Compositional Characteristics and Hydration Behavior of Mineral Trioxide Aggregates

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provided by Elsevier - Publisher Connector J Dent Sci 2010;5(2):53−59

REVIEW ARTICLE

Compositional characteristics and hydration behavior of mineral trioxide aggregates

Wen-Hsi Wang,1 Chen-Ying Wang,2 Yow-Chyun Shyu,2 Cheing-Meei Liu,2 Feng-Huei Lin,3 Chun-Pin Lin2,4*

1Orthopedic Device Technology Division, Medical Electronics and Device Technology Center, Industrial Technology Research Institute, Hsinchu, Taiwan 2Department of Dentistry, National Taiwan University Hospital, Taipei, Taiwan 3Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan 4School of Dentistry and Graduate Institute of Clinical Dentistry, National Taiwan University, Taipei, Taiwan

Received: Jan 21, 2010 Mineral trioxide aggregate (MTA) was one of most popular biomaterials for end- Accepted: Apr 5, 2010 odontic treatment in the past decade. Its superb biocompatibility, sealing ability and surface for tissue adhesion all make MTA a potential candidate for many dental KEY WORDS: applications, such as apexification, perforation repair, repair of root resorption, apexification; and as a root-end filling material. There are many review articles regarding the compositional characteristics; physical, chemical and biological properties of MTA. However, there are few reviews discussing the relationship between the composition and hydration behav- hydration behavior; ior of MTA. The aim of this article was to provide a systematic review regarding the mineral trioxide aggregates; compositional characteristics and hydration behavior of MTA. perforation repair

Introduction proper selection of materials plays a very important role in the success of the surgery. The procedure Endodontic surgery and root-end filling usually involves root-end exposure and resection, material as well as preparing a Class I cavity and placing root- end filling material.3 Hence, these materials should There are about 24 million endodontic procedures form a proper seal of the root canal content from performed in the US on an annual basis, with up to periradicular tissues and repair root defects.4 Under- 5.5% of these procedures involving endodontic apical standably, this material should also be biocompat- surgery, perforation repair, and apexification treat- ible with periodontal tissues. Moreover, dimensional ment.1 Endodontic surgeries, including retrograde stability, solubility in tissue fluid, non-resorbability filling and perforation repair, are major options for and radiopaque are very important criteria for root- failed teeth and those that cannot be treated with end filling material.2 conventional endodontic procedures. Moreover, surgical procedures also provide a better visual field and Mineral trioxide aggregate greatly reduce misadventures, such as root perforation, during canal instrumentation and post-space Many materials have been used for retrograde fill- preparation.2 In most endodontic surgical procedures, ing and perforation repair, but none of them meet

*Corresponding author. School of Dentistry and Graduate Institute of Clinical Dentistry, National Taiwan University, No. 1, Chang-Te Street, Taipei 10016, Taiwan. E-mail: [email protected]

©2010 Association for Dental Sciences of the Republic of China 54 W.H. Wang et al all of the criteria of an ideal material. Mineral tri- WMTA. A study by Oviir et al.23 in 2006 showed that oxide aggregate (MTA), developed at Loma Linda OCCM-30 cementoblast and OKF6/TERT1 keratino- University, California, USA, in 1993, is a potential cytes grew better on the surface of WMTA than GMTA. alternative to conventional materials,5 and received Moreover, there are also studies which show that cell approval by the US Food and Drug Administration as proliferation significantly increased when exposed ProRoot MTA (Tulsa Dental Products, Tulsa, OK, USA).6 to WMTA.23,24 Apoptosis was not induced in two cell The setting time of MTA is around 4 hours. The prop- lines after 24 hours of exposure to WMTA, and DNA erties of MTA vary with the particle size, powder synthesis also increased, which suggests a positive to water ratio, temperature, water presence, and effect on cellular proliferation.24 This was also in ac- entrapped water.7 In clinical applications, MTA is cordance with the result that WMTA had more of a mixed with supplied sterile water in a powder to stimulating effect on human dental pulp cells than liquid ratio of 3:1, and it is recommended that a did a commercial calcium hydroxide preparation.22,25 moist cotton pellet be