title: Stress reduction in resin-based composites cured with a two-step light-curing unit.
abstract: OBJECTIVE
  To examine the stress reduction of different resin-based composites, cured with a two-step polymerization unit (Elipar Highlight) by means of a photoelastic investigation.
  
  
  METHODS
  For each material (Pertac II, Tetric Ceram, Charisma F, Solitaire, Dyract, Dyract AP, Definite), a minimum of 10 resin samples, embedded in acrylic-glass plates, were polymerized using a standard polymerization process of 700 mW/cm for 40 s. Another 10 samples were polymerized with a light output of 150 mW/cm2 for 10 s and then with a light output of 700 mW/cm2 for 30 s.
  
  
  RESULTS
  For Pertac II the reduction of polymerization stress in the two-step-mode was 15.5%, for Tetric Ceram 14.5%, for Solitaire 8.1%, for Dyract AP 6.5% and for Definite 4.7%. These differences in polymerization stress between the standard and two-step-polymerization mode were statistically significant (P < 0.01, Wilcoxon test). No statistically significant differences in polymerization stress could be found for Charisma F and Dyract.
authors.affiliation: Department for Restorative Dentistry and Periodontology, Johannes Gutenberg-University Mainz, Germany. Ernst@mail.uni-mainz.de
authors.forename: C P
authors.initials: CP
authors.lastname: Ernst
authors.forename: R
authors.initials: R
authors.lastname: Kürschner
authors.forename: G
authors.initials: G
authors.lastname: Rippin
authors.forename: B
authors.initials: B
authors.lastname: Willershausen
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D020770:Compomers / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry* / Q000528:radiation effects; D004548:Elasticity; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008027:Light; D008689:Methacrylates / Q000737:chemistry; D010777:Photochemistry / Q000295:instrumentation; D011108:Polymers / Q000737:chemistry; D011829:Radiation Dosage; D017640:Silicates / Q000737:chemistry; D012833:Siloxanes / Q000737:chemistry; D018709:Statistics, Nonparametric; D013314:Stress, Mechanical; D013499:Surface Properties; D013729:Terpenes / Q000737:chemistry; D013997:Time Factors
chemical_list: C084111:Charisma composite resin; D020770:Compomers; D003188:Composite Resins; C421785:Definite composite resin; C088486:Dyract; D008689:Methacrylates; C079764:Pertac hybrid; D011108:Polymers; D017640:Silicates; D012833:Siloxanes; C113049:Solitaire composite resin; D013729:Terpenes; C121818:Tetric ceram; D017438:Bisphenol A-Glycidyl Methacrylate