Biochemistry of Saliva Flashcards
what determines Ph of oral environment?
Protons
When do salivary proteins precipitate onto tooth?
When pH = their isoelectric point
What drives dissolution of HAP leading to caries?
protons
what happens after Carb intake?
pH of plaque fall from neutral to 4.5
Why does pH fall after carb intake?
fermentation of carb. by plaque so organic acids
What is the critical pH?
below 5.5 where HP dissolves
How is Plaque pH restored to neutral?
Salivary buffering
What is remineralization?
new mineral precipitated when above critical pH
What does Urea do?
increase pH via conversion to ammonia
What does high saliva flow rate do?
increase Bicarbonate conc. so inc. buffering capacity so high pH1
Where are Bicarbonate ion buffers produced?
striated epithelium of secretory duct & parotid gland
What does Enzyme Carbonic Anhydrase do?
forms Carbonic acid (H2C03) from h20 & C02
where is carbonic anhydrase present?
made in serous acinar cells in parotid and submandibular glands
Where is Bicarbonate ions derived from?
metabolic activities of salivary glands & plasma
When does carbonic acid conc. increase?
with increased salivary flow
What does Na ion counter?
Bicarbonate ion
What does Potassium ion counter?
Phosphate ion
When do sodium concentrations increase?
with increased salivary flow
What is Potassium concentration in saliva?
CONSTANT
How is sodium pumped out of primary salivary fluid?
passes via acini of salivary gland via Na/K pumps
What are sources of Magnesium ions in Saliva?
Cell degradation
caries attack
What happens to Magnesium con. as flow rate increases?
Mg ions decrease
What secretes Ca2+ ions?
Major salivary gland
What are calcium ions needed for?
- remineralisation
- prevent mineral dissolution
What do calcium form complexes with?
Ca-binding salivary proteins
What does increased flow rate do to Calcium conc?
Ca concentration constant
What is parotid secretion of Ca compared to submandibular ?
Half the secretion
What happens to protein conc. as salivary flow rate increases to more than 1mL/min?
protein increases
Why is below 1mL/min, the protein conc. more variable?
proteins can bind to calcium
What do Phosphate ions act as?
Buffers
Role of Phosphate ions?
inhibit dissolution and bring about repair to mineral
What happens to inorganic Phosphate ion as flow rate increases?
DECREASES
Why does phosphate decrease with increased salivary flow rate?
Phosphate added to fluid via ducts
What does increased flow rate mean for PO43-
less time for phosphate to be added
What is HAP/
most stable Ca/ (P04)3- SALT
When does HAP precipitate?/
when solubility product is exceeded
what does really low conc. of Ca/PO43- mean?
dissolution
what does really High conc. of Ca/PO43- mean?
Dental calculus + salivary gland stones
What happens to phosphate group when pH falls?
increase protonation so form Calc.Phos salts of greater solubility so demineralization
When does caries occur?
when demineralisation rate exceed mineralisation rate
Where is Fluoride ion concentration high?
In plaque than saliva
What does fluoride replace in HAP ?
OH in crystal lattice structure
what does fluoride do to HAP?
Reprecipitates it and More stable and inhibits acid dissolution
what picks up fluoride from saliva?
porous enamel and dentine
What is fluoride amount in saliva?
small at 0.001-0.005 millimolar
What are inorganic components of Saliva?
Bicarbonate Na K Mg Ca P043- (orthophosphate) HAP Fluoride
