Dental crowns are an investment of your time and finances as well as your dentist's time, attention and care. Please do follow up with your dentist and see if this can somehow be resolved as you should feel happy with your recent dental care.
If you are currently in discomfort, a temporary splint can be fabricated in office by your dentist to relieve symptoms while in active treatment (restoring cavities). Once restored, the bite can be verified and adjusted until you feel minimal isolated pain from specific teeth. This is called equilibration. At that point you will most likely need a new splint and, depending on severity of symptoms, consult with a specialist for additional therapy.
Teeth will shift during ortho treatment, meaning they may feel slightly mobile. If the crown specifically feels loose as opposed to the tooth as a unit, then possibly there is some debonding as the ortho bracket is on the crown portion of the tooth. I suggest calling your dentist's office and scheduling a visit for an evaluation.
