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
Potential side effect of low caloric polyol sweeteners
laxative
Why is xylitol the most ideal sweetener?
Has an antibacterial effect (as well as being sugar-free)
Which sweeteners are sugar-free?
low / non-caloric sweeteners
Examples of bulk cariogenic sweeteners
sucrose, glucose, fructose, lactose
At what percentage of the normal salivary flow rate do patients complain of dry mouth?
Below 50% of normal
How many major salivary glands must loose their function for salivary flow rate to decrease below 50% of the normal?
more than one
Will surgical removal of the right salivary gland due to a duct blockage from salivary calculus/stone cause xerostomia?
no because only one gland is removed (more than one major salivary gland must be removed to cause a significant reduction in salivary flow rate.
Potential causes of decreased salivary flow
drug side effect, radiotherapy for head and neck tumours, diseases (of salivary glands, systemic, fluid/electrolyte loss or imbalance)
How many drugs have reduced salivary flow as a recognised side effect?
> 400 drugs
How may drugs cause reduced salivary flow as a side effect?
By interfering with ANS control of salivary glands
How can you identify whether the patient is suffering reduced salivary flow as a drug side effect?
Check drugs in the MH with the British National Formulary (BNF)
Potential side effects of radiotherapy for head and neck tumours
decreased salivary flow, damaged glands and epithelia, osteoradionecrosis (death of bone tissue)
Examples of diseases that can decrease salivary flow
infections and tumours in salivary glands. Sjogren’s syndrome (autoimmune disease targeting salivary and lacrimal glands)
Type of caries associated with reduced salivary flow
smooth surface caries (areas which are easy to brush)
Consequences of decreased salivary flow
increased caries, increased oral diseases, dysesthesia (burning), impaired oral function (chewing, speaking, swallowing), diminished taste, loss of protective components.
Example of protective components lost due to reduced salivary flow
Antimicrobial agents, mucins, gustin, bicarbonate, phosphate, proteins therefore decreased buffering, decreased remineralisation (histatins, statherins, PRP, Ca, PO4)
Why may people with reduced salivary flow be compelled to consume confectionary?
To increase salivation and wetten mouth
Questions to ask when diagnosing SG hypofunction?
does you mouth feel dry when eating a meal? Difficulty swallowing any foods? Sip liquids to help you swallow? does amount of saliva seem too little?
How can xerostomia be managed is functioning gland tissue is present?
Salivary flow can be stimulated by chewing or drugs
Name of drugs that increase salivary flow rate
sialogogue
How can xerostomia be managed if there is no functioning gland tissue?
Saliva substitutes can be used (e.g. mucin-based, cellulose-based) as water alone is not very effective.
