title: Effect of pre-heating on the mechanical properties of silorane-based and methacrylate-based composites.
abstract: BACKGROUND
  The use of composites in dental restoration has been commonly criticized, due to their underwhelming mechanical properties. This problem may be solved partially by preheating. The present research aims to determine the effect of preheating on the mechanical properties of two different classes of composites.
  
  
  METHODS
  A Silorane-based (Silorane) and a Methacrylate-based (Z250) composite were preheated to different temperatures (25, 37, and 68 °C) and afterwards were tested with the appropriate devices for each testing protocol. The material's flexural strength, elastic modulus, and Vickers microhardness were evaluated. Two-way ANOVA, and Tukey's post hoc were used to analyze the data.
  
  
  RESULTS
  Microhardness and elastic modulus increased with preheating, while flexural strength values did not increase significantly with preheating. Furthermore the methacrylate-based composite (Z250) showed higher values compared to the Silorane-based composite (Silorane) in all the tested properties.
  
  
  CONCLUSIONS
  Preheating Silorane enhances the composite's microhardness and elastic modulus but does not affect its flexural strength. On the other hand, preheating Z250 increases its microhardness but does not change its flexural strength or elastic modulus. In addition, the Z250 composite shows higher microhardness and flexural strength than Silorane, but the elastic modulus values with preheating are similar. Therefore Z250 seems to have better mechanical properties making it the better choice in a clinical situation.Key words:Composite, elastic modulus, flexural strength, microhardness, preheating.
authors.affiliation: Associate professor at the Operative Dentistry Department, Dental and Periodontal Research Center, Faculty of Dentistry, Tabriz University of Medical Sciences, Tabriz, Iran.
authors.forename: Narmin
authors.initials: N
authors.lastname: Mohammadi
authors.affiliation: Associate professor at the Operative Dentistry Department, Dental and Periodontal Research Center, Faculty of Dentistry, Tabriz University of Medical Sciences, Tabriz, Iran.
authors.forename: Elmira
authors.initials: E
authors.lastname: Jafari-Navimipour
authors.affiliation: Professor at the Operative Dentistry Department, Dental and Periodontal Research Center,Faculty of Dentistry, Tabriz University of Medical Sciences, Tabriz, Iran.
authors.forename: Soodabeh
authors.initials: S
authors.lastname: Kimyai
authors.affiliation: Assistant professor at the Operative Dentistry Department, Dental and Periodontal Research Center,Faculty of Dentistry, Tabriz University of Medical Sciences, Tabriz, Iran.
authors.forename: Amir-Ahmad
authors.initials: AA
authors.lastname: Ajami
authors.affiliation: Assistant professor at the Operative Dentistry Department, Dental and Periodontal Research Center,Faculty of Dentistry, Tabriz University of Medical Sciences, Tabriz, Iran.
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Bahari
authors.affiliation: Student of the Biomedical Engineering Masters Program, Koç University, Istanbul, Turkey.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Ansarin
authors.affiliation: DDS, private practice, Tabriz, Iran.
authors.forename: Mahsa
authors.initials: M
authors.lastname: Ansarin