placed in direct contact with MTA has been widely investigated for over 15 the material until the next follow-up appointment. years. However, the relationship between the composition and hydration behavior was seldom discussed. Properties of MTA The aim of this article is to present a systematic review of the compositional characteristics and There were many studies regarding clinical applica- relationships with hydration behaviors of MTA. tions of MTA in the past decade. Torabinejad et al.8 found statistically and significantly less leakage with MTA than with SuperEBA (Harry J. Bosworth Co., Compositional characteristics Skokie, IL, USA), intermediate restorative material (IRM; LD Caulk Co., Milford, DE, USA), and amalgam. Components of MTA Moreover, studies by Torabinejad et al.9,10 and Fischer et al.11 proved that MTA was superior compared with MTA is derived from ordinary Portland cement with a SuperEBA and IRM. MTA also showed better mar- slight difference in composition. MTA is mainly com- ginal adaptation with or without finishing when composed of three powdered ingredients, which are 75% pared with SuperEBA and IRM.12 Several in vitro and Portland cement, 20% bismuth oxide, 5% gypsum, and 26 in vivo studies demonstrated that the sealing ability trace amounts of SiO2, CaO, MgO, K2SO4 and Na2SO4. and biocompatibility of MTA are superior to those The major constituent responsible for the setting and of amalgam, IRM, and SuperEBA.13−15 In a study by biologic properties is from the Portland cement, and Torabinejad et al.15 in 1995, rhodamine B fluores- bismuth is added only for its radiopaque property. cent dye and a confocal microscope were used to There are four major components in Portland evaluate the sealing ability of amalgam, SuperEBA, cement: tricalcium silicate [(CaO)3•SiO2; abbrevi- and MTA as root-end filling material. On the other ation C3S], dicalcium silicate [(CaO)2•SiO2; abbrevi- hand, significantly higher microleakage was found ation C2S], tricalcium aluminate [(CaO)3•Al2O3; with amalgam compared with MTA using a fluid abbreviation C3A], and tetracalcium aluminofer- 16 conductive system in a study by Yatsushiro et al. rite [(CaO)4•Al2O3•Fe2O3; abbreviation C4AF]. Each in 1998. It also interestingly showed that the level of component is discussed in the following section. fluid conductance was very close to that of the neg- Tricalcium silicate is the most important constit- ative control group, and this was also confirmed in uent of Portland cement. It is the major component several bacterial leakage models.8,11,16,17 in the formation of calcium silicate hydrate (C-S-H) Evidence of healing of the surrounding tissue which gives early strength to Portland cement.27 was shown when MTA was used as a root-end filling There are seven polymorphs of tricalcium silicate material.15,18,19 In a study by Economides et al.,20 known, i.e., T1, T2, T3 (triclinic), M1, M2, M3 (mono- the presence of connective tissue was discovered clinic) and R (rhombohedral), depending on the after the first postoperative week. MTA showed presence of impurities.28 The symmetry of the crystal a high success rate as a root-end filling material in increases with a rise in temperature. The structure of a 2-year follow-up study.21 tricalcium silicate is stable (with respect to dicalcium silicate and calcium oxide) in the temperature range Gray MTA and white MTA of 1250−1800ºC, and it incongruently melts at 2150ºC. The high-temperature form of tricalcium silicate is Up to 2002, there was only one form of MTA that con- stabilized by the solid solution of impurities present sisted of gray-colored powder (gray MTA [GMTA]), in the raw materials. Tricalcium silicate with impuri- but in that year, white MTA (WMTA) was introduced ties is usually referred to as alite. The formation of because of esthetic concerns.22 There are also many solid solutions can effectively increase the per- studies that examined differences between GMTA and centage of tricalcium silicate in Portland cement.29 Mineral trioxide aggregates 55

