Abstract:
The invention relates to a dental implant which has an axis and a hole with a positioning section. Said positioning section has projecting parts and intermediate spaces distributed alternately, one after the other, along the periphery. Said intermediate spaces comprise several first intermediate spaces which create a division, and a second, wider intermediate space. A secondary and/or supplementary structural part can be attached in the implant, said part having a connecting section which extends into the hole. Said connecting section can have projecting parts for engaging in the intermediate spaces of the implant, and can be configured in such a way that it can be fixed to the implant in several different rotated positions or a single rotated position. The secondary and/or supplementary structural part can also be produced without projecting parts of the type mentioned, so that it can be screwed into the implant.

Description:
TECHNICAL FIELD 
     The invention relates to a dental implant. The implant can be used as an intraosteal implant and can be inserted into the bone of an upper or lower jaw. A secondary part can be fastened to the implant to serve for holding, and/or for the construction of, a dental prosthesis, i.e., a prosthesis with a single artificial tooth or a number of artificial teeth. The implant can furthermore serve to hold a special superstructure forming, for example, an entire single artificial tooth. 
     STATE OF THE ART 
     A device disclosed in DE 41 27 849 A has an implant and a secondary or holding part. The implant has an axial blind bore with a polygonal section. The secondary part has a polyhedral section fitting into the polyhedral section of the blind bore. The polyhedral sections are configured as dodecahedral sections, so that the secondary part can be set selectively in any one of twelve positions, i.e., can be joined non-rotationally to the implant. In many cases, however, it would be desirable if the secondary part could be joined in only a single, clearly defined position to the implant. Also, the dodecahedral mating sections provide but a relatively imprecise definition of the rotational position due to the necessary clearance. The polyhedral section of the blind bore is rather long and extends all the way to the mouth of the blind bore, so that the secondary part is never held well and accurately above the blind bore. Also, the secondary part is glued into the implant and accordingly can no longer be removed from it. 
     A device disclosed in EP 0 685 208 A likewise has an implant and a secondary part. The implant has an axis and a bore coaxial with it which has a tapering section and an internal thread. The secondary part can be inserted partially into the bore in the implant and has an external thread which can be driven into its internal thread. The secondary part is rotated about its axis when it is screwed into the implant, until it contacts with a tapered section the tapered section of the bore. The rotational position in relation to the axis of the secondary part which results in the assembled state depends on the production tolerances and on the torque with which the secondary part is screwed into the implant. So this implant does not permit any precise setting of the rotational position of a secondary part reaching into the bore in the implant. 
     DE 195 34 979 C has disclosed a device with an implant and a spacer sleeve. The implant has an axial blind bore. Its inside surface is provided with six grooves distributed about the axis of the implant. The spacer sleeve reaches into the blind bore of the implant and has lugs engaging in its grooves, so that the spacer sleeve can be set in six different rotational positions. This implant thus does not define any single, definite rotational position. Also the spacer sleeve is guided laterally only in a short cylindrical guiding portion of the bore, which has a relatively small diameter, and is supported against forces directed approximately squarely to the axis of the implant. If such forces act on a dental prosthesis held by the spacer sleeve, a long lever arm is created between the point of attack of these forces and the guiding portion of the bore, so that very great torques must be transferred from the spacer sleeve to the implant in the guiding portion of the blind bore. This, combined with the small dimensions of the guiding portion, results in a great danger that the prosthesis under stress will perform small movements—so-called micromovements—with respect to the implant, and thus a failure of the dental treatment is caused. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The invention is therefore addressed to the problem of creating a dental implant which eliminates the disadvantages of the known implants, and especially makes it possible to connect to the implant a secondary and/or superstructural part, depending on its shape and intended use, in only one, clearly defined rotational position or in one which can be selected from any of several possible rotational positions. 
     This problem is solved according to the invention by a dental implant with an axis and a bore coaxial with this axis for fastening a secondary and/or superstructural component, wherein the bore has a positioning section with projections and interstices alternating with one another around the axis, and the dental implant is characterized in that the interstices have a plurality of first interstices of equal size and a second interstice which in at least one direction has a larger dimension than the first interstices. 
     The invention further relates to a device with a dental implant and with a secondary and/or superstructural part, the device according to the invention being characterized in that it has a connecting section intended to reach into the bore in the implant and to be fastened in the latter. 
     Advantageous embodiments of the implant and the device will appear from the dependent claims. 
     The first and second interstices of the dental implant according to the invention make it possible to fasten to one and the same implant secondary and/or superstructural components of optionally different configuration, which, depending on their configuration, are able to assume only a single rotational position defined by the positioning section of the implant, or which can assume a rotational position selected from several possible rotational positions, or whose rotational position is not defined by the positioning section. 
