Original Article
Push-out bond strength of different types of mineral
trioxide aggregate in root dentin
Ahmed Rahoma1,2,
Emad AlShwaimi3,
Abdul Majeed3
ABSTRACT
Objective: The objective of this study was to measure the push-out bond strength of
three types of mineral trioxide aggregate (MTA) materials in root dentin.
1
Department of Restorative Dental Sciences,
College of Dentistry, Imam Abdulrahman Bin
Faisal University, Dammam, Saudi Arabia,
2
Department of Dental Biomaterial, College of
Dentistry, Al-Azhar University, Assuit, Egypt,
3
Department Restorative Dental Sciences,
Division of Endodontic, College of Dentistry,
Imam Abdulrahman Bin Faisal University,
Dammam, Saudi Arabia
Address for correspondence:
Ahmed Rahoma, Department of Restorative Dental
Science, College of Dentistry, Imam Abdulrahman
Bin Faisal Univeristy, Dammam, Saudi Arabia.
Tel.: +966 13-33-31449.
E-mail: amarahoma@iau.edu.sa
WEBSITE:
ijhs.org.sa
ISSN:
1658-3639
PUBLISHER: Qassim University
Methods: The study was carried out at the College of Dentistry, Imam Abdulrahman
Bin Faisal University from March 2014 to January 2015. Thirty extracted maxillary
central incisors were selected, instrumented, irrigated, and randomly assigned into three
groups (n = 10): Group 1 - Ortho MTA; Group 2 - MTA Angelus; and Group 3 - ProRoot
MTA. Materials were mixed following the manufacturers’ recommendations and
canals were filled. Teeth were stored in distilled water for 6 months. The push-out
bond strength was evaluated using 2-mm thick coronal root sections. The data were
analyzed with one-way ANOVA and Tukey-Kramer multiple comparison tests
statistically significant at P < 0.05.
Results: The mean bond strength values were 68.69 ± 29.63 MPa for Ortho MTA,
42.54 ± 32.78 MPa for MTA Angelus, and 72.75 ± 26.27 MPa for ProRoot MTA
groups. There were no significant differences between the bond strengths of tested
materials (P > 0.05).
Conclusion: Ortho MTA, MTA Angelus, and ProRoot MTA materials showed similar
push-out bond strength values in root dentin.
Keywords: Bond strength, mineral trioxide aggregate, push-out test, root dentin
Introduction
Mineral trioxide aggregate (MTA) was manufactured to seal
the undesirable pathways between the root canal system and
periodontal tissues because of its unique properties.[1] MTA has
been researched extensively for its use in clinical applications
such as retrograde filling,[2] pulp capping, repair of root
resorption, apexification,[3] and as an endodontic sealer.[4] The
new application trend is to fill the root canal system completely
with MTA such as in cases of apexification,[5] strip perforation
of the C-shaped root canals,[6] internal and external root
resorption,[7] reimplanted teeth,[8] and retained primary teeth.[9]
An ideal material to be used in endodontics is expected to
withstand the dislodgment forces produced during tooth
function or operative procedures.[10]
Different types of MTA materials have been introduced into the
market by different manufacturers. ProRoot MTA (Dentsply
Maillefer, Ballaigues, Switzerland), MTA Angelus (Angelus,
Londrina, PR, Brazil), and Ortho MTA (BioMTA, Seoul,
Republic of Korea) are some of the examples [Table 1]. These
materials demonstrate slight differences in their composition.
