title: Effect of preheating and shade on surface microhardness of silorane-based composites.
abstract: OBJECTIVE
  The aim of the present study was to evaluate the effect of preheating and shade on the surface microhardness of silorane-based composites.
  
  
  METHODS
  Three shades of two different types of composites were evaluated: a silorane-based composite and a methacrylate-based composite. The composites were tested at 23°C, and after preheating at 55°C. Five specimens were prepared for each experimental group. The top surface of the specimens was irradiated for 20 s using an LED unit. Vickers microhardness test was used to evaluate both top and bottom surfaces of the specimens, followed by 24-h storage in the dark. Statistical analysis was performed using one-way anova and Tukey's post-hoc test at a level of significance of α = 0.05.
  
  
  RESULTS
  There was a significant rise in microhardness as the temperature increased from 23 to 55°C for both the top and bottom surfaces of the tested composites (P < 0.05). The C2 shade of both composites exhibited the lowest microhardness (P < 0.05), while the A2 and A3 shades did not show significant differences compared to each other (P > 0.05) Filtek Silorane presented significantly lower microhardness than Filtek Z250 (P < 0.05), regardless of the temperature, shade, or depth of measurement.
  
  
  CONCLUSIONS
  Preheating, shade, and composition of the tested composite resins affected their surface microhardness.
authors.affiliation: Department of Operative Dentistry, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki, Greece.
authors.forename: Marios
authors.initials: M
authors.lastname: Theodoridis
authors.affiliation: Department of Operative Dentistry, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki, Greece.
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Dionysopoulos
authors.affiliation: Department of Operative Dentistry, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki, Greece.
authors.forename: Eugenia
authors.initials: E
authors.lastname: Koliniotou-Koumpia
authors.affiliation: Department of Operative Dentistry, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki, Greece.
authors.forename: Pavlos
authors.initials: P
authors.lastname: Dionysopoulos
authors.affiliation: Department of Operative Dentistry, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki, Greece.
authors.forename: Paris
authors.initials: P
authors.lastname: Gerasimou
mesh_terms: D003116:Color; D003188:Composite Resins / Q000737:chemistry*; D006244:Hardness; D006358:Hot Temperature; D008422:Materials Testing; D062047:Silorane Resins / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D003188:Composite Resins; D062047:Silorane Resins; C555513:silorane composite resin
keywords: composite resin; microhardness; preheating; shade; silorane