- Email: [email protected]
Evaluation of pH and calcium ion release of new root-end filling materials
Evaluation of pH and calcium ion release of new root-end filling materials Bruno Carvalho de Vasconcelos, DDS, MS,a,b Ricardo Affonso Bernardes, DDS, MS, PhD,b Suyane M. Luna Cruz, DDS, MS,c Marco Antonio Húngaro Duarte, DDS, MS, PhD,b Pedro de Magalhães Padilha, MS, PhD,d Norberti Bernardineli, DDS, MS, PhD,b Roberto Brandão Garcia, DDS, MS, PhD,b Clóvis Monteiro Bramante, DDS, MS, PhD,b and Ivaldo Gomes de Moraes, DDS, MS, PhD,b Ceará, Brazil BRAZILIAN DENTAL ASSOCIATION, UNIVERSITY OF SÃO PAULO, FEDERAL UNIVERSITY OF CEARÁ, UNIVERSITY OF SÃO PAULO STATE
Objective. The purpose of this study was to evaluate the pH and calcium ion release of 6 materials used for root-end filling and perforation repair. Study design. Gray ProRoot MTA, gray MTA-Angelus, white MTA-Angelus, and CPM were compared to 2 experimental ones: MTA-exp, also based in Portland cement with a modified mixing liquid, and MBPc, an epoxy-resin based cement containing calcium hydroxide. After 3, 24, 72, and 168 hours the water in which each sample had been immersed was tested to determine the ph and calcium ion release. Results. All the analyzed materials showed alkaline pH and capacity to release calcium ions; however, a tendency of reduction of these characteristics was noted for all the analyzed materials, except for the MBPc, which showed a slight increase of pH among the 3 initial periods. Conclusion. The results suggest that all materials investigated presented alkaline pH and ability of release of calcium ions. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009;108:135-139)
Since its introduction in dentistry by Lee et al.,1 several studies have demonstrated the excellent physicochemical properties of mineral trioxide aggregate (MTA), including the high sealing ability and adaptation to the dentinal walls,2 high radiopacity,3 alkalinity, and release of calcium ions.4,5 The MTA further presents antimicrobial activity,6,7 yet its most interesting property is the ability to stimulate deposition of mineralized tissue on its surface,8,9 assigning good biological properties. The combination of all these characteristics makes it the retrograde obturation and perforation repair material of choice in endodontic surgery. However, despite its good properties, MTA, introduced in the market under the commercial name ProRoot MTA (Dentsply/Tulsa Dental, Tulsa, OK, USA), presented some undesirable characteristics such as long setting a
Department of Endodontics, Brazilian Dental Association – Ceará Session, Ceará, Brazil. b Department of Endodontics, Faculty of Dentistry of Bauru, University of São Paulo. c Department of Dental Clinic, Faculty of Pharmacy, Dentistry and Nursing, Federal University of Ceará. d Department of Chemistry and Biochemistry, Bioscience Institute of Botucatu, University of São Paulo State. Received for publication Nov 15, 2008; returned for revision Feb 4, 2009; accepted for publication Feb 7, 2009. 1079-2104/$ - see front matter © 2009 Published by Mosby, Inc. doi:10.1016/j.tripleo.2009.02.026
time,3 difficult manipulation and insertion,5,10 and high cost.11 Thus, considering the composition of ProRoot MTA (75% Portland cement, 5% dihydrate calcium sulfate [gypsum] and 20% bismuth oxide),4 new Portland cement– based materials with different proportions and/or components were developed and introduced in the dental market trying to solve its undesirable characteristics. Angelus Odontológica (Londrina, PR, Brazil), a Brazilian laboratory, introduced alterations in the original composition of ProRoot MTA; the gray and white MTA manufactured by this company does not contain gypsum in its composition, being composed of only Portland cement (80%) and bismuth oxide (20%), attempting to reduce its setting time.4 Another example is the CPM, produced by E.G.E.O. (Buenos Aires, Argentina), an Argentine laboratory. Presented as a white modified Portland cement– based material, its most significant difference is the presence of a large amount of calcium carbonate, which intends to increase release of calcium ions, also offering good sealing properties, adhesion to the dentinal canal walls, adequate flow rate, and biocompatibility.12,13 The exact proportion of its components is not yet available; however, it is known that it is composed of Portland cement, calcium carbonate, barium sulfate, and bismuth trioxide.12 Besides these, other experimental materials have also been investigated. At Ilha Solteira, in São Paulo State 135
136
de Vasconcelos et al.
