Investigation of the effects of bioactive ceramic powders including boron, zinc, magnesium and calsium on the thermal and mechanical properties of acrylic bone cement

Acrylic bone cements are a two-component system consisting of powder and liquid phase. It is frequently used in orthopedic surgery to provide prosthesis fixation. The paste-like mixture formed after mixing the powder and liquid components of bone cement has a self-curing structure. Benzoyl radicals formed as a result of the reaction of benzoyl peroxide in the powder component and n,n dimethyl para-toluidine in the liquid component initiate the polymerization reaction of methyl methacrylate. The polymerization reaction is exothermic and a large amount of heat is released. This resulting heat damages the surrounding healthy bone tissue. One of the biggest causes of aseptic loosening in prostheses is thermal necrosis of bone tissue. Another reason is the low mechanical strength of bone cements. In this study, it was aimed to create a composite material by adding ceramic powders consisting of minerals known to be effective in bone formation and repair, such as boron, magnesium and calcium, to an acrylic bone cement with standard viscosity, thus reducing the polymerization temperature and increasing mechanical strength. Boric acid (H3BO3), zinc borate (2ZnO.3B2O3.3,5H2O), magnesium oxide (MgO) and tricalcium phosphate (Ca3(PO4)2) powders were preferred due to their easy local access and low cost. Ceramic powders were added to the powder component of acrylic bone cement in different amounts and particle sizes in single (unimodal) and binary (bimodal) forms. Temperature measurement, compression test and bending test were applied to the created composite bone cements. It has been determined that tricalcium phosphate is most effective in reducing the polymerization temperature of bone cement and zinc borate in increasing mechanical strength. The thermal and mechanical synergistic effects of these two materials were investigated by adding them to bone cement at different rates. By mixing 5% by weight of zinc borate with a particle size of less than 30 microns and 5% by weight of tricalcium phosphate with a particle size of more than 88 microns into the bone cement, the lowest polymerization temperature was 63°C±3 and the temperature reached by the control group bone cement as a result of polymerization was 31.9°C lower. The highest mechanical strength was achieved by bone cement mixed with 1% by weight of zinc borate with a particle size of less than 30 microns and 5% by weight of tricalcium phosphate with a particle size of more than 88 microns. The flexural modulus was recorded as 3370.5±331,5 MPa, the flexural strength as 61.03±10,4 MPa and the compressive strength as 116.3±16,45 MPa, making it more durable than the control group bone cement. As a result, it was reported in this study that the polymerization temperature of bone cement added with tricalcium phosphate and zinc borate decreased and its mechanical strength increased significantly.