Material Modifications and Related Materials

Base materials
Derivatives
Composition
Properties
Tricalcium silicate-based endodontic materials
Bioaggregate
Calcium silicate hydrate + calcium hydroxide + hydroxyapatite + tantalum oxide + amorphous silicon oxide
Nontoxic [53, 175, 177, 182], nontoxic [104], antibacterial effect [180], sealing ability [59, 108], fracture resistant [164]
EndoSequence root repair material
Calcium silicate + monobasic calcium phosphate + zirconium oxide + tantatum oxide + filler agent
Bioactive [5, 88, 115, 153], not bioactive [122], sealing ability [127], not sealing ability [87], antibacterial [114]
Biodentine
Tricalcium silicate + calcium carbonate + zirconium oxide + calcium chloride
Remineralization induction [81], odontoblast differentiation [107], adverse effect on the dentin toughness [111, 151], not sealing ability [37], low porosity [41]
Calcium-enriched mixture (CEM)
Calcium hydroxide + calcium oxide + calcium phosphate + calcium sulfate + calcium silicate + calcium carbonate
Hydroxyapatite formation [13], sealing ability [11, 84, 103], antimicrobial [14, 83], acceptable cytotoxicity [15, 125], suitable biocompatibility [1, 136], induce hard tissue formation [142], suitable for vital pulp therapy [810, 12, 63, 116, 128, 157]
Generex A
Calcium silicate + unique gels + hydroxyapatite
Suitable compressive strength, washout resistant and setting time [139]
Capasio
Calcium aluminosilicate + dental glass + bismuth oxide
Adequate physical and chemical properties [139], promote apatite deposition [138], osteoblast growth and nodule formation [171]
Theracal
CaO + calcium silicate particles + strontium glass + fumed silica + barium sulfate + barium zirconate + resin containing Bis-GMA and PEGDMA
Calcium ion release and hydroxyapatite formation [68], decreasing cell metabolism [85]
Endodontic cements not based on tricalcium silicate
Calcium aluminate cement
Calcium aluminate + calcium dialuminate
Rapid setting, good flow, improved handling properties, high mechanical strength, reduced porosity [131]
EndoBinder
Calcium aluminate based
Adequate physical and chemical properties [130], biocompatible [3, 48]
Castor oil
Polymer derived from the castor oil plant (triglyceride of ricinoleic acid)
Antibacterial [165], biocompatible [22, 112], acceptable cytotoxicity and genotoxicity [28, 29], sealing ability [51]
Ceramicrete D
Phosphosilicate ceramic + hydroxyapatite + cerium oxide + deionized water
Sealing ability [108], clinical handling and washout resistant [139]

7.3.1 Tricalcium Silicate-Based Endodontic Repair Cements

7.3.1.1 Bioaggregate

Bioaggregate (Innovative BioCeramic, Vancouver, Canada) is a relatively new product containing calcium silicate hydrate, calcium hydroxide, hydroxyapatite, tantalum oxide, and amorphous silicon oxide, which is intended to be used for perforation repair and as a retrograde filling material. In a study using X-ray diffraction analysis [137], the absence of aluminum-based compounds was demonstrated. Furthermore, tantalum oxide has been included as a radiopacifier. The hydrated material released less calcium in solution than Biodentine [79]. In vitro studies [53, 175, 177, 182] revealed that Bioaggregate is nontoxic to human fibroblasts and osteoblasts. In addition, it may induce fibroblast differentiation and expression of the mineralization-association gene in osteoblasts.
On evaluation of the systemic toxic effect of MTA and Bioaggregate on the kidney and liver, some adverse effects on liver and kidney cells in rats were demonstrated. The effect of MTA was significantly more severe than the Bioaggregate [104]. Evaluation of an antibacterial activity of this cement against E. faecalis revealed comparable results with MTA which was even enhanced after addition of the dentin powder [180]. Its sealing ability has been assessed by dye [59] and glucose [108] leakage, and results indicated similar ability to MTA as a root-end filling material. In one study [164], fracture resistance of immature teeth filled with Bioaggregate was higher than MTA, suggesting this cement can be used in immature teeth, as a root canal filling material.

