Should dentist redo all six front crowns to ensure the color matches?

Your dentist was right to tell you, to have all your teeth done at the same time !Now that the dental bridge needs replacement, I hope that your dentist or cosmetic dentist used a master ceramist, in which they record the exact shade, and with the help of digital photography, you will have probably not 100% color match but close to it. It all depends on how skilled is his dental lab?If you are happy with the color of the 3 other dental crowns, then I advise you not to have them removed, since it is much more work for you and the dentist ! if you are not happy with the color of your porcelain crowns, then talk to your dentist, so he can make you happy.I needed also photos of your teeth for a more detailed advise, and was wondering what kind of a dental bridge you had? wether it is emax? lava ? or porcelain fused to metal?Good luck to you. 

In my opinion, you should only have to remake the bridge only and still get a great color match. The dentist will section off your bridge and can send the porcelain back to the lab making it very easy for them to make the new bridge the same color.  No need to remake all six.  Don't worry.  Good luck!  

It is always best to have all the teeth done at the same time so that the shade matches, however, in your case I would only have the bridge redone.  If your dentist is skilled enough, he/she and the lab as a team should be able to color match it.  Make sure that your occlusion is correct in excursive movements before you leave.  Your bridge may have fractured because you may grind on it too hard.

I would not necessarily expect that the other three crowns would require replacement.  If the dental lab and dentist kept detailed records of unusual shading then there is a good chance they can replicate the shade of the new bridge.  Pictures would help the lab just in case as well.  I would advise you to look and approve the new bridge prior to it being cemented in place just to make sure.  If the shading is incorrect it is much easier to redo at this point prior to the bridge being cemented.