J. Biomedical Science and Engineering, 2010, 3, 955-962 JBiSE
doi:10.4236/jbise.2010.310126 Published Online October 2010 (http://www.SciRP.org/journal/jbise/).
Published Online October 20 10 in SciRes. http://www.scirp.org/journal/jbise
A PQAS-containing glass-ionomer cement for improved
antibacterial function
Yiming Weng1, Xia Guo1, Jun Zhao1, Richard L. Gregory2, Dong Xie1*
1Department of Biomedical Engineering, Purdue School of Engineering and Technology, Indiana University-Purdue University,
Indianapolis, USA;
2Department of Oral Biology, School of Dentistry, Indiana University, Indianapolis, USA.
Received 5 August 2010; revised 18 August 2010; accepted 26 August 2010.
ABSTRACT
The novel non-leachable poly (quaternary ammo-
nium salt) (PQAS)-containing antibacterial glass-
ionomer cement has been developed. Compressive
strength (CS) and S. mutans viability were used as
tools for strength and antibacterial activity evalua-
tions, respectively. All the specimens were condi-
tioned in distilled water at 37˚C prior to testing.
Commercial glass-ionomer cement Fuji II LC was
used as control. With PQAS addition, the studied
cements showed a reduction in CS with 25-95% for
Fuji II LC and 13-78% for the experimental cement
and a reduction in S. mutans viability with 40-79%
for Fuji II LC and 40-91% for the experimental
cement. The experimental cement showed less CS
reduction and higher antibacterial activity as com-
pared to Fuji II LC. The long-term aging study in-
dicates that the cements are permanently antibac-
terial with no PQAS leaching. It appears that the
experimental cement is a clinically attractive dental
restorative that can be potentially used for long-
lasting restorations due to its high mechanical s t r e n g t h
and permanent antibacterial function.
Keywords: PQAS; Antibacterial; Glass-Ionomer Cement;
CS; Aging
1. INTRODUCTION
In dental clinics, secondary caries is found to be the
main reason to the restoration failure of either composite
resins or glass-ionomer cements (GICs) [1-4]. Secondary
caries that often occurs at the interface between the res-
toration and the cavity preparation is mainly caused by
demineralization of tooth structure due to invasion of
plaque bacteria (acid-producing bacteria) such as Strep-
tococcu mutans (S. mutans) in the presence of ferment-
able carbohydrates [4]. Among all the dental restoratives,
GICs are found to be the most cariostatic and somehow
antibacterial due to release of fluoride, which is believed
to help reduce demineralization, enhance remineraliza-
tion and inhibit microbial growth [5,6]. However, annual
clinical surveys found that secondary caries was still the
main reason for GIC failure [1-4], indicating that the
fluoride-release from GICs is not potent enough to in-
hibit bacterial growth or combat bacterial destruction.
Although numerous efforts have been made on improv-
ing antibacterial activities of dental restoratives, most of
them have been focused on release or slow-release of
various incorporated low molecular weight (MW) anti-
bacterial agents such as antibiotics, zinc ions, silver ions,
iodine and chlorhexidine (CHX) [6-10]. However, re-
lease or slow-release can lead or has led to reduction of
mechanical properties of the restoratives over time,
short-term effectiveness, and possible toxicity to sur-
rounding tissues if the dose or release is not properly
controlled [6-10].
Macromolecules containing quaternary ammonium
(QAS) or phosphonium salt (QPS) groups have been
studied extensively as an important antimicrobial mate-
rial and used for a variety of applications due to their
potent antimicrobial activities [11-15]. These polymers
are found to be capable of killing bacteria that are resis-
tant to other types of cationic antibacterials [16]. The
examples of polyQAS or PQAS used as antibacterials
for dental restoratives include incorporation of a metha-
cryloyloxydodecyl pyridinium bromide (MDPB) as an
antibacterial monomer into composite resins [13], use of
DMAE-CB as a component for antibacterial bonding
agents [17,18], and incorporation of quaternary ammo-
nium polyethylenimine (PEI) nanoparticles into compos-
ite resins [19]. All these studies found that PQAS did
exhibit significant antibacterial activities. So far there
have been no reports on using PQAS as an antibacterial

Y. M. Weng et al. / J. Biomedical Science and Engineering 3 (2010) 955-962
956
agent for GICs.
