A Novel Layer-by-Layer Biomimetic Structure Structural Design, Mechanical Properties, and Failure Mechanism Adelina TJOKRONEGORO 1
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A Novel Layer-by-Layer Biomimetic Structure
Structural Design, Mechanical Properties, and Failure Mechanism
Adelina TJOKRONEGORO
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Background
• Oral health is a window to general health show health signs and infections
• Oral problems can affect the overall health
• Cavities is the most prevalent oral problem affecting both adult and child
• Filling is a way to restore back a tooth damage to its normal function and shape
• By closing off the spaces, enter of bacteria and further decay can be prevented
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Background• Common dental fillings used:
Porcelain fillings: http://www.webmd.com/oral-health/guide/dental-health-fillings#1
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Background• Metals:
- Tooth pain and sensitivity contact between metal of adjacent tooth
- Expensive- Immunoreactive mercury in amalgram may
induce allergies• Deteriorating fillings
- Composite fillings are cheap and safe, but have low mechanical properties
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Aim• To design new structure that aim to improve
mechanical properties and decrease failure rate of dental filling composites
• To compare the mechanical properties values of different structural design and determine the significance of structural design differences
• Provide alternative dental fillings with better structure and mechanical properties for commercial application
• Substitute the current dental fillings that are commonly used in the market
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Methodology
Materials Fabrication Testing
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Materials: Matrix
Function Quantity MassBisGMA Monomer Weight ratio:
1:1~ 20 gram
TEGDMA Monomer (Dilute)
~ 20 gram
Camphoquinone (CQ)
Photoinitiator 2 mole% ~ 0.4 gram
2-(dimethylamino)ethyl methacrylate (DMAEMA)
Coinitiator 2mole% ~ 0.4 gram
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Fabrication Process
Matrix
Composite
Sample Fabrication
- BisGMA- TEGDMA- Camphoquinone (CQ)- 2-(dimethylamino)ethyl methacrylate (DMAEMA)
Adding Zirconia (ZrO2) filler particles- 10.7vol%- 21.4vol%
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Fabrication Process: Matrix
Vacuum Twister ProcessThe final mixture is put in the vacuum for 1 hour and ready to be
used
Triple Roller MillsMatrix mixture is even out to have uniform particles distribution within the mixture
Matrix MixtureBisGMA is diluted with TEGDMA and photoinitiator CQ, coinitiator DMAEMA are added based on weight calculation
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Zirconia (ZrO2) Filler Particles
• High purity (~99%)• Have favorable influence on mechanical properties of
materials• Transformation toughening property: tetragonal form
into monoclinic symmetry stable and high toughness
Citation:Zych, L. (2009, September 27). The effect of nanometric zirconia particle additives on microstructure and mechanical properties of dense alumina. Processing and Application of Ceramics, 131- 135. Retrieved October 27, 2016, from http://www.tf.uns.ac.rs/publikacije/PAC/pdf/PAC 05 04.pdf
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Zirconia (ZrO2) Filler Particles
• Comparable mechanical properties to metals• Similar color to tooth color• Biocompatible inert material, no oncogenic or mutagenic
effects• Small radioactivity • Optical characteristics natural-looking teeth
Citation:Ali, S. A., Karthigeyan, S., Deivanai, M., & Mani, R. (2014, March). ZIRCONIA: PROPERTIES AND APPLICATION — A REVIEW. Pakistan Oral & Dental Journal, 34, 1st ser., 178-183. Retrieved October 28, 2016, from http://www.podj.com.pk/March_2014/PODJ-40.pdf Bavbek, A. B., Özcan, M., & Eskitascioglu, G. (2014, December 6). Radioactive potential of zirconium-dioxide used for dental applications. Journal of Applied Biomaterials and Functional Materials, 12(1), 35-40. Retrieved November 1, 2016.
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Zirconia Alumina Silica
Mechanical Stability ++ ++ +
High Surface Area ++ ++ ++
Control of Average Pore Diameter ++ ++ +Control of Average Particle Diameter ++ ++ ++
Chemically Flexible + ++ +
Energetically Homogeneous - - +
Swelling ++ ++ -Chemical Stability (to acid and base) ++ - ++
Thermal Stability ++ + -
++ = Very good; + = good performance; - = fair performance
In general, zirconia has a similar performance with alumina and silica. The significant advantage of zirconia over either silica or alumina is its chemical and thermal stability.Unlike alumina, Zirconia is completely stable over the entire pH range, which is an important aspect for dental application and unlike silica, zirconia is stable at elevated temperatures and does not shrink or swell as an organic content.
