Oral Microbiology Flashcards

Flashcards covering vocabulary terms from an Oral Microbiology lecture.

Oral Microbiology

The study of the bacteria that are natural inhabitants of the oral cavity.

Dental Plaque

Bacteria found on human tooth surfaces in microbial communities.

Biofilms

Microorganisms immobilized at a surface and frequently embedded in an organic layer.

Dental Caries

Bacteria in dental plaque are the etiological agents.

Gingivitis

Specific bacteria growing at the margin of the tooth and the soft tissue or gingiva (gums) are responsible for inflammation and bleeding of the gums.

Periodontal Disease

Failure to remove the bacteria at the gingival margin can lead to destruction of the tissue adjacent to the tooth, creating periodontal pockets.

Destructive periodontitis

Pockets are 8-10mm and filled with variety of anaerobic bacteria.

Interactions between microbial species

Can be physical:

Non-specific: electrostatic and hydrophobic

Specific (protein-protein):

Co-aggregation: between suspended cells

Co-adhesion: between a suspended cell and a biofilm cell

Example: corn-cobb-like structures between Candida albicans and Streptococcus sp.

Chemical-metabolical

Quorum sensing: release of signal molecules

Direct metabolic interactions: production of substrates that are useful for other microbes. Usually related to central carbón metabolism.

Quorum sensing competition

Mutacin 1140, produced by S. mutans with activity anti Gram positive

Salivaricin: produced by S. salivarius, inhibits the growth of S. pyogenes and S. pneumonia

Competence-stimulating peptide produced by S. mutans inhibits filamentation of Candida albicans.

Quorum sensing

Release of signal molecules in microbial species.

Saliva

Secreted into the mouth each day, flushes the epithelial surfaces and lubricates and protects tissues. Hypotonic with pH 6.7.

Major functions:

Physic-mechanical flushing

Tissue coating: lubrication and permeability barrier

Modulation of oral microbiota

Antiacid and neutralization of deleterious materials

Regulation of calcium and phosphate equilibrium

digestion

Normal Oral Flora

Diverse organisms, including bacteria, fungi, mycoplasmas, protozoa and viruses.

Pellicle

A layer of salivary proteins coating the teeth surface which allows bacteria to adhere. It is the first step in plaque formation.

The pellicle coated tooth is colonised by gram-positive bacteria, which are early colonisers. These include streptococcus, acintomyces…

Late colonisers like aggregator bacteria, eubacterium in plaque after 1 to 3 days.

Oral ecological zones

High biomass sites

Non-shedding surfaces

Supragingival tooth surfaces

Subgingival tooth surfaces

Shedding surface

The tongue: reservoir for anaerobic bacteria

Low biomass sites

Shedding oral mucosa surfaces

Saliva as a transitional zone

Materia alba

Exfoliated epithelial cells and food debris on the superficial surface of dental plaque.

Non-specific plaque hypothesis

Oral diseases are caused by the activity of all bacteria in plaque that accumulates on teeth and gingival crevices.The amount of plaque, instead of the composition, is considered to be the decisive factor in the development of oral disease. Founded in 1890 by miller

Specific plaque hypothesis

From the various components of the microflora found in the oral cavity, only some specific species are responsible for the initiation and progression of oral disease. Loesche in 1976

Ecological plaque hypothesis

Oral disease occurs when the host microbe balance is disrupted at the cellular or molecular level. Many oral diseases are polymicrobial in origin and both microbial and host factors contribute to the initiation and progression of disease Marsh in 1994

Keystone-pathogen hypothesis

Certain low-abundance microbial pathogens can trigger inflammatory disease that causes benign remodeling normal microbiota to a dysbiotic microbiota. 2012 by haji.

Oral Dysbiosis

Imbalance in the oral microbiome that can lead to oral and systemic diseases.

S.mutans, Candida, lactobacillus, scardovia and acintomyces thrive.

Causes caries and periodontists.

Fusobacterium necleatum

Present in plaque and linked to colorectal cancers.

Defence against caries

Caries

Enamel deminarilised by microbial acid, mainly due to strep mutant.

Factors include diet, saliva and teeth.

Occurs when normally low populations of acidogenic and aciduric bacterial species increase, following high-frequency carbohydrate exposure- carcinogenic plaque

Periodontal diseases

Gingivitis overgrowth of supra gingival plaque. Exacerbated by systemic conditions.

Periodontitis- inflammatory infection which causes destruction of ppl and alveolar bone. Chronic/aggressive.

Necrotizing necrosis and painful of ppl and alveolar bone.

Agressive perio is strongly associated with Aggregatibacter actinomycetemcomitans, either alone or synergistically with:

Capnocytophaga species

Porphyromonas gingivalis

Necrotizing is a specific, anaerobic, polymicrobial infection due to the combined activity of fusobacteria (Fusobacterium nucleatum), and oral spirochetes (Treponema spp.), called the Fusospirochaetal complex

Endodontic infections

Infections that occur within the tooth pulp in the root system or root apex.

Probiotics

Foods or supplements with live microorganisms to correct oral dysbiosis.