If you go to Turkey for dental work then you'll have to return yearly for checkups. My sisters boyfriend was struck off by his dentist after he went to Turkey.
Go for all on 4 implants if you're really keen though.
I imagine clinicians don't want to deal with other people's work. I come across it a lot, if surgery was done in one place then no one else wants to do any follow ups or deal with any issues following surgery.