CE: The agent Flashcards
Host (tooth surface)
age (deciduous teeth more susceptible to demineralization), fluoride presence, root surface exposure, saliva flow rate & buffering capacity
- Higher chance if low in nutrients (magnesium & Vit D) necessary for healthy tooth development
Substrate (food)
Oral clearance, oral hygiene, eating frequency, food detergency, consumption of carbohydrates, carcinogenicity of consumed carbs
- When not actively removed, consumed more frequently, more sugars (sucrose containing) and sticky food à higher risk of caries
Oral bacteria
Development of caries depends on microbial load, plaque composition & acidogenicity & aciduricity, oral hygiene, fluoride presence in plaque
Time
Shift in microflora occur over short period, significant amount of time needed for
demineralization à white-spot or carious lesions – acid production doesn’t instantly cause decay,
early stages of remineralization can restore enamel
Biofilm
bacteria collect on edge of gums in cream-colored mass = plaque
Formation of an acellular layer
acquired pellicle= salivary glycoproteins, phosphoproteins, and lipids but NO bacteria – forms almost immediately on naked
enamel surface
Initial attachment
free-floating early colonizers (Strep. sanguinis) normally inhabits
mouth and form initial attachment to pellicle by weak and reversible van der Waals forces – if bacteria not removed, anchor themselves w/ adhesive structures
Irreversible attachment
bacteria unable to attach to pellicle begin to adhere to 1st layer of colonizers via specific adhesion-receptor interactions – bacteria replicate and form
microcolonies embedded in ECM
Early maturation
increased dental plaque complexity due to allogenic factors (O2 consumption w/n plaque creating anaerobic zones) – cell division and recruitment of new bacteria & increase bacteria population
Later maturation
microbial diversity continues to increase, while rates of cell division decreases – constant turnover of cells but overall composition remains roughly the same & thick 3D layer of dental plaque biofilm
Dispersion
enzymes that degrade biofilm & bacteria detach themselves from biofilm (sometimes in response to deleterious environ conditions in order to spread/colonize new
surfaces
Sugar metabolism
Extracellular invertase cleaves energy rich bonds btw glucose & fructose & bacterial cell transports sucrose across cell mem & cleaves bond via intracellular invertase & extracellular glycosyltransferases polymerize glucose molecule
while liberating fructose molecule so its free to enter bacterial cell & extracellular fructosyltransferases polymerize fructose while glucose molecule liberated to be freely
Intervention: taken up by cell & salivary amylase cleave polysaccharides
Acid production
Convert glucose, fructose, and sucrose into acids via glycolysis (main
energy generating pathway in all bacteria)
- Additional intermediate steps for S. mutans (ability to metabolize pyruvate further
à more energy & acid byproducts) – when excess sugars available, favor lactate dehydrogenase & lactic acid (btw meals metabolize energy reserve & produce
formic & acetic acid instead)
Etiology in Health & Disease
mature dental plaque= highly complex community of microbes, population varies person to person & btw diff sites in oral cavity (800 distinct oral species) healthy person has 50-100 diff species @ 1time
Ecological plaque hypothesis
- Low pH: acid sensitive bacteria die but aciduric bacteria will thrive & disruption in natural balance, increasing demineralization
- pH neutral: acid-sensitive bacteria thrive and acid production decreases & increase remineralization
Shift in plaque ecology caused by acid formed from fermentation of sugars causes what?
low pH (lower 5.5) where plaque community stable
Plaque below 4.5
catastrophe for plaque microflora that normally inhabit healthy mouth, increase in S. mutans & Lactobacilli
Biofilm
an aggregate of microorganisms in which cells adhere to each other and/or to solid substrate exposed to an aqueous surface
What holds biofilm together?
Extracellular polysaccharides produced by oral bacteria hold biofilm together & triggers changes to make is hard to remove over time
What adheres to biofilm to tooth surfaces and how?
Streptococci are Gram+ form chains & constitute large portion of lactic acid when
excess sugars available – adheres to biofilm on tooth surface by converting sucrose into adhesive dextran polysaccharide by dextransucrase (caries can still occur w/o this strand)
What is extremely aciduric (endure very acidic conditions) do not significantly contribute to caries but frequently isolated from caries lesions due to ability to survive low pH?
Lactobacilli Gram+ rods present in plaque in small #s
Biofilm disease that results in localized destruction of tooth tissues by acid is by
dropping below 5.5 pH demineralizes tooth enamel, early stages are
reversible b/c natural process of remineralization – enough mineralization lost so that soft organic matrix left behind disintegrates causing a cavity
Infectious disease that is transmissible BUT one does not ‘catch’ caries
First enters the body when baby passes through birth canal – caused by shift in oral microflora to caries-causing
bacterial types in response to a shift to an acidic pH by metabolism of sugars
Decay begins on the surface of teeth by
bacterial growing on food particles that lodge btw teeth
causing destruction
