One of the main reasons why crowns can fall out is further decay to the tooth. While dental crowns are meant to protect the tooth, crowns do not make the tooth indestructible. The teeth can still decay underneath the dental crowns.
This is especially true if the patient does not brush or floss the teeth properly and does not visit the dentist regularly. In this case, the dentist will need to look at the crown and see if the tooth can take another crown. Because of the changed shape of the tooth, the patient will need to have a new crown made if there was decay.
Another reason a crown may fall off is because of sticky or hard foods. Over time, the glue that holds dental crowns in place may gradually loosen. Sticky foods especially can cause a weak crown to fall off.
If the patient eats a lot of sticky foods, the crown can become weak over time. The foods grab hold of the crown and gradually pull it loose. Eating many sticky foods such as caramels and sticky candies is generally not a good idea for patients who have crowns.
High stress levels can cause habits that loosen a crown. For example, a stressed patient may grind the teeth at night and unintentionally loosen the crown. A night guard can help in this case. A patient may also chew on their fingernails or ice cubes. This is generally bad for the teeth, but it is especially bad for those who have crowns.