Since 12/2013, the dentist has tried porcelain crown over zicronia base (with a metal abutment) screwed on the implant. But result was too opaque and the color was not right. Then he tried a metal ceramic crown (to be glued to the metal abutment). Dentist is now pleased to have captured the hue. At direct light it looks ok, but otherwise it stands out as a very gray unnatural tooth. Every crown was remade at least 2-3 times. I'm getting desperate. Should I change dentist?