There is a number of factors that can affect the growth and development of jaws and the correct placement of the teeth. Habits such as finger sucking or the use of the pacifier,breathing through the mouth because of allergies or because of obstructed airways from swollen adenoids and tonsils, hereditary factors and the size of the teeth in relation to the size of the jaws are some of the main reasons why a child may develop orthodontic abnormalities.