Patent Publication Number: US-2007111165-A1

Title: Polymer Core Prosthetic Dental Device with an Esthetic Surface

Description:
CROSS REFERENCE TO RELATED APPLICATION  
      This application is a continuation-in-part of pending U.S. patent application Ser. No. 11/420,024, filed May 24, 2006, which claims the benefit of U.S. Provisional Patent Application No. 60/684,743, filed May 26, 2005, both of which are fully incorporated herein for all purposes. 
    
    
     BACKGROUND  
      1. Field of the Invention.  
      The present invention relates to prosthetic dental devices and, more particularly, to methods and materials used to construct prosthetic dental devices.  
      2. Description of the Related Art.  
      Often, it is desirable to replace lost, missing, injured or diseased teeth using prosthetic dental devices. Prosthetic dental devices include, for example, implants which are inserted into the mandible or maxilla of a patient. Other dental devices temporarily cover the implant until a sufficient amount of bone osseointegrates with the implant to support and anchor the implant during mastication. Such devices used during this “healing process” include provisional gingival cuffs, healing screws, healing collars and healing caps. Other structures include abutments which are attached to the implant to serve as a mount for a prosthetic tooth, and may be permanent or provisional.  
      Some of these dental devices may be visible, or have portions that may be visible, when viewing a dental patient&#39;s face. For instance, an abutment which supports a prosthesis can have a visible area near the gums that is not covered by the prosthesis. When these visible areas are made of metals or plastics that do not have the color of natural teeth, the dental devices provide a non-esthetically pleasing appearance on a person&#39;s face. To attempt to address this shortcoming in appearance, there are dental devices that have the color of natural teeth. These devices, however, tend to lack adequate strength which may result in relatively frequent replacement or repair. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is an exploded, cross-sectional view of a prosthetic dental device in accordance with one embodiment with features of the present invention;  
       FIG. 2  is a perspective view of an abutment of the device of  FIG. 1 ;  
       FIG. 3  is a cross-sectional view of the abutment taken along line III-III on  FIG. 2 ;  
       FIG. 4  is an exploded, cross-sectional view of another embodiment of a prosthetic dental device with features in accordance with the present invention;  
       FIG. 5  is a cross-sectional view of an alternative abutment in accordance with features of the present invention;  
       FIG. 6  is an exploded, fragmentary, perspective view of yet another embodiment of a prosthetic dental device in accordance with features of the present invention;  
       FIG. 7  is a cross-sectional view of an alternative provisional device in accordance with features of the present invention;  
       FIG. 8  is a flow chart of a general exemplary process for manufacturing a dental prosthetic device with features of the present invention; and  
       FIG. 9  is a flow chart of further steps for the process of  FIG. 7 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Referring to  FIG. 1 , a prosthetic dental device  10  is illustrated and is used for restoring an edentulous area in a dental patient&#39;s mouth. The prosthetic dental device  10  has an abutment  12  threadedly mounted on an implant  14  on a person&#39;s jaw  16  during dental surgical procedures. The jaw  16  may be the mandible or the maxilla. The abutment  12  supports a tooth-shaped prosthesis  18  that may or may not cover the entire abutment  12 . A prosthesis or prosthetic tooth typically includes an inner cavity designed to accept an abutment and an outer portion that replicates the appearance and hardness of a natural tooth. The prosthetic tooth may be cemented, screwed, or otherwise fastened to the abutment.  
      Referring to  FIGS. 2-3 , the abutment  12  has a core or an inner portion  20  and an esthetic outer layer or portion  22  that may be integrally formed with a metal retaining screw  24  for attachment to the implant  14 . The abutment  12  has a bore  26  to provide access to the head of the screw  24  and may be plugged with cement or other material once mounted on the implant  14 . The inner portion  20  is not particularly limited to any color since it is covered, as explained below, by the esthetic outer portion  22 . Thus, the inner portion  20  may have a high strength polymer with a dark color or other esthetically displeasing color that is substantially different than the color of natural teeth and different than the color of the outer portion  22 .  