University (UNESP), a new Portland cement– based material (MTA-exp) was developed, yet using a gel composed of water, barium sulfate, and an emulsifier instead of distilled water, with a view to improve the manipulation of the cement. Santos et al.5 tested its release of calcium and hydroxide ions compared to gray MTA-Angelus, attributing this capacity to both materials; the authors also refer better manipulation characteristics of the experimental cement. In another research line, Moraes14 developed a pastepaste epoxy-resin cement-based material with vegetal polyurethane polyol (castor oil polymer) and a large amount of calcium hydroxide, still containing barium sulfate and bismuth subnitrate. This material exhibits physical-chemical characteristics and biological properties that allow its use as repair material and for retrograde obturation.14,15 Cintra et al.9 evaluated the tissue response after placement of tubes filled with this experimental cement, namely MBPc, in dental alveoli of rats. The authors observed similar results to those achieved by gray ProRoot MTA in all of different experimental periods. It has been suggested that the mechanism of stimulation of repair by deposition of mineralized tissue depends on the pH and the ability of release of calcium ions.4,8,16-18 It is known that the presence of specific agents in the composition of a dental material does not certainly imply their dissociation and release by the materials after curing, because the curing reaction and presence of another agent can inhibit the release of these ions.19 Thus, evaluation of such properties in these most recent and experimental materials is fundamental, because the influence of changes in the original composition of MTA on its properties is still not precisely known. Moreover, no study has evaluated these properties in most such materials so far, including the experimental epoxy cement MBPc. Therefore, the aim of this study was to evaluate the release of calcium and hydroxide ions of 4 retrograde obturation materials commercially available: gray ProRoot MTA, gray MTA-Angelus, white MTA-Angelus, and CPM, as well as 2 experimental cements, the MTA-exp and MBPc. MATERIAL AND METHODS The Portland cement– based materials were prepared following the manufacturers’ instructions. The MBPc, a resin cement available in paste-paste presentation, was prepared with a weight ratio of 3:1, i.e., 3 parts of base paste to 1 part of catalyst paste. As same as the commercial MTA cements, the MTA-exp manipulation uses a 3:1 powder-to-liquid proportion. Just after manipulation, the cements were inserted in plastic tubes (polyethylene) measuring 1.0 mm of internal diameter
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and 10.0 mm of length, with only one open end, with aid of a Lentulo spiral. After filled, the tubes were weighed to check the standardization of the amount of cement in each tube (⫾ 0.002 g). There were 5 samples used for each material. After filled and weighed, each specimen was immediately immersed in test tubes containing 10 mL of deionized water (Permution, Curitiba, PR, Brazil), which were then sealed with Parafilm (American National Can, Menasha, WI, USA) and placed in an oven at 37°C (Farmen, São Paulo, SP, Brazil), where they were kept throughout the study period. Previous to the immersion of specimens, the pH and calcium ion concentration of deionized water were verified, attesting pH 6.8 and total absence of calcium ions. Also, to avoid any type of interference in the outcomes, all laboratory equipment was previously treated with nitric acid. Evaluations were performed at periods of 3 hours, 24 hours, 72 hours, and 168 hours (7 days). After each measurement, the specimens were carefully moved to new tubes with fresh deionized water. Measurement of pH was performed with a pH meter (371, Micronal, São Paulo, SP, Brazil), previously calibrated with solutions with known pH (4, 7, and 14). After removal of the specimens, the test tubes were placed in a shaker (251, Farmen) for 5 seconds, before pH measurement. The release of calcium ions was measured using an atomic absorption spectrophotometer (AA6800, Shimadzu, Tokyo, Japan). The conditions for use of the appliance were determined following the manufacturer’s instructions, using a wavelength of 422.70 nm, gap of 0.2 nm, current of 10 mA in the lamp, and slightly reducing stoichiometry, kept by an acetylene flow of 2.0 L per minute, supported by the air. A lanthanum chloride solution at concentration 10 g/L was used to eliminate the interference of phosphates and sulfates and the possibility of formation of refractory oxides. A standard stock solution of 10 mg/dL was diluted in water to achieve the following concentrations: 0.025 mg/dL, 0.05 mg/dL, 0.1 mg/dL, 0.25 mg/dL, 0.5 mg/ dL, and 1.0 mg/dL. The results were calculated according to a standard curve, established on the basis of solutions with predefined calcium concentrations. The values achieved of pH and calcium ions released were plotted and placed on a normal curve, which revealed the parametric nature of data. Thus, the results were assessed by analysis of variance (ANOVA) and then by the Tukey test for individual comparisons (P ⬍ .05). RESULTS Tables I and II, respectively, present the mean values of pH and release of calcium ions of the materials at the
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Table I. pH values found at the different periods 3 hours
24 hours
72 hours
168 hours
Material
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Gray ProRoot MTA Gray MTA-Angelus White MTA-Angelus CPM MTA-exp MBPc Immersion water
9.36c,d 9.78a,b 9.42b,c 9.56a,b,c 9.86a 9.10d 6.80
0.23 0.13 0.22 0.18 0.11 0.14 0.00
8.88a,b 9.58a 8.58b 9.06a,b 9.54a 9.46a 6.80
0.38 0.41 0.41 0.50 0.36 0.23 0.00
8.74b 9.60a 8.48b 8.58b 8.80b 9.74a 6.80
0.38 0.24 0.28 0.57 0.45 0.09 0.00
8.16a 8.68a 8.16a 8.38a 8.46a 8.48a 6.80
0.18 0.32 0.26 0.58 0.27 0.13 0.00
Values followed by different letters indicate statistically significant differences according to the Tukey test (P ⬍ .05).
