UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

A study of short-term skeletal, dental, and soft tissue effects of Class II malocclusions treated with InvisalignⓇ with Mandibular Advancement Feature or Twin Block appliance compared with historical controls Blackham, Spencer Sonntag


Introduction: The purpose of this retrospective cephalometric study was to compare short-term skeletal, dental, and soft tissue effects in Class II malocclusions treated with Invisalign® with Mandibular Advancement Feature (IMAF) as compared to Twin Block (TB) appliance, and age and gender matched historical controls. Methods: 64 Class II malocclusion patients received phase I treatment with IMAF or TB, 32 in each group. Comprehensive phase II treatment was then completed for 19 of the IMAF group with Invisalign® clear aligner therapy and 19 patients of the TB group with full fixed edgewise appliances (FEA). 32 longitudinal historical controls were age and gender matched to the IMAF sample. Lateral cephalograms were obtained and intraoral photographs reviewed before treatment (T1), immediately following end of the active advancement of phase I (T2), and at completion of comprehensive phase II orthodontic treatment (T3). Radiographs were randomly traced by a single investigator blinded to group allocation. ANOVA and Tukey tests were used for inter-group comparisons. Intraclass correlations, t-tests, Dahlberg’s error, and scatter plots were utilized for reliability testing. Results: After phase I treatment, both TB and IMAF decreased the ANB angle, facial convexity, and overjet significantly more than the controls. IMAF decreased the overjet through significant retraction of the upper incisor and protrusion of the lower incisor. IMAF also impeded the vertical eruption of the lower incisor. TB decreased the overjet via retraction and retroclination of the upper incisor and protrusion of the lower incisor. Following phase II comprehensive treatment both treatment groups decreased the Wits Appraisal and overjet significantly more than the control sample. The lower incisor was significantly proclined and protruded in the TB and FEA group, and the lower incisor significantly protruded in the IMAF and Invisalign® group. Only the TB and FEA group significantly decreased the facial convexity more than the control group. Conclusions: IMAF with Invisalign® treatment and TB followed by FEA are effective in correcting a Class II malocclusion. Treatment with IMAF may result in less proclination of the lower incisors compared to the TB appliance.

Item Citations and Data


Attribution-NonCommercial-NoDerivatives 4.0 International