International Journal of Mechanical Engineering and Technology (IJMET)
Volume 10, Issue 01, January 2019, pp. 1437-1451, Article ID: IJMET_10_01_146
Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=10&IType=1
ISSN Print: 0976-6340 and ISSN Online: 0976-6359
© IAEME Publication
Scopus Indexed
EFFECT OF ADDING ALUMINIUM
MICROPARTICLES TO CONVENTIONAL
GLASS IONOMER CEMENT
Howrah M.A. Abbas, Ahmed R. Alhamaoy
College of Engineering, Al-Nahrain University, Baghdad, Iraq.
ABSTRACT
Glass Ionomer Cement (GIC) is one of the important dental materials used in
dental clinics, which is usually used in temporary restorative stages. This study aims
to evaluate the effect of adding Al micro particles to GIC powder (Riva self-cure) on
the mechanical and physical properties.The results showed that the addition of Al
micro particles has improved the compressive strength and biaxial flexural strength
where the highest values were at 3 wt. %, and then the compressive strength and
biaxial flexural strength decreased with increasing the added ratios. The addition of
Al particles improved the surface Vickers microhardness values where the highest
value was at 5 wt. %. The addition of Al has decreased the wear resistance of GIC;
however the wear resistance increased with increased adding ratios. The most acidic
beverages (the lowest value of pH) were the most effective in increasing the
absorption and solubility percentage of Al samples. Orange juice was more effective
followed by cola and then coffee and tea were less effective. We recommend that
patients reduce these acidic beverages because they have a harmful effect on dental
fillings.
Keywords: Glass Ionomer Cement; Al micro particles; Mechanical Properties; Physical
Properties; Riva self-cure.
Cite this Article: Howrah M.A. Abbas, Ahmed R. Alhamaoy , Effect of Adding
Aluminium Microparticles to Conventional Glass Ionomer Cement, International
Journal of Mechanical Engineering and Technology, 10(1), 2019, pp. 1437-1451.
http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=10&IType=1
1. INTRODUCTION
Glass ionomer cement (GIC) is a biocompatible dental restorative material created by Wilson
et al. in 1969 (Imran Alam Moheet, Norhayati Luddin, Ismail Ab Rahman, Sam’an Malik
Masudi, Thirumulu Pommuraj Kannan and Nik Rozainah Nik Abd Ghani, 2018).This
material is formed by an acid/base chemical reaction between silicate glass powder and
polyacrylic acid [2]. This material has certain unique advantages such as adhesion to natural
tooth structure, good biocompatibility, low toxicity, along with fluoride release, as well as
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Effect of Adding Aluminium Microparticles to Conventional Glass Ionomer Cement
coefficient of thermal expansion value close to that of natural tooth resulting in gaining its
popularity in clinical practice as luting, base, liners, and restorative materials[3]. However
GIC is brittle and has poor mechanical properties include low fracture strength, fracture
toughness and wear resistance. These drawbacks limited their extensive use in dentistry as a
filling material in high stress bearing areas [4]. Several attempts have been made on the GIC
material to improve their mechanical properties and enable their extensive use in stress
bearing application by adding different fillers types to the GIC powder component such as
fibers, metallic powder and ceramic powder etc.[5]. Therefore the purpose of this study was to
evaluate the effects of adding (3, 5 and 7) wt.% of Aluminum micro powder into conventional
GIC on the mechanical properties and its effect on absorption and solubility processes.
2. EXPERIMENTAL WORK
2.1. Materials
Commercial glass ionomer cement (Riva self-cure, shade A2, Australia, SDI limited) supplied
in powder/liquid form (23.739 μm particle size) was used in this study as a base material, and
Al micro powder (49.970 μm particle size and 99% purity) was used as an additive material.