The objective of this study was to synthesize a new
poly (acrylic acid-co-itaconic acid) with pendent qua-
ternary ammonium salt (PQAS) and explore the effects
of this PQAS on mechanical strength and antibacterial
activity of commercial Fuji II LC and recently developed
experimental high-strength cements.
2. MATERIALS AND METHODS
2.1. Materials
2-dimethylaminoethanol (DMAE), bromotetradecane
(BT), dipentaerythritol, 2-bromoisobutyryl bromide
(BIBB), acrylic acid (AA), itaconic acid (IA),
2,2’-azobisisobutyronitrile (AIBN), triethylamine (TEA),
CuBr, N, N, N’, N’, N’’ -pentamethyldiethylenetriamine
(PMDETA), dl-camphoroquinone (CQ), 2-(dimethylamino)
ethyl methacrylate (DMAEMA), pyridine, tert-butyl
acrylate (t-BA), glycidyl methacrylate (GM), hydrochlo-
ric acid (HCl, 37%), N, N’-dicyclohexylcarbodiimide
(DCC), pyridine, diethyl ether, dioxane, N,N-dimethyl-
formamide (DMF), methanol (MeOH), ethyl acetate
(EA), hexane and tetrahydrofuran (THF) were used as
received from VWR International Inc (Bristol, CT)
without further purifications. Light-cured glass-ionomer
cement Fuji II LC and Fuji II LC glass powders were
used as received from GC America Inc (Alsip, IL). Z100
resin composite was used as received from 3M ESPE (St.
Paul, MN).
2.2. Synthesis and Characterization
2.2.1. Synthesis of the Quaternary Ammonium Salt
(QAS)
The hydroxyl group-containing quaternary ammonium
salt (QAS) was synthesized following the procedures
described elsewhere with a slight modification [12].
Briefly, to a flask containing DMAE (0.056 mol) in me-
thanol (100 ml), BT (0.062 mol) was added. The reac-
tion was run at room temperature overnight. After most
of methanol was removed, the mixture was washed with
hexane 3 times. The formed 2-dimethyl-2-tetrade-
canyl-1-hydroxyethyl ammonium bromide (DTHAB)
was then dissolved in 10% HCl aqueous solution con-
taining a small amount of MeOH. After the solution was
stirred at 110˚C for 3 h, MeOH, HBr and water were
removed via a rotary evaporator. The formed 2-dimethyl
-2-tetradecanyl-1-hydroxyethyl ammonium chloride (DT
HAC) was purified by washing with hexane several
times before drying in a vacuum oven. The synthesis
scheme is shown in Figure 1.
2.2.2. Synthesis of the Poly (Acrylic Acid-co-Itaconic
acid) with Pendent QAS
The linear poly (acrylic acid-co-itaconic acid) or poly
(AA-co-IA) was prepared following our published pro-
cedures [20]. Briefly, to a flask containing a solution of
AA (0.08 mol) and IA (0.04 mol) in 40 ml THF, AIBN
(0.5 mmol) in 10 ml THF was added. After the reaction
was run under N2 purging at 60˚C for 18 h, poly (AA-
co-IA) was precipitated with ether, followed by drying in
a vacuum oven. Then DTHAC was tethered onto the
purified poly (AA-co-IA) [21]. Briefly, to a solution of
poly (AA-co-IA) in DMF, DTHAC was added with DCC
and pyridine. The reaction was kept at room temperature
overnight. After the insoluble dicyclohexyl urea was
filtered off, the formed poly(AA-co-IA) with pendent
QAS or PQAS was purified by precipitation from ether,
washing with ether and drying in a vacuum oven prior to
use (see Figure 1).
