Basic Research—Technology
The Properties of a New Endodontic Material
Saeed Asgary, DDS, MS,* Sima Shahabi, DDS, PhD,† Tahereh Jafarzadeh, DDS, PhD,‡
Sara Amini, DDS, MS,§ and Sanam Kheirieh, DDS,储
Abstract
The purpose of this study was to analyze the physical
properties and chemical compositions of a new experimental cement (NEC) and compare them with mineral
trioxide aggregate (MTA); pH, working time, setting
time, dimensional changes following setting, flow, film
thickness, and chemical composition of NEC and MTA
were assessed. For chemical compositions, all specimens were imaged and analyzed by scanning electron
microscopy and electron probe microanalysis (EPMA).
The physical properties were performed according to
ISO 6876:2001. Working time, pH, and dimensional
changes of NEC and MTA showed similar results.
Shorter setting time was obtained with the NEC compared with MTA (p ⬍ 0.05). The NEC showed more
flow than MTA. In addition, the film thickness of the
NEC was considerably less than the MTA (p ⬍ 0.01 and
p ⬍ 0.001, respectively). EPMA investigations indicated
that lime (CaO) was the dominant compound in NEC
and MTA; however, other compounds were significantly
different. It was concluded that the chemical composition of NEC is different compare with MTA; it can be
concluded that the NEC exhibits acceptable physical
properties. (J Endod 2008;34:990 –993)
Key Words
Composition, electron probe microanalysis, mineral trioxide aggregate, new material, physical properties,
root-end fillings
From the *Department of Endodontics, Iranian Center for
Endodontic Research, Dental Research Center, Dental School,
Shahid Beheshti University MC, Tehran, Iran; †Department of
Dental Materials, Laser Research Center, Research Center for
Science and Technology in Medicine, Medical Sciences/Tehran
University, Tehran, Iran; ‡Department of Dental Materials,
Research Center for Science and Technology in Medicine,
Medical Sciences/Tehran University, Tehran, Iran; §Dental Research Center, Shahid Beheshti University MC, Tehran, Iran;
and 储Iranian Center for Endodontic Research, Shahid Beheshti
University MC, Tehran, Iran.
Address requests for reprints to Dr Saeed Asgary, Department of Endodontics, Iranian Center for Endodontic Research,
Shahid Beheshti Dental School, Evin, Tehran, Iran. E-mail
address: saasgary@yahoo.com.
0099-2399/$0 - see front matter
Copyright © 2008 American Association of Endodontists.
doi:10.1016/j.joen.2008.05.006
990
Asgary et al.
R
oot-end fillings are able to seal the content of a root canal system. This sealing
prevents egress of microorganisms or byproducts into periradicular tissues (1). An
ideal root-end filling material should be biocompatible, antibacterial, nontoxic, and
radiopaque, and it should not be resorbable or soluble in an oral environment. Besides
these characteristics, it is also expected to be cost-effective, easy to handle, and adaptable to the cavity walls as closely as possible (1, 2). Some examples of the existing
root-end–filling materials are gutta-percha, zinc oxide eugenol-based cements (ie,
Super-EBA and IRM), composite resin, glass ionomer cement, Cavit, gold foil, polycarboxylate cement, polyvinyl cement, amalgam, Vitremer, and mineral trioxide aggregate
(MTA) (1–3). Unfortunately, most of them have shown different levels of weakness in
biocompatibility, leakage, solubility, handling properties, moisture incompatibility, and
price (3, 4). MTA was introduced to the market in 1998 in order to overcome the
mentioned disadvantages. The patent of this material was applied in 1995 (5, 6). MTA
is a powder consisting of fine hydrophilic particles set in the presence of moisture. This
material has a setting time of about 4 hours, and 3 hours after mixing, its pH value is 12.5
(7). White MTA replaced the gray one in 2002. MTA is a mechanical mixture of three
powder ingredients: Portland cement, bismuth oxide, and gypsum (8). Portland cement
as the major component of MTA is composed of dicalcium silicate, tricalcium silicate,
tricalcium aluminate, and tetracalcium aluminoferrite (5). The color changes between
gray and white MTA are because of a lesser amount of iron in white MTA (9). ProRoot
MTA is used for both surgical and nonsurgical purposes such as root-end filling, perforation repairs, direct pulp capping, and apexification (10, 11).
Recently, a new experimental cement (NEC) consisting of different calcium compounds (ie, calcium oxide, calcium phosphate, calcium carbonate, calcium silicate,
calcium sulfate, calcium hydroxide, and calcium chloride) was developed. Clinical uses
of NEC are similar to MTA. This material can be handled and set in an aqueous environment. It has good handling characteristics and forms an effective seal when used
as root-end–filling material (12). NEC is also able to produce hydroxyapatite with its
endogenous and exogenous ion sources (13). The results of an in vivo study on dogs
showed that as pulp capping materials, MTA and NEC showed similar favorable results.
