The Resorbable Bioglassceramics Based on Calcium Biophosphate
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THE RESORBABLE BIOGLASSCERAMICS BASED ON CALCIUM BIOPHOSPHATE
Tsung-Shune Chin*, D.C. Wu**, H.S. Liu*, M.P. Hung"*and C.P. Wang# * Department of Materials Science and Engineering, Tsing Hua University, Hsinchu, 300, Taiwan, Republic of China "**Departmentof Materials Engineering, Chen Kung University, Tainan, 701, Taiwan, Republic of China # Department of Biology, Cheng Kung University, Tainan, 701, Taiwan, Republic of China
ABSTRACT Novel resorbable bioglassceramic artificial tooth roots based on calcium biphosphate were synthesized, implanted into rabbits, and assessed. They were prepared by melting a glass composition of CaO/(CaO+P20 5 ) = 0.33, casting, crushing, loose powder sintering and crystallization annealing. The resultant porosity is 3 to 36 gtm. The three point bending strength is 33 to 150 MPa depending on annealing treatment. The crystallized phases are f3-Ca2P207 and CaP2 0 6. These porous implants show remarkable biocompatibility with the old bone and induce the growth of new bone within 30 days. The implants are partly resorbed after 90 days and replaced by new bone. The ingrowth of blood vessels into the implant is abundantly seen after 90 days despite a small original porosity, due probably to enlarged pores by preferential resorption of the implant material. The new ceramics are good candidates for resorbable bone bioimplant.
I. INTRODUCTION Bioceramics, including glassceramics, possess either inertness (eg., alumina and hydroxylapatite), or biodegradability (eg., calcium aluminate and tricalcium phosphate), and hence are widely used as prosthetic or artificial internal organ materials, for physiological functions [1,2]. Porous compacts, metallic or ceramic, are widely used as bioimplants. In these bioimplants, the tissue-implant bonding strength and the ingrowth of tissue are essential [1-4]. Porous bioceramic implants facilitate the ingrowth of tissue and hence the bonding strength. For the inert porous implants with pore size of 100 micrometers or larger, the growth of bone structure, new blood vessels, and Harversian systems in the pores can be observed by optical microscopy. There is mineralization and no infectious or abnormal cell growth at the interface [5]. For resorbable or biodegradable porous implants, the pore size is much smaller than in the case of inert implants due to their smaller strength [6]. In 1977, Koeneman et al. prepared a porous shell on a dense core and found that the implant as a whole can carry load yet the ingrowth of new bone is enhanced. This is found to be a good candidate for curing cancellous bone [7]. For inert implants such as alumina, a foaming agent such as CaCO 3 and/or PVA are mixed with the ceramic powder, compacted, and sintered [8]. The porosity and pore volume are controllable by the amount of foaming agents used. Sometimes surface leaching of soluble metal or oxide which was sintered onto the surface as a mixture leads to a porous surface with a dense interior [8].
Mat. Res. Soc. Symp. Proc. Vol. 252. '•1992 Materials Research Society
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