Basic Research—Technology
Evaluation of Compressive Strength of Hydraulic Silicate-based Root-end Filling Materials Ryan M. Walsh, DDS, Karl F. Woodmansey, DDS, Gerald N. Glickman, DDS, MS, and Jianing He, DMD, PhD Abstract Introduction: Hydraulic silicate cements such as mineral trioxide aggregate (MTA) have many clinical advantages. Newer hydraulic silicate materials have been developed that improve on the limitations of mineral trioxide aggregate such as the long setting time and difficult handling characteristics. The purpose of this study was to examine the effect of saline and fetal bovine serum (FBS) on the setting and compressive strength of the following hydraulic silicate cements: ProRoot MTA (white WMTA; Dentsply International, Tulsa Dental Specialties, Johnson City, TN), EndoSequence Root Repair Material (Brasseler USA, Savannah, GA), MTA Plus (MTAP; Avalon Biomed Inc, Bradenton, FL), and QuickSet (QS; Avalon Biomed Inc, Bradenton, FL). Methods: Samples of root-end filling materials were compacted into polyethylene molds. Samples were exposed to FBS or saline for 7 days. A universal testing machine was used to determine the compressive strengths. Results: QS had significantly lower compressive strength than all other materials (P < .001). White MTA and MTAP mixed with liquid had lower compressive strengths after exposure to FBS compared with saline (P = .003). ERRM, MTAP mixed with gel, and QS were not affected by the exposure to FBS. Conclusions: New silicate-based root-end filling materials, other than QS, have compressive strength similar to MTA. Within the limits of this study, premixed materials and those mixed with antiwashout gel maintain their compressive strength when exposed to biological fluids. (J Endod 2014;-:1–4)
Key Words Compressive strength, hydraulic silicate cement, MTA, root-end filling
From the Department of Endodontics, Texas A&M University Baylor College of Dentistry, Dallas, Texas. Address requests for reprints to Dr Jianing He, Department of Endodontics, Baylor College of Dentistry, 3302 Gaston Avenue, Dallas, TX 75246. E-mail address: [email protected] 0099-2399/$ - see front matter Copyright ª 2014 American Association of Endodontists. http://dx.doi.org/10.1016/j.joen.2013.11.018
JOE — Volume -, Number -, - 2014
T
he goal of endodontic surgery is to resolve periapical pathosis when orthograde endodontic treatment is no longer an option (1). The root-end filling material must possess adequate sealing properties, dimensional stability, radiopacity, and biocompatibility (1, 2). Many materials have been advocated for root-end fillings, but today hydraulic silicate cements are commonly used. ProRoot MTA (white mineral trioxide aggregate [WMTA]) (Dentsply International, Tulsa Dental Specialties, Johnson City, TN) is a commonly used hydraulic cement (3). These materials have also been recommended for apexification of immature teeth, perforation repair, and vital pulp therapy (4). Hydraulic silicate cements set in contact with moisture via a hydration reaction (3, 5, 6). Clinically, both the manufacturer’s liquid and biological fluids at the surgical site provide moisture for the setting of the material. These bodily fluids have been reported to affect the set of WMTA (7–9). Torabinejad et al (10) evaluated the effect of blood exposure on dye leakage, and they showed that blood has no effect on the sealing properties of gray mineral trioxide aggregate (MTA). Nekoofar et al (7) found that exposing WMTA to blood altered the physical properties and decreased the compressive strength of the material. Tingey et al (9) exposed WMTA samples to fetal bovine serum (FBS) and saline to evaluate any change in the surface microstructure. They found that exposing WMTA to blood significantly altered the surface morphology of the WMTA samples. WMTA has many desirable properties and continues to be the gold standard for root-end filling materials (3, 11, 12). Newer hydraulic silicate cements have recently been introduced to the marketplace to improve on the limitations of MTA such as the long setting time and difficult handling characteristics. One of these newer cements is MTA Plus (MTAP) (Avalon Biomed Inc, Bradenton, FL). MTAP is a tricalcium and dicalcium silicate–based cement that can be mixed with a liquid or a gel. The gel improves handling properties and washout resistance of the material (13). MTAP also has the benefit of decreased setting time of approximately 75 minutes compared with WMTA (14). Similarly, QuickSet (QS) (Avalon Biomed Inc, Bradenton, FL) is an experimental calcium aluminosilicate material that has a comparatively reduced setting time (15). When mixed with antiwashout gel, QS exhibits improved handling properties (16). Both MTAP and QS have shown similar biocompatibility to WMTA (15, 16). Another calcium silicate–based hydraulic cement is EndoSequence Root Repair Material (ERRM) (Brasseler USA, Savannah, GA). Unlike other products, it comes premixed in a ready-to-use container. ERRM is a calcium phosphate silicate material with a bioceramic component. It has similar biocompatibility compared with MTA and other calcium silicate–based materials (17–19). ERRM also overcomes the basic handling difficulties associated with MTA (19). Compressive strength is a measure of multiple material properties including the hydration reaction that is critical to the setting of hydraulic silicate cements (4, 20, 21). Compressive strength is an indirect measure of material setting (20, 21). Although dimensional stability and adequate sealing are of great importance to the clinician when choosing a root-end filling material, compressive strength is also an important property that may affect the clinical performance of the material (2). Compared with MTA, little research has been done involving the setting of these newer materials, and no study has compared the compressive strengths of these hydraulic silicate cements. This study evaluates and compares the compressive strengths of WMTA, MTAP, QS, and ERRM after exposure to saline and FBS.
