title: Comparison of time-dependent changes in the surface hardness of different composite resins.
abstract: OBJECTIVE
  The aim of this study was to evaluate the change in surface hardness of silorane-based composite resin (Filtek Silorane) in time and compare the results with the surface hardness of two methacrylate-based resins (Filtek Supreme and Majesty Posterior).
  
  
  METHODS
  From each composite material, 18 wheel-shaped samples (5-mm diameter and 2-mm depth) were prepared. Top and bottom surface hardness of these samples was measured using a Vicker's hardness tester. The samples were then stored at 37°C and 100% humidity. After 24 h and 7, 30 and 90 days, the top and bottom surface hardness of the samples was measured. In each measurement, the rate between the hardness of the top and bottom surfaces were recorded as the hardness rate. Statistical analysis was performed by one-way analysis of variance, multiple comparisons by Tukey's test and binary comparisons by t-test with a significance level of P = 0.05.
  
  
  RESULTS
  The highest hardness values were obtained from each two surfaces of Majesty Posterior and the lowest from Filtek Silorane. Both the top and bottom surface hardness of the methacrylate based composite resins was high and there was a statistically significant difference between the top and bottom hardness values of only the silorane-based composite, Filtek Silorane (P < 0.05). The lowest was obtained with Filtek Silorane. The hardness values of all test groups increased after 24 h (P < 0.05).
  
  
  CONCLUSIONS
  Although silorane-based composite resin Filtek Silorane showed adequate hardness ratio, the use of incremental technic during application is more important than methacrylate based composites.
authors: Department of Restorative Dentistry, Faculty of Dentistry, University of Gazi, Ankara, Turkiye.
authors: Suat
authors: S
authors: Ozcan
authors: Department of Restorative Dentistry, Faculty of Dentistry, University of Gazi, Ankara, Turkiye.
authors: Ihsan
authors: I
authors: Yikilgan
authors: Department of Restorative Dentistry, Faculty of Dentistry, University of Gazi, Ankara, Turkiye.
authors: Mine Betul
authors: MB
authors: Uctasli
authors: Department of Restorative Dentistry, Faculty of Dentistry, University of Gazi, Ankara, Turkiye.
authors: Oya
authors: O
authors: Bala
authors: Public Dentist, Adana, Turkiye.
authors: Zeliha Gonca
authors: ZG
authors: Bek Kurklu
keywords: Composite resin; silorane-based composite resin; surface hardness