Thumb Sucking

Most children stop sucking on thumbs, pacifiers or other objects on their own between 2 and 4 years of age. No harm is done to their teeth or jaws until permanent teeth start to erupt. The only time it might cause concern is if it goes on beyond 6 to 8 years of age. At this time, it may affect the shape of the oral cavity or dentition.
Thumbsucking leads to Open bite, a high arched palate because of the pressure created in the mouth . This habit can also cause the maxillary central incisors to tip labially and the mandibilar incisors to tip lingually as the thumb rests on them during the course of sucking. Aside from the damaging physical aspects of thumb sucking, there are also additional risks, which unfortunately, are present at all ages. These include increased risk of infection from communicable diseases, due to the simple fact that non-sterile thumbs are covered with infectious agents, as well as many social implications. Some children experience social difficulties, as often children are taunted by their peers for engaging in what they can consider to be an “immature” habit. This taunting often results the child being rejected by the group or being subjected to ridicule by their peers, which can cause understandable psychological stress.

To prevent their children from sucking their thumbs some parents use bitterants or piquant substances on their child's hands.Parents could get a series of sharp prongs known as "hay-rakes" cemented to a child's teeth to discourage sucking

Praise children for not sucking, instead of scolding them when they do.
If a child is sucking its thumb when feeling insecure or needing comfort, focus instead on correcting the cause of the anxiety and provide comfort to your child.
If a child is sucking on its thumb because of boredom, try getting the child's attention with a fun activity.
Involve older children in the selection of a means to cease thumb sucking.
The pediatric dentist can offer encouragement to a child and explain what could happen to its teeth if it does not stop sucking.
Only if these tips are ineffective, remind the child of its habit by bandaging the thumb or putting a sock/glove on the hand at night.