Title of Invention

PREPARATION OF A COMPOSITE BIOCERAMIC MATERIAL FOR BIOMEDICAL APPLICATIONS

Abstract

This invention relates to a process for the preparation of a bioceramic composite material comprising of the steps of preparation of a SiO2 Cao- P20S glass ceramic system by sol-gel process and preparing calcium phosphate powder by precipitation method and freeze drying followed by mixing the Sio2-Cao-P2Os glass ceramic and calcium phosphate powder in a ratio ranging from 10:90 to 90:10 weight percentages, compacting the mix and sintering to obtain the bioceramic composite.

Full Text

FIELD OF INVENTION : This invention relates to bloceramic composites and to a process for the preparation thereof for biomedical and other application. BACKGROUND OF INVENTION : Today surgical interventions are possible in cases of highly degenerative situations, tumors or minute fractures, wi th an aim of replacing skeletal parts. Such substitutions can be effected with different materials and each material is preferred in certain applications. A number of materials have been tried but only few met with certain degree of success, mainly because the degree of adhesion of the prosthetic material to bone. In order to regenerate the funct ionality of impaired ^keletal tissue, di fferent approaches have been tried. Apart from the autograft and allograft materia Is, some of the following i terns like coral, dimineralised bone, alumina, calcium phosphate ceramics, bioactive glasses etc have been used for different surg ical purposes. Among these materials, calc ium phosphate based ceramics and SiO -CaO-P O glasses form a direct bond to the bone without fibrous tissue in between. This is by virtue of the formation of Carbonated hydroxyapatite (HCA layer over these c 1 ass of compounds from the natura1 t i ssue env i ronment Hydroxyapati te 10 4 6 2 presently used for skeletal repair applications which is generated from natural or synthet ic routes. This compound is similar, with respect to chemical and physical properties, to the bone mineral except the fact that natural bone may always be 2- 2+ - subst i tuted wi th addi tional ions such as CO , hg ,F etc .Because of this si mi 1 ari ty, implants of calcium hydroxyapat i t e is most often used clinically in the form of powders,granules and blocks. The disadvantage of dense hydroxyapati te materials is that they take longer time to get replaced by natural bone when implanted at bony si tes duf? to si ow d issolu t ion rate of sintered matrix- Another class of compounds, namely bioactive glasses, known in the art possess excellent bone bonding and bioresorbable characteristics. They are compounds containing mainly CaO, SiO2 and P2O5. A number of formulations have been identified in this family with or without additives such as Na20, MgO, NaF etc. which show direct bonding with host bone through Si-on groups. The function of silica is also to provide a low solubility molecular matrix whose network of silica chains act as a container for other ions such as Na, P, Ca etc. These ions dissolve into the surrounding body fluid, thereby activating the biochemical environment ledading to the formation of HAC. OBJECTS OF THE INVENTION : A primary object of this invention is to propose a new composite bioceramic material containing calcium silicate and calcium phosphates and a process for the preparation thereof. Another object of this invention is to propose a new composite bioceramic material containing calcium silicate and calcium phosphates and a process for the preparation thereof and wherein the system contains lesser amount of silica than conventional bioactive glasses available in market and has better bone inducting capacity than pure hdroxy apatite bioceramic. Yet another object of this invention is to prepose a new composite bioceramic material containing calcium silicate and calcium phosphates and a process for the preparation thereof which has better biocompatibility and bone growth. Still another object of this invention is to propose a new composite bioceramic material containing calcium silicate and calcium phosphates and a process for the preparation thereof which can be used for repairing, filling or augmentation of bone defects. DESCRIPTION OF INVENTION ; According to this invention there is provided a process for the manufacture of dense or porous sintered bioceramic composites comprising a mixture of SiO2-CaO-P2O5 glass and calcium phosphates and present in ratios ranging from 10:90 to 90:10 veight percentages. Bioactive glasses are normally synthesized by usual melting and annealing route. In the present invention SiO2-CaO-P2O5 glass was synthesized