Bioactive Glass-containing Anti-microbial Dental Composites: Flexural Strength, Modulus and Hardness

Objectives: The primary reason dental composites are clinically replaced is the appearance of recurrent decay at the interface or below the restoration. This is principally due to bacterial colonization of the interfacial gap. The sol-gel bioactive glasses (BAGs) synthesized in our lab to release silver or copper ions in addition to calcium and phosphate ions, have been shown to render composites more resistant to bacterial colonization. For this project, we prepared and mechanically tested novel dental polymer composite restorative materials using these BAGs as fillers.
Methods: The five types of BAG shown in Table 1 were synthesized in our laboratory. These glasses were ground/micronized and incorporated into a 1:2.5 bisGMA/EBPADMA visible light-cured resin. Bars for flexure testing (strength and E) in 3-point bending (25mm x 2mm x 2mm) were prepared, as well as 15mmX1mm discs for hardness testing. Commercial composite (Empress Direct, Ivoclar Vivadent, Amherst, NY) containing no BAG served as a control. Samples were aged for 24 hours in 100% humidity at 37°C prior to testing. ANOVA with post-hoc Tukey tests were used to statistically compare mean differences between the groups (α=0.05).
Results: All BAG-containing samples had similar flexural strength - no significant differences were seen amongst any of the BAG-containing compositions. The Cu-containing BAG composites had lower modulus than the Ag-containing one. The composites prepared using Cu- and Ag-containing BAGs were harder than those containing BAG65. All of the BAG-containing composites had significantly lower flexural strength, modulus, and hardness when compared to the commercial composite.
Conclusions: The complete replacement of the filler component of dental resin composite with anti-bacterial BAG may ultimately increase longevity and service life of dental restorations. However, increasing the filler load levels to increase strength, hardness and stiffness will be necessary to provide a clinically acceptable material with handling properties that practitioners will accept.