Novel Fast-Setting Mineral Trioxide Aggregate: Its Formulation

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Biological and Medical Applications of Materials and Interfaces

A novel fast-setting mineral trioxide aggregate: Its formulation, chemical-physical properties and cytocompatibility Song Chen, Liyang Shi, Jun Luo, and Håkan Engqvist ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b04946 • Publication Date (Web): 22 May 2018 Downloaded from http://pubs.acs.org on May 22, 2018

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ACS Applied Materials & Interfaces

and zirconium oxide was designed to obtain fast-setting property. The optimized formulation can achieve initial setting in 10 min and final setting in 15 min, which are much faster than commercial mineral trioxide aggregate. In addition, the optimized fast-setting MTA showed adequate radiopacity and good biocompatibility. The ion concentrations after storage in water for 1 day were 52.3 mg/L Ca, 67.7 mg/L Al, 48.8 mg/L Si and 11.7 mg/L Mg. The hydration products of hardened cements were investigated by XRD, SEM and FTIR, showing the accelerated setting time was due to the formation of honeycomb-like C-S-H gel. The novel MTA could be a promising material for dental applications.

1. INTRODUCTION Mineral trioxide aggregate (MTA) was first introduced to dentistry in 1995 and applied in endodontic in 1998 1. The first type of commercial MTA mainly consists of tri-calcium silicates (Ca3SiO5, C3S) and di-calcium silicates (Ca2SiO4, C2S), which are the main components of Portland cement as well. The first type of MTA contains a small amount of Fe which makes it grey in color. Later a MTA without Fe was invented, which is called ‘white MTA’ (WMTA) 2. Several research studies have been made since then and these efforts give more information on the properties such as radiopacity, osteogenesis, immune response etc., and greatly expand the application of MTA 3. Nowadays, MTA has been used as root-end filling materials capping materials

6-7

, root canal sealers

8-9

4-5

, pulp

and pulpal revascularization protective materials

10

.

MTA is beneficial in dental clinic because of its excellent sealing property, biocompatibility and apatite-forming ability

11

. In addition, the strong alkalinity of MTA makes it a bactericidal

material 12. All these advantages make MTA more and more popular in the dental clinic. Despite all these advantages, one of the main drawbacks of MTA is its long setting time. The setting time is defined as the time from mixing of the cement to the hardening of the cement. 2 ACS Paragon Plus Environment

ACS Applied Materials & Interfaces 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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Setting property is crucial for the clinical application of dental cement. The setting times of commercial MTA range from 0.5 to 4 hour 1. For example, ProRoot MTA is reported to have a setting time of 4 hours and MTA Plus has a setting time more than 2 hours 13. The long setting time of current MTA greatly increases the risk of wash-out by blood during the surgery and limits its applications where short setting times are required. Moreover, the properties of MTA such as sealing ability and cytocompatibility might be adversely affected during the long setting period 14. Formulating novel MTA with proper setting property is not easy. The setting of MTA is a very complicated hydration process and various hydration products could coexist. When mixed MTA with water, C3S and C2S start to hydrate and form calcium silicate hydrate (C-S-H) gel. The C-S-H gel is largely amorphous and it forms a solid network, which results in the hardening of the cements. The setting time is largely depended on the hydration speed of these calcium silicates. The hydration process of C3S is slow and complete hydration requires 28 days, which is responsible for the long setting time of MTA. Many attempts have been made to accelerate the process and shorten the setting time of MTA. E.g. CaCl2 and NaOCl gel have been proposed as an additive to decrease the setting time 15. Na2HPO4 solution as a liquid phase could reduce the setting time to 26 min when mixed with WMTA effective in shortening the setting time shortened by removing the CaSO4

17

16

. Calcium lactate gluconate has been found

. Other research show that the setting time could be

18

or incorporating 2-hydroxyethyl methacrylate-

triethyleneglycol-dimethacrylate (HEMA-TEGDMA) based resin to produce light-curable MTA 19

. All these attempts have provided potential methods to improve the setting properties of MTA,

however, these improvements are often at the cost of compromised mechanical properties and biological performance. For example, with 5% CaCl2 the compressive strengths of the set

3 ACS Paragon Plus Environment

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materials are significantly lower than MTA mixed with water have shown cytotoxicity on L929 mouse fibroblasts

