FR2602969A1 - BIOLOGICALLY ACTIVE PERMANENT IMPLANTS FOR STOMATOLOGY APPLICATIONS - Google Patents

Abstract

BIOLOGICALLY ACTIVE PERMANENT IMPLANTS CONSISTING OF A BIOLOGICALLY ACTIVE CERAMIC MATERIAL THAT CAN BE WORKED MECHANICALLY AND HAVING THE FOLLOWING WEIGHT COMPOSITION, IN: SIO 29.5 TO 32.5, ALO 14.5 TO 17.5, MGO 14.5 TO 16, 5, NAO 2.0 A 3.0, KO 5.5 A 6.5, F 5.0 A 6.0, CAO 13.0 A 15.0, PO 10.0 A 12.0, AND BY SEPARATE CRYSTALLINE PHASES CONSISTING OF 50 TO 80 BY VOLUME OF MICA AND BY 15 TO 20 BY VOLUME OF APATITE FOR APPLICATIONS IN STOMATOLOGY.

Description

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  The present invention relates to biologically active permanent implants, consisting of special vitreous ceramic materials, which can be used in human medicine, especially for the replacement of hard tissue. Permanent implants can be used, for example, in orthopedics, stomatology,

  in facial and maxillary surgery, otolaryngology and ophthalmology.

  The technical solutions known in the field of the development of permanent implants for use in human medicine must be examined in particular from two points of view, taking into account, on the one hand, the deficiencies of the state of the art. the technique, due to the nature of the material, and, secondly, the shortcomings of known permanent implants, due to their structure and their external shape. As materials which can be used as implants for the replacement of hard tissues in human medicine, sintered ceramic materials, glasses and vitreous ceramic materials have been known for some time in addition to metals. While metals have the disadvantage of not being biologically active, it has been possible to develop ceramic materials, for example based on hydroxyl apatite, "bio-glasses" and ceramic materials with "bio-glasses" Which are biologically active, that is, which provide a direct connection without connective tissue to the living bone. Glassy ceramic materials of this type are described, for example, in DE-OS 281 863 O, DE-OS 232 610 0 and DE-OS 343 534 8. However, these glasses, ceramic materials and biologically active vitreous ceramic materials have, despite their biological activity properties, sometimes significant disadvantages in

  regarding their use as permanent implants.

  This is evidenced by the following examples of actual use cases. These examples at the same time highlight the existing reciprocal relationship

  between the type of material and the shape of the implants, which may be biologically active implants, such as, for example, glass and ceramic materials, or biologically compatible implants, such as, for example, metals.

  For the replacement of hard tissue in human medicine, the replacement of teeth or tooth roots is of particular importance. However, all the plants made up to now have the disadvantage that their shape does not exactly correspond to that of the extracted tooth or tooth root, but that being prefabricated they have a definite shape (DE-OS 311). 286 8,

  DE-OS 273 339 4, DE-OS 275 575 1, DE-OS 271 750 6,

  DE-OS 265 959 1) and that the realization of the bed of the implant in the patient's bone requires complicated milling operations. Any adaptation of the implant to physiological or anatomical conditions is excluded and it is the reason why the use of implants known until now for the replacement of premolars and molars in the upper jaw is not possible and poses problems for the lower jaw. Metal coating, which is biologically compatible and causes only contact osteogenesis, with a biologically active material, has made it possible to obtain the desired binding osteogenesis (biological activity) for dental implants. Vitreous ceramic materials and glasses of various compositions have been used (DE-OS 30 265 959 1, DE-OS 271 750 6, DE-OS 273 339 4, DE-OS 311 286 8, in particular). The disadvantage of these solutions is that the implants in question require a partially complicated mechanical device for the insertion of the prosthesis replacing the dental crown, in particular for the reduction of the chewing pressure.

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  in the bone. Another disadvantage of the known biologically active implants used for the replacement of dental crowns is the lack of control of the surface solubility and resulting nick in the connective tissues, which weakens the tendency for binding osteogenesis. , by aging of the material and modification of the surfaces. The known bio-glass ceramic materials are internally acting and can not be sufficiently corrected or, therefore, adapted to anatomical conditions, which has drawbacks for the stabilization of the root of the tooth. Calcium hydroxide preparations comprising a self-hardening cement which

  are used to cover the cavity of the pulp in the teeth have the disadvantage of risking to cause toxic alterations and mechanical irritation of the sensitive tissue of the dental pulp.

