J. Nihon
Univ.
Sch.
Dent.,
Vol.
34. 196-207,
1992
Synthesis of Radiopaque Monomers, Properties and
their
Application
Cyclophosphazene of Bulk Polymers to Composite
Resin
Misaki ANZAI, Masanori KOBORI, Kazue YOSHIHASHI, Hisaji KIKUCHI, Hideharu HIROSE and Minoru NISHIYAMA (Received12 December1991and accepted10 February 1992) Key words:
octachlorocyclotetraphosphazene, radiopaque cyclophosphazene monomers, radiopaque composite resin, physical properties Abstract
A series of studies was conducted on the synthesis of polyfunctional cyclophosphazene monomers having radiopacity and a polymerization group in the same molecule, and their properties and applicability to composite resin were examined. Using octachlorocyclotetraphosphazene, P4N4Cl8 (4PNC), monomers were synthesized by replacing the 1-4 of chlorine (Cl) with p-bromophenol (BrC6H4OH, BrPh), and replacing the residual number of C 1, 7-4, with 2hydroxyethyl methacrylate [CH2:C(CH3)COOCH2CH2OH] (HEMA), so as to obtain four kinds of transparent monomer having radiopacity and a polymerization group in the same molecule. We then analyzed these monomers and examined their physical properties after bulk-polymerization. Next, we prepared an organic composite filler using 4PN-(BrPh)3-(EMA)5 monomer, which showed comparatively good radiopacity, to produce a new experimental radiopaque composite resin. Although radiopacity improved in accordance with the increase in the number of BrPh molecules replaced, the mechanical properties of the polymer became poorer. Similarly it was proved that the radiopacity of composite resin made with 4PN-(BrPh)3-(EMA)5 monomer was equivalent or even superior, compared with the radiopacity of the front tooth. Consequently, it was shown that these synthesized monomers can be applied to visible light-cured radiopaque composite resin. Introduction The present paper describes a series of studies aimed at the development of a restorative composite resin having radiopacity for dental use. The radiopacity of commercial radiopaque composite resin is due mainly to barium glass mixed with the resin[1,2].However, it has been pointed out that this composite resin may lose its physical properties after immersion in water for a long period[3]. Therefore we synthesized and analyzed monomers having radiopacity 安斎
碕,小 堀 雅教,吉 橋 和 江,菊 地 久二,廣 瀬英 晴,西 山
實
Department of Dental Materials, Nihon University School of Dentistry To whom all correspondence should be addressed: Dr. Misaki ANZAI, Department of Dental Materials, Nihon University School of Dentistry, 1-8-13, Kanda-Surugadai, Chiyoda-ku, Tokyo 101, JAPAN.
197
and a polymerization group in the same molecule, then polymerized them, and examined the radiopacity and physical properties of the polymers. Furthermore, using the synthesized monomers, a new radiopaque composite resin was prepared. Synthesis and analysis of monomers 1. Experimental Methods 1) Synthesis of monomers Octachlorocyclotetraphosphazene, P4N4Cl8 (4PNC, Nippon Soda Co., Tokyo) whose structure is shown in Fig. 1, was used. Its 1-4 Cl (chlorine) atoms were replaced with p-bromophenol (BrC6H4OH, BrPh, Tokyo Kasei Kogyo Co., Tokyo), and the residual 7-4 Cl atoms were replaced with 2-hydroxyethyl methacrylate [CH2: C(CH3) COOCH2CH2OH] (HEMA, distilled under reduced pressure). Then, by the method[4,5] shown in Fig. 2, four kinds of radiopaque cyclophosphazene monomers, 4PN (BrPh)1-4-(EMA)7-4, were synthesized. 2) Analysis of composition The synthesized monomers were analyzed using an infrared spectrophotometer (FT-IR 4300, Shimadzu, Kyoto) and also by NMR (JNM-FX100 (FT-NMR) , JEOL, Tokyo).
Fig.
Fig.
2
Scheme
1
Octachlorocyclotetraphosphazene,
for
synthesis
of radiopaque
P4N4C18
cyclophosphazene
monomers
198
Fig. 3
IR spectra of BrC6H4OH (upper) and 4PN- (BrPh)4- (EMA) 4(lower)
Fig. 4
'H-NMR of 4PN- (BrPh) 4-(EMA)4 monomer
199
2.
