Fig.2 (CBCT coronal section at the site of #19), the crest is narrow.  In order to place a 5x10 mm bone level implant with sufficient bone around, the implant has to be placed 2.44 mm subcrestal.  There will 2.76 mm distance from the Inferior Alveolar Canal.

To place a longer implant, the latter should be placed more coronally.  One way to do it is to increase the crestal width by bone expansion.

Narrow Crest with Low Bone Density

Xin Wei, DDS, PhD, MS 1st edition 09/26/2015, last revision 09/26/2015