Products and Distinctions

Dicalcium silicate:

$$ \begin{array}{c}2{\mathrm{Ca}}_2{\mathrm{SiO}}_4+5{\mathrm{H}}_2\mathrm{O}=3\mathrm{CaO}\cdot 2{\mathrm{SiO}}_2\cdot 4{\mathrm{H}}_2\mathrm{O}\\ {}+\mathrm{Ca}{\left(\mathrm{OH}\right)}_2\end{array} $$
Secondary or lesser hydration reactions occur involving the minor phases, but the strength and the release of calcium hydroxide for bioactivity arise from these two reactions. The key to the bioactivity of MTA-type products is the precipitation of hydroxyapatite when the calcium hydroxide reacts with phosphate ions in body fluids, as shown in Eq. 8.3.

$$ \begin{array}{c}7\mathrm{Ca}{\left(\mathrm{OH}\right)}_2+3\mathrm{Ca}\left({\mathrm{H}}_2{\mathrm{PO}}_4\right){}_2\\ {}\to {\mathrm{Ca}}_{10}\left({\mathrm{PO}}_4\right)6\left(\mathrm{OH}\right){}_2+12{\mathrm{H}}_2\mathrm{O}\end{array} $$
Calcium silicate, CaSiO3 (wollastonite), is not part of this discussion because this compound does not react with water and hydrate. However, this distinction is not always clear in the literature. Calcium silicate was used in another experimental magnesium phosphate dental product [32, 79, 93]. The calcium silicate was not a hydraulic phase but a phase that reacted in situ contributing to bioactivity.

8.2 Commercial Products

From 1993 to 1998, Dr. Torabinejad of Loma Linda University (Loma Linda, CA, USA) distributed experimental samples of MTA from his laboratory to endodontists. Commercial introduction of MTA products began in 1998 by the Tulsa Dental Specialties division of Dentsply International with ProRoot® MTA. This product was introduced after two applications to the US Food and Drug Administration (FDA) for clearance of these indications: repair of pulpal exposures, apexification, root perforation, root-end filling, and management of internal resorption. A picture of this gray MTA product is shown in Fig. 8.1a. In 2008, the US FDA cleared additional indications of cavity liner, pulpotomies, obturation, and root canal sealer, for MTA-type products from Dentsply. In Korea, MTA-type products are used for replantation [36, 72], transplantation, file separation, and vertical cracks. MTA-type products are generally suitable for dental procedures that contact with pulpal or periapical tissues, as described in this chapter and others. The performance and the convenience of products for a procedure have varied, as can be gleaned in the following discussion.