7.3.1.2 EndoSequence Root Repair Material

Recently, a new root repair material has been introduced to the market: EndoSequence Root Repair Material (ERRM; Brasseler, Savannah, GA). According to the manufacturer, it is composed of calcium silicate, monobasic calcium phosphate, zirconium oxide, tantatum oxide, and filler agents and is available as paste in preloaded syringes and also in a moldable putty form. The preloaded syringe also has intracanal tips that can be bent to facilitate its placement in clinical situations. According to the manufacturer instruction, it has a working time of 30 min and a setting reaction initiated by moisture with a final set achieved approximately 4 h thereafter.
Although in one study, elutes of ERRM significantly reduced the bioactivity and alkaline phosphatase activity of human osteoblast-like cells [122], the results of other studies conducted on its bioactivity revealed that it may have cell viability similar to MTA in both set and fresh conditions [5, 88, 115, 153]. Sealing ability of this novel material was compared with MTA, and the results showed no significant difference in bacterial leakage between either of them [127]. In contrast, by using a bacterial leakage model [87], it was concluded that samples in ERRM group leaked significantly more than those in MTA group.
Antibacterial activity of ERRM was compared with MTA, and results demonstrated similar antimicrobial properties during their setting reaction against ten clinical strains of E. faecalis [114]. In an in vitro study [82], simulated root resorption defects were prepared, and after filling the root canal with either ERRM or MTA, the pH at the root surface of the teeth was measured. In the ERRM group, pH values declined during the first 24 h, and its 1-week evaluation was comparable with MTA during the 1st and 2nd weeks [82].

7.3.1.3 Biodentine

Biodentine is manufactured by Septodont (Septodont, Saint-Maur-Fosses Codex, France) and is composed of tricalcium silicate, calcium carbonate, and zirconium oxide as the radiopacifier, while its liquid form contains calcium chloride as the setting accelerator and water-reducing agent. This composition has been verified in a recent publication [46]. The calcium chloride accelerates the setting time of Biodentine, while the other additives enhance the physical properties [80]. According to the manufacturer, Biodentine is produced using a novel technological platform called Active Biosilicate Technology, which guarantees the purity of the material. An investigation of the presence of leachable arsenic, lead, and chromium from Biodentine exhibited the low levels of toxic heavy elements in this material [42]. The fine particle size [46] accompanied by the presence of calcium carbonate which enhances the material hydration results in the release of calcium hydroxide in solution [79]. A study demonstrated the formation of a silicate- and calcium-rich layer in dentin in contact with Biodentine and MTA. Silicon is known to enhance the rate of new bone growth and also induce remineralization of demineralized dentin when released from bioactive materials [81].
When Biodentine is applied directly onto the pulp, it induces an early odontoblast differentiation and the initiation of mineralization, probably due to a modulation of TGF-β1 secretion from the dental pulp cell [107]. Prolonged contact of mineralized dentin with calcium silicate-based materials, such as Biodentine, has an adverse effect on the dentin toughness and integrity of the dentin collagen matrix; therefore, caution is recommended when these materials are applied to the thin dentinal walls [111, 151].
When Biodentine was used as a dentin replacement material in the sandwich technique overlaying with composite, significant leakage occurred at the dentin-material interface [37]. Drying of Biodentine results in cracking and micro-leakage. Biodentine exhibits very low porosity when compared to MTA Bioaggregate and intermediate restorative material (IRM) (Dentsply Caulk, Milford, Delaware) [41].

7.3.1.4 Calcium-Enriched Mixture

Asgary et al. [16] introduced a new endodontic cement in 2008 to combine the superior biocompatibility of MTA with appropriate setting time (less than 1 h), handling characteristics, chemical properties, and reasonable price. This newly formulated biomaterial, named calcium-enriched mixture (CEM) cement (BioniqueDent, Tehran, Iran), was made using different calcium compounds; the patent is granted from US Patent and Trademark Office (USPTO) (endodontic filling material; USA, 7,942,961, 2011 May 17).
The manufacturer claimed that the mixed paste of CEM is not sticky; it does not tend to adhere to the applicator and can be easily condensed by the operator. In addition, some calcium compounds in CEM such as calcium sulfate and calcium silicate may cause a slight expansion of the material through continuous hydration after initial setting of the material and further crystalline maturation.
The results of recent investigations revealed that CEM comprises water-soluble calcium and phosphate ions and forms hydroxyapatite after setting [13]. Its sealing ability as a root-end filling material has been also evaluated and comparable results with MTA have been shown [11, 84, 103]. In presence of saliva contaminations, CEM showed superior sealing ability compared to MTA [84].
Antimicrobial properties of CEM against gram-negative, gram-positive, and cocci/bacilli bacteria were compared with MTA and calcium hydroxide (CH) using agar diffusion test. Results showed comparable antibacterial effects with CH and significantly better results than MTA [14, 83]. In addition, recent studies in cell culture revealed its cytotoxicity to be within acceptable range [15, 125], suitable biocompatibility [1, 136], and ability to induce hard tissue formation [142]. The results of in vivo studies on dogs showed that as pulp capping materials, MTA and CEM showed similar favorable biological outcomes, and both better than CH especially in terms of inducing the formation of the dentinal bridge [12, 157]. In several clinical trials in primary and permanent teeth [810, 63, 116, 128], CEM was used as a vital pulp therapy agent, and results indicated that the performance of new biomaterials may trend toward more biological treatments.

