Oral environment 3 Flashcards
volume of saliva in the mouth
1.1 ml (0.5 - 2.1 ml dispersed over 200cm2)
How thick is the film of saliva that covers the mucosa?
50-100um
Where in the mouth is the salivary film velocity flow the highest?
lower, lingual region (more calcium phosphate so more calculus)
Where in the mouth is saliva flow velocity the slowest?
Buccal and labial regions (higher caries risk as cariogenic sugars retained longer)
Directions of salivary flow in the mouth
From anterior to posterior, between buccal and lingual surfaces, vertically in vestibule and drawn across occlusion to centre.
What is clearance?
The rate at which substances are removed from the mouth
What factors affect clearance?
The region in the mouth (velocity of salivary flow), how many times you swallow, volume of saliva
Advantages of fast clearance
removal of harmful materials (e.g. sucrose) increased by high salivary flow rate.
Advantage of slow clearance
retention of beneficial substances (F-, chlorhexidine) improved by low salivary flow rate
Why should topical fluoride preparations be tasteless?
Gustation stimulates salivary flow which increases clearance and removed the fluoride.
Why should fluoride tablets be sucked not chewed?
Chewing creates mechanical pressure on PDL which increases salivary flow rate and increases clearance.
Clearance cycle
Stimulus increases salivary flow leading to saliva accumulating in the mouth. Triggers swallowing. There is a residual volume which is accumulates with saliva secreted triggering swallowing (cycle repeats)
Name of graph of plaque pH change over time
Stephan curve
What happens if there is an imbalance of remineralisation and demineralisation?
caries
What is the critical pH?
pH 5.5 - if pH decreases below 5.5, demineralisation occurs, if pH increases over 5.5, remineralisation occurs.
Why is the number of sugar exposures a day important?
Each exposure, the pH will decrease below the critical pH causing demineralisation (Stephan curve)
How does chewing gum immediately after receiving a sucrose rinse alter Stephan curve?
pH does not decrease as much to critical pH due to increased salivary flow which increases buffering (by bicarbonate) and clearance.
How does chewing gum affect the salivary flow rate?
Salivary flow rate increases initially, then decreases and plateaus at just above the stimulated flow rate.
How does chewing gum affect pH?
pH increases by 0.5 and it remains high (plateaus at approx pH 7) because HCO3- concentration continues to increase (despite decreasing salivary flow)
How can salivary pH increase by more than 1 pH unit from chewing gum?
When the gum contains bicarbonate
Why may chewing gum promote remineralisation?
Saliva contains calcium and phosphate and the pH does not decrease as much to below critical pH (due to buffering and clearance)
Advantage of sugar-free sweeteners
have a sweet taste but cannot be metabolised by plaque bacteria to produce acid
Examples of non-caloric sweeteners
aspartame, cyclamates, saccharin, sucralose
Examples of low caloric sweeteners
mannitol, sorbitol, xylitol
