Plaque, gingivitis, periodontitis

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Plaque, gingivitis and periodontitis



A tenacious microbial deposit (biolfilm), which forms on hard tissues of the mouth, comprising of living, dead and dying bacteria and their byproducts, embedded in a matrix of salivary proteins.


  • microbes surrounded by an organic matrix
  • the organic matrix is derived from both the host and the microbes
  • composition varies at different sites on the same tooth, at the same site on different teeth and at different times on the same tooth site


  • in general it is found in anatomical sites protected from host defences
  • supragingival, fissure, approximal, smooth surface
  • subgingival
  • appliance associated


  • pellicle formation
  • deposition of bacteria
  • climax community
  • calculus formation


Early colonisation

  • Gram-positive cocci e.g. Streptococcus
  • Gram-positive rods increase e.g. Actinomyces
  • Gram-negative cocci (increase with time) as the plaque thickens, oxygen levels reduce and more anaerobic bacteria start to appear

Late colonisation and maturation

  • if the plaque is left undisturbed, periodontal pathogenic organisms increase, such as:
    • Porphyromonas gingivalis
    • Prevotella intermedia
    • Actinobacillus actinomycetemcomitans

How is dental plaque harmful?

  • dental plaque has a direct and indirect effect
  • direct metabolic products e.g. ammonia, hydrogen sulphide, organic acids etc.
  • indirect - endotoxins on the bacteria cause activation of the host's own immune response

Evidence that poor plaque control causes gingivitis

  • Loe's study, 1965:
    • dental students examined before study and amount of gingivitis noted
    • students abstained from brushing for two weeks - gingivitis occurred
    • when students reinstated brushing the gingivitis resolved

Dental calculus (tartar)

  • calcified plaque
  • forms adjacent to salivary ducts if plaque is left on the teeth
  • supragingival calculus is yellow-white but may stain darker with smoking
  • subgingival calculus is dark brown to black due to blood breakdown byproducts

Salivary ducts

  • parotid duct is in the cheek adjacent to the upper first permanent molar
  • submandibular and sublingual ducts open below the tongue on the floor of the mouth just lingual to the lingual aspect of the lower incisor



Inflammation of the gingival tissue without loss of tooth attachment i.e. periodontal ligament (reversible)


  • initiating factor is dental plaque accumulation
  • predisposing factors (local factors in the mouth which cleaning)
    • crowding
    • calculus
    • restorations/prostheses
    • soft tissues e.g. fraenum
    • tooth form variations e.g. root grooves, enamel pearls
  • modifying factors (systemic factors)
    • pregnancy/hormonal
    • diabetes mellitus
    • blood dyscrasias e.g. leukemia
    • immunodeficiency e.g. HIV/AIDS
    • drugs e.g. phenytoin (given for epilepsy and causes overgrowth of the gums)

Healthy gingivae


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