The border with Mexico is open. I very recently got a root canal in Los Algodones MX. Total cost? $550 for the root canal and the CEREC crown. They also threw in some x-rays and a cleaning and fluoride treatment. Prices are usually about 20% to 30% of U.S. prices. Some of the dentists are American and a couple have offices in Mexico and the US.
Bring your passport. About 8 miles west of Yuma on I-8 is the exit for Los Algodones Rd. Turn left and drive another 2 miles or so to a parking lot. Pay the Native American $6 and park. Walk a couple hundred yards into Los Algodones.
There are so many dentists it's hard to know where to start. I've been going to Dental Topete for the past 10 years. Most of the dentists have US phone numbers and email.
The town is jammed with US and Canadian snowbirds. They are getting eyeglasses, hearing aids, dental work, cosmetic procedures, and buying meds at the many pharmacies in the small town. You can also eat and drink there during the winter season when the bars and restaurants are open. There are food trucks if you're into adventure eating. You will see many many MAGA baseball caps. You will also see a portion of Trump's attempted wall, uncompleted.
The pharmacias are currently in a phase where they're selling controlled substances on request, based upon my overheard conversations requesting things like Vicodin and Soma (50 Soma tabs for $6!). Be aware that the penalties for getting caught bringing controlled meds back to the US are rather harsh. Eventually, los federales will shut down a couple pharmacias for selling narcotics, and they will all stop selling them. For awhile.
Trip Advisor has some info and reviews. But it always surprises me how little constructive information is to be found there. There are also shills on TA advertising unknown, no-reputation dentists in los Algodones, so be careful.
Because covid, the border closes early these days, at 2pm. This means that you can't usually get same-day crowns done in time for one-day service. You can spend the night in Los Algodones, or you can stay at the NA casino up the road, or you can stay in Yuma. The customs office at the border (Andrade, California), is modern and sophisticated, with from 2 to 4 officers working. Waits can be long, up to 2 hours, whether on foot or in-car (some people do drive in). These days with limited Customs hours the lines are long all day from about 9 am until border closing.