Abstract:
A support for sustaining and/or forming a dental prosthesis, comprises an axle, an anchoring part which can be anchored in a bone or a master model, and a head part which protrudes out of said bone or master mode. The head part has intermediate spaces distributed around the axis, i.e., several first intermediate spaces forming a divided circle, and a second, wider and/or deeper intermediate space. A cap can be fixed to the support. The cap has at least one projecting part for engaging in an intermediate space and, optionally, can be configured for fixing in several different rotational positions or a single rotational position, the support allowing exact positioning. The cap can also be produced without a projecting part of the type mentioned. The same support can be used to form different types of dental prostheses.

Description:
TECHNICAL AREA 
     The invention relates to a support for holding and/or forming a dental prosthesis with an axis, an anchoring part for anchoring in a bone of the lower or upper jaw of a patient and/or in a master model and a head part intended to project from the bone and/or master model. This head part serves to support an originally separate element attachable to the support with a cap. The cap can for example be a part of a dental prosthesis such as an individual artificial tooth or a bridge or a prosthesis having several teeth. The possibility also exists however of first attaching a so-called burnout cap made of plastic to the support. The burnout cap can serve for making a casting model and a casting impression, then be burned off from the latter and replaced by a impression cap when the cast impression is used. 
     PRIOR ART 
     For certain applications, it should be possible to attach the cap in a specific rotational position on the support. A support known from EP 0 685 208 A has an implant and a secondary part having an external thread screwed into the internal thread of the implant and a head projecting from the implant. This forms the head part of the support and has an octagonal section as well as a conical section that tapers away from the latter to the front side of the head. A superstructure element or impression element with a cap can be associated with the known secondary part and have an internal space with an octagonal section. FIG. 1 of the present patent application is a cross section through an area of the octagonal section of the head of a known secondary part  1 . The secondary part defines an axis  5  and straight lines running radially thereto through the corners of the octagonal head section, one of which is designated  7 . Cap  10  is shown in FIG. 1 in the central intended rotational position provided. In this position, each corner of the octagonal section of the internal space of the cap is on the straight line  7  running through the associated corner of secondary part  1 . The cap rests on the secondary part with radial play so that the mutually associated octagonal surfaces of the secondary part and the cap are at a distance a from each other. The radial play must be so great, particularly when burnout caps are used, that the internal weight of the superstructure element then made by casting can differ due to shrinking processes and the like from the internal weight of the burnout cap. Because of the play, cap  10  can be turned starting in its central desired rotational position in two rotational directions through an angle designated a in FIG. 2 until the octagonal surfaces of the cap are located at the corners of the secondary part. Distance a is typically approximately 0.02 mm and possibly even more with burnout plastic caps. Angle a then amounts to approximately 2.25° or more. The cap can be rotated back and forth through an angle  2   a , namely approximately 4.50° or more. The octagonal head section of the known support thus makes possible only very inexact positioning of the cap relative to rotations about the axis. If large forces act on the cap approximately perpendicularly to the axis and bring about shear forces or torsional forces between the cap and the support, there is the danger that the cap will execute small rotational or swiveling movements relative to the support. Such tiny rotational movements may cause the dental treatment to fail. The cap can be mounted on the head in one of eight selectable rotational positions. Sometimes, however, it is advantageous for the cap to be placed on the support in only a single rotational position, which is not possible with the known support. Moreover, the cap rests only on the octagonal section, but not on the conical section of the head. In this known head, it would also be practically impossible to design a cap so that it abuts both the flat surfaces of the octagonal section and the conical section of the head. Since the octagonal section has only a relatively small axial dimension, the cap receives little support with respect to laterally acting forces, i.e. forces transverse to the axis, impairing the stability of the connection of the cap or the superstructure element to the additional support. 
     DE 195 34 979 C discloses a support with an implant and a spacing sleeve. The latter serves as a head for attaching a dental prosthesis. The implant has an axial blind hole. Its internal surface is provided with six grooves distributed around the axis of the implant. The spacing sleeve projects into the blind hole of the implant and has noses engaging these grooves so that the spacing sleeve can be positioned in six different rotational positions in the implant. This support has the disadvantage however that the spacing sleeve is guided laterally only in a short cylindrical guide area of the hole having a relatively small diameter below the grooves and is supported against the forces directed approximately transversely at the implant axis. If such forces act on the dental prosthesis, a long lever arm is produced between the point where these forces act and the guide area of the hole, so that very high torques have to be transmitted from the spacing sleeve to the implant in the guide area of the blind hole. In combination with the small dimensions of the guide area, this results in a high risk of the dental prosthesis executing micromovements relative to the implant when stressed, leading to failure of the dental treatment. Moreover, the implant of this known support must be inserted approximately flush with the ridge of the bone. This subgingival arrangement of the implant has the disadvantage that the gum (gingiva) knits over the implant during the healing phase and requires a further incision to attach the spacing sleeve. Moreover, the dental prosthesis cannot be removably fastened to the spacing sleeve. Moreover, the known support is not suitable for anchoring bridges, either. 
     A support shown in FIGS. 1-3 of CA 1,313,597 A has an implant and a generally conical sleeve. There are two axial projections at the upper end of the implant which, when the device is assembled, engage flats on the sleeve and position it non-rotatably in one of two possible rotational positions. In the version shown in FIGS. 4 and 6, the implant has a projection that is generally cylindrical but is provided on one side with a flat. The flat permits non-rotatable positioning of the sleeve in a single rotational position. Since the two projections and the flat of these known implants each have only one flat surface tangential to the axis of the implant that abut a flat matching surface on the sleeve, these implants define the rotational position of the sleeve in the same way no more exactly than the supports commented on above and known from EP 0 685 208 A. In addition, these implants can position a sleeve in only two different rotational positions or even in only one single rotational position. In many applications, the rotational position of a cap, however, must be selectable from more than two rotational positions. In addition, the crown prosthesis in these implants must clearly be supported at least essentially by one additional cap whose rotational position is not defined at all. The supports known from CA 1,313,597 A that serve to hold a screw-on cap are also composed of at least three separate parts. This large number of parts makes dental treatment complicated and adversely affects the stability of the dental prosthesis in the mouth of a patient. 
     A support shown in FIGS. 1-3 of CA 1,313,597 A contains an implant and a generally conical sleeve. The implant has two axially projecting projections at the upper end which engage flats on the sleeve when the device is assembled and position them non-rotatably in one of two possible rotational positions. In the version shown in FIGS. 5 and 6, the implant has an extension which is generally cylindrical but provided on one side with a flat. The flat permits non-rotational positioning of the sleeve in a single rotational position. Since the two projections and the flat of these known implants each abut the flat opposite surface of the sleeve with only one flat surface tangential to the axis of the implant, just like the supports commented on above and known from EP 0 685 208 A, these implants define the rotational position of the sleeve only imprecisely. In addition, these implants can position the sleeve only in two different rotational positions or even in only a single rotational position. In many applications, however, the rotational position of a cap must be selectable from more than two rotational positions. In addition, the artificial crown in these implants is clearly supported at least essentially by an additional cap whose rotational position is not even defined. The supports known from CA 1,313,597 A that serve to hold a cap that can be screwed on are also composed of at least three separate parts. This large number of parts makes dental treatment complicated and adversely affects the stability of the dental prosthesis in the mouth of a patient. 
     EP 0 475 299 A teaches an implant or a basic body, a spacing sleeve upper part, and a spacing sleeve bottom part that can be screwed into the basic body. The basic body has an axial blind hole with female snap connectors distributed along its circumference into which the male snap connectors of the spacing sleeve upper part engage when the implant is assembled. The spacing sleeve upper part is guided in the implant only by an annular recess in the blind hole and is supported against lateral forces, in other words forces directly approximately transversely to the axis of the implant. Between the annular recess and the dental prosthesis, not visible, there is a relatively long lever arm. In addition, the annular recess is only relatively short and indeed must be short because the blind hole contains an internal thread and the female snap connectors as well. When forces act approximately transversely to the axis of the implant in the dental prosthesis, there is the danger that the spacing sleeve will make micromovements relative to the implant. In addition, additional separate parts in addition to the parts shown in EP 0 475 299 A are also probably necessary for fastening an artificial crown so that the entire device is composed of many individual parts, adversely affecting the stability even more. 
     GIST OF THE INVENTION 
     The goal of the invention is to avoid the disadvantages of the known supports and of a device formed therefrom, as well as a superstructure and/or impression element and/or a healing element. In particular the opportunity is to be offered for an element with a cap to be normally positioned stably on the support in a rotational position defined as accurately as possible so that the cap, even with high forces acting on it approximately transversely to one axis of the support and/or torsional stresses, remains connected with the support permanently and in stable fashion. In addition, it should preferably be possible to secure a cap to a given support, depending on the design of the cap, in a rotational position selectable from one of several rotational positions or only in a single rotational position on the support. In addition, a device is to be created having a cap that can be fastened in stable fashion in any free rotational position to a support that permits the rotational position to be established. 
     This goal is achieved according to the invention by a support for holding and/or forming a dental prosthesis with an axis, and anchoring part intended for anchoring in a bone and/or a master model, and a head part intended to project out of the bone and/or master model and an annular shoulder surface located between the anchoring part and the head part and forming an angle with the axis; the head part has a peripheral surface as well as a face and the support is characterized by the fact that the head part has several projections and interstices located at the periphery and/or face and alternating around the axis. 
     The invention also relates to a device with a support and with an element that can be fastened to the support, with the device being characterized by the fact that the element has a supporting surface intended to rest on the shoulder surface and surrounds the head part in cross section in the state in which it rests on the shoulder surface. 
     Advantageous improvements on the support and the device follow from the dependent claims. 
     For example, the support can consist of a metal implant or primary part and an originally separate metal secondary part, preferably removably fastened to the implant, for example screwed thereto, which is provided with the projections and interstices serving for positioning. However, the support can instead have a one-piece body which extends from the free end of the anchoring part up to the free end of the head part and forms these ends so that the support consists at least essentially completely of a one-piece implant made of metal for example. In addition, the support can be made as a manipulating support placed by a dental technician in a master model made of plaster for example and is used to form a superstructure. The head part projecting out of the master model of such a manipulating support should then have the same design as a support used for insertion into a bone of a patient while the anchoring part of the manipulating support inserted into the master model usually differs from the anchoring part of the support placed in a bone. 
     The head part of the support according to the invention has interstices distributed around the axis. These interstices form positioning surfaces that are not rotational symmetrical with the axis for non-rotational positioning of a superstructure and/or impression element. Each interstice preferably forms a depression relative to a line that lies in a plane at right angles to the axis and contacts the head part on sides of the interstice facing away from one another. Each interstice for example is in the form of a groove or formed by a groove; the terms “groove-shaped interstice” and “groove” shall be construed to include both an elongate interstice and an elongate groove as well as an interstice or groove that has a width approximately the same size as the length or even greater than the length of the interstice or the groove. The interstices or grooves are open for example on the two ends that face away from each other. Each interstice is preferably delimited least partially by flats which are approximately parallel to a radial center line that runs through the axis and through the middle of the interstice or a central plane or form an angle of at most 60° and preferably no more than 45° with such a line or plane. Each interstice for example has two essentially flat, lateral surfaces and is approximately U-shaped or V-shaped in cross section. The interstices can however be at least partially or completely arcuate in cross section and for example can be at most or approximately semicircular. In this case then, for example at least certain flats of the arcuate limiting surface of each interstice can be located relative to a center line or center plane of the type mentioned above in the manner described above and/or define tangential planes arranged in the manner described. 
     An element, for example a superstructure element and/or an impression element and/or a healing element, can be fastened or possibly non-removably fastened on the support. Such an element can have a cap and/or be formed by a cap. The element can also have a burnout cap made of plastic or can consist exclusively of such a cap. The element or cap can rest on the annular shoulder surface of the support by a smooth, annular supporting surface surrounding the head part in axial projection, with no interruptions or gaps around the axis. The element can also have a least one projection which can engage an interstice of the head part of the support. The support can position such an element in at least one rotational position. 
