Light Transmittance of Experimental Bioactive Glass Composites

Objectives: To evaluate the effect of two resin systems on light transmittance of experimental composite materials containing bioactive glass 45S5 (BG).

Methods: Two series of experimental composites were prepared based on a Bis-EMA/TEGDMA and a UDMA/TEGDMA resin system. Each composite series comprised five materials with 0, 5, 10, 20, and 40 wt% of BG and a total filler load of 70 wt%. After mechanical mixing, obtained composite pastes were applied in black Teflon rings (d=6 mm, h=2 mm, n=5) and pressed between two glass plates. Light curing was performed with 1000 mW/cm²for 60 s and the intensity of light that passed through the specimen was monitored using a charge-coupled device array fiber spectrometer, at a datacollection rate of 20 s^-1. Light transmittance was calculated as the ratio of the intensity of light that passed through the specimen and the intensity of light that passed through the empty specimen compartment.

Results: For all composites, a significant increase in light transmittance (1.4-5.0 %) was observed during light-curing. Therefore, light transmittance data were reported and analyzed as initial and final values. Light transmittance (%) of UDMA/TEGDMA series (initial: 1.9-4.1, final: 5.2-7.5) was generally higher than that of Bis-EMA/TEGDMA series (initial: 1.5-3.2, final: 3.2-7.5). In Bis-EMA/TEGDMA series, light transmittance declined with increasing BG amount, as shown by final light transmittance (%) of 7.6, 5.7, 4.4, 3.4, and 3.2 for composites with 0, 5, 10, 20, and 40 wt% of BG, respectively. In UDMA/TEGDMA series, differences in light transmittance were observed among materials with different amounts of BG but with no consistent trend of decline as a function of the BG amount.

Conclusions: Unlike Bis-EMA/TEGDMA series, UDMA/TEGDMA series of experimental composites showed no systematical effect of the BG amount on light transmittance. For a given BG amount, UDMA/TEGDMA series showed higher light transmittance.