CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority to German applications DE 10 2005 027 184.7 filed on Jun. 7, 2005 and DE 10 2005 014 582.5 filed Mar. 24, 2005.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The invention concerns an implant analog for the production of custom-made prosthetic structures on dental implants using a master cast.  
         [0004]     2. Related Art  
         [0005]     Implant analogs represent the implant present in the mouth of the patient. If abutments are already mounted on the implant, the implant analogs can also represent the abutments. Likewise, implant analogs can also represent parts of the abutment and of the implant in some implant systems.  
         [0006]     Implant analogs used to make master casts for subsequent production of custom-made prosthodontic superstructure in exact agreement with the implants in the jawbones are themselves known. The implant analog is included in the master cast, with the future prosthodontic superstructure being attached to the head of the implant analog and, after the implant superstructure has been produced, transferred to the implant inserted in the mouth of the patient. The anatomic structure of the jaw (morphology) of the patient often does not allow the dental implant to be inserted perpendicularly. In the fabrication of the master cast, this presents substantial difficulties in placing the implant analogs in a manner that ensures simple production and manipulation of the waxup and of the cast structure on the master cast in the event that implants are present that are not inserted perpendicularly. The objective of the invention is to develop the generic implant analog such that the working casts for the implant-based dental work can be produced reliably and easily.  
         [0007]     This objective is attained according to the invention with implant analog for custom production of prosthetic superstructures for inserted dental implants, inserted into a master cast directly or indirectly via a model sleeve comprising an implant head equipped with elements to hold and fasten an implant system; a base of said implant analog, having a cross section that tapers over at least part of its length; an implant head having a working surface and a connecting piece; a tenon-like projection on a bottom end surface of said implant head; and an external thread dimensioned to connect with a screw element.  
         [0008]     In the implant analog according to the invention, the base of the implant analog which has a head for mounting the dental implant is designed so that its cross-section is tapered over at least part of its length. Due to this form of the base, it is possible to remove the implant analog from the master cast without stress.  
         [0009]     Other features of the invention appear from the other claims, the description, and the drawings.  
       SUMMARY OF THE INVENTION  
       [0010]     The invention concerns an improved implant analog for production of custom-made prosthetic structures for inserted dental implants.  
         [0011]     The anatomic structure of the jaw often does not allow dental implants to be inserted perpendicularly. That results in unavoidable problems in producing prosthetic implants, combined with high expenditures and costs.  
         [0012]     The invention eliminates those disadvantages for an implant analog ( 2 ). The implant head ( 5 ) has a working surface ( 11 ) and connecting piece ( 12 ) on which the implant reconstructions to be made can be seated and fastened and the bottom end surface ( 45 ) of implant analog ( 2 ) has a tenon-like projection ( 36 ) with an external thread intended for connecting a screw element ( 39 ,  54 ,  58 ).  
         [0013]     The implant analog can be used equally well for single-tooth implants and for implanted bridges.  
         [0014]     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     The invention is explained by means of some embodiments shown in the drawings. Those show:  
         [0016]      FIG. 1  depicts a partial section of a master cast in a partially perspective representation with implant analogs inserted according to the invention.  
         [0017]      FIG. 2  depicts an enlarged perspective representation of the implant analog according to the invention.  
         [0018]      FIG. 3  depicts another embodiment of the implant analog of  FIG. 2 .  
         [0019]      FIG. 4  depicts a third embodiment of the implant analog corresponding to  FIG. 2  in which the working surface is set obliquely to the longitudinal axis of the basic body of the implant analog.  
         [0020]      FIG. 5  depicts a perspective representation of an equalizing sleeve for the implant analog.  
         [0021]      FIG. 6  depicts the perspective representation of an outer sleeve for the equalizing sleeve of the implant analog.  
         [0022]      FIG. 7  depicts the underside of the outer sleeve in a perspective representation.  
         [0023]      FIG. 8  depicts another embodiment of an implant analog according to the invention, which can be screwed into the master cast with a backing piece.  
         [0024]      FIG. 9  depicts a plan view of the implant analog according to  FIG. 8  in the direction of arrow IX with an oval structure for the mounting cone, which is cast into the master cast.  
         [0025]      FIG. 10  depicts variant embodiments of the implant analog shown in  FIGS. 8 and 9 .  
         [0026]      FIG. 11  depicts variant embodiments of the implant analog shown in  FIGS. 8 and 9 .  
