INTERFACIAL TISSUE-RESPONSE TO BIOACTIVE GLASSES WITH REDUCED SURFACEREACTIVITY

Bone bonding of surface active glasses paralleled compositional change s of the reacting glass surface. These reaction layers, however, were susceptible to mechanical failure upon loading. The objective of the c urrent work was to study the relationship between the kinetics of the thickness of the interfacial layers and the glass composition. Specifi cally the composition was changed by adding CaF2 and by increasing the SiO2 concentration. Three samples of each of five glass compositions were implanted in the partial edentulous jaws of beagle dogs. After 3 months, they were resected and prepared for histological analysis with the implants in situ. Bone bonding was observed at the surface of all five glass compositions. The glasses with low CaF2 content showed lar ge areas of bone bonding and the bone growth along the implant surface was enhanced by osteoconductivity. The bone bonding around glasses wi th high CaF2 content was rather patchy. Small areas of bone bonding al ternated with small islands of fibrous tissue contact. Osteoconductivi ty was observed also around these glass compositions. Scanning electro n microscopy analysis revealed that the thickness of the reacted glass decreased with an increase of the CaF2 concentration. The glasses wit h high CaF2 concentrations showed spots of excessive ion dissolution w hich could delay the bone bonding in this area. This was due probably to local variations of the microstructure of the glass. CaF2 addition increased the risk for crystallization of the glass. It was suggested that the interface boundaries between the crystalline and amorphous ph ases were more susceptible for ion dissolution.