What happens if decay develops under a crown?

Treatment depends on how much decay is present and how much healthy tooth structure remains. In mild cases, the crown can be removed, the decay cleaned out, and a new crown placed. In more severe cases, a root canal may be needed before a new crown. If the decay has destroyed too much tooth structure, extraction may be necessary.

How long do crowns last?

Most crowns last 10–20 years or longer. Longevity depends on the material, your bite forces, and how well you maintain oral hygiene — especially at the gumline margin. Regular checkups allow your dentist to catch problems early before they compromise the crown.

Does flossing around a crown damage it?

No — flossing is essential for crowned teeth. Use a gentle C-shape motion around the crown margin. Slide the floss out rather than snapping it up, which could loosen the crown. Water flossers are also effective and gentle around crowns.

Can a crown fall off because of decay?

Yes. If decay develops at the margin and progresses under the crown, it can dissolve the cement that holds the crown in place. A crown that feels loose or comes off should be evaluated promptly — do not try to re-cement it yourself.

Is decay under a crown covered by insurance?

Treatment for decay under a crown is typically covered under your dental insurance like any other restorative procedure, subject to your plan limits and waiting periods. A replacement crown may have a frequency limitation — many plans only cover a new crown on the same tooth every 5–7 years.

Can a Crown Get a Cavity? | Dental Learning Center

Q: How do I know if I have decay under my crown?

Often you will not know without an X-ray — which is one reason regular checkups matter even for crowned teeth. Symptoms that may indicate a problem include sensitivity to hot, cold, or sweets around the crowned tooth, pain when biting, a bad taste or odor, visible darkening at the gumline, or a crown that feels loose.

Quick Answer

Cross-section of a tooth showing decay developing beneath a dental crown at the gumline

The crown itself cannot get a cavity — the porcelain or metal material is not susceptible to decay. However, the natural tooth structure underneath the crown absolutely can. Decay most commonly develops at the margin where the crown meets the tooth at the gumline. If bacteria and plaque accumulate there, the tooth underneath can decay — which is why brushing, flossing, and regular checkups remain essential even after a crown is placed.

What You'll Learn

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Where decay forms

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Warning signs

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Prevention tips

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Treatment options

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Why the Tooth Under a Crown Is Still Vulnerable

A dental crown covers the visible portion of a tooth above the gumline, but it does not seal the tooth off from the oral environment completely. The margin — the edge where the crown meets the tooth — is the most vulnerable area.

Over time, the cement that seals the crown can wash out slightly, the gumline can recede, or the margin can develop a microscopic gap. Any of these changes creates an entry point for bacteria. Once bacteria reach the tooth structure beneath the crown, decay can develop just as it would on an uncrowned tooth.

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Where Decay Most Commonly Develops

The most common location for decay under a crown is at the gumline — the cervical margin. This area is difficult to clean thoroughly with a toothbrush alone, and it is the point where the crown transitions to natural tooth structure.

Decay can also develop if the crown was placed over a tooth that already had a small amount of decay that was not fully removed, or if the crown cement fails and bacteria infiltrate the space between the crown and the tooth.

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Warning Signs of Decay Under a Crown

Decay under a crown does not always cause obvious symptoms, especially in the early stages. This is one reason why regular X-rays and checkups are important even for crowned teeth — your dentist can detect decay before it becomes symptomatic.

Symptoms that may indicate a problem include sensitivity to hot, cold, or sweets around a crowned tooth, pain when biting or chewing, a bad taste or odor near the crown, visible darkening at the gumline, or a crown that feels loose or moves slightly.

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How to Protect a Crowned Tooth

Brush the gumline carefully

Use a soft-bristled toothbrush and angle the bristles toward the gumline to clean the margin of the crown. This is where plaque accumulates and where decay begins.

Floss daily — even around crowns

Flossing removes plaque from between teeth and at the gumline. Use a gentle C-shape motion around the crown margin. Water flossers can also be helpful for cleaning around crowns.

Keep your regular checkups

Your dentist checks the margins of all your crowns at every exam and takes X-rays periodically to look for decay that is not visible. Early detection means simpler treatment.

Address dry mouth if you have it

Saliva neutralizes acids and washes away bacteria. Dry mouth — often caused by medications — significantly increases cavity risk, including under crowns. Talk to your dentist if you experience dry mouth.