     The implant is preferably elongated and generally rotationally symmetrical with its axis. The bore is preferably a blind bore and has a mouth situated at one end of the implant. Each interstice of the implant is preferably straight and parallel as well as symmetrical with a plane passing through the said axis and through the middle of the groove in question. The positioning section of the implant is furthermore generally cylindrical, for example, so that the projections present between the interstices of the implant have an apex lying in a cylindrical surface coaxial with the axis. The positioning section of the implant, however, can possibly be generally conical instead of cylindrical, narrowing away from the mouth of the bore, and can have projections which separate the interstices from one another and have apexes lying in a conical surface. 
     The positioning section of the implant preferably defines a pitch circle, both in the case of generally cylindrical and in the case of generally conical shape, which is coaxial with the axis and conforms with the apexes of the projections of the implant. In a preferred embodiment, the second interstice is wider and/or deeper than the first interstices. The first interstices adjacent one another are at equal distances apart as measured along the pitch circle, and together they define a pitch circle division or—simply—a division. For clarification let it also be noted that the division is equal to the nth part of a full circle, n being a whole number and preferably at least 6, or better at least 10, and amounting to no more than 72, for example. The second, wider and/or deeper interstice has a dimension measured along the pitch circle that is preferably greater than one division, for example approximately or exactly equal to the sum of the dimension of a first interstice measured along the pitch circle and of one whole division or several whole divisions. 
     A secondary part designed to be fastened to the implant can have an inside section or connecting section, and an outside or head section. When the secondary part is fastened to the implant the inside or connecting section is situated in the bore in the implant and the outside or head section outside of the implant. The secondary parts can be configured differently according to the intended use and the medical indications. The inside or connecting section of the secondary part can have, for example, a positioning section with projections distributed along its circumference, and separated from one another by interstices. When the secondary part is fastened to the implant, the projections of the implant and of the secondary part can then engage interstices of the other part and thereby establish a rotational position of the secondary part with respect to rotations about the axis defined by the bore in the implant. In one possible embodiment of the secondary part, all projections of the secondary part have equal shapes and dimensions, so that the secondary part can be fixed in different rotational positions on the implant. The rotational position of the secondary part is thus optional and variable step by step, while each selectable rotational position is defined by the intermeshing projections and grooves of the implant and secondary part, and the angle of rotation between adjacent rotational positions is equal to the dividing angle established by the division of the equally configured (first) interstices. This method of joining a secondary part to the implant is referred to hereinafter as the multipositioning of the secondary part. 
     The secondary part can furthermore have a projection which in at least one direction has a greater dimension than the first interstices of the implant and is configured such that it can enter in the second interstice, but not in the first interstices of the implant. This projection of the secondary part can especially be wider than the first interstices of the implant and/or have a height that is greater than the radial depth of the first interstices of the implant. The positioning section of the secondary part then preferably has, in addition to the said projection, narrower projections for engaging the narrower first interstices of the implant, but possibly can have only just the projection engaging the second, wider and/or deeper interstice of the implant. The secondary part can then be joined to the implant only in a single rotational position as regards rotations about the axis defined by the implant. This way of joining a secondary part to the implant will be referred to hereinafter also as single positioning of the secondary part. 
     The secondary part, however, can also be made without a positioning section, and can be so configured that, when inserted into the bore of the implant and after it is fastened to the latter, it will not enter into the interstices of the implant. The secondary part is then continuously rotatable upon insertion into the bore in the implant, until the secondary part is fastened to the implant. 
     Each interstice in the implant is defined preferably at least partially by flats which are approximately or precisely parallel to a straight line passing radially to the axis through the center of the interstice in question, or form with such a straight line an angle of at most 60° and preferably no more than 45°. Furthermore, each interstice has, for example, two substantially planar lateral surfaces. The interstices can be approximately V-shaped in cross section, or they can have also a base surface and be approximately U-shaped. The interstices can furthermore be substantially completely curved, and form an arc, for example, which is no more than equal to a semicircle and, for example, smaller than a semicircle. The projection, or every projection, of the secondary part and implant engaging in an interstice has a certain free play, so that in spite of possible manufacturing inaccuracies and in spite of dimensional changes caused by temperature changes, the projection can be inserted easily into the interstice. The free play of a projection, measured tangentially to the above-mentioned pitch circle is preferably made so small that the secondary or superstructural part can be turned back and forth by no more than an angle amounting preferably to no more than 2°, or better 1°, or even no more than 0.5°. 
