To evaluate the clinical efficacy of Twin-block and Bionator appliance in the treatment of Angle Class Ⅱ division 1 malocclusion (Ⅱ¹), and explore the mechanism of functional appliance in the treatment of Class Ⅱ malocclusion, so then to provide a theoretical basis for clinical application.

A retrospective study was conducted and we selected forty-two patients with Angel Class Ⅱ¹ malocclusion in the growth period, including 22 patients (10 males and 12 females) in Twin-block group, with an average age of (10.3±1.5) years old; In Bionator group, there were 20 patients (10 males and 10 females) with an average age of (10.9±1.2) years old. The lateral cephalometric radiographs before and after treatment were analyzed. Paired sample t-test and independent sample t-test were used to compare the differences of measurement items before and after treatment and the differences between groups.

The overjet and facial appearance of the two groups of patients were significantly improved. There was a statistically significant difference in the change of SNA between the two groups, which decreased by (1.65±1.76)° in Bionator group and (0.23±1.16)° in Twin-block group (P= 0.034); There was significant difference in the change of mandibular convex angle between the two groups, which decreased by (2.21±2.16)° in Bionator group and (4.26±2.74)° in Twin-block group (P=0.027); There was a significant difference in the change of the vertical distance from the subspinale to the vertical line of SN plane through S point between the two groups, it increased by (0.17±1.24) mm in the Bionator group and (0.72±1.05) mm in the Twin-block group (P=0.044); There was a significant difference in the change of the vertical distance from the mesial point of the maxillary first molar to the vertical line of SN plane through S point between the two groups. The Twin-block group increased by (1.07±1.84) mm, and the Bionator group decreased by (1.55±1.95) mm (P=0.024).

Twin-block and Bionator appliances are both effective in the treatment of Angle Class Ⅱ¹ malocclusion, but the inhibition effect of Bionator on maxilla growth in sagittal direction is more obvious than that of Twin-block appliance. Twin-block is conducive to the correction of Class Ⅱ relationship and the improvement of the patients' profile.

Twin-block appliance; Bionator appliance; Angel Class Ⅱ division 1 malocclusion; Cephalometrics