Study on soft tissue changes of angle class Ⅱ division Ⅰ mandibular retraction patients during mixed dental pe⁃ riod with MRC functional correction

Objective To observe the changes of soft tissue in patients with Angle class Ⅱ division Ⅰ malocclusion during mixed dentition treated with MRC functional appliance. Methods Twenty patients with Class Ⅱ division Ⅰ malocclusion of Angle were treated with functional MRC. The facial features before and after treatment were measured by software and the results were analyzed statistically. Results The patients′soft tissue profiles were improved signifi⁃ cantly before and after treatment, The OE⁃Prn⁃Pos angle, OE⁃N′⁃B′ angle, OE⁃N′⁃Pos angle, OE⁃Prn⁃N′angle, Cm⁃Sn⁃ UL angle, and N′⁃Sn⁃Pos angle increased significantly (P < 0.05). The OE⁃Sn⁃UL angle, and Sn⁃N′⁃B′ angle decreased significantly (P < 0.05); the distance between the lateral soft tissue line and the middle Sn⁃H line, UL⁃E line and LL⁃E line were significantly different (P < 0.05). The distances were all reduced, and the difference was statistically significant (P < 0.05). Conclusion The application of an MRC functional appliance can improve the relationship among nasolabial soft tissue, upper and lower lip soft tissue, and chin⁃lip soft tissue, thus improving the protrusion profile of patients.