosthesis. 
     This is particularly important when the prosthesis is fabricated of ceramic. Since most ceramic restorations have inherent translucency, it is incumbent that the abutment be shaded so that it complements the desired shade of the restoration. This process is similar to determining the shade of a natural tooth prior to the fabrication of an all ceramic crown. In that case, it is recognized that the underlying natural tooth or “stump” will influence the shade of the final restoration. 
     U.S. Pat. Nos. 6,231,342 and 5,989,029 are directed to customized abutments and are hereby incorporated by reference. The abutments are customized by taking a series of measurements at the tooth site and fabricating an abutment based on the measurements. Although the abutments, are customized single-unit structures, there are no color and shade considerations. 
     Conventional abutments, such as PureForm™ Ceramic Coping (Centerpulse Dental Inc., Carlsbad, Calif.), Bio-Cera™ (Bio-Lock International, Inc., Deerfield Beach, Fla.), CerAdapt™ (Nobel Biocare™ AB, Goteborg, SE) and ZiReal™ (Implant Innovations, Inc., Wilmington, Del.), are typically available in one standard color chosen by the manufacturer, regardless of the material they are made from. Thus, an “exact match” between the abutment and prosthesis is not achieved. CerAdapt™ abutments for example, are available in Vita-Shade™ A-3 (Vita Shade™ Guide, Vident, Brea, Calif.). 
     SUMMARY OF THE INVENTION 
     In one embodiment, the present invention provides an aesthetic implant abutment for attaching a restorative dental prosthesis within a patient&#39;s mouth. In accordance with the invention, the implant abutment includes a core and a cuff surrounding the core, wherein the cuff is colored to match the color of the prosthesis. 
     In various embodiments, the core is fabricated from metal, such as titanium or a titanium alloy, and the cuff and prosthesis are fabricated from a ceramic or polymeric material. In a preferred embodiment, both the cuff and prosthesis are formed of ceramic. 
     The invention further provides a dental implant restoration system that includes an implant, a dental abutment having a core and a cuff surrounding the core fixed to the implant, and a dental prosthesis fixed to the abutment, wherein the abutment cuff is colored to match the color of the prosthesis. 
     The invention also provides a method of fabricating a dental implant restoration that includes, fixing an implant within a patient&#39;s mouth; fixing a dental abutment having a core and a cuff surrounding the core, to the implant; and fixing a dental prosthesis to the abutment, wherein the abutment cuff is colored to match the color of the prosthesis. 
     In yet another embodiment, a single unit abutment is fabricated of a ceramic material, shaded to match the color of the dental prosthesis, and/or the surrounding dentition and the surrounding gingival tissue. The abutment is anatomically shaped and shaded to match the near net shape and shade of the prosthesis that is attached thereto. As the abutment gets closer to the net shape and becomes more naturally shaded, it obviates the need for a restoration on top and becomes the restoration itself. Additionally, the abutment is shaded to match the color of the surrounding dentition and gingival tissue. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a partial cross-sectional view of a prior art dental abutment fixed within a dental implant restoration system. 
         FIG. 2  is a partial cross-sectional view of a prior art dental abutment fixed within a dental implant restoration system. 
         FIG. 3  is a partial cross-sectional view of a dental restorative system according to one embodiment of the present invention. 
         FIG. 4  is a perspective view of the facial side of the abutment according to an embodiment of the present invention. 
         FIG. 5  is a perspective view of the lateral side of the abutment of  FIG. 4 . 
         FIG. 6  is a perspective view of the top side of the abutment of  FIG. 4 . 
         FIG. 7  is a partial cross-sectional view of a dental implant system according to another embodiment of the present invention. 
         FIG. 8  is a perspective view of a dental implant system according to another embodiment of the present invention. 
         FIG. 9  is a perspective view of the facial side of the abutment in the implant system of  FIG. 8 . 
         FIG. 10  is a perspective view of the facial side of the abutment in the implant system of  FIG. 8 . 
         FIG. 11  is a perspective view of a bore in the abutment in  FIGS. 9 and 10 . 
         FIG. 12  is a perspective view of an alternative bore disposed in the abutment in  FIGS. 9 and 10 . 
         FIG. 13  is a close-up cut-away view of the top of the implant shown in  FIG. 8 . 
         FIG. 14  is a top plan view of the implant in  FIG. 13 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 3  shows a dental restorative system  100  that includes a prosthesis  102 , an abutment  104 , and an implant  106 . The abutment and prosthesis are attached together and connected to the implant as illustrated. 
