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ARTICLE IN PRESS d e n t a l m a t e r i a l s x x x ( 2 0 1 4 ) xxx–xxx
Available online at www.sciencedirect.com
ScienceDirect journal homepage: www.intl.elsevierhealth.com/journals/dema
Influence of composition on setting kinetics of new injectable and/or fast setting tricalcium silicate cements H.M. Setbon a,d,∗ , J. Devaux b,d , A. Iserentant e , G. Leloup a,c,d , J.G. Leprince a,c,d a
Advanced Drug Delivery and Biomaterials, Louvain Drug Research Institute, Université catholique de Louvain, Brussels, Belgium b Institute of Condensed Matter and Nanosciences – Bio- and Soft-Matter, Université catholique de Louvain, Louvain-la-Neuve, Belgium c School of Dentistry and Stomatology, Université catholique de Louvain, Brussels, Belgium d Center for Research and Engineering on Biomaterials (CRIBIO), Université catholique de Louvain, Brussels, Belgium e Earth and Life Institute – Environmental Sciences, Université catholique de Louvain, Louvain-la-Neuve, Belgium
a r t i c l e
i n f o
a b s t r a c t
Article history:
Objectives. New commercial tricalcium silicate based cements were elaborated to improve
Received 11 February 2014
handling properties and setting time. The goals of the present work were: (i) to determine
Received in revised form
the composition of the new injectable and/or fast setting calcium silicate based cements,
16 June 2014
and (ii) to investigate the impact of the differences in composition on their setting kinetics.
Accepted 16 September 2014
Methods. The materials considered were Angelus MTATM , BiodentineTM , MM-MTATM , MTA-
Available online xxx
CapsTM , and ProRoot MTATM as control.
Keywords:
Emission Spectroscopy and X-ray Energy Dispersive analysis, whereas phases in presence
Elemental composition of materials was studied by Inductively Coupled Plasma-Atomic Tricalcium silicate cements
were analyzed by Micro-Raman spectroscopy and X-ray Diffraction analysis and cement
Mineral trioxide aggregate
surface by Scanning Electron Microscope. Setting kinetics was evaluated using rheometry.
Setting kinetics
Results. Elemental analysis revealed, for all cements, the presence of three major com-
EDX
ponents: calcium, silicon and oxygen. Chlorine was detected in MM-MTA, MTA-Caps
XRD
and Biodentine. Different radio-opacifiers were identified: bismuth oxide in ProRoot MTA,
SEM
Angelus MTA and MM-MTA, zirconium oxide in Biodentine and calcium tungstate (CaWO4 )
Raman
in MTA-Caps. All cements were composed of di- and tri-calcium silicate, except Biodentine
Rheometry
for which only the latter was detected. Major differences in setting kinetics were observed:
Biodentine
a modulus of 8 × 108 Pa is reached after 12 min for Biodentine, 150 min for MM-MTA, 230 min for Angelus MTA and 320 min for ProRoot MTA. The maximum modulus reached by MTACaps was 7 × 108 Pa after 150 min. Significance. Even if these cements possess some common compounds, major differences in their composition were observed between them, which directly influence their setting kinetics. © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
∗ Corresponding author at: Université catholique de Louvain, Louvain Drug Research Institute, Avenue E. Mounier 73, B-1200 Brussels, Belgium. Tel.: +32 2 764 57 50. E-mail address: [email protected] (H.M. Setbon).
http://dx.doi.org/10.1016/j.dental.2014.09.005 0109-5641/© 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Setbon HM, et al. Influence of composition on setting kinetics of new injectable and/or fast setting tricalcium silicate cements. Dent Mater (2014), http://dx.doi.org/10.1016/j.dental.2014.09.005
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1.
Introduction
Mineral Trioxide Aggregate (MTA) is a tricalcium silicate based cement for dental applications, which was initially developed as a root-end filling material. The first formulation, commercialized during the 90s under the name ProRoot MTA (dentsply, Tulsa, OK, USA), was a 4:1 Portland cement:bismuth oxide mixture [1]. This cement was composed of hydrophilic particles of di- and tri-calcium silicate. During the hydration reaction, these particles react and form a calcium silicate hydrated gel (C-S-H) that hardens with time, and calcium hydroxide. Besides the application as a root-end filling material, ProRoot MTA possesses many qualities needed for other applications in endodontics: setting in wet conditions, good marginal adaptation [2,3], dimensional stability, anti-bacterial activity due to its high alkalinity, biocompatibility [4–6] and bioactivity [7]. Recently, it has been shown that ProRoot MTA can interact with phosphate containing fluids and generate a mineral precipitate on its surface [8]. An interfacial layer can also be created between the tooth and the cement, along with intra-tubular mineral precipitation, which was described as biomineralization [9]. Biocompatibility and bioactivity of ProRoot MTA have largely been demonstrated by previous studies [4–7,10], as well as its capacity to promote dental pulp cell proliferation [11] and to induce cell differentiation [12], without affecting cellular viability [12,13]. It is therefore used in numerous clinical applications, such as pulp capping procedures, repair of perforation, management of root resorptions, apexification of immature necrotic tooth, root-end filling or in the more recently introduced regenerative endodontic procedures [14–17]. ProRoot MTA (Dentsply, Tulsa, OK, USA) is the most widely studied material among calcium silicate based cements but it has two major drawbacks: poor handling properties and long setting time (165 min) [18]. Therefore, several new silicate-based cements were developed and introduced to the market, claiming improved setting and/or handling characteristics: Angelus MTA (Angelus, Londrina, PR, Brazil), Biodentine (Septodont, Saint Maur des Fosses, France), MMMTA (Micromega, Besanc¸on, France), and MTA-Caps (Acteon, Merignac, France). Like ProRoot MTA, Angelus MTA promotes the biomineralization