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Physicochemical Properties of Calcium Silicate Cementsfor Endodontic TreatmentChun-Cheng Chen, DDS, PhD,* Chia-Che Ho, MS,

Chan-Hen David Chen, PhD,

and

Shinn-Jyh Ding, PhD

AbstractIntroduction: The purpose of this study was to examinethe physicochemical properties of novel calcium silicatecements (CSCs) prepared by using a sol-gel method.Methods: The compressive strength, morphology, andphase composition of various cements were evaluatedafter mixing with water, in addition to setting timeand pH value. Results: As solid phases, the sol-gelderived powders mainly consisted of b-dicalcium sili-cate. Setting times for cements mixed with water ranged

from 1242 minutes and were lower for cements withhigher starting CaO content. The compressive strengthof the CSCs ranged from 0.315.2 MPa; these valueswere significantly different (P < .05). Calcium silicatehydrate (C SH) was the principal phase that formedin the hydration process. The CSCs pH values changedfrom an initial 11 to a high of 13. Conclusions: CSCsdisplay advantageously shortened setting times andmight have potential for endodontic use, althoughfurther tests are necessary to confirm this. (J Endod2009;35:12881291)

Key Words

Calcium silicate, mineral trioxide aggregate, Portlandcement, root-canal filling material

Calcium silicatebased Portland cement, which has been shown to be biocompatible(14), contains tricalcium silicate, dicalcium silicate, and tricalcium aluminate.Mineral trioxide aggregate (MTA) powder is basically a mixture of Portland cementand bismuth (III) oxide (5, 6) and has been used successfully in dental applicationsfor the past decade. MTA is composed of a variety of oxide components, typicallySiO2, CaO, and Al2O3. In a previous study (7), SiO2, CaO, and Al2O3 were used toconstruct a new MTA-like material by high-temperature solid state sintering. TheMTA-like cement displayed an advantageously shortened setting time, although it wasweaker than white-colored MTA. Among the oxides, aluminum (Al), a neurotoxin, is

detrimental to human health because of its ability to disrupt cellular calcium homeo-stasis (8) and promote cellular oxidation (9). It has been suggested that Al mightcontribute to Parkinsons and Alzheimers disease (10). Therefore, removal of Alfrom the cement is necessary.

The sol-gels are transformed into ceramics by heating at relatively low tempera-tures and have better chemical and structural homogeneity than ceramics obtainedby conventional glass melting or ceramic powder methods such as solid state sintering.It has been reported that materials prepared by a sol-gel process are more bioactivethan materials of thesame compositionspreparedby other methods (11). Thepurposeof this study was to examine the physicochemical properties of Al-free calcium silicatecements (CSCs), which powders werepreparedby using a sol-gel method, withdifferentmolar ratios of SiO2:CaO ranging from 7:33:7.

Materials and MethodsSpecimen Preparation

The sol-gel method has been described elsewhere (12). Reagent grade tetraethylorthosilicate (Si(OC2H5)4; Sigma-Aldrich, St Louis, MO) and calcium nitrate (Ca(N-O3)2$4H2O; Showa, Tokyo, Japan) were used as precursors for SiO2 and CaO, respec-tively. Nitric acid was used as the catalyst and ethanol as the solvent. For simplicity,throughout this study, the sintered powders and the cements derived from suchpowders were designated by the same codes, as listed in Table 1. Briefly, Si(OC2H5)4was hydrolyzed with the sequential addition of 2 mol/L HNO3 and absolute ethanol,with 1 hour of stirring separately. The required amount of Ca(NO3)2$4H2O was addedto the above solution, and the mixed solutions were stirred for an additional hour. Thesolsolution wassealed andaged at 60 C for1 day. After vaporizationof thesolvent in anoven at 120 C, the dried gel was heated in air to 800 C at a heating rate of 10 C/min

for 2 hours by using a high-temperature furnace and then cooled to room temperaturein the furnace to produce a powder. The sintered granules were then ball-milled for 12hoursin ethyl alcohol by using a RetschS 100centrifugal ball mill (Hann,Germany) anddried in an oven at 60 C.

Phase Composition and MicrostructureTo investigate the phase composition, the specimens were ground to fine powders

and then characterized with an x-ray diffractometer (XRD; Shimadzu XD-D1, Kyoto,Japan). Fourier transform infrared spectroscopy (FTIR, Bomem DA8.3; Hartman &Braun, Quebec, Canada) was used to analyze the powders. Scanning electron micros-copy (SEM; JEOL JSM-6700F, Tokyo, Japan) was used to characterize the microstruc-ture of the various specimens.

