The missing substance is built up in the lower jaw, so-called sinus elevation or sinus lift is necessary in the posterior upper jaw, which means the elevation of the maxillary sinus or the elevation of the jaw cavity base. This treatment is always planned very thoroughly, for which a three-dimensional CT scan is required. Depending on the extent of the bone loss, there are two different techniques: we work with a so-called closed technique for smaller bone loss, we lift the lower wall of the maxillary sinus using a special instrument and fill the resulting gap with bone replacement material. In the case of greater bone loss, we picture a small window on the side of the maxillary sinus and separate the mucous membrane from the bone, and also insert bone substitutes between both. Antibiotics must then be taken. After the necessary healing time of about six months, implants can be safely placed.