title: Replacement of glass particles by multidirectional short glass fibers in experimental composites: Effects on degree of conversion, mechanical properties and polymerization shrinkage.
abstract: To test the null hypothesis that the replacement of a small fraction of glass particles with random short glass fibers does not affect degree of conversion (DC), flexural strength (FS), fracture toughness (FT) and post-gel polymerization shrinkage (PS) of experimental composites.
  
  
  
  Four experimental photocurable composites containing 1 BisGMA:1 TEGDMA (by weight) and 60vol% of fillers were prepared. The reinforcing phase was constituted by barium glass particles (2μm) and 0%, 2.5%, 5.0% or 7.5% of silanated glass fibers (1.4mm in length, 7-13μm in diameter). DC (n=4) was obtained using near-FTIR. FS (n=10) was calculated via biaxial flexural test and FT (n=10) used the "single edge notched beam" method. PS at 5min (n=8) was determined using the strain gage method. Data were analyzed by ANOVA/Tukey test (DC, FS, PS) or Kruskal-Wallis/Dunn's test (FT, alpha: 5% for both tests).
  
  
  
  DC was similar among groups (p>0.05). Only the composite containing 5.0% of fibers presented lower FS than the control (p<0.001). FT increased significantly between the control (1.3±0.17MPam(0.5)) and the composites containing either 5.0% (2.7±0.6MPam(0.5)) or 7.5% of fibers (2.8±0.6MPam(0.5), p<0.001). PS in relation to control was significantly reduced at 2.5% fibers (from 0.81±0.13% to 0.57±0.13%) and further reduced between 5.0% and 7.5% (from 0.42±0.12% to 0.23±0.07%, p<0.001).
  
  
  
  The replacement of a small fraction of filler particles with glass fibers significantly increased fracture toughness and reduced post-gel shrinkage of experimental composites.
authors.affiliation: University of São Paulo, School of Dentistry, Department of Biomaterials and Oral Biology, Av. Prof. Lineu Prestes, 2227, 05508-000 São Paulo, SP, Brazil. Electronic address: anne.bocalon@usp.br.
authors.forename: Anne C E
authors.initials: AC
authors.lastname: Bocalon
authors.affiliation: University of São Paulo, School of Dentistry, Department of Biomaterials and Oral Biology, Av. Prof. Lineu Prestes, 2227, 05508-000 São Paulo, SP, Brazil. Electronic address: danielamita17@gmail.com.
authors.forename: Daniela
authors.initials: D
authors.lastname: Mita
authors.affiliation: University of São Paulo, School of Dentistry, Department of Biomaterials and Oral Biology, Av. Prof. Lineu Prestes, 2227, 05508-000 São Paulo, SP, Brazil. Electronic address: isahn77@gmail.com.
authors.forename: Isabela
authors.initials: I
authors.lastname: Narumyia
authors.affiliation: Private Practice, Sydney, Australia. Electronic address: pshouha@bigpond.net.au.
authors.forename: Paul
authors.initials: P
authors.lastname: Shouha
authors.affiliation: University of São Paulo, School of Dentistry, Department of Biomaterials and Oral Biology, Av. Prof. Lineu Prestes, 2227, 05508-000 São Paulo, SP, Brazil. Electronic address: tathy_ap@yahoo.com.br.
authors.forename: Tathy A
authors.initials: TA
authors.lastname: Xavier
authors.affiliation: University of São Paulo, School of Dentistry, Department of Biomaterials and Oral Biology, Av. Prof. Lineu Prestes, 2227, 05508-000 São Paulo, SP, Brazil. Electronic address: rrbraga@usp.br.
authors.forename: Roberto Ruggiero
authors.initials: RR
authors.lastname: Braga
mesh_terms: D003188:Composite Resins; D005898:Glass; D008422:Materials Testing; D058105:Polymerization
chemical_list: D003188:Composite Resins; C009753:fiberglass
keywords: Composites; Glass fibers; Mechanical properties; Shrinkage