     The projection, or each projection, engaging an interstice of the support of a superstructure element and/or impression element or other element and the projection (or each projection) of the support preferably engaging an interstice of the element can for example have a certain amount of play in the interstice so that the projection, despite possible inaccuracies in manufacture and despite changes in dimensions caused by changes in temperature, can be inserted easily into the interstice. The play measured along a circle surrounding the axis of the support or tangentially to such a circle can however be made so small that the superstructure element, in the state in which it has been positioned but not yet fastened, can be rotated back and forth through an angle that is preferably no more than 2° and for example even only 1° at most. This also is the case in particular in a burnable cap and a superstructure element cast and made with the aid of such a cap. The support therefore permits exact positioning of a superstructure element having at least one projection and/or impression element. 
     The head part of the support preferably has a section parallel to the axis and generally cylindrical and a generally conical section that tapers away from the latter toward the free end of the head part. The head part can then for example have groove-shaped interstices or grooves arranged on the peripheral surface and extending approximately axially, which extend at least through an area of the generally cylindrical section and through the conical section of the head part to the free end of the latter. The head part, instead of the interstices or grooves that are axial and arranged on the circumferential surface or in addition to such, can have interstices or grooves located on the face and running approximately radially, at least some of which have openings located in the circumferential surface of the conical section of the head part, or form such openings. 
     When an element is fastened to the support removably or non-removably and rests on the shoulder surface of the support, it can be supported by the head part at least at the conical section with at most a small amount of play with the conical peripheral surface and/or—when the head part has approximately axial interstices or grooves located at the peripheral surface—in the interstices or grooves. The peripheral surface of the conical head section and/or the boundary surfaces of the interstices support the element in directions that run approximately at right angles to the conical circumferential surface and/or the axis of the support. When the interstices are located on the face of the head part and the element has projections that extend into such interstices, the lateral surfaces of the interstices support the element, among other things, also in directions that are at right angles approximately to the axis. The play between the conical peripheral surface of the conical section of the head part and the conical internal surface of an element fastened to the support can be made very limited. The play for example in the surface sections provided for support can be, for example in the radial direction and/or in directions that are at right angles to the conical surfaces, a maximum of 0.02 mm or only 0.01 mm at most and especially at the conical surfaces the play is preferably in the micron range, for example a maximum of 5 microns or 3 microns at most. 
     The axial dimension or height of the head part is advantageously so small that the implant can be placed optionally subgingivally or transgingivally or in a position in which it is semi-submerged in the gingiva in the mouth of a patient. The design of the head part makes it possible for the latter to support a superstructure element or impression element held by the support, despite a small axial dimension of the head part, in all directions running approximately transversely to the axis in all applications. This in turn ensures that the superstructure element fastened to least one support in the mouth of a patient will be connected stably and permanently with the support (or each support) serving to fasten it and will not be loosened even by high forces directed approximately transversely to the axis of the support or to the axes of the supports. 
     A superstructure or other element can therefore be fastened very stably, at least approximately free of micromovements, and permanently on the support relative to approximately axial forces, with respect to forces directed approximately transversely to the axis, and with respect to torsional rotation about the axis. 
     In a preferred embodiment, the interstices of the support include a plurality of first interstices with identical shapes and identical dimensions, especially identical widths and identical depths, and a second interstice which has a larger dimension in at least one direction than the first interstices and for example is wider and/or deeper than they. The first interstices adjacent to one another are equally spaced apart from one another as measured along a partial circle coaxial with the axis of the support and together define a division of a circle or simply a division. For clarification, it should be pointed out that the division is equal to the n-th part of a full circle where n is a whole number and is advantageously at least 6 and at most 72 so that the division angle is advantageously in the range from 60° to 5°. In one advantageous embodiment, n is at least 8 and especially when the interstices are arranged on a peripheral surface, it is still more preferably at least 10° and for example 12° to 36°. The second interstice for example can be formed by the fact that, at least theoretically, one can start with identical projections and first interstices distributed uniformly on a full circle and remove or omit at least one and possibly more of these projections. The resultant second, wider interstice has a dimension measured along the partial circle which is equal to the sum of a dimension measured along the partial circle of a first interstice and one complete division or several complete divisions. A second, wider interstice can however be formed instead by making one projection or two adjacent projections narrower than the remaining projections. 
     An element fastened to the support for example can have a positioning section with projections distributed uniformly along its periphery which all have the same shapes and dimensions and are separated from one another by likewise similarly designed interstices and can engage all the interstices of the support. Such an element can be fastened relative to the axis of the support in various selectable positions, in other words rotational positions on the support, with each selectable position, i.e. rotational position, being defined by the mutually meshing projections and interstices of the superstructure element and/or impression element and/or the support and with the rotational angle between the adjacent rotational positions being equal to the divisional angle established by the division of the identically designed (first) interstices in the head part. This manner of connecting an element with the support is referred to below as multipositioning of the element. 
     The element can also have a projection that has a larger dimension in at least one direction than the first interstices of the support and is so designed that it can engage the second interstice but not the first interstices of the support. This projection for example can be wider than the first interstices of the support and/or have a height greater than the depth of the first interstices of the support. The positioning section of the element then for example has, in addition to this projection, projections that are even narrower and/or lower for engaging the narrower, first interstices of the support but possibly have only the projections that engage the second, wider and/or deeper interstice of the support. The element can then be connected relative to the axis of the support only at a single rotational position with the support. This manner of connecting an element with the support is referred to below as single positioning of the element. 
     However, the element can also be produced without a positioning section and especially without positioning projections and be made so that, after fastening to the support, it does not engage any interstices of the support. The element can then be rotated continuously when mounted on the support until it is fastened so that the element can be fastened for example at any rotational position. This is referred to below as free positioning of the element. 
     In one advantageous embodiment of the support, an element with multipositioning or an element with single positioning or an element with free positioning can be fastened freely to the support. The type of element that is best depends on its purpose, the type of dental prosthesis to be formed, and the individual medical symptom. If for example a crown for an individual tooth is to be produced as the superstructure element, preferably a superstructure element is used that permits multiple or possibly single positioning so that the crown is precisely positioned and protected against rotation. A prosthesis that replaces a plurality of teeth for example can be fastened by least two supports, each of which has a telescoping base that has a cap for single positioning. To form a soldered base, a cap can likewise be used for single positioning. A bridge or a rib structure for a prosthesis can be secured for example by caps for free positioning on supports. A laboratory that makes supports for example can make caps that fit on a support and are provided for various types of positioning, and for example on a set of identical supports, as needed, can supply the dentist with a set of identical caps or a set of caps for various types of positioning. The dentist can then use these caps as impression elements and/or for making different superstructure elements such as crowns, bridges, and prostheses, and/or healing elements. Therefore, a given type of support can be used to hold a plurality of different types of superstructure elements and impression elements. 
     Bridges, partial prostheses, and full prostheses are frequently fastened with two or possibly even more supports. In this case, the supports ideally have axes parallel to one another. However in practice the axes are frequently at an angle to each another and for example diverge or converge toward the free ends of the head parts. The device according to the invention is designed in one advantageous embodiment such that an element, for example an impression element or superstructure element, is mounted on the head part in a displacement direction inclined to the axis of a support and can be pulled off the latter. It is then possible to pull two or more elements held on supports away from the supports simultaneously if the axes of the supports are not parallel to one another and form angles with one another that measure up to 30° or even up to 40° for example. The element, when pulled away from the support and when connected with the latter, can be displaced in a direction over the head part which forms an angle of up to 15° or even up to 20° with the axis of each support. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     The subject of the invention will now be described with reference to the embodiments shown in the drawings. 
     FIG. 1 shows a cross section through a known support and a cap that shows in a desired rotational position with respect thereto; 
     FIG. 2 shows a cross section through the parts shown in FIG. 1, with the cap rotated out of the desired rotational position; 
     FIG. 3 shows a diagonal view of a support according to the invention with an implant and a secondary part removably attached thereto; 
     FIG. 4 shows a top view of the head of the secondary part shown in FIG. 3; 
     FIG. 5 shows a device drawn partially in section and partially in side view with the support designed according to FIG.  3  and installed in a bone, and a healing cap; 
     FIG. 6 shows a device drawing partially in section and partially in side view with the support according to FIG. 3 with a superstructure element with a cap for multipositioning; 
     FIG. 7 shows a cross section through the device shown in FIG. 6 along line VII—VII, but without the lining of the cap; 
     FIG. 8 shows a section from FIG. 7 on a larger scale, with the cap resting on the support in the central desired rotational position; 
     FIG. 9 shows a section similar to FIG. 8, but with the cap rotated out of its position shown in FIG. 8; 
     FIG. 10 shows a cross section similar to FIG. 7 through a device with a cap for single positioning; 
     FIG. 11 shows a cross section similar to FIG. 7 through a device with another cap for single positioning; 
     FIG. 12 shows a representation similar to FIG. 6 of a device with a cap without a positioning section; 
     FIG. 13 shows a cross section through the device according to FIG. 12 along line XIII—XIII; 
     FIG. 14 shows a diagonal view of another support; 
     FIG. 15 shows a top view of the head part of the support according to FIG. 14; 
     FIG. 16 shows an axial section through a variant of a device with yet another support, in which one half of a cap designed for multipositioning and one half of a cap without a positioning section is shown; 
     FIG. 17 shows a section along line XVII—XVII in FIG.  16  through the support and the cap halves according to FIG. 16; 
     FIG. 18 shows a diagonal view of a device with yet another support and of a cap separated from this support; 
     FIG. 19 shows a top view of the head part of the support according to FIG. 18; 
     FIG. 20 shows an axial section through the device according to FIG. 18, with the cap resting on the support; 
     FIG. 21 shows an axial section through a device with a support according to FIGS. 18 to  20 , but with a cap having no positioning section; 
     FIG. 22 shows an exploded view of another device; 
     FIG. 23 shows an axial section through another device; 
     FIG. 24 shows an axial section through parts of another device; 
     FIG. 25 shows a section designated XXV in FIG. 24 of the device according to FIG. 24 on a larger scale; 
     FIG. 26 shows a diagonal view of the head part of the device according to FIGS. 24 and 25; 
     FIG. 27 shows a diagonal view of a positioning sleeve of the device according to FIGS. 24 and 25, designed for multipositioning; 
     FIG. 28 shows a development of sections of the head part and the positioning sleeve of the device shown in FIGS. 24 and 25; 
     FIG. 29 shows a diagonal view of a positioning sleeve for single positioning; 
     FIG. 30 shows a representation analogous to FIG. 28 with a variant of the positioning sleeve; 
     FIG. 31 shows a diagonal view of a one-piece, partially cut-open implant forming a support, the anchoring part of which has grooves interstices inclined to the axis; 
     FIG. 32 shows a cross section through the head of the implant visible in FIG. 31 along line XXII—XXII in FIG. 31; 
     FIG. 33 shows a simplified cross section through the implant according to FIG. 32, running through the grooves of the anchoring part; 
     FIG. 34 shows an implant shown partially in side view and partially in axial section, whose anchoring part has grooves or holes terminating in each other; 
     FIG. 35 shows a diagonal view of the implant according to Sic—perhaps the intention was to delete one of these two words. Translator. FIG. 34; 
     FIG. 36 shows a simplified cross section along line XXXVI—XXXVI in FIG.  35  through the implant visible therein; 
     FIG. 37 shows a cross section analogous to FIGS. 35 and 36 through an implant, whose anchoring part has grooves extending to its free end; 
     FIG. 38 shows a diagonal view of a cut-away implant, which has an axial blind hole terminating in the free end of the anchoring part, and holes terminating therein; 
     FIG. 39 shows the lower end section of the implant according to FIG. 38 shown partially in side view and partially in section; 
     FIG. 40 shows an implant shown partially in side view and partially in axial section with an axial hole matching a small outside diameter of the anchoring part; 
     FIG. 41 shows a section through a bone, the gingiva, and a section of a subgingivally inserted implant provided with a healing cap; 
     FIG. 42 shows a representation analogous to FIG. 41, but with an implant countersunk relative to the gingiva; 
     FIG. 43 shows a representation analogous to FIG. 41, but with a transgingivally inserted implant; 
     FIG. 44 shows a device shown partially in side view and partially in axial section, with an implant according to FIGS. 34 to  36  and with a cap; 
     FIG. 45 shows an axial section through a device with an implant inserted into a bone with another cap; 
     FIG. 46 shows a diagonal view of the cap of the device according to FIG. 45; 
     FIG. 47 shows an axial section through a device with an implant inserted into a bone and a cap designed for multipositioning; 
     FIG. 48 shows a cross section through the axially parallel head section of the implant and the cap of the device according to FIG. 47; 
     FIG. 49 shows a cross section analogous to FIG. 48, but with the cap designed for single positioning; 
     FIG. 50 shows a device with an angled cap; 
     FIG. 51 shows a diagonal view of the cap according to FIG. 50; 
     FIG. 52 to  54  are devices with various cap variants; 
     FIGS. 55 to  62  are work steps in forming a dental prosthesis; 
     FIG. 63 shows a section through a bone and a part of a variant of an implant, shown in side view; 
     FIG. 64 shows an axial section through a region of the anchoring part of an implant with a thread; 
     FIG. 65 shows a cross section through the head part of a support, in which all the groove-shaped interstices of the head part have the same shape; 
     FIG. 66 shows a diagonal view of a support consisting of a one-piece implant, the head part of which has axial, flat positioning surfaces; and 
     FIG. 67 shows a cross section through the head part of the support according to FIG. 66 along line VXVII-VXVII in FIG.  66 . 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     The support  21  shown in FIG. 3 is generally rotationally symmetrical about an axis  22  and at the bottom has an anchoring part  23  intended for anchoring in a bone of an upper or lower jaw and a head part  24  for projecting out of the bone. Support  21  has two originally separate elongate one-piece metal parts, namely an implant  31  and a secondary part  51  removably attachable thereto. 
