Prevention of caries by saliva

Question 1

Name the 4 static effects of saliva

Answer 1

1. Antibacterial
2. Supersaturated Ca/P
3. Pellicle formation
4. Plaque substrates (e.g. urea)

Question 2

Name the 3 Dynamic effects of saliva

Answer 2

Buffering (bicarbonate increases with flow)

Clearance of sugars/acids

Supersaturation (increases with flow)

Question 3

Which salivary gland do you find under the tongue?

Answer 3

Sublingual

located under floor of the mouth and below either side of the tongue

Question 4

Where are the parotid salivary glands located?

Answer 4

Located just in front of the ears

Question 5

Where are the submandibular glands located?

Answer 5

Located below the jaw

Question 6

Minor salivary glands contribute what percentage of total salivary flow?

Answer 6

around 10%

Question 7

Do all the salivary glands produce saliva with the same components?

Answer 7

No - each gland has a specific salivary protein profile; salivary proteins are synthesised specifically by the glands

Question 8

What type of process is making saliva?

Answer 8

It is an osmotic process - saliva glands secrete lots of sodium and chloride into ducts which helps draw in water via osmosis

Question 9

Which 2 ions stay at a similar level in both resting and stimulated states?

Answer 9

Phosphate

Calcium

Question 10

Levels of which ions increase when the parotid salivary gland is stimulated/increase with flow rate? (3)

Answer 10

Sodium
Chloride
Bicarbonate

Question 11

What cells make saliva?

Answer 11

Acini cells (sing. Acinus)

Question 12

What 2 cells are involved in salivary glands?

Answer 12

Acini

Striated ducts

Question 13

What do the striated ducts do in the formation of saliva? (2)

Answer 13

They absorb some sodium and chloride out of the saliva (but this process cannot keep up with stimulation - which is why levels increase)
They take up potassium and bicarbonate into the saliva

Question 14

Outline how saliva is bacteriostatic (2)

Answer 14

1. PRPs (proline-rich proteins), SIgA (secretory IgA) and mucins bind bacteria through glycosylation > then they aggregate. It is then easier to remove these via swallowing.
2. Lactoferrin, cystatins, histatins, lysozyme actively kill bacteria

Question 15

Which proteins actively kill bacteria in saliva? (4)

Answer 15

Lactoferrin
Cystatins
Histatins
Lysozyme

Question 16

If teeth are left in water, they would eventually dissolve - how does saliva combat this?

Answer 16

By having high levels of calcium and phosphate

Saliva is able to maintain high calcium and phosphate levels in solution

Question 17

Why does saliva require chelators?

What are 2 examples of these?

Answer 17

This is to prevent high levels of CaP precipitating - as calcium and phosphate like to bind to each other.

Statherin and acidic PRPs

Question 18

How do components of saliva bind with teeth? Why is this important?

Answer 18

Via their phosphate groups binding with the calcium in teeth/hydroxyapatite
(Statherin, acidic PRPs and histatin 1 bind as they all contain phosphate groups)

This is important because it is important in forming a stable pellicle of proteins on the teeth surface

Question 19

What is the approximate size of the surface area of the mouth?

Answer 19

~ 200-400cm2

Question 20

What is the approx film thickness of saliva in the mouth?

How is saliva able to cover so much surface area?

Answer 20

0.01- 0.001 mm

Because it has a low surface tension so can spread easily over mucosa and teeth

Question 21

Where is saliva film velocity the fastest?

Answer 21

Next to ductal openings

Question 22

If saliva film is moving fast, what are the implications of this?

Answer 22

Faster moving film means a greater exchange but urea causes pH to rise - this leads to ‘brushite’ formation and calculus

Question 23

What is Stephan’s curve?

Answer 23

The Stephan Curve is a graph that shows what happens after the consumption of sugar in relation to dental caries. After sugar intake, demineralisation of the tooth surfaces takes place due to the drop in pH as the bacteria in the mouth convert the sugar to acid. (i.e. it shows the buffering effect of saliva)

Question 24

What does bicarbonate do?

Answer 24

It ‘mops up’ acidity i.e. hydrogen ions/protons

Question 25

Outline the formula in which bicarbonate clears acid/hydrogen ions from the mouth?

Answer 25

H+ + HCO3- (bicarbonate) > H2CO3 (carbonic acid) > carbon dioxide + water

(carbonic acid used carbonic anhydrase 6 enzyme to convert to CO2 and water)

CO2 lost when we breathe

Question 26

What are the effects of increased flow rate? (5)

Answer 26

• Increased clearance of sugars and acids
• Increased buffering by bicarbonate
• Increased bicarbonate increase pH
• Increased pH makes saliva more saturated with calcium (leads to calculus)
• More antibacterial proteins

Question 27

What may make a person more susceptible to caries? (5)

Answer 27

Low salivary flow rate (e.g. over 65s, xerostomia etc)
Foods with high levels of sugar/fermentable carbohydrate/liquid/acidic (encourages dissolution of enamel)
Regular snacking
Low salivary bicarbonate/urea/CaP levels
Poor oral hygiene (snacking during night).