Background: Orthodontic palatal expansion appliances have been widely used with satisfactory and, most often,\npredictable clinical results. Recently, clinicians have successfully utilized micro-implants with palatal expander designs to\nwork as anchors to the palate to achieve more efficient skeletal expansion and to decrease undesired dental effects. The\npurpose of the study was to use finite element method (FEM) to determine the stress distribution and displacement\nwithin the craniofacial complex when simulated conventional and micro-implant-assisted rapid palatal expansion\n(MARPE) expansion forces are applied to the maxilla. The simulated stress distribution produced within the palate and\nmaxillary buttresses in addition to the displacement and rotation of the maxilla could then be analyzed to determine if\nmicro-implants aid in skeletal expansion.\nMethods: A three-dimensional (3D) mesh model of the cranium with associated maxillary sutures was developed using\ncomputed tomography (CT) images and Mimics modeling software. To compare transverse expansion stresses in rapid\npalatal expansion (RPE) and MARPE, expansion forces were distributed to differing points on the maxilla and evaluated\nwith ANSYS simulation software.\nResults: The stresses distributed from forces applied to the maxillary teeth are distributed mainly along the trajectories\nof the three maxillary buttresses. In comparison, the MARPE showed tension and compression directed to the palate,\nwhile showing less rotation, and tipping of the maxillary complex. In addition, the conventional hyrax displayed a\nrotation of the maxilla around the teeth as opposed to the midpalatal suture of the MARPE. This data suggests that the\nMARPE causes the maxilla to bend laterally, while preventing unwanted rotation of the complex.\nConclusions: In conclusion, the MARPE may be beneficial for hyperdivergent patients, or those that have already\nexperienced closure of the midpalatal suture, who require palatal expansion and would worsen from buccal tipping of\nthe teeth or maxillary complex
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