Anne C E Bocalon1, Daniela Mita2, Isabela Narumyia3, Paul Shouha4, Tathy A Xavier5, Roberto Ruggiero Braga6. 1. 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. 2. 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. 3. 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. 4. Private Practice, Sydney, Australia. Electronic address: pshouha@bigpond.net.au. 5. 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. 6. 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.
Abstract
OBJECTIVE: 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. METHODS: 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). RESULTS: 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). SIGNIFICANCE: The replacement of a small fraction of filler particles with glass fibers significantly increased fracture toughness and reduced post-gel shrinkage of experimental composites.
OBJECTIVE: 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. METHODS: 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). RESULTS: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). SIGNIFICANCE: The replacement of a small fraction of filler particles with glass fibers significantly increased fracture toughness and reduced post-gel shrinkage of experimental composites.