FR2597091A1 - Permanent biologically active implants - Google Patents

Abstract

Permanent biologically active implants, characterised in that they consist of a biologically active vitreous ceramic matter which can be wrought mechanically and which has 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, P2O5 10.0 to 12.0 and of separate crystalline phases consisting of 50 to 80 % by volume of mica and of 15 to 20 % by volume of apatite.

Description

The present invention relates to biologically active permanent implants, constituted by special vitreous ceramic materials, which can be used in human medicine, in particular for the replacement of hard tissues. Permanent implants can be used, for example, in orthopedics, stomatology, facial and jaw 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 inadequacies of the state of the technique, due to the nature of the material, and, on the other hand, 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, it has been known for some time, in addition to metals, sintered ceramics, glasses and vitreous ceramics. not to be 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 that is to say which realize a direct connection without connective tissue with the living ltos. Glassy ceramics of this type are described, for example, by DE-OS 281 863 O, DE-OS 232 610 0 and DE-OS 343 534 8. However, these biologically active glasses, ceramics and vitreous ceramics exhibit, despite their properties of biological activity, sometimes significant drawbacks with regard to their use as permanent implants.

This is evidenced by the following examples of concrete use cases. These examples demonstrate at the same time the reciprocal relationship existing between the type of material and the shape of the implants, which can be biologically active implants, such as, for example, glasses and vitreous ceramic materials, or biologically compatible implants, like, 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 implants produced up to now have the drawback that their shape does not correspond exactly to that of the tooth or the tooth root extracted, but that, being prefabricated, they have a specific 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 implant bed in the patient's back requires complicated milling operations.

Any adaptation of the implant to physiological or anatomical conditions is excluded and this 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. Covering with metals, which are biologically compatible and cause only contact osteogenesis, with a biologically active material, has provided the desired binding osteogenesis (biological activity) for dental implants. Vitreous ceramic materials and glasses of various compositions have been used (DE-OS 265 959 1, DE-OS 271 750 6, DE-OS 273 339 4, DE-OS 311 286 8, in particular). The solutions consist in 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 in the bone. Another disadvantage of the known biologically active implants used for the replacement of dental crowns is the lack of control of surface solubility and the resulting notching in connective tissues, which weakens the tendency for bonding osteogenesis, by aging of the material and modification of the surfaces. Known "bio-glass" ceramic materials are internally acting and cannot otherwise be sufficiently corrected nor, therefore, adapted to anatomical conditions, which has drawbacks for the stabilization of the body. root of the tooth. The preparations based on calcium hydroxide comprising a self-hardening cement which are used to cover the pulp cavity in the teeth have the disadvantage of risking toxic damage 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, it is used extensively, alongside transplants taken from the body, which involves the risks of a double operation and a biological weakening of the area of removal of the transplant, metal implants. These metal implants, such as metal networks (DE-PS 3 106 917) or screws and plates, have the drawback that due to the electrolysis phenomena which occur and the fact that in general the materials used are not do not behave in a biologically inert manner, they can only stay in the body for a short time, i.e. they do not constitute permanent implants A direct connection between the bone and the implant in the case of metallic materials is moreover not possible due to the porosity and the difference in structure of the surfaces, as indicated in DE-OS 2 127 843, and DE-OS 2 755 762. In the the best case, the intense mechanical endurance amounts to contact osteogenesis. The covering of metallic 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, obviously made it possible to obtain properties of biological activity, but the absence control of the surface solubilities leads to drawbacks. Another drawback of these implants is that they cannot be mechanically worked by traditional tools, so that a correction of the shape under the operating conditions is not necessary. 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 comprising the use of implants, in particular for orthopedic applications, have the additional drawback that, for the anchoring of biologically active implants, for example metals or sintered corundum, it is necessary, in addition , a bone cement.

Disadvantages analogous to those of metals are also exhibited by organic polymeric materials which are used as implants for the replacement of hard tissue. Even if the two groups of materials present notable differences, for example as regards the physical properties and if the polymers (plastic materials), because of the machining facilities which they offer, allow the manufacture of relatively complicated parts which can perform binding and holding functions, these materials are not biologically active.

The development of biologically active vitreous ceramics which can be machined and, in view of the results obtained in the veterinary field, can be used in medicine, is described in DD-wP 219 017 and DD- P 238 619.

