Stages of Tooth Decay

Tooth decay is so common that it is actually the most common communicable infectious disease condition for humans. In fact, it is so common that most people consider that it is inevitable that they will get more cavities as time goes on. It doesn’t have to be that way. With diligence and a little knowledge, we don’t have to keep getting cavities as the years go by.

Tooth decay (a cavity) always starts on the outside of the tooth and works its way in. On the part of the tooth that is designed to be out in the open in the mouth, there is a hard and decay resistant substance called enamel covering the entire tooth. Inside of that or underneath the enamel is another less hard and less decay resistant substance called dentin. Underneath the dentin is the soft tissue we call the pulp. It is made up mostly of blood vessels, but also has some nerve tissue. In spite of being made up of mostly blood vessels, most patients know the inside layer of the tooth simply as “the nerve”. Of course, as we age, it becomes more common for roots to be in the open on a tooth or on many teeth. Root structure has no enamel covering.

When a dentist looks at your teeth while doing a checkup (called a recall exam or a recare exam in the dental field), he is looking for several disease conditions, the most common being tooth decay. The official name for tooth decay or a cavity is caries. Traditionally, the only way to tell for sure that there is a spot of tooth decay is to poke at the surface of the tooth with a sharp instrument and see if it is sticky. Clinically, tooth decay is sticky like wet hard candy. This is why the dentist usually uses a sharp instrument called an explorer to feel the surface of the teeth to see if there are any sticky areas. In recent years, other ways to find tooth decay have come about. There are some dyes that stain decayed areas helping the dentist see decay on visually accessible areas of the teeth, although dyes are actually less accurate for finding tooth decay than the traditional way. Recently, lasers have been used to find tooth decay. This is rapidly gaining acceptance in the field, but at present cannot detect decay in visually inaccessible areas like between the teeth. There are areas of the teeth that are not visually accessible, and radiographs (x rays) help to “see” many of those areas. Radiographs cannot find tooth decay as early in its progression as clinically probing the tooth surface with a sharp instrument, but where the dentist cannot see the surface of the tooth, radiographs are the only way to diagnose decay.

On enamel covered areas of the teeth, tooth decay that has not penetrated all the way through the enamel surface is reversible. This means with a change in what is happening at home with brushing, flossing, and application of fluoride, as well as diet can reverse the decay process. On visually accessible areas of the teeth, decay in the enamel only looks like tan or brown areas where no chips of enamel have been lost. On a radiograph (x ray) the affected area looks like a very small “tick” in the surface between the teeth. Your eyes will have to be very good, and likely you will need a little bit of training from your dentist to see these areas. Whether the enamel only decay is seen on the teeth directly or on a radiograph, it is called incipient decay. Often the dentist will tell you there are some areas he wants “to watch”. Then he will give you some specific instructions on how to enhance home care to reverse these areas of early tooth decay. The incipient decay came from inadequate cleaning of the affected areas at home. What this means is that if something (brushing, floss, fluoride, or diet) is not changed in what is being done at home by the patient, the incipient areas will become larger, enter the dentin layer and require removal of the decay. Decay in dentin will not reverse meaning it has to be removed (drilled out) and replaced with some other material (a filling, a crown, or something else) or it will inevitably progress to the pulp of the tooth and cause an abscess.

When the dentist tells you that there is incipient decay or that you have some areas he wants “to watch”, this needs to be a wakeup call notifying you that home care must be enhanced or else there will certainly be cavities to be filled within a year or so. Without a change at home, you could consider incipient decay a ”time bomb” of sorts.

If a patient is one of those people who only goes to the dentist every 4 or 5 years and incipient decay is located, most dentists will fill it since if nothing changes at home and 4 or 5 years goes by, there will be some teeth requiring some expensive major work or may even be lost. For those unable to access dental care for a few years like soldiers (who might become prisoners) or missionaries going to third world countries, incipient decay is usually filled for the same reason. Of course, on root surfaces, there is no enamel covering. For decay on roots, there is no “grace period”. Roots are either decayed or they aren’t. There is no such thing as incipient decay on roots. Decay on roots needs to be removed as soon as it is detected. If you have questions about tooth decay, make sure you ask your dentist about it.


This article was written by Dr. Mike Christensen and published in the Daily Miner and News, and Enterprise. Local Kenora News Publicatons (1998-2006)