Variation in adhesion of Streptococcus mutans and Porphyromonas gingivalis in saliva-derived biofilms on raw materials of orthodontic brackets

To evaluate differences in the adhesion levels of the most common oral pathogens, and , in human saliva-derived microcosm biofilms with respect to time and raw materials of orthodontic brackets. The samples were classified into three groups of bracket materials: 1) monocrystalline alumina ceramic (CR), 2) stainless steel metal (SS), and 3) polycarbonate plastic (PL), and a hydroxyapatite (HA) group was used to mimic the enamel surface. Saliva was collected from a healthy donor, and saliva-derived biofilms were grown on each sample. A real-time polymerase chain reaction was performed to quantitatively evaluate differences in the attachment levels of total bacteria, and at days 1 and 4. Adhesion of and to CR and HA was higher than the other bracket materials (SS = PL < CR = HA). Total bacteria demonstrated higher adhesion to HA than to bracket materials, but no significant differences in adhesion were observed among the bracket materials (CR = SS = PL < HA). From days 1 to 4, the adhesion of decreased, while that of and total bacteria increased, regardless of material type. The higher adhesion of oral pathogens, such as and to CR suggests that the use of CR brackets possibly facilitates gingival inflammation and enamel decalcification during orthodontic treatment.