     The blind bore of the implant has preferably an internal thread serving for the removable attachment of the secondary part. If the secondary part has a positioning section with a projection or, preferably, a plurality of projections, the secondary part can be releasably fastened to the implant with an external thread which can be screwed into the internal thread of the implant. The fastening means can consist, for example, of a screw with a head urged against a surface of the secondary part, or of a headless screw which can be threaded into the secondary part. The headless screw can then have, in addition to the external thread which can be screwed into the internal thread of the implant, an external thread which can be screwed into an internal thread in the secondary part, and one of the external threads can be right-handed, for example, and the other left-handed, and/or the two external threads can have different pitches. To attach a secondary part to provide positioning, therefore, only a single additional element is needed, namely the said fastening means. If the secondary part, however, has no projection designed to engage a positioning groove in the implant, the secondary part can either also be fastened releasably to the implant, likewise with a separate fastening means of the kind described, or it may be provided with an external thread which can be screwed into the internal thread of the implant and consists, together with the remaining sections of the secondary part, of a one-piece body. Possibly a secondary part can also be provided which is fastened to the implant, not by screwing, but one which when used is first inserted releasably into the hole in the implant, and then, when it must no longer be removed, it is cemented or glued in the bore in the implant. The bore in the implant can then nevertheless have an internal thread so that the same type of implant can also be used to accommodate a threaded secondary part. If desired, however, the internal thread can be omitted from the implant. The secondary part can be joined securely and free of micromovements to the implant by the above-described screwing, cementing or gluing methods, so that in a physiological environment, it will not loosen due to micromovements. 
     A firm manufacturing implants according to the invention can, for example, also manufacture different variants of secondary parts to be fitted to the implants and offer one type of implant and various secondary parts to dentists and dental clinics and the like. Then, for example, a superstructure serving for the formation of a dental prosthesis can be built unreleasably on the secondary part or can be fastened releasably to the latter. Also, two or more devices each with an implant and a secondary part can serve for fastening a bridge or a dental prosthesis containing a plurality of teeth. 
     As already mentioned, instead of a secondary part, a special superstructural part can be fastened to an implant. Such special superstructural part can then, instead of the firm producing the implants, be custom made by a dental technician for special purposes and/or for a specific patient. What has been described above concerning the joining of a secondary part to the implant can then apply in a substantially similar way to the attachment of a special superstructural part to an implant. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The subject matter of the invention is explained below with the aid of embodiments represented in the drawings. In the drawings: 
     FIG. 1 shows an axial section taken through a part of an implant in which the bore has a positioning section in the vicinity of the bottom end of a cylindrical section, 
     FIG. 2 an enlarged cross section taken through the implant of FIG. 1, 
     FIG. 3 an angular elevation of the implant of FIGS. 1 as well as  2 , 
     FIG. 4 an angular elevation of an implant with a positioning section disposed as in FIG. 1, but of a different configuration, 
     FIG. 5 an angular elevation of an implant with a positioning section arranged at its upper end, 
     FIG. 6 an angular elevation through an implant whose positioning section is arranged below the narrower end of a tapered section of the bore, 
     FIG. 7 an axial section taken through a straight secondary part with a positioning section arranged in the vicinity of the lower end, 
     FIG. 8 an enlarged cross section taken along line VIII—VIII of FIG.  7  through the secondary part drawn therein and configured for multipositioning, 
     FIG. 9 a cross section similar to FIG. 8 taken through a secondary part for single positioning, 
     FIG. 10 an axial section taken through a bent secondary part, 
     FIG. 11 an axial section taken through a secondary part fitting the implant of FIG. 5, 
     FIG. 12 an axial section taken through a straight secondary part with an internal thread for fastening a stud bolt, 
     FIG. 13 an axial section taken through a secondary part whose internal and connecting portion has a tapered external surface section, 
     FIG. 14 an angular view of a bent secondary part with an internal thread for fastening a stud bolt, 
     FIG. 15 an elevation of a screw, 
     FIG. 16 an elevation of a stud bolt with two threads, 
     FIG. 17 an elevation of another stud bolt, 
     FIG. 18 an angular view of a secondary part according to FIGS. 7 and 8, and of a screw inserted in the latter, 
     FIG. 19 an axial section taken through a device with an implant according to FIGS. 1 to  3  and the parts according to FIG. 18, 
     FIG. 20 a cross section taken along line XX—XX of FIG.  19  through the device seen in the latter. 
