To study the effect of invisible appliance without brackets in the treatment of adolescents patients with skeletal class Ⅱ mandibular retrusion malocclusion and the changes of temporomandibular joint (TMJ) , and to provide basis for the design of clinical scheme.

A total of 30 adolescent patients with skeletal classⅡ mandibular retrusion (13 males, 17 females, average 11.5 years old) in Department of orthodontics of Suzhou Stomatological Hospital were selected from 2018 to 2021 and treated with the Angelalign A6 appliance. The lateral cephalograms and CBCT data before and after treatment were collected and measured. Paired t-test was used for statistical analysis, and P<0.05 indicated a statistically significant difference.

After the treatment of invisible appliance without brackets in 30 adolescents patients with skeletal class Ⅱ mandibular retrusion malocclusion, expected results were obtained with SNB increased (t = -2.382, P = 0.021) , ANB decreased (t = 7.138, P<0.001) , U1-SN decreased (t = 5.195, P<0.001) , and Ns-Sn-Pos decreased (t = 3.443, P = 0.001) , the difference between pre-treatment and post-treatment was statistically significant. The B point, Pog, Pos, LL were significantly moved relative to the Gall line. The Pog point moved forward (t = 6.048, P<0.001) , as well as the Pos point (t = 6.127, P<0.001) . But the statistical differences of SNA, FMA, Z angle, UL Gall and IMPA between pre- and post-treatment were not found (P>0.05) . The anterior space of TMJ decreased (t = 7.812, P<0.001) , while the posterior space increased (t = -5.636, P<0.001) , and the vertical height of the condyle increased (t = -2.257, P = 0.028) . The width of maxillary between canines increased significantly (t = -2.938, P = 0.005) .

The treatment of skeletal classⅡ mandibular retrusion in adolescents with invisible appliance without brackets can achieve the expected goal. According to the imaging data, personalized scheme should be established to reduce the treatment risk.