Stress distribution in miniscrews with different insertion angles: A finite element analysis study

Orthodontic miniscrews serve as critical temporary anchorage devices (TADs), but their clinical success is often limited by biomechanical instability. This research was done to evaluate the biomechanical impact of different miniscrew insertion angles on stress distribution and micromotion using finite element analysis (FEA).

FEA was performed on a total of 225 mandibular models derived from cone beam computed tomography scans of Indian adults. Titanium alloy (Ti-6Al-4V) miniscrews with Sandblasted, Large-grit, Acidsurface modification was inserted at angles of 30°, 45°, 60°, and 90°. Each setup was subjected to vertical and oblique orthodontic loads of 2 N and 5 N. Stress, displacement, and micromotion were analyzed, and the obtained data were statistically evaluated.

Miniscrew insertion at 45° demonstrated the most favorable biomechanical profile, with the lowest von Mises stress (61.2 MPa), minimal micromotion (0.033 mm), and optimal stress distribution. Insertion angle had a significant effect on stress (P < 0.001), and regression analysis identified insertion angle and bone density as significant predictors of stress and micromotion (adjusted R² = 0.89). The odds of failure due to high stress and micromotion were highest at insertion angles of 90° and 30°, respectively. Multivariate regression revealed that both insertion angle and bone density significantly influenced miniscrew stress and micromotion, with optimal 45° angulation and higher bone density minimizing failure risk (adjusted R² = 0.89).

A 45° insertion angle offers biomechanical superiority for miniscrew placement, reducing stress concentrations and the risk of micromotion. These findings provide evidence-based guidance for clinical orthodontic practice, particularly in Indian populations.