I have had patients who have been to other dentists and from time to time I get a patient who comes in with the same story. "Dr., I had this crown done a number of years ago and about once every year or two the crown comes off and the dentist recements it. Is this normal? Why is this happenning?"
Well if the crown keeps coming off it means that either the glue holding the tooth is not strong enough or there is not enough tooth to actually hold onto. Is this normal? Probably not.
Lets first talk about the glue, there are weak cements used if we want to take a crown off at a later date and there are stronger cements so that even if we don't have that much tooth under the crown then hopefully a strong adhesive or bonding cement will still hold the crown on. Unfortunately, if the dentist is using a strong cement and the crown keeps coming off then you are in trouble. Most likely there is not enough length of tooth under the crown. If we don't have much tooth under the crown, that can be a real problem since even with strongest adhesive cements you still need something to cement to. The forces of eating and chewing are really quite great. The tooth is subject to forces that pull and push the tooth in every direction and this is happening hundreds of times a day.
If you have a short tooth to begin with and then it must be even shortenned further to prepare the crown you may not have enough tooth structure to retain the crown.
This may be the case but should be planned for before placing the crown such as lenthening the crown before placement or placing retentive devices into the preparation. A tooth that has been on for many years and now is falling off there is a different problem there. A tooth that has only been on for a short period of time most likely the tooth is not long enough and the cement now matter how good just can't hold it.
What should you do? Go back to your dentist and ask him what should be done as it is not right to have this crown coming off every 1-2 years. He does have the solutions just ask!
All the best
Dr. Ron Barzilay
Doing dentistry in Hamilton Ontario