Simulation of Mini-screw Fracture when Inserted into the Mandibular Body, through Finite Element Analysis

Abstract

Introduction: Finite element analysis helps to predict the stress, compression, and deformation of a body under load. Objective: To assess the fracture risk of a stainless steel mini-screw when inserted into the mandibular body using finite element analysis. Materials and Methods: A 3D-printed mandibular model was obtained from a CBCT of a patient with class III malocclusion. A 2 x 12 mm long stainless steel mini-screw was then inserted into the mandibular body of the model to simulate the same direction in the tomography; 150 slices were obtained from the volumetric tomography, which was imported into the InVesalius 3.1.1 program. The tension levels exerted at 10 N-cm and 14 N-cm were measured at 2, 4, 6, 8, and 10 mm depths, both in the mini-screw and in the bone of the insertion area of the mandibular body. Results: When the mini-screw was inserted at 2 mm depth, at 10 N-cm2 and 14 N-cm2, the mini-screw presented greater tension at the tip and the circumferential bone edge of the insertion. When inserted at 10 mm, the mini-screw received greater tension in the body's upper part and neck. In the images, we observed that the self-tapping mini-screw received greater tension at the neck and upper part of the body than the self-drilling mini-screws, which received tension at the tip. A greater statistically significant difference was shown at 14 N-cm2 compared to 10 N-cm2. Conclusions: It is suggested to use self-drilling stainless steel mini screws of 2 mm width and 12 mm length in the first instance, applying a force of 10 to 12 N cm² to achieve optimal stability, decreasing the force when fully inserting the mini screw to avoid fracture of its head.