Evaluation of miniscrew-assisted maxillary expansion in the treatment of unilateral maxillary constriction: A finite element study

Abstract

Objective: The present study focused on evaluating and comparing the stresses and displacements generated by various designs of miniscrew-assisted maxillary expansion appliances. The primary focus of this study is on a modified design for treating unilateral maxillary constriction, analyzed using the finite element method (FEM).

Materials and methods: Using computed tomography (CT) scans and the modeling software Mimics, a three-dimensional (3D) mesh model of the skull and related maxillary structures was created. First, the necessary material characteristics were determined using FEM. Three models of miniscrew-assisted maxillary expansion appliances were then tested with ANSYS simulation software: (a) a bone-anchored rapid palatal expander (BARPE), (b) a conventional miniscrew-assisted rapid palatal expansion (C-MARPE), and (c) an asymmetric design of a MARPE focusing on unilateral expansion (U-MARPE). The asymmetric U-MARPE design features an attachment connecting the expander to the teeth on only one half of the maxilla. The stress, displacement, and distribution predictions for all three types of expanders were subsequently evaluated via FEM.

Results: Tooth displacement in the U-MARPE (on the expander-to-tooth attachment side) and C-MARPE groups was greater than that in the BARPE group. The stresses on the teeth were lowest in the BARPE and U-MARPE groups (on the expander-to-no-tooth attachment side). C-MARPE exhibited a symmetrical stress distribution around the miniscrew areas. Overall, U-MARPE generated the greatest amount of asymmetric von Mises stress and displacement on the dental landmarks.

Conclusion: This research indicates that, compared to other models, U-MARPE achieves more favorable unilateral expansion effects. The current U-MARPE design can be effectively used to correct unilateral transverse anomalies.

Keywords: Crossbite; finite element method; maxillary expansion; orthodontic appliance designs; palatal expansion technique.

Figure 1

Designs of maxillary expanders (a) Bone-anchored rapid palatal expander (BARPE). (b) Conventional miniscrew-assisted rapid palatal expansion (C-MARPE). (c) The asymmetric design of MARPE focusing on the unilateral expansion (U-MARPE). The asymmetric-design U-MARPE comprised an attachment connecting the expander to the teeth on only one half of the maxilla

Figure 2

Palatal and dental displacements of each model after activation. (a) BARPE, (b) C-MARPE, and (c) U-MARPE

Figure 3

von Mises stress distribution (MPa) over the teeth in each model

Figure 4

von Mises stress distribution (MPa) observed near screw areas in each model