Thumbsucking can pose a problem for your child once their permanent teeth start growing in. If they continue to suck on their thumbs, this can cause misalignment of teeth or change the shape of the roof of their mouth. This essentially is the same as sucking on a pacifier, but that habit is often more easy to break. The intensity of thumbsucking correlates to the likelihood that dental problems may happen. If your child passively leaves their thumb in their mouth, they are less likely as opposed to having a child who vigorously sucks their thumb.