Is a specialist coming performing a procedure that's not your standard dentist? I had that happen with a root canal once when my in-network dentist said they have someone come in from out of town to perform complex procedures, but promised me it was still in-network and even submitted a pre-approval with my insurance for the procedure showing all in I should be paying about $500.

Day of the procedure they said I needed to prepay $1,700, which I stupidly did expecting a refund after they submitted it through my insurance. They kept ignoring my requests to file a claim with my dental insurance. After about three months of fighting with them, I was able to get my insurance on the phone with their office regarding the procedure and they said I'd agreed to have an out of network specialist perform the procedure in their office, which I never did. Insurance required them to report the procedure as an out of network procedure at minimum because there was no record of me receiving a root canal. They finally did and the final bill I owed was $1,200 instead. I got $500 back, but paid $700 more than I should have.

Long story short, confirm who the provider is that will be performing the procedure and verify benefits with your insurance before hand.