A comparative evaluation of Angle Class II Division 1 malocclusion treatment effects using an activator versus an EF Line® preformed appliance in the Vietnamese population: a randomized controlled trial

Background: The study aimed to evaluate skeletal, dental, and soft tissue changes in patients with Class II Division 1 malocclusion after 6 months of treatment with a conventional functional appliance (the Activator) versus a prefabricated myofunctional appliance (PMA). Methods: A randomized clinical trial was conducted on 60 patients diagnosed with Angle Class II Division 1 malocclusion (ANB ≥4◦, normal maxillary position) and an overjet ≥6 mm. All participants were in the cervical vertebral maturation (CVM) stages 1–3 (CS1–CS3). The sample included 29 girls and 31 boys with a mean age of 9.7 ± 1.31 years. Patients were randomly allocated by lottery to receive either an Activator or a PMA, with 30 subjects in each group. Skeletal, dental, and soft tissue parameters were recorded at baseline and after 6 months of treatment. Blinding was not performed. Results: Both appliances produced significant skeletal improvements. In the Activator group, ANB angle and Wits appraisal were reduced by −1.03◦ and −2.09 mm, respectively (p < 0.001). Comparable reductions were observed in the PMA group (0.73◦ and 1.68 mm; p < 0.001). Mandibular length, as well as anterior and posterior facial heights, increased significantly in both groups (p < 0.001). The Activator demonstrated greater increases in mandibular length and posterior facial height (p = 0.034 and p = 0.035), whereas the PMA resulted in significantly larger increases in Pg–Pg′ distance and total chin thickness (p = 0.039 and p = 0.037). Conclusions: Both the Activator and PMA were effective in reducing overjet and improving skeletal and dental relationships in growing patients with Class II Division 1 malocclusion. The Activator produced slightly greater skeletal effects on mandibular growth, while the PMA showed more pronounced soft tissue changes, supporting its role as a functional and habit-modifying appliance. Clinical Trial Registration: ClinicalTrials.gov, ID: NCT06566027 (Retrospective registration).