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 UNIT The basic building block of all salivary glands Saliva formed in acini flows down DUCTS to empty into the oral cavity. ACINI - water and ions derived from plasma

Hypotonic final saliva into mouth TWO STAGE HYPOTHESIS OF SALIVA FORMATION Most proteins Na+ Cl- resorbed Hypotonic final saliva into mouth Water & electrolytes Some proteins electrolytes K+ secreted Isotonic primary saliva

Inorganic components Saliva compositon

Calcium and phosphate Help to prevent dissolution of dental enamel 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 Thiocyanate Sodium, potassium, chloride 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

Concentration (mM) FLOW RATE ml/min

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 Amylases, Cystatins, Carbonic anhydrases, Histatins, Mucins, Peroxidases Carbonic anhydrases, Histatins Anti- Bacterial Buffering Amylases, Mucins, Lipase Cystatins, Mucins Anti- Viral Digestion Salivary Functions Mineral- ization Anti- Fungal Cystatins, Histatins, Proline- rich proteins, Statherins Histatins Lubricat- ion &Visco- elasticity Tissue Coating Amylases, Cystatins, Mucins, Proline-rich proteins, Statherins Mucins, Statherins 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

CIRCAIDIAN RHYTHM OF SALIVA FLOW No sleep sleep 12 am 6 am 12 pm 6 pm 30 20 10 Time of day

Effect of feeding on salivary secretion Meal during this period 10 min collection periods

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 fluid Cervicular fluid Sulcular fluid Similar composition as interstitial fluid Flow rate related to degree of gingival inflamation, circa 0,5-2,4 ml/day

Composition Cells Inorganic ions Organic components 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

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