Results and Discussion Analysis and confirmation of composition Figure 3 shows the IR spectra of p-bromophenol and 4PN-(BrPh)4-(EMA)4 as representative examples of the synthesized monomers. Absorption due to phenyl ring was recognized at 1590, 1490 and 1200 cm-1, and absorption due to C-Br at 605 cm-1. On the other hand, from the results of 1H -NMR
analysis
shown
in Fig . 4, it was
proved
that
the replacement
number
of
BrPh matched the theoretical one. Through the reaction shown in Fig. 2, four kinds of monomer were obtained. Table 1 shows the specific gravity, refractive index and viscosity of each synthesized monomer. Both the specific gravity and refractive index increased as the number of BrPh replacements increased. In the case of 4PN (BrPh)i-(EMA)7, the viscosity was 30 poise, but in the other cases it was 50 poise. Table
1
Polymerization physical 1.
of
of
at
radiopacity
Radiopacity
was
Tokyo)
The
aluminum
and
absorption
was
density.
ratio
of
Compressive
of
of
their
radiopacity
and
were an
tube
voltage
cm
0.3 at
and
an
the
BPO
were
for
apparatus of
60
MAT Sakura,
a tube
time TL.
of
sensitivity
1.0
of
to E)
for
of
100
mA,
s. density
First,
(log
calculated
Toshiba
current
Photographic
Tokyo).
simultaneously
was
under
(DRX-191D,
kVp,
exposure
X-O
relative
polymerized
2 h.
used. X-ray
photographed
equivalent
wt% 120•Ž
the measure the
was
specimen the film
comparison
and respec-
was
deter-
the
X-ray
as
[61.
tester,
universal
mm
(PDA-15,
Then,
aluminum
with then
using
Kodak
were
Measurement
hardness
100
a densitometer
the
Hardress
X-ray
of
step-wedge
optical
3)
an
employed
with
and
10ƒÓ•~3
distance film
measured
6 h
measured
with
a focus-to-film
speed
of measuring
mined
investigation
mixed
for
Specimens
Ltd.,
tive
monomers
monomers
60•Ž
Measurement
Co.,
and
monomers
pressure
2)
of synthesized
Methods
synthesized
reduced
a
monomers
Polymerization The
properties
properties
Experimental 1)
Physical
of
physical
specimens with
a
50-g
strength testing
1 mm/min.
properties
measuring
machine
load of
9ƒÓ•~10 for
specimens (TCM-5000A,
30
mm
was
determined
using
a Knoop
s. measuring Minebea,
5ƒÓ•~10
mm
Nagano),
was
measured with
a
using crosshead
200
Transverse a
strength
universal
speed
testing
of The
machine,
above
Water
water
at
sorption
immersed
in and
mm
water
at
weighed
Water
of
30
measured
mm
and
using
a
crosshead
with
both
dry
and
as
follows:
wet
specimens
were
and
to
measured
be
of
weighed
fixed
weight
(Ww)
again.
First,
(Wo),
and
Finally,
specimens
then
the
they
were
specimens
were
(Wd).
was
calculated
both
represented
as
(Ww-Wo)/Wo•~100,
as
and
solubility
as
wt%.
Discussion
5
shows
the
that
case
for
increase
radiopacity
of
as
the
absorption
number
be
polymerized
the was
of of
would
Physical
the
forms
of
the
synthesized
equivalent.
4PN-(BrPh)1-(EMA)7,
coefficient
replacements,
Table
of
aluminum
4PN-(BrPh)4-(EMA)4
in
2)
the
represented
In
BrPh
6.5
aluminum
mm,
replacements.
It
4PN-(BrPh)4-(EMA)4, increased
in
equivalent
increasing
in
was
presumed
having
comparison
a
with
was
accordance that
large
1.5
mm,
with
number
the
the
mass
of
BrPh
Figs.
6-10
4PN-(BrPh)i-(EMA)7.
properties
2 shows
the
physical
properties
of
the
polymers,
from
which
obtained. As
showed
shown
in
a tendency
BrPh
replacements
(BrPh)4-(EMA)4,
Figs. to
6 and
were
7, hardness
decrease
for
in
both
compared
strength
ization
decreased,
dry with
and
compressive
accordance and
with
wet
cases.
strength
the That
4PN-(TF)1-(EMA)7,
presumably
due
is, both
to
the
of
increase
decrease
in in
the
hardness of
the
the
polymers number
case
of
of 4PN-
and
compres-
the
polymer-
EMA,
group. As
BrPh
distance
was
7 days).
made
again
and
Figure
showed
mm
Radiopacity
monomers,
sive
fulcrum
solubility
37•Ž
sorption
Results
were
3•~3•~40
performed
for
were
(Wd-Wo)/Wo•~100,
and
a
were
37•Ž
and
50•~10
1)
measuring
with
experiments
in
measuring
2.
specimens
1 mm/min.
