Prolonged thumb-sucking may cause a child to develop dental problems. Thumb-sucking can cause a child’s teeth to become improperly aligned (malocclusion) or push the teeth outward, sometimes malforming the roof (upper palate) of the mouth. Malocclusion usually corrects itself when the child stops thumb-sucking. But the longer thumb-sucking continues, the more likely it is that orthodontic treatment will be needed to correct any resulting dental problems.

A child may also develop speech problems, including mispronouncing Ts and Ds, lisping, and thrusting out the tongue when talking.

Shown Above is a compilation of images showing the extensive damage that can be caused by prolonged thumb sucking.

Source: WebMD. “Thumb-Sucking- Topic Overview”. http://children.webmd.com/tc/thumb-sucking-topic-overview