I ahve been to dentists both in Belize and in Chetumal. I was really impressed with my dentist (Dr. Maldonado) in Chetumal. Not only is it a state of the art clinic, super hygenic, but the prices are much less than in Belize (immagine that!) and the work much better in my opinion. Dr. Maldonado is also fluent in English. His receptionist is still learning English though, and phone calling will require some patience.
I had a root canal and a crown and was charged about $300 U.S. (2 years ago) The work is tight and secure. He installed a temporary crown which looked almost as good as the permanent crown, the next day after he did the root canal and prep work. 1 week later installed the permanent crown. And while its more convenient to just go to Belize City, for anything extensive, I would check out Chetumal if you have the time. I also had a thorough cleaning done by the dentist himself and all of my little fillings fixed up for around $100 U.S.