Table II. Calcium ion release (mg/dL) observed at the different periods 3 hours Material Gray ProRoot MTA Gray MTA-Angelus White MTA-Angelus C.P.M. MTA-exp MBPc Immersion Water
Mean a
1.22 1.23a 1.22a 1.20a 1.23a 1.23a 0.00
24 hours SD 0.01 0.01 0.02 0.03 0.03 0.01 0.00
Mean a
0.51 0.49a 0.40b.c 0.33c 0.35c 0.47a.b 0.00
72 hours SD 0.03 0.04 0.06 0.03 0.03 0.05 0.00
Mean a
0.99 0.99a 0.88b 0.89a.b 0.88b 0.96a.b 0.00
168 hours SD 0.05 0.04 0.04 0.03 0.03 0.05 0.00
Mean a.b
1.30 1.28b 1.32a.b 1.31a.b 1.30a.b 1.36a 0.00
SD 0.02 0.03 0.05 0.02 0.01 0.05 0.00
Values followed by different letters indicate statistically significant differences according to the Tukey test (P ⬍ .05).
different study periods, as well as the statistically significant differences found. All cements presented alkaline pH, with tendency of reduction of alkalinity potential at longer periods; statistical differences between all periods were noted, except between 24 and 72 hours. The highest values were noted for MTA-exp, mean of 9.86, yet in the first study period. Different from the others, the MBPc cement presented increasing pH values when evaluated at the 3 initial periods, mean of 9.10, 9.46, and 9.74, respectively. With regard to the release of calcium ions, all materials released considerable amounts at the study periods; however, similar to the evaluation of pH, they demonstrated a tendency of reduction of this potential considering the time interval between each experimental period. The statistical analyses showed differences between all study periods. The highest values were observed for gray MTA-Angelus and the 2 experimental materials, with mean of 1.23 mg/dL. DISCUSSION The ability to allow and/or stimulate repair by deposition of mineralized tissue and its good physicochemical characteristics strengthen the utilization of MTAbased cements as retrograde obturation materials and for sealing of communications between the root canal
system and the external tooth surface. Holland et al.8 demonstrated the formation of Von Kossa–positive granules on the gray ProRoot MTA surface, thus stating that the calcium oxide in the material composition would probably react with the tissue fluids and produce calcium hydroxide, which in turn would dissociate into hydroxide and calcium ions. The hydroxide ions would be responsible for alkalinization of the medium, and consequently for activation of alkaline phosphatase. Considering the calcium ions, their extracellular presence has been reported to induce BMP-2 expression.20,21 Conversely, calcium ions would react with the carbonate ions present in the periapical tissue, leading to precipitation of calcite granules, which would trigger the process of deposition of mineralized tissue. The methodology used in the present study was similar to those used by Duarte et al.4 and Santos et al.5 All materials evaluated presented satisfactory release of calcium and hydroxide ions, yet demonstrated a reduction in values considering the time interval between each experimental period, presenting higher values at the initial periods, i.e. during setting, as also observed by Duarte et al.4 and Santos et al.5 With regard to the pH values, different from the present study, which observed a maximum value of 9.36 for gray ProRoot MTA, values higher than 12.0 were found by Torabinejad et al.3 and Chng et al.22,23
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This discrepancy might be explained by the fact that these authors measured the pH directly from the material mass with aid of microelectrodes instead of immersion tubes in water, as in the present study. The method described in this study has the advantage of allowing pH measurements at periods longer than the setting time, not representing the pH of the material, but rather its ability of alkalinization. In the present study, the CPM, white MTA-Angelus, and gray ProRoot MTA showed lower pH values than gray MTA-Angelus and MTA-exp. For white cements, this fact may be probably attributed to the lower presence of metallic oxides that could facilitate ion dissociation. For the gray ProRoot MTA, this difference could be assigned to the lower presence of Potland cement in its composition (75% compared to other cements containing 80% of Portland cement), even with the presence of dihydrate calcium sulfate, which provides longer setting time4 and more intensive initial drying.24 The MBPc cement had an interesting increase in pH in the first 3 periods, leading to higher mean values in the third period, namely 9.74, possibly a result of its longer setting time and solubility rate,25 characteristics that could contribute to its more intense dissociation of components, despite being a resin-based material. Concerning the values found for the release of calcium ions, the present study agrees with the findings of Duarte et al.4 and Santos et al.5 All tested materials released a very proximally amount of calcium ions, also decreasing this release with time. However, the highest values were observed for gray ProRoot MTA and MBPc cement. The former contains 5% of gypsum, which could be an additional source of calcium ions; conversely, the experimental epoxy-resin cement contains a large amount of calcium hydroxide, which associated with the previously mentioned