Effect of conventional water-bath and experimental microwave polymerization cycles on the flexural properties of denture base acrylic resins (original) (raw)
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Chemical Industry
Acrylic restorations in the mouth are exposed to strong occlusal forces. Their mechanical properties depend on the type and method of their polymerization. The aim of this study is a comparative analysis of mechanical properties (flexural strength and modulus of elasticity) of acrylic materials before and after the post-polymerization treatments (water boiling, microwave irradiation and water storage). The study included denture base resins, as well as an acrylate for orthodontic appliances impregnated with aesthetic beads. Flexural strength, modulus of elasticity and the deflection were measured immediately after polymerization, after a hot and microwave post-polymerization and after immersion in a water bath at the temperature of 37?C. The applied post-polymerization methods resulted in an increase in flexural strength and modulus of elasticity relative to the initial values for all tested materials. Being aware of the reduction in fracture risk of dental prosthesis after a propos...
Flexural strength of acrylic resins polymerized by different cycles
Journal of Applied Oral …, 2007
Despite the large number of studies addressing the effect of microwave polymerization on the properties of acrylic resin, this method has received limited clinical acceptance. This study evaluated the influence of microwave polymerization on the flexural strength of a denture base resin. A conventional heat-polymerized (Clássico), a microwave-polymerized (Onda-Cryl) and a autopolymerizing acrylic (Jet) resins were used. Five groups were established, according to polymerization cycles: A, B and C (Onda-Cryl, short cycle 500W/3 min, long 90W/13 min + 500W/90 sec, and manufacturing microwave cycle - 320W/3 min + 0W/3 min + 720W/3 min); T (Clássico, water bath cycle 74ºC/9h) and Q (Jet, press chamber cycle 50ºC/15 min at 2 bar). Ten specimens (65 x 10 x 3.3mm) were prepared for each cycle. The flexural strength of the five groups was measured using a three-point bending test at a cross-head speed of 5 mm/min. Flexural strength values were analyzed by one-way ANOVA and the Tukey's test was performed to identify the groups that were significantly different at 5% level. The microwave-polymerized groups showed the highest means (p<0.05) for flexural strength (MPa) (A = 106.97 ± 5.31; B = 107.57 ± 3.99; C = 109.63 ± 5.19), and there were no significant differences among them. The heat-polymerized group (T) showed the lowest flexural strength means (84.40 ± 1.68), and differ significantly from all groups. The specimens of a microwavable denture base resin could be polymerized by different microwave cycles without risk of decreasing the flexural strength.
2016
Background: Poly-methyl-methacrylate (PMMA) and microwaveable acrylic resin are used for complete denture and removable partial denture services. This study was conducted to comparatively evaluate dimensional changes in microwave processed acrylic resin and in conventional heat polymerized resin cured by water bath and microwave energy. Materials and Methods: A total of 30 maxillary denture bases (3 mm thick) were made on cast in our study. These samples were demarcated into 3 groups. Group 1: Control, conventional heat cure PMMA cured by water bath method; Group 2 denotes conventional heat cure PMMA cured by microwave energy (500 W for 3 min); Group 3 denotes microwave acrylic resin cured by microwave energy (500 W for 3 min). After polymerization of test samples, the base/cast sets were cut transversally in the posterior palatal seal area. The measurements were made at the right marginal limit, left marginal limit, right ridge crest, left ridge crest, and the palatal midline. Ster...
Brazilian Dental Journal, 2009
The present study evaluated the effect of repeated simulated microwave disinfection on physical and mechanical properties of Clássico, Onda-Cryl and QC-20 denture base acrylic resins. Aluminum patterns were included in metallic or plastic flasks with dental stone following the traditional packing method. The powder/liquid mixing ratio was established according to the manufacturer's instructions. After water-bath polymerization at 74ºC for 9 h, boiling water for 20 min or microwave energy at 900 W for 10 min, the specimens were deflasked after flask cooling and finished. Each specimen was immersed in 150 mL of distilled water and underwent 5 disinfection cycles in a microwave oven set at 650 W for 3 min. Non-disinfected and disinfected specimens were subjected to the following tets: Knoop hardness test was performed with 25 g load for 10 s, impact strength test was done using the Charpy system with 40 kpcm, and 3-point bending test (flexural strength) was performed at a crosshead speed of 0.5 mm/min until fracture. Data were analyzed statistically by ANOVA and Tukey's test (α= 0.05%). Repeated simulated microwave disinfections decreased the Knoop hardness of Clássico and Onda-Cryl resins and had no effect on the impact strength of QC-20. The flexural strength was similar for all tested resins.
