Four years and a half ago when the tooth #21 needed root canal therapy (RCT; black *: periapical radiolucency), the tooth #19 showed bone loss (Fig.1 arrowheads) and hidden caries (white *). 

Long Implant for Lower Molar

Xin Wei, DDS, PhD, MS 1st edition 01/18/2015, last revision 01/18/2015