Introduction to Dental Plaque Flashcards
Define Dental Plaque.
-Structure, resilient yellow-greyish substance that adheres to intraoral handsurfaces, including removable and fixed restorations.
Define dental biofilm.
- Complex microbial community that develops on a tooth surface, and other hard non-shedding materials, embedded in a matrix of polymers of bacterial and salivary origin.
What is the link between caries and plaque?
- Plaque requires a tooth surface, time and sugar to develop
- Caries requires a tooth surface, plaque, time and sugar
- Streptococcus mutans bacteria causes caries
How does long does it take for gingivitis to occur because of plaque accumulation?
- Symptoms of gingivitis present within 21 days - subsidided in a week after tooth cleaning.
What are the different types of dental plaque?
- Supragingival plaque (found at or above gingival margin)
- Marginal plaque (found in contact with gingival margin)
- Subgingival plaque (found below gingival margin, between tooth and gingival pocket epithelium)
Outline the composition of dental plaque biofilm
- 70-80% bacteria
- 20-30% intracellular matrix
- Water channels
What are the organic components of plaque?
- Glycoproteins from saliva
- Polysaccharides produced by saliva
- Proteins
- Lipids
What are the inorganic components of plaque?
- Mainly calcium and phosphorus
- Minerals like sodium, potassium and fluoride
What are the sources of inorganic components in different types of dental plaque?
- Saliva is the source in supragingival plaque
- Gingival crevical fluid is the source in subgingival plaque
How does the mineral content change the plaque?
- Increasing mineral content changes the plaque mass to become calculus as it is calcified
What are the 3 phases of dental plaque formation?
- Formation of pellicle on tooth surface
- Initial adhesion of bacteria
- Colonisation/maturation
Outline stage 1 of dental plaque formation
- Forms in seconds after teeth have been cleaned
- Contains 180+ peptides, proteins and glycoproteins e.g. keratin, mucins and other adhesion sites for bacteria - bacteria bind to pellicle, not tooth directly.
Outline stage 2 of dental plaque formation
- Adhesin molecules on microbial cell surface interact with receptors in pellicle and adhere to it (primary colonisers)
- Over 4-8 hours, 60-80% of bacteria present are members of Streptococcus genus, rest are obligate aerobes and faculative anaerobes
Outline stage 3 of dental plaque formation (coadhesion)
- Coadhesion - primary colonisers provide new binding sites for secondary colonisers
- Oxygen removed, primary colonisers provide conditions for obligate anaerobes growth
Outline stage 3 of dental plaque formation (coaggregation)
- Genetically distinct bacteria become attached to one another via specific molecules
- Coadhesion + coaggregation develop complex microcolonies, eventually forming mature biofilm
How does dental plaque shift from early to mature plaque?
- Shift in microbial population from mainly gram positive organisms, to mainly gram negative organisms
What are the differences between gram positive and gram negative bacteria?
- Gram+ stain crystal violet, gram- stain red or pink
- Gram+ have no outer cell membrane, gram- do
- Gram- have a cell wall high in peptidoglycans (retains crystal violet dye), making them more resistant to antibodies
What is the corncob structure seen in supragingival plaque?
- Found in supragingival plaque near gingival margin
- Cocci held together by an extracellular polysaccharide matrix with web of central filamentous micro-organisms
How does rate of formation and location of plaque vary between individuals?
- Influenced by age, diet, salivary secretion, oral hygiene, tooth alignment, systemic disease and host factors
- Gram+ cocci and short rods predominate at tooth surface
- Gram- rods predominate in outer surface of mature plaque
What are the natural factors that aid plaque retention?
- Calculus
- Enamel projections
- Tooth fissures, grooves, pits and cracks
- Cervical and root caries
- Tooth crowding
