Microbubble-induced detachment of coadhering oral bacteria from salivary pellicles

The presence and maturity of the salivary pellicle influences microbial adhesion and its tenacity in the oral cavity, posing a challenge to different plaque-control systems. Some plaque-control systems rely on surface-tension forces arising from passing microbubbles sprayed over the pellicle. Passage of such bubbles is accompanied by a high fluid flow, but systematic studies are lacking on the contribution of fluid flow vs. microbubbles towards plaque removal. Therefore, the aim of this study was to determine the detachment efficacy of laminar fluid flow (wall shear rates 11,000-16,000 s(-1)), with and without microbubbles, towards the detachment of Actinomyces naeslundii T14V-J1 and Streptococcus oralis J22, and their coadhering aggregates, from salivary pellicles formed over 2 h or 16 h from reconstituted human whole saliva. Microbubbles in a fluid flow were more efficient at inducing single bacterial detachment, resulting in almost complete (97%) removal for S. oralis J22 and a 15-fold increase in A. naeslundii T14V-J1 removal as compared to the detachment caused by fluid flow alone. A. naeslundii was more difficult to remove and apparently formed the strongest bonds with high-molecular-weight proteins in 16-h pellicles. The detachment of coaggregates after 2 min left a substantial amount of adhered bacterial mass, including more than 60% of singly attached A. naeslundii on the pellicle surface, providing nucleation sites for the de novo adhesion of coadhering streptococci.