Physico/Chemical Characterization, In Vitro, and In Vivo Evaluation of Hydroxyapatite/PLGA Composite and Tricalcium Phosphate Particulate Grafting Materials

Background: The purpose of this study was to physico/chemically characterize and evaluate the in vitro cytotoxicity/in vivo bone regeneration of two grafting materials in a rat calvaria model. Materials and Methods: Two particulate grafting materials, Hydroxyapatite (HA)/PLGA (poly [L-lactide-co-glycolide]) composite (MA1) and Tricalcium Phosphate (MA2), were characterized by SEM, TEM, XRD (Rietveld), and FTIR. The cytotoxicity was evaluated by the ISO10993-5 method. Two critical defects with 5.5 mm in diameter were created bilaterally in the calvaria of 20 Wistar rats. One defect was filled with a grafting material, and the other was the control (C, blood clot). After four and eight weeks in vivo, the amount of new bone filling the defects was evaluated using micro-computed tomography with a slice resolution of 30 μm. Statistical analysis was performed by one-way ANOVA at 95% level of significance. Results: The physico/chemical analytical tools showed that MA1 was a Siand Mg-doped Hydroxyapatite/PLGA composite, and MA2 was a ß-TCP-based powder presenting ~9% Ca2P2O7 secondary phase. Both powders were not cytotoxic up to 50% extract concentration. The new bone volume to total defect volume ratios at four weeks were (mean ± SD) MA1=14.8±7.9%a, MA2=16.1±7.2%a, and C=6.5±1.6%b. At eight weeks, the values were MA1=22.6±7.2%a, MA2=19.9%±4.0a, and C=7.4±5.2%b. Conclusion: Despite substantial compositional differences, non-signifi cant differences in the amount of new bone formation were observed. Both materials presented osseoconductive properties.