Influence of inorganic filler content on the radiopacity of dental resin ...

Dental Materials Journal 2012; 31(2): 266–272
<strong>Influence</strong> <strong>of</strong> <strong>inorganic</strong> <strong>filler</strong> <strong>content</strong> on the radiopacity <strong>of</strong> dental resin cements
Gabriel FURTOS 1,2 , Bogdan BALDEA 3 , Laura SILAGHI-DUMITRESCU 1 , Marioara MOLDOVAN 1 ,
Cristina PREJMEREAN 1 and Luminita NICA 4
1Department <strong>of</strong> Dental Materials, "Raluca Ripan" Institute <strong>of</strong> Research in Chemistry, 30 Fantanele Street, 400294 Cluj-Napoca, Romania
2Faculty <strong>of</strong> Chemistry and Chemical Engineering, Babes-Bolyai University, Cluj-Napoca, Romania
3Department <strong>of</strong> Prosthodontics, Faculty <strong>of</strong> Dental Medicine, Victor Babes University <strong>of</strong> Medicine and Pharmacy Timisoara, 9 Revolutiei 1989 Avenue,
300070 Timisoara, Romania
4Department <strong>of</strong> Endodontics, Faculty <strong>of</strong> Dental Medicine, Victor Babes University <strong>of</strong> Medicine and Pharmacy Timisoara, 9 Revolutiei 1989 Avenue,
300070 Timisoara, Romania
Corresponding author, Gabriel FURTOS; E-mail: gfurtos@yahoo.co.uk
Digital radiography was used to measure the radiopacity <strong>of</strong> 18 resin cements to determine the influence <strong>of</strong> <strong>inorganic</strong> <strong>filler</strong> <strong>content</strong> on
radiopacity. Four disk specimens (n=4) <strong>of</strong> each light-curing cement were digitally radiographed alongside an aluminum step wedge
using an intraoral sensor (XIOS Plus, Sirona, Germany), and their mean gray value measured. Percentage <strong>of</strong> <strong>filler</strong> by weight was
determined using an analytical combustion furnace. Data were statistically analyzed using one-way ANOVA and Tukey’s test
(�=0.05). All materials were more radiopaque than dentin and 12 materials were more radiopaque than enamel. Filler percentage
ranged between 17.36 to 53.56 vol% and radiopacity between 1.02 to 3.40 mm Al. There were no statistically significant differences
in <strong>inorganic</strong> <strong>filler</strong> percentage and radiopacity among the different shades <strong>of</strong> the same material (p>0.05), but the highest radiopacity
was measured for the material which contained a higher percentage <strong>of</strong> <strong>filler</strong>.
Keywords: Radiopacity, Inorganic <strong>filler</strong>, Resin cements, X-ray, Dental
INTRODUCTION
To facilitate non-invasive detection and for a clear
localization <strong>of</strong> the interface between a restorative
material and the tooth structure, radiopacity is an
essential property for restorative materials so that they
can be distinguished from tooth. A survey <strong>of</strong> published
literature revealed that radiopacity is a desirable
property <strong>of</strong> intraoral materials such as denture base
materials 1) , denture liners 2) , elastomeric impression
materials 3) , endodontic sealers 4) , retrograde filling
materials 5) , direct filling restorative materials and
composite resin luting cements 6,7) , and fiber-reinforced
resin posts 8) . Secondary caries is the principal cause for
the failure and replacement <strong>of</strong> dental restorations.
Therefore, detection <strong>of</strong> secondary caries adjacent to
filling materials 9) on a radiograph is as important as the
recognition <strong>of</strong> faulty proximal contours, voids, inadequate
marginal adaptation, and interfacial gaps 10) .
Endodontically treated teeth are more susceptible to
fractures than unrestored vital teeth. Several factors
compromise the strength <strong>of</strong> these restored teeth: loss <strong>of</strong>
hard tooth tissue after access cavity preparation,
dehydration <strong>of</strong> dentin after chemomechanical
preparation, and excessive pressure during obturation 11) .
If 50% <strong>of</strong> coronal tooth structure is lost as a result <strong>of</strong>
endodontic treatment, it might be necessary to insert a
post in the root canal to retain the core.
