A bilinear elastic constitutive model applied for midpalatal suture behavior during rapid maxillary expansion

Abstract

Introduction: This study aims to evaluate the influence of the biomechanical behavior of the midpalatal suture (MPS) during the rapid maxillary expansion (RME) when modeled by the Finite Element Method. Methods: Four simulation alternatives are discussed and, for each analysis, the suture is considered as a functional unit with a different mechanical behavior: (i) without MPS elements, (ii) MPS with Young's modulus (E) equal to 1 MPa, (ii) MPS with E equal to 0.01 MPa and (iv) MPS with bilinear elastic behavior. Results: The stress analysis showed that, when MPS is not considered in the model, stress peaks are reduced in magnitude and their distribution is restricted to a smaller area when compared to the model with the inclusion of MPS (E=1 MPa).The increased suture stiffness also has a direct influence on MPS displacements after 30 expander activations. Conclusion:The consideration of the MPS in RME computer models influences greatly the calculated displacements between the suture bone ends, even as the stress levels in maxillary structures. Furthermore, as proposed for the described model, the elastic bilinear behavior assigned to MPS allows coherent prediction of stresses and displacements results, being a good representation for this suture overall behavior.

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

“…Bone‐borne expanders are often the subject of recent orthodontic computational studies but there is no consensus in the literature on their clinical activation protocol, and it is still unclear if it could be possible to use the same one applied to tooth‐borne expanders without damage. Important factors to evaluate aiming to establish a protocol are the bone stresses and strains.…”

“…Considering that oral mucosa has significantly lower stiffness than the other materials and it was not our main focus in the analysis, it was not considered in this study. To represent the MPS, a solid block was added to the maxilla mid region with a 1 mm thickness, as used in previous study .…”

“…Rapid maxillary expansion (RME), reported in 1860 by Angell , consists essentially of separating the midpalatal suture (MPS) bone ends for orthopedic purposes, i.e., when treating transversal atresia of the maxilla. This orthodontic treatment has proved to affect the entire craniofacial complex and different types of expanders were studied, anchored only by tooth or by tooth and mucosa .…”

“…Furthermore, the RME tooth effect is very unstable , so great skeletal effect (MPS separation) and low amount of tooth movement results in more stable prognosis. Bone‐borne expander devices have been subjected to computational , laboratory , and clinical studies .…”

A comparative finite element analysis of maxillary expansion with and without midpalatal suture viscoelasticity using a representative skeletal geometry

“…One element missing from previous FEA studies surrounding ME treatment is that they neglected to incorporate the viscoelasticity of the MPS/IMS 7 . Suture material properties have been prescribed commonly either by (1) removing the structure completely 8,9 , (2) assigning linear 8,10 or bilinear 9 elastic properties, or (3) artificially reducing the accumulated stresses to zero 11,12 – an assumption yet to be verified. Depending on the specific goals of the ME simulation, which are case dependent, these approaches may prove sufficient.…”