Straumann Bone Ceramic (SBC) and BioOss will be used as bone grafting materials when there is a need for bone augmentation in the posterior upper jaw. The bone grafting materials will be placed into the sinus cavity,(a routine procedure), one material randomly at each side and a micro-implant will be inserted simultaneously. 9 months later the micro-implant is removed and a regular Straumann SLActive implant is inserted. The micro-implant is evaluated histologically. The site is evaluated every 12 months for 3 years in regards to clinical measurements. The study hypothesis is that the SBC is not worse than BioOss.