In vitro dissolution of Synthos ceramics in an acellular physiological environment

"Synthos" (beta-tricalcium phosphate) implants in bone are resorbed and replaced with endogenous bone. This investigation was conducted to study by continuous flow and static system techniques, whether or not resorption of synthos occurs by passive dissolution at 37 degrees C. Calcium and phosphates were released in a time dependent manner from synthos in calcium and phosphate free Tris-Hcl buffer (pH 7.4). Scanning electron micrographs (SEM) of buffer exposed ceramics indicated breakdown of grain structure. In contrast, levels of human plasma calcium and phosphate were not altered by ceramics. Significant amounts of 32p were absorbed by the ceramics in the first hour and 45Ca in the second hour of exposure to plasma containing the radioactive isotopes. Exposure of ceramics to plasma did not alter the levels of plasm isotopes significantly for the remaining duration of the experiment. However, breakdown of grain structure was evident in SEM's of ceramics exposed to plasma. It appears that in an acellular physiological environment, dissolution of synthos is diffusion dependent and is limited to a localized surface exchange phenonmenon.