The aim of the invention is the production of biologically active permanent plants from a material of universal use which, in comparison with the implants hitherto known for the replacement of hard tissues in human medicine, is distinguished by a combination outstanding properties and, by allowing new shapes to be realized, opens up new possibilities and new areas of use.

The aim 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 consisting of the type, composition and structure of the material and the shape and appearance of the products and a single base material to guarantee a complete modeling of the permanent implants by the use of the advantageous properties of the material.

This object is achieved, according to the invention, owing to the fact that the biologically active permanent implants consist of a biologically active vitreous ceramic material, which can further be mechanically machined and having the following composition, in
SiO2 = 29.5 to 32.5
Al2O3 = 14.5 to 17.5
MgO = 14.5 to 16.5
Na20 = 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
25 and by the separate crystalline phases, that is to say 50% to 80/0 by volume of mica and 15% to 30% by volume of apatite, and that the massive bodies made from this vitreous ceramic material for replacement of diseased, malformed or damaged human bones have the same shape as healthy human bones and that, for the correction of defective attitudes or deformities, the massive bodies in question have a simple shape deviating from the natural shape of the bones humans.

In this connection, the surprising finding has been made that with a practically single implant material, as the very close composition limits show, a material of universal application is available for the replacement of hard tissue. This is obviously only possible because it is only with this specific composition that the structure of the material constituted by 50 to 80 0.0 'by volume of mica, by 15 to 30 ep by volume of apatite and by the vitreous phase allows the manufacture of the 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 vitreous phase is of great importance in this case. The advantageous properties of the biologically active permanent implants according to the invention above all encompass multiple possibilities of molding, comprising for example centrifugal casting and compression, the possibility of specifically mechanical machining, the biological activity of a surprising magnitude, the 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 whole constituted by the nature of the material, its composition and its structure, the special properties and shape of the products allows wide use and the elimination of the disadvantages corresponding to the state of the art.

The advantages which result from the fact that a single material is capable of being used in a wide field as a biologically active permanent implant are many and varied. It is first of all the fact that the forming, for similar starting products, can be carried out under similar or identical technical and technological conditions. Then, the machining and further processing of the vitreous ceramic material can be carried out according to unified criteria and its handling for direct application in medicine, which also has advantages for the shipment of products. permanent implants according to the invention consists in that the material may contain adducts, for example FeO, Fe203,
TiO2, MnO2, NiO, Cor203 up to 25S by mass and Cl up to 1> by mass, to ensure the coloring, without its advantageous properties being altered. The additions of Cl even cause an improvement in the melting properties.

This coloring of the implants is particularly advantageous in dentistry, where it makes it possible, for aesthetic reasons, to practically reconstitute the natural coloring of the teeth.

The advantageous solution which consists in giving the desired shape to the permanent implants by a unitary operation comprising the initial shaping and the machining makes it possible to directly reproduce the human bones with their primitive form, which presents many advantages for the use of the implants. as a replacement material for hard tissue in the human body and constitutes a considerable advance over the state of the art. There is a need for special implants of this type, for example in maxillofacial surgery or in otolaryngology where, until now, part of the implants formed of parts, of often unsuitable shape and poorly anchored mechanically, have been used. type of permanent implants according to the invention belong, for example, implants directly reproducing the skull or some of its parts, 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, dental implants, which are, together with the base of the orbit etc. implants, the typical representatives of their group, occupy a special place. These biologically active permanent implants according to the invention having the shape of human teeth are produced by direct reproduction, in each case, of a human tooth extracted from its socket. Then, after modeling the human tooth, for example after wax modeling, a centrifugal casting process can be used to manufacture the implant semi-finished product. The advantage of this process compared to the state of the art consists above all in that it makes it possible to obtain a better mechanical anchoring of dental implants, because the implant is firmly engaged in the socket and the high biological activity ensures a direct connection between the implant and the socket.

In the case of known dental implants, retention devices are used on their surface to prevent rotation and to improve the anchoring of the implants.

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 can, according to the invention, be a combination of individual solid bodies of vitreous ceramic material. These individual bodies are shaped like roots or crowns of teeth or parts of them. At the same time, it is possible that on a tooth root made of vitreous ceramic material is, for example, placed a metal crown or some of its parts. Certain special shapes, such as those which have, according to the invention, semicircular or elliptical sections or coml) ortent posts at the level of the root of the tooth for the fixation of crown implants, ensure a good adaptation of the shapes and excellent behavior of the implants This excellent behavior of the parts subjected to the most important loads can be further improved by the use of a body of high mechanical resistance, for example a metal plug inserted in the tooth root implant . For this, the tooth root implant has a bore comprising a thread. Apart from the direct reproduction of roots of human teeth, the tooth root implants according to the invention make it possible to produce a shape which differs from that of the roots of human teeth.

