Addition of bioactive glass to glass ionomer cements: Effect on the physico-chemical properties and biocompatibility.

OBJECTIVES: Glass ionomer cements (GICs) are a subject of research because of their inferior mechanical properties, despite their advantages such as fluoride release and direct bonding to bone and teeth. Recent research aims to improve the bioactivity of the GICs and thereby improve mechanical properties on the long term. In this study, two types of bioactive glasses (BAG) (45S5F and CF9) are combined with GICs to evaluate the physico-chemical properties and biocompatibility of the BAG-GIC combinations. The effect of the addition of Al3+ to the BAG composition and the use of smaller BAG particles on the BAG-GIC properties was also investigated. MATERIALS AND METHODS: Conventional aluminosilicate glass (ASG) and (modified) BAG were synthesized by the melt method. BAG-GIC were investigated on setting time, compressive strength and bioactivity. Surface changes were evaluated by Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), EDS and PO43- -and Ca2+ uptake in SBF. Biocompatibility of selected BAG-GICs was determined by a direct toxicity assay. RESULTS: The addition of BAG improves the bioactivity of the GIC, which can be observed by the formation of an apatite (Ap) layer, especially in CF9-containing GICs. More BAG leads to more bioactivity but decreases strength. The addition of Al3+ to the BAG composition improves strength, but decreases bioactivity. BAGs with smaller particle sizes have no effect on bioactivity and decrease strength. The formation of an Ap layer seems beneficial to the biocompatibility of the BAG-GICs. SIGNIFICANCE: Bioactive GICs may have several advantages over conventional GICs, such as remineralization of demineralized tissue, adhesion and proliferation of bone- and dental cells, allowing integration in surrounding tissue. CF9 BAG-GIC combinations containing maximum 10mol% Al3+ are most promising, when added in ≤20wt% to a GIC.

Bioactivity and biocompatibility of two fluoride containing bioactive glasses for dental applications.

OBJECTIVE: Bioactive glasses (BAG) form, in contrast to formerly used implant materials, a stable bond with tissues, especially bone, when implanted. Nowadays BAGs are often mixed with a cement/composite that hardens in situ to broaden its applications in dentistry or orthopedics. The bioactivity and biocompatibility of possible BAG candidates for BAG-cement/composite development were evaluated. METHODS: Two fluoride containing BAGs were tested: a Na+-containing (45S5F), based on the first commercial BAG, and a Na+-free BAG (CF9), with a higher Ca2+ and PO43- content. BAGs were tested on their bioactivity upon immersion in SBF for 7days by evaluating the surface changes by FT-IR, SEM, EDS and PO43- and Ca2+ uptake and/or release from SBF. Moreover, the biocompatibility of the BAGs was investigated with a direct contact cell viability study with HFF cells and a cell adhesion study with MG-63 cells. RESULTS: The Na+-free BAG, CF9, showed the highest potential to bioactivate cements because of its high Ca2+-release and apatite (Ap) formation, as evidenced by SEM pictures and corresponding EDX patterns. FT-IR confirmed the formation of an Ap layer. Moreover CF9 had a higher biocompatibility than 45S5F. SIGNIFICANCE: For the bioactivation of GICs/composites in order to enhance bonding and remineralization of surrounding tissues, fluoride containing BAG may have advantages over other BAGs as a more stable fluorapatite can be formed. CF9 may be an excellent candidate therefore.

The influence of particle size and fluorine content of aluminosilicate glass on the glass ionomer cement properties.

OBJECTIVE: Glass ionomer cements (GIC) are clinically accepted dental restorative materials mainly due to their direct chemical adhesion to both enamel and dentin and their ability to release fluoride. However, their mechanical properties are inferior compared to those of amalgam and composite. The aim of this study is to investigate if combinations of nano- and macrogranular glass with different compositions in a glass ionomer cement can improve the mechanical and physical properties. METHODS: Glasses with the composition 4.5 SiO2-3 Al2O3-1.5 P2O5-(5-x) CaO-x CaF2 (x=0 and x=2) were prepared. Of each type of glass, particles with a median size of about 0.73 µm and 6.02 µm were made. RESULTS: The results show that the setting time of GIC decreases when macrogranular glass particles are replaced by nanogranular glass particles, whereas the compressive strength and Young's modulus, measured after 24 h setting, increase. The effects are more pronounced when the nanogranular glass particles contain fluoride. After thermocycling, compressive strength decreases for nearly all formulations, the effect being most pronounced for cements containing nanogranular glass particles. Hence, the strength of the GIC seems mainly determined by the macrogranular glass particles. Cumulative F--release decreases when the macrogranular glass particles with fluoride are replaced by nanogranular glass particles with(out) fluoride. SIGNIFICANCE: The present study thus shows that replacing macro- by nanogranular glass particles with different compositions can lead to cements with approximately the same physical properties (e.g. setting time, consistency), but with different physicochemical (e.g. F--release, water-uptake) and initial mechanical properties. On the long term, the mechanical properties are mainly determined by the macrogranular glass particles.

Infrared spectrometric study of acid-degradable glasses.

The composition of glasses used in glass-ionomer cements affects their leaching behavior and hence the properties of the cement. The aim of this study was to correlate the composition and leaching behavior of these glasses with their infrared absorption characteristics. The wavenumber of the absorption band of the Si-O asymmetric stretching vibration shifts to a higher value with decreasing content of mono- and bivalent cations in the glass. This effect can be ascribed to the influence of these extraneous ions on the glass network order and connectivity. Preferential leaching of these ions induces an increase of asymmetric stretching vibration and a general modification of the band profile. The results can be correlated with the x-ray diffraction characteristics of the glass.