      The outer portion  22  is made of an outer material with an esthetically pleasing color that is substantially the same color as natural teeth. In this example, the illustrated outer portion  22  covers substantially the entire inner portion  20 . This may be provided when the prosthesis  18  is translucent and a dark colored inner portion  20  may show through the prosthesis. Of course, the outer portion  22  may also be provided covering substantially the entire inner portion  20  when it is more cost effective to do so during molding processes.  
      In order to provide an appropriate natural-tooth color for the outer portion  22 , the outer portion is made of a polymer with a colorant. Thus, to form a strong and stable bond at the interface of the inner portion  20  and the outer portion  22 , it is also desirable to form the inner portion  20  with a polymer. Optionally, the inner portion  20  and/or the outer portion  22  may be made of a composite material including a polymer mixed with a reinforcing component such as particulates, fibers, and/or porous foams described below.  
      Referring to  FIG. 4 , by another approach, a prosthetic dental device  40  has an abutment  42  with a through-bore  44  for receiving a separate retaining screw  46  which attaches the abutment  42  to an implant  48 . The implant  48  and the abutment  42  may have an anti-rotational and tactile connection structure, such as a hex connection and/or splines  50  (shown in dashed lines).  
      The abutment  42  has an outer portion  52  that covers at least parts of an inner portion  54  that are most likely to be left uncovered by the prosthesis  18  (shown in phantom line) such as by the gum line. Thus, when the prosthesis configuration is known, the outer portion  52  may be shaped to cover substantially only those parts of the inner portion  54  that will be left uncovered by the prosthesis. Alternatively, the outer portion  52  may have extensions  56  (as shown in dashed line), to cover more of the inner portion  52  including parts of the inner portion  52  covered by the prosthesis  18 . The outer portion  54  also may have a cylindrical inner portion  58  to optionally cover the surface forming the through-bore  44 .  
      Referring to  FIG. 5 , a substantially cylindrical abutment  60  is illustrated and has a polymer-containing inner portion  62  of a dark, non-tooth color (such as black) covered by a polymer-containing, outer esthetic portion  64  that is substantially the same color as natural teeth (such as a white, ivory, or white-yellow shade, to name some possible examples). The abutment  60  has a bore  66  to provide access to an integrally formed retaining screw  68 . The bore  66  is not coated with the material of the outer portion  64  in this example. The cylindrical abutment  60  of  FIG. 5  was used for producing nine test examples, and the specific composition of the inner and outer materials for each of the nine produced examples are described in detail below.  
      It will be appreciated that in addition to, or instead of, an abutment, the structure with an outer esthetic, polymer portion covering an inner polymer portion, may be provided on other pieces of a prosthetic dental device, including the prosthesis, the implant, and/or the retaining screw. Referring to  FIG. 6 , in another example, a prosthetic dental device  70  has a healing screw  78  with the described inner and outer portions. The prosthetic dental device  70  includes a threaded dental implant  72  that engages a hole  74  in a mandible  76  or maxilla, which is created during a surgical procedure or following tooth extraction. The healing screw  78  includes a threaded shaft  80  extending from a head  82 . The threaded shaft  80  engages a threaded aperture  84  of the implant  72 . The healing screw  78  prevents debris from entering, and gingival tissue from growing into, the aperture  84  while the mandible  76  heals during the osseointegration of the implant  72  with the mandible  76 . In this case, at least the top of the head  82  of the healing screw  78  may have a polymer-based esthetic outer portion over a polymer-based inner portion.  