process and is considered as a biocompatible and bioactive material [19–22]. Biodentine was commercialized in 2010 [23] and was proposed for similar applications as ProRoot MTA (i.e. pulp capping, perforation repair, apexification and root-end filling) but also as a dentin substitute. Beside its good biocompatibility [24] and reduced setting time, Biodentine showed improved mechanical properties compared to ProRoot MTA and Angelus MTA [25,26], but comparable efficacy for dental pulp capping and induction of dentin bridge formation [5,27]. Recently, Biodentine was demonstrated to possess the ability to stimulate biomineralization and induce odontoblastic differentiation of dental pulp cells [28]. Finally, a recent clinical study evaluating Biodentine as posterior restoration has reported satisfactory results for up to 6 months [29]. MM-MTA and MTA-Caps, which are presented in injectable capsules, were also proposed for similar applications as ProRoot MTA. There is currently no literature available on their mechanical properties but a recent study demonstrated a comparable biocompatibility and
odontogenic potential between MM-MTA and ProRoot MTA [30]. According to the manufacturers, the setting time of these alternative materials are reduced to 15 min for Angelus MTA, 9 min for Biodentine, and about 20 min for MM-MTA and MTA-Caps. These reduced setting times could allow onevisit treatments, which is not possible with the ProRoot MTA. Regarding handling characteristics, Biodentine is presented in mixing capsules, but needs to be placed in the cavity using hand instruments. MM-MTA and MTA-Caps are dispensed in capsules with a tip, enabling mixing and direct injection into the cavity (Fig. 1). The improvements put forward for these new products are potentially very valuable for clinicians. However, little or no information is currently available regarding the composition of these new materials. The importance of material composition is especially important at the surface of the cements, as it influences their interaction with the restorative materials on the one hand (glass ionomer cements, resin-based adhesives and composites, etc.), and with the living tissues on the other hand (pulp, periodontal ligament, or periapical bone). Material composition is also crucial in terms of setting kinetics. For example, the presence of elements like chlorine and sulfur, or the increased proportion of tricalcium instead of dicalcium silicate, were shown to impact the setting reaction significantly [31,32]. Hence, the aim of the present work was to first to determine the composition of the new injectable and/or fast setting tricalcium silicate cements, and second to investigate the impact of the differences in composition on their setting kinetics.
2.
Materials and methods
The five cements considered in this work (ProRoot MTA, Angelus MTA, MM-MTA, Biodentine, and MTA-Caps) were prepared according to the manufacturers recommendations. ProRoot MTA (batch number 10003598) was mixed at a 3:1 powder:liquid ratio and Angelus MTA (batch number 21013) at a ratio of one powder spoon for one liquid drop, both on a non-absorbent paper. Biodentine (batch number B03844) was mixed by adding five liquid drops to the powder, MMMTA (batch number 7111803) and MTA-Caps (batch number 7203285) were activated, and all three cements were then mixed in an amalgamator at 4300 oscillations per minute during 30 s. Cements were allowed to set during three days at 37.5 ◦ C and saturated humidity in an incubator (INE400, Memmert GmbH, Germany), as described by Camilleri et al. [33].
2.1.
Elemental composition
Cements were prepared in stainless steel molds (1 mm thick, 10 mm diameter) and powder was spread on doublesided tape. Semi-quantitative analysis of both powders and hydrated cements were obtained by X-ray energy dispersive analysis (EDX) (Jeol JSM 7600f, Jeol Ltd., Tokyo, Japan) under a 20 kV accelerating voltage, during 400 s per sample (n = 3) at 750× magnification. Quantitative analysis of powders were performed by Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) using a iCAP 6500 ICP Spectrometer (Thermo Scientific, Waltham, MA, USA).
Please cite this article in press as: Setbon HM, et al. Influence of composition on setting kinetics of new injectable and/or fast setting tricalcium silicate cements. Dent Mater (2014), http://dx.doi.org/10.1016/j.dental.2014.09.005
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3
Fig. 1 – Packaging of the calcium silicate based cements: ProRoot MTA, Angelus MTA, Biodentine, MTA-Caps and MM-MTA.
Surface analysis was performed by X-ray Spectroscopy (XPS) (AXIS-ULTRA, Kratos, Manchester, UK) with Al X-ray under a 15-kV accelerating voltage and a 10-mA filament current in a vacuum of 1.32 × 10−7 Torr. Cement bars (7 mm length, 1.5 mm width and thickness) were prepared and stored for 3 days at 37.5 ◦ C. Prior to analysis, the cements were fractured perpendicularly to the long axis and dehydrated at 110 ◦ C during 5 days. 160 eV and 40 eV pass energy were used to obtain general scans and narrow high resolution scans, respectively.
2.2.
Phase composition
Powders were spread on a microscope slide, and cement bars were prepared in a Teflon mold (7 mm length, 1.5 mm width and thickness). Phase compositions of powders and hydrated cements were analyzed by MicroRaman Spectroscopy and X-ray Diffraction analysis (XRD). MicroRaman spectra were obtained using a 532 nm laser with a power of 20 mW during 20 s (10× magnification) (n = 3) (DXR Raman Microscope, Thermo Scientific, Madison, WI, USA). Prior to XRD analysis, hydrated cement bars were crushed and heated to 105 ◦ C to obtain a fine powder. The data were collected with a diffractometer (D8 Advanced, Bruker AXS GmbH, Karlsruhe, Germany) using a Cu K␣ radiation from 2Â = 15–90◦ at 30 mA, 40 kV and I = 0.15418 nm. Then, the diffraction patterns obtained were compared to the International Center for Diffraction Date (ICCD) database in order to identify the phase in presence.
2.3.