Fiber-reinforced resin posts, cemented in the root
canal using adhesive resin cements, are used extensively
to restore endodontically treated teeth 11) . For the fiber
Color figures can be viewed in the online issue, which is avail-
able at J-STAGE.
Received Oct 24, 2011: Accepted Nov 30, 2011
doi:10.4012/dmj.2011-225 JOI JST.JSTAGE/dmj/2011-225
post, the radiopaque property allows its visualization
and identification on X-ray films against the surrounding
tooth structure and core material 8,11) , and hence the
implied importance <strong>of</strong> radiopacity for core build-up
materials too. For the adhesive resin cement used to
cement the post in the root canal, the radiopaque
property allows clinicians to use X-ray images to
determine the quality <strong>of</strong> the restoration, absence/
presence <strong>of</strong> voids, adaptation <strong>of</strong> post to the root canal
walls, and structural integrity <strong>of</strong> the post-core foundation.
Two methods are commonly used to measure the
radiopacity <strong>of</strong> dental resin cements: conventional X-rays
versus digital X-rays. To determine radiopacity using
conventional X-ray films, measurements were done
using densitometers 10) , spectrophotometers 12) , chargecoupled
device (CCD) sensors 13) , or storage phosphor
plate systems 13) . X-ray film images are scanned using a
CCD camera, a laser scanner or a flatbed scanner, and
these scanned X-ray film images are subsequently
converted into digital images for quantitative analysis
using an image analysis s<strong>of</strong>tware 14) .
With regard to technical capability and clinical
convenience, digital radiographs wield several
advantages over conventional X-ray films. Digital
radiographs can be manipulated in the following ways:
enlargement to focus on particular regions <strong>of</strong> interest,
contrast and density adjustments to sharpen images for
better image quality, smoothing and false color
representation, and quantitative measurements.
Clinical advantages <strong>of</strong>fered by digital radiographs
include reduced patient exposure to radiation, ease <strong>of</strong>
use and the ability to manipulate image during
interpretation, easy image storage and data exchange

for referral, reduced potential operator exposure to
radiation 15) , and no need for film development chemicals.
Traditional film development, unless performed
carefully, can produce significant variations in the final
radiograph. In contrast, a digital method provides more
consistent results 16) .
The aim <strong>of</strong> this study was to use digital radiography
to measure the radiopacity <strong>of</strong> 18 dental resin cements
and compare them against the radiopacity <strong>of</strong> human
enamel and dentin. All the materials examined in this
study are clinically used in the restoration <strong>of</strong>
endodontically treated teeth as core build-up materials
and/or as adhesive cements for fiber-reinforced resin
posts. Percentage <strong>of</strong> <strong>inorganic</strong> <strong>filler</strong> <strong>content</strong>, by weight
and volume, was calculated for each dental resin cement
to determine its influence on the latter’s radiopacity.
Dent Mater J 2012; 31(2): 266–272 267
MATERIALS AND METHODS
Dental resin cement specimens
Eighteen commercially available dental resin cements
were selected for investigation in this study. Their
details, such as indications (core build-up material or
luting cement) and chemical compositions, are listed in
Table 1.
