After using 4.5x5.3 mm and 3.5x7.3 mm drill at #14 with guide, the sinus floor is not perforated.  When a 4.5x11 mm dummy implant is placed to the 2nd line (12 mm offset), the sinus membrane is perforated (Fig.1). 

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Xin Wei, DDS, PhD, MS 1st edition 06/05/2020, last revision 06/05/2020