The Mexican border towns have websites that list all the local clinics and their specialties. From there you can link to the individual clinics' websites, where they list their offerings and their prices.
The clinics have toll-free phone numbers and English-speaking receptionists, who can make an appointment for you.
They don't take insurance, but they do take plastic, so you don't have to take cash with you. Many will send a vehicle to pick you up at the border, but most are within a block or two of the border, so it's a quick walk.
I had two root canals and crowns done at a clinic in Palomas, south of Deming NM, about twelve years ago. My total cost was about $1k. My dental insurance co-pay would have been about $3k in the US. The crowns were made in a US lab in El Paso. The Dental office's equipment was more state-of-the-art than the equipment in my Dentist's office in the US.
YMMV and it's best to get recommendations from someone you know, or at least from a US retirement newsletter
A lot of US retirees in the US SW travel across the border for dental care. Also Snowbirds, who come down from the US NW and from Canada in the Winter, also keep the clinics busy.
If you have retirement-age friends in the SW, they might be able to refer you to someone they know who has been there, to give you a personal referral.