Caries

Also known as tooth decay, is the most prevalent noncommunicable disease (NCD) in humans. A preventable and multifactorial disease which causes cavities within teeth.

Cause (Time + Substrate + Susceptible Tooth Surface + Microorganism/plaque)
Dental caries is caused when bacteria within the oral cavity metabolize sugars and producing acids that demineralizes the hard tissues of the teeth i.e. enamel and dentine.
Bacteria: Streptococci (e.g.Streptococcus mutans, streptococcus sobrinus), Lactobacillus species(e.g. acidophilus), Actinomyces, Nocardia
Cariogenic sugars: Simple sugars: Sucrose, Glucose, Fructose, Lactose, Galactose

• Enamel Caries (4 Zones of Demineralisation)
  • Zone 1 – Translucent Zone
    Deepest zone which represents the advancing front of the carious lesion. Structureless
    
  • Zone 2 – Dark Zone
    Second deepest zone. Loss of crystalline structure indicates the process of demineralisation and remineralisation. During remin. this is the largest zone
    
  • Zone 3 – Body Zone
    During demin. this is the largest zone. May contain bacteria within the pores.
    
  • Zone 4 – Surface Zone
    Relatively unaffected by caries; partially demineralised.

• Dentine Caries (5 Zones of Progression)
  • Zone 1 – Normal Dentine
    
  • Zone 2 – Subtransparent Dentine
    Deepest/Advancing front. Layer of fat globules. Fatty Degeneration of Tomes Fibers,
    No bacteria found here and dentine is capable of remineralisation
    Stimulation of the dentine gives a painful response
    
  • Zone 3 – Transparent Dentine – Dentine Sclerosis
    Softened Dentine, no bacteria found here
    Decalcification of dentine tubules, narrow zone
    Remineralisation may take place here as collgen cross-linking remains intact
    Stimulation of the dentine gives a painful response
    
  • Zone 4 – Turbid Dentine
    Zone of bacterial invasion.
    Irreversible damage of collagen matrix – Dentine CANNOT be remineralised.
    Dentine tubules are widened and distorted
    This zone must be removed before a restoration is placed
    
  • Zone 5 – Infected Dentine
    Zone of decomposed dentine – no longer resembles any form of dentine
    Highest concentration of bacteria
    This zone must be removed before a restoration is placed