Fig. 8.1

(a) Packet of ProRoot MTA powder, ampoule of water and powder, introduced in 1998. (b) Packet of tooth-colored (white) ProRoot MTA powder, ampoule of water and powder, introduced in 2002
Since the introduction of ProRoot MTA, a shorter setting time has been desired, so that the clinician can feel confident that the product has set before the procedure is finished, as is conventional for dental materials. Several products and many researchers have sought to achieve this goal, often by the addition of calcium chloride, a known accelerant for Portland cement setting even though calcium chloride is not necessarily the most effective salt for accelerating the set. The elimination of calcium sulfate is known to reduce setting time for Portland cement [68], and this approach has also been used by several manufacturers. Calcium sulfate is necessary in construction concrete pouring to avoid flash or “false” setting, as described in Chap. 1. In dentistry, flash setting is unimportant and may be beneficial as noted below.
Researchers and clinicians have reported that the ProRoot MTA product had poor handling characteristics and “looses consistency in the presence of excess liquid, even at the proportion recommended by the manufacturer,” creating a low viscosity, “soupy mix” [62]. Since 1998, many investigators and companies have developed alternatives that were less “sandy”, faster setting and less expensive.
The key characteristics for comparisons of MTA products are crystalline phases, particle-size distribution, setting time, handling adjuvants, radiopacifier, and resistance to washout. All of these characteristics contribute to the clinician’s ability to satisfactorily prepare and mix the material. Washout resistance is important for stable placement of the material, particularly for the products that have a long setting time. The evolution of the available products and supporting research is described here.
The first patented MTA was a blend of a particular Portland cement composition, which included about 5 % iron oxide, and was believed to be unique in its ability to “work” (private communication about US Patents 5,415,547 and 5,769,638). Dentsply fabricated the patented cement formula under controlled environmental conditions and created a finer powder than the original samples, with better bismuth oxide distribution. This product became ProRoot MTA. The color of the powder was dark gray, as shown in Fig. 8.1a. The powder was packaged in foil pouches and supplied with ampoules of water in the kit (Fig. 8.1a). In 2002, a “tooth-colored” (white) ProRoot MTA (US Patent 7,892,342) product superseded the gray ProRoot MTA. This product was very similar but contained less than 0.5 % iron, so that the cement was yellowish white in color. The bismuth oxide contributed the yellow cast. In many articles, the tooth-colored ProRoot MTA product is denoted as white ProRoot MTA (Fig. 8.1b). Market demand required the original gray-colored ProRoot MTA to be reintroduced, and it has been sporadically available since then. Some papers have proposed greater biocompatibility for the gray version [37, 78].
The Angelus company in Londrina, Brazil, founded by Dr. Roberto Q. M. Alcântara, commercialized a more affordable MTA product in 2001. This product was available in Brazil and now is available through Henry Schein distributors. The format of their gray and white Angelus products is bottles of powder and water in a vial, different from ProRoot MTA powder in 1 g pouches with water ampoules. Originally, commercial Portland cement was used to create MTA Angelus, a gray-colored powder with bismuth oxide, which was followed by MTA Bianco, a white Portland cement with bismuth oxide.
When evaluating products, researchers have often repeated the term “sandy” feel of MTA [64]. Coarse particles give this sensation and scratchy sound when a powder is mixed with water on a glass slab. Therefore, the particle-size distributions have been compared for several powders. The particle-size distribution of the experimental samples of MTA from Loma Linda University is shown in Fig. 8.2a, and this powder has a significant portion of particles coarser than 40 μm, hence the “sandy feel.” The material was coarser than ProRoot MTA [65] and had incompletely dispersed bismuth oxide which appeared as bright spots in radiographs. The particle-size distributions in Fig. 8.2b, c are for the Angelus company’s white and gray MTA powders. The median particle sizes are below 10 μm, but each powder contains many particles which are coarser than 40 μm, up to 100 μm. The line at 20 μm allows a comparison of the number of particles that are coarse. Figure 8.2d–f show the distributions of particle sizes in ProRoot (gray and white) and DiaRoot powders (DiaDent Group International, Burnaby, British Columbia, Canada), which have significantly fewer coarse particles than the original MTA or the Angelus materials. Figure 8.3 has particle-size distributions for three newer materials, which are remarkably finer: Biodentine, EndoSequence sealer, and RetroMTA powders. None of these powders is “nano-sized.” Nano-sized particles are 1/1,000 of a micron and none of these materials is even submicron (1/10 of a micron).

Fig. 8.2

(a) Original, pre-commercial MTA powder particle-size distribution. (b) MTA Bianco from Angelus Corporation powder particle-size distribution. (c) MTA Angelus (gray) from Angelus Corporation powder particle-size distribution. (d) Early version of (gray) ProRoot MTA powder particle-size distribution. (e) Tooth-colored (white) ProRoot MTA powder particle-size distribution. (f) DiaRoot powder particle-size distribution
Fig. 8.3

