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

Tape casting procedures were used to form thin polymeric sheets (100 mum th ickness) loaded with bioactive glass particulate. Blanks were punched from the sheets, stacked, laminated, and heated in air to 500 degreesC to remove the organic phase. The resulting bioactive glass discs were sintered at 80 0 degreesC, 900 degreesC, or 1000 degreesC. Because the material is built u p in layers and can be machined in the green state, such a processing techn ique can be used to form complex-shaped materials. The in vitro bioactivity of the tape cast sintered (TCS) bioactive glass-ceramic discs was then ass essed 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 degreesC and 1000 degreesC formed crystalline hydroxyapatite layers after 24 h in Tris buffer as indicated by FTIR, SEM, and EDS analysis. Dec reasing the SA/V ratio to 0.013 cm(2)/mL allowed for the formation of cryst alline hydroxyapatite layers on the surface of 800C TCS bioactive glass-cer amic. Given the dependence of the bioactive response as a function of the p rocessing schedule and SA/V ratio, it may be possible to tailor the respons e to that desired in vivo or in vitro for tissue engineering studies. Biaxi al flexural strength of TCS bioactive glass-ceramic increased with increasi ng sintering temperature. Strength of samples sintered at 1000 degreesC for 3 h increased from 87 to 120 MPa after 2 weeks' immersion in Tris buffer. (C) 2001 John Wiley & Sons, Inc.