saliva

SALIVA

Seminar

Stomatology

MAJOR FUNCTIONS OF SALIVA

Solvent Buffering Lubrication Remineralization Digestion Anti-bacterial Anti-fungal Temperature regulation Production of growth factors and other regulatory

peptides

A CONSIDERABLE VOLUME OF SALIVA IS PRODUCED OVER A DAY

0.5 to 1.5 liter of fluid is secreted in a day This represents about 1/5 of the total plasma

volume This fluid is not lost as most of it is swallowed

and reabsorbed by the gut Parotis, submandibularis, sublingualis

THE SECRETORY UNITThe basic building block of all salivary glands

ACINI - water and ions derived from plasma

Saliva formed in acini flows down DUCTS to empty into the oral cavity.

TWO STAGE HYPOTHESIS OF SALIVA FORMATION

Water & electrolytes

Isotonic primary saliva

Most proteins

Some proteins electrolytes

Na+ Cl- resorbed

K+ secreted

Hypotonic final saliva into mouth

Inorganic components

Saliva compositon

Calcium and phosphate Help to prevent dissolution of dental enamel Calcium

1,4 mmol/l (1,7 mmol/l in stimulated saliva) only cca 50% in ionic form sublingual > submandibular > parotis

Phosphate 6 mmol/l (4 mmol/l in stimulated saliva) 90% in ionic form

pH around 6 - hydroxyapatite is unlikely to dissolve

Increase of pH - precipitation of calcium salts => dental calculus

Hydrogen carbonate

Buffer Low in unstimulated saliva, increases with

flow rate Pushes pH of stimulated saliva up to 8 pH 5,6 critical for dissolution of enamel Defence against acids produced by

cariogenic bacteria Derived actively from CO2 by carbonic

anhydrase

Other ions Fluoride

Low concentration, similar to plasma

Thiocyanate Antibacterial (oxidated to hypothiocyanite OSCN- by

active oxygen produced from bacterial peroxides by lactoperoxidase)

Higher conc. => lower incidence of caries Smokers - increased conc.

Sodium, potassium, chloride Lead, cadmium, copper

May reflect systemic concentrations - diagnostics

FLOW RATE ml/min

Con

cen

trat

ion

(m

M)

Organic components

Saliva composition

Organic components of saliva Mucins Proline-rich proteins Amylase Lipase Peroxidase Lysozyme Lactoferrin sIgA Histatins Statherin Blood group substances, sugars, steroid hormones,

amino acids, ammonia, urea

Multifunctionality

SalivaryFunctions

Anti-Bacterial

Buffering

Digestion

Mineral-ization

Lubricat-ion &Visco-elasticity

TissueCoating

Anti-Fungal

Anti-Viral

Carbonic anhydrases,Histatins

Amylases,Mucins, Lipase

Cystatins,Histatins, Proline-rich proteins,Statherins

Mucins, Statherins

Amylases,Cystatins, Mucins, Proline-rich proteins, Statherins

Histatins

Cystatins,Mucins

Amylases, Cystatins,Histatins, Mucins,Peroxidases

adapted from M.J. Levine, 1993

Mucins Lubrication Glycoproteins - protein core with many

oligosaccharide side chains attached by O-glycosidic bond

More than 40% of carbohydrates Hydrophillic, entraining water (resists

dehydration) Unique rheological properties (e.g., high

elasticity, adhesiveness, and low solubility) Two major mucins (MG1 and MG2)

Amylases Calcium metalloenzyme Hydrolyzes (1-4) bonds of starches such as amylose

and amylopectin Several salivary isoenzymes Maltose is the major end-product (20% is glucose) Parotis; 30% of total protein in parotid saliva “Appears” to have digestive function - inactivated in

stomach, provides disaccharides for acid-producing bacteria

Why is it also present in tears, serum, bronchial, and male and female urogenital secretions?

A role in modulating bacterial adherence?