2.2.3. Synthesis of the GM-Tethered Star-Shape Poly
(Acrylic Acid)
The GM-tethered 6-arm star-shape poly (acrylic acid)
(PAA) was synthesized similarly as described in our
previous publication [22]. Briefly, dipentaerythritol (0.06
mol) in 200 ml THF was used to react with BIBB (0.48
mol) in the presence of TEA (0.35 mol) to form the
6-arm initiator. t-BA (0.078 mol) in 10 ml dioxane was
then polymerized with the 6-arm initiator (1% by mole)
at 120˚C in the presence of CuBr (3%)-PMDETA (3%)
catalyst complex via ATRP. The resultant 6-arm poly
(t-BA) was hydrolyzed with HCl and dialyzed against
distilled water. The purified star-shape PAA was obtained
via freeze-drying, followed by tethering with GM (50%
by mole) in DMF in the presence of pyridine (1% by
weight) [22]. The GM-tethered star-shape PAA was re-
covered by precipitation from diethyl ether, followed by
drying in a vacuum oven at room temperature. The syn-
thesis scheme for the 6-arm star-shape PAA is also
shown in Figure 1.
2.2.4. Characteri zation
The chemical structures of the synthesized QAS and
PQAS were characterized by Fourier transform-infrared
(FT-IR) spectroscopy and nuclear magnetic resonance
(NMR) spectroscopy. The proton NMR (1HNMR) spec-
tra were obtained on a 500 MHz Bruker NMR spec-
trometer (Bruker Avance II, Bruker BioSpin Corporation,
Billerica, MA) using deuterated dimethyl sulfoxide and
chloroform as solvents and FT-IR spectra were obtained
on a FT-IR spectrometer (Mattson Research Series FT/
IR 1000, Madison, WI).
2.3. Evaluation
2.3.1. Sample Preparati on f or St rength Tests
The experimental cements were formulated with a
two-component system (liquid and powder) [22]. The
liquid was formulated with the light-curable star-shape
poly (acrylic acid), water, 0.9% CQ (photo-initiator, by

Y. M. Weng et al. / J. Biomedical Science and Engineering 3 (2010) 955-962
957
weight) and 1.8% DC (activator). The polymer/water
(P/W) ratios (by weight) = 70:30. Fuji II LC glass pow-
der was either used alone or mixed with the synthesized
PQAS to formulate the cements, where the PQAS mix-
ing ratio (by weight) = 1, 3, 5, 10, or 30% of the glass.
The detailed formulations are shown in Ta b l e 1 . Fuji II
LC and Z100 were used as controls and prepared per
manufacturers’ instructions, where the P/L ratio = 3.2 for
Fuji II LC and premixed paste for Z100.
Specimens were fabricated at room temperature ac-
cording to the published protocol [22]. Briefly, the cy-
lindrical specimens were prepared in glass tubing with
dimensions of 4 mm in diameter by 8 mm in length for
compressive strength (CS), 4 mm in diameter by 2 mm
in length for diametral tensile strength (DTS) and 4 mm
in diameter by 2 mm in depth for antibacterial tests. All
the specimens were exposed to blue light (EXAKT 520
Blue Light Polymerization Unit, EXAKT Technologies,
Inc., Oklahoma City, OK) for 2 min, followed by condi-
tioned in 100% humidity for 15 min, removed from the
mold and conditioned in distilled water at 37˚C for 24 h
unless specified, prior to testing.
n
m
CH2CH CH2C
COOH
CH2
C
COOH
O
O
CH2CH2 N
CH3
CH3
CH3(CH2)12CH2+
Cl-
(1) 3-dimethylaminoethanol
poly(AA-c o-IA)/DCC
pyridine
A.
B.
Where m = 7 and n = 3
Where x = y = 50
y
x
y
x
x
y
x
y
y
x
y
x
O
O
O
O
O
O
OO
O
O
OO
O
CO2H
Br
OCH2CH
O
O
OH
H2OC Br
H2OC
O
Br
CO2H
O
CHCH2O
O
O
Br
OOCH2CH OO
OH
CO2H
Br
OOCH2CH
CO2H
O
CHCH 2O
O
O
OH
Br
O
CHCH2O
O
O
OH
O
OOH
OH
CH3(CH2)12CH2Br CH3(CH2)12CH2NCH2CH2OH
CH3
CH3
+
Cl-
(2) HCl
Figure 1. Schematic diagrams for synthesis of poly(AA-co-IA) with pendent QAS or
PQAS and chemical structure of the 6-arm star-shape poly(acrylic acid) tethered with
methacylate groups: (A): synthesis of PQAS; (B) chemical structure of the 6-arm
star-shape poly(acrylic acid) tethered with polymerizable methacrylates.

