Yes if he has a generous income and you can't afford necessary dental treatment, and you're married, that's really terrible. You don't earn, because you have been raising his kids, that is the contribution you have brought in recent years and in return you should have access to the money, which is not his money, it;s family money.
If you're living a life where you're personally skint while he's personally wealthy, he is financially abusing you. The good news is divorce (if and when you're ready) will force him to cough up.
I think it would really help you to start reading up on financial abuse, emotional abuse etc, contact women's aid, talk to CAB about your potential options etc., all in secret of course. You don't have to "decide to leave" but you can lay the groundwork for what you would do and it will help you to feel stronger and less controlled by him. You do have an out, it will be waiting for you anytime you are ready to take it. Biding your time, if that's what you want to do, won't change that. I'd get school under way, get a job, change the dynamic a little and check out all your options.