What does the "pa" in the title john doe, md/dmd, pa mean?

PA: The pa stands for professional association or sometimes pc, professional corporation. The doctors name is also the name of his company in this case. John smith, md, pa. So john smith is the doctor, but dr. John smith works for john smith, md, pa.

Degrees : MD and DO are degrees signifying that the practitioner is a Physician. DDS and DMD are degrees signifying that the practitioner is a Dentist. PA and PC are legal notifications that the practitioner is employed by a corporate entity.