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Design and Fabrication of Thermoelastic Nitinol Implant with Radius Variation for Denture Base Replacement

Karimi, Farzad | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 50684 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Sadrnezhad, Khatiboleslam
  7. Abstract:
  8. In this research to solve the problems related to titanium implants, a new type of dental implant was designed and fabricated by using shape memory and pseudoelasticity properties of porous nitinol alloys. The elastic modulus of this implant (equal to 0.8 GPa) is similar to the cancellous jaw bone (equal to 0.3-1 GPa) which causes a normal distribution of stress and prevents bone resorption. The current approach is use of radius variation to facilitate implant surgery. These radial changes are created by using one way shape memory effect. First, the implant enters the jaw cavity by decreasing the radius and after reaching the body temperature and restoring the initial shape, the radius of the implant increases and contacts the wall of the cavity. Considering the larger diameter of the implant's initial diameter in relation to the diameter of the jaw cavity, stress has been created that stabilizes the implant in the jaw cavity and activates the ossification cells. The amount of this stress depends on the initial diameter of the implant. In order to create mechanical properties like cancellous bone, in the manufacture of implant 70 volume percent of the urea space holder agent has been used. In order to improve the implant properties, the effect of porosity size on the properties of the shape memory alloy has been investigated. By increasing the size of the space holder agent, these results are obtained: The reduction in porosity from 72 to 67 volumes percent and consequently increase density from 1.78 to 2.12 grams per cubic centimeter, reducing the specific surface area from 5.2 to 3 square meters per gram, the increase of the start and finish temperatures for the transformation of martensite to austenite from 8 to 13 and 33 to 42 degrees Celsius and for the transformation of austenite to martensite from -25 to 4 and -44 to -28 degrees Celsius and increasing the percentage of recoverable superelastic strain. Due to changes in density, the changes of the elastic modulus and the compressive strength are not regular, but it can be said that here with increasing size of the space holder agent, these properties are reduced. Finally, Abacus software and the mechanical model of porous shape memory alloy have been used to design the implant dimensions. First, the model was evaluated with experimental data and then by using it, the radius change of the implant was simulated in the jaw cavity
  9. Keywords:
  10. Shape Memory Alloy ; Dental Implant ; Nitinol Alloy ; Superelasticity ; Simulation ; Porous Implants ; Porosity Size

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