In my hands, from doing so many implants and dental surgeries in my life, I will say the most common reason for osseointegration failure is smoking. I repeat, in my experience, smoking is the most common and important reason for osseointegration failure.
After the implant is placed, the patient is normally very happy without much pain or swelling. They think they are out of the woods and they start smoking again.
Smoking has a way of slowing down the body's natural immune system as well as healing potential, so most of my osseointegration failure cases are those that I encounter in patients who actually smoke.
Of course, there are other factors as well, like overloading, stressing out the implant with biting, constant chewing on the implant, but smoking is by far the most critical risk factor. So much so, if now my patient does immediate implants, they have to sign a waiver that they are banned from smoking for at least 2-3 months after surgery.
Because if they start smoking and the implant doesn't heal and there's osseointegration failure, they would have lost all their effort, time, energy money doing surgery the first time around.
