Not all results are thumb sucking damage to the teeth or mouth. For example, passive holding the thumb in the mouth usually does not cause damage. However, active finger sucking with a lot of movement can cause damage to the primary (baby) teeth, although this usually corrects itself as the permanent teeth come in. 

Strong thumb sucking can have finger sucking teeth and mouth problems. It was due to repeated stress and sucking your thumb in the teeth, jawbone, and the roof of the mouth. It may cause one of the following:

Overbite, where the protruding front teeth of the jaw and mouth

Another bite problem, such as the bottom of the tooth ends inward toward the back of the jaws or an open bite, in which the lower and upper teeth do not meet when the mouth is closed changes in the shape of the mouth, which can also affect the order of the teeth and speech patterns, such as developing a lisp the sensitivity of the roof of the mouth.

Most of these problems resolve or will not develop at all if the thumb sucking decreases when the permanent teeth are in. Infants who suck their fingers for a long time and continue to suck their fingers vigorously may be at developed risk for this side effect.