Paolo, I'll offer a slightly happier dental story, since this thread is otherwise making me clench my jaw.
I arrived in Portugal with a crown that had been giving me trouble for a year, fully prepared to fly back to England to deal with it. A neighbour sent me to her dentist, a very calm woman who spoke better English than I do and had a small practice above a pharmacy. She explained everything, showed me the X-ray, gave me a written quote before doing anything, and fixed it over two appointments. The quote was exactly what I paid, which is more than I can say for my old dentist in Reading.
What I took from it:
- ask neighbours, not the internet, for a recommendation
- always ask for a written estimate before treatment, in any country
- check whether routine check-ups are covered by anything you already have. In our case they aren't, so we budget for two a year as a normal expense
The trick, I think, is to treat dental as its own line in the budget rather than as a surprise.