Do crowns have an "expiration date"?

 When patients ask how long do crowns last, I usually answer about 10-20 years. That being the case, I do not automatically replace crowns that have been in service longer. Last week a patient came in and asked if it was time to replace his single gold crown since it was pretty old. I replied that crowns do not have any expiration date and that I would tell him when it was time for his crown to be replaced. 

It is true that some long standing crowns that look  good on a radiograph may have some cement wash out along some of their margins, mostly we do not replace crowns until there is evidence of some deterioration around the margins or there is a perforation on the occlusal surface. 

There is a risk of causing a problem when replacing a crown that is still serviceable iincluding  the crowned tooth becoming more sensitive or even requiring a root canal procedure. While this risk is small,  to my mind it's best to continue monitoring older crowns to see deterioration of the adjacent tooth structure. This can occur either to recurrent decay or dentin erosion. If a tooth has decay around the margin of the crown this could be a good indicator that it is time to replace it with a new one. Sometimes for small discrete carious lesions a filling can be placed to so that my patients crown can obtain some more years of useful service.