      Other dental devices also may have the described inner and outer portions such as a gingival cuff which is meant to be placed near the gum line. Provisional devices used during osseointegration between the implant and the jaw bone or while a restoration, such as a coping or crown, is being fabricated, also may have the described structure. This may include a temporary healing cap or collar placed over an abutment integrally formed with an implant. In some embodiments, a provisional device, such as a fixture mount  90  as shown in  FIG. 7 , may be used to place the implant into the surgical site. For example, a screw shaped implant connected to the fixture mount  90  could be threaded into the site by applying a driving tool to a polygonal recess  92  on the fixture mount. This fixture mount  90  would be pre-assembled to the dental implant by the manufacturer. An inner polymer portion  94  of the fixture mount  90  would have adequate material strength to withstand loads associated with driving the thread. An outer portion  96  would provide a tooth colored covering so that the fixture mount  90  can remain in place during healing and provide an esthetic temporary restoration.  
      In any of the embodiments illustrated as described herein, both the inner portion and the outer portion are made of a polymer material. The polymer material can be a thermoplastic polymer including, without limitation, a poly(aryl ketone), including aromatic polyether ketones, such as polyether ether ketone (PEEK), polymethylmethacrylate (PMMA), polyaryl ether ketone (PAEK), polyether ketone (PEK), polyether ketone ether ketone ketone (PEKEKK), polyether ketone ketone (PEKK), and/or polyetherimide (PEI), polysulfone (PSu), and polyphenylsulfone (PPSu), or a combination of thermoplastic polymers. One suitable polymer is ULTEM® polyetherimide available from General Electric Plastics, Inc. headquartered in Pittsfield, Mass. Another suitable polymer is Radele® polyphenylsulfone available from Solvay Advanced Polymers, LLC, headquartered in Alpharetta, Ga. Other sufficient PEEK polymers include PEEK GATONE™ (provided by Gharda, Inc., Mumbai, India), PEEK 450 (provided by Victrex, Inc., Lancashire, United Kingdom), and PEEK-CLASSIX® (provided by Invibio, Inc., Lancashire, United Kingdom). An acceptable PEKK polymer includes PEKK A1050 (provided by Polymics, Inc., State College, Pa.).  
      By one approach, and as used for the nine produced examples, at least one of the inner portion and the outer portion are formed of PEEK or PEKK. Alternatively, both the inner portion and the outer portion may be formed of the same polymer or one portion may be formed of PEEK while the other portion is formed of PEKK.  
      In order to strengthen the inner and/or outer portions, the inner and /or outer material may be a composite material that includes a reinforcing component. The reinforcing component can be particles, fibers, and/or porous foams, including, without limitation, carbon, alumina, zirconia, yttria-stabilized zirconia, magnesium-stabilized zirconia, E-glass, S-glass, calcium phosphates, alumina, titanium dioxide, and/or calcium phosphates, such as hydroxyapatite or a biphasic calcium phosphate comprised of hydroxyapatite and tricalcium phosphate which also improve osseointegration of the dental device with surrounding bone. The fibers also may be other metal or alloy-based materials such as titanium, Ti 6 Al 4 V, Ta, stainless steel, and/or 316L stainless steel, or may even be made of the polymers themselves, such as PEEK, PEKK, or other aramid fibers such as Kevlar® (provided by E.I.duPont de Nemours and Co., Wilmington, Del.). A polymer reinforcing component may be placed in the same polymer material forming the bulk or matrix of the inner or outer portions.  
      The proportion of reinforcing component, such as ceramic particles or fibers, in the inner or outer composite material is equal to or less than approximately 70% by weight of the total inner or outer composite material, preferably between approximately 20 to 60% and, most preferably, between approximately 30 to 50%. In one case, the fibers are provided at about 30%, and in another case, the fibers are provided at about 35%. The proportion may be equal to or less than approximately 99% when, for example, the reinforcing component is relatively heavy, metal-based fibers or foam, such as a Ta foam.  
      The reinforcing component, also referred to as a filler material, can include, without limitation, spherical shapes, elongate fibers, or other shapes. In one example, the reinforcing component includes nanoparticles with a size range from about 1 nm to about 100 nm, and/or microparticles with a size range from about 100 nm to about 100 μm. These fibers may have a length-to-diameter ratio in a range of about 1 to 1000. In some cases, this ratio may be as low as about 10, 20, or 25 and as high as about 100, 150 or 1000. The length of the fibers can vary to as short as about 1 mm and as long as about 50 mm. In a number of the nine produced examples described below, fibers were about 1-2 mm long and had length-to-diameter ratios of about 8-16. Other examples provide more desirable length-to-diameter ratios of about 250 to 860, where the lengths of the fibers are 5-6 mm.  
