by Jeff Vidrine

Created on: July 21, 2007

A decay is actually a bacterial infection of the hard tooth structure of your tooth. Teeth are covered in an outer, pearly-white layer of tooth structure called enamel. It has no blood supply or nerve endings and averages 2-3 mm in thickness. Just below this is a layer of tooth structure called dentin. Dentin is softer than enamel, more yellow in color and is formed by cells in the pulp or "nerve" of the tooth. Dentin has connections from the cells in the pulp, like little tubes, projecting into the dentin. That is why dentin is the sensitive part of the structure of your tooth.

When you eat, a material called plaque, like in the toothpaste commercials, accumulates on and around your teeth. Plaque consists of many things, one of which is a bacteria that uses the sugar in your diet to live and grow. A by-product of their metabolism is an acid. If allowed to stay on your tooth, the acid dissolves the minerals in your enamel creating an area that is softer and having less calcium. This process is called demineralization, a loss of the mineral content, or decalcification. Dentistry now knows that demineralization can be reversible at this stage when it involves the surface of the enamel. Great home oral hygiene practices are essential, along with the use of prescription strength fluoride or fluoride varnish.

If the decalcification process continues, it will penetrate deeper into the dentin. This is when some people feel symptoms, like sensitivity to cold or sweets. The little tube-like projections from the pulp are now involved and bacteria from your mouth can infect these tubules. This is very irritating to the pulp but fortunately is reversible.

And this is the reason dentists do fillings in decayed areas. The dentist removes the diseased tooth structure, usually with a drill but also with hand instruments or even lasers! The filling restores the tooth to function and prevents any further destruction of the tooth structure. Because the pulp is irritated when you have a decay, the tooth is often sensitive at first as the pulp tissue heals.

Untreated decays continue to grow, involving more extensive areas of the tooth. The bacteria and decay can eventually reach the pulp which can cause the pulp tissue to be infected. This is the origin of most dental abscesses, although many are caused by gum disease. This is painful, the classic "toothache", and must be treated by root canal therapy or extraction. In one sense, having a filling done while a decay is small is preventive dentistry because it prevents the pain, infection, and expense of delaying treatment. More information is available on this topic and many other dental-related questions at www.ada.org.

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