An assessment of late fixed functional treatment and the stability of Forsus appliance effects

Abstract Objective: To evaluate the treatment effects and stability of Forsus appliance therapy. Methods: Thirty-one patients (15 males, 16 females) with a mean age of 15.8 ± 3.1 years (range 13 to 17.6 years, 15.3 ± 1.2 years for females and 16.5 ± 1.6 years for males) were selected. All patients had passed beyond their pubertal growth phase (after CS4 or MP3cap). Lateral cephalograms and three-dimensional (3D) models were analysed before treatment (T0), at the end of treatment (T1) and at a follow-up visit (T2). The mean period from T1 to T2 was 25 months and ranged from 17 to 32 months. Tooth position and angulations, together with maxillary and mandibular position, were measured on cephalograms. The inclinations and vertical distance changes of mandibular incisors were measured on a 3D digital model. Results: The Forsus appliance produced significant skeletal and dental changes during treatment (from T0 to T1). In the sagittal plane, mandibular length (Co-Gn) increased 6.47 mm, the maxillary incisors and molars uprighted (∠U1-SN decreased 8.97° and ∠U6-SN decreased 3.51°), the mandibular incisors proclined (∠L1-MP increased 3.93°) and the mandibular molars advanced (L6-SP increased 3.61 mm). In the vertical plane, the maxilla and mandible rotated clockwise (∠PP-SN, ∠MP-SN, ∠OP-SN increased significantly) and the mandibular molars extruded (L6-MP increased 3.06 mm). All of the changes remained relatively stable after treatment. Cephalometric sagittal and vertical changes affecting the mandibular incisors from T1 to T2 were statistically insignificant (p > 0.05) except for lower incisor extrusion (L1-MP, p < 0.05). Conclusion: The Forsus appliance induced significant skeletal and dental changes, which remained relatively stable during the observation period. The mandibular incisors, in particular, were stable two years after treatment.