Abstract:
An implant analog for use in dental procedures has a plastic member which has a central bore. A metal insert which has a female thread is located in the central bore. The outer surface of the metal insert has a series of projections which lock the metal insert and the plastic body and prevent relative rotation or axial motion between the metal insert and the plastic member.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to the field of dental prosthetics and more particularly, to a plastic implant analog. 
       BACKGROUND OF THE INVENTION 
       [0002]    In the field of dental implant technology, there is a requirement for an implant analog. The implant analog is a replica of a dental implant which is used in a dental laboratory to fabricate the crown which fits over the dental implant. 
         [0003]    Implant analogs or replicas have been difficult and extremely costly to fabricate as the internal aspects of the dental implant must be duplicated very precisely in order to assure an accurate fit of the various components. The accurate fit of components is required in order to assure the proper clinical results. 
         [0004]    During the construction of an implant crown, the dentist will take a rubber impression of the patient&#39;s mouth with an implant impression coping that is connected to the dental implant which has been inserted in the patient&#39;s jaw bone. After the impression has been taken, the impression coping is removed from the patient&#39;s dental implant and is connected to an implant analog or replica. 
         [0005]    The new assembly of the impression coping and the analog is inserted into the rubber mold and a plaster cast is made. The impression coping is removed once the plaster has set, leaving the implant replica in the exact correct position in the plaster cast of the patient&#39;s mouth. 
         [0006]    Prior art replicas made of metal are relatively difficult to manufacture and typically cost almost as much to fabricate as the original implant. 
       OBJECTS AND SUMMARY OF THE INVENTION 
       [0007]    It is an object of the present invention to provide a plastic implant analog which incorporates a threaded insert. 
         [0008]    Another object of the present invention is to provide a plastic implant analog which incorporates a relatively high degree of strength in the threaded section. 
         [0009]    Yet another object of the present invention is to provide a plastic implant analog which can be manufactured efficiently in volume resulting in a relatively low unit cost. 
         [0010]    Other objects and a more complete understanding of the invention will be made clear hereinafter. 
         [0011]    In accordance with the present invention, there is provided a plastic implant analog which has a central bore. A metal insert which has a female thread is located in the central bore. The outer surface of the metal insert has a series of projections which lock the metal insert and the plastic body and prevent relative rotation or axial motion between the metal insert and the plastic member. 
         [0012]    Additional objects, features and advantages of the invention will be apparent from the following detailed description of the invention when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a cross-sectional view of a plastic implant analog made according to the present invention; 
           [0014]      FIG. 2  is a cross-sectional view of the plastic implant analog with the metal insert shown removed for clarity of illustration; 
           [0015]      FIG. 3  is a cross-sectional view showing the metal insert; 
           [0016]      FIG. 4  is a top view of the metal insert taken along the line  4 - 4  of  FIG. 3 ; 
           [0017]      FIG. 5  is an elevation view of the metal insert taken along the line  5 - 5  of  FIG. 3 ; 
           [0018]      FIG. 6  is an elevation view of an alternative embodiment of the invention; 
           [0019]      FIG. 7  shows an alternative embodiment of the invention in which the projecting portions of the insert extend to the peripheral surface of the implant; 
           [0020]      FIG. 8  shows another alternative embodiment of the invention in which a female thread is molded into the plastic implant analog; 
           [0021]      FIG. 9  shows a cross-sectional view of the metal insert of another alternative embodiment of the invention; 
           [0022]      FIG. 10  shows a top view of the metal insert of  FIG. 9  taken along the line  10 - 10  of  FIG. 9 ; 
           [0023]      FIG. 11  shows a cross-sectional view of the metal insert of another alternative embodiment of the invention; 
           [0024]      FIG. 12  shows a top view of the metal insert of  FIG. 11  taken along the line  12 - 12  of  FIG. 11 ; 
           [0025]      FIG. 13  show a cross-sectional view of the metal insert of another alternative embodiment of the invention in which the surface of the metal insert is roughened; and 
           [0026]      FIG. 14  shows a cross-sectional view of the metal insert of another alternative embodiment of the invention in which the surface of the metal insert has a recess. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]    With reference to the drawings, there is shown in  FIGS. 1-5  a primary embodiment of a plastic implant analog  10  which includes a plastic body  12  and a metal insert  14 . 
         [0028]    The plastic body  12  is generally cylindrical in configuration and includes a bottom surface  16 , an outer surface  18 , and a top surface  20 . 
         [0029]    The upper end  22  of the outer surface  18  leads to an outwardly tapered portion  24  which in turn leads to an upper portion  26  which is of increased diameter relative to the diameter of the outer surface  18 . 
         [0030]    A central bore  28  is provided which leads inwardly from the top surface  20 . The upper portion  30  of the central bore is inwardly tapered. The bottom  32  of the upper portion  30  leads to a first cylindrical portion  34 , the bottom  36  of which leads to a relatively short inwardly curved portion  38 . The inwardly curved portion  38  leads to a second cylindrical portion  40  which has an inner diameter slightly smaller than the first cylindrical portion  34 . The bottom  42  of the second cylindrical portion  40  leads to the inner surface  44  of the bottom  46  of the plastic body  12 . The central bore  28  thus forms a blind cavity. 
         [0031]    The upper portion  30  of the central bore  28  includes one or more peripherally disposed cavities  48  which may correspond to and accommodate complementary projections in a tool and may also serve a locating and indexing function. The shape of the peripheral cavity  48  is defined in part by a portion  50  which may be flat or curved. 
         [0032]    The second cylindrical portion  40  accommodates the metal insert  14  which forms a key feature of the present invention. 