20

15

. MTA mixed with 3% NaOCl

. Moreover, the compositions of

commercial MTA are proprietary, making it difficult to investigate the mechanism of accelerated setting reaction. Therefore, developing novel MTA with fast-setting property and better understanding the accelerated hydration process have both clinical and scientific significance. Despite of the importance of setting property, other chemical-physical properties such as radiopacity, ion release, and biocompatibility are also essential for the successful application of MTA. These properties should also be taken into account when designing a new formulation of MTA. Therefore, the aim of this study is to formulate a fast-setting MTA which could fulfil the requirements of dental application. The formulation is using calcium silicates (CaSi), calcium aluminates (CaAl) and zirconium oxide (ZrO2) as its solid phase. The setting time, radiopacity, cytotoxicity and ion release of the cements were evaluated. The hydration process was investigated by X-ray diffraction (XRD), scanning electron microscope (SEM)/ energy dispersive X-ray analysis (EDX) and fourier-transform infrared spectroscopy (FTIR). 2. MATERIALS AND METHODS 2.1 Sample preparation CaSi (white Portland cement, Aalborg Portland) and CaAl (TERNAL®WHITE, Kerneos) were sieved (200 µm), and mixed together with ZrO2 by a Turbula mixer (Willy A.Bachofen AG, Swizerland). Five groups with different weight percentages of CaSi were formulated, see Table 1. The liquid part was the mixture of 10 ml polyacrylic acid solution (Advanced Healthcare Ltd) and 30 ml 10 wt% sodium hydroxide solution. All the cements were prepared by mixing the

liquid with solid phase (P:L=3:1) on a plastic pad using a stainless spatula. The cements were filled into molds and stored in water for predetermined times after final setting. When preparing



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samples for XRD, SEM and FTIR measurement, the cements were crushed into powders after final setting.

Table 1 Compositions of the groups with different weight percentages of CaSi Composition (wt%) Groups CaSi

CaAl

ZrO2

0% CaSi

0

80

20

20% CaSi

20

60

20

40% CaSi

40

40

20

60% CaSi

60

20

20

80% CaSi

80

0

20

2.2 Setting times Setting times was determined by the Gilmore needle method

21

. Briefly, a light needle with

113.4 g in weight and 2.12 mm in tip diameter was used to measure the initial setting time, while a heavy one with 453.6 g in weight and 1.06 mm in tip diameter was used to determine the final setting time. The needle was placed on the surface of cement every one minute. The cement was considered as set when no mark could be observed on the surface of cements. 2.3 pH measurement Disc-shaped specimens (Ø = 6 mm, h = 1 mm) were prepared and exposed to 7.5 ml distilled water at 37 °C. The water was replaced every day and the pH was measured every two days. 2.4 Ion release Disc-shaped specimens (Ø = 8 mm, h = 3 mm) were prepared and each sample was exposed to 20 ml distilled water. Samples were then placed in incubator at 37 °C for 1 day or 7 days.


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Soaking water was collected for ion release measurement. Ion concentrations were measured by inducted coupled plasma-atomic emission spectroscopy (ICP-AES, Spectro Analytical Instrument, Kleve, Germany), measuring atomic Ca at 396.847 nm, Al at 167.078 nm, Mg at 279.553 nm and Si at 251.612 nm. 2.5 Radiopacity The radiopacity was measured as suggested by ISO 1997-1; 2007

22

. To measure the

radiopacity, three disc-shaped specimens (Ø = 10 mm; h = 1 mm) for each group were prepared. After setting, the specimens were placed on an X-ray imaging plate adjacent to a calibrated aluminum step wedge with 0.5 mm increments and irradiated using a micro computed tomography (SkyScan 1172, Bruker microCT, Kontich, Belgium). The tube voltage was set at 65 kV. Radiographs were taken and a standard curve (amount of light vs. mm Al) was generated. The amounts of light of the specimens were determined using the curves feature in Adobe Photoshop CS4 software. The radiopacity (in mm Al) then can be read through the standard curve. 2.6 Particle size distribution Particle size and distributions of calcium silicates, calcium aluminates and ZrO2 were measured by laser diffraction (Mastersizer microplus, Malvern, UK) using isopropanol as a dispersant. 2.7 X-ray Diffraction The phase analysis of raw materials and the cements were conducted using a D8 diffractometer (Bruker Corporation, Billerica, United States). The step size was 0.02 degree and the scan speed was 2 s per step. 2.8 Scanning electron microscopy



