Ask the Experts: Thumbsucking
Are thumbsucking and pacifier habits harmful for a child's teeth? Thumb and pacifier sucking habits will generally only become a problem if they go on for a very long period of time. Most children stop these habits on their own, but if they are still sucking their thumbs or fingers past the age of three, a mouth appliance may be recommended by your pediatric dentist.
Are pacifiers a safer habit for the teeth than thumbs or fingers?
Thumb, finger and pacifier sucking affect the teeth and jaws in essentially the same way. However, a pacifier habit often is easier to break.
Information provided by the American Academy of Pediatric Dentistry