Abstract:

Objective To investigate the effects of the high-pull headgear-activator combined with a tongue crib appliance on the skeleton, teeth, lateral profile soft tissue, and hyoid bone in growing patients with skeletal Class Ⅱ high-angle malocclusion. Methods A randomized controlled study design was adopted. Seventy-six patients with skeletal Class Ⅱ high-angle malocclusion were randomly assigned to either the experimental group (n=38) or the control group (n=38). The experimental group received sequential treatment with the high-pull headgear-activator combined with a tongue crib, while the control group received treatment with the high-pull headgear-activator alone. Standard lateral cephalograms were obtained for all patients before and after treatment. Cephalometric analysis was performed using Dolphin software to compare the differences in treatment outcomes between the two groups. Results Compared to the control group, the experimental group showed significant reductions in the hard tissue measurements including L1-NB distance, L1-NB angle, lower incisor inclination (L1-MP), mandibular plane angle (FMA), and Y-axis angle (P<0.05). This indicated that the combined appliance was more effective in retracting the lower incisors and inducing counterclockwise rotation of the mandible. Regarding the lateral profile, mentum convexity (B-NPo) and mentolabial sulcus depth (Bs-LLPos) increased (P<0.05), while the soft tissue mentum retroversion angle (Bs-Pos-C) decreased (P<0.05), suggesting that the combined appliance better promoted mandibular development and significantly improved chin morphology. For hyoid bone position, the horizontal distance from the hyoid bone body to the orbitale (H-Or), the vertical distance from the hyoid bone body to the Frankfort horizontal plane (H-FH), and the vertical distance from the hyoid bone body to the palatal plane (H-PP) all decreased (P<0.05), while the distance from the hyoid bone body to the most anteroinferior point of the third cervical vertebra (H-C3) increased (P<0.05), indicating an anterior-superior displacement of the hyoid bone. Conclusion The high-pull headgear-activator combined with a tongue crib appliance can more effectively retract lower incisors, promote mandibular development, improve chin morphology, and guide the hyoid bone to move anteriorly and superiorly. It may represent an efficient comprehensive treatment approach for growing patients with skeletal Class Ⅱ high-angle malocclusion.

Key words: high-pull headgear-activator, tongue crib, skeletal Class Ⅱ malocclusion, high angle