There are 2 sockets at #3 when the residual roots are extracted; osteotomy is established in the palatal one for 11 mm (gingival level; Fig.1), ~  2 mm from the sinus floor (red dashed line).  *: space of the palatal socket, to be filled with bone graft after implant placement.

Sinus Lift with Implant Next Xin Wei, DDS, PhD, MS 1st edition 09/13/2017, last revision 08/18/2018