Antibacterial effect of a new bioactive glass on cariogenic bacteria

Abstract

Objectives: To investigate the antibacterial effect of a new bioactive glasses on cariogenic bacteria. Methods and materials: A newly developed bioactive glass named Huaxi bioactive glass-ceramic (HX-BGC) and its antibacterial effects were investigated. 3 M™ Specialty Glass 19933 (SG) was used as the positive control while deionized water was used as a negative control. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of HX-BGC and SG against four cariogenic bacteria (Streptococcus mutans, Streptococcus sobrinus, Lactobacillus acidophilius, Lactobacillus rhamnosus) were determined by a microdilution method. Subsequently, bacterial growth and acid production were assessed by co-culturing the four cariogenic bacteria species with HX-BGC or SG at different concentrations anaerobically at 37 °C. Optical density (at 660 nm) was assessed by a microplate reader and the acidity of the supernatant was measured by a pH electrode at 6, 12, 24, and 48 h. Microbial kinetics, morphology and viability were evaluated by counting colony forming units (CFU), scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM), respectively. Results: The MBC of HX-BGC againstS.mutans, S.sobrinus, L.acidophilus and L.rhamnosus were 15.63 mg/mL, 15.63 mg/mL, 7.81 mg/mL and 62.5 mg/mL, respectively. The optical density (7.8 mg/mL) value of the bacterial suspensions did not change during the 48 h of culture. The acidity of bacterial suspension kept steady at around pH 8.8. Results from counting the CFU indicated that HX-BGC had stronger antibacterial effect when compare to SG, which is consistent with the SEM and CLSM results. Conclusions: HX-BGC inhibits acid production and growth of cariogenic bacteria.