Considering limited bone height at the site of #14, one alternative is to place a small implant obliquely between #14 and 15 (Fig.2: 3.5x11 mm), use an angled abutment (red line) and fabricate an atypical bridge between #13 and 14/15.  This approach is not adopted, since there is 2 mm between the oblique implant and the one at the site of #15.

Internal Sinus Lift Perforation

Xin Wei, DDS, PhD, MS 1st edition 05/20/2015, last revision 05/20/2015