Zirconium Oxide - thin strong margins like gold, very pure, white, non electrical-conducting.
So why aren't they making zirconium oxide inlays? Because the computer software that drives the lathe machines aren't set up to handle inlays - they can only make larger crowns and bridges etc... Apparently some labs are "tweaking" their current software to make ZO inlays now. I found a lab owner who is making zirconium oxide inlays with a layer of porcelain on top, for his wife.
Companies like 3M and Ivoclar are coming out with new ZO with a translucent core (instead of opaque) and new computer software that can make ZO inlays. This is supposed to come out in 6 months.