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Formulation and Investigation of Thermal Behavior and Flexural Properties of PMMA Denture base Reinforced with Modified Nanoparticles m-HAP and m-MWCNTs

Shahkar, Lachin | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56131 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Nemati, Ali; Malek Khachatourian, Adrineh
  7. Abstract:
  8. This study investigates the effect of adding hydroxyapatite nanoparticles and multi-walled carbon nanotubes in pure and modified form on the flexural properties and hardness of denture base Polymethyl Methacrylate. Polymethyl Methacrylate (PMMA) is still the most common denture base material. In fact, the mechanical properties of this resin have played a significant role in expanding its use in dentistry. But in the long-term use of resins, defects such as low resistance to crack growth, low flexural strength and brittleness can be seen. In fact, flexural fatigue occurs as a result of repeated flexural stresses, and it can be described as the main reason for crack growth and propagation in stress concentration areas. Therefore, in order to achieve more fracture-resistant denture, there is a need to strengthen the mechanical properties, including the flexural strength of polymethyl methacrylate. In this research, the samples were prepared from commercial dental heat curing acrylic resin (Acrosun) with percentages of 3%, 5%, 10% of hydroxyapatite and 0.25%, 0.5% and 1% of multi-walled carbon nanotubes. First, hydroxyapatite powder was synthesized by sol-gel method and in order to analyzes the synthesized hydroxyapatite, simultaneous thermal analysis (STA) was performed. Then hydroxyapatite nanoparticles and carbon nanotubes were modified by triethoxyvinyl silane agent and XRD, FTIR and FESEM analyzes were used to examine the modified powders. Also, in order to investigate the thermal behavior and mechanical properties of nanocomposites, DSC thermal analysis, TGA, Three-point flexural test and Shore D hardness were used, respectively. Finally, in order to ensure the obtained data, the probability value of P-Value was calculated in the statistical hypothesis test. According to the results obtained from hydroxyapatite powder, the powder synthesis was observed in nano scale. Also, the successful surface modification of hydroxyapatite nanoparticles and carbon nanotubes was confirmed by XRD, FTIR and FESEM analyses. According to the results of DSC and TGA analysis, it was found that the interaction of modified nanoparticles and polymer chains improves the properties and flexural modulus of nanocomposites. So that, in the sample containing 3% modified hydroxyapatite and 0.25% modified carbon nanotubes, the flexural strength increased by 45% compared to the control sample, and in the sample containing 3% modified hydroxyapatite and 0.5% modified carbon nanotubes, the flexural modulus increased 71% compared to the control sample (Pvalue<0.01). The hardness of nanocomposites increased by about 10 units compared to the control sample, but there was no significant relationship between the hardness of nanocomposites (Pvalue>0.01)
  9. Keywords:
  10. Denture Base ; Hydroxyapatite ; Surface Modification ; Flexural Strength ; Carbon Nanotubes ; Poly Methylmethacrylate ; Thermal Behavior

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