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.

Objective The objective of this study was to evaluate the effect of nano-SiO2 addition on the flexural strength (FS) of repaired acrylic denture base. Materials and Methods Heat-polymerized acrylic resin specimens were fabricated in dimensions of (65 × 10 × 2.5 ± 0.1 mm3 ) and then sectioned and prepared, creating repair gap with butt (90 degrees) and bevel (45 degrees) repair surface designs forming two main groups according to joint design. Further subdivision was done into four groups (n = 10) according to nano-SiO2 concentration: one unmodified group and three modified groups (0.25, 0.5, and 0.75 wt %) in the autopolymerized repair resin. Each pair of a specimen was assembled in a mold and repaired according to manufacturer’s recommendations. Statistical Analysis Three-point bending test was done to measure FS, followed by scanning electron microscope (SEM) examination for fracture surface analysis. Data were analyzed using ANOVA and Tukey’s post hoc test (α = 0.05). Results The addition of nano-SiO2 significantly improved FS of repaired acrylic resin in comparison to the unmodified group (p ˂ 0.05). For butt joint, significant differences between nano-SiO2 reinforced groups were noticed (p ˂ 0.05), while reinforced beveled groups did not differ significantly (p ˃ 0.05). Bevel design remarkably increased FS compared with butt design per respective filler concentration. From the SEM images, improved FS was presented with a homogeneous distribution of nano-SiO2 within polymethyl methacrylate. Conclusion Nano-SiO2 addition to repair resin and 45 degree-beveled repair surface increased FS of repaired acrylic resin.

Purpose:To evaluate the combined effect of mechanical surface treatment with intermediate bonding agents (methyl methacrylate [MMA] and silane coupling agents) and ZrO 2 nanoparticle (nano-ZrO 2 ) 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-ZrO 2 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 multiplecomparison 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-ZrO 2 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-ZrO 2 addition in combination with surface treatment improved the repair bond strength.