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In order to mimic more accurately the fast and feast periods experienced by natural dental plaque, the supragingival “feeding” model was established [34]. Therefore, the standard experimental protocol described above was modified as follows: (1) the proportion of saliva and mFUM was reversed to 30% saliva and 70% mFUM, and (2) the exposure to this altered medium was time limited. This means that after inoculation the discs remained for only 45 min in the feeding solution containing 0.3% glucose. Thereafter, they were subjected to three consecutive 1-min washes in 2 mL of 0.9% NaCl to remove growth medium and free-floating cells but not bacteria adhering firmly to the hydroxyapatite discs. The biofilms were then further incubated in new wells containing 1.6 mL of saliva and no mFUM. Only after 16, 20, 24, 40, 44, and 48 h were the biofilms pulse fed by transferring the discs for 45 min into 30% saliva/70% mFUM with 0.15% glucose and 0.15% sucrose. Thereafter, they were washed as described above and reincubated in saliva. Fresh saliva was provided after 16 and 40 h, respectively. After 64 h, the biofilms were washed and processed for further analyses.

These “feeding” biofilms are denser than supragingival biofilms generated by the batch biofilm model (see Fig. 1b) and adhere very strongly to the substrate. This model is therefore suitable for studies investigating mechanical or hydrodynamic effects on biofilms. In this context, the “feeding” biofilm model was used to investigate the biofilm removal capacity of ultrasonic scaler tips under standardized conditions, for example [29, 35].