For fussy babies, a pacifier can calm and soothe. However, dental experts warn that once a child reaches the preschool years, a pacifier can become a habit that impedes the development of healthy teeth. If a child continues using a pacifier past the age of 3, serious dental malformation can occur. The most common malformation is an open space in the front teeth or an overbite in which the upper teeth protrude. "Unlike sucking the thumb, using a pacifier is a learned response,