     Implant  31  has an upper end section  32  that tapers downward. It is abutted at the bottom by a generally cylindrical section  33  which is provided for example with an external thread  34  and forms at least the largest part of anchoring part  23  of the support. The lower end of section  33 , not visible in FIG. 3, forms the first free end of the total support. Implant  31  has an implant shoulder  35  at the upper end. This shoulder has an annular conical flat shoulder surface  37  that fully surrounds the axis and tapers upward away from the anchoring part. Head part  24  in axial projection is enclosed by at least the outer area of shoulder surface  37 , namely by the entire shoulder surface  37 . The shoulder surface forms an angle of 40° to 50° with axis  22  and has a circular edge  38  outside. The implant is provided with a stepped blind hole  41  that is generally coaxial with axis  22 . This hole has an opening  42  located at the upper end of the implant and surrounded by the inner edge of implant shoulder  35  and has, in the downward direction therefrom, in the following order, a downwardly tapering conical main section  43 , a shoulder  44 , and a threaded hole  45  with an internal thread  46 . 
     The secondary part  51 , also visible in FIGS. 4 to  8 , has an internal connecting section  52  which, when support  21  is assembled, is located in blind hole  41  of the implant. Connecting section  52  has a downwardly tapering conical section  53  resting in the conical hole/main section  43  of the implant, and a threaded part  54  with an external thread  55  that is screwed into internal thread  46  of the implant with a torque of preferably 30 to 50 N cm. At the upper end of internal connecting section  52 , the secondary part has a flat shoulder  57  flush with opening  42  of hole  41  and a head  59  located outside the implant and extending upward, said head forming at least a large part of head part  24  of support  21 . Head  59  has a peripheral surface  60 . This forms a positioning section  62  connected with shoulder  57  by an annular groove  61 . Positioning section  62  at the bottom has a section  63  that is essentially parallel to axis  22  and is generally cylindrical and at the top, an upwardly tapering conical section  64 . The peripheral section of the latter forms an angle with axis  22  that is smaller than the angle formed by shoulder surface  37  with axis  22  and preferably 10° to 30°, particularly preferably 15° to 25°, namely for example approximately 20° The free, upper end of the head has an annular, flat face  65  at right angles to axis  22  and forms the second, upper end of the total support. 
     Along its circumference, positioning section  62  has positioning projections  67  alternating with positioning interstices  68 ,  69 . Positioning projections  67  are all the same shape. Positioning interstices  68 ,  69  consist of ten first, narrow positioning interstices  68  and a second, wider positioning interstice  69 . Each positioning projection  67  consists of a straight, axial rib with two lateral surfaces, a top, and a bevel. The tops and the bevels are located in cylindrical section  63  or conical section  64  and define a cylindrical or conical surface coaxial to axis  22 . Each interstice  68 ,  69  is approximately U-shaped in cross section and has two flat, lateral surfaces that are of course formed by the lateral surfaces of two adjacent projections and are approximately or exactly parallel to a plane running through axis  22  and the middle of the interstice in question. Also, each interstice  68 ,  69  has a bottom surface parallel to axis  22  forming for example a section of a cylindrical surface coaxial with axis  22 , but which could instead consist of a plane parallel to the axis. 
     The second, wider interstice  69  is formed by leaving out one projection between two first interstices. The ten remaining first interstices  64  together define a circle with divisions of 12° to 30°. The radial depth of interstices  68 ,  69  is preferably dimensioned such that interstices  68 ,  69  extend up to the upper end of head  59  until they abut flat, annular end face  65  and form sections of its outer edge. The cylindrical surfaces defined by the bottom surfaces of interstices  68 ,  69  can have for example the same diameters as the upper, thinner ends of conical section  64 , so that the lateral surfaces of interstices  68 ,  69  taper to a point at the upper end of the head. Also, the diameters of the cylindrical surfaces defined by the bottom surfaces of interstices  68 ,  69  can be approximately the same as the diameter of the lowest point of annular groove  61 , so that the latter and the interstices blend continuously with one another for example. The axial dimension or the height of head  59  measured from shoulder  57  is preferably a maximum of 2 mm, preferably a minimum of 1 mm, more preferably at least 1.2 mm and for example approximately 1.5 mm. The first interstices  68  are preferably formed of grooves whose axial dimension is larger than their width. On the other hand, the second interstice  69  may have a width that is greater than its axial dimension. Secondary part  51  has a blind hole  71  terminating at its upper end, with an internal thread  72 . FIG. 5 shows a bone  81  belonging for example to the lower jaw, covered with soft tissue  82 , i.e. the gingiva, of a patient and a device designated as a whole by  83 . The latter has the support  21  also shown in FIG. 1, a healing element  85 , and an occlusal screw  86 . Healing element  85  is cap-shaped and will be called “healing cap  85 ” below. To form device  83 , a dentist can make an incision into soft tissue  82 , create a hole in bone  81 , insert implant  51  into the hole in bone  81 , screw secondary part  51  tightly to implant  31 , then screw healing cap  85  to the secondary part. Anchoring part  23  of support  21  is, at least for the most part, inside bone  81 , while head part  24  projects therefrom. The upper end of secondary part  51  is approximately at the level of the ridge of the soft tissue  82  covering the bone, or a little higher. The conical supporting surface of healing cap  85  rests on implant shoulder  35 . The healing cap has no projections that fit into the positioning interstices of the positioning section of the support and can thus be attached in any desired rotational position on the support. The healing cap then remains attached to support  21  for a certain period of time, so that the latter heals and the bone can knit to the implant to some degree. The above-mentioned small axial dimension of secondary part head  59  makes it possible for the covering surface of healing cap  85  that forms the upper end of device  83  to project at most slightly above soft tissue  82 . This largely prevents forces exerted on device  83 , arising when the patient chews, from interfering with the healing process of the implant. Also, the healing cap acts to shape the soft tissue that grows subsequently. 
     When bone  81  and soft tissue  82  have healed to at least some degree, healing cap  85  is removed from support  21  and forms the device  91  serving as a dental prosthesis visible in FIG.  6  and partially in FIG.  7 . This can be done without further surgery and with no further incisions into the soft tissue, so that the dental prosthesis is created and attached in a one-phase operation, namely with a single surgical procedure. Device  91  also has a superstructure element  93  on support  21 . This is cap-shaped and has an originally separate cap  101  that is generally rotationally symmetrical with respect to axis  22 . The cap has an axial stepped through-hole forming the interior  103  of the cap. The lowest conical section of the latter forms a conical supporting surface  104  that, when device  91  is joined to axis  22 , forms the same angle as shoulder surface  37 , rests continuously without gaps on shoulder surface  37  around axis  22 , and thus centers the cap coaxially on axis  22 . A positioning section  105  connects the conical interior section of cap  101 . This section is generally cylindrical, but according to FIG. 7 has positioning projections  106  and positioning interstices  108  alternating along the periphery of interior  103 . Thus there are twelve projections  106  with identical shapes and dimensions and twelve interstices  108  with identical shapes and dimensions distributed uniformly along the inner circumference. Cap  101  is thus formed for multipositioning and can be positioned in twelve different positions, i.e. rotational positions, when it is connected to the support, the angle between the adjacent rotational positions being 30°. Projections  106  consist of straight, axial ribs and have a top and two lateral surfaces. Interstices  108  accordingly consist of straight axial grooves, are approximately U-shaped in cross section, and have a bottom surface and two lateral surfaces. Interior  103  has a taper above positioning section  105  and a supporting surface  109  on the upper side of the latter that widens conically upward. Cap  101  is attached with an occlusal screw  121  to the secondary part when connected with support  21 . Screw  121  has a countersunk head disposed in hole  103  of cap  101 , resting on conical supporting surface  109 , and a threaded part with an external thread screwed into internal thread  72  of the secondary part. Cap  101  consists for example of a metal material such as a gold alloy or titanium. Superstructure element  93  can have a metal casting  125  cast on the cap and a lining  126  of porcelain or plastic and serve as a crown for forming an artifical single tooth or a bridge. The lower end section of the external surface of cap  101  connects to the external surface of implant  31  at edge  38  of the implant shoulder seamlessly, without steps, and preferably at least approximately smoothly and continuously. The external surface of casting  125  and/or lining  126  for its part connects for example seamlessly, without steps, and preferably at least approximately smoothly and continuously to the lower end section of the cap external surface. The cooperation of positioning sections  62  and  105  of secondary part  51  and cap  101  will now be described in greater detail. Ten of the twelve positioning projections  106  of cap  101  project with limited lateral play and limited radial play into a first, narrow positioning interstice  68 . The other two projections project with limited radial play into the second, wider positioning interstice  69  of secondary part  51  in such a way that one lateral surface of each of these projections with limited lateral play faces a lateral surface of the second, wider interstice  69 . FIGS. 8 and 9 show a straight line  131  that runs radially to axis  22  of the support through the middle of a first interstice  68  of secondary part  51 . In FIG. 8, cap  101  is in the central desired rotational position with respect to rotations about axis  22  of the support. In this position, each of projections  106  of the cap that project into a first interstice  68  of the secondary part is located in the middle between the two lateral surfaces of the interstice  68  in question so that one straight line  132  that passes through the middle of projection  106  and is radial to axis  22  coincides with straight line  131 . Because of the play, each lateral surface of an interstice  68  of the secondary part is at a distance b from the lateral surface opposite to it of a projection  106 . If the positioning sections of the secondary part and the cap engage each other when the cap is connected to the support, the cap can be rotated in either direction through an angle marked b in FIG. 9, starting from its central desired rotational position shown in FIG. 8, until the screw is tight, and until the projections  106  of cap  101  projecting into the first interstices  68  of secondary part  51  according to FIG. 9 have one lateral surface in contact with one lateral surface of an interstice  68 . The circumference of a circle abutting the top of projections  67  or running through them is approximately 10 mm for example. The distance b is approximately 0.01 mm for example so that a projection  106  projecting into a first interstice  68  has a total play measured tangentially to this circle of approximately 0.02 mm. Angle b is then approximately 0.36° so that the cap can be turned in either direction through an angle  2   b  of approximately 0.72°. The radial play between positioning sections  62  and  105  of the secondary part or the cap, namely the distance between the opposing bottom surfaces of the positioning interstices and top surfaces of the positioning projections, is approximately 0.01 mm for example. 
     The positioning sections that engage each other provide exact positioning and secure the cap against rotations relative to the support. If one disregards the play, the positioning projections  106  of the cap are located approximately from the bottom quarter of the head  59  of the secondary part up to its upper end at the bottom surfaces and the lateral surfaces of the positioning interstices of the secondary part of the head. Also, once again disregarding the play, the cap abuts the tops of the positioning projections of the secondary part. Since the cap also abuts implant shoulder  35  tightly and without play, it is guided laterally so that large forces, i.e. forces directed approximately transversely to axis  22  and torques or torsional stresses created by such forces, are properly transmitted from the cap to the support without the cap tilting. When screw  121  has been tightened, the cap is thus connected in a stable matter with the support. Implant shoulder  35  and the supporting surface  104  of the cap are located below the ridge of the soft tissue  82  inside the latter and can thus contact each other without a gap, averting problems with microorganisms. 