      The fibers may have a varying diameter in order to increase resistance to wear, and may include various types of fibers and particles including nanoparticles that fuse to fibers to increase the fracture toughness of the composite material or to control the color of the composite material. These alternative features are explained in detail in the parent U.S. patent application.  
      As mentioned above, the outer material is substantially the same color as natural teeth. The raw polymer materials PEEK-CLASSIX® and ULTEM® are obtained with the colorant already mixed with the polymer. For other raw polymer materials, the colorant must be added to the polymer to obtain the desired natural-tooth color. In one example, the colorant mixed with the polymer is an inorganic material, such as rutile and/or titanium dioxide (TiO 2 ). In this case, the colorant is provided, by total weight of the inner or outer composite material, at about approximately less than 20%, but preferably approximately between 5 to 15% and, more preferably, between 7 to 12%. For some of the nine produced examples, the colorant is provided at approximately 10% of the composite material weight. The colorant also is provided with a particle size of about 0.1 to 100 μm and, more preferably, from about 0.1 to 10 μm and, most preferably, from about 0.5 to 5 μm.  
      Referring to  FIGS. 8-9  , a method for forming  100  a prosthetic dental device includes providing  102  an outer material. As mentioned above, a raw polymer material that already has a desired esthetic color and/or is pre-mixed with a reinforcing component may be obtained. In this case, the raw material is provided in pellets that may only need milling to a desired size before the pellets are ready to be heated for injection into a mold.  
      In the alternative, a compounding process may be used to heat a polymer material  116 , a separately provided colorant  118  (if present), and/or a separately provided reinforcing component  120  (if present) into a viscous state and mechanically mix  124  the heated substances into a composite material  126 . Before compounding, dry pre-blending may be performed to better achieve good dispersion using a suitable mixer, such as a Sigma-type mixer, if necessary. In one embodiment, the polymer material may possess a desired viscous state at substantially room temperature and may not need to be heated. It is desirable to mix the composite material  126  until the colorant  118  and the reinforcing component  120  is substantially evenly distributed throughout the polymer material. Subsequently, the composite material  126  is extruded or pressed through an orifice of a die. As the composite material exits the orifice, it is cut into small, semi-cylindrical pieces, or pellets. This compounding process may be performed using a ZSK-25 twin screw extruder. Alternatively, the composite material may be directly inserted into a mold. It will also be understood that the composite material could be formed into at least one block that is subsequently altered into a desired shape.  
      Prior to, or contemporaneous with, the compounding process described above, the reinforcing component  120 , or the composite material  126 , may optionally be treated with a coupling agent  122  in order to increase molecular bonding in the material and between the inner and outer portions. The coupling agents, such as silane and others, and their use are described in detail in the parent U.S. patent application.  
      Pellets ready for injection molding are then transferred into an injection molding machine, in which the outer material, for example, and particularly the polymer material component, is heated to obtain a desired viscosity unless the outer material possesses a desired viscous state at substantially room temperature. Once the material is in a desired viscous state, it is injected as described below. During this process, the reinforcing component and colorant, if present, remains substantially suspended within the polymer material. The same process for providing the outer material may be used to provide the inner material  104  as well.  
      For the nine produced examples described below, an over-molding or two-stage molding injection process (also called multi-component, transfer or insert molding) was used to form the prosthetic devices with an Engel 100 TL injection molding machine. In order to mold the inner and outer portions, the material for the inner portion was injected  106  into a first mold for forming the inner portion or core of an abutment and over a retainer screw. Once the core was sufficiently cooled and solidified, it was inserted into a second mold. The material for the esthetic outer portion was then injected  108  into the second mold and over the solidified inner portion. Although the two materials are injected separately, a chemical bond or a mechanically interlocking structure may be formed between the two portions. The materials are then permitted to cool to form  110  of the dental device.  