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Morphologies of cements were studied using a scanning electron microscopy (SEM, LEO 1550, Zeiss, Oberkochen, Germany) equipped with a backscattered electron (BSE) detector. The samples were coated with gold and palladium to prevent charging. 2.9 IR spectroscopy IR spectra were obtained by a Fourier transform infrared spectrometer (Varian 610-IR FTIR, Santa Clara, California, United States). The spectra (400 - 4000 cm-1) were obtained at a resolution of 4 cm-1, using average signal of 64 scans. 2.10 In vitro study The cytotoxicity of the cements was evaluated by indirect contact assay using cement leaching liquid. Herein, we used murine pre-osteoblast (C2C12 cells) as a model. The cells were cultured in complete DMEM/F12 medium (Gibco, ThermoFisher Scientific, USA) supplemented with 10% fetal bovine serum (Thermo Scientific Hyclone) and 1 % penicillin/streptomycin (Thermo Scientific Hyclone). All the cements were sterilized by autoclaving. The cement leaching liquids were prepared by immersing a cement disk with 12mm diameter and 2 mm height into 1 mL of complete cell culture media, corresponding to 3 cm2/mL of surface-to-volume ratio to fulfill the ISO standard ISO-10993-11. 3200 C2C12 cells 200 µL complete cell culture were added into each well of 96-well plate and cultured in 5% CO2 humidified atmosphere at 37 °C. After culturing 24 h, the medium was refreshed with the obtained (100%), diluted twofold (50%) and diluted fivefold (20%) cement leaching liquids. The cell viabilities were measurement using AlamarBlue® (ThermoFisher Scientific, USA) assay after incubation for 24 h. Briefly, the cells were incubated with 10% (w/v) AlamarBlue® DMEM/F12 medium solution for 2 h, and the fluorescence intensity was determined by a spectrophotometer (Tecan plate reader, Männedorf,


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Switzerland) with 560 nm excitation wavelength and 590 nm emission wavelength. The complete medium was used as a control. 2.11 Statistic analysis One-way analysis of variance (ANOVA) followed by Turkey post-hoc test was used to do the statistic analysis. 3. RESULTS 3.1 Characterization of raw materials Particle size distribution: All the ZrO2 particles had a diameter smaller than 4 µm, see Fig.1 (a). 90% of the CaSi particles had a diameter that is smaller than 26.7 µm (D0.9 = 26.7 µm) while 90% of the CaAl particles fall under the size of 26.0 µm (D0.9 = 26.0 µm). Phase compositions: The ZrO2 particles were single phase without any impurities, see Fig.1 (b). The CaSi cement was composed of Ca3SiO5, Ca2SiO4 and a small amount of CaSO4, see Fig.1 (c). The principle phase of CaAl cement is Calcium Aluminate (CaAl2O4, CA) and Grossite (CaAl4O7, CA2), see Fig.1 (d). 3.2 Setting times CaSi cement without CaAl required 25 minutes for initial setting and 237 min for final setting, see Fig.2. The setting time decreased with the increase of CaAl. 40% CaSi cements showed the shortest initial and final setting times, 5 min and 15 min respectively. Further increase the amount of CaAl resulted in increase of the setting time. CaAl cement without CaSi showed 51 min in initial setting and 210 min for final setting. 3.3 Characterization of cements before and after hydration X-ray diffraction pattern: The crystal phases in hardened CaSi cement were C3S and C2S. In pure CaAl cement the main phases were CA, CA2 and 3CaO•Al2O3•6H2O (C3AH6), see Fig.3.



