Thumbsucking is a natural reflex for children. Sucking on thumbs, fingers, or pacifiers may make babies feel secure and happy. After permanent teeth come in, sucking may cause problems with proper growth of the mouth and alignment of the teeth. Pacifiers can affect the teeth in the same ways as thumbsucking but it is often an easier habit to break.
The intensity of the sucking is the factor that determines whether or not dental problems may result. If children rest their thumbs passively in their mouths, they are less likely to create dental issues than those who vigorously suck their thumbs.
Children usually stop sucking between the ages of two and four. If a child has reached the age of four and still has a strong thumb sucking habit it is best to try to gradually eliminate the habit through encouragement at home. Your dentist can explain the effects of the habit to your child at their dental exam and if needed can offer to place a dental appliance that will prevent thumbsucking.