Morphological analysis
Qualitative analysis of powders and hydrated cements were conducted using a Scanning Electron Microscope (SEM) (Jeol JSM 7600f, Jeol Ltd., Tokyo, Japan). Powders were spread on a double-sided tape bonded to a sample holder and coated with a 30 nm thick layer of gold. Secondary electron images were taken at 2000× magnification under 5 kV. For hydrated cements analysis, samples (7 mm length, 1.5 mm width and thickness) were resin embedded (EpoFix, Struer, Denmark) and were fractured perpendicularly to their long axis. Then they were dried in a vacuum desiccator and
gold coated for SEM examination. Secondary electron images of the fractured surfaces were taken at 2500× magnification under 5 kV. Back-scattered images of the cements surface were taken at 200× magnification under 15 kV to evaluate the spreading of radio-opacifier particles.
2.4.
Modulus of rigidity
Setting kinetics was monitored by following the real-time build-up of the storage (elastic) shear modulus G (Pa) using a Kinexus rheometer (Malvern Instruments Ltd., Worcestershire, UK), under a sinusoidal strain of 0.0005% with an oscillation frequency of 1 radian per second. These conditions seem appropriate for the tested materials, since the strain is lower than the critical strain above which the structure of the cement is destroyed [34]. In that way, the build-up of elastic modulus can be monitored without any risk of disturbing the setting kinetics. Under these conditions, the rupture point of the cement will not be reached. An 8 mm diameter upper plate was used and a gap of 2 mm was maintained between the upper and lower plate. Constant temperature of 37.5 ◦ C and saturated humidity were maintained throughout the measurement (n = 3).
3.
Results
3.1. Elemental composition of powders and hydrated cements According to EDX measurements, all cements are composed by calcium, silicon, and oxygen. Chlorine was found in un-hydrated and hydrated MM-MTA and MTA-Caps, and in hydrated Biodentine. Aluminum was detected in all cements, except in Biodentine, and sulfur was present in ProRoot MTA, MM-MTA and MTA-Caps. Different radio-opacifiers were identified, i.e. bismuth in ProRoot MTA, Angelus MTA and MM-MTA, zirconium in Biodentine and tungsten in MTA-Caps (Fig. 2a and b). The quantitative measurements (ICP-AES) are in accordance with those found by EDX, except for the radio-opacifiers, which are underestimated (Table 1). Regarding minor
Please cite this article in press as: Setbon HM, et al. Influence of composition on setting kinetics of new injectable and/or fast setting tricalcium silicate cements. Dent Mater (2014), http://dx.doi.org/10.1016/j.dental.2014.09.005
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Fig. 2a and b – EDX spectra of powders (a), hydrated cements (b). O = oxygen, Al = aluminum, Si = silicon, S = sulfur, Bi = bismuth, Ca = calcium, Cl = chlorine, W = tungsten, Zr = zirconium.
Please cite this article in press as: Setbon HM, et al. Influence of composition on setting kinetics of new injectable and/or fast setting tricalcium silicate cements. Dent Mater (2014), http://dx.doi.org/10.1016/j.dental.2014.09.005
ARTICLE IN PRESS
DENTAL-2447; No. of Pages 13
%wt ICP % wt
9.7 38.5 41.9 7.7
2.2
% at
17.5 52.3 22.8 6.0
0.5
2.7
46.3 9.8
ICP-AES EDX
Biodentine
10.5 6.2 0.8
33.1 5.2 0.4 4.5 2.9 31.6 5.1 0.5 4.2 2.2 14.4
10.8 36.5 33.3 4.4 0.5 5.6 2.7 19.8 50.4 18.3 3.4 0.4 3.5 2.1 10.8 36.1 35.9 4.8 0.3 7.4 2.5 2.1 1.8 16.5 0.8 17.4
2.1 1.2
2.4 10.1 0.9 12.7 0.7 1.5
37.4 10.0 0.6
8.4 54.1 27.0 6.5
4.0 23.0 42.4 7.1 5.1 36.6 36.6 7.4 0.7 10.4 56.7 22.6 6.5 0.6
39.3 8.1
19.5 48.7 19.3 3.7 0.2 4.5 1.9 0.2
%wt ICP % at % wt ICP % wt ICP % wt % at
Phase composition
Micro-Raman Spectroscopy analysis showed, in all cements, the presence of peaks between 830 and 850 cm−1 , corresponding to tri- and di-calcium silicate phases (Fig. 2c). Two other characteristic peaks were found in MM-MTA, MTACaps and Biodentine powder and in all hydrated cement: a strong one at 1085 cm−1 and a weak one at 713 cm−1 , which corresponds to calcium carbonate. Peaks corresponding to radio-opacifier oxides were also detected: calcium tungstate (CaWO4 ) (strong at 330 and 911 cm−1 , weak at 208, 396 and 797 cm−1 ) in MTA-Caps powder, zirconium oxide (ZrO2 ) in Biodentine powder, and bismuth oxide (Bi2 O3 ) were found in ProRoot MTA, Angelus MTA and MM-MTA. The spectra of powder and hydrated cements were normalized based on the radio-opacifier peaks. According to XRD patterns, the phase composition of the investigated powders was the following (Fig. 2d). ProRoot MTA powder was composed of tricalcium silicate (ICDD: 049-0442), dicalcium silicate (ICDD: 033-0303), tricalcium aluminate (ICDD: 00-038-1429), bismuth oxide (ICDD: 01-071-0465) and anhydrite (ICDD: 01-072-0916); Angelus MTA powder was composed of tricalcium silicate (ICDD: 00031-0301), dicalcium silicate (ICDD: 00-031-0297), tricalcium aluminate (ICDD: 00-038-1429), calcium oxide (ICDD: 01-0772376), silicon oxide (ICDD: 01-082-1576) and bismuth oxide (ICDD: 01-071-0465); MM-MTA powder was composed of tricalcium silicate (ICDD: 00-049-0442), dicalcium silicate (ICDD: 00-033-0302), tricalcium aluminate (ICDD: 00-038-1429), calcium carbonate (ICDD: 01-070-0095), calcium sulfate (ICDD: 00-026-0328) and bismuth oxide (ICDD: 01-071-2274); MTACaps powder was composed of tricalcium silicate (ICDD: 00-049-0442), dicalcium silicate (ICDD: 00-033-0302), tricalcium aluminate (ICDD: 00-038-1429), calcium carbonate (ICDD: 01-070-0095), calcium sulfate (ICDD: 00-026-0328) and calcium tungstate (ICDD: 01-072-1624); and Biodentine powder was composed of tricalcium silicate (ICDD: 00-031-0301 and 00-049-0442), calcium carbonate (ICDD: 01-072-1214) and zirconium oxide (ICDD: 00-037-1484), but no dicalcium silicate; Generally, comparable observations were made regarding XRD patterns for hydrated cements, except one major change, i.e. the detection of calcium hydroxide in all hydrated materials (ICDD: 00-044-1481) (Fig. 2e).
