Inferior dental work - where to complain?!

Hi - I went to the dentist to have porcelain crowns made for my 4 front teeth and they did an inferior job with the cosmetic appearance. These do not look like normal teeth. There is a layer around the bottom of each tooth that has a translucent appearance, resulting in a two-tone effect. Others have told me it looks like I have acrylic along the bottoms of my teeth and another person told me it appears as if I am wearing a form-fitting clear retainer. I paid $1,600 out of pocket, plus whatever my insurance covered. When I contacted the dentist the day I got home from having the work done to explain the situation, they told me they would make a new set of crowns for $600. Now, why should I have to pay for their mistake? This should have been done correctly in the first place. Secondly, I was not even given the opportunity to physically point out what the problems are. I was just told that it would cost $600! It seems unfair that they didn't even look to see what I am talking about as far as the weird acrylic look being along the bottoms of my 4 front teeth. I would like to know where I can lodge complaints? I just don't feel that I should have to pay for THEIR inadequate products and service. If it weren't for the fact that these are right in the front of my smile, I wouldn't care so much, but it is extremely noticeable and my smile looks worse than it did before I even got the crowns!