It is a surgical procedure which is done in cases where there is pneumatization of the maxillary sinus on one or both the sides. Implants can not be placed directly in the sinus cavity thus the sinus lining needs to be taken out and the implants are placed pushing the lining away. This surgical procedure requires lots of understanding and expertise. Your doctor decides either augment the sinus using a bone graft material and re enter the region after 4-5 months and place the implants thereafter the prosthetic treatment after next 3-4 months. It depends on the the condition of the bone and the patient acceptance of bone graft.