Functions of Saliva
Functions of Saliva
The functions of saliva can be broadly categorized into 7 categories: (LAB-MM-TB)
- Lubrication and Protection
- Antimicrobial Action
- Buffering Action
- Maintenance of Tooth Integrity
- Mechanical Cleansing
- Taste and Digestion
- Bolus formation
1. Lubrication and Protection
Saliva acts as lubricant and keep the oral mucosa moist which prevents it from cracking.Mucins present in saliva are the best lubricating agents.
Lubrication of oral mucosa helps in mastication, speech and swallowing.
Fluidity of saliva helps in mechanical washing of debris.
Mucins have antibacterial actions which prevents adhesion of microbes to tissues.
Mucins helps in formation of enamel pellicle.
2. Antimicrobial Action
Saliva contains antimicrobial agents like peroxidase, lysozyme, IgA which act on microbes.
Secretory IgA coats the bacteria and are easily phagocytosed by leukocytes. (Opsonization)
Lactoferrin binds to some bacterial species like Staphylococci, Sterptococcus Mutans and prevent supply of nutrients essential for its growth.
Mucins limit the colonization of bacteria
3. Buffering Action
Saliva has almost neutral pH with little inclination to acid. The pH value ranges from 6.3 to 7.0. Bicarbonate is the principle buffer of saliva.
Sialin is a salivary peptide plays a crucial role in raising pH after exposure to carbohydrates or sugar.
Saliva has 3 main buffers, Bicarbonate (HCO3-), Phosphates (PO4+) and Proteins.
4. Maintenance of Tooth Integrity
The buffering action of saliva regulates the pH of plaque surrounding the enamel, there by reducing caries progression.
Calcium and phosphate ions help to maintain normal intra-oral pH and helps in remineralization from the surface.
Statherin in saliva helps in preventing the precipitation of calcium phosphates and inhibits calculus formation.
Greens factor attaches to lactobacilli and inhibits its growth.
Calcium, phosphorus, magnesium, chloride increase the hardness of tooth, decrease permeability.
Fluoride helps in prevention of dental caries by forming fluorapatite crystals.
Clotting factors like VII, VIII, IX and calcium help in clotting.
Epidermal growth factor (EGF), transforming growth factors, fibroblast growth factor (FGF), insulin-like growth factors (IGF’s) and nerve growth factor fasten the wound healing.
5. Mechanical Cleansing Action
Saliva being watery in nature removes debris.
Saliva clears dietary acids and protects tooth from erosion.
6.Taste and Digestion
Saliva helps in taste which is activated during initial stage of ingestion of food.
Gustin binds to zinc which is essential for maturation of taste buds.
Starch breakdown is initiated by amylase which dissolves sugar. Most of sugar is broken down by pancreatic amylase and not salivary amylase.
Lipase in saliva helps in fat digestion.
7. Bolus Formation
Moistening nature of saliva helps to make the food into a bolus making it easy to be swallowed.
Saliva helps in mixing of food within the mouth and will assist in swallowing of food.