This study evaluated the mechanical properties of various dental cement and core materials over time. Compressive strength increased for all materials from 15 minutes to 1 hour to 24 hours after mixing. Ketac Silver showed the highest compressive strength at all time periods. Diametral tensile strength also increased over time for most materials. At 24 hours, Chelon Silver, Ketac Silver, and Miracle Mix showed the highest values. For flexural strength, Ketac Silver produced the highest values at 24 hours, increasing more than any other material from 1 hour. In conclusion, setting time influences mechanical properties, and Ketac Silver demonstrated the strongest performance overall.

1. Laboratory Strength of Glass Ionomer
and Zinc Phosphate Cements
Andree Piwowarczyk, Dr med dent,1
Peter Ottl, Dr med dent,1
and
Hans-Christoph Lauer, Dr med dent2
Purpose: The present in vitro study examined 3 mechanical properties, namely compressive,
flexural, and diametral tensile strength, of various commercially available cements and core
materials as a function of time after mixing.
Materials and Methods: The examined materials were 2 cermet cements (Ketac Silver [ESPE,
Seefeld, Germany] and Chelon Silver [ESPE]), 1 metal-reinforced glass ionomer cement (Miracle
Mix [GC Dental Industrial Corp, Tokyo, Japan]), 2 conventional glass ionomer cements (Ketac Bond
[ESPE] and Ketac Cem [ESPE]), 1 standard cure zinc phosphate cement (Harvard Cement [Richter
and Hoffmann, Berlin, Germany]), and 1 zinc phosphate cement with the addition of 30% silver
amalgam alloy powder (Harvard Cement 70% with Dispersalloy 30% [Richter and Hoffmann/
Johnson and Johnson, East Windsor, NJ]). Properties were measured using a universal testing
machine at 15 minutes, 1 hour, and 24 hours after first mixing.
Results: Compressive strengths varied widely between the 3 times of measurement from 5.8 ؎
6.6 MPa for Ketac Cem to 144.3 ؎ 10.2 MPa for Ketac Silver. Twenty-four hours after mixing, the
Bonferroni test showed significant (p < .01) differences between Ketac Silver and all other
materials tested. Diametral tensile strengths ranged widely from 4.4 ؎ 0.9 MPa for Ketac Cem to
11.5 ؎ 2.2 MPa for Chelon Silver. At 15 minutes, 1 hour, and 24 hours after first mixing, the analysis
of variance did not show any significant differences between Ketac Silver, Chelon Silver, and
Miracle Mix. The 3-point flexural strength of Ketac Silver showed, at 15 minutes with 13.5 ؎ 3.9
MPa and at 24 hours with 27.2 ؎ 7.4 MPa, the highest values.
Conclusions: Setting time influences the mechanical properties of the materials tested in this
study. Ketac Silver, a glass ionomer cement reinforced with sintered glass-silver particles, showed
the highest mechanical properties of the examined materials.
J Prosthodont 2001;10:140-147. Copyright © 2001 by The American College of Prosthodontists.
INDEX WORDS: core restoration, mechanical properties, compressive strength, flexural
strength, diametral tensile strength
FIXED PROSTHODONTIC restorations often
require the placement of foundation restora-
tions to establish retentive and resistance forms to
the teeth used as prosthesis retainers. These resto-
rations will ideally possess sufficient mechanical
strength, retention to the hard dental tissues, and a
high degree of biocompatibility.1
Glass ionomer cements2,3 have been used as core
build-up materials. They provide mechanical and
chemical adhesion to the hard dental tissues that is
on the order of one fifth to one third of that ob-
tained with composite resins using the acid-etch
technique.2 The reported results differ on the basis
of brand of material4 and conditioning techniques.5
Metal-reinforced glass ionomer cements, known as
cermet cements, are a mixture of glass and metal
powder6 sintered to high density. This material sets
to form a cement via an acid-base reaction.7 By
sintering metal particles into the glass phase, it is
possible to improve the material’s abrasion,8,9 and
to yield a modest increase in diametral tensile
strength.10
The objective of this study was to determine and
compare the mechanical properties of various ce-
ments used as core build-up materials relative to
time after first mixing. The parameters examined
were compressive strength, flexural strength, and
diametral tensile strength at times of 15 minutes, 1
hour, and 24 hours.
From Department of Prosthetic Dentistry, School of Dentistry, Johann
Wolfgang Goethe University, Frankfurt, Germany.
1
Assistant Professor.
2
Professor and Director.