(immersed
dried,
of
to
transverse
a tendency replacements.
strength to
shown
increase
However,
Table
2
in
Fig.
in
accordance
under
wet
Physical
8,
conditions,
properties
in
with
the
case
the
increase
it was
of polymers
of
dry
decreased
in
conditions, the
number considerably
it of
201
Fig.
Fig.
6
5
Relationship
Relationship
between
between
replacement
replacement
number
number
of p-bromophenol
of p-bromophenol
and
and
radiopacity
Knoop
hardness
202
Fig.
Fig.
7
8
Relationship
Relationship
between
between
replacement
replacement
number
number
of p-bromophenol
of p-bromophenol
and
and
compressive
transverse
strength
strength
203
Fig.
Fig.
9
Relationship
10
Relationship
between
between
replacement
replacement
number
number
of p-bromophenol
of p-bromophenol
and
water
and
sorption
solubility
204
irrespective of the number of BrPh replacements. This was due presumably to polymers becoming fragile because of water sorption. Water sorption and solubility are shown, respectively, in Figs. 9 and 10. Both showed a tendency to decrease in accordance with the increase in the number of BrPh replacements, due presumably to BrPh itself being hydrophobic{51. Consequently it was proved that 4PN-(BrPh)3-(EMA)5 had comparatively low water sorption, and that its solubility was suitable for use as a radiopaque composite resin monomer and organic composite filler. Trial visible light-cured radiopaque composite resin 1. Experimental Methods 1) Monomer composition Of the four kinds of synthesized monomer, 4PN-(BrPh)3-(EMA)5 was selected, as the polymer showed comparatively superior mechanical properties. Again, to increase the transverse stength, dimethacryloxyethyl-2, 2, 4-trimethylhexamethylene diurethane (U-2TH, Shin-Nakamura Chemical Co., Wakayama), UDMA monomer, was mixed at 50 wt% as a co-monomer[71. 2) Organic composite filler As the monomer for an organic composite filler, 4PN-(BrPh)3-(EMA)5 was used with silica (SiO2, R972, Degussa, F. R. G.) mixed at 20 wt%, and ground, after polymerization, into particles less than 42 pm in diameter. The monomer prepared in 1) and the organic composite filler prepared in 2) were each mixed at 50 wt% to a paste form. 3) Photosensitizers As photosensitizers, camphorquinone (CQ, Aldrich, U. S. A.) 0.30 wt%, dibenzoyl(DB, Tokyo Kasei Kogyo Co.) 0.15 wt% and 2-methacryloxyethyl p-dimethylamino benzoate (DMAB-EMA, Toa Gosei Chemical, Co. Ltd., Tokyo) 1.40 wt% were mixed[81. Table 3 shows the composition of the trial visible light-cured radiopaque composite resin. Table 3
Composition
of trial composite resin (wt%)
205
4)
Polymerization Specimens
XS,
were
Kulzer, 5)
F.
R.
Measurement
strength
transverse as
6)
polymer
of
hereafter) a
2.
and tooth
1)
resin
and The
than
that
apparatus or
180
(Dentacolor
s in
total.
the
hardness
with
Testing
test,
a fulcrum instruments
40•~6
distance
mm of
and
methods
mm
were
for
20
mm, were
the for the
specimens
the
(No. Silux
incisor)
10ƒÓ•~3
sections.
two
light-S
central
measuring
preceding
kinds US
were
of
209,
(No.
For
comparison,
commercial
product,
Tokuyama
5502U,
Soda
3M,
obtained four
U.
S.
Co. A.,
by
kinds
of
radiopaque Ltd.,
Silux,
Palfique, hereafter),
used.
Discussion properties
shows
the
commercial hardness of
for mm,
used.
non-radiopaque
Physical 4
were
monomers),
and
Table
mm
2•~2•~25
of
Palfique
(upper
Results
curing side,
radiopacity
in
(synthesized resin
s each
above.
described
composite
and
test
light
90
properties
and
images
methods
a visible for
90•~10
test
Measurement Radiographic
the
physical
strength
described
with
irradiation
measuring
compressive
same
by of
Specimens
the
polymerized G.)
mechanical composite
of
the
trial
properties resin product,
of
the
trial
dry
and
radiopaque
composite
Palfique. both
in
a
a wet
state,
was
lower
Palfique.
