title: Dynamic thermomechanical properties and sorption characteristics of two commercial light cured dental resin composites.
abstract: OBJECTIVE
  The first objective of this work is the study by DMTA of viscoelastic properties (E', E'', tandelta, Tg) of two current dental resin composites Tetric EvoCeram (nanohybrid) and Heliomolar (microfilled) in dry condition and in water for up to 30 days. The second objective is to determine the sorption characteristics of these composites in water and ethanol/water solution 75vol.%.
  
  
  METHODS
  For DMTA the bar-shaped specimens divided into five groups of three samples each. The first group consisted of dry samples measured 1h after curing. The second and third group consisted of samples, which had been heated in air at 80+/-1 degrees C for 1 day or had been stored in distilled water at 80+/-1 degrees C for 1 day. The fourth and fifth group consisted of samples, which had been stored in distilled water at 37+/-1 degrees C for periods 1 and 7 days correspondingly. Also specimen discs (15mm in diameter and 1mm in thickness) were immersed in water or a 75vol.% ethanol/water solution at 37+/-1 degrees C. At fixed time intervals they were removed, blotted dry to remove excess liquid, weighted and returned to the liquid. This process continued for 30 days.
  
  
  RESULTS
  The viscoelastic properties (E', E'', tandelta, Tg) of the two composites treated under different conditions were recorded and compared. Also the mass uptake, diffusion coefficient, solubility and volumetric changes for immersion of composites in water and ethanol/water solution 75vol.% at 37+/-1 degrees C were determined.
  
  
  CONCLUSIONS
  Tetric EvoCeram a nanohybrid composite with similar about resin matrix with Heliomolar which is a microfilled showed better dynamic thermomechanical properties and sorption characteristics than Heliomolar.
authors: Laboratory of Organic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Hellas, Greece. siderid@chem.auth.gr
authors: Irini D
authors: ID
authors: Sideridou
authors: Maria M
authors: MM
authors: Karabela
authors: Evagelia Ch
authors: ECh
authors: Vouvoudi
mesh_terms: D000042:Absorption; D000180:Acrylic Resins / Q000737:chemistry; D000327:Adsorption; D000388:Air; D003188:Composite Resins / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D003890:Desiccation; D004058:Diffusion; D004548:Elasticity; D000431:Ethanol / Q000737:chemistry; D006358:Hot Temperature; D006801:Humans; D007101:Immersion; D008422:Materials Testing; D053758:Nanoparticles / Q000737:chemistry; D011140:Polyurethanes / Q000737:chemistry; D012995:Solubility; D012997:Solvents / Q000737:chemistry; D013314:Stress, Mechanical; D013696:Temperature; D013997:Time Factors; D014783:Viscosity; D014867:Water / Q000737:chemistry
chemical_list: D000180:Acrylic Resins; D003188:Composite Resins; D003764:Dental Materials; C513708:Heliomolar; D011140:Polyurethanes; D012997:Solvents; C501891:Tetric EvoCeram; D014867:Water; D000431:Ethanol