If a pt is billed with dental codes, comes back to the ofc and then is billed with medical codes. Is the E/M billed with a new pt code or a est pt E/M code?

If a patient has been seen in the office in the past 3 years by any provider in the practice they are considered an established patient. It does not matter if you are billing medical or dental.

To answer your question specifically you would use and established patient E/M code,