Your dental crown has fallen off more than once. That's not normal. Here are the most common reasons crowns fail to stay on — and what to ask your dentist.

A crown should stay firmly cemented to your tooth. If it keeps coming off, something is wrong. The good news is that there are usually clear explanations. And once you know the cause, your dentist can fix it.

The most common reason is that the tooth underneath has changed shape. This can happen through decay, wear, or simply that the original crown was made from an impression that no longer matches your tooth.

Another common cause is a problem with the cement. Some cements are designed to be temporary. Others fail over time if the crown wasn't prepared properly before cementation. Your dentist should check whether the fit of the crown is accurate.

Sometimes the crown itself is the problem. If it's too short, too narrow, or doesn't have enough surface area to grip the tooth, it will loosen. This is often the case with crowns that have been in place for many years — the tooth structure underneath can gradually wear away.

First, don't panic. Keep the crown safe and call your dentist as soon as possible. You can use a dental cement kit from a pharmacy as a temporary measure, but this is not a permanent fix.

Don't be tempted to leave it off. The underlying tooth is likely to be sensitive, and without the crown, it can shift or wear down further. The sooner you see your dentist, the simpler the solution is likely to be.

This depends on why it came off. If the tooth and crown are both in good condition, your dentist may simply clean them and re-cement it. If there's decay underneath, or the crown no longer fits properly, a new crown may be needed.

Ask your dentist to explain what they found. They should be able to show you on an X-ray whether the tooth structure is sound. If you keep having the same problem, it's worth asking whether a different type of crown or a longer cement would help.

A crown that keeps falling off is a sign that something needs attention. Your dentist can help you find the reason — and stop it happening again.