Because of pain, the bridge has been removed partially.  Caries in the tooth #20 (Fig.7 *) is confirmed; root canal therapy has been done.  With bone expansion, the bone level implant can be placed at the crest.  That is, it can be longer (13.5 mm) than the one placed subcrestally (Fig.2: 10 mm).   Make sure that the implant is placed in the middle of the edentulous space.

Narrow Crest with Low Bone Density

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