  To correct defective attitudes or malformations of the carrier and locomotor system of the human body, we use extensively, next to the transplants taken from the body, which implies the risks of a double operation and a weakening of the biological zone. transplant harvesting, metal implants. These metal implants, such as metal networks (DE-PS 3 106 917) or screws and plates, have the disadvantage that due to the phenomena of electrolysis that occur and the fact that in general the materials used do not do not behave in a biologically inert manner, they can only stay in the body for a short time, that is, they do not constitute permanent implants. A direct connection between the bone and the implant in the case of metallic materials is not possible because of the porosity and the difference in surface structure, as indicated by DE-OS 2 127 843, and DE-OS 2,755,762. In the best case, the intense mechanical endurance is reduced to contact osteogenesis. The coating of metal implants with glasses and biologically active ceramic materials, as in the case of

  DE 2,659,591, DE-OS 2,717,506, DE-OS 2,755,751, DE-OS

  2,733,394, DE-OS 3,112,868, has obviously enabled biological activity properties to be obtained, but the lack of control of surface solubilities leads to disadvantages. Another disadvantage of these implants is that they can not be worked mechanically by traditional tools, so that a correction of the shape in the operating conditions is not possible. This disadvantage also exists

  in the case of calcium phosphate coatings on titanium bodies (DE-OS 292 800 7).

  Other known technical solutions involving the use of implants, in particular for orthopedic applications, have the additional disadvantage that, for the anchoring of biologically active implants, for example metals or sintered corundum, it is necessary to

in addition, a bone cement.

  Metal-like disadvantages are also presented by polymeric organic materials which are used as implants for hard tissue replacements. Even if the two groups of materials have significant differences, for example as regards the physical properties and if the polymers (plastic materials), because of the machining facilities they offer, allow the manufacture of 30 relatively complicated pieces which can perform fixing and holding functions, these materials do not

are not biologically active.

  The development of biologically active vitreous ceramic materials which can be machined by machines and, taking into account the results obtained in

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  veterinary field, can be used in medicine,

  is described in DD-WP 219,017 and DD-WP 238,619.

  The object of the invention is the production of biologically active permanent implants from a material of universal use which, in comparison with the implants hitherto known for the replacement of hard tissues in human medicine, stands out by a combination of eminent properties and, allowing

  to create new forms, open new possibilities and new areas of use.

  The object of the invention is therefore the development of biologically active permanent implants for the replacement of hard tissues in human medicine, this development being that of a whole constituted by the type, the composition and the structure of the material and the shape and appearance of the products and a single basic material to ensure complete modeling of permanent implants by

  the use of the advantageous properties of the material.

  According to the invention, this object is achieved by the fact that the biologically active permanent implants consist of a vitreous biologically active ceramic material which can be machined mechanically and having the following composition, SiO2 = 29.5 to 32.5

A1203 = 14.5 to 17.5

  MgO = 14.5 to 16.5 Na2 0 = 2.0 to 3.0 H2O = 5.5 to 6.5 F = 5.0 to 6.0 CaO = 13.0 to 15.0

P205 = 10.0 to 12.0

  P205 and by the separated crystalline phases, that is to say 50% to 80% by volume of mica and 15% to 30% by volume of apatite, and that the massive bodies made from this vitreous ceramic material for bone replacement

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  Sick, malformed or damaged human beings have the same form of healthy human bones and, for the correction of defective attitudes or malformations, the massive bodies in question have a simple form deviating from the natural form of human bones. Surprisingly enough, it has been found that with a virtually unique implant material, as the composition limits show, very close together, there is a universal application material for the replacement of hard tissue. . This is obviously possible only because it is only with this specific composition that the structure of the material constituted by 80% by volume of mica, by 15 to 30% by volume of apatite and by the glassy phase allows the manufacture of permanent implants according to the invention in their form and with their particular properties. The structure, that is to say the dimensions and the arrangement of the crystals with respect to each other and with respect to the glassy phase, is of great importance in this case. The advantageous properties of the biologically active permanent implants according to the invention include especially multiple molding possibilities, including for example centrifugal casting and compression, the possibility of specifically mechanical machining, the biological activity of a surprising magnitude, excellent stability over a long period as well as the combination of physicochemical and mechanical parameters. Only this combination of all these properties or the complex realization of this structure in the set consisting of the nature of the material, its composition and structure, the special properties and shape of the products allows a wide use and elimination of cons

  corresponding to the state of the art.