Y. M. Weng et al. / J. Biomedical Science and Engineering 3 (2010) 955-962
958
Table 1. Materials and formulations used in the study.
Code Liquid formula-
tion1
PQAS % (by
weight)2
P/L ratio (by
weight)3
FIILC N/A 0 3.2
FIILC (1%) N/A 1 3.2
FIILC (3%) N/A 3 3.2
FIILC (5%) N/A 5 3.2
FIILC (10%) N/A 10 3.2
FIILC (30%) N/A 30 3.2
EXP 70/30 0 2.7
EXP (1%) 70/30 1 2.7
EXP (3%) 70/30 3 2.7
EXP (5%) 70/30 5 2.7
EXP (10%) 70/30 10 2.7
EXP (30%) 70/30 30 2.7
1Liquid formulation: N/A = not available; Liquid for EXP =
6-arm star-shape poly (acrylic acid) vs. water (by weight);
2PQAS = poly (AA-co-IA) with pendent QAS; PQAS was
mixed with Fuji II LC filler; 0 = only Fuji II LC filler was used;
3P/L ratio = a total amount of glass filler powder (Fuji II LC
glass + PQAS) vs. polymer liquid.
2.3.2. Strength Measuremen ts
CS and DTS tests were performed on a screw-driven
mechanical tester (QTest QT/10, MTS Systems Corp.,
Eden Prairie, MN), with a crosshead speed of 1 mm/min.
Six to eight specimens were tested to obtain a mean val-
ue for each material or formulation in each test. CS was
calculated using an equation of CS = P/r2, where P =
the load at fracture and r = the radius of the cylinder.
DTS was determined from the relationship DTS =
2P/dt, where P = the load at fracture, d = the diameter
of the cylinder, and t = the thickness of the cylinder.
2.3.3. Antibacterial Test
The antibacterial test was conducted following the pub-
lished procedures [23]. S. mutans (oral bacterial strain)
was used for evaluation of antibacterial activity of the
studied cements. Briefly, colonies of S. mutans (UA159)
were suspended in 5 ml of Tryptic soy Broth (TSB),
supplemented with 1% sucrose. Specimens pretreated
with ethanol were incubated with S. mutans in TSB at
37˚C for 48 h under anaerobic condition with 5% CO2.
After equal volumes of the red and the green dyes were
combined in a microfuge tube and mixed thoroughly for
1 min, 3 μl of the dye mixture was added to 1 ml of the
bacteria suspension, mixed by vortexing for 10 sec, so-
nicating for 10 sec as well as vortexing for another 10
sec, and kept in dark for about 15 min, prior to analysis.
Then 20 μl of the stained bacterial suspension was ana-
lyzed using a fluorescent microscope (Nikon Micro-
phot-FXA, Melville, NY, USA). Triple replica was used
to obtain a mean value for each material.
2.3.4. Statisti cal analysis
One-way analysis of variance (ANOVA) with the post
hoc Tukey-Kramer multiple-range test was used to de-
termine significant differences of both CS and antibacte-
rial tests among the materials in each group. A level of α
= 0.05 was used for statistical significance.
3. RESULTS
3.1. Characterization
Figure 2 shows the 1HNMR spectra for BT, DMEA,
DTHAC, poly (AA-co-IA) and poly (AA-co-IA) with
pendent QAS or PQAS. The characteristic chemical
shifts (ppm) are shown below: BT: 3.35 (-CH2Br), 1.80
(-CH2CH2Br), 1.38 (-CH2-, all) and 0.89 (-CH3); DMEA:
4.40 (-OH), 3.42 (-CH2OH), 2.30 (-CH2N-) and 2.10
(H3CN-); DTHAC: 5.30 (-OH), 3.82 (-CH2OH),
3.35-3.45 (-CH2N(CH3)2), 3.10 (H3CN-), 1.65 (-CH2
CH2N(CH3)2), 1.25 (-CH2- all) and 0.89 (-CH3); poly
(AA-co-IA): 12.2 (-COOH), 3.45 (-CH(COOH)-) and
1.2-2.5 (-CH2-, all); PQAS: 3.80 (-CH2(COOH)-),
3.30-3.45 (-CH2N-), 3.10 (H3CN-), 1.65 (-CH2CH2N
(CH3)2), 1.25 (-CH2- all) and 0.89 (-CH3). The appearance
of all the new peaks in the spectrum at the top of Figure
2 confirmed the successful attachment of DTHAC onto
the poly (AA-co-IA).
