amalgam ref

1. Solubility of Root-end–Filling Materials: A Comparative
Study
Claudio Poggio, DMD,* Marco Lombardini, DDS, PhD,* Conti Alessandro, DDS,*
and Rindi Simonetta†
Abstract
This study tested solubility of 3 root-end filling mate-
rials (IRM, Pro Root, and Superseal) and an endodontic
sealer (Argoseal) used as positive control. The test was
performed according to the International Standards
Organization 6876 standard and the American Dental
Association specification #30. Six specimens of each
material were prepared and immersed in water. Solu-
bility was determined after 24 hours and 2 months and
analyzed statistically with a one-way analysis of vari-
ance test. All retrograde filling materials were of low
solubility. Under the conditions of the present study,
IRM, Superseal, and Pro Root are virtually insoluble;
this is an adequate physical property for use as root-
end filling materials. (J Endod 2007;33:1094–1097)
Key Words
Endodontic sealer, root-end filling materials, solubility
When nonsurgical root canal treatment has been unsuccessful or is inadvisable,
surgical root canal treatment is often carried out to save teeth. This procedure
routinely consists of root-end exposure of the involved apex, resection of its apical end,
a retrofilling preparation, and the placement of a root-end filling material to seal the
root canal system. A number of materials have been evaluated for use as root-end
fillings. They include amalgam, gutta-percha, zinc oxide–eugenol cements, composite
resins, glass ionomers, polycarboxylate cements, ethoxybenzoic acid (EBA) cement,
and mineral trioxide aggregate (MTA) (1). Ideal materials for sealing root-end cavities
should prevent leakage (2). They should have dimensional stability, should adhere to
the walls of the cavity, should be resistant to resorption, and should be moisture-
resistant; they should also be nontoxic and biocompatible to promote healing (3).
Johnson (4) reviewed the different root-end filling materials, highlighting the indica-
tions and contraindications of each one.
Originally amalgam was the material of choice for root-end fillings; however,
several disadvantages are associated with amalgam, including initial marginal leakage,
secondary corrosion, moisture sensitivity, and concerns over mercury toxicity.
Although some investigators have shown glass ionomer cements (5) and compos-
iteresins(6)toprovideabettersealthanamalgam,theissueofmoisturecontamination
remains a valid concern with these materials. The seals of 2 glass ionomers were
adversely affected when the root-end cavities were contaminated with moisture at the
time of material placement (7). Intermediate restorative material (IRM) has addressed
some of the disadvantages concerning amalgam; this material also has potential disad-
vantages including moisture sensitivity, irritation to vital tissues, solubility, and difficulty
in handling.
Among the available root-end filling materials, super-EBA and MTA have been
shown to have superior sealing characteristics (8, 9), although both these materials
have specific drawbacks. Super-EBA is zinc oxide–eugenol cement, modified with EBA
to improve the setting time and increase the strength of the mixture. Super-EBA has
much better physical properties than zinc oxide–eugenol. It shows high compressive
strength, high tensile strength, neutral pH, and low solubility. Even in moist conditions,
super-EBA adheres to tooth structure. Super-EBA adheres well to itself and can be
added incrementally as necessary. Reports showed a good healing response to super-
EBA with minimal chronic inflammation at the root apex (10). On the other hand,
super-EBA is sensitive to moisture, radiolucent, and technique sensitive. The eugenol
content can irritate periradicular tissues. Leakage studies on the use of EBA cement as
a retrograde filling material show conflicting results (11).
MTA was developed by Torabinejad et al (12) to address shortcomings of com-
monly used root-end filling materials. The main components in MTA cement are trical-
cium silicate, tricalcium aluminate, tricalcium oxide, and silicate oxide (12). MTA is a
powder consisting of hydrophilic particles that set in the presence of moisture. Hydra-
tion of the powder results in a colloidal gel that solidifies to a hard structure. Several
studies on MTA have demonstrated that this material possesses many ideal properties.
The sealing ability of MTA in root-end fillings was found to be superior to that of
amalgam, IRM, and super-EBA with both dye and bacterial leakage methods (13–16),
but extended setting time and difficulties in handling MTA have resulted in limited use
in many surgical situations.
Marginal adaptation and crack formation with super-EBA and MTA were analyzed
after subjecting them to occlusal loads equivalent to those generated by masticatory
From the *Department of Operative Dentistry and †
De-
partment of Biochemistry, University of Pavia, Pavia, Italy.
Address requests for reprints to Claudio Poggio, DMD,
Department of Operative Dentistry, Policlinico “San Matteo”,
Piazzale Golgi 3, 27100 Pavia, Italy. E-mail address:
c.poggio@unipv.it.
