Aspects of bioactive glass in dental resin composites

Abstract

Resin composites have been widely used as restorative materials in dentistry. However, the resin composites might pose a risk of secondary caries due to the bacteria accumulation at the interface (i.e. marginal gap) between the restoration and dental hard tissue. Bioactive glass (BAG) has been extensively studied regarding its mineralization and antibacterial properties. Hence, a narrative review was first conducted to cover the main aspects of BAG-loaded resin composites and adhesives, particularly focusing on physicochemical properties, mechanical properties, mineralization abilities, and in vitro biological responses. The review suggested that BAG fillers with small particle sizes and no more than 20 wt% loading amounts should be used to guarantee the appropriate mechanical properties. Additionally, BAG-loaded resin composites, especially for high BAG loading, showed mineralization ability manifested by an enhanced ions release, pH elevation, and apatite formation. Furthermore, the remineralization of teeth and antibacterial potential were shown to be enhanced. Nevertheless, it is essential to find an optimal balance between different properties.

Consequently, experimental resin composites were developed in this study by incorporating low quantities of 45S5 BAG (0.0, 1.9, 3.8, and 7.7 vol%) into UDMA/TEGDMA-based resin. The first laboratory study investigated the effects of BAG incorporation on the physical and mechanical properties of the experimental resin composites. Results showed that 7.7 vol% BAG loading had no influence on surface nanohardness, flexural strength, and flexural modulus, while slightly reducing compressive strength and biaxial flexural strength. The second study explored various mineralizing solutions other than standard simulated body fluid (SBF) that were sensitive to evaluate the mineralization potential for low quantities of BAG-loaded resin composites. Self-formulated “SHARP” solution was shown to induce a controlled growth of urchin-like carbonated hydroxyapatite microspheres self-assembled by nanorods from nano-sized octacalcium phosphate (OCP) on BAG-containing resin composite over time. For other solutions, nano-sized OCP particles could be deposited using HBSS and MEM, whereas SBF could not induce any apatite formation. The third study determined the in vitro biocompatibility with MC3T3-E1 cells when using composites extracts and direct exposure to BAG-loaded resin composites. Results demonstrated that preconditioning treatments using MEM and SHARP solutions would lead to unimpaired or even better cellular processes on BAG-loaded resin composites, implying good biological responses of BAG-loaded resin composites in vivo. In addition, the fourth study provided novel data concerning the antibacterial efficiency of the BAG-loaded resin composites in the S. mutans biofilm over time. Resin composites with 7.7 vol% BAG could not only reduce the cell viability in S. mutans biofilm on the resin composite surface but also disturb biofilm structure and reduce the biofilm thickness and bacterial aggregations, suggesting its inhibition effects on bacterial attachment or adherence with each other.

In summary, low quantities of BAG-loaded resin composites, in particular 7.7 vol% 45S5 BAG, were developed with a proper balance of mechanical properties, mineralization ability, in vitro biocompatibility, and antibacterial capabilities on S. mutans biofilms. Resin composites with low quantities of BAG seemed to be promising for clinical application.