Co-relationship between bioactivity and mechanical properties on addition of ZrO2 in borophosphate glasses: In-vitro studies

The present study endeavours toward the investigation on the bioactivity and mechanical behaviour of ZrO₂ added borophosphate glasses having composition 40 B₂O₃ - 15 P₂O₅ - 20 CaO - (25-x) Li₂O - x ZrO₂ (where x (mol %) = 0.5, 1, 1.5, and 2) synthesized by melt quenching method. The effects of incorporating ZrO₂ into borophosphate glass matrix on its structural, physical, morphological, mechanical, and biological properties were studied. In-vitro bioactive behaviour of the glasses was confirmed by the formation of flake-like hydroxyapatite as observed in the FESEM image. Additionally, XRD and FTIR results showed a decrease in bioactive behavior with increasing ZrO₂ content in the glass matrix. The physical properties like density, molar volume, and excess volume, were measured to assess the changes in the borophosphate glass network. The weight loss of the ZrO₂ added borophosphate glasses and the change in the pH of the simulated body fluid were also studied. The assessment of mechanical properties suggests that the compressive strength ranged from 62.97–172.8 MPa and the micro-Vickers hardness value ranged from 4.36 to 5.7 GPa. The specific wear of the glass was calculated by measuring the weight loss that occurred during abrasion wear on a pin-on-disc setup. Cytotoxic behaviour was tested by using the MTT assay, which shows MG-63 cells are viable up to a concentration of 200 µg/mL. The present study evidently shows the fact that the incorporation of ZrO₂ in borophosphate glass matrix increases the mechanical properties at the expense of bioactivity.