title: Effect of thickness of bonded composite resin on compressive strength.
abstract: OBJECTIVE
  The aim of this study was to investigate the compressive strength of composites with different physical properties bonded as a restoration to dentin in layers of varying thicknesses.
  
  
  METHODS
  Four types of direct composite materials: a midway-filled (Tetric EvoCeram); a compact-filled (Clearfil AP-X); a nano-filled (Filtek Supreme); and a micro-filled material (Heliomolar) were bonded in 0.5-3.0mm thick layers onto bovine dentin. Each material group contained 25 samples, which were loaded until fracture.
  
  
  RESULTS
  The nano-filled and the compact filled material showed a significant association between layer thickness and compressive strength. The midway-filled composite was the most consistent material showing similar failure load over the complete thickness range.
  
  
  CONCLUSIONS
  A clear influence of layer thickness on compressive strength was found in some composite resin materials. When restorations are placed that are heavily loaded, such as in patients with severe wear due to bruxism it may be advisable to choose a material that is adequately strong in all thicknesses.
authors.affiliation: Department of Preventive and Restorative Dentistry, Radboud University Nijmegen Medical Centre, Philips van Leydenlaan 25, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands. Electronic address: jorien.hamburger@radboudumc.nl.
authors.forename: Jorien T
authors.initials: JT
authors.lastname: Hamburger
authors.affiliation: Department of Preventive and Restorative Dentistry, Radboud University Nijmegen Medical Centre, Philips van Leydenlaan 25, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands.
authors.forename: Niek J M
authors.initials: NJ
authors.lastname: Opdam
authors.affiliation: Department of Preventive and Restorative Dentistry, Radboud University Nijmegen Medical Centre, Philips van Leydenlaan 25, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands.
authors.forename: Ewald M
authors.initials: EM
authors.lastname: Bronkhorst
authors.affiliation: Dental Material Sciences, ACTA, Amsterdam, The Netherlands.
authors.forename: Joost J M
authors.initials: JJ
authors.lastname: Roeters
authors.affiliation: Department of Preventive and Restorative Dentistry, Radboud University Nijmegen Medical Centre, Philips van Leydenlaan 25, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands.
authors.forename: Marie-Charlotte D N J M
authors.initials: MC
authors.lastname: Huysmans
mesh_terms: D000818:Animals; D002417:Cattle; D003188:Composite Resins / Q000737:chemistry*; D019245:Compressive Strength; D058250:Dental Restoration Repair; D003804:Dentin; D007180:Incisor; D008422:Materials Testing; D013329:Structure-Activity Relationship
chemical_list: D003188:Composite Resins
keywords: Adhesion; Composite resin; Compressive strength; Dental materials; Thickness