Dopant effects on bioresorption and mechanical strength enhancement in calcium phosphate bioactive glasses

This study investigates the effects of dopant SiO₂, Na₂O, MgO, and K₂O into calcium phosphate-based bone materials, with a particular focus on bioresorption and mechanical strength. Calcium phosphate-based bone materials were characterized by distinguishing between four-component bioactive glass system, doped with SiO₂ and Na₂O, and six-component bioactive glass system, additionally doped with MgO and K₂O, to evaluate their properties. Bioresorption was evaluated through an in vitro dissolution of the synthesized bioactive glass (BG) following ISO 23317 (In vitro evaluation for the apatite-forming ability of implant materials) at 37 °C for 29 days. The dissolution results revealed the ion dissolution rates for the four-component and six-component bioactive glass system as follows: Si⁴⁺ ions, 1048.48 mg/L and 987.72 mg/L, respectively; Na⁺ ions, 986.36 mg/L and 462.66 mg/L, respectively; Ca²⁺ ions, 157.50 mg/L and 323.25 mg/L, respectively; and P⁵⁺ ions, 174.99 mg/L and 340.04 mg/L, respectively. These findings demonstrate that the dissolution rates of ions associated with bone formation were higher in the six-component bioactive glass system compared to the four-component bioactive glass system. Furthermore, the mechanical properties of both BG were evaluated via compressive strength testing. The results showed compressive strengths of approximately 45 MPa and 55 MPa for the four-component and six-component bioactive glass system, respectively, with the six-component bioactive glass system exhibiting superior strength. Thus, the incorporation of Mg²⁺ and K⁺ positively influenced both compressive strength and ion dissolution, resulting in higher compressive strength and faster ion release in the six-component bioactive glass system compared to the four-component bioactive glass system.