title: Mechanical properties of fiber reinforced restorative composite with two distinguished fiber length distribution.
abstract: The purpose of this study was to investigate the reinforcing effect of discontinuous glass fiber fillers with different length scales on fracture toughness and flexural properties of dental composite.
  
  
  
  Experimental fiber reinforced composite (Exp-FRC) was prepared by mixing 27wt% of discontinuous E-glass fibers having two different length scales (micrometer and millimeter) with various weight ratios (1:1, 2:1, 1:0 respectively) to the 23wt% of dimethacrylate based resin matrix and then 50wt% of silane treated silica filler were added gradually using high speed mixing machine. As control, commercial FRC and conventional posterior composites were used (everX Posterior, Alert, and Filtek Superme). Fracture toughness, work of fracture, flexural strength, and flexural modulus were determined for each composite material following ISO standards. The specimens (n=6) were dry stored (37°C for 2 days) before they were tested. Scanning electron microscopy was used to evaluate the microstructure of the experimental FRC composites. The results were statistically analyzed using ANOVA followed by post-hoc Tukey׳s test. Level of significance was set at 0.05.
  
  
  
  ANOVA revealed that experimental composites reinforced with different fiber length scales (hybrid Exp-FRC) had statistically significantly higher mechanical performance of fracture toughness (4.7MPam(1/2)) and flexural strength (155MPa) (p<0.05) compared to other tested composites.
  
  
  
  The use of different length scales of discontinues fiber fillers (hybrid) with polymer matrix yielded improved mechanical performance compared to commercial FRC and conventional posterior composites.
authors.affiliation: Department of Biomaterials Science and Turku Clinical Biomaterial Center -TCBC Institute of Dentistry, University of Turku, Turku, Finland.
authors.forename: Lippo
authors.initials: L
authors.lastname: Lassila
authors.affiliation: Department of Biomaterials Science and Turku Clinical Biomaterial Center -TCBC Institute of Dentistry, University of Turku, Turku, Finland. Electronic address: sufgar@utu.fi.
authors.forename: Sufyan
authors.initials: S
authors.lastname: Garoushi
authors.affiliation: Department of Biomaterials Science and Turku Clinical Biomaterial Center -TCBC Institute of Dentistry, University of Turku, Turku, Finland; City of Turku Welfare Division, Oral Health Care, Turku, Finland.
authors.forename: Pekka K
authors.initials: PK
authors.lastname: Vallittu
authors.affiliation: Research Development and Production Department, Stick Tech Ltd. - Member of GC Group, Turku, Finland.
authors.forename: Eija
authors.initials: E
authors.lastname: Säilynoja
mesh_terms: D003188:Composite Resins; D003764:Dental Materials; D003799:Dental Stress Analysis; D005898:Glass; D008422:Materials Testing; D018583:Pliability; D013314:Stress, Mechanical; D013499:Surface Properties
chemical_list: D003188:Composite Resins; D003764:Dental Materials
keywords: Discontinuous fiber reinforced composite; Fiber length; Fracture toughness