     Implant  106  has a coronal or gingival end with a threaded bore  110  and a male engaging feature  112  extending upwardly. The coronal end extends downwardly along a cylindrical body to a distal end. The male engaging feature  112  connects to the abutment and may be a plurality of upwardly extending tines, a polygon, or other type feature known to those skilled in the art. Alternatively, the implant may have female engaging features that correspond with male projections on the abutment core. The implant may be any one of various implants known in the art, such as those manufactured by Sulzer Calcitek Inc. (Carlsbad, Calif.). 
     Abutment  104  has two different and distinct sections preferably formed from two different materials. Core section  120  has a cylindrical configuration and extends from a top portion to a bottom portion. A passageway  126  extends centrally through the core. The bottom portion abuts against the coronal end of implant  106 . Abutment  104  may be provided with a female engaging feature  128  that engages with the male engaging feature  112  to provide an anti-rotational connection between the abutment and implant. The engaging features would have matching configurations to provide the noted anti-rotational connection. Numerous configurations of engaging features known to those skilled in the art (such as Spline® tines, octagons, and other polygons) may be used. 
     Core  120  typically includes a shoulder  130  located along the interior of the passageway  126  at the top portion. A corresponding ledge  132  is formed along the exterior surface adjacent shoulder  130 . Preferably, the core is made from a biocompatible metal, such as titanium or its alloys. The metallic core provides strength to the abutment and a framework for connecting the prosthesis to the implant. 
     An abutment cuff section  140  connects to the exterior surface of the core  120  and, preferably, surrounds the entire exterior surface. The cuff has a somewhat cylindrical configuration and extends from an upper portion to a lower portion. The cuff can be shaped around the core to have various configurations, such as a cylindrical or elliptical configuration or an anatomical shape that resembles the cross section of a natural tooth. 
     As shown in  FIG. 3 , the cuff  140  tapers outwardly and upwardly away from the coronal end of the implant  106  and forms a frusto-conical shape. This tapering continues to a ledge  146  and then transitions to taper inwardly at the upper portion of the cuff  140 . A shoulder  148  is located along the inner surface. This shoulder  148  fits with the mating ledge  132  on the exterior of the core. 
     The prosthesis  102  is shaped as a natural tooth and includes a passageway  150  that aligns with the passageway  126  of the abutment. A screw  152  passes into these passageways until a head  154  of the screw abuts against the top portion of the core. As shown, the lower portion of the head includes a taper  156  that abuts against the shoulder  130  along the interior of the core. The screw includes a shank  158  extending from the head. This shank has a threaded portion  160  that fits into the coronal end of the implant to engage corresponding threads in threaded bore  110 . The screw holds the abutment and attached prosthesis to the implant. The head  154  also includes a recess  162 . The recess may be provided to engage a tool (not shown) for tightening and loosening the screw or provided to threadably engage another screw (not shown) to secure the prosthesis. 
     In accordance with one embodiment of the invention, the color of the abutment cuff  140  matches the color of the prosthesis  102 . While the cuff  140  and the prosthesis  102  are preferably made from a ceramic material, such as the zirconia/alumina composite described in U.S. Pat. No. 6,380,113 to Kim et al., various polymers and polymer combinations such as acrylic polymers; fiber, glass, silica, and alumina reinforced polymers; thermosetting and photosensitive polymers; vinylesters; and epoxy type materials, may also be used. Suitable polymers include Sculpture™ or FibreKor™ of Jeneric/Pentron, Inc. (Wallingford, Conn.) and Targis™ or Vectris™ of Ivoclar Vivadent, Inc. (Schaan, LI). 
     In the context of the present invention, “matching” the color of the abutment cuff to the color of the prosthesis means choosing a color for the abutment cuff that is most similar to the color of the prosthesis. Generally, a restoration is fabricated in more than one color shade, typically with a darker shade at the gingival surface and a brighter shade at the top. However, the abutment color is selected to match the overall color of the prosthesis, especially at the interface of the abutment  140  and the restoration  104 . 
     Several methods are known in the art for determining the color of a dental restoration. Most commonly used is a dental shade guide, which generally has a base supporting a plurality of tabs or other indicia, each of which corresponds to a different color. The colors of the tabs/indicia represent a range of standard tooth colors. U.S. Pat. No. 6,139,318 to Foser, for example, the entire content of which is incorporated herein by reference, describes a particularly useful color key for selecting a proper color for a dental restoration. The color key includes a number of detachable, tooth sample elements that are formed of the same materials and colored in the same manner, as the dental restoration. In addition, the tooth sample elements include a first surface having a texture and curvature that matches a natural tooth, and a second surface that is smooth and flat. The first surface provides the possibility to test the impression the identically produced restoration will have in the same location, while the second surface provides an improved evaluation of color only, as it can be positioned more easily within the patient&#39;s mouth for comparison with surrounding dentition. 
