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Hydration characteristics of Biodentine and Theracal used as pulp capping materials Josette Camilleri ∗ Department of Restorative Dentistry, Faculty of Dental Surgery, University of Malta, Medical School, Mater Dei Hospital, Msida MSD 2090, Malta

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Article history:

Objectives. Investigation of the hydration and characterization of Theracal and Biodentine

Received 10 November 2013

used for pulp capping.

Accepted 27 March 2014

Methods. The setting mechanism and characterization of set Biodentine and Theracal after

Available online xxx

immersion in Hank’s balanced salt solution (HBSS) for 28 days was investigated by scan-

Keywords:

The bioactivity and surface microstructure of cements immersed in HBSS or water was

ning electron microscopy (SEM) of polished specimens and X-ray diffraction (XRD) analysis. Tricalcium silicate

also assessed by similar techniques together with leaching in solution investigated by ion

Hydration

chromatography (IC).

Theracal

Results. Biodentine hydration resulted in the formation of calcium hydroxide which was

Biodentine

present in the material matrix and also on the material surface. Theracal was composed of large cement particles which showed some evidence of reaction rims on hydration. The material matrix included a barium zirconate phase as radiopacifier and also a glass phase composed of strontium, silicon and aluminum. This phase could not be detected in XRD analysis. Formation of a calcium phosphate phase was demonstrated on Theracal immersed in HBSS. Both materials leached calcium ions in solution. Conclusions. The presence of a resin matrix modifies the setting mechanism and calcium ion leaching of Theracal. The clinical implications of these findings need to be investigated. © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

1.

Introduction

Calcium hydroxide has been the material of choice as a pulp capping material. More recently mineral trioxide aggregate (MTA) has been suggested for use as a pulp capping material [1]. MTA mixed with water hydrates to form calcium silicate hydrate and calcium hydroxide [2–4]. The clinical success rates of MTA and calcium hydroxide used as pulp capping materials have been shown to be comparable [5,6]. MTA is



composed mostly of tricalcium silicate. Tricalcium silicate cement exhibits a similar hydration profile to MTA [7]. The main disadvantage of using MTA as a pulp capping material is its extended setting time. MTA utilized as a pulp capping material needs to be layered with other materials while still fresh. Layering of MTA with zinc oxide eugenol cements and glass ionomer cements has been shown to affect the setting of the material [8]. Zinc is taken up by MTA from the adjacent zinc oxide cement and retards the hydration further. On the other hand MTA causes micro-cracking of glass

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http://dx.doi.org/10.1016/j.dental.2014.03.012 0109-5641/© 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Please cite this article in press as: Camilleri J. Hydration characteristics of Biodentine and Theracal used as pulp capping materials. Dent Mater (2014), http://dx.doi.org/10.1016/j.dental.2014.03.012

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ionomer cement at the interface [8]. Materials based on tricalcium silicate with a reduced setting time have thus been introduced. Biodentine, which is composed of tricalcium silicate, zirconium oxide and calcium carbonate mixed with water, chloride accelerator and water-soluble polymer exhibits a clinically acceptable setting time and physical properties [9]. It hydrates also in a similar way to MTA [10,11]. Biodentine has been investigated clinically and it elicits dentin bridge formation over the dental pulp in a similar manner as MTA [12]. Layering of Biodentine with composite resin without any surface treatment resulted in an adequate seal [13]. Biodentine exhibited micro-leakage and surface erosion when etched with 37% phosphoric acid used under composite resin restorations [14]. Acid etching has also been shown to affect the compressive strength and surface micro-hardness of ProRoot MTA [15]. Light curable tricalcium silicate-based materials are indicated for use as liner under composite restorations aiming to achieve a bond between the different layers of materials thus reducing micro-leakage. Theracal, a light curable resin modified Portland cement-based material has been investigated and it was shown to release significantly more calcium than ProRoot MTA and Dycal and thus was able to alkalinize the surrounding fluid [16]. Regardless the calcium ion release contact of Theracal with pulp cells resulted in a reduction in cell metabolism and reduced protein expression [17].

