Long-term in vivo bioactivity and degradability of bulk sol-gel bioactive glasses

Melt-derived bioactive glasses have been used with success in various clini cal applications for over 10 years. Recently, particles of sol-gel-derived bioactive glasses with an initial high specific surface area have been show n to exhibit excellent osteoconductive properties as well as significant de gradability. In this work, we explored the longterm in vivo bioactivity and degradability of bulk sol-gel-derived glasses in a rabbit model. Two sol-g el compositions (58S and 77S Bioglass(R)) were used. Bulk 45S5 Bioglass(R) was used as a control. Both sol-gel-derived glasses demonstrated osteocondu ctive properties similar to 45S5 Bioglass(R). In addition, absorbability wa s observed for both sol-gel-derived glasses starting after 12 weeks of impl antation. Total absorption reached 40% after 52 weeks. No degradation could be measured in the case of bulk 45S5 melt-derived Bioglass(R) within 1 yea r of implantation. The degradation process was highly time dependent, as de monstrated by regression analysis. New bone formation was found to fill in areas that had been resorbed, similar to bone remodeling. This absorbabilit y can be assumed to be at least partially related to an osteoclastic resorp tion as viable osteoclasts-like cells were found to be in direct contact wi th the glass surfaces. (C) 2000 John Wiley & Sons, Inc.