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ZrO2 showed diffraction peak with very high intensity, indicating it was inert during the hydration process. SEM: Unhydrated particles and hydrated flowerlike plates could be seen in 0% CaSi and 20% CaSi samples, see Fig.4 (a) and (b). In 40% CaSi and 60% CaSi samples, honeycomb-like network could be observed, see Fig.4 (c) and (d). Irregular particles and some fiber-like network were co-existed in pure CaSi hardened cement, see Fig.4 (e). ZrO2 particles uniformly distributed in the cement’s matrix, see Fig.4. (f). FTIR: As shown in Fig.5, the broad peaks at around 916 cm-1 and 874 cm-1 were due to Si-O stretching in the clinker phase and C-S-H gel 23. The adsorption at 1416 cm-1 was from thee C-O bond of carbonate. The peak observed near 746 cm-1 was attributed to AlO4- tetrahedral groups and the peaks near 515 cm-1 and 447 cm-1 were due to AlO6- octahedral groups 24. Peaks at 2324 cm-1 and 2361 cm-1 were attributed to CO2. 3.4 pH measurement and ion release The pH of CaSi cement without CaAl were 11.5 at the 2nd day and 11.6 at the 4th day, see Table 2. Although the incorporation of CaAl resulted in slight decrease in pH, the pH of all the cements were still above 11 at the 4th day. 80% CaSi specimen showed the lowest Al (7.5 mg/L for 1 day, 11.5 mg/L for 7 days) and the highest Ca concentration (102.8 mg/L for 1 day, 350.3 mg/L for 7 days) for all times (p < 0.05), see Fig.6. 0% CaSi cement showed the highest Al (111.4 mg/L) for 1 day (p < 0.05), but there were no significant differences among the cements with 0%, 20 % and 40% CaSi for 7 days. No significant difference (p ˃ 0.05) of Ca concentration existed among the 0%, 20%, 40%, 60% CaSi groups for all times. All the cements showed similar Si and Mg release after storage in water for 1 day and 7 days. Cements with 60% CaSi showed the highest Si release (53.7 mg/L) after 7 days.


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Table 2 pH of the samples after storage in water for 2 days and 4 days pH Groups

2nd day

4th day

0% CaSi

10.9

11.1

20% CaSi

11.0

11.0

40% CaSi

10.8

11.1

60% CaSi

11.0

12.0

80% CaSi

11.5

11.6

3.5 Radiopacity All the cements showed a radiopacity larger than 3 mm Al, see Fig.7. No significant difference could be observed among all the groups. 3.6 In vitro study Cell viability after incubation pre-osteoblast cells in cement extracts with different dilutions were shown in Fig.8. The cell viability slightly increased using 50% extract compared with that of undiluted extract. In undiluted extracts, cell viability of 60% CaSi and 80% CaSi samples were lower than that of other samples (p < 0.05). The sample with 60% CaSi showed the lowest cell viability. Using 50% extracts, samples with 0% CaSi showed slightly higher viability than samples with 40% and 60% CaSi. No significant difference can be observed among other groups.



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When culturing cells with 20% extracts, there were no significant differences in viability among all the samples. 4. DISCUSSION Setting time is crucial for the clinical application of mineral trioxide aggregate. On one hand, it should be long enough to ensure adequate time to complete the filling process. On the other hand, prolonged setting time results in cement wash-out and makes the surgery more complicated. Therefore, novel MTA which has accelerated setting properties, excellent chemical-physical and biological properties is still urgently required. Our study proposed a new type of MTA with improved setting properties, adequate radiopacity and good biocompatibility. The results showed that the initial and final setting time of calcium silicates (CaSi) and calcium aluminates (CaAl) composite cements shortened to 5 min and 15 min respectively. A minimum setting time was achieved when calcium silicates was account for 40% of the solid phase (Fig.2). As showed by other researchers, the setting time of MTA is influenced by many factors such as powder to liquid ratio 25, moisture and modifier 26. The particle size distribution and mechanical grinding time, which determine the specific surface area and reactivity of particles, also have large effects on the setting time of MTA 27-28. Usually the smaller the particle size and the larger the surface area, the faster the setting and the more water are required to mix with the cement 29. 90% of the CaSi and CaAl particles used in this study had a diameter smaller than 27 µm (Fig.1), and these particles had relatively broad distributions compared with some commercial MTA30, indicating the setting reaction could be further adjusted by using particles with selected particle size distribution. Ordinary Portland cements set through a hydration process between C3S, C2S and water. The hydration product calcium silicate hydrate (C-S-H) is a largely amorphous gel which provides


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most of the mechanical strength of ordinary Portland cement. The structure of C-S-H is still not clear and the mean Ca/Si ratio of C-S-H in Portland cement varies from 0.7 to 2.3