7.3.1.5 Generex A

Generex A (Dentsply Tulsa Dental Specialties, Tulsa, OK) is a calcium silicate-based material with similarities to ProRoot MTA. However, Generex A is mixed with unique gels instead of water and, together with a powder consistency, results in improved material handling and shorter setting time. Generex A powders contain hydroxyapatite to nucleate the production of hydroxyapatite in vivo which might be responsible for acceleration of osteoblastic activity in rats [170]. In addition, in an in vitro study, its compressive strength, washout resistance, and setting time were found to be better than MTA [139].

7.3.1.6 Capasio

Capasio (Primus Consulting, Bradenton, FL) is the new calcium aluminosilicate-based material which has been introduced in an effort to improve the weaknesses of previous materials. It is composed primarily of bismuth oxide, dental glass, and calcium aluminosilicate with a water-based gel. Upon the final setting (e.g., 9 min), this material is slightly more acidic (pH = 10.9) than WMTA (pH = 11.6). Moreover, it has demonstrated similar or improved physical characteristics such as setting time, radiopacity, compressive strength, pH, and washout resistance [139].
When used as a root-end filling material, Capasio is more likely to penetrate dentinal tubules, and similar to MTA, it promotes apatite deposition when exposed to synthetic tissue fluid [138]. In a comparative study, Capasio has not been shown to support the primary osteoblast growth and facilitate nodule formation in comparison with MTA and Generex A [21]. Recently, Capasio powder has been refined and renamed as QuickSet (Primus Consulting), and the cationic surfactant was removed from the liquid gel component, which was proposed to interfere with cell cytocompatibility. In a study, Quick-Set demonstrated similar cytotoxicity profile to MTA [171].

7.3.1.7 TheraCal

TheraCal (Bisco Inc., Schaumburg, IL, USA) is a new light-cured resin-modified paste containing CaO, calcium silicate particles (type III Portland cement), strontium glass, fumed silica, barium sulfate, barium zirconate, and resin containing Bis-GMA and poly(ethylene glycol) dimethacrylate (PEGDMA) (International Patent A61K33/42), which has been introduced as a pulp capping material. It has the ability to release calcium ions and create an environmental pH close to physiological pH after 7 days. The latter characteristic favors the formation of apatite and induces the differentiation of new odontoblasts, thus resulting in the formation of new dentin. Its ability to polymerize to a depth of 1.7 mm may eliminate the risk of untimely dissolution [68]. Although bioactive and calcium-releasing properties have been demonstrated for TheraCal, decreased cell metabolism when compared to the control has been demonstrated [85].

7.3.2 Endodontic Cements Not Based on Tricalcium Silicate

7.3.2.1 Calcium Aluminate Cement

A novel calcium aluminate endodontic cement was developed at the Federal University of São Carlos, Brazil, by Pandolfelli et al. [133] (Patent registration INPI 0704502–6). This cement aims to preserve the positive properties and clinical applications of MTA while increasing the possibility of extended applications without the disadvantages of the original material. The calcium aluminate cement is comprised of calcium aluminate (CaO·Al2O3) and calcium dialuminate (CaO.2Al2O3) phases, which are responsible for the hydraulic setting process [138]. In one study, the chemical, physical, and mechanical properties of the cement were assessed, and results showed more rapid setting, better flow, improved handling properties, rather high mechanical strength, and reduced porosity with lower pore size compared to MTA Angelus [131]. On the other hand, on the surface of this cement in combination with accelerator, stoichiometric hydroxyapatite was detected after immersion in simulated body fluid solution [130].

