Influence of biphasic calcium phosphate granulometry on bone ingrowth, ceramic resorption, and inflammatory reactions: Preliminary in vitro and in vivo study

Calcium-phosphate ceramics used in surgery, as bone-bending materials, are currently available in different forms (blocks, granules, etc.). However, p rogress in noninvasive surgery has favored the development of injectable co mposite materials associating a polymeric and a dusty mineral phase. The pu rpose of this study was the in vivo evaluation of biphasic calcium phosphat e of various grains sizes, to elucidate the role of granulometries in ceram ic degradation/resorption, bone ingrowth, and inflammatory reactions. Three particle sizes were compared: 10-20, 80-100, and 200-400 mu m. The 10-20-m u m powders provided the best bone ingrowth, with a higher resorption/degra dation rate in conjunction with stronger early inflammatory reactions. The 200-400-mu m powders showed higher bone ingrowth than 80-100-mu m ones, ind icating that properties of cell recruitment for osseous apposition and mech anical support for bone bonding may both play a role in both ingrowth mecha nisms. Our results suggest that the strong inflammatory reaction in 10-20-m u m granulated powders was due to a faster reversal of the resorption/appos ition sequence in bone. This may have resulted from massive release of bone ingrowth factors, which implies that the brief inflammatory process observ ed in the early stages of implantation was favorable to the osteoconduction process. (C) 1999 John Wiley & Sons, Inc.