Urgent: Filling up previous NHS medical service history

I did my MSc in UK on 2014-2015. During that time I took a NHS dental service and visited a dentist. I paid full amount also (Which was around 20 pound that time). As I had to took the appointment over phone, I don't remember the month when i took the service and i forgot the name of place from where i took the service.

How should I fill up my NHS medical service history part in my visa application now? It requires to fill up full details.

See this previous 2016 topic on the same question. It is still relevant.

uk-tier-4-student-visas/pbs-tier-4-onli ... 15847.html