Composition and Structure
Four types of tissue make up the human tooth: enamel, dentin, cementum, and the dental pulp. Of these four, the enamel is the only one which is directly visible in a healthy tooth. It covers the visible part of the tooth. It is both a decoration and an armor. Tooth enamel is the hardest structure in the human body. While it is the hardest dental tissue, it is also brittle. Chemical action can easily cause it to decay and be destroyed.
The reason for its hardness is the high percentage of minerals found in it. The mineral content is nearly 96%, and the other four percent is made up of water and organic material. Of the minerals, a crystalline form of calcium phosphate, called hydroxyapatite, is the major constituent.
Enamel is formed on human teeth even before they emerge from the gum. Once a tooth is fully formed, the enamel is totally devoid of any blood vessels and nerves. The thickness of the enamel layer is greatest at the cusp. It could be up to 2.5 millimeters in a fully grown tooth. The enamel layer gets thin as we move towards the root, reducing to zero near the gum.
The normal color of enamel varies from bluish white to light yellow. Since enamel is partially transparent, the color of the dentin below it will affect the appearance. In baby teeth, the enamel is less transparent, hence baby teeth appear whiter than adult teeth.
Demineralization and Remineralization
Bacteria, present in the plaque on a person’s teeth, act on sugars and carbohydrates to produce acid. This acid reacts chemically with the mineral crystals, and ‘dissolves’ them, thus wearing away the enamel layer. The enamel layer becomes porous and thin. This process is called demineralization. Excessive loss of minerals, without replacement, will ultimately result in tooth decay. This is why dentists advise regular brushing and flossing.
This demineralization is partially cancelled by the remineralization provided by saliva. Human saliva contains fluoride in addition to calcium, phosphate, and hydroxyl ions, the very stuff which makes up the enamel. The fluoride, among its various beneficial roles, aids remineralization with ions in the saliva. Under normal conditions, there should be a balance between demineralization and remineralization.
Fluoride, externally applied to the teeth, will also accelerate remineralization of the teeth. However, such remineralization can repair tooth damage to a limited extent only.
Role of Good Habits
It is obvious that preservation of the enamel is very important. The remineralization due to salivary action is not sufficient if we do not keep our oral cavity clean. Brushing and flossing after every intake is very helpful. This routine will save a lot of pain and money at no material cost. Similarly, certain non-food intakes, like alcohol and tobacco, should be avoided because they suppress the action of the salivary glands, in addition to other adverse effects due to their chemical composition. Chewing gum promotes salivary action, but the gum must be sugar free. Junk foods are very attractive, but must be avoided. They are rich in carbohydrates, and tend to increase the frequency at which the teeth get polluted.
A choice of good food and good oral hygiene are an essential requirement for healthy teeth.