From the *Department of Dentistry and Institute of OralBiology and Biomaterials Science, Chung-Shan MedicalUniversity; and Institute of Veterinary Microbiology, NationalChung-Hsing University, Taichung, Taiwan, Republic of China.

Address requests for reprints to Prof Shinn-Jyh Ding, Insti-tute of Oral Biology and Biomaterials Science, Chung-ShanMedical University, Taichung 402, Taiwan, Republic of China.E-mail address: [email protected]/$0 - see front matter

Crown Copyright 2009 Published by Elsevier Inc. onbehalf of the American Association of Endodontists.

doi:10.1016/j.joen.2009.05.036

Basic ResearchTechnology

1288 Chen et al. JOEVolume 35, Number 9, September 2009
mailto:[email protected]:[email protected]


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Setting Time and pH VariationAll specimens were hand-mixed at a liquid-to-powder ratio of

0.5 g/mL, with distilled water as the liquid phase. After mixing,the cement was placed into a cylindrical stainless steel mold (diam-eter, 6 mm and height, 12 mm) and stored in an incubator at 100%relative humidity and 37C. The setting times of the cements were

tested by using a 400-gauge Gillmore needle with a 1-mm diameter,according to ISO 9917-1 for water-based cements. The pH values ofthe cement specimens during the setting process were measuredwith a pH meter (IQ120 miniLab pH meter; IQ Scientific Instru-ments, San Diego, CA). Triplicate measurements were used.

Compressive StrengthCompressive strength (CS) was measured on an EZ-Test machine

(Shimadzu) at a loading rate of 0.5 mm/minute.

Statistical AnalysisOne-way analysis of variance statistical analysis was used to eval-

uate the significance of differences between the mean CS or setting

time values. Scheffemultiple comparison testing was used to determinethe significance of the deviations in the data for each specimen. In allcases, the results were considered statistically significant at a P valueless than .05.

ResultsPhase Composition and Morphology

Fig. 1A shows the XRD patterns of the 5 SiO2CaO powders sin-tered at 800 C and indicates that the phase evolution is dependenton the Si/Ca ratio of the precursors. The major diffraction peaks at2q between 32 and 34 were attributed to the b-dicalcium silicate(b-Ca2SiO4) phase. The peak intensities of b-Ca2SiO4 and CaO

increased with increasing CaO content in the precursors. The trendsin the FTIR spectra (Fig. 1B) are similar to those indicated by XRD.For the specimen with the greatest amount of silica (S70C30), thebroad IR absorption band corresponding to SiO4 asymmetric stretch-ing extended over a wide wave-number range of 1300950 cm1. Anobvious sharpening and shifting to lower frequency in SiOSi asym-metric stretching bands were detected as the silica contentdecreased.

When the powder solid was mixed with water, the products of thehydration process were CSH at 29.3 and incompletely reacted inor-ganic component phases (Fig. 2A). The lower the Si/Ca ratio was in theprecursor, the higher the CSH content was in the cement. Except forS70S30 cement, which had a loose and rough surface (Fig. 2B), allother specimens had a smooth appearance with entangled particles

(Fig. 2CF). Moreover, it seemed that S50C50 had a denser structurethan the other cements.

Setting TimeThesetting times of the5 CSCcementsranged from 1242 minutes

(Table 1); these values were significantly different (P< .05).

TABLE 1. Composition (molar ratio), Setting Time (Ts), and CompressiveStrength (CS) of the 5 CSCs after Mixing with Water

Specimen codeComposition

(SiO2:CaO) Ts (min) CS (MPa)

S70C30 7:3 42 2a

0.3 0.1f

S60C40 6:4 31 2b

9.4 2.1g

S50C50 5:5 24 2c

15.2 2.5h

S40C60 4:6 16 2d

12.0 2.6i

S30C70 3:7 12 2e

3.2 0.5j

Values are mean standard deviation. Eight specimens were measured for setting time data. At least

20 specimens were used for CS measurement. Mean values followed by the same superscript letter

were not significantly different (P> .05) according to Scheffe post hoc multiple comparisons.

Figure 1. (A) XRD patterns and (B) Fourier transform infrared spectra of 5calcium silicate powders sintered at 800 C.R, CaO;;, b-Ca2SiO4.


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Compressive StrengthTable 1 also shows the CS values of cement specimens. One-way

analysis of variance of the CS data showed that the variations in strengthbetween specimens are significant (P< .05).

pH VariationThere wasno significant difference (P> .05)between the pH values

of different CSCs at the same time periods. The pH value at fresh mixingwas between 10.4 and 11.1, indicating a slight increase with an increasedCaO amount. After 1 hour of setting, all cements reached a pH value of12.0. By 6 hours, they approached a steady state of up to pH 13.6.

