M.B.
Okay, my 21 month old still uses a pacifier. I had tried around 18 months to have it only when he slept, but unfortunately with two older sisters and a husband who couldn't stand the crying it didn't work out quite as well as I had planned. So I gave in. But now we are really forcing the issues that it's only to be used when he sleeps. Everyone is cooperating. When my son gets up I tell him to give me "Bob" (his nickname for his pacifier). He usually shakes his head no, but then will hand it to me. I remind him it's only for sleeping. He will ask for it a few times throughout the day, but usually I can distract him. Then when it's naptime or bedtime I ask him to go get Bob and he'll walk right to his room and is so ready to get in bed for his Bob time. It's been a few weeks now and it's going well. I'm not ready for him to be without it to sleep yet. And I think it's fine if they only have it to sleep. I think at this age the pacifier impedes them from talking. So I think it's fine to make it only a bedtime thing for now and see how it goes. But if you feel he's totally ready to give it up for sleeping and all then I would either just "lose" it or put a hole in it so he wants to get rid of it. Have him pick out something to replace it with if you want and tell him it's time to give the paci to the new babies. Honestly though for now I don't see any harm in letting him have it just to sleep. He might even lose interest all on his own if it's limited to just bedtime. Especially since he has a twin who isn't using one at all.
As far as the ruining the teeth goes I heard a dentist say that if they are 5 and still using it that's a problem, but at this age it's fine. It's really more a matter of them learning how to form words at this age where there's a concern. They can't say words properly if they've got something in their mouth all of the time. So that's why having it only to sleep makes it not such a bad thing.