Fig.4 preop PA shows that the three roots (M: mesial; DB: distobuccal; *: distolingual) have minimal bone support.  The Inferior Alveolar Canal appears out of view.  A second PA is taken to show the lower portion of the mandible.

Non-Resorbable Membrane

Xin Wei, DDS, PhD, MS 1st edition 08/20/2015, last revision 08/28/2015