2.2. Samples preparation
Before preparing the samples, the used materials were characterized using X-ray diffraction
(XRD) analysis (D2, PHASER, Bruker) with diffraction angles between 20° and 80°.The
XRD result illustrates that the Al powder was pure with the presence of small quantities of
iron (Fig. 1). The Al peaks is compatible with pattern98-005-2611 from ICSD databases
while the Fe peaks is compatible with pattern98-000-0460 from same databases. Four
different samples were prepared in total, one represents the control sample (the basic material
without adding), while the others represent the basic material with the additions of (3, 5 and
7) wt. % of Al micro particles. A calibrated electronic balance with four digits accuracy
(Sartorius, BL210S) was used to prepare the mixed powders (and where ever needed in this
work), where the mixed powders were kept in glass tubes to avoid particles from stacking on
the wall of the tube. Then, the powders mixture were mixed using a tube roller mixer machine
with rotation speed 60 rpm for 2 hours in order to obtain homogenous and uniform powders
mixture. The combination powder and the aqueous solution (hardener liquid) were mixed
according to the manufacturer's instruction with a 1:1ratio. The paste was immediately
introduced into stainless steel molds and then covered form both sides with glass slides to
obtain a relatively smooth and flat surface. The cement was clamped for couple of minutes
and left it in an incubator at 37°C for 5 minutes for set and harden. After that the samples
were carefully removed from the mold and stored at room condition until the examination [6].
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Howrah M.A. Abbas, Ahmed R. Alhamaoy
Figure 1 XRD analysis results for Al micro particles powder
2.3. Compressive strength test
Cylindrical shape specimen was prepared for each group of materials using stainless steel
mold (10 mm in height and 5 mm in diameter) according to ISO 9917-1[7]. The Compressive
strength evaluation was carried using the testometric machine (AX M500-capacity load of
25kN) computerized system with crosshead speed of 0.5 mm/min.
2.4. Microhardness test
Cylindrical specimens were prepared for each ratio of material (4 samples in total) in a
stainless steel mold (5 mm in diameter and 10 mm in height). After 24 hr. from prepare
samples, Vickers surface microhardness test was performed using Digital Micro-hardness
tester (Q-Time, TH-715). The indenter was applied on the surface of each sample with a 50g
load and dwell time of 10s. Three indentations were made on the surface of each specimen at
different locations and the mean value of them was taken.
2.5. Biaxial flexural strength test
The biaxial flexural strength (bfs) was measured with piston on three ball technique using the
Testometric AX M500-25kN computerized system. Three stainless steel balls of 3.2 mm
diameter that were equidistant from each other were placed on a circle with a diameter of 10
mm surrounded by a ring of 14 mm diameter and 2 mm height to prevent sample movement.
Disk specimen for each group of materials was prepared in a stainless steel mold (14 mm in
diameter and 1.25 mm in thickness). The mixed paste was inserted in the mold until set then
left in room condition. After 24 hr., the specimen was centered and supported on steel balls
and the load was applied vertically on the center of specimen by a 1.2 mm diameter flat tip of
piston with a cross head speed of 0.1 mm/min as shown in (Fig. 2). The fracture load for each
specimen was recorded by the system software and then the bfs value was calculated using the
following equation (Wille S, Hölken I, Haidarschin G, Adelung R and Kern M, 2016):
S=
−0.2387 P (X−Y)
d2
(1)
X and Y were determined as following:
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2
r
X = (1 + v)ln (r2 ) + [
3
1−v r2 2
] (r )
2
3
2
r
(2)
2
r
Y = (1 + v)[1 + ln (r1 ) ] + (1 − v) (r1 )
3
(3)
3
Where S is biaxial flexural strength (MPa), P fracture load (N), d specimen disk thickness
at fracture origin (mm), v Poisson’s ratio (0.25), r1 radius of the support circle, r2 radius of the
loaded area and r3 specimen radius.