There are five polymorphs of dicalcium silicate, oxide, and magnesium oxide. The resulting Portland 30 designated α, α′H, α′L, β, and γ. Dicalcium sili- cement can differ according to where the rock was cate hydrates much more slowly than tricalcium quarried. This indicates that there will be impuri- silicate and is responsible for the latter’s strength. ties which may be toxic when Portland cement is The impure form of dicalcium silicate is referred to applied to medical applications. This point of view as belite, the β form of which is usually found, but was also reinforced by X-ray photoelectron spectros- occasionally the α′ form is found. Belite is stabilized copy, energy-dispersive X-ray analysis and inductively by foreign ions in solid solution with respect to γ-C2S. coupled plasma optical emission spectroscopy re- Generally, there is a higher content of foreign ions sults regarding the exact composition of cements taken into solid solution than with alite. Cations, tested and the resulting physical and chemical such as Al3+, Fe3+, Mg2+ and K+, and anions, such specifications in a study by Dammaschke et al.35 in 2+ 3− SO4 and PO4 , stabilize dicalcium silicate at high 2005. Modifications to Portland cement and subse- temperatures. No link was found among the impu- quent extensive tests had to be conducted to ensure rity content, dislocation density, and reactivity of that the resultant materials met the requirements different kinds of dicalcium silicate.29 set out by the US Food and Drug Administration for Tricalcium aluminate is the most reactive con- medical devices. If the setting time and compres- stituent in Portland cement. Tricalcium aluminate sive strength are improved, clinical applications usually exists as a cubic form in Portland cement. could be expanded,38 such as for restorative mate- The structure of tricalcium aluminate is composed rials.39 On the other hand, MTA has a smaller mean 2+ 30 of rings of six AlO4 tetrahedrals and Ca ions. Even particle size and fewer toxic impurities, and un- though tricalcium aluminate reacts vigorously with dergoes extra processing/purification compared with water, it contributes very little to the strength. regular Portland cement. Actually, the US patent The reactivity of tricalcium aluminate with water is for MTA states that the Blaine number of Portland ce- decreased by the incorporation of sodium, but evi- ment which is used for manufacturing MTA should dence showed that the early reactivity increased.29 be in the range of 450−460 m2/kg.40,41 Moreover, Calcium aluminoferrite belongs to a series of the compressive strength is also much greater than 38,39 42 C2A−C2F (2CaO · Al2O3−2CaO · Fe2O3) solid solutions. Portland cement. In a study by Danesh et al. The structure of C2F is stable under ambient condi- in 2006, Portland cement was significantly more tions, but the structure of C2A is only stable at high soluble, achieved lower microhardness values, and pressure.29 Calcium aluminoferrite forms a solid so- was less radiopaque than MTA. lution series of formulae of Ca2(AlxFe1−x)2O5 for all value of x in the range of 0−0.7.31 The usual level Compositional differences between GMTA observed in Portland cement is 0.5, and C4AF is used and WMTA for the mineral, which is sometimes referred to as brownmillerite. Calcium aluminoferrite is the only WMTA was named after its tooth-colored appearance. strong color component in the quaternary system. It was reported that the contents of Al2O3, MgO It has moderate reactivity with water, which in- and Fe2O3 are much less than in GMTA (Table 1). The creases with an increasing alumina content, but the lower amounts of Fe2O3 in WMTA are responsible hydraulicity is slight.29

Compositional differences between MTA Table 1. Electron probe microanalysis results of gray and Portland cement mineral trioxide aggregate (GMTA) and white mineral trioxide aggregate (WMTA)

Since Portland cement is the major constituent of Chemical GMTA (wt%) WMTA (wt%) MTA, there are also studies regarding differences between MTA and Portland cement.32−37 According CaO 40.45 44.23 to a study by Dammaschke et al.35 in 2005, the gyp- SiO2 17.00 21.20 sum content of MTA is approximately half that in Bi2O3 15.90 16.13 Al O 4.26 1.92 Portland cement, which indicates that a prolonged 2 3 MgO 3.10 1.35 maximum setting time is required for MTA. Moreover, SO3 0.51 0.53 there were also fewer aluminum species found, Cl 0.43 0.43 and this also leads to longer setting times. FeO 4.39 0.40 Even though Portland cement is the major con- P2O5 0.18 0.21 stituent of MTA, these two materials still greatly TiO2 0.06 0.11 differ. Conventionally, the raw materials of Portland H2O + CO2 13.72 14.49 cement are quarried from local rock, which contains Adapted from Asgary et al.43 calcium oxide, silicon oxide, aluminum oxide, ferric 56 W.H. Wang et al for its tooth-colored appearance. This is because of Table 2. Hydration reactions of each component of free d electrons in the late transitional elements Portland cement (e.g., Cr, Mn, Fe and Cu), the oxide forms of which have strong colors. In contrast, the oxides of ele- Reactions of principal phases in Portland cement