Saudi Cultural Missions Theses & Dissertations
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Item Restricted The effect of surface treatment on the adhesive strength of chairside hard liners to dental polymers used for the conventional, additive, and subtractive fabrication of complete dentures(The Ohio State University, 2022) Aldosari, Abdullah Mohammed A; Azer, Shereen S.; Schricker, Scott R.; Lee, Damian J.Objectives: The aim of this in vitro study was to evaluate the tensile bond strength of two hard denture relining materials on denture bases fabricated from conventional, subtractive, and additive polymers. In addition, this study assessed the effect of a polymer to resin primer on the tensile bond strength of hard denture liners to different denture bases. Methods: A total of 120 hard relined denture base samples were fabricated, 40 per denture base group (Lucitone 199, Ivo Base CAD, and NextDent Denture 3D+). For each denture base group 20 samples were hard relined with one of two chair side hard denture liner (GC Reline, MucoHard). Among the hard reline groups, 10 of each group was primed with a composite to PMMA primer (Visio.link). All samples underwent thermocycling. The adhesive strength was evaluated through tensile testing. The surface contact angle was measured on each denture group sample to evaluate the wettability of the material. The data was analyzed using Inverse-variance weighted linear regression. Results: In this study overall the denture bases relined with MucoHard denture liner had significantly higherbond strength than the GC reline groups (P<0.016). The highest tensile bond strength was achieved by combining MucoHard denture liner and primed 3D printed denture base, followed by the non-primed conventional denture base, and non-primed milled denture base to MucoHard denture liner. The surface primer used in this study (Visio.Link primer, Bredent UK Ltd. Chesterfield, UK.) had a significant effect on the tensile bond strength of all tested groups (P<0.0003). However, the primer only positively influenced the bond strength of the 3D printed denture base to MucoHard denture liner, while the other groups were inversely affected. Conclusion: There was no significant difference in the tensile bond strength of chairside denture liners to denture bases fabricated using additive, subtractive, and conventional methods (P>0.05). The highest bond strength was achieved with the combination of MucoHard denture liner and primed 3D printed denture bases. MucoHard denture liner has overall significantly higher tensile bond strength in comparison to GC reline. (P<0.016) The primer only positively influenced the bond strength of MucoHard to 3D printed denture bases. The primer significantly alters the wettability of the denture bases.53 0Item Restricted Design and rapid prototyping of orthopaedic device for lower limb fractures(The University of Manchester, 2024-05-31) Alqahtani, Mohammed; Bartolo, PauloBone fractures are a prevalent occurrence on a daily basis, posing significant challenges to healthcare systems in terms of hospital admissions, surgical procedures, and medication requirements. These fractures primarily result from either pathological conditions or highenergy trauma, including incidents such as car accidents, falls, and natural disasters. The treatment of bone fractures necessitates the use of bone fixation devices, which can be either internal or external, to provide stability to the injury, promote bone healing, and enable the patient to regain full functionality. The current designs of fixation devices, along with the materials utilised in their manufacturing, lead to fixators that are excessively heavy, lack comfort and lack of customisation to meet the unique requirements of individual patients. These concerns highlight the necessity of continued progress in the development of fixation devices to achieve improved and personalised medical treatments, with the aim of enhancing clinical outcomes and reducing costs. Therefore, the aim of this research project is to overcome the identified limitations by developing an innovative, customised, and optimised bone fixation system that is both costeffective and lightweight, while ensuring its structural integrity through the utilisation of topology optimisation, polymeric material and additive manufacturing. The bone fixation systems were successfully optimised, taking into consideration various loading conditions and mass reduction values. Fused deposition modelling additive manufacturing was employed to fabricate the optimised models. Subsequently, the bone fixation systems underwent numerical and mechanical evaluation and validation. The results indicate that an increase in mass reduction leads to higher stress and displacement, which can be attributed to material removal. Furthermore, it was observed that these optimised systems possess adequate mechanical characteristics, as evidenced by the IFM falling within the acceptable range and the stresses generated in the system remaining below the yield strength. This demonstrates the potential of utilising polymeric materials and topology optimisation in the development of bone fixation devices. This research presents a novel approach involving the use of polymeric materials and topology optimisation to create custom fixation devices tailored to individual patient anatomy. This is the first type of fixation that could represent a potential alternative to the existing conventional fixations, offering promising prospects.7 0Item Restricted Evaluation of 3D printed shielding for radiotherapy patients with skin cancer(The University of Sydney, 2024-05-24) Bakhaydhir, Bashaer; Hill, RobinLead (Pb) shielding presents considerable health and environmental risks, prompting the need to investigate alternative materials. This study evaluates the effectiveness of W-PLA and Cu-PLA as 3D printed composite shielding materials upon the standard shielding for skin cancer radiotherapy. Five beam qualities (80-150 kVp) were used in this study, which were generated by an XSTRAHL 150 x-ray unit. The investigation involved various dosimetric measurements for all three shielding materials, including half-value layer (HVL) and relative output factors (ROF) measured by an Advanced Markus ionization chamber and Gafchromic EBT3 radiochromic film. This included determining the required thickness of each material to achieve 5% transmission as required for shielding to the patient to minimize the dose to healthy tissue. HVL and W-PLA transmission measurements were verified through Monte Carlo calculations using SpekPy to generate beam spectra. While the results indicate that both 3D printed materials require larger thicknesses for 5% transmission, only 1 mm thickness of W-PLA provided ≤ 4% transmission across all beam energies tested. In contrast, up to 16 mm of Cu-PLA is required, demonstrating its suitability for lower beam energies only. This study supports the integration of custom 3D printed materials into radiotherapy shielding, eliminating exposure to Pb toxicity.34 0