Three-Dimensional Finite Element Analysis Of Hyrax Expander Design

Simple geometric shapes facilitate the analysis of underlying principles. This study used finite element analysis with 3D beam elements to investigate the mechanics of different Hyrax expander designs and identify influencing factors for clinical orthodontic reference. A 3D Hyrax expander model was constructed using BEAM 188 elements in ANSYS 2020 R2 (ANSYS, USA). The model, made of cobalt-chromium alloy (Elastic modulus 200 GPa, Poisson’s ratio 0.3), featured a circular solid cross-section with a radius of 1.5 mm and consisted of 40 elements. Thirteen models were generated by varying the arch width, palate height, and the screw position. A displacement load of 0.125 mm was applied along the x-axis at the force application end to simulate a 1/4-turn expansion and to evaluate the expansion force. As the arch width or palate height increased, the expansion force decreased (arch width: from 33.312 N to 27.824 N; palate height: from 64.029 N to 17.130 N). When the screw was positioned in the middle, a larger force was observed (from 29.644 N to 30.679 N); as the screw was moved posteriorly, the dislocation force increased (from 2.380 N to 6.566 N). There is a functional relationship between arch width, palate height, screw position, and the expansion force. The magnitude of the expansion force can be optimized by adjusting the anteroposterior position of the screw and/or its distance from the hard palate.