7.3.2.2 EndoBinder

A new calcium aluminate-based endodontic cement (Patent Number PI0704502-6-2007) called EndoBinder (Binderware, Săo Carlos, SP, Brazil) has been developed, with the aim of preserving the properties and clinical applications of MTA without its negative characteristics. The cement is produced by the process of aluminum oxide and calcium carbonate calcination at temperatures between 1,315 and 1,425 °C. The formed calcium aluminate is cooled and then triturated until an adequate particle size is obtained. Free magnesium oxide and calcium oxide, which are responsible for the undesired expansion, and ferric oxide which leads to tooth darkening have been eliminated. This material has been shown to present adequate physical and chemical properties [130] and induce a higher rate of osteogenic cells differentiation compared to those exposed to MTA [48]. In addition, when tested on rat subcutaneous tissues, it proved to be biocompatible [3]. In a 1-year in vitro study, GMTA, WMTA, and EndoBinder with and without radiopacifying agent displayed color alteration after 360 days [71].

7.3.2.3 Castor Oil Cement

Recently, a material-based polymer derived from the castor oil plant (Ricinus communis) was introduced to endodontics, also known as castor bean polyurethane cement (COB, Poliliquil, Araraquara, SP, Brazil), is composed of 81–96 % triglyceride of ricinoleic acid, and is considered as a natural polyol containing three hydroxyl radicals.
This cement has been reported to have antibacterial activity against E. coli [165] and is progressively integrated into the alveolar bone in the wound-healing process [47]. Aiming at evaluation of its cytotoxicity and genotoxicity, this material proved to be biocompatible when used in maxillary sinus floor augmentation [22] and is well osseo-integrated [112], without any negative influence on the cell survival [28, 29]. The sealing ability of this cement has been evaluated by the dye leakage method, and results have shown an efficient sealing ability [51].

7.3.2.4 Ceramicrete

Ceramicrete is a self-setting phosphate ceramic developed at the Argonne National Laboratory that sets in an ambient condition formed by acid-base reaction between an acid phosphate (KH2PO4) and a negligible soluble basic metal oxide (calcined MgO). More recently, a biocompatible, radiopaque Ceramicrete-based dental/bone material has been created by incorporating hydroxyapatite powder and cerium oxide radiopaque filler into the phosphosilicate ceramic. The Ceramicrete-based material has an initial setting time of 6 min and a final setting time of 12 min, it can also be rolled into a sausage-like formation for easier manipulation with dental instruments and sets under water with minimal washout [143]. A modified version of the material (Ceramicrete D) was introduced by mixing the powder with deionized water. The sealing ability of Ceramicrete D was reported to be favorable [161].
In another study by Leal et al. [108], two endodontic bioceramic repair cements (Bioaggregate and Ceramicrete D) displayed similar leakage results to white MTA when used as root-end fillings materials. Ceramicrete D had significantly lower glucose penetration. Physical and chemical analyses showed that the clinical handling and washout resistant of the Ceramicrete D were superior to those of MTA; however, it was weaker, less radiopaque, and initially more acidic than Generex A and Capasio [139].

7.3.3 MTA-Based Sealers

Despite favorable characteristics, MTA presented some physical properties that hinder its application for root canal filling. An appropriate material for using as a root canal filling should be biocompatible, induce mineralized tissue formation, has suitable flow rate and manipulation. Recently, in an effort to incorporate the desirable biological properties of MTA into an easy to manipulate and insert material, some manufacturers have added specific components to MTA-based cements. Materials resulting from this attempt are listed in Table 7.2.

Table 7.2

Properties of MTA-based sealers
Sealers
Composition
Biocompatibility
Antibacterial
Sealing ability
Calcium ion release
Endo-CPM-Sealer
MTA + calcium chloride + calcium carbonate
(+) [76, 77]
(+) [159]
(+)[50]
(+) [160]
(−)[124]
iRoot SP Sealer
Calcium silicate based (unknown)
(+) [181]
(+) [179]
(+) [61, 178]
(+) [23]
MTA Fillapex
MTA + salicylate resin + natural resin + silica nanoparticles + bismuth oxide + dehydrated calcium sulfate
(+) [78, 149]
(+) [124]
(+) [75]
(+) [23]
(−) [20]
(−) [154]
MTA Obtura
White MTA + viscous fluid
N/Y/Ea
N/Y/Ea
(−) [168]
N/Y/Ea
ProRoot Endo Sealer
Tricalcium silicate + dicalcium silicate + calcium sulfate + calcium aluminate + bismuth oxide
N/Y/Ea
N/Y/Ea
(+) [172]
N/Y/Ea
aNot yet evaluated

