Diagnosis of Dental Caries

Introduction:

Early detection and diagnosis of dental caries reduces irreversible loss of tooth structure, the treatment costs and the time needed for restoration of the teeth. Dental caries often initiates at the fissures in the occlusal surface of the tooth. Conventional examination for caries detection is primarily done using visual inspection, tactile sensation and radiographs. While these methods give satisfactory results in detection of cavitated lesions, they are usually inadequate for the detection of initial lesions. Because of these deficiencies, new detection methods have been developed to aid better diagnosis.

Conventional Methods Used in Diagnosis of Dental Caries

It is one of the most common diagnosis methods implemented by dentists. In order to make an accurate assessment, the teeth should be clean, dry and examined under a light source. In visual examination, changes in tooth structure such as; enamel dissolution, white spot lesions, discoloration, surface roughness and presence of cavitation are assessed. When illuminated, the carious tissues scatter the light and make enamel look whiter and opaque. This is due to increased porosity caused by demineralization. Similarly, when dentin undergoes demineralization, a shadow is observed under the intact enamel. When caries progress, the surface breaks down and a cavitation is formed.

The explorer and the dental floss are used for tactile examination but the use of an explorer is not preferred because:

  1. Sharp tip of the explorer can produce traumatic defects on the enamel surface,
  2. The cariogenic bacteria may be transferred from one tooth surface to another,
  3. Probing may cause cavitation and fracture in the incipient lesions,
  4. Explorers have low sensitivity resulting in undetected lesions.

If the explorer catches or resists removal when moderate pressure is applied, and when this is accompanied by one of the following;

  • Softness at the base of the lesion,
  • Opacity adjacent to the pit or fissure,
  • The enamel is softened adjacent to the pit and fissure, we can conclude that the area is carious.

Pickard, proposed the use of dental floss for the detection of caries. When there is food packing between the teeth and the floss is frayed when passed through the contact area, this might be the indication of caries.

Clinically “sound” and apparently intact occlusal surfaces, however, may develop lesions which penetrate into the dentin, which can be observed only through radiographic examination

Radiographic examination has great value in detecting caries lesions especially when they are not clinically visible. In low caries population, as a result of fluoride use, the surface of enamel does not break down, making the caries detection harder. In recent years, the incidence of such lesions has increased dramatically. According to studies, bitewing radiography has been proven to be an effective method in the detection of proximal caries and hidden caries.
Besides its advantages, radiographs also have some limitations too. For this reason, it is advisable to use clinical evaluation along with radiographic imaging. The disadvantages of radiography are as follows:
• Proximal contacts are overlapped,
• The lesion depth may appear to be increased due to angulation and this may lead to false diagnosis,
• Occlusal lesions may not be detected because of the superposition of the buccal and lingual cusps,
• The real cause of the radiolucency can’t be determined whether it is due to caries, resorption or wear,
• The superficial demineralization of the buccal and lingual surfaces may seem like proximal caries,
• Active and arrested caries can’t be distinguished in the radiographs.
• Radiographs may give false positive results due to a phenomenon called “Mach band effect”. In this perceptual phenomenon, the contrast between the dark and lighter areas has increased, resulting in a dark demarcation band. This effect causes formation of a radiolucent area in dentin enamel junction.


Cervical burn out is another optical phenomenon where a wedge shaped radiolucent area is seen between the bone and the cemento-enamel junction. This effect is due to tissue density and the low penetration of X-rays at the cervical region.

Despite the disadvantages, radiographs are the most commonly used diagnosis tool and with the development of new techniques many of the problems are solved.

There are two layers of decalcification in carious dentin. The first one is the soft and infected layer which doesn’t have the capacity of remineralization. The second one is hard, intermediately decalcified and has the ability of remineralization. Many studies were carried out to differentiate these layers. Although there are opinions stating the benefit of caries detection dyes, there are also opinions that dyes can lead to over-reduction in the dentin.

Most clinical investigations have concluded that, caries detection dyes don’t stain bacteria but stain the less mineralized organic matrix. In a study of Demarco et al. they suggested that dye remnants that remained on the walls of the cavity may cause a decrease in the shear bond strength between the composite restorations and the enamel.

In the upcoming blog post we will learn about the Novel Methods for Caries Detection..

Happy Reading😊

References: Meandros Med Dent J 2018;19:1-8, Image source: Google

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