         [0027]      FIG. 12  depicts the arrangement of implant analogs according to the invention, which are inserted into the outer sleeve and screwed to it.  
         [0028]      FIG. 13  depicts the arrangement of implant analogs according to the invention, which are inserted into the outer sleeve and screwed to it.  
         [0029]      FIG. 14  depicts another embodiment, with which the implant analog is screwed, at its underside, to a conical backing piece. 
     
    
     LIST OF REFERENCE NUMBERS  
       [0000]    
       
           1  Master cast  
           2  Implant Analog  
           3  Base  
           4  Anti-rotation element  
           5  Head  
           6  Sleeve  
           7  Retention element  
           8  Bevel  
           9  End  
           10  Jacket  
           11  End  
           12  Connecting piece  
           13  Compensating shell/inner sleeve  
           14  Base  
           15  Edge  
           16  Slot  
           17  Inner wall  
           18  Retention element  
           19  Outer sleeve  
           20  End  
           21  Bar  
           22  Bar  
           23  Jacket surface  
           24  Jacket surface  
           25  Inner wall  
           26  Bar  
           27  Opening  
           28  Bar  
           29  Circular section  
           29 ′ Opening  
           30  Pin  
           31  Profile  
           32  Rib  
           32  Rib  
           34  Diagonal  
           35  End surface  
           36  Stop  
           37  Outside thread  
           38  Outer sleeve  
           39  Screw  
           40  Seat  
           41  Cylindrical outside  
           42  Seat part  
           43  Sleeve part  
           44  End surface  
           45  Shoulder surface  
           46  Inner wall  
           47  Screw slot  
           48  Shoulder  
           49  Outer sleeve  
           50  Seat part  
           50 ′ Inner wall  
           51  Jacket surface Sleeve part  
           52  Retention element  
           52 ′ Retention element  
           53  Shoulder surface  
           54  Screw  
           55  Taper  
           56  Taper  
           57  Jacket surface  
           58  Backing piece  
           59  Annular wall  
           60  Opening  
           61  Thread hole  
           62  End surface  
       
     
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0095]     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.  
         [0096]     The implant analogs described in the following are selected according to the space available in the impression and are placed in the impression, connected reversibly to the impression post. Subsequently, a casting is made of the impression, giving the master cast. The implant analogs are equally suitable for single-tooth implants and for bridge implants, as well as for telescope crown and bridge work or zirconia-based restorations in the dental laboratory. With the appropriate working surface, they can be used for any implant system.  
         [0097]     In implant technology, shaped pieces, preferably made of titanium, are initially used as root replacements. They are generally made up of an implant that is inserted into a previously drilled hole in the jawbone. As a general rule, a spacer or abutment of titanium is fastened to that shaped piece or implant. Subsequently the artificial tooth or superstructure is anchored to that spacer or abutment. An accurate model of the patient&#39;s jaw is made so that the artificial tooth or bridge can be fitted exactly to the jaw. First, a negative impression of the jaw is produced with an impression tray filled with impression compound, using system-specific impression posts as carriers. It is removed from the jaw and filled with a casting material that, after hardening, represents an accurate model of the patient&#39;s jaw. In place of the implant, an implant analog is inserted into the so-called master cast. The implant analog is placed in the model with its working surface oriented and positioned by exact analogy with the implant in the patient&#39;s jaw. Divergences between the implants can now be compensated in a very advantageous manner by the implant analog according to the invention.  
         [0098]      FIG. 1  shows such a master cast ( 1 ) with four implant analogs ( 2 ) inserted. They, or their bases, are embedded in the master cast ( 1 ) in exactly the same positions and orientations as the implant working surfaces in the mouth of the patient. The implant analogs ( 2 ) are tapered in the direction of insertion, and can otherwise have any desired cross section, as will be explained later.  
         [0099]     As  FIG. 2  shows, the implant analog ( 2 ) has a circular cross section and a conical base ( 3 ), which has at least one flat ( 4 ) on its outside which acts as an anti-rotation means to prevent rotation of the implant analog ( 2 ). The base ( 3 ) can also have at least one longitudinal slot as the anti-rotation means, for example. In the example embodiment shown, the anti-rotation element ( 4 ) extends from the open end of the base ( 3 ) over about half of its length. Obviously, the anti-rotation element ( 4 ) can also be shorter or longer, or applied only to the base of the implant analog ( 2 ), that is, directly opposite the working surface ( 5 ).  