Table
4
Physical
properties
of composite
resin
Compressive strength (yield point) of the trial product was 117.3 MPa, whereas that of Palfique was 126.5 MPa in a dry state. Transverse strength of the trial product was 94.1 MPa, whereas that of Palfique was 109.6 MPa in a dry. state. Thus it was proved that the trial composite resin, in comparison with the commercial product, showed low values of hardness, and approximately the same values for both compressive and transverse strength. 2) Radiopacity Figure 11 shows radiographic images of the four kinds of polymer, the trial composite resin, the commercial radiopaque composite resin (Palfique), the nonradiopaque composite resin (Silux) and the tooth. The photographic density of the polymers of synthesized monomers increased in accordance with the increase in the number of BrPh replacements, and it was proved that the trial product showed the
206
1
5
2
6
3
7
4
Fig. 11
Radiographic images of polymers (synthesized monomers), trial composite resin, commercial composite resin and natural tooth 1. 4PN- (BrPh),- (EMA) 7, 2. 4PN- (BrPh) 2-(EMA) 6 3. 4PN- (BrPh) 3- (EMA) 5, 4. 4PN- (BrPh) 4-(EMA) 4 5. trial composite resin, 6. non-radiopaque composite resin, Silux 7. radiopaque composite resin, Palfique light-S 8. natural tooth (upper central incisor)
same radiopacity as Palfique and natural tooth. The above results proved that the mechanical properties and radiopacity of the trial radiopaque resin were approximately the same or slightly inferior to those of commercial products. The results of cytotoxicity and Ames tests on the trial composite resin were satisfactory. The authors intend to continue these studies to achieve further improvement of the physical properties. Conclusion In order to produce an improved radiopaque composite resin, four kinds of radiopaque monomer were synthesized. These monomers were then bulkpolymerized and their physical properties examined. Composite resin was prepared using synthesized cyclophosphazene monomer 4PN-(BrPh)3-(EMA)5, and we examined its physical properties. The radiopacity of the trial composite resin was compared with that of a commercial composite resin, Palfique, and natural tooth. The results were as follows: 1) The four kinds of synthesized monomer had properties close to those
207
2)
3)
4) 5)
6)
expected. The aluminum equivalents of the polymerized synthesized monomers were 1.5 mm for 4PN-(BrPh)1-(EMA)7, and 6.5 mm for 4PN-(BrPh)4-(EMA)4. On the other hand, Palfique and natural tooth had values of 4.5 and 4.8 mm, respectively. Hardness and compressive strength of the polymers decreased in accordance with the increase in the number of BrPh replacements, but transverse strength increased. Both water sorption and solubility showed a tendency to decrease in accordance with the increase in the number of BrPh replacements. Values of both compressive and transverse strength of the trial visible light-cured composite resin were approximately the same as those of Palfique, but hardness was lower. The radiopacity of the trial visible light-cured composite resin was approximately the same or slightly lower than that of Palfique and natural tooth. References
[1] RYGE, G. and JENDRESEN, M.: CompositeResinRestorativeMaterials.In ClinicalDentistry, Vol. 4, 1-10,Clark, J. W., Ed., Harper & Row., Philadelphia,U. S. A., 1981 [2] Council on dentalmaterials,instrumentsand equipment:Statusreporton posteriorcomposites, J. Am. Dent. Ass., 107, 74-76,1983 [3] KOBORI, M., KAWASHIMA, S., MARUHASHI, K., SATOH, S., KIMURA, K., HASHIMOTO, K., ANZAI, M. and OHASHI, M.: The basic study of radiopaqueresin monomer(1), Nihon Univ.Dent. J., 63, 493-498,1989(in Japanese) [4] ANZAI, M. and OHASHI, M.: Studies on the reaction product of hexachlorocyclotriphosphazene and 2-hydroxyethylmethacrylate and on the physical properties of its polymer, J. Nihon Univ.Sch. Dent., 26, 109-118,1984 [5] HIROSE, H., ANZAI, M.,YONEYAMA, M.,KAWAKAMI, T., WATANABE, I. and OHASHI, M.: Studies on polyfunctionalcyclophosphazenemonomersfor dental use (1), J. Nihon Univ. Sch. Dent., 29, 287-297,1987 [6] KATO, Y., IIZUKA, H., IIJIMA, K., OHASHI, M., KIMURA, K., KAWASHIMA, S., TOGAWA, K. and SAIRENJI, E.: A study of radio-opacityof dental filling materials compositeresins,Nihon Univ.Dent. J., 59, 746-751,1985(in Japanese) [7] NASU, T.: Basicstudieson visible light-curedcrownand bridgeresin (II), Nihon Univ.Dent. J., 63, 456-464,1989(in Japanese) [8] HIROSE, H., KIKUCHI, H., YOSHIHASHI, K., ANZAI,M. and NISHIYAMA, M.: Conversion in visible light-curedresins,Jpn. J. Dent. Mater., 10, 213-218,1991(in Japanese)
Univ.
