How is a patient who has secondary insurance billed?

I need to know how to bill a patient who has both primary and secondary dental insurance. Is the patient's co-pay limited to the primary carrier's contracted amount or, because of the secondary, would they owe the full doctor's fee? If the secondary carrier's payment doesn't fully cover the patient's co-pay portion, what amount is the patient then responsible for? If the provider is bound to the primary carrier's contracted fee, regardless of what the secondary allows, does any remaining charge exceeding that contratced amount get written off? If the patient has deductibles on both plans, do they owe both deductibles? If I have left out any relevant questions, any and all pertinent information would be most helpful. Thank you.
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As "Zippy" suggests, you can bill the patient after you receive the primary's response to the claim. However -- you can ONLY do this if you don't participate with the secondary. If you're also a par provider for the secondary, you cannot bill the patient instead of billing the secondary. That would be a blatent violation of your contract with the secondary. Assuming you participate with both, your best tactic is to send the bill along with the primary's EOP to the secondary. Let the secondary tell you what the patient is responsible for. Some secondary contracts cover the primary's co-pay and others don't. You won't know what the patient is truely liable for until the secondary processes the claim. Your office's agreement to accept the primary's fee as payment in full doesn't prevent you from attempting to collect payment for the patient's co-payment from the secondary. However, if there is no co-pay remaining after the primary has paid, AND you're contractually bound to accept the amount the primary has paid as payment in full, there's nothing to bill the secondary, is there?
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