Although calcium release has been shown in Theracal, the setting mechanism and characterization of set material is still not known. The aim of this research was to investigate the setting mechanisms and characterize Theracal and compare it to Biodentine, which is also proposed for use as a pulp capping material.

2.

Methodology

The materials used in this study included:

TheraCalTM (Bisco, Schaumburg, IL, USA) and Biodentine (Septodont, Saint Maur-des-Fosses, France)

Biodentine was mixed according to manufacturer’s instructions. The Theracal was dispensed from the syringe and light cured with a LED light-curing unit for 20 s per increment. Cylindrical specimens 10 mm in diameter and 2 mm high were prepared and immersed in Hank’s balanced salt solution (HBSS; H6648, Sigma–Aldrich, St. Louis, MO, USA) for 28 days at 37 ◦ C. For surface morphological analysis and ion chromatography additional specimens immersed in water were also prepared.

Fig. 1 – Back scatter scanning electron micrographs and energy dispersive spectroscopic analysis of the different microstructural features of set Theracal and Biodentine stored in Hank’s balanced salt solution for 28 days at 37 ◦ C.

Please cite this article in press as: Camilleri J. Hydration characteristics of Biodentine and Theracal used as pulp capping materials. Dent Mater (2014), http://dx.doi.org/10.1016/j.dental.2014.03.012

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2.1.

Characterization of materials

The set materials were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analysis.

2.1.1.

Microscopy and elemental analysis

The specimens were vacuum desiccated and embedded in resin (Epoxyfix, Struers GmbH, Ballerup, Denmark) and then were ground using progressively finer diamond discs and pastes using an automatic polishing machine (Tegramin 20, Struers GmbH, Ballerup, Denmark). The polished specimens

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were attached to aluminum stubs, carbon coated and viewed under the scanning electron microscope (SEM; Zeiss MERLIN Field Emission SEM, Carl Zeiss NTS GmbH, Oberkochen, Germany). Scanning electron micrographs of the different material microstructural components at different magnifications in back-scatter electron mode were captured and energy dispersive spectroscopy was carried out.

2.1.2.

X-ray diffraction (XRD) analysis

Phase analysis was carried out using X-ray diffraction. The materials were dried in a vacuum desiccator and crushed to a very fine powder using an agate mortar and pestle. The

Fig. 2 – X-ray diffractograms of Biodentine and Theracal showing the main phases present. For Biodentine a close up of the region between 30 and 40◦ 2Â is shown embedded in the image. Please cite this article in press as: Camilleri J. Hydration characteristics of Biodentine and Theracal used as pulp capping materials. Dent Mater (2014), http://dx.doi.org/10.1016/j.dental.2014.03.012

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diffractometer (Rigaku, Tokyo, Japan) used Cu K␣ radiation at 40 mA and 45 kV and the detector was set to rotate between 15 and 45◦ , with a sampling width of 0.05◦ and scan speed of 1◦ /min at 15 revs/min. Phase identification was accomplished using a search-match software utilizing ICDD database (International Center for Diffraction Data, Newtown Square, PA, USA).

2.2.

Characterization of material surface

2.2.1.

Microscopy and elemental analysis

After storage in HBSS or water for 28 days the specimens were dried in a vacuum desiccator, mounted on aluminum stubs, carbon coated and viewed under the scanning electron microscope. Scanning electron micrographs of the material surface at different magnifications in secondary electron mode were captured and energy dispersive spectroscopy was carried out.

2.2.2.

X-ray diffraction (XRD) analysis

Surface analysis of materials immersed in water or HBSS was performed by glancing angle XRD at a fixed angle of 3◦ . The materials were dried in a vacuum desiccator and surface assessment of the materials was performed using an X-ray diffractometer (Rigaku, Tokyo, Japan) used Cu K␣ radiation at 40 mA and 45 kV from 15 to 45◦ 2Â with a sampling width 0.05◦ , scan speed 1◦ /min. The other settings included divergent slits at 1 mm, divergent height slit 10 mm, scintillator slit 8 mm and receiver slit 13 mm. Phase identification was accomplished using a search-match software utilizing ICDD database (International Center for Diffraction Data, Newtown Square, PA, USA).

