Biochemical events in Dental Plaque Flashcards
What are risk factors for caries
- Orthodontic appliances
- Xerostemia (dry mouth)
- Gum tissue recession
- Radiation therapy
- Smokeless tobacco
- Excessive alcohol consumption (xerostemia)
- Patients with poor oral hygiene = bacteria
What is the plaque composed of
Bacterial and salivary protein - 50%
Carbohydrates and lipids - 20-30% - extra and intracellular polysaccharides synthesised by bacteria
Inorganic components - 25% like Ca, P etc
What is the function of plaque fluid
Provides an aqueous medium for diffusion and exchange of substances between saliva and tooth surface
What is the main acid involved in caries formation
Lactic acid
What contributes to the extent of oral pH drop after eating glucose
- Type and amount of CHO available
- Bacteria present
- Salivary composition and flow
- Other food ingested
- Thickness and age of dental plaque
Write down the reaction of the conversion of glucose to lactic acid in yeast i think
Glucose –> Lactic acid + CO2 + Ethanol
What is glycolysis also known as
Embden-Meyerhof-Parnas Pathway (EMP)
What is the end product of glycolysis
Pyruvate
What can pyruvate be converted into
- Lactate (anaerobic)
- Acetaldehyde and then Ethanol
- Acetyl CoA and then further oxidation
Name some cariogenic bacteria
- Streptococci (S. mutans)
- Actinomyces
- Lactinobacilli spp
What kind of bacteria is S. mutans, what does it metabolise and where is it found in the mouth
Gram positive
Sucrose
Fissures
Where is Actinomyces found in the mouth and what disease is it associated with
Found in gingival plaque
Gingivitis
How can Lactobacilli produce caries
It produces lactic acid and acetate but this requires lactic acid
What is acidogenicity
The ability to produce acid rapidly from fermentable carbohydrate
What is aciduricity
The ability to survive and continue to produce acid at acidic pH
How do extracellular polysaccharides from cariogenic bacteria aid caries formation
Dietary sucrose to facilitate adherence to tooth surfaces and build up of large bacterial deposits
How do intracellular polysaccharides from cariogenic bacteria aid caries formation
Storage components to prolong acid formation and acidic pH
Write down the reaction for glucose to lactic acid in anaerobic conditions in humans
Glucose –> 2 lactic acid + 2 ATPs
What do homofermentative bacteria produce
Almost entirely lactic acid
What do heterofermentative bacteria produce
A mixture of metabolites - organic acids like acetic, propionic, succinct and formic acid
Ethanol
What is the ecologic plaque hypothesis
- Low level of MS or lactobacilli or other bacteria produce acid
- Frequent consumption of fermentable carbohydrate
- Best acid adaptated bacteria survive
- Increase level of MS and lactobacilli
How can bacteria maintain an optimum intracellular pH despite the acidic environment
- Low proton permeability of the cell membrane: cell wall thickening
- Production of bases
- Buffering capacity of the cytoplasm
- Active transport of proton out of cell
What form are intracellular polysaccharides stored as
Glycogen-amylopectin
When are intracellular polysaccharides used
Used as energy production and acid production when dietary CHO is depleted
How can Intracellular polysaccharides contribute to aciduricity
IPS –> Energy for ATPase –> Drive protons out of cell –> Adapt to low pH environment
What is the role of glucans around the plaque
- Major component of inter bacterial matrix
- Barrier to the outward diffusion of acids from plaque
Where can alkali generation come from in the mouth
- Ureolysis
- Strickland Reaction
- Arginine deiminase system - major source of ammonia, S. gordonii, S. rates, S. sanguinis, lactobacilli and spirochetes use enzyme arginine deaminase to catabolise arginine in diet
Describe the process of ureolysis
S. salivarius, A. Naeslundii, haemophili use enzyme urease to hydrolyse urea in saliva
Describe the strickland reaction
Peptostreptococci oxidise proline in amino acids and reduce protons in plaque
Describe the mechanism of the Arginine deaminase system
Major source of ammonia, S. gordonii, S. rates, S. sanguinis, lactobacilli and spirochetes use enzyme arginine deaminase to catabolise arginine in diet
What treatment options are there for cariogenic bacteria
- Specific Bacterial
- Bacteriocides
- Pathway inhibiting chemicals
- Acid neutralising smart materials
- Inhibiters of IPS formation pathways
What is dental plaque
An aggregation of bacteria and products onto the tooth surface
What is the pellicle
Salivary components adsorbed onto the HAP surface, forms rapidly and salivary glycoproteins tend to adhere to the surface well.
What about plaque fluid can cause cariogenic conditions
Changes in the ionic composition of plaque fluid can cause cariogenic conditions
What is rested and starved plaque fluid
Rested - one to several hours after eating
Starved - Following overnight fasting
What is the rough organic conc. and pH of Rested plaque fluid
High organic acid conc
Low pH
What is the rough organic conc. and pH of Starvedplaque fluid
Low organic acid conc
Higher pH
How long does it take bacteria to metabolise sucrose
about 5 mins its very quick then lactic acid will die off but won’t disappear as IPS/EPS can still be used
How does salivary pH of patients with high caries activity differ to those with low caries activity after a glucose challenge
- pH starts lower
- pH drops to lower pH
- pH recovery to resting is much slower
Due to presence of different bacteria
What contributes to the different starting pHs of patients with different levels of caries activity
- Bacterial composition affects metabolic properties of plaque, storage form of CHO = energy source when dieting so lactic acid is present in higher cones at rest
Even though sucrose consumption in the population hasn’t dropped hugely, why has the caries prevalence decreased largely
- Due to more use of fluoride
- More knowledge of affects of sugar
Just shows that caries aren’t entirely linked to sugar consumption
What sugars are the ones that are the most caries promoting
Small sugars - glucose, fructose, galactose etc
Are sugar alcohols cariogenic
NOPE
How do bacteria convert Glucose –> lactic acid
Anaerobic respiration
What can pyruvate be converted into depending on the type of bacteria
Ethanol
Totally to CO2 and H2O
Lactate
What is the key thing to remember about glycolysis and why
That enzymes catalyse each step, so inhibitors for certain enzymes can be used to prevent lactate production
AY BAWS CAN I HAE DE NOTE PLZZ
The fate of bacterial pyruvate depends entirely on the type of bacteria present