Accepted June 25, 2001.
Correspondence to: Dr. A. Piwowarczyk, Department of Pros-
thetic Dentistry, School of Dentistry, Johann Wolfgang Goethe Uni-
versity, Theodor-Stern-Kai 7, D-60590 Frankfurt, Germany. E-mail:
piwowarczyk@t-online.de
Copyright © 2001 by The American College of Prosthodontists
1059-941X/01/1003-0003$35.00/0
doi:10.1053/jpro.2001.27338
140 Journal of Prosthodontics, Vol 10, No 3 (September), 2001: pp 140-147

2. Materials and Methods
This study evaluated 2 cermet cements (Ketac Silver
[ESPE, Seefeld, Germany] and Chelon Silver [ESPE]), 1
metal-reinforced glass ionomer cement (Miracle Mix
[GC Dental Industrial Corp, Tokyo, Japan]), 2 conven-
tional glass ionomer cements (Ketac Bond [ESPE] and
Ketac Cem [ESPE]), 1 standard cure zinc phosphate
cement (Harvard Cement [Richter and Hoffmann, Ber-
lin, Germany]), and 1 zinc phosphate cement with the
addition of 30% silver amalgam alloy powder (Harvard
Cement 70% with Dispersalloy 30% [Richter and Hoff-
mann/Johnson and Johnson, East Windsor, NJ]) under
compressive, tensile, and flexural forces (Table 1).
Powder was weighed using an analytical balance (Ϯ1
mg) following the manufacturer’s recommendation,
while the liquid volume suggested by the manufacturer
was established using a measuring pipette with an accu-
racy of Ϯ0.03 mL. One material, Ketac Silver, was sup-
plied in premeasured capsules. For this material, the
manufacturer’s recommendation of a trituration time of
10 seconds was used for the Capmix (ESPE) amalgam-
ator. To measure the compressive and tensile strengths,
specimens were prepared in cylindrical Teflon molds
(Figs 1 and 2) to the dimensions of 6 and 8 mm diameter
and 12 and 4 mm height, respectively, as dictated by the
British Standards Institute Specification 6039.11 The
specification BS 6039 refers to the manufacturer’s rec-
ommendations concerning the mixing process along with
the need to fill the molds within 2 minutes of the initia-
tion of mixing.
Specimens used to determine flexural strength were
produced in brass molds 25 ϫ 2 ϫ 2 mm in size that had
been insulated with polytetrafluoroethylene spray (DIN
13922/EN 24049).12 The molds were placed in an incu-
bator (Heraeus Kulzer, Hanau, Germany) at 37.0 Ϯ
1.0°C and at 95% to 100% relative humidity 3 minutes
after mixing. Specimens were removed from the mold
within 60 minutes of testing. Specimens for the 24-hour
measurements were stored in the incubator submerged
in distilled water until examined. The dimensions of the
specimens were checked with a micrometer (Mauser,
Figure 1. Precision mold and specimen for determining
the compressive strength (6 ϫ 12 mm).
Table 1. Core Materials and Manufacturers
Material Classification Manufacturer
Mixing
Process
Powder/Liquid
Ratio
Ketac Silver Cermet cement Espe, Seefeld, Germany Mechanical
Chelon Silver Cermet cement Espe, Seefeld, Germany Manual 3.8:1
Miracle Mix Metal-reinforced glass
ionomer cement
GC Dental Industrial
Corporation, Tokyo, Japan
Manual 5.0:1
Ketac Bond Conventional glass
ionomer cement
Espe, Seefeld, Germany Manual 3.4:1
Ketac Cem Conventional glass
ionomer cement
Espe, Seefeld, Germany Manual 3.4:1
Harvard Cement Zinc phosphate cement Richter & Hoffmann, Berlin,
Germany
Manual 2.5:1
Harvard Cement 70%/
Dispersalloy 30%
Zinc phosphate cement
with admixture
amalgam alloy
powder
Richter & Hoffmann, Berlin,
Germany/Johnson &
Johnson, East Windsor, NJ
Manual 2.5:1
Figure 2. Precision mold and specimen for determining
the diametral tensile strength (4 ϫ 8 mm).
