inorganic components of saliva Flashcards
typical salivary pH
6-7.4
why is pH important in mouth?
-mantaining ionic product for hydroxyapatite
-isoelectric point for salivary protein precipitation on tooth surfaces
-optimal pH for salivary enzymes
Explain Stephan’s curve
-pH decreases to 4.5 due to fermentation of carbohydrates by plaque microorgs generating acids
-hydroxyapatite dissolves below 5.5, some demineralisation occurs
-pH restored to neutrality due to salivary buffering, new mineral precipitated
-for remineralisation, pH must be above critical pH (5.5), takes 20-40mins to happen
what does data on wax chewing graph show
-if pH below 5.5, hydroxyapatite dissolves, the longer it stays below this value the more tooth mineral will be lost
-greater amount of sucrose given, the lower the plaque pH
-stimulating saliva increases buffering capacity
rate of ph with flow rate
higher flow rates increases salivary buffering (increases pH)
effect of flow rate on pH of saliva
Higher the flow rate higher the pH
-more buffering/alkaline species
-this is due to bicarbonate ions competent (most important buffer)
What are bicarbonate ions
important buffer at high flow rates
how are bicarbonate ions produced?
-by striated epithelium of secretory ducts and parotid glands
How does conc of bicarbonate vary?
-bicarbonate content of saliva increases with metabolic activity of salivary glands
range of bicarb
1mM-60mM
how much bicarb in mechanically stimulated saliva
15mM
Effect of flow rate on bicarbonate conc in saliva
Increased salivary flow results in increased bicarb concs
What is pka of bicarbonate
At pH 6.1 equal conc of carbonic acids and bicarbonate ions
-as pH falls, forward reaction will be favoured
bicarbonate formula
HCO3-
where is bicarbonate produced
Bicarbonate derived partly from plasma and partly from metabolic activity of salivary glands
-Carbonic acid conc in plasma is stable at 1.3milimolar and is equiliburm with alveolar carbon dioxide conc in lungs
-conc in gland increases with increased salivary flow due to increased metabolic activity
H2O + CO2–H2CO3–HCO3- + H+
What are sodium and potassium ions used for
-counter ions to preserve electrical neutrality
-sodium counter ion for bicarbonate
-potassium counter ion for phosphate
conc range of sodium
6-26mM
conc range of potassium
14-32mM
effect of increase in flow rate on Na and K ions
increases Na+, K+ stays same
what is role of Mg ions in saliva?
role unclear
possible: cellular degradation, early carious attack
conc range of Mg
0.2-0.5mM
effect of increase in flow rate on Mg ion
decreases
what is Ca++ secreted by
major salivary glands
what does Ca bind with
complexes with calcium-binding salivary proteins
