Biodegradation of three different bioactive glasses for the repair of bone defects in dentistry

Granules of three different types of new active glasses (A, AKRA 15, AKRA 18) were implanted in holes surgically created in sheep's jaws in order to check their biodegradation at different times (2, 4, 8 and 12 months). The results show that: a) no osteodeposition occurs even after 12 months from the implant; b) after 8 months, only AKRA 15 granules are stili present in the hole, and after 12 months al so these granules disappear completely; e) after 2 months all the elements of the three glasses diffuse toward the biological surroundings with different velocities; d) in the outer degradation zone of the granules, a Ca-P rich layer exists, but the Ca/P ratio is such as to take into consideration a diffusion of these ions from the biological environment toward the glass surface.