Problem statement: The advent of 3D-printing technology has brought a revolution in the field of dentistry, offering a quick, reliable, and economical method for fabricating various dental appliances, including denture bases. Nevertheless, the mechanical and physical properties of 3D-printed denture base materials tend to be relatively poor compared to conventional denture base materials. On the other hand, the printing parameters such as printing orientation, layer thickness, light wavelength, curing time etc. can affect the properties of the printed resin. Furthermore, the denture base materials are prone to attract micro-organism resulting in oral diseases like denture stomatitis. To counter this, metal or metal oxide nanoparticles were incorporated into the denture base materials to create an innovative nanocomposite material that displays enhanced physical, mechanical and biological characteristics. Aim: This research aimed to optimise the printing parameters, and to develop a novel denture base nanocomposite material by infusing varying concentrations of TiO2 nanoparticles with 3D-printed denture base resin. The study also intended to evaluate their mechanical, physical, and biological properties, and to investigate the effect of hydrolytic ageing in artificial saliva on the mechanical properties. Methods: Initially, various printing parameters were examined to ascertain the ideal print settings encompassing different printing orientations (0°, 45°, 90°) and different curing times (20, 30, 50 min) in relation to the unmodified 3D-printed denture base resin (NextDent). Following this, the optimal printing parameters were applied to evaluate the physical and mechanical properties of the unmodified 3D-printed denture base resin in terms of degree of polymerisation, sorption, solubility, flexural strength, flexural modulus, Vickers hardness, Martens hardness, and impact strength to compare the 3D-printed resins (NextDent® and Formlabs®) with conventional heat-cured resin (Schottlander®) as a control. The specimens were subsequently exposed to hydrolytic ageing in artificial saliva for a three-month duration. After this period, the mechanical properties were re-examined to assess the effect of ageing. Next, the 3D-printed resin (NextDent®) was reinforced with different concentrations (0.10, 0.25, 0.50, and 0.75 wt.%) of silanated TiO2 nanoparticles. The resultant nanocomposite materials were then characterised in terms of degree of conversion, sorption/solubility, Vickers hardness, Martens hardness, flexural strength/modulus, impact strength, antifungal properties, cytotoxicity, and biocompatibility. These properties were compared with the unmodified 3D-printed resin (NextDent®) and conventional heat-cured resin (Schottlander®) materials as controls. Following exposure to artificial saliva ageing, the nanocomposites were re-evaluated in terms of the mechanical properties. The fractured surface was also analysed using an optical and scanning electron microscopes. Results: The results showed that 90° printing orientation produced significantly higher values of flexural strength, Vickers hardness, and water sorption compared to a 0° orientation (p 0.05). Notwithstanding, a post-curing time of 30 minutes yielded marginally improved characteristics compared to 20 min, with no detectable difference observed with 50 min. After establishing the optimal printing parameters and using them to compare 3D-printed materials with conventional heat-cured resin, the data demonstrated that 3D-printed resins had significantly higher sorption values than the control (p0.05). There were no significant differences in Vickers and Martens hardness, or impact strength, among the materials tested. However, the 3D-prin
| Date of Award | 31 Dec 2023 |
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| Original language | English |
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| Awarding Institution | - The University of Manchester
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| Supervisor | Julfikar Haider (Supervisor), Hugh Devlin (Supervisor) & Nick Silikas (Supervisor) |
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