Well, we haven't yet, bc I'm procrastinating. They say that its a good idea to take them in starting around 2 yrs now, bc it gets them used to the setting...kind of like having well-visits. Then, when real things start happening, like cleaning, they don't freak out as much.
I haven't done it yet, for either of the boys...shame on me. But, then again, I really have no worries for them. They both are addicted to brushing their teeth (and I help) and are in good shape there.