The aim of this study was investigate by the finite element method the distribution of stress in the maxillar undergoing subtotal Le Fort I osteotomies to surgically assisted maxillary expansion. Five maxillary models were built virtually: M1-no surgery, M2-Le Fort I with a step on zygomatic buttress; M3-Le Fort I with step on zygomatic and pterygoid disruption, M4-Conventional Le Fort I M5-Conventional Le Fort I with pterygoid disruption. According to the coherence analysis larger displacements were observed in the region of alveolar anterior ridge and first premolar decreasing the in the posterior region, as a “V” form in surgery models. Comparing the displacement of the models, M4 and M5 had a higher dental displacement in relation to bone displacement, than recorded in M2 and M3. The maximum principal stress showed areas of tension spreading to the jaw and the region between alveolar ridge and the palate, and a critical point in the median suture for M2, M3, M4 and M5. In models M2 and M4, MPS has spread further in the direction and the pterygoid process. The analysis of von Mises stress showed large stress concentration in the appliance and metal poles in the region of orthodontic bands and wire junction for all models.

Conclusion: M3 had better performance than other models because it showed less dental displacement in relation to bone displacement, and the tensile stress was interrupted by posterior osteotomy.

Conflict of interest: None declared.