0099-2399/$0 - see front matter
Copyright © 2007 by the American Association of
Endodontists.
doi:10.1016/j.joen.2007.05.021
Basic Research—Technology
1094 Poggio et al. JOE — Volume 33, Number 9, September 2007

2. movements for 5 years (17). Both materials were found to offer excel-
lent marginal adaptation, with somewhat superior performance when
using MTA.
Insolubility of root-end fillings might have a great impact on the
success rate of the surgical procedure. Moreover, sealers should have
low solubility because components leaching from the root canal might
have undesirable biologic effects on the surrounding tissues (18). Sur-
prisingly, few studies have been carried out on the solubility of these
materials (19).
The purpose of this study was to compare solubility at 24 hours
and at 2 months of different root-end filling materials: 2 zinc oxide–
eugenol cements (IRM and Argoseal), 1 EBA cement (Superseal), and
MTA.
Materials and Methods
Three root-end filling materials, representing different chemical
classes of materials, and one endodontic sealer (used as positive con-
trol) were included in the present study. Table 1 shows chemical com-
position of the materials tested.
The solubility of IRM, ProRoot, Superseal, and Argoseal was de-
termined in accordance with the International Standards Organization
(ISO) 6876 method and with American Dental Association (ADA) spec-
ification #30 (20, 21). This International Standard specifies require-
ments for “materials used for permanent obturation of the root canal
with or without the aid of obturating points.” Stainless steel ring molds
with an internal diameter of 20 Ϯ 0.1 mm and a height of 1.5 Ϯ 0.1 mm
were used for sample preparation. All molds were cleaned with acetone
in an ultrasound bath for 15 minutes. All molds were weighed 3 times
before use (accuracy, Ϯ0.0001 g) on a Mettler AE-163 (Mettler To-
ledo) balance, which was used throughout the experiment. The molds
were placed on a glass plate and filled to slight excess with the mixed
materials. All root-end fillings were mixed by the same operator in
accordance with manufacturers’ instructions (Table 2). After filling the
molds, another glass plate covered with a Mylar strip was placed on top
ofthemolds,exertingalightpressuretoremoveanyexcessmaterial.Six
sets of specimens for each material were prepared in 1 operation. All
sampleswerelefttosetfor24hoursonagratinginacabinetat37°Cand
100% relative humidity. The samples in their molds were then exposed
to air for 15 minutes and weighed 3 times, and the average reading was
recorded to 3 decimal places. The specimens of each material were
individually placed in tarred bottles containing 5 mL of distilled water.
The bottles were then transferred to an oven at 37°C in which they
remained for 24 hours. They were then removed from the oven and
rinsed with distilled water, which was then collected in the same bottles.
After that, the water was evaporated at a temperature slightly below
boiling point. Bottles and residues were dried in an oven at 105°C,
cooled down in the same desiccator, and weighed. The differences
found between this weight and the original bottle weight were divided by
the initial dry weight of the specimens and multiplied by 100. The result
was recorded as solubility (22, 23). The solubility test was performed
again at 2 months by using the same method. Results were analyzed by
analysis of variance test. Statistical difference was set at P Ͻ.01.
Results
The results of solubility test (after 24 hours and after 2 months)
are listed in Table 2. All the materials fulfilled the requirements of the
International Standard 6876, demonstrating a weight loss of less than
3%. There was no statistical significance in solubility among the mate-
rials tested after 24 hours (P Ͻ 0.01). The weight loss of the 4 root-end
fillings after 2 months was not statistically significant; thus the materials
were virtually insoluble.
Discussion
The purpose of inserting a root-end filling material is to provide an
apical seal that inhibits the leakage of irritants from the root canal
system into the periradicular tissues (24). Sutimuntanakul et al (25)
experimentally investigated the sealing properties of MTA in relation to
other materials such as super-EBA, Ketacfill, and gutta-percha. They
reported less leakage with MTA compared with amalgam. Pichardo et al
(26) compared apical leakage of Geristore, MTA, and super-EBA root-
end filling materials in human teeth previously stored in 10% formalin;
they found less leakage in teeth restored with Geristore compared with
MTA and super-EBA, regardless of storage medium.
Torabinejad et al (12) and Bonson et al (27) suggested that MTA
promotes healthy apical tissue formation more often than other mate-
rials, as confirmed by a lower incidence of inflammation. Shahi et al
(28) studied biocompatibility of grey MTA, white MTA, and amalgam.
