title: Dimensional changes of acrylic resin denture bases: conventional versus injection-molding technique.
abstract: OBJECTIVE
  Acrylic resin denture bases undergo dimensional changes during polymerization. Injection molding techniques are reported to reduce these changes and thereby improve physical properties of denture bases. The aim of this study was to compare dimensional changes of specimens processed by conventional and injection-molding techniques.
  
  
  METHODS
  SR-Ivocap Triplex Hot resin was used for conventional pressure-packed and SR-Ivocap High Impact was used for injection-molding techniques. After processing, all the specimens were stored in distilled water at room temperature until measured. For dimensional accuracy evaluation, measurements were recorded at 24-hour, 48-hour and 12-day intervals using a digital caliper with an accuracy of 0.01 mm. Statistical analysis was carried out by SPSS (SPSS Inc., Chicago, IL, USA) using t-test and repeated-measures ANOVA. Statistical significance was defined at P<0.05.
  
  
  RESULTS
  After each water storage period, the acrylic specimens produced by injection exhibited less dimensional changes compared to those produced by the conventional technique. Curing shrinkage was compensated by water sorption with an increase in water storage time decreasing dimensional changes.
  
  
  CONCLUSIONS
  Within the limitations of this study, dimensional changes of acrylic resin specimens were influenced by the molding technique used and SR-Ivocap injection procedure exhibited higher dimensional accuracy compared to conventional molding.
authors.affiliation: Professor, Dental Research Center, Department of Prosthodontics, School of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Jafar
authors.initials: J
authors.lastname: Gharechahi
authors.affiliation: Associate Professor, Department of Prosthodontics, Dental Research Center, School of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Nafiseh
authors.initials: N
authors.lastname: Asadzadeh
authors.affiliation: Assistant Professor, Department of Prosthodontics, Dental Research Center, School of Dentistry, Ahvaz University of Medical Sciences, Ahvaz, Iran.
authors.forename: Foad
authors.initials: F
authors.lastname: Shahabian
authors.affiliation: Assistant Professor, Dental Material Research Center, Department of Endodontics, School of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Maryam
authors.initials: M
authors.lastname: Gharechahi
keywords: Acrylic resin; Denture base; Physical processes