These results were better than calcium hydroxide CH (14).
The aim of this in vitro study was to analyze the physical and chemical properties
of NEC as a new root-end–filling material and compare it with white MTA as a gold
standard.
Materials and Methods
In this experiment, MTA (tooth-colored formula, ProRoot MTA; Dentsply, Tulsa,
OK) and NEC were used. For each material, working time, setting time, dimensional
changes, film thickness, and flow were measured three times according to International
Organization for Standardization (ISO) 6876:2001. The mean values and standard
deviation were calculated and recorded. A Metrohm 744 pH meter (Metrohm Ltd,
Herisa, Switzerland) was applied for pH measurement. This pH meter was previously
calibrated with standard solutions at pH 4.0 and 7.0. The cements were inserted into
plastic tubes (length ⫽ 10 mm, diameter ⫽ 1.5 mm), and the tubes were weighted
before and after filling to define and standardize the mass of cement in each tube. Five
samples were used for each material. Then, each tube was sealed in a flask containing
10 mL of deionized distilled water, sealed, and stored at 37°C. The tubes were removed
after an hour, and the electrode was inserted into the flask and readings were taken at
24°C. The data were statistically analyzed by one-way analysis of variance with ␣ ⫽ 0.05
as the level for statistical significance.
JOE — Volume 34, Number 8, August 2008
Basic Research—Technology
Figure 1. Scanning electron micrograph of test materials. (Left) A complex mix of two mineral phases of white MTA. The presence of bismuth oxide white particles
in MTA is shown. (Right) NEC shows the presence of coarse crystalline particles in a groundmass of finer amorphous material (bar ⫽ 100 ␮m).
For electron probe microanalysis (EPMA), the samples were
mounted in individual discs with three holes in each to ensure compatibility with the electron probe microanalysis. After insertion of fresh
mixed cements in cavities, the samples were immersed in saline solution and allowed to set in an incubator at 37°C for 48 hours. All samples
were polished and carbon coated by using a Dynavac coating unit
(CS300; Dynavac, Sydney, Australia). A JEOL SEM (JSM6400; JEOL,
Tokyo, Japan) equipped with an Oxford Instruments light element dispersive spectrometer detector (Oxford Instruments, Abingdon, England)
was used for imaging and determining the composition. All analyses
were carried out at 15 kV and 1 nA of probe current. Atomic number,
absorption, and fluorescence corrections were applied throughout
(15). Each analysis was performed by using an area scan taken at 200⫻
magnification to provide an average value for the overall composition.
The final result for each sample was based on the average of 12 analyses
(four analyses for each of the three cavities in the disc) with the overall
error provided by the standard deviation. Carbon concentrations were
not measured, and the amounts of carbon and water were therefore
assumed by difference.
revealed the presence of coarse crystalline particles in a general
groundmass of finer amorphous material (Fig. 1).
The results of EPMA are presented in Table 1. This analysis revealed that lime (CaO), silica (SiO2), and bismuth oxide (Bi2O3)
formed 81.57% of the total weight of the white MTA. Oxides of iron,
sulfur, phosphorus, titanium, and sodium as well as elemental chlorine
were found at trace (⬍0.99 wt %) levels in white MTA. According to
Table 1, the results of the EPMA of NEC cements revealed that lime is the
predominant component of this material, and the concentration of
other constituents, except some trace elements, is considerably different from the white MTA.
The mean and standard deviation of working time, setting time,
dimensional changes, film thickness, and flow measured for the test
materials are presented in Table 2. A considerable significant difference
was found between the results of setting times, film thickness, and flow
of test materials (p ⬍ 0.01). There was no significant difference in pH,
working times, and dimensional changes between white MTA and NEC.
Results
MTA acted as a gold standard in this in vitro study. A number of
investigations reported MTA as a root-end–filling material presenting
excellent apical sealing and showed its superiority in comparison with
other commonly used materials (16 –18). Using MTA as a root-end
filling in periradicular surgery causes the healing of periapical lesions to
a nearly normal condition (19, 20).
