Microchemical transformation of bioactive glass particles of narrow size range, a 0-24 months study.

Previous studies demonstrated the capacity of bioactive glass particles of narrow size range (300-355 microm, Biogran) to stimulate bone tissue formation without contact with pre-existing bone tissue. Chemical interactions between the bioactive glass and the surrounding tissue fluids caused the glass transformation. This study quantifies the time-dependent transformation process. Particles were implanted in the jaws of beagle dogs and resected after 1, 2, 3, 6, 12 and 24 months. Microchemical analysis was performed using a scanning electron microscope equipped with an energy dispersive X-ray analysis system. After one month, Na-ions were leached out and the particles transformed into two layers. In the center, a Si-rich gel was found on the outer surface, a Ca- and P-rich shell. After two months, the concentration levels of the outer Ca- and P-rich shell remained. In the center the Si-concentration decreased and the Ca and P concentration increased. After three months, Si disappeared completely from the center of the particle, while the Ca and P concentration increased. At one and two years, the Ca and P concentrations in the transformed particles equalled those of bone tissue, turning the transformed particle into a chemical equivalent of the bone mineral phase.