Evaluation of stress in bone by 9 different mini implants based on placement angle with relation to enmasse retraction force - An FEM study

Abstract

The aim of this study was to evaluate the stress in bone at the mini implant site, placed at 5 different insertion angles with relation to en-mass retraction force using a Finite element analysis. Evaluation of stress in bone and their distribution pattern at the mini implants. Evaluation of stress distribution in surrounding cortical bone on application of retraction force at 5 different insertion angle. Force applied was 200 grams on the model. The mini implants were modelled with varying diameters (1.3mm, 1.6mm, and 2.3mm) and varying lengths (7mm, 8mm, 10mm). The implant insertion angulations used were 30°, 45°, 60°, 90°, 120°.The pitch of the implant thread used was 0.5mm. This was fixed in all implant designs in this study. After the models were created, a process called meshing in which the models were divided individually into a finite number of elements,. The model was meshed with a tetrahedral configuration. The complete geometry has an assembly of discrete pieces called elements and is connected to gather at a finite number of points called nodes.In bone Von Mises stress was high in 1.3 × 8 mm implant at 60angulation and least was in 2.3 × 7 mm implant at 30angulation. In Implant of 1.3 × 10 mm in 90angulation showed high Von Mises stress and in Implant of 2.3 × 8 mm in 30angulation showed least Von Mises stress.Mini implant which has got smaller diameter, long length and high inclination angle showed higher stresses when compared to other mini implants.