Abstract
The purpose of this study was to verify the mechanism related to correction of an anterior crossbite with a mouthpiece type functional orthodontic appliance. Tooth movements were simulated by use of a finite element method.
Finite element models of the upper and lower dentitions were constructed based on a dental study model. The teeth were assumed to be rigid bodies, the periodontal ligament (PDL) a linear elastic material, and the maxillary and mandibular bones rigid bodies. A finite element model of a mouthpiecetype functional appliance was constructed based on CT imaging. With placement of the appliance onto the dentitions, the maxillary bone was fixed and the mandibular bone moved forward. Tooth movement was simulated by repeating the following two steps. First, initial movements of the teeth,produced by elastic deformation of the PDL, were calculated. Second, movement of the alveolar sockets was performed in the same direction as during the initial movement. The mandibular bone was moved 0.1 mm with each repetition.
Results of the present simulation verified the mechanism for correcting anterior crossbite. The dentitions were located in the working bite by placing the appliance onto them with anterior crossbite. When returning the dentitions to their initial positions, labial and lingual forces acted on the upper and lower incisors, respectively, with the incisors tipping in labial and lingual directions, respectively. The two incisal edges moved in opposite directions, which corrected the crossbite condition. Additionally, the anterior teeth showed slight intrusion, while the other teeth showed nearly no movement.