Lingual Lipase Secreted by lingual glands and parotis Involved in first phase of fat digestion Hydrolyzes medium- to long-chain

triglycerides Important in digestion of milk fat in

new-born Unlike other mammalian lipases, it is

highly hydrophobic and readily enters fat globules

Statherins Calcium phosphate salts of dental enamel

are soluble under typical conditions of pH and ionic strength

Supersaturation of calcium phosphates maintain enamel integrity

Statherins prevent precipitation or crystallization of supersaturated calcium phosphate in ductal saliva and oral fluid

Produced by acinar cells in salivary glands Also an effective lubricant

Proline-rich Proteins (PRPs)

40% of AAs is proline Inhibitors of calcium phosphate crystal

growth Part of pellicula dentis Subdivided into three groups

Acidic 45%Basic 30%Glycosylated 25%

Lactoferrin Iron-binding protein „Nutritional“ immunity (iron starvation) Some microorganisms (e.g., E. coli) have

adapted to this mechanism by producing enterochelins.bind iron more effectively than lactoferrin iron-rich enterochelins are then reabsorbed by

bacteria Lactoferrin, with or without iron, can be

degraded by some bacterial proteases.

Lysozyme Present in numerous organs and most

body fluids Also called muramidase hydrolysis of (1-4) bond between N-

acetylmuramic acid and N-acetylglucosamine in the peptidoglycan layer of bacteria.Gram negative bacteria generally more

resistant than gram positive because of outer LPS layer

Histatins A group of small histidine-rich proteins Potent inhibitors of Candida albicans

growth

Cystatins Are inhibitors of cysteine-proteases Are ubiquitous in many body fluids Considered to be protective against unwanted

proteolysis bacterial proteases lysed leukocytes

May play inhibit proteases in periodontal tissues

Also have an effect on calcium phosphate precipitation

Salivary peroxidase systems

Sialoperoxidase (SP, salivary peroxidase) Produced in acinar cells of parotid glands Also present in submandibular saliva Readily adsorbed to various surfaces of mouth

enamel, salivary sediment, bacteria, dental plaque

Myeloperoxidase (MP) From leukocytes entering via gingival crevice 15-20% of total peroxidase in whole saliva

24

CIRCAIDIAN RHYTHM OF SALIVA FLOWCIRCAIDIAN RHYTHM OF SALIVA FLOW

No sleep

sleep

12 am 6 am 12 pm 6 pm 12 am 6 am 12 pm 6 pm 12 am

30

20

10

Time of day

25

Effect of feeding on salivary secretion

0

0,005

0,01

0,015

0,02

0,025

0,03

0,035

Volu

me

of s

aliv

a co

llect

ecd

each

10

min

10 min collection periods

Mealduringthis period

Variations in salivary composition

Unstimulated flow Submandibular g. 70% Parotid g. 20% Accesory g. 7% Sublingual 2%

Acid stimulation Submandibular g. 45% Parotid g. 45%

Chewing Submandibular g. 30% Parotid g. 60%

Variations in salivary composition

Parotid secretion increased amylase content

Submandibular secretion increased calcium concentrations

Gingival cervicular fluid

Seminar

Stomatology

Gingival cervicular fluid

Synonyms:Gingival fluidCervicular fluidSulcular fluid

Similar composition as interstitial fluid Flow rate related to degree of gingival

inflamation, circa 0,5-2,4 ml/day

Composition Cells

Desquamated epithelial cells Neutrophils Small amount of lymphocytes and monocytes Bacteria

Inorganic ions Similar to plasma Potassium 2 x higher than in plasma (cell break-up) Calcium higher than in oral fluid

Organic components Similar to plasma - serum albumin, globulins, complement,

protease inhibitors Small organic molecules - lactate, urea, hydroxyproline Enzymes

Function

Protective flow towards oral cavity - washes out potentially harmful cells and molecules

Antibacterial - immunoglobulins Calcium assists pellicle and plaque

fromation but may contribute to calculus formation

Rather response to inflamation