Figure 3 shows the FT-IR spectra for BT, DMEA,
DTHAC, poly (AA-co-IA) and PQAS. The characteristic
peaks (cm-1) are listed below: BT: 2924 (C-H stretching
on -CH2-), 2853 (C-H stretching on -CH3), 1466, 1377
and 1251 (C-H deformation on –CH2-), 721 and 647
(C-Br deformation); DMEA: 3399 (O-H stretching),
2944 (C-H stretching on -CH2-), 2861 (C-H stretching
on -CH3), 2820 and 2779 (C-H stretching on –N(CH3)2),
1459, 1364 and 1268 (C-H deformation on –CH2-), 1090
(O-H deformation), 1040 and 776 (C-N deformation);
DTHAC: 3349 and 3248 (= N+ = stretching), 2917 (C-H
stretching on -CH2-), 2850 (C-H stretching on -CH3),
1470 (C-H deformation on –CH2-), 1090 and 730 (O-H
deformation); poly(AA-co-IA): 3800-2400 (O-H stretching
on –COOH), 1716 (-C=O stretching), 1196-1458 (C-H
deformation on –CH2-); PQAS: 3353 (= N+ = stretching),
3800-2400 (O-H stretching on –COOH), 2923 (C-H
stretching on -CH2-), 2853 (C-H stretching on -CH3),
1732 (-C = O stretching), 1167-1466 (C-H deformation
on –CH2-) and 776 (C-N deformation). The significant
peaks at 3353 for = N+ = group, 2923 and 2853 for
–CH2- group and 1736 for carbonyl group confirmed the
formation of PQAS.
3.2. Evaluation
Table 1 shows the codes, materials and formulations

Y. M. Weng et al. / J. Biomedical Science and Engineering 3 (2010) 955-962
959
used in this study. Both Fuji II LC and experimental
(EXPGIC) cements with and without PQAS were evalu-
ated. PQAS was incorporated in a ratio of 1, 3, 5, 10 and
30% (by weight) of the total glass fillers.
Figure 4 shows the mean CS values of Fuji II LC and
Figure 2. 1HNMR spectra for BT, DMEA, DTHAC,
poly(AA-co-IA) and PQAS: (a) BT; (b) DMEA; (c) DTHAC;
(d) poly(AA-co-IA) and (e) PQAS.
Figure 3. FT-IR spectra for BT, DMEA, DTHAC, poly (AA-
co-IA) and PQAS: (a) BT; (b) DMEA; (c) DTHAC; (d)
poly(AA-co-IA) and (e) PQAS.
EXPGIC cements with and without PQAS addition. The
CS value (MPa) was in the decreasing order of EXPGIC
> EXPGIC (1%) > EXPGIC (3%) > Fuji II LC >
EXPGIC (5%) > Fuji II LC (1%) > Fuji II LC (3%) >
EXPGIC (10%) > Fuji II LC (5%) > Fuji II LC (10%) >
EXPGIC (30%) > Fuji II LC (30%). There were no
statistically significant differences between EXPGIC
(3%) and Fuji II LC and between Fuji II LC (3%) and
EXPGIC (10%) (p > 0.05). Increasing PQAS decreased
the CS values of both cements. However, the decreasing
rate for Fuji II LC was much faster than that for EX-
PGIC. With 1 to 10% PQAS addition, Fuji II LC de-
creased 25 to 78% of its original CS whereas EXPGIC
only decreased 12 to 57%. Ta bl e 2 shows the results of
yield strength (YS), compressive modulus, CS and DTS.
