Three-dimensional finite element analysis of the effects of different force vectors on tooth movement in miniscrew-assisted en masse retraction
Purpose: This study evaluates the effects of different force directions on tooth movement in miniscrew-assisted en masse retraction using finite element analysis (FEA).
Materials and Methods: A three-dimensional (3D) finite element model was constructed to simulate en masse retraction in sliding mechanics. A retraction force of 200 g was applied from the anterior retraction hook (ARH) to a miniscrew, and force vectors were resolved along the X, Y, and Z axes. Six different configurations were analysed by varying the ARH (5 mm and 8 mm) and miniscrew heights (6 mm, 8 mm, and 12 mm). Displacement values of anterior and posterior teeth were examined to assess movement patterns in mesiodistal, buccopalatal, and vertical directions.
Results: The analysis revealed that increasing the retraction hook length enhanced mesiodistal tipping of anterior teeth, while higher miniscrew placement reduced mesiodistal tipping of posterior teeth. On the buccopalatal plane, anterior teeth exhibited greater palatal movement when the miniscrew height was reduced, whereas an increased retraction hook height intensified palatal tipping of anterior teeth. Posterior teeth displayed more palatal tipping with a low retraction hook, and greater miniscrew height increased posterior palatal tipping when the hook length remained constant. On the vertical plane, a higher retraction hook induced more intrusion in anterior teeth. Additionally, when a low retraction hook was used, an increase in miniscrew height further enhanced anterior intrusion.
Conclusion: The force direction in en masse retraction should be optimized based on the desired movement in vertical, horizontal, and buccopalatal dimensions. According to the FEA findings, the low hook–low miniscrew combination resulted in maximum palatal crown tipping, while a high miniscrew position was beneficial for torque control by reducing palatal tipping. The low hook–high miniscrew configuration generated significant anterior intrusion, making it a suitable strategy for deep bite correction.
