Saliva is what keeps the oral cavity moist protecting the teeth, oral mucosa, etc by maintaining and preserving the oral health. We know how important Composition of Saliva is to Oral health when the quality and quantity of saliva reduces leading to complications such as Dry mouth, increase in caries, gingival inflammation. We all know that Saliva is produced by Salivary Glands but the quality and quantity of the saliva is altered by many factors – Hormonal changes, medicines, diseases, etc.

Saliva is also called as – Whole Saliva, Mixed Saliva and Oral Fluid depending on its composition. Saliva is produced by Major and Minor Salivary Glands – Parotid glands, Submandibular glands and Sublingual glands are Major Salivary glands while Minor Salivary Glands are – Buccal/Labial, Palatine, Tonsillar (Webers Glands), Molar or Retromolar Gland (Carmalt’s glans), Anterior lingual glands (Blandin-Nuhn), Posterior lingual glands (Von-Ebner). Saliva is of three types – Serous, Mucous and Mixed types which are secreted by different Salivary Glands.

Type of Saliva produced by each Salivary Glands:

  1. Parotid gland – Purely Serous
  2. Sub Mandibular: Mixed with Serous units predominating
  3. Sub Lingual: Mixed with mucus units predominating
  4. Palatine & Glossopalatine: Purely mucous
  5. Glands of Blandin & Nuhn: Chiefly mucous
  6. Von Ebner glands: Purely serous

Whole Saliva: It is not just the contents of the saliva which is produced or released from the Salivary Glands but the Saliva which is found in the Oral Cavity.

Composition of Saliva and its Functions

Contents of Whole Saliva:

Salivary Glands: Water, proteins, Electrolytes and small organic molecules

Microbiota: It consists of Oral bacteria (enzymes and bacterial products), Virus, Fungi

Blood and its derivatives: Intraoral bleeding with serum and cells, GCF or Gingival crevicular fluid consists of serum exudate and inflammatory cells

Extrinsic Substances: Food debris, toothpaste, mouthwash substance, Cigarette, Pan, ghutka, etc remnants of habits.

Other fluids: Nasal and Bronchial secretions

Lining Cells: Epithelial keratins

Composition of Saliva:

It consists of three main components –

  1. Water: 99.5%
  2. Organic Substances
  3. Inorganic Substance

Organic Substances:

Proteins: Alpha Amylase, Maltase, Lingual Lipase, Immunoglobulin, Agglutinin, Other polypeptides – Proline rich protein, Slatherins, Cystatins, Histatins

Immunoglobulins: IgG – 1.5 mg/100 ml, igM – 0.2 mg/ml from crevicular fluid, igA comprises of 90% of the total with 20 mg/100 ml.

Non- Immunologic Protein: Antibacterial Proteins – Lysozymes, Lactoferrin, Sialoperoxidase, Glycoproteing (MG1 and MG2), Von Ebner’s gland protein, Secretory leucocyte proteinase inhibitor, Chitinase, Calprotein, chromogranin.

Other Organic Compounds:

Urea – 12-20 mg/100ml – Hydrolyzed by bacteria with release of Ammonia, Rise in pH

Glucose: 0.5 – 1mg/100ml – Too low for bacterial growth, increase in D.M

Vitamins: Water soluble vitamins

Free Amino Acids: Below 0.1 mg/100ml, too low to provide nutrient source for bacterial growth

Inorganic Substances

  • Sodium
  • Bicarbonate
  • Calcium
  • Chloride
  • Fluoride
  • Phosphate
  • Potassium
  • Thiocynate

Cells:

  • Epithelial cells
  • Leucocytes – Polymorphs, Lymphocyte, Monocyte
  • Bacteria: Facultative and Obligatory
  • Yeast and Protozoa
  • Amoeba Salivaris

Gases: Oxygen, Nitrogen, Carbon Dioxide

Functions of contents of Saliva:

Salivary Amylase is one of the most important components of Saliva which acts as an amylolytic which starts the Digestion of Starch in the mouth, the rest of which is completed in the Lower Gastro Intestinal tract. The rest of the digestion is completed by Pancreatic amylase

Salivary Lipase is secreted by Von Ebner’s glands which helps in the digestion of fats, it initiates the digestion of fats.

Maltase: It helps in converting maltose into glucose

Immunoglobulins: Saliva consists of IgG, IgM and IgA out of which IgA is the most predominant. IgA helps in reducing bacterial growth by binding to specific bacterial antigen, affects specific enzymes essential for bacterial metabolism and inhibits bacterial colonization.

Lysozymes: It acts as anti bacterial by attacking the cell wall component or lysis of the cell wall, it is seen to act on Streptococci mutans. It is seen in new born babies as well giving pre-eruptive antimicrobial function.  Gram-negative bacteria are resistant to this enzyme because of the lipopolysaccharide layer.

Lactoferrin: It acts as bacteriostatic as it reduces the amount of free iron in the blood which is required for metabolism.

Peroxidase or Sailoperoxidase: It inhibits growth and acid production of micro organisms such as bacteria, fungi and entreric bacteria. H2O2 combines with thiocynate ions and produces Hypothiocyanite which is an anti bacterial substance.

Glycoproteins or Mucins: This acts as a lubricant which helps in swallowing, chewing or mastication, speech and also acts as a protective barriers against excessive wear. It also has Antibacterial properties by selective adhesion and clearance of microbes.

Histatins: The histatins present in saliva are histatin 1, 3 and 5 which are the most common types. These show Anti microbial properties on some strains of Streptococcus mutans and Inhibit hemoagglutination of the periopathogen Porphyromonas gingivalis. It acts as an Anti Fungal as well and works on Candida Albican in yeast form and mycelial form.

Von Ebners Gland protein: It acts as an Anti Viral agent

Agglutinin: It has sticky properties which helps in clumping of bacteria which can be easily flushed away by saliva and swallowed.

Statherin and Proline rich proteins: It helps in preventing formation of Dental calculus, by inhibiting the precipitation of calcium phosphate salts and helps in the growth of hydroxyapetite crystals on the surface of the tooth.

Cystatins: It helps in the hydroxyapetite crystal equilibrium which prevents acquired film formation and also due to its protein inhibiting properties it controls proteolytic activity.

Histatins: These are histidine rich proteins which are known to have anti microbial activity against certain bacteria such as – Streptococcus mutans, and also act on P. Gingivalis by inhibiting hemoagglutination of the periopathogen. They also act on Fungal infections like Candida Albicans in yeast form and mycelial form. The histatins present in saliva are 1, 3 and 5.

Sodium, Potassium and Bicarbonates – Help in Osmolarity, Bicarbonates act as the main buffering ion.

Thiocynate: Antibacterial

Calcium and Phosphate: Soluble complexes with carbonate lactate, it bounds to protein.