Composites made of rapidly resorbable ceramics and poly(lactide) show adequate mechanical properties for use as bone substitute materials

Porous composite materials made of poly(L, DL-lactide) and a ceramic compon ent, alpha -tricalcium phosphate (alpha -TCP) or one of the rapidly resorba ble glass ceramics, GB9N or GB14N, respectively, were developed to be used as bone substitutes. The present article describes the mechanical propertie s and the in vitro degradation characteristic of the different composite ma terials. The yield strength, the elastic modulus, and the molecular weight were measured after in vitro degradation up to 78 weeks. The initial streng ths 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, respec tively). The initial elastic moduli of the composites were between 450 and 650 MPa. The mechanical properties remained constant until a degradation pe riod of 26 weeks. Then they decreased continuously until they were complete ly lost at week 52. The molecular weight (M-w) decreased steadily from 91,0 00 D in the case of the alpha -TCP composite and 78,000 D and 85,000 D in t he 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 pro perties in the range of cancellous bone and a suitable degradation characte ristic to be used as bone substitute materials. (C) 2001 John Wiley & Sons, Inc.