https://www.dentaldepartures.com is a great resource. We've used Ciro Dental for a few years and have had cleanings, crowns and my DW has had an implant there. There are dental labs in Los Algodones so a crown, etc. only takes a couple days.
We did try one of the large clinics once because our Dentist was out of town and were thoroughly disappointed. First we had to pay up front, then came the hard sell for all kinds of services. Finally after sitting over an hour waiting for our cleaning and seeing people walking up and getting serviced before us we decided to give up. Took over an hour to get our money back.
There are a couple hundred dentists in Los Algodones so there is much competition to provide great prices and service. Nice parking lot at the border, walk across, then go through customs to get back into the USA.
Bring your Rx's list and check out eyeglass prices there also.