3.3. Carbon Oxygen Calcium Silicon Sulfur Chlorine Aluminum Bismuth Zircon Tungsten
% at
EDX ICP-AES EDX
% wt
ICP-AES
EDX
% wt
%wt ICP
% at
% wt
ICP-AES EDX ICP-AES
MTA-Caps MM-MTA Angelus MTA
5
components, some differences are noticed between the cements, notably a higher concentration of magnesium and sodium in MM-MTA and MTA-Caps, and the presence of strontium in Angelus MTA (Table 2). EDX data are expressed in atomic (%at) and weight percentage (%wt), whereas ICP-AES data are given in weight percentage (%wt). Trace element concentrations are given in mg/g. XPS analysis revealed that 35–51% of the cement extreme surface was covered by carbon (data not shown).
3.2.
ProRoot MTA
Table 1a – Elemental composition of powders obtained by X-ray Energy Dispersive Analysis (EDX, in weight and atomic percentage) and by Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES, in weight percentage).
d e n t a l m a t e r i a l s x x x ( 2 0 1 4 ) xxx–xxx
Morphological analysis
In all powders except Biodentine, the size of the particle was inhomogeneous particularly in Angelus MTA, where rod particles corresponding to bismuth oxide were observed. MM-MTA
Please cite this article in press as: Setbon HM, et al. Influence of composition on setting kinetics of new injectable and/or fast setting tricalcium silicate cements. Dent Mater (2014), http://dx.doi.org/10.1016/j.dental.2014.09.005
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Table 1b – Elemental composition of cements obtained by X-ray Energy Dispersive Analysis (EDX, in weight and atomic percentage).
Carbon Oxygen Calcium Silicon Sulfur Chlorine Aluminum Bismuth Zircon Tungsten
ProRoot MTA
Angelus MTA
MM-MTA
MTA-Caps
Biodentine
EDX
EDX
EDX
EDX
EDX
% at
% wt
% at
% wt
% at
% wt
% at
% wt
% at
% wt
9.2 57.0 23.9 7.0 0.4
4.5 37.0 38.9 8.0 0.6
11.3 58.3 21.4 5.7
5.8 39.8 36.6 6.8
4.1
2.6 8.4
12.3 39.1 33.7 3.9 0.5 4.1 2.5
2.6
2.1 0.9
21.6 51.5 17.7 2.9 0.3 2.4 1.8
7.8 38.1 42.0 6.4
0.8 10.2
8.2 35.0 31.5 3.7 0.4 16.1 2.7 2.4
14.6 53.5 23.5 5.2
0.7 1.2
15.1 48.8 17.5 2.9 0.3 10.1 2.1 0.3
0.4
1.6
0.4
3.8
and MTA-Caps powders looked similar (Fig. 3a). The surface of all cements looks like a matrix with entrapped unreacted particles. The surface of both ProRoot MTA and Angelus MTA looks more irregular than the other materials. The rod particle in Angelus MTA does not seemed to be fully integrated into the matrix (Fig. 3b). The back-scattered analysis highlighted the homogeneous repartition of the radio-opacifier over the cements surface (Fig. 3c).
3.4.
Modulus of rigidity
All curves presented an exponential increase of G on a logarithmic time scale, except for Angelus MTA, for which a linear increase was observed (Fig. 4). For Angelus MTA and Biodentine, G started to increase within the first three minutes after mixing, whereas it took 15 min for MM-MTA, MTA-Caps and ProRoot MTA. G reached 3 × 108 Pa for ProRoot MTA after 165 min, which is its documented setting time. It took 8 min for Angelus MTA and Biodentine to reach that modulus, and more than 50 min for MTA-Caps and MM-MTA. A modulus of 8 × 108 Pa is reached after 12 min for Biodentine, 150 min
for MM-MTA, 230 min for Angelus MTA and 320 min for ProRoot MTA. The maximum modulus reached by MTA-Caps was 7 × 108 Pa after 150 min.
4.