     Device  151  shown partially in FIG. 10 has a support with the same shape as the support shown in FIGS. 3 to  9  and likewise designated  21 , of which only the positioning section  62  of secondary part  51  can be seen. Device  151  also has a superstructure element  153  with a cap  161 . This is designed for single positioning and has a positioning section  165  with ten first, narrow identically shaped and sized positioning projections  166 , a second, wider positioning projection  167 , and positioning interstices  168 . First positioning projections  166  are shaped similarly to positioning projections  106  of cap  101  and project into the first interstices  68  of the secondary part. The second, wider projection  167  of the cap projects with limited play into the second, wider interstice  69  of the secondary part. Cap  161 , similarly to cap  101 , is removably attached to secondary part  51  with an occlusal screw  121 . 
     Device  191  shown in part in FIG. 11 also has a support  21  of which only positioning section  62  of secondary part  51  can be seen. Device  191  also has a superstructure element  193  with a cap  201 , which is attached with an occlusal screw  121  to the secondary part. Cap  201  has a positioning section  205 . The latter is designed for single positioning and has only a single, wide positioning projection  207 , which fits into the second, wider interstice  69  with limited play. Cap  201  thus has no projections fitting into the first, narrow interstices  68 . 
     The superstructure elements  153  and  193  shown in FIGS. 10 and 11 respectively can be designed for example as so-called telescoping or soldered-base superstructures. Unless stated to the contrary above, devices  151  and  191  can be designed similarly to the device  91  described in relation to FIGS. 6 to  9 . 
     Device  251  shown in FIGS. 12 and 13 in turn has a support  21  formed as already described with an implant  31  and a secondary part  51 . Device  251  also has a superstructure element  253  with a cap  261 . The latter has an interior space  263  formed of an axial through-hole and at the very bottom forms a conical supporting surface  264 . This is abutted by a likewise conical but steeper internal surface  265  that forms the same angle with axis  22  as conical section  64  of the secondary part. Above conical surface  265 , interior space  263  has a constriction and on the top side of the latter has a conical supporting surface  269 . Cap  261  is attached to secondary part  51  similarly to cap  101  by an occlusal screw  121  whose head rests on supporting surface  269 . Cap  261  is designed such that in the tightened state its supporting surface  264  abuts at least the outer region of shoulder surface  37  tightly and without a gap, while between the conical section  64  of the secondary part and the conical internal surface  265  of the cap a very small gap with a width of for example approximately 0.01 to 0.02 mm is present. The cap is then likewise guided by the conical section  64  of the secondary part, centered, and supported against the influence of lateral forces acting approximately transversely to axis  22 . As can be seen particularly clearly in FIG. 13, cap  261  has no projections projecting into positioning interstices  68 ,  69  of the secondary part and is thus not positioned with respect to rotations about axis  22 . Superstructure element  253  having cap  261  can be designed for example as a rib or bridge for forming several artificial teeth and can have at least one other cap that can also be attached to a support. 
     Support  321  shown in FIGS. 14 and 15 is generally rotational symmetrical about an axis  322  and has an anchoring part  323  and a head part  324 . Support  321  consists solely and completely of a one-piece body, i.e. an implant  331 , whose lower part forms anchoring part  323  and whose upper part forms the head part  324  of the support. The lower part of implant  331  is shaped similarly to implant  31  and in particular has a conical implant shoulder  335  with a conical shoulder surface. The upper part of implant  331  forming head part  334  has a positioning section  362  with a lower generally cylindrical section  363  and an upper, generally conical, section  364 . The latter is abutted at the upper end of the implant by an annular, flat face  365 . Positioning section  362  has positioning projections  367  and positioning interstices  368 ,  369  alternating along the periphery. Positioning projections  367  all have the same shape, straight and parallel to axis  322 , and project outwardly away therefrom; their cross sections taper in the outward direction toward their tops, and they are approximately V-shaped or triangular in cross section. The positioning interstices are also straight and parallel to axis  322  and have several narrow, first positioning interstices  368  that have the same shapes and sizes and a single wider, second positioning interstice  369 . Each first positioning interstice  368  consists of a groove or notch having an approximately V-shaped cross section and has two essentially flat, lateral surfaces sloping away from their bottoms and from axis  2 , and therefore outward and away from one another. The wider, second positioning interstice  369  has a flat or slightly curved bottom surface and two lateral surfaces sloping outwardly from the bottom surface and hence away from one another. The projections have tops formed by cylindrical section  363  and bevels formed by conical section  364 . The tops of projections  367  define a partial circle and lie on a cylindrical surface. The bottoms of the interstices together also define a cylindrical surface. The narrow, first positioning interstices  368  adjacent to each other are all at the same distance from each other and define a circle with divisions of 15° or 24° for example. The wider, second positioning interstice  369  is formed by omitting one projection  367 . Implant  331  has an axial blind hole  371  (corresponding to blind hole  71  of secondary part  51 ) with an internal thread  372  for screwing in an occlusal screw. Unless stated to the contrary above, support  321  consisting of implant  331  can be made the same as or similar to support  21  and used similarly thereto. 
     Support  421  shown in FIGS. 16 and 17 has an axis  422  and an implant  431 . The implant has an annular stepped face at its upper end with an implant shoulder  435  that consists of a hollow with a flat shoulder surface  437  at right angles to axis  422  and a short, conical centering surface  439  inclined upward toward the axis. Implant  434  has an axial blind hole  441  with an internal thread into which a secondary part  451  is screwed. The head of the latter has a positioning section  462  that for example is formed similarly to positioning section  62  of secondary part  51 . A cap  471  drawn cut in half or a cap  481  drawn cut in half can be removably attached to support  421  with an occlusal screw  491 . Cap  471  shown on the left in FIGS. 16 and 17 has a positioning section that is formed for example like positioning section  105  of cap  101  for multipositioning. The cap  481  shown on the right in FIGS. 16 and 17 does not have a positioning section so that it can be attached in any rotational position on the support analogously to cap  261 . 
     Device  501  shown in FIGS. 18,  19 , and  20  has a support  521  with an axis  522 . Support  521  has an anchoring part  523  and a head part  524  and consists for example exclusively of a one-piece implant  531 . The latter has an axial blind hole  541  that ends in the face at the free end of head part  524 .  10  The implant has a head  551  with a cylindrical section  552  and a generally conical section  553  that tapers toward the free end of the head. The head also has a positioning section  562  that is located at the thinner end of conical section  553  and on the face of the head. Positioning section  562  is delimited externally by the end section of the conical external surface of conical section  553 , internally by a cylindrical section of hole  541 , and on the face of the head part by an annular, flat face  565  at right angles to axis  522 . 
     Positioning section  562  has positioning projections  566 ,  567  and positioning interstices  568 ,  569  distributed in alternating fashion around axis  522 . Projections  566 ,  567  consist of cams that project away in the axial direction from the bottom surfaces of interstices  568 ,  569  and have tops formed by sections of flat face  565 . The bottom surfaces of interstices  568 ,  569  consist of sections of a flat annular surface at right angles to axis  522 . The lateral surfaces of the projections and interstices are for example flat and parallel to a plane running through the axis and the center of the interstice in question. The projections have several identically formed and dimensioned wide first projections  566  and two narrower, second projections  567  that are adjacent to each other. The interstices have several identically formed and dimensioned narrow first interstices  568  and a wider, second interstice  569  that is located between the two narrower, second projections  567 . Positioning section  562  has for example a total of eight projections and interstices defining an  80  or 45° division. Device  501  also has a superstructure element  593  of which only part of cap  601  is shown in FIGS. 18 and 20. This cap has an interior space  603  with a positioning section  605 . The latter has eight positioning projections  606 - distributed around its periphery and, between them, eight positioning interstices  608 . The positioning interstices consist for example of cams that project inward away from a stepped cylindrical internal surface in the radial direction and, when device  501  is assembled, fit into the interstices  566 ,  567  of support  521 . However, instead of projecting from above, for example away from a flat radial plane, the positioning projections could project downward in the axial direction. Moreover, positioning section  605  of cap  601  can be shaped either for multipositioning or for single positioning. Device  501  can accordingly, unless stated to the contrary above, be designed similarly to device  91  or  151 . 
     Device  651  shown in FIG. 21 has a support  521  formed in the same way as in FIGS. 18 to  20  and, like the latter, consisting of an implant  531 . Device  651  has a superstructure element  653  of which once again only cap  661  is depicted. This does not have projections fitting into positioning interstices  568  of the support or implant, but an interior space  663  with a conical internal surface  665  guided with limited play by conical section  553  of head  551  of implant  431 . Unless otherwise described above, device  651  can be formed similarly to device  251  shown in FIGS. 12 and 13. 
     Device  701  shown in FIG. 22 has a support  721  with an axis  722 , an anchoring part  723 , and a head part  724 . Support  721  has an implant  731  consisting of a one-piece metal body. Implant  731  has a head  759  with a positioning section  762 . The latter has a generally cylindrical section  763 , a generally conical section  764  tapering upward away from the latter, and an annular, radial, flat face  765 . Cylindrical section  763  is provided with an external thread  766  that is formed for example as a trapezoidal thread and has a top formed of sections of a cylindrical surface. Support  721  also has an axial blind hole  771  with an internal thread  772 , said hole terminating in the face of the head part. The partly cylindrical and partly conical external or peripheral surfaces of positioning section  762  are provided with axially extending and radially outwardly projecting positioning projections  776 ,  777  and positioning interstices  778 ,  779 , with for example several first, wide projections  776 , two second narrower projections  777 , several first, narrow interstices  778  and one second, wider interstice  779  disposed between the two narrower projections being present. The interstices formed by grooves divide external thread  766  so that only sections of the external thread are present on the tops of the projections. Positioning section  762  is additionally provided on the face with axially projecting positioning projections  786 ,  787  and positioning interstices  788 ,  789 , with for example, analogously to the case of support  521 , several first, wide projections  786 , two second, narrower projections  787 , several first, narrow interstices  788 , and one second, wider interstice  789  being present. Device  701  also has a superstructure element  793  with a cap  801 . The cap has an interior space  803  with a positioning section  805  formed similarly to that of cap  601  as well as projections that can fit into endwise interstices  788 ,  789  of the support. Cap  801  can be attached to support  621  with an occlusal screw  821 . 
     Cap  801  can be replaced by a cap with positioning projections that fit into the interstices  788 ,  769  of support  721  on the external or peripheral surface. Also, support  721  can have attached to it a cap that does not have positioning projections but has an internal thread screwed to the external thread  766  of the support when the cap is attached. 
     Device  901  shown in FIG. 23 has a support formed of a one-piece implant  931 . Head part  924  of the support, formed by the head of the implant, has first and second positioning interstices, of which one of the first is visible and designated  948 . This extends from the bottom half of the generally cylindrical head section to the thinner, top end of the generally conical head section and is milled thereinto for example with a disk mill such that its bottom runs out at the bottom end into the cylindrical external and/or jacket surface of the cylindrical head section. 
     Cap  961  belonging to device  901  is formed partially similarly to cap  661  shown in FIG. 21 and, like the latter, has a generally conical internal surface designated  965  in FIG.  23 . Cap  961  shown in FIG. 23 is however formed for multipositioning or single positioning and has positioning projections of which one is shown, designated  976 , which projects into positioning interstice  948 . 
     The axial dimension of each positioning projection is considerably smaller than the total axial dimension of the cylindrical and the conical head sections, amounting to at most 30% of the total axial dimension of these two head sections and of course of the head as a whole. The positioning projections are thus at a distance from the bottom end of the cylindrical head section and from the top end of the conical head section  17  and are approximately at the level at which the two head sections are connected together. Between the top of projection  976  and the bottom of positioning interstice  847  containing the latter is an open gap or interstice whose radial dimension at the lowest point of the interstice is for example at least the same as half the depth of interstice  948 . The lateral surfaces of the positioning projection are at most separated by very narrow gaps from the lateral surfaces of the interstice. The positioning projections thus have very limited play in interstice  948  along a circle concentric with the axis of the support and tangential thereto. The cap is therefore well supported laterally, i.e. against forces directed approximately transversely to the axis, by conical internal surface  965  and the lateral surfaces of projections  976 , although there is a relatively large gap between the tops of projections  976  and the bottoms of interstices  948 . 
