The last 2 implants (Fig.5: #12, 13) are a little too small to have immediate crowns.   In contrast, the front 2 implants are big and long enough to support 2 temporary crowns (#10 and 11).

Bone Shrinks after Extraction

Xin Wei, DDS, PhD, MS 1st edition 09/19/2015, last revision 09/19/2015