Three-Dimensional Force Characterizations in Maxillary Molar Distalization: A Finite Element Study

Class II malocclusion is a very common condition in orthodontic patients. The reaction force and moment on the teeth induced by a maxillary segmental distalizer (MSD) are essential for understanding tooth movement, tipping, and rotation. This work quantified the three-dimensional (3D) reaction force and moment on canine and molar teeth induced by three different MSDs: the JVBarre (JVB), Carriere Motion 3D (CM3D), and CM3D Clear. A patient-specific mandibular model was reconstructed based on cone-beam computed tomography (CBCT) images. Each of the three MSDs was implanted using finite element analysis (FEA). The reaction force and moment were obtained. The results show that the JVB induced less extrusion force (15% less), tipping (90% less), and rotational moment (70% less) on the canine, compared with the other two CM3Ds. However, the JVB induced a relatively larger extrusion force, tipping, and rotational moment on the molar due to the hook location changing from the end to the middle of the bar. These observations were consistent with the 3D stress distribution of the MSDs. The mechanical understanding from this work may shed light on the optimal design of MSDs.