31

. X-ray

diffraction was used in this study to identify the crystal phases in the hardened cements. The XRD showed some C3S, C2S, CA, CA2, C3HA6 and ZrO2 crystals existed in hardened 40% CaSi cements (Fig.3). However, due to the multiple phases existing in the system, it is not easy to identify all the hydration products through XRD. The C-S-H was not observed in X-ray diffraction pattern, maybe due to its poor crystallinity during the early hydration period or overlapping of diffraction peaks. ZrO2 showed strong diffractions peaks, indicating ZrO2 is not involved in the hydration process. It usually takes 28 days for C3S to fully hydrate and longer for C2S to hydrate, therefor it could be expected that the C3S, C2S, CA and CA2 would continue to hydrate to strength the network. Four morphological types of C-S-H gel have been identified by other researchers on fracture surfaces of cement pastes. Fiber and honeycomb C-S-H gels are the normal early products 32. In this study, various hydration products and unreacted particles coexisted in the hardened cements (Fig.4). However, the honeycomb C-S-H network was only observed in the hardened 40% and 60% CaSi cements, which indicates the accelerated setting time was due to accelerated formation of C-S-H gel. From backscattered SEM figure (Fig.4 (f)), it could be seen that ZrO2 was distributed evenly in hardened cement, providing radiopacity for the cements. pH is crucial for the antibacterial property and bioactivity of MTA. All the modified cements showed pH above 11 at the 4th day, which are higher compared with most types of MTA

33

.

MTA are able to release various ions for long time during its storage. The released Ca is beneficial for the apatite formation between the MTA and dentin. Moreover, Ca released during the setting could diffuse into the dentin and increase its concentration within time, making MTA



a potential candidate in inflammatory root resorption treatment

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34

. Our results confirmed the

continuous release of Ca in the calcium silicate cement, around 350.3 mg/L for 7 days, as shown Fig.6 (b). The incorporation of CaAl resulted in the decrease of Ca. However, the release of Ca was still higher compared with other types of MTA

9, 35-36

. All the cements release a small

amount of silicon and magnesium and the amount of these ions were similar among the samples. The incorporation of CaAl resulted in the increase of Al concentration (Fig.6(b)), however, the concentrations of Al are too low to be toxic

37

. The low cytotoxicity was further confirmed by

our cytotoxicity study (Fig.8). All the undiluted samples showed a slight cytotoxicity, but not for the twofold diluted samples. This concentration-dependent cytotoxicity of MTA has been discussed by other researchers, showing that probably the slight decrease in cell viability is due to the high pH of undiluted extract

11, 38

. Calcium silicate cements have demonstrated excellent

biocompatibility 10 and this is further confirmed by our study. In addition, our results show that the new type of MTA cement which contains calcium aluminates has comparative biocompatibility as calcium silicate cements. Radiopacity is also crucial for the applications of MTA in endodontics. Calcium silicate cements are radio-transparent therefore additional radiopacifiers are required for the MTA to provide adequate radio-opacity. These radiopacifiers, such as ZrO2, BiO2 and BaSO4, usually includes inorganic salts with high atomic number which distinguish the cements on a radiograph 39-41

. In this study, 20% ZrO2 provides adequate radio-opacity for the cements, making it suitable

to be used in endodontic applications. 4. CONCLUSIONS In this study, a novel fast-setting MTA using calcium silicates, calcium aluminates and zirconia as its solid phases is developed. The MTA are able to set within 10 min by forming a


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honeycomb-like C-S-H network. It shows low Al release, sufficient radiopacity and biocompatibility, which make it a promising material for dental applications.

* Corresponding Authors Håkan Engqvist

E-mail address: [email protected]

Song Chen

E-mail address: [email protected]

Present Address † Department of Chemistry, Konstanz University, Konstanz, Germany Figure captions Fig.1 Size distribution of the particles (a) and X-ray diffraction patterns of ZrO2 (b), CaSi (c), CaAl (d). Fig.2 Initial and final setting times determined by Gilmore needles. Fig.3 XRD diffraction patterns of the cements after setting for 4 h at ambient atmosphere. Fig.4 Morphologies of MTA cements after setting for 4 h at ambient atmosphere. (a)-(e) In-lens electron micrographs: (a) 0% CaSi (b) 20% CaSi (c) 40% CaSi (d) 60% CaSi (e) 80% CaSi (f) Back-scattered electron micrographs of hardened 40% CaSi cement, showing the distribution of ZrO2 (white particles) in cement matrix. Fig.5 FTIR spectra of MTA cements after setting for 4 h at ambient atmosphere. Fig.6 Ion concentrations of different samples (mg/L) considering (a) Al, (b) Ca, (c) Si and (d) Mg. Different letters indicate significant differences (P˂ 0.05). (E.g. group labeled with a,b has no significant difference with group labeled with b, but having significant difference with group labeled with c). Fig.7 Radiopacity of cements with different amounts of CaSi (mm Al). Fig.8 Viability of pre-osteoblast C2C12 cells cultivated for 24 h in cement extracts with 0%, 20%, 40%, 60% and 80% calcium silicates. The extracts were used undiluted (100 %), twofold diluted (50 %) and fivefold diluted (20 %). Samples with the same diluted multiple, different letters indicate significant difference (P ˂ 0.05).