Compressive Strength of Root-end Filling Materials
1
Basic Research—Technology Materials and Methods Four hydraulic silicate cements were evaluated: WMTA, ERRM, MTAP, and QS. Cylindrical polyethylene molds with double open ends (length = 5 mm and diameter = 4.17 mm) were used to make samples with standardized size and shape. ERRM was removed from the container and placed directly into the mold. WMTA powder was mixed according to the manufacturer directions with the liquid from the provided ampoules. QS and MTAP powder were mixed with the antiwashout gel according to the manufacturer’s directions. In an additional group, MTAP was mixed with the liquid provided from the manufacturer. A single operator mixed all samples. All materials were mixed in a 3:1 powder:liquid/gel ratio by weight as recommended by the manufacturers. Freshly mixed materials were compacted into the molds using an amalgam plugger. Forty samples of each material were then divided into 2 groups: saline (0.9% Sodium Chloride Irrigation USP; B Braun Medical Inc, Irvine, CA) or FBS (Gibco, Life Technologies, Grand Island, NY). The filled molds were placed into floral foam soaked with either saline or FBS and maintained at 37 C at 100% humidity for 7 days. After 7 days, the ends of the hardened samples were sanded with fresh 400-grit sandpaper to remove any material flash from the ends of the molds. The samples were released from the mold with a Hu-Friedy PLG 1/2 NS amalgam plugger (Hu-Friedy, Chicago, IL). The compressive strengths of the samples were evaluated using a universal testing machine (The Mechanical Tester; TestResources Inc, Shakopee, MN). The machine measured the minimum force in N/mm2 required to break the samples at a speed of 1 mm/s. The minimum force required to fracture the samples was recorded using MTestWr software version R 1.3.6 (TestResources Inc, Shakopee, MN). The means and standard deviations were calculated. Statistical analysis included 2-way analysis of variance and Tukey multiple comparison post hoc with a significance level set at P < .05.
Results The results for mean compressive strength are displayed in Figure 1. All samples were completely set and able to be evaluated for compressive strength. QS had significantly lower compressive strength among all the other materials exposed to either saline or FBS (P < .001). MTAP with gel and ERRM had significantly higher mean compressive strength than WMTA and QS (P = .01). ERRM was not significantly different in mean compressive strength from MTAP with gel or liquid (P = .669 and .306).
WMTA was not significantly different in compressive strength from MTAP mixed with water (P = .671). MTAP mixed with gel had significantly higher mean compressive strength than MTAP with liquid (P < .05). The condition the materials were exposed to had a statistically significant impact on compressive strength (P = .003). Tukey post hoc test showed that WMTA and MTAP mixed with water had significantly lower compressive strength after the exposure to FBS compared with saline.
