title: Resin pattern material with low polymerization shrinkage.
abstract: OBJECTIVE
  The purpose of this study was to develop a material with low polymerization shrinkage for resin patterns to improve the fit of a long superstructure to implants.
  
  
  METHODS
  Three different chemical substances were added at 1, 2, 3, 5, 10, and 20 wt% to the liquid component of a self-curing acrylic resin. Specimens for measuring shrinkage during self curing were prepared in a metal mold that took the form of a conical cavity with slightly tapered walls. The specimens were prepared using three different methods: (1) a brush-on technique, (2) an injection method, and (3) an injection-press method. The percentage of linear shrinkage was calculated from the protrusion of the specimen from the bottom of the cavity.
  
  
  RESULTS
  The injection-press method and the brush-on method gave the lowest polymerization shrinkage results (P < 0.05). The standard deviation of the former method was smaller than that of the latter. The linear shrinkage in the injection-press method decreased with the increase of the powder-to-liquid ratio (P < 0.05). All three additives reduced shrinkage to about 1/3 of the shrinkage of the basic resin using the injection-press method and a 2.00:1.00 powder-to-liquid ratio.
  
  
  CONCLUSIONS
  The addition of three different chemical substances to liquid reduces linear shrinkage to about 1/3 of the shrinkage of the original self-curing acrylic resin.
authors.affiliation: Department of Dental Materials Science and Technology, Osaka University Faculty of Dentistry, Japan. j-takaha@dent.osaka-u.ac.jp
authors.forename: J
authors.initials: J
authors.lastname: Takahashi
authors.forename: K
authors.initials: K
authors.lastname: Kitahara
authors.forename: F
authors.initials: F
authors.lastname: Teraoka
authors.forename: F
authors.initials: F
authors.lastname: Kubo
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D000438:Alcohols / Q000737:chemistry; D000704:Analysis of Variance; D003734:Dental Casting Investment / Q000737:chemistry*; D017267:Dental Prosthesis Design; D019094:Dental Prosthesis, Implant-Supported; D007192:Indenes / Q000737:chemistry; D008422:Materials Testing; D009025:Morpholines / Q000737:chemistry; D011108:Polymers / Q000737:chemistry; D018709:Statistics, Nonparametric
chemical_list: D000180:Acrylic Resins; D000438:Alcohols; D003734:Dental Casting Investment; D007192:Indenes; D009025:Morpholines; D011108:Polymers