title: Influence of mechanical and chemical polishing in the solubility of acrylic resins polymerized by microwave irradiation and conventional water bath.
abstract: OBJECTIVE
  The aim of this work was to evaluate the solubility of acrylic resin activated by microwave irradiation (MI) or water bath (WB), when submitted to chemical (CP) or mechanical (MP) polishing.
  
  
  METHODS
  Forty acrylic resin samples were made and processed either by water bath (74 +/- 1 degrees C, 9 h) or microwave irradiation (500 W, 3 min). After deflasking, the samples were finished with aluminum oxide sandpapers in decreasing granulations till reaching similar dimensions. The samples were divided into four groups according to the association between kind of polymerization and polishing: A (WB + CP), B (WB + MP), C (MI + CP) and D (MI + MP). Solubility test was performed for each group and percentile solubility was calculated. Data were statistically analyzed using variance analysis and Kruskal-Wallis.
  
  
  RESULTS
  The average of percentile solubility (%) was obtained: A = 0.07, B = 0.02, C = 0.04, D = -0.14, however, no significant difference was found between types of polishing in the samples polymerized by water bath (A and B). When processed by microwave irradiation (C and D), there was significant difference between the applied methods of polishing, so that mechanical polishing lead to a lower solubility.
  
  
  CONCLUSIONS
  Solubility is a property of acrylic resins, representing not reacted substances releasing that could promote tissular reactions in prosthesis users. The association between polymerization by microwave irradiation and mechanical polishing showed less residual substances releasing for heat-cured acrylic resins, reducing the probability of developing tissular reactions.
authors.affiliation: Department of Prosthesis and Periodontology, Removable Partial Prosthodontic, Piracicaba Dental School, University of Campinas, Av. Limeira, 901. Areião, 13414-018, São Paulo, Brazil.
authors.forename: Cristiane
authors.initials: C
authors.lastname: Machado
authors.forename: Célia M
authors.initials: CM
authors.lastname: Rizzatti-Barbosa
authors.forename: Morgana N
authors.initials: MN
authors.lastname: Gabriotti
authors.forename: Fábio A
authors.initials: FA
authors.lastname: Joia
authors.forename: Margarete C
authors.initials: MC
authors.lastname: Ribeiro
authors.forename: Rodrigo L S
authors.initials: RL
authors.lastname: Sousa
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry / Q000528:radiation effects; D003775:Dental Polishing / Q000379:methods*; D006358:Hot Temperature; D008422:Materials Testing; D008872:Microwaves; D015394:Molecular Structure; D044367:Phase Transition; D012995:Solubility; D018709:Statistics, Nonparametric; D014867:Water
chemical_list: D000180:Acrylic Resins; D014867:Water