ments without easily excited electrons, such as Mg, C3S + H 2O C-S-H* + Ca(OH)2 Al, Si, P, S, K, Ca and Ti, tend to be colorless or + + 44 C2S H 2O C-S-H* Ca(OH)2 white. Moreover, a smaller particle size was also † + + 45 2C3A 18H2O C 2AH8 C 4AH10 observed in a study by Duarte et al. in 2003. In a † + + 2+ + 2− 43 2C3A 32H2O 3(Ca (aq) SO4 (aq)) C 6AS3H32 study by Asgary et al., the particle size distribution C AS H + 2C A† 3C ASH of WMTA was approximately eight times smaller than 6 3 32 3 4 12 that of GMTA, and this could provide more surface *Amorphous hydrogel with a variable composition in terms of † area for hydration reactions and foster greater early the Ca:Si and H2O:SiO2 ratios; C4AF [(CaO)4•Al2O3•Fe2O3] strength. Moreover, a smaller particle size also leads has analogous reactions to C3A, e.g., it produces C6(A,F)S3H32. C = CaO; S = SiO ; H = H O; A = Al O . Adapted from MacPhee.48 to a smoother surface which causes less irritation 2 2 2 3 when in direct contact with living tissues.46 This smaller particle size distribution could also indicate space among cubic crystals.2 The hydration mecha- shorter setting times, but there is still no publicized nism of Portland cement is very complicated be- report on this issue. Even distributions of Mg, Al and cause there are four components in the system, and Fe were shown in WMTA, while dense, localized dis- each component contributes to the hydration reaction. tributions of these three elements were observed in The hydration reaction of each component is 43 6 GMTA. In a study by Camilleri et al., small irregular listed in Table 2. C3S is most reactive, providing particles interspersed with some elongated needle- early strength, but C2S has a better longer-term like particles were observed in WMTA, and small ir- contribution. C-S-H is the principal binding phase of regular particles with some much larger particles as calcium silicate, and it is quantitatively the most well as elongated particles were observed in GMTA. significant hydration product. C-S-H not only forms the majority of the solid volume in the hydrated cement paste but is also the primary strength-giving Hydration behavior phase in Portland cement paste.49 The hydration of C3S is controlled by the growth of C-S-H, which Hydration mechanisms of Portland cement is formed almost immediately during the first wet- ting.50 Minor constituents in the raw material of According to a previous discussion about composi- Portland cement affect its activity and hydration tional differences between MTA and Portland ce- behavior. Cationic impurities are doped in C3S in- ment, many aspects of the compositions greatly corporated into the crystal structure as a defect, differ. For example, there is a lower level of trical- such as a solid solution, and significantly affect the 51 cium aluminate in MTA, and this leads to lower lev- hydration kinetics of C3S. C-S-H formed by the hy- els of ettringite and monosulfate in hydrated MTA, dration of C3S has very poor crystallinity, and only which are the major hydration products of trical- a few broad, weak bands can be detected by the cium aluminate. Moreover, bismuth is also in MTA, X-ray diffraction (XRD) patterns. The reason the but it does not exist in Portland cement. The pres- C-S-H notation is generally used is because of its ence of bismuth acts as an unreacted filler in hy- uncertain composition. The reactivity of C3S can be drated MTA and forms part of the structure of C-S-H. enhanced by rapid cooling.29 The reaction rate of The presence of bismuth also alters the microstruc- C3A is the fastest and generates the most heat, but ture of the paste and calcium oxide, and C-S-H ap- contributes little to the ultimate strength derived pears to be more closely intermixed.47 Other than from this phase, although it significantly contributes these two differences, the major constituents re- to early strength. Calcium silicates are principal sponsible for hydration are almost identical in MTA contributors to long-term strength. The reaction and Portland cement. Hence, the hydration be- rate of C4AF is intermediate between C3S and C2S, havior of MTA can be explained by the hydration but C4AF has an important long-term contribution mechanism of Portland cement. Hydration can be to strength and durability.29 Le Chatelier52 proposed considered the dissolution of anhydrous phases that hydration products, such as C-S-H and calcium followed by crystallization of hydrates as an inter- hydroxide, are precipitated from supersaturated locking mass. The hydrated mass is composed of two solutions produced by tricalcium silicate. Hydrated kinds of crystals. All cubic crystals interlock with calcium silicates immediately cover the surface of each other with a constant angle and direction to unreacted tricalcium silicate particles. After the form the basic framework of hydrated MTA. On surface layer is deposited, the hydration reaction the other hand, needle-like crystal form in thick slows and becomes diffusion-dependent, until reac- bundles with sharp extremities to fill the inter-grain tive species pass through this layer.27 Mineral trioxide aggregates 57