Acrylic resins have been in the centre stage of Prosthodontics for more than half a century. Hence superior physical and mechanical properties are expected from autoploymerising resins. The aim of the present study was to evaluate flexural strength of three different autoploymerising resins processed by two different polymerization techniques after microwave postpolymerization treatment. A metal die was formed measuring 64x10x3.3 mm according to ISO/FDI 1567 specification. Sixty test specimens were prepared of three different materials. The specimens were divided into two groups; first group was cured conventionally under room temperature and pressure. The second group was cured in a pressure pot at temperature of 40 degree Celsius and pressure of 2.5 bars for 30 minutes. The specimens in each group were again divided into two subgroups .The first subgroup was kept as control and the others were subjected to microwave postpolymerization treatment. After this the specimens were teste...
Journal of clinical and diagnostic research : JCDR, 2013
Disinfection of prostheses with chemical solutions has deleterious effects on dentures. The appropriate power setting of microwave for disinfection, without affecting denture base properties, is a controversy. To evaluate and compare the effect of simulated microwave disinfection at a recommended power setting on the mechanical properties of three denture base heat polymerized acrylic resins. Ninety rectangular specimens of each acrylic resin of 65mm × 10mm × 3 mm dimensions were divided into three groups. Group A (Trevalon), Group B (Trevalon- HI), Group C (Ivocap). In each group, thirty specimens were divided into three subgroups with ten specimens in each and they were submitted to MicroVickers hardness, flexural strength, and impact strength tests. In each subgroup, five specimens were tested before the simulated microwave disinfection and they served as the control group. The remaining five were tested after simulated microwave disinfection and they were considered as the exper...
World Journal of Dentistry
Aims and objective: The drawback of poly-methyl-methacrylate (PMMA) is the absence of adaptation accuracy in acrylic resin affected by polymerization shrinkage and resin flask method. The present study was conducted to compare adaptation of acrylic resin cured by injection moulded technique and microwave energy. Materials and methods: 40 standardized maxillary record bases (2 mm thick) were processed from 40 maxillary master casts. SR-Ivocap High Impact Resin was used for injection moulding technique and microwaveable acrylic resin (Onda-Cryl, Artigos Odontológicos, Clássico Ltd, Sao-Paulo, SP, Brazil) was cured by microwave energy (320 W for 3 minutes + 0 W for 3 minutes + 720 W for 3 minutes). These specimens were divided into two groups. Group I: 20 maxillary record bases were fabricated using injection moulding technique. Group II: 20 maxillary record bases were fabricated using microwave energy (320 W for 3 minutes + 0 W for 3 minutes + 720 W for 3 minutes). The base/cast sets were sliced transversally in the posterior palatal seal zone. The gap between the resin base and casts was evaluated at the right marginal limit, left marginal limit, right ridge crest, left ridge crest and the palatal midline. The adaptation accuracy was examined utilizing a stereomicroscope. Results: There was a significant difference between the microwaveable acrylic resin (Onda-Cryl) cured by microwave energy (320 W for 3 minutes + 0 W for 3 minutes + 720 W for 3 minutes) and the SR-Ivocap high impact resin cured by injection moulding technique. Conclusion: The microwaveable acrylic resin (Onda-Cryl) cured by microwave energy (320 W for 3 minutes + 0 W for 3 minutes + 720 W for 3 minutes) showed fewer adaptation inaccuracies and more accurate denture base than injection moulding techniques. Clinical significance: The microwaveable acrylic resin (Onda-Cryl) cured by microwave energy (320 W for 3 minutes + 0 W for 3 minutes + 720 W for 3 minutes) have more accurate denture bases when differentiated to those polymerized by injection moulding techniques. Therefore microwaveable acrylic resin (Onda-Cryl) cured by microwave energy (320 W for 3 minutes + 0 W for 3 minutes + 720 W for 3 minutes) can be a viable option for fabrication of dentures.