It seems necessary to place the 1st implant at #19 because of the cantilever FPD (Fig.4). Please note the submandibular fossa associated with implant placement at #19 and 31 (Fig.3,4 *).
CT Analysis of Molar Implant Placement
Xin Wei, DDS, PhD, MS 1st edition 02/04/2018, last revision 02/04/2018