title: Effect of water storage, thermocycling, the incorporation and site of placement of glass-fibers on the flexural strength of veneering composite.
abstract: OBJECTIVE
  To evaluate the effects of water storage, thermocycling, and the incorporation of glass-fibers, on the flexural strength of veneering composites.
  
  
  METHODS
  Veneering composites with different fillers, matrices and polymerization methods (Belleglass Kerr Inc., Orange, CA, USA; Sculpture, Pentron Inc. Wallingford CT, USA; Sinfony, 3M Espe, Seefeld, Germany; SR Adoro LC and HP, Targis, Ivoclar Vivadent, Schaan, Liechtenstein), a glass-fiber framework material (Vectris Pontic VP, Ivoclar Vivadent) and a direct restorative composite control (Tetric Ceram, Ivoclar Vivadent) were selected. For the first part of the study, 30 bar specimens (25 x 2 x 2 mm3) per material were fabricated. Ten were stored for 24 h and 10 for 14 days in water at 37 degrees C. Ten were thermocycled (3000 x; 5-50-5 degrees C). Three-point bending tests (crosshead speed: 0.5 mm/min) were performed. For the second part of the study, all veneering materials were combined with a glass-fiber framework (VP). Sixty specimens were produced for each material (25 x 4 x 2 mm3) and treated as in the first part. Three-point bend tests were performed with the reinforcing glass-fiber framework either on the tension or the compression side. Data was evaluated by ANOVA and Weibull analysis.
  
  
  RESULTS
  A decrease in flexural strength was observed after water storage or thermocycling for all veneering materials tested. None of the tested materials exhibited significant advantages compared to the control. The flexural strength of glass-fiber reinforced frameworks was ten times higher and not influenced by water storage or thermocycling. A significant reinforcing effect from glass fibers was observed when they were placed on the tension but not when placed on the compression side.
  
  
  CONCLUSIONS
  A glass-fiber framework on the tension side significantly improved the flexural strength of veneering composites. There was less deterioration due to water storage and thermocycling with the glass-fiber reinforced veneering composite compared to the non-reinforced materials.
authors.affiliation: Clinic for Preventive Dentistry, Periodontology and Cariology, Center for Dental and Oral Medicine, University of Zurich, Plattenstrasse 11, CH-8028 Zurich, Switzerland. till.goehring@zzmk.unizh.ch
authors.forename: Till N
authors.initials: TN
authors.lastname: Göhring
authors.forename: Luigi
authors.initials: L
authors.lastname: Gallo
authors.forename: Heinz
authors.initials: H
authors.lastname: Lüthy
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D003801:Dental Veneers; D005898:Glass / Q000737:chemistry*; D005899:Glass Ionomer Cements / Q000737:chemistry; D006801:Humans; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D018583:Pliability; D011092:Polyethylene Glycols / Q000737:chemistry; D011108:Polymers / Q000737:chemistry; D011109:Polymethacrylic Acids / Q000737:chemistry; D011140:Polyurethanes / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D012823:Silicate Cement / Q000737:chemistry; D013314:Stress, Mechanical; D013696:Temperature; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: D003188:Composite Resins; D005899:Glass Ionomer Cements; D008689:Methacrylates; D011108:Polymers; D011109:Polymethacrylic Acids; D011140:Polyurethanes; D019279:Resin Cements; C477352:Sinfony composite resin; C121818:Tetric ceram; C110370:belleGlass; C111282:dental polyglass; C009753:fiberglass; D014867:Water; C029824:urethane dimethacrylate luting resin; D012823:Silicate Cement; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate