Crown on Implant Keeps Coming Loose: Why?

There are several reasons why a crown on an implant can get loose. From your description, I assume that the crown loosens but the implant and abutment are fine. The first thing that can cause premature loosening of the crown is a very short abutment or post, since the shorter the post, the less structure that the crown has to hang on to. Another reason could be the way the abutment or post is prepared, for example, if the post looks too tapered (like a tipi) it affords very little retention and is easy for the crown to loosen. An abutment with sides that are close to parallel to each other is much more retentive. If the abutment does not have retention grooves it is also less retentive. If the crown has to put up with an extremely hard bite such as a grinder or clencher it is also more likely to loosen or break. And finally, if it has been cemented with temporary cement (for retreivability) it is more likely to loosen than if it is cemented with a harder more permanent cement.. What are your options? Look at every single point mentioned above and ask your dentist if any of them need to be addressed in your particular case. Good luck! Carlos Boudet, DDS