CH673579A5 - - Google Patents

Description

DESCRIPTION

The invention relates to bioactive permanent implants made of special glass ceramics which can be used in human medicine, in particular as a hard tissue substitute. The permanent implants can e.g. used in orthopedics, stomatology, maxillofacial surgery, ear, nose and throat and ophthalmology.

To characterize the known technical solutions in the field of the development of permanent implants for use in human medicine, two aspects in particular need to be analyzed in more detail:

First, the shortcomings of the prior art, which are caused by the type of material, and secondly, the shortcomings of known permanent implants, which are caused by their shape, their outer shape.

With regard to suitable materials for implants for hard tissue replacement in human medicine, in addition to metals, sintered ceramics, glasses and glass ceramics have recently become known. While the metals have the disadvantage that they have no bioactive properties, ceramics, e.g. B. are based on hydroxyapatite, bio glasses and bio glass ceramics that are bioactive, that is, form a direct connective tissue-free bond to the living bone. Such bioactive glass ceramics are e.g. in DE-OS 2 818 630, DE-OS 2 326 100 and DE-OS 3 435 348.

However, these bioactive glasses, ceramics and glass ceramics also have considerable disadvantages in terms of their suitability as permanent implants - despite their bioactive properties. This becomes clear in the following examples of specific applications.

The examples also demonstrate the interrelation between the type of material and the shape of the implants. In this discussion, bioactive implants, such as. B. glasses and glass ceramics and biocompatible implants, e.g. the metals to be included:

- For the hard tissue replacement in human medicine, the tooth replacement or the tooth root replacement is of particular importance. However, all implants developed so far have the disadvantage that they do not match the specific extracted tooth or. the tooth root are reproduced in their shape, but that they represent finished products of a predetermined shape (DE-OS 3 112 868, DE-OS 2 733 394, DE-OS 2 755 751, DE-OS 2 717 506, DE-OS 2 659 591) and complicated milling tools are required to manufacture the implant bed in human bone. Adaptation of the implant to physiological or anatomical conditions is excluded and the use of previously known implants for premolar and molar replacement in the upper jaw is therefore not possible and there are problems in the lower jaw. By coating metals that are biocompatible and only cause contact osteogenesis with bioactive material, the desired composite osteogenesis (bioactivity) for dental implants could be achieved. Glass ceramics and glasses of different compositions were used (DE-OS 2 659 591, DE-OS 2 717 506, DE-OS 2 733 394, DE-OS 3 112 868 and others). The disadvantage, however, is that the implants developed require mechanics that are sometimes complicated to accommodate the prosthetic crown replacement, in particular to reduce the chewing pressure in the bone.

Another disadvantage of previously known bioactive implants for tooth root replacement is the uncontrolled surface solubility and the resulting connective tissue incision, which results in a reduction in the excitation for composite osteogenesis due to material aging and changes in the surfaces. The known bioglass ceramics can only be insufficiently corrected intraoperatively and thus cannot be adapted to anatomical conditions, which is disadvantageous for the stabilization of the tooth root. The calcium hydroxide preparations with self-hardening dental cement used for the intradental covering of the pulp cavity have the disadvantage that toxic damage and mechanical irritation of the sensitive tooth pulp tissue can occur.

- In order to correct malpositions or deformities of the human support and locomotor system, metal implants are used to a large extent in addition to the body's own transplants, which contain the risks of a second operation and the biological weakening of the chip removal bearing. Such metal implants such as metal nets (DE-PS 3 106 917) or screws and plates have the disadvantage that they can only remain temporarily in the organism due to electrolysis processes and the mostly non-bioinert behavior of the materials, ie they are not permanent implants. A direct bond between the bone bed and the implant is also possible with metallic materials by means of appropriate porous or different surface designs, e.g. described in DE-OS 2 127 843 and in DE-OS 2 755 762, not possible. The intensive mechanical interlocking is at best due to contact osteogenesis.

A coating of the metal implants with bioactive glasses and glass ceramics, e.g. DE 2,659,591, DE-OS

2,717,506, DE-OS 2,755,751, DE-OS 2,733,394, DE-OS

3 112 868, achieved the achievement of bioactive properties, but uncontrolled surface solubilities occurred disadvantageously. Another disadvantage of these implants is that they cannot be machined mechanically with conventional tools, so that the shape cannot be corrected under operating conditions. This disadvantage also applies to calcium phosphate coatings on titanium bodies (DE-OS 2 928 007).

