SYNTHESIS AND CHARACTERIZATION OF CALCIUM

CARBONATE DERIVED FROM EGGSHELL FOR DENTAL MODEL

FABRICATION
1.0 INTRODUCTION

Dental model is an important tool for dental students to improve their skills during

training. At the moment, dental model is quite expensive in the market since it is imported

from overseas. The high demand for this dental model has led the researchers to focus on

low-cost material, also at the same time produce a similar dental model to that of

commercially available products in the market. Dental model that is used by dental students

basically made up of polymer resin matrix and inorganic fillers [1]. Polymer resin is based on

methcrylate materials, especially cross-linking dimethcrylates. Bis-GMA and TEDGMA are

the most commonly used resins for the restoration of impaired teeth.

Since the filler in the dental materials has been changed significantly, the source from

biowaste can be manipulated to produce an affordable yet functional filler. To date, a few

studies have used various shells as a primary source of CaCO 3. In the past, shells from

oysters, cockles, crabs, eggs and other shells have been previously used as an alternative

source of natural CaCO3 [2]. Since the eggshell is widely known to be readily available as a

waste product in Malaysia, it is proposed to be used as filler for the fabrication of dental

models. The eggshells will be processed into powder form and will be used as a filler in

combination with Bis-GMA and TEDGMA.

1.1 Problem Statement

The currently available dental model in the market for dental training is expensive due

to the material used. Moreover, the model was manufactured from overseas. To date, a few

studies have used various shells as a primary source of CaCO 3. The use of CaCO3 derived

from eggshells as a filler in the fabrication dental models is scarcely reported in the literature.

In this study, the eggshell powder will be introduced to the resin composites. The literatures

stated that raw eggshell particles from SEM analysis exhibited irregular shape with varying

sizes, produce a little porous on the surface, agglomeration and bulky form [3, 4]. Besides,

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eggshell powder has aesthetic issues because it is brown in colour. Therefore, in the current

study, the eggshell powder will be synthesized to obtain white CaCO 3 to be used as a filler in

fabricating a low-cost and eco-friendly dental model.

1.2 Objectives

1. To synthesize and characterize CaCO3 derived from eggshells by sol-gel method and

compare it with commercial CaCO3.

2. To characterize the dental model incorporated with CaCO 3 derived from eggshells in

combination with Bis-GMA and TEDGMA resin and compare it with dental model

using commercial CaCO3.

3. To determine the physical and mechanical properties of dental model using CaCO 3

derived from eggshells in combination with Bis-GMA and TEDGMA resin and

compare it with dental model using commercial CaCO3.

2.0 LITERATURE REVIEW

2.1 Dental Model

The dental model is a 3-dimensional (3D) model that is used to study the anatomy of

human teeth. Dental models are commonly made of plastic materials such as ivorine,

melamine, polycarbonate, and many more. It is used as an educational tool for dental trainee

and students, allowing them to practice certain dental procedures on the plastic teeth of a

model before actually performing the procedures on patients [5]. Commercial teeth model

typically have replacement, screw-in teeth made of materials that let students drill out

cavities, fill them with amalgam or composite, or prepare the plastic teeth for crowns and

bridges [5].

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2.2 Primary elements of dental model

2.2.1 Resin matrix

Resin matrix is composed of polymerizable monomers which is initially a fluid

monomer and converted to a highly crosslinked polymer by a radical addition reaction [6].

Bis-GMA (2, 2-bis [4-(2-hydroxy-3-methacryloyloxypropoxy) phenyl] propane) is derived

from the reaction of bisphenol-A and glycidyl-methacrylate. This compound is commonly

used as the organic phase for both anterior and posterior resin because of its high strength and

hardness [7]. The aromatic backbone structure of Bis-GMA, is rigid which helps to reduce

the polymerization shrinkage, increase modulus and reduced toxicity due to its low volatility

and diffusivity into tissues [8]. However, BisGMA is highly viscous fluid because of the

hydrogen bonding between the hydroxyl groups, which limits the incorporation of inorganic

fillers and lead to the low final degree of conversion of resin composites [9]. Therefore, low

viscosity monomer such as triethylene glycol dimethacrylate (TEGDMA) is added to

improve the viscosity, reactivity and the final conversion of the matrix phase [10]. In

addition, its low molecular weight results in high polymerization shrinkage and degree of

conversion, as well as low mechanical properties [11].

