Caries (also known as cavities) are one of the most common of all diseases and still a major cause of loss of teeth. Dental caries may be defined as a pathogenic process of decalcification of dental hard tissue due to acid produced by microorganism in which gradual destruction of tooth surfaces occurs.


Pathophysiology of dental caries is a very complex one; it cannot be explained in terms of single events. It is explained with the help of some theories.

  1. Acidogenic theory
  2. Proteolytic theory
  3. Proteolytic chelation theory
  4. Sucrose chelation theory
  5. Autoimmune theory

Causes of Dental Caries

There are four important factors which influence the process of tooth destruction by dental caries are:

1. Carbohydrates: The fermentable carbohydrates are –glucose, sucrose and fructose etc. among them sucrose is considered as the criminal one. These sugars are easily and rapidly fermented by cariogenic bacteria in the oral cavity to produce acids and cause dissolution of the hydroxyapatite crystals of the enamel followed by the dentine.

2. Microorganisms: A large number of microorganisms play their role in the development of dental caries, among them the most important is Streptococcus mutans. Others are streptococcus sobrinus, strep. mitior, strep. Salivarius, strep. Sanguis and peptostreptococcus.

3. Acids: The exact mechanism of carbohydrate degradation to form acid in the oral cavity is not known. It probably occurs through enzymatic breakdown of sugar and formation of acids. These acids are: Lactic acids, aspartic acid, butyric acid and glutamic acid etc. These organic acids cause demineralization of enamel followed by dentine and causes the teeth decay.

4. Dental plaque: It is a thin, transparent film produced on the tooth surface. Plaque is composed of salivary mucin, desquamated epithelial cells, microorganisms, food debris etc.

Classification of Dental Caries:

  1. Pit and fissure caries: Appear brown or black, with little softening and opaqueness of the surface.
  2. Incipient caries: Presents a chalky white appearance, presence of intact enamel surface.
  3. Smooth surface caries: It occurs in the proximal surface of the teeth just below the contact point.
  4. Rampant caries: It is an acute fulminating type of carious infection, characterized by simultaneous involvement of multiple numbers of teeth, in multiple surfaces within a short time and early involvement of the pulp. The common age is 4 to 8 years for deciduous teeth and 11 to 19 years for permanent teeth.
  5. Nursing bottle caries: Occurs in children who take milk or fruit juice by the nursing bottle for a considerably long duration of time, even during sleep. Both rampant and nursing bottle caries cause early involvement of pulp.
  6. Chronic caries: This type of caries progresses slow, pulp gets sufficient time to produce secondary dentine to protect itself.
  7. Arrested caries: Arrested caries is a lesion. It presents a hard, black or brown coloured dentinal surface at its base.
  8. Recurrent caries: It is a carious lesion that begins around the margins of a defective restoration.
  9. Forward caries: When caries progress unidirectionally – is called forward caries.
  10. Backward caries: when dentine to enamel it is called backward caries.
  11. Root caries: cementum exposed. Actinomycotic group responsible.
  12. Radiation caries: actual cause is not known, but it may be due to the reduced salivary secretion.

Role of Fluoride in the Prevention of Caries:

Fluorides convert hydroxyapatite crystals of enamel into fluorapatite crystals which are highly resistant to bacterial induced acid demineralization.

They prevent the activity of the enzyme glucose transferase which is essential for the formation of extracellular polysaccharides (dextran, levan etc.) and reduce the bacterial adhesion on to the tooth surface.

The fluoride ions can limit the rate of carbohydrate metabolism by the cariogenic bacteria and reduce the acid attacks on the tooth.

In high concentrations, the fluoride ions can be directly toxic to the streptococcus mutans.

Methods of Caries Prevention:

1. Limit substrate:

  • Eliminate sucrose from the diet or reduce its amount.
  • Eliminate sucrose from the in between meals and snacks.

2. Modify oral microflora:

  • Bactericidal mouthrinse by chlorhexidine.
  • Topical fluoride treatments.
  • Antibiotic treatment by vancomycin tetracycline.

3. Plaque disruption by brushing and flossing etc. can prevent dental caries

4. Modify tooth:

  • Systemic fluorides.
  • Topical fluorides.
  • Maintain a smooth surface of the tooth.

5. Stimulate salivary flow:

  • Eat non-cariogenic fibrous foods that require lots of chewing.
  • Use of sugarless chewing gums.
  • Administer sialagogues.

6. Restore tooth surfaces:

  • Restore all caveated lesions.
  • Seal pits and fissures at caries risk.
  • Correct all defects e.g. marginal crevices, proximal over hangs etc.

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