How do I find a dentist who will file my insurance up front?

I need extensive dental repair work done that is going to cost thousands of dollars all said and done.My employer provides me good insurance that will cover 50-80% of the cost but finding a dentist who will file that insurance before doing the work is so far a bust. So far all of the dentists I have contacted expect all of the money up front and then they will reimburse after insurance. I don't have thousands of dollars to pay up front and my credit score is horrible so I can not get a loan or do "carecredit". I can however pay a smaller amount upfront (the balance after insurance pays) or I can make payments. I desperately need this work done asap! Can anyone here please tell me how to find a dentist who will work with me?
--------------------
Keep in mind that you have an annual maximum that your insurance company will pay... so if your annual maximum is $1500, and you've had 3 crowns, the well has run dry until the next cycle. A pre-treatment estimate should be submitted to your insurance company, especially if there's alot of work that needs to be done. This way, both you and the office will know how much your personal, out of pocket expenses will be before the treatment begins. Also, treatment can be spread out over the course of December of this year, so you can max out, into 2008... then you should have more benefits to work with. If all else fails, come to my office... we have payment plans! :)
Source