     Other, commercially available dental shade guides include, for example, Chromoscop™ (Ivoclar Vivadent, Inc., Schaan, LI); Vitapan Classical™ (Vita-Lumin™ Vacuum Shade Guide) and Vitapan 3-D Master™ (Vident, Brea, Calif.); and Bioform™ and TruMatch™ (Dentsply International, Inc., Milford, Del.). 
     Once the color of the prosthesis has been determined, an abutment having a cuff that most similarly matches that color is used in the implant restoration. Depending upon the dental shade guide system being used, a series of colored abutments, specific for that system, would be available to choose from. 
     The principles of the present invention thus provide several advantages over conventional dental implant restoration systems. The invention simplifies the restoration process, in that the fabrication of the prosthesis no longer has to take the color of the abutment into consideration. The abutment includes a cuff matching the color chosen for the prosthesis. Therefore, the interface between the abutment and the restoration is aesthetically enhanced and visually less detectable. In contrast, in accordance with the prior art, the color of the restoration was determined by the combination of the colors of the abutment and the prosthesis. Typically, the technician creating the restoration would obtain a standard abutment and then determine a color for the prosthesis that, when combined with the color of the abutment, would result in the desired color for the final restoration. 
     By utilizing an abutment having the same color as the prosthesis, the final restoration has a greater depth, providing a much more natural appearance. Just as the “stump” of a damaged tooth provides a natural-colored framework for the reconstruction of the tooth, the abutment of the present invention provides a natural-colored framework for the fabrication of a prosthesis. 
     In some instances, the restoration may include a layer of dental cement between the abutment and the prosthesis. Prior to the present invention, the practitioner would choose a cement having a color that would properly combine with the colors of the abutment and the prosthesis, to obtain the desired color for the final restoration. With the present invention, however, because the abutment matches the color of the prosthesis, no additional determinations are required, and a clear cement may be used. 
     In a typical jawbone anchored dental restoration, after the implant system has been fixed within the patient&#39;s mouth, the gum is restored around the system, such that it extends above the lower surface of the prosthesis. With normal aging however, it is not uncommon that the gum line will recede, exposing the lower surface of the prosthesis, as well as a portion of the abutment. With prior art abutments, this could cause an unsightly, unnatural appearance. In accordance with the present invention, however, as the color of the prosthesis and the abutment cuff are matched, the appearance of the abutment is not noticeable even if exposed, and the implant restoration blends naturally with the surrounding dentition. 
       FIGS. 4 through 6  show another embodiment of an abutment  200  of the present invention. Abutment  200  is a monolithic or single-unit structure, which can be anchored to an implant  202  shown in  FIG. 7 . A dental prosthesis, such as a crown  204  shown in  FIG. 7 , is positioned over abutment  200 , which is connected to implant  202  with an attachment screw  206  through bore  207  in abutment  200 . In such design, the abutment has a female connection component and the implant body has a male connection component. It should be mentioned that the means of attachment of abutment  200  to an implant is not limited to an exterior anti-rotational connection as depicted in  FIG. 3 . Other modes and methods of attachment may be used, including but not limited to, internal connection components. The abutments herein may be adapted to connect to any type of implant. 
     Abutment  200  is a single-unit structure fabricated of a ceramic material. As shown in  FIGS. 4 through 7 , abutment  200  combines the core and cuff of the previous embodiments into a single unit, which is fabricated of a single piece of ceramic material. The base of the abutment includes a collar  208 , having a planar bottom side  210  which may fit flush against an implant, such as implant  202 . The upper side of collar  208  has a lip  212  that extends around the periphery of collar  208 . The coronal or top section  214  extends upwardly and is shaped similar to a tooth structure. A dental prosthesis, such as crown  204  in  FIG. 7  fits upon lip  212  and atop upper section  214  of abutment  200 . 
     Collar  208  is preferably gingival or pink-colored to match the gingival tissue surrounding implant  202  in a patient&#39;s mouth. By shading collar  208  with a pink or gingival-colored shade, the abutment will camouflage with surrounding dentition and gingival tissue in the patient&#39;s mouth if the gingival tissue in the patient&#39;s mouth should recede. 