         [0100]     A head ( 5 ), which can be designed in the known manner, corresponding to the particular implant system, sits at the wider end of the base ( 3 ). The head ( 5 ) forms the working surface, which corresponds to the surface of the implant in the jawbone. The dental technology product is set onto the implant analog in the direction of the arrows.  
         [0101]     The conicity of the base ( 3 ) varies depending on the size, length, and shape of the implant analog ( 2 ). In the example embodiment, the cone angle is only a few degrees, and is in the range of about 15°. Because of their conicity, the implant analogs can also be used for implants that have not been inserted perpendicularly into the jawbone. In that case, the angulation of the implant analog is equal to the relative angulation of the implants and allows the bridge to be removed from the master cast in one piece and optionally together with the implant analogs. It is advantageous to use the implant analogs ( 2 ) so that they can be removed from the master cast ( 1 ) and reinserted into it it. In particular, it is possible, in this way, to produce a model for implant-supported bridges using wax so that the modeled wax bridge, together with the conical implant analog ( 2 ), can be removed from the master cast ( 1 ) without strain and without stress. Furthermore, every individual implant analog ( 2 ) can be removed from the master cast without problem. That prevents distortion of the modulation on removal of the framework, so that no tedious soldering or laser-welding necessitated by distortion or new production are required, as is the case with the usual designs. To be able to arrange the implant analog in the master cast ( 1 ) better, a sleeve ( 6 ) can optionally be used ( FIG. 1 ). It is also designed to be conical ( FIGS. 5-6 ) or biconical ( FIG. 14 ), and has an internal shape that matches the external shape of the implant analog ( 2 ) to be embedded in the model. The sleeves ( 6 ,  14 ,  34 ,  38 ) are preferably provided on their outsides with retention elements ( 7 ,  16 ,  21 ,  22 ,  52 ,  52 ′) with which they can be anchored securely in the master cast ( 1 ). These retention elements ( 7 ,  16 ,  21 ,  22 ,  52 ,  52 ′) can each have suitable shapes. The sleeves are cast into the model in production of the master cast ( 1 ), with the retention elements acting simultaneously to prevent any twisting.  
         [0102]     So that it is possible to check that the base ( 3 ) of the implant analog ( 2 ) is sitting securely in the sleeve ( 6 ,  14 ,  34 ,  50 ,  38 ), the sleeve or the implant analog ( 2 ) has, in the region visible after casting of the model, a defined transition region to the implant analog ( 2 ), preferably a step or a bevel ( 8 ) which extends radially past the wider end of the base ( 3 ). The implant analog ( 2 ) is inserted into the sleeve ( 6 ) so far that the implant analog ( 2 ) fits, preferably precisely, with this bevel ( 8 ) on the end ( 9 ) of the sleeve. The sleeve ( 6 ,  14 ,  34 ,  50 ,  38 ) can be produced of metal or similarly stable material. As the region in which the bevel ( 8 ) of the implant analog ( 2 ) fits closely to the end ( 9 ) of the sleeve ( 6 ,  14 ,  34 ,  50 ,  58 ) can be exposed by a removable papilla, a visual check of the satisfactory seating of the implant analog ( 2 ) in the sleeve ( 6 ,  14 ,  34 ,  50 ,  38 ) at any time is assured. The head has a centrally projecting connecting piece ( 12 ).  
         [0103]      FIG. 3  shows an implant analog ( 2 ) that is designed the same as the implant analog of  FIG. 2  except for the head ( 5 ). It also has a conical base ( 3 ) provided with at least one anti-rotation element ( 4 ). In the present example embodiment, the anti-rotation element ( 4 ) is executed as a flattening. At the transition from the head ( 5 ) to the base ( 9 ) there is the bevel ( 8 ), which the implant analog ( 2 ) fits against in the manner previously described at the end ( 9 ) of the sleeve ( 6 ,  13 ,  34 ,  50 ,  38 ) if the implant analog ( 2 ) is placed in the master cast ( 1 ) so that it can be removed. The head ( 5 ) differs from the previous embodiment in that it has no connecting piece.  