2.2.2 Inorganic fillers

Since pure resin matrix by itself usually exhibits insufficient physical - mechanical

properties, inorganic fillers need to be added to the organic polymer matrix to strengthen and

minimise thermal expansion, polymerization shrinkage and water sorption [12]. The fillers

include fused quartz, colloidal amorphous silica, glass particle containing metals for

radiopacity, lithium aluminium silicates, short glass fibers metal oxides, hydroxyapatite

powder, glass fibers, prepolymerized organic particles, nanoporous sol-gel silica, silica-fused

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silicon nitride ceramic single-crystalline whiskers and organic-inorganic hybrid sol-gel

materials [13].

As mentioned by Toro et al., (2007), around 150,000 tonnes of eggshells are disposed

in landfills in the United States. The characteristics qualify eggshell as a good candidate for

bulk quantity, inexpensive, lightweight and low load-bearing composite applications.

Therefore, CaCO3 derived from eggshells will be chosen as an alternative filler for dental

model compared with the commercial CaCO3.

2.3.3 Polymerization initiator

Initiators are commonly used in chain-growth polymerization processes such as

radical polymerization in order to control initiation by light or heat [14]. Thermal

polymerization initiators are compounds that generate radicals or cations when exposure to

heat. Well-known thermal radical initiators include azo compounds such as 2,2'-

azobis(isobutyronitrile) (AIBN) and organic peroxides such as benzoyl peroxide (BPO).

Whereas, thermal cation initiators include benzenesulfonic acid esters and alkylsulfonium

salts. The current study will focus on thermal polymerization initiators, where a heat-cure

dental model that composed of CaCO 3 powder derived from eggshell as filler containing an

organic peroxide (benzoyl peroxide (BPO)), and liquid monomer. When powder and liquid

are mixed, pre-polymerized polymer chains are released from the surface of the particles.

Although the mixture seems to gradually stiffen, this is actually a physical interaction

between the powder and liquid and not a sign of polymerization. However, when the powder-

liquid mixture containing BPO is heated above 60°C, the weak peroxy bond in BPO

decomposes homolytically [15].

2.4 Chicken eggshell as a filler for polymer composite

Chicken eggshell is normally made of ceramic materials with a three-layered

structure, namely the cuticle on the outer surface, a spongy (calcareous) layer and an inner

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lamellar (or mammillary) layer [16]. The spongy and mammillary layers form a matrix

composed of protein fibres bonded to calcite (calcium carbonate) crystal. The two layers are

also constructed in such a manner that there are numerous circular openings (pores). This

structure allows gaseous exchange to occur throughout the shell. An eggshell’s outer surface

is covered with a mucin protein, which acts as a soluble plug for the pores in the shell. The

cuticle is also permeable to gas transmission [16]. According to reports, biowaste eggshell

contained chemical composition (by-weight) of calcium carbonate (94%), magnesium

carbonate (1%), calcium phosphate (1%) and organic matter (4%) [1, 16]. Since eggshell

composed of 94% calcium carbonate, it is possible to be used as a filler in preparation of

dental training models to simulate real human teeth, as known that human teeth are calcium-

rich.

3.0 DESIGN AND METHODOLOGY

The overall flowchart of the study is presented in Figure 3.1. The study needs to be gone

through into a few phases before obtaining the dental model.

START

Review of Literature

Material preparation (Eggshell)

Sample preparation

Testing

No
Result

Yes

Fabrication
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 FINISH

Figure 3.1: Overall flowchart of the study

3.1 Materials

The material preparation in this study is to collect the eggshell from the “roti canai” stall,

then their surfaces will be mechanically cleaned to minimize the smell. Most of the reagents

used in this study were purchased from local companies.

3.2 Sample preparation

3.2.1 Preparation of raw eggshell

The raw eggshell will be crushed using a mortar and pestle and finely ground using a

blender machine. Stainless-steel sieving device will be used to sieve the powder into an

aperture size of 63μm.

