Interesting is that the sinus membrane is thickened at #2 and 3 (Fig.3 M), as compared to the clear sinus before surgery (Fig.3').  Bone graft is limited in the sinus (Fig.3 arrowheads). 

Thickened Sinus Membrane Last Next Xin Wei, DDS, PhD, MS 1st edition 06/18/2019, last revision 06/18/2019