Impact of anterior bite plane on skeletal relationships and airway space in class II retrognathic mandibular cases: A retrospective study

To evaluate the effects of an anterior bite plane (ABP) appliance on skeletal anteroposterior (A-P) and vertical relationships and upper airway dimensions in patients with Class II retrognathic mandibles, using digital cephalometric analysis. This retrospective study included 65 patients divided into four groups: Group I (control, n=17): Class I malocclusion, aged 9–18 years; Group II (control, n=16): Class I malocclusion, older than 18 years; Group III (n=20): Class II retrognathic mandible, aged 9–18 years, treated with an anterior bite plane appliance; and Group IV (n=12): Class II retrognathic mandible, older than 18 years, treated with an anterior bite plane appliance. All patients received preadjusted edgewise appliances, starting with the upper arch and progressing to 0.018-inch NiTi wires. Mandibular advancement to an edge-to-edge incisor position (zero overjet and overbite) was guided by a groove on the lingual surface of the anterior bite plane (functional Twin Block effect). After achieving a 1–2 mm overjet and overbite, nighttime-only wear continued for 2 months during the retention phase, while fixed orthodontic treatment advanced to 0.019 × 0.025–inch stainless-steel archwires in both arches. Cephalometric analysis was performed using Dolphin Imaging software, and statistical evaluation included paired t-tests and ANOVA with a significance set at p < .05. In Group IV, the angle between the hyoid bone and the mandible showed a significant decrease. In Group II, the Hy-S distance significantly increased, suggesting posterior displacement of the hyoid bone. In Group III, the depth of the nasopharynx at point A (Pre-treatment 14.9±3.2 post-treatment 17.3±4.2) and the oropharynx at the level of U1 (Pre-treatment 9±2.2 post-treatment 10.4±3) increased significantly (p < 0.01). Incorporating an anterior bite plane appliance during orthodontic treatment in skeletal Class II retrognathic patients younger than 18 years can increase the airway dimensions.