Estudo do comportamento do polímero de mamona como material de substituição óssea em defeito diafisário no fêmur de ratos frente a alterações secundárias à associação com nanopartículas de sílica e zircônia

Abstract

The aim of this study was to evaluate the biological behavior of the polymer of castor oil as a substitute in bone defects in the femoral diaphysis of rats with the presence of nanoparticles of silica and zirconia at different times of evolution. We used 36 male Wistar rats, divided into four groups and subdivided by period of analysis, as follows: group 1 (G1) - bone defect filled with polymer of castor oil plus calcium carbonate, group 2 (G2) - polymer of castor oil with calcium carbonate doped with 5% of silica nanoparticles, group 3 (G3) - castor oil polymer with calcium carbonate doped with 10% of nanoparticles of silica, and group 4 (G4) - polymer of castor oil plus calcium carbonate doped with 5% zirconia. After the observation period of 15, 30 and 60 days, the animals were euthanized and the femurs removed and sent for histological evaluation and scanning electron microscopy. The porosity depended on the dopant, according to electron microscopy. Histological evaluation showed that there was bone growth in all groups studied, with larger growth trend of the group containing polymer of castor oil containing only calcium carbonate. In the initial period of assessment (15 days) there was no new bone formation in the animals of G2, which showed, together with the animals in the G4, intense presence of fibroblasts and a pseudocapsule of fibrous tissue around the implant. At 30 days, all groups showed similar results, and the differences were not statistically significant. After 60 days, it was noted less new bone formation in animals in groups 2 and 4 when compared to those of groups 1 and 3, however, increased growth and invagination into the bone material was observed in group 1 and increased presence of fibroblasts, osteoblasts and osteoclasts in group 3. There was no statistical difference regarding the presence of inflammatory reaction between the groups and moments studied. In conclusion, the association of the polymer of castor oil with nanoparticles of silicon oxide and zirconium is viable since both the silica and zirconia shown to be biocompatible, allowing bone growth into the pores of materials. However, at all times studied there was a higher estimated quantity of mature bone tissue in animals with implants of polymer of castor oil without dopant. The greater presence of osteoblasts, osteocytes and osteoclasts in the animals of the group containing 10% of silica in the polymer of castor oil suggests that the silica has an osteoinductive potential, favoring the aggregation and cell differentiation, persisting the integrated activity of the three types of cells involved in the process of activation-resorption-bone formation, even after long period of observation. The roughness may be an important morphological characteristic in the material studied with respect to aggregation and bone growth.