• polymerization shrinkage;
  • dental polymer;
  • composite;
  • degree of polymerization;
  • FTIR


To compare two kind of resin-based dental composites, the polymerization shrinkage, contraction stress (CS), and degree of conversion (DC) of four dimethacrylate-based and one silorane-based composite were investigated. To determine shrinkage, the composites were packed, respectively, into a cylindrical cavity in human teeth and imaged using X-ray microcomputed tomography to determine the precise volume before and 30 min after photopolymerization. To determine CS, the sample was applied in a similarly sized cylinder in a universal testing machine and monitored for 30 min. FTIR spectroscopy was used to determine DC. The volumetric shrinkage (range: 1.1–3.1%) and maximum CS (range: 1.2–3.5 MPa) differed significantly among the tested composites but not the final DC (range: 62.3–69.1%). The silorane-based composite displayed the lowest volumetric shrinkage and CS of all composites. No correlation was observed between the stress and volumetric shrinkage values of the dimethacrylate-based composites. A moderate correlation was found between stress and DC (r = 0.836), which was significant at 20 and 40 s. The silorane-based composite exhibited superior shrinkage behavior compared with conventional dimethacrylate composites with comparable polymerization kinetics. The CS was dependent on multiple variables, including the volumetric shrinkage, DC, and curing rate. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011