2.3.

Assessment of leaching

Assessment of leaching was performed using ion chromatography on leachate recovered from pre-weighed specimens immersed in 5 mL water or HBSS for 28 days. Calcium ion release was calculated taking into consideration the sample weight and volume of solution used. A blank solution was also tested and the calcium ions recovered from the blank solutions reduced from the results of the test materials.

3.

Results

3.1.

Characterization of materials

Biodentine was characterized by extensive reaction product and occasional radiopacifier particles (Fig. 1). EDS analysis of the different microstructural elements exhibited the presence of calcium, oxygen and carbon interspersed in a matrix rich in silicon and calcium. This was verified by X-ray diffraction analysis (Fig. 2) where the different phases namely tricalcium silicate (ICDD: 31-0301), zirconium oxide (ICDD: 37-1484), calcium carbonate (ICDD: 005-0686) and Portlandite (ICDD: 441481) were observed. The Portlandite peak at circa 18◦ 2Â was very intense reaching around 12,000 counts per second. This together with the low intensity of tricalcium silicate phase denotes high reactivity of the material. The Theracal exhibited a complex microstructure with the presence of various particles (Fig. 1). The cement particles varied in size and some particles were larger than the cement particles present in Biodentine. The cement

Fig. 3 – Secondary electron scanning electron micrographs of set materials stored in water and HBSS for 28 days at 37 ◦ C showing surface microstructural features. Please cite this article in press as: Camilleri J. Hydration characteristics of Biodentine and Theracal used as pulp capping materials. Dent Mater (2014), http://dx.doi.org/10.1016/j.dental.2014.03.012

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particles exhibited some reaction byproduct. The cement matrix included shiny particles with barium, and zirconium peaks and other particles which exhibited peaks for silicon, strontium aluminum and calcium. The presence of aluminum in the cement analysis suggests that the main cementitious phase is a Portland cement which includes tricalcium aluminate together with tricalcium and dicalcium silicate phases. The XRD analysis (Fig. 2) exhibited peaks for tricalcium silicate (ICDD: 073-2077), zirconium oxide (ICDD: 011-8815) and

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barium strontium zirconium oxide (ICDD: 001-7473). No calcium hydroxide peak was evident for Theracal.

3.2.

Characterization of material surface

The surface of Biodentine immersed in water was coated by very small particles, which exhibited peaks for calcium and silicon while the Theracal surface was bare. Both materials

Fig. 4 – Surface X-ray diffractograms of Biodentine and Theracal showing the main phases present. Please cite this article in press as: Camilleri J. Hydration characteristics of Biodentine and Theracal used as pulp capping materials. Dent Mater (2014), http://dx.doi.org/10.1016/j.dental.2014.03.012

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Fig. 5 – Calcium ion leaching in solution.

exhibited the presence of globular deposits on their surfaces when immersed in HBSS (Fig. 3). The surface XRD scans of Biodentine (Fig. 4) exhibited peaks for calcium hydroxide and tricalcium silicate regardless the immersing solution. On the other hand Theracal exhibited no crystalline deposits when immersed in water (Fig. 4). Storage in HBSS resulted in the deposition of calcium phosphate on the material surface. Peaks for barium strontium zirconium oxide were also observed.

3.3.

Assessment of leaching

The results for calcium ion leaching in water and HBSS are shown in Fig. 5. Biodentine leached more calcium in both solutions when compared to Theracal. The leaching was marginally higher in physiological solution for both materials.

4.