      Alternatively, the examples may be formed by co-injection molding. In this process, a single mold is used and the outer material is injected  112  into the mold first to form the esthetic outer portion. When the outer material is injected, it forms a fountain flow and begins to fill and coat the outer surfaces of the mold cavity. The inner material is then injected  114  immediately following the outer material before can cool and solidify. This results in improved bonding and interlocking properties at the interface between the inner and outer portions. The materials then set in the mold to form  110  the prosthetic dental device.  
      After sufficient time has elapsed, the prosthetic dental device is in a substantially solid form and can be removed from the mold. Subsequent to either injection molding process  106  or  112 , the prosthetic dental device can be machined and polished to reduce undesired deformities and surface roughness. Additionally, the outer surface of the dental device may be treated by a gas plasma cleaning process to enhance bonding between the prosthetic dental device and an adhesive that may be used to attach to a prosthesis, for example, if desired.  
      With this method, any number of different composite and non-composite materials may be injected sequentially to form an integrated dental device. Thus, the prosthetic dental device may have other layers in addition to the inner and outer portions described above. The color of each layer may be selected to provide a range or gradient of colors in the same device. Further, the materials for each layer may be selected to provide different structural or chemical properties in different regions of the prosthetic dental device. Such extra layer or layers may be formed under the inner portion, between the inner and outer portions, or over the outer portion. It will be appreciated that the surface finish and other optical properties, including, without limitation, reflectance, opacity and specularity also can be adjusted by the selection of the polymer material, the reinforcing component, and/or additives as mentioned herein.  
     EXAMPLES  
      Below are descriptions of nine produced examples of prosthetic dental device structures with inner and outer portions as described above. The compositions of the materials for each produced example are listed in Table I as well as described below. While these examples were provided for a cylindrical abutment such as that depicted in  FIG. 5 , the composition for the inner and outer portions for each example could be used on any of the other dental devices described herein and any other dental device that requires both strength for mastication and a natural-tooth color. All percentages below are weight percentages unless indicated otherwise.  
      For Examples 1-6, the outer esthetic material is made from a raw polymer or composite material that is already premixed with a colorant to provide a natural tooth color. For Examples 7-9, a separate colorant is mixed with the raw polymer or composite material to establish the natural-tooth color.  
                           TABLE I                                      ABUTMENT INNER PORTION   ABUTMENT OUTER PORTION                                             Reinforcing       Reinforcing           EX.   Polymer   Component   Polymer   Component   Colorant               1   PEEK GATONE ™   30% wt. carbon fiber   ULTEM ®   none   (not available)           5330 CF       1010       2   PEEK GATONE ™ 5330   30% wt. carbon fiber   PEEK-   none   N/A           CF       CLASSIX ®       3   PEEK 450   30% wt. alumina fibers.   PEEK-   none   N/A                   CLASSIX ®       4   PEKK A1050   30% wt. alumina fibers.   PEEK-   none   N/A                   CLASSIX ®       5   PEKK A1050   30 wt. % zirconia fibers   ULTEM ®   none   N/A                   1010       6   PEKK A1050   30 wt. % zirconia fibers   PEEK-   none   N/A                   CLASSIX ®       7   PEKK A1050   None   PEKK A1050   35 wt. % E-glass   10 wt. %                       fibers   TiO 2         8   PEEK GATONE ™ 5330   30% wt. carbon fiber   PEKK A1050   35 wt. % E-glass   10 wt. %           CF           fibers   TiO 2         9   PEEK 450   None   PEKK A1050   35 wt. % E-glass   10 wt. %                       fibers   TiO 2                    
 
