RESORPTION OF, AND BONE-FORMATION FROM, NEW BETA-TRICALCIUM PHOSPHATE-MONOCALCIUM PHOSPHATE CEMENTS - AN IN-VIVO STUDY

Hard cylinders (4.7 x 10 mm) of two kinds of beta-tricalcium phosphate -monocalcium phosphate monohydrate-calcium sulfate hemihydrate (beta-T CP-MCPM-CSH) cements with and without beta-TCP granules (500-1000 mu m ) were implanted into holes drilled in rabbit femoral condyles for up to 16 weeks. Empty cavities were used as control. Cement resorption an d new bone formation in the cylinders were evaluated with contact micr oradiography and quantified through an automatic image analysis system . At 4 weeks, both kinds of cement cylinders were surrounded by new bo ne. At 8 weeks, except for beta-TCP granules, both cement cylinders we re almost completely resorbed and replaced by bone tissue. At 16 weeks the bone in the cavities of both cements recovered a trabecular patte rn, but only the bone trabeculae in the initial cavity of the cement w ith beta-TCP granules became thick and mature. However, the cavities o f the empty control were still empty and large. These results show tha t the beta-TCP-MCPM-CSH cements stimulate bone formation and are rapid ly replaced by bone tissue. When added with nonresorbable beta-TCP gra nules, this cement maintains bone formation for a longer time. (C) 199 6 John Wiley & Sons, Inc.