comparison of the skeletal and dental changes of tooth-borne vs.bone-borne expansion devices in surgically assisted rapid palatal expansion: a finite element study

background: the aim of this study was to compare the skeletal and dental changes of a toothborne (hyrax) and a bone-borne (smile distractor) expansion devices using three-dimensional model of a human skull. materials and methods: a finite element model of human skull was generated using data from 3-d ct scans of an 11-year-old female child. then a hyrax expander (tooth-borne appliance) and smile distractor (bone-borne appliance) in three different positions were adapted to the finite element model and expanded for 0.5 mm simulating the clinical situation. the 3-d pattern of displacement and stress distribution was then analyzed. results: the results of this study showed that screw position affects the stress and displacement pattern within the nasomaxillary complex and maxillary dental arch. conclusion: closer teeth feel more stress and undergo more displacement than the farther ones. moreover, skeletal effects of the smile distractor were greater than of hyrax in all different positions. key words: dental, expansion device, finite element method, skeletal