26 implant failed, previously placed at the same time as 16, both with sinus lifting. Possible sinus infection causing failure. Loss of some crestal bone . Prepared osteotomy short of sinus floor, remainder with densah drills, entry into sinus chamber with densah drills, no evidence of membrane perforation, packed about .25-.5cc of sticky bone from allograft, good pushback of bone, implant placed, buccal grafted with same bone followed by collagen membrane soaked in prf fluid