title: Determination of polymerization shrinkage stress by means of a photoelastic investigation.
abstract: OBJECTIVE
  This study examined the polymerization stress of different established composite resins (Tetric Ceram, Vivadent; EsthetX, Surefil, Dentsply/DeTrey; Clearfil AP-X, Clearfil Photo Posterior, Kuraray; Prodigy Condensable, sds Kerr; Filtek P 60, 3M ESPE; Solitaire 2, Heraeus-Kulzer) by means of a photo-elastic investigation and investigated six new, experimental composite resins, which have been claimed to exhibit less polymerization shrinkage (InTen-S, Vivadent; K 112, K 051, Dentsply/DeTrey; Compox, Pluto, Hermes 3M ESPE).
  
  
  METHODS
  Cylindrical cavities (phi 5 mm) in Araldit B epoxide resin plates (40 x 40 x 3 mm3) were pretreated with the Rocatec system to ensure bonding of the composite resin. Ten composite resin specimens of each material, embedded in the Araldit plates, were exposed for 60 s (Elipar TriLight, Standard-mode, 800 mW/cm2). Polymerization contraction stress data (MPa) were calculated at 4 min and 24 h after exposure, based on the diameter of the isochromatic curves of first order obtained from the Araldit-plates. The statistical analysis was carried out with the Wilcoxon test (5% level).
  
  
  RESULTS
  After 24 h, the calculated mean polymerization stress values were 4.4+/-0.1 MPa for Tetric Ceram, 4.6+/-0.1 MPa for EsthetX, 3.7+/-0.1 MPa for Z 250, 4.6+/-0.1 MPa for Clearfil AP-X, 4.1+/-0.1 MPa for Prodigy Condensable, 4.0+/-0.1 MPa for Filtek P 60, 4.5+/-0.1 MPa for Surefil, 4,5+/-0.1 MPa for Clearfil Photo Posterior, 5.4+/-0.04 MPa for Solitaire 2, 3.2+/-0.1 MPa for In Ten-S, 3.9+/-0.1 MPa for K 112, 3.1+/-0.04 MPa for K 051, 3.2+/-0.1 MPa for Compox, and 2.0+/-0.1 MPa for Hermes.
  
  
  CONCLUSIONS
  The new and experimental composite resins In Ten-S, K 051, Compox, and Hermes showed significantly less polymerization shrinkage stress than the controls (p < 0.0005, Bonferroni correction). For the experimental material Pluto, no determination of isochromatic rings was possible.
authors.affiliation: Department of Operative Dentistry, Johannes Gutenberg-University Mainz, Augustusplatz 2, Mainz 55131, Germany. ernst@mail.uni-mainz.de
authors.forename: Claus-Peter
authors.initials: CP
authors.lastname: Ernst
authors.forename: Gerrit R
authors.initials: GR
authors.lastname: Meyer
authors.forename: Kerstin
authors.initials: K
authors.lastname: Klöcker
authors.forename: Brita
authors.initials: B
authors.lastname: Willershausen
mesh_terms: D001718:Birefringence; D003188:Composite Resins / Q000737:chemistry* / Q000528:radiation effects*; D003799:Dental Stress Analysis / Q000379:methods; D004548:Elasticity; D008027:Light; D008422:Materials Testing / Q000379:methods; D015394:Molecular Structure; D044367:Phase Transition; D011108:Polymers / Q000737:chemistry; D013314:Stress, Mechanical
chemical_list: D003188:Composite Resins; D011108:Polymers