  The advantages that result from the fact that a single material is likely to be used in a vast

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  field as a biologically active permanent implant are multiple and varied. It is first of all the fact that the forming, for similar starting materials, can be carried out under similar or identical technical and technological conditions. Subsequently, the machining and subsequent processing of the vitreous ceramic material can be carried out according to unified criteria and its handling for direct application in medicine, which has advantages also for the shipping of the products. Another advantage of the permanent implants according to the invention is that the material may contain addition products, for example FeO, Fe 2 O 3, TiO 2 ,. > n02, NiO, Cr203 up to 2% by mass and C1 up to 1% by mass, to ensure the coloration, without

  its advantageous properties are altered. The additions of C1 even give rise to an improvement in the melting properties.

  This staining of the implants is particularly advantageous in dentistry, where it allows, for

  aesthetic reasons, to virtually restore the natural color of the teeth.

  The advantageous solution of giving the permanent implants the desired shape through a unitary operation comprising initial forming and percutting makes it possible to directly reproduce the human bones with their original shape, which has many advantages for the use of the implants. implants as a substitute for hard tissue in the human body and represents a considerable advance in relation to the state of the art. Special implants of this type are needed, for example in maxillofacial surgery or otolaryngology where, up to the present time, implants formed of parts, of shape that are often unsuitable and mechanically anchored, have been used in part. To this type of permanent implant according to the invention belong, for example, the

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  implants directly reproducing the skull or parts thereof, the molar bone or the base of the orbit or the teeth. Additional anchors can be made,

for example bores.

  Among the permanent implants according to the invention which directly reproduce the shape of human bones, the dental implants, which are, with the implants of the base of the orbit etc., the typical representatives of their group, occupy a special place. These biologically active permanent implants of the invention having the shape of human teeth are manufactured by direct reproduction, in each case, of a human tooth extracted from its socket. Then, after shaping the human tooth, for example after wax modeling, a centrifugal casting process can be used to manufacture the implant half-product. The advantage of this method compared to the state of the art is primarily that it allows to obtain a better mechanical anchoring of dental implants, because the implant is firmly engaged in the cell and the high activity biological

  ensures a direct connection between the implant and the cell.

  In the case of known dental implants, there is provided on their surface, to prevent rotation and to improve the anchoring of the implants, retention devices. In the case of dental implants according to the invention,

  these retention devices are not absolutely essential.

  The permanent implants according to the invention which reproduce human teeth may, according to the invention, be a combination of individual solid bodies of vitreous ceramic material. These individual bodies have the shape of roots or crowns of teeth or parts of them. It is at the same time possible that on a vitreous ceramic tooth root 35 is for example placed a metal crown or some of its parts. Certain special shapes, such as those having, according to the invention, semicircular or elliptical sections or comprise tenons at the level of the root of the tooth for fixing the crown implants, ensure a good fit of the shapes and an excellent implant behavior. This excellent behavior of the most heavily loaded parts can be further improved by the use of a body of high mechanical strength, for example a metal peg inserted into the root implant. For this, the tooth root implant has a bore having a thread. Apart from the direct reproduction of human tooth roots, the root implants of 15 teeth according to the invention make it possible to perform a

  shape that deviates from that of the roots of human teeth.

  For example, using the advantage of their mechanical machining capability, tooth root implants can be provided with the shape of tree trunks comprising

  rounded corners and retention corners (Figure 2).

  It is also advantageous for the retention wedges to have a rectangular cross-section which tapers towards the tip of the root at an angle θ of 5, the closure surface 5 of which with the surface of the implant 25 is at an angle θ of 90 to 150 and whose sides 4 are at an angle of 90 to 105 with each other. It is also advantageous for transition zones 11 to provide support against the gingiva. According to the invention, other

  Teeth root implants are characterized by the fact that the sections have two semicircular sides 9 which can tap towards the apex and two flat surfaces 10 which may be in the form of a triangle.

  In order to cover the top of the pulp, it is advantageous to use special, small, round and conical implant pads incorporated in the tooth.

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  The invention has made it possible, in view of the particular combinations of properties of vitreous ceramic materials, to develop, alongside biologically active permanent implants, which have the shape of human bones, also other biologically active permanent implants which have a form that deviates from that of human bones. Implants in the latter category fill, in the same way as natural bones or bone-like implants, all the main functions, for example the holding and support functions, ie to say the transmission and absorption of efforts in the broadest sense, fixation, symbiosis by biological activity with the living hard tissue, etc. The function that the permanent implants according to the invention must fulfill at specific locations of the carrier and locomotive apparatus of the man determines at the same time their external form. The basic type of these implants is a prism, a cylinder, a pyramid, a truncated pyramid and a trunk of cene. Implants having an X-, Y-, or parallelepipedal or kidney-shaped section are deduced according to the invention. Additional arrangements of the surfaces, for example frames for vertebral body implants, for corners etc. improve the anchoring of bones and implants. Other assembly devices, for example bores or passages in the implants, allow a

  better anchoring and attachment and softening of the ridges, which is very possible due to the machinability of the implants, improves tissue compatibility and promotes symbiosis.

