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UBC Theses and Dissertations

A comparison of skeletal, dental changes in Class II patients treated with Invisalign® with Mandibular Advancement and Herbst appliance Hosseini, Hamid Reza


Objectives: Align Technology Inc introduced the Invisalign with Mandibular Advancement (IMA) features in 2017, which has been reported to function similarly to a removable functional appliance for growth modification in Class II patients. The IMA appliance utilizes precision wings on the aligners to posture the mandible forward for Class II correction. There is a lack of literature comparing the skeletal and dental changes, as well as their relative contribution to the overall treatment effect between fixed functional appliances and this novel removable appliance. The objective of this study is to characterize the skeletal and dental changes of growing patients with Class II malocclusions treated with the novel Invisalign Mandibular Advancement (IMA) appliance and also the changes caused by a more traditional method of Class II treatment, the Herbst appliance. Methods: Consecutively treated patients with the Herbst appliance and with the IMA appliance from two orthodontic practices were compared using lateral cephalometrics taken at three different time periods: T1: Before treatment, T2: Immediately after the functional advancement stage with the MA or Herbst appliance, and T3: After completion of comprehensive treatment. The skeletal and dental changes across the three time periods (T1, T2, T3) were analyzed for each treatment group separately using paired t-test. A two-sided p-value of less than .05 was considered statistically significant. Results: After the advancement phase, significant forward movement of the mandible, lower molars, lower incisors, and restraining of the maxillary molars were achieved with either the removable IMA or the fixed Herbst appliance; however, these changes were greater for the Herbst appliance. By the end of comprehensive treatment, these changes persisted except for a slight forward movement of the upper molars. Invisalign MA had less proclination of the lower incisors when compared to the fixed Herbst appliance. Conclusion: The Invisalign MA appliance was effective at treating Class II malocclusions by a combination of both dental and skeletal treatment effects, consisting of repositioning the mandible and mandibular teeth forward and by restricting the forward movement of the maxilla and maxillary molars.

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