I have done a number e.max implant abutment-crowns and they are working very well.  I use them in the posterior region when the implant alignment provides a screw access retention option.  A Sirona TiBase is seated and then scanned.  The CEREC 4.0 scan and mill algorithms are precise enough to generate a tight/snug fit.  TiBase anti-rotational factors are increased with additional preparation to the TiBase cylinder.  Cervical emergence is virtually design using the Shape/Circular tool.  Cementation of e.max restoration on the TiBase was accomplished with Monobond Plus and opaque Mutlilink.  Video is soon coming to CEREC Liftoff Online Training for this technique.