Barbara,
There are several reasons to dive a full face mask and physiological issues such as TMJ are certainly valid. There are quite a few options, depending on how much you want to spend. Take the time to research the different masks, learn what makes one mask better than others.
There are lots of reasons why some masks cost more than others, but price doesn't necessarily mean quality. Take the AGA (Interspiro Divator MKII), one can be had for around $500 retail. This is in the ball park of an Ocean Reef Neptune, yet the AGA is a MUCH higher quality mask (I'm refraining from giving my honest opinion of the Neptune). I agree with Mare-by-the-Sea that it's the best mask available. The Poseidon Atmosphere is a lot more money, although a pretty good mask, I'd debate the improvement over the AGA. I do like the strap buckles better, but you can't adjust the nose block without cutting it and then you're stuck with that level and the oral nasal obviously wasn't designed for clearing water. It's another mask made for a different purpose adapted to diving. The Scuba Pro isn't a bad mask, make sure it fits and that the plate in the front of the oral pocket doesn't jam you in the mouth, not a lot of room in the oral pocket. If you have a smaller face, there is the Mantis mask made in Japan and it's pretty well priced if you can find it. Keep this in mind, a smaller face fits deeper into a full face mask.
All these masks can be fitted with communications. You can talk to your buddy that's next to you without electronics, but it's pretty muffled.
Do consider a full face mask as advanced equipment. SeaDiver5's information about bailout proceedures very true, learn how to use the mask well in a controlled environment before venturing into open water. Don't let this scare you off though, full face masks have saved more people than they have harmed.
More on this if you like.