Discussion This study was the first to evaluate compressive strength of novel hydraulic silicate cements, and it replicated a clinical scenario in which serum and saline are present at the surgical site. Other studies have shown that MTA and related materials both have a decreased setting time and compressive strength in the presence of blood and blood components (7, 8). The current study confirmed the earlier findings and reports that WMTA was significantly affected by exposure to FBS. MTAP mixed with the liquid had lower compressive strength after exposure to FBS. This finding was similar to the WMTA group and earlier findings by Nekoofar et al (7). The current study mixed MTAP with both the proprietary liquid and gel. The data indicate that the MTAP mixed with gel was not negatively affected by the exposure to FBS. MTAP and QS mixed with gel maintained constant compressive strength when exposed to both saline and FBS. Gel products had more consistent compressive strength. It is possible that the gel provides some surface protection to the hydraulic cements that guards them from detrimental surface defects induced by the serum. It is also plausible that the liquid was less able to hydrate all molecules of the sample. This could result in a decreased hydration reaction and overall decreased compressive strength noted in the samples. The compressive strength of premixed ERRM was minimally affected by exposure to FBS. ERRM was premixed by the manufacturer, and it may have a more homogenous mixture. Products that require chairside mixing may have inconsistencies within the material because of variations in operator mixing. QS had lower compressive strength than any of the materials evaluated. The level of compressive strength required for root-end filling materials is unknown based on our current literature. Although QS has lower compressive strength, it may still be clinically sufficient. The accelerated setting time may be a more desirable property than compressive strength in clinical scenarios that cannot afford the longer setting times of other hydraulic silicates such as WMTA. Overall, the
Figure 1. Mean compressive strength values (N/mm2) with standard deviations. MTAPG and MTAPL are MTAP mixed with gel or liquid, respectively. *Statistically significant difference (P < .05).
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JOE — Volume -, Number -, - 2014
Basic Research—Technology
Figure 3. Color stability of ERRM with Ta2O5 radiopacifier (left). Discoloration of MTAP with Bi2O3 radiopacifier (right).
Figure 2. ERRM mushrooming above the polyethylene mold.
compressive strength of ERRM and MTAP performed similarly to the gold standard WMTA. This is an encouraging finding because these materials were created, in part, to overcome the limitations of WMTA such as the long setting time and difficult handling properties. They both have improved handling properties, and MTAP mixed with both proprietary liquid and gel handled better than WMTA. One important finding from the study was that compressive strength of ERRM and MTAP with gel was not negatively affected by exposure to FBS, suggesting these materials are suitable replacements for WMTA. A 7-day interval was chosen to allow each material adequate time for setting. The use of floral sponges soaked in saline or MTA was similar to previous studies evaluating MTA (8, 22). Floral foam was used to replicate in vivo surgical site moisture. Blood was not used as a test group because clotting would prevent longer incubation periods. In the course of this study, we also observed an interesting phenomenon where mushrooming occurred as ERRM expanded (Fig. 2) above the polyethylene mold. The expansion was observed consistently in all ESRRM samples in both saline and FBS. The height of the expansion was not measured but was typically between 1 and 3 mm above the upper edge of the molds. No previous authors have reported expansion of ERRM with either saline or FBS. A slight expansion in the material may be desirable to potentially improve marginal adaptation and seal. However, excessive expansion may increase the risk of root fracture. Another additional finding was that the materials containing bismuth oxide (Bi2O3), including WMTA, MTAP, and QS, were found to have surface discoloration (Fig. 3). Other authors have reported discoloration of WMTA both in vitro and in vivo (4, 23, 24). Studies have indicated that Bi2O3 used as a radiopacifier may contribute to the observed discoloration (23, 24). Bismuth has variable oxidation states that may allow for an interchange with compounds within the sponge. These compounds may not react equally with tantalum oxide (Ta2O5) or zirconium oxide (ZrO2). Compounds that use Ta2O5 or ZrO2, such as ERRM, display more color stability, and they do not have the ‘‘graying effect’’ seen by other Bi2O3-based root filling materials. It is the thought of the authors that this ‘‘graying effect’’ is directly correlated with the presence of Bi2O3. JOE — Volume -, Number -, - 2014
In conclusion, WMTA, MTAP, and ERRM have higher compressive strength than QS. In addition, premixed materials (ERRM) and materials mixed with an antiwashout gel (MTAP and QS) were not significantly affected by exposure to FBS. Further research is needed to further understand the clinical implications of hydraulic silicate cements. Clinical studies need to be conducted to evaluate the significance of compressive strengths in various clinical scenarios. Lastly, the expansion of ERRM must be addressed before it can be confidently used for root-end fillings and beneath coronal restorations.
Acknowledgments The authors thank Avalon Biomed Inc for supplying materials used in this study. Supported in part by a research grant from the AAE Foundation. The authors deny any conflicts of interest.
