Mechanical Properties of Experimental Composites With a Customized Bioactive Glass

Objectives: The aim of this in vitro study was to investigate the effect of a customized low-sodium fluoride-containing bioactive glass (F-BG) on the mechanical properties of experimental resin composites by comparing it to the conventional bioactive glass 45S5 (C-BG).
Methods: Two series of experimental light-curable resin composites were prepared by admixing 5, 10, 20, and 40 wt% of either C-BG or F-BG into a Bis-GMA/TEGDMA (70:30 wt%/wt%) resin matrix. Reinforcing fillers were added up to a total of 70 wt%. The composites were light-cured to obtain 2x2x16 mm sticks for measuring flexural strength and modulus using the three-point bending test. To evaluate the effects of aging on the degradation of mechanical properties, separate groups of specimens (n=20 per experimental group and time point) were prepared for testing after the following artificial aging protocols: 1 day (water, 37 °C), 30 days (water, 37 °C), and 30 days (water, 37 °C) + 10,000 thermocycles between 5 – 55 °C. The data were analyzed using a mixed model ANOVA and Weibull statistics.
Results: A dose-dependent reduction in flexural strength and modulus was observed for both experimental composite series; however, the reduction was significantly less extensive for the composites functionalized with F-BG. The ISO 4049 requirement for a minimum flexural strength (80 MPa after 1 day in water) was fulfilled for up to 20 wt% of C-BG and 40 wt% of F-BG. Aging-induced degradation of mechanical properties was less extensive for the F-BG composites compared to the corresponding C-BG composites. Weibull analysis showed highly material-dependent reliability, which was generally reduced as the amount of bioactive glass was increased.
Conclusions: Incorporating the customized low-sodium fluoride-containing bioactive glass as a functional filler in ion-releasing resin composites resulted in better mechanical properties compared to the corresponding materials functionalized with the conventional bioactive glass 45S5.