Comparative Analysis of Dentoalveolar Effects Induced by Various Fixed Functional Appliances: A Three-Dimensional...

Background/Objectives: The aim of this study was to quantify the dentoalveolar effects of three different orthodontic fixed functional appliances used to correct Class II Division 1 malocclusion using the finite element method. Methods: Three-dimensional models of the mandible, maxilla, and skull were generated from cone-beam computed tomography scans of a patient with Class II malocclusion. The PowerScope2, Forsus Fatigue Resistant Device (FFRD), and Herbst appliances were scanned, digitally reconstructed and positioned on simulated dental arches. Appliance forces were applied to the meshed models to create three different loading conditions. Von Mises and principal stresses in the dentoalveolar structures and instantaneous tooth displacements were calculated using the finite element method. Results: In all simulations, the maxillary teeth moved distally, whereas the mandibular teeth moved mesially, with the latter showing greater overall movement. The Herbst appliance produced the greatest maxillary distalization, while the PowerScope2 caused the greatest mandibular mesialization. Von Mises stress was mainly concentrated on the buccal surfaces, especially on the maxillary first molars, with appliance-specific increases in the premolars/canines and additional palatal stress in the Herbst simulation. Principal stress patterns were similar for the FFRD and PowerScope2, whereas the highest principal stress values were observed in the Herbst simulation. Conclusions: Within the specific boundary conditions of this patient-derived model, the Herbst simulation produced the highest stress values while inducing minimal initial mesial displacement in the mandible, theoretically indicating a potential for reduced mandibular dentoalveolar displacement. In addition, the Herbst appliance demonstrated a more pronounced initial distalizing effect on the maxillary dentition under these simulated conditions. However, due to the inherent reliance on specific static muscle force assumptions, these biomechanical trends should be interpreted with caution and require further dynamic and clinical validation before drawing definitive conclusions regarding clinical advantages.