         [0104]      FIG. 4  shows an embodiment in which the head ( 5 ) is placed at an angle to the base ( 3 ). The base ( 3 ) is again conical and has at least one anti-rotation element ( 4 ) that is provided, for instance, as a flattening on the outside of the base ( 3 ). Differing from the previous example embodiments, this anti-rotation means extends along the entire length of the base ( 3 ). The bevel or a collar ( 8 ) is placed at the transition from the base ( 3 ) to the head ( 5 ). The axis of the head ( 5 ) runs at an obtuse angle to the axis of the base ( 3 ). The head ( 5 ) has a cylindrical jacket ( 10 ) and a flat front end  11 , from which the connecting piece ( 12 ) projects centrally. This implant analog ( 2 ) is used particularly for implants that are not inserted perpendicularly into the jaw because the angulation provides that all the implant analogs can be arranged to run parallel with each other in spite of divergences of the implants used in a model. Thus, the prosthetic workpiece can later be removed from the master cast ( 1 ) in one piece with the implant analogs.  
         [0105]     A compensating sleeve, described by FIGS.  5  to  7 , is used for implants inserted extremely non-perpendicularly. Even standard model implants can be used when these sleeves are used. The compensating sleeve is used if the angle is large, more than about 25°, for instance. The angled implant analogs are selected appropriately by the dental technician.  
         [0106]     The compensating sleeve ( 13 ) according to  FIG. 5  is an inner sleeve that holds the implant analog ( 2 ) and is fastened that of the implant analog. If the inner sleeve ( 13 ) is to be placed in the master cast ( 1 ) so that it is removable, then the outer sleeve ( 19 ) shown in  FIGS. 6 and 7  is also used, which is anchored in the master cast ( 1 ) and in which the inner sleeve ( 13 ) is inserted according to  FIG. 5 . The inner sleeve ( 13 ) and the outer sleeve ( 19 ) are designed slightly conical, and can consist of metal or plastic.  
         [0107]     The compensating sleeve ( 13 ) according to  FIG. 5  has a conical base ( 14 ) which has on its outer side a peripheral edge ( 15 ) directed radially outward. The sleeve ( 13 ) is designed open at its narrower end. There is a slot ( 16 ) extending over the length of the base ( 14 ) in the outer side of the base ( 14 ). It is parallel to the axis, and can be formed by shaping the jacket of the base ( 14 ) or by depressing into the jacket of the base.  
         [0108]     The conic inner wall ( 17 ) of the base ( 14 ) is provided with retention elements ( 18 ), which project into the sleeve ( 13 ) and can have any suitable form. These retention elements assure interlocking with the plastic, resin, or impression compound put into the sleeve later.  
         [0109]     The radially projecting edge ( 15 ) acts as a stop if the sleeve ( 13 ) is inserted into sleeve ( 19 ) according to  FIGS. 6 and 7 . That is the case if the sleeve ( 13 ) is arranged in the master cast ( 1 ) so that it can be removed along with the implant analog ( 2 ) and can be replaced in the master cast again if necessary. In this case, the sleeve ( 13 ), as the inner housing, is inserted into the outer housing ( 19 ) so far that the edge ( 15 ) fits tightly against the end ( 20 ) of the outer housing ( 19 ). The outer sleeve ( 19 ) is firmly anchored axially in the master cast ( 1 ). For that purpose, it has, for instance, two peripheral bars ( 21 ,  22 ) in radial planes on its outer conical side  34 , which are separated axially from each other and form an anchor by means of which the outer sleeve ( 19 ) can be firmly anchored in the master cast ( 1 ). The bars ( 21 ,  22 ) can have profiles and the like on their outer surfaces ( 23 ,  24 ) to improve the anchoring in the master cast ( 1 ). To achieve anti-rotation protection for the outer sleeve ( 19 ), it is provided with at least one rib ( 32 ,  33 ) running perpendicular to the bars ( 21 ,  22 ) and protruding beyond the outside of the outer sleeve ( 19 ). The example embodiment has two ribs ( 32 ,  33 ) which are perpendicular to the peripheral bars ( 21 ,  22 ), which cross the ribs ( 32 ,  33 ) at their midpoints. The two ribs ( 32 ,  33 ) are at the same height and are separated from each other. Other ribs may be distributed over the periphery of the outer sleeve ( 19 ). The ribs ( 32 ,  33 ) can also be moved apart from each other in the peripheral direction and, deviating from the design shown, can have any other suitable shape that assures protection of the outer sleeve ( 19 ) against rotation.  