     Example 1  
      In this example, the inner material is a composite with polyether ether ketone and specifically PEEK GATONE™ 5330 CF (provided by Gharda, Inc.). The PEEK is provided in pellets premixed with about 30 wt. % carbon fibers. More specifically, the carbon fibers comprise about 30% of the combined weight of the carbon fibers and PEEK mixed together. The inner composite material has a dark black color.  
      For the outer material, ULTEM® 1010 polyetherimide (by GE Plastics, Inc.) is provided as pellets pre-mixed with colorant in its raw form. This outer material is substantially the same color as natural teeth and has low translucency so that the black inner material is substantially undetectable through the outer material.  
      As explained above for the process illustrated in  FIGS. 8-9 , the inner composite material was heated and injected into a first mold for forming the core of the abutment. It was then permitted to cool before placing the solidified core in a second mold. The outer material was then heated and injected into the second mold and over the inner material where it was permitted to cool to complete the dental abutment. Once cooled, the abutment was removed from the mold and machined and/or cleaned as required.  
     Example 2  
      In this example, the method of producing an abutment was the same method as described in Example 1, except the ULTEM® 1010 polyetherimide for the outer material was replaced with the PEEK-CLASSIX® polymer which is also substantially the same color as natural teeth and has low translucency. The carbon fibers in the inner composite material have a length of about 5-6 mm and a diameter of about 7 μm for a length-to-diameter ratio in a range of about 715 to 860.  
     Example 3  
      In this example, the inner composite material includes the polymer PEEK 450 (by Victrex Inc.) provided as pellets. The PEEK was milled into a powder and sieved with a 200 mesh sieve. About 30 wt. % alumina fibers (AlO 2 ) were then mixed with the PEEK in a Sigma-type mixer to provide the reinforcing component. The alumina fibers have a diameter of about 120 μm and a length of about 1-2 mm for a length-to-diameter ratio of about 8 to 16. The inner composite material in powder form was then compounded with a ZSK-25 twin-screw extruder into composite pellets. This forms an inner material that is dominantly grey with the fibers visible as light colored specks. The outer material included PEEK-CLASSIX® polymer prepared as explained above for the outer material of Example 2. Thereafter, the inner and outer mixtures were heated and separately injected into a mold cavity to form a dental abutment as also explained above in Example 1.  
     Example 4  
      In this example, the esthetic outer material is the same as Example 3 and is prepared in the same manner. For the inner composite material, the PEKK A1050 polymer (by Polymics, Inc.) is mixed and compounded with about 30 wt. % alumina fibers (AlO 2 ) of about the same size as the fibers of Example 3. The inner composite material is black with fibers showing as light colored specks. Both the inner and outer materials were injected as explained above for Example 1.  
     Example 5  
      In this example, the inner composite material includes PEKK A1050 with about 30 wt. % zirconia fibers (ZrO 2 ) present as a reinforcing component. The zirconia fibers also have a diameter of about 120 μm and a length of about 1-2 mm. The PEKK and zirconia fibers were mixed and compounded as described above for the inner material of Example 3 and formed a black substance with the zirconia fibers showing as light colored specks. Here, the substantially tooth-colored ULTEM® 1010 was used as the esthetic outer material. Both the inner and outer materials were injected as explained above for Example 1.  
     Example 6  
      In this example, the method of producing an abutment was the same as the method described in Example 5, except the esthetic outer material was PEEK-CLASSIX® instead of the ULTEM® 1010.  
      Example 7  
      In this example, the inner material is the black PEKK A1050 polymer without a further reinforcing component, and the outer composite material is the PEKK A1050 polymer mixed and compounded with 35 wt. % of E-glass fibers as the primary reinforcing component and 10 wt. % of titanium dioxide (TiO 2 ) as a colorant to provide the outer composite material with a color substantially the same as natural teeth. The E-glass fibers have a length of about 5-6 mm and a diameter of about 10-20 μm for length-to-diameter ratios of about 250 to 600. Both the inner and outer materials were injected as explained above for Example 1.  
     Example 8  
      In this example, a mechanically strong carbon reinforced material is used to form the inner portion of a prosthetic component while a TiO 2  filled material is used to form the outer portion. The carbon reinforced inner portion, composite material is a dark color, which is unattractive for a dental application, but is covered with a white, esthetically pleasing TiO 2  filled outer, composite material. More specifically, the outer composite material is the same as that for Example 7, while the inner composite material is the PEEK GATONE™ 5330 CF with pre-mixed carbon fibers instead of the PEKK A1050. Thus, the method for mixing and compounding the outer composite material is as explained for Example 7 and the method of injecting both the inner and outer materials is as explained for Example 1. The carbon fibers of the inner material provided a length-to-diameter ratio of 715 to 860, while the length-to-diameter ratio of the outer material is about 250 to 600.  
     Example 9  
      In this example, the outer composite material was the same as that for Example 7 including the TiO 2  colorant, while the inner material is the black PEEK 450 without a further reinforcing component. Thus, the method for mixing and compounding the outer material is as explained for Example 7, while the method of injecting both the inner and outer materials is as explained for Example 1.  
               TABLE II                          INNER PORTION MECHANICAL PROPERTIES                                                                     Average       Average                                       Modulus       Tensile       Avg.           Izod                   of       Yield   Yield   Tensile   Max       Impact                   Elasticity   Modulus   Strength   Strength   Max Strain   Strain   Shore D   Energy       EX   Polymer   Ceramic   (ksi)   Std. Dev.   (ksi)   Std. Dev.   (%)   Std. Dev.   Hardness   (J/m)                                                                 1   PEEK   30 wt. %   3146   *   31.5   *   2.5   *   *   80           GATONE ™   Carbon           5330CF   fibers       2   PEEK   30 wt. %   3146   *   31.5   *   2.5   *   *   80           GATONE ™   Carbon           5330CF   fibers       3   PEEK 450   30 wt. %   746   58   12.5   0.1   8.3   1.6   *   *               Al 2 O 3                 fibers       4   PEKK   30 wt. %   791   100    11.2   0.1   6.8   1.2   *   *           A1050   Al 2 O 3                 fibers       5   PEKK   30 wt. %   712   82   11.8   0.1   *   *   *   *           A1050   ZrO 2  fibers       6   PEKK   30 wt. %   712   82   11.8   0.1   *   *   *   *           A1050   ZrO 2  fibers       7   PEKK   NONE   500   *   13   *   80   *   86   50           A1050       8   PEEK   30 wt. %   3146   *   31.5   *   2.5   *   *   80           GATONE ™   Carbon           5330CF   fibers       9   PEEK 450   NONE   522   *   13.3   *   50   *   *   *                  
 