(a) Biodentine powder particle-size distribution. (b)EndoSequence sealer powder particle-size distribution. (c) RetroMTA powder particle-size distribution
Nano-sized particles are of interest because of the high surface-to-volume ratio versus micron-sized particles. The surface-to-volume ratio changes from less than 10 % for micron-sized particles to more than 50 % for nanoparticles, which is important because a higher surface-to-volume ratio can dramatically increase reactivity, such as hydration. Fumed or colloidal silica are nano-sized particles that are commonly added to many dental products. Such silica products may be a minor addition to some MTA products; however, no MTA product has been identified that is primarily composed of nanoparticles.
Calcium sulfate is used in construction uses of Portland cement to delay setting. Without calcium sulfate, the calcium aluminate phase of Portland cement quickly hydrates and causes initial setting by stiffening the cement, which is undesirable for bulk pouring of concrete. For MTA indications, faster setting is desired. The Angelus company has integrated the manufacture of the tricalcium silicate powders into their operations so that their MTA products are now made with fewer trace metal oxides and without calcium sulfate (private communication, 2013). The initial setting time of their products is reported to be only 10 min, by allowing the tricalcium aluminate phase to quickly hydrate [54]. Later, the Angelus Corporation developed a sealer containing MTA powder (MTA Fillapex®), which is described in the ensuing sealer section.
DiaRoot® from DiaDent® was introduced by 2007, and this material was manufactured without tricalcium aluminate; therefore, no calcium sulfate phase is needed to control the rapid hydration of the tricalcium silicate. Tantalite (Ta2O5) is used as the radiopaque powder, making this material very white, by comparisons to gray ProRoot MTA or tooth-colored (white) ProRoot MTA that contain bismuth oxide. DiaRoot was advertised as containing calcium phosphate monobasic, but no phosphate phase was detected with XRD (Table 8.1), indicating that the phosphate was either amorphous or was present at less than 1 %. The format of this product is very similar to ProRoot MTA with one gm sachets of powder and water ampoules shown in Fig. 8.4. Currently, this product is sold through Verio Dental Co. (Vancouver, Canada) from Innovative BioCeramix Inc. (IBC) (Vancouver, Canada).

Table 8.1

X-ray diffraction results for some MTA products (weight percent)
Phase detected by XRD
(White) ProRoot MTA
MTA + (Cerkamed)
MTA Plus
MTA Caps
CPM Endo-XRD analysis
Tricalcium silicate
Dicalcium silicate
Tricalcium aluminate
Calcium sulfate
Calcium carbonate
Tetracalcium aluminoferrite
Calcium hydroxide
Bismuth oxide
Calcium tungstate
Zirconium oxide
Barium sulfate
Calcium phosphate (various)
Magnesium oxide
Calcium chloride hydrate
Amorphous (silica)
Tetracalcium monocarboaluminate
Fig. 8.4

DiaRoot BioAggregate product showing powder sachet, water ampoule, and mixing tools
The Brasseler Co. (Savannah, GA, USA) offers MTA-type products, under the trade name EndoSequence BC or Bioceramic. These products appear to be related to the DiaRoot and iRoot products, and IBC is believed to be the supplier/manufacturer. The Brasseler products are based on fine tricalcium silicate powders that do not contain alumina. The products are offered in four formats: powder for mixing with water, a paste, a putty, and a sealer (Fig. 8.5). The EndoSequence BC putty, paste, and sealer have the powder mixed with various carrier liquids that do not cause setting; hence, the liquid must be anhydrous. These paste/putty forms of the EndoSequence BC material do not require mixing before placement and they allow a clinician to choose a viscosity suitable for the indication or case. When placed, water must diffuse from the tissues into the paste, putty, or sealer to displace the carrier liquid and cause hydration/setting of the tricalcium silicate powder. The percentage of the ceramic powder in any of the products is not known, but is estimated as 60–80 % MTA-type powder. The fine powders and convenience as putty or paste are solutions to the criticisms of MTA being coarse and hard to place. The time for diffusion of water to cause setting will vary with the indication and location. Brasseler EndoSequence putty sets more slowly than ProRoot MTA [28], but the setting times for these materials are more than 24 h, therefore irrelevant for the procedure. In vitro testing shows that setting of the sealer takes more than 1 week [71]. However, the ability to place the putty and complete the procedure may outweigh other concerns.

