title: Effects of ethanol on the surface and bulk properties of a microwave-processed PMMA denture base resin.
abstract: OBJECTIVE
  This study evaluated the effect of different concentrations of ethanol on hardness, roughness, flexural strength, and color stability of a denture base material using a microwave-processed acrylic resin as a model system.
  
  
  METHODS
  Sixty circular (14 x 4 mm) and 60 rectangular microwave-polymerized acrylic resin specimens (65 x 10 x 3 mm(3)) were employed in this study. The sample was divided into six groups according to the ethanol concentrations used in the immersion solution, as follows: 0% (water), 4.5%, 10%, 19%, 42%, and 100%. The specimens remained immersed for 30 days at 37 degrees C. The hardness test was performed by a hardness tester equipped with a Vickers diamond penetrator, and a surface roughness tester was used to measure the surface roughness of the specimens. Flexural strength testing was carried out on a universal testing machine. Color alterations (DeltaE) were measured by a portable spectrophotometer after 12 and 30 days. Variables were analyzed by ANOVA/Tukey's test (alpha= 0.05).
  
  
  RESULTS
  For the range of ethanol-water solutions for immersion (water only, 4.5%, 10%, 19.5%, 42%, and 100%), the following results were obtained for hardness (13.9 +/- 2.0, 12.1 +/- 0.7, 12.9 +/- 0.9, 11.2 +/- 1.5, 5.7 +/- 0.3, 2.7 +/- 0.5 VHN), roughness (0.13 +/- 0.01, 0.15 +/- 0.07, 0.13 +/- 0.05, 0.13 +/- 0.02, 0.23 +/- 0.05, 0.41 +/- 0.19 mum), flexural strength (90 +/- 12, 103 +/- 18, 107 +/- 16, 90 +/- 25, 86 +/- 22, 8 +/- 2 MPa), and color (0.8 +/- 0.6, 0.8 +/- 0.3, 0.7 +/- 0.4, 0.9 +/- 0.3, 1.3 +/- 0.3, 3.9 +/- 1.5 DeltaE) after 30 days.
  
  
  CONCLUSIONS
  The findings of this study showed that the ethanol concentrations of tested drinks affect the physical properties of the investigated acrylic resin. An obvious plasticizing effect was found, which could lead to a lower in vivo durability associated with alcohol consumption.
authors.affiliation: Department of Dental Materials and Prosthodontics, School of Dentistry of Ribeirão Preto, São Paulo 14040-904, Brazil.
authors.forename: Rômulo Rocha
authors.initials: RR
authors.lastname: Regis
authors.forename: Natércia Carreira
authors.initials: NC
authors.lastname: Soriani
authors.forename: Alessandra Miranda
authors.initials: AM
authors.lastname: Azevedo
authors.forename: Cláudia Helena
authors.initials: CH
authors.lastname: Silva-Lovato
authors.forename: Helena Freitas Oliveira
authors.initials: HF
authors.lastname: Paranhos
authors.forename: Raphael Freitas
authors.initials: RF
authors.lastname: de Souza
mesh_terms: D000287:Administration, Topical; D000434:Alcoholic Beverages; D000704:Analysis of Variance; D003116:Color; D003764:Dental Materials / Q000737:chemistry* / Q000528:radiation effects; D003819:Denture Bases; D004305:Dose-Response Relationship, Drug; D000431:Ethanol / Q000008:administration & dosage / Q000737:chemistry*; D006244:Hardness; D006801:Humans; D008872:Microwaves; D019904:Polymethyl Methacrylate / Q000737:chemistry* / Q000528:radiation effects; D012997:Solvents / Q000008:administration & dosage / Q000737:chemistry; D013499:Surface Properties
chemical_list: D003764:Dental Materials; D012997:Solvents; D000431:Ethanol; D019904:Polymethyl Methacrylate