View metadata, citation and similar papers at core.ac.uk brought to you by CORE 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, sur- gical procedures also provide a better visual field and Mineral trioxide aggregate greatly reduce misadventures, such as root perfo- ration, 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 compo- sition 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 com- posed 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.