I have the same experience. He assured me that it wouldn't exceed the limit but finally it did for more than $700 and for that portion, he charged me based on his office rate which is much higher than the insurance company required for their in network dentist. When I called to argue, he said that's how much he should be charging and I could ask the insurance company if I didn't believe he's right. I asked the insurance company and I ended up paying around $200 which was based on my insurance company's in network rate. I guess you can argue part of it but not the full amount and he must charge you base on the insurance company's rate instead of his own rate. Also, in the future, you should ask your dentist to do a pre-assessment/evaluation and get approval from the insurance company before starting the treatment. That way you know for sure how much it's going to cost before hand. In addition, if you know how much you have to pay out of your own pocket, you should put the money aside in your company's flexible spending account.