The rationale for a degradable bioactive glass coating is to lead the bone to appose gradually to the metal without the release of non-degradable particles. Two formulations of bioactive glasses, already described in the literature, have been studied: bg A and bg F. A non-bioactive glass (glass H) was sprayed as a control. Glass-coated Ti6Al4V cylinders were implanted in the femoral canal of New Zealand White rabbits. Samples were analysed by back scattered electron microscopy (BSEM) and electron dispersive analysis (EDX).

Bone was in tight apposition with the coating. As time progressed, images were found where bone showed features of physiological remodelling (newly formed bone filling areas of bone resorption) close to the coating. At the interface the apposition was so tight that it was not possible to discern a clear demarcation, even at higher magnification (more than 2500x). There was a gradual degradation during time and at 10 months bone was found apposed directly to the metal in more than half of the samples. In contrast, the non-bioactive glass coating showed complete integrity at any time examined and a clear demarcation with the coating was evident. Two peculiar features of the behaviour of bioactive glass coatings in vivo are: (a) degradation during time; and (b) promotion of a tight apposition with the newly formed bone.