For each dental resin cement, four disks (n=4)
measuring 8 mm diameter and 1 mm thickness were
prepared and polymerized by a photocuring source
(XL3000, 3M Dental Products, St Paul, MN, USA) for
40 s. As per the manufacturers’ recommendations,
Super-Bond C&B (J Morita Europe, Dietzenbach,
Hessen, Germany) was prepared at a polymer/monomer
ratio <strong>of</strong> 1.2 and HybridCem (J Morita Europe) at a
powder/liquid ratio <strong>of</strong> 1/1. Specimen thickness was
Table 1 Details <strong>of</strong> the dental resin cements investigated in this study, as provided by the manufacturers
No. Type <strong>of</strong> material Materials (Brand) Shade Composition
1 Core build-up
material
2 Core build-up
material
3 Core build-up
material
4 Core build-up
material
5 Core build-up
material
6 Core build-up
material
7 Core build-up
material
8 Core build-up
material
9 Luting cement
material
Build-It FR
(Pentron Clinical, Wallingford, CT,
USA)
CromaCore
(J Morita Europe, Dietzenbach,
Germany)
Core Paste XP
(DenMat, Santa Maria, CA, USA)
Mirafit Core
(Hager & Werken, Duisburg,
Germany)
ParaPost ParaCore Automix
(Coltene Whaledent, Altstatten,
Switzerland)
ParaPost ParaCore Automix
(Coltene Whaledent)
Rock Core
(Danville Materials Inc., San
Ramon, CA, USA)
Sealacore Core Composite
(PDSA Produits Dentaires, Vevey,
Switzerland)
Duo Cement Plus
(Coltene Whaledent)
Gold Bis-GMA, UDMA, HDDMA, mixture <strong>of</strong>
bariumborosilicate, calcium alumin<strong>of</strong>luro-silicate,
silica and chopped glass
fiber. 68% wt.; 52% vol. <strong>inorganic</strong> <strong>filler</strong>.
Enamel
w/Fluoride
NC
Glass <strong>filler</strong>s in methacrylate resin
NC% wt.; vol. <strong>inorganic</strong> <strong>filler</strong>
A3 Bis-GMA, UDMA, HDDMA, silane
treated bariumborosilicate, glass fibers,
fluoride, pigments with initiators,
stabilizers and UV absorber. NC% wt.;
vol. <strong>inorganic</strong> <strong>filler</strong>
Dentin Methacrylate, fluoride barium glass,
amorphous silica
≈ 68% wt; 50% vol. <strong>inorganic</strong> <strong>filler</strong>
White Methacrylate, fluoride barium glass,
amorphous silica.
68% wt; 50% vol. <strong>inorganic</strong> <strong>filler</strong>
C2 Bis-GMA, barium glass 69%, silica 3%,
NC% wt.; 49% vol. <strong>inorganic</strong> <strong>filler</strong>
Universal Mixture <strong>of</strong> resins based on Bis-GMA
(methacrylates), catalysts, stabilizers,
pigments. NC% wt.; NC% vol. <strong>inorganic</strong>
<strong>filler</strong>
Base
Catalyst
Bis-EMA, Bis-GMA, TEGDMA, barium
glass silanized, amorphous silicic acid,
hydrophobed. 71% wt.; 54.5% vol.
<strong>inorganic</strong> <strong>filler</strong>

268
Table 1 (continued)
Dent Mater J 2012; 31(2): 266–272
No. Type <strong>of</strong> material Materials (Brand) Shade Composition
10 Luting cement
material
11 Luting cement
material
12 Luting cement
material
13 Luting cement
material
14 Luting cement
material
15 Luting cement
material
16 Luting cement
material
17 Luting cement
material
18 Luting cement
material
Hybrid Cem
(J Morita Europe)
Maxcem
(Kerr Corp.,
Orange, CA, USA)
Microcem duo
(Saremco Dental AG, Rebstein,
Switzerland)
Multilink Sprint
(Ivoclar Vivadent, Schaan,
Liechtenstein)
Multilink Sprint
(Ivoclar Vivadent, Schaan,
Liechtenstein)
ParaPost Cement
(Coltene Whaledent)
ParaCem Universal DC
(Coltene Whaledent)
RelyX ARC
(3M ESPE, St. Paul, MN, USA)
Super-Bond C&B
(J Morita Europe)
4-META, MMA, HEMA, acetone, water
Powder/Liquid=1/1,
NC% wt.; vol. <strong>inorganic</strong> <strong>filler</strong>
Clear GPDM, - self-etching/self-adhering
acidic monomer; comonomers including
mono-, di-, and tri-functional
methacrylate monomers, initiator,
photoinitiator, stabilizer, barium glass
<strong>filler</strong>, fluoroaluminosilicate glass <strong>filler</strong>,
fumed silica, average <strong>filler</strong> particle size
<strong>of</strong> 3.6 µm. 67% wt.; 46% vol. <strong>inorganic</strong>
<strong>filler</strong>
Barium glass, silanized with silane
A-174, Bis-GMA, Bis-EMA, TEGDMA,
higly dispersed silicium, dioxide,
silanized, catalysts, inhibitors,
pigments. NC% wt.; vol. <strong>inorganic</strong>
<strong>filler</strong>.
