Three-dimensional finite element analysis of the effects of MARPE and RME on the expansion of the arches of craniomandibular complexes with different degrees of suture fusion

Objective To analyze the stress distribution and displacement trends after on craniomandibular complexes with different degrees of bone seam fusion MARPE and RME for arch expansion using three-dimensional finite element analysis to provide biomechanical guidance for future clinical applications of MARPE. Methods A 26-year-old adult female patient with transverse maxillary hypoplasia underwent CBCT, and a 3D finite element model of the craniomandibular complex with unfused and partially fused sutures and two different arch expansion techniques, MARPE and RME, was constructed by setting the material parameters. Four groups of models were created according to the experimental design: Model A was of MARPE with an unfused bone suture; Model B was of MARPE with a partially fused bone suture; Model C was of RME with an unfused bone suture; and Model D was of RME with a partially fused bone suture. Ansys Workbench 2019 software was used to design a transverse forced displacement of 0.25 mm for the model with reference to the clinical arch expander load once and to analyze the stress distribution and displacement of the craniofacial bone, teeth and periodontal tissues under these loading conditions. Results The stress distributions on the left and right midpalatal sutures were not completely symmetrical in all the models, and the midpalatal suture was subjected to greater stresses and displacements during MARPE than during RME. The midpalatal suture was closer to a parallel flare with the anterior part slightly larger than the posterior part after MARPE, and the midpalatal suture in Model A was subjected to greater stresses and displacements than Model B was. RME led to a wedge-shaped flare with a large anterior and small posterior area, and the stresses on and displacements of the midpalatal suture in Model C were greater than those in Model D. The jaws were largely displaced laterally in Models A, B, and C and minimally displaced in Model D. The sagittal displacements of the four models tended to be posterior, with outward and backward displacements. The maximum periodontal hydrostatic stresses in all four models were greater than − 0.0047 MPa for all teeth except the abutment teeth and greater than − 0.0047 MPa for the first molar in Model A, whereas the first molar in Model B and the first premolar and first molar in Models C and D were all less than − 0.0047 MPa. The magnitude of the periodontal hydrostatic pressure of the first molar was as follows: Model D > Model C > Model B > Model A. The magnitude of hydrostatic pressure of the periodontium of the first premolar was as follows: Model D > Model C > Model B > Model A. Conclusions MARPE led to greater lateral displacement of the jaws and teeth, and the midpalatal suture was closer to parallel expansion with asymmetric stresses on the left and right sides. The stresses on the craniofacial skeleton and lateral displacement of the midpalatal suture, jaws and teeth are greater after MARPE than after RME, suggesting that MARPE is more appropriate for late adolescents and young adults with underdeveloped transverse maxillary structures who have highly fused bone sutures.