1. Maximizing Ceramic Filler in a
Composite with a Polymer Matrix
Nathan Cloeter
Materials Science and Engineering
Senior Laboratory Project
Fall 2014
1
3. Background
3
0 Cavities form in our teeth
0 Different Materials have been
developed to fix this.
0 Each has a weakness.
0 Current composites
0 Ceramic filler with polymer
matrix.
0 Current ceramic is silica
0 Lack of durability (10 years)
Overview Background Goals Procedure Results Conclusions Summary
Image Courtesy of studiodentaire.com
4. Titania Filler
4
Silica (SiO2)
0 Commercial composites use agglomerated silica.
0 Nanosilica and microsilica (~0.2 micron) are easier to mix.
New Material needs to be selected
0 Titania (TiO2) and alumina (Al2O3) have more favorable
properties.
0 E Alumina (340 MPa)>E Titania (240 MPa)>E Silica (70 MPa)
0 Alumina is the strongest, but samples turn gray.
0 Titania, silica do not have this issue.
0 Percentage of filler volume needs to be high enough for modulus
that compares with enamel.
0 After certain amount of filler is added to the matrix, it becomes
too difficult to add more.
Overview Background Goals Procedure Results Conclusions Summary
5. Matrix
5
BisGMA
0 2,2-Bis [4-(2-Hydroxy-3-Methacryloxypropoxy) Phenyl] Propane
0 Monomer that is commonly used as a polymer matrix in dental
composite research due to it being able to adhere to enamel.
TEGDMA
0 tri(ethylene-glycol) dimethacrylate
0 Added to BisGMA matrix to lower viscosity of the matrix.
BPO
0 Benzoyl Peroxide
0 Used as a heat initiator for polymerization.
Matrix is a 50/50 mixture of BisGMA-TEGMA with 1% BPO added
as an initiator.
Overview Background Goals Procedure Results Conclusions Summary
6. Silane
6
0 MPTMS
0 Methacryloxypropyltrimethoxysilane
0 Previously used: (3-
Mercaptopropyl)trimethoxysilane
0 New Silane has a higher amount of
agglomeration compared to the previous
type.
0 Covalent Crosslinking across surface of
filler.
0 Siloxane surface is created.
0 Surface becomes hydrophilic.
0 Increases surface hardness.
0 Downside: causes agglomeration.
0 One gram of MPTMS added for every ten
of Titania.
Overview Background Goals Procedure Results Conclusions Summary
Image Courtesy of Cornell.edu
Image Courtesy of UCDavis.edu
7. Solvents
7
0 Protic Solvents
0 Solvent that has a hydrogen
atom bound to an oxygen
(hydroxyl) or nitrogen (amine).
0Acetic Acid
0Isopropyl Alcohol
Overview Background Goals Procedure Results Conclusions Summary
0 Change from previous
semester of aprotic solvents.
0 New MPTMS as silane requires
acetone in control to give a
base reading.
Solvent Chemical
Formula
Boiling
Point (ᵒC)
pKa Polarity FDA Limit
Acetic Acid 𝐶𝐻3 𝐶𝑂2 𝐻 118.1 20 6.2 5000 ppm
Isopropyl
Alcohol
𝐶3 𝐻8 𝑂 82.5 16.5 3.9 5000 ppm
Acetone 𝐶3 𝐻6 𝑂 56 20 5.1 5000 ppm
8. Goals
8
1. Overall Goal: Reach high enough volume percent
of filler where mechanical properties are
favorable to replace the current commercial
model.
0 Should be attainable with volume percent of titania > 60%.
0 Through density calculations, this means weight percent of
titania > 80%.
2. Evaluate effect of diluents on mixing mechanical
properties after curing.
0 See if any are capable of being used to raise filler% more
effectively than any of the others.
0 Test effectiveness of polar protic solvents to see if effective.
Introduction Background Goals Procedure Results Conclusions Summary
9. Procedure
9
0 Silanize nanopowder with MPTMS
0 Washed powder with ethanol to remove MPTMS.
0 Add BPO as an initiator to Pre-mixed BisGMA-TEGMA matrix
0 Add 3 mL of solvent for every two grams of matrix.
0 Add powder in stepwise process to matrix, mechanically stirring
each time until uniform.
