Plaque-left-behind after brushing: intra-oral reservoir for antibacterial toothpaste ingredients.

OBJECTIVES: Plaque is never fully removed by brushing and may act as a reservoir for antibacterial ingredients, contributing to their substantive action. This study investigates the contribution of plaque-left-behind and saliva towards substantivity of three antibacterial toothpastes versus a control paste without antibacterial claims. MATERIALS AND METHODS: First, volunteers brushed 2 weeks with a control or antibacterial toothpaste. Next, plaque and saliva samples were collected 6 and 12 h after brushing and bacterial concentrations and viabilities were measured. The contributions of plaque and saliva towards substantivity were determined by combining control plaques with experimental plaque or saliva samples and subsequently assessing their viabilities. Bacterial compositions in the various plaque and saliva samples were compared using denaturing gradient gel electrophoresis. RESULTS: The viabilities of plaques after brushing with Colgate-Total® and Crest-Pro-Health® were smaller than of control plaques and up to 12 h after brushing with Crest-Pro-Health® plaques still contained effective, residual antibacterial activity against control plaques. No effective, residual antibacterial activity could be measured in saliva samples after brushing. There was no significant difference in bacterial composition of plaque or saliva after brushing with the different toothpastes. CONCLUSIONS: Plaque-left-behind after mechanical cleaning contributes to the substantive action of an antibacterial toothpaste containing stannous fluoride (Crest-Pro-Health®). CLINICAL RELEVANCE: The absorptive capacity of plaque-left-behind after brushing is of utmost clinical importance, since plaque is predominantly left behind in places where its removal and effective killing matter most. Therewith this study demonstrates a clear and new beneficial effect of the use of antibacterial toothpastes.

Acute and substantive action of antimicrobial toothpastes and mouthrinses on oral biofilm in vitro.

The aim of this study was to compare acute action by killing or disrupting oral biofilms through the use of antimicrobial toothpastes and mouthrinses in vitro and to investigate substantive action by absorption of antimicrobials in a biofilm. Biofilms from freshly collected human saliva were grown in 96-well microtitre plates. After removal of saliva, the wells of the microtitre plates were washed with sterile water (control), or exposed to a dilution series of mouthrinses (Corsodyl, Listerine, Meridol, Crest Pro Health) or to toothpaste slurries (Prodent Coolmint, Colgate Total, Zendium Classic, Crest Pro Health, Oral B Pro Expert, Crest Cavity Protection). Acute action was concluded from reduced continued (16 h) growth of treated biofilms with respect to the control. Substantive action was studied by exposing dead biofilms to mouthrinses or to toothpaste slurry. Substantive action through the absorption and subsequent release of antimicrobials from biofilm was concluded from reduced growth on top of the treated biofilms. All formulations showed acute action at the highest concentrations studied. Further dilution yielded loss of efficacy, or even stimulation of biofilm growth. Antimicrobial absorption in and the release of effective concentrations of antimicrobials from dead biofilms, was demonstrated for three selected antimicrobial products, indicating that antimicrobials remain bio-available for substantive action on new biofilms.