solubility21 could justify this high values of calcium ion release. Considering the results of the present study, both experimental cements demonstrated very similar pH and ability of release of calcium ions as the commercially available cements, with even higher values at some periods. Considering these properties, it allows the statement that these 2 materials have potential for use as retrograde obturation materials or for sealing of communications of the root canal system, especially the MBPc, which is a resin material whose consistence is close to that of SuperEBA, even though presenting easy manipulation and insertion combined with good biological properties.9 CONCLUSION Based on the aforementioned results, it could be concluded that all materials investigated presented alkaline
pH and ability of release of calcium ions, indicating that changes introduced in these material compositions did not significantly influence the characteristics evaluated. UNCITED REFERENCES This section comprises references that occur in the reference list but not in the body of the text. Please position each reference in the text or, alternatively, delete it. Any reference not dealt with will be retained in this section.16 REFERENCES 1. Lee SJ, Monsef M, Torabinejad M. Sealing ability of a mineral trioxide aggregate for repair of lateral root perforations. J Endod 1993;19:541-4. 2. Torabinejad M, Watson TF, Pitt Ford TR. Sealing ability of a mineral trioxide aggregate when used as a root end filling material. J Endod 1993;19:591-5. 3. Torabinejad M, Hong CU, McDonald F, Pitt Ford TR. Physical and chemical properties of a new root-end filling material. J Endod 1995;21:349-53. 4. Duarte MA, Demarchi ACCO, Yamashita JC, Kuga MC, Fraga SC. pH and calcium ion release of 2 root-end filling materials. Oral Surg Oral Med Oral Pathol Oral Radiol and Endod 2003;95:345-7. 5. Santos AD, Moraes JC, Araujo EB, Yukimitu K, Valerio Filho WV. Physico-chemical properties of MTA and a novel experimental cement. Int Endod J 2005;38:443-7. 6. Estrela C, Bammann LL, Estrela CR, Silva RS, Pecora JD. Antimicrobial and chemical study of MTA, Portland cement, calcium hydroxide paste, Sealapex and Dycal. Braz Dent J 2000;11:3-9. 7. Sipert CR, Hussne RP, Nishiyama CK, Torres SA. In vitro antimicrobial activity of Fill Canal, Sealapex, Mineral Trioxide Aggregate, Portland cement and EndoRez. Int Endod J 2005; 38:539-43. 8. Holland R, Souza V, Nery MJ, Otoboni Filho JA, Bernabé PEF, Dezan Júnior E. Reaction of rat connective tissue to implanted dentin tube filled with mineral trioxide aggregate, Portland cement or calcium hydroxide. Braz Dent J 2001;12:3-8. 9. Cintra LT, Moraes IG, Estrada BP, Gomes Filho JE, Bramante CM, Garcia RB, et al. Evaluation of the tissue response to MTA and MBPC: microscopic analysis of implants in alveolar bone of rats. J Endod 2006;32:556-9. 10. Bozeman TB, Lemon RR, Eleazer PD. Elemental analysis of crystal precipitate from gray and white MTA. J Endod 2006;32: 425-8. 11. Duarte MA, Demarchi ACO,Yamashita JC, Kuga MC, Fraga SC. Arsenic release provided by MTA and Portland cement. Oral Med Oral Pathol Oral Radiol and Endod 2005;99:648-50. 12. Castro G. Trióxidos minerales agregados—CPM y EndoCPMsealer [monograph]. Buenos Aires, Argetina: Centro de Investigaciones Odontológicas; 2003. 13. Bramante CM, Bramante AS, Moraes IG, Bernardineli N, Garcia B. CPM es MTA: nuevos materiales de uso en endodoncia— exemplos clinicos en el manejo de los materiales. Rev Fac Odontol 2006;17:7-10. 14. Moraes IG. Propriedades físicas de cimentos epóxicos experimentais para obturação de canais radiculares, baseados no ah26 [dissertation]. São Paulo, Brazil: Faculty of Dentistry of Bauru/ University of São Paulo; 1984. 15. Silva-Neto UX. Capacidade seladora e adaptação marginal proporcionadas por alguns materiais quando utilizados em perfurações na
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16.
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22.
região de furca de molares humanos [thesis]. São Paulo, Brazil: Faculty of Dentistry of Bauru/University of São Paulo; 2002. Stanley HR. Pulp capping: conserving the dental pulp— can it be done? Is it worth it? Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1989;68:628-39. Seux D, Couble ML, Hartmann DJ, Gauthier JP, Magloire H. Odontoblast-like cytodifferentiation of human dental pulp cells in vitro in the presence of a calcium hydroxide-containing cement. Arch Oral Biol 1991;36:117-28. Okabe T, Sakamoto M, Takeuchi H, Matsushima K. Effects of pH on mineralization ability of human dental pulp cells. J Endod 2006;32:198-201. Staehle HJ, Spiess V, Heinecke A, Muller HP. Effect of root canal filling materials containing calcium hydroxide on the alkalinity of root dentin. Endod Dent Traumatol 1995;11(4):163-8. Rashid F, Shiba H, Mizuno N, Mouri Y, Fujita T, Shinohara H, et al. The effect of extracellular calcium ion on gene expression of bone-related proteins in human pulp cells. J Endod 2003;294:104-7. Yasuda Y, Ogowa M, Apakawa T, Kadowaki T, Saito T. The effect of MTA on the mineralization abality of rat dental pulp cells: an in vitro study. J Endod 2008;34:1057-60. Chng HK, Islam I, Yap AU, Tong YW, Koh ET. Properties of a new root-end filling material. J Endod 2005;31:665-8.
