A comparative evaluation of polymerization stress data obtained with four different mechanical testing systems

Flávia Gonçalves, Leticia C. Boaro, Jack L. Ferracane, Roberto R. Braga

Research output: Contribution to journalArticlepeer-review

28 Scopus citations


Objectives: The null hypothesis was that mechanical testing systems used to determine polymerization stress (σ pol) would rank a series of composites similarly. Methods: Two series of composites were tested in the following systems: universal testing machine (UTM) using glass rods as bonding substrate, UTM/acrylic rods, "low compliance device", and single cantilever device ("Bioman"). One series had five experimental composites containing BisGMA:TEGDMA in equimolar concentrations and 60, 65, 70, 75 or 80 wt% of filler. The other series had five commercial composites: Filtek Z250 (3M ESPE), Filtek A110 (3M ESPE), Tetric Ceram (Ivoclar), Heliomolar (Ivoclar) and Point 4 (Kerr). Specimen geometry, dimensions and curing conditions were similar in all systems. σ pol was monitored for 10 min. Volumetric shrinkage (VS) was measured in a mercury dilatometer and elastic modulus (E) was determined by three-point bending. Shrinkage rate was used as a measure of reaction kinetics. ANOVA/Tukey test was performed for each variable, separately for each series. Results: For the experimental composites, σ pol decreased with filler content in all systems, following the variation in VS. For commercial materials, σ pol did not vary in the UTM/acrylic system and showed very few similarities in rankings in the others tests system. Also, no clear relationships were observed between σ pol and VS or E. Significance: The testing systems showed a good agreement for the experimental composites, but very few similarities for the commercial composites. Therefore, comparison of polymerization stress results from different devices must be done carefully.

Original languageEnglish (US)
Pages (from-to)680-686
Number of pages7
JournalDental Materials
Issue number6
StatePublished - Jun 2012


  • Elastic modulus
  • Polymerization stress
  • Resin composites
  • Volumetric shrinkage

ASJC Scopus subject areas

  • Materials Science(all)
  • Dentistry(all)
  • Mechanics of Materials


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