The same trend was observed in Table 2 as shown in
Figure 4. With 1 to 10% PQAS addition, Fuji II LC
showed a decrease of 26-82% in YS, 22-78% in modulus
and 12-70% in DTS, which decreased much faster than
EXPGIC (1.9-43% in YS, 2.7-34% in modulus and
1.5-43% in DTS). Figure 5 shows the effect of the ce-
ment aging on CS. After one month of aging in water, all
the cements showed an increase in CS, especially from 1
h to 1 day. There was a slight increase (statistically no
difference) for each formulation tested from 1 day to 1
week and from 1 week to 1 month.
Figure 6 shows the mean S. mutans viability values
after culturing with Fuji II LC and EXPGIC with and
without PQAS addition. The mean S. mutans viability
was in the decreasing order of Z100 > Fuji II LC >
0
50
100
150
200
250
300
350
FIILC
FIILC(1 %) FIILC(3%) FIILC(5%)
FIILC(10%)
FIILC(30%)
EXP
EXP(1%)
EXP(3%)
EXP(5%)
EXP(10%)
EXP(30%)
CS (MPa)
Figure 4. CS of Fuji II LC and experimental cements with and
without PQAS addition: FIILC = Fuji II LC; EXP = EXPGIC;
For Fuji II LC cements, P/L = 3.2; Filler = Fuji II LC or Fuji II
LC + PQAS. For experimental cements, MW of the 6-arm poly
(acrylic acid) = 17,530 Daltons; Filler = Fuji II LC or Fuji II
LC + PQAS; Grafting ratio = 50%; P/L ratio = 2.7; P/W ratio =
70:30. Specimens were conditioned in distilled water at 37˚C
for 24 h prior to testing.

Y. M. Weng et al. / J. Biomedical Science and Engineering 3 (2010) 956-963
960
0
50
100
150
200
250
300
350
400
FIILCFIILC(3%) FIILC(5%)EXPEXP(3%)EXP(5%)
CS (MPa)
1 h1 d1 w1m
Figure 5. Effect of aging on CS: The formulations were the
same as those described in Figure 4. Specimens were condi-
tioned in distilled water at 37˚C for 1 h, 1 day, 1 week and 1
month prior to CS testing.
0
10
20
30
40
50
60
70
80
90
100
Z100
P60
FIILC
FIILC(1%) FIILC(3%) FIILC(5%)
FIILC(10%) FIILC(30%)
EX P
EXP(1%) EXP(3%) EXP(5%)
EX P(10%) EX P(30%)
S. mutans viability (%)
Figure 6. The S. mutans viability after culturing with Fuji II
LC and experimental cements with and without PQAS addition:
The formulations were the same as those described in Figure 4.
Specimens were conditioned in distilled water at 37 ˚C for 24 h,
followed by incubating with S. mutans before antibacterial
testing.
EXPGIC > Fuji II LC (1%) > EXPGIC (1%) > Fuji II
LC (3%) > Fujii II LC (5%) > Fuji II LC (10%) = EX-
PGIC (3%) > EXPGIC (5%) > EXPGIC (10%) > Fuji II
LC (30%) > EXPGIC (30%). There were no statistically
significant differences among Z100, Fuji II LC and
EXPGIC, among Fuji II LC (1%), Fuji II LC (3%) and
EXPGIC (1%), among Fuji II LC (5%), Fuji II LC (10%)
and EXPGIC (3%), and among Fuji II LC (30%), EX-
PGIC (5%) and EXPGIC (10%) (10%) (p > 0.05). In-
creasing PQAS decreased the S. mutans viability. With 3
to 30% PQAS addition, Fuji II LC killed 45 to 79% of S.
mutans whereas EXPGIC killed 63 to 91%, indicating
that the killing power of EXPGIC was much higher than
that for Fuji II LC. Figure 7 shows the effect of the ce-
ment aging on the S. mutans viability. No significant
changes in the S. mutans viability were found for each
formulation tested except Fuji II LC and EXP, where the
S.mutans viability was significantly higher in 1 day than
in either 3 days or 1 week (p > 0.05).