     FIG. 21 an angular view of a straight secondary part according to FIG.  9  and of a screw inserted in the latter, 
     FIG. 22 a cross section through a device with an implant according to FIGS. 1 to  3  and the parts according to FIG. 21, 
     FIG. 23 an angular view of a device with an implant according to FIG. 4, a secondary part configured for single positioning, and a stud bolt, 
     FIG. 24 an angular view of a bent secondary part for multipositioning, and a screw, 
     FIG. 25 an axial section taken through a device with an implant according to FIG.  4  and parts according to FIG. 24, 
     FIG. 26 a cross section taken along line XXVI—XXVI of FIG.  24  through the device shown therein, 
     FIG. 27 an axial section taken through a device with an implant according to FIG. 6 and a bent secondary part according to FIG. 14, 
     FIG. 28 an angular view of a device with an implant according to FIG. 6 and a straight secondary part, 
     FIG. 29 an angular view of a device with an implant according to FIGS. 1 to  3  and a straight secondary part without positioning section, and 
     FIG. 30 a cross section taken through the device according to FIG.  29 . 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     The dental implant  1  represented in FIGS. 1 to  3  is elongated as well as generally rotationally symmetrical with an axis  2  and has at the top a cylindrical, smooth circumferential surface  10 . The lower part of implant  1 , which is not seen in FIGS. 1 and 3, can be configured, for example, in any known or novel manner, and have, for example, a smooth cylindrical exterior or a screw thread. Also, the unseen lower part of the implant can have, for example, a cavity open at the bottom or a solid cross section at the bottom end. 
     The implant  1  has at the upper end an implant shoulder  11  which is formed by a planar annular surface radial to the axis  2 . The implant is provided with a stepped blind bore  12  generally coaxial with the axis  2 . This bore has a mouth  13  situated at the upper end of the implant and surrounded by the inner margin of the annular surface forming the shoulder  11 , and downward from the latter a cylindrical main section  14 , a positioning section  15 , a short, generally cylindrical recess  16 , a radial and/or inclined shoulder  17 , a narrower cylindrical section  18 , and a section  19  with an internal thread  20 , in that order. The axial dimension of the positioning section  15  amounts, for example, to approximately 0.5 mm to 1 mm. The diameter of the recess  16  is equal to that of the cylindrical main section  14 . The diameter of the narrower, cylindrical section  18  is at least or approximately equal to the maximum diameter of the internal thread  20 . Moreover, let it be noted that the narrower cylindrical section  18  could possibly be omitted and the internal thread could directly adjoin the recess  16 . 
     As it can be seen especially clearly in FIGS. 2 and 3, the positioning section  15  has positioning projections  23  and positioning interstices  24 ,  25  alternating with one another along the circumference. The positioning projections  23  are all equally configured, extend inwardly toward the axis  2  from the cylindrical surface defined by the cylindrical main section  14 , taper inwardly in cross section toward their apex, and are approximately V-shaped or triangular in cross section. The positioning interstices have a plurality of equally shaped as well as equally dimensioned, especially of equal width, namely narrow, first positioning interstices  24  and a single, wider second positioning interstice  25 . Each first positioning gap  23  consists of a groove or notch of approximately V-shaped cross section and has two substantially planar flanks which slope away from one another inwardly from its base toward the axis  2 . The wider second positioning gap  25  has a planar or slightly curved base surface and two lateral surfaces inclined inwardly therefrom away from one another. The lateral surfaces of the gaps and the apexes of the projections are straight in axial sections and run parallel to the axis  2 . The apexes of the projections  23  define a pitch circle  27  and lie on a cylindrical surface. The bases of the interstices  24 ,  25  together also define a cylindrical surface which coincides approximately or precisely with the cylindrical surfaces of the main section  14  and of the recess  16 . The narrow first positioning interstices  24  adjacent one another are all at the same distance apart and define a division on the pitch circle  27 , for example a 10° or 36-pitch division. The wider, second positioning interstice  25  is formed by the omission of one projection  23  or of two or even more projections  23  adjacent one another. 
     The dental implant  31  seen in FIG. 4 is very similar to implant  1 , defines an axis  31  and has an implant shoulder  41 , a blind bore  52  with a mouth  53 , a cylindrical main section  54 , a positioning section  55  and an internal thread  60 . The positioning section is arranged similar to the positioning section  15  and has positioning projections  63  and positioning interstices  64 ,  65  following one another alternately along its circumference. The positioning projections  63  are again all of the same configuration. The positioning interstices  64 ,  65  have a plurality of first, narrow positioning interstices  64  and a second, wider positioning interstice  65 . Each positioning projection  63  consists of a cog and has an apical surface that is arcuate in cross section. The apical surfaces of the projections form parts of a cylindrical surface coaxial with the axis of the implant  31  and they define a pitch circle. The second, wider positioning interstice  65  is formed by the omission of one positioning projection  63 . Each positioning interstice  64 ,  65  is approximately U-shaped in cross section and/or quadrangular, and has two lateral surfaces which are planar and approximately or precisely parallel to a plane running through the axis  32  and the center of the positioning interstice in question. Also, each interstice  64 ,  65  has a base surface which is parallel to the axis  32  as well as arcuate or straight in cross section, and approximately coincides with the surface of the main section  54 . The first, narrow positioning interstices  64  together define a division, for example a 30° or 12-pitch division. 
