Effect of insertion angle on the stability of orthodontic mini-implants in a rabbit tibia model: A finite element analysis.

INTRODUCTION

Mini-implants are an alternative to traditional methods of anchorage in orthodontic treatment. However, there are still questions concerning their application, in particular, with the insertion angle.

OBJECTIVE

To determine whether the angle of insertion of the mini-implant is a determining factor in their primary stability when they support orthodontic loads.

MATERIALS AND METHODS

A finite element model (FEM) of tibia bone, spring and mini-implant was developed. The three-dimensional model of the rabbit tibia was constructed based on tomographic slices. The angles that were analyzed were 90°, 80°, 70°, 60°, 50°, 45°, 40°, and 30°. A horizontal force of 2 N applied to the head of the mini-implants was simulated. The von Mises stresses and displacements were determined using FEM.

RESULTS

Von Mises stresses were lower for an insertion angle of 40° followed by 90° and 70°; likewise, the displacements of the mini-implants with respect to the spring were lower for the 40° angle followed by 90° and 70°, we found a statistically significant association between the insertion angle and displacement.

CONCLUSION

All mini-implants underwent a degree of angulation and displacement; however, mini-implants inserted to the bone surface at 40° tend to have better primary stability, and they can withstand loads immediately.