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 (∅ 5 mm) in Araldit B epoxide resin plates (40×40×3 mm 3) 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/cm 2). 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.