Permanent dental bridge feels loose, what could this be? (photos)

I would really need more information to answer this question accurately.Based on the information that you provided, the looseness that you are sensing may be from the abutment. This is the piece that connects the dental crown to the implant, and it may just need to be tightened. The darkness that you are seeing might be from the metal of the abutment for metal that is on the underside of the dental crown. If this is the problem, then it can be corrected by replacing a metal abutment with a white one and replacing the crown with one that does not have a metal under-structure. Your dentist can go over these options with you.I hope you found this information to be helpful,Dr. Champagne

The bridge could feel loose for a variety of reasons.  One could be it wasn't fully seated during cementation and the bridge itself is actually loose. It could also be your dentist cemented it temporarily to evaluate esthetics and the temporary cement amount was inadequate and it's too weak of a bond. The bite. The bite being too high can also cause the teeth to move, although this would usually take more time.  If the teeth were loose in temporaries because they were high then this could also be a cause. The darkness at the gum line is most likely from the metal framework of the bridge or tissue inflammation from the cementing process . You should see your dentist to evaluate