- Other known technical solutions for implants, in particular for use in the orthopedic field, have the additional disadvantage that for anchoring the bioinactive implants, such as. B. metals or sintered corundum, additional bone cement is required.

- Similar disadvantages as the metals also have organic polymer materials, which are used as implants for hard tissue replacement. Although e.g. There are considerable differences with regard to the physical properties of the two material groups, and relatively complex parts that can perform fixation and holding functions can also be produced from polymers (plastic materials) due to good processing options, but these materials are not bioactive.

The development of bioactive glass ceramics which can be machined and which can be used in medicine from the experience of animal experiments are described in DD-WP 219 017 and DD-WP 238 619.

The aim of the invention is the development of bioactive permanent implants made of a universally usable material, which is to be distinguished from the previously known implants for hard tissue replacement in human medicine by outstanding combinations of properties and which is intended to open up completely new areas of application and possibilities in some cases by appropriate design.

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The object of the invention is to develop bioactive long-term implants for hard tissue replacement in human medicine, this development being carried out in the unity of material type, composition and structure, shape and design of the products and only one basic material for comprehensive shaping of long-term implants using the to guarantee advantageous material properties.

This object is achieved according to the invention in that the bioactive permanent implants made of machine-workable bioactive glass ceramic of the composition in

Dimensions-%

SiO-.

= 29.5-

■ 32.5

A1-.Ö,

= 14.5-

■ 17.5

MgO

= 14.5-

16.5

Na-> 0

= 2.0-

3.0

K? Ö

= 5.5-

6.5

F

= 5.0-

6.0

CaO

= 13.0-

15.0

PÏOÎ

= 10.0-

12.0

and the excreted crystal phases of mica from 50% by volume to 80% by volume and apatite from 15% by volume to 30% by volume, and that the solid bodies made of this glass ceramic for the substitution of diseased, malformed or damaged human bones of the shape correspond to healthy human bones and that to correct malpositions or deformities, the solid bodies have a simple shape that deviates from the natural shape of human bones.

It was surprisingly found that with a single permanent implant material, as evidenced by the very narrowly limited composition range, a material that is universally applicable for hard tissue replacement is particularly suitable. This was obviously made possible by the fact that the structure of the material made of 50-80% by volume of mica, 15-30% by volume of apatite and glass phase was achieved only with this special composition, the manufacture of the permanent implants according to the invention in their shape and with their particular Properties allowed. The microstructure, such as the size and «arrangement» of the crystals to each other and in relation to the glass phase, is of great importance. The advantageous properties of the bioactive permanent implants according to the invention will above all be the diverse possibilities of the original formation. the z. B. centrifugal casting and pressing include, the excellent machinability, the surprisingly high bioactivity, the excellent long-term stability and the combination of the physical-chemical and mechanical parameters. Only this interaction of all these properties or the complex realization of this condition structure in the unity of the type of material, composition, structure, special properties and shape of the products enabled the broad application and overcoming of the disadvantages of the prior art.

The advantages that a single material ensures extensive use as a long-term bioactive implant are many. It starts with the advantageous master shaping, which can take place for different starting products under similar or the same technical and technological conditions. Furthermore, the processing and upgrading of the glass ceramic can be carried out according to uniform parameters and the handling for direct use in medicine can be standardized, even for shipping there are advantages.

Another advantage of the permanent implants according to the invention is that additional components in the material such as. B. FeO. Fe203. TiCK Mn02, NiO. Cr2Oj up to 2% by mass and CI "up to 1% by mass, for example for coloring, can be contained without its advantageous basic properties being impaired. In the case of the Cl" additions, an improvement in the technological properties of the melt is even achieved.

This staining of implants is particularly favorable for applications in the tooth area, where natural tooth staining can largely be achieved for aesthetic reasons.

The advantageous shaping of the permanent implants according to the invention in the unit of original shaping and processing enables human bones to be directly reproduced in their original shape, which is very advantageous for use as a hard tissue replacement material in humans and brings about a significant advance over the prior art. Such special implants are e.g. in maxillofacial surgery or ear, nose and throat medicine, where implants that are sometimes made up of individual parts and are often not fit, are mechanically poorly anchored. This type of permanent implant according to the invention includes e.g. the implants directly simulating the skull bones or partial areas, the zygomatic bone or the orbital floor or the teeth. Additional anchors, e.g. Drilling is possible.

