THUMB-SUCKING SYNDROME
Does thumb-sucking lead to crooked teeth? Most experts don't think occasional thumb-sucking in infancy causes any problems with teeth. But there is a general agreement among dentists that prolonged and intensive thumb-sucking past the time the first permanent teeth erupt - at 5 to 6 years of age- can lead to misshapen mouths and displaced teeth.
Actually, the position of individual teeth displaced by thumb-sucking is of less concern to orthodontists than the effect on the bony support of the teeth - and the development of abnormal, deforming muscle activity. If, for example, the habit persists past two years, it could alter the child's swallowing pattern. This is called a myofunctional imbalance and can lead to a perpetuation of numerous problems. Once this happens, the youngster may develop a protrusion of the upper front teeth (buck teeth), a narrowness of the upper dental arch, and an obvious malocclusion (improper bite) problem, such as severe crowding and the mouth breathing syndrome.
As long as there are infants, there will be thumbsuckers. However, if the habit continues longer than usual, it is best to have the child checked by a dentist before it causes any permanent problems.