Maxillary protraction with and without maxillary expansion: A finite element analysis of sutural stresses

Introduction: In this finite element study, we compared the stress patterns along the various craniofacial sutures with maxillary protraction with and without expansion. Methods: Two 3-dimensional analytic models were developed, 1 simulating maxillary protraction and the other simulating maxillary protraction with expansion. The model consisted of 108799 10 node solid 92 elements (tetrahedron), 193633 nodes, and 580899 degrees of freedom. Results: The overall stresses after maxillary protraction with maxillary expansion were significantly higher than with a facemask alone. The magnitude of stress on the craniofacial sutures with maxillary protraction alone was in the range of a few millinewtons per square millimeter, whereas, with maxillary protraction with maxillary expansion, the stresses ranged from a few newtons per square millimeter to a few hundred newtons per square millimeter. The pattern of stress distribution also differed with the 2 treatment modalities as did the sutures experiencing maximum and minimum stresses. Conclusions: The osteogenic potential of such low stresses after maxillary protraction can be questioned. High stresses generated in various craniofacial sutures after maxillary protraction with expansion are responsible for disrupting the circummaxillary sutural system and presumably facilitating the orthopedic effect of the facemask.