Can Emax crowns be used in a case of dark anterior roots? Would a masking cement be sufficient to cover the darkness? (Photo)

The first question is whether the teeth with dark roots have had root canal treatment.The dark roots need to be addressed with a restoration that extends inside the root to block out the dark color prior to the crown.  If the teeth have had root canal treatment this is easier.  This is a basic rule with anterior cosmetic work for over 25 years since advent of all ceramic crowns.Second, it is a good idea to evaluate the smile line.  Sometime crown lengthening can move the margins to an area where they don't show with smiling. In general E-Max give nicer anterior esthetic restorations than zirconia.

Hi:
An emax crown can be used as long as an opaquer cement  is used to cover the dark tooth.
Best,
Dr. Maddahi

Often times, translucency must be developed within the crown itself especially in situations where the tooth is dark. It isn't necessarily the type of crown used, but the dental ceramist's ability to create a natural looking crown that also masks the underlying tooth darkness that will give you a great result. You might not be able to lighten the roots of the tooth unfortunately. 

Emax is not as opaque as zirconia, so discolorations CAN shine through.  One option is to have the lab create a zirconia coping to cement over the tooth, and emax can be cemented over the coping.  It may be more simple to have the lab create a PFZ crown, where all this is made into one, but a drawback is that porcelain may chip off of the zirconia and the entire thing would need to be replaced.