When 3.5x7.3 mm drill with 5 O-rings is used as shown in Fig.11, use 2.2x7.3 mm one with 4 O-rings, remove the guide and check whether the sinus floor is perforated with perio probe and nose blowing test.  If not, use the 4x10 mm dummy implant or 4 mm cortical tap for sinus lift, followed by bone graft. 

Sinus Lift with Guide Last Next 2nd Use

Xin Wei, DDS, PhD, MS 1st edition 02/09/2019, last revision 07/06/2019