     The abutments described herein may be used as is, or it may be necessary to alter and prepare the abutment to customize it to more precisely fit a patient. As shown in  FIGS. 4 and 5 , lip  212  forms the original cervical line of abutment  200 . In preparing the abutment to better fit the patient&#39;s mouth, it may be necessary to move the cervical line to coincide with the cervical line in the patient&#39;s mouth, if gum tissue has receded. In order to adjust the cervical line, collar  208  may be fabricated of different colored layers of material. The inner core of collar  28  may be dentin-colored (to match the cervical area of the tooth) and the outer layer may be gingival-colored. The gingival-colored layer may vary in thickness from about 0.25 to about 1.00 mm The technician may lower the cervical line as shown in  FIGS. 4 and 5  by removing the gingival-colored layer covering the area  213  from the point of the original cervical line  212  to the new cervical line  215 . By removing the gingival layer in area  215 , the dentin-colored layered is revealed and the cervical line is moved from line  212  to line  213 . The abutment is able to effectively camouflage with the patient&#39;s existing dentition and gingival tissue. 
     Upper or coronal section  214  is preferably divided into three regions, namely the cervical region  216 , the central region  218  and the incisal region  220 , which will have different shades or color to simulate the natural appearance of a tooth. These regions are mere approximations and vary from abutment to abutment, depending on the size, shape and dentition to which the abutment must correlate or match. Each region will have different requirements with regard to visual appearance. Thus, the appearance of lower or cervical region  216  of the abutment, which may vary from piece to piece, is preferably matched to the cervical region of the prosthesis and the cervical region of the surrounding dentition. The central region  218  of the abutment is preferably matched to the central region of the prosthesis and central region of the surrounding dentition. The incisal region  220  is preferably matched to the incisal region of the prosthesis and the incisal region of the surrounding dentition. Shade determination for the three coronal regions may be customized for the individual patient using one of the commercially available dental shade guides, for example, Chromoscop™ (Ivoclar Vivadent, Inc., Schaan, LI); Vitapan Classical™ (Vita-Lumin™ Vacuum Shade Guide) and Vitapan 3-D Master™ (Vident, Brea, Calif.); and Bioform™ and TruMatch™ (Dentsply International, Inc., Milford, Del.), or by using one of the commercially available intraoral spectrophotometers , for example, Easyshade (Vident, Brea, Calif.) and Shade Vision (X-Rite, Inc., Grand Rapids, Mich.). Accordingly, the natural tooth color of the abutment will enhance the natural appearance of the prosthesis. 
     Reference is further made to  FIGS. 8 through 10  which illustrate an abutment  300  showing an alternate form of attachment to an implant  302  and crown  303 . Abutment  300  includes a bore  304  which fits flush with the conically-shaped top  306  of implant  302 . Top  306  of implant  302  and bore  304  may vary in size, shape and/or design. It is preferable that bore  304  is tapered.  FIG. 9  is a facial view of abutment  300  and  FIG. 10  is a lateral view of abutment  300 .  FIGS. 11 and 12  show variations in the shape of bore  304 .  FIG. 11  shows a conical-shaped bore with beveled edges  306 .  FIG. 12  shows a semispherical-shaped bore  308 . As with abutment  200 , abutment  300  is a single-unit structure fabricated of a ceramic material. 
       FIGS. 13 and 14  show a close-up view of an alternate embodiment of the top  310  of implant  302 . Top  310  includes one or more chamfered sections  312  which prevent rotation of abutment  300  on implant  302  when stress is applied by the patient, for example, during chewing. 
     All the variations discussed above with respect to abutment  200  apply to abutment  300 . The abutments herein may be customized in shape and color to enhance the natural effects provided by the dental prosthesis. By taking measurements of the site of desired tooth replacement and determining the type of tooth to be replaced, a model of an abutment can be selected from the inventory and/or customized to the proper shape and color to fit naturally with the patient&#39;s existing dentition. 
     As with abutment  104  having core section  120  and cuff  140 , all configurations and anatomical variations discussed above are applicable to single-unit abutments  200  and  300 , which combine the core and cuff into one monolithic unit. 
     The abutments may be shaded during manufacturing by coating oxide powder with one or more coloring substances to produce a colored powder, pressing the colored powder to produce a shaped body and sintering the compressed shaped body. Reference is made to commonly owned co-pending U.S. Patent Application Publication No. 20070292597 which discloses a method of making zirconia multi-colored blanks and products thereof, U.S. Pat. No. 6,379,593, which discloses a method of making a multi-colored ceramic body, and U.S. Pat. No. 4,970,032, which discloses layered blanks for milling dental materials, all of which are hereby incorporated by reference in their entirety. It is also possible to fabricate partially or fully sintered blanks, which can be further milled into the desired abutment shape. 