Figure 2 The biaxial flexural strength test
2.6. Wear rate losses determination
The wear test was performed using a pin on disc apparatus. The samples dimensions were 5
mm in dia. and 10 mm length. Before test, the samples were weighed using same system
above, and then the sample was held in contact with the disk surface and loaded with a
vertical load of one kg. The operation time was 90 seconds and the disk was rotate with a
constant rotational speed of 487.7 rpm. The length of each sliding stroke was approximately
30 cm. The normal saline liquid was used as lubrication that was dropped continuously during
operation period by distillation device connected to the specimen holder to avoid friction
heating effects [9], and simulate the wet environment in the oral cavity [10]. After each trial
the surface of steel disk was cleaned and the sample was taken, cleaned, wiped up by drying
paper and weighed again. Then wear rate is calculated using the following equation [11]:
W.R. = ΔM/ω r t
(4)
Where: W.R. Wear rate (µg/m), ΔM mass losses (∆M= M1-M2), ω rotational speed of
disk (rad/sec), r radius of the disk (m) and t slipping time (sec).
2.7. Absorption test
Disc specimens were prepared from each ratio of materials using ring mold of 8.5 mm in
diameter and 1.9 mm thickness. Then specimens were weighed and stored in individual closed
glass tube containers in distilled water, black tea, coffee, orange juice and carbonated soft
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Howrah M.A. Abbas, Ahmed R. Alhamaoy
drink (coca cola) at room temperature. Each drink was renewed every 24 hr. (M.R.
Ayatollahi, Mohd Yazid Yahya, A. Karimzadeh, M. Nikkhooyifar and Amran Ayob, 2015;
Aliping-McKenzie M, Linden RW and Nicholson JW, 2004). The pH of each drink was
measured before immersing the sample in it and the results shown in (table-1).For all
specimens, after storage process, the samples were washed prior weighing with distilled water
to remove the depositions of the layers of the beverages on the surface area, and the sample
surface was wiped up by dry paper to remove any stacked liquid drops. The samples were
weighed after one and two days intervals where difference between the sample weight after
stored and weight before stored represents the earned weight. The absorption percentage of
each sample was calculated according to the following formula:
𝑊2−𝑊1
𝑋100
𝑊1
Absorption percentage=
(5)
Where W1: weight of specimen before immersion in beverage and W2: weight of
specimen after storage process.
Table 1 The pH level of used beverages
Beverage
pH value
Distilled
water
7
Tea
Coffee
6
5.9
Orange
juice
3.4
Coca cola
2.9
2.8. Solubility test
The samples were prepared and stored in drinks for 7 days intervals using the same procedure
of absorption test. After 7 days of storage period, the samples were taken out of the containers
and washed with distilled water to remove the deposits resulting from drinks on their surface
area. Then, the specimens were dried using an electric furnace at temperature 70 ℃ for 30
minutes. After that, the samples were taken from the furnace and weighed on a balance and
equation 5 was used to calculate the solubility ratio.
3. RESULTS AND DISCUSSION
3.1. Compressive strength test
The addition of Al micro particles increased the compressive strength as shown in (Fig.-3).
This is due to the fact that the addition of Al particles lead to increase the joining in material,
in addition to the strength of bonds formed between the particles of Al and the particles of
GIC that will need to force breaking above the strength of breaking the bonds of the GIC
material[14]. Increase the additive ratio after 3wt.%, the compressive strength start to
decrease but it still greater than basic materials and the reason for that due to the nature of
aluminium which is ductile, and there is another reason that is due to a decrease in the
strength of bonds between the added Al particles and the particles of GIC [15], therefore the
resistance of material to compression will decreased and will require less force to break the
bonds between the particles. In addition to increase speed reaction of particles with liquid acid
with increase the ratio of added Al and thus may cause a lack of homogeneity of the material.
This will reduce the strength of cohesion of the material, provide weak areas and reduce
resistant of material to the growth and formation of cracks and will lead to faster failure of
samples. The max. value and variation percentage was 132.984 MPa and 18.453% for 3 wt. %
Al and the min. value and variation percentage was 116.532MPa and 3.799% for 7 wt. % Al.
