When the osteotomy is finished with 4.3 mm drill at ~ 9 mm, the sinus membrane is found to perforate.  A dummy implant (5x9 mm, 2 mm shorter than design) is placed short of the sinus floor (Fig.3 ^) to prevent further trauma to the sinus membrane.

Repair Sinus Membrane Perforation

Xin Wei, DDS, PhD, MS 1st edition 12/29/2016, last revision 01/19/2018