The Role of Teeth in Digestion

Importance of Teeth

• Mechanical Breakdown: Teeth are instrumental in tearing and grinding food into smaller pieces, increasing surface area for digestive enzymes.
• Facilitation of Chemical Breakdown: This mechanical process enhances the efficiency of subsequent chemical digestion.

Types of Teeth

• Primary (Deciduous) Teeth: Also known as baby teeth, milk teeth, or temporary teeth.
  • Eruption starts at around 6 months.
  • Additional teeth appear roughly every two months until 24 months, totaling 20 teeth.
  • Named "deciduous" as they fall out like leaves from trees.
• Permanent Teeth: Develop under deciduous teeth, resorb their roots, leading to their falling out.
  • Total of 32 permanent teeth, mostly erupting by late adolescence.
  • Third molars (wisdom teeth) may or may not erupt by age 25.

Classes of Teeth and Their Functions

• Incisors: Chisel-shaped for cutting food.
• Canines: Fang-like for tearing or piercing meat.
• Premolars (Bicuspids): Broad crowns for grinding and crushing.
• Molars: Larger crowns for primary grinding.
• Dental Formula: Multiplied by two for right/left sides; shows upper/lower jaw ratio:
  • 2 incisors, 1 canine, 2 premolars, 3 molars (third molars may be absent).

Anatomy of a Tooth

• Crown: Exposed part above the gum line.
  • Covered by enamel, a hard, avascular, mineral-based substance with no collagen.
• Root: Embedded in the gum and jawbone.
  • The neck is the connection point below the gum line.
• Enamel: Cannot regenerate naturally if damaged.
• Roots: Vary by type of tooth, e.g., canines and incisors have one; upper molars typically have three; lower molars have two.

Tooth Structure

• Dentin: Beneath enamel, a bone-like structure without blood vessels.
  • Produced by odontoblasts near the pulp cavity.
• Pulp Cavity: Contains pulp with connective tissue, blood vessels, and nerves (from trigeminal nerve, cranial nerve 5).
  • Blood supply from superior and inferior alveolar arteries via the apical foramen and root canal.
• Cement: Adjacent hard substance to dentin in the root, calcified connective tissue.
  • Important for connecting to periodontal ligament.

Tooth and Gum Disease

• Cavities (Dental Caries):
  • Result from enamel mineral loss due to acidic foods or bacteria.
  • Initiated by bacterial adhesion converting sugars to dextran, forming a plaque.
  • Lactobacillus bacteria produce lactic acid, weakening enamel.
• Gingivitis: Inflammation due to calcified plaque (tartar), creating anaerobic conditions for bacteria.
  • Removing tartar reintroduces oxygen, killing anaerobic bacteria.
  • If untreated, leads to periodontal ligament inflammation and eventual bone dissolution by osteoclasts.
• Periodontitis: Advanced gum disease causing tooth loss and potential systematic effects like clot formation.