Is it unusual for a dentist to charge more than the dental insurance says is my share when they are in network?

The last two dentists I've visited ask the patients to pay the patient portion of the charges prior to doing the dental work. After I received the explanation of benefits from the insurance company, it showed that their charges were in excess of the agreed upon cost for the procedure and they had asked me to pay too much for my portion. When I pointed this out, the dentists were not very gracious in responding to my inquiries to the point where I feel uncomfortable returning to them for services unless I am willing to let them continue to charge me more than they've agreed to with the insurance company. Is this a usual occurrence? Does it happen to other people regularly and they just ignore it? Should I consider the overpayment (ranges from $10 to $35 each visit) a tip for services rendered or should I insist that the dentist stick to the cost they've contracted with the insurance company for and ask for a refund? Does this mean it's time to find another dentist?
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This is NOT common practice and something that you need to bring up to your health insurance provider. You will need to go with the copy of your bill and explanation of benefits from the insurance company and speak with the office manager. If they still will not resolve the issue then you should definitely speak with your health insurance company again, let them know exactly what happened, and see if they will do something about it. If they can't, depending upon the amount you had to pay out of your pocket in excess of your copay or whatever the insurance company would not cover, then you can either forget about it or speak with the board of dentistry for your state.
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