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Purpose: To evaluate and compare the effects of glass fiber (GF), Zirconium oxide nanoparticles (nano-ZrO2 ), and silicon dioxide nanoparticles (nano-SiO2 ) addition on the flexural strength and impact strength of repaired denture base material.
Materials and Methods: Heat-polymerized acrylic resin specimens were fabricated. All specimens were sectioned centrally and beveled creating 2.5 mm repair gap except for 10 controls. Specimen grouping (n = 10/group) was done according to filler concentration of 0%, 0.25%, 0.5%, and 0.75% of auto-polymerized acrylic powder. Modified resin was mixed, packed in the repair gap, polymerized, finished and polished. Three-point bending test and Charpy type impact testing were done. Data were analyzed using one-way-ANOVA and Post-Hoc Tukey test (α = 0.05).
Results: All additives significantly increased flexural strength and impact strength (p < 0.05). Within the modified subgroups, no significant differences were found for GF. Significant increase for nano-ZrO2 and significant decrease for nano-SiO2 as the concentration of additive increased were noted for both flexural strength and impact strength. Highest flexural strength was found with 0.75%-nano-ZrO2 (69.59 ± 2.52MPa) and the lowest was found with 0.75%-nano-SiO2 (53.82 ± 3.10MPa). The 0.25%-nano-SiO2 showed the highest impact strength value (2.54 ± 0.21 kJ/m2 ) while the lowest impact strength value was seen with 0.75%-nano-SiO2 (1.54 ± 0.17 kJ/m2 ).
Conclusion: Nano-filler effect was concentration dependent and its addition to repair resin increased the flexural and impact strengths. The incorporation of 0.75%-ZrO2 or 0.25%-SiO2 into repair resin proved to be a promising technique to enhance repair strength and avoid repeated fractures.
(© 2019 by the American College of Prosthodontists.)
Purpose: To evaluate the combined effect of mechanical surface treatment with intermediate bonding agents (methyl methacrylate [MMA] and silane coupling agents) and ZrO2 nanoparticle (nano-ZrO2 ) addition to repair material on the shear bond strength (SBS) of repaired denture bases.
Materials and Methods: Heat-polymerized acrylic resin was used to fabricate 130 cylindrical blocks (15 mm × 10 mm) and divided into a control group without treatment (C, n = 10), and 3 repair groups (n = 40/group) divided into specimens treated with alumina blasting alone (AB), specimens blasted with alumina combined with silane coupling agent (AB + SCA), or combined with MMA-based composite bonding agent (AB + MA). Treated groups were further subdivided according to nano-ZrO2 concentrations into 0 wt%, 2.5 wt%, 5 wt%, and 7.5 wt% added to repair resin powder. Repair resin monomer and polymer were combined and packed on the repair area and then placed in a pressure pot at 37°C for 15 minutes for polymerization. Shear bond test was performed using a universal testing machine. Scanning electron microscopy (SEM) was used to examine the effect of surface modifications on repair surfaces and to evaluate the topography of fracture surfaces. Tukey-Kramer multiple-comparison test was used to detect significant differences between groups (p ≤ 0.05).
Results: SBS (MPa) of specimens treated with alumina blasting and application of intermediate agents were significantly higher than the control group (p < 0.05), while no significant differences were found between AB and control group (p > 0.05). Nano-ZrO2 addition significantly increased SBS except for AB, and 5%, 7.5% MA (p > 0.05). SEM evaluation showed that alumina blasting created rougher and more porous surfaces, while SCA and MA reduced the irregularities and fissures.
Conclusion: Application of bonding agents to repair surfaces after alumina blasting improved the repair bond strength and proved to be a possible new adhesive method for denture repair. Moreover, nano-ZrO2 addition in combination with surface treatment improved the repair bond strength.
(© 2018 by the American College of Prosthodontists.)
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