The dental enamel is the outer-most covering of the visible portion of our teeth. It is the hardest tissue in the tooth as well as the human body, in addition to being quite brittle. It is white and translucent; the color of the underlying dentin affects the visible color of the tooth. It is highly mineralized and contains nearly 96% mineral content, mostly hydroxyapatite, which is a crystalline form of calcium phosphate. The remainder is water and organic matter.
Tooth enamel exists in the form of mineral rods that have a mean diameter between 4 and 8 micrometer. The axis of the rods themselves is oriented radially outwards. The rods are circular but with a ridge on one side running down the length. Thus the cross section is somewhat in the shape of a key hole. The ridged sides of the rods point towards the root end of the tooth. The rod consists of tightly packed enamel crystals which are mostly aligned along the axis of the rod but in the ridge they are inclined at an angle of about 65° from the rod axis.
Enamel covers the visible part of the tooth, and a little under the gum line. The mineral in the enamel and the minerals in the saliva are in equilibrium at the pH level of the mouth’s saliva. However, sugars and carbohydrates in food particles that stick to the teeth and between the gums can be broken down into smaller sugars by acidic bacteria already present. The acidic environment tilts the balance of minerals between saliva and the enamel. As a result, more mineral leaves the enamel than enters it. The enamel gets ’demineralized’ and becomes more porous and susceptible to further etching.
The dental enamels serves as a protective layer around the teeth that prevents sensitivity and infection. Demineralization can be checked by use of fluoride orally or in local application. If the process is allowed to continue unchecked, cavities can form. Enamel is avascular, i.e., does not have any blood supply within it. Therefore, once lost, enamel cannot be replaced. Affected teeth must be restored with fillings immediately to stop further damage which ultimately can result in tooth loss.