Will dental bridges cover a grey tooth?

Your dark tooth due to root canal, can definitely be covered if your dentist uses a porcelain fused to metal bridge, either precious metal or gold.However if you do want to have a non metal bridge, it is best to use lava, with an opaque core, however I have seen even with a lava bridge, some grey showing, in that case depending on the integrity of the tooth and the root canal performed on the tooth,I suggest you do internal bleaching.If your dentist is going to use Lithium Disilicate, such as Emax, which is usually translucent, Definitely the gray color must be addressed before preparation, Since your DDS must know the gray will show much darker after the preparation of your tooth, and will be flashing through the porcelain, on your new dental bridge.

If you have the bridge made with porcelain fused to gold crowns ,the grey will be blocked out. Depending on the color of your teeth, the result may not be as perfectly matched as using an all porcelain bridge. In this case, the grey may not be blocked out unless certain modifications are taken into account. By making the porcelain on the grey tooth thicker by reducing the tooth more or by using more of a block out or different shading, the match could be very nice. Bleaching the tooth may be helpful but it is not permanent ,so matching it the way it is sounds like the best way to go.

There is a good probability that a bridge will block out the gray of the tooth you have.  This, to some extent, depends on the material your dentist uses for the bridge.  Some of the newer material can allow the color of the tooth underneath to show through though this can also be addressed if the lab knows the color problem exists and the gray color is not too intense.  Bleaching may also help but is not always necessary.  Have a conversation with your dentist and discuss your concerns.  I am sure you will have a good result.  Good luck!