Thumbsucking is a natural reflex for children. Sucking on thumbs, fingers, pacifiers or other objects may make babies feel secure and happy and help them learn about their world.
Young children may also suck to soothe themselves and help them fall asleep.
After permanent teeth come in, sucking may cause problems with the proper growth of the mouth and alignment of the teeth. It can also cause changes in the roof of the mouth.
Pacifiers can affect the teeth essentially the same ways as sucking fingers and thumbs, but it is often an easier habit to break.
The intensity of the sucking is a factor that determines whether or not dental problems may result. If children rest their thumbs passively in their mouths, they are less likely to have difficulty than those who vigorously suck their thumbs. Some aggressive thumbsuckers may develop problems with their baby (primary) teeth.
Children usually stop sucking between the ages of two and four years old, or by the time the permanent front teeth are ready to erupt. If you notice changes in your child’s primary teeth or are concerned about your child’s thumbsucking consult your dentist.
If these tips don’t work, remind the child of their habit by bandaging the thumb or putting a sock on the hand at night. Your dentist or pediatrician may prescribe a bitter medication to coat the thumb or the use of a mouth appliance.
From: ADA MouthHealthy