Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-04-17
2002-08-27
Yoon, Tae H. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S599000, C523S113000, C523S115000, C528S302000, C424S426000
Reexamination Certificate
active
06441073
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a biomaterial comprising calcium phosphate and a copolymer of lactic acid, glycolic acid and &egr;-caprolactone and, more particularly, it relates to an excellent material for organism which is applied to reconstruction of hard tissues and soft tissues in vivo and is gradually degraded and absorbed together with the tissue formation. The present invention further relates to a biomaterial for the induction of osteoanagenesis where periosteum is provided to the above biomaterial by means of suture or adhesion and, particularly, to a biomaterial for the induction of osteoanagenesis which is applied as a quick therapy of big bone defect and is gradually degraded and absorbed. The present invention furthermore relates to a biomaterial for the prevention of adhesion which is applied for the prevention of adhesion of the tissues produced as a result of a self-repair after an operation or by damage of tissues of organism and is gradually degraded and absorbed.
2. Description of the Related Art
Defected area in organism which is caused by injury, inflammation, tumor excision or reconstructive cosmetology of hard tissues such as bone tissue and cartilaginous tissue and soft tissues such as epithelial tissue, connective tissue and nervous tissue has already been subjected to a prosthetic treatment and to a functional recovery by various methods and there have been also many studies for the materials used therefor.
In subjecting the bone defect area in organism to a prosthetic treatment, a self bone implantation showing abetter take to implanted area and having less infection of virus, prion, etc. or less immunological problem than homoimplantation and heteroimplantation has been carried out already. However, in the case of the self bone implantation, there is a limitation in a collectable amount and, in addition, there are problems such as a risk for infection by formation of new surgical wound for obtaining the bone to be implanted and a tendency that pain of the patient becomes longer.
As a substitute for a self bone implantation, there is a method where metal materials such as stainless steel and titanium alloy are used as artificial biomaterials and, because of a significant progress of biomaterials and an easy availability of the materials, they have been used actually.
However, in those biomaterials, their physical and mechanical strength is much more than that of tissues of organism and there is a toxicity of the metal contained therein due to corrosion. In addition, their affinity to organism is inferior as well.
Therefore, as a method for improving the affinity to organism, there has been conducted a method where the surface of the metal material is subjected to a surface treatment by a bioaffinitive material such as hydroxyapatite whereby its affinity to the surrounding tissues is improved but that is still insufficient.
On the other hand, as bioaffinitive materials, polymers of lactic acid, glycolic acid, trimethylene carbonate or lactone such as &egr;-caprolactone and copolymers thereof which are biodegradable aliphatic polyesters have been investigated as reparative materials as well and, in addition, a block copolymer of polylactic acid, poly-&egr;-caprolactone and polyglycolic acid as mentioned in Japanese Patent Laid-Open Hei-09/132638 has also been investigated. However, those materials lower their mechanical strength upon degradation in vivo resulting in a fatigue deterioration and, although bone conduction is not inhibited, they rarely show an action for bone induction.
On the other hand, bioceramics such as alumina, bioglass, A-W crystallized glass and hydroxyapatite have a high bioaffinity, have been utilized as materials for artificial bone, dental implant, etc. and noted of formation of new bone on the surface in organism and have excellent filling function and adhesion to bone tissues.
However, since those are the materials which are not absorbed in organism, there is a problem that they remain in the formed bone tissues and affect the growth of new bones and that strength of the bone lowers. Tricalcium phosphate is a material which is absorbed in vivo and, when it is used to a defected area of bone, it is absorbed or collapsed from the surface of the material and is substituted for the new bone, but its mechanical strength is weak as compared with the bone, its use to the area where load such as body weight is applied is limited.
In addition, tricalcium phosphate is in granules and, therefore, it has little ability of giving a shape to a bone implantation material and of maintaining/stabilizing thereof whereupon there is a problem that a filling operation is difficult to a complicated and broad defect and that cure is delayed due to flowing-out of the granules.
In order to solve such problems, many materials where bioceramics and polymers are compounded have been studied. In U.S. Pat. No. 4,347,234, a complex of bioceramics with collagen is proposed. However, when such collagen i s used, its molecular weight, amino acid composition, quantity, water-holding amount, etc. are not constant because it is a material derived from nature and, in addition, a complete removal of it causes a foreign body reaction in vivo and foreign body giant cell and other phagocytes, etc. are activated whereupon a bone induction is hardly expressed.
In place of collagen, there have been proposals for many materials where aliphatic polyesters such as polylactic acid having no problem in terms of immunology are compounded with hydroxyapatite. In Japanese Patent Laid-Open Hei-10/324641, there is disclosed an absorbable isolating membrane consisting of calcium phosphate and a lactic acid type polyester having a dicarboxylic acid and a diol where a polymerization catalyst is inactivated. In U.S. Pat. No. 4,595,713, there is disclosed a complex consisting of a osteoanagenetic substance such as calcium &bgr;-phosphate and hydroxyapatite and a copolymer of lactic acid with &egr;-caprolactone where &egr;-caprolactone occupies the most of the amount. The former is absorbable in vivo and has a bone induction property but, since a lactic acid segment and other components are blocked, property of calcium phosphate appears and properties of forming, retaining and stabilizing the shape are little. In the latter, its mechanical strength to the applied tissue is low and a degradation rate of the material is slow whereby osteoanagenesis is suppressed. In any of the materials, the problem of little osteoanagenetic amount of calcium &bgr;-phosphate in vivo is not solved.
In Japanese Patent Laid-Open Hei-06/298639, there is disclosed a sustained-released material where tricalcium &bgr;-phosphate is dispersed in a complex of an antibiotic substance with a lactic acid/glycolic acid copolymer.
Although there have been many other studies concerning reconstruction of soft tissues such as blood vessel and peripheral nerve, a sufficient material has not been available and, accordingly, there has been a demand for a material having a metabolism similar to that of tissues where a biocompatibility is excellent, strength can be maintained until the tissues are regenerated and degradation and absorption take place after the implantation.
With regard to a biomaterial for induction of osteoanagenesis, a sole use of a material has a limitation for the therapeutic effect and, therefore, with an object of supplementing the osteoanagenetic amount, there have been many studies for a substitution therapy where filling of bone marrow is utilized. Since bone marrow has many osteoanagenetic cells, its bone inducing property is high. However, with regard to the use of bone marrow, there is a limitation in the collecting amount thereof. In addition, its application is complicated and, to a defect in a broad area, a filling operation is difficult and there has been no satisfactory material in terms of a shape-giving property and a retention-stabilizing property. for the prevention of flowing out.
On the other hand, with regard to a material having
Ichikawa Shunji
Imamura Yukari
Itoh Takatoshi
Kikuchi Masanori
Koyama Yoshihisa
Kennedy Covington Lobdell & Hickman LLP
Taki Chemical Co. Ltd.
Yoon Tae H.
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