For example, using the advantage of their mechanical machining ability, tooth root implants can be shaped as truncated cones with rounded tops and retention wedges (Figure 2).

It is also advantageous that the retention wedges have a rectangular section which tapers towards the tip of the root at an angle 7 of 50, the closure surface of which 5 makes with the surface of the implant an angle 6 of 900 to 1500. and whose sides 4 make an angle 4 with each other from 900 to 1050. It is also advantageous that the transition zones II allow support against the gum tissue. According to the invention, other tooth root implants are characterized in that the sections have two semi-circular sides 9 which can be thinned towards the top and two flat surfaces 10 which can have the shape of a triangle.

To cover the top of the pulp, it is advantageous to use special small, round and tapered implant pads that are incorporated into the tooth.

The invention has made it possible, taking into account the combinations of particular properties of vitreous ceramic materials, to develop, besides biologically active permanent implants, which have the shape of human bones, also other biologically active permanent implants which have a shape that deviates from that of human bones. Implants of the latter category perform, in the same way as natural bones or implants having a shape similar to that of bones, all the main functions, for example the functions of maintenance and support, that is to say say the transmission and absorption of forces in the broadest sense, fixation, symbiosis by biological activity with living hard tissue, etc. The function that the permanent implants according to the invention must fulfill at specific locations on the device human carrier and locomotor simultaneously determine their external form. The basic type of these implants is a prism, cylinder, pyramid, trunk pyramid and trunk cone. According to the invention, implants having an X-, Y-, H- or parallelepipedal or kidney-shaped section are deduced therefrom. Additional arrangements of surfaces, for example frames for body implants of vertebrae, for wedges etc.

improve the anchoring of bones and implants. Other assembly devices, for example bores or passages formed in the implants, allow better anchoring and better fixation and softening of the edges, which is very possible due to the ease of machining of the implants, improves tissue compatibility and promotes symbiosis.

These advantageous embodiments make it possible to use wedge-shaped permanent implants having edges of different shapes, for example pointed, rounded, truncated, in particular for correcting 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 fixation. In some special embodiments, the head portions are cylindrical implants having a hexagonal bore and slots. The rod can, for example, be prismatic, cylindrical or truncated cone while, to ensure better stabilization in the bone or in the tissue, the surfaces are provided with grooves and moldings.

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

In particular, the ease of mechanical machining, the biological activity and the biological compatibility have made it possible to develop permanent implants according to the invention having the form of a hollow cylinder comprising an external thread and a support disc.

The manufacture of the permanent implants according to the invention is carried out in two stages which are the manufacture of the starting glass and the subsequent heat treatment of the starting glass to obtain crystallization in situ between 6000 and 1100 C.

The possibilities of heat treatment are, for example
a) 1000 C / 1 h
b) 750 C / 0.5 h and 9000C / 5 h.

The particular properties of the permanent implants according to the invention are as follows - very good machining possibility which can even be
excellent - chemical stability according to "hydrolytic class 2 to 3 - excellent biological activity - very good mechanical resistance, resistance to breakage
by bending up to 220 Fa - high resistance to pressure, over 500 E ~ IPa - hardness over 300 HV 10 - modulus E from 70 to so GPa - the coefficient of linear thermal expansion, which
is about 12.5. 10, -1, allows at the same time
combinations with very resistant basic bodies
tants, for example based on metals.

Biological activity has been demonstrated in animal studies or clinical observations in humans. For the quantitative determination of a value defining the biological activity, the percentage of binding between the biologically active vitreous ceramic material and the biologically active vitreous ceramic material was determined in animal tests after periods of up to 2 years. living. Thus, for example, the expression "excellent" indicates a binding to more than 70%, in figure 70 0% being reached already at the end of 16 weeks after the implantation, the proportion in question increasing with the increase. implantation time and the bond remaining stable after years. This result is explained by the fact that the permanent implants according to the invention have, compared with all the biologically active materials known hitherto, the advantage that the reaction zone between the vitreous ceramic biologically active material and the os is, even after years, only 10 Hm at most. At the same time, this is an essential advantage of these permanent implants for their use as a solid material or in a thin layer or as aggregates, because the bond is maintained and no alteration of the properties is manifested in the biological material or in the bonding zone. .

