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.