They stated that after 3 and 7 days, amalgam produces a more severe
TABLE 1. Chemical Composition of Materials Tested
Type of Rootend
Fillup
Material Manufacture Chemical Composition
Zinc oxide–eugenol IRM Dentsply, Johnson
City, TN
Powder ZnO 80%; polymethyl methacylate 20%
Liquid Eugenol 99%
MTA Pro Root Dentsply, Johnson
City, TN
Powder Calcium phosphate, calcium oxide,
silica, bismuth oxide
Liquid Sterile distilled water
EBA Superseal Ogna, Milano,
Italy
Powder Zinc oxide 30%; aluminum oxide 38%;
calcium tungstate and resin
Liquid Eugenol 37.5%; 2 EBA 66%
Zinc oxide–eugenol Argoseal Ogna, Milano,
Italy
Powder Silver 30%; zinc oxide 40%; natural
resin 15%; diiodothymol 15%
Liquid Bidistilled eugenol 78%; purified
olcoresin 22%
TABLE 2. Solubility Percentage After 24 Hours and 2 Months and Standard
Deviation of Weight Loss for Each Material and for Each Immersion Period
Material
Solubility After
24 Hours
(in Percentage)
and SD
Solubility After
2 Months
(in Percentage)
and SD
IRM 0.65% (0.19) 1.01% (0.22)
Pro Root 0.70% (0.26) 0.91% (0.29)
Superseal 0.23% (0.25) 0.40% (0.24)
Argoseal 0.97% (0.33) 1.50% (0.35)
SD, standard deviation.
Basic Research—Technology
JOE — Volume 33, Number 9, September 2007 Solubility of Root-end–Filling Materials 1095

3. inflammatory response than grey and white MTA. However, after 3
weeks, the inflammatory response was the same for all 3 materials.
Endodontic surgery has now evolved into endodontic microsur-
gery. Following their clinical experience and published research, Kim et
al (29) affirmed that endodontic microsurgery with MTA is a reliable
procedure to save teeth. In a retrospective study, Tsesis et al (30)
confirmed that modern surgical endodontic treatment with operative
microscope and ultrasonic tips significantly improves the outcome of
the therapy compared with the traditional technique; however, only
cases that used IRM as a retrograde filling material were included in the
study.
The choice of root-end filling material is not the only factor that
caninfluencetheoutcomeofthesurgicaltherapy;italsodependsonthe
way the material is handled. Walker et al (31) stated that a moistened
cotton pellet should be placed onto the intracanal MTA surface under
temporary restoration; this procedure could significantly improve its
mechanical properties. The capacity of tooth-colored MTA to maintain
an apical seal in the presence of bacteria, when contaminated with
blood, saline, or saliva, was investigated (32). Tooth-colored MTA con-
taminatedwithsalivaleakedsignificantlymorethantheuncontaminated
tooth-colored MTA.
Solubility is a very important factor in assessing the suitability
of potential substances to be used as restorative materials in den-
tistry. Lack of solubility has also been stated as an ideal character-
istic for root-end filling materials (33). In the ISO 6876, the pro-
cedure for determining the solubility of root canal sealers in water
is described. The solubility test performed in the present study
followed the procedures laid out in this International Standard. At
present, root-end fillings are not included in the scope of this stan-
dard, and they are, as yet, not subjected to standardization. This
procedure was followed because root-end fillings get direct contact
with periapical tissues as endodontic sealers. The results might at
least be qualitatively transferable to a clinical situation. However, in
any clinical situation, only part of the root-end fillings will be in
contact with the aqueous environment (ie, the periapical tissues),
whereas under the conditions of the present study, the osmotic
effect would be more important, because the whole specimen is in
contact with a large amount of distilled water (22). The test was
repeated after 2 months, because Schafer et al (19) stated that the
24-hour period of the specification test is not sufficient.
This study indicated that IRM, Superseal, and MTA showed no
signs of solubility in water. As for MTA, our results are in accordance
with the studies of Torabinejad et al (12) and Danesh et al (8). On the
contrary, Fridland et al (23) demonstrated with the same method that
MTA might partially release its soluble fraction to an aqueous environ-
mentduringalongperiodoftimewithdecreasingrate.Theauthorsalso
confirmed that this soluble fraction is mainly composed of calcium
hydroxide, which yields high pH values.
IRM gave good results, but in clinical studies (34) the use of MTA
as a root-end filling material resulted in a high success rate, better than
that of IRM although not statistically significant.
Argoseal, a zinc oxide–eugenol endodontic sealer, was used as a
control. This material also provided a very low weight loss, lower than
the one accepted by the ISO 6876 International Standard.
The root-end filling materials are normally in contact with perira-
dicular tissue fluid until they are covered with fibrous connective tissue
or cementum. Clinically, biocompatible root-end filling materials with
good sealing ability should generate little or no inflammatory response
in periradicular tissues and encourage formation of connective tissue
covering the entire root-end.
Within the limitation of this in vitro study, the root-end fillings
studiedshowedminimalsolubility,whichisanimportantphysicalprop-
erty of root-end filling materials.
Acknowledgments
We would like to thank Sheila McVeigh, language assistant at
the University of Pavia, for the revision of the text.
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