3.2.2 Preparation of CaCO3 powder derived from eggshell

A known quantity of eggshell powder will be dissolved with hydrochloric acid (HCl)

using electric mixer at 500 rpm to obtain calcium chloride (CaCl 2) solution. Equation for

reaction can be written as:

CaCO3 + 2HCl  CaCl2 + H2O + CO2 (3.1)

Then the CaCl2 solution will be filtered using filter paper in order to remove impurities.

Commercially available potassium carbonate (K2CO3) will be diluted and then will be titrated

in the prepared CaCl2 solution, according to the following equation:

CaCl2 + K2CO3  CaCO3 + 2KCl (3.2)

The mixed solutions will be transferred into 50ml Eppendorf tubes and centrifuged. The

acidity of the resultant solution will be neutralized by washing it three times with distilled

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water. The solid product will be placed in alumina crucible, covered with perforated

aluminium paper, and then will be oven dried at 110 °C for 24 hours. The solid product will

be then ground into fine powder manually using mortar and pestle.

3.2.3 Fabrication of dental model using prepared CaCO3 powder derived from

eggshell as a filler

The prepared CaCO3 filler derived from eggshell will be mixed with Bis-GMA and

TEDGMA resin. The compound will be moulded into a rectangular form and then will be

heated into an oven at 100°C for 1 hour. After that, the specimen will be left at room

temperature for overnight.

A total weight of the specimen will be prepared for 4g. Bis-GMA and TEDGMA will

be mixed at a ratio of 1:1. The CaCO 3 filler will be varied from 30, 40 and 50 wt% (Table

3.1). Benzoyl peroxide (BPO) which acts as a polymerization initiator will be added at the

amount of 1 wt% of the total mixture. The preparation of the dental model is shown in Figure

3.2.
Bis-GMA Bis-GMA

Monomer mixture
Benzoyl peroxide
(BPO)

Monomer mixture + BPO

CaCO3 filler

Dental model

Figure 3.2: Sample preparation of dental model

Table 3.1: Ratio of resin composites for preliminary study

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 1 50 50 30 0
2 50 50 40 0
3 50 50 50 0
4 50 50 0 30
5 50 50 0 40
6 50 50 0 50
3.3 Material testing

In this study, several testing will be conducted to achieve the objective. Characterization of

specimen will be done using a variety of different techniques, basically drawn from materials

science.

3.3.1 Field Emission Scanning Electron Microscopy (FESEM)

The surface morphology of biowaste-derived filler under different parameters will be

observed using a Field Emission Scanning Electron Microscopy (FESEM). The morphology

observation will be carried out at magnification of 5 000× with 5 kV acceleration voltage.

The FESEM analysis will be conducted in the School of Health Sciences, Health Campus,

Universiti Sains Malaysia.

3.3.2 Fourier Transformed Infrared (FTIR) spectroscopy

Fourier transformed infrared (FTIR) spectroscopy will be used to determine the

functional groups of the biowaste-derived filler. The wavelength of FTIR spectrometer was

verified from 4000 to 400 cm-1 at the resolution of ± 4 cm-1 with 4 scans using transmittance

mode. The FTIR analysis will be carried out in the School of Dental Sciences, Universiti

Sains Malaysia.

3.3.3 Surface roughness testing

A roughness tester will be used to measure the roughness and texture of the samples. The

parameter for the testing is shown in Table 3.2.

Table 3.2: Parameter for roughness testing and its value

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 Parameter Value
Cut of Value, λc 0.8 mm
Evaluation length, ln 5 mm
Speed 0.6 mm/s

3.3.4 Vickers microhardness testing

The surface hardness test of the samples will be examined using Vickers Hardness

testing machine prepared with dimension of 12 mm diameter and 2.5 mm height. Each group

consisted of 5 samples.

3.3.5 Compressive strength and modulus

The compressive strength test will be carried out according to ISO Specification 9917

(International Organization for Standardization, 2003). The test will be performed by a

Universal test machine (UTM) with a 10 kN load cell and a crosshead speed of 1 mm/min.

3.3.6 Flexural strength and flexural modulus

The test will be carried out according to ISO Specification 4049 (International

Organization for Standardization, 2000), with a span of 20 mm between the supports using a

three-point bending setup. Strength tests will be performed by a Universal test machine

(UTM) with a 10 kN load cell and a crosshead speed of 1 mm/min.