Opaque Dimethacrylates, acidic monomers,
barium glass, YbF3, silicon oxide.
NC % wt.; 48% vol. <strong>inorganic</strong> <strong>filler</strong>
Yellow Dimethacrylates, acidic monomers,
barium glass, YbF3, silicon oxide
NC % wt.; 48% vol. <strong>inorganic</strong> <strong>filler</strong>
Base: Methacrylates, barium glass,
silanized, amorphous silica,
Catalyst: Methacrylates, barium glass,
silanized, amorphous silica, BPO
NC% wt.; vol. <strong>inorganic</strong> <strong>filler</strong>
B3 Base: Bis-EMA, Bis-GMA, TEGDMA,
barium glass silanized, amorphous
silica, Initiators.
Catalyst: Bis-EMA, Bis-GMA,
TEGDMA, Barium glass silanized,
amorphous silica, BPO.
NC% wt.; vol. <strong>inorganic</strong> <strong>filler</strong>
A3 Bis-GMA, TEGDMA, zirconia/silica
<strong>filler</strong>, pigments, amine and
photoinitiator system (Paste A), BPO
(Paste B).
67.5% wt.; NC % vol. <strong>inorganic</strong> <strong>filler</strong>
L-Type
Radiopaque
4-META/MMA-TBB, metal oxide
Polymer/Monomer=1.2
NC% wt.; NC% vol. <strong>inorganic</strong> <strong>filler</strong>
Bis-EMA: Bisphenol A diethoxymethacrylate; Bis-GMA: Bisphenol A diglycidyl methacrylate; BPO: Benzoyl peroxide; CQ:
Camphorquinone; GPDM: Glyceroldimethacrylate dihydrogen phosphate; HEMA: 2-hydroxyethyl methacrylate; HDDMA:
1,6-hexanediol dimethacrylate; MMA: methyl methacrylate; TBB: tri-n-butylborane (initiator); TEGDMA: Triethyleneglycol
dimethacrylate; UDMA: Urethane dimethacrylate; 4-META: 4-methacryloxyethyl trimellitic anhydride; NC: Information
not collected; % wt: Percentage <strong>of</strong> <strong>filler</strong> by weight; % vol.: Percentage <strong>of</strong> <strong>filler</strong> by volume.

measured using a micrometer. Specimens with thickness
greater than 1 mm (±0.01) were sanded using 800-grit
sandpaper until their thickness was 1 mm (±0.01).
Specimens with voids were excluded from this study.
Human enamel and dentin specimens
This study was approved by the Commission on Bioethics
<strong>of</strong> the Victor Babes University <strong>of</strong> Medicine and Pharmacy,
Timisoara. Two freshly extracted human molars and
one premolar tooth —free from caries, hypoplastic
defects or cracks and extracted for orthodontic reason
from the same subject— were selected for use in this
study. The subject/patient signed an informed consent
before any clinical procedure was performed.
The extracted teeth were stored in buffered formalin
for 24 h after extraction and then in water at room
temperature (23±1°C). After embedding the teeth in a
methyl-methacrylate casting resin (Dentacryl,
Sp<strong>of</strong>aDental Western Europe, Bioggio Ticino,
Switzerland), one mesiodistal section <strong>of</strong> 1 mm (±0.01)
thickness was cut from each tooth using a rotary cutting
machine (IsoMet, Buehler, Lake Bluff, IL, USA).
Digital radiography
An aluminum step wedge consisting <strong>of</strong> 1- to 5-mm steps
was prepared to be used as a radiographic reference.
The radiopacity <strong>of</strong> 18 commercially available dental
resin cements were determined with reference to the
aluminum step wedge and human enamel and dentin
slices <strong>of</strong> equivalent thickness.
