The comparison of zygoma anchorage and extraoral anchorage applications in buccal segment distalization

This thesis study was carried out to evaluate the skeletal, dentoalveolar and soft tissue effects of zygoma anchorage system in buccal segment distalization and to compare these effects with extra-oral cervical headgear anchorage. Patients with Class II dental malocclusion with bilateral Class II posterior dental and Class I or Class II sagittal skeletal relation were included in the study. Criterions such as low angle or normal vertical growth pattern, presence of all permanent teeth, anterior crowding in the maxillary dental arch and/or increased overjet, minimum or no crowding in the mandibulary dental arch, normal or increased overbite, completely erupted maxillary second molars were also checked for inclusion. 30 patients fulfilling these criteria were divided into 2 groups. The first group, which consisted of 15 patients with average age of 14.74 years at the beginning of distalization received buccal segment distalization with zygoma anchorage system. A distalization force of 450 grams was applied on each side with nickel-titanium closed coil springs attached to the zygoma anchor and extended to the crimpable arch wire power hooks placed mesial to the first premolar brackets. The second group, which consisted of 15 patients with average age of 15.26 years at the beginning of distalization received buccal segment distalization with cervical headgear. A distalization force of 450 grams was applied on each side with the facebow?s outer bow parallel to the occlusal plane at the beginning and bent 10-15° upwards after diastemas occurred at the buccal segment. The patients were instructed to wear their headgears at least 20 hours a day. In all patients, the Class II buccal relation was successfully corrected to Class I buccal relation. The mean duration of the buccal segment distalization was 9.03 ± 0.62 months in the first group and 9.00 ± 0.76 months in the second group, and the difference between the groups was not significant. In order to define the changes that occurred in the groups, 43 parameters were measured on lateral cephalometric films and 6 parameters on dental casts. The group means of age and distalization time parameters were compared by Student t test. The group means of variables including repeated measures and normally distributed with homogeneous variances were compared with 2x2 Repeated Measures Analysis of Variance and Bonferroni adjusted t test. For the comparison of the group means of variables not normally distributed with heterogeneous variances, Mann Whitney U test was used for the independent groups and Wilcoxon test was used for the dependent groups. As a result of buccal segment distalization, point `A? moved backwards, the mandible rotated posteriorly and the anterior facial heights increased in both treatment groups. All maxillary posterior teeth were distalized significantly (P<0.001) in both groups. Besides, distal tipping was observed at all maxillary posterior teeth in both groups, except for the premolars in the zygoma anchorage group. The maxillary posterior teeth did not show vertical movements in the zygoma anchorage group, but the premolars extruded in the cervical headgear group. The maxillary incisors were retruded and overjet was decreased in both groups. Overbite decreased only in the cervical headgear group. The upper and lower lips showed significant retrusions in both groups. Both maxillary posterior teeth rotated distobuccaly, but the rotations of the premolars were more profound in the zygoma anchorage group. It was observed that without using any extraoral appliance, similar effects to cervical headgear were obtained and Class II relation was corrected with the zygoma anchorage system.