engleski

Surface Precipitation of Hydroxyapatite by Experimental Bioactive Glass-containing Composites

Objectives: To formulate experimental composites containing bioactive glass (BG) that are capable of forming a hydroxyapatite (HA) layer on their surface. This effect has multiple potential benefits, such as sealing of the tooth/restoration interface for prevention of secondary caries, remineralization of dental hard tissues and occlusion of dentinal tubules. Methods: Five light-curable composites were prepared in a dual asymmetric mixer by blending a Bis-GMA/TEGDMA resin mixture with 4 µm particles of 45S5 BG, barium glass and silica in variable ratios. Total filler load was 70 wt%, whereas the ratio of BG varied from 0-40 wt%. The light-cured composite specimens (n=5) were immersed in phosphate- buffered saline for 7 days at 37 C° and their surfaces were examined for the presence of HA as a evidence of bioactivity. For the HA detection, Fourier-transform infrared (FTIR) and Raman spectroscopy, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used. A semi-quantitative assessment of HA was possible by analyzing the peak heights of the PO4 group vibrations in FTIR spectra and the HA layer density in SEM micrographs. Results: The presence of HA was confirmed by means of FTIR, SEM and EDS, while Raman spectroscopy proved insufficient sensitivity. The amount of HA precipitate increased with the BG wt%, while HA layers were consistently present in composites with more than 10 wt% of BG. Traces of BG were detected in composites containing 5 wt% of BG, however with poor reproducibility. The presence of silica fillers facilitated the HA precipitation, also enabling the precipitation at lower BG weight ratios. Composites with more than 20 wt% of BG were covered with thick, visually observable, HA precipitates. Conclusions: Experimental bioactive composites were produced, with the potential to resolve some of the issues pertinent to contemporary composite materials. The novel formulations will be subjected to a further comprehensive characterization.

bioactive glass ; hydroxyapatite ; remineralizing composite

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