An in vitro evaluation of the property of acrylic bone cements mixed with different types and proportions of contrast agents

Objective: To investigate the changes of the polymerizing process, X-ray density and ultimate compressive strength after polymerization of PMMA mixed with different types and proportions of contrast agents. Methods: PMMA was classified into four experimental groups according to the ratio of powder/liquid/pure powder of barium sulphate as 15:10:3, 15:10:1.5 and the ratio of powder/liquid/non-ionic liquid contrast agents as 15:10:5, 15:10:3. The ratio of powder/liquid as 15:10 of PMMA was taken for control experiment. Polymerizing process in vitro was measured respectively in each group including 8 samples. 40 cylinders were respectively created from five groups with the density of X-ray and ultimate compressive strength measured. Results: The periods of the polymerizing processes were prolonged significantly for about 60 -120 seconds after PMMA was mixed with different proportions of the powder of barium sulphate. The temperature changes during the polymerization were significantly different. X-ray density increased after PMMA mixing with the powder of barium sulphate, or with the liquid of non-ionic contrast agents. The highest density achieved in the group of PMMA mixed with pure powder of barium sulphate according to the ratio of 15:10:3. Comparing with the controlled group, the ultimate compressive strength of the PMMA mixed with non-ionic contrast agents decreased about 25%-31% (P<0.05), and the groups mixed with pure powder of barium sulphate showed no significant differences. Conclusions: After PMMA mixed with different proportions of barium sulphate powder, the period of the polymerizing processes could be prolonged significantly with increase of X-ray density to the highest hin the ratio of 15:10:3. The ultimate compressive strength of PMMA would not be influenced by adding barium sulphate in any proportion. (authors)