Among the long-term implants according to the invention, which are directly modeled on the shape of human bones, the dental implants, as typical representatives of their main group, take on special importance in addition to orbital floor implants, etc. These bioactive permanent implants according to the invention in the form of human teeth are produced individually by direct replication / molding according to the respective human tooth removed from its tooth compartment. For this, after modeling the human tooth, e.g. B. by wax modeling, for example, a centrifugal casting process are used to manufacture the semi-finished implant products. The advantage over the prior art is above all that a significantly improved mechanical anchoring of the dental implants is achieved because the implant has a firm fit in the tooth compartment, and the high bioactivity leads to a direct bond between the implant and the tooth compartment. In known dental implants, the surface is provided with retentions to prevent rotation and to improve the anchoring of the implants. These retentions are not absolutely necessary for the implants according to the invention.

The permanent implants according to the invention in the form of human teeth can, according to the invention, represent a combination of solid individual bodies made of glass ceramic. These individual bodies have the shape of tooth roots and tooth crowns or parts thereof. At the same time, it is possible for the glass ceramic tooth root according to the invention, e.g. a metal crown or parts of it are applied. Special shapes, as represented by semicircular or elliptical cross sections and peg arrangements on the tooth root for receiving crown implants, ensure good fit and increased functionality of the implants. This functionality for particularly stressed areas can be achieved by inserting a high-strength body e.g. a metal pin can be raised into the tooth root implant. For this purpose, the tooth root implant has a threaded bore.

In addition to the direct replication of human tooth roots, the tooth root implants according to the invention can have a shape that deviates from the shape of human tooth roots. For example, by using the advantageous machinability, the tooth root implants have the shape of truncated cones5

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ten tips and retention wedges (Figure 2). It is also advantageous if the retention wedges have a triangular cross section which tapers at an angle 7 of 5 ° to the root tip, the end face 5 of which forms an angle 6 of 90 ° to 150 ° with the implant surface and the legs of which form an angle 4 of 90 ° to 105 °. Transition zones 11 for attachment of the gingiva are also advantageous. According to the invention, further tooth root implants are characterized in that the cross sections have two semicircular sides 9, which can decrease in size towards the tip, and two flat surfaces 10, which can have the shape of a triangle.

Special small round conical implant plates are very suitable as part of a tooth to cover the pulp roof.

According to the invention, due to the special combinations of properties of the glass ceramic material, in addition to long-term bioactive implants which have the shape of human bones, long-term bioactive implants which have a shape different from that of human bones could also be developed. These last-mentioned permanent implants thus fulfill all main functions in the same way as natural bone or implants with a bone-like shape and shape, e.g. Hold and support function, i.e. Power transmission and absorption in the broadest sense, fixation, bioactive ingrowth with the living hard tissue etc. With this function determination of the permanent implants according to the invention at certain points in the supporting and musculoskeletal system of the human being, his outer shape is determined and determined at the same time. The basic type of these implants is a prism, a cylinder, a pyramid, a truncated pyramid and a truncated cone. Implants according to the invention are derived therefrom, for example with an X, Y, H or cuboid or non-renal cross section. Additional surface designs e.g. B. grid for vertebral body implants, for wedges, etc., bring about an improved anchoring of bone and implant. Additional structural designs, such as. B. Holes and breakthroughs in implants allow better anchoring and fixation and blunting of edges, which are very possible due to the good mechanical processing of the implants, ensure increased tissue friendliness and promote overgrowth.

While maintaining these advantageous design elements, wedge-shaped permanent implants with different cutting edge designs, e.g. B. pointed, rounded, blunted, especially used to correct misalignments and deformities of the human musculoskeletal system.

According to the invention, cylindrical and conical permanent implants with a head, shaft and tip part were further developed, in particular for fixation. Special designs are head parts as cylindrical implants with a central hexagon socket and slots. The shaft can e.g. prism-like, cylindrical or a truncated cone, while for special stabilization in the bone or tissue the surfaces are provided with grooves and knobs.

The tip can be a cone, truncated cone or pyramid.

