Penetration of Biofilm

Mouth rinses kill plaque bacteria by penetration of the biofilm

Oral bacteria can be planktonic (free floating) or found as part of the biofilm. A biofilm is an accumulation of microbial cells within a matrix.1

The cooperative communal nature of this microbial community provides advantages to the participating micro-organisms. These include a broader habitat range for growth and an enhanced resistance to antimicrobial agents and host defenses. It may also enhance their ability to cause disease. In other words, micro-organisms in a biofilm create their own habitat, interact with each other, and are implicated in disease severity. Due to this community, biofilm organisms are better prepared to cope with adverse conditions such as attack by chemical agents or antimicrobials,1 in effect biofilms form a shield, impeding access of the agent.2 Additionally, bacteria may undergo phenotypic changes within biofilm that increase resistance.2 Bacteria found in the biofilm, such as F .nucleatum, P. gingivalis, and Veillonella sp. are associated with gingivitis and periodontal disease.3,4

Most mouth rinses are effective against planktonic bacteria but many are ineffective against bacteria in biofilm. For instance, one study compared 3 mouth rinses and a control (phosphate buffered saline). All the mouth rinses produced statistically significant 99.99% reductions (p≤0.0001) in two planktonic bacterial strains compared to the control. Only one of the mouth rinses (essential oils, LISTERINE®) produced significant reductions in biofilm strains, the other two (an amine fluoride/stannous fluoride-containing mouth rinse, and a triclosan and PVM/MA copolymer-containing mouth rinse) failing to show significant reductions versus control.5


  1. Ciancio SG (ed.). Efficacy of antiseptic mouthrinses on plaque biofilm. Biological Therapies in Dentistry 2009; 24(Supplement 2): 1–4.
  2. Barnett ML. The role of therapeutic antimicrobial mouthrinses in clinical practice: control of supragingival plaque and gingivitis. J Am Dent Assoc 2003; 134: 699–704.
  3. Fine DH et al. Effect of rinsing with an essential oil-containing mouthrinse on subgingival periodontopathogens. J Periodont 2007; 78: 1935–1942.
  4. Fine DH et al. Effect of an essential oil-containing antimicrobial mouthrinse on specific plaque bacteria in vivo. J Clin Periodont 2007; 34: 652–657.
  5. Fine DH et al. Comparative antimicrobial activities of antiseptic mouthrinses against isogenic planktonic and biofilm forms of Actinobacillus actinomycetemcomitans. J Clin Periodont 2001; 28: 697–700.