Abstract
BackgroundThe purpose of this study was to evaluate the stress patterns produced in mini-implant and alveolar bone, for various implant dimensions, under different directions of simulated orthodontic force, using a three-dimensional finite element method.MethodsEight finite element (FE) models of mini-implant and bone were generated with insertion angles of 30° and 60°, diameters of 1 and 1.3 mm, and lengths of 6 and 8 mm. A simulated constant orthodontic force of 2 N was applied to each of these FE models in three directions simulating anterior retraction, anterior intrusion and retraction, and molar intrusion.ResultsComparison of the maximum von Mises stress in the mini-implant showed that the 1-mm diameter produced significantly high stress, and the amount of stress produced was more for a mini-implant inserted at an angle of 60°. The cortical bone showed that high stresses were generated for the 1-mm-diameter mini-implant and on increasing the insertion angulation from 30° to 60°, the stress produced increased as well. The comparison of von Mises stress in the cancellous bone was insignificant as the amount of stress transmitted was very low.ConclusionsThe 1-mm-diameter mini-implants are not safe to be used clinically for orthodontic anchorage. The 1.3 × 6 mm dimension mini-implants are recommended for use during anterior segment retraction and during simultaneous intrusion and retraction, and the 1.3 × 8 mm dimension mini-implant is recommended for use during molar intrusion. All mini-implants should be inserted at a 30° angle into the bone for reduced stress and improved stability.
Highlights
The purpose of this study was to evaluate the stress patterns produced in mini-implant and alveolar bone, for various implant dimensions, under different directions of simulated orthodontic force, using a three-dimensional finite element method
The present study involves the consideration of four primary elements in the development of the threedimensional finite element model: (1) mini-implant design—which includes the length, diameter, and pitch of the screw; (2) geometry of the mini-implant and bone structures—the geometry and design of the miniimplant head and taper and the thickness of cortical and cancellous bones to be modeled; (3) establishment of three-dimensional finite element model of the miniimplant—i.e., FE model of the mini-implant inserted in bone; and (4) material properties—Poisson’s ratio and Young’s modulus for the mini-implant and cortical and cancellous bones
Within the limitations of this study, the following conclusions were drawn: 1. The comparison of the maximum von Mises stress in the mini-implant showed that the 1-mm diameter produced significantly high stress and the amount of stress produced was more for a mini-implant inserted at an angle of 60°, with the stress being concentrated at the neck and head of the mini-implant, immaterial of length 6 mm or 8 mm
Summary
The purpose of this study was to evaluate the stress patterns produced in mini-implant and alveolar bone, for various implant dimensions, under different directions of simulated orthodontic force, using a three-dimensional finite element method. The FE method is way of getting a numerical solution to a specific problem. It involves cutting a structure into several smaller pieces to describe the behavior of each element in a simplified way and reconnecting them at nodal points. These devices are used for specific periods of time and rely only on mechanical retention with the surrounding bone. It is imperative that mini-implants remain stable during their period of use to provide sufficient anchorage during treatment
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