Hydration products Table 3. Setting times for mineral trioxide aggregate mixed with various additives Hydration products of Portland cement vary with the Ca:Si ratio of the surrounding environment. In the Setting time Additive early stage of hydration, the major phase observed is (min) referred to as C-S-H, an amorphous hydration prod- Sterile water 50 uct. According to previous studies, C-S-H is a com- Chlorhexidine gluconate gel − pound with varying stoichiometric values, and the (Consepsis V; Ultradent Products, Ca:Si ratio is generally between 0.8 and 2.1, with a Inc., South Jordan, UT, USA) 53,54 highly variable water (H) content. As the Ca:Si NaOCl gel (ChlorCid V; 20 ratio increases, a hydration product with higher crys- Ultradent Products, Inc.) tallinity, portlandite, is formed and is usually used K-Y jelly (K-Y; Johnson & Johnson, 20 as a hydration index for Portland cement and Portland Inc., New Brunswick, NJ, USA) cement-derived materials.55−57 Portlandite is the 2% lidocaine HCl with 1:100,000 120 natural mineral form of calcium hydroxide. Calcium epinephrine hydroxide is produced as a reaction product of Saline 90 Portland cement and MTA. In studies by Lee et al.2 3% CaCl2 50 5% CaCl 25 and Lin et al.,55 XRD analysis was utilized to deter- 2 mine calcium hydroxide. However, XRD is only useful Adapted from Kogan et al.59 for the crystalline phase of hydration products, which are formed in later stages. Moreover, it is also very Table 4. Compressive strengths for mineral trioxide difficult to quantitatively determine the content aggregate mixed with various additives* of hydration products according to XRD, even though semiquantitative data can be obtained through Compressive Additive software calculations. strength (MPa) ± Environment and reagents Sterile water 28.4 8.2 Chlorhexidine gluconate gel N/A (Consepsis V; Ultradent Products, As described in the previous section, the hydration Inc., South Jordan, UT, USA) behavior of MTA is significantly influenced by the NaOCl gel (ChlorCid V; 17.1 ± 3.8 surrounding environment. Hence, there are studies Ultradent Products, Inc.) regarding the relationship between the environ- K-Y jelly (K-Y; Johnson & Johnson, 18.3 ± 3.4 ment and hydration behavior for improving the han- Inc., New Brunswick, NJ, USA) dling and antibacterial properties of MTA. In a study 2% lidocaine HCl with 1:100,000 32.6 ± 12.7 by Lee et al.2 in 2004, a lower environmental pH epinephrine ± (pH 5) retarded the dissolution of certain components Saline 39.2 7.5 ± in MTA, such as C S, C S and C A, thus inhibiting 3% CaCl2 19.3 3.7 3 2 3 5% CaCl 19.6 ± 2.9 the hydration reaction of MTA. Stowe et al.58 also 2 tried to use chlorhexidine gluconate (0.12%) instead *Data are presented as mean ± standard deviation. N/A = not of sterile water as a mixing agent for MTA, and en- applicable. Adapted from Kogan et al.59 hanced antibacterial activity was found. In a study by Kogan et al.,59 the setting time of MTA was found needle-like crystals are observed because of more to decrease to 20−25 minutes if NaOCl gel, K-Y jelly nucleation sites provided by the high concentra- + − (Johnson & Johnson, Inc., New Brunswick, NJ, USA), tions of Na and Cl in normal saline. On the other and 5% CaCl2 were used as additives (Table 3), but the hand, no crystal structure was observed when MTA compressive strength was also found to be much was hydrated with EDTA. This indicates an inhibi- lower than MTA mixed with water (Table 4). In a study tion of MTA hydration, and this may have been due + by Huang et al.,60 sodium chloride, Tris-HCl buffer, to Ca2 chelation by EDTA.57 15% NaOH, 15% Ca(OH)2, Na2HPO4, and NaH2PO4 were used as the setting accelerators for MTA. Moreover, morphologic observations revealed that MTA hydrated Differences in hydration behaviors with distilled water possessed an epitaxial growth between GMTA and WMTA pattern, which consisted of cubic and needle-like crystals. The cubic structure dominated in the hy- There are also studies examining differences in hydration product of MTA, whereas the needle-like dration behaviors between GMTA and WMTA. It was structure was much scarcer and was likely to form in reported that hydration products of both GMTA the inter-grain spaces between the cubic crystals.2 and WMTA in phosphate-buffered saline (PBS) were When MTA is hydrated in normal saline, many more hydroxyapatite. Moreover, the amounts of calcium 58 W.H. Wang et al released into the PBS by both GMTA and WMTA did 3. Torabinejad M, Hong CU, McDonald F, Pitt Ford TR. Physical not significantly statistically differ (55 ± 12 vs. and chemical properties of a new root-end filling material. − 47 ± 8 mg/L, respectively; P > 0.05). However, it J Endod 1995;21:349 53. 