Dental resin cement specimens and human enamel
and dentin specimens were placed alongside the
aluminum step wedge on an intraoral sensor (XIOS Plus,
Sirona Dental Systems, Bensheim, Germany). Imaging
was done using an intraoral X-ray machine (MinRay,
Soredex, Tuusula, Finland) at 70 kV, 7 mA, and 0.04 s
with a target-sensor distance <strong>of</strong> 30 cm.
The mean gray values <strong>of</strong> each step <strong>of</strong> the aluminum
step wedge and the specimens were measured by
outlining a region <strong>of</strong> interest using the equal-density
area tool <strong>of</strong> a dental imaging s<strong>of</strong>tware (Image J 1.37v,
Wayne Rasband, National Institutes <strong>of</strong> Health, Bethesda,
MD, USA). With each specimen, five regions were
selected for measurement: one in the central area and
four in the different quadrants <strong>of</strong> each disk specimen.
Each region selected was devoid <strong>of</strong> any air bubbles inside
the material, and the average gray value was recorded
for every specimen. For each radiographic image, its
gray scale value was converted into equivalent aluminum
thickness using a generated calibration curve correlating
gray scale values to aluminum thickness. The radiopacity
value <strong>of</strong> each specimen was expressed in terms <strong>of</strong> the
equivalent thickness <strong>of</strong> aluminum per 1 mm unit
thickness <strong>of</strong> material.
Percentage <strong>of</strong> <strong>filler</strong> <strong>content</strong> by weight and volume
For each dental resin cement, its <strong>inorganic</strong> <strong>filler</strong> <strong>content</strong>
was measured by combustion analysis in a furnace (n=5).
Percentage <strong>of</strong> <strong>filler</strong> by weight was determined by
calculating the difference in the weight <strong>of</strong> the crucible
Dent Mater J 2012; 31(2): 266–272 269
before and after ashing in air. Percentage <strong>of</strong> <strong>filler</strong> weight
was converted to volume percentage using the following
formula:
wf/df
Filler volume fraction = ×100%
wf/df + wr/dr
where wf and wr are the weight fractions <strong>of</strong> <strong>filler</strong> and
resin respectively, and df and dr are the densities <strong>of</strong> <strong>filler</strong>
and resin at 2.4 g/cm 3 and 1.2 g/cm 3 respectively.
Statistical analysis
Data were statistically analyzed using one-way analysis
<strong>of</strong> variance ANOVA (SPSS version 11.5, SPSS Inc., USA)
and Tukey’s test with level <strong>of</strong> significance set at 0.05 to
determine the presence <strong>of</strong> statistically significant
differences between the mean values <strong>of</strong> the tested
materials.
RESULTS
Radiopacity <strong>of</strong> dental resin cements in comparison to
enamel and dentin
The mean radiopacity values and standard deviations <strong>of</strong>
the investigated materials are shown in Fig. 1. Among
the tested dental resin cements, there were no
statistically significant differences (p>0.05) according to
one-way ANOVA. However, the radiopacity values <strong>of</strong>
some tested materials were statistically different from
those <strong>of</strong> enamel or dentin.
Multilink Sprint <strong>of</strong> Opaque and Yellow shades
(Ivoclar Vivadent, Schaan, Liechtenstein) had the
highest radiopacity values <strong>of</strong> 3.40 mm Al and 3.36 mm Al
respectively, which were statistically different from that
<strong>of</strong> enamel (p

270
Percentage <strong>of</strong> <strong>filler</strong> <strong>content</strong> by weight and volume
Combustion analysis revealed that the <strong>filler</strong> <strong>content</strong> <strong>of</strong>
the tested dental resin cements ranged between 29.56
wt% (17.36 vol%) for Super-Bond C&B (J Morita Europe)
and 69.75 wt% (53.56 vol%) for Multilink Sprint <strong>of</strong>
Yellow shade (Ivoclar Vivadent) (Table 2).
