Soft tissue and dentoskeletal profile changes associated with maxillary expansion and protraction headgear treatment

Abstract

One of the goals of early treatment of Class III malocclusion with maxillary expansion and protraction headgear is to significantly improve the dentofacial profile. The objectives of the present study were to determine (1) the interrelationships of the soft tissue and dentoskeletal profiles after maxillary expansion and protraction headgear treatment and (2) which cephalometric variables could contribute to an accurate prediction of the protraction effect on the soft tissue profile. Lateral cephalometric radiographs of 20 consecutively treated Class III patients (10 males, 10 females) by protraction headgear were included in this study. Their ages at the start of protraction headgear treatment ranged from 6 to 11 years, with an average of 8.1 ± 2.1 years. None of the patients had previous orthodontic treatment. For each patient, the first lateral cephalogram was taken 6 months before the initiation of headgear treatment (T o), and the second radiograph at the start of treatment (T 1). Therefore (T 1 − T o) represented 6 months of growth with no treatment. A third radiograph was taken 6 months after start of treatment (T 2). In this way, (T 2 − T 1) − (T 1 − T o) represented the effect the result of appliance therapy alone and each subject served as his/her own control. A computerized cephalometric analysis was used including variables assessing sagittal and vertical relationships of skeletal and soft tissue profiles, incisal relationships, soft tissue thickness, and lip structure. Data were analyzed by means of paired t tests, Pearson's product-moment coefficient correlation, and multiple regression analyses. The results showed significant improvements in dentofacial profile after 6 months of maxillary protraction. The skeletal and soft tissue facial profiles were straightened and the posture of the lips was improved. The normal incisal relationship (overjet) that was achieved had a significant impact on the soft tissues overlying both upper and lower incisors resulting in better lip competence and posture. Significant correlations were found between changes in the sagittal relationships of skeletal and soft tissue profiles in both the maxilla and the mandible ( p < 0.05). The forward movement of the maxilla was accompanied by a corresponding forward movement of the soft tissue profile at 50% to 79% of the hard tissue. In the mandible, the downward and backward movements of the soft tissues were equivalent to 71% to 81% of the corresponding hard tissues. The lack of high r square values in the multiple regression analyses reflected a low prediction value for the maxillary variables, but moderately high prediction value for the mandibular variables that could be used in preorthopedic treatment planning. This study showed that significant dentoskeletal changes and improvements in dentofacial profile resulted from 6 months of treatment with maxillary expansion and protraction. (A M J O RTHOD D ENTOFAC O RTHOP 1996;109:38-49.)