Biofilm formation and release of fluoride from dental restorative materials in relation to their surface properties

Objectives To elucidate the impact of surface properties and the release of fluoride from different glass ionomer cements on biofilm formation. Methods Standardized specimens manufactured from various classes of glass ionomer cements (GICs), a resin-based composite (RBC), and human enamel were subjected to surface analyses. Subsequent to simulation of salivary pellicle formation, Streptococcus mutans biofilm formation was initiated using a drip flow reactor for 48 h and 96 h. Biofilms were characterized by determining viable bacterial biomass and 3D biofilm architecture using SEM and CLSM; the release of fluoride from the specimens was measured using the ion selective micro method in dependence on various experimental conditions (incubation with sterile broth/bacteria/acid). Results Surface properties and biofilm formation correlated poorly, while the release of fluoride correlated well with viable streptococcal biomass and SEM/CLSM analyses. For all investigated materials, biofilm formation was lower than on enamel. The release of fluoride showed a significant dependency on the experimental conditions applied; the presence of biofilms reduced fluoride release in comparison to sterile incubation conditions. Conclusions Within the limitations of a laboratory study, the results suggest that biofilm formation on GICs cannot be easily predicted as a function of substratum surface parameters. The release of fluoride from glass ionomer cements contributes to control biofilm formation particularly in its early phases. Clinical significance Glass ionomer cements can actively control microbial biofilm formation, while biofilms modulate the release of fluoride from GIC materials.