It appears that a 15 or 16 mm long implant should be placed to engage into the apical native bone （3 毫米）and sinus floor (*) for stability (Fig.3,4).  Further stability is obtained by contact with the mesial (M), distal (D) wall or both.

Sinus Floor       Last     Next  Xin Wei, DDS, PhD, MS 1st edition 06/14/2021, last revision 06/30/2021