A bone substitute composed of polymethylmethacrylate and α-tricalcium phosphate: results in terms of osteoblast function and bone tissue formation

The biological properties of a composite polymeric matrix (PMMA+α-TCP) made of polymethylmethacrylate (PMMA) and alfa-tricalciumphosphate (α-TCP) was tested by means of in vitro and in vivo investigations. PMMA was used as a comparative material. Osteoblast cultures (MG 63) demonstrated that PMMA+α-TCP significantly and positively affected osteoblast viability, synthetic activity and interleukin-6 level as compared to PMMA. At 12 weeks, the PMMA+α-TCP implants in rabbit bone successfully osteointegrated in trabecular and cortical tissue (affinity index: 57.14±8.84% and 68.31±6.18%, respectively). The newly formed bone after tetracycline labelling was histologically observed inside PMMA+α-TCP porosity. The microhardness test at the bone–PMMA+α-TCP interface showed a significantly higher rate of newly formed bone mineralization compared with PMMA (+83.5% and +58.5%, respectively), but differences still existed between newly formed and pre-existing normal bone. It is herein hypothesized that the present positive results may be ascribed to the porous macroarchitecture of PMMA+α-TCP and the presence of the bioactive ceramic material that could have a synergic effect and be responsible for the improvement of (a) the material colonization by bone cells, (b) osteoblast activity, (c) osteoinduction and osteoconduction processes, (d) bone remodelling.