Dr. Eric Cohen, an ear nose and throat specialist at Lenox Hill Hospital in New York, said that dental implants can migrate if they do not properly integrate into the jawbone. "The bone may have been too thin" for the implant to properly integrate, said Cohen, who was not involved with the woman's case.
Because the roots of upper teeth can extend up into the floor of the sinus, dental implants (which are designed to act as tooth roots) can push into the sinus, and allow bacteria to enter, he said.
http://www.huffingtonpost.com/2013/10/25/dental-implant-sinus-xray-photo_n_4163269.html