Analysis of insertion torque of inter- and intra-radicular (buccal shelf, palatine and infrazygomatic) orthodontic mini implants using experimental and the Finite Element Method

• Grant number: 23/16227-6
• Support Opportunities: Regular Research Grants
• Start date: December 01, 2025
• End date: May 31, 2028
• Field of knowledge: Engineering - Mechanical Engineering - Mechanics of Solids
• Principal Investigator: Bruno Agostinho Hernandez
• Grantee: Bruno Agostinho Hernandez
• Host Institution: Faculdade de Engenharia (FE). Universidade Estadual Paulista (UNESP). Campus de Bauru. Bauru , SP, Brazil
• Associated researchers: Edson Antonio Capello Sousa ; Josete Barbosa Cruz Meira ; Omar Melendres Ugarte ; Rafael Yagüe Ballester ; Sabina Gheduzzi

Abstract

Introduction. Orthodontic Mini-Implants (OMIs) have been increasingly used as temporary orthodontic anchorage devices. However, there is still a high number of failures related to a lack of anchorage and stability of this device. Studies have shown that there may be a relationship between the insertion torque of the mini-implant and its primary and secondary stability, but few studies have analysed this issue in depth or evaluated the relationship of insertion torque with deformation in the peri-implant bone. Additionally, few studies have examined insertion in specific regions and with different bone characteristics. Aims. This project aims to evaluate, using experimental methods and finite element models, the insertion torque of mini-implants placed in inter-radicular and extra-radicular regions (palatal, infrazygomatic, and buccal shelf), its relationship with bone deformation in the peri-implant tissue, and to examine the behaviour of mini-implants when subjected to various types of orthodontic loadings. Materials and Methods. Mini-implants will be inserted into representative synthetic bones of inter and extra-radicular regions (palate, buccal shelf, and infrazygomatic) and the insertion torque will be monitored. The intended insertion depth will be 4 mm for inter-radicular mini-implants, 6 mm for extra-radicular mini-implants, and 6 and 8 mm for palatal mini-implants. The mini-implant should rotate 1 turn and for each 0.6 mm deep. After insertion, pull-out tests will be conducted to evaluate the degree of stability of the mini-implant. Geometrical (Rhinoceros, Robert McNeel & Associates, USA) and finite element models (Ansys, Ansys Inc., USA) will be developed to represent the experimental procedures of mini-implant insertion, and the torque obtained in the model will be compared with the experimental one, validating the finite element model. Sequentially, the mechanical properties of the synthetic bone in the model will be changed to those of the real mandibular bone obtained by a systematic review. The (energies of) deformations caused by the torque in the peri-implant bone will then be analysed and whether these are within the range of bone response representative of the applied load. Finally, through finite element models, it will be evaluated whether the types of loading to which the mini-implants are subjected influence the peri-implant bone region. Results. There is some uncertainty in the relationship between insertion torque and stability in mini-implants. This project aims to contribute more to the studies in this area through the execution of experimental practices combined with finite element simulations, which, based on the authors' knowledge, has not yet been conducted. It is expected to understand, in a greater depth, whether there is a connection between torque and mini-implant stability and the deformations in the peri-implant tissue. (AU)