Question regarding a dental bill?

Late last week, I received a bill in the mail for "pulp cap - indirect" for $50. I have a couple of questions about this. My first one being, what exactly does this term mean? Onto my issue... I had a filling done about 3 months ago. At the time I was told he was going to put some type of medicine under the filling to protect whatever is underneath, and prevent further problems (I'm assuming maybe that's what the bill is for?). I have medicaid, and at the time I was not working, so I had no income of my own. I did receive child support payments, and social security benefits for my brother. I was completely baffled after seeing the bill, so I called today in question of it, since I'd thought my insurance covered most things. I was told that this just happened to be something my insurance did not cover, a first for me in my 2 years having it. Still, I didn't think it was a huge issue, I mean it's only $50. However, I'm pretty upset that no one at the dental office told me I might be billed, and now 3 months later - surprise! I was told from someone in the billing dept that if I can prove my wages for the time this was done, they might be able to bring down the bill a little bit. Problem is, I didn't have any wages! So my questions... Firstly, am I wrong for being upset that no one told me I'd be billed for this? Is there any way to prove my wages from 3 months ago? I plan on setting up a sliding fee with them in case this happens again (since I didn't know until today I could do that). I'm not trying to get out of the bill, I am just upset I didn't know about it until now. Thanks for any help!
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That term could very well refer to the filling. As for proving what you were earning so that the billing department could consider bringing down your bill, ask them what information they need to prove what you weren't making. As for them waiting for three months - WOW! You heard back from them soon! The way things go with our dental insurance plan, we often don't get bills until six months or longer after the procedure when we have something to pay on it. (And my husband and I each have dental insurance through our employers with a well known and trustworthy dental insurer.) The dental office may not have told you about this because they might not have known just what you were going to have to pay or not pay until after medicaid had finished with the bill.
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