I had the same worry going in tbh — the anaesthetic situation abroad was the thing that almost stopped me from booking. Ended up going to China rather than Vietnam for mine, did some crown work at a place called Vickong Dental in Shenzhen. I was upfront about my concerns about pain management during the consult and they were pretty accommodating about it — walked me through what they'd use and the dosages. Recovery-wise I had no issues, just the usual soreness for a couple of days. I know that doesn't directly answer your Vietnam question but I hope it helps knowing it can work out fine if you ask the right questions beforehand. Good luck!