Development and In Vitro Characterization of Bioactive Glass based Dental Composites

Objectives: It is desirable for a dental composite to have bioactive properties in order to suppress the formation of secondary caries at the restoration-tooth interface. Therefore, the aim of this study is to develop a novel bioactive glass composite with improved properties.
Methods: The bioactive glass (BAG) SiO2-CaO-CaF2-Na2O was prepared via the melt quench route. The composition was based on a chemical analysis of the reactive glass used in an existing composite. The resin was prepared using Bisphenol A ethoxylate dimethacrylate (BisEMA), Tri (ethylene glycol) dimethacrylate (TEGDMA), 2-(Dimethylamino) ethyl methacrylate (DMAEM), camphorquinone and 4-meta was added to enhance the bond with the tooth mineral. The glass to resin ratio was 80:20 by weight. Either the BAG or an inert barium boro-aluminosilicate glass (IG) (Schott Glass Lanshut GERMANY) was used. Discs measuring 10mm and 1.2mm thickness were made using a Teflon mould. These were immersed in artificial saliva (AS) with different pH values (pH=4 ,pH=7 and pH=6.5). After different time intervals the pH and fluoride content of the solutions were measured. The discs were characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), 19F MAS-NMR spectroscopy and Scanning electron Microscopy (SEM) for apatite formation.
Results: All BAG samples showed an increase in pH with time. FTIR spectra and XRD patterns showed characteristics peaks for the formation of apatite for the BAG composites SEM images on the BAG-resin discs In AS7 and AS6.5 showed apatite formation on the surface of the discs. The BAG composites released fluoride, however the amount released depended on the immersion media used. The 19F MAS-NMR spectra indicated the formation of both fluorapatite and calcium fluoride. No changes were observed with the IG composites in any of the immersion media.
Conclusions: The SiO2-CaO-CaF2-Na2O BAG imparts desirable properties to the composite including an increase in pH and apatite formation that may be beneficial in reducing the incidence of secondary caries in marginal gaps.