  These advantageous embodiments make it possible to use permanent corner-shaped implants with edges of different shapes, for example pointed, rounded, truncated, in particular for the correction of defective attitudes and malformations.

of the human musculoskeletal system.

  The invention also allows the development of cylindrical and conical permanent implants comprising a head, a rod and a tip, in particular for fixing. In some special embodiments, the head portions are cylindrical implants having a hex bore and slots. The stem may, for example, be prismatic, cylindrical or truncated, while for better stabilization in bone or tissue the surfaces are provided with

grooves and moldings.

  The tip may be a cone, a truncated cone or

a pyramid.

  In particular, mechanical machining facilities, biological activity and biological compatibility have made it possible to develop permanent implants according to the invention in the form of a hollow cylinder comprising

  an external thread and a support disc.

  The production of permanent implants according to the invention is carried out in two stages which are the manufacture of the starting glass and the heat treatment.

  subsequent flow of the starting glass to obtain a crystallization in situ between 600 and 1100 C.

  The possibilities of heat treatment are,

for example:

  a) 1000 C / i h (b) 750OC / 0.5 h and 900 C / 5 h. The particular properties of the permanent implants 30 according to the invention are as follows: very good machining possibility that can even be excellent - chemical stability according to "hydrolytic class" 2 to 3 - excellent biological activity - very good mechanical strength, resistance to fracture

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  bending up to 220 MPa - high pressure resistance, greater than 500 KPa - hardness greater than 300 HV 10 - modulus E from 70 to 80 GPa - the linear coefficient of thermal expansion, which is approximately 12.5 . 106 K-1, at the same time allows combinations with very strong base bodies, for example based on metals. Biological activity has been demonstrated in animal testing or clinical observations in humans. For the quantitative determination of a value defining the biological activity, the percentage of bonding between biologically active vitreous ceramic material and the period of time up to 2 years was determined in animal tests. the living bone. Thus, for example, the term "excellent" indicates a greater than 70% connection, 70% being achieved already after 16 weeks after implantation, the proportion in question increasing with implantation time and the link remaining stable after years. This result is explained by the fact that the permanent implants according to the invention have, with respect to all the biologically active materials known hitherto, the advantage that the reaction zone between the biologically active vitreous ceramic material and the The bone is, even after years, only 10 "m at the same time, at the same time it is an essential advantage of these permanent implants for their use as solid material or in thin layer or as granular material, because the connection is maintains and no alteration

  properties do not manifest in the biological material or in the binding zone.

  For the advantageous properties in question, a decisive factor, in addition to the composition, is the structure. Experience has shown that only the structure

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  according to the invention, consisting of apatite, mica and a vitreous phase, makes it possible to obtain the particular properties in question and to produce from the material permanent implants according to the invention having the desired shape.

  The invention is described below in more detail by means of exemplary embodiments

referring to the drawing.

Example 1

  This example relates to a biologically active permanent implant according to the invention which is representative of the main group of implants which have the shape

  human bones. It is a dental implant having the outer shape of human teeth of the upper jaw and the lower jaw.

  Fig. 11 shows a dental implant which consists of a tooth root implant and a vitreous ceramic tooth crown implant according to the invention and whose shape directly reproduces the original natural tooth which was in the same cell. Figure lb, which is a section along the line

  X-Y of FIG. 1a, shows that the implant of the tooth root comprises a post or pivot 1 for receiving the crown implant 2.

  Figure 1c shows another variant of the tooth root implant, in which the tooth root implant has a threaded bore for the placement of, for example, a high strength metal peg. . This solution is advantageous in

  the case of dental implants subject to significant mechanical forces.

Example 2

  This example relates to a biologically active permanent implant according to the invention which belongs to the main group of implants which have, compared to

  to natural human bones, a simplified modified form.

  Figure 2 depicts permanent implants for the

  replacement of teeth in human medicine.