4.0 EXPECTED OUTCOMES

This study is expected to produce a low-cost dental model using eggshells in combination

with Bis-GMA and TEDGMA resin.

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REFERENCES

1. Toro, P., et al., Eggshell, a new bio-filler for polypropylene composites. Materials
letters, 2007. 61(22): p. 4347-4350.
2. Mohamed, M., et al., Effects of experimental variables on conversion of cockle shell
to calcium oxide using thermal gravimetric analysis. Journal of Cleaner Production,
2012. 37: p. 394-397.
3. Shekhawat, P., G. Sharma, and R.M. Singh, Microstructural and morphological
development of eggshell powder and flyash-based geopolymers. Construction and
Building Materials, 2020. 260: p. 119886.
4. Zhorifah, H.F.N., et al. Optimization of the mastication strength of hydroxyapatite as
an eggshell-based tooth filler. in AIP Conference Proceedings. 2019. AIP Publishing
LLC.
5. Hemasathya, B.A. and S. Balagopal, A study of composite restorations as a tool in
forensic identification. Journal of forensic dental sciences, 2013. 5(1): p. 35.
6. Van Noort, R. and M. Barbour, Introduction to dental materials-e-book. 2014:
Elsevier Health Sciences.
7. Lovell, L.G., et al., Effects of composition and reactivity on the reaction kinetics of
dimethacrylate/dimethacrylate copolymerizations. Macromolecules, 1999. 32(12): p.
3913-3921.
8. Sideridou, I., V. Tserki, and G. Papanastasiou, Effect of chemical structure on degree
of conversion in light-cured dimethacrylate-based dental resins. Biomaterials, 2002.
23(8): p. 1819-1829.
9. Atai, M. and D.C. Watts, A new kinetic model for the photopolymerization shrinkage-
strain of dental composites and resin-monomers. Dental Materials, 2006. 22(8): p.
785-791.
10. Asmussen, E. and A. Peutzfeldt, Influence of UEDMA, BisGMA and TEGDMA on
selected mechanical properties of experimental resin composites. Dental Materials,
1998. 14(1): p. 51-56.
11. Sideridou, I., V. Tserki, and G. Papanastasiou, Study of water sorption, solubility and
modulus of elasticity of light-cured dimethacrylate-based dental resins. Biomaterials,
2003. 24(4): p. 655-665.
12. Siang Soh, M., A. Sellinger, and A. Uj Yap, Dental nanocomposites. Current
Nanoscience, 2006. 2(4): p. 373-381.
13. Klapdohr, S. and N. Moszner, New inorganic components for dental filling
composites. Monatshefte für Chemie/Chemical Monthly, 2005. 136(1): p. 21-45.
14. Imai, Y., et al., Importance of polymerization initiator systems and interfacial
initiation of polymerization in adhesive bonding of resin to dentin. Journal of dental
research, 1991. 70(7): p. 1088-1091.
15. Kwon, T.Y., et al., Cure mechanisms in materials for use in esthetic dentistry. Journal
of investigative and clinical dentistry, 2012. 3(1): p. 3-16.
16. Tsai, W., et al., Characterization and adsorption properties of eggshells and eggshell
membrane. Bioresource technology, 2006. 97(3): p. 488-493.

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BUDGET

Chemical Reagent
No Item Quantity Unit Total
Price (RM)
(RM)
1 benzoyl peroxide,75% 1 150.00 150.00
Packing :5g/bottle
Brand Sigma
2 hydrochloric acid 1 553.00 553.00
Packing:2.5L/Bottle
3 (2, 2-bis [4-(2-hydroxy-3- 1 227.00 227.00
methacryloyloxypropoxy) phenyl] propane)
Packing :100ml/bottle
Brand Sigma
4 triethylene glycol dimethacrylate 1 250.00 250.00
Packing :100ml/bottle
Brand Sigma

Analysis Testing
No Item Quantity Unit Total
Price (RM)
(RM)
1 Fourier Transform Infrared (FTIR) 3 30.00 90.00
2 Field Emission Scanning Electron Microscopy 3 200.00 600.00
(FESEM)

3 Universal Testing Machine (Shidmazu) for 60 400.00 400.00

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TIMELINE
Research Project Timeline

Year 2022 Year 2023

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