Stresses and Strains Analysis Using Different Palatal Expander Appliances in Upper Jaw and Midpalatal Suture.

Rapid maxillary expansion (RME) is the technique of increasing the transverse dimension of the upper jaw using lateral forces applied by palatal expander. Usually, this palatal appliance is anchored on posterior teeth. The purposes of this computer simulation study were to analyze the stress and strain distribution generated in the maxilla, mainly in midpalatal suture (MPS), during RME by tooth-borne and bone-borne expanders and to study the correlation between mechanical strain and Wolff's Law. The analysis was performed with finite element models developed based on Cone Beam computed tomography (CT). To simulate the expansion load, displacements were applied concerning one (0.125 mm) and three (0.375 mm) activations in the medial sides of the tooth-borne expander, and one activation (0.125 mm) for miniscrews (MSIs) in transverse and lateral direction. It was observed that to obtain approximately the same spacing in the MPS activating once the expander with bone support, three activations for the tooth-borne were necessary. However, the strain level caused by bone-borne expansion, when applying a single activation, reached 900 and 5000 μɛ, with peaks up to 20 000 μɛ, in a region very close to the MSIs. Comparing the results, bone-borne appliance anchorage in the palatine bone is more effective than tooth-borne expander. Nevertheless, the stresses and strains increased significantly in the entire jaw when the bone-borne expander is used.