Dental Caries-Part 6: Prevention

Fig1: Caries free beautiful teeth with proper maintenance #

The carious process can be termed as metabolic activity in the plaque. The result of the metabolic activity may not be anything to see or there may be demineralisation resulting in a visible carious lesion. As we have discussed earlier, plaque is the cause of caries and a tooth completely free of plaque will not have caries. However, it is not always possible to show a strong association between the presence of dental plaque and caries. Mostly because people are unable to completely remove plaque themselves, even when guided properly. In addition, although the bacterial biofilm is the cause of caries, there are other factors involved. This is the reason that caries is described as a multifactorial disease. These factors, when combined, may increase or decrease the rate of demineralization.

Dental Caries-Part 5: Clinical Aspect of Caries Pathology

Arrested caries and remineralization

Pre-Cavitation, or “white spot” caries lesions, can stop when the balance between demineralization and remineralization is changed in favor of remineralization. This could follow the restriction of sucrose, the application of fluoride, or the loss of an adjacent tooth to a proximal caries. This loss of tooth uncovers the area of stagnation and allows proper oral hygiene procedures. The source of the calcium and phosphate for remineralization of the lesion is saliva and plaque. The caries progresses slowly, and even under natural conditions, about 50% of proximal enamel lesions may show no radiographic evidence of progression for 3 years, showing that a small change may be needed to encourage reversal of the process. Although remineralization can bring the mineral content of an enamel lesion closer to that of the original enamel, the deposition is irregular and disorganized at the single crystal level, and the structure of the original enamel cannot be recovered. Despite this, remineralized lesions that have incorporated fluoride may be less prone to caries attack than intact enamel. Arrested enamel cavities can remain dull and white or more often discolored due to the incorporation of an extrinsic dye. This is known as inactive lesion or brown spot.

Normal Structure of Dentin

Dentine is the part of the tooth that is covered by enamel and covers the pulp tissues. It comprises of inorganic hydroxyapatite 45-50%, organic matrix 30% and water 25%.

It is a vital tissue as opposed to enamel. It is elastic and permeable. Therefore, it is never possible for a restorative material to create a totally hermetic seal between itself and the cavity wall.

Dentine consists of dentinal tubules, peritubular dentine and inter tubular dentine. Dentinal tubules contain extensions of the odontoblast cells that line along the inner surface of the dentine and remain in the pulp. The peritubular dentine makes the walls of the dentinal tubules, are devoid of collagen matrix and are highly mineralised. The inter tubular dentine is the main structural component; present between the dentinal tubules; consists of hydroxyapatite crystals lying in the collagen matrix.

Clinical and Histological Features of Dental Caries

Now we shall describes the clinical features of carious lesions on smooth,

occlusal, and root surfaces. We shall relate the clinical features to their histological

features. We shall consider Enamel and Dentine together, the reasons being:

As a clinician, you will see them in the same way.
You can not understand changes in dentine during caries progression and caries arrest without considering the spread of the enamel lesion.
Changes in Dentine occur before the enamel lesion cavitates. Removal of the biofilm will arrest the lesion in dentine as well as the lesion in enamel.
The lesion, in both enamel and dentine, entirely reflects the activity of the bacterial biofilm.

Before I start talking about the clinical and histological features of dental caries, You must know the

Basic Structure of Enamel

Sound enamel consists of crystals of hydroxyapatite packed tightly together in an orderly arrangement which is known as enamel prisms. The amount of hydroxyapatite ranges between 86 to 95%; the organic component between 1% to 2 % and water between 4% to 12% by volume. The total inorganic content of enamel ranges between 95% to 98% by mass, thats why it looks like crystals.

The crystals are so tightly packed that the enamel gets a glass-like appearance and appears translucent. This is the reason that it allows the varying degrees of yellow colour of the dentine to shine through it. Here, you should know that even though the crystal packing is very tight, each crystal is actually separated from its neighbours by tiny intercrystalline spaces or pores. These spaces are filled with water and organic material. When enamel is exposed to acids produced in the microbial biofilm, mineral is removed from the surface of the crystal which shrinks in size. Thus, the intercrystalline spaces enlarge and the tissue becomes more porous. This increase in porosity can be seen clinically as a white spot.