| dc.description.abstract | In recent years, orthodontic miniscrew implantation is one of the most commonly used methods of orthodontic treatment. The failure rate of miniscrew implantation is about 20%. There are many reasons for failure, the most important being stability. In addition to the patient′s own problems, the design, material, implant angle and loading direction of the miniscrew are related to the stability. In this study, some important factors affecting the stability of miniscrew implants were discussed. Clinically, the implantation angle and loading mode of the miniscrew are very diverse. The simulation analysis in this study was divided into three implant angles (90°, 60° and 30°), with eight different loading directions. The material properties of the bones were set as isotropic or orthogonality, respectively, for comparison. Immediately after the insertion of the miniscrew, the fixation of the miniscrew to the bone can be divided into two stages. The first stage is the state of non-osseointegration at the time of implantation, and then the bone gradually grows into the implant over time and enters the second stage of osseointegration. The index of stability of implant was the deformation, equivalent stress and equivalent strain of miniscrew and bone. In addition, the lateral bending simulation analysis and experiment of the miniscrew implant were carried out to understand the stiffness of the implant, and the method of modifying the analytical model of artificial bone albinism was proposed.
The results showed that the deformation of the miniscrew was maximum at the implantation angle of 90° and minimum at 30°. The loading direction of the miniscrew should not be perpendicular to the implantation angle, otherwise it is easy to cause larger deformation of the miniscrew and larger maximum principal stress of the bone, resulting in the decrease of stability. The results of orthogonality in bone properties tend to be close to reality, while those of isotropy are underestimated. The displacement of the miniscrew is relatively large in the non-osseointegration state. In the state of osseointegration, the maximum principal stress of bone is relatively large. It shows that the stability of the miniscrew is poor without osseointegration. The simulated values of implant stiffness were significantly higher than the experimental values without considering the influence of bone autogenous layer. In this study, a modified model was proposed to adjust the size of the whitening area of the model and reduce the Young′s modulus of this area, so as to make the simulated stiffness value close to the experimental value. | en_US |