4. Chong BS. A surgical alternative. In: Chong BS, ed. Managing seems that GMTA produces 43% more surface hy- Endodontic Failure in Practice. Chicago: Quintessence droxyapatite crystals than WMTA in an environ- Publishing, 2004:123−47. ment with PBS.61 There are also studies regarding 5. Lee SJ, Monsef M, Torabinejad M. Sealing ability of a min- the setting expansion of GMTA and WMTA.62 It was eral trioxide aggregate for repair of lateral root perfora- − shown that a significant linear setting expansion tions. J Endod 1993;19:541 4. 6. Camilleri J, Montesin FE, Brady K, Sweeney R, Curtis RV, existed between GMTA and WMTA, and this also ex- Ford TRP. The constitution of mineral trioxide aggregate. 63 plains why WMTA had greater leakage than GMTA. Dent Mater 2005;21:297−303. In a study by Watts et al.64 in 2007, WMTA showed 7. Adamo HL, Buruiana R, Schertzer L, Boylan RJ. A compari- a higher mean compressive strength than GMTA. son of MTA, Super-EBA, composite and amalgam as root- end filling materials using a bacterial microleakage model. Moreover, GMTA showed significantly greater linear − 62 Int Endod J 1999;32:197 203. setting expansion than WMTA. 8. Torabinejad M, Rastegar AF, Kettering JD, Pitt Ford TR. Bacterial leakage of mineral trioxide aggregate as a root- end filling material. J Endod 1995;21:109−12. Conclusion 9. Torabinejad M, Higa RK, McKendry DJ, Pitt Ford TR. Dye leakage of four root end filling material: effects of blood contamination. J Endod 1994;20:159−63. MTA is widely used in many clinical applications, such 10. Torabinejad M, Watson TF, Pitt Ford TR. Sealing ability of as apexification, perforation repair, repair of root mineral trioxide aggregate when used as a root end filling resorption, and as a root-end filling material.7,16,65,66 material. J Endod 1993;19:591−5. Its superb sealing ability, biocompatibility, and excel- 11. Fischer EJ, Arens DE, Miller CH. Bacterial leakage of min- lent interactions with tissues were proven in many eral trioxide aggregate as compared with zinc-free amalgam, intermediate restorative material, and Super-EBA as studies. However, it is not easy to handle, with long a root-end filling material. J Endod 1998;24:176−9. 67 setting times, and obtaining consistent results in 12. Gondim EJ, Zaia AA, Gomes BPFA, Ferraz CCR, Teixeira FB, clinical applications can be difficult. According to Souza-Filho FJ. Investigation of the marginal adaptation of the discussion above, there are possible ways to root-end filling materials in root-end cavities prepared overcome these obstacles by changing the composi- with ultrasonic tips. Int Endod J 2003;36:491−9. 13. Koh ET, McDonald F, Pitt FTR, Torabinejad M. Cellular re- tion of MTA. Tricalcium aluminate is the most reac- sponse to mineral trioxide aggregate. J Endod 1998;24:543−7. tive component in MTA, and tricalcium silicate is 14. Osorio RM, Hefti A, Vertucci FJ, Shawley AL. Cytotoxicity of responsible for the early strength during the hydra- endodontic materials. J Endod 1998;24:91−6. tion reaction. Hence, proper changes in the composi- 15. Torabinejad M, Hong CU, Lee SJ, Monsef M, Pitt Ford TR. tions of tricalcium silicate and tricalcium aluminate Investigation of mineral trioxide aggregate for root-end filling in dogs. J Endod 1995;21:603−8. in MTA could enormously change the hydration be- 16. Yatsushiro JD, Baumgartner JC, Tinkle JS. Longitudinal havior. However, there is a limit to the concentration study of the microleakage of two root-end filling materials of tricalcium silicate that can be used because of its using a fluid conductive system. J Endod 1998;24:716−9. toxicity as confirmed by Lee.68 As mentioned above, 17. Lindeboom JAH, Frenken JWFH, Kroon FHM, van den Akker there are efforts to use accelerating agents to im- HP. A comparative prospective randomized clinical study of prove this material,59,60,64 and more evidence is re- MTA and IRM as root-end filling materials in single-rooted teeth