Biomechanical Assessment of a Novel Self-Ligating Orthodontic Bracket Using Finite Element Analysis: The LUMACA...

Objectives: This study aimed to comparatively assess, using a two-dimensional static finite element analysis (FEA), the initial biomechanical response associated with two LUMACA bracket configurations and a conventional bracket configuration under identical loading and modelling conditions. Methods: A two-dimensional finite element model comprising the tooth, cortical and trabecular bone, and periodontal ligament (PDL) was constructed using COMSOL Multiphysics. Three configurations were simulated under a palato-vestibular load: (1) the LUMACA bracket in the standard position, (2) the LUMACA bracket in a gingival (apical) position, and (3) a conventional bracket in the standard position. Each configuration was analysed at five force levels ranging from 0.25 to 2.00 N, with 1.47 N used as the reference load. Von Mises stress, longitudinal and transverse strain distributions, and the displacements of coronal and apical probe points were analysed to characterise the mechanical response and tooth-movement pattern. Results: In all three configurations, the crown and apex moved in the same direction and the centre of rotation lay beyond the root apex; therefore, all configurations produced controlled tipping. The apex-to-crown ratio of the displacement components along the applied load, which equals 1 for pure bodily translation and 0 for rotation about the apex, was 0.771 for the gingivally bonded LUMACA bracket, 0.469 for the LUMACA bracket in the standard position, and 0.227 for the conventional bracket. The corresponding centres of rotation were located 37.0, 9.7, and 3.2 mm beyond the root apex, respectively. Under a load of 1.47 N, the differential displacement between the crown and apex was 0.050, 0.211, and 0.516 micrometres, respectively; thus, the conventional bracket produced approximately ten times the differential displacement observed with the gingivally bonded LUMACA bracket. The response was linear across the entire force range examined, indicating that the ranking of the three configurations was independent of load magnitude. Conclusions: Bracket slot position substantially influenced the biomechanical response of the tooth-PDL complex. The apically bonded LUMACA bracket displaced the centre of rotation farther beyond the root apex and produced a more uniform PDL deformation pattern than the conventional design. The calculated stress distributions and displacements should be interpreted as comparative metrics between bracket configurations and not as direct predictors of clinical outcomes.