Depending on how much bone you have remaining will determine which sinus lift approach is taken — either the lateral window or the crestal approach. The crestal approach can be performed at the time of implant placement in one appointment. The lateral window approach requires two appointments because it necessitates time to allow the placed bone graft to integrate. At the first appointment, the maxillary sinus is lifted and a bone graft is positioned beneath it. About six months later, the implant can be placed.