title: Dynamic viscoelastic behavior of resin cements measured by torsional resonance.
abstract: OBJECTIVE
  The purpose of the study was to measure the viscoelastic properties of four dental resin composite cements using a dynamic mechanical analysis technique.
  
  
  METHODS
  Dynamic torsional loading was conducted in the frequency range from 1 to 80 Hz. Cement specimens were tested after storage in 37 degrees C water for 24 h. One group was thermal cycled prior to testing. Measurements were taken at 21, 37, and 50 degrees C. Storage modulus, loss tangent and other viscoelastic parameters were determined from the amplitude/frequency curves.
  
  
  RESULTS
  Storage moduli of the cements ranged from 2.9 to 4.1 GPa at 37 degrees C. Loss tangents ranged from 0.054 to 0.084. Storage moduli decreased in a regular way with increasing temperature, whereas, loss tangents increased. Thermal cycling caused small decreases in storage moduli.
  
  
  CONCLUSIONS
  Resin cements with higher filler loading were found to have higher storage moduli and lower loss tangents. Since these properties have been associated with better clinical performance in the areas of retention and prevention of fracture of porcelain and resin restorations, the more highly filled cements may be recommended. Temperature variations influenced viscoelastic behavior of the cements. However, within the temperature range studied no sharp drop in modulus was seen, so the materials should function satisfactorily in the oral cavity.
authors.affiliation: Department of Operative Dentistry, Dental School, Aristotle University of Thessaloniki, Thessaloniki, Greece.
authors.forename: Y
authors.initials: Y
authors.lastname: Papadogiannis
authors.forename: D B
authors.initials: DB
authors.lastname: Boyer
authors.forename: M
authors.initials: M
authors.lastname: Helvatjoglu-Antoniades
authors.forename: R S
authors.initials: RS
authors.lastname: Lakes
authors.forename: C
authors.initials: C
authors.lastname: Kapetanios
mesh_terms: D000704:Analysis of Variance; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003799:Dental Stress Analysis; D004356:Drug Storage; D004548:Elasticity; D008422:Materials Testing / Q000379:methods; D011092:Polyethylene Glycols / Q000737:chemistry; D011109:Polymethacrylic Acids / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D018709:Statistics, Nonparametric; D019415:Torque; D014732:Vibration; D014783:Viscosity
chemical_list: C433207:Lute-It; D011109:Polymethacrylic Acids; C462240:RelyX ARC; D019279:Resin Cements; C072541:Duo Cement; C103502:Variolink; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate