Age Dependent Protection by Oral Biofilms Against Chemical Plaque Control

The biofilm mode of growth in the oral cavity offers protection against chemical plaque control. The degree of protection offered likely depends on the age of the plaque and can be assessed by Confocal Scanning Laser Microscopy (CSLM). Objectives: Aim of this study is to compare the protection offered by 9 and 72 h old dental plaques against chemical plaque control by dentifrice components. Methods: The left two quadrants of the dentition of five human volunteers were sampled for plaque after refraining from all oral hygiene during 9 or 72 h. Plaque was dispersed by sonication and divided in two portions. One portion (control) was immediately analysed after Baclight staining, while the second portion of dispersed plaque was exposed to a dentifrice slurry or a chlorhexidin rinse prior to CSLM. Volunteers subsequently flushed their mouths with a slurry of the same dentifrice or a chlorhexidin rinse, after which plaques were collected from the right two quadrants and analysed. Results: On average, 9 and 72 h old dental plaques contained 51% and 41% vital organisms, respectively. Exposure of dispersed plaques to dentifrice slurries and chlorhexidine yielded a reduction in vitality to between 1% to 4%. The biofilm protection offered was relatively small and 9 h old plaques exposed to dentifrice slurries and chlorhexidine in vivo had vitalities of 8% and 22%. 72 h old plaque offered significantly more protection against the dentifrice slurries and vitalities were on average 16 % higher than for 9 h old plaque. The chlorhexidine rinse, however, yielded a similar reduction in vitality for a 72 h as for a 9 h old plaque. Conclusions: The protection offered by the biofilm mode of growth as compared with bacteria in a planktonic state is relatively small, but increases with aging of the plaques.