     The dental implant  71  seen in FIG. 5 has an axis  72 , an implant shoulder  81  and a blind bore  82  with a mouth situated at the upper end of the implant and surrounded by the implant shoulder  81 , a cylindrical main section  84 , a positioning section  85  and an internal thread  90 . The positioning section is situated approximately at the upper end of the implant between the mouth  83  and the cylindrical main section  84 , and is separated from the latter by a recess  86 . The positioning section has, for example, projections and interstices of a configuration similar to that of the positioning section  15  of implant  1 , but could also be configured similar to the positioning section  55  of implant  31 . The apexes of the projections of the positioning section define a cylindrical surface whose diameter is, for example, approximately or at least equal to that of the cylindrical main section  84 . 
     The dental implant  101  represented in FIG. 6 has an axis  102 . The circumferential surface of implant  101  has at the top a flaring section  102 . At the lower end thereof a cylindrical section  10  adjoins it. The implant shoulder  11  is formed by a conical, upwardly tapering annular surface. The blind bore  112  has a mouth  113  surrounded by the implant shoulder  111  and from there on down a downwardly tapering, conical main section  114 , a positioning section  115 , a recess  116 , a cylindrical section  118  and a section  119  with an internal thread  120 , in that order. The positioning section  115  is configured to be, for example, similar to positioning section  55  of implant  31 , but could be configured similar to the positioning section  15  of implant  1 . Let it be noted that the apexes of the positioning projections  115  define a cylindrical surface, but could possibly define a conical surface. 
     The secondary part  201  represented in FIGS. 7 and 8 is generally rotationally symmetrical with an axis  202  as well as straight, and has at the bottom a generally cylindrical internal and connecting section  210  intended for insertion into an implant and for releasable connection therewith. This connecting section is provided near the bottom end  212  of the secondary part with a positioning section  215 . The secondary part furthermore has an outside or head section  220  tapering conically upward from the internal or connecting section and intended for arrangement outside of the implant, and it forms the upper end  221  of the secondary part. The head section  220  extends radially beyond the connecting section  210  and, when these two sections are joined, it forms a shoulder  225  with an annular, radial, planar bearing surface. The secondary part  201  is provided with an axial through-bore  230 . This bore is provided near the upper end  221  of the secondary part with an internal thread  231  and has downward therefrom a shoulder  232 , a cylindrical seat  233  with an annular groove  234  arranged a little below the shoulder  25 , a downwardly tapering conical section  235  and a downwardly flaring, conical section  236  which extends down to the bottom end  212  of the secondary part, in that order. The two conical sections  235 ,  236  together form a constriction  237 . A portion of the internal connection section  210  is divided by axial slits  240  from the bottom end  212  into axial, elastic, resilient tongues  241  which can be spread apart against a restoring force. For example, there are four slits and tongues, but the number and depth of the slits  240  can be varied. The slits  240  reach from the bottom end  212  to beyond the constriction, approximately to the annular groove  234  serving to improve the ability of the tongues to spread, but are not to extend all the way to the shoulder  225 . 
     The positioning section  215  is situated in the area of the tongues  241  and has axial grooves in the outside surface of the latter which form the positioning interstices  243 , between which positioning projections  245  are present. The apexes of the latter lie in the cylindrical outside surface of the inner, connecting section  210 . The interstices  243  and projections  245  are, except for the gaps at the slits  240 , uniformly distributed along the circumference of the secondary part. The positioning interstices  243  are all of the same shape and dimensions, have the same spacing as the positioning projections  23  of implant  1  and are at least approximately complementary to the latter. The positioning projections  245  of the secondary part  201  are likewise all of the same shape and dimensions, have the same spacing as the first positioning interstices  24  of implant  1  and are at least approximately complementary to the latter. The positioning section  215  of the secondary part  201  permits—as will later be explained—the multipositioning of the secondary part  201  with respect to the implant  1 . The secondary part  251  seen in FIG. 9 has an internal connecting section  260  with a positioning section  265  configured for single positioning, and an external head section  270 . The positioning section  265  has positioning interstices  273  formed by axial grooves, a plurality of first, narrow, identically shaped positioning projections  275 , and a second, wider positioning projection  276 . The positioning interstices  273  and the first positioning projections  275  have the same spacing as the first positioning interstices  24  of implant  1 . The second, wider positioning projection  276  can clearly be formed by omitting or bridging at least one interstice of two or possibly more adjacent first positioning projections. The positioning interstices  273  of the secondary part  251  are approximately complementary to the positioning projections  23  of implant  1 . Also, the first positioning projections  275  and the second positioning projection  276  of the secondary part  251  are approximately complementary to the first positioning interstices  24  or second positioning interstice  25  of implant  1 . 
