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1. SALIVA BIOCHEMISTRY
Germain INTWALI
UR-CMHS
School of Dentistry
Dental therapy dpt.

2. Intended learning outcomes
Biochemistry of saliva and teeth
14.1. Describe the biochemical composition of saliva
14.2. Describe the biochemical composition of teeth
14.3. Explain the pH changes of saliva
14.4. Describe the functions of saliva

3. THE BIOCHEMISTRY OF
SALIVA
Saliva is produced in and secreted from acinar cells in
salivary glands
Secretion volume per day: 1.0-1.5 liters from major s. glands
(Parotid, sub mandibular and sublingual)
This include resting flow and stimulated during eating
pH of saliva: 7-8

4. THE BIOCHEMISTRY OF
SALIVA
 Composition of saliva:
 Water 94-99.5%
 Solid substance range from 0.5% to 6% in unstimulated and
stimulated saliva
 Solid substances are:
 Inorganic constituents: Ca, Mg, F, Na, HCO3, K, Na, Cl and NH4 ions
 Organic contituents: Ure, Uric acid, free glucose, free amino acids,
lactate and fatty acids,
 Organic micromolecules: Proteins, amylase, peroxidase, thiocyanate,
lysozymes, lipids, IgA, IgM, and IgG
 Elements from oral cavity: Desquamated epithelial cells, PMNL, and
bacteria
 Gases: O2, Co2, and N2.

5. THE BIOCHEMISTRY OF
SALIVA
Composition in groups:
Aqueous: water, salivary amylase, lingual lipase, IgA,
Kallikrein, Muramidase and Lactoferrin
Electrolytes: Ca, PH, F, K, Na, Cl
Mucus secretion proteins: Mucin, Statherins, Proline rich
proteins, antimicrobial proteins such as; Lactoferrin,
Histatins, Lysozymes, Cystatins, Peroxidases, Secretory
immunoglobins

6. THE BIOCHEMISTRY OF
SALIVA
Saliva is hypotonic to plasma
Na+, Cl- low in saliva than plasma
K+, HCO3- higher in saliva than plasm
pH changes from acidic (6-7) at rest to basic (pH 8) at
ultimate stimulation due to Higher HCO3- in the saliva

7. THE BIOCHEMISTRY OF
SALIVA
Functions:
Moistening food
Beggining of digestion
Adjust salt appetite
Contains factors that inhibit adhesion and destroy bacteria (Anti-
bacteria)
Antifungal (Histatins)
Antiviral (Cystatins, Mucins)
Buffering

8. THE BIOCHEMISTRY OF
SALIVA
Functions:
Lubrication and visco-elasticity
Mineralizations
Buffering oral environment

9. HYDROGEN IONS
1. PROTONS (H+
)
Concentration dictates pH of the oral environment
pH of saliva varies according to flow rate
(young infants also have slightly more alkaline saliva)
Why is pH important in the mouth?
Typical salivary pH (adult) is around 6 – 7.4
-a- Maintaining ionic product for hydroxyapatite (see later)
-b- Isoelectric point for salivary protein precipitation on
to tooth surfaces
-c- Optimal pH for salivary enzymes

10. EFFECT OF CARBOHYDRATE
CONSUMPTION ON PLAQUE pH
Time (min)
pH
4
5
6
7
8
0 40 80
CHO CHO
The Stephan Curve: Stephan, RM, J Am Dent Ass. 27: 718-723, 1940
Mineral
dissolves

11. EFFECT OF SUCROSE ON PLAQUE pH
4
5
6
7
pH
Sucrose
0.025%
Sucrose
1.25%
Sucrose
2.5%
Sucrose
5%
Sucrose
10%
3% UREA 3% UREA
Time (min)
0 113
Chew wax
3 min
Chew wax
3 min
Chew wax
3 min
Chew wax
3 min
Chew wax
3 min
Chew wax
3 min
Telemetric data from: Imfeldt, 1977

12. pH of SALIVA (cont)
The pH of saliva varies with flow rate
Higher flow rates increase salivary buffering
Flow rate pH
In general:
=

13. EFFECT OF FLOW RATE ON pH OF SALIVA
0.25 mL/min
0.5 mL/min
1 mL/minstimulation begun
unstimulated
0 5 10 15 20 25
5.8
6.2
6.6
7.0
7.4
pH
Time (min)

14. 2. BICARBONATE IONS
Important BUFFER at high flow rates
Concentration in saliva varies with salivary flow as bicarbonate
content of saliva increases with metabolic activity of the
salivary glands
Range: < 1 mM (unstimulated) to 60 mM (highest flow rates)
Concentration in mechanically stimulated saliva typically around 15 mM
Produced by the striated epithelium of the salivary gland ducts

15. EFFECT OF FLOW RATE ON BICARBONATE
CONCENTRATION IN SALIVA
0
8
16
24
32
HCO3(mM)
stimulation begun
unstimulated
1 mL/min
0.5 mL/min
0.25 mL/min
Time (min)
5 10 15 20 25
0

16. BUFFERING OF PROTONS BY
BICARBONATE
H+
+ HCO3 H2CO3 H2O + CO2
-
pKa = 6.1
Carbonic anhydrase
Carbonic anhydrase is present in salivary glands
(and also in saliva)

17. BICARBONATE PRODUCTION IN SALIVA
HCO3
H2CO3 H2O + CO2
H+
LUNGS
CATABOLISM IN GLAND
HCO3
H2CO3 H2O + CO2H+
Excess in
saliva
PLASMA
SALIVARY GLAND
-
-