In particular, the advantageous mechanical processing, bioactivity and biocompatibility enabled the development of permanent implants according to the invention in the form of a hollow cylinder with an internal thread and a supporting disk.

The permanent implants according to the invention are produced in two process stages, namely the production of the starting glass and the thermal aftertreatment of the starting glass in order to achieve in situ crystallization in the range from 600 ° to 1100 ° C.

Thermal treatment options include:

a) 1000 ° C / 1 h b) 750 ° C / 0.5 h and 900 ° C / 5 h.

Selected, special properties of the permanent implants according to the invention are as follows:

- very good to excellent machinability;

- chemical resistance according to hydrolytic classes 2 to 3;

- excellent bioactivity;

- very good mechanical strength, as bending strength up to 220 MPa;

- high compressive strength of more than 500 MPa;

- hardness higher than 300 HV 10;

- modulus of elasticity of 70-80 GPa;

- The linear thermal expansion coefficient of approx. 12.5 • IO "6 K-1 allows combination options with high-strength base bodies, eg based on metal.

The bioactivity was demonstrated on the basis of animal experimental and clinical trials on humans. With regard to the quantitative determination of a value for the biologically active behavior, the bond area in% between bioactive glass ceramic and living bone was determined in animal experiments after lying down for up to 2 years. For example, the statement “excellent” means that more than 70% of the bond is achieved, whereby a bond share of approx. 70% is reached 16 weeks after implantation and this share increases with increasing implantation time, and this bond remains stable even after years. One reason for this is that the permanent implants according to the invention have the advantage over all previously known bioactive materials that the reaction zone between bioactive glass ceramic and bone is only a maximum of 10 (im even after years. This is simultaneously for use as a solid material or as a thin layer material or Granules are a very important advantage of these permanent implants, because the composite is retained and there are no interferences affecting the biomaterial and the composite area, which have disadvantageous properties.

In addition to the composition, the structure is a very important factor for the advantageous properties. It was shown that only with the structure according to the invention made of apatite, mica and glass phase can the special properties be achieved and the permanent implants according to the invention with a largely sophisticated shape can be produced from the material.

The following examples provide a more detailed explanation of the shapes and advantageous possible uses of the permanent implants according to the invention based on brief explanations of FIGS. 1-5.

example 1

Such a bioactive permanent implant according to the invention is described below, which is representative of the main group of those implants which have the shape of human bones.

An example of a dental implant that has the outer shape of human teeth of the upper and lower jaw is shown.

Figure la) shows a tooth implant, which consists of a tooth root implant and a tooth crown implant of the glass ceramic according to the invention and the shape of which was directly modeled on the original natural tooth that was in the same tooth compartment.

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Figure 1b) shows in the section of X-Y in Figure la) that the tooth root implant has a pin 1 for receiving the crown implant 2.

Figure lc) shows a further variant of the design of the tooth root implant, namely in that the tooth root implant has a threaded bore for receiving e.g. a high-strength pin made of metal. This solution is advantageous for dental implants that are exposed to increased mechanical stress.

Example 2

Such a bioactive permanent implant according to the invention, which belongs to the main group of those implants which have a modified, simplified form in relation to natural human bones, is shown below. Figure 2 describes permanent implants for dentures in human medicine.

FIG. 2a) shows a tooth root implant that is suitable for holding a tooth crown implant. This tooth root implant has retention wedges 3 which are triangular in cross section and which, starting from the center of the implant part located in the bone, are tapered to the tip. The outer edge of the retention wedges 3 directed towards the jawbone forms an angle 7 of 5 ° or less with the implant surface. The end faces 5 of the retention wedges prevent the implant from slipping out. The end faces of the retention wedges form an angle 6 of 90 ° to 150 ° with the implant surface. The two legs of the retention wedge 3 enclose an angle 4 of at least 90 ° to 105 °. The angle 8 is formed by the implant surface and the implant axis and is known by the size of the implant in comparison to the natural tooth. The implant has a transition zone 11, which is characterized by a larger angle 6 or 7 than described above.

Figure 2b) shows a tooth root implant, the cross section of which consists of two semicircular surfaces 9 and two flat surfaces 10. In addition, retention wedges can be attached.

Figure 2c) represents a permanent implant for tooth roots. The shape of the implant, as a round conical plate with one-sided pin, allows use as a pulp roof in natural teeth.