     The device shown in part in FIGS. 24,  25 ,  26 ,  27 , and  28  has a support similar to the support shown in FIGS. 18 to  21  and is likewise designated  521 . The support  521  shown in FIGS. 24 to  26  has in particular, disposed on the face of head part  524 , first positioning interstices  568  and a second positioning interstice  569 . In the head part  524  shown in FIGS. 24 to  26 , however, each interstice  568 ,  569  is trapezoidal in a side view and in a cross section running perpendicularly to its radial lengthwise direction and has a flat bottom surface  571  at right angles to the axis and two flat, lateral surfaces  572 . The latter two slope away from each other upwardly from bottom surface  571  so that the interstices expand in the direction away from the bottom surface. Cap  601  shown in FIGS. 24 and 25 is partially formed similarly to the cap with the same number shown in FIGS. 18 and 20 but originally consists of two separate parts, namely a metal, sleeve-shaped main body  611  and a positioning sleeve  621 . Main body  611  has an axial through-hole and at the bottom, another conical internal surface  613  as well as a cylindrical hole section  614  above the latter. Positioning sleeve  621  is essentially cylindrical and attached to main body  611 , namely pressed and/or glued into cylindrical hole section  614 . The positioning sleeve also has a section projecting downward from cylindrical hole section  614  with at least one positioning projection  626  that projects axially downward; according to FIG. 27 for example two or more positioning projections  626  with the same shapes are present. Each of them is trapezoidal looking in the radial direction and has a flat face at right angles to the axis and two flat, lateral surfaces sloping away from each other in the direction away from the face. Each projection  626  is sized so that, when the device according to FIG. 29 is assembled, it projects into a first interstice  568  of support  521  with very limited lateral play. Positioning sleeve  621  makes multipositioning of the cap relative to the support possible. 
     The positioning sleeve  621  shown in FIG. 27 can be replaced by the positioning sleeve  621  shown in part in FIG.  29 . This sleeve has a positioning projection  627  which fits into the second positioning interstice  569  of support  521  shown in FIG.  26 . Also, the positioning sleeve shown in FIG. 29 can have additional projections, not shown, that fit into first interstice  568  of the support. 
     The device shown in part in FIG. 30 has a support  521  with the same shape as the support shown in FIGS. 24,  25 ,  26 , and  28  and has a first positioning interstices  568  at the end of the head part. The positioning sleeve shown in part in FIG. 30 has a least two positioning projections  636 . Each of them has a face at right angles to the axis, two lateral surfaces parallel to the axis, and, when the face is connected to the lateral surfaces, edges  637 . At least one of projections  636  projects into a first interstice  568  of support  521  when the device is assembled. The two edges  637  then abut the lateral surfaces of the interstice with extremely limited play. 
     The devices shown in FIGS. 23 to  30  are advantageous in particular for applications where a superstructure element or impression element having a cap can be pulled out from or placed on the support diagonally to its axis. This may be the case with two caps belonging to one bridge or the like, that have to be placed simultaneously on two implants with sharply diverging or converging axes. 
     In the embodiments described below, corresponding, identical, or similar parts in the various embodiments will be designated with the same reference numerals. 
     The support  1000  shown in FIGS. 31,  32 , and  33  consists entirely of a one-piece metal implant  1001 , has an axis  1003 , and is essentially rotationally symmetrical therewith. Implant  1001  has an anchoring part  1005  at the bottom and a head  1007  at the top, which forms the head part of the support. The free ends of the anchoring part and the head, that face away from each other, form first end  1008  and second end  1009  of implant  1001 . The first end  1008  located at the bottom the implant has a slightly convexly curved end surface in axial section. Anchoring part  1005  has, from bottom to top, a generally cylindrical section  1011  and a trumpet-shaped section  1013  expanding in the direction away from the latter, whose external surface is always flush with the external surface of the generally cylindrical section  1011 . Generally cylindrical section  1011  is provided with a single-pitch right-hand external thread  1015 . This thread has a more or less serrated profile and has a helical rib  1016  with a top  1017  and two flanks that are asymmetric in axial section. The lower flank located near first end  8  forms an angle of for example approximately 70° to 75° with axis  1003 . The upper flank forms in axial section a smaller angle with the axis than does the lower flank. Additionally, this angle decreases with increasing distance from the top, so that the upper end of the upper flank is almost parallel to the axis. The axial dimension of helical rib  1016  is therefore—measured half-way down the thread or half-way up the rib—considerably less than the axial dimension, measured at the same radius, of the grooves between sequential turns or windings of rib  1016 . The core diameter D of the thread measures at most preferably 4 mm, preferably at least 3 mm, and for example approximately 3.5 mm. The radial thread depth or height of the rib is for example approximately 0.3 mm. The pitch of the thread is for example approximately 1 mm. The external thread  1015  is formed as a normal combination thread, i.e. a non-self-cutting thread. The anchoring part has a short (approximately 1 to 2 mm long) cylindrical, smooth (i.e. threadless) end section  1018  between first end  1008  and external thread  1015 ; said section  1018  is continuously connected with the convex end surface at first end  1008  by means of a rounded transition and its diameter is approximately the same as the core diameter of the external thread. The diameter of the upper end of cylindrical section  1011  and the diameter at the lower end of trumpet-shaped section  1013  that contacts the upper end is the same as the core diameter of external thread  1015  so that rib  1016  of the external thread projects radially beyond the sections of the implant contacting its ends. 
     At the upper, wider end of trumpet-shaped section  1013  is a shoulder  1021  with a conical shoulder surface  1022  sloping upward and inward in the direction away from the first end. This surface forms an angle of 40° to 50° and for example 45° with axis  1003 . A flat annular surface  1023  at right angles to axis  1003  abuts the upper, narrower end of conical shoulder surface  1022 . 
     Head  1007  extends upward away from annular surface  1023  and has a head section  1025  essentially parallel to axis  1003  and a generally conical head section  1027  that tapers upward away from head section  1025  toward the free end of the head and hence toward the second end  1009  of the entire implant. Head section  1025  parallel to the axis is delimited from the upper end of shoulder  1021  by an annular groove curved concavely in axial section. The head has a peripheral surface  1030  and a flat, annular end surface  31  at its free end, forming the second end  1009  of the implant. Both head sections  1005 ,  1027  are generally rotationally symmetrical with axis  1003  and/or each have a sheathing surface rotationally symmetrical with the axis, namely cylindrical or conical. The conical sheathing surface of the generally conical head section  1027  forms an angle with axis  1003  that is smaller than the angle formed by conical shoulder surface  1022  with axis  1003  and is matched to the distance between the conical head section and the shoulder such that the prolongation of the conical surface defined by the conical head section intersects shoulder  1021  within the outer edge of conical shoulder surface  1022 , namely for example intersects the inside half of shoulder surface  1022  or possibly flat annular surface  1023 . The angle formed between the conical surface of the conical head section and the axis is preferably 15° to 25° and for example approximately 20°. The axial dimension or height of head  1007 , measured from flat annular surface  1023  to the second end  1009  of the implant, is a maximum of 2 mm, preferably 1.2 mm to 1.8 mm, and for example approximately 1.5 mm. The axial dimensions of axially parallel head section  1025  and annular groove  1029  added together are for example approximately 1 mm. The axial dimension of the generally conical head section  1027  is for example approximately 0.5 mm. 
     Implant  1001  is provided with a blind hole  1035  coaxial with axis  1003 . This hole has an opening  1036  located at second end  1009 , surrounded by annular end face  1031 , formed by a very short cylindrical hole section, and proceeding away therefrom and downward in the following order: an internal thread  1037 , metric for example, a cylindrical, smooth (i.e. threadless) hole section  1038 , and a bottom  1039 . The lower end of internal thread  1037  further from the opening is inside the expanding trumpet-shaped section  1013  of the implant. The diameter of the cylindrical hole section  1038  is approximately the same as the core diameter of the internal thread. Bottom  1039  is inside the lower half of the generally cylindrical section  11  of anchoring part  1005 , for example approximately at the lower end of the external thread, tapers to its deepest point, and is delimited by a surface, curved in axial section, that is joined continuously and smoothly with the surface of the cylindrical hole section. This shape of bottom  1039  reduces the risk of the implant breaking in the vicinity of bottom  1039 . 
     Anchoring part  1005  is provided with at least one lengthwise groove  1051  and namely with three grooves  1051  distributed around axis  1003 . Each groove  1051  is longitudinal and inclined in a radial view to axis  1003  of the groove in question relative to the axis on the same side in the same direction as the rib of the right-hand thread, namely upward to the right. The center line of a groove running in the lengthwise direction and the lateral surface sections of the groove parallel thereto form, in radial view, an acute angle with a plane at right angles to axis  1003 , that is larger than the angle formed by rib  1017  with such a plane, i.e. than the pitch angle of the thread. Grooves  1051  in the vicinity of the end section of external thread  1015  located nearer to the first end  1008  of the implant, are however at a distance from first end  1008 . Each groove  1051  intersects at least one turn of rib  1017  or delimits the beginning of a rib and forms a face  1053  with at least one turn of the rib  1016  which, in cross section, forms an acute angle b with a straight line running radially to axis  1003  through this axis and top  1017 . Face  1053  also forms an acute lead angle of for example approximately 20° with axis  1003  at top  1017 . Grooves  1051  form chip grooves, but do not extend further from the end of external thread  1015  remote from the first end  1008  of the implant so that the end of the external thread has a section between grooves  1051  and its end facing away from first end  1008 , that surrounds axis  1003  without a break at least once and for example at least two or at least three times. Blind hole  1035  terminating in second end  1009  of the implant extends for example up to the lengthwise area of anchoring part  1005  that has grooves  1051 . The depths of grooves  1051  are such that the grooves do not extend into blind hole  1035 . Grooves  1051  can for example be milled at low cost with a disk mill into the anchoring part. The starting section of external thread  1015 , serving for thread-cutting, located in the lengthwise area of grooves  1051  and intersected thereby, preferably has a maximum diameter or outside diameter that is slightly smaller, preferably at least 0.01 mm, preferably at most 0.10 mm, and for example 0.02 mm to 0.05 mm smaller than the maximum diameter or outside diameter of the section of the external thread located above grooves  1051 . This has the advantage that the upper section of the external thread is firmly and securely anchored in the bone from the outset when the implant is screwed into a bone. 
     If a thread is cut into a bone with self-cutting external thread  1015 , because of grooves  1051  only the lower flank of rib  1017  engages the bone so that only a relatively small torque is required to cut the thread. The chips of bone material produced by cutting the thread can collect in grooves  1051  and knit with the bone surrounding the anchoring part. This improves the stability of the connection between the implant and the bone. 
     Peripheral surface  1030  of head  1007  has axial positioning projections  1065  distributed around axis  1003  and axial positioning interstices disposed therebetween, namely several positioning interstices  1068  with the same shape and a wider and deeper positioning interstice  1069 . Axial positioning interstices  1068 ,  1069  are groove-shaped, also designated “positioning grooves  1068 ,  1069 ” below, and form with axis  1003  non-rotationally symmetric, concavely curved positioning surfaces  1033 , namely several identically shaped first positioning surfaces formed by first grooves  1068  and a wider and deeper second positioning surface. The second positioning surface has for example a circle center closer to axis  1003  and/or a larger radius of curvature than the first positioning surfaces. 
     Interstices  1068 ,  1069  and positioning surfaces  1033  formed by them—or at least the deepest area thereof in cross section—extend in turn over the entire length of head section  1025  parallel to axis  1003  and at least approximately and for example exactly up to the thinner end of conical head section  1027  and thus also up to second end  1009  of the entire implant. The section of each positioning surface  1033  located in the vicinity of the axially parallel head section  1025  forms an arc of a circle in cross section, which forms at most a semicircle so that it is smaller than a semicircle. The projections  1067  between two first interstices or grooves  1068  all have the same shapes and dimensions. The two projections next to interstice  1069  or the second groove are somewhat narrower than the remaining projections  1067 . The sections of positioning surfaces  1033  located in the vicinity of the generally conical head section  1027  then form smaller arcs of a circle and extend for example up to the thinner end of the conical section in annular face  1031 . The projections  1067  between the positioning grooves have external peripheral sections that form parts of a cylindrical or conical surface. Eight for example positioning grooves  1068 ,  1069  are present and together they define a circle divided into eight parts in which however more than eight (for example twelve or more) positioning grooves may be present. 