ProRoot MTA consists of 75% Portland cement, 20% bismuth
International Journal of Health Sciences
Vol. 12, Issue 5 (September - October 2018)
oxide, and 5% calcium sulfate dihydrate.[11] MTA Angelus
contains 80% Portland cement and 20% bismuth oxide, with
no calcium sulfate, to reduce the setting time.[12] Ortho MTA
was introduced with lesser heavy metal content than ProRoot
MTA.[13]
Bond strength of endodontic materials to root dentin is an
important factor to consider for long-term clinical success.[14]
Adherence of a material to surrounding dentin resists any
dislodgment forces applied during function or operative
procedures.[15] Tensile shear bond strength and push-out bond
strength tests have been used to determine the adhesiveness of
a material to its surrounding dentin. However, push-out test has
been appraised as a more reliable and practical approach.[16,17]
Therefore, this study evaluated the push-out bond strength of
mature teeth filled with different types of MTA.
Methods
The in vitro cross-sectional study was conducted in conformity
with the World Medical Association Declaration of Helsinki.
Ethical approval was obtained from the Ethics Committee of
Imam Abdulrahman Bin Faisal University (#2013260). Thirty
66
Rahoma, et al.: Bond strength of mineral trioxide aggregate
Table 1: Chemical composition of the three tested materials
Chemical composition
ProRoot MTA
Ortho MTA
MTA angelus
Tricalcium silicate, (CaO)3 SiO2
Dicalcium silicate, (CaO)2 SiO2
Tricalcium aluminate, (CaO)3 Al2O3
Free calcium oxide, CaO
Bismuth oxide, Bi2O3
Tetracalcium aluminoferrite, (CaO)4 Al2O3 Fe2O3
Gypsum, CaSO4$2H2O
MTA: Mineral trioxide aggregate
extracted human maxillary central incisors with mature roots,
having approximately similar length and buccolingual diameter,
and apical size corresponding to the size 15 K-file were selected
for this study. Tooth surfaces were ultrasonically cleaned and
examined under a stereomicroscope as well as using mesiodistal
and buccolingual radiographs. Teeth with previous root canal
treatment, dentin pins, coronal restorations, caries, fractures or
cracks, and internal or external resorption were excluded from
the study. The teeth were stored in normal saline containing
0.1% sodium azide to inhibit bacterial growth.
Root canal treatment procedure
Standardized access cavities were prepared in all the teeth
using a cylindrical diamond bur. The working lengths (WLs)
were determined using radiographs of size 15 K-files in the
canals. Root canals were instrumented with ProTaper Universal
rotary system (Dentsply Maillefer, Ballaigues, Switzerland) up
to F5 using crown-down technique. Canals were irrigated with
1 mL of 2.4% sodium hypochlorite solution after using each
file. Then, 1 mL of 17% EDTA (Ultradent Dental Products,
South Jordan, UT, USA) solution was placed using a plastic
syringe and 30-gauge needle (NaviTip, Ultradent Dental
Products, South Jordan, UT, USA) at the proximities of the
WL for 1 min to remove the smear layer. The residual irrigant
was flushed with 5 mL of distilled water and size 40 paper
points were used to dry the canals. Teeth were randomly
divided into three experimental groups (n = 10) and filled with
the tested materials. All materials were mixed following the
manufacturers’ recommendations.
• Group 1: In this group, root canals were filled with Ortho
MTA. The powder and distilled water were dispensed into
the Eppendorf tube and mixed in an auto-mixer. Once
mixed, the material was placed into the canal in increments
with a ProRoot MTA delivery gun (Dentsply Maillefer,
Ballaigues, Switzerland). Each increment was condensed
with a preselected plugger (BioMTA, Seoul, Republic of
Korea). The canal was filled coronally up to 1 mm below
the cementoenamel junction. Access cavity was cleaned
with a wet cotton pellet and the temporization procedure
was done by placing a wet cotton pellet in the chamber
and the access cavity was restored with a temporary
material (Coltosol; Coltene/Whaledent AG, Altstatten,
Switzerland).
67
•
Group 2: In this group, root canals were filled with MTA
Angelus paste placed into the canals using the similar method
described above for Group 1. Access cavity was cleaned and
the temporization procedure similar to that of Group 1.
