UCSF

Introduction: This retrospective clinical study analyzed the Iino molar distalization appliance, as used in the initial phase of the correction of Class II malocclusions and subsequently in combination with fixed orthodontic appliance treatment. The specific objectives of this study were to evaluate the outcomes of the Iino molar distalization appliance with respect to changes in the position of the maxillary 1st molar, maxillary 2nd premolar, maxillary central incisor, mandibular plane angle and effect on second molar eruption. Methods: Lateral cephalograms of 42 consecutively treated patients (27 female, 15 male) taken pretreatment, after distalization and after full fixed orthodontic treatment were analyzed by structural superimposition. Mean age at treatment start (T1) was 12.16 years (SD = 1.2) with an average distalization time (T2) of 7.56 months (SD = 2.18) and total treatment time (T1-T3) of 27.46 months (SD = 5.16). Results: The Iino appliance effectively distalized maxillary first molars into a Class I position at T2. Significant distal tipping and extrusion were noted of the maxillary first molar as well as anchorage loss through mesial protrusion and tipping of the premolar and incisors. Additionally, the mandibular plane increased significantly from T1-T3 which was associated with downward and backward rotation of the mandible. By treatment completion (T3), the maxillary molars and premolars had returned to their pre-treatment position, but the incisors remained significantly more proclined. At the end of treatment all patients had achieved a Class I molar relationship. The amount of mesial or distal movement by treatment completion was highly variable between patients and correlated to the amount of anterior movement of B-point, i.e. anterior mandibular growth vector. Furthermore, there were no statistically significantly differences between the patients with and without maxillary second molars erupted. Conclusions: The Iino appliance showed no significant differences with respect to the initial and final molar positions. After completion of full fixed appliance treatment, it did effectively restrict the normal mesial migration of the maxillary posterior dentition thus in part helping the Class II correction. This study showed that the final molar position was highly variable between patients but the changes were correlated with the amount of anterior movement of the, mandible, as represented by B-point.