Any litigant, individual or business, may be sanctioned for filing a frivolous complaint with the court. You being in pain isn't what determines if the complaint is frivolous. It is frivolous if the complaint has absolutely no merit, i.e. a complaint that has no basis in the law. If you sue the dentist for refusing to help you then you need to be able to point to some law that required the dentist to help you or you may face not only dismissal but perhaps sanctions as well. You cannot sue simply on the basis that it was "wrong" for the dentist to refuse to serve you. There are many things that people do that may be considered wrong, rude, inconsiderate or whatever that are not prohibited by law.