Stress distribution in lower second molar mesialization using mini-implants: a pilot study using 3D finite element analysis

Objective: to analyze the stress distribution in a 3D model that simulates second molar mesialization using twodifferent types of mini-implants. Material and Methods: a mandible bone model was obtained by recomposinga computed tomography performed by a software program. The cortical and trabecular bone, a lower secondmolar, periodontal ligament, orthodontic tube, resin cement and the mini-implants were designed and modeledusing the Rhinoceros 4.0 software program. The characteristics of self-drilling orthodontic mini-implants were:one with 7 mm length, 1 mm transmucosal neck section and 1.6 mm diameter and another with 5 mm lengthand 1.5 mm diameter. A total of 235.161 and 224.505 elements were used for the mesh. These models wereinserted into the bone block and then subjected to loads of 200 cN (centinewton). The results were calculatedand analyzed by the Ansys 17.0 software program for qualitative verification through displacement and maximumprincipal stress maps. Results: it was possible to observe that the periodontal ligament presented low displacementand stress values. However, the physiological values presented are among those capable to provide orthodonticmovement, with compression and tensile area visualization staggered between 0.1 and -0.1 MPa (megapascal).Conclusion: within the limitations of the study, the mini-implants tested showed similar results where theload on the tooth allowed dental displacement (molar mesialization), with a tendency to rotate it, theoreticallyallowing the second molar to take the location of the first molar. KEYWORDSFinite element analysis; Orthodontic anchorage procedures; Fixed orthodontic appliances; Mini dental implants;Tooth dislocation.