After extraction (Fig.5 black), the distal portion of the mesial crest will be resorbed (Fig.6), leading to gingival papilla atrophy and food impaction. Keeping the mesial portion of the root (Fig.7 *, socket shield) is able to prevent mesial crestal bone loss. The (immediate) implant will be placed ~ 2 mm short of the depth and checked whether it touches the retained root or not.
Xin Wei, DDS, PhD, MS 1st edition 04/27/2020, last revision 04/27/2020