4. Prevention Of Caries By Saliva Flashcards
LOs
Static and dynamic effects of preventing caries
Static Effects
* No flow rate of saliva produces static effects on caries prevention on teeth
* They have antibacterial effects
* They are supersaturated with calcium and phosphate
* Formation of a salivary film across teeth is known as acquired pellicle formation
* Saliva also has some substrates for bacteria (plaque formation)
Dynamic Effects
- saliva moves
* Buffering effects of bicarbonate in saliva increases with increased salivary flow (buffering capacity changes with flow rate)
* Main effect is clearance of sugars and acids - prevents caries
* Supersaturation also increases with increased flow (of Ca2+)
3 pairs of major salivary glands
(lateral view image)
- submandibular
- just under jaw bones - sublingual
- just under tongue - parotid
- largest
- near ears
how many minor salivary glands are there
- hundreds of them all around the oral mucosa (hard palate, lip, etc)
- Percentage contributions of each gland to whole mouth saliva
- flow rates?
- 2 flow rates
At rest (0.2-0.5 ml/min)
- Parotid 20
- Submandibular/
- Sublingual 70
- Minor glands 10
Stimulated (1-2 ml/min)
- Parotid 60
- Submandibular/ 35
- Sublingual
- Minor glands 5
- hard to quantify sublingual and submandibular separarately
saliva protein profile
- probably over 1000 different proteins in saliva
ions in parotid saliva
- how is saliva made?
- important ions in parotid saliva?
1.
- making saliva is osmotically driven process
- to make saliva, lots of sodium and chloride ions are secreted into ducts that lead into the mouth
- this helps to draw water by an osmotic process
- secreting ions attracts water
(more detail in later lecture)
2.
- sodium
- chloride
- bicarbonate ions
- calcium
- phosphate
In the image…
* At rest, phosphate is greatest in amount
* Upon stimulation, sodium, chloride and bicarbonate
concentration increases
* Calcium and phosphate concentration does not
change much with flow rate
modifications of ions in saliva
- acinus
- striated duct
- Sodium, chloride and bicarbonate are reabsorbed whereas potassium is secreted into the striated duct
- Calcium is thought to enter saliva through cellular channels or bound to mucin in saliva
- acinus
make saliva - striated duct
modifies saliva
EXTRA Q FROM AZ NOTES
why can we taste tears and blood?
- We can taste tears and blood because the salt has been reabsorbed therefore our taste buds have become adapted to the non-salty environment
Bacteriostatic effects of saliva
- Bacteriostatic chemicals prevent bacteria from multiplying rather than killing them
- Bacteria like to bind to sugar as it can help drive their metabolism
- Many Proline Rich Proteins (PRPS), Secretory IgA’s (antibodies) and mucins bind bacteria through glycosylation
- They then agglutinate and are removed by swallowing
Bactericidal (kill bacteria) effects of Saliva
Bactericidal (kill bacteria) effects of Saliva
* Lactoferrin has an iron binding ligand within the centre
* It binds the iron with bacteria to prevent it from multiplying
* Cystatins and histatins are also found in saliva
* Lysozymes actively kill bacteria
Supersaturation of Saliva
* Saliva is supersaturated compared to enamel
what does this mean?
- Teeth left in water for a long time would dissolve
BUT
saliva prevents this with high levels of calcium and phosphate - However, saliva requires chelators (calcium binding proteins) to prevent high levels of calcium phosphate precipitating to form plaque (bind and stabilise Ca is sol so does not bind to phosphate.
- EG of chealators
- Why they’re important
- EXTRA FROM AZ NOTES
- 1.
- Statherin, acidic PRPs and histatin 1 are the main chelators which all contain a phosphate group
2. - These proteins are important in forming a stable pellicle of proteins on the surface of the tooth
3. - The dental pellicle, or acquired pellicle, is a protein film that forms on the surface enamel by selective binding of glycoproteins from saliva that prevents continuous deposition of salivary calcium phosphate. - It forms in seconds after a tooth is cleaned or after chewing.
dynamic effects of saliva on teeth (saliva film)
(think of more Qs)
- saliva only enters mouth when you’re awake
what is Stephan’s curve?
Effect of saliva on Stephan’s curve?
main buffering mechanism within saliva?
- Urea to ammonia, fasted plaque pH can be
higher than saliva due to bacterial urease, more important at lower flows
why may you have an increased saliva flow rate
- eating
- chewing gum
- naturally may have a higher salivary flow rate (children have higher flow rate)
effect of increased saliva flow rate
- Increased clearance of sugars & acids
- Increased buffering by bicarbonate
- Increased bicarbonate, increases pH
- Increased pH makes saliva more
saturated with Calcium (leads to calculus) - More anti-bacterial proteins
what increases caries susceptibility?
- Low salivary flow rate (seen in over 65 age bracket)(also if taken certain drugs - a lot of drugs have xerostomic affect (drug reduced resting salivary flow rate))
- Foods with high levels of sugar/ fermentable carbohydrate/ liquid/ acidic
- Regular snacking
- Low salivary bicarbonate/ urea/ CaP levels
- Poor oral hygiene (snacking during night - while sleeping salivary flow drops)(having milk before bed)
EXTRA Q - AZ NOTES
Salivary Proteins and Their Function
- peroxidase
- cystatins
- Peroxidase = Inhibits acid production and growth
- Cystatins = Related to pellicle formation and has
proteinase inhibiting properties so it controls proteolytic activity
main points of lecture
Main points:
1. Caries caused by acid secretion by bacteria
2. Salivary proteins are anti-bacterial, eg lactoferrin & Secretory IgA
3. Saliva supersaturated with calcium and phosphate
4. Saliva buffered by bicarbonate and plaque by urea
5. Increased salivary flow decreases caries
Further reading
1) Good start point: Saliva and oral health, Ed Mullane etc., - several copies in our
library.
2) Describes how flow rate is a major risk factor for caries
Relationships between medication intake, complaints of dry mouth, salivary flow
rate and composition, and the rate of tooth demineralization in situ
Bardow, Nyvadb
, & Nauntoftea Archives of Oral Biology
Volume 46, Issue 5, May 2001, Pages 413–423- get from Pubmed or Web of Knowledge
3) A controversial but important paper worth a read: Diet and Dental Caries: The Pivotal
Role of Free Sugars Reemphasized
A. Sheiham1 and W.P.T. James2
Journal of Dental Research
2015, Vol. 94(10) 1341–1347
3) A good paper describing the scale of the problem.
Dental caries
By:Selwitz, RH (Selwitz, Robert H.); Ismail, AI (Ismail, Amid I.); Pitts, NB (Pitts, Nigel B.)
LANCET
Volume: 369 Issue: 9555 Pages: 51-59
DOI: 10.1016/S0140-6736(07)60031-2
Published: JAN 6 2007
Self test Q’s
1) What is saliva supersaturated with and how is this maintained?
2) Name five anti-bacterial salivary proteins
3) What does the Stephan curve refer to and how is it modified by saliva?
4) Describe the main buffers in the mouth
5) What is calculus and why is it formed preferentially at certain sites
in the mouth?