4. DISCUSSION
Currently there is a growing interest in preventing or
reducing biofilm formation in many biomedical areas. In
preventive restorative dentistry, secondary caries is a
critical issue and prevention of secondary caries plays a
key role in long-lasting restorations [1-4]. PQAS re-
presents a new trend of antimicrobial agents in biomedi-
cal applications [11,14]. PQAS can be incorporated in
many ways, including mixing with fillers, copolymeriz-
ing with other monomers and grafting onto the polymer
skeletons [11-15]. The beauty of using QAS is that they
can kill the microorganism by touch or simple contact.
The mechanism of QAS to kill bacteria is believed to
disrupt the surface membrane of bacteria by changing
membrane permeability or surface electrostatic balance
[12,19]. Unlike other leachable antibacterial agents such
as silver ions, antibiotics, CHX and low MW QAS,
PQAS are not leachable due to their high MW [15]. In
this regard, we purposely synthesized the new PQAS,
incorporated it into both Fuji II LC and our experimental
high-strength cements and evaluated the CS and anti-
bacterial function of the formed cements.
Table 2. YS, modulus, CS and DTS of Fuji II LC and EXP
cements.
Material YS1 [MPa] Modulus [GPa] CS2 [MPa] DTS3 [MPa]
FIILC 138.4 (2.2)a, 46.91 (0.42)d 237.9 (4.5)g43.4 (4.5)
FIILC (1%)101.3 (2.9)b5.40 (0.09)e 179.6 (1.2)38.3 (4.6)
FIILC (3%)86.4 (5.2)b 4.53 (0.01) 149.8 (1.4)h29.6 (1.8)i
FIILC (5%)50.4 (2.6) 3.22 (0.24) 91.6 (2.7) 24.3 (1.5)
FIILC (10%)24.4 (2.6) 1.54 (0.09) 52.3 (2.9) 12.9 (0.3)
EXP 173.9 (7.1)c7.74 (0.04)f 325.3 (4.2)58.8 (0.2)j
EXP (1%) 170.6 (5.5)c7.53 (0.16)f 284.4 (15) 57.9 (2.2)j
EXP (3%) 173.9 (10)c 7.25 (0.13)d, f 253.7 (11)g50.3 (1.7)k
EXP (5%) 137.7 (12)a 6.68 (0.08)d 212.0 (4.1)g49.9 (3.8)k
EXP (10%)98.8 (2.6)b 5.09 (0.09)e 136.9 (6.7)h33.7 (2.2)i
1YS = CS at yield; 2CS = ultimate CS; 3DTS = diametral tensile
strength; 4Entries are mean values with standard deviations in
parentheses and the mean values with the same superscript letter
were not significantly different (p > 0.05). Specimens were con-
ditioned in distilled water at 37˚C for 24 h prior to testing.

Y. M. Weng et al. / J. Biomedical Science and Engineering 3 (2010) 955-962
961
0
10
20
30
40
50
60
70
80
90
FIILC
FIILC(5%)
FIILC(10%)
EXP
EXP(5%)
EXP(10%)
S. mutans viability (%)
1 d3 d1 w1 m
Figure 7. Effect of aging on the S. mutans viability after cul-
turing with Fuji II LC and experimental cements with and
without PQAS addition: The formulations were the same as
those described in Figure 5. The specimens were conditioned
in distilled water for 1 day, 3 days, 1 week and 1 month, fol-
lowed by incubating with S. mutans before antibacterial testing.
From the results in Figure 4 and Ta b l e 2 , apparently
both Fuji II LC and EXPGIC cements showed a decrease
in CS, YS, modulus and DTS with increasing PQAS.
This can be attributed to the reason that the incorporated
QAS contains a 14 carbon long chain that does not con-
tribute to any strength enhancement. On the other hand,
EXPGIC showed a slower decreasing pace with nearly
30% less in CS decrease as compared to Fuji II LC (see
Figure 4). This result implies that there may be some
strong intermolecular interactions between PQAS and
star-shape polymers. Furthermore, EXPGIC still kept its
CS above 200 MPa at PQAS = 5% or less, which may be
attributed to its original high strength (325 MPa).
Regarding the antibacterial activity, we also tested a
commercial dental composite resin Z100 for comparison.
