Orthodontist hasn't put on my bottom Braces yet. Will he ever?What do I do?

So I have unfilled cavaties on my top and bottom. More on my bottom though. I went to the orthodontist and he put on my top braces. He said he woulld put on my bottom when I got them filled. SO I got all of them filled and months later I go back to him and he doesnt put on my bottom. He says he will put it on next time. So when I go in next time and he doesnt put them on what do I do? What are my rights? I have payed in full and I feel like he is trying to steel form me. I also have hope that he likes his job and will do it but what are my rights? What can I do if he denies me my bottom? I feel defensless and as if he wont do them and mighte even fine me.(they have changed thier price aprx 17times. They ended up using excuses and getting at least 500$ more than the original price. ) I am fed up and I feel extremely used, please help me.