A Answers (3)
Sometimes if you have poor oral hygiene and periodontal disease that is not under control, implants can fail. Another scenario would be if a person has a poor bite, it will compromise the foundation. A bad bite can cause trauma to the implant and the surrounding tissues, just as it would to real teeth.
While few dental implants fail in today's dentistry, there are a few things that can contribute to failure. First, many implants are comprised of many parts, the implant itself which is in the bone, the abutment (that part that connects to the implant) and the crown. The implant, just as a normal tooth, is subject to all of the conditions leading to periodontal disease and may be lost if inadequate oral health is maintained. Although extremely rare it is also possible that an implant may be rejected by the body and need to be removed.
In my personal experience, I have never seen an implant rejection. Any of the other components may fracture or come loose and need to be replaced even though the implant itself is still sound and will provide a good foundation for replacement parts. All-in-all implants have improved dramatically over the past several years and seldom fail.