title: Effect of simulated microwave disinfection on the linear dimensional change, hardness and impact strength of acrylic resins processed by different polymerizing cycles.
abstract: OBJECTIVE
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Prosthodontics and Periodontics, Piracicaba Dental School, State University ofCampinas, Piracicaba, Brazil - rconsani@fop.unicamp.br.
authors.forename: R L
authors.initials: RL
authors.lastname: Xediek Consani
authors.forename: V
authors.initials: V
authors.lastname: Chorwat
authors.forename: M
authors.initials: M
authors.lastname: Ferraz Mesquita
authors.forename: M B
authors.initials: MB
authors.lastname: Fernandes Santos
authors.forename: A
authors.initials: A
authors.lastname: Bortolazzo Correr
authors.forename: S
authors.initials: S
authors.lastname: Consani