18. 3. POTASSIUM AND SODIUM IONS
Both present as counter ions to preserve electrical neutrality
Concentration range: Sodium: 6 – 26 mM
Potassium: 14 – 32 mM
Sodium is the counter ion for bicarbonate
Potassium is the counter ion for phosphate
Flow rate Na+
In general:
= but K+

19. EFFECT OF FLOW RATE ON SODIUM AND
POTASSIUM CONCENTRATIONS IN
SALIVA
Rate of secretion mL / 6 min
Concentrationmeq/L
20
40
60
1 2 3
Na
K

20. 4. CALCIUM AND MAGNESIUM IONS
Mg++
Present in saliva but role and origin unclear.
Possible origins: Cellular degradation (host / bacterial);
Early carious attack
(Mg++
rich mineral is first to be removed
during acid attack)
Concentration range in saliva: 0.2 – 0.5 mM
Flow rate Mg++
In general:
=

21. 4. CALCIUM AND MAGNESIUM IONS (cont)
Ca++
Actively secreted by major salivary glands
Forms complexes with calcium-binding salivary
proteins
Concentration range in saliva: 1 – 2 mM
Flow rate Ca++
In general:
=
Behaviour with flow rate variable due to protein
binding
Important role in maintenance of ionic product for
hydroxyapatite (see later)
(& protein)

22. EFFECT OF FLOW RATE ON Ca++
AND Mg++
CONCENTRATIONS IN SALIVA
Ca(mM)
0
40
80
120
Mg(µM)
stimulation begun
unstimulated
0 5 10 15 20 25
0.9
1.1
1.3
0.04 mL/min
1.00 mL/min
Time (min)
1.5
Ca++
Mg++

23. EFFECT OF FLOW RATE ON
CONCENTRATION OF PROTEIN IN SALIVA
Time (min)
1 mL/min
0.5 mL/min
0.25 mL/minunstimulated
stimulation begun
Protein(mg%)
110
190
270
350
5 10 15 20 25

24. 5. PHOSPHATE IONS
Flow rate H2PO4
-
/ HPO4
=
In general:
=
Concentration range in saliva: 2 -23 mM
Acts as a buffer, especially in unstimulated saliva
Important in maintenance of ionic product for hydroxyapatite

25. EFFECT OF FLOW RATE ON INORGANIC
ORTHOPHOSPHATE CONCENTRATION IN SALIVA
Time (min)
4
8
12
Inorganicphosphate(mM)
unstimulated
stimulation begun
0.25 mL/min
0.5 mL/min
1 mL/min
5 10 15 20 250

26. HYDROXYAPATITE
The mineral component of the mammalian skeletal tissues
is a calcium phosphate salt:
HYDROXYAPATITE (HAP; HA, OHA)
Ca10(PO4)6(OH)2
Ionic product for HAP:
Pi = [Ca]10
x [PO4]6
x [OH]2

27. ROLE OF CALCIUM AND PHOSPHATE IN
MAINTAINING TOOTH MINERAL INTEGRITY
AND REMINERALISATION
Saliva is supersaturated with respect to hydroxyapatite
This is essential for:
Maintenance of ionic product
Remineralisation
BUT
Without the presence of inhibitors in saliva,
spontaneous precipitation would occur

28. ROLE OF CALCIUM AND PHOSPHATE IN
MAINTAINING TOOTH MINERAL INTEGRITY
AND REMINERALISATION
The mineral component of enamel and dentine is a
substituted hydroxyapatite; HAP. Ca10(PO4)6(OH)2
HAP dissolution (and precipitation) therefore depends
upon the concentration of Ca++
, PO4
3-
(and OH-
) in saliva.
Protonation of the phosphate group is pH dependent
PO4
3-
HPO4
2-
H2PO4
-
H3PO4
+H+
+H+
+H+
-H+
-H+
-H+
pKa = 12.7 pKa = 7.2 pKa = 2.12

29. ROLE OF CALCIUM AND PHOSPHATE IN
MAINTAINING TOOTH MINERAL INTEGRITY
AND REMINERALISATION
When pH falls, increasing protonation of the phosphate
groups results in the formation of salts of greater solubility
and vice versa
Ca10(PO4)6(OH)2HAPHydroxyapatite
Brushite /
Dicalcium phosphate
CaHPO4 / CaHPO4.2H2ODCPD
Octacalcium phosphate OCP Ca8(PO4)4(HPO4)2.5H2O
Tricalcium phosphate TCP Ca3(PO4)2
Monocalcium phosphate MCP Ca(H2PO4)2

30. 6. CHLORIDE IONS
Preserves electrical neutrality
Activates salivary amylase
Concentration range in saliva: 17 – 29 mM
Flow rate Cl-
In general:
=

31. 6. FLUORIDE ION
Fluoride ion is normally present at very low concentrations in
whole saliva (range = 0.001 – 0.005 mM)
Fluoride replaces (OH) in the HAP lattice structure, increasing its
stability and inhibiting acid dissolution
Fluoride facilitates HAP precipitation and therefore promotes
remineralisation.
Fluoride accumulates in porous enamel (and dentine),
including caries lesions
Fluoride concentrations in plaque are higher than those in saliva
Salivary fluoride in patients living in areas of water fluoridation is
approx. 2x that of patients living in non-fluoridated regions.
This is a small absolute difference but the benefits in caries reduction
are highly significant.

32. Special thanks
To Dr. Mumena Chrispinus:
A senior lecture and vice Dean of the school of Dentistry at
the College of Medicine and Health Sciences-
UNIVERSITY OF Rwanda.
Addition: Dean of the OPHTALMOGY DEPT. at UR-
CMHS