Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
1998-09-28
2001-11-27
McDermott, Corrine (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
C623S023610
Reexamination Certificate
active
06322592
ABSTRACT:
FIELD
The invention relates to the field of bio-materials that can be used to replace a part of the bone system.
The bio-materials are materials used to replace a part of the living system or to function with it. They are made up of materials that are foreign to the receiver, implanted in him in order to restore the morphology and/or the function of tissues damaged by trauma or by a disease. Therefore they all have the novelty of having to work under biological constraints.
The bio-material must satisfy physico-chemical characteristics appropriate to the site where it will be implanted and to the function that it will have to fulfil. The chances of success of a bio-material in an organism result from the product of many factors which will all have to be controlled.
From the point of view of implants carried out with such bio-materials, the bio-compatibility of them is defined as the control of reactions of the organism with respect to them during the entire duration of contact between the bio-material being considered and the organism. Mechanical and biological properties of such a product are therefore very closely linked.
The invention relates more precisely to bio-materials that can be used as bone reconstitution materials.
BACKGROUND
In this field, coral has been proposed and has been widely used for ten years or so. This natural material has a mineral exoskeleton of open porosity formed, in the main, of aragonite. Aragonite is an allotropic form of calcium carbonate, which crystallises in an orthorhombic system with lattice parameters a=4.9623 (3)Å, b=7.968 (1)Å, c=5.7439 Å for Z=4. Its theoretical density is d=2.93.
Within the state of the technology, it has been proposed to use preparations based on coral as bone reconstitution materials within the field of paradontology (paradontal diseases, bone surgery correcting loss of substance). This material is used in this context in the form of granules of size ranging from 300 to 450 gm for the filling in of paradontal defects and from 600 to 1000 pm for the filling of sockets after dental extractions. Granules are preferred to blocks which lead to the exfoliation of the coral fragment after its implantation, the size of the particles recommended for the filling in of paradontal defects then being from 300 to 500 pm.
French patent application FR 2637502 describes a bone reconstitution material made up of madreporous coral washed of any original organic substances and containing an organic osteogenesis accelerator in the form of a proteinic gel based on Type I collagen.
International patent application WO 94/26322 discloses a porous material made up of a coral skeleton (of the Porites, Acropora, Goniopora, Lobophyllia, Simphyllia or Millipora type) and a growth factor capable of being an osteo-inductive agent.
European patent application EP 395187 describes a bio-material made up of coral coated with a layer of hydroxyapatite.
Experience has shown that coral has a high bio-compatibility that confirms that it is of interest as a material for bone reconstitution.
However, such a material has the major disadvantage of high cost brought about by its processing when it is to be used as an implant material. In practice, coral gathered from nature must be divided up, then washed and incubated for several days in products such as sodium hypochlorite in order to remove all organic substances from it. Such an incubation must be carried out in such a way that the product used is able to penetrate into the entire structure of the porous coral. Blocks of coral treated in this way must then be broken up and sorted into granule size ranges, or machined in order to be made geometrically suitable for the implantation sites and then washed once again.
Furthermore, coral has a porosity that it is not possible to control. In relation to the desired speed of resorption, it is advisable to choose this or that type of coral in relation to its natural porosity.
SUMMARY
The main objective of this invention is to provide a bio-material that can be used as a bone reconstitution material and which permits this problem to be resolved.
Another objective of the invention is to disclose such a material that can be produced in such a way that its properties, notably its porosity properties, can be modulated as a function of the use to which it is to be put.
Yet another objective is to provide such a material that is able to include one or more medicinal substances with a view to administering these substances with their release being to varying extents.
These various objectives as well as others which will become apparent in what follows have been achieved thanks to the invention which relates to a macro-porous composite that can be used as a bone reconstitution material, characterised in that it is made up of a combination of synthetic aragonite and at least one medicinal substance.
Such a composite has numerous advantages.
In the first place, it is a material based on aragonite and it can be resorbed slowly in situ. The medicinal substance that it includes will be able to be progressively released into the organism and there can be a delay effect.
The fact that at least one medicinal substance is included in the synthetic aragonite substrate offers additional interesting potential therapeutic features through the local action of this medicinal substance at a high concentration.
Furthermore and above all, since the aragonite used is synthetic, it will be possible to modulate certain parameters at the time it is synthesised. Hence it will be possible to provide an aragonite substrate having pores of smaller or greater size, having open or closed porosity, or a substrate that allows the production of a material that is more or less dense or more or less rigid. Furthermore one may modulate the nominal concentration of the medicinal substance or substances in the composite. The use of synthetic aragonite therefore offers a considerable advantage compared with natural substrates, the pores of which obviously cannot be varied in size or nature depending on the objective sought and into which one cannot simply introduce foreign substances in specific quantity.
Finally, it should be noted that the cost price of such a composite will be much less than that of preparations based on coral from the state of the technology. More precisely, one may estimate that the cost price would be about 10 times less than that for preparations based on coral.
The composite according to the invention will notably be used in odontology, in particular in buccal surgery and in paradontology and in surgical orthopaedics. However it should be noted that the field of application of such composites is not limited to this one domain of dentistry and that later extension to bone surgery in general is totally conceivable.
Preferably, the synthetic aragonite will represent between about 85% and 99.5% of the total mass of the said composite. However depending on the use that will be made of the composite produced, one may consider in certain cases going outside of such a range.
According to a particularly interesting variant, said medicinal substance is an antibiotic. The significance of antibiotics is known and, as mentioned above, the composite according to the invention allows the medicinal substance included in the composite to be administered with a retard effect. This is particularly of interest for antibiotics. Furthermore, one may consider that such an antibiotic associated with an aragonite substrate in this way could have a local action at high concentration, with a quantity 100 to 1000 times less than that required when administered through the normal route.
Advantageously said antibiotic is a broad spectrum antibiotic such as metronidazole, the action of which on anaerobic germs is much sought after in bone surgery.
The invention also relates to a method of manufacturing such a macro-porous composite characterised in that it consists of producing a mixture that includes grains of synthetic aragonite and at least one porogenic agent
Carel Claude
Gaude Jean-Francois
Lucas Anita
Michel Jean-Francois
McDermott Corrine
Merchant & Gould P,C,
Phan Hieu
Universite de Rennes
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