Is there anyway you can sign up to Westfield or a company like that through your work? At least that way you’d be able to claim some of the money back. Do you have a union at work?
Really sorry you’re feeling like this. Some dentists are nasty with their charges. Did you ask if theirs a pay monthly thing you could do? I don’t know if dentists do this, but you can ask?
Hope you get sorted soon x