Biomechanical Analysis for Total Arch Distalization according to Location of Force Application and Types of Temporary Skeletal Anchorage Devices

Introduction: The purposes of this study were to analyze the displacement pattern of the maxillary dentition according to the location of the force applied and the vertical position of the hook on the palatal retraction arch (PRA) when the dentition is distalized using the palatal plate, and to compare those done by buccal miniscrew using finite element analysis. Methods: A finite element model was created and consisted of four treatment modalities with fifteen models. Modalities 1, 2, and 3 used modified C-palatal plates (MCPPs) with a short, medium, and long length PRA respectively and each modality included four models that had anterior hooks with vertical position of 0, 4, 7, and 10mm respectively. In modality 4, miniscrews were placed on the buccal side. For each model, a force of 300 g per side was applied. Results: The long length PRA with a hook at 0 mm was the most effective model for distalization of the maxillary dentition. The short and medium-length PRAs caused uncontrolled distal tipping. Displacement of the molars using a long length PRA with a short hook led to intrusion, but with the long hook, it caused extrusion. Buccal miniscrews with hook lengths at zero caused first molars to distally tip and intrude. The molar crowns showed more distal displacement and extrusion as the hook length increased. Conclusions: Long length PRAs with MCPPs were the most effective for bodily distal movement of the maxillary molars. This information should be useful when applying temporary skeletal anchorage devices (TSADs) during total arch distalization.