Saliva medium

Saliva's Role in Oral Health

• Saliva safeguards the oral cavity during caries formation through multiple mechanisms.
• It forms a protective layer, the salivary pellicle, composed of glycoproteins. This pellicle shields against acids but also encourages the adherence of harmful plaque bacteria.
• Saliva is supersaturated with inorganic ions, which act as buffers to regulate pH levels. This continuous buffering action counteracts the effects of demineralization and remineralization.
• Serous saliva aids in cleansing the oral cavity, reducing the availability of fermentable carbohydrates for bacteria to convert into acids.

Salivary Flow and Caries

• Salivary flow varies significantly throughout the day and night. During the day, our bodies produce between 1-1.5 liters of saliva, while at night, the production drops significantly to approximately 10 ml.
• This fluctuation can impact caries formation. Individuals who experience a decrease in salivary flow during sleep may be more susceptible to caries.
• Those who work shift work – with their sleep and eating habits altered – may experience a reduction in salivary flow, making them more prone to caries.

Components of Saliva

• Organic Components:

  • Proteins:
    • Mucin: Gives saliva its viscosity and stickiness.
    • Enzymes:
      • Lysozyme: Destroys harmful bacteria by lysing their cell walls.
      • Lactoferrin: Prevents bacterial metabolism by binding to free iron.
      • Lactoperoxidase: Inhibits bacterial metabolism.
      • Amylase: Begins the breakdown of cooked starches.
      • Ribonuclease: An enzyme involved in RNA breakdown.
      • Phosphatase: Plays a role in calculus formation and remineralization of caries.
  • Immunoglobulins (Ig's):
    • Contribute to bacterial disposal through agglutination.
    • IgA, IgG and IgM contribute to bacterial agglutination.
  • Waste Products:
    • Urea, Uric Acid, Ammonia: All are byproducts of cell metabolism and can influence pH levels.
  • Cells:
    • Desquamated epithelial cells: Continuously shed as worn/dead cells are replaced.
    • White blood cells: Found in the gingival crevice, especially during inflammation.
    • Commensal bacterial cells: Exists in a symbiotic equilibrium with the host, preventing other harmful bacteria from taking hold.
  • Hormones:
    • Estrogen and Progesterone are present in saliva.

• Inorganic Components:

  • Ions:
    • Calcium phosphate ions: Major contributors to caries incidence and calculus formation.
    • Sodium, Potassium, Magnesium, Chloride, Fluoride, Bicarbonate, Sulphate, Hydrogen: These ions play a vital role in buffering saliva and maintaining pH balance.
  • Gas Components:
    • Oxygen, Nitrogen, Carbon Dioxide: Carbon Dioxide levels are higher in the salivary glands and its release may be linked to calculus formation.

Functions of Saliva

• Protective:
  • Glycoproteins lubricate and waterproof the oral cavity tissues.
  • Aids in speech.
  • Maintains a healthy mucosa.
  • Forms the salivary pellicle which protects the enamel surface.
  • Serous saliva cleanses the oral cavity.
• Buffering:
  • Ions help maintain pH, making the environment unsuitable for bacterial growth.
  • Neutralizes acids and alkalis.
• Digestive:
  • Salivary amylase begins the digestion of cooked starches.
  • Formation of the bolus.
• Taste:
  • Facilitates taste sensation by dissolving food particles.
• Antimicrobial:
  • Proteins and immunoglobulins contribute to the prevention and destruction of harmful bacteria.
• Tooth Integrity:
  • Saliva plays a role in remineralization, aided by the presence of fluoride.

Factors Influencing Salivary Flow

• Increased Flow:

  • Chewing food (mastication).
  • Irritants.
  • Gingival conditions.
  • Hunger.
  • Smell/sight of food.
  • Teething in babies.

• Reduced Flow:

  • Drugs.
  • Diabetes.
  • Alcohol.
  • Fear.
  • Radiotherapy.
  • Surgery.

Medical Conditions Affecting Salivary Flow

• Hypersalivation: Excessive production of saliva.
  • Neurological conditions: Parkinson's, Motor Neurone Disease, Cerebral Palsy.
• Xerostomia: Dry mouth due to reduced or absent saliva production.
  • Saliva gland disorders: Sjogren's Syndrome.
  • Systemic conditions: Diabetes, HIV/AIDS.
  • Treatments: Radiation/Chemotherapy.