         [0033]    The metal insert  14  is best shown in  FIGS. 3-5  in which the metal insert  14  has been shown as being removed from the plastic body  12  for purposes of clarity of illustration. 
         [0034]    The metal insert  14  is generally cylindrical in configuration and has a flat top  52  and bottom  54  surfaces. 
         [0035]    The metal insert  14  has a through bore  56  which has a female thread  58 . The outer surface  60  of the metal insert  14  has a plurality of projecting portions  62 ,  64 ,  66 ,  68 ,  70 ,  72 ,  74 ,  76 . As shown in  FIGS. 4 and 5 , there are two rows each having four projecting portions. As shown in  FIG. 4 , the projecting portions  70 ,  72 ,  74 ,  76  are below the projecting portions  62 ,  64 ,  66 ,  68 , respectively. 
         [0036]    The number of projecting portions  62 ,  64 ,  66 ,  68 ,  70 ,  72 ,  74 ,  76  may be varied within the scope of the invention and may be increased beyond the quantity of eight projecting portions  62 ,  64 ,  66 ,  68 ,  70 ,  72 ,  74 ,  76  as shown or alternatively, the number of projecting portions  62 ,  64 ,  66 ,  68 ,  70 ,  72 ,  74 ,  76  may be decreased below the quantity of eight projecting portions shown. 
         [0037]    In an alternative embodiment of the invention  100  shown in  FIG. 6 , the projecting portions previously described may be formed as a pair of continuous peripheral flanges  102 ,  104  or a band encircling the outer surface  106  resulting in a total quantity of projecting portions  102 ,  104 . 
         [0038]    As is shown in  FIG. 1 , the outer surfaces  78  of the projecting portions  62 ,  64 ,  66 ,  68 ,  70 ,  72 ,  74 ,  76  extend to a position which is inward relative to the surface portions  80  of the plastic body  12 . This results in the plastic body  12  having portions  82  which are outward relative the projecting portions  62 ,  64 ,  66 ,  68 ,  70 ,  72 ,  74 ,  76 . 
         [0039]    As is shown in  FIG. 5 , each of the projecting portions has a pair of side portions  84 ,  86 , a top portion  88 , a bottom portion  80 , and an outer surface  78 . 
         [0040]    The incorporation of the projecting portions  62 ,  64 ,  66 ,  68 ,  70 ,  72 ,  74 ,  76  and  102 ,  104  increases the surface area of the metal insert  14  which is in direct contact with the plastic body  12 . This increase in a surface area decreases the unit stress on the contact area or interface area between the plastic body  12  and the metal insert  14  and prevents relative rotation between the metal insert  14  and the plastic body  12 . 
         [0041]    In addition, the projecting portions  62 ,  64 ,  66 ,  68 ,  70 ,  72 ,  74 ,  76  provide a positive mechanical lock between the metal insert  14  and the plastic body  12  which prevents relative rotation or relative axial or longitudinal motion. 
         [0042]    In an alternative embodiment  200  which is shown in  FIG. 7 , the outer surfaces  202  of the projecting portions  208 ,  210 ,  212 ,  214  extend to the surface  204  of the plastic body  206 . 
         [0043]    In addition to the projecting portions  208 ,  210 ,  212 ,  214  which are generally similar to the projecting portions  62 ,  64 ,  66 ,  70 ,  72 ,  74 ,  76  previously described,  FIG. 7  also shows longitudinal projecting portions  216 ,  218  formed on the metal insert  220 . 
         [0044]    In another embodiment of the invention  300  shown in  FIG. 8 , the metal inserts previously described have been eliminated and a threaded portion  302  is molded in the surface  304  of the bore  306  of the plastic body  308 . 
         [0045]    In another embodiment of the invention  400  shown in  FIGS. 9 and 10  the projecting portion  402  of the metal insert  404 , which provides an anti-rotation feature, has a generally square configuration having sides  406 ,  408 ,  410 ,  412 . 
         [0046]    In another embodiment of the invention  500  shown in  FIGS. 11 and 12  the projecting portion  502  of the metal insert  504 , which provides an anti-rotation feature, has a generally octagonal configuration having sides  506 ,  508 ,  510 ,  512 ,  514 ,  516 . 
         [0047]    It should be understood that in additional alternative embodiments the configuration of the projecting portion may be generally hexagonal or a range of regular and non-regular configurations. 
         [0048]    In another embodiment of the invention  600  shown in  FIG. 13  the surface  602  of the metal insert  604  is roughened thereby providing an anti-rotation feature. The roughened surface  602  may be irregular as shown in  FIG. 13  or it may regular in configuration such as may be produced by knurling. 
         [0049]    In another embodiment of the invention  700  shown in  FIG. 14  the surface  702  of the metal insert  704  includes at least one recess  706 . The recess may be rectangular, square, circular or irregular in configuration. The recess  706  accepts the plastic material previously described and provides an anti-rotation feature. 
         [0050]    The process for forming the threaded portion  302  includes the following steps:
       forming a cavity in an injection mold corresponding to the outer shape of the plastic member;   forming a mold member having a male thread and portions corresponding to the bore, and forming a fillable mold cavity;   rotationally mounting the mold member in the cavity;   injecting a moldable plastic material into the fillable mold cavity, thereby forming the plastic body and unscrewing the mold member from the plastic body leaving a female thread in the plastic body.       
 
         [0055]    The abutment&#39;s engaging features include the portion of the plastic body  12  which is disposed above the metal threaded insert  14  when viewed as in  FIG. 1 . 
         [0056]    The foregoing specific embodiments of the present invention as set forth in the specification herein are for illustrative purposes only. Various deviations and modifications may be made within the spirit and scope of this invention, without departing from a main theme thereof.