Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1996-06-13
1998-09-29
Merriam, Andrew E. C.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
523115, 523116, 524264, 524417, 604191, 604416, 2221455, 2221456, A61L 2500, A61K 608, C08K 332
Patent
active
058146814
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a restorative composition for hard tissue, which is used as a bone cement, a bone prosthesis, an artificial bone, and the like, and to a method for dispensing the restorative composition for hard tissue.
BACKGROUND ART
A bone cement comprising a powder agent containing polymethyl methacrylate and benzoyl peroxide (polymerization initiator), and a liquid agent containing methyl methacrylate and a tertiary amine such as N,N-dimethyl-p-toluidine (accelerator) has been conventionally used for fixing artificial joints. This bone cement is prepared immediately before fixing artificial joints during operation by mixing the powder agent and the liquid agent. The obtained mixture is applied to the affected part by a dispenser called a cement gun and allowed to cure. Such bone cement is associated with problems in that 1 the toxicity of methyl methacrylate causes vasodepression in patients undergoing operation, 2 the heat generated during polymerization could give damages to the tissues of the patients, 3 the fixed artificial joints could get loose with time due to the failure in adhering polymethyl methacrylate to hard tissues, 4 the mixing of the powder agent and the liquid agent just before use makes bad smell of polymethyl methacrylate fill the operation room and gives detrimental effect 5 slow mixing of the powder agent and the liquid agent leads to initiation of curing of the mixture, thereby making the mixture unavailable as a bone cement, and 6 insufficient mixing of the powder agent and the liquid agent results in too low a strength of the cured material, so that the artificial joints cannot be firmly fixed with hard tissues.
In an attempt to improve the biocompatibility of bone cements, Japanese Patent Examined Publication No. 42384/1979 has proposed a bone cement comprising a composition containing polymethyl methacrylate and methyl methacrylate, and bioactive glass having an apatite crystal phase superior in biocompatibility, and Japanese Patent Application under PCT laid-open under Kohyo No. 503148/1987 has proposed a bone cement comprising di(meth)acrylate and inorganic filler particles which are at least partially absorbed by the bone.
The above-mentioned bone cements are characterized by the use of a biocompatible filler, and the latter is particularly advantageous in that it does not contain methyl methacrylate which is problematic in terms of toxicity and adhesive strength. These bone cements may provide favorable results in terms of biocompatibility, whereas are not necessarily satisfactory in terms of operability.
Speaking from the aspect of operability, quick and thorough mixing is required to simultaneously solve the above-mentioned problems 5 and 6 which may seem inconsistent. In addition, the bone cement is required to have an adequate flowability before curing to facilitate filling into the affected part.
A practical bone cement should afford sufficient adhesive strength between the cured material and hard tissues, and the cured material should have sufficient water resistance permitting retention of suitable strength in the body for an extended period of time.
The present invention aims at providing a restorative composition for hard tissue, which is capable of exhibiting the above-mentioned properties requested as a practical bone cement, and which is superior in biocompatibility and operability.
The present invention also aims at providing a method for dispensing such restorative composition for hard tissue.
DISCLOSURE OF THE INVENTION
The present inventors have found that a restorative composition for hard tissue comprising a paste obtained by mixing, at a certain ratio, an inorganic calcium phosphate powder superior in biocompatibility and adhesion to bone, and a polymerizable monomer capable of imparting sufficient mechanical strength and water resistance to the cured material meets the aforementioned objects of the present invention, and further studies resulted in the completion of the present invention.
Accordingly, the present
REFERENCES:
patent: 4380432 (1983-04-01), Orlowski et al.
patent: 5033650 (1991-07-01), Colin et al.
patent: 5430074 (1995-07-01), Barnes et al.
Hino Ken-ichi
Nakashima Toshihide
Kuraray Co. Ltd.
Merriam Andrew E. C.
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