Two Class II, division 1 patients with congenitally missing lower central incisors.

Although orthodontic treatment objectives and procedures for apparent protrusion of the maxillary teeth vary among orthodontists and specific cases, the differences are even greater where there is disharmony of jaw relationship between the maxilla and the mandible. The two cases presented in this article resemble each other in appearance, but the growth patterns and reactions to appliance, as well as treatment progress, are quite different. The initial excessive overjet seemed equally severe. Treatment was started at the same age, both patients were eldest daughters, both had a convex type facial pattern and an abnormal perioral muscle function with mouth breathing. In addition to the marked overjet, deep bite, and Class II molar relationship, lower central incisors were missing, and second molars had not erupted. They both had a steep curve of Spee, disharmony between the upper and lower arch forms, and slight diastemata. The facial appearance has been improved significantly in both, and patient satisfaction is high. A Kloehn-type cervical headgear was used in both cases. Case 1 showed improvement in the relationship between the maxilla and the mandible with reduction of the overjet. However, in Case 2, the sagittal relationship became worse, and an open bite developed. The obvious question is why the big difference in treatment response? What role did clearing of the nasopharyngeal airway play?