     The bent secondary part  301  seen in FIG. 10 has two axes  302 ,  303 , forming an obtuse angle with one another, an inner connecting section  310  generally rotationally symmetrical with the axis  302  and having a positioning section  315 , and a tapering outside head section  320  which is generally rotationally symmetrical with the axis  303 . The shoulder  325  present between the latter and the connecting section  310  is radial as well as at right angles to the axis  302 . The secondary part  301  has an angled through bore  330  which has a portion extending through the connection section  310  and the lower part of the head section  320  and coaxial with the axis  302 , with a cylindrical seat  333  as well as an annular groove  334 , and above the seat  333  it has a portion coaxial with the axis  303  with an internal thread  331 . 
     The straight secondary part  351  represented in FIG. 11 has an internal or connecting section  360  with a positioning section  365 , an outer or head section  370  and, at the transition between the two sections  360  and  370 , a shoulder  375 . The positioning section  365  is situated near the upper end of the connecting section  360  and the shoulder  375 . 
     The straight secondary part  401  represented in FIG. 12 has an internal or connecting section  410  with a positioning section  415 , an outer or head section  420  and an axial through-bore  430 . The latter has an upper internal thread  431  near the head section  420 , which serves to mount an occluding screw, a lower internal thread  433  located below the latter, substantially in the connecting section  410 , and an annular groove  434  between the two threads. The connecting section in this variant is free of recesses and thus has the shape of a compact, uninterrupted ring in its cross sections through its entire length. 
     The secondary part  451  in FIG. 13 is bent at an angle and has an internal or connecting section  460  that is substantially rotationally symmetrical with its one axis  452 . The latter has a conical section  461  tapering from the top down, an annular groove  463 , and a positioning section  465  with a cylindrical envelope surface. The internal or connecting section  460  is configured such that its conical section  461  fits into the conical main section  114  and its positioning section  465  into the positioning section  115  in bore  112  of the implant  101  seen in FIG.  6 . 
     The angled secondary part  501  seen in FIG. 14 has an internal or connecting section  510 , which like that of the previously described secondary part  451  has a conical section  512  and a positioning section  515 . The bore  530  of the secondary part  501  is, as in the secondary part  401 , provided with an upper internal thread  531  and a lower internal thread  533 . 
     The positioning sections  315  and  415  of the secondary parts  301  and  401 , respectively, shown in FIGS. 10 and 12, respectively, can be configured for multipositioning or single positioning such that they fit the implants  1  or  31 . The positioning section  365  of the secondary part  351  in FIG. 11 can likewise be configured for multipositioning or single positioning, and will fit those of implant  71  in FIG.  5 . The positioning section  465  of the secondary part  451  shown in FIG. 13 can also be configured for multipositioning or single positioning and will fit the implant shown in FIG. 6 or a generally similar implant whose positioning section is shaped similarly to that of implant  1 . The positioning section  515  of the implant  501  shown in FIG. 14 fits an implant whose bore, like that of implant  101  in FIGS. 7 and 8, has a conical section, but has a positioning section whose profile is similar to that of implant  1  shown in FIGS. 1 to  3 , but it could also be fitted entirely into implant  101 . Unless otherwise described above, the implants  31 ,  71 ,  101 , can be configured the same as or similar to implant  1 . Also, the secondary parts  251 ,  301 ,  351 ,  401 ,  451 ,  501 , unless otherwise described above, can be configured the same as or similar to the secondary part  201 . Furthermore, each implant and secondary part consists preferably of an integral metal body. 
     The screw  601  represented in FIG. 15 serves as fastening element for fastening one of the secondary parts  201 ,  251 ,  301 ,  351 ,  451 , releasably to one of the implants  1 ,  31 ,  71 ,  101 . The screw  601  has, in order from top to bottom, a cylindrical head  603  with a polygonal blind hole  604 , e.g., a hexagonal blind hole, a downwardly tapering conical section  605 , a cylindrical shaft  606 , and a threaded portion  607  with an external thread  608 . The cylindrical head  603  and the conical section  605  fit virtually free of radial clearance into the cylindrical seat  233  and conical section  235  of bore  230  of the secondary part  201  as well as the corresponding bore sections of the secondary parts  251 ,  301 ,  351 ,  451 . The threaded portion  607  with the external thread  608  can be screwed into the internal thread  20  in implant  1  or one of the other implants. The diameter of the shaft  606  is, for example, equal to the core diameter of the external thread  608 . 
     The integral bolt  701  shown in FIG. 16 serves as a fastening means for the releasable fastening of the secondary part  401  or  501  to one of the implants  1 ,  31 ,  71 ,  101 , and has an upper external thread  703 , an unthreaded cylindrical center section  704 , and a bottom external thread  705 . The bolt  701  is furthermore provided at the upper end with a polygonal blind hole  707 , a hexagonal hole, for example. The bottom external thread  705  can be screwed into the internal thread  20  of implant  1  or other implant, and can be configured, like this internal implant thread, as a metric, right-hand standard thread. The upper external thread  703  has preferably a smaller pitch than the bottom thread, can be screwed into the bottom internal thread  433  or  533  of the secondary part  401  or  501 , respectively, and consists, like the internal thread  433 ,  533 , of a right-hand fine thread, for example. The diameter of the middle section  704  is approximately or at most equal to the core diameter of the two threads  703 ,  704 . 