Sch.
Dent.,
Vol.
34. 196-207,
1992
Synthesis of Radiopaque Monomers, Properties and
their
Application
Cyclophosphazene of Bulk Polymers to Composite
Resin
Misaki ANZAI, Masanori KOBORI, Kazue YOSHIHASHI, Hisaji KIKUCHI, Hideharu HIROSE and Minoru NISHIYAMA (Received12 December1991and accepted10 February 1992) Key words:
octachlorocyclotetraphosphazene, radiopaque cyclophosphazene monomers, radiopaque composite resin, physical properties Abstract
A series of studies was conducted on the synthesis of polyfunctional cyclophosphazene monomers having radiopacity and a polymerization group in the same molecule, and their properties and applicability to composite resin were examined. Using octachlorocyclotetraphosphazene, P4N4Cl8 (4PNC), monomers were synthesized by replacing the 1-4 of chlorine (Cl) with p-bromophenol (BrC6H4OH, BrPh), and replacing the residual number of C 1, 7-4, with 2hydroxyethyl methacrylate [CH2:C(CH3)COOCH2CH2OH] (HEMA), so as to obtain four kinds of transparent monomer having radiopacity and a polymerization group in the same molecule. We then analyzed these monomers and examined their physical properties after bulk-polymerization. Next, we prepared an organic composite filler using 4PN-(BrPh)3-(EMA)5 monomer, which showed comparatively good radiopacity, to produce a new experimental radiopaque composite resin. Although radiopacity improved in accordance with the increase in the number of BrPh molecules replaced, the mechanical properties of the polymer became poorer. Similarly it was proved that the radiopacity of composite resin made with 4PN-(BrPh)3-(EMA)5 monomer was equivalent or even superior, compared with the radiopacity of the front tooth. Consequently, it was shown that these synthesized monomers can be applied to visible light-cured radiopaque composite resin. Introduction The present paper describes a series of studies aimed at the development of a restorative composite resin having radiopacity for dental use. The radiopacity of commercial radiopaque composite resin is due mainly to barium glass mixed with the resin[1,2].However, it has been pointed out that this composite resin may lose its physical properties after immersion in water for a long period[3]. Therefore we synthesized and analyzed monomers having radiopacity 安斎
碕,小 堀 雅教,吉 橋 和 江,菊 地 久二,廣 瀬英 晴,西 山
實
Department of Dental Materials, Nihon University School of Dentistry To whom all correspondence should be addressed: Dr. Misaki ANZAI, Department of Dental Materials, Nihon University School of Dentistry, 1-8-13, Kanda-Surugadai, Chiyoda-ku, Tokyo 101, JAPAN.
197
and a polymerization group in the same molecule, then polymerized them, and examined the radiopacity and physical properties of the polymers. Furthermore, using the synthesized monomers, a new radiopaque composite resin was prepared. Synthesis and analysis of monomers 1. Experimental Methods 1) Synthesis of monomers Octachlorocyclotetraphosphazene, P4N4Cl8 (4PNC, Nippon Soda Co., Tokyo) whose structure is shown in Fig. 1, was used. Its 1-4 Cl (chlorine) atoms were replaced with p-bromophenol (BrC6H4OH, BrPh, Tokyo Kasei Kogyo Co., Tokyo), and the residual 7-4 Cl atoms were replaced with 2-hydroxyethyl methacrylate [CH2: C(CH3) COOCH2CH2OH] (HEMA, distilled under reduced pressure). Then, by the method[4,5] shown in Fig. 2, four kinds of radiopaque cyclophosphazene monomers, 4PN (BrPh)1-4-(EMA)7-4, were synthesized. 2) Analysis of composition The synthesized monomers were analyzed using an infrared spectrophotometer (FT-IR 4300, Shimadzu, Kyoto) and also by NMR (JNM-FX100 (FT-NMR) , JEOL, Tokyo).
Fig.
Fig.
2
Scheme
1
Octachlorocyclotetraphosphazene,
for
synthesis
of radiopaque
P4N4C18
cyclophosphazene
monomers
198
Fig. 3
IR spectra of BrC6H4OH (upper) and 4PN- (BrPh)4- (EMA) 4(lower)
Fig. 4
'H-NMR of 4PN- (BrPh) 4-(EMA)4 monomer
199
2.
