title: In vitro hardness, water sorption, and resin solubility of laboratory-processed and autopolymerized long-term resilient denture liners over one year of water storage.
abstract: BACKGROUND
  The clinical properties of resilient denture liners may be influenced by the method by which they are polymerized.
  
  
  OBJECTIVE
  This in vitro study investigated material property changes of 2 new resilient denture lining materials that represent 2 different curing modes: autopolymerization and conventional laboratory processing.
  
  
  METHODS
  Two silicone-based liner products were tested; one was allowed to autopolymerize (Tokuyama Soft Relining Paste), and the other was laboratory processed (Luci-Sof). Ninety-six disk-shaped specimens (31 x 10 mm) were fabricated in aluminum ring molds for hardness testing. Sixty bar-shaped specimens (44 x 8.5 x 1.2 mm) were fabricated in aluminum molds for water sorption and resin solubility testing. Shore A hardness was determined directly after specimen fabrication and after 1 day, 1 week, 1 month, 6 months, and 1 year of water storage at 37 degrees C. Water sorption and resin solubility were determined at the same time intervals. Analysis of variance and appropriate t tests were used to determine the effect of immersion duration both within and between the products tested. All statistical testing was performed at alpha=.05.
  
  
  RESULTS
  The hardness values of the laboratory-processed material were consistently greater than those of the autopolymerized material. After 1 week of water storage, the hardness of the autopolymerized specimens stabilized, whereas the hardness of the laboratory-processed specimens increased with immersion duration. Water sorption values for the 2 test products were similar after 6 months and after 1 year of water storage. At 1 month, 6 months, and 1 year, significantly lower resin solubility (P<.05) was recorded for the autopolymerized specimens compared with their laboratory-processed counterparts.
  
  
  CONCLUSIONS
  Within the limitations of this study, the laboratory-processed material was harder than the autopolymerized product and demonstrated greater resin solubility over time. The latter result was not expected.
authors.affiliation: Department of Oral Rehabilitation, School of Dentistry, The Medical College of Georgia, Augusta, GA 30912-1260, USA. gparr@mail.mcg.edu
authors.forename: Gregory R
authors.initials: GR
authors.lastname: Parr
authors.forename: Frederick A
authors.initials: FA
authors.lastname: Rueggeberg
mesh_terms: D000042:Absorption; D000704:Analysis of Variance; D003822:Denture Liners; D004356:Drug Storage; D006244:Hardness; D008422:Materials Testing; D008689:Methacrylates; D011108:Polymers / Q000737:chemistry; D012117:Resins, Synthetic / Q000737:chemistry; D012826:Silicone Elastomers; D012995:Solubility; D013674:Technology, Dental; D014867:Water / Q000737:chemistry
chemical_list: D008689:Methacrylates; D011108:Polymers; D012117:Resins, Synthetic; D012826:Silicone Elastomers; D014867:Water