Bone Loss Around Upper Threads

Randy, a dentist, asks:

On several occasions patient have come to me with the beginning of bone loss around the upper threads of dental implants a couple of years after they were restored. For some reason most were single dental implant cases (although not all) and they usually had proper restorations.

I have tried building new bone over these dental implants after treating them with citric acid for 90 seconds using autogenous bone, xenografts and alloplastic materials alone or in combinations with each other with and without membranes. None of the cases I tried to treat were HA coated. Although in rare cases new bone has formed, in most instances there is nothing there upon re-entry several months later.

Am I the only one out there with this complication? Any suggestions that may help improve prognosis? Do we know the etiology of bone loss around dental implants that look fine as far as the position of the fixture and the restoration they support? Is there any point trying to save these fixtures? Thanks for any comments.