title: Dental biofilm: ecological interactions in health and disease.
abstract: BACKGROUND
  The oral microbiome is diverse and exists as multispecies microbial communities on oral surfaces in structurally and functionally organized biofilms.
  
  
  OBJECTIVE
  To describe the network of microbial interactions (both synergistic and antagonistic) occurring within these biofilms and assess their role in oral health and dental disease.
  
  
  METHODS
  PubMed database was searched for studies on microbial ecological interactions in dental biofilms. The search results did not lend themselves to systematic review and have been summarized in a narrative review instead.
  
  
  RESULTS
  Five hundred and forty-seven original research articles and 212 reviews were identified. The majority (86%) of research articles addressed bacterial-bacterial interactions, while inter-kingdom microbial interactions were the least studied. The interactions included physical and nutritional synergistic associations, antagonism, cell-to-cell communication and gene transfer.
  
  
  CONCLUSIONS
  Oral microbial communities display emergent properties that cannot be inferred from studies of single species. Individual organisms grow in environments they would not tolerate in pure culture. The networks of multiple synergistic and antagonistic interactions generate microbial inter-dependencies and give biofilms a resilience to minor environmental perturbations, and this contributes to oral health. If key environmental pressures exceed thresholds associated with health, then the competitiveness among oral microorganisms is altered and dysbiosis can occur, increasing the risk of dental disease.
authors.affiliation: Department of Oral Biology, School of Dentistry, University of Leeds, Leeds, UK.
authors.forename: P D
authors.initials: PD
authors.lastname: Marsh
authors.affiliation: Department of Preventive Dentistry, Academic Centre for Dentistry Amsterdam, University of Amsterdam and Vrije Universiteit, Amsterdam, The Netherlands.
authors.forename: Egija
authors.initials: E
authors.lastname: Zaura
mesh_terms: D018441:Biofilms; D006801:Humans; D056265:Microbial Interactions; D064307:Microbiota; D009059:Mouth Diseases / Q000382:microbiology*; D009909:Oral Health; D014070:Tooth / Q000382:microbiology*
keywords: ecology; gene transfer; interactions; metabolism; oral microbiome; signalling