     
       
         
           
               
             
               
                 TABLE III 
               
             
            
               
                   
               
               
                   
               
               
                 OUTER PORTION MECHANICAL PROPERTIES 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                   
                   
                   
                 Average 
                   
                 Average 
                   
                   
                   
                   
                   
               
               
                   
                   
                   
                 Modulus 
                   
                 Tensile 
                   
                 Avg. 
               
               
                   
                   
                   
                 of 
                   
                 Yield 
                 Yield 
                 Tensile 
                 Max 
                   
                 Izod Impact 
               
               
                   
                   
                   
                 Elasticity 
                 Modulus 
                 Strength 
                 Strength 
                 Max Strain 
                 Strain Std. 
                 Shore D 
                 Energy 
               
               
                 EX 
                 Polymer 
                 Ceramic 
                 (ksi) 
                 Std. Dev. 
                 (ksi) 
                 Std. Dev. 
                 (%) 
                 Dev. 
                 Hardness 
                 (J/m) 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 1 
                 ULTEM ® 
                 NONE 
                 475 
                 * 
                 16.5 
                 * 
                 80 
                 * 
                 * 
                 27 
               
               
                   
                 1010 
               
               
                 2 
                 PEEK- 
                 NONE 
                 391 
                 28 
                 14.2 
                 0.1 
                 76.5 
                 3.9 
                 * 
                 36 
               
               
                   
                 CLASSIX ® 
               
               
                 3 
                 PEEK- 
                 NONE 
                 391 
                 28 
                 14.2 
                 0.1 
                 76.5 
                 3.9 
                 * 
                 36 
               
               
                   
                 CLASSIX ® 
               
               
                 4 
                 PEEK- 
                 NONE 
                 391 
                 28 
                 14.2 
                 0.1 
                 76.5 
                 3.9 
                 * 
                 36 
               
               
                   
                 CLASSIX ® 
               
               
                 5 
                 ULTEM ® 
                 NONE 
                 475 
                 * 
                 16.5 
                 * 
                 80 
                 * 
                 * 
                 27 
               
               
                   
                 1010 
               
               
                 6 
                 PEEK- 
                 NONE 
                 391 
                 28 
                 14.2 
                 0.1 
                 76.5 
                 3.9 
                 * 
                 36 
               
               
                   
                 CLASSIX ® 
               
               
                 7 
                 PEKK A1050 
                 35 wt % 
                 957 
                 82 
                 16.4 
                 0.1 
                 2.3 
                 0.1 
                 * 
                 52 
               
               
                   
                   
                 E-glass 
               
               
                   
                   
                 fibers, 
               
               
                   
                   
                 10 wt % 
               
               
                   
                   
                 TiO 2   
               
               
                 8 
                 PEKK 
                 35 wt % 
                 957 
                 82 
                 16.4 
                 0.1 
                 2.3 
                 0.1 
                 * 
                 52 
               
               
                   
                 A1050 
                 E-glass 
               
               
                   
                   
                 fibers, 
               
               
                   
                   
                 10 wt % 
               
               
                   
                   
                 TiO 2   
               
               
                 9 
                 PEEK 
                 35 wt % 
                 957 
                 82 
                 16.4 
                 0.1 
                 2.3 
                 0.1 
                 * 
                 52 
               
               
                   
                 A1050 
                 E-glass 
               
               
                   
                   
                 fibers, 
               
               
                   
                   
                 10 wt % 
               
               
                   
                   
                 TiO 2   
               
               
                   
               
            
           
         
       
     
