Why do receding gums lead to cavities?

When gums recede, the roots of the teeth become exposed. The tooth root is not covered with enamel. The root surface is softer than enamel, and it is more susceptible to cavities. Many times, the roots are sensitive and patients avoid brushing these areas. Plaque accumulates, produces acids, and cavities result. If you have receding gums, you should talk to your dentist. Good oral hygiene and fluoride rinses can help prevent cavities in these areas.

Recession of the gums away from the teeth, combined with an increased incidence of periodontal (gum) disease, can expose tooth roots to plaque. Tooth roots are covered with cementum, a softer tissue than enamel. They are susceptible to decay and are more sensitive to touch and to hot and cold.

Your teeth are covered with enamel, which is one of the hardest surfaces on your body. In other words, it's a great protector for your teeth. When your gums recede, it exposes parts of your tooth (the roots) that don't have enamel over them. This leads to easier formation of cavities.

The gums cover the supporting bone where the roots reside. When the gum recedes, it exposes the roots to the oral environment where biofilm, plaque and (with improper brushing technique leads to) calculus (tartar) build-up.

The roots are made of cementum, hard tissue that covers the dentin where the root canal resides; the crown has the enamel, hard tissue that covers the dentin. Unlike the enamel, the cementum is not built to resist the decaying effect of plaque, thus leading to cavities.

Receding gums expose the root of the tooth to decay. With the root exposed, plaque builds up and bacteria can easily spread to the inner part of the tooth. Cementum is a coating that covers the root, but when it is exposed the coating disintegrates. When cementum is no longer present, the softer region of the tooth, called dentin, can easily decay. Receding gums is one reason why older people are more inclined to cavities.

Dan Jenkins
Once the gums have receded the roots are exposed. The root surface is 9 times softer than enamel and has many nerves in it. Once the gums have receded the contour of the side of the tooth down to the gum is changed and food will trap there easier.

With food trapped the bacteria in the mouth can break down the food and produce an acid that will cause the cavities. Since the root is so much softer than the enamel the cavities are started easier.
Receding gums expose the root surface of teeth. The root is not as strongly mineralized as the tooth enamel. The decreased mineralization makes it easier for bacteria to degrade the root surface in the presence of dietary sugar.
Receding gums can lead to a cavity because as the gum tissue goes further down the tooth the roots can get exposed. Roots are made of a much softer material then the crown of the tooth and can wear away more easily and expose the underlying dentin. When food and plaque get trapped at the gum line, it can be more difficult to clean and thus can lead to a cavity. 

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.