I have gone to the dentist 3 times in Chiang Mai, Thailand in the last 1.5 years (2 different dentists). The cost for cleaning has been about $30, $14, and $8. The last 2 were with a cheaper dentist. The last time it was only a 4 month gap between cleanings and my teeth were so clean that they charged me less but only worked on my mouth about 15 minutes or so.
There is a lot of competition for foreigner's business there and virtually all those dentists speak English, many of them speak it quite well.
My philosophy is to ask around and do research, and find the dentist that you would trust to have major work done with. Then go to that dentist regularly, including for cleanings, not the cheap one. I am going back to the more expensive dentist for my next cleaning there. They have state of the art facilities and a team of dentists with different specialties. I mean for the small difference in cost, it pays to go with quality care. The cheaper dentist, who has a sterling reputation and is about 60 years old, is transitioning her practice over to a younger dentist.
When getting work done in a foreign country, you need to do more research. But from the many folks I have talked to, in Thailand at least, the care by the good dental outfits is basically equivalent to what you get in the USA. (in reality, I think USA dental care is probably slightly better)
In fact, please don't take this the wrong way, but after having gone to overseas dentists for the last 2 years, I found many of the fears on this thread somewhat humorous.
In many ways, the research for a foreign dentist in an expat area is easier. There is a popular expat forum for Chiang Mai, for instance, and you can get all kinds of opinions and information about local dentists there from local expats.
After my experiences, I would never really consider getting major dental work done in the USA because the cost difference is too high and the quality difference too low.
One funny cultural difference -- in Thailand when they are working on your teeth, they cover your eyes, too. The dentist does not want to be stared at.
One person mentioned the water? Please. Of course they use clean water at the dentist, not tap water -- even local restaurants do not have a tap water option. The vast majority of people in Thai cities, for instance, drink bottled water only. Here in Medellin, Colombia, the water is completely potable and I drink it everyday (this is an exception in the developing world, however).
Kramer