Discussion
Scanning electron microscopy of white MTA showed two specific
phases throughout the material. The samples contained a complex mixture of mineral phases with highly visible randomly distributed 5 to 40
␮m particles of bismuth oxide, which were added to the composition as
the opacifier. The mineral phases of white MTA and NEC specimens
TABLE 1. Electron Probe Microanalysis Results (Concentration wt% and Error) for White MTA and NEC
MTA (n ⫽ 2)
NEC (n ⫽ 2)
CaO
SiO2
Bi2O3
AJ2O3
MgO
FeO
SO3
P2OS
TiO2
Na2O
CI
H&C
SUM
44.27 (3.28)
51.81 (1.26)
21.19 (1.60)
6.28 (0.79)
16.11 (4.91)
ND
1.89 (0.10)
0.95 (0.31)
1.32 (0.13)
0.23 (0.12)
0.42 (0.17)
ND
0.51 (0.13)
9.48 (1.46)
0.22 (0.10)
8.52 (0.41)
0.12 (0.09)
ND
0.02 (0.04)
0.35 (0.07)
0.40 (0.13)
0.18 (0.04)
13.53
22.2
100
100
ND, not detected; H&C, water, carbon dioxide, and other not mentioned elements.
JOE — Volume 34, Number 8, August 2008
Properties of a New Endodontic Material
991
Basic Research—Technology
TABLE 2. The Working Time, Setting Time, Dimensional Change, Film Thickness, Flow, and pH of White MTA and NEC
MTA (n ⫽ 3)
NEC (n ⫽ 5)
p value
Working Time
(min)
Setting Time
(min)
Dimensional Change
(mm)
Film Thickness
(␮m)
Flow
(mm)
pH
5 (0.79)
4.5 (0.77)
—
70 (8.5)
50 (7.5)
⬍0.05
0.085 (0.042)
0.075 (0.032)
—
452 (63)
174 (25)
⬍0.001
10 (0.79)
14 (1)
⬍0.01
10.61 (0.24)
10.71 (0.19)
—
MTA showed slight expansion upon setting, which was not significantly different from NEC. However, the new material exhibited reasonable film thickness and flow, which was statistically different from MTA.
The slight expansion and reasonable flow and film thickness of MTA can
ensure an effective seal after setting and reduction the subsequent leakage. These physical properties may account for the superior sealing
ability of MTA over other root-end–filling materials (21–24). Also, NEC
showed acceptable film thickness, flow, and comparable sealing ability
compared with MTA (12).
The fineness of cement is a major factor influencing its rate of
hydration and, consequently, its strength and setting characteristics.
The United States patent for MTA states that the Portland cement used in
the manufacture of MTA had a Blaine number in the range of 450 to 460
m2/kg (5, 6). Although NEC is finer, the NEC tested in this study appeared to fulfill the physical requirements of a root-end–filling material
from the point of consistency, workability, adaptability, and setting time.
The EPMA results showed that the predominant elements in white
MTA were calcium, silicon, and bismuth (presented as oxides), respectively. These were in agreement with our previous findings (9, 25). The
predominant elements in NEC were calcium, sulfur, phosphorus, and
silicon, respectively, which are dissimilar with MTA.
It was reported that calcium and phosphorous were the main
components of MTA (7). This study, however, showed that the observed
concentrations of phosphorus in MTA in contrast with NEC were close to
the limit of detection (Table 1). These results appear to be entirely in
agreement with previous findings (9, 25, 26) and the information supplied by the Dentsply Tulsa dental company, in which the phosphorus is
not reported as a significant element in MTA (27).
The cementogenic activity of MTA is because of its release of an
abundance of calcium ions, which interact with phosphate groups in the
surrounding tissue fluid to form hydroxyapatite on the surface of white
and gray MTA (28). Therefore, the clinical success of MTA can be
attributed to its biocompatibility. On the other hand, EPMA revealed
endogenous phosphate in NEC (Table 1). Therefore, it seems reasonable to suspect that the presence of significant calcium and phosphate
ions in NEC is most likely to form the hydroxyapatite compared with
white MTA (13).
Calcium in its hydroxide form is the main chemical compound
released by MTA when mixed with water (29). This may be explained
with the similarities in the behavior of MTA and CH when used in direct
pulp-capping procedures (30, 31). The CH release, along with the
sealing ability, may account for the greater success obtained with MTA in
direct contact with vital tissues. NEC consists of CH, so the same reaction
may occur for NEC.
Our result showed that high alkalinity of NEC is comparable with
white MTA, a favorable property related to its bactericidal properties
(7), providing an excellent tight seal (16), and biocompatibility (32).
The important constituents of NEC are alkaline earth metal oxides and
hydroxides (eg, calcium oxide and CH), calcium phosphate, and calcium silicate. During and after mixing with its liquid, hydration reactions take place, producing CH. This production is mostly because of the
reactions involving calcium silicates, calcium phosphate, and calcium
oxide in addition to the presence of CH. CH dissociated into calcium and
hydroxyl ions, increasing the pH and calcium concentration.
992
Asgary et al.
Based on the results obtained from this in vitro study, it was concluded that NEC as an experimental root-end–filling material differs
chemically from MTA. NEC also exhibited acceptable physical properties. Further research is needed to establish clinical use.
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Properties of a New Endodontic Material
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