Discussion

Two characterization techniques namely scanning electron microscopy and EDS analysis together with X-ray diffraction analysis were used to assess the materials. The scanning electron microscopy of polished sections is a suitable technique with which hydration of cement can be assessed. This technique has been used to assess hydration kinetics of MTA [3] and tricalcium silicate cement [7]. X-ray diffraction is useful to characterize crystalline materials. In the current study both powder diffractometry and glancing angle X-ray diffraction analysis was performed. The powder diffractometry resulted in analysis of crystalline phases within the test material while the glancing angle X-ray diffraction allowed surface scanning of the materials at a fixed angle thus surface characterization of crystalline structures coating the material surface was possible. Hydration of Biodentine resulted in the formation of calcium silicate hydrate and calcium hydroxide. This is in agreement with other studies investigating the hydration of Biodentine [10,11]. Biodentine reacted with water and released calcium hydroxide, which was evident in the X-ray diffractogram. The Biodentine surface did not encourage crystal deposition as evidenced by the results of glancing angle XRD.

This indicates that although calcium hydroxide is produced in large quantities by the material it is not deposited on the material surface. This feature very likely is related to material porosity. Biodentine is less porous than other tricalcium silicate-based materials [18]. The low porosity is due to the presence of a water reducing agent added to the mixing liquid of Biodentine [19]. This water-based polymer increases the material flow thus for a given material workability less water needs to be added. The reduction in water quantity reduces the material porosity [20]. Materials with low porosity do not encourage crystal deposition and attachment. A high calcium ion release was verified by ion chromatography. Theracal exhibited a complex microstructure. There were various additives present in the material matrix including barium strontium zirconium oxide and zirconium oxide. The zirconium oxide is not listed as an additive by the manufacturer. It could be present from improper sintering of the barium zirconate phase during material preparation. The radiopacifer in Theracal is noted as barium zirconate by the manufacturer however strontium was found in EDS analyses. The scanning electron micrographs show the presence of a glass present in the material matrix which consisted of silicon, aluminum, strontium and calcium. This phase was not identified in EDS analysis thus it is very likely an amorphous phase. Theracal did not exhibit any formation of calcium hydroxide on hydration; however cement particles exhibited some reaction by-product which was less than that exhibited for Biodentine. Calcium phosphate was deposited over the Theracal surface. A recent study on Theracal showed an alkalinizing pH, which neutralized after a few days [16]. The high pH is indicative of calcium releasing ability. Thus it can be postulated that calcium ions are released in solution and are responsible for the calcium phosphate deposition. The calcium ions are not in the hydroxide form as no Portlandite (calcium hydroxide peak) was demonstrated in the XRD scans of the powdered Theracal after 28 day immersion in HBSS. The leaching of calcium ions was much lower in Theracal than in Biodentine. This is in contrast to a previous study reporting a higher calcium releasing ability of Theracal compared to MTA and Dycal [16]. Although MTA and Dycal were not investigated in the current study, the calcium ion release of Biodentine was comparable to that reported for MTA [4]. The leaching of calcium ions in the study investigating Theracal, MTA and Dycal [16] used a calcium ion probe for analysis. Calcium ion probes are not as effective in measuring leachate levels as ion chromatography used in the current study and inductively coupled plasma (ICP) used to assess the calcium ion leaching of MTA [4].

5.

Conclusions

The presence of a resin matrix modifies the setting mechanism and calcium ion leaching of Theracal. The clinical implications of these findings need to be investigated.

Please cite this article in press as: Camilleri J. Hydration characteristics of Biodentine and Theracal used as pulp capping materials. Dent Mater (2014), http://dx.doi.org/10.1016/j.dental.2014.03.012

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Acknowledgements Nicholas Gautier of Septodont and Ralph Rawls of the University of Texas for the materials. The University of Malta Research Grant committee for funding. Ing. James Camilleri of the Department of Metallurgy and Materials Engineering, Faculty of Engineering, University of Malta and Ms Colette Grima of the Department of Chemistry, Faculty of Science for their technical expertise. ERDF (Malta) for the financing of the testing equipment through the project: “Developing an Interdisciplinary Material Testing and Rapid Prototyping R&D Facility” (Ref. no. 012). The author declares no conflict of interest.

