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BDS1 > Oral environment 3 > Flashcards

Oral environment 3 Flashcards

1
Q

volume of saliva in the mouth

A

1.1 ml (0.5 - 2.1 ml dispersed over 200cm2)

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2
Q

How thick is the film of saliva that covers the mucosa?

A

50-100um

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3
Q

Where in the mouth is the salivary film velocity flow the highest?

A

lower, lingual region (more calcium phosphate so more calculus)

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4
Q

Where in the mouth is saliva flow velocity the slowest?

A

Buccal and labial regions (higher caries risk as cariogenic sugars retained longer)

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5
Q

Directions of salivary flow in the mouth

A

From anterior to posterior, between buccal and lingual surfaces, vertically in vestibule and drawn across occlusion to centre.

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6
Q

What is clearance?

A

The rate at which substances are removed from the mouth

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7
Q

What factors affect clearance?

A

The region in the mouth (velocity of salivary flow), how many times you swallow, volume of saliva

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8
Q

Advantages of fast clearance

A

removal of harmful materials (e.g. sucrose) increased by high salivary flow rate.

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9
Q

Advantage of slow clearance

A

retention of beneficial substances (F-, chlorhexidine) improved by low salivary flow rate

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10
Q

Why should topical fluoride preparations be tasteless?

A

Gustation stimulates salivary flow which increases clearance and removed the fluoride.

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11
Q

Why should fluoride tablets be sucked not chewed?

A

Chewing creates mechanical pressure on PDL which increases salivary flow rate and increases clearance.

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12
Q

Clearance cycle

A

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)

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13
Q

Name of graph of plaque pH change over time

A

Stephan curve

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14
Q

What happens if there is an imbalance of remineralisation and demineralisation?

A

caries

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15
Q

What is the critical pH?

A

pH 5.5 - if pH decreases below 5.5, demineralisation occurs, if pH increases over 5.5, remineralisation occurs.

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16
Q

Why is the number of sugar exposures a day important?

A

Each exposure, the pH will decrease below the critical pH causing demineralisation (Stephan curve)

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17
Q

How does chewing gum immediately after receiving a sucrose rinse alter Stephan curve?

A

pH does not decrease as much to critical pH due to increased salivary flow which increases buffering (by bicarbonate) and clearance.

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18
Q

How does chewing gum affect the salivary flow rate?

A

Salivary flow rate increases initially, then decreases and plateaus at just above the stimulated flow rate.

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19
Q

How does chewing gum affect pH?

A

pH increases by 0.5 and it remains high (plateaus at approx pH 7) because HCO3- concentration continues to increase (despite decreasing salivary flow)

20
Q

How can salivary pH increase by more than 1 pH unit from chewing gum?

A

When the gum contains bicarbonate

21
Q

Why may chewing gum promote remineralisation?

A

Saliva contains calcium and phosphate and the pH does not decrease as much to below critical pH (due to buffering and clearance)

22
Q

Advantage of sugar-free sweeteners

A

have a sweet taste but cannot be metabolised by plaque bacteria to produce acid

23
Q

Examples of non-caloric sweeteners

A

aspartame, cyclamates, saccharin, sucralose

24
Q

Examples of low caloric sweeteners

A

mannitol, sorbitol, xylitol

25
Q

Potential side effect of low caloric polyol sweeteners

A

laxative

26
Q

Why is xylitol the most ideal sweetener?

A

Has an antibacterial effect (as well as being sugar-free)

27
Q

Which sweeteners are sugar-free?

A

low / non-caloric sweeteners

28
Q

Examples of bulk cariogenic sweeteners

A

sucrose, glucose, fructose, lactose

29
Q

At what percentage of the normal salivary flow rate do patients complain of dry mouth?

A

Below 50% of normal

30
Q

How many major salivary glands must loose their function for salivary flow rate to decrease below 50% of the normal?

A

more than one

31
Q

Will surgical removal of the right salivary gland due to a duct blockage from salivary calculus/stone cause xerostomia?

A

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.

32
Q

Potential causes of decreased salivary flow

A

drug side effect, radiotherapy for head and neck tumours, diseases (of salivary glands, systemic, fluid/electrolyte loss or imbalance)

33
Q

How many drugs have reduced salivary flow as a recognised side effect?

A

> 400 drugs

34
Q

How may drugs cause reduced salivary flow as a side effect?

A

By interfering with ANS control of salivary glands

35
Q

How can you identify whether the patient is suffering reduced salivary flow as a drug side effect?

A

Check drugs in the MH with the British National Formulary (BNF)

36
Q

Potential side effects of radiotherapy for head and neck tumours

A

decreased salivary flow, damaged glands and epithelia, osteoradionecrosis (death of bone tissue)

37
Q

Examples of diseases that can decrease salivary flow

A

infections and tumours in salivary glands. Sjogren’s syndrome (autoimmune disease targeting salivary and lacrimal glands)

38
Q

Type of caries associated with reduced salivary flow

A

smooth surface caries (areas which are easy to brush)

39
Q

Consequences of decreased salivary flow

A

increased caries, increased oral diseases, dysesthesia (burning), impaired oral function (chewing, speaking, swallowing), diminished taste, loss of protective components.

40
Q

Example of protective components lost due to reduced salivary flow

A

Antimicrobial agents, mucins, gustin, bicarbonate, phosphate, proteins therefore decreased buffering, decreased remineralisation (histatins, statherins, PRP, Ca, PO4)

41
Q

Why may people with reduced salivary flow be compelled to consume confectionary?

A

To increase salivation and wetten mouth

42
Q

Questions to ask when diagnosing SG hypofunction?

A

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?

43
Q

How can xerostomia be managed is functioning gland tissue is present?

A

Salivary flow can be stimulated by chewing or drugs

44
Q

Name of drugs that increase salivary flow rate

A

sialogogue

45
Q

How can xerostomia be managed if there is no functioning gland tissue?

A

Saliva substitutes can be used (e.g. mucin-based, cellulose-based) as water alone is not very effective.

BDS1 (50 decks)

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