Example 3

This exemplary embodiment describes permanent implants according to the invention which have an outer shape which deviates from the natural shape of the human bones in order to correct malpositions and deformities on the human musculoskeletal and supporting apparatus. 3 shows cross sections through corresponding implants, such as e.g. 3a) implant in the form of a hollow cylinder; 3b) U-shaped bent implant; 3c) implant in the form of a double T-beam; 3d) cruciform implant; 3e) cuboid implant with bore. By additional surface design according to the invention, such as grid arrangement or by e.g. convex shape and in connection with the advantageous material properties, these permanent implants are preferably suitable for e.g. overgrown with adjacent natural vertebral bodies and can therefore be used advantageously as an implant for ventral spondylodesis.

Another type of a permanent implant according to the invention is shown in FIG. 3f) with a kidney-shaped cross-section in a side view and FIG. 3g) in a top view. These figures show the preferred arrangement of the grid area 12, which contributes to the fact that the natural human being adjacent to the grid area Bones are anchored more easily and grown together with the permanent implant. This makes the preferred use as a vertebral body implant obvious.

Example 4

This exemplary embodiment provides a further reduction of implants according to the invention, which are to be classified in the same main group as that described in Example 3. They are implants that have a shape other than natural bones and are preferably used to correct the human musculoskeletal system. In addition to the implants set out in Example 3, wedge-shaped and prism-shaped permanent implants are shown in more detail in this example.

4a) shows a cross section through a prism-shaped implant and FIGS. 4b) and 4c) show a top view of a permanent implant derived from the typical wedge shape in the form of a semicircular disk (FIG. 4b); Figure 4c) in side view. By using the wedge effect of the implants according to the invention, for example, a lifting of the tibial head and thus a correction of the human musculoskeletal system can be effectively achieved.

In Figure 4d) (top view) and 4e) (side view), a disc-shaped permanent implant with a square cross-section and a central bore, as well as a countersink on one side, is shown that contains grooves on its underside and is advantageously used as a washer for fixation.

Example 5

In the following, further exemplary embodiments of permanent implants according to the invention are presented which differ in their outer shape from natural bones. Permanent implants according to the invention with a cylindrical or conical shape are reduced in size (FIG. 5). The cylindrical implants according to the invention are advantageously used in the field of hand surgery. FIG. 5 a) represents a fixation implant for knee constructions in the form of a truncated cone. According to the invention, the implants can be provided with a head and tip part. These latter implants, shown in Figure 5b) are e.g. can advantageously be used as an implant for the fixation of ligaments on the skeletal system.

Figure 5c) shows a permanent implant according to the invention in the form of a hollow cylinder. The hollow cylinder 13 is surrounded here with a curved support disk 14, in the openings 15 with e.g. circular diameter can be incorporated. The hollow cylinder contains an internal thread. Since a known interchangeable lens can be screwed into this hollow cylinder implant in a watertight manner and the implants have the advantageous properties mentioned, use in ophthalmology as a keratoprosthesis is advantageous.

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3 sheets of drawings

Claims (28)

