Thanks again to everyone who replied to my initial post and to those who have messaged me directly with dentist recommendations.
My belated update:
I ended up visiting a dental practice in Central. As it turned out, most of the small restorations (i.e. resin "fillings") that I'd had done in HK by other dentists had not been done properly. The dentist used an LED-illuminated magnifying video camera, hooked up to a large monitor, to show me what they were doing in my mouth and to point out the problems with my old dentists' work.
After removing the old restorations, in one case, she showed me that the cavity (while relatively small) hadn't been completely removed -- just covered over with resin. In another case, the previous dentist had failed to go beneath the gum line to remove a small bit of a cavity that was still festering and would have caused me a great deal of trouble down the line.
This new dentist fixed the glued-together teeth problem, but they still left a tiny bit of resin sticking out very slightly that caused dental floss to "catch" on it for a moment whenever I'd floss that gap. When I pointed out this problem at the start of the next visit, they confirmed the issue and fixed it (for the most part) free of charge. They offered to completely redo that restoration (presumably also at no additional charge) but I'm satisfied at the moment.
I had several restorations done during each visit, which took a couple of hours, with the dentist working very methodically and carefully. Because each restoration was a bit different, and I had several done during each visit, the cost of the visits varied but came down to about $HKD 10k each time.