DISCUSSION
The radiopacity <strong>of</strong> a material increases with a higher
<strong>filler</strong> percentage and a higher amount <strong>of</strong> high atomic
number elements in <strong>filler</strong> particles 10,17) . This explained
why the chemical compositions <strong>of</strong> some dental composites
available on the market included high atomic number
<strong>filler</strong> elements such as barium, strontium, zirconium,
zinc, ytterbium, titanium, tantalum, lanthanum, or
indium (Table 1) 17-21) . When <strong>filler</strong> volume is increased to
70% or beyond and the amount <strong>of</strong> radiopaque oxide in
<strong>filler</strong> particles is above 20%, the radiopacity <strong>of</strong> a dental
composite would exceed that <strong>of</strong> human enamel 17) .
In the present study, all the dental resin cements
tested met the ISO 4049 standard 19) in that their
radiopacity values exceeded 1 mm Al and were higher
than that <strong>of</strong> human dentin. For different shades <strong>of</strong> the
same material, namely Multilink Sprint (Opaque,
Yellow) and ParaPost ParaCore Automix (White,
Dentin), there were no statistically significant differences
in radiopacity and percentage <strong>of</strong> <strong>filler</strong> among the two
Dent Mater J 2012; 31(2): 266–272
Fig. 1 Mean (SD) radiopacity values <strong>of</strong> 18 commercially available composite resin cements, in comparison to dentin and
enamel. (Horizontal bars indicate mean values are not statistically significant different from each other when
analyzed using the Tukey’s test, p>0.05.)
shades <strong>of</strong> the same material.
For Multilink Sprint Opaque and Multilink Sprint
Yellow, not only did they have the highest <strong>filler</strong> <strong>content</strong>s
as revealed by combustion analysis, they had radiopaque
<strong>filler</strong>s such as barium glass and YbF3 in their <strong>filler</strong>
compositions. These dual <strong>filler</strong>-related factors caused
them to have the highest radiopacity among the tested
materials and which was significantly higher than that
<strong>of</strong> enamel. Ranking just below Multilink Sprint Opaque
and Multilink Sprint Yellow in terms <strong>of</strong> <strong>filler</strong> <strong>content</strong>
were ParaPost ParaCore Automix White and ParaPost
ParaCore Automix Dentin. Apart from their high <strong>filler</strong>
percentages, they also had barium glass in their <strong>filler</strong>
compositions, thereby rendering them with radiopacity
values significantly higher than that <strong>of</strong> enamel.
Maxcem, ParaCem Universal DC, Duo Cement Plus,
Build-It FR, Rock Core, Mirafit Core, and Microcem duo
also contained barium in their <strong>filler</strong> compositions. It was
highly probable that their radiopacity values were
influenced by the amount <strong>of</strong> barium in their <strong>filler</strong>
particles. Microcem duo had a low radiopacity value
which was not significantly different from that <strong>of</strong> dentin
(p>0.05), and this could be due to a low barium <strong>content</strong>
in its <strong>filler</strong> particles.
Super-Bond C&B had the lowest <strong>filler</strong> percentage,
but a radiopacity <strong>of</strong> 2.56 mm Al which was significantly
higher than that <strong>of</strong> dentin. This radiopacity value could
be caused by the presence <strong>of</strong> high atomic number

elements in the <strong>filler</strong> particles. RelyX ARC had zirconium
oxide/zirconia in its <strong>filler</strong> composition, a radiopaque
oxide which was composed <strong>of</strong> a high atomic number
element. For this reason, its radiopacity was statistically
higher than that <strong>of</strong> dentin.
