A sinus lift is a surgery that adds bone to your upper jaw usually towards the back side of mouth. It’s sometimes called a sinus augmentation. A sinus lift is done when there is not enough bone height in the upper jaw, or the sinuses are too close to the jaw, for dental implants to be placed. There are several reasons for this, tooth loss may have led to a loss of bone as well. Once teeth are gone, bone begins to be resorbed (absorbed back into the body). If teeth have been missing for a long time, there often is not enough bone left to place implants.  The maxillary sinus may be too close to the upper jaw for implants to be placed. The shape and the size of this sinus vary from person to person. The sinus also can get larger as you age.