• Group 3: In this group, root canals were filled with white
ProRoot MTA paste placed into the canals using the
similar method described above for Group 1. Access cavity
was cleaned and the temporization procedure similar to
that of Group 1.
Mesiodistal and buccolingual radiographs were taken to
ensure complete filling of the canals and to evaluate the
quality of the filling. Specimens were stored in distilled water
at 37°C for 6 months.[18] The distilled water was changed
weekly. After 6 months, specimens were reexamined under a
stereomicroscope to confirm the integrity of the roots.
Push-out bond strength test
Crown with coronal 3-mm section was removed from the roots
and then 2-mm thick sections were obtained from the remaining
roots using a low-speed water-cooled diamond saw (Isomet;
Buehler, Lake Bluff, NY, USA). The canal area filled with the
test material was measured on both the coronal and apical side of
the cut sections, and the apical surfaces were marked. Specimens
having a diameter of ≈1.2 mm on both sides were selected. The
push-out test was performed using a universal testing machine
(Instron 8871, Servo Hydraulic System, Merlin 2 software,
Instron®, Buckinghamshire, UK). Dentin sections were placed
on a custom plate and aligned to the hole in the center of the
plate. This allowed the 1-mm thick stainless steel plunger to pass
through freely under a constant downward force at a speed of
1 mm/min. The plunger had a flat tip which was positioned to
contact the test material only. The force was applied until a total
bond failure occurred and recorded in Newton (N). Following
formula was used to calculate the bond strength in MPa:
Bond Strength (MPa ) =
Debonding force (N)
Bonded surface area (mm 2 )
Bonded surface area = 2πrh
Where π = 3.14 (constant), r is the radius and h is the thickness
of dentin section.
International Journal of Health Sciences
Vol. 12, Issue 5 (September - October 2018)
Rahoma, et al.: Bond strength of mineral trioxide aggregate
Data were analyzed with a statistical package (NCSS 2007,
NCSS, LLC, Kaysville, UT, USA). One-way ANOVA followed
by Tukey-Kramer multiple comparison tests was used to
compare groups at a significance level of P < 0.05.
Results
Figure 1 presents the box-and-whisker plot of the bond
strength values for the tested groups. The mean values in MPa
were 68.69 ± 29.63 for Ortho MTA, 42.54 ± 32.78 for MTA
Angelus, and 72.75 ± 26.27 for ProRoot MTA groups. Multiple
comparison tests showed no significant differences in the bond
strength values of tested materials (P > 0.05).
Discussion
The study evaluated the push-out bond strength of different types of
MTA. The push-out test is a valid method to estimate the adherence
of a material to root dentin, simulating clinical stresses.[19] In this
testing procedure, fracture occurs parallel to the cement-dentin
interface and represents the true shear bond strength of a material.[14]
This study showed insignificant differences in the bond
strength values of tested materials. However, ProRoot- and
Ortho- MTA showed higher bond strength values than MTA
Angelus. The variations in the composition and particle size
of the three cements could be the reason for the different
bond strength values observed. Although there is no chemical
bonding between MTA and root dentin, it has been reported to
form interfacial deposits by interaction between the phosphate
in body fluid and the calcium and hydroxyl ions released
from MTA.[20] These deposits filled up the gaps between the
MTA and root dentin that increased the frictional resistance of
MTA.[21] However, in the present study access, cavities were
sealed by placing a moist cotton pellet and specimens were
stored in distilled water for 6 months.
