Evaluation of Strain and Insertion Torque of Mini-implants at 90° and 45° Angulations on a Bone Model using Three-Dimensional Finite Element Analysis.

Background: Temporary anchorage devices or mini-implants have gained great attraction due to its capability to provide absolute anchorage, low cost, versatility, and can be loaded immediately after placement.

Aims and objectives: The aim of this study is to use FEA analysis to assess the strain and insertion torque of mini-implants on a bone model at two distinct angulations of 45° and 90°.

Materials and methods: A computer-aided three-dimensional (3-D) model representing alveolar bone and mini-implants were developed using ANSYS software. Computed tomography scan images of the implant and the alveolar bone were taken and exported in DICOM format for 3-D image processing. The thickness of the bone model is 1 mm. Ti6Al4V orthodontic single and double threaded mini-implants (L = 7 mm, D = 1.5 mm) were inclined at 45° and 90° on to the bone surface to measure the insertion torque and strain produced.

Results: Maximum insertion torque (MIT) for single-threaded mini implant at 45° and 90° angulations are 20.001 Nmm and 19.977 Nmm, respectively. MIT for double-threaded mini-implants obtained is 19.977 Nmm at 90° and 19.991 Nmm at 45° angulation. The strain of the bone at 90° angulation for single-threaded mini-implant is 0.00893 mm and for single-threaded mini implant at 45° angulation is 0.01257 mm. The strain in double-threaded mini-implant at 90° angulation is 0.0125 mm and that of 45° angulation is 0.01773 mm.

Conclusion: For maximum stability single-threaded mini-implant with perpendicular insertion, angle is preferred.