title: Effect of repeated disinfections by microwave energy on the physical and mechanical properties of denture base acrylic resins.
abstract: 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 74 degrees C 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 (alpha= 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.
authors.affiliation: Department of Prosthodontics and Periodontics, Piracicaba Dental School, State University of Campinas, Piracicaba, SP, Brazil. rconsani@fop.unicamp.br
authors.forename: Rafael Leonardo Xediek
authors.initials: RL
authors.lastname: Consani
authors.forename: Douglas Duenhas de
authors.initials: DD
authors.lastname: Azevedo
authors.forename: Marcelo Ferraz
authors.initials: MF
authors.lastname: Mesquita
authors.forename: Wilson Batista
authors.initials: WB
authors.lastname: Mendes
authors.forename: Paulo César
authors.initials: PC
authors.lastname: Saquy
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry / Q000528:radiation effects*; D003799:Dental Stress Analysis; D003819:Denture Bases; D004203:Disinfection / Q000379:methods*; D006244:Hardness; D008872:Microwaves; D018583:Pliability
chemical_list: D000180:Acrylic Resins; C488492:QC 20 (denture base resin); C539103:onda cryl