Oral microbiology Flashcards
What is plaque?
a biofilm of microorganisms which forms its own microenvironment
Where on the tooth does most bacterial growth occur?
Gingival crevice
Why is the oral mucosa a habitat for bacteria?
Stratified non-keratinized epithelia
Readily colonised by commensals which can become opportunistic
What is gingival crevice fluid (GCF)?
serum components from the flow of serum-like fluid through the epithlial-gingival junction
Explain how GCF acts against infection
Increased production during infection -> localised small rises in pH -> shifts type of bacteria that can grow
Contains enzymes that can contribute to tissue destruction
Has antimicrobial properties: carries IgG and can contain leucocytes
What are the non-specific/physical antimicrobial factors in the oral cavity?
Saliva flow
Mucins and agglutinin
Sloughing off surface epithelial cells
What are the general antimicrobial/innate antimicrobial factors in the oral cavity and how do they work?
Lysozyme - bacterial cell wall lysis
Lactoferrins - block viral receptors, antibacterial
Sialoperoxidase - inhibit glucose
Antimicrobial peptides - disrupt microbial membranes of bacteria and yeast
PMNs (neutrophils) - engulfments and destruction of pathogens
What are the specific antimicrobial/adaptive antimicrobial factors in the oral cavity and how do they work?
Serum immunoglobulins/antibodies - prevent adhesion to reduce ability to colonise
Complement - bind to and promote phagocytosis of pathogens by activating neutrophils
Describe the process of dental plaque development
- initial deposition and colonisation of glycoproteins onto a clean surface
- forms microcolonies with polysaccharides, salivary proteins and glycoproteins via aerobic growth - pioneer species
- development of environment for anaerobic growth (more bacteria -> loss oxygen in environment)
- establishment of anaerobic bacteria and deposition (black pigmented anaerobes)
- mineral depositions
Which bacteria are the first to colonise the dental biofilm in plaque formation?
Streptococci and actinomycetes
Have adherence properties
Which anaerobic bacteria are established onto developed plaque?
Porphyromonas
gram -ve, anaerobic rods
What changes in plaque development allows more bacteria to colonise?
Nutrition varies as flora changes
Change in plaque pH
How can plaque lead to gingivitis?
sub-gingival mineral deposits and growth triggers inflammation
Bacteria also secretes enzymes weakening tissue -> more damage
How can plaque lead to periodontal disease?
Plaque and calculus get into gingival crevice -> inflammation and irritation -> changes in maintenance of dental and bone structure
These changes and host response -> changes in odontoblast and odontoclast activity -> demineralisation of enamel
What factors affect plaque development
Genetic
Ageing
Allogenic development (due to non microbial origin e.g., tooth eruption, dentures)
Autogenic development (due to changes in microbiology)
Bacterial factors (e.g., pili allow easy adhesion of bacteria)
