Evaluation of the stress distribution during maxillary expansion in patients with different types of cleft lip and palate using the finite element analysis

Maxillary expansion is often applied to cleft palate patients (CLPs) because of the posterior crossbite related to maxillary transverse deficiency. The purpose of this study was to evaluate the displacement pattern and stress distribution in the craniofacial complex using rapid maxillary expansion appliance in three patients with different types of CLP using finite element analysis (FEA). The construction of the three-dimensional finite element model was based on computer tomography scans of CLPs who needs maxillary expansion. Von Mises stress distribution after 0.2 mm expansion and displacement distributions after 5 mm expansion were investigated. The highest amount of transverse expansion was recorded for the bilateral cleft model. Similar expansion amount has been observed in the affected side of the unileteral cleft model. Less expansion was recorded in the isolated cleft patient model and finally in the non-affected side of the in unilateral cleft patient's model. Anatomical structures expressed posterior displacement tendency in the unilateral cleft models in the anteroposteriorly plane. In the isolated palate cleft model, structures close to the midline showed anterior displacement, while structures in the lateral parts showed posterior displacement. Structures showed anterior displacement tendency in bilateral complete cleft lip and palate model. Anatomic structures in the bilateral cleft model showed inferior displacement tendency; while in the isolated cleft palate and unilateral cleft models only the structures close to the midline showed inferior displacement. The lateral structures in those two models showed superior displacement tendency. In matter of stress accumulation areas, the highest values were recorded in the nasal area for the isolated CLP model, in suture zygomaticamaxillaris area for the unilateral cleft patient model in suture zygomaticotemporalis and suture zygomaticomaxillaris areas for the the bilateral cleft patient model. Key Words: Unilateral cleft lip and palate; Bilateral cleft lip and palate; Isolated cleft palate; Rapid maxillary expansion; Finite element method.