Does a zirconium crown start showing metal on the gum line? (Photo)

It's very difficult to make out a dark gum line in your photo, but Zirconium crowns do not show a dark metal line.  If your bridge is truly Zirconium, then the dark line has to be bacteria that has colonized at the gum line.  If the bridge is not Zirconium, then the line is most likely metal.  Either could be the case, but if you go to another dentist or the same dentist, you should be able to confirm the material used for the bridge.  Good luck and I hope this helps. Follow me if you have more questions.Sarah Thompson, DMDSoft Touch Dentistry

Zirconium is very white and should not look dark at all at the gumline. If you are seeing a dark area it is likely that your crown is not made of Zirconium, but another type of metal substructure.  

If you are getting a dark appearance at the gum line then most likely your bridge is made of porcelain baked over a metal substructure.  Bridges in the cosmetic area such as yours should be made out of emax or zirconium which are both metal free restorations.  Even if the gum recedes over time no black line will show.