Arunchander, G J (2015) Evaluation of variables affecting distribution of stresses in orthodontic miniscrews and in surrounding cortical/cancellous bone: A Three Dimensional Finite Element Analysis. Masters thesis, Tamilnadu Government Dental College and Hospital, Chennai.
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Abstract
SUMMARY & CONCLUSION: Anchorage control is one of the challenges for an orthodontist. Efficient attainment and control of anchorage is fundamental to successful orthodontic and dentofacial orthopedic treatment. The clinical success of an implant is largely determined by the manner in which the mechanical stresses are transferred from the implant to the surrounding bone, without generating forces of a magnitude that would damage the integrity of the supporting bone and consequently the longevity of the implant. Hence, this study was carried out to evaluate the distribution of stresses in implants and in the bone surrounding the orthodontic implant, by testing various parameters that may affect the stability of the miniscrews in bone. The finite element method was chosen for this study because it has proven to be an useful non-invasive tool in examining the mechanical behaviour of bone, wherein complex structures are formulated as mathematical models in Ansys and Hypermesh software on a Windows platform were used to perform the study. The study was done by measuring the miniscrews and uploading the measurements to the solid works modeling software. The geometric models of the implant were thus obtained using the reverse engineering technique creating a 3D CAD mode. The 3D CAD models in .IGES format were subsequently uploaded to the meshing software Hypermesh CAE. A solid bone block of 20mm × 20mm × 10mm was constructed. The whole assembly of miniscrews and the bone block was imported into the finite element workbench Ansys. Various parameters that may affect the stability of miniscrews such as cortical bone thickness (anatomic variable), pitch, diameter, taper (design variables), insertion depth, angulation of force (clinical variables) were tested. A 2N force which is clinically desirable was applied to the miniscrews. All the three types of stress Maximum, Minimum, Von-mises stress were studied in all the simulations. Additionally the pattern of stress distribution was also studied. All the results were compared to the yield strength of the materials in the model (bone and titanium) was equated with those obtained from existing studies45. This data was compared with the maximal stress levels found in the simulations run in this study to determine if there is a significant chance for clinical failure of the implant or of the bone based upon the excessive stress levels. The following conclusions were obtained in the study: a) Between tapered and cylindrical implants no clinically relevant differences were seen in the stress levels obtained. b) The magnitude of stress generated did not exceed the yield strength of the material (bone, titanium) at all simulations except in the case of exposure length. c) The magnitude of stress was significantly higher in cortical bone than in cancellous bone for all the simulations. d) Of all the variables tested cortical bone thickness (anatomic variable) and exposure length (clinical variable) and diameter (design variable) played a very significant role in determining the magnitude of stress in bone. e) The neck of the implant showed the maximum stress in all the simulations.
| Item Type: | Thesis (Masters) |
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| Uncontrolled Keywords: | orthodontic miniscrews ; surrounding cortical/cancellous bone ; Three Dimensional Finite Element Analysis. |
| Subjects: | DENTAL > Orthodontics and Dentofacial Orthopedics |
| Depositing User: | Subramani R |
| Date Deposited: | 14 Oct 2018 19:41 |
| Last Modified: | 14 Oct 2018 19:41 |
| URI: | http://repository-tnmgrmu.ac.in/id/eprint/9894 |
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