It is best for the development of the teeth, that the baby stops using the pacifier before the age of three. Children who still use a pacifier after the age of three risk that their tooth position changes. This can affect the baby's chewing or biting ability, and it can have consequences for the baby's jaw joint and its appearance. This may ultimately mean that the child must have adjusted the permanent teeth with braces. However, if the baby stops sucking before the age of 3, the baby teeth will usually straighten on their own and the position of the permanent teeth will not have been affected. The Danish Dentist Association
If it is not possible to wean the baby off the sucking habit before the age of three, try to get the baby to suck as little as possible and with the least possible intensity.
It is important to remember that all children are different, and it is the long-term use of the pacifier that influences the alignment of the teeth. It will depend on how much they use it, for how long and the intensity. You know your child best, and if you are in doubt you should take the advise of your dentist.