I need financial law help. Should I have to pay?

First, he has most likely done this to other clients before if he is doing it to you. You should be the one to take him to court and have his license to practice dentistry taken away. He does not deserve to be a dentist and obviously does not have the intelligence to be one. Second, you could probably sue this idiot for thousands. Would it be worth it? Yes, you are damn right it would be. Talk to a lawyer ASAP, and have this idiot put on the streets.