     Alternatively, the abutment may be fabricated of a ceramic material which has been partially or fully sintered and thereafter shaded by staining the partially or fully sintered abutment with stains to match the prosthesis, surrounding tooth surface and surrounding gingival tissue. 
     It is preferable that the ceramic material is a high strength ceramic material such as zirconia, alumina, and mixtures thereof whereby the flexural strength is greater than about 1000 MPa, more preferably greater than about 1500 MPa, and most preferably greater than about 2000 MPa. Some applicable materials are known in the art as yttria or ceria-stabilized tetragonal zirconia (Y-TZP and Ce-TZP), zirconia toughened alumina (ZTA), alumina-toughened zirconia (ATZ), mixtures thereof, composites thereof and functionally graded composites thereof. The flexural strength of these materials customarily exceeds 1000 MPa with better ones exceeding 1500 MPa and even 2000 MPa. Examples of materials useful herein include, but are not limited to, ZirCAD™ blocks from Ivoclar Vivadent, nanoZir™ zirconia from Hint-ELs and Ziraldent™ material from Metoxit AG. 
     In addition to the abutment being anatomically shaded as described above to simulate natural dentition and to further match the surrounding dentition and gingival tissue in a patient&#39;s mouth, the abutment may also be anatomically shaped to match the shape of the surrounding dentition, gingival tissue and prosthesis which is positioned thereon. It is most preferable that abutment  200  has a shape that is near the net tooth shape of the prosthesis to which it will be attached and a shade that is anatomically shaded to match natural dentition such that the color and translucency distribution characteristics simulate natural dentition. The anatomically shaded multicolor abutment mimics the color and translucency distribution in natural teeth in such a way that a crown, positioned on the abutment, will require no or very little veneering porcelain to mimic the replaced tooth. The near net shape and shade of the abutment obviates the need to use a thick crown over the abutment, improving the overall strength and structural integrity of the implant system without compromising aesthetics. Since more strength is provided by the abutment, less strength is needed in the crown or veneering layer (porcelain or composite), which sits atop the abutment. The esthetic contribution of the veneering layer becomes, if not less important, at least more consistent and predictable. As the abutment gets closer to the net shape and becomes more naturally shaded, it obviates the need for a restoration on top, and it becomes the restoration itself. In addition to the materials mentioned above, the net shaped abutment may be fabricated of lithium disilicate with flexural strength exceeding 600 MPa, as disclosed in commonly owned, copending U.S. Patent Application Publication No. 20070042889, which is hereby incorporated by reference in its entirety. 
     In selecting the correct shades for the abutment, the color components, hue, chroma and value, are evaluated,. Hue is the dimension of color that enables us to distinguish one family of color from another; chroma defines the relative intensity of a particular color, i.e., the more intense a color is, the higher its chroma level; and value describes the relative whiteness or blackness of a particular color, i.e., the brighter the color, the higher its value. In addition to these components, characteristics such as opacity, fluorescence, and translucency may also be considered during the determination of the correct shades for the abutment. 
     A finished dental restoration should match the color of the patient&#39;s teeth, i.e., it should be “tooth colored”. The colors of human teeth appear to range from a light, almost white-tan to a light brown, and occupy a very specific color space. This color space can be described by the commonly used CIE (Commission Internationale de l&#39;Eclariage) L*, a*, b* conventions, which represents colors in a three-dimensional Cartesian coordinate system. L*, or “value”, is a measure of luminance or lightness, and is represented on the vertical axis (black is 0 and white is 100). The a*, b* coordinates, are a measure of chromaticity and are represented on the horizontal coordinates, with positive a* representing red and negative a* representing green, and positive b* representing yellow and negative b* representing blue. U.S. Pat. No. 6,030,209, which is incorporated herein by reference, presents the CIE L*, a*, b* color coordinates of tooth colors represented by the Vita Lumen® shade guide system manufactured by Vita Zahnfabrik (i.e., it presents the color space of tooth colors). Herein, “tooth color” is taken to mean CIE L*, a*, b* color coordinates that fall within, or very close to, this color space. 
     In the fabrication of the abutment herein, the ranges of the L*a*b* values are set forth in Table 1 below along with the amount of opacity preferred. 
     