in endodontic surgery. Oral Surg Oral Med Oral quired to confirm the outcomes. On the other hand, Pathol Oral Radiol Endod 2005;100:495−500. there are also studies on developing calcium silicate 18. Torabinejad M, Ford TRP. Root end filling materials: a re- alternatives for MTA with better handling properties view. Dent Traumatol 1996;12:161−78. and shorter setting times.55,56,69 This could also be a 19. Torabinejad M, Smith PW, Kettering JD, Pitt Ford TR. solution for further improving clinical applications. Comparative investigation of marginal adaptation of mineral trioxide aggregate and other commonly used root-end Overall, the more we know about the relationship filling materials. J Endod 1995;21:295−9. between the composition and hydration behavior of 20. Economides N, Pantelidou O, Kokkas A, Tziafas D. Short-term MTA, the more we can manipulate the material for periradicular tissue response to mineral trioxide aggregate better performance in endodontic applications. (MTA) as root-end filling material. Int Endod J 2003;36:44−8. 21. Chong BS, Ford TRP, Hudson MB. A prospective clinical study of mineral trioxide aggregate and IRM when used as root-end filling materials in endodontic surgery. Int Endod References J 2003;36:520−6. 22. Roberts HW, Toth JM, Berzins DW, Charlton DG. Mineral 1. Nash KD, Brown LJ, Hicks ML. Private practicing endodon- trioxide aggregate material use in endodontic treatment: tists: production of endodontic services and implications a review of literature. Dent Mater 2008;24:149−64. for workforce policy. J Endod 2002;28:699−705. 23. Oviir T, Pagoria D, Ibarra G, Geurtsen W. Effects of gray 2. Lee YL, Lee BS, Lin FH, Yun Lin A, Lan WH, Lin CP. Effects of and white mineral trioxide aggregate on the proliferation physiological environments on the hydration behavior of min- of oral keratinocytes and cementoblasts. J Endod 2006;32: eral trioxide aggregate. Biomaterials 2004;25:787−93. 210−3. Mineral trioxide aggregates 59

24. Moghaddame-Jafari S, Mantellini MG, Botero TM, McDonald 46. Spangberg L, Langland K, Farinington S. Biologic effects of NJ, Nor JE. Effect of ProRoot MTA on pulp cell apoptosis dental materials, 1. Toxicity of root canal filling materials and proliferation in vitro. J Endod 2005;31:387−91. on HeLa cells in vitro. Oral Surg Oral Med Oral Pathol 25. Takita T, Hayashi M, Takeichi O, et al. Effect of mineral 1973;35:402−14. trioxide aggregate on proliferation of cultured human den- 47. Camilleri J. Hydration mechanisms of mineral trioxide ag- tal pulp cells. Int Endod J 2006;39:415−22. gregate. Int Endod J 2007;40:462−70. 26. Sarkar NK, Caicedo R, Ritwik P, Moiseyeva R, Kawashima I. 48. MacPhee DE. Cement chemistry. Available at: http:// Physicochemical basis of the biologic properties of mineral www.abdn.ac.uk/chemistry/uploads/files/Staff%20Files/ trioxide aggregate. J Endod 2005;31:97−100. cemhon.doc 27. Greenberg SA, Chang TN. The hydration of tricalcium sili- 49. Stepkowska ET, Blanes JM, Real C, Perez-Rodriguez JL. cate. J Phys Chem 1965;69:553−61. Hydration products in two aged cement pastes. J Therm 28. de Noirfontaine MN, Dunstetter F, Courtial M, Gasecki G, Anal Calorim 2005;82:731−9. Signes-Frehel M. Tricalcium silicate Ca3SiO5, the major 50. Gartner EM, Gaidis JM. Hydration mechanisms. In: Skalny component of anhydrous Portland cement: on the conser- J, ed. Materials Science of Concrete I. Westerville, OH: vation of distances and directions and their relationship to America Ceramic Society, 1989:99−125. the structural elements. Z Kristallogr 2003;218:8−11. 51. Katyal NK, Ahluwalia SC, Parkash R. Solid solution and hy- 29. Bye GC. Introduction and composition of Portland cement. dration behaviour of magnesium-bearing tricalcium silicate In: Bye GC, ed. Portland Cement: Composition, Production phase. Cem Concr Res 1998;28:867−75. and Properties. Oxford: Pergamon Press, 1983:7−13. 52. Le Chatelier H. Experimental Researches on the Constitution 30. Odler I. Constituents and composition. In: Odler I, ed. Special of Hydraulic Mortars. New York: McGraw-Hill Publishing, 1905. Inorganic Cements. Oxford: Taylor & Francis, 2000:9−12. 53. Henderson E, Bailey JE. The compositional and molecular 31. Taylor HFW. High temperature chemistry. In: Taylor HFW, ed. character of the calcium silicate hydrates formed in the Cement Chemistry. New York: Academic Press, 1990:28−32. paste hydration of 3CaO · SiO2. J Mater Sci 1993;28:3681−91. 