141September 2001, Volume 10, Number 3

3. Nu¨rnberg, Germany; precision: 0.01 mm). Testing was
performed at 23.0 Ϯ 1.0°C and 50% Ϯ 5% relative hu-
midity. A Zwick 1435 Universal testing machine (Zwick,
Ulm, Germany) was used at a crosshead speed of 1
mm/min to test compressive and diametral tensile
strengths (Fig 3). Specimens were loaded until fracture
at a constant crosshead speed of 1 mm/min (BS 6039).11
Measurements for the 3-point flexural strength test (Fig
4) were performed at a constant crosshead speed of 1
mm/min (DIN 13922/EN 24049). Flexural, compressive,
and diametral tensile strengths were assessed at 15 min-
utes, 1 hour, and 24 hours after first mixing. Ten mea-
surements each were made for each material and for
each of the 3 parameters examined.
Statistical data analysis was performed by one-way
analysis of variance with regard to the time factor and by
2-sided t tests with regard to the compressive, flexural,
and diametral tensile strength variables. The level of
significance was fixed at p Յ .05 for significant differ-
ences. The Bonferroni test was used for post-hoc analysis
of variance comparing multiple means.
Results
Compressive Strength
At the earliest testing period of 15 minutes after
mixing, mean compressive strength values ranged
from 35.8 Ϯ 6.6 MPa for Ketac Cem to 74.9 Ϯ 7.2
MPa for Harvard zinc phosphate cement with ad-
mixture of silver amalgam alloy powder (Fig 5).
Compressive tests at 1 hour showed increased com-
pressive strength for all materials. Metal-reinforced
glass ionomer cements Ketac Silver and Chelon
Silver increased by 40.1% and 47.8%, respectively.
The lowest value was found for the glass ionomer
cement Ketac Cem with 64.2 Ϯ 7.3 MPa after 1
hour. At 24 hours, the compressive strength values
showed further increases to 144.3 Ϯ 10.2 MPa by
Ketac Silver, followed by Chelon Silver and Miracle
Mix with values of 119.2 Ϯ 17.8 MPa and 111.4 Ϯ
13.2 MPa, Harvard cement with 95.7 Ϯ 19.1 MPa,
and the admixture of Harvard cement with amal-
gam alloy powder with 91.5 Ϯ 15.0 MPa. The
Bonferonni test identified statistically significant
differences among groups concerning the times
of measurement (Table 2).
Diametral Tensile Strength
Diametral tensile strength means and standard
deviations are displayed in Fig 6. At 15 minutes, the
highest value of 7.8 Ϯ 1.0 MPa was obtained with
the combination of Harvard cement and amalgam
alloy powder; conventional glass ionomer cements
(Ketac Bond, Ketac Cem) were measured at 5.3 Ϯ
0.7 MPa and 4.4 Ϯ 0.9 MPa. At 1 hour, results for
the tested materials ranged from 6.3 Ϯ 1.0 MPa
(Ketac Cem) to 8.5 Ϯ 1.9 MPa (Miracle Mix). At 24
hours, Chelon Silver at 11.5 Ϯ 2.2 MPa, Ketac
Silver at 11.2 Ϯ 1.6 MPa, and Miracle Mix at 10.7 Ϯ
1.5 MPa showed the highest values. Between 1 and
24 hours after first mixing, Chelon Silver, Ketac
Silver, Miracle Mix, and Ketac Cem showed a sig-
nificant (p Յ .01) increase in diametral tensile
strength. In addition to the 3 times of measure-
Figure 3. Testing procedure for determining the diame-
tral tensile strength.
Figure 4. Testing procedure for determining the flex-
ural strength.
142 Laboratory Strength of Cements ● Piwowarczyk, Ottl, and Lauer

4. ment, the analysis of variance again identified sig-
nificant differences among the materials (Table 3).
Three-point Flexural Strength
Figure 7 illustrates the 3-point flexural strength
means and standard deviations. At 15 minutes after
first mixing, Harvard cement with amalgam alloy
powder at 16.2 Ϯ 1.4 MPa, Harvard cement at
14.5 Ϯ 1.7 MPa, and Ketac Silver at 13.5 Ϯ 3.9 MPa
yielded the highest values. At 15 minutes, Ketac
Cem showed the value of 4.7 Ϯ 1.7 MPa. During
the first hour, the flexural strength value for Mir-
acle Mix increased by 87.3% to 17.7 Ϯ 4.3 MPa. The
corresponding values for Chelon Silver and Ketac
Silver were 15.9 Ϯ 5.0 MPa and 15.0 Ϯ 4.6 MPa.