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(17) Hsieh, S. C.; Teng, N. C.; Lin, Y. C.; Lee, P. Y.; Ji, D. Y.; Chen, C. C.; Ke, E. S.; Lee, S. Y.; Yang, J. C. A novel accelerator for improving the handling properties of dental filling materials. J Endod 2009, 35 (9), 1292-1295. (18) Camilleri, J. The physical properties of accelerated Portland cement for endodontic use. Int Endod J 2008, 41 (2), 151-157. (19) Gandolfi, M. G.; Taddei, P.; Siboni, F.; Modena, E.; Ciapetti, G.; Prati, C. Development of the foremost light-curable calcium-silicate MTA cement as root-end in oral surgery. Chemicalphysical properties, bioactivity and biological behavior. Dent Mater 2011, 27 (7), e134-157. (20) Jafarnia, B.; Jiang, J.; He, J.; Wang, Y. H.; Safavi, K. E.; Zhu, Q. Evaluation of cytotoxicity of MTA employing various additives. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009, 107 (5), 739-744. (21) American Society for Testing and Materials. ASTM C266-03: Standard test method for time and setting of hydrauliccement paste by Gilmore needles. 2006. (22) International Organization for Standardization. ISO 9917-1: Dentistry: Water-based cements. Part 1. Powder/liquid acid–base cements. 2007. (23) Ren, Q.; Zou, H.; Liang, M.; Wang, Y.; Wang, J. Preparation and characterization of amphoteric polycarboxylate and the hydration mechanism study used in portland cement. RSC Adv. 2014, 4 (83), 44018-44025. (24) Tarte, P. Infra-Red Spectra of Inorganic Aluminates and Characteristic Vibrational Frequencies of Alo4 Tetrahedra and Alo6 Octahedra. Spectrochim Acta a-M 1967, A 23 (7), 2127-&. (25) Fridland, M.; Rosado, R. Mineral trioxide aggregate (MTA) solubility and porosity with different water-to-powder ratios. J Endod 2003, 29 (12), 814-817. (26) Brykov, A. S.; Vasil’ev, A. S.; Mokeev, M. V. Hydration of portland cement in the presence of aluminum-containing setting accelerators. Russ. J. Appl. Chem. 2013, 86 (6), 793-801. (27) Kelly, J. R. Ceramics in restorative and prosthetic dentistry. Annu Rev Mater Sci 1997, 27, 443-468. (28) Mammen, J. Nano-White Mta: A Review. International Journal of Advanced Research 2018, 6 (2), 1564-1571. (29) Ha, W. N.; Bentz, D. P.; Kahler, B.; Walsh, L. J. D90: The strongest contributor to setting time in mineral trioxide aggregate and portland cement. J Endod 2015, 41 (7), 1146-1150. (30) Komabayashi, T.; Spangberg, L. S. Comparative analysis of the particle size and shape of commercially available mineral trioxide aggregates and Portland cement: a study with a flow particle image analyzer. J Endod 2008, 34 (1), 94-98. (31) Richardson, I. G. Tobermorite/jennite- and tobermorite/calcium hydroxide-based models for the structure of C-S-H: applicability to hardened pastes of tricalcium silicate, β-dicalcium silicate, Portland cement, and blends of Portland cement with blast-furnace slag, metakaolin, or silica fume. Cem. Concr. Res. 2004, 34 (9), 1733-1777. (32) Taylor, H. F. W. Cement chemistry, 2nd ed.; Thomas Telford Publishing,: London, 1997. (33) Gandolfi, M. G.; Siboni, F.; Primus, C. M.; Prati, C. Ion release, porosity, solubility, and bioactivity of MTA Plus tricalcium silicate. J Endod 2014, 40 (10), 1632-1637. (34) Ozdemir, H. O.; Ozcelik, B.; Karabucak, B.; Cehreli, Z. C. Calcium ion diffusion from mineral trioxide aggregate through simulated root resorption defects. Dent Traumatol 2008, 24 (1), 70-73.



