"I Can't Tell Which is the Implant Tooth!"

Ms. Ma returned for cleaning yesterday.  She is happy with her 3 month-old implant tooth in the top mouth.  She said that she could not figure out which one it is.  Fig.1 shows five teeth on the top.  You may be able to identify, but the patient is not.  Because she cannot feel the difference between the real teeth and the implant tooth.  It appears that an implant has capability of restoring functions of our natural teeth to fullest degree.  Anyway, which is the implant tooth?

Xin Wei, DDS, PhD, MS 1st edition 07/13/2014, last revision 07/13/2014