Abstract: BACKGROUND: Bioactive glass bone repair material has bone-bonding ability, bone induction ability and bone conduction characteristics. However, the performance of bioactive glass does not meet the requirements of clinical application, and the addition of boron is expected to improve the performance of bioactive glass.
OBJECTIVE: To study the effect of different contents of B2O3 replacing SiO2 on the mechanical properties and bioactivity of bioactive glass.
METHODS: Based on bioactive glass containing phosphorus nitrogen and oxygen (composition: SiO2-CaO-ZnO-Na2O-Si3N4-P2O5), B2O3 was used to partially replace the SiO2. The basic glass containing B2O3 with a mass fraction of 0% (group A), 5% (group B), 10% (group C), and 15% (group D) was fired using the high-temperature melting method (the total mass fraction of SiO2 and B2O3 in the basic broken glass was 41%). Porous bioactive glass scaffolds were fabricated by the organic foam impregnation method. Uniaxial compression and three-point bending method of universal mechanical testing machine were used to test mechanical properties. Four groups of scaffolds were immersed in simulated body fluids to detect the degradation performance of scaffolds. Scanning electron microscopy was used to observe the morphological changes of scaffolds before and after soaking. X-ray diffraction was used to analyze the phase composition of scaffolds before and after soaking.
RESULTS AND CONCLUSION: (1) With the increase of the mass fraction of B2O3, the compressive strength and bending strength of the porous bioactive glass scaffold increased, and there was a significant difference between the compressive strength and bending strength of the four groups (P ≤ 0.05). (2) After soaking in simulated body fluids, the porous bioactive glass scaffolds degraded gradually with the extension of time. At the same soaking time point, the degradation rate of the scaffolds was accelerated with the increase of the mass fraction of B2O3, and the compressive strength and bending strength of the scaffolds in the four groups were significantly different (P ≤ 0.05). (3) Scanning electron microscopy after soaking in simulated body fluids showed that a large number of granular materials were deposited on the surface of group A and group B after soaking for 1 day. After 3 days, the granular materials on the surface fused with each other to form film-like deposits. After 7 days, the films on the surface fused with each other to form pieces, basically covering the entire surface of the specimen. After soaking for 1 day, film-like material deposition was formed on the surface of group C, and after 3 days, the films on the surface were fused into pieces, basically covering the whole surface of the specimen. After soaking for 1 day in group D, flake material covering the whole surface of the specimen could be seen. (4) X-ray diffraction analysis after 1 day of immersion in simulated body fluids showed that the deposits on the surface of the four groups of scaffolds were crystallized hydroxyapatite. (5) B2O3 replacement of SiO2 can enhance the mechanical properties, degradation properties and in vitro mineralization activity of porous bioactive glass scaffolds.

Key words: bioactive glass, bone repair material, scaffold, mechanical property, bioactivity