DiscussionIn the1990s, Torabinejad et al(13, 14) developed a Portland-like

cement known as MTA. After that, the formulation of hydraulic calcium

(alumino) silicate cements was investigated with respect to their poten-tial clinical use in dental surgery applications (2, 3, 12, 1518).

In this study, the sol-gel technique was used to prepare 5 differentcalcium silicate powders. The XRD analyses indicatedthat S70C30, con-taining the highest amount of SiO2, had an amorphous phase withoutcharacteristic peaks. With a greater amount of CaO than SiO2, thediffraction peaks ofb-Ca2SiO4 became stronger, even with a small totalamount of CaO. Similarly, the CaO peak intensities increased withincreasing CaO content of the powders.

In the FTIR spectra, the broad band of 1300950 cm1 furthersplit into 2 appreciable adsorption bands, indicating increased crystal-linity with increasing CaO content, which is in agreement with the XRDresults. A new band at 850 cm1 emerged that was associated with theSiOsymmetricstretching mode, withone non-bridgingsiliconoxygenbond (SiONBO) (19). The band at 550500 cm1 originated fromthe vibration of the siloxane backbone (20). The presence of Ca2+ as

Figure 2. (A) XRD patterns of 5 CSCs. SEMs of (B) set S70C30, (C) S60C40, (D) S50C50, (E) S40C60, and (F) S30C70 cements.R, CaO;;, b-Ca2SiO4;>,C SH.


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the network modifier in the silicates led to a disruption in the continuityof the glassy network as a result of breaking of some of the SiOSibonds and resulted in the formation of SiONBO (19). The bandsbetween 1550 and 1380 cm1 might have arisen from the vibrationalmode of the CO3 group, which came from atmospheric carbonation.The XRDand FTIR results of thepowders consistentlyindicated calciumamounts significantly affected the phase evolution.

The present CSCs exhibited distinctly shortened setting times as

compared with the setting time of MTA (>2 hours) (21). This fastset reduces the risk of dislodgement and contamination when cementsare used as root-end filling material (22). Particle size, sinteringtemperature, liquid phase, and composition of powders, as well asthe ratio of liquid to powder, played crucial roles in the setting timeof the paste materials (23). When the powder and liquid phases weremixed in an appropriate ratio, they formed a paste that hardened byentanglement of the crystals precipitated in the paste at body or roomtemperature, as observed by SEM (Fig. 2B F). The entanglementstructure, consisting of fine particle agglomerates, could be considereda hydration product of a C SH gel (Fig. 2A) that might be respon-sible forcausingthe particlesto adhereto oneanother. In analogy to thesetting reaction of calcium silicatebased Portland cement (24), it isspeculated that the product was related to the hardening mechanism

of the present CSCs. The setting time was significantly inversely propor-tional to Si/Ca ratio. This result might be interpreted by the amount (orcrystallinity) of the b-Ca2SiO4 phase that could affect the formation of C SH gel. Higher C SH content in the final hydrated product willyield a better and faster hydration reaction with a shorter setting time(25), as observed in the present 5 cements. The peak at 2q = 37.5

was attributed to a CaCO3 phase, which decreased after mixing withwater, and might have also contributed to the shortened setting time.

The 5 CSCs were alkaline, possibly as a result of the release ofcalcium ions (24, 26), similar to MTA(7, 14, 16). The S30C70 cementhad a slightly higher pH because of its high CaO content, which trans-formed into Ca(OH)2 when set.

Thecement specimen with thegreatestSiO2 content (S70C30) had

a strength of only 0.3 MPa, whereas the specimen with the lowest SiO2content (S30C70) reached a strength of 3.2 MPa. It is worth noting thatthe highest CS value was 15.2 MPa and belonged to the equimolar ratioof SiO2/CaO (S50C50), which appeared denser in structure than theothers. Although the detailed mechanism underlying the changes inCS has not been fully clarified, differences in surface structure, suchas porosity of the hydration products, might play a crucial role in themechanical properties of cement (27). The mechanical strength ofthe cements examined here decreased with increasing porosity.

The Al-free hydraulic CSCs that exhibited shortened setting timeswere successfully developed. Among the 5 cements studied, bothS40C60 and S30C70 might prove the most useful for endodontic treat-ment requiring a setting time of a few minutes, such as root-end filling/

sealing and pulp capping/cavity lining. Additional studies, includingbiocompatibility tests, are currently underway to evaluate the clinicalpotential of quick-set CSCs.

