title: Physical properties of polyamide-12 versus PMMA denture base material.
abstract: OBJECTIVE
  Polyamide-12 (PA) is a flexible material suited for denture bases and clasping. This study investigated its potential aging effects with a focus on surface roughness, color stability, and elasticity.
  
  
  METHODS
  PA specimens (Valplast) of 40×10×2 mm and equally measuring PMMA specimens (Palapress) as control were fabricated. Color changes after storage in air, water, coffee, and red wine (n=10) were measured using the CIE L*a*b* color specification. Elasticity after thermocycling (1000, 3000, and 7000 cycles,  n=15) was measured by three-point bending testing. Mean surface roughness (Ra) was determined after storage in the liquids mentioned above and thermocycling (n=10).
  
  
  RESULTS
  Tukey's HSD test (P<0.05) revealed statistically significant color changes of PA in red wine (ΔE=4.27 after 12 days, ΔE=6.90 after 12 days) and coffee (ΔE=3.93 after 36 days) but no color changes in PMMA. Elastic modulus of PA was 845 MPa and not affected by thermocycling (Tukey's HSD test,  P>0.81). Dry specimens showed significantly decreased elasticity (P<0.001). Mean surface roughness (PA 0.20  μ m, PMMA 0.28  μ m) did not change significantly after thermocycling or storage (Mann-Whitney U-test,  0.16<P<0.65).
  
  
  CONCLUSIONS
  PA exhibited a higher susceptibility to discoloration than PMMA. Neither surface roughness nor elasticity of PA was altered by artificial aging.
authors.affiliation: Division of Dental Materials, Faculty of Dentistry, Wroclaw Medical University, 26 Krakowska street, 50-425 Wroclaw, Poland.
authors.forename: Mieszko
authors.initials: M
authors.lastname: Wieckiewicz
authors.affiliation: Department of Prosthetic Dentistry, Faculty of Medicine, Dresden University of Technology, Fetscherstraße 74, 01307 Dresden, Germany.
authors.forename: Volker
authors.identifier: 0000-0001-6582-1879
authors.initials: V
authors.lastname: Opitz
authors.affiliation: Department of Prosthetic Dentistry, Faculty of Medicine, Dresden University of Technology, Fetscherstraße 74, 01307 Dresden, Germany.
authors.forename: Gert
authors.initials: G
authors.lastname: Richter
authors.affiliation: Department of Prosthetic Dentistry, Faculty of Medicine, Dresden University of Technology, Fetscherstraße 74, 01307 Dresden, Germany.
authors.forename: Klaus W
authors.initials: KW
authors.lastname: Boening
mesh_terms: D000388:Air; D001672:Biocompatible Materials / Q000737:chemistry; D003069:Coffee; D003116:Color; D003764:Dental Materials; D003778:Dentures; D004548:Elasticity; D008422:Materials Testing; D009757:Nylons / Q000737:chemistry*; D019904:Polymethyl Methacrylate / Q000737:chemistry*; D011312:Pressure; D013499:Surface Properties; D013696:Temperature; D014867:Water; D014920:Wine
chemical_list: D001672:Biocompatible Materials; D003069:Coffee; D003764:Dental Materials; D009757:Nylons; D014867:Water; C036222:nylon 12; D019904:Polymethyl Methacrylate
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