Functions Of Saliva

• What is the secretory pattern for whole mouth saliva in a typical 24hr period?

  
• Describe the contributions of different salivary glands to saliva in the mouth.


  - the submandibular and sublingual glands make the greatest volume contribution to the resting flow rate

  - the parotid glands contribute a higher proportion of the stimulated flow

  
• What are some potential reasons for variations in salivary flow rates?

  - It decreases in the elderly (which can be due to prescribed medications and can be age related)

  - It's reduced by a wide range of prescribed medications

  - It's correlated with size of salivary glands

  - It tends to be higher in males than females (in general the glands are smaller in females)
• What figures are regarded as low & normal levels of saliva?

  ----> Unstimulated whole mouth saliva:

  <0.1 ml/min (very low); 0.1-0.2 ml/min (low); 0.25- ml/min (normal)

  
  

  ----> Chewing stimulated whole mouth saliva:

  <0.7 ml/min (very low); 0.7-1.0 ml/min (low); 1.0- ml/min (normal)
• What happens when saliva is secreted onto the mouth?

  - It forms a film on the oral surfaces: the soft tissue surfaces

  - It forms a slightly thinner film on the hard tissue surfaces (teeth)
• What are the estimated saliva film thicknesses on the different oral surfaces?

  Upper labial: 25 microns

  Lower labial: 25 microns

  Buccal: 30 microns

  Ant. hard palate: 10 microns

  Soft palate: 30 microns

  Ant. tongue: 50 microns
• Describe the composition of whole mouth saliva.

  - glandular saliva

  - whole mouth saliva (which is glandular saliva that is affected and altered by contributions from biofilm, enamel/denitne, gingival, Gingival crevicular fluid (GCF), shedding from epithelial cells and tissue transdudate.

  
• What are the 4 broad areas you can divide the functions of saliva into?

  1. Tooth protection

  - Increased flow and oral clearance

  - Buffers pH

  - Acquired enamel pellicle

  - Saliva supersaturation with calcium phosphate

  
  

  2. Protection & maintenance of oral mucosa

  - Wound healing

  - Lubrication

  - Moistening/hydration

  - Barrier formation

  
  

  3. Regulate oral microbiota

  - Clearance, killing, agglutination of pathogens

  - Colonisation, adhesion, feeding of commensals

  
  

  4. Taste & processing of food/nutrients
• What is the clinical effect of very low salivary flow?

  It greatly reduces the clearance of sugar and bacteria, and increases the risk of dental caries.
• What is the equation for buffering in saliva by bicarbonate?

  
• Describe the pH of plaque in the presence & absence of saliva.

  With saliva, plaque pH is a lot higher (~6.3)

  
  

  Without saliva, plaque pH is a lot lower (~5.5)
• What is the acquired enamel pellicle?

  a protein film with unique composition and properties, which is formed by the selective adsorption of a variety of oral fluid-derived proteins onto tooth enamel surfaces.

  
  

  - It's less than 1 micron thick & the early pellicle is formed mainly by calcium binding salivary proteins in saliva (including statherin, histatins & acidic proline-rich proteins).
• What does the acquired enamel pellicle do?

  - Modifies the adherence of microorganisms to teeth. Salivary proteins (e.g. salivary agglutinin, mucins etc.) in the enamel pellicle provides binding sites for commensal bacteria and they can aggregate microorganisms & facilitate their clearance from the mouth

  - It prevents surface mineralisation (calcium and phosphate, are deposited onto the surface of tooth enamel) but enhances sub-surface remineralisation (restoring minerals to the subsurface layers of tooth enamel that have been affected by demineralization)

  - It lubricates the tooth surface which reduces friction by 20 fold
• what is remineralisation of teeth dependent upon?

  supersaturation of saliva with calcium and phosphate

  (proteins like statherin bind to calcium to increase its concentration in saliva)

  ( so hydroxyapatite is formed from Ca2+, PO43- 2, OH - = mineralisation)
• at what PH will demineralisation of teeth surface occur?


  If saliva pH decreases to approximately pH 5.5 due to dietary or plaque acid then demineralization occurs since saliva no longer saturated with Ca 2+ PO4 3- 2 OH -.

  ( so hydroxyapatite is broken down to get Ca2+, PO43- 2, OH - = demineralisation)
• so, Which components of saliva are particularly important in maintaining tooth mineralization?

  - Calcium and Phosphate Ions:

  for mineralisation

  
  

  - Saliva has a buffering capacity:

  it can neutralize acids produced by bacteria in the mouth. So, it helps maintain the pH balance in the oral environment for mineralisation and preventing demineralisation

  
  

  - Salivary Proteins like statherin:

  which binds to calcium and phosphate ions and form hydroxyapatite for mineralisation
• What does salivary film contain?

  Pore-containing network of proteins (mucin)
• Which glycoprotein is particularly important in determining the properties of saliva?

  mucin
• What does the flow of saliva in the mouth do?

  Clears microorganisms from the mouth
• What do dry mouth sufferers experience?

  - Dry mouth during the day

  - Night waking due to dryness

  - Burning sore mouth & tongue

  - Candidiasis

  - Bad taste

  - Dental caries

  - Discomfort wearing dentures

  - Difficulty speaking/swallowing/eating

  
  

  ->These affect nutrition and psychological wellbeing
• What is the significance of the network of mucin in saliva?

  - It controls the way that certain components of saliva have access to the mucosal surface.

  (creates a barrier to oral bacteria from oral epithelium)

  - It also helps to increase lubrication of the soft tissue surfaces
• How can salivary proteins modulate (regulate) microbial growth?

  Example: the sugars on mucin glycoproteins (MUC5B) can provide nutrition for commensal (do not harm) bacteria
• What does saliva contain to inhibit microbial growth?

  Many anti-microbial, growth limiting factors, e.g. histatins, immunoglobulin A, defensins
• Why do changes in the environment affect the oral microbiome?

  Because the oral microbiome is a complex mix of species adapted to the oral environment so changes in the environment leads to dysbiosis (altered composition of microorganisms) and disease
• show some of the bacteriostatic and antimicrobial proteins in saliva