0 Store in vacuum to let solvent evaporate from mixture.
0 Pack into molds.
0 Cure in an oven at 80 degrees Fahrenheit.
0 Polish the samples.
0 Perform mechanical tests.
Overview Background Goals Procedure Results Conclusions Summary
10. Result of adding diluent
10Overview Background Goals Procedure Results Conclusions Summary
Diluent
Added
Behavior
During
Sample
Prep?
Weight
Percent
Achieved
(60/70)
Notes after
curing
No Diluent Stiff and hard
to mix
55 wt% Is polishable.
Some
porosity.
Acetic Acid Unable to
fully remove
solvent.
(Yes, No) Extremely
porous.
Difficult to
polish.
Isopropyl
Alcohol
Had difficulty
mixing.
(Yes, No) Some pores.
Not as bad as
acetic acid.
Acetone Behaved
Normally
(Yes, Yes*) Came out the
best.
11. Modulus/Flexural Strength
11Overview Background Goals Procedure Results Conclusions Summary
o Despite having the same weight percent of filler, Fall 2 doesn’t perform as
well.
o High porosity affected results.
o Only one sample survived
o Isopropyl alcohol had samples that had the potential to work the best.
o Extremely sporadic.
o Flexural Strength is the highest due to dependence on max load that is
applied.
Sample Average
Flexural
Modulus
Standard
Deviation
Average
Flexural
Strength
Standard
Deviation
Fall 2 2.55 GPa N/A 31.5 Mpa N/A
Fall 3 4.87 GPa 0.208 62.9 MPa 11.47
Fall 4 6.36 GPa 0.133 55.0 MPa 0.67
12. Toughness/Hardness
12
o Similar trend of results compared to last slide.
o Isopropyl alcohol has much higher levels of toughness, with yet again a
high deviation.
o The hardness levels seem to be constant with each sample.
Overview Background Goals Procedure Results Conclusions Summary
Sample Average
Toughness
Standard
Deviation
Average
Hardness
Standard
Deviation
Fall 2 204.4 MPa N/A 42.5 HV 9.70
Fall 3 422.9 MPa 140.8 58.3 HV 9.55
Fall 4 244.1 MPa 13.09 63.1 HV 8.46
13. Conclusions
Overview Background Goals Procedure Results Conclusions Summary 13
• Acetone was the most promising diluent.
• Still haven’t reached the 80 weight percent goal.
• None of the solvents could be used to reach levels
already achieved in earlier semesters.
• Includes control.
• May be a result of new silane.
• Directions for future research:
• Reduce amount of silane used.
• 50-50 mixture of different solvent types.
• Find a protic solvent that evaporates more effectively.
• Change ratio of polymer matrix.
14. Project Summary
Introduction Approach Design Experimental Prototype Conclusions Summary 14
• Goal is to reach eighty weight percent filler for sample.
• Attempted to add diluent to the sample to increase filler
percent.
• Unable to reach levels from previous semester.
• Due to combination of new silane, as well as the new solvents being
ineffective.
• Could not get samples above 60 weight %.
• Potential is there to raise weight percent, as well as change other
areas to raise results.
15. References
Introduction Approach Design Experimental Prototype Conclusions Summary 15
0 Wang Y, James J. Lee, Lloyd IK, Wilson OC, Rosenblum M, and Thompson V.
"High Modulus Nanopowder Reinforced Dimethacrylate Matrix Composites
for Dental Cement Applications." Journal of Biomedical Materials Research
Part A 82A.3 (2003): 651-57.
0 Chen Q, Zhao Y, Wu W, Xu T, Fong H. "Fabrication and Evaluation of Bis-
GMA/TEGDMA Dental Resins/ Composites Containing Halloysite
Nanotubes." Dent Mater 28.10 (2007): 1071-079.
0 Chen YH, Lloyd IK. "Mechanical Properties of Dental Composites with Mixed
Alumina and Silica Fillers." Thesis. University of Maryland, n.d. Print.
0 Chan, K. S., Y. -D. Lee, D. P. Nicolella, B. R. Furman, S. Wellinghoff, and R.
Rawls. "Improving Fracture Toughness of Dental Nanocomposites by
Interface Engineering and Micromechanics." Engineering Fracture Mechancis
74 (2007): 1857-871.
0 Ferracane JL. "Resin Composite—State of the Art." Dental Materials 27
(2011): 29-38.
0 Udomphol, T. "Laboratory 7: Bend Testing." Suranaree University of
Technology.
0 England G. "Vickers Hardness Test." GordonEngland. Surface Engineering
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