title: Influence of curing method, sealer, and water storage on the hardness of a soft lining material over time.
abstract: OBJECTIVE
  The purpose of this study was to determine the hardness of plasticized acrylic resin soft lining materials over time when curing procedures were modified and when surface sealers were either used or omitted.
  
  
  METHODS
  A chairside plasticized acrylic resin material and a heat processed plasticized resin material were made into disks 40 mm in diameter and 10 mm in thickness. Materials were cured by processing at an elevated temperature or at mouth temperature. Five samples were used with each processing method. Half of all samples were treated with a surface sealer, whereas the other samples received no surface treatment. After processing, the samples were immersed in 37 degrees C water for a total time of 1 year. Specimens were tested to determine hardness on a monthly basis. Testing was accomplished using a Shore A durometer.
  
  
  RESULTS
  Hardness testing showed differences relative to material and to time after processing. The heat-processed plasticized resin material showed significantly higher Shore A hardness values than the chairside over the entire experimental period (p <.01). Increased hardness was seen for all materials over time, but this was more pronounced with plasticized acrylic resin in which the hardness increased from 28.4% to 115.8% depending on processing method and surface treatment. Surface treatment showed significant softening only when the samples were cured at simulated mouth temperature (p <.05).
  
  
  CONCLUSIONS
  Processing method and time after processing have an effect on surface hardness of the tested materials, but neither of these effects is as profound as the initial choice of material. J Prosthodont 2001;10:42-45.
authors.affiliation: Department of Removable Prosthodontics, University of Athens, Dental School, 2 Thivon Street, 115 27 Athens, Greece. gpolyz@cc.uoa.gr
authors.forename: G L
authors.initials: GL
authors.lastname: Polyzois
authors.forename: M J
authors.initials: MJ
authors.lastname: Frangou
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D000704:Analysis of Variance; D001831:Body Temperature; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003822:Denture Liners; D006244:Hardness; D006358:Hot Temperature; D006801:Humans; D007101:Immersion; D008422:Materials Testing; D010968:Plasticizers / Q000737:chemistry*; D013223:Statistics as Topic; D013499:Surface Properties; D013997:Time Factors; D014867:Water / Q000737:chemistry*
chemical_list: D000180:Acrylic Resins; D010968:Plasticizers; D014867:Water