Cavities and Fillings 101

Cavity Basics

What the dentists sees when he/she finds a cavity.
What the dentists sees when he/she finds a cavity.

Dental cavities, or caries, have plagued mankind for thousands of years. Fossilized remains of men and women from the Iron Age discovered in Warwickshire, England showed a cavity rate of only 8%. When today's Warwickshire inhabitants were compared, a remarkable high cavity rate of 48% was found. A modern diet consisting of highly processed, sugar-containing foods is the most likely culprit. The problem of dental cavities has been steadily increasing for the last four centuries in industrialized nations, and despite a recent dip due to the advent of fluoride, it continues to the present day.

Dental cavities are an infection caused by a combination of carbohydrate-containing foods and bacteria that live in our mouths. The bacteria are contained in a film that continuously forms on and around our teeth. We call this film plaque. Although there are many different types of bacteria in our mouths, only a few are associated with cavities. Some of the most common include Streptococcus mutans, Lactobacillus casei and acidophilus, and Actinomyces naeslundii. When these bacteria find carbohydrates, they eat them and produce acid. The exposure to acid causes the PH on the tooth surface to drop. Before eating, the PH in the mouth is about 6.2 to 7.0, slightly more acidic than water. As "surgery foods" (candy, sugar frosted breakfast cereals, ice cream, soda an kool-aid, etc.) and other carbohydrates are eaten, the PH drops. At a PH of 5.2 to 5.5 of below, the acid begins to dissolve the hard enamel that forms the outer coating of our teeth. Every exposure to these foods allows an acid attack on the teeth for about twenty minutes!

As the cavity progresses, it invades the softer dentin directly beneath the enamel, and encroaches on the nerve and blood supply of the tooth contained within the pulp.

Cavities attack the teeth in two main ways. The first is through the pits and fissures, which are grooves that are visible on the top biting surfaces of the back teeth (molars and premolars). The pits and fissures are thin areas of enamel that contain recesses that can trap food and plaque to form a cavity. The cavity starts from a small point of attack, and spreads widely to invade the underlying dentin

The second route of acid attack is from a smooth surface, which is between, or on the front or back of teeth. In a smooth surface cavity, the acid must travel through the entire thickness of the enamel. The area of attack is generally wide, and comes to point or converges as it enters the deeper layers of the tooth.