      Referring to Table II, the inner composite material produced by the method disclosed in Examples 1, 2 and 8 has a modulus of elasticity, or tensile modulus, of about 3146 ksi. To determine the modulus of elasticity, or tensile modulus, a specimen of the inner and outer material was placed in tension using ASTM D-6389 Standards and the resulting deflection was recorded. The modulus of elasticity also can be determined by placing a specimen of the composite material in compression and similarly recording the deflection. One way the modulus of elasticity for the inner material can be increased above 3146 ksi, if desired, is by increasing the amount of fiber present. Alternatively, the modulus of elasticity may be increased by (1) increasing the fiber aspect ratio (length-to-diameter ratio), where applicable, (2) further improving the interface or bonding between the reinforcing component and polymer materials via coupling agents, and (3) improving the compounding and molding processes to better mix the reinforcing component within the plastic material to achieve a more even distribution and to decrease the inclusion of impurities and porosities in the composite material. Thus, one examplary desired range for the plastic modulus of the inner material is 3146 ksi or greater. The ways to increase the modulus of elasticity are not limited to the inner material and apply equally to the outer material.  
      Referring to Table III, the outer composite material produced by the method disclosed in Example 2 had an average modulus of elasticity, of about 391 ksi. This includes values within ±28 standard deviation from the average value. Thus, in this example, the range of an average modulus of elasticity of about 391 ksi would include values as low as about 363 ksi and as high as about 419 ksi. For the outer composite material of Example 8, the average modulus of elasticity is about  957  ksi including a modulus as low as about 875 ksi and as high as 1039 ksi due to a ±82 standard deviation. Thus, the desired elastic modulus is equal to or greater than about 363 ksi (Example 2) or equal to or greater than 875 ksi (Example 8).  
      With either Example 2 or Example 8, it is shown that an abutment can be formed with a modulus of elasticity of the inner portion greater than the modulus of elasticity of the outer portion. This permits the use of esthetically pleasing but relatively weaker materials to form the outer portion. In Example 2, the elastic modulus of the inner portion is at least about eight times greater than that of the outer portion, while for Example 8 the elastic modulus of the inner portion is at least about three times greater than that of the outer portion.  
      As seen in Tables II and III, the modulus of elasticity of the composite material generally depends on at least the polymer material, and the type and quantity of reinforcing components mixed within the polymer material. The modulus of elasticity also depends on whether the reinforcing component includes continuous or non-continuous fibers, and whether the fibers are oriented with the load directions. For a continuous fiber-reinforced composite, i.e., composites where the fiber length is much larger than the critical fiber length, in which the fiber is aligned in the same direction of the load, the modulus of elasticity of the composite, Ec, is determined by Equation (1) below: 
 
 E   c   =V   m   E   m   +V   f   E   f   Equation (1) 
 
 wherein E m  and E f  are the moduli of the polymer matrix and the ceramic fibers, respectively, and V m  and V f  are the volumes of polymer matrix and ceramic fibers, respectively, such that V m +V f =1. The critical length of the fiber is dependent on the fiber diameter, the fiber&#39;s ultimate strength, and the bond strength between the fiber and the plastic matrix. For a number of combinations, this critical length is on the order of about 1 mm. For a continuous fiber-reinforced composite in which the fiber is aligned in the transverse direction to the load, the composite modulus of elasticity is determined by Equation (2) below: 
 
1/ E   c   =V   m   /E   m   +V   f   /E   f .  Equation (2) 
 
 For discontinuous and randomly oriented fibers, the composite modulus of elasticity is determined by Equation (3) below: 
 
 E   c   =V   m   E   m   +KV   f   E   f   Equation (3) 
 
 in which K is a fiber efficiency parameter which depends upon the ratio of V f  and E f /E m . K is usually in the range of 0.1-0.6. In any event, the upper and lower bounds of the modulus of elasticity for the composites composed of particulate fillers are determined by Equations (4) and (5) below: 
 
 E   c  (upper)= V   m   E   m   +V   p   E   p   Equation (4) 
 
E c  (lower)= E   m   E   p /( V   m   E   p   +V   p   E   m )  Equation (5) 
 
      For an alternative prosthetic dental device, a composite material for the inner or outer portions may include a ceramic matrix with pores, and an organic material, such as a thermoset plastic, contained in the pores. This alternative composite material also is fully described in detail in the parent application.  
      It will be understood that various changes in the details, materials, and arrangements of parts and components, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.