Sucking when permanent teeth have come in may cause problems with the alignment of the teeth and development of the mouth. As the thumb or object the child is sucking on rests against the mouth and teeth, the continual contact and pressure with the teeth can force teeth and the child's bite out of alignment. The degree and severity of any problems that may arise depends on the intensity of the sucking. If a child merely rests their thumb in their mouth, then the developmental consequences will likely be minor. If the children vigorously sucks, then the consequences may be greater.
Most children naturally stop between the ages of two and four.
For those children still sucking their thumb when they reach five and beyond, peer pressure from their school mates is usually enough to cause them to stop. Remember that pacifiers are basically the same as sucking on a thumb. It is the sucking action and the constant contact with an object in the mouth that causes the problem, not the object being sucked. Because thumb sucking is often linked to feelings of security, a gentle approach is often more effective in getting children to stop. Instead of scolding your child when they are sucking their thumb, praise them when they are not.