32. Estrela C, Bammann LL, Estrela CRA, Silva RS, Pecora JD. 54. Mehta PK, Monteiro PJM. Concrete: Structure, Properties, and Antimicrobial and chemical study of MTA, Portland ce- Materials, 2nd ed. Englewood Cliffs, NJ: Prentice-Hall, 1993. ment, calcium hydroxide paste, Sealapex and Dycal. Braz 55. Lin FH, Wang WH, Lin CP. Transition element contained Dent J 2000;11:3−9. partial-stabilized cement (PSC) as a dental retrograde-filling 33. Funteas UR, Wallace JA, Fochtman EW. A comparative material. Biomaterials 2003;24:219−33. analysis of mineral trioxide aggregate and Portland ce- 56. Wang WH, Lee YL, Lin CP, Lin FH. Synthesis of partial- ment. Aust Endod J 2003;29:43−4. stabilized cement (PSC) via sol-gel process. J Biomed Mater 34. Saidon J, He J, Zhu Q, Safavi K, Spangberg LSW, Conn F. Res A 2008;85:964−71. Cell and tissue reactions to mineral trioxide aggregate and 57. Lee YL, Lin FH, Wang WH, Ritchie HH, Lan WH, Lin CP. Portland cement. Oral Surg Oral Med Oral Pathol Oral Effects of EDTA on the hydration mechanism of mineral tri- Radiol Endod 2003;95:483−9. oxide aggregate. J Dent Res 2007;86:534−8. 35. Dammaschke T, Gerth HUV, Zuchner H, Schafer E. Chemical 58. Stowe TJ, Sedgley CM, Stowe B, Fenno JC. The effects of and physical surface and bulk material characterization of chlorhexidine gluconate (0.12%) on the antimicrobial prop- white ProRoot MTA and two Portland cements. Dent Mater erties of tooth-colored ProRoot mineral trioxide aggregate. 2005;21:731−8. J Endod 2004;30:429−31. 36. Till D, Hans UVG, Harald Z, Edgar S. Chemical and physical 59. Kogan P, He J, Glickman GN, Watanabe I. The effects of vari- surface and bulk material characterization of white ProRoot ous additives on setting properties of MTA. J Endod 2006; MTA and two Portland cements. Dent Mater 2005;21:731−8. 32:569−72. 37. Camilleri J. A review of the methods used to study biocom- 60. Huang TH, Shie MY, Kao CT, Ding SJ. The effect of setting patibility of Portland cement-derived materials used in accelerator on properties of mineral trioxide aggregate. dentistry. Malta Med J 2006;18:9−14. J Endod 2008;34:590−3. 38. Islam I, Chng HK, Yap AUJ. Comparison of the physical 61. Bozeman TB, Lemon RR, Eleazer PD. Elemental analysis of and mechanical properties of MTA and Portland cement. crystal precipitate from gray and white MTA. J Endod 2006; J Endod 2006;32:193−7. 32:425−8. 39. Abdullah D, Pitt Ford TR, Papaioannou S, Nicholson J, 62. Storm B, Eichmiller FC, Tordik PA, Goodell GG. Setting expan- McDonald F. An evaluation of accelerated Portland cement sion of gray and white mineral trioxide aggregate and as a restorative material. Biomaterials 2002;23:4001−10. Portland cement. J Endod 2008;34:80−2. 40. Torabinejad M, White DJ, inventors; Loma Linda University, 63. Matt GD, Thorpe JR, Strother JM, McClanahan SB. Compara- assignee. Tooth filling material and method of use. US patent tive study of white and gray mineral trioxide aggregate 5415547. May 16, 1995. (MTA) simulating a one- or two-step apical barrier tech- 41. Torabinejad M, White DJ, inventors; Loma Linda University, nique. J Endod 2004;30:876−9. assignee. Tooth filling material and method of use. US Patent 64. Watts JD, Holt DM, Beeson TJ, Kirkpatrick TC, Rutledge RE. 5769638. June 23, 1998. Effects of pH and mixing agents on the temporal setting of 42. Danesh G, Dammaschke T, Gerth HUV, Zandbiglari T, tooth-colored and gray mineral trioxide aggregate. J Endod Schafer E. A comparative study of selected properties of 2007;33:970−3. ProRoot mineral trioxide aggregate and two Portland ce- 65. Bates CF, Carnes DL, del Rio CE. Longitudinal sealing ability ments. Int Endod J 2006;39:213−9. of mineral trioxide aggregate as a root-end filling material. 43. Asgary S, Parirokh M, Eghbal M, Stowe S, Brink F. A qualitative J Endod 1996;22:575−8. X-ray analysis of white and grey mineral trioxide aggregate 66. Wu MK, Kontakiotis EG, Wesselink PR. Long-term seal provided using compositional imaging. J Mater Sci Mater Med 2006; by some root-end filling materials. J Endod 1998;24:557−60. 17:187−91. 67. Vasudev SK, Goel BR, Tyagi S. Root end filling materials— 44. Asgary S, Parirokh M, Eghbal MJ, Brink F. Chemical differ- a review. Endodontology 2003;15:12−8. ences between white and gray mineral trioxide aggregate. 68. Lee YL. Development and Application of Calcium Silicate J Endod 2005;31:101−3. Bioceramics in Endodontic Therapy. Taipei: National Taiwan 45. Duarte MA, Demarchi AC, Yamashita JC, Kuga MC, Fraga Sde C. University, 2006. pH and calcium ion release of 2 root-end filling materials. 69. Kao CT, Shie MY, Huang TH, Ding SJ. Properties of an acceler- Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2003;95: ated mineral trioxide aggregate-like root-end filling material. 345−7. J Endod 2009;35:239−42.