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Fabrication Process: 10.7vol%
Layer-by-layer assembling
Repeating the same structural design up to 10 layers
SolidificationUV exposure to fix each layer structure
Create structural designUsing cover glass as reference of height (~2mm) and
transparency as the support the structure
TransparencyCover Glass
Microscope Slide
~2mm
~2mm~30mm
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Fabrication Process: Stepped (0 & 21.4vol%)
Layer-by-layer assemblingCreate second layer with 21.4vol% and repeat the same
steps to create 10 layers of stepped design
SolidificationUV exposure to fix each layer structure
Create structural designUsing cover glass as reference of height (~2mm) and transparency as the support the pure resin structure
Pure Resin (0vol%)
21vol%
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Testing: Three-Point Flexural Test• For polymers, wood and composites, brittle materials• Obtain failure from tension and compression stress
and avoid shear stress• Full control of span and depth ratio• Ease of specimen preparation and testing procedure
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Three-Point Flexural Test
• Measures bending force (F) and bending displacement (D) simultaneously
• Helps in determining modulus of elasticity (Ef), flexural stress (), flexural strain ()
• Above neutral axis will experience compression, below neutral axis will experience tension
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Three-Point Flexural Test
Calculation:• Flexural strength: = • Flexural strain: = • Modulus of elasticity: Ef =
F = load at a given point on the load deflection curve (N)L = Support span (mm)b = Width of test beam (mm)d = Height of tested beam (mm)D = maximum deflection of the center of the beam (mm)m = Slope of the initial straight-line portion of the load deflection
Notes:The modulus of elasticity tension is equal to modulus of elasticity compression when the beam material is isotropic and homogeneoushttp://www.dtic.mil/dtic/tr/fulltext/u2/a113937.pdf
Testing Result: 10.7vol%
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949698
100102104106
Mean: 97.89
Mean: 103.80
ADELINA JI
Flex
ure
Stre
ngth
(MPa
)
STD: 17.65
STD: 6.11
0.0440.0450.0460.0470.0480.049
0.050.0510.052
Mean: 0.047
Mean: 0.051
ADELINA JI
Flex
ure
Stra
in STD: 0.010
STD: 0.006
2.85
2.9
2.95
3
3.05
3.1
Mean: 2.95
Mean: 3.085
ADELINA JI
Mod
ulus
(GPa
) STD: 0.36
STD: 0.31
1.941.961.98
22.022.042.062.08
2.12.12
Mean: 2.007
Mean: 2.106
WIDTH HEIGHT
Sam
ple
Size
(mm
)STD: 0.113
STD: 0.366
Testing Result: Stepped (0 & 21.4vol%)
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2.85
2.9
2.95
3
3.05
3.1
3.15
3.2
3.25
Mean: 2.97
Mean: 3.18
ADELINA JI
Mod
ulus
(GPa
) STD: 0.41 STD: 0.35
84.4
84.6
84.8
85
85.2
85.4
85.6
85.8
86
86.2
Mean: 85.97
Mean: 84.96
ADELINA JI
Flex
ure
Stre
ngth
(MPa
)
STD: 12.66 STD: 13.47
0.028
0.029
0.03
0.031
0.032
0.033
0.034
0.035
Mean: 0.03
Mean: 0.034
ADELINA JI
Flex
ure
Stra
in
STD: 0.0048 STD: 0.0098
0
0.5
1
1.5
2
2.5
3
3.5 Mean: 2.065 Mean: 2.97
WIDTH HEIGHT
Sam
ple
Size
(mm
) STD: 0.042 STD: 0.19
Discussion• Based on the overall 3-point bending test results, 10.7vol% has
higher flexure strength and strain in comparison to stepped composite– Fracture characteristics of 2 dissimilar materials can be
significantly influenced by interaction between the concentrated strain at the crack tip possibly has negative interaction which results in weakening the structure
Citation:Landes, J. D. (1988). Nonlinear Fracture Mechanics: Elastic-Plastic Fracture. ASTM International.
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Conclusion• Fabrication, measurement, and testing method might
influence the final results, however the overall estimation is acceptable and lead to conclusion that:– Singular 10.7vol% has better mechanical properties
comparing to stepped 0 & 21.4vol%– Singular 10.7vol% can be said to have more desirable
structure comparing to stepped 0 & 21.4vol%
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Reference• J. Nawrocki, M.P. Rigney, A. McCormick, and P.W. Carr, Review,
"Chemistry of Zirconia and Its Use in Chromatography," J. Chromatogr. A 657, 229-82 (1993)
• Vizcarra, C. (n.d.). Biocompatible Dental Material. Retrieved October 26, 2016, from http://www.biodentistrydrvizcarra.com/?
s=8&sub=1