| Polymethyl methacrylate(PMMA) has been commonly used in dentistry as a denture base material in service. PMMA shows sufficient material properties and ease of application. However, due to its very limited fracture toughness and anti-fatigue properties, the fracture of the PMMA denture has been frequently noticed after certain period of clinical service. In literature, various methods have been employed to enhance the flexural strength of PMMA. The present study analyzed the effects of reinforcing methods on the flexural strength of PMMA with the aim to optimize the material properties and to provide patient satisfaction.Part 1 Effects of stainless wires on the flexural strength of polymethyl methacrylate denture resinsExperiment 1 Effects of the cross sectional area of the embedded stainless wires on the flexural strength of polymethyl methacrylate denture resinsObjectives:This part of the experiment aimed to evaluate the effects of the cross sectional area of the embedded stainless wires on the flexural strength of polymethyl methacrylate denture resinsMaterials and methods:Forty-eight bar-shaped specimens were fabricated using the PMMA materials. The specimens of standard dimensions(specimen size: 64 X 10 mm X 3.3 mm) were prepared for each of the 4 groups(n=12): unreinforced PMMA resin and PMMA resin reinforced with 3 types of stainless wires(0.8 mm in diameter, 0.9 mm in diameter, and 1.2 X 0.7 edgewise). Six specimens of each group were randomly selected and submitted to the flexural strength test. The remaining 6 specimen of each group were thermal cycled and then submitted to the flexural strength test. All the data were recorded and statistically analyzed.Results:After stainless wire reinforcements, the flexural strength of the PMMA materials were statistically improved regardless they were thermal cycled or not. Although no statistical significances were found, specimens reinforced with 1.2 X 0.7 mm edgewise wire exhibited highest flexural strength. Significant aging effects were noticed for all the specimens submitted to thermal cycling. The reinforcement of denture base resin with 1.2 X 0.7 mm edgewise wire may be a useful means of strengthening denture bases.Experiment 2 Effects of the quantity of the embedded stainless wires on the flexural strength of polymethyl methacrylate denture resinsObjectives:This part of the experiment aimed to evaluate the effects of the quantity of the embedded stainless wires on the flexural strength of polymethyl methacrylate denture resinsMaterials and methods:One hundred and fifty-six bar-shaped specimens were fabricated using the PMMA materials. The specimens of standard dimensions(specimen size: 64 X 10 mm X 3.3mm) were prepared for each of the 13 groups(n=12): unreinforced PMMA resin and PMMA resin reinforced with 1-4 pieces of Φ0.8 mm, Φ0.9 mm, or 1.2 X 0.7 mm edgewise stainless wires. Six specimens of each group were randomly selected and submitted to the flexural strength test. The remaining 6 specimen of each group were thermal cycled and then submitted to the flexural strength test. All the data were recorded and statistically analyzed.Results:After stainless wire reinforcements, the flexural strength of the PMMA materials were statistically improved regardless they were thermal cycled or not. When 1-3pieces of stainless wire were embedded as reinforcements, positive linear relationship between the quantity of the wire and the flexural strength of the PMMA materials were found for all the experimental groups. However, the flexural strength of the specimens reinforced with 4 pieces of stainless wires was significantly lower compared with the negative controls.Experiment 3 Effects of the different surface treatments of the embedded stainless wires on the flexural strength of polymethyl methacrylate denture resinsObjectives:This part of the experiment aimed to evaluate the effects of the different surface treatments of the embedded stainless wires on the flexural strength of polymethyl methacrylate denture resinsMaterials and methods:One hundred and forty-four bar-shaped specimens were fabricated using the PMMA materials. The specimens of standard dimensions(specimen size: 64 X 10 mm X 3.3mm) were all reinforced with 3 pieces of Φ0.8 mm, Φ0.9 mm, or 1.2 X 0.7 mm edgewise stainless wires for each of the 4 groups(n=12). The embedded stainless wires of each group were received one of the following surface treatments: no surface treatment(control), treated with alloy primer only, sandblasting only, and sandblasting followed by applying alloy primer. Six specimens of each group were randomly selected and submitted to the flexural strength test. The remaining 6specimen of each group were thermal cycled and then submitted to the flexural strength test. All the data were recorded and statistically analyzed.Results:After stainless wire reinforcements, the flexural strength of the PMMA materials were statistically improved regardless they were thermal cycled or not. The optimum surface treatment for reinforcing wire was sandblasting followed by applying alloy primer. The reinforcement of denture base resin with surface-treated 1.2 X 0.7 mm edgewise wire may be a useful means of strengthening denture bases.Part 2 Effects of the different reinforcements on the flexural strength of polymethyl methacrylate denture resinsObjectives:This part of the experiment aimed to evaluate the effects of the different reinforcements on the flexural strength of polymethyl methacrylate denture resinsMaterials and methods:Forty-eight bar-shaped specimens were fabricated using the PMMA materials. The specimens of standard dimensions(specimen size: 64 X 10 mm X 3.3 mm) were prepared for each of the 4 groups(n=12): unreinforced PMMA resin and PMMA resin reinforced with stainless mesh, quartz fiber mesh, and surface-treated 1.2 X 0.7mm edgewise stainless wire. Six specimens of each group were randomly selected and submitted to the flexural strength test. The remaining 6 specimen of each group were thermal cycled and then submitted to the flexural strength test. All the data were recorded and statistically analyzed.Results:After stainless wire and quartz fiber mesh reinforcements, the flexural strength of the PMMA materials were statistically improved regardless they were thermal cycled or not. The optimum surface treatment for reinforcing wire was sandblasting followed by applying alloy primer. The reinforcement of denture base resin with surface-treated 1.2 X 0.7 mm edgewise wire may be the optimum means of strengthening denture bases.Conclusions:Within the limitations of the present study, the conclusions can be drawn as follows:1. The reinforcement of denture base resin with surface-treated stainless wire may be the optimum means of strengthening denture bases. There were positive relationship between the cross sectional area of the reinforcing wire and the flexural strength of the PMMA materials. Meanwhile, significant positive correlation were found between the quantity of the wires and the flexural strength of the PMMA materials.2. Quartz fiber mesh could be a useful alternative reinforcing methods of strengthening denture bases.3. After thermal cycling, significant aging effects were found on the PMMA materials. Reinforcing the PMMA materials with stainless wire and quartz fiber mesh was beneficial to their anti-aging properties. |
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