       
         
           
               
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Range 
                 L* 
                 a* 
                 b* 
                 Opacity (CR) % 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Min 
                 27.00 
                 −17.00 
                 −29.00 
                 5.00 
               
               
                   
                 Max 
                 96.00 
                 +28.00 
                 +52.00 
                 99.00 
               
               
                   
                   
               
            
           
         
       
     
     The values will vary in the abutment, depending on the area to be shaded. Table 2 sets forth ranges for the gingival, cervical, central (matched to dentin) and incisal regions. 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 Abutment Areas 
                 L* 
                 a* 
                 b* 
               
               
                   
                   
               
             
            
               
                   
                 Gingival 
                 40-75 
                 12-25  
                  6-20 
               
               
                   
                 Cervical 
                 70-90 
                 −2-+10 
                 12-36 
               
               
                   
                 Dentin 
                 60-80 
                 −3-+10 
                 12-36 
               
               
                   
                 Incisal 
                 50-75 
                 −1 + 10 
                 −1 + 30 
               
               
                   
                   
               
            
           
         
       
     
     The single-unit abutment is facile and effective way to provide a natural-looking prosthesis. The gingival-colored base section of the abutment is able to camouflage with the surrounding gingival tissue and the coronal section enhances the natural look of the prosthesis. 
     EXAMPLE 
     Adequate alveolar bone must first be present at an edentulous site in order to properly treat a patient with a dental implant. After the secure placement of the dental implant in the patient&#39;s jawbone, an appropriate abutment type is selected that will provide support for the final restoration. Where the final restoration being considered is an all-ceramic restoration, selection of an implant abutment according to the present invention, that is color-shaded similar to natural teeth is suggested, as opposed to a metallic abutment which may shadow through the ceramic prosthesis and affect the color of the all-ceramic restoration. An impression and shade is taken using one of the known shade guide systems and sent to the laboratory for fabrication of the final restoration. The color of the abutment is matched to the chosen color for the restoration. The final restoration is then fit within the patient&#39;s mouth and permanently mounted. 
     Although preferred embodiments have been depicted and described in detail herein, it will be apparent to those skilled in the relevant art that various modifications, additions, substitutions, and the like can be made without departing from the spirit of the invention and these are therefore considered to be within the scope of the invention as defined in the claims which follow.