The effects of 3-D Screw on the nasomaxillary complex in skeletal class III malocclusion: A FEM analysis

Aim of the study is to evaluate the Stress distribution and displacement of various structures of nasomaxillary complex with 3- D screw in skeletal class III malocclusion. An analytical model was developed from a human skull of a 15-year-old male. CT scan images of the skull were taken in axial direction parallel to the F-H plane, which was processed using Mimics software, required portion of the skull & 3-D screw appliance was converted into geometric model using reverse engineering technique. ANSYS software was used to solve the mathematical equation. Contour plots of the displacement and stresses were obtained from the results of the analysis performed. Maximum transverse displacement was 3.18mm at the permanent first maxillary teeth. Maximum antero-posterior displacement was 1.26mm at the anterior part of zygomatic bone and 1.35mm of displacement frontozygomatic suture. maximum vertical displacement was 2.81 mm representing the inferior and medial portion of the nasal bone and indicating downward displacement. Pyramidal displacement of maxilla was evident. Apex of pyramid faced towards nasal bone and base was located on the oral side. There was downward, forward movement of maxilla with a tendency toward posterior rotation. Maximum von Mises stresses were found along midpalatal, zygomaticomaxillary, nasomaxillary, frontozygomatic sutures