     Implant  1001  is made of titanium for example. The external surface of anchoring part  1005  is for example from first end  1008  to near shoulder  1021 , namely up to approximately 1 mm to 3 mm below the upper, wider end of trumpet-shaped section  1013 —rough and porous, for example by blasting with solid particles such as ceramic or sand particles, or roughened by etching or provided with a porous coating of sprayed-on titanium. On the other hand, the uppermost area of trumpet-shaped section  1013 , conical shoulder surface  1022 , annular surface  1023 , and the various surfaces of head  1007  are smooth and pore-free. 
     Implant  1001  shown in FIGS. 34 to  36  has an anchoring part  1005  with a generally cylindrical section  1011 . This section is provided with a self-cutting external thread  1015  and in the vicinity of its lower end with several, for example three, lengthwise grooves and/or lengthwise holes  1071  distributed around axis  1003 . These serve as chip grooves and/or chip holes and are inclined as viewed in the radial direction, analogously to grooves  1051 , to axis  1003  and form a lead angle therewith designated a in FIG.  35 . One lateral surface of each groove and/or hole  1071  also forms a chip surface  1053 . These chip surfaces in turn form, in right-angled cross sections to axis  1003 , an acute chip angle b with the straight lines radial to axis  1003 . Grooves and/or holes  1071  are however deeper than grooves  1051  of the implant shown in FIGS. 3 to  5 , so that they intersect each other and their central bottom sections penetrate each other. Grooves and/or holes  1071  thus have, in the central cross-sectional area of anchoring part  1005 , a common central hollow space and together form the passages that pass through the implant in cross section. The bone chips entering in grooves and/or holes  1071  when a thread is cut can thus, together with the bone material that grows during the subsequent healing process, form a complete penetrating framework of bone. These provide highly stable and durable anchoring of the implant in the bone even when the anchoring part is comparatively short. Cylindrical hole section  1038  of blind hole  1035  terminating in head  1007  in the second end  1009  of implant  1001  is shorter in the implant shown in FIGS. 34 to  36  than in the implant shown in FIGS. 31 to  33 , so that bottom  1039  of blind hole  1035  is above grooves and/or holes  1071 . Head  1007  and shoulder  1021  of the implant shown in FIGS. 34 to  36  have the same shapes as in the implant according to FIGS. 31 to  34 . 
     In the implant  1001  shown in FIG. 37, blind hole  1035  extends up to the lengthwise section of anchoring part  1005  having grooves  1081 , namely chip grooves, similarly to the case in the implant according to FIGS. 31 to  33 . Grooves  1081  extend however up to the lower, first end of the implant shown in FIG.  37 . 
     Implant  1001  shown in FIGS. 38 and 39 has once again a first end  1008  formed by anchoring part  1005  and a second end  1009  formed by head  1007 . The generally cylindrical section  1011  of anchoring part  1005  is provided with an external thread  1015 . Blind hole  1035  of the implant has once again an opening  1036  located at second end  1009  of the implant, and has an internal thread  1037 , a cylindrical hole section  1038 , and a bottom  1039  that is located above the lower end of external thread  1015 . Blind hole  1035  may also have, at the lower, inner end of internal thread  1037 , an annular groove  1091  most of which is curved in axial section, and forms a transition between internal thread  1037  and cylindrical hole section  1038 , and whose surfaces at least approximately continuously transition into that of cylindrical hole section  1038 . The implant shown in FIGS. 38 and 39 also has a lower, short blind hole  1093  coaxial with axis  1003  with a opening  1094  located at first end  1008  of the implant and a bottom  1095  located inside the lower half of anchoring part  1005  at a short distance from bottom  1039  of upper blind hole  1035 . Lower blind hole  1093  tapers from opening  1094  to bottom  1095  essentially for its entire length and is limited by a surface that, at its bottom, and for example at least approximately for the entire length of the blind hole in axial section, is concavely curved, smooth, and continuously and for example approximately parabolic. Anchoring part  1005  is also provided, at the lower end of external thread  15 , with lengthwise holes  1097  that terminate in blind hole  1093  and have a center line running in the lengthwise direction and lateral surfaces parallel thereto, that form an acute lead angle a with axis  1003  as viewed in the radial direction. The implant according to FIGS. 38 and 39 is particularly advantageous for applications in which the implant is to have relatively little penetration into the bone and the length of the generally cylindrical section  1001  can be only approximately 6 to 8 mm. 
     Implant  1001  shown in FIG. 40 has an anchoring part  1005  whose generally cylindrical section  1001  is once again provided with an external thread  1015 . Its core diameter D is less than that of the implants shown in FIGS. 31 to  39  and is preferably 3 mm at most, preferably at least 2.5 mm, and for example approximately 2.8 mm. The maximum diameter of head  1007  and shoulder  1021  are on the other hand for example approximately the same as those of the implants shown in FIGS. 31 to  39 . Blind hole  1035  also has an opening  1036  at the second end  1009  of the implant, an internal thread  1037 , a cylindrical hole section  1038 , and a bottom  1039 . Internal thread  1037  is for example formed as a round thread or Whitworth thread. The inner end of internal thread  1037  at a greater distance from the opening is again inside the expanding, trumpet-shaped section  1013  of the implant. The diameter of cylindrical hole section  1038  is at most the same as the core diameter of the internal thread and for example a little smaller than the core diameter. Blind hole  1035  has an annular groove  1091  between the inner end of internal thread  1037  that is further from opening  1036  and cylindrical section  1038 , said groove forming a transition between internal thread  1037  and cylindrical hole section  1038 . The maximum diameter of groove  1091  is at least the same as the maximum diameter or nominal diameter of internal thread  1037  and for example a little larger than its maximum thread diameter. The section of groove  1091  that immediately abuts the internal thread is concavely curved in axial section. It is abutted by an approximately conical and/or (in axial section) slightly convexly curved section that in axial section is approximately parallel to the section surrounding it in cross section of the external surface of trumpet-shaped section  13  of the implant and connects the deepest point of the groove, having the largest diameter, at least approximately continuously and smoothly with cylindrical hole section  1038 . The wall of the implant surrounding blind hole  1035  then has, between the deepest point of groove  1091  having the largest diameter and cylindrical hole section  1038 , approximately the same thickness as at the lower, thinner end of trumpet-shaped section  1013  and at the core diameter of external thread  1015 . Bottom  1039  of blind hole  1035 , as in the embodiments described above, is formed by a surface concavely curved in axial section, which surface in axial section at least approximately continuously and smoothly abuts the surface of cylindrical hole section  1038 . By these shapes of internal thread  1037 , groove  1091 , and bottom  1039 , despite the small core diameter D of external thread  1015 , the implant is largely prevented from breaking when heavily stressed. Cylindrical section  1011  of the implant is provided with lengthwise, sloping grooves and/or holes  1071  forming chip surfaces  1053  in the vicinity of lower, first end  1008 ; due to the smaller core diameter, it may be possible for only two such grooves and/or holes to be present. 
     Moreover, internal thread  1037  can be formed as a round or Whitworth thread for maximum uniformity of shape, as can the implant types described above whose external thread core diameter is approximately 3.5 mm. 
     FIGS. 41,  42 , and  43  show a jawbone  1111  and the gingiva  1113  of a patient and various implants  1001  inserted at various depths into the bones, with a one-piece element  1115  or healing cap  1115  attached to the implant. Healing cap  1115  has a conical bearing surface  1116  that abuts conical shoulder surface  1022  of implant  1001  without a gap. The interior space of healing cap  1115  has a cylindrical section guided with limited radial play by the axially parallel head section  1025  of head  1007 . The external surface of the healing cap is vaulted, continuously curved in axial section, and at the outer edge of conical shoulder surface  1002  contacts the external surface of trumpet-shaped section  1013  of the implant smoothly and continuously in an essentially gap-free manner. The healing cap is removably attached with a screw  1119  to implant  1001 . Screw  1119  has a head countersunk into the top section of the healing cap flush with the top surface of the healing cap and a thread screwed into internal thread  1037  of the implant. 
     Implant  1001  shown in FIG. 41 is inserted subgingivally into the patient&#39;s mouth. The edge formed by the upper end of trumpet-shaped section  1013  and the outer edge of conical shoulder surface  1022  is then approximately at the level of the ridge of the bone. Gingiva  1113 , namely the soft tissue, is fitted against implant  1001  over the healing cap once healing cap  1115  has been attached and sutured at  1120 . After a healing phase of 3 to 4 months, another incision is made into the gingiva and a one-piece or multipart superstructure element is attached to the implant. Subgingival insertion of the implant is done in two phases: in the first phase the implant is inserted and in the second phase another incision is made into the gingiva and the superstructure element is attached. 
     Implant  1001  shown in FIG. 42 is semi-submerged relative to the gingiva. The outer edge of conical shoulder surface  1022  in this case is between the ridge of the bone and the highest point of the gingiva. The cap is then approximately flush with the gingiva or partly projects somewhat from it. This arrangement of the implant is used primarily for forming individual artificial teeth and bridges. The superstructure element serving as a crown or bridge then lies slightly, for example 1 to 2 mm, under the gingival surface on shoulder surface  1022 , so that the join is no longer visible and is not unaesthetic. 
     Implant  1  shown in FIG. 43 is inserted transgingivally. The outer edge of conical shoulder surface  1022  is then approximately at the highest point of gingiva  1113 . The operation can then be done in one phase, i.e. only one incision need be made into the gingiva. The transgingival arrangement is used for example for attaching bone structures and in cases in which appearance is less important. 
     There is thus a choice of inserting identically shaped implants subgingivally, transgingivally, or semi-submerged. 
     This is an important advantage for dentists and dental hospitals. 
     Device  1151  shown in FIG. 44 has an implant  1001  whose anchoring part  1005  is inserted for example into the interforaminal region of a lower jawbone, not shown. Head  1007  of implant  1001  has positioning surfaces formed by grooves for example. Device  1151  has a superstructure element  1153  with a cap  1161  attached to an implant  1001  rotationally symmetrically to axis  1003  and for example another rib, not visible, and another head, also not visible, attached to another implant. Cap  1161  is made of a metal material, for example a gold alloy or titanium, and has an interior space  1163  formed by a through-hole coaxial to axis  1003  and has a conical supporting surface  1164  at the bottom. This is abutted by a likewise conical but steeper internal surface  1165  that forms the same angle with axis  1003  as conical head section  1027  of implant  1001 . Interior space  1163  has a constriction above conical surface  1165  and a conical supporting surface  1167  on the top side of the latter. Cap  1161  is attached to the implant with an occlusal screw  1171  whose cylindrical head  1772  has a multi-sided hole and is countersunk in the cap. Head  1172  is abutted by a conical section  1173  supported on supporting surface  1167  and connected by a cylindrical shaft section  1174  with threaded part  1175 . The thread of the latter is screwed into internal thread  1037  of the implant. The screw presses the cap against the implant, so that the cap with its supporting surface  1164  rests firmly and without gaps at least on the outer area of shoulder surface  1022  of the implant while a very narrow gap is present between the conical surface sections of head section  1027  of the implant and the conical internal surface  1165  of the cap, the width of this gap being a maximum of 0.02 mm or preferably only a maximum of 0.01 mm and for example in the micron range. The cap is then further guided by conical section  1027  of the implant, centered, and supported when lateral forces act on it approximately transversely to axis  1003 . Cap  1161  is designed for free positioning and thus does not have the surfaces abutting positioning surfaces  1033  of implant  1001  formed by positioning grooves. The cap has an upwardly conically tapering external surface and a flat top surface at the upper end. The shape of interior space  1163  of cap  1161  makes it possible easily to place the cap on head  1007  using little force and practically without friction, and remove it therefrom, if axes  1003  of the implants serving to hold superstructure element  1153  are not parallel to each other and form an angle of up to 40° for example with each other. 