7.3.3.1 Endo-CPM-Sealer

The EndoCPMSealer (Egeo S.R.L., Buenos Aires, Argentina) was introduced in an attempt to combine the physicochemical properties of a root canal sealer with the biological properties of MTA. According to the manufacturer, CPM Sealer is composed of MTA, SiO2, CaCO3, Bi2O3, BaSO4, propylene glycol alginate, propylene glycol, sodium citrate, and calcium chloride after mixing. Calcium carbonate, as a component that reduces the pH of the mixture, restricts the surface necrosis of cells in contact with the material and thus allows the action of the alkaline phosphatase and, consequently, the deposition of mineralized tissue [76]. Hydroxyl and calcium ions have also been shown to release from this cement similar to MTA, and therefore, they may act as an alternative root-end filling material [160]. Researchers demonstrated that Endo-CPM-Sealer has a good antimicrobial activity [159]. In addition, fibroblast cultures revealed that Endo-CPM-Sealer is not cytotoxic [77]. According to the manufacturer and study results [50], Endo-CPM-Sealer can be considered as an alternative sealing material in the treatment of root perforations. When used as an apical plug, the CPM and MTA had similar adaptation to the dentin walls.

7.3.3.2 iRoot SP Sealer

A new bioceramic-based sealer iRoot SP (Innovative Bioceramix, Vancouver, Canada) is described by the manufacturer as a convenient, premixed, ready-to-use, injectable, white hydraulic cement paste. This material uses the natural moisture of the dentinal tubules to initiate and complete its setting reaction. According to the manufacturer, iRoot SP is an aluminum-free, hydrophilic, calcium silicate-based material that requires the water to set and harden. In addition to its antibacterial activity and biocompatibility [179, 181], it showed good sealing ability [61, 178] and bonding to root canal dentin even under different degrees of dentin moisture [60, 126]. Intracanal placement of calcium hydroxide seems to improve the dislodgment resistance of the iRoot SP [7].

7.3.3.3 MTA Fillapex

MTA Fillapex (Angelus, Londrina PR, Brazil) is a new double paste MTA-based root canal sealer. Its composition after mixing is basically mineral trioxide aggregate, salicylate resin, natural resin, bismuth oxide, and dehydrated calcium sulfate. This material has excellent radiopacity, easy handling, and good working time. MTA Fillapex showed antibacterial activity against E. faecalis before setting [124]. According to the manufacturer, this is the only root canal sealer that promotes cementum regeneration. However, one study showed lower cell viability rates when compared with the control group [20]. On the contrary, other investigations on human osteoblast-like cells and rat tissues showed the sealer presents suitable bioactivity [78, 149]. In some studies, MTA Fillapex presented lower sealing ability than MTA [154] and lower push-out bond values to root dentin compared with other sealers [148].

7.3.3.4 MTA Obtura

MTA Obtura (Angelus, Solucoes Odontologicas, Londrina, PR, Brazil) is a mixture of white MTA with a proprietary viscous liquid. In an in vitro study, MTA Obtura showed progressive increased leakage during extended experimental periods [168]. On the other hand, another study concluded that MTA Obtura presented greater flow than the minimum recommended level in the ADA57 specification [19].

7.3.3.5 ProRoot Endo Sealer

ProRoot Endo Sealer (Dentsply Maillefer, Ballaigues, Switzerland) is reported to be calcium silicate based with liquid-to-powder ratio of 1:2. The liquid is composed of water and a viscous water-soluble polymer. The addition of a polymer to improve the workability had been reported previously [44]. The polymer addition does not seem to affect the biocompatibility of the material [34, 44]. Sealing property of ProRoot Endo Sealer is comparable to other tested sealers [172], and also the presence of spherical amorphous calcium phosphate-like and apatite-like phases after immersion in simulated body fluid is demonstrated [94].

7.4 Conclusion

The introduction of mineral trioxide aggregate (MTA) in 1993 started a new revolutionary phase in endodontic practice. However, despite solving many problems in the treatment of complicated cases, some difficulties have been reported with MTA. The loose and sandy nature and also lack of uniformity in MTA mixture have caused some difficulties for application of MTA paste into the desired space.
While some modifications have been proposed for easier application of MTA in order to overcome its disadvantages, these modifications have had a negative influence on some properties of the material.
A new generation of materials with at least similar properties to those of original ProRoot MTA have also been introduced as its suitable alternatives in complicated cases. More evidence is required to support these materials as an improved MTA or as its new alternatives.
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Nov 4, 2015 | Posted by in General Dentistry | Comments Off on Material Modifications and Related Materials
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