Fig. 8.5

Two of Brasseler’s EndoSequence products, putty (a) and sealer (b), are shown
Brasseler and IBC companies use the terms bioaggregate and bioceramic for their products. Bioaggregate has no technical meaning, but does imply the bioactivity that occurs when tri- and dicalcium silicates are placed in contact with tissue fluid. Bioceramic is a term used to refer any ceramic (nonmetallic and inorganic) material, including glass, in the body of suitable biocompatibility. Bioceramics are not limited to the Brasseler products, but include resorbable ceramics and inert ceramics such as alumina or zirconia used in dentistry and other medical devices.
Brasseler also manufactures EndoSequence BC gutta-percha points that contain the same tricalcium silicate powder used in their other tricalcium silicate products. This product is their approach to bonding the sealer to the gutta-percha and the dentin as a “monoblock” [94]. The use of MTA powder in gutta-percha has been patented (US 7,838,573).
Biodentine® (Septodont, Saint-Maur-des-Fossés, France) is a fast-setting tricalcium silicate product, which has the same indications as ProRoot MTA. The company has emphasized using the material to replace dentine lost to caries. Its use as a dentine replacement may not prevent leakage [22]. A composite resin should be placed over the Biodentine as the material will not be sufficiently stable when exposed to the oral cavity. Biodentine powder is packaged in unit doses of 0.75 g, more than is usually used for endodontic or vital pulp therapy indications (Fig. 8.6). The user manually adds the liquid to the powder’s capsule and the mixture is triturated. The water-based liquid, supplied in ampoules, contains a “plasticizer” (polycarboxylate) and calcium chloride to enhance the properties and speed the setting. Although advertised as “dentin in a capsule,” the Biodentine powder contains mostly tricalcium silicate (83 %) with 14 % calcium carbonate and 4 % zirconia (Table 8.1) and does not contain hydroxyapatite and collagen. Biodentine does not contain dentine and should not be confused with bone grafting material, which is hydroxyapatite. However, its fine powder and faster setting are improvements over the original MTA. The low amount of zirconia in Biodentine makes the material only as radiopaque as dentin. High radiopaque contrast is desired for dental materials, such as composite resins, which are also dentin replacements, for X-ray visibility. However, this product was stable to discoloration [95], unlike ProRoot MTA [9, 12, 59, 67, 70].

Fig. 8.6

Biodentine by Septodont, showing the triturator capsule and its foil packaging, liquid for addition to the capsule
TheraCal™ LC (Bisco Inc. Schaumburg, IL, USA) is the only commercial light-curing version of MTA to date and is indicated for pulpal tissue contact. This material contains less than 20 % MTA powder, a radiopacifier of barium zirconate (BaZrO3), and dimethacrylate resins. The product literature describes the MTA component as Type III Portland cement, which denotes a finer powder than Type I Portland cement. The particle size is less important for a premixed material that needs no spatulation prior to light curing. TheraCal has been tested and shown to release more calcium ions than Dycal® (Dentsply International, York, Pennsylvania, USA), a calcium hydroxide-based pulp-capping material [44]. Also the TheraCal product has higher radiopacity, lower solubility, and better bonding than Dycal, the current “gold standard” for pulp capping. TheraCal is not indicated for the endodontic indications for which MTA has become known and may not be suitable for such indications based on cytotoxicity studies [55].
New endodontic cement (NEC, AKA calcium-enriched mixture or CEM) has been introduced (BioniqueDent, Tehran, Iran) and contains calcium compounds not found in ProRoot MTA. The NEC material contains more calcia than MTA does by the addition of [8] calcium oxide, calcium phosphate, calcium carbonate, calcium silicate, calcium sulfate, calcium hydroxide, and calcium chloride. Over time, calcium oxide powder will form hydroxide and then carbonate in the container, to create more calcium carbonate. Asgary has not disclosed the presence of tri- or dicalcium silicates, nor a radiopaque agent in the literature; however, the material’s similar performance to MTA makes this material likely to be based on the familiar MTA phases of tri- and dicalcium silicate phases. NEC has been reported to be bioactive and have good handling and sealing [6] as a root-end filling material. Its film thickness was lower than ProRoot MTA’s and its flow was higher, indicative of a finer particle size than the ProRoot MTA, which has the same indications. A study with pulp capping in canines has shown equivalent results of MTA and NEC, and NEC’s superiority to calcium hydroxide-based IRM® [91]. A root-end filling study in canines was successful (after 60 days) versus MTA when apical lesions were induced [5]. Pulpotomies in humans showed similar success (about 75 %) for NEC and MTA [76] for apical development for as long as a 1-year follow-up. A second study in humans compared conventional root canal therapy to pulpotomies (with NEC) for postoperative pain and 6-month radiographic outcome. Significantly less pain occured in the first 7 days for pain and radiographic superiority [4].
Two manufacturers from Korea have introduced MTA products to the USA and elsewhere: OrthoMTA and RetroMTA (BioMTA, Daejeon, Korea), and Endocem MTA (Maruchi, Gangwon-do, Korea) shown in Fig. 8.7. OrthoMTA and RetroMTA products are fine powders, advertised as having an average particle size of 2.6 μm, although independent testing has shown that the powders have a median particle size of about 10 μm (Fig. 8.3c). The indications for OrthoMTA and RetroMTA overlap, although RetroMTA has more vital pulp indications. OrthoMTA is sold in (centrifuge vials) containing 0.2 g of powder. The user adds his/her own water to the powder in the vial and places the vial in a battery-powered centrifuge to spin for 20 s. Then the excess water is decanted and the retained powder is considered hydrated for dispensing. Special instruments are used for dispensing. Initial setting time is 3 min. and the final setting is about 6 h. The phases present are said to include tri- and dicalcium silicate, tricalcium aluminate, tetracalcium aluminoferrite, less than 1 % free calcia, and 3 % of amorphous phase. Its radiopaque component is bismuth oxide. The material is indicated for orthograde use.

