Dental plaque in vivo is a mixture of different strains of bacteria. To be able to compare different modes of plaque removal in vitro, this requires biofilm models with comparable properties as in vivo dental plaque.

Objectives: Here, we compare single strain and dual, co-adhering strain biofilms as well as plaque from human whole saliva with respect to their ease of mechanical removal in vitro.

Methods: Single strains of S. mutans, S. oralis and A. naeslundii were either adhered to pellicle-coated glass for 2h, or subsequently grown for 16h. Similarly, a co-adhering pair (S. oralis and A. naeslundii) and bacteria from whole saliva were allowed to adhere and form a biofilm. Biofilm removal was evaluated after manual, electric-rotary or sonic brushing.

Results: After 2h adhesion, single strains were 93% removed, regardless of the mode of brushing. Removal was slightly less after growth (81% removal). A biofilm consisting of co-adhering bacteria was 93% removed after 2h adhesion, but adhered significantly (p<0.05) stronger after growth (68% removal). Contrary, plaque from whole saliva was significantly (p<0.05) easier to remove after growth (97% removal) than after 2h adhesion (78% removal). Probably, adhesion of whole plaque weakens after growth with respect to a co-adhering biofilm because the many different colonizers present in whole saliva do not contribute to strong adhesion of the biofilm. Co-adhering S. oralis and A. naeslundii both belong to the initial colonizers of dental hard surfaces.

Conclusions: Biofilms consisting of early, co-adhering colonizers of dental hard tissues form the most strongly adhering biofilms, and are therewith best for use in mechanical plaque removal studies in vitro. Moreover, its composition is accurately controlled, opposite to the situation with whole plaque grown from whole saliva.

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