Abstract

Fixed orthodontic appliances remain a cornerstone of clinical orthodontics, yet their design and biomechanical optimization are still largely guided by empirical considerations and simplified mechanical models. This review revisits the biomechanics of fixed orthodontic appliances from a mechanics-driven perspective, with particular emphasis on the role of bracket geometry, force application point, and moment-to-force ratios in governing tooth movement and periodontal response. After outlining the historical evolution of orthodontic brackets and the classical biomechanical framework commonly adopted in clinical practice, the limitations of conventional finite element models, based on linear elastic, static, and homogeneous representations of the periodontal ligament, are critically discussed. To overcome these limitations, the tooth–periodontal ligament–bone system is reinterpreted as a mechanically enriched, microstructured medium, motivating the adoption of generalized continuum theories, including micropolar, strain-gradient, and nonlocal formulations, as well as viscoelastic and poroelastic extensions. The natural variational structure of these models and their suitability for advanced finite element implementations are highlighted, together with strategies for micro–macro identification of constitutive parameters and characteristic length scales. In this paper, the LUMACA bracket is presented as a biomechanics-informed orthodontic bracket design developed to enhance mechanical control during tooth movement in fixed orthodontic appliances. Accordingly, the manuscript aims to analyze the biomechanical rationale, mechanical behavior, and design perspectives of the LUMACA bracket. Overall, the paper positions advanced mechanical modeling as a unifying framework for bridging orthodontic biomechanics, numerical simulation, and personalized treatment strategies.

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