It would be safer to start osteotomy in the middle of the remaining septum (Fig.6, as compared to Fig.5).  After sinus lift with PRF membrane (Fig.7 yellow curved line) and implant placement (green), another piece of PRF membrane will be placed against the palatal wall of the socket, followed by bone graft (red circles) and a 25-degree angled abutment (pink). RCT Retreat or Extract Last Next Xin Wei, DDS, PhD, MS 1st edition 10/08/2018, last revision 10/08/2018