Evaluation and Comparison of Stress Patterns and Teeth Displacement with Intrusion of Maxillary Posterior Segment by Skeletal Anchorage System (Infrazygomatic Crestal Bone Screw) and High Pull Headgear: A 3D Finite Element Study

Abstract

Introduction: In the last decades the application of the Finite Element Methodology (FEM) has become popular. It can calculate stresses and displacement in complex structures and can anticipate the tissue responses to orthodontic mechanics applied for treating different malocclusions. This study evaluated and compared the stress patterns and teeth displacement with application of 450g of intrusive force bilaterally on maxillary posterior segment utilizing a conventional old method, High-Pull Headgear (HPHG) and a newer method, Infrazygomatic Crestal Bone Screw (IZC-BS) using 3D-FEM. Method: A 3D-FEM model of the craniomaxillary segment with maxillary teeth was reconstructed from the Cone Beam Computed Tomographic image of a patient with class II div I malocclusion on class II skeletal base with anterior open bite and 450g of intrusive force was applied bilaterally on maxillary posterior segment utilizing HPHG and IZC-BS and stress patterns and teeth displacement were studied and compared. Result: Von Mises stresses on Zygomaticomaxillary, Zygomaticotemporal and Pterygomaxillary sutures and surface landmarks on maxillary, zygomatic, temporal and sphenoid bones were more pronounced and generalized for HPHG group. Intrusion, expansion and sagittal displacement of maxillary posterior segment were also more pronounced with HPHG group. Stresses weren’t present at the apical root areas of the maxillary posterior teeth for both the groups. Conclusion: On applying equal amount of intrusive force bilaterally to the maxillary posterior segment, stress patterns and teeth displacement were more pronounced and effective for HPHG group however; apical root areas of the maxillary posterior teeth in both the groups didn’t show any stresses.