As long as you do well in dental school, you can specialize from anywhere. The dental school you go to does not instantly make it easier or harder. That said, if the school does not have a department for the specialty you're interested in, it will be more difficult to get exposure.
Thats an interesting question, as MWU aims to produce general dentists. Some people do end up specializing and you will get in provided your grades are good. The good thing/ bad thing about MWU schools is the residencies won't take any of your hard/ interesting cases since they don't have residencies. I would imagine as long as your ranking is fine you shouldn't have a problem getting into a specialty.