It appears that the most apical thread is contacted by the possible native bone (Fig.4 >) with apparent sinus lift (open arrow).  In other word, the sinus floor thickens from 1 to 9 mm 3-4 years after implant placement at #14 (twice).

To get the apical end of the implant, this PA is taken with angulation again.

Sinus Floor Thickens after Neighboring Implant

Xin Wei, DDS, PhD, MS 1st edition 05/19/2017, last revision 08/12/2017