How to get a 21 month old to give up the paci?

The dentist just told me that I need to start weaning my 21 month old daughter off of the pacifier. She is very attached to it, but it is causing problems with her teeth. Does anyone have any suggestions? The dentist did suggest to just start using it during naps and at bedtime, but like I said, my daughter is VERY attached to her paci. I also have a 7 week old daughter who also uses a pacifier, but isn't as attached to it.