We found that Z100 hardly killed S. mutans. After 48 h
incubation with S. mutan s, Z100 only killed 10% S. mu-
tans (see Figure 5). Composite resins usually do not
have antibacterial functions [5,6]. Both Fuji II LC and
EXPGIC cements without PQAS addition killed about
20% S. mutans, which can be attributed to the release of
fluoride. It is known that GICs have inhibitory effects on
bacteria due to its fluoride release [6]. With PQAS addi-
tion, both Fuji II LC and EXPGIC increased their anti-
bacterial function significantly. More interestingly, EXP
GIC showed an even stronger antibacterial activity than
Fuji II LC with 3 to 30% PQAS addition. The possible
reason may be explained below. Since PQAS is com-
posed of 50% carboxylic acid and 50% QAS and both
components are very hydrophilic, they like to have in-
teractions with other hydrophilic components from the
cement in the presence of water. EXPGIC contains only
hydrophilic GM-tethered poly (acrylic acid) (70%) and
water (30%), whereas Fuji II LC contains a substantial
amount (approximately 25-35%) of 2-hydroxyethyl me-
thacrylate (partially hydrophilic) and dimethacrylaye/
oligomethacrylte (very hydrophobic), except for the linear
poly (acrylic acid) (20-30%) and water (20-30%) [24].
Therefore, the components in EXPGIC may help the
PQAS chains better extend on the surface of the cements
but dimethacrylaye/oligomethacrylte and 2-hydroxyethyl
methacrylate in Fuji II LC may restrict or interfere with
the extension of the PQAS chains on the surface. Obvi-
ously, the more the QAS exposed the higher the antibac-
terial activity anticipated. The results imply that to reach
the same or similar antibacterial results less PQAS might
be required for EXPGIC than Fuji II LC. This outcome
is very encouraging because it will allow us to use the
minimum amount of PQAS in EXPGIC to obtain the
maximum antibacterial activity without significantly
reducing mechanical strengths.
As previously discussed, most antibacterial dental
materials rely on the release of chemicals or antibacterial
agents including antibiotics, silver ions, zinc ions, etc
[6-10]. However, release or slow-release can lead or has
led to reduction of mechanical properties of the restora-
tives over time, short-term effectiveness, and possible
toxicity to surrounding tissues if the dose or release is
not properly controlled [6-10]. Our hypothesis was to
develop an antibacterial glass-ionomer cement without
leachable. To confirm if the incorporated PQAS was not
leachable, we examined both CS and antibacterial func-
tion of EXPGIC (containing 5% PQAS) after aging in
water for 1 day, 3 days, 1 week and 1 month. The result
in Figure 5 showed that there was a slight increase in
CS for all the formulations tested after one month of
aging, indicating no PQAS leaching. The result in Fig-
ure 7 showed that there was no change or reduction in
antibacterial function for all the formulations tested, also
suggesting no leaching. Otherwise, both strength and
antibacterial function would decrease with aging. The
reason can be attributed to the fact that the PQAS is the
polyacid-containing polymer. It is known that the car-
boxylic acid group is the key to GIC setting and
salt-bridge formation. The PQAS polymer synthesized in
the study not only provided QAS for antibacterial func-
tion but also supplied carboxyl groups for salt-bridge
formation. The latter helped the PQAS polymer firmly
attached to the glass fillers.
5. CONCLUSIONS
We have developed novel antibacterial glass-ionomer
cement containing non-leachable PQAS. With PQAS

Y. M. Weng et al. / J. Biomedical Science and Engineering 3 (2010) 956-963
962
addition, both Fuji II LC and experimental cements
showed a reduction in CS with 25-95% for Fuji II LC
and 13-78% for the experimental cement and a reduction
in S. mutans viability with 40-79% for Fuji II LC and
40-91% for the experimental cement. The experimental
cement showed less CS reduction and higher antibacte-
rial activity as compared to Fuji II LC. The result also
indicates that the cements are permanently antibacterial
with no PQAS leaching. It appears that the experimental
cement is a clinically attractive dental restorative that
can be potentially used for long-lasting restorations due
to its high mechanical strength and permanent antibacte-
rial function.
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