         [0110]     A bar  26  projecting inward and running in the axial direction is provided on the conical inner wall ( 25 ) of the outer sleeve ( 19 ). Its shape is matched to that of the slot ( 16 ) of the sleeve ( 13 ). If the sleeve ( 13 ) is inserted into the outer sleeve ( 19 ), then the bar  26  engages with the slot ( 16 ), so that the two sleeves ( 13 ,  19 ) fit together so that they cannot rotate.  
         [0111]     The outer sleeve ( 19 ) is designed open at its narrower end ( FIG. 7 ). A bar ( 28 ) running radially, which is fastened to the inner side of the sleeve ( 19 ) is provided in the opening ( 27 ). There is a circular section  29  with a central opening ( 29 ′) at the midpoint of the bar ( 28 ), or concentric with the opening ( 27 ), into which a pin ( 30 ) can be inserted. It has a circular cross-section and has retention elements or profiles ( 31 ) at its end to assure that the pin ( 30 ) is firmly anchored in the casting material.  
         [0112]     In production of the master cast ( 1 ) the outer sleeve ( 19 ) is first placed on the inner sleeve ( 13 ) and the pin ( 30 ) is inserted into the opening ( 29 ′) of the bar ( 28 ) of the outer sleeve ( 19 ). Then that unit is clamped in a dental surveyor with which the compensating sleeve ( 13 ) and the outer sleeve ( 19 ) are fixed in the selected direction on the implant analog already inserted into the impression. The height of the pin ( 30 ) is adjusted accurately by sliding it. Then the inner or compensating sleeve ( 13 ) is filled with a liquid plastic or resin. In this process, the end of the pin ( 30 ) with the profiling  31  is included in the casting. After the model is produced, a silicone molding which serves to make a removable papilla is made over the jaw region of the implant. Thus, the edge ( 15 ) of the compensating sleeve ( 13 ) is exposed on the plaster model, so that the seating of the compensating sleeve ( 13 ) in the outer sleeve ( 19 ) can be checked properly.  
         [0113]     Because of the use of the outer sleeve ( 19 ), the compensating or inner sleeve ( 13 ) with the implant analog can be removed from the master cast ( 1 ) and replaced exactly. If this removability is not needed, the compensating sleeve ( 19 ) can also be cast and anchored directly in the master cast ( 1 ).  
         [0114]     FIGS.  8  to  13  show other embodiments of implant analogs ( 2 ), each of which have different cross-sectional shapes.  
         [0115]     The implant analog ( 2 ) according to  FIGS. 8 and 9  differs from the one shown in  FIG. 2  in that its base ( 3 ), tapering in the direction of insertion into the master cast ( 1 ) according to  FIG. 1 , has an oval or elliptical cross section. The head ( 5 ) and the collar ( 8 ) are made circular and have a diameter that is greater than the maximum width of the base ( 3 ). Because the cross sectional shape of the base ( 3 ) is not circular, no additional protection against rotation is needed.  
         [0116]     The oval shape of the base ( 3 ) or of the holding cone further makes it possible for this implant analog ( 2 ) to be cast directly into the master cast without further protection against rotation.  
         [0117]     In the example embodiment, the small exposed end ( 35 ) of the base ( 3 ) is larger than in the embodiment shown in  FIG. 2 . A tenon-like projection ( 36 ) with an external thread ( 37 ) is provided on the exposed end surface ( 35 ). By means of this external thread ( 37 ), the implant analog ( 37 ) can be mounted in an outer sleeve ( 38 ) by means of a screw ( 39 ) and screwed to it— FIG. 12 . Instead of the projection ( 36 ), a hole with an internal thread can be provided, into which a screw or the like can be screwed to fasten the implant analog ( 2 ) in an outer sleeve ( 38 ).  
         [0118]     The implant analog ( 2 ) according to  FIGS. 10 and 11  differs from the implant analog described previously in that its base ( 3 ), designed as a taper, has an angular cross section, square in the example embodiment. The head ( 5 ) of the implant analog ( 2 ) has a circular periphery. As  FIG. 11  shows, the bevel ( 8 ) has a circular periphery such that its diameter is the same as the length of the diagonal ( 34 ) of the largest cross-sectional surface of the base ( 3 )— FIG. 11 . The smaller end surface ( 35 ) of the base ( 3 ) again carries a tenon-like projection ( 36 ) with an external thread ( 37 ). A hole with an internal thread, not shown, can also be provided instead of the projection ( 36 ).  
