Inorganic Components of Saliva

Question 1

what is the typical pH in adults

Answer 1

neutral, pH 7

• but more alkaline in babies
• depends on FLOW rate

Question 2

at what pH values does HAP dissolve/de-mineralisation (Stephan’s curve)

Answer 2

below pH 5.5- critical pH

Question 3

why does pH fall after eating a meal

Answer 3

fermentation of carbohydrates by plaque micro-organisms produces ORGANIC acids

Question 4

how is pH restored back to neutral so that HAP can re-mineralise

Answer 4

salivary buffer properties

Question 5

how long does it take for pH to be restored back to normal

Answer 5

20-49 minutes

Question 6

the effect of sucrose on plaque was shown via…

Answer 6

telomeric data from Imfeldt

Question 7

what were the key findings from Imfeldt and co. data

Answer 7

1. the greater the amount of sucrose given, the lower the resulting plaque
2. the longer at acidic pH, the more HAP will dissolve
3. as SALIVA FLOW RATE increases= the BUFFERING CAPACITY ALSO INCREASES

Question 8

list all the inorganic components of saliva

Answer 8

H+ ions 
Bicarbonate, Hc03- ions
Na+ ions
K+ ions 
Mg2+ ions 
Ca2+ ions 
Phosphate ions 
Fluoride, Fl- ions

Question 9

what is the importance of bicarbonate ions and why are they able to perform this function

Answer 9

1. important buffer system of saliva

pKa= 6.1 therefore at pH 6.1 the concentration of H2CO3 is equal to Hc03-
carbonic acid= bicarbonate ion

Question 10

concentration of bicarbonate HCO3- in stimulated saliva

and unstimulated saliva

Answer 10

60mM stimulated saliva

1mM = unstimulated saliva

Question 11

function of carbonic anyhdrase in salivary glands

Answer 11

generates carbonic acid …therefore bicarbonate

carbonic anhydrase found in salivary pellicle

Question 12

what is the concentration of carbonic acid in plasma

Answer 12

stable at 1.3 mM

equilibrium with the alveolar carbon dioxide concentration

Question 13

sodium is the counter ion for

Answer 13

bicarbonate

Question 14

potassium is the counter ion for

Answer 14

phosphate

Question 15

function of both sodium and potassium

Answer 15

to preserve the electrical neutrality

Question 16

salivary sodium concentration in stimulated and un-stimulated saliva

Answer 16

increases when saliva flow rate increases

stimulated= 30mM
unstimulated= 6mM

Question 17

salivary potassium concentration in stimulated and un-stimulated saliva

Answer 17

remains CONSTANT as saliva flow rate increases

stimulated/ unstimulated= 14-32 mM

Question 18

why does salivary potassium concentration remain constant

Answer 18

potassium is added to ductal fluid throughout their passage through the duct

Question 19

salivary magnesium concentrations in stimulated and unstimulated saliva

Answer 19

decreases
already low at unstimulated= 0.4mM
stimulated= 0.2 mM

dilution effect

Question 20

origin of mg2+ions in saliva

Answer 20

not identified

• cellular degradation within oral env.
• from the dissolution of mineral

Question 21

salivary calcium

Answer 21

calcium can exist in pure form/ complexed to proteins/ other ions

pure ca2+ in unstimulated saliva= 1-2mM
generally remains constant at this concentration in stimulated saliva also

Question 22

ca2+ concentration in saliva is affected by the fact that…

Answer 22

1. different glands secrete different ca2+ concentrations

2. protein content changes with salivary flow rate and different proteins bind to ca2+ to different extents

Question 23

which gland has high ca2+ secretions and which has low

Answer 23

submandibular= high ca2+ 
parotid= low ca2+

Question 24

what is the function of ca2+ in saliva

Answer 24

maintaining HAP- re-mineralising it and preventing its dissolution

Question 25

what is the function of phosphates in saliva

Answer 25

• buffer, especially in UNSTIMULATED saliva

- repair HAP and inhibit its dissolution (alongside ca2+)

Question 26

concentration of phosphate ions depending on flow rate is…

Answer 26

varies from 2-13 mM depending on flow rate

INORGANIC ortho-phosphate concentrations DECREASE with salivary flow rate

Question 27

why does inorganic orthophosphate concentration decrease with increase in saliva flow

Answer 27

phosphate is added actively as it passes through the ducts

- if fast moving saliva, less TIME to add phosphate

Question 28

an increase in saliva flow rate changes the proportions of phosphate ions present. what are they

Answer 28

H2po04- decreases

HPO42- and PO43- increase= make HAP

Question 29

HAP will spontaneously ____ out of solution when its ___ product is ____

Answer 29

• precipitate
• solubility
• exceeded

governed by the concentration of its constituent ions in solution (ca2+, phosphate and hydroxyl ions).

Question 30

so at low concentrations of ca/ phosphate, HAP will spontaneously

Answer 30

dissolve

Question 31

at normal level os ca/phosphate, HAP will spontaneously

Answer 31

re-precipitate

Question 32

saliva is supersaturated with respect to HAP at neutral pH. what does supersaturated mean

Answer 32

saliva contains OVER the threshold/ sufficient ions of a given salt for its spontaneous precipitation to occur

Question 33

why does pH have such a profound effect on the solubility product of HAP

Answer 33

the protonation of the phosphate group is pH dependant

Question 34

symbol for orthophosphate

Answer 34

PO43-

Question 35

in acidic conditions the phosphate groups will be…

Answer 35

increasingly protonated - H3PO4

and vice versa

Question 36

fluoride ion concentration in saliva is..

Answer 36

0.001- 0.005 mM

varies very little with flow of saliva

Question 37

the fluoride ion concentration is higher in plaque than it is in saliva. how does fluoride affect HAP

Answer 37

replaces the OH in HAP to make a more stable mineral that is less soluble in acid.
promotes the repair of HAP mineral

Question 38

how may saliva be accumulated within HAP mineral

Answer 38

dentine and porous enamel pick it from saliva