de Vasconcelos et al. 139 23. Islam I, Chng HK, Yap AU. Comparison of the physical and mechanical properties of MTA and portland cement. J Endod 2006;32:193-7. 24. Dammaschke T, Gerth HU, Zuchner H, Schafer E. Chemical and physical surface and bulk material characterization of white ProRoot MTA and two Portland cements. Dent Mater 2005;21: 731-8. 25. Vasconcelos BC. Avaliação de algumas propriedades físicoquímicas de cimentos retroobturadores à base de agregado trióxido mineral e de um cimento epóxico experimental [thesis]. São Paulo, Brazil: Faculty of Dentistry of Bauru/University of São Paulo; 2006.
Reprint requests: Bruno Carvalho de Vasconcelos, DDS, MS Faculty of Dentistry of Bauru and Brazilian Dental Association – Ceará Session Department of Endodontics Rua Ana Bilhar 940, apto 704 (60160-110) Fortaleza, Ceará, Brazil [email protected]
Objective. The purpose of this study was to evaluate the pH and calcium ion release of 6 materials used for root-end filling and perforation repair. Study design. Gray ProRoot MTA, gray MTA-Angelus, white MTA-Angelus, and CPM were compared to 2 experimental ones: MTA-exp, also based in Portland cement with a modified mixing liquid, and MBPc, an epoxy-resin based cement containing calcium hydroxide. After 3, 24, 72, and 168 hours the water in which each sample had been immersed was tested to determine the ph and calcium ion release. Results. All the analyzed materials showed alkaline pH and capacity to release calcium ions; however, a tendency of reduction of these characteristics was noted for all the analyzed materials, except for the MBPc, which showed a slight increase of pH among the 3 initial periods. Conclusion. The results suggest that all materials investigated presented alkaline pH and ability of release of calcium ions. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009;108:135-139)
Since its introduction in dentistry by Lee et al.,1 several studies have demonstrated the excellent physicochemical properties of mineral trioxide aggregate (MTA), including the high sealing ability and adaptation to the dentinal walls,2 high radiopacity,3 alkalinity, and release of calcium ions.4,5 The MTA further presents antimicrobial activity,6,7 yet its most interesting property is the ability to stimulate deposition of mineralized tissue on its surface,8,9 assigning good biological properties. The combination of all these characteristics makes it the retrograde obturation and perforation repair material of choice in endodontic surgery. However, despite its good properties, MTA, introduced in the market under the commercial name ProRoot MTA (Dentsply/Tulsa Dental, Tulsa, OK, USA), presented some undesirable characteristics such as long setting a
Department of Endodontics, Brazilian Dental Association – Ceará Session, Ceará, Brazil. b Department of Endodontics, Faculty of Dentistry of Bauru, University of São Paulo. c Department of Dental Clinic, Faculty of Pharmacy, Dentistry and Nursing, Federal University of Ceará. d Department of Chemistry and Biochemistry, Bioscience Institute of Botucatu, University of São Paulo State. Received for publication Nov 15, 2008; returned for revision Feb 4, 2009; accepted for publication Feb 7, 2009. 1079-2104/$ - see front matter © 2009 Published by Mosby, Inc. doi:10.1016/j.tripleo.2009.02.026
time,3 difficult manipulation and insertion,5,10 and high cost.11 Thus, considering the composition of ProRoot MTA (75% Portland cement, 5% dihydrate calcium sulfate [gypsum] and 20% bismuth oxide),4 new Portland cement– based materials with different proportions and/or components were developed and introduced in the dental market trying to solve its undesirable characteristics. Angelus Odontológica (Londrina, PR, Brazil), a Brazilian laboratory, introduced alterations in the original composition of ProRoot MTA; the gray and white MTA manufactured by this company does not contain gypsum in its composition, being composed of only Portland cement (80%) and bismuth oxide (20%), attempting to reduce its setting time.4 Another example is the CPM, produced by E.G.E.O. (Buenos Aires, Argentina), an Argentine laboratory. Presented as a white modified Portland cement– based material, its most significant difference is the presence of a large amount of calcium carbonate, which intends to increase release of calcium ions, also offering good sealing properties, adhesion to the dentinal canal walls, adequate flow rate, and biocompatibility.12,13 The exact proportion of its components is not yet available; however, it is known that it is composed of Portland cement, calcium carbonate, barium sulfate, and bismuth trioxide.12 Besides these, other experimental materials have also been investigated. At Ilha Solteira, in São Paulo State 135
136
de Vasconcelos et al.
