ABSTRACT
BACKGROUND AND OBJECTIVE: The orthopedic Maxillary Expansion (ME) procedure is used for treating the transverse maxillary deficiency. This pathology consists in a smaller transverse dimension in the maxilla and leads to malocclusion. The treatment takes advantage of the existence of the midpalatal suture (MPS), which corresponds to the junction at the palatine bones of its horizontal portions. The technique employs a device, conventionally a palatal expander attached to the posterior teeth, to separate the two maxillary bones in the MPS. The objective of this study was to analyze, using the Finite Element Method, the biomechanical behavior of the MPS when an expansion is applied. METHODS: A Computer Tomography image of the maxilla was reconstructed, the suture geometry was modeled with different interdigitation levels and types of hyrax devices. A total of 12 geometric models (three levels for interdigitation and four types of hyrax devices) were prepared and analyzed taking into account the chewing forces and the expansion displacement. For each case, maximum principal stresses on the maxilla (bone), and equivalent stresses on the expander device (stainless steel) were observed. In the MPS, maximum principal stresses and directional displacement were evaluated. RESULTS: The results showed that the interdigitation does not have an important influence on the deformation behavior of the maxilla but it affects the stress distribution. In addition, the type of expander device and anchorage have a direct relationship with the treatment effectiveness; larger deformation in the expansion direction was obtained with skeletal when compared to dental anchorage. CONCLUSIONS: A study that allows a better understanding of the oral biomechanics during the application of ME was presented. To our knowledge, it is the first study based on computational simulations that takes into account bone structures, like maxilla and part of the skull, to analyze the interdigitation influence on the MPS behavior when exposed to a ME.
