Current practice and application of finite element analysis in clear aligners: A scoping review

Abstract

Clear aligner therapy (CAT) has become increasingly popular in orthodontics; however, concerns persist about its predictability and effectiveness. The finite element method (FEM) has become an important tool for studying aligner biomechanics and force delivery, offering insights that are often hard to obtain clinically. This scoping review aimed to map FEM applications in CAT research and critically assess their methodological approaches, highlighting strengths, limitations, and areas for improvement. Six electronic databases were searched up to June 2, 2025. A total of 448 records were screened, resulting in 149 full-text articles, of which 50 met the inclusion criteria. Studies were examined concerning model development, representation of the periodontal ligament (PDL) and bone, material property assignment, meshing strategies, boundary conditions, contact interactions, and post-processing analyses. Significant methodological variation was observed. About half of the studies modeled bone as a single structure, whereas others distinguished cortical from cancellous bone. Most assumed a linear, isotropic PDL, although some employed bilinear or nonlinear viscoelastic models. Boundary conditions usually fixed the maxilla and mandible, while contact constraints connected biologically linked tissues. Meshing strategies differed between native and external software, with tetrahedral elements being most common. Displacement was assessed using either global or local coordinate systems, influencing clinical interpretation. Stress analysis was primarily limited to von Mises stress, although a few reports also included principal stresses. Validation was infrequent, with only isolated attempts using radiological or in vitro data. FEM offers useful insights into CAT biomechanics, but its conclusions are constrained by methodological differences and a lack of validation. Developing standardized protocols is crucial for enhancing reproducibility and clinical applicability.