dental caries: microbiology

dental caries

dynamic process taking place within dental plaque covering a tooth surface which results in a disturbance of the equilibrium between tooth substance and the surrounding plaque fluid so that over time there is a net loss of mineral from tooth surface

ecological plaque hypothesis

a change in environmental condition can, over time, cause a change in plaque species composition that can result in an ecological shift in plaque and allow a subset of species to predominate

EPH relation to dental caries

prolonged pH in plaque → species thats prefers acidic environment predominating

∴ net demineralisation of enamel

impact of long-term acidic plaque (due to high sugar diet)

• proliferation of aciduric and acidogenic bacteria

• demineralisation occurs over remineralisation

• incr. mutans strep. + lactonacilli = more acid + faster rates = increased demineralisation

properties of cariogenic bacteria

sugar transport, acidogenity, aciduricity, adherence, polysaccharides (super and ah!love are peak)

Sugar transport

able to rapidly transport sugars - efficient + flexible

• uptake of variety of carbohydrates over a wide range of substrate conc. + pH

acidogenity (creating acid)

high rate of glycolysis → produces lactic acid ∴ low pH

acidurity/acidurance (enduring acid)

can grow, metabolise, survive in low pH

• S. mutans → exhibits changes upon exposure to acid (e.g Acid Tolerance Response ATR → protect+repair molecules, maintain intercellular pH abv extracellular environment)

adherence

able to attach to site → not removed by saliva

via adhesin molecules on cell surface

Polysaccharides

storing sugars for later metabolism in case of limited dietary sugar available

Polysaccharides - extracellular

structural integrity, enhances adhesion, diffusion barrier for L.A efflux (keeps acid in plaque), diffusion barrier for chemicals in plaque (prevents antimicrobials from reaching bacteria), protects bacteria from host, carb. storage

polysaccharides - intracellular

forms when limited carbohydrate available: carb. storage → prolonged exposure of tooth to acid, acidic environment to select for aciduric species