Clinically, the coronal portion of MTA will be exposed to
distilled water or saline to provide moisture or wet environment
required for the setting reaction of MTA. During mixing of
MTA powder reacts with water and produces calcium silicate
hydrate, calcium hydroxide phases, and calcium ions.[22]
Calcium ions are continuously released and react with carbon
dioxide and water forming deposits of calcium carbonate and
calcium hydroxide.[23] Poor solubility of calcium carbonate in
water results in the formation of precipitates that improve the
sealing ability and thus frictional resistance of MTA.[24] Here,
all the root samples were filled with different types of MTA
after preparation of the canals. Once the material was set, it
acted as a post or primary monoblock.[21,25] This along with
increased frictional resistance of MTA might have increased
the push-out bond strength of MTA.[21]
As explained above, even in the presence of distilled water,
MTA produces calcium carbonate and calcium hydroxide
precipitates.[22,23] The longer the storage time, the higher the
precipitates.[10] These precipitates fill in the gaps between
the material and the root dentin and deposit in dentinal
tubules. This increases the resistance of the material to any
dislodgement forces applied.[24] Gancedo-Caravia and GarciaBarbero[10] reported that moisture was important for the
setting of the MTA, especially during the first 3 days to resist
dislodgment forces and bond strength increased, as the time
for specimens to be kept under wet conditions was increased.
Aggarwal et al.[26] showed a significant increase in the bond
strength values of canals filled with MTA and allowed to set
for 7 days compared to those tested after 1 day of storage.
Nikhade et al.[14] also demonstrated that bond strength for
calcium silicate-based materials was significantly increased
when incubation times were increased. Ertas et al.[27] compared
the bond strengths of three commercial MTA products and
reported that ProRoot MTA had the highest bond strength
values compared to MTA angelus and calcium enriched
mixture cement. Another study comparing three calcium
silicate-based materials also reported that biodentine and
ProRoot MTA demonstrated similar but significantly higher
bond strength values compared to BioAggregate material in
root dentin samples.[28]
Conclusions
Ortho MTA, MTA Angelus, and ProRoot MTA showed similar
push-out bond strength values. Although MTA Angelus showed
relatively lower bond strength values, difference was not
statistically significant compared to other tested materials.
Acknowledgments
Figure 1: Box-and-Whisker plot for push-out bond strength of all
groups. Top and bottom lines indicate the maximum and minimum
values in Newton. The box represents 75% of the values, and the line
in the box indicates the median value
International Journal of Health Sciences
Vol. 12, Issue 5 (September - October 2018)
The authors declare no conflicts of interest in this research.
The study was supported by a grant (#2013260) from the
Deanship of Scientific Research, Imam Abdulrahman Bin
Faisal University, Saudi Arabia.
68
Rahoma, et al.: Bond strength of mineral trioxide aggregate
14.
Yildirim T, Tasdemir T, Orucoglu H. The evaluation of the influence of
using MTA in teeth with post indication on the apical sealing ability.
Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009;108:471-4.
Nikhade P, Kela S, Chandak M, Chandwani N. Comparative evaluation
of push-out bond strength of calcium silicate based materials: An
ex-vivo study. IOSR-JDMS 2016;1:65-8.
15.
2.
Samiee M, Eghbal MJ, Parirokh M, Abbas FM, Asgary S. Repair of
furcal perforation using a new endodontic cement. Clin Oral Investig
2010;14:653-8.
Shahi S, Rahimi S, Yavari HR, Samiei M, Janani M, Bahari M, et al.
Effects of various mixing techniques on push-out bond strengths of
white mineral trioxide aggregate. J Endod 2012;38:501-4.
16.
3.
Torabinejad M, Chivian N. Clinical applications of mineral trioxide
aggregate. J Endod 1999;25:197-205.
Saghiri MA, Garcia-Godoy F, Gutmann JL, Lotfi M, Asatourian A,
Ahmadi H, et al. Push-out bond strength of a nano-modified mineral
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Shokouhinejad N, Nekoofar MH, Iravani A, Kharrazifard MJ,
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EL-Ma’aita AM, Qualtrough AJ, Watts DC. Resistance to vertical
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19.
Hong ST, Bae KS, Baek SH, Kum KY, Shon WJ, Lee W, et al. Effects
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J Endod 2010;36:1995-9.
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Vol. 12, Issue 5 (September - October 2018)