Prevention of caries by saliva Flashcards
What are the static and dynamic effects of saliva?
Static
- Antibacterial
- Super saturated with calcium and phosphate
- Pellicle formation
- Plaque substrates
Dynamic
- Buffering (bicarbonate increases with flow)
- Clearance of sugars
- Supersaturation (increases with flow)
What are the 3 main salivary glands found in the head?
Parotid
Sublingual
Submandibular
When are the salivary glands active?
Parotid - when eating
Sublingual and submandibular more activate at rest.
Give details on each gland having a specific salivary protein profile
Salivary proteins are synthesised by salivary glands and are different for each gland.
Larger proteins provide the thickness to saliva.
Can see there’s lots of mucin in minor salivary gland.
Parotid has no mucins. It is a serous salivary gland. It has a lot of amylase instead to break up starch. It also has a lot of proline rich proteins.
Submandibular and lingual - less amylase and less mucin. Large flow rate gland.lots of systanin sample.
The whole mouth will have all the proteins from the individual glands.
Some of the proteins are missing here as they stick onto the tooth and dont sit in saliva.
How are different ions added to saliva?
Osmotic process
The gland secretes lots of sodium and chloride into the ducts that lead into the mouth. This helps to draw water out.
Na, Cl and HCO3 increase in concentration in saliva with flow rate.
Phosphate and calcium dont have much change.
Two cells in gland:
acini
striated duct
Acini tend to make salivary and ducts modify it.
The acini cells transport large concentrations of sodium into the lumen and chloride follows in. This creates a high osmotic gradient that draws water through and forms saliva.
Striated ducts reabsorb a lot of sodium and chloride and secrete more bicarbonate in at lower flow rates for salvia to have a buffering affect.
Less reabsorption of sodium and chloride ions as reabsorption cannot keep up with secretion. This is why the conc of these ions increases with the increased flow rate.
Calcium and phosphate have similar concentrations regardless of flow rate. We dont know much about this. We think a lot of the calcium is present in secretory granules. They follow protein secretion.
How does saliva have a bacteriostatic effect?
Saliva contains many proteins. A lot of these have binding functions.
Proline rich proteins like to bind lots of bacteria as the proteins have lots of sugars on protein surface which the bacteria like to bind to as they can use the sugars to drive metabolism.
By binding the bacteria, this helps to agglutinate the bacteria to help the aggregate them so makes it easier to swallow the bacteria away from mouth.
This is not killing the bacteria but instead just moving them away.
Secretly IgA is the most abundant antibody in saliva.
How does saliva have a bactericidal effect?
We have bactericidal bacteria also. This includes lacterferrin, cystatins, histamines, lysozyme.
Lactoferrin binds to certain ions that helps create reactive oxygen species to kill the bacteria.
Lysosome punches holes in bacteria membrane.
Statins form pores in bacterial membranes.
Explain the super saturation of saliva
Saliva has a high calcium and phosphate level to protect tooth.
Can’t put calcium and phosphate ions in the saliva as they rapidly bind and precipitate out the solution. To stabilise calcium and phosphate, saliva contains proteins (statherin) that help to bind calcium. The proteins have phosphate groups to do this.
This helps to maintain a high calcium concentration in saliva.
What are HA binding proteins?
The proteins in the saliva that bind to calcium in saliva also like to bind to the tooth due to calcium presence here.
This forms the pellicle.
Only proteins with phosphate groups are in the pellicle as they can bind to the tooth.
How is saliva dynamic? What is the thickness of saliva in the mouth?
Where is the fastest movement of saliva?
Saliva moves around the mouth. Saliva has a low surface tension so it can be this thin and spread easily over mucosa and teeth.
Of you measure the SA of mouth it is 200-400cm.
If you divide this by the amount of saliva, we have 0.01mm of saliva film.
The saliva is in contain movement. The fastest movement is near the ductal opening due to greater volume.
Slowest film rates is tongue and anterior teeth.
Fastest film has the creates buffering effect. This is where the greatest amount of calculus forms. This is because the pH in these areas is very high so the plaque is not dissolved away.
What did Stephan find when we added sucrose to plaque?
The recovery of the pH was due to the buffering of the saliva.
This gave us the values for the critical pH, of around 5.5 for enamel. It is the pH where enamel starts to dissolve.
To keep pH high, we use saliva.
Without saliva, the pH will stay a lot lower for a lot longer. The speed of recovery is proportional to recovery of the pH. Higher flow rate = faster recovery.
How does saliva have a buffering effect?
Salivary glands produce lots of bicarbonate. This ion mop up acidity (H+). This forms carbonic acid.
A enzyme in saliva called carbonic anhydrase 6 helps to convert the carbonic acid into carbon dioxide and water.
The carbon dioxide is lost when you breathe.
AS WELL AS THIS:
Phosphate ions in saliva and salivary proteins both have capacity with buffering also.
Salivary glands also push lots of urea into mouth. The urease enzyme converts urea to ammonia and ammonia has a high pH to help neutralise the mouth.
What is the effect of an increased flow rate of saliva?
Increased clearance of sugars and acid.
Increased buffering by bicarbonate.
Increased bicarbonate, increases pH.
Increased pH makes saliva more saturated with calcium (leads to calculus).
More anti-bacterial proteins.
What makes someone susceptible to caries?
Low salivary flow rate
Foods with high levels of sugar/fermentable carbohydrate
Regular snacking - pH dropping below the critical pH
Low salivary bicarbonate - not such a big one as we have lots of mechanisms to buffer
Poor oral hygiene
Snacking at night - salivary flow dropping overnight