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Compressive strength (MPa)
Effect of Adding Aluminium Microparticles to Conventional Glass Ionomer Cement
135
130
125
120
115
110
2
3
4
5
6
Additives wt. %
GIC
7
8
Al
Figure 3 The relation between compressive stress and Al additives wt. %
3.2. Microhardness test
(Microhardness test is a parameter frequently used to evaluate the material surfaces resistance
to plastic deformation by penetration) [16]. Hardness is the property of the material that
enables it to keep the shape of the surface intact under the influence of different stresses, or is
the ability of the material to resist penetrating an even harder substance. Fig. 4 showed that
the addition of aluminum micro particles increases the value of surface microhardness, as the
behavior of the material recorded the highest value at 5 wt. % and then the value of the
surface microhardness decreased by increased the added ratios while maintaining their values
higher than basic materials. The reason for increasing the surface microhardness values with
increasing the additives ratios may be due to the increased the strength of the bonds that bind
the particles with each other's, therefore the strength of surface resistance to plastic
deformation will increase. When increasing the added ratios after 5 wt. %, the surface
microhardness values start to decrease while maintaining their values higher than the basic
material. The reason for this is due to the fact that Al is softer than the glass particles, in
addition to the large particle size of Al which is 49.97 μm as compared to the particle size of
GIC which is 23.739 μg/m this might cause reduction in the strength of cohesion the material
and will therefore provide areas of weak and easy of spread the cracks and then their
resistance to permanent deformation will decrease. All these reasons will decrease the surface
microhardness. The max. value and variation percentage was 96.875 kg/mm2 and 69.524% at
5 wt. % Al while the min. value and variation percentage was 74.690 kg/mm2 and 30.703% at
7 wt. % Al.
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Howrah M.A. Abbas, Ahmed R. Alhamaoy
Mean HV (kg/mm2)
120
100
80
60
40
20
2
4
6
8
Additives wt. %
GIC
Al
Figure 4 The relation between Vickers microhardness number (mean value) and Al additives wt%.
3.3. Biaxial flexural strength test
Fig. 5 showed that the addition of Al micro particles has improved the bfs. This is due to the
formation of strong bonds between the particles of the additive and GIC [14,17], therefore
will need more force to break the bonds and greater strength to spread the cracks that leads to
failure of the material. When increasing the ratio of the additive after 3 wt. %, a decrease in
bfs was observed because of the increase speed reaction of particles with liquid acid and thus
may cause a lack of homogeneity of the material. This will reduce the strength of cohesion of
the material, provide weak areas and reduce resistant of material to the growth and formation
of cracks and will lead to faster failure of samples. The max. value and variation percentage
was 48.992MPa and 60.382% for 3 wt. % Al and the min. value and variation percentage was
25.977MPa and -14.961% for 7 wt. % Al.
60
σbfs (MPa)
50
40
30
20
2
4
6
Additives wt. %
GIC
8
Al
Figure 5 The relationship between Biaxial flexural strength and Al additives wt. %
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Effect of Adding Aluminium Microparticles to Conventional Glass Ionomer Cement
3.4. Wear rate losses determination
Wear rate losses (μg/m)
Fig. 6 showed that the addition of Al microparticles decreased the wear rate losses. The
reason for this may be due to the strength of the bonds formed between the particles of Al and
GIC, resulting in a stronger surface of the material and high resistance to wear, therefore the
number of missing layers from the surface of sample reduced and the losses of weight of
sample will be lower. The wear rate losses increased with increasing the additives ratios and
become close to the basic material at 7 wt. % may be due to the reduction in the strength of
bonds consisted between the particles of Al and GIC and those will increased the coefficient
of friction and decreased the wear resistance, therefore the number of missing layers from the
surface of sample will increases and those will increased the weight losses and hence will
increased the wear rate losses. In addition, increasing the speed of the reaction between
particles and liquid acid by increasing the ratio of Al added may be one of the reasons that led
to increased wear rate as it may cause a decrease in the uniformity of the material and reduce
the strength of cohesion of material. The min. value and max. variation percentage was
5.756(μg/m) and 42.851% respectively at 3 wt. % Al and the max. value and min. variation
percentage was 10.072 (μg/m) and 0.000% respectively at 7 wt. %.
