Finite element analysis of the effects of different miniscrew–assisted rapid maxillary expansion appliances and surgical corticotomy on the maxillofacial complex in unilateral posterior crossbite cases

Aim: The aim of this study was to evaluate the effects of different miniscrew–assisted rapid maxillary expansion appliances that can be used in the treatment of unilateral posterior crossbite in adult individuals using the finite element analysis (FEA) method. In this context, in addition to the application of a unilateral surgical corticotomy, the effects of differences in the number, position, and insertion angles of the mini-implants used on maxillary expansion were investigated. Material and Methods: A three-dimensional finite element model of the craniofacial and maxillofacial complex was constructed using open-access anatomical data. Within the scope of the study, seven different MARPE models designed according to the number and placement of mini-implants were evaluated. In Models I–III, unilateral median and lateral osteotomies were applied on the side requiring expansion, whereas no surgical incision was performed in Models IV–VII. The expansion appliances were modeled as tooth-borne systems supported by two, three, or four mini-implants, and the displacements occurring during maxillary expansion as well as the Von Mises stress distributions were analyzed. Results: On the side requiring expansion, the transverse displacements measured in the anterior maxillary region were found to be greater in the models (Models I, II, III, V, and VII) compared with the side without expansion requirement. In all models except those in which the number of mini-implants was reduced (Models V and VI), the amount of transverse displacement in the dental structures decreased progressively from the central incisors toward the posterior teeth. A lateral rotational separation pattern was observed in all models (Models I–VII); however, this movement was more limited on the side where the surgical incision was performed (Models I–III). In the Von Mises stress analyses, the models with surgical incisions (Models I–III) demonstrated reduced stress values on the mini-implants and the anchorage teeth on the side requiring expansion. Conclusion: In cases with unilateral maxillary constriction, it was observed that the displacement and stress distributions occurring on the side requiring expansion may vary depending on the applied anchorage configuration and surgical support. In scenarios where surgical assistance and sufficient skeletal anchorage were provided, expansion tended to occur predominantly at the skeletal level on the targeted side. In contrast, in the absence of surgical support and in situations where the number of mini-implants was reduced, increased tipping of the dental structures and higher localized stress concentrations were observed. Key Words: Unilateral Posterior Crossbite, Finite Element Analysis, MARPE, Asymmetric Maxillary Expansion