Effect of simulated microwave disinfection on the linear dimensional change, hardness and impact strength of acrylic resins processed by different polymerization cycles.

AIM: This study investigated the effect of simulated microwave disinfection (SMD) on the linear dimensional changes, hardness and impact strength of acrylic resins under different polymerization cycles. METHDOS: Metal dies with referential points were embedded in flasks with dental stone. Samples of Classico and Vipi acrylic resins were made following the manufacturers' recommendations. The assessed polymerization cycles were: A) water bath at 74 ºC for 9 h; B) water bath at 74 ºC for 8 h and temperature increased to 100 ºC for 1 h; C) water bath at 74 ºC for 2 h and temperature increased to 100 ºC for 1 h; and D) water bath at 120 ºC and pressure of 60 pounds. Linear dimensional distances in length and width were measured after SMD and water storage at 37 ºC for 7 and 30 days using an optical microscope. SMD was carried out with the samples immersed in 150 mL of water in an oven (650 W for 3 min). A load of 25 gf for 10 s was used in the hardness test. Charpy impact test was performed with 40 kpcm. Data were submitted to ANOVA and Tukey's test (5%). RESULTS: The Classico resin was dimensionally steady in length in the A and D cycles for all periods, while the Vipi resin was steady in the A, B and C cycles for all periods. The Classico resin was dimensionally steady in width in the C and D cycles for all periods, and the Vipi resin was steady in all cycles and periods. The hardness values for Classico resin were steady in all cycles and periods, while the Vipi resin was steady only in the C cycle for all periods. Impact strength values for Classico resin were steady in the A, C and D cycles for all periods, while Vipi resin was steady in all cycles and periods. CONCLUSION: SMD promoted different effects on the linear dimensional changes, hardness and impact strength of acrylic resins submitted to different polymerization cycles when after SMD and water storage were considered.

Effect of simulated microwave disinfection on the linear dimensional change, hardness and impact strength of acrylic resins processed by different polymerizing cycles.

AIM: This study investigated the effect of simulated microwave disinfection (SMD) on the linear dimensional changes, hardness and impact strength of acrylic resins under different polymerization cycles. METHODS: Metal dies with referential points were embedded in flasks with dental stone. Samples of Classico and Vipi acrylic resins were made following the manufacturers' recommendations. The assessed polymerization cycles were: A-- water bath at 74ºC for 9 h; B-- water bath at 74ºC for 8 h and temperature increased to 100ºC for 1 h; C-- water bath at 74ºC for 2 h and temperature increased to 100ºC for 1 h;; and D-- water bath at 120ºC and pressure of 60 pounds. Linear dimensional distances in length and width were measured after SMD and water storage at 37ºC for 7 and 30 days using an optical microscope. SMD was carried out with the samples immersed in 150 mL of water in an oven (650 W for 3 min). A load of 25 gf for 10 sec was used in the hardness test. Charpy impact test was performed with 40 kpcm. Data were submitted to ANOVA and Tukey's test (5%). RESULTS: The Classico resin was dimensionally steady in length in the A and D cycles for all periods, while the Vipi resin was steady in the A, B and C cycles for all periods. The Classico resin was dimensionally steady in width in the C and D cycles for all periods, and the Vipi resin was steady in all cycles and periods. The hardness values for Classico resin were steady in all cycles and periods, while the Vipi resin was steady only in the C cycle for all periods. Impact strength values for Classico resin were steady in the A, C and D cycles for all periods, while Vipi resin was steady in all cycles and periods. CONCLUSION: SMD promoted different effects on the linear dimensional changes, hardness and impact strength of acrylic resins submitted to different polymerization cycles when after SMD and water storage were considered.

Effect of polymerization cycles on the linear dimensional change, hardness and impact strength of denture base acrylic resins.

AIM: This study verified the effect of polymerizing cycles on the linear dimensional change, hardness and impact strength of denture acrylic resins. METHODS: One hundred and twenty samples (N.=10) each for the Classico and Vipi acrylic resins were made according to the manufacturers' instructions. The polymerization cycles were: 1- water bath at 74 ºC for 9 hr; 2- water bath at 74ºC for 8 hr and temperature increased to 100 ºC for 1 hr; 3- water bath at 74 ºC for 2 hr and temperature increased to 100 ºC for 1 hr; and 4- water bath at 120ºC and 60 pounds pressure for 1 hr. Samples were deflasked after flask cooling and submitted to finishing. Linear distances between referential points in the samples were measured at deflasking and after water storage for 7 and 30 days with a comparator microscope with an accuracy of 0.0005 mm. Knoop hardness test was accomplished in a durometer with a load of 25 gf for 10 sec and an average of three indentations was considered for the sample hardness. Impact strength (kgf/cm²) was measured by the Charpy system with load of 40 kpcm. Data were submitted to ANOVA and Tukey's test (5%). RESULTS: Dimensional changes in the A-B and A-C distances, hardness values and impact strength for Classico and Vipi resins were differently influenced by the polymerization cycles, when deflasking and water storage for 7 and 30 days were considered. CONCLUSION: Linear dimensional change, hardness and impact strength of denture acrylic resins were differently affected by the polymerization cycles.

Effect of monomer content in the monomer-polymer proportion on the adaptation of complete denture bases.

AIM: This study verified the effect of the monomer/polymer proportion on the base adaptation of the complete upper dentures. METHODS: Thirty stone cast-wax baseplate sets were packed in metallic flasks and the acrylic resin polymerized in water at 74 °C for nine hours. Three transverse cuts were made through each stone cast-resin base set, corresponding to regions: A) canines (anterior); B) first molars (median), and C) posterior palate (posterior). Measurements were made using an optical micrometer at five points for each cut to determine base adaptation: left and right marginal limits of the flanges, left and right ridge crests, and midline. Data were analyzed using to ANOVA and Tukey's test (5%). RESULTS: In region A there was significant difference among the monomer-polymer proportions, with a greater value of misfit for the content -25% monomer group and lower for the manufacturer's proportion group. In region B there was significant difference between the manufacturer's content (lowest value) and the monomer contents of +25% and -25% (both statistically similar). In region C there was significant difference among the monomer-polymer proportions, with greater value for the -25% monomer group than for the manufacturer's proportion. There was significant difference when the regions were compared in relation to the same monomer content. The best adaptation was in the region A and the worst in the region C. CONCLUSION: The amount of monomer exerted different effects on the adaptation of the denture base. In all regions, the smallest misfit was observed when the manufacturer's recommended proportion was used and the greatest misfit was observed in the -25% monomer.