  Figure 2a shows a tooth root implant designed to receive a tooth crown implant. This tooth root implant has retention wedges 3 which have a triangular section and are arranged to tap from the implant portion 10 located in the middle of the bone to the tip. Under these conditions, the outer edge of the retention wedges 3 which is directed towards the maxillary bone makes with the implant surface an angle of 50 or less. The outer surfaces 5 of the retention wedges prevent any sliding of the implant to the outside. These surfaces of

  retention wedges make with the surface of the implant an angle of 90 to 1500. The two sides of the retaining corner 3 delimit an angle 4 from 90 to 1500 at least.

  The angle 8 is formed by the implant surface and the implant axis and is determined by the ratio of the

  dimensions of the implant and those of the natural tooth.

  The implant has a transition zone 11 which is characterized by an angle 6 or 7 greater than that which

has been indicated above.

  Figure 2b shows a tooth root implant whose section consists of two semicircular surfaces 9 and two planar surfaces 10. It may comprise, in addition, retention corners may be ellipsoidal. Figure 2c shows a permanent implant for tooth root. The shape of the inplant, which is a round conical plate with a tenon or pivot of a single side, allows its use as a cover of

pulp in natural teeth.

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Example 3

  This example relates to permanent implants according to the invention which, for the correction of defective attitudes and deformations of the human carrier and locomotor apparatus, have a shape which deviates from the natural shape of the bone. human.

  Figure 3 shows corresponding implant sections.

  Figure 3a, for example, shows an implant in the form of a hollow cylinder.

  Figure 3b shows a U-shaped curved implant.

  Figure 3c shows an implant having a double I section. Figure 3d shows a cruciform section implant.

  Figure 3e shows a parallelepipedic implant having a bore.

  By bringing to their surface additional modifications according to the invention, for example by providing a weft or by giving it a convex shape and taking into account the advantageous properties of the material, these permanent implants can be made capable of achieving symbiosis with the bodies. neighboring natural vertebrae 25 and, therefore, to be advantageously used as

  implant for ventral spondylosis.

  FIG. 3f is a side view of another type of permanent implant according to the invention, the section of which

in the form of a braid.

  Figure 3g is a top view of the same implant.

  These figures show the preferred arrangement of the weft surface 12 which facilitates the anchoring of natural human bones contiguous to the weft surface and their symbiosis

  with the permanent implant. This example highlights the advantages of using the implant for vertebrae.

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Example 4. This example relates to another category of implants following

  which are in the same main group as those of Example 3. These are implants which have a shape other than natural bones and are preferably used for the correction of the locomotive apparatus of man. Next to the implants presented in Example 3, the current example relates to permanent implants in the form of corners and prisms. Fig. 4a is a cross section of a prismatic implant. Figures 4b and 4c show, in top view (Figure 4b) and in side view (Figure 4_), an implant

  permanent derived from the corner and having the shape of a semicircular disk.

  By the use of the wedge effect, the implant according to the invention can cause for example a lifting of the head of the tibia and, consequently, an effective correction of the human motor apparatus.

  FIGS. 4d and 4e respectively show a top view and a side view of a disk-shaped, permanent implant having a square cross-section and having a central bore and a re-entrant portion of a side, which has its lower part and can be advantageously used as a disk

lower fixation.

Example 5

  The following examples of embodiments relate to permanent implants according to the invention which are distinguished by their external shape of natural bones. Permanent implants according to the invention having a cylindrical or conical shape are used (FIG. 5). The cylindrical implants according to the invention are advantageously used in the field of hand surgery. Figure 5a shows a fixation implant

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  frustoconical for reconstructions of the knee.

  According to the invention, the implants may comprise

  a head part and a tip part.

  Figure 5b shows implants of this category, which can be advantageously used, for example, for binding webs to the skeleton.

  Figure 5c shows a permanent implant according to the invention in the form of a hollow cylinder. In this case, the hollow cylinder 13 is surrounded by a curved porous disk 14 which may comprise through openings 15 having for example a circular section. The hollow cylinder contains an internal thread. As it is therefore possible to screw into this hollow cylinder shaped implant, in a sealed manner, a known optical replaceable system and as the implants have the advantageous properties already indicated, their use in ophthalmology as a keratoprosthesis

is advantageous.

