Dental Caries-Part 1: Etio-pathogenesis and Clinical Features

This lesson presents basic definitions, terminologies, etiologies, demineralisation-remineralisation of enamel and clinical characteristics of the caries lesion in the context of clinical operative dentistry. 

Definitions of Dental Caries and Dental Plaque 

Dental caries is defined as a multifactorial, transmissible, infectious oral disease caused primarily by the complex interaction of cariogenic oral flora (biofilm) with fermentable dietary carbohydrates on the tooth surface over time.

Dental plaque is a gelatinous mass of bacteria adhering to the tooth surface. Carious lesions occur only under the plaque. The plaque bacteria metabolises the refined carbohydrate (sucrose mainly) for energy production and produces organic acids as a by product. These acids cause dissolution of crystalline structures of enamel that result in caries lesions of the tooth.  

These lesions usually are found on the facial and lingual surfaces of teeth. They can also occur in the proximal surfaces but are difficult to detect as the contact areas are difficult to see.

Image of dental caries on occlusal surfaces of mandibular teeth.

Mechanism of Dental Caries  

Traditionally, the tooth-biofilm-carbohydrate interaction has been illustrated by the classical Keyes Jordan diagram. However, dental caries onset and activity are, in fact, much more complex than this three-way interaction, as not all persons with teeth, biofilm, and consuming carbohydrates will have caries over time. Several modifying risk and protective factors influence the dental caries process. At the tooth surface and sub-surface level, dental caries results from a dynamic process of attack (demineralization) and restitution (remineralization) of the tooth substance.

Individuals in whom the balance tilts predominantly toward protective factors (remineralization) are much less likely to develop dental caries than those in whom the balance is tilted toward pathologic factors (demineralization). Once, you understand the process of balance between demineralization and remineralization, you get the key to caries management.

See this Video.

Stephan curve

There are two types of people, in one type of individual, the protective factors are dominant, thereby favouring remineralization process compared to the other type in whom the pathologic factors are relatively dominant favouring demineralization. So, whether the development of caries will take place depends on dominant factor present in an individual mouth. Understanding the process of remineralization and demineralization is vital for the long-term management of dental caries although treating the symptoms means providing restorative services is also very important.  

Aetiology of Dental Caries 

Dental caries is caused by a complex interaction between the following five factors. 

  1. Biofilm 
  2. Tooth structure providing habitat to bacteria 
  3. Diet 
  4. Saliva 
  5. Oral hygiene 

Clinical Features of Normal and Carious Enamel 

The clinical features of caries described are keeping in mind the varying conditions of the oral cavity. They are described when the enamel is in normal, hydrated, and desiccated state. They are also described in terms of surface texture and hardness. 

The normal enamel will btranslucence whether in hydrated or desiccated state. The surface texture will be smooth and hard. 

The hypocalcified enamel will be opaque in both hydrated and desiccated state. The surface texture will be smooth and hard. 

The non-cavitated enamel lesions (caries below enamel surface) will be translucent when in hydrated state but opaque when desiccated. The surface will be smooth and softened. 

The enamel with active caries will be opaque in both hydrated and desiccated state. The surface will be cavitated and very soft. 

The enamel with inactive (arrested) caries will be opaque and dark in hydrated and desiccated state. The surface will be rough and hard. 

Once you become familiar with clinical characteristics of enamel under various conditions, you will start understanding its clinical correlation and treatment. For further understanding, read further for viva voce in ADC practical examination.