     The bolt  751  seen in FIG. 17 is configured similarly to bolt  701  and like the latter has an upper external thread  753  as well as a bottom external thread  755 . The latter is right-handed and can be screwed into the internal thread of one of the implants, while the upper thread  753  is left-handed and has the same pitch as the bottom thread  755  or possibly a smaller pitch than the latter. The upper thread can then be screwed in a secondary part configured similar to the secondary parts  401  and  501  having a left-handed thread as their internal thread. 
     Now an explanation will be given with the aid of FIGS. 18,  19  and  20  of the use of a dental implant  1 , a secondary part  201  and a screw  601  to form a device identified as a whole by  801  in FIGS. 19 and 20 for holding or forming a dental prosthesis. In FIG. 19, a jaw bone  803  of the lower jaw of a patient and the gum tissue  804 , i.e., the gingiva, covering the jaw bone, are indicated. The implant  1  is anchored in a bore in the jaw bone  803  such that the implant shoulder  11  protrudes from the latter. 
     Before the secondary part  201  is joined to the implant  1 , the head  603  of screw  601  has preferably already been introduced from below, with a momentary spreading of the tongues  241 , into the bore  230  of the secondary part  201  by the manufacturer of the various parts of the device  801 , so that the head  603  and the beveled section  605  enter into the cylindrical seat  233  in which they are rotatable and axially adjustable to a limited degree between the shoulder  232  and the beveled section  235 . The secondary part  201  then holds the screw  601 , as represented in FIG.  18 . The screw  601  and the secondary part  201  are then inserted together axially into the blind bore  12  of the implant  1 . The cylindrical main section  14  of bore  12  of the implant then centers the connecting section  210  of the secondary part on the axis  2 . When the screw is introduced into the implant and reaches the start of the internal thread  20  of the implant, its head is momentarily set back in bore  230  of the secondary part. The secondary part  201  can then be rotated on its axis  202 , and the axis  2  of implant  1  coinciding therewith, such that the secondary part  201  arrives at the desired position—i.e., rotational position—with respect to implant  1 . The secondary part is then inserted more deeply into the implant until the shoulder  225  of the secondary part contacts the implant shoulder  11 . Thus, most of the positioning projections  245  of the positioning section  215  of secondary part  201  enter into one of the first positioning interstices  24  of the positioning section  15  of the implant. Also, depending on the width of the second positioning interstice  25  of the implant, two or more positioning projections  245  of the secondary part enter into the second positioning interstice  25 , unless perchance one of the slits  240  is there. Anyway, positioning projections  23  engage positioning interstices  24  of the secondary part. The intermeshing positioning projections and interstices of the implant and secondary part secure the latter against rotation and define its orientation. Since all the positioning projections  245  of the secondary part  201  are of the same configuration, the latter accepts multipositioning and it can be positioned selectively in any of 36 possible, precisely defined rotational positions corresponding to the ten-degree or 36-point division of the first, narrow positioning interstices  24  of the implant. After the secondary part is positioned the screw  601  can be driven into the internal thread of the implant by means of a tool introduced from above into the bore  230  of the secondary part and into the polygonal blind hole in the screw, until the beveled section  605  of the screw is (again) in contact with the conical section  235  of the hole in the secondary part, drives the secondary part downward, spreads the tongues  241  and thereby additionally clamps the secondary part to the implant. The conical peripheral or external surface of the external or head section  220  of the secondary part  201  then seamlessly merges with the cylindrical surface  10  of the implant at the outer margins of the joined shoulders  225  and  11  of the secondary part and implant, respectively. 
     FIGS. 21 and 22 illustrate the formation of a device  811  with an implant  1 , a straight secondary part  251  formed as in FIG. 11 for single positioning and a screw  601 . The secondary part seen in FIG. 21 contains the screw  601  and can be inserted together with the latter into the implant  1  represented in FIG. 22, which previously has been anchored in a jaw bone, not shown. When the secondary part  251  is joined to the implant, the second, wider positioning projection  276  of the positioning section  265  of the secondary part  251  can engage the second, wider positioning interstice  25  of the implant. The first, narrow positioning projections  275  of the secondary part can then be engaged in first, narrow positioning interstices  24  of the implant  1 . The secondary part  251  can therefore be fastened in only one position, i.e., rotational position, on the implant  1 . 
