Dental caries

Dental caries

Definition

A reversible disease process of dental hard tissues, instigated by the action of bacteria upon fermentable carbohydrates in the plaque biofilm at tooth surfaces, leading to acid demineralisation and ultimately proteolytic destruction of the organic component of dental tissues

• results in softening and ultimate destruction of tooth substance
• same name for both condition and process
  
• carious process
  • the histopathological interactions occuring in the plaque biofilm causing disease - this process is always ongoing and prevalent in all individuals and can only be controlled
    
• carious lesion
  • the signs of the disease on dental hard tissues i.e. tooth decay, early lesions, cavities etc.
• provisionalisation is the process of stabilisation and is not the end result

Causative factors - acidogenic theory

• bacteria - Streptococcus Mutans (associative, not causative)
• tooth surface
• carbohydrate (produces acid)
• time

Plaque incidence

• increased by plaque, carbohydrate and time, producing a low pH environment
• decreased by saliva, good oral hygiene, good diet and fluoride reducing the low pH environment

Stephan curve - acid attack

• after sugar intake, pH levels drop rapidly, but then gradually recover
• time is needed for this recovery; for this reason, grazing is discouraged
• the critical pH is the level at which demineralisation will occur; for dentine this is 6.2 and for enamel. 5.5

Caries diagnostic regime

• remove calculus, plaque and stains
• drying the tooth
• early clinical detection
• diagnosis
• observation --> recall and diagnosis
• preventative measures --> monitor success
• invasive preparation --> control of resolved caries

Visual detection

• sharp eyes and magnification
• good illumination
• clean, dryable tooth surface
• dental explorer (blunt) e.g. periodontal probe
• time

Caries diagnosis

• caries history/risk assessment
• signs/detection
• symptoms i.e. pain histtory
• special investigations
  • vitality tests (checks if pulp is still alive)
  • radiographs

Evaluation of caries risk - contributing factors

• medical - drug therapy, sucrose-based medication
• social - stress, lifestyle change
• dietary - prolonged breast feeding, grazing
• host resistance - previous caries experience, lesions on certain tooth surfaces, soft, light coloured regions
• salivary - low secretion and buffering
• microbiology - high numbers of S. mutans and lactobacilli (can be tested chairside)

Development of the incipient enamel lesion

• does not start at surface, but begins subsurface

Effects on enamel - biochemical

• mature >95% mineral, <5% organic matrix, water
• enamel crystals arranged as prisms (lock and key, type III)
• prism boundaries contain…