PA-28 Instructor Pilot reported during landing losing the right brake resulting in a runway excursion. The Flight Instructor was able to taxi back onto the runway and exit the runway. The Flight Instructor departed the airport to return to their home airport without incident.

Narrative

On this day I was conducting a flight training mission from ZZZ1-ZZZ-ZZZ1 to work on un-towered communication and landings skills with a student. Upon start up at ZZZ1 we did a brake check and noticed the right brake was slightly less effective than the left brake but still operational and safe. We taxied to the runup off XXL and took off without an issue. After flying to ZZZ and one landing on XYL; my student safely taxied off the runway and we back taxied for another take off. We took off Runway XYR and landed XYR again; this time when my student tried to exit the runway but was unable to do so as the right brake had began failing. It was at this point I took over on the controls and decided to taxi down to the end of XYR and exit at the end. When I began to apply brake pressure the right brake did not have enough pressure leading the left brake to be too much and the aircraft began turning to the left. As I tried to regain control and slow down it caused me to drift further to the left eventually causing the aircraft to go off the runway and enter into the dirt between XYR and XYL. I made a radio call on CTAF and began figure out what to do. I decide to back taxi XYR cautiously and exited the runway. I tested the brakes again and felt the right brake pressure come back. It was in this moment I decided it was safe to take off and fly back to ZZZ1 and land XXL. I flew the aircraft back to ZZZ and made sure to maximize the available landing distance and use aerodynamic braking to slow down the aircraft to a safe speed and exit on 1.The decision to fly back and land XXL was made by me as I felt the brake situation had improved. Furthermore I have majority of my flight time and experience at ZZZ1 with hundreds if not thousands of landings on XXL. I knew available landing distance would be more than adequate to come to a stop by using aerodynamic braking from my previous experience as a CFI. In addition I felt very comfortable landing at ZZZ1 as I knew they had the capabilities to roll Airport Rescue and Firefighting (ARFF) if needed. I have made the flying club and management aware of the situation that unfolded.