         [0119]     The implant analog ( 2 ) according to  FIG. 12  is essentially equivalent to the embodiment in  FIGS. 10 and 11 . The base ( 3 ) is made circular, while the connecting piece ( 12 ) has a hexagonal shape. Again, a flat ( 4 ) acts to prevent rotation. It extends over part of the length of the base ( 3 ) and preferably has the same width over its longitudinal extent. A tenon-like projection ( 36 ) with an external thread ( 37 ) connects to the smaller end ( 35 ) of the base ( 3 ). Again, a hole with an internal thread can be provided instead of this projection ( 36 ).  
         [0120]     The implant analog ( 2 ) is inserted into an outer sleeve ( 38 ) and is fastened in that outer sleeve ( 38 ) by a screw ( 39 ) that is screwed onto the projection ( 38 ). The outer sleeve ( 38 ) has a seat part ( 42 ) for the base ( 3 ) of the implant analog ( 2 ) and has a conical seat ( 40 ), with the base ( 3 ) of the implant analog fitting tightly to its internal wall. The internal wall of the seat ( 40 ) is provided with a corresponding flat in the region of the anti-rotation element ( 4 ).  
         [0121]     A sleeve part ( 43 ) having a cylindrical inner wall ( 46 ) connects to the seat part ( 42 ) and accepts the screw ( 39 ). The transition between the seat ( 40 ) and the cylindrical inner wall ( 46 ) forms an internal shoulder surface ( 45 ) that supports the screw ( 39 ) when the implant analog ( 2 ) is mounted. The implant analog ( 2 ) is screwed into the seat ( 40 ) until its collar ( 8 ), which is made circular, fits tightly against the end surface ( 44 ) of the seat part ( 42 ). The diameter of the bevel ( 8 ) is the same as the outside diameter of the seat part ( 42 ).  
         [0122]     The sleeve part ( 43 ), which has the same outside diameter as the seat part ( 42 ), keeps the casting material away from the screw ( 39 ) during production of the master cast ( 1 ). The screw ( 39 ) can be turned easily with a screwdriver through the open end of the sleeve part ( 43 ). The screw ( 39 ) has a screw slot ( 47 ) for that purpose. The implant analog ( 2 ) can be clamped in the outer sleeve ( 38 ) with the screw ( 39 ), so that it cannot be separated accidentally. Retentions, such as bars, ribs or the like can be provided on the cylindrical outside ( 41 ) of the outer sleeve ( 38 ) as anti-rotation means and/or as anchoring means (not shown). It is possible to make at least the sleeve part ( 43 ) oval, elliptical, or angular in its cross section so that no special anti-rotation means is required.  
         [0123]     As shown in  FIG. 13 , the implant analog is seated in an outer sleeve ( 49 ). The implant analog ( 2 ) can be designed according to one of the example embodiments  2  to  12 . The outer sleeve ( 49 ) has a seat part ( 50 ) and a sleeve part ( 51 ). The seat part ( 50 ) has a seat ( 50 ′), and the inner wall of the base ( 3 ) of the implant analog ( 2 ) lies tightly against it. The outer jacket surface ( 57 ) of the seat part ( 50 ) is a conical jacket, the diameter of which tapers toward the sleeve part ( 51 ). Its external jacket surface is cylindrical.  
         [0124]     The outer sleeve ( 49 ) is designed in one piece, corresponding to the embodiment of  FIG. 12 . It can consist of a metallic material or a plastic, especially a thermosetting plastic. The outer sleeve ( 49 ) is given a retention element ( 52 ,  52 ′), which can be formed by projecting knobs, tenons, bars, and the like in the vicinity of the seat part ( 50 ) and the sleeve part ( 51 ).  
         [0125]     There is a shoulder surface ( 53 ) directed radially inward at the transition from the cylindrical inner wall ( 46 ) of the sleeve part ( 51 ) to the conical inner wall ( 50 ′) of the seat part ( 50 ). Differing from the previous embodiment, it projects radially inward over the inner wall ( 50 ′). This produces a thin annular wall ( 59 ). The annular wall ( 59 ) bounds an opening ( 60 ) through which the tenon-like projection ( 36 ) of the base ( 3 ) projects, with the outer thread in the inner space of the cylindrical sleeve part ( 51 ).  