     The device  821  seen in FIG. 23 has an implant  31  and a straight secondary part  401  which has a positioning section configured for single positioning and fitting the positioning section  55  of implant  31 , with a plurality of first, narrow positioning projections and a second, wider positioning projection  415 . To assemble the device  821 , the external thread  703  of bolt  701  is screwed, for example, so far into the lower internal thread  433  of secondary part  401 , that the bolt  701  stops at least approximately at the bottom end of the upper internal thread  431 . The bolt and the secondary part joined thereto can then be introduced together into the implant fastened in a jaw bone, so that the positioning section of the secondary part comes into engagement with the positioning section  55  of the implant as well as fastens it non-rotatably to the implant, while the bolt is still situated above the internal thread  60  of the implant. Thereafter the bolt can be rotated with a tool engaging its hexagonal socket so as to drive the lower external thread  705  of the bolt into the internal thread  60  of implant  31 . The upper external thread  703  of the bolt which previously had been screwed into the secondary part is thus also driven downward, but remains in the internal thread  824  of the secondary part. 
     The device  841  represented in FIGS. 24,  25 ,  26 , has an implant  31  inserted into a jaw bone  843 , a bent secondary part  301  and a screw  601 . The positioning section  315  of the secondary part is configured to fit the implant  31  and for multipositioning, and accordingly it has only positioning projections which are all equally wide. 
     The device  861  seen in FIG. 27 has an implant  101 , a bent secondary part  451  and a screw  601 . The conical section  461  of the secondary part  451  is seated in the conical main section  114  of the blind bore  112  of implant  101 . The conical main section  114  centers the secondary part on the axis  102  and simultaneously forms an abutment which establishes the axial position of the secondary part. The secondary part  451  is positioned by positioning section  465  in a rotational position in the implant and is fastened releasably to the implant by the screw  601 . 
     The device  881  represented in FIG. 28 has an implant  101 , a screw  601 , and a secondary part  891 . The latter is in part similar to the secondary part  451  represented in FIG. 13, but is configured straight and for a single positioning in the implant  101 . The device  881  is shown in FIG. 28 in a state wherein the screw  601  is not yet screwed into the internal thread  120  of the implant, but the secondary part is already positioned. 
     The device  901  represented in FIGS. 29 and 30 has an implant  1  and a one-piece secondary part  905  with an internal, connecting section  910 . The latter has, in order from top down, three cylindrical sections  912 ,  915 ,  917 , which become thinner in steps, and an external thread  919 . The cylindrical section  912  is seated with little or no radial clearance in the cylindrical main section  14  of the blind bore  12  of the implant. The cylindrical section  915  is near the level of the positioning section  15  of the implant and has a diameter that is no more than equal to the diameter of the cylinder defined by the apexes of the positioning projections of the implant and preferably less than this diameter. The external thread  919  is screwed into the internal thread  20  of the implant. The secondary part  905  has furthermore an external, head section  920 , a shoulder  915  and an axial blind bore  930  with an internal thread  931 . The secondary part thus has no section entering into the positioning section  15  of the implant and to screw the secondary part&#39;s external thread  919  into the internal thread  20  of the implant it can be rotated around the axis of the implant until the shoulder  925  of the secondary part lies on the implant shoulder  11  and the secondary part is tightly joined to the implant. The device  901  can be used, for example, whenever the implant is used in the interforaminal area of the lower jaw. 
     Unless otherwise stated above, the devices described in connection with FIGS. 21 to  30  are assembled like the device shown in FIGS. 18 to  20  and have properties similar thereto. 
     Also, features of different implants described can combined with one another and, for example, in the case of implant  101  shown in FIG. 6, the positioning section can be arranged in a manner similar to the implant  71  shown in FIG. 5, at the upper end of the blind bore  112  or in the middle of the length of the conical main section of the blind bore. Likewise, features of different secondary parts described can be combined with one another. For example, a secondary part can also be made for the implant  101  of FIG. 6 which, like the secondary part  905  seen in FIGS. 29 and 30, can be screwed into the implant  101  without positioning. Also, the described implants, secondary parts and fastening means can be combined as well as fastened together in other ways to form devices or connecting arrangements. 
     Furthermore, a secondary part or special superstructure can be fastened to the implant, which has an internal, connecting section situated in the blind bore and is not screwed into the blind bore of the implant but is cemented or glued into this blind bore and even, for example, in its internal thread. The secondary part or superstructural part can also have a pillar-like outside section which does not lie on the implant shoulder. Also, a crown or the like can be fastened, say by cementing and/or gluing, to the pillar-like outside section. This crown can then lie with a bearing surface on the implant shoulder in a gap-free manner and have an outside surface which adjoins in gap-free, step-less and to some extent smooth as well as steady manner the circumferential and/or outside surface of the implant.