Active digit-sucking results in 1) reduced vertical growth of the frontal parts of alveolar process which creates an anterior open bite; 2) proclination of the upper incisors as a result of the horizontal force crested by the digit; 3) anterior displacement of the maxilla for the same reason; 4) anterior rotation of the maxilla, resulting in an increased prevalence of posterior crossbite in the deciduous dentition; and 6) proclination or retroclination of the lower incisors which seems to be due to the strength of the tightness of the lower lip and tongue activity during sucking. When the sucking habit stops, the anterior open bite will correct itself spontaneously, due to increased growth of the alveolar processes, provided that the patient is still growing. If the lip activity and the lip/teeth relationship is normal, the upper incisors will upright themselves, and sometimes, due to the anterior displacement of maxilla, become somewhat retroclined. The skeletal effect of the sucking habit will remain. Improper use oi a pacifier can create quite disastrous effects on the occlusion, if, for instance, the child has the shield inside the lower lip or is biting into the shield. Otherwise, the effect of the pacifier is limited to the vertical and the transversal plane. The anterior openbite is normally more obvious and visible earlier in pacifier-suckers than in digit-suckers. As in digit-suckers, the open bite is associated with tongue thrust during swallowing. Also in pacifier-suckers, the open bite will correct itself spontaneously when the habit stops despite the tongue-thrust. Sucking a pacifier is more clearly related to a posterior crossbite in the deciduous dentition than is digit-sucking. When the pacifier is in the child’s mouth, the teat occupies the upper part of the anterior and middle part of the mouth thus forcing the tongue to a lower position. In the upper jaw, the teeth in the canine area lack palatal support from the tongue during the sucking activity of the cheeks. This reduces the arch width and increases the risk of a transversal malrelation between the upper and lower arches. The low tongue position widens the lower jaw in the same area thus enhancing the probability of the development of a posterior cross-bite.
Larsson, E. (1994). Artificial sucking habits: Etiology, prevalence and effect on occlusion, International Journal of Orofacial Myology, 20 (1), 10-21.