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

Azita Tehranchi, Nazila Ameli, Zahra Najirad, Fatemeh Sadat Mirhashemi


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


Key Words: Dental, expansion device, finite element method, skeletal

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