Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1997-02-18
1999-02-16
Szekely, Peter A.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
524417, 2641761, 264211, 26432818, A61F 202, A61C 1300, C08K 332, B28B 320
Patent
active
058721592
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a process for obtaining a material for medical or veterinary uses, designed especially, but not exclusively, for the execution of endo-osseous implants, notably dental ones, or the execution of osseous prosthesis. The invention also relates to the material obtained by the process as well as its applications.
BACKGROUND OF THE INVENTION
Numerous types of materials, either metallic or plastic, are used in the medical or veterinary field, for the replacement of biological structures (bones especially) or the fixation of functional organs (dental implants or others, . . .).
The selection of the material is made in relation to its structural intrinsic characteristics and also in relation to its biocompatibility, in terms of integration or, what is better, in terms of biological tolerance.
For informative purposes, the document EP-A-0378102 describes an implantation material obtained by extrusion moulding of a thermoplastic polymer mixture with calcium hydroxyapatite and additional charging constitutive elements.
The document US-A-4645503 suggests a bone reparation material comprising a biocompatible and biodegradable thermoplastic polymer, mouldable at ordinary temperature and mixed with a filler, preferably calcium hydroxyapatite, tricalcium phosphate or glass granules, used alone or in combination.
SUMMARY OF THE INVENTION
The purpose of the present invention is to offer a cheap and easy to implement process, enabling to obtain a material which combines good general mechanical qualities and excellent biocompatibility in terms of biological tolerance, liable to allow particularly efficient usage in the medical and veterinary fields.
Another purpose of the invention is to offer a process allowing to obtain a material whose constitution is close to that of the bone.
The process complying with the present invention consists in mixing homogeneously a biocompatible thermoplastic polymer with tricalcium phosphate (Ca.sub.3 (PO.sub.4).sub.2). The mixture obtained then undergoes an injection or extrusion type moulding operation, under suited conditions (especially temperature and pressure) to ensure the transformation of the tricalcium phosphate into calcium hydroxyapatite (Ca.sub.5 (PO.sub.4).sub.3 OH).
The transformation during the moulding operation is performed according to the following reaction: OH+H.sub.3 PO.sub.4
The presence of calcium hydroxyapatite allows the moulded material to come close to the natural composition of the bone in order to enhance its biocompatibility.
In addition to the calcium hydroxyapatite formed out of the tricalcium phosphate, one can expect to add a small proportion to the basic mixture, before moulding.
The above reaction is carried out partially and the moulded end-product contains residual tricalcium phosphate. Tricalcium phosphate is one of the basic biological compounds for the formation of calcium hydroxyapatite; it also exhibits a healing function and it is resorbable.
Orthophosphoric acid (H.sub.3 PO.sub.4) as such is prescribed as calcium fixative and as acidifying agent; this therapy is little active; however, it enjoys newly found favours by the use of high doses of alkaline phosphates and of glycerophosphates in affections where the calcium metabolism is disturbed. The orthophosphoric acid is a fundamental constitutive element of the nucleotides: a nucleotide is formed of a puric or pyrimidic basis to which has been attached by a glucosidic link a sugar combined to a molecule of phosphoric acid. Nucleotide is the basis unit of the nucleic acids. Nucleic acids combined to one or several protein molecules produce nucleoproteins, which constitute an important part of the cores of the cells and can also be traced in the cytoplasm. Thus, phosphorus is a fundamental element of living matter and of biochemistry.
Orthophosphoric acid (H.sub.3 PO.sub.4) is derived from the transformation process of tricalcium phosphate into calcium hydroxyapatite; this product is volatile, but it remains present in the moulded end-material. P
REFERENCES:
patent: 4645503 (1987-02-01), Lin et al.
patent: 4863974 (1989-09-01), Mallouk et al.
patent: 5246457 (1993-09-01), Piez et al.
patent: 5290494 (1994-03-01), Coombes et al.
patent: 5425770 (1995-06-01), Piez et al.
patent: 5639402 (1997-06-01), Barlow et al.
Cougoulic Julie
Cougoulic Linda
Szekely Peter A.
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