Comparison of dental midline correction mechanics: A finite element analysis study

Objective: The aim of this study; To evaluate the effect of three different treatment techniques used in dental midline deviation on teeth and dental arch with finite element analysis method. Material and method: Maxillary and mandibular bones, all permanent teeth except third molars, mini screw, orthodontic bracket, and arch wire were modeled in three dimensions to be used in finite element analysis. In the first scenario, In the right quadrant of the mandible, a mini-screw was placed between the canine-first premolar teeth, parallel to the occlusal plane, and a hook on the arch wire distal to the second premolar in the same region. In the left quadrant of the mandible, a mini-screw perpendicular to the occlusal plane was placed between the first and second molars and a hook on the arch in the mesial of the canine in the same region. Forces were applied from these hooks to the mini screws. In the second scenario, class 2 elastics were applied to the right quadrant, class 3 elastics were applied to the left quadrant, and diagonal intermaxillary elastics were applied in the anterior region. In the third scenario, forces were applied to the dental arch with a class 2 intermaxillary elastic plus a compensating diagonal intermaxillary elastic in the opposite direction to the side where midline shift is desired. Results: In three scenarios, the lower incisors moved to the left on the transverse axis. The most movements were seen in the first scenario. In the second and third scenarios, the upper incisors through which the elastic passes are displaced to the right. The maximum upper incisor movement was in the third scenario. For the second scenario in the sagittal direction, distalization was observed in the upper right and lower left posterior teeth, and mesialization was observed in the upper left and lower right posterior teeth. In the third scenario, distalization was observed in the right and left posterior teeth of the upper jaw, and mesialization was observed in the right and left posterior teeth of the lower jaw. The second scenario was found to be more effective than the third scenario in providing total tooth movement in the sagittal direction. In the evaluation on the vertical axis, In the first scenario, the mesiobuccal cusp of the lower right molar tooth was intruded, while in the second scenario, the same cusp of this tooth was extruded. In addition, in the second and third scenarios, the right upper molars were intruded. Upper and lower incisors were extruded in all scenarios. Conclusion: In the vertical direction, a significant amount of occlusal cant was observed in the second scenario. For the third scenario, there is a lesser amount of occlusal cant. Total tooth movement in the sagittal direction is higher in the second scenario than in the third scenario. Midline correction with mini screws is an effective method without causing occlusal cant. Key words: finite element, midline, miniscrew