Dental Caries Overview and Classification

Dental Caries

A disease that causes demineralization of the inorganic part of the tooth, followed by dissolution of the organic part by bacteria.
Most common dental disease worldwide.

Classification

Pits & Fissures Caries: Occurs in grooves and pits of the tooth surface.
Smooth Surface Caries: Occurs on smooth surfaces of the tooth.
Cemental (Root) Caries: Occurs on the root surface of the tooth exposed due to gum recession.
Recurrent Caries: Occurs around a pre-existing restoration.
Acute (Rampant) Caries: Rapidly progressing caries affecting multiple teeth.
Arrested Caries: Caries that has stopped progressing.

Contributing Factors

Susceptible Tooth Surface:
- Tooth Position: Teeth that are crowded or misaligned are more susceptible.
- Tooth Morphology: Teeth with deep pits and fissures are more susceptible.
- Tooth Structure: Teeth with thin enamel are more prone to caries.
- Genetic Factors: Some individuals are genetically predisposed to caries.
- Fluoride: Fluoride strengthens tooth enamel, making it less susceptible to caries.
  - Reduces enamel solubility by converting hydroxyapatite to fluoroapatite crystals.
  - Enhances remineralization of carious lesions.
  - Exhibits antibacterial activity by reducing lactic acid production, glucose uptake, and bacterial adhesion.
Carbohydrates:
- Type: Monosaccharides, disaccharides, and polysaccharides contribute to caries formation.
- Amount: Higher intake of carbohydrates increases caries risk.
- Frequency: Frequent consumption of carbohydrates increases caries risk.
- Consistency: Sticky carbohydrates adhere to teeth for longer, increasing caries risk.
Microorganisms:
- Acidogenic bacteria:
  - Lactobacilli and Streptococci (Streptococcus mutans) produce acids that demineralize enamel.
- Proteolytic bacteria:
  - Actinomyces, Clostridia, and Pseudomonas degrade the organic matrix of the tooth.
- Chromogenic bacteria:
  - Aspergillis bacteria contribute to tooth discoloration.
Essential Features of Cariogenic Bacteria:
- Acidogenic
- Produce low pH (lower than 5.5)
- Aciduric (resistant to acidic conditions)
- Possess attachment mechanisms for adhesion to tooth surfaces
- Produce abundant polysaccharides for plaque matrix formation
Dental Plaque:
- Adherent bacterial structure formed on tooth surfaces.
- Contains a large number of microorganisms surrounded by extracellular material.
- Two major interfaces:
  - Internal (pellicle): Adheres to the tooth surface.
  - External (plaque saliva interface): Exposed to saliva.
- Types:
  - Subgingival: Found below the gum line.
  - Supragingival: Found above the gum line.
- Composition:
  - Microorganisms
  - Matrix: Protein, lipids, carbohydrates, inorganic components, and water.
- Role of plaque matrix:
  - Acts as a diffusion limiting membrane, retaining acids in high concentrations to initiate caries.
  - Slows down the entry of buffers from saliva, delaying neutralization.
- Factors affecting plaque formation:
  - Anatomy and position of teeth
  - Presence of appliances
  - Tooth surface structure
  - Friction from diet
  - Oral hygiene procedures
  - Diet composition
- Mechanism of action:
  - Allows bacteria and acids to adhere to tooth surfaces.
  - Prevents escape of acids and entry of salivary buffers.

Saliva & Caries

Role of saliva in caries:
- Washing effect: Removes food debris and bacteria.
- Buffering effect: Phosphate and bicarbonate content neutralize acids.
- Salivary antibodies (IgA): Fight against bacteria.
- Antibacterial substances: Lysozymes, peroxidases, and lactoferrin inhibit bacterial growth.

Theories of Dental Caries

Acidogenic theory (Miller's chemico-parasitic theory): Most accepted theory.
Proteolytic theory: Explains penetrating caries under restorations and caries of impacted teeth.
Proteolosis-chelation theory: Not as widely accepted.

Pathology of Enamel Caries

Clinical Picture

Initial stage: White chalky area.
Progression: Rough to the probe with staining.
Advanced stage: Cavitations occur.
Lesion is cone-shaped:
- Pits & fissures caries: Base towards the dentoenamel junction (DEJ), apex towards the surface.
- Smooth surface caries: Base towards the surface, apex towards the DEJ.

Microscopic Picture

Polarized light microscope reveals four phases of enamel caries:
- Initiation phase:
  - Translucent zone: Initial demineralization, 1-2% pores.
  - Dark zone: Further demineralization, 2-4% micropores.
  - Body of the lesion: Advanced demineralization, 5% pores at periphery, 25% pores at center, translucent.
  - Surface zone: Appears radio-opaque and harder than deeper zones due to continuous remineralization, fluoride, insoluble proteins, and prism-less enamel.
- Phase of bacterial invasion: Bacteria invade the enamel through the spaces created by acids.
- Phase of destruction: Proteolytic bacteria degrade the organic matrix of the enamel.
- Phase of secondary enamel caries: Acid and bacteria spread laterally along the DEJ, invading the enamel from beneath.

Pathology of Dentin Caries

Clinical Picture

Brownish and soft to the probe.
Cone-shaped with the base towards the DEJ and the apex towards the pulp.

Microscopic Picture

Initial Uninfected Lesions: Occurs before enamel cavitations.
- Zone 1: Reactionary or reparative dentin formation (secondary dentin).
- Zone 2: Sclerotic or translucent dentin formation (calcium ion deposition).
- Zone 3: Body of the lesion (dead tract).
Infected Lesion: Occurs after enamel cavitations, bacteria invade dentin through dentinal tubules:
- First wave: Acidogenic bacteria decalcify dentin, leaving organic matrix intact.
- Second wave: Mixed infection containing proteolytic bacteria distort the organic matrix.
- Zone 1: Mild pulp inflammation.
- Zone 2: Reparative or reactionary dentin.
- Zone 3: Sclerotic dentin.
- Zone 4: Body of the lesion:
  - Decalcified uninfected zone
  - Decalcified infected zone
  - Destruction zone
  - Beading: Lateral distension of dentinal tubules by bacteria.
  - Liquefaction foci: Coalescence of neighboring beads, located along the long axis of dentinal tubules.
  - Transverse clefts: Liquefaction foci located at right angles to the dentinal tubules due to lateral branches.