Study On The Effect Of Invisible Mandibular-advancement Functional Appliance In The Treatment Of Teenage Skeletal Class Ⅱ Patients

Objective: To assess the clinical efficacy of invisible mandibular-advancement appliance（Angelalign A6,China）to skeletal Class Ⅱ teenagers with Twin-Block as the control.Treatment efficacy was assessed from dental,skeletal and soft issue indexes,providing a basis for clinical application.Methods: 49 patients treated in Department of Orthodontics,Stomatological Hospital of Jilin University from 2018 to 2021 were involved in the retrospective study（21 in Invisible group and 28 in TB group）.These patients’ lateral cranial radiographs taken pre-and pro-treatments were traced and analyzed in Dolphin Imaging 11.9.Dental,skeletal indexes and Holdaway analysis results of two groups were statistically compared using SPSS 24.0 software.Results: Both kinds of functional appliances,applied by specialists,improved coordination of maxilla and mandible for Teenage Skeletal Cass Ⅱ Patients,whose facial convexity and overjet were also decreased.1.Due to treatments,SNB increased significantly in both groups,while ANB and Wits decreased（P<0.01）.Increase amount of SNB in Invisible group was significantly more than that of TB group（P=0.013）.Reduction of ANB and Wits in Invisible group had a larger trend.2.SNA decreased significantly after treatment in TB group（P<0.01）,while Invisible group showed no significant difference.3.Go-Gn increased significantly in both groups after treatment（Invisible group P=0.018,TB group P=0.019）,with no difference within them.4.S-Go/N-Me（P=0.010）and Ar-Go（P<0.01）increased significantly after treatment in TB group,while difference in Invisible group wasn’t significant.5.There wasn’t remarkable difference of MP-SN after treatment in both groups,but a decreasing trend in Invisible group.6.After treatment,U1-SN（Invisible group P=0.046,TB group P<0.001）,U1-PP（Invisible group P=0.004,TB group P<0.001）,OB（Invisible group P=0.005,TB group P<0.001）and OJ（P<0.001）decreased significantly in both groups,while respective change between groups showed no difference.L1-MP（P=0.001）increased significantly in TB group,while Invisible group did not.7.After treatment,H angle（Invisible group P=0.019,TB group P<0.001）and Si-H（Invisible group P=0.003,TB group P<0.001）decreased significantly,while nose prominence（Invisible group P=0.039,TB group P=0.002）increased significantly in both groups,with no difference in respective change.Soft tissue facial angle（P=0.001）increased significantly in TB group,while not in Invisible group.Conclusions: 1.Invisible mandibular-advancement appliance displayed a similar effect of mandibular advancement with TB in the treatment of skeletal class Ⅱ patients.2.Invisible mandibular-advancement appliance showed more forward amount,TB inhibited maxilla much more.3.Both appliances promoted mandibular growth.Invisible appliance showed trend of rotating jaw counterclockwise.Despite the stimulation of ramus,TB appeared to rotate jaw clockwise due to the pattern posterior teeth establishing occlusion during treatment.4.Invisible mandibular-advancement appliance seemed recommended when control of incisors’ inclination is needed.5.Both appliances could significantly reduce the soft tissue protrusion and demonstrated major improvement of profiles,while TB coordinated chin shape with more effect.