Results and Discussion Analysis and confirmation of composition Figure 3 shows the IR spectra of p-bromophenol and 4PN-(BrPh)4-(EMA)4 as representative examples of the synthesized monomers. Absorption due to phenyl ring was recognized at 1590, 1490 and 1200 cm-1, and absorption due to C-Br at 605 cm-1. On the other hand, from the results of 1H -NMR
analysis
shown
in Fig . 4, it was
proved
that
the replacement
number
of
BrPh matched the theoretical one. Through the reaction shown in Fig. 2, four kinds of monomer were obtained. Table 1 shows the specific gravity, refractive index and viscosity of each synthesized monomer. Both the specific gravity and refractive index increased as the number of BrPh replacements increased. In the case of 4PN (BrPh)i-(EMA)7, the viscosity was 30 poise, but in the other cases it was 50 poise. Table
1
Polymerization physical 1.
of
of
at
radiopacity
Radiopacity
was
Tokyo)
The
aluminum
and
absorption
was
density.
ratio
of
Compressive
of
of
their
radiopacity
and
were an
tube
voltage
cm
0.3 at
and
an
the
BPO
were
for
apparatus of
60
MAT Sakura,
a tube
time TL.
of
sensitivity
1.0
of
to E)
for
of
100
mA,
s. density
First,
(log
calculated
Toshiba
current
Photographic
Tokyo).
simultaneously
was
under
(DRX-191D,
kVp,
exposure
X-O
relative
polymerized
2 h.
used. X-ray
photographed
equivalent
wt% 120•Ž
the measure the
was
specimen the film
comparison
and respec-
was
deter-
the
X-ray
as
[61.
tester,
universal
mm
(PDA-15,
Then,
aluminum
with then
using
Kodak
were
Measurement
hardness
100
a densitometer
the
Hardress
X-ray
of
step-wedge
optical
3)
an
employed
with
and
10ƒÓ•~3
distance film
measured
6 h
measured
with
a focus-to-film
speed
of measuring
mined
investigation
mixed
for
Specimens
Ltd.,
tive
monomers
monomers
60•Ž
Measurement
Co.,
and
monomers
pressure
2)
of synthesized
Methods
synthesized
reduced
a
monomers
Polymerization The
properties
properties
Experimental 1)
Physical
of
physical
specimens with
a
50-g
strength testing
1 mm/min.
properties
measuring
machine
load of
9ƒÓ•~10 for
specimens (TCM-5000A,
30
mm
was
determined
using
a Knoop
s. measuring Minebea,
5ƒÓ•~10
mm
Nagano),
was
measured with
a
using crosshead
200
Transverse a
strength
universal
speed
testing
of The
machine,
above
Water
water
at
sorption
immersed
in and
mm
water
at
weighed
Water
of
30
measured
mm
and
using
a
crosshead
with
both
dry
and
as
follows:
wet
specimens
were
and
to
measured
be
of
weighed
fixed
weight
(Ww)
again.
First,
(Wo),
and
Finally,
specimens
then
the
they
were
specimens
were
(Wd).
was
calculated
both
represented
as
(Ww-Wo)/Wo•~100,
as
and
solubility
as
wt%.
Discussion
5
shows
the
that
case
for
increase
radiopacity
of
as
the
absorption
number
be
polymerized
the was
of of
would
Physical
the
forms
of
the
synthesized
equivalent.
4PN-(BrPh)1-(EMA)7,
coefficient
replacements,
Table
of
aluminum
4PN-(BrPh)4-(EMA)4
in
2)
the
represented
In
BrPh
6.5
aluminum
mm,
replacements.
It
4PN-(BrPh)4-(EMA)4, increased
in
equivalent
increasing
in
was
presumed
having
comparison
a
with
was
accordance that
large
1.5
mm,
with
number
the
the
mass
of
BrPh
Figs.
6-10
4PN-(BrPh)i-(EMA)7.
properties
2 shows
the
physical
properties
of
the
polymers,
from
which
obtained. As
showed
shown
in
a tendency
BrPh
replacements
(BrPh)4-(EMA)4,
Figs. to
6 and
were
7, hardness
decrease
for
in
both
compared
strength
ization
decreased,
dry with
and
compressive
accordance and
with
wet
cases.
strength
the That
4PN-(TF)1-(EMA)7,
presumably
due
is, both
to
the
of
increase
decrease
in in
the
hardness of
the
the
polymers number
case
of
of 4PN-
and
compres-
the
polymer-
EMA,
group. As
BrPh
distance
was
7 days).
made
again
and
Figure
showed
mm
Radiopacity
monomers,
sive
fulcrum
solubility
37•Ž
sorption
Results
were
3•~3•~40
performed
for
were
(Wd-Wo)/Wo•~100,
and
a
were
37•Ž
and
50•~10
1)
measuring
with
experiments
in
measuring
2.
specimens
1 mm/min.