Discussion
Several previous works have used both ICP-AES and EDX analysis in order to characterize tricalcium silicate based dental cements [33,35–37]. The quantitative and semi-quantitative analyses using both ICP-AES and EDX revealed differences in composition between the materials considered. Their components can be grouped in three categories: major elements, minor elements and radio-opacifiers. The three majors components of all materials are oxygen, calcium and silicon (Table 1), which is in line with the previously cited works. The latter two are important elements regarding the interactions with pulp and periapical tissues, specifically regarding the formation of mineralized tissues (dentin and bone). Calcium was indeed demonstrated to be osteoinductive by up-regulating the expression of genes such as BMP-2, Osteopontin, or even
Table 2 – Element composition of powders obtained by Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) (in mg/g). ProRoot MTA Al Bi Ca Cl Cr Fe K Mg Mn Na Ni P S Si Sr Ti W Zn Zr
8.19 174.00 373.84 –
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Available online at www.sciencedirect.com
ScienceDirect journal homepage: www.intl.elsevierhealth.com/journals/dema
Influence of composition on setting kinetics of new injectable and/or fast setting tricalcium silicate cements H.M. Setbon a,d,∗ , J. Devaux b,d , A. Iserentant e , G. Leloup a,c,d , J.G. Leprince a,c,d a
Advanced Drug Delivery and Biomaterials, Louvain Drug Research Institute, Université catholique de Louvain, Brussels, Belgium b Institute of Condensed Matter and Nanosciences – Bio- and Soft-Matter, Université catholique de Louvain, Louvain-la-Neuve, Belgium c School of Dentistry and Stomatology, Université catholique de Louvain, Brussels, Belgium d Center for Research and Engineering on Biomaterials (CRIBIO), Université catholique de Louvain, Brussels, Belgium e Earth and Life Institute – Environmental Sciences, Université catholique de Louvain, Louvain-la-Neuve, Belgium
a r t i c l e
i n f o
a b s t r a c t
Article history:
Objectives. New commercial tricalcium silicate based cements were elaborated to improve
Received 11 February 2014
handling properties and setting time. The goals of the present work were: (i) to determine
Received in revised form
the composition of the new injectable and/or fast setting calcium silicate based cements,
16 June 2014
and (ii) to investigate the impact of the differences in composition on their setting kinetics.
Accepted 16 September 2014
Methods. The materials considered were Angelus MTATM , BiodentineTM , MM-MTATM , MTA-
Available online xxx
CapsTM , and ProRoot MTATM as control.
Keywords:
Emission Spectroscopy and X-ray Energy Dispersive analysis, whereas phases in presence
Elemental composition of materials was studied by Inductively Coupled Plasma-Atomic Tricalcium silicate cements
were analyzed by Micro-Raman spectroscopy and X-ray Diffraction analysis and cement
Mineral trioxide aggregate
surface by Scanning Electron Microscope. Setting kinetics was evaluated using rheometry.
Setting kinetics
Results. Elemental analysis revealed, for all cements, the presence of three major com-
EDX
ponents: calcium, silicon and oxygen. Chlorine was detected in MM-MTA, MTA-Caps
XRD
and Biodentine. Different radio-opacifiers were identified: bismuth oxide in ProRoot MTA,
SEM
Angelus MTA and MM-MTA, zirconium oxide in Biodentine and calcium tungstate (CaWO4 )
Raman
in MTA-Caps. All cements were composed of di- and tri-calcium silicate, except Biodentine
Rheometry
for which only the latter was detected. Major differences in setting kinetics were observed:
Biodentine
a modulus of 8 × 108 Pa is reached after 12 min for Biodentine, 150 min for MM-MTA, 230 min for Angelus MTA and 320 min for ProRoot MTA. The maximum modulus reached by MTACaps was 7 × 108 Pa after 150 min. Significance. Even if these cements possess some common compounds, major differences in their composition were observed between them, which directly influence their setting kinetics. © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
∗ Corresponding author at: Université catholique de Louvain, Louvain Drug Research Institute, Avenue E. Mounier 73, B-1200 Brussels, Belgium. Tel.: +32 2 764 57 50. E-mail address: [email protected] (H.M. Setbon).
http://dx.doi.org/10.1016/j.dental.2014.09.005 0109-5641/© 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Setbon HM, et al. Influence of composition on setting kinetics of new injectable and/or fast setting tricalcium silicate cements. Dent Mater (2014), http://dx.doi.org/10.1016/j.dental.2014.09.005
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1.
Introduction
Mineral Trioxide Aggregate (MTA) is a tricalcium silicate based cement for dental applications, which was initially developed as a root-end filling material. The first formulation, commercialized during the 90s under the name ProRoot MTA (dentsply, Tulsa, OK, USA), was a 4:1 Portland cement:bismuth oxide mixture [1]. This cement was composed of hydrophilic particles of di- and tri-calcium silicate. During the hydration reaction, these particles react and form a calcium silicate hydrated gel (C-S-H) that hardens with time, and calcium hydroxide. Besides the application as a root-end filling material, ProRoot MTA possesses many qualities needed for other applications in endodontics: setting in wet conditions, good marginal adaptation [2,3], dimensional stability, anti-bacterial activity due to its high alkalinity, biocompatibility [4–6] and bioactivity [7]. Recently, it has been shown that ProRoot MTA can interact with phosphate containing fluids and generate a mineral precipitate on its surface [8]. An interfacial layer can also be created between the tooth and the cement, along with intra-tubular mineral precipitation, which was described as biomineralization [9]. Biocompatibility and bioactivity of ProRoot MTA have largely been demonstrated by previous studies [4–7,10], as well as its capacity to promote dental pulp cell proliferation [11] and to induce cell differentiation [12], without affecting cellular viability [12,13]. It is therefore used in numerous clinical applications, such as pulp capping procedures, repair of perforation, management of root resorptions, apexification of immature necrotic tooth, root-end filling or in the more recently introduced regenerative endodontic procedures [14–17]. ProRoot MTA (Dentsply, Tulsa, OK, USA) is the most widely studied material among calcium silicate based