12
10
8
6
4
2
4
6
8
Additives wt. %
GIC
Al
Figure 6 The relationship between Wear rate losses and Al additives wt. %
3.5. Absorption test
As Fig. 7 shows, the absorption percentage of Al samples in distilled water decreases with
increased wt. % of Al. The max. absorption after 1 day is 2.7425% for 3 wt. % Al while the
min. absorption is 1.9399% for 7 wt. % Al. Also, the max. absorption after 2 day is 3.6567%
for 3 wt. % Al while the min. absorption is 2.4248% for 7 wt. % Al. This is due to the fact
that the Al particles fill the voids and reduce the porosity of the cement.
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Absorbability (%)
4
3.5
3
2.5
1 day
2
2 days
1.5
1
GIC
3%Al
5%Al
Additives wt. %
7%Al
Figure 7 The results of absorption after 1 and 2 days for Al additives by distilled water
Fig. 8 shows that Al samples have reduced absorption percentage in tea due to the fact that
the particles of Al reduced the porosity and filling the voids in GIC. The max. absorption after
1 day is 2.2329% for 3 wt. % Al while the min. absorption is 1.6137% for 7 wt. % Al. Also,
the max. absorption after 2 days is 2.5518% for 3 wt. % Al while the min. absorption is
2.2843% for 7 wt. % Al.
3.5
Absorbability (%)
3
2.5
2
1 day
1.5
2 days
1
0.5
0
GIC
3%Al
5%Al
Additives wt. %
7%Al
Figure 8 The results of absorption after 1 and 2 days and for Al additives by tea effect
As shown in Fig. 9, Al samples are the least absorbent of coffee compared to the pure GIC
sample because the Al particles fill the voids and reduce the porosity of the material.
However, when the added Al ratio increases, the absorption rate increases, but it is still lower
than the pure GIC because the coffee drink is more acidic. Therefore, the coffee components
began to dissolve the particles and penetrate the sample and thus increase its porosity and
absorption. The max. absorption after 1 day is 2.5330% for 7 wt. % Al while the min.
absorption is 2.3983% for 3 wt. % Al. Also, the max. absorption after 2 days is 2.6913% for 7
wt. % Al while the min. absorption is 2.6069% for 3 wt. % Al.
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Effect of Adding Aluminium Microparticles to Conventional Glass Ionomer Cement
Absorbability(%)
3.5
3
2.5
1 day
2
2 days
1.5
1
GIC
3%Al
5%Al
Additives wt. %
7%Al
Figure 9 The results of absorption after 1 and 2 days for Al additives by coffee effect
The absorption rate of Al samples in orange juice has increased by increasing the
percentage of added Al as shown in Fig. 10 because orange juice is more acidic, so the
components of this juice began to dissolve the particles in the samples and penetrated into the
sample and thus increase porosity of sample and absorption rate. The max. absorption after 1
day is 2.7968% for 7 wt. % Al while the min. absorption is 2.3436% for 3 wt. % Al. Also, the
max. absorption after 2 days is 3.3798% for 7 wt. % Al while the min. absorption is 2.5968%
for 3 wt. % Al.
Absorbability (%)
3.5
3
2.5
1 day
2
2 days
1.5
1
GIC
3%Al
5%Al
Additives wt. %
7%Al
Figure 10 The results of absorption after 1 and 2 days for Al additives by orange effect
The ratio of the absorption of cola by Al samples as compared with pure GIC sample
decrease only at 3 wt. %, but with the increase in the ratio of added Al, the absorption rate
increased as shown in Fig. 11. The max. absorption after 1 day is 1.7301% for 7 wt. % Al
while the min. absorption is 0.6410% for 3 wt. % Al. Also, the max. absorption after 2 days is
1.9278% for 7 wt. % Al while the min. absorption is 0.9615% for 3 wt. % Al. This is due to
the fact that the cola is more acidic, so its components begin to decompose the particles into
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Howrah M.A. Abbas, Ahmed R. Alhamaoy
the sample and penetrate into it, thus increasing the porosity of the sample and its
absorbability.
