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
role of Ca ions
-mantainance of ionic product for hydroxyapatite
conc range for Ca
1-2 mM
effect of flow rate increase on Ca +
stays same
effect of flow rate on protein in saliva
-some proteins bind to calcium
-increases protein
What are phosphate ions role
-acts as buffer esp in unstimulated saliva
-important in mantanaince of ionic product for hydroxyapatite
conc range of phosphate ions
2-13mM
effect of increase flow rate on phosphate ions
decrease, increased flow rate produces more alkaline pH due to increased bicarbonate
Diff phosphate species
-changes the proportions of diff ionic phosphate species. H2PO4- decreases and HPO42- and PO43- increase–these less protonated phosphate ions important to solubility of tooth mineral
What can increasing Ca and phosphate ions do
-increasing ca and phosphate ions in saliva will encourage reprecipitation of mineral BUT too much ca and po4 will lead precipitation of minerals at other sites leading to tartar
What is saturated/supersaturated
-when sufficient ions of salt, solution is saturated
-above threshold is supersaturated
-saliva is supersaturated with hydroxyapatites at neutral pH
Conc of fluoride ion in saliva
0.001-0.005mM
where is fluoride ions found
porous enamel, including caries (higher conc in plaque)
what is role of fluoride
replaces OH in HAP lattice structure, increasing its stability
-facilitates HAP precipitation and promotes remineralisation
read 3 slides on HAP
one note