References1. Camilleri J, Pitt Ford TR. Mineral trioxide aggregate: a review of the constituents and

biological properties of the material. Int Endod J 2006;39:74754.2. Ribeiro DA, Duarte MAH, Matsumoto MA, Marques MEA, Salvadori DMF. Biocom-

patibility in vitro tests of mineral trioxide aggregate and regular and white Portlandcements. J Endod 2005;31:6057.

3. Chen CL, Huang TH, Ding SJ, Shie MY, Kao CT. Comparison of calcium and silicatecement and mineral trioxide aggregate biologic effects and bone markers expres-sion in MG63 Cells. J Endod 2009;35:6825.

4. Gandolfi MG, Perut F, Ciapetti G, Romano Mongiorgi R, Prati C. New Portlandcement-based materials for endodontics mixed with articaine solution: a study ofcellular response. J Endod 2008;34:3944.

5. ProRoot MTA, product literature. Tulsa, OK: Dentsply Tulsa Dental; 2004.6. Islam I, Chng HK, Yap AUJ. Comparison of the physical and mechanical properties of

MTA and Portland cement. J Endod 2006;32:1937.7. Kao CT, Shie MY, Huang TH, Ding SJ. Properties of an accelerated mineral trioxide

aggregate-like root-end filling material. J Endod 2009;35:23942.8. Guo GW, Liang YX. Aluminum-induced apoptosis in cultured astrocytes and its effect

on calcium homeostasis. Brain Res 2001;888:2216.9. Zatta P, Kiss T, Suwalsky M, Berthon G. Aluminum (III) as a promoter of cellular

oxidation. Coord Chem Rev 2002;228:27184.10. Forbes WF, Gentleman JF. Risk factors, causality, and policy initiatives: the case of

aluminum and mental impairment. Exp Gerontol 1998;33:14154.11. Li P, de Groot K. Better bioactive ceramics through sol-gel process. J Sol-Gel Sci

Technol 1994;2:797806.12. Ding SJ, Shie MY, Wang CY. Novel fast-setting calcium silicate bone cements with

high bioactivity and enhanced osteogenesis in vitro. J Mater Chem 2009;19:118390.

13. Torabinejad M, White DJ. Tooth filling material and method of use. U.S. patent no.5,415,547; 1995.

14. Torabinejad M, Hong CU, McDonald F, Pitt Ford TR. Physical and chemical prop-erties of a new root-end filling material. J Endod 1995;21:34953.

15. Asgary S, Parirokh M, Eghbal MJ, Brink F. Chemical differences between white andgray mineral trioxide aggregate. J Endod 2005;31:1013.

16. Ding SJ, Kao CT, Shie MY, Hung C Jr., Huang TH. The physical and cytological prop-erties of white MTA mixed with Na2HPO4 as an accelerant. J Endod 2008;34:74851.

17. Chng HK, Islam I, Jin Yap AU, Tong YW, Koh ET. Properties of a new root-end fillingmaterial. J Endod 2005;31:6658.

18. Al-Rabeah E, Perinpanayagam H, MacFarland D. Human alveolar bone cells interactwith ProRoot and tooth-colored MTA. J Endod 2006;32:8725.

19. Pereira MM, Clark AE, Hench LL. Homogeneity of bioactive sol-gel-derived glasses in

the system CaO-P2O5-SiO2. J Mater Syn Process 1994;2:18996.20. Yoshino H, Kamiya K, Nasu H. IR study on the structural evolution of sol-gel derived

SiO2 gels in the early stage of conversion to glasses. J Non-Cryst Solids 1990;126:6878.

21. Huang TH, Shie MY, Kao CT, Ding SJ. The effect of setting accelerator on propertiesof mineral trioxide aggregate. J Endod 2008;34:5903.

22. Camilleri J. The physical properties of accelerated Portland cement for endodonticuse. Int Endod J 2008;41:1517.

23. Bohner M. Reactivity of calcium phosphate cements. J Mater Chem 2007;17:39806.

24. Older I. Hydration, setting and hardening of Portand cement. In: Hewlett PC, ed.Leas chemistry of cement and concrete. 4th ed. Oxford: Butterworth-Heinemann;2007:24197.

25. Lin FH, Wang WH, Lin CP. Transition element contained partial-stabilized cement(PSC) as a dental retrograde-filling material. Biomaterials 2003;24:21933.

26. Asgary S, Shahabi S, Jafarzadeh T, Amini S, Kheirieh S. The properties of a new

endodontic material. J Endod 2008;34:9903.27. Ishikawa K, Asaoka K. Estimation of ideal mechanical strength and critical porosityof calcium phosphate cement. J Biomed Mater Res 1995;29:153743.


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