A bilateral sinus lift is a surgical procedure used to increase the bone height in the upper jaw (maxilla) to allow for the placement of dental implants, especially in cases where the natural bone has been resorbed. The technique involves gently elevating the sinus membrane and placing a bone graft material in the newly created space, which encourages bone growth. This procedure is performed on both sides of the upper jaw (bilateral) and is commonly required when implants are planned in the back regions of the upper jaw where the sinuses are located.