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

The invention is described below in more detail by way of exemplary embodiments with reference 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 of human bones. It is a dental implant having the outer shape of human teeth of the upper jaw and lower jaw.

Figure la shows a dental implant which is constituted by a tooth root implant and by a vitreous ceramic tooth crown implant according to the invention and the shape of which directly reproduces the original natural tooth which was in the tooth. same alveolus.

Figure lb, which is a section along the line
XY of figure la, shows that the implant of the tooth root comprises a post or pivot 1 to receive the crown implant 2.

FIG. 1c shows another variant of the tooth root implant, in which the tooth root implant comprises a bore provided with a thread for the establishment, for example, of a high strength metal plug. This solution is advantageous in the case of dental implants subjected to significant mechanical stresses.

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 with 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 which are arranged so as to taper from the part of the implant 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 jawbone makes with the implant surface an angle 7 of 50 or less. The outer surfaces 5 of the retention wedges prevent any sliding of the implant outward. These retention wedge surfaces form an angle 6 of 900 to 1500 with the implant surface. The two sides of the retention wedge 3 define an angle 4 of at least 900 to 1500.

The angle 8 is formed by the implant surface and the axis of the implant and is determined by the ratio of the dimensions of the implant to those of the natural tooth.

The implant has a transition zone 11 which is characterized by an angle 6 or 7 greater than what has been indicated above.

FIG. 2b shows a tooth root implant, the section of which is constituted by two semicircular surfaces 9 and by two flat surfaces 10. It can also include retention wedges which can be ellipsoidal.

Figure 2c shows a permanent tooth root implant. The shape of the implant, which is a round tapered insert with a post or pivot on one side only, allows its use as a pulp cover in natural teeth.

Example 3
This example relates to permanent implants according to the invention which, for the correction of defective attitudes and deformations of the carrier and locomotor apparatus of man, have a shape which deviates from the natural shape of the human body.

FIG. 3 represents sections of corresponding implants.

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

Figure 3b shows a curved U-shaped implant.

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

FIG. 3d represents an implant with a cruciform section.

FIG. 3e represents a parallelepipedal implant comprising a bore.

By making additional modifications to their surface according to the invention, for example by making a frame or by giving it a convex shape and taking into account the tantagous properties of the material, these permanent implants can be made capable of achieving symbiosis with the bodies of neighboring natural vertebrae and, therefore, to be used advantageously as an implant for ventral spondylodesis.

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

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

These figures show the preferred arrangement of the raster surface 12 which facilitates the anchoring of natural human bones contiguous to the raster surface and their symbiosis with the permanent implant. This example highlights the advantages of using the implant for the vertebrae.

Example 4.

This example relates to another category of implants according to the invention which are classified 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 correction of the musculoskeletal system of man. Besides the implants presented in Example 3, the current example relates to permanent implants in the form of wedges and prisms.

Figure ka is a cross section of a prism implant.

Figures 4b and 4c show, in top view (Figure 4b) and in side view (Figure 4c), a permanent implant derived from the wedge and having the shape of a semicircular disc.

By using the wedge effect, the implant according to the invention can cause, for example, a lifting of the head from the tibia and, therefore, an effective correction of the human motor system.

Figures 4d and 4e show a top view and a side view, respectively, of a permanent, disc-shaped implant having a square cross-section and having a central bore and a recessed portion on one side, which has grooves at its portion. lower and can be advantageously used as lower fixing disc.

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

FIG. 5a represents a frustoconical fixation implant for knee reconstructions.

According to the invention, the implants can include a head part and a tip part.

Figure 5b shows implants of the latter category, which can be advantageously used, for example, for the attachment of bands to the skeleton.

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

Claims (2)

1. Biologically active permanent implants, characterized in that they consist of a biologically active vitreous ceramic material capable of being mechanically workable and having the following composition by weight, in% S1O2 = 29.5 to 32.75 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 P2O5 = 10.0 to 12.0 and by the separated crystalline phases consisting of 50 to 80% by volume of mica and 15 to 20% by volume of apatite. 2. Biologically active permanent implants according to claim 1, characterized in that the biologically active vitreous ceramic material which can be mechanically worked contains, in addition, in its composition, isolated or as a mixture, constituents which are FeO, Fe2O, TiO2, MnO2, NiO, Cr2O3, up to 2% by weight and Cl up to 1% by weight.