by a sol-gel method. The fine powder generated by that method is mixed with a free flowing freeze dried calcium phosphate powder/ with or without a pre former, and compacted. The pore former is introduced to create interconnected porosity in the matrix which will help in bone ingrowth into the material. these green compacts are sintered at high temperature to sintered blocks. The blocks are porous and wisere made into various shapes by grinding or by crushing technique. EXAMPLE No. 1 ; a. Preparation of glass powder : A solution of Calcium nitrate (15 gm) and Phosphorous pentoxide (1.3 gm) in 10 ml of water was added to 10 ml of tetra ethoxy silane solution. This ' sol' was then allowed to gel at room temperature for 24 hours. The resultant gel was heat treated at 150 degree and made into a powder using a ball mill. b. Preparation of calcium phosphate powder : Calcium phosphate powder was prepared by precipitation method- Ammonium phosphate (IM, pH 11) solution was added to an ammoniated calcium nitrate (IM) solution. The Ca/P ratio was maintained at 1.67. The precipitate was then aged for a day and filtered, washed and freeze dried to generate free lowing HAP powder. c. Preparation of composite bioceramic : Above powders were mixed in 50:50 weight ratio in a ball milled for one hour. The powder mix was then compacted in a uniaxial press into circular or rectangular blocks. These samples were then fired at 1300-1350 degree C to get composite ceramic shapes. The sintered blocks were later crushed and sieved to granules of various size ranges. EXAMPLE No, 2 ; a. Bioactive glass powder and calcium phosphate powders were prepared as per Experiment la and lb respectively. b. Preparation of porous composite bioceramic : Above powders were mixed in 50:50 weight ratio and ball milled for one hour along with 50 vol% naphthanein (100-400 micron size powders) was added and milled for another hour. The powder mix was then compacted in a uniaxial press into circular or rectangular blocks. These samples were then fired at 1300-1350 degree C to get porous composite ceramic shapes. The sintered blocks were later crushed and sieved to granules of various size ranges. c. The granular samples prepared by Example Nos. 1 and 2 were tested for biocompatibility studies such as cytotoxicity, subcutaneous implantation and bone implantation. It was found that the samples are biocompatible, non cytotoxic and showed good bone growth in and around the sample when implanted in bony sites. They also showed growth of natural bone around the implant within 3 months. WE CLAIM: 1. A process for the preparation of a composite bioceramic material comprising of the steps of preparation of a SiO -CaO- 2 P O glass ceramic system by sol-gel process and preparing 2 5 calcium phosphate pouider by precipitation method and freeze drying followed by mixing the SiO -CaO-P O glass ceramic and 2 2 5 calcium phosphate powder in a ratio ranging from 10:90 to 90:10 weight percentages, compacting the mix and sintering to obtain the bioceramic composi te. 2. The process as claimed in claim 1 wherein SiO -CaO-P 0 glass 2 2 5 consists of essentially to 10-35 weight percent phosphorous pentoxide, 30 to 60 percent of calcium oxide made by a sol gel method involving silicon alkoxide and salts of calcium and phosphorous. 3. The process as claimed in claim 1 wherein the calcium phosphate is made by precipitation of calcium hydroxyapatite from a solution of calcium salt and ammonium phosphate. 4. The process as claimed in claim 1 wherein the mixture is pressed into discs and sintered at temperature ranging from 1200- o 1350 C. 5. The process as claimed in claim 4 wherein the sintered material is crushed to various size fractions ranging from 100 microns to 3000 microns were collected and graded into various size fractions. 6. A process for the preparation of a porous bloceramic composite comprising a mixture of SiO -CaO-P O class and calc ium 2 2 5 phosphates and optionally 10 to 60 vol% pore former, such as naphthalein, camphor, pressing mixture into discs and sintering o Bh temperature ranging from 1200-13S0 . 5. The process as claimed in claim 6 wherein said pore former has a particle si;ze ranging from 100-500 microns- B* A process for the manufacture of sintered bioceramic composi tes suostant ial ly ss herein described.

Documents:

173-mas-2000-abstract.pdf

173-mas-2000-claims.pdf

173-mas-2000-correspondence other.pdf

173-mas-2000-correspondence po.pdf

173-mas-2000-description complete.pdf

173-mas-2000-form 1.pdf

173-mas-2000-form 13.pdf

173-mas-2000-form 26.pdf

173-mas-2000-form 3.pdf

173-mas-2000-form 4.pdf

173-mas-2000-form 9.pdf