     FIG. 45 shows a bone  1111 , a gingiva  1113 , and a device  1151  having a semi-submerged implant  1001 , a cap  1161  also shown separately in FIG. 46, an occlusal screw  1171 , and a porcelain crown  1201 . Like the cap shown in FIG. 44, cap  1161  is rotationally symmetrical with the axis and designed for free positioning, and its supporting surface  1164  abuts shoulder surface  1022 . External surface  1211  of the cap shown in FIGS. 45 and 46 generally tapers upward from the bottom, but has an external surface section  1212  at the bottom that slopes outwardly upward and abuts the upper end of trumpet-shaped section  1013  of the implant at least approximately smoothly. External surface  1211  is also provided with an annular groove  1213  that is arcuate in axial section. Occlusal screw  1171  shown in FIG. 45 differs from the occlusal screw shown in FIG. 44 in that, instead of cylindrical shaft section  1174 , it has a bent shaft section  1224  that is concave in axial section and at least approximately continuously joins conical section  1173  with threaded part  1175 , thus reducing the risk that the occlusal screw will break. 
     Device  1151  shown in FIG.  47  and partially in FIG. 48 has an implant  1001  inserted into a bone  1111  and a superstructure element  1153 . Superstructure element  1153  has a cap  1161  attached by an occlusal screw  1171  to implant  1001 , and a crown used to form a single artificial tooth. Head  1007  of the implant has eleven for example identically shaped first positioning interstices  1068  or positioning grooves  1068  and a second, wider and deeper positioning interstice  1069  or a second positioning groove  1069 . The head thus has a total of twelve positioning grooves forming positioning surfaces  1033 . 
     Cap  1161  shown in FIGS. 47 and 48 is partially similar to the cap shown in FIGS. 45 and 46 but above conical supporting surface  1164  has a positioning section  1241 . The latter is generally cylindrical but, along the periphery of interior space  1163 , has alternating sequential positioning projections  1243  and positioning interstices  1245 . Thus, twelve identically shaped and dimensioned projections  1243  uniformly distributed along the periphery of the interior space and twelve likewise uniformly distributed and identically shaped interstices  1245  are present. Of the twelve projections  1243  of the cap, eleven engage a first positioning groove  1231  and one engages second positioning groove  1232 . The cap is accordingly designed for multipositioning and can be positioned on the implant in twelve different positions (i.e. rotational positions) when it is connected to the implant, with the angle between adjacent rotational positions being 30°. Projections  1243  have straight, axial ribs and have surfaces shaped like arcs of circles in cross section. When head section  1025  is axially parallel, these surfaces are at least approximately complementary to the first positioning grooves  1068 . Projections  1243  engaging first positioning grooves  1068  have a play therein that amounts to at most 0.02 mm, preferably at most 0.01 mm, and for example in the range of a few microns in the radial direction, in particular along a circle coaxial with axis  1003 . On the other hand, projection  1243  of the cap, that engages second positioning groove  1069 , is separated from the second positioning surface by a fairly wide gap. Positioning interstices  1245  of the cap also fit with at most very limited play into the cylindrical surface sections of the axially parallel head section. Positioning projections  1243  of the cap also engage conical head section  1027  up to the free end of head  1007 , i.e. up to second end  1009  of implant  1001 , in the positioning grooves of the head and are thus guided in head sections  1025 ,  1027  up to second end  1009  of the implant with very limited play by the first positioning grooves and supported against forces acting perpendicularly to axis  1003 . The cap formed for multipositioning is thus, despite the small height of the head, also well-supported against lateral forces by the implant and is connected with the implant in stable fashion. 
     Head  1007  of implant  1001  shown in FIG. 49 has the same shape as the in the implants shaped as in FIGS. 47 and 48 and has several first, identical positioning grooves  1068  and a second, wider and deeper positioning groove  1069 . Cap  1161  shown in FIG. 49 is formed for single positioning and has, for each positioning groove  1068 , a first positioning projection  1253  projecting thereinto and a second positioning projection  1254  projecting into second positioning groove  1069 . The latter is wider and higher than the first positioning projections, so that it fits with very limited play into second positioning groove  1069  and cannot engage any first positioning groove  1068 . 
     Implant  1001  of the device  1151  shown in FIG. 50 has a head  1007  with several first positioning grooves  1065  and a second positioning nut, not shown. The device also has a superstructure element  1153  with a cap  1161  shown separately in FIG. 51, an occlusal screw  1171 , and a crown  1201 . Cap  1161  or, to be more precise, its external surface  1211 , is at an angle. Lower external surface section  1271  is generally rotationally symmetrical with axis  1003  of the implant up to and including annular groove  1213 . Upper external surface section  1273  located above annular groove  1213  is approximately coaxial with an axis  1275  that forms an acute angle with axis  1003 . The top surface of the cap is flat and approximately perpendicular to axis  1003 . Interior space  1163  of the cap is coaxial with axis  1003  and generally rotationally symmetrical therewith up to the upper end of the cap. Cap  1161  has a conical supporting surface  1164  resting on shoulder surface  1022  of the implant and also, similarly to the caps in FIGS. 44 and 45, a conical internal surface  1165  supported with limited play by conical head section  1027 . However, the cap also has a positioning section  1241  with positioning projections that for example all have the same shapes and are designated “1243,” so that the cap is designed for multipositioning. The height of positioning projections  1243  is however considerably less than the depth of positioning grooves  1068 ,  1069  of the head, so that their tops are at a distance from the deepest points of the positioning grooves. Moreover, positioning projections  1243  are also considerably shorter than the positioning grooves of the head, so that they engage the positioning grooves for example only in the vicinity of the connection of the two head sections  1025 ,  1027 . The dimension or width of projections  1243  measured along the periphery is such, however, that it allows precise positioning. The cap shown in FIGS. 50 and 51 is particularly applicable to bridge constructions that have two implants with axes that are not parallel to each other and diverge or converge. Superstructure element  1153  that forms a bridge construction can then be readily placed on and removed from the implants even when the implant axes are not parallel. Also, despite the small positioning projections of the cap, good positioning and good protection against lateral forces are achieved. 
     The device  1151  shown in FIG. 52 has an implant  1001  with positioning grooves and a superstructure element  1153  with a cap  1161  designed for multipositioning or single positioning. The conical supporting surface  1164  of said cap abuts the conical shoulder surface  1022  of the implant. The outer edge of supporting surface  1164  however has a smaller diameter than the outer edge of shoulder surface  1022 , so that this surface still has a section surrounding the cap. The head of occlusal screw  1171  is approximately flush with the upper end of the cap. With this cap, the dentist can make a impression directly without using a special impression cap, just as with a natural tooth. A crown  1201  can be made based on this impression, that also abuts shoulder surface  1022 . 
     The device according to FIG. 53 has a cap  1161  that is generally rotationally symmetrical with axis  1003  of implant  1001  but designed for multipositioning or single positioning, and an occlusal screw  1171 , whose head is countersunk fairly deep into the cap and is at a relatively long distance from the upper, free end of the cap. The cap can be ground for example for use, resulting in the grinding surface  1291  shown in dashed lines. 
     The device shown in FIG. 54 has a implant  1001  with positioning grooves, a cap  1161 , and an occlusal screw  1171 . With this cap, the supporting surface  1164  abutting shoulder surface  1022  of the implant is once again rotationally symmetrical with axis  1003 , while the entire external surface  1211  of the cap is rotationally symmetrical with an axis inclined to axis  1003 , and for example conical. The top surface of the cap is for example at right angles to the aforementioned axis. The cap can be ground for use if necessary. Also, a crown or bridge or the like can be cemented onto the cap. 
     The caps shown in FIGS. 52 to  54  can be made of a metal material for example such as a gold alloy or titanium. However, a cap can first be made of a burnable plastic which is then replaced by a cast cap. 
     The steps for creating a dental prosthesis will now be explained with reference to FIGS. 55 to  62 . FIG. 55 shows the lower jawbone  1111  of a patient, gingiva  1113 , and a semisubmerged implant  1  after the healing phase. Head  1007  of the implant is provided with positioning surfaces formed by grooves. 
     Once the implant  1001  has healed in, an impression element  1301  shown in FIG. 56 is removably attached to the implant—clipped on or screwed, for example. Impression element  1301  consists of a one-piece or multipart impression cap and rests on shoulder surface  1022  of implant  1001  without leaving a gap. The cap of impression element  1301  is designed for example—as described for caps of superstructure elements—for multipositioning or single positioning, so that the impression element is positioned in a specific rotational position. Once the impression element has been attached, an impression spatula  1303  filled with deformable impression material  1305  is pressed over impression element  1301  against the ridge of bone and gingiva  1113 , and an impression is taken. Once it has hardened, the impression material forms a impression surface  1307 . 
     Impression spatula  1303  together with impression material  1305  and the impression element  1301  embedded therein is then removed from implant  1001 . A manipulating implant  1311  shown in FIG. 57 has an anchoring part  1315 , a head  1317 , and a shoulder  1321  between them. Head  1317  and shoulder  1321  of the manipulating implant have the same shapes as for the implant shown in FIGS. 55 and 56, while anchoring part  1315  is usually different from that of implant  1001 . 
     Head  1317  of manipulating implant  1311  is now placed in the interior space of impression element  1301  according to FIG. 58, positioned in a specific rotational position, and removably attached, for example clipped, to the impression element. The conical shoulder surface of the manipulating implant then rests on the conical supporting surface of the impression element, with the outer edges of these surfaces being visible from outside. Then a modeling material, plaster for example, is pressed over anchoring part  1315  of manipulating implant  1311  against impression surface  1307  and the master model  1331  shown in FIG. 58 is made from the modeling material. Once the modelling material has hardened, anchoring part  1315  of the manipulating implant is anchored in the master model. 
     Manipulating implant  1311  is then separated from the impression element. Head  1317  and the conical shoulder surface of shoulder  1321  of the manipulating implant then project out from master model  1331  according to FIG.  59 . 
     In the next step, a cap  1161  shown in FIG. 60 serving as a component of a superstructure element is placed on the head of manipulating implant  1311  and removably attached thereto with an occlusal screw. Then a crown  1201  shown in FIG.  61  and made of porcelain for example is made and attached to cap  1161 . The crown then forms a superstructure element  1153  together with cap  1161 . The latter is then placed in the patient&#39;s mouth according to FIG.  62  and attached to implant  1001 . 
     Implant  1001  shown in FIG. 63 has for example yet another head, not shown, but could belong to a support that has another secondary part also not shown. The implant is in general rotationally symmetrical with an axis  1003 . Anchoring part  1005  once again has a generally cylindrical section  1011  and a generally trumpet-shaped section  1063  adjoining its upper end and expanding in the direction away therefrom. At the upper end of section  1013  is a conical shoulder surface  1022 . Trumpet-shaped section  1013  is provided with depressions  1425  at a distance from each other along the axis, namely annular grooves surrounding axis  1003 . Each groove has in axial section a bottom  1427 , a first surface  1428 , and a second surface  1429 . First surface  1428  is above bottom  1427  and is inclined away from the latter and from axis  1003  outward and upward in the direction of shoulder surface  1022 . Second surface  1429  is located beneath the bottom, is considerably smaller than first surface  1428 , and is inclined outward and downward away from the bottom, i.e. away from shoulder surface  1422 . Second surface  1429  forms a considerably larger angle with axis  1403  than first surface  1428 . The projections or ribs between adjacent grooves thus have an approximately serrated profile. The first and second surfaces are however continuously connected together at each bottom and at their ends facing way from the bottoms, by a section that is arcuate in axial section. When the implant is inserted into a bone  1111 , the bone can grow into the depression or groove  1425  and thus improve the anchoring of the anchoring part in the bone. If the depressions or grooves  1425  project out of the bone, gingiva  1113  can also grow into the depressions or grooves  1425 . 