There were small differences between the <strong>filler</strong>
Dent Mater J 2012; 31(2): 266–272 271
Table 2 Percentages <strong>of</strong> the <strong>inorganic</strong> <strong>filler</strong> <strong>content</strong> <strong>of</strong> dental resin cements, as revealed by combustion analysis
No Product_Shade (Brand)
Mean (SD)wt%
by combustion
Mean (SD) vol%
by combustion
1 Multilink Sprint_Yellow (Ivoclar Vivadent) 69.75 (0.17) 53.56 (0.20)
2 Multilink Sprint_Opaque (Ivoclar Vivadent) 69.37 (0.42) 53.11 (0.49)
3 ParaPost ParaCore Automix_White (Coltene Whaledent) 67.27 (0.16) 50.69 (0.18)
4 ParaPost ParaCore Automix_Dentin (Coltene Whaledent) 67.19 (0.26) 50.59 (0.29)
5 Build-it_Gold (Pentron) 67.04 (1.51) 50.44 (1.73)
6 Maxcem Clear_Clear (Kerr) 66.75 (0.42) 50.09 (0.48)
7 Duo Cement Plus (Coltene Whaledent) 66.25 (0.12) 49.53 (0.14)
8 RelyX ARC_A3 (3M ESPE) 65.88 (0.96) 49.12 (1.08)
9 Core Paste XP Enamel w/Fluoride (DenMat) 65.71 (0.29) 48.93 (0.32)
10 Mirafit Core_A3 (Hager & Werken) 64.43 (0.24) 47.53 (0.26)
11 ParaCem Universal DC (Coltene Whaledent) 64.13 (0.28) 47.19 (0.30)
12 CromaCore (J Morita Europe) 60.11 (0.32) 42.97 (0.33)
13 Rock Core_C2 (Danville Materials Inc.) 59.98 (0.33) 42.84 (0.34)
14 Sealacore Core Composite_Universal (PDSA Produits
Dentaires)
59.56 (0.11) 42.41 (0.11)
15 ParaPost Cement (Coltene Whaledent) 58.86 (1.42) 41.72 (1.44)
16 Microcem duo (Saremco Dental AG) 43.34 (2.46) 27.69 (2.04)
17 HybridCem (J Morita Europe) 32.38 (0.91) 19.32 (0.64)
18 Super-Bond C&B (J Morita Europe) 29.56 (1.69) 17.36 (1.18)
SD: Standard deviation;
Vertical bars indicate that mean values are not statistically significant different from each other when compared using
Tukey’s test.
fraction values provided by the manufacturers and those
obtained by combustion analysis in this study. A
reasonable explanation was that the manufacturers
used their own original methods to calculate the <strong>filler</strong>
fractions, or that they had included the percentage <strong>of</strong>
silane coating in their calculations.

272
In the case <strong>of</strong> endodontically treated teeth restored
with carbon fiber or glass fiber posts which are <strong>of</strong> low
radiopacity 8) , dental cements <strong>of</strong> higher radiopacity are
the better and preferred choice. For commercially
available dental cements <strong>of</strong> low radiopacity 6,18,22) , they
will show up as a separate layer 7) especially if the
radiopacity is lower than that <strong>of</strong> dentin and the
restorative material.
CONCLUSIONS
Within the limitations <strong>of</strong> the present study, the following
conclusions were arrived at:
1. Some commercially available dental resin cements
showed a direct correlation between <strong>filler</strong> <strong>content</strong>
and radiopacity. Between the different shades <strong>of</strong>
the same material, there were no statistically
significant differences in <strong>filler</strong> <strong>content</strong> and
radiopacity.
2. Use <strong>of</strong> low-radiopacity materials should be avoided
because it may lead to incorrect diagnosis.
3. Dental resin cements are recommended to have
higher radiopacity than dentin, and ideally similar
to or even slightly higher radiopacity than enamel
to improve their clinical detection.
4. Digital image analysis might be a suitable
alternative to transmission densitometry for the
evaluation <strong>of</strong> the radiopacity <strong>of</strong> dental resin
cements.
ACKNOWLEDGMENTS
The authors are grateful to Coltene Whaledent, DenMat,
Hager & Werken, Ivoclar Vivadent, J Morita Europe,
Saremco Dental AG, PDSA Produits Dentaires, and 3M
ESPE for their generous donations <strong>of</strong> the dental
composite materials.
The authors would like to thank the Romanian
Ministry <strong>of</strong> Education, Research and Youth for their
support with the grant, IDEI 1047. One <strong>of</strong> the authors
(G.F.) wishes to thank the Babes-Bolyai University <strong>of</strong>
Cluj-Napoca that this work was made possible with
financial support provided through the Sectoral
Operational Program for Human Resources Development
2007–2013, co-financed by the European Social Fund,
under the project number POSDRU 89/1.5/S/60189 with
the title “Postdoctoral Programs for Sustainable
Development in a Knowledge Based Society”.
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