(immersed
dried,
of
to
transverse
a tendency replacements.
strength to
shown
increase
However,
Table
2
in
Fig.
in
accordance
under
wet
Physical
8,
conditions,
properties
in
with
the
case
the
increase
it was
of polymers
of
dry
decreased
in
conditions, the
number considerably
it of
201
Fig.
Fig.
6
5
Relationship
Relationship
between
between
replacement
replacement
number
number
of p-bromophenol
of p-bromophenol
and
and
radiopacity
Knoop
hardness
202
Fig.
Fig.
7
8
Relationship
Relationship
between
between
replacement
replacement
number
number
of p-bromophenol
of p-bromophenol
and
and
compressive
transverse
strength
strength
203
Fig.
Fig.
9
Relationship
10
Relationship
between
between
replacement
replacement
number
number
of p-bromophenol
of p-bromophenol
and
water
and
sorption
solubility
204
irrespective of the number of BrPh replacements. This was due presumably to polymers becoming fragile because of water sorption. Water sorption and solubility are shown, respectively, in Figs. 9 and 10. Both showed a tendency to decrease in accordance with the increase in the number of BrPh replacements, due presumably to BrPh itself being hydrophobic{51. Consequently it was proved that 4PN-(BrPh)3-(EMA)5 had comparatively low water sorption, and that its solubility was suitable for use as a radiopaque composite resin monomer and organic composite filler. Trial visible light-cured radiopaque composite resin 1. Experimental Methods 1) Monomer composition Of the four kinds of synthesized monomer, 4PN-(BrPh)3-(EMA)5 was selected, as the polymer showed comparatively superior mechanical properties. Again, to increase the transverse stength, dimethacryloxyethyl-2, 2, 4-trimethylhexamethylene diurethane (U-2TH, Shin-Nakamura Chemical Co., Wakayama), UDMA monomer, was mixed at 50 wt% as a co-monomer[71. 2) Organic composite filler As the monomer for an organic composite filler, 4PN-(BrPh)3-(EMA)5 was used with silica (SiO2, R972, Degussa, F. R. G.) mixed at 20 wt%, and ground, after polymerization, into particles less than 42 pm in diameter. The monomer prepared in 1) and the organic composite filler prepared in 2) were each mixed at 50 wt% to a paste form. 3) Photosensitizers As photosensitizers, camphorquinone (CQ, Aldrich, U. S. A.) 0.30 wt%, dibenzoyl(DB, Tokyo Kasei Kogyo Co.) 0.15 wt% and 2-methacryloxyethyl p-dimethylamino benzoate (DMAB-EMA, Toa Gosei Chemical, Co. Ltd., Tokyo) 1.40 wt% were mixed[81. Table 3 shows the composition of the trial visible light-cured radiopaque composite resin. Table 3
Composition
of trial composite resin (wt%)
205
4)
Polymerization Specimens
XS,
were
Kulzer, 5)
F.
R.
Measurement
strength
transverse as
6)
polymer
of
hereafter) a
2.
and tooth
1)
resin
and The
than
that
apparatus or
180
(Dentacolor
s in
total.
the
hardness
with
Testing
test,
a fulcrum instruments
40•~6
distance
mm of
and
methods
mm
were
for
20
mm, were
the for the
specimens
the
(No. Silux
incisor)
10ƒÓ•~3
sections.
two
light-S
central
measuring
preceding
kinds US
were
of
209,
(No.
For
comparison,
commercial
product,
Tokuyama
5502U,
Soda
3M,
obtained four
U.
S.
Co. A.,
by
kinds
of
radiopaque Ltd.,
Silux,
Palfique, hereafter),
used.
Discussion properties
shows
the
commercial hardness of
for mm,
used.
non-radiopaque
Physical 4
were
monomers),
and
Table
mm
2•~2•~25
of
Palfique
(upper
Results
curing side,
radiopacity
in
(synthesized resin
s each
above.
described
composite
and
test
light
90
properties
and
images
methods
a visible for
90•~10
test
Measurement Radiographic
the
physical
strength
described
with
irradiation
measuring
compressive
same
by of
Specimens
the
polymerized G.)
mechanical composite
of
the
trial
properties resin product,
of
the
trial
dry
and
radiopaque
composite
Palfique. both
in
a
a wet
state,
was
lower
Palfique.
