On the dissolution/reaction of small-grain Bioglass 45S5 and F-modified bioactive glasses in artificial saliva (AS)

The reaction of small-grain Bioglass® 45S5 in artificial saliva (AS), to produce a layer of hydroxy-apatite(HA) and/or hydroxy-carbonate apatite (HCA), has been studied and compared to the results obtained in asimple buffered solution (TRIS). Some potentially bioactive glasses based on the composition of Bioglass®and containing CaF2 (HCaCaF2 5% and HNaCaF2 5%) have also been studied, in order to analyze theeffects/changes produced when a F-containing glass surface is contacted with AS. The insertion of fluorinehas been proposed to improve bioactive glass bone-bonding ability, and to parallel fluorine-containingglass-ceramics currently used in dentistry. ICP-OES analysis of the solution, and FTIR spectroscopy of thesolid samples provided compositional information on the stages of reaction. These data were integratedwith XRD and the textural and morphological data, obtained by specific surface areas determination andTEM-EDS measurements. In the case of Bioglass® 45S5, a comparison at corresponding reaction timesindicates that the precipitation of an amorphous Ca-phosphate phase is faster in AS, but the crystallizationof HA/HCA is delayed in AS with respect to the TRIS solution. For fluoride-containing glasses, the sampleHCaCaF2 5%, in which CaF2 replaces part of CaO, possesses the fastest rate for HA/HCA crystallization (1week) in AS. Some lines of interpretation for these results are proposed.