| Abstrakt: |
Objective: The purpose of this investigation was to quantitatively evaluate mini-screw deflection and stress distribution associated with two different cortical bone thicknesses (CBTs) under loading with two applied forces at four different angles. Material and methods: Four finite element models (ANS YS 11) of bone with mini-screws (Dentos) inserted at 90" angulation to the cortical surface were made as follows: model A: CBT 1.5 mm, load 200 g; model B: CBT 2 mm, load 200 g; model C: CBT 1.5 mm, load 300 g; model D: CBT 2 mm, load 300 g. In each model, the loading force was applied at angulations of 70, 90, 110 and 130° to the long axis of the mini-screw. The elastic modulus of the cortical bone, cancellous bone and mini-screw were kept at 15, 1.5 and 114 GPa, respectively. The maximum equivalent stress (MES) distribution and maximum deflection (MD) at the mini-screw to bone interface was evaluated in the four models at each angulation. Results: In each model, MES and MD of the mini-screw decreased when the angulation of loading increased from 70 (MES=2.81 MPa) to 130° (MES=1.92 MPa). Mean MES with model A=2.21 MPa, model B=1.83 MPa, model C=3.06 MPa and model D=2.67 MPa. Conclusions: The MES and MD both decrease as the angulation of mini-screw loading increases, with increasing load differences occur in MD but the MES remains similar, whilst differences were observed in both MES and MD as CBT increased. [ABSTRACT FROM AUTHOR] |
