Finite Element Comparison of 10 Orthodontic Microscrews with Different Cortical Bone Parameters
Jordi Marcé-Nogué, PhD/Andre Walter, MD, DDS, MS/Lluís Gil, PhD/Andreu Puigdollers, PhD
Purpose: Unlike standard dental implants, the stabilization of orthodontic microscrews removed after treatment is done without osseointegration and achieved by several components: cortical bone thickness (CBT), microscrew geometry, and drilling depth. The purpose of this study was to evaluate 10 different microscrews and the influence of their geometric parameters with different CBT and drilling depths. Materials and Methods: The influence of geometric parameters in cortical bone was analyzed with a series of computational simulations with finite element models to obtain von Mises stresses and deformations in the microscrew when loaded with a perpendicular traction force of 1 N and considering the angle of incidence as a random parameter. Results: There was variability in the angle of incidence, with less clinical influence. Biomechanical parameters such as microscrew diameter, CBT, and drilling depth had significant influences on the results. At a drilling distance of 8 mm, narrow microscrews (Abso Anchor 1.2) showed maximum von Mises stress of 500.698 MPa and maximum deformation in the shank of 0.08549 mm. Microscrews with a diameter of 1.5 mm (Dentaurum, Jeil, Mondeal, Tekka, Spider) showed von Mises stresses ranging from 56.97 to 136 MPa and deformation between 0.0062055 and 0.0476 mm. Microscrews with a diameter of 2.0 mm (Jeil, Mondeal, Tekka) showed von Mises stresses ranging from 17.172 to 54.861 MPa and deformation of 0.000172 to 0.0161 mm. Conclusions: The shape and geometry of an orthodontic microscrew are highly important in its behavior. Optimal characteristics of a microscrew would include a diameter of 2.0 mm, a cylindric shape, a short and wide head, a short and wide shank, and threads of an appropriate size.