Quantitative determination of adhesion patterns of cariogenic streptococci to various orthodontic brackets

Introduction: Information about the adhesion of cariogenic streptococci to orthodontic brackets can help to determine a means for preventing enamel demineralization. The purpose of this study was to investigate the adhesion levels of 4 cariogenic streptococci strains to various orthodontic brackets with respect to bracket type, bacterial strain, incubation time, and saliva coating. Methods: Five bracket types (monocrystalline sapphire, polycrystalline alumina, stainless steel, plastic, and titanium) were incubated with unstimulated whole saliva or phosphate-buffered saline solution for 2 hours. Binding assays were then performed by incubating tritium-labeled streptococci with the brackets for 3 or 6 hours. Results: Each cariogenic streptococci strain showed a characteristic adhesion pattern. The adhesion amounts were highest in the plastic brackets and lowest in the monocrystalline sapphire brackets. Longer incubation time generally increased bacterial adhesion. Saliva coating did not significantly influence the adhesion of S mutans strains, but it had a significant effect on the adhesion of S sobrinus strains. However, saliva coating tended to decrease the adhesion of cariogenic streptococci with the longer incubation time compared with the noncoated control. Conclusions: This study suggests that cariogenic streptococci have various patterns of adhesion according to the bracket type.