title: The effect of temperature on the viscoelastic properties of nano-hybrid composites.
abstract: OBJECTIVE
  The purpose of this study was to examine the viscoelastic properties of nanofilled dental composites under both static and dynamic testing and to determine the influence of temperature, medium of storage and storage time.
  
  
  METHODS
  Three nanofilled composites, one packable and one ormocer were tested. The specimens were examined dry at 21 degrees C and wet at 21, 37 and 50 degrees C after being stored for 24h and 1 month under both static and dynamic testing. Shear modulus, elastic modulus, loss tangent, Poisson's ratio and other viscoelastic parameters were calculated. Data were analyzed with one-way and two-way analysis of variance (ANOVA) (p=0.05).
  
  
  RESULTS
  All materials tested showed a significant decrease in their moduli with the increase of temperature, while the effect of water storage was different among the composites. Grandio was the composite with the highest Young's modulus followed by Filtek P60.
  
  
  CONCLUSIONS
  Most of the materials tested did not have elastic moduli near to that of dentin, making them less satisfactory in posterior restorations. The materials possessing nanosized filler particles had different elastic properties among them and this implies that filler size is not the only factor that affects the elastic behavior of dental composites.
authors.affiliation: University of Athens, School of Dentistry, Department of Biomaterials, Greece. papady@dent.auth.gr
authors.forename: D Y
authors.initials: DY
authors.lastname: Papadogiannis
authors.forename: R S
authors.initials: RS
authors.lastname: Lakes
authors.forename: Y
authors.initials: Y
authors.lastname: Papadogiannis
authors.forename: G
authors.initials: G
authors.lastname: Palaghias
authors.forename: M
authors.initials: M
authors.lastname: Helvatjoglu-Antoniades
mesh_terms: D002516:Ceramics / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D004548:Elasticity; D006801:Humans; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D053761:Nanocomposites / Q000737:chemistry; D053758:Nanoparticles / Q000737:chemistry*; D063225:Organically Modified Ceramics; D018583:Pliability; D012821:Silanes / Q000737:chemistry; D012833:Siloxanes / Q000737:chemistry; D013314:Stress, Mechanical; D013696:Temperature; D013997:Time Factors; D014783:Viscosity; D014867:Water / Q000737:chemistry
chemical_list: D003188:Composite Resins; C438835:Filtek P60 Composite Resin; C474035:Filtek Supreme; C509998:Grandio; D008689:Methacrylates; D063225:Organically Modified Ceramics; D012821:Silanes; D012833:Siloxanes; C510232:Simile composite resin; C479084:admira; D014867:Water