Evaluation of TCP-TTCP Cement in Rat Calvarial Model

Objectives: A calcium phosphate cement consisting of α-tricalcium phosphate and tetracalcium phosphate (TCP-TTCP: overall Ca/P ratio=1.8) as the solid phase and a calcium phosphate solution as the liquid phase was developed. TCP-TTCP cement provided good handling properties, desired hardening time, sufficiently high strengths, and was expected to have good biocompatibility and osteoconductivity. The aim of this study was to evaluate TCP-TTCP cement when used for repairing artificially created bone defects ( diameter: 5 mm ) in calvaria of rats.
Methods: TCP-TTCP cement included trisodium citrate anhydrous and polyvinylpyrrolidone-k90 as water reducing agent and washout resistance enhancer, respectively. Cement powder and liquid were mixed at a powder/liquid ratio of 3. A commercially available calcium phosphate cement, Osteovation, was used as a positive control. Defects filled without material were used as the negative control. Methods: Surgically created bone defects were filled with TCP-TTCP or a control cement. At 0 and 8 weeks after surgery, x-ray micro-CT for each surgical site was taken. At 8 weeks after the surgery, the animals were sacrificed, and biopsies were obtained. Subsequently, the sections were subjected to HE and TB staining and examined under a microscope. The value of new bone formation in each surgical site was evaluated quantitatively using NIH image analysis. Student’s t-test was used to establish statistical significance.
Results: TCP-TTCP cement showed good adaptability to defect sites and exhibited excellent washout resistance. The defects filled with either TCP-TTCP or the control cement were partially covered by newly formed bone and converted to natural bone. TCP-TTCP cement showed faster bone formation compared to the control cement. The defect without material, showed little or no new bone formation in the defects. These results were also confirmed by x-ray micro-CT observations.
Conclusions: The new TCP-TTCP cement showed superior handling properties and has high osteoconductive potentials comparable to those of the control cement in clinical use.