Table
4
Physical
properties
of composite
resin
Compressive strength (yield point) of the trial product was 117.3 MPa, whereas that of Palfique was 126.5 MPa in a dry state. Transverse strength of the trial product was 94.1 MPa, whereas that of Palfique was 109.6 MPa in a dry. state. Thus it was proved that the trial composite resin, in comparison with the commercial product, showed low values of hardness, and approximately the same values for both compressive and transverse strength. 2) Radiopacity Figure 11 shows radiographic images of the four kinds of polymer, the trial composite resin, the commercial radiopaque composite resin (Palfique), the nonradiopaque composite resin (Silux) and the tooth. The photographic density of the polymers of synthesized monomers increased in accordance with the increase in the number of BrPh replacements, and it was proved that the trial product showed the
206
1
5
2
6
3
7
4
Fig. 11
Radiographic images of polymers (synthesized monomers), trial composite resin, commercial composite resin and natural tooth 1. 4PN- (BrPh),- (EMA) 7, 2. 4PN- (BrPh) 2-(EMA) 6 3. 4PN- (BrPh) 3- (EMA) 5, 4. 4PN- (BrPh) 4-(EMA) 4 5. trial composite resin, 6. non-radiopaque composite resin, Silux 7. radiopaque composite resin, Palfique light-S 8. natural tooth (upper central incisor)
same radiopacity as Palfique and natural tooth. The above results proved that the mechanical properties and radiopacity of the trial radiopaque resin were approximately the same or slightly inferior to those of commercial products. The results of cytotoxicity and Ames tests on the trial composite resin were satisfactory. The authors intend to continue these studies to achieve further improvement of the physical properties. Conclusion In order to produce an improved radiopaque composite resin, four kinds of radiopaque monomer were synthesized. These monomers were then bulkpolymerized and their physical properties examined. Composite resin was prepared using synthesized cyclophosphazene monomer 4PN-(BrPh)3-(EMA)5, and we examined its physical properties. The radiopacity of the trial composite resin was compared with that of a commercial composite resin, Palfique, and natural tooth. The results were as follows: 1) The four kinds of synthesized monomer had properties close to those
207
2)
3)
4) 5)
6)
expected. The aluminum equivalents of the polymerized synthesized monomers were 1.5 mm for 4PN-(BrPh)1-(EMA)7, and 6.5 mm for 4PN-(BrPh)4-(EMA)4. On the other hand, Palfique and natural tooth had values of 4.5 and 4.8 mm, respectively. Hardness and compressive strength of the polymers decreased in accordance with the increase in the number of BrPh replacements, but transverse strength increased. Both water sorption and solubility showed a tendency to decrease in accordance with the increase in the number of BrPh replacements. Values of both compressive and transverse strength of the trial visible light-cured composite resin were approximately the same as those of Palfique, but hardness was lower. The radiopacity of the trial visible light-cured composite resin was approximately the same or slightly lower than that of Palfique and natural tooth. References
[1] RYGE, G. and JENDRESEN, M.: CompositeResinRestorativeMaterials.In ClinicalDentistry, Vol. 4, 1-10,Clark, J. W., Ed., Harper & Row., Philadelphia,U. S. A., 1981 [2] Council on dentalmaterials,instrumentsand equipment:Statusreporton posteriorcomposites, J. Am. Dent. Ass., 107, 74-76,1983 [3] KOBORI, M., KAWASHIMA, S., MARUHASHI, K., SATOH, S., KIMURA, K., HASHIMOTO, K., ANZAI, M. and OHASHI, M.: The basic study of radiopaqueresin monomer(1), Nihon Univ.Dent. J., 63, 493-498,1989(in Japanese) [4] ANZAI, M. and OHASHI, M.: Studies on the reaction product of hexachlorocyclotriphosphazene and 2-hydroxyethylmethacrylate and on the physical properties of its polymer, J. Nihon Univ.Sch. Dent., 26, 109-118,1984 [5] HIROSE, H., ANZAI, M.,YONEYAMA, M.,KAWAKAMI, T., WATANABE, I. and OHASHI, M.: Studies on polyfunctionalcyclophosphazenemonomersfor dental use (1), J. Nihon Univ. Sch. Dent., 29, 287-297,1987 [6] KATO, Y., IIZUKA, H., IIJIMA, K., OHASHI, M., KIMURA, K., KAWASHIMA, S., TOGAWA, K. and SAIRENJI, E.: A study of radio-opacityof dental filling materials compositeresins,Nihon Univ.Dent. J., 59, 746-751,1985(in Japanese) [7] NASU, T.: Basicstudieson visible light-curedcrownand bridgeresin (II), Nihon Univ.Dent. J., 63, 456-464,1989(in Japanese) [8] HIROSE, H., KIKUCHI, H., YOSHIHASHI, K., ANZAI,M. and NISHIYAMA, M.: Conversion in visible light-curedresins,Jpn. J. Dent. Mater., 10, 213-218,1991(in Japanese)
