Physical Disturbance Effects on the Microbiota of Dental Plaque Microcosms

Flossing, important in oral hygiene, disturbs but does not necessarily remove plaque. Disturbance itself may reduce plaque periodontpathogenicity. Objective: To investigate effects of different modes of disturbance on the microbial composition of dental plaque microcosms, and test the ‘Intermediate Disturbance Hypothesis’. Methods: Plaque microcosms initiated from the same plaque-enriched saliva were cultured in the ‘Multiplaque Artificial Mouth’ (MAM) for 21 d under the same conditions; a constant supply of artificial saliva (DMM) and 3x6 min pulses of 5 % w/v sucrose daily. The microbiota were characterized by checkerboard DNA:DNA hybridization (CKB) analysis of 40 species. Duplicate plaques were disturbed by: (i) removing a small wedge sample every 2 days for CKB analysis, or (ii) removing a wide segment on d10 and d16, (iii) punching a pattern of 1mm holes into the plaque every 3 d, or (iv) a pair of 5mm holes on d6 and d16, or were (v) undisturbed. Simultaneously, plaques were cultured in a Constant Depth Film Fermenter (CDFF). Results: There was no detectable effect on the microbiota by amount of disturbance caused by wedge removal, and minimal effect by 1mm holes. The 2-day wedge-sampled sequence showed that during plaque maturation, aerobes, Streptococcus gordonii and S. mitis 2 decreased, and some anaerobes and lactobacilli increased. Removal of the wide segment and the creation of 5mm holes yielded increased levels of Neisseria mucosa, and S. gordonii. CDFF plaques with constant removal of fresh surface growth were more different and anaerobic than MAM plaques, Peptostreptococcus micros especially increased. All species probed were present in all plaques. Conclusions: Moderate disturbance of plaque appears to promote the less pathogenic early colonisers as predicted by the ‘Intermediate Disturbance Hypothesis’. Selective removal of plaque growth surface ‘early colonisers’ by the CDFF combines disturbance with an increased proportion of anaerobic climax species.