Twenty-four hours after first mixing, Ketac Silver,
at 27.2 Ϯ 7.4 MPa, yielded the highest values of all
the cements examined, while also showing the
greatest increase in strength (81.0%) over the
1-hour value. The other materials showed results
ranging from 9.6 Ϯ 4.6 MPa for Ketac Bond to
24.8 Ϯ 8.0 MPa for Chelon Silver (Fig 7). The
analysis of variance showed that Ketac Silver and
Chelon Silver differed significantly from Miracle
Mix (p Յ .01), Ketac Cem (p Յ .01), Ketac Bond
(p Յ .01), Harvard cement (p Յ .01), and Harvard
cement with amalgam alloy powder (p Յ .05). As a
result of the Bonferonni test at p Յ .05, the vertical
lines in Table 4 bracket statistically equivalent
groups.
Discussion
In designing this study, the decision was made to
make evaluations on standardized molds. This al-
lowed the testing to conform to the British Stan-
Figure 5. Compressive
strength (BS 6039) of various
core restoration materials
(0.25, 1, and 24 hours after
first mixing; n ϭ 10 measure-
ments each per material and
time). KS, Ketac Silver; CS,
Chelon Silver; MM, Miracle
Mix; KB, Ketac Bond; KC,
Ketac Cem; HZ, Harvard ce-
ment; HA, Harvard cement
with amalgam alloy powder.
Table 2. Compressive Strength (BS 6039) of Various Core Restoration Materials (0.25, 1, and 24 Hours After First
Mixing; n ϭ 10 Measurements Each per Material and Time)
Material
0.25 h 1 h 24 h
x (MPa) x (MPa) x (MPa)
Ketac Silver 66.0 Ϯ 3.5 92.5 Ϯ 9.5 144.3 Ϯ 10.2
Chelon Silver 55.1 Ϯ 2.6 81.5 Ϯ 5.9 119.2 Ϯ 17.8
Miracle Mix 40.7 Ϯ 4.1 77.6 Ϯ 6.1 111.4 Ϯ 13.2
Ketac Bond 37.7 Ϯ 4.0 66.2 Ϯ 6.7 84.1 Ϯ 18.3
Ketac Cem 35.8 Ϯ 6.6 64.2 Ϯ 7.3 80.1 Ϯ 201
Harvard cement 72.9 Ϯ 5.9 84.0 Ϯ 13.3 95.7 Ϯ 19.1
Harvard cement 70%/
amalgam alloy powder
(Dispersalloy) 30% 74.9 Ϯ 7.2 86.9 Ϯ 11.4 91.5 Ϯ 15.0
Note. The vertical bars in respective lines to the right of the points of measurement indicate groups that do not significantly differ as
measured by the Bonferroni test (p Յ .05).
Abbreviations: x, arithmetic mean; s, standard deviation.
143September 2001, Volume 10, Number 3

5. dards Institute Specification 6039.11 The alternative
use of extracted teeth brought with it the variability
associated with differences in dimensions, degree of
calcification, water content, and the potential for
pre-existing hard tissue defects.13-15 Although the
latter approach may allow simpler interpretation of
clinical expectations, it eliminates standardization
and complicates meaningful comparisons.
Considerable differences in compressive, flex-
ural, and diametral tensile strength were seen
among the tested materials. All 3 of the recognized
tests showed a similar ranking order for the mate-
rials (Figs 5, 6, and 7). Under the conditions of this
study, Ketac Silver presented the highest values of
compressive and flexural strengths at 24 hours of
all the cements examined. This material showed
statistically significant differences (p Յ .05) in test-
ing compressive strength at all times of measure-
ment.
Between 1 and 24 hours, Ketac Silver showed a
significant (p Յ .01) increase in strength within all
the 3 testing parameters. Previous reports showed
that the setting reaction of glass ionomer cements
is complex, requiring 24 hours for maturation.7,16,17
This is in contrast to the zinc phosphate materials,
Harvard cement, and Harvard cement with added
amalgam alloy, which showed less increase in
strength over time.
The data in this report failed to show a consis-
tent relationship between the method of mixing
(manual or mechanical) and strength properties.
Strict adherence to the prescribed mixing ratio is
Figure 6. Diametral tensile
strength (BS 6039) of various
core restoration materials
(0.25, 1, and 24 hours after
first mixing; n ϭ 10 measure-
ments each per material and
time). KS, Ketac Silver; CS,
Chelon Silver; MM, Miracle
Mix; KB, Ketac Bond; KC,
Ketac Cem; HZ, Harvard ce-
ment; HA, Harvard cement
with amalgam alloy powder.
