Stress Analysis of Mandibular Molar Uprigthing Using Mini-Implant by 3D-FEA

Objectives: The aim of this study was to evaluate stress distribution on periodontal ligament, mini-implant and bone around mini-implant in simulated cases of mandibular uprighting using orthodontic mini-implant as distal anchorage.
Methods: Recomposition of a CT Scan of a mandible was made to modeling a bone block that was divided in cortical and trabecular bone using InVesalius 3.0 and Rhinoceros 4.0 software. Sections of a second mandibular molar were used to reconstruct a 3D model of this tooth that was inserted at bone block in an angle of 30° mesially. Similar methodology was used to draw a 3D model of a mini-implant (1.5x2.0x8.0mm) that was inserted vertically in the bone block 10 mm distally to the tooth. Using FEMAP 11.0 software was generated the FEA models simulating elastic loads at buccal and lingual sides of the tooth in direction to the mini-implant to analyze three different situations: Buccal load of 75cN; Lingual load of 75cN; Buccal and lingual loads of 37.5cN simultaneously. All models were solved in NEi Nastran 10.0 software. Stress distribution on periodontal ligament, on mini-implant and in the bone around mini-implant was evaluated.
Results: Model with buccal and lingual loading shows more uniform stress distribution. Buccal load isolated shows lingual stress compression tendency associated with uprighting while lingual load isolated shows buccal compression tendency associated with uprighting. No significant differences were showed in the stress on minimplant and bone around it.
Conclusions: Within methodology limitations, all simulated situations generate upright tendency. According to orthodontic need it is possible to determine load localization if necessary a lingual or buccal tilting associated with upright movement. All simulated situations did not jeopardize the mini-implant or bone around it.