No abstract

No abstract

ObjectivesThe aim of this study was to clarify the effect of the play between the bracket and the archwire on anterior tooth movement subjected to the retraction force from various lengths of power arms in sliding mechanics.Materials and MethodsA three-dimensional finite element method was used to simulate en masse anterior tooth retraction in sliding mechanics. The displacements of the maxillary incisor and the archwire deformation were calculated when the retraction force was applied.ResultsWhen a play did not exist, bodily movement was obtained at 5.0 mm length of power arm. In case a play existed, bodily movement was observed at the power arm length of 11.0 mm.ConclusionsIn the actual clinical situation, a bracket/archwire play and the torsion of the archwire within the bracket slot should be taken into consideration to prescribe an optimal power arm length and to achieve effective anterior tooth movement.

No abstract

Abstract:The aim of this study was to fabricate biodegradable poly-L-lactic acid (PLLA) bone screws containing iron oxide (Fe3O4) nanoparticles, which are radiopaque and 3D-printable. The PLLA composites were fabricated by loading 20%, 30%, and 40% Fe3O4 nanoparticles into the PLLA. The physical properties, including elastic modulus, thermal properties, and biocompatibility of the composites were tested. The 20% nano-Fe3O4/PLLA composite was used as the material for fabricating the 3D-printed bone screws. The mechanical performance of the nano-Fe3O4/PLLA bone screws was evaluated by anti-bending and anti-torque strength tests. The tissue response and radiopacity of the nano-Fe3O4/PLLA bone screws were assessed by histologic and CT imaging studies using an animal model. The addition of nano-Fe3O4 increased the crystallization of the PLLA composites. Furthermore, the 20% nano-Fe3O4/PLLA composite exhibited the highest thermal stability compared to the other Fe3O4 proportions. The 3D-printed bone screws using the 20% nanoFe3O4/PLLA composite provided excellent local tissue response. In addition, the radiopacity of the 20% nano-Fe3O4/PLLA screw was significantly better compared with the neat PLLA screw.