cements but it has two major drawbacks: poor handling properties and long setting time (165 min) [18]. Therefore, several new silicate-based cements were developed and introduced to the market, claiming improved setting and/or handling characteristics: Angelus MTA (Angelus, Londrina, PR, Brazil), Biodentine (Septodont, Saint Maur des Fosses, France), MMMTA (Micromega, Besanc¸on, France), and MTA-Caps (Acteon, Merignac, France). Like ProRoot MTA, Angelus MTA promotes the biomineralization process and is considered as a biocompatible and bioactive material [19–22]. Biodentine was commercialized in 2010 [23] and was proposed for similar applications as ProRoot MTA (i.e. pulp capping, perforation repair, apexification and root-end filling) but also as a dentin substitute. Beside its good biocompatibility [24] and reduced setting time, Biodentine showed improved mechanical properties compared to ProRoot MTA and Angelus MTA [25,26], but comparable efficacy for dental pulp capping and induction of dentin bridge formation [5,27]. Recently, Biodentine was demonstrated to possess the ability to stimulate biomineralization and induce odontoblastic differentiation of dental pulp cells [28]. Finally, a recent clinical study evaluating Biodentine as posterior restoration has reported satisfactory results for up to 6 months [29]. MM-MTA and MTA-Caps, which are presented in injectable capsules, were also proposed for similar applications as ProRoot MTA. There is currently no literature available on their mechanical properties but a recent study demonstrated a comparable biocompatibility and
odontogenic potential between MM-MTA and ProRoot MTA [30]. According to the manufacturers, the setting time of these alternative materials are reduced to 15 min for Angelus MTA, 9 min for Biodentine, and about 20 min for MM-MTA and MTA-Caps. These reduced setting times could allow onevisit treatments, which is not possible with the ProRoot MTA. Regarding handling characteristics, Biodentine is presented in mixing capsules, but needs to be placed in the cavity using hand instruments. MM-MTA and MTA-Caps are dispensed in capsules with a tip, enabling mixing and direct injection into the cavity (Fig. 1). The improvements put forward for these new products are potentially very valuable for clinicians. However, little or no information is currently available regarding the composition of these new materials. The importance of material composition is especially important at the surface of the cements, as it influences their interaction with the restorative materials on the one hand (glass ionomer cements, resin-based adhesives and composites, etc.), and with the living tissues on the other hand (pulp, periodontal ligament, or periapical bone). Material composition is also crucial in terms of setting kinetics. For example, the presence of elements like chlorine and sulfur, or the increased proportion of tricalcium instead of dicalcium silicate, were shown to impact the setting reaction significantly [31,32]. Hence, the aim of the present work was to first to determine the composition of the new injectable and/or fast setting tricalcium silicate cements, and second to investigate the impact of the differences in composition on their setting kinetics.
2.
Materials and methods
The five cements considered in this work (ProRoot MTA, Angelus MTA, MM-MTA, Biodentine, and MTA-Caps) were prepared according to the manufacturers recommendations. ProRoot MTA (batch number 10003598) was mixed at a 3:1 powder:liquid ratio and Angelus MTA (batch number 21013) at a ratio of one powder spoon for one liquid drop, both on a non-absorbent paper. Biodentine (batch number B03844) was mixed by adding five liquid drops to the powder, MMMTA (batch number 7111803) and MTA-Caps (batch number 7203285) were activated, and all three cements were then mixed in an amalgamator at 4300 oscillations per minute during 30 s. Cements were allowed to set during three days at 37.5 ◦ C and saturated humidity in an incubator (INE400, Memmert GmbH, Germany), as described by Camilleri et al. [33].
2.1.
Elemental composition
Cements were prepared in stainless steel molds (1 mm thick, 10 mm diameter) and powder was spread on doublesided tape. Semi-quantitative analysis of both powders and hydrated cements were obtained by X-ray energy dispersive analysis (EDX) (Jeol JSM 7600f, Jeol Ltd., Tokyo, Japan) under a 20 kV accelerating voltage, during 400 s per sample (n = 3) at 750× magnification. Quantitative analysis of powders were performed by Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) using a iCAP 6500 ICP Spectrometer (Thermo Scientific, Waltham, MA, USA).
Please cite this article in press as: Setbon HM, et al. Influence of composition on setting kinetics of new injectable and/or fast setting tricalcium silicate cements. Dent Mater (2014), http://dx.doi.org/10.1016/j.dental.2014.09.005
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Fig. 1 – Packaging of the calcium silicate based cements: ProRoot MTA, Angelus MTA, Biodentine, MTA-Caps and MM-MTA.
Surface analysis was performed by X-ray Spectroscopy (XPS) (AXIS-ULTRA, Kratos, Manchester, UK) with Al X-ray under a 15-kV accelerating voltage and a 10-mA filament current in a vacuum of 1.32 × 10−7 Torr. Cement bars (7 mm length, 1.5 mm width and thickness) were prepared and stored for 3 days at 37.5 ◦ C. Prior to analysis, the cements were fractured perpendicularly to the long axis and dehydrated at 110 ◦ C during 5 days. 160 eV and 40 eV pass energy were used to obtain general scans and narrow high resolution scans, respectively.
2.2.
Phase composition
Powders were spread on a microscope slide, and cement bars were prepared in a Teflon mold (7 mm length, 1.5 mm width and thickness). Phase compositions of powders and hydrated cements were analyzed by MicroRaman Spectroscopy and X-ray Diffraction analysis (XRD). MicroRaman spectra were obtained using a 532 nm laser with a power of 20 mW during 20 s (10× magnification) (n = 3) (DXR Raman Microscope, Thermo Scientific, Madison, WI, USA). Prior to XRD analysis, hydrated cement bars were crushed and heated to 105 ◦ C to obtain a fine powder. The data were collected with a diffractometer (D8 Advanced, Bruker AXS GmbH, Karlsruhe, Germany) using a Cu K␣ radiation from 2Â = 15–90◦ at 30 mA, 40 kV and I = 0.15418 nm. Then, the diffraction patterns obtained were compared to the International Center for Diffraction Date (ICCD) database in order to identify the phase in presence.
2.3.
