Can I sue my employer?

I started working in a dental office about a year and a half ago. I pay for health insurance through the company and do not have dental insurance because as stated in our employee handbook all of our dental needs are supposed to be done in house at a discounted rate of what normal insurance would come out to be. Since I have been there I have only had my teeth cleaned. No cavities done and now they have been neglected so long that one of them needs a root canal. One of my crowns fell off and that tooth cracked about three months ago. I asked several times to be fixed and everytime I have been put in the schedule I get removed for a paying customer, I have asked the office manager to take a day off to go to a dentist and am told that I can have it done in house and they could not let me have off because I am needed there and threatened to write me up. Anyone out there know anything about the law and if I have any grounds for a law suit here. Also any suggestions would be great because the only suggestions I can think of will basically cost me my job. Unfortunately at this time there arent a lot of other jobs in my area to just walk away from this one.
--------------------
Is that dental agreement covered in a contract? If so, what were the terms? How long could they make you wait, how much of a discount, do you make an appointment, etc. If it was just some discussion you had, you may sue your employer, but you won't win anything. First because you haven't been paying for anything and are therefore not "damaged" at this point. Second, your employers are in no way obligated to provide dental insurance. Most cities have at least one dental network that offers a plan instead of insurance. In Denver there's a really good one that costs $76 a year and covers up to six cleanings a year, four filled cavities, free x-rays, etc. Your alleged discount probably isn't that good anyway.
Source