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Ask Dr. K: Unchecked tooth decay leads to cavities

DEAR DOCTOR K: What is tooth decay? Is it the same as a cavity?

DEAR READER: Tooth decay is not the same as a cavity — but tooth decay can lead to the formation of a cavity.

Tooth decay (also known as dental caries) originates with plaque, the sticky, bacteria-laden film that collects on your teeth between brushings. In recent years, we’ve learned that many types of bacteria produce filmy substances that act like a protective foam. Millions of bacteria live together inside the foam bubble they collectively have made. It’s their house, and helps them keep out threatening things.

Protected from destruction by the film, the bacteria in plaque produce acid that gradually destroys the surface of the teeth. When decay creates a hole in the enamel — the hard outside layer of your tooth — this is a cavity.

Here’s a quick look at how tooth decay progresses to cavity formation. (I’ve put an illustration of this process on my website, AskDoctorK.com.)

(1) Cavity-causing bacteria accumulate on the teeth.

(2) These bacteria produce acid that dissolves the enamel surface of the teeth in a process called demineralization. Ordinarily, the body has time to remineralize, or replenish the enamel. But when enough bacteria accumulate, acid dissolves enamel faster than the body can rebuild it. Tiny pits mar the surface of the tooth.

(3) First-stage decay, the earliest stage of decay, appears as a white or brown area on a tooth. This “white spot” is visible only to your dentist.

(4) Unchecked, the acid eventually penetrates the enamel and a cavity forms.

If decay is caught early enough — while it’s still an area of demineralization, or a “white spot” — the tooth may be able to repair itself. Your dentist may be able to stop the decay to give your body a chance to remineralize and repair the tooth:

— Fluoride applied to the teeth in the form of a gel or varnish can boost remineralization.

— Applying a gel or varnish containing a powerful antiseptic can reduce the level of cavity-causing bacteria in your mouth, slowing demineralization.

— Your dentist may apply a liquid plastic sealant to create a physical barrier against bacteria. Sealants can help even after there is evidence of decay.

Once a cavity has formed, the emphasis shifts from prevention to restoration. The tooth cannot at this point repair itself; your dentist must correct the damage. Repair usually means cleaning out the area and filling the cavity.

We live in a world full of microbes. Sometimes they ignore us, and sometimes they prey on us. We have 13 trillion cells in our body, and we have 10 times 13 trillion bacteria living inside and on us all the time. Some of them actually help us — such as gut bacteria that make vitamins that we need. Sometimes they lie waiting for our defenses to falter and then attack. It’s like that with tooth decay and cavities: It’s best for us to keep a step or two ahead of them, through brushing and flossing and regular checkups.

To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.

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