University (UNESP), a new Portland cement– based material (MTA-exp) was developed, yet using a gel composed of water, barium sulfate, and an emulsifier instead of distilled water, with a view to improve the manipulation of the cement. Santos et al.5 tested its release of calcium and hydroxide ions compared to gray MTA-Angelus, attributing this capacity to both materials; the authors also refer better manipulation characteristics of the experimental cement. In another research line, Moraes14 developed a pastepaste epoxy-resin cement-based material with vegetal polyurethane polyol (castor oil polymer) and a large amount of calcium hydroxide, still containing barium sulfate and bismuth subnitrate. This material exhibits physical-chemical characteristics and biological properties that allow its use as repair material and for retrograde obturation.14,15 Cintra et al.9 evaluated the tissue response after placement of tubes filled with this experimental cement, namely MBPc, in dental alveoli of rats. The authors observed similar results to those achieved by gray ProRoot MTA in all of different experimental periods. It has been suggested that the mechanism of stimulation of repair by deposition of mineralized tissue depends on the pH and the ability of release of calcium ions.4,8,16-18 It is known that the presence of specific agents in the composition of a dental material does not certainly imply their dissociation and release by the materials after curing, because the curing reaction and presence of another agent can inhibit the release of these ions.19 Thus, evaluation of such properties in these most recent and experimental materials is fundamental, because the influence of changes in the original composition of MTA on its properties is still not precisely known. Moreover, no study has evaluated these properties in most such materials so far, including the experimental epoxy cement MBPc. Therefore, the aim of this study was to evaluate the release of calcium and hydroxide ions of 4 retrograde obturation materials commercially available: gray ProRoot MTA, gray MTA-Angelus, white MTA-Angelus, and CPM, as well as 2 experimental cements, the MTA-exp and MBPc. MATERIAL AND METHODS The Portland cement– based materials were prepared following the manufacturers’ instructions. The MBPc, a resin cement available in paste-paste presentation, was prepared with a weight ratio of 3:1, i.e., 3 parts of base paste to 1 part of catalyst paste. As same as the commercial MTA cements, the MTA-exp manipulation uses a 3:1 powder-to-liquid proportion. Just after manipulation, the cements were inserted in plastic tubes (polyethylene) measuring 1.0 mm of internal diameter
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and 10.0 mm of length, with only one open end, with aid of a Lentulo spiral. After filled, the tubes were weighed to check the standardization of the amount of cement in each tube (⫾ 0.002 g). There were 5 samples used for each material. After filled and weighed, each specimen was immediately immersed in test tubes containing 10 mL of deionized water (Permution, Curitiba, PR, Brazil), which were then sealed with Parafilm (American National Can, Menasha, WI, USA) and placed in an oven at 37°C (Farmen, São Paulo, SP, Brazil), where they were kept throughout the study period. Previous to the immersion of specimens, the pH and calcium ion concentration of deionized water were verified, attesting pH 6.8 and total absence of calcium ions. Also, to avoid any type of interference in the outcomes, all laboratory equipment was previously treated with nitric acid. Evaluations were performed at periods of 3 hours, 24 hours, 72 hours, and 168 hours (7 days). After each measurement, the specimens were carefully moved to new tubes with fresh deionized water. Measurement of pH was performed with a pH meter (371, Micronal, São Paulo, SP, Brazil), previously calibrated with solutions with known pH (4, 7, and 14). After removal of the specimens, the test tubes were placed in a shaker (251, Farmen) for 5 seconds, before pH measurement. The release of calcium ions was measured using an atomic absorption spectrophotometer (AA6800, Shimadzu, Tokyo, Japan). The conditions for use of the appliance were determined following the manufacturer’s instructions, using a wavelength of 422.70 nm, gap of 0.2 nm, current of 10 mA in the lamp, and slightly reducing stoichiometry, kept by an acetylene flow of 2.0 L per minute, supported by the air. A lanthanum chloride solution at concentration 10 g/L was used to eliminate the interference of phosphates and sulfates and the possibility of formation of refractory oxides. A standard stock solution of 10 mg/dL was diluted in water to achieve the following concentrations: 0.025 mg/dL, 0.05 mg/dL, 0.1 mg/dL, 0.25 mg/dL, 0.5 mg/ dL, and 1.0 mg/dL. The results were calculated according to a standard curve, established on the basis of solutions with predefined calcium concentrations. The values achieved of pH and calcium ions released were plotted and placed on a normal curve, which revealed the parametric nature of data. Thus, the results were assessed by analysis of variance (ANOVA) and then by the Tukey test for individual comparisons (P ⬍ .05). RESULTS Tables I and II, respectively, present the mean values of pH and release of calcium ions of the materials at the
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Table I. pH values found at the different periods 3 hours
24 hours
72 hours
168 hours
Material
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Gray ProRoot MTA Gray MTA-Angelus White MTA-Angelus CPM MTA-exp MBPc Immersion water
9.36c,d 9.78a,b 9.42b,c 9.56a,b,c 9.86a 9.10d 6.80
0.23 0.13 0.22 0.18 0.11 0.14 0.00
8.88a,b 9.58a 8.58b 9.06a,b 9.54a 9.46a 6.80
0.38 0.41 0.41 0.50 0.36 0.23 0.00
8.74b 9.60a 8.48b 8.58b 8.80b 9.74a 6.80
0.38 0.24 0.28 0.57 0.45 0.09 0.00
8.16a 8.68a 8.16a 8.38a 8.46a 8.48a 6.80
0.18 0.32 0.26 0.58 0.27 0.13 0.00
Values followed by different letters indicate statistically significant differences according to the Tukey test (P ⬍ .05).
