Sometimes a brace has to be bonded onto a filling. The bond between the brace and the adhesive is weaker than the bond between the adhesive and a tooth-coloured composite filling, so the pressure applied to the brace with the pliers will not make the filling come out. However, if the filling is defective and was not placed properly, it may come off together with the brace. In that case, you should be glad you found out about the faulty filling before the tooth underneath it started to decay.
This answer is for general information. Your own case needs an examination by an orthodontist.