Numerous studies show that dental decay can be transmitted to a child when an adult sucks on the pacifier to clean it.
A recent study in the journal Pediatrics goes into detail about this issue. There are few, if any, immunizing effects from adult saliva. Therefore, licking or sucking something to clean it off does nothing to get rid of germs.
It’s also important that parents don’t drip pacifiers in honey, juice, sweetened drinks or any kind of sugar. When exposed to those substances or anything with sugar, the result is often cavities or tooth decay.
The best way to clean a pacifier is to use something that is proven to be a disinfectant.