A patient has caries and some non-restorable teeth, but wants to extract ALL of his teeth. Which two ethical principles are in conflict?

The patient has the autonomous right to choose his own treatment (even one the dentist disagrees with), but the dentist's duty of beneficence is to recommend and encourage what is actually in the patient's best interest (preserving restorable teeth rather than extracting them unnecessarily) — creating a classic autonomy-vs-beneficence conflict.