Dental work is my most common healthcare experience abroad. I cannot recommend Thailand enough, especially for dental work, nothing but 5 out of 5 dentistry for me so far.
What it all boils down to is: how can you know the work done was good? You can't. You can know it looks good superficially. You can know the dentist was nice, or that their office was clean, and that the bill was low. You can't know if the work is actually good. You don't know if they are intentionally overlooking long-term health for doing what the patient/customer wants right now. You don't know if the materials or techniques would be considered substandard in the US. Yes, other countries often have a different "standard of care". I have seen ABYSMAL work from Asia and the Middle East. I have seen appalling work from Mexico, Central America, and Eastern Europe. Yes I also see bad work done by local US dentists - primarily those who advertise themselves as being some kind of affordable, emergency, or discount office -- but consistently the worst dental treatment I see is foreign. How do I know? I'm the one who has to fix it, if it can be fixed.
Dental tourism scares the hell out of me as a dentist in the US, but I understand why it appeals to people when quality care here is expensive. I have seen bad work from every country in the world, including the US, but the trend is you largely get what you pay for. The offices that accept every insurance under the sun are doing work at discounted fees, and usually cutting corners to do more of it. Medicaid? Pays less than the cost of providing the service unless serious corners are cut. Those are the US-side problems, but the dentists working for poverty wages in India are doing much worse things, on average.
Why is it often worse? With dental tourism you get no follow-up care. You also have no recourse if they fuck up your mouth. Good luck suing a dentist in Mexico or Thailand for malpractice. Turns out, the more financial incentive you have to practice high-quality care, the more you have to lose from fucking up and losing your license.
EDIT: This is "Work Reform", not "Fuck Everyone Who Has More Skills And Makes More Money Than Me", although you wouldn't know it from the types of responses sometimes. Quite frankly dentists are workers, whether employees or practice owners. They only earn what the work of their hands allows. They are not exploiting other workers to do the billable labor, because legally they cannot allow non-dentists to do the vast majority of billable work (there are small exceptions that account for a tiny % at most practices). They are not capitalists. The downvoters just hate the message and would rather shoot the messenger than listen to someone who knows from the inside.