         [0126]     A screw ( 54 ) with internal thread is inserted into the inner space of the sleeve part ( 51 ) and screwed onto the projection ( 36 ) to hold the implant analog ( 2 ) to the outer sleeve ( 49 ). In this way the base ( 3 ) of the implant analog ( 2 ) is drawn into the inner cone of the seat part ( 50 ) until the bevel ( 8 ) or the collar lies tightly against the end surface ( 56 ) of the seat part ( 50 ).  
         [0127]     Instead of the projection ( 36 ) with the external thread ( 37 ), a hole with an internal thread can be provided in the base ( 3 ) of the implant analog ( 2 ), into which an ordinary screw can be screwed to fasten the implant analog ( 2 ) in the cylindrical part of the outer sleeve ( 49 ).  
         [0128]      FIG. 14  shows another preferred fastening of the implant analog ( 2 ) in an outer sleeve ( 38 ). The outer sleeve ( 38 ) has an upper cone ( 55 ) that serves as a seat for the implant analog ( 2 ), and a lower cone ( 56 ) that runs in the opposite direction from cone ( 55 ) and holds a conical backing piece ( 58 ). The backing piece ( 58 ), which has a threaded hole ( 61 ), is inserted from the underside of the master cast ( 1 ) into the outer sleeve and screwed to the implant analog ( 2 ) with the external thread ( 37 ) of the tenon-like projection ( 36 ) to hold it to the outer sleeve ( 38 ). When the backing piece ( 58 ) is screwed in, the base ( 3 ) of the implant analog ( 2 ) is drawn into the upper cone ( 55 ) until the collar or bevel ( 8 ) lies against the end surface ( 62 ) of the outer sleeve ( 38 ). To the extent that exact repositioning in the master cast ( 1 ) is assured, the implant analog ( 2 ) and the backing piece ( 58 ) can also be clamped together directly in the master cast ( 1 ) even without an outer sleeve ( 38 ), and the implant analog ( 2 ) can be positioned reliably in this relatively simple manner.  
         [0129]     In the example shown, the working surface or head ( 5 ) of the implant analog ( 2 ) has a hexagonal connecting piece ( 12 ). Other polygonal shapes such as triangular, quadrangular, or octagonal connecting pieces can also be provided instead of this hexagonal connecting piece ( 12 ). Alternatively, connecting pieces can also be provided in the form of an internal cone, internal cones combined with an internal polygon, a bayonet connection, Torx designs or combinations of those in the working surface or in the head of the implant analog ( 2 ). The choice is guided solely by the particular implant desired.  
         [0130]     Instead of the screw connections described, it is also possible to fasten the implant analog ( 2 ) into the outer sleeve with other fastening means, for example, with a notch or clip connection, with a bayonet connection, with a bolt, a split pin, and the like.  
         [0131]     The base ( 3 ) of the implant analog ( 2 ) can also be designed in a star or kidney shape or have some other configuration, instead of the conical, oval, elliptical or angular cross-sectional shapes. In any case, the base ( 3 ) must be tapered in the direction of insertion.  
         [0132]     The implant analogs described ( 2  or  13 ) can also be used with extremely oblique position of the inserted implants as well as to produce implant reconstructions for single-tooth implants and for implant-supported bridges. Quite different implant analogs ( 2 ) can be inserted into the seating sleeves ( 6 ,  19 ,  38 ,  49 ), each of them lying with its base ( 3 ) tightly against the inner wall of the seats of the seating sleeves. The implant analogs according to the invention are usable in all the usual dental implant systems. However, the implant analogs are also suitable for scanning implant reconstructions for virtual models.  
         [0133]     As various modifications could be made to the exemplary embodiments, as described above with reference to the corresponding illustrations, without departing from the scope of the invention, it is intended that all matter contained in the foregoing description and shown in the accompanying drawings shall be interpreted as illustrative rather than limiting. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims appended hereto and their equivalents.
Implant analog for custom production of prosthetic superstructures for inserted dental implants, inserted into a master cast directly or indirectly via a model sleeve comprising an implant head equipped with elements to hold and fasten an implant system; a base of said implant analog having a cross section that tapers over at least part of its length; an implant head having a working surface and a connecting piece; a tenon-like projection on a bottom end surface of said implant head; and an external thread dimensioned to connect with a screw element.