Absorbability (%)
2.5
2
1.5
1 day
1
2 days
0.5
0
GIC
3%Al
5%Al
Additives wt. %
7%Al
Figure 11 The results of absorption after 1 and 2 days for Al additives by cola effect
3.6. Solubility test
Fig. 12 shows that the solubility percentage of Al samples is much lower than control GIC
sample where the max. solubility is 5.5162% at 5 wt. % Al while the min. solubility is
3.4918%at 7 wt. % Al as compared with pure GIC 9.1211%.This is because the addition of Al
has increased material resistance to degradation in distilled water.
Solubility (%)
10
8
6
4
2
2
4
6
Additives wt. %
GIC
8
Al
Figure 12 The results of solubility after 7 days for Al additivesby distilled water
As shown in Fig. 13 addition of Al particles to GIC has improved their resistance to
decompose in tea where the max. solubility 4.8900% is at 5 wt. % Al and the min. solubility
is 3.4556% at 3 wt. % Al.
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5.5
Solubility (%)
5
4.5
4
GIC
3.5
Al
3
2.5
2
2
4
6
Additives wt. %
8
Figure 13 The results of solubility after 7 days for Al by tea effect
The solubility percentage of Al samples in the coffee decreased with the increase of the
ratio of the added Al as shown in Fig.-14. The max. solubility is 3.5024%for 3 wt. % Al while
the min. solubility is 3.1135% for 7 wt. % Al. This is due to the fact that the Al samples are
more resistance to decompose in coffee compared with pure GIC sample.
Solubility (%)
10
8
6
4
2
0
2
4
6
Additives wt. %
GIC
8
Al
Figure 14 The results of solubility after 7 days for Al additives by coffee effect
As Fig.-15 shows the solubility of Al samples is increased compared with pure GIC due to
the fact that orange juice is more acidic, therefore its components decompose the particles of
Al samples. The max. solubility is 5.6034% for 3 wt. % Al while the min. solubility is
4.7413% for 7 wt. % Al.
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6
Solubility (%)
5
4
3
2
1
0
2
3
4
5
6
Additives wt. %
GIC
7
8
Al
Figure 15 The results of solubility after 7 days for Al additives by orange juice effect
Solubility (%)
As shown in Fig. 16, the addition of Al has reduced the solubility percentage of GIC at 3
wt. %, but with the increase in the ratio of added Al after 3 wt. % the solubility percentage
increases and become higher than pure GIC. This is due to the fact that the cola is more
acidic, therefore their components decompose the particles of Al sample. The max. solubility
is 5.7692%for 5 wt. % Al while the min. solubility is 2.6849% for 3 wt. % Al.
7
6
5
4
3
2
1
0
2
4
6
Additives wt. %
GIC
8
Al
Figure 16 The results of solubility after 7 days for Al additives by cola effect
4. CONCLUSIONS
The addition of aluminum micro particles to GIC improved the mechanical properties
(compressive strength, biaxial flexural strength, Vickers micro hardness and wear
resistance).The addition of Al has improved the compressive strength and biaxial flexural
strength where the highest values were at 3 wt. %, and then the compressive strength and
biaxial flexural strength decreased with increasing the added ratios.The addition of Al has
decreased the wear resistance of GIC; however the wear resistance increased with increased
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Effect of Adding Aluminium Microparticles to Conventional Glass Ionomer Cement
adding ratios. The most acidic beverages (the lowest value of pH) were the most effective in
increasing the absorption and solubility percentage of Al samples. Orange juice was more
effective followed by cola and then coffee and tea were less effective. We recommend that
patients reduce these acidic beverages because they have a harmful effect on dental fillings.
ACKNOWLEDGEMENT
The authors would like to express thanks for the Mechanical and Materials Engineering
Department-College of Engineering at Al-Nahrain University-Baghdad, Iraq.
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