Saliva: Organic and Antimicrobial Composition Notes

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Dr. Yeger Khazo I: Dentist by training, epidemiologist, data scientist.
- Currently a second-year PhD student.
- PhD project: Development and validation of diagnostic and prognostic prediction tools on early childhood caries in a cohort of young children.

Topic: Organic and antimicrobial composition of saliva.
Lecture Outline:
  - Review of salivary functions.
  - Organic content of saliva.
  - Proteins that interact with calcium and phosphate.
  - Contribution of proteins in pellicle formation.
  - Proteins that initiate digestion.
  - Role of organic buffers.

Comprehend the role of proteins in saliva.
Appreciate the multifunctionality of salivary proteins.
Understand tethering and proline-rich proteins' role in stabilizing calcium and phosphate.
Grasp the various functions of mucins in the oral environment.
Appreciate the importance of the salivary pellicle.
Recognize the importance of organic buffers in the oral environment.

Diverse roles categorized by:
  - Teeth
  - Food
  - Microbes
Example breakdown of salivary functions:
  - Threefold Division:
    - Role related to teeth.
    - Role in digestion of food.
    - Role in microbial balance.

Composition in unstimulated vs. stimulated saliva:
  - Unstimulated Saliva: 1.7 g protein/L.
  - Stimulated Saliva: 1 to 6.4 g protein/L (~200 mg/100 ml of saliva, ~0.2% to 0.3%).
  - Saliva consists of 99.5% water; organic and inorganic components make up 0.5%.
Key organic constituents include:
  - Mucins (varied forms: low and high molecular weight).
  - Amylase.
  - Proline-rich proteins.
  - Statherin.
  - Urea and ammonia (important for pH control).

Saliva is supersaturated with respect to fluorapatite, hydroxyapatite, octacalcium phosphate, and dicalcium phosphate pH range of 6-9.
This state maintains tooth integrity, preventing demineralization while enabling remineralization.
Proteins inhibit unwanted crystal formation in the saliva.

Produced in:
  - Parotid gland.
  - Submandibular glands.
  - Von Ebner's salivary glands.
Structure: 43 amino acids, low molecular weight.
- Hydrophobic and relatively uncharged with a negatively charged N-terminus.
Functions:
  - Inhibits spontaneous precipitation of calcium phosphate.
  - Stabilizes amorphous calcium phosphate (ACP).
  - Binds to tooth surfaces, contributing to pellicle formation.
  - Functions as a lubricant.
  - Inhibits demineralization of enamel.

Synthesized in: Parotid glands.
Structure: 150 amino acids, rich in proline, glycine, glutamic acid, and glutamine.
- Binds to hydroxyapatite and calcium via N-terminal.
Functions:
  - Inhibits crystal growth of hydroxyapatite.
  - Binds to tooth surfaces, assisting in pellicle formation.
  - Acts as a lubricant and inhibits demineralization.

Classification: Mucus glycoproteins, high molecular weight, highly glycosylated (~60% carbohydrate content).
Structure:
- Polypeptide backbone with multiple carbohydrate side chains.
- Terminal components: sialic acid, sulfate, fucose.
Functions:
  - Maintain moisture of mucosal surfaces.
  - Protect against dehydration and microbial attachment.
  - Serve in lubrication (gel-like properties) and aggregation of pathogens (agglutination).

A protein-based layer covering teeth, essential for oral health.
Forms quickly after dental prophylaxis and consists of multiple proteins (mucins, PRPs, amylase, lysozymes, immunoglobulins).
Functions:
  - Lubrication of teeth and prevention of attrition.
  - Protects against demineralization (reduces enamel erosion by up to 61%).
  - Acts as a diffusion barrier and selective membrane for microbial control.

Significant enzyme making up 40-50% of salivary gland produced protein.
Function: Hydrolyzes starch into smaller components (maltose, maltotriose, and dextrins).
Helps to clear food debris from the oral cavity, thereby reducing the risk of demineralization.

Proteins act as buffers, especially at pH < 5, but less effective than bicarbonate and phosphate systems.
Important in biofilms and pellicles for maintaining pH balance and preventing enamel erosion.
Urea: Present in similar concentrations to blood (approx. 3 mmol), contributes to pH increase via urease activity of bacteria.
Ammonia: Comes from urea or deamination of amino acids (e.g., arginine), helps to stabilize pH.

Identify and explain key organic components of saliva (distinct proteins, their functions, and interactions).
Describe the role of statherin and proline-rich proteins in oral health.
Discuss saliva's contribution to remineralization and prevention of demineralization.
Explain pellicle formation, functions, and importance for oral health.
Analyze how saliva maintains pH balance and buffers the oral cavity.