Table II. Calcium ion release (mg/dL) observed at the different periods 3 hours Material Gray ProRoot MTA Gray MTA-Angelus White MTA-Angelus C.P.M. MTA-exp MBPc Immersion Water
Mean a
1.22 1.23a 1.22a 1.20a 1.23a 1.23a 0.00
24 hours SD 0.01 0.01 0.02 0.03 0.03 0.01 0.00
Mean a
0.51 0.49a 0.40b.c 0.33c 0.35c 0.47a.b 0.00
72 hours SD 0.03 0.04 0.06 0.03 0.03 0.05 0.00
Mean a
0.99 0.99a 0.88b 0.89a.b 0.88b 0.96a.b 0.00
168 hours SD 0.05 0.04 0.04 0.03 0.03 0.05 0.00
Mean a.b
1.30 1.28b 1.32a.b 1.31a.b 1.30a.b 1.36a 0.00
SD 0.02 0.03 0.05 0.02 0.01 0.05 0.00
Values followed by different letters indicate statistically significant differences according to the Tukey test (P ⬍ .05).
different study periods, as well as the statistically significant differences found. All cements presented alkaline pH, with tendency of reduction of alkalinity potential at longer periods; statistical differences between all periods were noted, except between 24 and 72 hours. The highest values were noted for MTA-exp, mean of 9.86, yet in the first study period. Different from the others, the MBPc cement presented increasing pH values when evaluated at the 3 initial periods, mean of 9.10, 9.46, and 9.74, respectively. With regard to the release of calcium ions, all materials released considerable amounts at the study periods; however, similar to the evaluation of pH, they demonstrated a tendency of reduction of this potential considering the time interval between each experimental period. The statistical analyses showed differences between all study periods. The highest values were observed for gray MTA-Angelus and the 2 experimental materials, with mean of 1.23 mg/dL. DISCUSSION The ability to allow and/or stimulate repair by deposition of mineralized tissue and its good physicochemical characteristics strengthen the utilization of MTAbased cements as retrograde obturation materials and for sealing of communications between the root canal
system and the external tooth surface. Holland et al.8 demonstrated the formation of Von Kossa–positive granules on the gray ProRoot MTA surface, thus stating that the calcium oxide in the material composition would probably react with the tissue fluids and produce calcium hydroxide, which in turn would dissociate into hydroxide and calcium ions. The hydroxide ions would be responsible for alkalinization of the medium, and consequently for activation of alkaline phosphatase. Considering the calcium ions, their extracellular presence has been reported to induce BMP-2 expression.20,21 Conversely, calcium ions would react with the carbonate ions present in the periapical tissue, leading to precipitation of calcite granules, which would trigger the process of deposition of mineralized tissue. The methodology used in the present study was similar to those used by Duarte et al.4 and Santos et al.5 All materials evaluated presented satisfactory release of calcium and hydroxide ions, yet demonstrated a reduction in values considering the time interval between each experimental period, presenting higher values at the initial periods, i.e. during setting, as also observed by Duarte et al.4 and Santos et al.5 With regard to the pH values, different from the present study, which observed a maximum value of 9.36 for gray ProRoot MTA, values higher than 12.0 were found by Torabinejad et al.3 and Chng et al.22,23
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This discrepancy might be explained by the fact that these authors measured the pH directly from the material mass with aid of microelectrodes instead of immersion tubes in water, as in the present study. The method described in this study has the advantage of allowing pH measurements at periods longer than the setting time, not representing the pH of the material, but rather its ability of alkalinization. In the present study, the CPM, white MTA-Angelus, and gray ProRoot MTA showed lower pH values than gray MTA-Angelus and MTA-exp. For white cements, this fact may be probably attributed to the lower presence of metallic oxides that could facilitate ion dissociation. For the gray ProRoot MTA, this difference could be assigned to the lower presence of Potland cement in its composition (75% compared to other cements containing 80% of Portland cement), even with the presence of dihydrate calcium sulfate, which provides longer setting time4 and more intensive initial drying.24 The MBPc cement had an interesting increase in pH in the first 3 periods, leading to higher mean values in the third period, namely 9.74, possibly a result of its longer setting time and solubility rate,25 characteristics that could contribute to its more intense dissociation of components, despite being a resin-based