Table 3. Diametral Tensile Strength (BS 6039) of Various Core Restoration Materials (0.25, 1, and 24 Hours After
First Mixing; n ϭ 10 Measurements Each per Material and Time)
Material
0.25 h 1 h 24 h
x (MPa) s (MPa) x (MPa) s (MPa) x (MPa) s (MPa)
Ketac Silver 6.5 1.5 8.1 1.5 11.2 1.6
Chelon Silver 7.2 1.6 8.2 1.4 11.5 2.2
Miracle Mix 7.2 1.0 8.5 1.9 10.7 1.5
Ketac Bond 5.3 0.7 6.9 1.2 7.4 1.2
Ketac Cem 4.4 0.9 6.3 1.0 7.5 1.3
Harvard cement 6.9 0.9 7.4 1.1 7.9 1.7
Harvard cement 70%/
amalgam alloy powder
(Dispersalloy) 30% 7.8 1.0 8.3 1.1 9.2 1.8
Note. The vertical bars in respective lines to the right of the points of measurement indicate groups that do not significantly differ as
measured by the Bonferroni test (p Յ .05).
Abbreviations: x, arithmetic mean; s, standard deviation.
144 Laboratory Strength of Cements ● Piwowarczyk, Ottl, and Lauer

6. said to be especially important for the successful
use of glass ionomer cements. Negative influences
on strength, solubility, and surface structure as a
result of having too little powder have been cited in
the literature. Conversely, with too high of a pow-
der-to-liquid ratio, a reduction in setting time and
bond strength has been described.18,19 The manu-
ally mixed product Chelon Silver, chemically iden-
tical to Ketac Silver, has a lower compressive
strength at 15 minutes (p Յ .01), 1 hour (p Յ .05),
and 24 hours (p Յ .01), but Chelon Silver and
Ketac Silver showed no significant differences in
flexural and diametral tensile strengths over these
time periods (p Յ .05).
The present study showed significantly (p Յ .05)
lower values for the glass ionomer cements Ketac
Cem and Ketac Bond concerning compressive, flex-
ural, and diametral tensile strengths at all times of
measurement, compared with the cermet cements,
Ketac Silver and Chelon Silver. The data reported
by Chung10 showed higher diametral tensile
strength values for metal-reinforced materials,
Ketac Silver and Miracle Mix, compared with the
glass ionomer cement, Fuji II (GC Dental Indus-
trial Corp). Cermet cements were intended to pos-
sess higher flexural strength than glass ionomer
cements.20 Walls and coworkers21 showed an in-
crease in compressive strength and compressive
fatigue limit for cermet-type materials compared
with the strength of a conventional glass ionomer
cement from the same manufacturer. In contrast to
the above-mentioned studies, Cho et al22 docu-
mented that silver-reinforced glass ionomer cement
Ketac Silver did not improve the compressive and
diametral tensile strength in comparison with the
conventional glass ionomer cement, Ketac Fil
Figure 7. Three-point flex-
ural strength (DIN 13922/EN
24049) of various core resto-
ration materials (0.25, 1, and
24 hours after first mixing;
n ϭ 10 measurements each
per material and time). KS,
Ketac Silver; CS, Chelon Sil-
ver; MM, Miracle Mix; KB,
Ketac Bond; KC, Ketac
Cem; HZ, Harvard cement;
HA, Harvard cement with
amalgam alloy powder.
Table 4. Three-point Flexural Strength (DIN 13922/EN 24049) of Various Core Restoration Materials (0.25, 1, and
24 Hours After First Mixing; n ϭ 10 Measurements Each per Material and Time)
Material
0.25 h 1 h 24 h
x (MPa) s (MPa) x (MPa) s (MPa) x (MPa) s (MPa)
Ketac Silver 13.5 3.9 15.0 4.6 27.2 7.4
Chelon Silver 11.8 4.1 15.9 5.0 24.8 8.0
Miracle Mix 9.5 1.1 17.7 4.3 18.5 1.9
Ketac Bond 8.4 3.2 7.3 4.4 9.6 4.6
Ketac Cem 4.7 1.7 8.2 3.4 11.6 5.6
Harvard cement 14.5 1.7 17.7 2.9 20.3 1.6
Harvard cement 70%/
amalgam alloy powder
(Dispersalloy) 30% 16.2 1.4 18.8 1.3 22.0 1.6
Note. The vertical bars in respective lines to the right of the points of measurement indicate groups that do not significantly differ as
measured by the Bonferroni test (p Յ .05).
Abbreviations: x, arithmetic mean; s, standard deviation.