references

[1] Torabinejad M, Chivian N. Clinical applications of mineral trioxide aggregate. J Endod 1999;25:197–205. [2] Camilleri J, Montesin FE, Brady K, Sweeney R, Curtis RV, Pitt Ford TR. The constitution of mineral trioxide aggregate. Dent Mater 2005;21:297–303. [3] Camilleri J. Hydration mechanisms of mineral trioxide aggregate. Int Endod J 2007;40:462–70. [4] Camilleri J. Characterization of hydration products of mineral trioxide aggregate. Int Endod J 2008;41:408–17. [5] Al-Hezaimi K, Salameh Z, Al-Fouzan K, Al Rejaie M, Tay FR. Histomorphometric and micro-computed tomography analysis of pulpal response to three different pulp capping materials. J Endod 2011;37:507–12. [6] Mente J, Geletneky B, Ohle M, Koch MJ, Friedrich Ding PG, Wolff D, Dreyhaupt J, Martin N, Staehle HJ, Pfefferle T. Mineral trioxide aggregate or calcium hydroxide direct pulp capping: an analysis of the clinical treatment outcome. J Endod 2010;36:806–13. [7] Camilleri J. Characterization and hydration kinetics of tricalcium silicate cement for use as a dental biomaterial. Dent Mater 2011;27:836–44.

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[8] Camilleri J. Scanning electron microscopic evaluation of the material interface of adjacent layers of dental materials. Dent Mater 2011;27:870–8. [9] Grech L, Mallia B, Camilleri J. Investigation of the physical properties of tricalcium silicate cement-based root-end filling materials. Dent Mater 2013;29:e20–8. [10] Grech L, Mallia B, Camilleri J. Characterization of set IRM, Biodentine, Bioaggregate and a prototype calcium silicate cement for use as root-end filling materials. Int Endod J 2013;46:632–41. [11] Camilleri J, Sorrentino F, Damidot D. Investigation of the hydration and bioactivity of radiopacified tricalcium silicate cement, Biodentine and MTA Angelus. Dent Mater 2013;29:580–93. [12] Nowicka A, Lipski M, Parafiniuk M, Sporniak-Tutak K, Lichota ´ D, Kosierkiewicz A, Kaczmarek W, Buczkowska-Radlinska J. Response of human dental pulp capped with biodentine and mineral trioxide aggregate. J Endod 2013;39:743–7. [13] Raskin A, Eschrich G, Dejou J, About I. In vitro microleakage of Biodentine as a dentin substitute compared to Fuji II LC in cervical lining restorations. J Adhes Dent 2012;14:535–42. [14] Camilleri J. Investigation of Biodentine as dentine replacement material. J Dent 2013;41:600–10. [15] Kayahan MB, Nekoofar MH, Kazandag˘ M, Canpolat C, Malkondu O, Kaptan F, Dummer PM. Effect of acid-etching procedure on selected physical properties of mineral trioxide aggregate. Int Endod J 2009;42:1004–14. [16] Gandolfi MG, Siboni F, Prati C. Chemical-physical properties of TheraCal, a novel light-curable MTA-like material for pulp capping. Int Endod J 2012;45:571. [17] Hebling J, Lessa FC, Nogueira I, Carvalho RM, Costa CA. Cytotoxicity of resin-based light-cured liners. Am J Dent 2009;22:137–42. [18] Camilleri J, Grech L, Galea K, Keir D, Fenech M, Formosa L, Damidot D, Mallia B. Assessment of porosity and sealing ability of tricalcium silicate-based root-end filling materials. Clin Oral Investig 2014. PMID: 24100638. [19] Camilleri J, Kralj P, Veber M, Sinagra E. Characterization and analyses of acid-extractable and leached trace elements in dental cements. Int Endod J 2012;45:737–43. [20] Paillere AM. Applications for admixtures in concrete. RILEM Report 10 E & FN Spon 1994.

Please cite this article in press as: Camilleri J. Hydration characteristics of Biodentine and Theracal used as pulp capping materials. Dent Mater (2014), http://dx.doi.org/10.1016/j.dental.2014.03.012

Hydration characteristics of Biodentine and Theracal used as pulp capping materials.

Investigation of the hydration and characterization of Theracal and Biodentine used for pulp capping...
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