Fig.3: CBCT coronal section at the site of #3.  An implant is going to be placed in the bone the sinus (S) and the nasal cavity (N) following bone expansion.  In contrast the sinus floor (between arrowheads) appears to be too thin for internal sinus lift.  The axis of the implant is favorable for restoration.

In fact the bone available for untraditional implant placement is more exactly located between the sinus and the palate (Fig.3' pink dashed line). 

Since it is narrow, it should be expanded prior to implant placement.  A small pilot drill, 1.2 or 1.6 mm in diameter, is used to initiate bone expansion (Fig.3'' red line).

When a large bone expander (Fig.3''' red arrow) is placed, the bone on either sinus or palatal side is displaced (green arrow)

Implant Placed Between Sinus and Palate

Xin Wei, DDS, PhD, MS 1st edition 01/22/2016, last revision 01/22/2016