Fig. 8.7

(a) RetroMTA shown in sachet, packaged with water ampoule. (b) OrthoMTA shown in vial placed in centrifuge (Image courtesy of Dr. Yoojin Shin, BioMTA.) (c) Endocem shown in vial, having a gray color
RetroMTA has a different format from OrthoMTA. Sachets of 0.3 g of powder are packaged in a flat plastic container disk with separate ampoules of water, which are manually mixed by the user. This light gray tri- and dicalcium silicate powder has about 25 % zirconia, some tricalcium aluminate phase, calcium chloride, and silica (Table 8.1). It is advertised as containing calcium aluminozirconate for radiopacity, but this was not detected by X-ray diffraction. The RetroMTA brochure lists “lack of discoloration” as an attribute; discoloration has been attributed to bismuth oxide [23]. RetroMTA does not contain bismuth oxide, so the discoloration claim seems valid. The initial setting time of RetroMTA is said to be 1.5 min, which is likely caused by the calcium chloride.
Endocem MTA shown in Fig. 8.7c is advertised as setting in 3:15 min. Like the OrthoMTA, the powder is sold in a flip-top vial of the kind that is often used in centrifuging biological samples. The Endocem product literature states that zirconia is present, but bismuth oxide was identified in X-ray diffraction (Table 8.1). Endocem was the only product tested that contained only dicalcium silicate, with no tricalcium silicate for the hydraulic reaction. The setting was not tested independently; however, dicalcium silicate is slower setting than tricalcium silicate. About 40 % calcium carbonate was also identified, with minor amounts of calcium phosphate, crystalline silica, and magnesia. This excess calcium carbonate indicates that the material is pozzolanic.
Cerkamed PPH (Wojciech Pawlowski, Nisko, Poland) has introduced an MTA +  product (Fig. 8.8), which is distinct from the product MTA Plus® described below. The MTA +  product is distributed in small polymer bottles containing 0.3 g of powder with a separate vial of water. This white powder contained primarily tricalcium silicate (63 %) with silica, and about 9 % each of bismuth oxide and zirconia, and a small amount of an aluminate phase (Table 8.1) in X-ray diffraction.

Fig. 8.8

MTA + material from Cerkamed, shown in vial, having a white color
Medcem GmbH (Weinfelden, CH) offers a Portland cement powder for use instead of formocresol [83]. However, this powder has no radiopaque material; therefore, its radiopacity is similar to dentin.
Two MTA Plus® products are available and both are tri/dicalcium silicate powders with bismuth oxide. The white version is sold outside the USA, and is manufactured by Prevest Denpro (Jammu, India); its phase composition is substantially identical to that of tooth-colored ProRoot MTA (Table 8.1). Grey MTA Plus is manufactured in the USA by Avalon Biomed Inc. (Bradenton, FL, USA). Both products include a powder and gel for mixing.
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Nov 4, 2015 | Posted by in General Dentistry | Comments Off on Products and Distinctions
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