Morphological analysis
Qualitative analysis of powders and hydrated cements were conducted using a Scanning Electron Microscope (SEM) (Jeol JSM 7600f, Jeol Ltd., Tokyo, Japan). Powders were spread on a double-sided tape bonded to a sample holder and coated with a 30 nm thick layer of gold. Secondary electron images were taken at 2000× magnification under 5 kV. For hydrated cements analysis, samples (7 mm length, 1.5 mm width and thickness) were resin embedded (EpoFix, Struer, Denmark) and were fractured perpendicularly to their long axis. Then they were dried in a vacuum desiccator and
gold coated for SEM examination. Secondary electron images of the fractured surfaces were taken at 2500× magnification under 5 kV. Back-scattered images of the cements surface were taken at 200× magnification under 15 kV to evaluate the spreading of radio-opacifier particles.
2.4.
Modulus of rigidity
Setting kinetics was monitored by following the real-time build-up of the storage (elastic) shear modulus G (Pa) using a Kinexus rheometer (Malvern Instruments Ltd., Worcestershire, UK), under a sinusoidal strain of 0.0005% with an oscillation frequency of 1 radian per second. These conditions seem appropriate for the tested materials, since the strain is lower than the critical strain above which the structure of the cement is destroyed [34]. In that way, the build-up of elastic modulus can be monitored without any risk of disturbing the setting kinetics. Under these conditions, the rupture point of the cement will not be reached. An 8 mm diameter upper plate was used and a gap of 2 mm was maintained between the upper and lower plate. Constant temperature of 37.5 ◦ C and saturated humidity were maintained throughout the measurement (n = 3).
3.
Results
3.1. Elemental composition of powders and hydrated cements According to EDX measurements, all cements are composed by calcium, silicon, and oxygen. Chlorine was found in un-hydrated and hydrated MM-MTA and MTA-Caps, and in hydrated Biodentine. Aluminum was detected in all cements, except in Biodentine, and sulfur was present in ProRoot MTA, MM-MTA and MTA-Caps. Different radio-opacifiers were identified, i.e. bismuth in ProRoot MTA, Angelus MTA and MM-MTA, zirconium in Biodentine and tungsten in MTA-Caps (Fig. 2a and b). The quantitative measurements (ICP-AES) are in accordance with those found by EDX, except for the radio-opacifiers, which are underestimated (Table 1). Regarding minor
Please cite this article in press as: Setbon HM, et al. Influence of composition on setting kinetics of new injectable and/or fast setting tricalcium silicate cements. Dent Mater (2014), http://dx.doi.org/10.1016/j.dental.2014.09.005
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Fig. 2a and b – EDX spectra of powders (a), hydrated cements (b). O = oxygen, Al = aluminum, Si = silicon, S = sulfur, Bi = bismuth, Ca = calcium, Cl = chlorine, W = tungsten, Zr = zirconium.
Please cite this article in press as: Setbon HM, et al. Influence of composition on setting kinetics of new injectable and/or fast setting tricalcium silicate cements. Dent Mater (2014), http://dx.doi.org/10.1016/j.dental.2014.09.005
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%wt ICP % wt
9.7 38.5 41.9 7.7
2.2
% at
17.5 52.3 22.8 6.0
0.5
2.7
46.3 9.8
ICP-AES EDX
Biodentine
10.5 6.2 0.8
33.1 5.2 0.4 4.5 2.9 31.6 5.1 0.5 4.2 2.2 14.4
10.8 36.5 33.3 4.4 0.5 5.6 2.7 19.8 50.4 18.3 3.4 0.4 3.5 2.1 10.8 36.1 35.9 4.8 0.3 7.4 2.5 2.1 1.8 16.5 0.8 17.4
2.1 1.2
2.4 10.1 0.9 12.7 0.7 1.5
37.4 10.0 0.6
8.4 54.1 27.0 6.5
4.0 23.0 42.4 7.1 5.1 36.6 36.6 7.4 0.7 10.4 56.7 22.6 6.5 0.6
39.3 8.1
19.5 48.7 19.3 3.7 0.2 4.5 1.9 0.2
%wt ICP % at % wt ICP % wt ICP % wt % at
Phase composition
Micro-Raman Spectroscopy analysis showed, in all cements, the presence of peaks between 830 and 850 cm−1 , corresponding to tri- and di-calcium silicate phases (Fig. 2c). Two other characteristic peaks were found in MM-MTA, MTACaps and Biodentine powder and in all hydrated cement: a strong one at 1085 cm−1 and a weak one at 713 cm−1 , which corresponds to calcium carbonate. Peaks corresponding to radio-opacifier oxides were also detected: calcium tungstate (CaWO4 ) (strong at 330 and 911 cm−1 , weak at 208, 396 and 797 cm−1 ) in MTA-Caps powder, zirconium oxide (ZrO2 ) in Biodentine powder, and bismuth oxide (Bi2 O3 ) were found in ProRoot MTA, Angelus MTA and MM-MTA. The spectra of powder and hydrated cements were normalized based on the radio-opacifier peaks. According to XRD patterns, the phase composition of the investigated powders was the following (Fig. 2d). ProRoot MTA powder was composed of tricalcium silicate (ICDD: 049-0442), dicalcium silicate (ICDD: 033-0303), tricalcium aluminate (ICDD: 00-038-1429), bismuth oxide (ICDD: 01-071-0465) and anhydrite (ICDD: 01-072-0916); Angelus MTA powder was composed of tricalcium silicate (ICDD: 00031-0301), dicalcium silicate (ICDD: 00-031-0297), tricalcium aluminate (ICDD: 00-038-1429), calcium oxide (ICDD: 01-0772376), silicon oxide (ICDD: 01-082-1576) and bismuth oxide (ICDD: 01-071-0465); MM-MTA powder was composed of tricalcium silicate (ICDD: 00-049-0442), dicalcium silicate (ICDD: 00-033-0302), tricalcium aluminate (ICDD: 00-038-1429), calcium carbonate (ICDD: 01-070-0095), calcium sulfate (ICDD: 00-026-0328) and bismuth oxide (ICDD: 01-071-2274); MTACaps powder was composed of tricalcium silicate (ICDD: 00-049-0442), dicalcium silicate (ICDD: 00-033-0302), tricalcium aluminate (ICDD: 00-038-1429), calcium carbonate (ICDD: 01-070-0095), calcium sulfate (ICDD: 00-026-0328) and calcium tungstate (ICDD: 01-072-1624); and Biodentine powder was composed of tricalcium silicate (ICDD: 00-031-0301 and 00-049-0442), calcium carbonate (ICDD: 01-072-1214) and zirconium oxide (ICDD: 00-037-1484), but no dicalcium silicate; Generally, comparable observations were made regarding XRD patterns for hydrated cements, except one major change, i.e. the detection of calcium hydroxide in all hydrated materials (ICDD: 00-044-1481) (Fig. 2e).
