What causes crowns to crack?

Cracks occur when tooth colored ceramics experience flexing forces. Ceramics are glass like and have a limited ability to flex. No matter how tough a ceramic material is, if it flexes more than a very small amount it is likely to experience a crack. Concentrated forces in small areas can cause cause crowns to crack. These can be experienced during chewing, tooth grinding at night, or even when a crown is initially fitted prior to cementation.

To help minimize the likelihood of a crown cracking, dentists carefully check a crowns occlusion when fitting a crown.  The patient's bite is checked out in their normal closed position as well as in their "excursions". Adjustments to the crown are made as needed. If after a patient with a new crown notices that it has a high bite in any position, they should notify their dentist and possibly return for an adjustment. 

 Another cause of cracked crowns can be night time bruxing or tooth grinding. Many people seem to experience episodes of night time bruxing that can result in both cracked teeth and crowns. Occlusal night guards are also a good way to protect both teeth and crowns from experiencing undue forces at night.

About the author: Lawrence Spindel DDS is a dentist in New York City, who has has maintained  a general and cosmetic dental practice for over thirty years.