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(35) Vitti, R. P.; Prati, C.; Sinhoreti, M. A.; Zanchi, C. H.; Souza, E. S. M. G.; Ogliari, F. A.; Piva, E.; Gandolfi, M. G. Chemical-physical properties of experimental root canal sealers based on butyl ethylene glycol disalicylate and MTA. Dent Mater 2013, 29 (12), 1287-1294. (36) Massi, S.; Tanomaru-Filho, M.; Silva, G. F.; Duarte, M. A.; Grizzo, L. T.; Buzalaf, M. A.; Guerreiro-Tanomaru, J. M. pH, calcium ion release, and setting time of an experimental mineral trioxide aggregate-based root canal sealer. J Endod 2011, 37 (6), 844-846. (37) Kanjevac, T.; Milovanovic, M.; Milosevic-Djordjevic, O.; Tesic, Z.; Ivanovic, M.; Lukic, A. Cytotoxicity of glass ionomer cement on human exfoliated deciduous teeth stem cells correlates with released fluoride, strontium and aluminum ion concentrations. Arch. Biol. Sci. 2015, 67 (2), 619-630. (38) Eid, A. A.; Gosier, J. L.; Primus, C. M.; Hammond, B. D.; Susin, L. F.; Pashley, D. H.; Tay, F. R. In vitro biocompatibility and oxidative stress profiles of different hydraulic calcium silicate cements. J Endod 2014, 40 (2), 255-260. (39) Camilleri, J. Characterization and hydration kinetics of tricalcium silicate cement for use as a dental biomaterial. Dent Mater 2011, 27 (8), 836-844. (40) Cutajar, A.; Mallia, B.; Abela, S.; Camilleri, J. Replacement of radiopacifier in mineral trioxide aggregate; characterization and determination of physical properties. Dent Mater 2011, 27 (9), 879-891. (41) Camilleri, J.; Cutajar, A.; Mallia, B. Hydration characteristics of zirconium oxide replaced Portland cement for use as a root-end filling material. Dent Mater 2011, 27 (8), 845-854.

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Fig.1 Size distribution of the particles (a) and X-ray diffraction patterns of ZrO2 (b), CaSi (c), CaAl (d). 202x141mm (300 x 300 DPI)

ACS Paragon Plus Environment


Fig.2 Initial and final setting times determined by Gilmore needles. 208x159mm (300 x 300 DPI)


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Fig.3 XRD diffraction patterns of the cements after setting for 4 h at ambient atmosphere. 226x207mm (300 x 300 DPI)



Fig.4 Morphologies of MTA cements after setting for 4 h at ambient atmosphere. (a)-(e) In-lens electron micrographs: (a) 0% CaSi (b) 20% CaSi (c) 40% CaSi (d) 60% CaSi (e) 80% CaSi (f) Back-scattered electron micrographs of hardened 40% CaSi cement, showing the distribution of ZrO2 (white particles) in cement matrix. 254x190mm (220 x 220 DPI)


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Fig.5 FTIR spectra of MTA cements after setting for 4 h at ambient atmosphere. 201x141mm (300 x 300 DPI)



Fig.6 Ion concentrations of different samples (mg/L) considering (a) Al, (b) Ca, (c) Si and (d) Mg. Different letters indicate significant differences (P˂ 0.05). (E.g. group labeled with a,b has no significant difference with group labeled with b, but having significant difference with group labeled with c). 206x158mm (300 x 300 DPI)


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Fig.7 Radiopacity of cements with different amounts of CaSi (mm Al). 201x141mm (300 x 300 DPI)



Fig.8 Viability of pre-osteoblast C2C12 cells cultivated for 24 h in cement extracts with 0%, 20%, 40%, 60% and 80% calcium silicates. The extracts were used undiluted (100 %), twofold diluted (50 %) and fivefold diluted (20 %). Samples with the same diluted multiple, different letters indicate significant difference (P ˂ 0.05). 206x158mm (300 x 300 DPI)


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Novel Fast-Setting Mineral Trioxide Aggregate: Its Formulation

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