material. Concerning the values found for the release of calcium ions, the present study agrees with the findings of Duarte et al.4 and Santos et al.5 All tested materials released a very proximally amount of calcium ions, also decreasing this release with time. However, the highest values were observed for gray ProRoot MTA and MBPc cement. The former contains 5% of gypsum, which could be an additional source of calcium ions; conversely, the experimental epoxy-resin cement contains a large amount of calcium hydroxide, which associated with the previously mentioned solubility21 could justify this high values of calcium ion release. Considering the results of the present study, both experimental cements demonstrated very similar pH and ability of release of calcium ions as the commercially available cements, with even higher values at some periods. Considering these properties, it allows the statement that these 2 materials have potential for use as retrograde obturation materials or for sealing of communications of the root canal system, especially the MBPc, which is a resin material whose consistence is close to that of SuperEBA, even though presenting easy manipulation and insertion combined with good biological properties.9 CONCLUSION Based on the aforementioned results, it could be concluded that all materials investigated presented alkaline
pH and ability of release of calcium ions, indicating that changes introduced in these material compositions did not significantly influence the characteristics evaluated. UNCITED REFERENCES This section comprises references that occur in the reference list but not in the body of the text. Please position each reference in the text or, alternatively, delete it. Any reference not dealt with will be retained in this section.16 REFERENCES 1. Lee SJ, Monsef M, Torabinejad M. Sealing ability of a mineral trioxide aggregate for repair of lateral root perforations. J Endod 1993;19:541-4. 2. Torabinejad M, Watson TF, Pitt Ford TR. Sealing ability of a mineral trioxide aggregate when used as a root end filling material. J Endod 1993;19:591-5. 3. Torabinejad M, Hong CU, McDonald F, Pitt Ford TR. Physical and chemical properties of a new root-end filling material. J Endod 1995;21:349-53. 4. Duarte MA, Demarchi ACCO, Yamashita JC, Kuga MC, Fraga SC. pH and calcium ion release of 2 root-end filling materials. Oral Surg Oral Med Oral Pathol Oral Radiol and Endod 2003;95:345-7. 5. Santos AD, Moraes JC, Araujo EB, Yukimitu K, Valerio Filho WV. Physico-chemical properties of MTA and a novel experimental cement. Int Endod J 2005;38:443-7. 6. Estrela C, Bammann LL, Estrela CR, Silva RS, Pecora JD. Antimicrobial and chemical study of MTA, Portland cement, calcium hydroxide paste, Sealapex and Dycal. Braz Dent J 2000;11:3-9. 7. Sipert CR, Hussne RP, Nishiyama CK, Torres SA. In vitro antimicrobial activity of Fill Canal, Sealapex, Mineral Trioxide Aggregate, Portland cement and EndoRez. Int Endod J 2005; 38:539-43. 8. Holland R, Souza V, Nery MJ, Otoboni Filho JA, Bernabé PEF, Dezan Júnior E. Reaction of rat connective tissue to implanted dentin tube filled with mineral trioxide aggregate, Portland cement or calcium hydroxide. Braz Dent J 2001;12:3-8. 9. Cintra LT, Moraes IG, Estrada BP, Gomes Filho JE, Bramante CM, Garcia RB, et al. Evaluation of the tissue response to MTA and MBPC: microscopic analysis of implants in alveolar bone of rats. J Endod 2006;32:556-9. 10. Bozeman TB, Lemon RR, Eleazer PD. Elemental analysis of crystal precipitate from gray and white MTA. J Endod 2006;32: 425-8. 11. Duarte MA, Demarchi ACO,Yamashita JC, Kuga MC, Fraga SC. Arsenic release provided by MTA and Portland cement. Oral Med Oral Pathol Oral Radiol and Endod 2005;99:648-50. 12. Castro G. Trióxidos minerales agregados—CPM y EndoCPMsealer [monograph]. Buenos Aires, Argetina: Centro de Investigaciones Odontológicas; 2003. 13. Bramante CM, Bramante AS, Moraes IG, Bernardineli N, Garcia B. CPM es MTA: nuevos materiales de uso en endodoncia— exemplos clinicos en el manejo de los materiales. Rev Fac Odontol 2006;17:7-10. 14. Moraes IG. Propriedades físicas de cimentos epóxicos experimentais para obturação de canais radiculares, baseados no ah26 [dissertation]. São Paulo, Brazil: Faculty of Dentistry of Bauru/ University of São Paulo; 1984. 15. Silva-Neto UX. Capacidade seladora e adaptação marginal proporcionadas por alguns materiais quando utilizados em perfurações na
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Reprint requests: Bruno Carvalho de Vasconcelos, DDS, MS Faculty of Dentistry of Bauru and Brazilian Dental Association – Ceará Session Department of Endodontics Rua Ana Bilhar 940, apto 704 (60160-110) Fortaleza, Ceará, Brazil [email protected]