Finite element analysis for stresses in the craniofacial sutures produced by maxillary protraction forces applied at the upper canines.

The purpose of this study was to investigate the nature of stress distributions in the craniofacial sutures produced by orthopaedic maxillary protraction forces applied to the upper canines. A three-dimensional finite element model of the craniofacial complex was developed for finite element analysis. An anteriorly directed force of 1.0 kg was applied to the upper canines in three different directions, i.e. parallel, 30 degrees upwards and downwards to the functional occlusal plane. Normal stresses acting on the sutural systems were greatest when force was applied in the 30 degrees upward direction. Furthermore, relatively large compressive stresses were induced in the frontonasal and frontomaxillary sutures, indicating that forward and upward rotation of the nasomaxillary complex was produced with substantial distortion of the complex, by the forces applied in both parallel and 30 degrees upward directions. A 30 degrees downward force produced almost uniform tensile stresses in the zygomaticotemporal and zygomaticomaxillary sutures, with least compressive stresses in the frontonasal and frontomaxillary sutures located in the superior region of the complex. This would indicate a uniform stretch of the nasomaxillary complex in both anterior and inferior directions, with negligible distortion of the complex and would be appropriate for accelerating natural growth of the nasomaxillary complex.