title: Effect of beverages and mouthwashes on the hardness of polymers used in intraoral prostheses.
abstract: OBJECTIVE
  The mechanical properties of acrylic resins used in intraoral prostheses may be altered by frequent exposure to liquids such as beverages and mouthwashes. This study aimed to evaluate the effect of thermocycling and liquid immersion on the hardness of four brands of acrylic resins commonly used in removable prostheses (Onda Cryl, QC-20, Clássico, Lucitone).
  
  
  METHODS
  For each brand of resin, seven specimens were immersed in each of six solutions (coffee, cola, red wine, Plax-Colgate, Listerine [LI], Oral B), and seven more were placed in artificial saliva (control). The hardness was tested using a microhardness tester before and after 5000 thermocycles and after 1, 3, 24, 48, and 96 hours of immersion. The results were analyzed using three-way repeated-measures ANOVA and Tukey's test (p < 0.05).
  
  
  RESULTS
  The hardness of the resins decreased following thermocycling and immersion in the solutions. Specimens immersed in cola and wine exhibited significant decreases in hardness after immersion for 96 hours, although the greatest significant decrease in hardness occurred in specimens immersed in LI. However, according to American Dental Association specification 12, the Knoop hardness of acrylic resins for intraoral prostheses should not be below 15. Thus, the median values of superficial hardness observed in most of the acrylic resins in this study are considered clinically acceptable.
  
  
  CONCLUSIONS
  The microhardness of polymers used for intraoral prostheses decreases following thermocycling. Among specimens immersed in beverages, those immersed in cola or wine experienced the greatest decrease in microhardness. Immersion of acrylic resins in LI significantly decreased the microhardness in relation to the initial value. Among the resins assessed, QC-20 exhibited the lowest initial hardness.
authors.affiliation: Department of Dental Materials and Prosthodontics, Faculty of Dentistry of Araçatuba, UNESP - Univ Estadual Paulista, Araçatuba, Brazil.
authors.forename: Marcelo Coelho
authors.initials: MC
authors.lastname: Goiato
authors.forename: Daniela Micheline
authors.initials: DM
authors.lastname: Dos Santos
authors.forename: Agda Marobo
authors.initials: AM
authors.lastname: Andreotti
authors.forename: Adhara Smith
authors.initials: AS
authors.lastname: Nobrega
authors.forename: Amalia
authors.initials: A
authors.lastname: Moreno
authors.forename: Marcela Filié
authors.initials: MF
authors.lastname: Haddad
authors.forename: Aldiéris Alves
authors.initials: AA
authors.lastname: Pesqueira
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D000891:Anti-Infective Agents, Local / Q000737:chemistry; D001565:Benzoates / Q000737:chemistry; D001628:Beverages; D002253:Carbonated Beverages; D003069:Coffee; D003764:Dental Materials / Q000737:chemistry*; D003819:Denture Bases; D004338:Drug Combinations; D006244:Hardness; D006801:Humans; D007101:Immersion; D008422:Materials Testing; D009067:Mouthwashes / Q000737:chemistry*; D012459:Salicylates / Q000737:chemistry; D012464:Saliva, Artificial / Q000737:chemistry; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry; D013499:Surface Properties; D013696:Temperature; D013729:Terpenes / Q000737:chemistry; D013997:Time Factors; D014260:Triclosan / Q000737:chemistry; D014920:Wine
chemical_list: D000180:Acrylic Resins; D000891:Anti-Infective Agents, Local; D001565:Benzoates; D003069:Coffee; D003764:Dental Materials; D004338:Drug Combinations; D009067:Mouthwashes; C070868:Plax; C488492:QC 20 (denture base resin); D012459:Salicylates; D012464:Saliva, Artificial; D013729:Terpenes; C539103:onda cryl; D012967:Sodium Dodecyl Sulfate; D014260:Triclosan; C057473:Listerine; C040291:Lucitone
keywords: Denture; acrylic resins; complete; hardness; polymers