Claims (13)

  1. Biologically active permanent implants for stomatological applications made from a biologically active vitreous ceramic material that can be mechanically worked and having the following weight composition, in%: SiO2 = 29.5 to 32.5 Al2O3 = 14.5 to 17.5 MgO = 14.5 to 16.5 Na2O = 2.0 to 3.0 K2O = 5.5 to 6.5 F- = 5.0 to 6.0 CaO = 13.0 to 15.0 P205 = 10.0 to 12.0   which may additionally contain, separately or in admixture, as adducts, the components FeO, Fe 2 O 3, TiO 2, MnO 2, NiO, Cr 2 O 3 up to 2% by weight and Cl up to 1% by weight and which contains simultaneously the crystalline phases of 50% to 80% by volume of mica and 15% to 30% by volume of apatite, characterized in that they have the shape of human teeth of the upper jaw and the lower jaw, the outer shape of the permanent implants 20 corresponding to that of the natural teeth extracted by   suite of direct individual imitation.   2. Biologically active permanent implants for stomatological applications according to claim 1, characterized in that they constitute a combination of massive individual bodies which together have the shape   exterior of natural human teeth.   3. Biologically active permanent implants for stomatological applications according to claim 2, characterized in that the solid bodies have the form of roots of teeth, dental crowns or parts of the teeth. these elements.   4. Biologically active permanent implants for stomatological applications according to claim 3, characterized in that the tooth root implants have a semicircle-shaped or elliptical section and have a tenon on their base surface. 5. Biologically active permanent implants for stomatological applications according to claim 4, characterized in that the implants for tooth roots   have a bore with an internal thread.   6. Biologically active permanent implants for stomatological applications, made from a biologically active vitreous ceramic material which can be mechanically worked and having the following weight composition, in%: SiO2 = 29.5 to 32.5 Al203 = 14.5 at 17.5 MgO = 14.5 to 16.5 Na2O = 2.0 to 3.0 K2O = 5.5 to 6.5 F = 5.0 to 6.0   CaO = 13.0 to 15.0 P205 = 10.0 to 12.0 which may additionally contain, separately or in admixture, as adducts, the constituents FeO, Fe 2 O 3, TiO 2, MnO 2, NiO, Cr 2 O 3, 2% by weight and Cl up to 1% by weight and which simultaneously contains the crystalline phases of 50% to 80% by volume of mica and 15% to 30% by volume of apatite, characterized in that they constitute dental implants forms of dental crowns and roots of teeth, the implants for tooth roots having a simplified form which deviates from the natural form of roots of human teeth.   7. Biologically active permanent implants for stomatological applications according to claim 6, characterized in that the roots of the teeth are in the form of rounded-pointed cone trunks and comprise wedges. Retention (3) (Figure 2a).   8. Biologically active permanent implants for   applications in stomatology according to one of the claims   6 or 7, characterized in that the retention wedges (3) have a triangular section which tapers toward the tip of the root at an angle (7) of 5 and whose end surface (5) forms with the surface of the implant an angle (6) ranging from 90 to 150 maximum and whose sides enclose an angle (4) ranging from 90 to 105 at the maximum (Figure 2a). 10 9. Biologically active permanent implants for   applications in stomatology according to one of the claims   6-8, characterized in that the tooth root implants have a transition zone (11) for the contact   with the marginal gingiva (Figure 2a).   10. Biologically active permanent implants for   applications in stomatology according to one of the claims   6-9, characterized in that the sections of the tooth root implants comprise two semicircular sides (9)   and two planar surfaces (10) and that these implants may further comprise retention wedges (3) (Fig. 2b).   11. Biologically active permanent implants for   applications in stomatology according to one of the claims   6 to 10, characterized in that the radii of the semicircular sides (9) decrease in the direction of the tip (Fig. 2b).   12. Biologically active permanent implants for   applications in stomatology according to one of the claims   6 to 11, characterized in that the flat surfaces (10) have the shape of a triangle whose base is on the side of the ring and that the two surfaces enclose a common angle to the tip corresponding to the selected rays.   13. Biologically active permanent implants for stomatological applications made from a biologically active vitreous ceramic material that can be mechanically worked and having the following weight composition, in%: SiO2 = 29.5 to 32.5 Al2O3 = 14.5 to 17.5 MgO = 14.5 to 16.5 Na2O = 2.0 to 3.0 K20 = 5.5 to 6.5 F- = 5.0 to 6.0 CaO = 13.0 to 15.0 F205 = 10.0 to 12.0, which may additionally contain, as additives, the FeO, Fe 2 O 3, TiO 2, MnO 2, NiO, Cr 2 O 3 components up to 2 wt. up to 1% by weight and which simultaneously contains the crystalline phases of 50% to 80% by volume of mica and 15% to 30% by volume of apatite, characterized in that they are dental implants having the shape round conical plates having on one side a post or pivot as a holding element,   implants that can be used as a pulp cover in natural teeth.