Author’s Accepted Manuscript Mechanical properties of fiber reinforced restorative composite with two distinguished fiber length distribution Lippo Lassila, Sufyan Garoushi, Pekka K. Vallittu, Eija Säilynoja www.elsevier.com/locate/jmbbm

PII: DOI: Reference:

S1751-6161(16)00064-3 http://dx.doi.org/10.1016/j.jmbbm.2016.01.036 JMBBM1812

To appear in: Journal of the Mechanical Behavior of Biomedical Materials Received date: 21 September 2015 Revised date: 11 January 2016 Accepted date: 27 January 2016 Cite this article as: Lippo Lassila, Sufyan Garoushi, Pekka K. Vallittu and Eija Säilynoja, Mechanical properties of fiber reinforced restorative composite with two distinguished fiber length distribution, Journal of the Mechanical Behavior of Biomedical Materials, http://dx.doi.org/10.1016/j.jmbbm.2016.01.036 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Mechanical properties of fiber reinforced restorative composite with two distinguished fiber length distribution

Lippo Lassila1, Sufyan Garoushi1*, Pekka K.Vallittu1,2, Eija Säilynoja3

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2

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 3

Reseach Development and Production Department, Stick Tech Ltd – Member of GC Group, Turku, Finland

*Corresponding author: Dr. Sufyan Garoushi, BDS, PhD, Docent Department of Biomaterials Science Institute of Dentistry and TCBC University of Turku Turku, FINLAND E-mail address: [email protected]

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Abstract

Objectives. 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. Materials and Methods. Experimental fiber reinforced composite (Exp-FRC) was prepared by mixing 27 wt% 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 23 wt% of dimethacrylate based resin matrix and then 50 wt% 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 analysed using ANOVA followed by post hoc Tukey's test. Level of significance was set at 0.05. Results. ANOVA revealed that experimental composites reinforced with different fiber length scales (hybrid Exp-FRC) had statistically significantly higher mechanical performance of fracture toughness (4.7 MPam1/2) and flexural strength (155 MPa) (p0.05).

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180.0 160.0

Flexural Strength MPa

140.0 120.0 100.0 80.0 60.0 40.0 20.0 0.0 Exp-FRC1

Exp-FRC2

Exp-FRC3

everX Posterior

Alert

Supreme XT

Figure 2. Bar graph illustrating means flexural strength (MPa) and standard deviation (SD). Groups joined by a horizontal line are not significantly difference (p >0.05).

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18.0 16.0 14.0

Flexural Modulus GPa

12.0 10.0 8.0 6.0 4.0 2.0 0.0 Exp-FRC1

Exp-FRC2

Exp-FRC3

everX Posterior

Alert

Supreme XT

Figure 3. Bar graph illustrating means flexural modulus (GPa) and standard deviation (SD). Groups joined by a horizontal line are not significantly difference (p >0.05).

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2.5

Work of fracture energy Ncm

from preload to Maximum Load

A

from preload to Maximum Extension 2.0

1.5

1.0

0.5

0.0 Exp-FRC1

Exp-FRC2

Exp-FRC3

everX Posterior Supreme XT

Alert

Load (N) 90

B

Exp-FRC1 80 70

Exp-FRC2

60

Exp-FRC3 50

everX Posterior

40

Break 30

Supreme XT 20 10

Alert

0 -0,20

-

0,10

0,10

0,00

0,20

0,30

0,40

Extension from Preload (mm)

Figure 4. (A) Bar graph illustrating work of fracture energy (Ncm) from preload to maximum load and extension. (B) The graph shows typical load-strain curves of all tested composites.

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Figure 5. Optical microscopic images (x6.5, scale bar 1000 µm) of the experimental FRC composites. (A) Exp-FRC1, (B) Exp-FRC2, (C) Exp-FRC3.

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Figure 6. Fracture surface of the experimental FRC single-edge-notched-beam specimen showing pull-out of fibers.

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Figure 7. Millifibers orientation in everX Posterior (A). Random orientation of microfibers; (B) In hybrid Exp-FRC1 composite between longer fibers. (C) In plain Exp-FRC3 composite.

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16.0% everX Posterior Exp-FRC1

14.0% 12.0%

Fraction %

10.0% 8.0% 6.0% 4.0% 2.0%

0.0% 0.09 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

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1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0

Fiber length in mm

Figure 8. Length distribution of discontinuous fibers in hybrid experimental FRC1 and everX Posterior.

Highlights

By using dual discontinuous fiber length mechanical properties improved Toughing and work of fracture were most clearly increased Dual fiber length distribution enables packing of the composite to cavity

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Mechanical properties of fiber reinforced restorative composite with two distinguished fiber length distribution.

The purpose of this study was to investigate the reinforcing effect of discontinuous glass fiber fillers with different length scales on fracture toug...
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