     Implant  1001 , partially visible in FIG. 64, has an axis  1003  and an anchoring part  1005 . The latter has a generally cylindrical section  1011  with an external thread  1015 . This thread has a single pitch and has a rib  1016 , but could be multi-pitch and thus have more than one rib. Rib  1016  has helical turns  1451 , a top  1017 , a foot  1453 , and two flanks  1454 . A channel  1461  with a cylindrical bottom surface is present between two adjacent turns  1451 . Each flank  1454  has a flank section that is straight in axial section. The straight flank sections of the rib are continuously connected with each other by a section with a radius of curvature R 1  that forms top  1017  and is arcuate in axial section. The flank sections that are straight in axial section are also continuously connected at the foot of the rib by a section with radius of curvature R 2  arcuate in axial section with the cylindrical bottom surface or channel  1461 . 
     The flank sections that are straight in axial section form an angle g with a radial straight line  1465 . This is an angle of 15° to 25°, preferably 18° to 22°, and for example approximately 20°. The axial distance between corresponding points of two adjacent turns  1451  of the rib is designated s and with a single-pitch thread is identical with its pitch. Halfway up the rib, i.e. in the middle between its top and its foot, the rib has an axial dimension a. This is a maximum of 30% and for example preferably 15% to 25% of distance s. Channel  1461  has an axial dimension b half-way up rib  1016 , which is considerably larger than dimension a. The height of the rib is for example approximately 0.5 mm. Radius of curvature R 1  is for example approximately 0.05 mm to 0.1 mm. Radius of curvature R 2  is at least 0.1 mm and for example approximately 0.15 mm or even more. 
     When the implant shown in FIG. 64 is inserted into a bone, the space between a cylindrical surface in contact with top  1017  and a cylindrical surface defined by the bottom of the channel contains considerably more, namely approximately three to five times more, bone material than metal implant material. Also, the angle g of for example approximately 20° provides good transmission of compressive and tensile forces between the implant and the bone. 
     Head  1007  of implant  1001  shown in FIG. 65 has positioning interstices or grooves  1468  uniformly distributed along its periphery, all of which have the same shapes and dimensions. 
     The implant shown in FIGS. 66 and 67 has, instead of positioning grooves, flat positioning surfaces  1033  parallel to axis  1003  and thus not rotationally symmetrical with the axis. These surfaces are all uniformly distributed and have the same shapes and dimensions. The radial distances of the axial center lines of positioning surfaces  33  are approximately or exactly the same as the radius of the narrower, upper end of conical head section  1027 . Flat positioning surfaces  1033  extend in an axial direction over the entire length of axially parallel head section  1025  and at least approximately and preferably exactly up to the thinner, upper end of conical head section  1027  and hence also up to second end  1009  of the entire implant. Flat positioning surfaces  1033  together essentially form a polygon, i.e. an octagon. Axially parallel head section  1025  however still has narrow peripheral sections of a cylindrical jacket surface between the flat positioning surfaces. The generally conical head section  1027  should in any event still have sections of a conical jacket surface between flat positioning surfaces  1033 . 
     The implants described according to the embodiments of the implant shown in FIGS. 31 to  33  can, unless otherwise described, have the same or similar shapes to the implant described with reference to FIGS. 31 to  33  or another previously described implant. The same applies to the caps, screws, superstructure elements, and other parts described according to corresponding parts described above. 
     As already mentioned in the preamble, the caps can be made of a burnable plastic instead of a metal material. A dental technician can then place a meltable and/or burnable impression material such as wax on the plastic cap and thereby produce a casting model for a crown or another superstructure element. A casting impression can then be formed around it and the casting model located therein can be burned and/or melted. A superstructure element made of a casting material such as a gold alloy is then cast. The radial play between a burnable cap and the positioning section of a support supporting it may if necessary be made slightly larger than described for a device with a metal cap  101  according to FIGS. 8 and 9, for example up to approximately 0.02 mm. On the other hand, the play between the lateral surfaces of the projections of the burnable cap and the lateral surfaces of the projections of the support bearing this cap can be set for example similarly to those described for the device with a metal cap according to FIGS. 8 and 9. The burnable cap and the cap cast using it can then be positioned approximately the same as far as rotation is concerned as described for cap  101 . 
     The supports and the elements attached thereto can be modified in other ways as well. In particular, features of various embodiments described can be combined with each other. 
     Instead of removably attaching a superstructure element and/or a cap to a support by a screw, a superstructure element can be made with a pin that is cemented or glued into the blind hole of the support with a binder, i.e. a cement or glue, and the superstructure element and/or the cap can be non-removably connected with the support. The support can nonetheless have an internal thread, which improves the adhesion of the binder in the support. Such a method of attachment may be of especial advantage with a superstructure element attached to two supports, for example a bridge. 
     The healing element or healing cap may instead be screwed to the support by a clamping and/or latch connection. 
     Finally, reference is made to the priorities of Swiss Patent Applications 1220/97 and 1222/97 filed by the same applicant, the content whereof is incorporated into this patent application provided there are no contradictions. 
     Friatec AG Case 4+7/Doss. 19787 PCT Project  2000-1    
     List of Parts 
     FIGS. 1 and 2 (Prior Art) 
       1  support 
       5  axis 
       7  radial straight line 
       10  cap 
     FIGS. 3-8 
       21  support 
       22  axis 
       23  anchoring part 
       24  head part 
       31  implant 
       32  end section 
       33  section 
       34  external thread 
       35  shoulder of implant 
       37  shoulder surface 
       38  edge 
       41  blind hole 
       42  opening 
       43  conical main part 
       44  shoulder 
       45  threaded hole 
       46  internal thread 
       51  secondary part 
       52  internal connecting section 
       53  conical section 
       54  threaded part 
       55  external thread 
       57  shoulder 
       59  head 
       60  peripheral surface 
       61  annular groove 
       62  positioning section 
       63  cylindrical section 
       64  conical section 
       65  annular face 
       67  positioning projection 
       68  first positioning interstice 
       69  second positioning interstice 
       71  blind hole 
       72  internal thread 
       81  bone 
       82  soft tissue (gingiva) 
       83  device 
       85  healing element or healing cap 
       86  occlusal screw 
       91  device 
       93  superstructure element 
       101  cap 
       103  interior space 
       104  conical supporting surface 
       105  positioning section 
       106  positioning projection 
       108  positioning interstice 
       109  supporting surface 
       121  occlusal screw 
       125  casting 
       126  lining 
       131  straight line 
       132  straight line 
     FIG. 10 
       151  device 
       153  superstructure part 
       161  cap 
       165  positioning section 
       166  first positioning projection 
       167  second positioning projection 
       168  positioning interstice 
     +Parts of FIGS. 3-9 
     FIG. 11 
       191  device 
       193  superstructure element 
       201  cap 
       205  positioning section 
       207  positioning projection 
     +Parts of FIGS. 3-9 
     FIGS. 12 and 13 
       251  device 
       253  superstructure element 
       261  cap 
       263  interior space 
       264  conical supporting surface 
       265  conical internal surface 
       269  conical supporting surface 
     +parts of FIGS. 3-9 
     FIGS. 14 and 15 
       321  support 
       322  axis 
       323  anchoring part 
       324  head part 
       331  implant 
       335  implant shoulder 
       362  positioning section 
       363  cylindrical section 
       364  conical section 
       365  face 
       367  positioning projection 
       368  first positioning interstice 
       269  second positioning interstice 
       371  blind hole 
       372  internal thread 
     FIGS. 16 and 17 
       421  support 
       422  axis 
       4331  implant 
       435  implant shoulder 
       437  shoulder surface 
       439  centering surface 
       441  blind hole 
       451  secondary part 
       462  positioning section 
       471  cap 
       481  cap 
       491  occlusal screw 
     FIGS. 18,  19 , and  20   
       501  device 
       521  support 
       522  axis 
       523  anchoring part 
       5243  head part 
       531  implant 
       541  blind hole 
       551  head 
       552  cylindrical section 
       553  conical section 
       562  positioning section 
       565  face 
       566  first positioning projection 
       567  second positioning projection 
       568  first positioning interstice 
       569  second positioning interstice 
       593  superstructure element 
       601  cap 
       603  interior space 
       605  positioning section 
       606  positioning projection 
       608  positioning interstice 
     FIG. 21 
       651  device 
       653  superstructure element 
       661  cap 
       663  interior space 
       665  conical internal surface 
     +parts of FIGS. 18-20 
     FIG. 22 
       701  device 
       721  support 
       722  axis 
       723  anchoring part 
       724  head part 
       731  implant 
       759  head 
       762  positioning section 
       763  cylindrical section 
       764  conical section 
       765  face 
       766  external thread 
       771  blind hole 
       772  internal thread 
       776  first positioning projection 
       777  second positioning projection 
       778  first positioning interstice 
       778  second positioning interstice 
       786  first positioning projection 
       787  second positioning projection 
       788  first positioning interstice 
       789  second positioning interstice 
       793  superstructure element 
       801  cap 
       803  interior space 
       805  positioning section 
       821  occlusal screw 
     FIG. 23 
       901  device 
       924  head part 
       931  implant 
       948  first positioning interstice 
       961  cap 
       965  conical internal surface 
       976  positioning projection 
     FIGS. 24-28 
       571  bottom surface 
       572  lateral surface 
       611  main body 
       613  conical internal surface 
       614  cylindrical hole section 
       621  positioning sleeve 
       626  positioning projection 
       627  positioning projection 
     +Numbers in FIGS. 18-20 
     FIG. 29 
       627  positioning projection 
     FIG. 30 
       636  positioning projection 
       637  edge 
     +Numbers in FIGS. 24-28 
     FIGS. 31,  22 , and  33   
       1000  support 
       1001  implant 
       1003  axis 
       1005  anchoring part 
       1007  head or head part 
       1008  first end 
       1009  second end 
       1011  cylindrical section 
       1013  expanding trumpet-shaped section 
       1015  external thread 
       1016  rib 
       1017  top 
       1018  end section 
       1021  shoulder 
       1022  shoulder surface 
       1023  annular surface 
       1025  head section parallel to axis 
       1027  conical head section 
       1029  annular groove 
       1030  peripheral surface 
       1031  end surface 
       1033  positioning surface 
       1025  bind hole 
       1036  opening 
       1037  internal thread 
       1038  cylindrical hole section 
       1039  bottom 
       1051  groove (=chip groove) 
       1053  chip surface 
       1067  positioning projections 
       1068  first positioning interstice (=positioning groove) 
       1069  second positioning interstice (=positioning groove) 
     FIGS. 34,  35  and  36   
       1071  groove and/or hole 
       1027  central hollow space 
     FIG. 37 
       1081  groove 
     FIGS. 38 and 39 
       1091  annular groove 
       1093  blind hole 
       1094  opening 
       1095  bottom 
       1097  lengthwise hole 
     FIG. 40 
     As Previous Figures 
     FIGS. 41 to  43   
       1111  bone 
       1113  gingiva 
       1115  healing element or healing cap 
       1116  supporting surface 
       1117  cylindrical section 
       1119  screw 
       1120  suture 
     FIG. 44 
       1151  device 
       1153  superstructure element  163  interior space 
       1164  conical supporting surface 
       1165  conical internal surface 
       1167  conical supporting surface 
       1171  occlusal screw 
       1172  head 
       1173  conical section 
       1174  cylindrical shaft section 
       1175  thread part 
     FIGS. 45 and 46 
       1201  crown 
       1211  external surface 
       1212  section of external surface 
       1213  annular groove 
       1224  shoulder section 
     FIGS. 47 and 48 
       1241  positioning section 
       12243  positioning projections 
       1245  positioning interstice 
     FIG. 49 
       1243  first positioning projection 
       1254  second positioning projection 
     FIGS. 50 and 51 
       1271  lower section of out surface 
       1273  upper section of external surface 
       1275  axis 
     FIG. 52 
     As Previous Figures 
     FIG. 53 
       1291  ground surface 
     FIG. 54 
     As Previous Figures 
     FIGS. 55 to  58   
       1301  impression element (=impression cap) 
       1303  impression spatula 
       1305  impression material 
       1307  impression surface 
       1311  manipulating implant 
       1315  anchoring part 
       1317  head 
       1321  shoulder 
       1331  master model 
     FIG. 63 
       1425  annular depression (=groove) 
       1427  bottom 
       1428  first surface 
       1429  second surface 
     FIG. 64 
       14351  turn of rib 
       1453  foot 
       1454  flank 
       1461  depression or channel 
       1464  radial straight line 
     FIG. 65 
       1468  positioning interstices or positioning grooves 
     +Numbers of FIGS. 31 and 32