3.3. Carbon Oxygen Calcium Silicon Sulfur Chlorine Aluminum Bismuth Zircon Tungsten
% at
EDX ICP-AES EDX
% wt
ICP-AES
EDX
% wt
%wt ICP
% at
% wt
ICP-AES EDX ICP-AES
MTA-Caps MM-MTA Angelus MTA
5
components, some differences are noticed between the cements, notably a higher concentration of magnesium and sodium in MM-MTA and MTA-Caps, and the presence of strontium in Angelus MTA (Table 2). EDX data are expressed in atomic (%at) and weight percentage (%wt), whereas ICP-AES data are given in weight percentage (%wt). Trace element concentrations are given in mg/g. XPS analysis revealed that 35–51% of the cement extreme surface was covered by carbon (data not shown).
3.2.
ProRoot MTA
Table 1a – Elemental composition of powders obtained by X-ray Energy Dispersive Analysis (EDX, in weight and atomic percentage) and by Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES, in weight percentage).
d e n t a l m a t e r i a l s x x x ( 2 0 1 4 ) xxx–xxx
Morphological analysis
In all powders except Biodentine, the size of the particle was inhomogeneous particularly in Angelus MTA, where rod particles corresponding to bismuth oxide were observed. MM-MTA
Please cite this article in press as: Setbon HM, et al. Influence of composition on setting kinetics of new injectable and/or fast setting tricalcium silicate cements. Dent Mater (2014), http://dx.doi.org/10.1016/j.dental.2014.09.005
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d e n t a l m a t e r i a l s x x x ( 2 0 1 4 ) xxx–xxx
Table 1b – Elemental composition of cements obtained by X-ray Energy Dispersive Analysis (EDX, in weight and atomic percentage).
Carbon Oxygen Calcium Silicon Sulfur Chlorine Aluminum Bismuth Zircon Tungsten
ProRoot MTA
Angelus MTA
MM-MTA
MTA-Caps
Biodentine
EDX
EDX
EDX
EDX
EDX
% at
% wt
% at
% wt
% at
% wt
% at
% wt
% at
% wt
9.2 57.0 23.9 7.0 0.4
4.5 37.0 38.9 8.0 0.6
11.3 58.3 21.4 5.7
5.8 39.8 36.6 6.8
4.1
2.6 8.4
12.3 39.1 33.7 3.9 0.5 4.1 2.5
2.6
2.1 0.9
21.6 51.5 17.7 2.9 0.3 2.4 1.8
7.8 38.1 42.0 6.4
0.8 10.2
8.2 35.0 31.5 3.7 0.4 16.1 2.7 2.4
14.6 53.5 23.5 5.2
0.7 1.2
15.1 48.8 17.5 2.9 0.3 10.1 2.1 0.3
0.4
1.6
0.4
3.8
and MTA-Caps powders looked similar (Fig. 3a). The surface of all cements looks like a matrix with entrapped unreacted particles. The surface of both ProRoot MTA and Angelus MTA looks more irregular than the other materials. The rod particle in Angelus MTA does not seemed to be fully integrated into the matrix (Fig. 3b). The back-scattered analysis highlighted the homogeneous repartition of the radio-opacifier over the cements surface (Fig. 3c).
3.4.
Modulus of rigidity
All curves presented an exponential increase of G on a logarithmic time scale, except for Angelus MTA, for which a linear increase was observed (Fig. 4). For Angelus MTA and Biodentine, G started to increase within the first three minutes after mixing, whereas it took 15 min for MM-MTA, MTA-Caps and ProRoot MTA. G reached 3 × 108 Pa for ProRoot MTA after 165 min, which is its documented setting time. It took 8 min for Angelus MTA and Biodentine to reach that modulus, and more than 50 min for MTA-Caps and MM-MTA. A modulus of 8 × 108 Pa is reached after 12 min for Biodentine, 150 min
for MM-MTA, 230 min for Angelus MTA and 320 min for ProRoot MTA. The maximum modulus reached by MTA-Caps was 7 × 108 Pa after 150 min.
4.
Discussion
Several previous works have used both ICP-AES and EDX analysis in order to characterize tricalcium silicate based dental cements [33,35–37]. The quantitative and semi-quantitative analyses using both ICP-AES and EDX revealed differences in composition between the materials considered. Their components can be grouped in three categories: major elements, minor elements and radio-opacifiers. The three majors components of all materials are oxygen, calcium and silicon (Table 1), which is in line with the previously cited works. The latter two are important elements regarding the interactions with pulp and periapical tissues, specifically regarding the formation of mineralized tissues (dentin and bone). Calcium was indeed demonstrated to be osteoinductive by up-regulating the expression of genes such as BMP-2, Osteopontin, or even
Table 2 – Element composition of powders obtained by Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) (in mg/g). ProRoot MTA Al Bi Ca Cl Cr Fe K Mg Mn Na Ni P S Si Sr Ti W Zn Zr
8.19 174.00 373.84 –