673,579 2nd PATENT CLAIMS 1. Bioactive permanent implants in the form of solid bodies for the substitution of diseased, malformed or damaged human bones and for the correction of deformities or malformations of the human supporting and musculoskeletal system, characterized in that they contain machinable bioactive glass ceramics of the composition in mass%: 29.5-32.5% Si02 14.5-17.5% AI2O3 14.5-16.5% MgO 2.0-3.0% Na20 5.5-6.5% KzO 5.0-6 , 0% F 13.0-15.0% CaO 10.0-12.0% P205 and excreted crystal phases: Contain 50-80 vol% mica and 15-30 vol% apatite. 2. Bioactive permanent implants according to claim 1, characterized in that the machinable bioactive glass ceramic in its composition additionally the components FeO, Fe203, TÌO2, MnC> 2, NiO, Cr2Û3 to 2% by mass and Cl ~ to 1% by mass individually or in a mixture. 3. Bioactive permanent implants according to claim 1 and 2, characterized in that they have the outer shape of human teeth of the upper and lower jaw. 4. Bioactive permanent implants according to claim 1 to 3, characterized in that they represent a combination of solid individual bodies, which in their entirety have the outer shape of natural human teeth. 5. Bioactive permanent implants according to claim 4, characterized in that the solid individual bodies have the shape of tooth roots, tooth crowns or parts thereof. 6. Bioactive permanent implants according to claim 5, characterized in that the tooth root implants have a semicircular or elliptical cross section and have a pin on their base surface. 7. Bioactive permanent implants according to claim 5, characterized in that the tooth root implants have a bore with an internal thread. 8. Bioactive permanent implants according to claim 1 and 2, characterized in that they represent dental implants consisting of tooth crowns and tooth roots, the tooth root implants having a simplified form deviating from the natural shape of the human tooth roots. 9. Bioactive permanent implants according to claim 8, characterized in that the tooth roots represent shapes of truncated cones with rounded tips and are provided with retention wedges (3) (Figure 2a). 10. Bioactive permanent implants according to claim 8 and 9, characterized in that the retention wedges (3) have a triangular cross section which tapers to the root tip at an angle (7) of 5 °, the end face (5) with the implant surface at an angle (6) forms from 90 ° to a maximum of 150 ° and its leg encloses an angle (4) from 90 ° to a maximum of 105 ° (Figure 2a). 11. Bioactive permanent implants according to claim 8 to 10, characterized in that the tooth root implants have a transition zone (11) for the attachment of the marginal gingiva (Figure 2b). 12. Bioactive permanent implants according to claim 8 to 11, characterized in that the cross sections of the tooth root implants have two semicircular sides (9) and two flat surfaces (10) and these implants can have additional retention wedges (3) (Figures 2a and 2b). 13. Bioactive permanent implants according to claim 8 to 12, characterized in that the radii of the round sides (9) decrease towards the tip (Figure 2b). 14. Bioactive permanent implants according to claim 8 to 13, characterized in that the flat surfaces (10) have the shape of a triangle, the base being crown-up and that both surfaces form a common angle towards the tip corresponding to the selected radii. 15. Bioactive permanent implants according to claim 1 and 2, characterized in that they have as tooth implants the shape of round conical plates with one-sided pin as a holding element, wherein the implants can be used as a pulp roof in natural teeth. 16. Bioactive permanent implants according to claim 1 and 2, characterized in that they are simulated for the substitution of sick or damaged bones or bone parts in the skull area of the natural bone shape. 17. Bioactive permanent implants according to claim 1 and 2, characterized in that they have a simple outer shape deviating from the natural shape of human bones to correct malpositions and malformations, the shape being defined by the area in which the implants are received in the supporting and locomotor system of humans, and the basic type is a prism, a cylinder, a pyramid, a truncated pyramid or a truncated cone. 18. Bioactive permanent implants according to claim 17, characterized in that they have an X, Y, H, U, rectangular, square or kidney-shaped cross section. 19. Bioactive permanent implants according to claim 17, characterized in that the surfaces are provided with a grid, flat or convex. 20. Bioactive permanent implants according to claim 17 and 19, characterized in that they are wedge-shaped, the cutting edge having a pointed shape, blunted or rounded. 21. Bioactive permanent implants according to claim 17, characterized in that they have single or multiple bores or breakthroughs of any geometric designs. 22. Bioactive permanent implants according to claim 17, 20 and 21, characterized in that all corners, edges, openings and bores are blunted or rounded. 23. Bioactive permanent implants according to claim 17, characterized in that they represent cylindrical and conical implants with head, shaft and tip part. 24. Bioactive permanent implants according to claim 23, characterized in that the head part is a 3- to versatile prism or a cylinder with a central hexagon socket, slots, cross slots, 3- to versatile prisms and retention ellipsoids. 25. Bioactive permanent implants according to claim 23, characterized in that the shaft is prismatic or cylindrical or represents a truncated cone or truncated pyramid. 26. Bioactive permanent implants according to claim 25, characterized in that the surface of the shaft has depressions, knobs and thread-like courses of any geometry. 27. Bioactive permanent implants according to claim 23, characterized in that the tip is designed as a cone, pyramid, truncated cone or truncated pyramid and the resulting stump surfaces are round or ellipsoid. 28. Bioactive permanent implants according to claim 17, characterized in that they have hollow cylinders (14) with inner5 10th 15 20th 25th 30th 35 40 45 50 55 60 65 3rd 673,579 thread and outer curved support disc (15), represent (Figure 5c).