145September 2001, Volume 10, Number 3

7. (ESPE). The work of Williams et al23 did not show
any significant reduction in compressive and diame-
tral tensile strengths for the glass ionomer ce-
ments, Chelon Fil (ESPE) and Fuji II (GC Dental
Industrial Corp), compared with reinforced mate-
rials, Chelon Silver and Miracle Mix. Peutzfeldt24
reported a similar flexural strength of Ketac Silver
and Miracle Mix to 5 conventional glass ionomer
cements.
In the present study, Miracle Mix, a metal-
reinforced, nonsintered glass ionomer cement,
showed a marked increase in compressive, tensile,
and flexural strengths during the first hour after
first mixing. At 24 hours, Miracle Mix was inferior
to the cermet cements Ketac Silver (p Յ .01) and
Chelon Silver (p Յ .05) in flexural strength. After 7
days, Peutzfeldt24 found, in the 3-point flexural
strength tests with specimens of 10 ϫ 2 ϫ 2 mm, a
flexural strength of 13 Ϯ 2 MPa for Miracle Mix
and 29 Ϯ 13 MPa for Ketac Silver. Nakajima et al25
showed no significant differences in 3-point flexural
strength tests on Miracle Mix glass ionomer ce-
ments (23.0 Ϯ 3.1 MPa) and Ketac Silver (22.6 Ϯ
10.4 MPa) when tested at 24 hours after storage
in 100% humidity at 37°C. When measuring com-
pressive strengths (American Dental Association
[ADA] specification #66), values of 132.1 Ϯ 13.7
MPa and 121.9 Ϯ 12.7 MPa for Miracle Mix and
Ketac Silver, respectively, were shown.
Cohen et al26 examined the diametral tensile
strength and compressive strength (ADA specifica-
tion #27) of titanium-reinforced composite resins,
Ti-Core (Essential Dental Systems, Hackensack,
NJ) and Flexi-Flow Cem (Essential Dental Sys-
tems), compared with commercially available core
build-up materials and cements. All specimens had
been stored at 100% humidity for 24 hours. The
glass ionomer cements Ketac Silver, Miracle Mix,
and Ketac Cem yielded 60.1% to 80.8% lower values
than titanium-reinforced composite resins. Of the
3 glass ionomer cements tested, Ketac Silver
achieved the highest values with regard to diame-
tral tensile strength and compressive strength at
12.5 Ϯ 2.2 MPa and 115.1 Ϯ 16.0 MPa, respectively.
The present study showed that after 24 hours,
zinc phosphate cement, with and without the ad-
mixture of silver amalgam alloy powder, is stronger
than conventional glass ionomer cements and
weaker than cermet cements under compressive,
tensile, and flexural forces. The cement strength is
almost linearly dependent on the powder:liquid ra-
tio.27 For zinc phosphate cement, Abraham28 deter-
mined an increasing compressive strength and de-
clining solubility by increasing the powder-to-liquid
ratio. On a graphic curve, this results in a rise to a
maximum value and subsequently a decline in re-
lation to the compressive strength. Smith29 con-
cluded that the compressive and tensile strengths
of properly mixed zinc phosphate cement are ade-
quate to resist masticatory stress.
The reported results concerning the mechanical
properties of cements are broad and variable. In
particular, measurements of strength are depen-
dent on the method of specimen preparation, the
operator, and labor variability.30 In addition to me-
chanical properties, other factors such as pulp com-
patibility,31-33 allergic potential,34-36 and expansion
caused by water absorption37-39 should be consid-
ered when choosing a material for a foundation
restoration. To confirm the results of laboratory
studies, longitudinal clinical trials should be con-
ducted to establish the most important predictors
of clinical success for core materials.
Conclusions
1. Compressive strength, flexural strength, and
diametral tensile strength varied among the
tested materials.
2. Under the conditions of this study, 24 hours after
first mixing, cermet cements were stronger than
metal-reinforced glass ionomer cement, conven-
tional glass ionomer cements, and zinc phos-
phate cement without and with the addition of
silver amalgam alloy powder.
3. The compressive strength of Chelon Silver was
significantly lower than the chemically identical
capsule product Ketac Silver at the 3 times of
measurement.
Acknowledgment
The authors would like to thank the Institute for Medical
Information Processing, Biometry, and Epidemiology (di-
rector: Professor K. U¨berla) of the University of Munich
for its support in performing the statistical analysis of the
data.
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147September 2001, Volume 10, Number 3