Porous composite materials made of poly(L, DL-lactide) and a ceramic component, alpha -tricalcium phosphate (alpha -TCP) or one of the rapidly resorbable glass ceramics, GB9N or GB14N, respectively, were developed to be used as bone substitutes. The present article describes the mechanical properties and the in vitro degradation characteristic of the different composite materials. The yield strength, the elastic modulus, and the molecular weight were measured after in vitro degradation up to 78 weeks. The initial strengths of the alpha -TCP composite (12.5 +/- 0.7 MPa) was higher than that of the GB9N and GB14N composites (8.3 +/- 0.2 MPa and 10.9 +/- 0.2 MPa, respectively). The initial elastic moduli of the composites were between 450 and 650 MPa. The mechanical properties remained constant until a degradation period of 26 weeks. Then they decreased continuously until they were completely lost at week 52. The molecular weight (M-w) decreased steadily from 91,000 D in the case of the alpha -TCP composite and 78,000 D and 85,000 D in the case of the GB9N or GB14N composites, respectively, to about 10,000 D at week 78. It was concluded that the composites show adequate mechanical properties in the range of cancellous bone and a suitable degradation characteristic to be used as bone substitute materials. (C) 2001 John Wiley *** Sons, Inc.
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