Sintering temperature effects on the in vitro bioactive response of tape cast and sintered bioactive glass-ceramic in Tris buffer

Abstract

Tape casting procedures were used to form thin polymeric sheets (100 microm thickness) loaded with bioactive glass particulate. Blanks were punched from the sheets, stacked, laminated, and heated in air to 500 degrees C to remove the organic phase. The resulting bioactive glass discs were sintered at 800 degrees C, 900 degrees C, or 1000 degrees C. Because the material is built up in layers and can be machined in the green state, such a processing technique can be used to form complex-shaped materials. The in vitro bioactivity of the tape cast sintered (TCS) bioactive glass-ceramic discs was then assessed in Tris buffer. The sample surface area to volume buffer (SA/V) ratio was approximately 0.1 cm(2)/mL. Tape cast bioactive glass-ceramic sintered at 900 degrees C and 1000 degrees C formed crystalline hydroxyapatite layers after 24 h in Tris buffer as indicated by FTIR, SEM, and EDS analysis. Decreasing the SA/V ratio to 0.013 cm(2)/mL allowed for the formation of crystalline hydroxyapatite layers on the surface of 800C TCS bioactive glass-ceramic. Given the dependence of the bioactive response as a function of the processing schedule and SA/V ratio, it may be possible to tailor the response to that desired in vivo or in vitro for tissue engineering studies. Biaxial flexural strength of TCS bioactive glass-ceramic increased with increasing sintering temperature. Strength of samples sintered at 1000 degrees C for 3 h increased from 87 to 120 MPa after 2 weeks' immersion in Tris buffer.