Histological observations on biopsies harvested following sinus floor elevation using a bioactive glass material of narrow size range

We evaluated the bone augmenting capacity of bioactive glass particles, size range 300-355 microns (BG-particles), in human sinus floor elevations using histomorphometrical methods. A total of 10 patients underwent bilateral grafting, using a 1:1 mixture of autogenous bone particles (from iliac crest) and BG-particles at one side (experimental side), and bone particles only at the other side (control side, split mouth design). A total of 72 bone biopsies were taken at the time of fixture installation; that is, 3 patients at 4 months, 3 at 5 months and 3 at 6 months after grafting and 1 patient at 16 months (when she presented again). In each case 6 biopsies were taken, 3 left and 3 right. Histomorphometry showed that in grafts at control sides, trabecular bone was present after 4 months, comprising almost 41% of the tissue volume. This bone contained viable osteocytes and was of mature lamellar type and showed a mature histological appearance. Bone volume continued to increase slightly, to 42% at 5 months, 44% at 6 months and 45% at 16 months. The graft volume at experimental sides consisted at 4 months for 28% of woven and some lamellar bone, and increased to 35% at 5 months and 38% at 6 months, when mainly lamellar bone was found. At 16 months a lamellar bone volume of 45% was found. The BG-particles transformed and became excavated with time, starting at 4 months, and their centers gradually filled with bone tissue. All BG-particles had disappeared by resorption at 16 months after grafting and had been replaced by bone tissue. Parameters of bone turnover (% osteoid surface, % resorption surface, mineral apposition rate as measured by tetracycline labeling) indicated that bone remodeling was very active at both sides, during more than 6 months, despite the mature histological appearance of the bone tissue. From these histological observations, we conclude that a 1:1 mixture of autogenous bone/BG-particles seems a promising alternative to autogenous bone only, when low amounts of bone tissue are available for sinus augmentation.