Effect of different angulation of forces on mini implant and abutment at various levels

Abstract

The objective of the study was to evaluate the effect of varying loads of forces at different angulation at various levels of orthodontic mini implant system by using finite element analysis. A 3-dimensional model of the mini implant was constructed to simulate force magnitudes and directions, screw diameters and lengths, and implanted depths of mini implants. Finite element study was conducted with horizontal forces of 100, 150, and 200 g were applied to the mini implant and abutment at angulations 90° and 120. Von Mises stress, strain and displacement values were then evaluated using the ANSYS software. Both stress and displacement increased with increasing the amount of loading force. These 2 indexes were linearly proportional to the force magnitude and produced the highest values when the force was 200 g applied at 120° to the long axis of the miniimplant. The peak deformation and von Mises stress was concentrated on the miniscrew at the cervical level under 200 g at 120°. A wider screw diameter provided superior mechanical advantages. No remarkable differences in the strain distribution were observed at both angulations. However, the stress distribution of the abutment models showed a remarkable difference as compared with the models of mini implant. The high-level area (shown in orange) was localized to the head of the implant and the abutment (cervical part). Compared with 90° group, the orange coloured area was easily observed more in the cervical part of abutment. The von Mises stress values in the MI, were found to be lowest under 100 g force at 90°. Higher initial loading on the mini implant should be avoided and horizontal force on the cervical level of MI should be prevented or minimized for better stability. The abutment has maximum stress concentration which is significantly useful in decreasing the stress concentration on the bone, and has a buffering action on MI. Force range used is within clinically recommended levels; however, the increase in load causes a proportional increase in the stress values.