SACM - United Kingdom
Permanent URI for this collectionhttps://drepo.sdl.edu.sa/handle/20.500.14154/9667
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Item Restricted Comparison of an experimental single application two-step 25600 ppm Ammonium Fluoride / 34100 - 48600 ppm Nano-Calcium Fluoride solution vs. a one-step 7700 ppm Ammonium Fluoride varnish for Preventing Enamel Loss from Erosion and Attrition in vitro(King’s College London, 2024) Almejrad, Lamya; Austin, Rupert; Bartlett, DavidIntroduction: The potential for high-fluoride treatments to prevent progression of erosion and attrition is not fully understood. This thesis investigated the effect of an experimental two-step ammonium fluoride/nano-calcium fluoride formulation (25600 ppm NH4F plus 34100 - 48600 ppm CaF2) versus a single-application one-step 7700 ppm ammonium fluoride (NH4F) varnish on step height loss (μm) of polished and natural human enamel undergoing erosion and attrition in vitro. Material and methods: Three restorative dental materials and human enamel (Occlusal vs. Buccal) samples were used to validate the attrition simulation method. Samples were subjected to attritional wear using leucite-reinforced CAD/CAM ceramic antagonists in an electrodynamic wear simulator (200 cycles, 80 N load, 0.7 mm horizontal slide). Following validation, polished and natural (unpolished) enamel samples were pre-treated with either deionized water (DIW negative control), NH4F varnish (positive control) or a two-step NH4F/CaF2 solution. After surface wiping, samples were subjected to erosion (0.3% citric acid solution immersion, pH 3.8, for 5, 10, 15, 20 and 60 minutes) and attrition (200 strokes). Enamel wear was measured using non-contact laser profilometry (NCLP). Enamel surface and sub-surface mechanical testing was conducted using micro- and nanoindentation. Enamel surface and sub-surface qualitative examination was conducted using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Results: The attrition method revealed that the glass ionomer material experienced the most wear, measuring 177.8 μm (±16.9). This was significantly more than the fine particle composite, which showed 22.2 μm (±1.3) of wear, and the micro-filled composite, which had the least wear at 13.6 μm (±1.02) (P < 0.001). Enamel samples from buccal vs. occlusal sources experienced non-significantly different step height enamel wear (P<0.05). The attrition wear generation was consistent with co-efficient of variation <10%. Polished enamel samples treated with surface fluoride treatments showed significantly reduced step height enamel loss vs. control (p<0.001): Mean (SD) enamel loss for DIW treatment was 1.97 μm (±0.14) after erosion and 36.55 μm (±1.79) after erosion/attrition. NH4F treatment reduced loss to 0.58 μm (±0.08) after erosion and 32.71 μm (±2.63) after erosion/attrition (p<0.001). NH4F/CaF2 treatment further reduced loss to 0.41 μm (±0.06) after erosion and 24.08 μm (±3.15) after erosion/attrition (p<0.001). This was supported by the microhardness data: fluoride-treated enamel experienced reduced hardness changes following both erosion and erosion/attrition vs. non-fluoride treated enamel (p<0.001). For natural enamel, the experimental NH4F/CaF2 solution significantly reduced enamel loss after all erosion durations (5, 20, 60 minutes) and after 200 strokes of attrition. After 5 minutes of erosion, enamel loss compared to DIW was significantly reduced (p<0.001). Mean (SD) enamel loss in the NH4F/CaF2 treated group was reduced to 0.21 μm (±0.13) after erosion and 9.82 μm (±1.46) after erosion/attrition in comparison with DIW treated groups which was 0.79 μm (±0.32) after erosion and 15.58 μm (±2.49) after erosion/attrition. The surface and sub-surface SEM and EDS data supported these findings. Conclusion: The two-step ammonium fluoride solution (NH4F/CaF2) reduced step height enamel loss and hardness changes occurring in polished and natural enamel during simulated erosion and attrition in vitro.17 0Item Restricted Physico-mechanical characterisation of polymeric CAD/CAM materials for aesthetic and prosthetic applications(2023-06-28) Babaier, Rua; Silikas, Nick; Watts, DavidPolymer-based CAD/CAM blocks have been suggested as a viable metal-free alternative to meet the needs of aesthetics, biomimetics, and minimally invasive dentistry. Therefore, this research characterised various optical, surface, and mechanical aspects of new reinforced polymeric CAD/CAM materials, subdivided based on their clinical applications into aesthetic (Part I) and prosthetic (Part II) sections. The blocks investigated for Part I were three resin composites, one polymer-infiltrated ceramic network (PICN), and one feldspathic ceramic; for Part II, three high-performance polymer (HPP) composites, which included two fibre-reinforced composites (TRINIA, TR, and CarboCAD 3D Dream Frame, CC), and one ceramic-filled polyetherether ketone (DentoKeep, PK). For Part I, firstly, thickness-dependent apparent radiopacity and material composition were investigated for five aesthetic blocks versus that of direct resin-based substrates. PICN appeared relatively radiolucent even at 2.5 mm thickness, posing challenges for its identification from tooth structure and other substrate materials, such as luting cements. Secondly, material- and thickness-dependent translucency, blue-light transmittance, and its consequences on polymerising two IvocerinTM-containing luting cements (light-cured, LC, and dual-cured, DC) were investigated after 1 h of irradiation through four CAD/CAM substrates. PICN showed the least favourable optical features, resulting in significantly lower hardness of the underlying DC cements. Overall, LC cement exhibited greater early hardness compared to DC, irrespective of the substrate thickness. For Part II, the surface and mechanical stability of HPP composites were examined after 1 and 7 days of ageing in three food-simulating solvents (water, 70% ethanol/water, and MEK). Significant material variations in terms of microstructural composition have reflected on the properties investigated, such as roughness, hardness, flexural strength, and fracture toughness. In comparison to TR and CC, PK demonstrated relative stability after accelerated aging. CC and TR were sufficiently strong at sections as thin as 1 mm. However, their increased deterioration in FSLs requires full protection with a veneer material. This research concludes that although initial results were promising, more material enhancement and a review of the currently proposed clinical applications are necessary.13 0