References 1. Kim S, Kratchman S. Modern endodontic surgery concepts and practice: a review. J Endod 2006;32:601–23. 2. Johnson BR. Considerations in the selection of a root-end filling material. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1999;87:398–404. 3. Darvell B, Wu R. ‘‘MTA’’—an hydraulic silicate cement: review update and setting reaction. Dent Mater 2011;27:407–22. 4. Parirokh M, Torabinejad M. Mineral trioxide aggregate: a comprehensive literature review—part III: clinical applications, drawbacks, and mechanism of action. J Endod 2010;36:400–13. 5. Camilleri J. Hydration mechanisms of mineral trioxide aggregate. Int Endod J 2007; 40:462–70. 6. Nair U, Ghattas S, Saber M, et al. A comparative evaluation of the sealing ability of 2 root-end filling materials: an in vitro leakage study using Enterococcus faecalis. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2011;112:74–7. 7. Nekoofar M, Stone D, Dummer P. The effect of blood contamination of the compressive strength and surface microstructure of mineral trioxide aggregate. Int Endod J 2010;43:782–91. 8. Kim Y, Kim S, Shin Y, et al. Failure of setting of mineral trioxide aggregate in the presence of fetal bovine serum and its prevention. J Endod 2012;34:536–40. 9. Tingey M, Bush P, Levine M. Analysis of mineral trioxide aggregate surface when set in the presence of fetal bovine serum. J Endod 2008;34:45–9. 10. Torabinejad M, Higa R, McKendry D, et al. Dye leakage of four root end filling materials: effects of blood contamination. J Endod 1994;20:159–63. 11. Torabinejad M, Parirokh M. Mineral trioxide aggregate: a comprehensive literature review—part II: leakage and biocompatibility. J Endod 2010;36:190–202. 12. Parirokh M, Torabinejad M. Mineral trioxide aggregate: a comprehensive literature review—part I: chemical, physical and antibacterial properties. J Endod 2010;36: 16–27. 13. Formosa L, Mallia B, Camilleri J. A quantitative method for determining the antiwashout characteristics of cement-based dental materials including mineral trioxide aggregate. Int Endod J 2013;46:179–86.
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Basic Research—Technology 14. Camilleri J, Formosa L, Damindot D. The setting characteristics of MTA Plus in different environmental conditions. Int Endod J 2013;46:831–40. 15. Avalon Biomed. Avalon Biomed Inc. Available at: http://avalonbiomed.com/quickset/. Accessed March 20, 2013. 16. Wei W, Qi Y, Nikonov S, et al. Effects of an experimental calcium aluminosilicate cement on the viability of murine odontoblast-like Cells. J Endod 2012;38:936–42. 17. Shokouhinejad N, Nekoofar MH, Razmi H, et al. Bioactivity of EndoSequence root repair material and bioaggregate. Int Endod J 2012;45:1127–34. 18. Hirschman WR, Wheater M, Bringas J, et al. Pulp-capping agents with a new bioceramic root repair putty. J. Endod 2012;38:385–8. 19. Damas M, Wheater M, Bringas J, et al. Cytotoxicity comparison of mineral trioxide aggregates and EndoSequence bioceramic root repair materials. J. Endod 2011;37: 372–5.
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20. Danesh G, Dammaschke T, Gerth H, et al. A comparative study of selected properties of ProRoot mineral trioxide aggregate and two Portland cements. Int Endod J 2006; 39:213–9. 21. Kayahan M, Nekoofar M, Kazandag M, et al. Effect of acid-etching procedure on selected physical properties of mineral trioxide aggregate. Int Endod J 2009;42: 1004–14. 22. 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. 23. Watts JD, Holt DM, Beeson TJ, et al. Effects of ph and mixing agents on the temporal setting of tooth-colored and gray mineral trioxide aggregate. J Endod 2007;33: 970–3. 24. Krastl G, Allgayer N, Lenherr P, et al. Tooth discoloration induced by endodontic materials: a literature review. Dent Traumatol 2013;29:2–7.
JOE — Volume -, Number -, - 2014
Evaluation of Compressive Strength of Hydraulic Silicate-based Root-end Filling Materials Ryan M. Walsh, DDS, Karl F. Woodmansey, DDS, Gerald N. Glickman, DDS, MS, and Jianing He, DMD, PhD Abstract Introduction: Hydraulic silicate cements such as mineral trioxide aggregate (MTA) have many clinical advantages. Newer hydraulic silicate materials have been developed that improve on the limitations of mineral trioxide aggregate such as the long setting time and difficult handling characteristics. The purpose of this study was to examine the effect of saline and fetal bovine serum (FBS) on the setting and compressive strength of the following hydraulic silicate cements: ProRoot MTA (white WMTA; Dentsply International, Tulsa Dental Specialties, Johnson City, TN), EndoSequence Root Repair Material (Brasseler USA, Savannah, GA), MTA Plus (MTAP; Avalon Biomed Inc, Bradenton, FL), and QuickSet (QS; Avalon Biomed Inc, Bradenton, FL). Methods: Samples of root-end filling materials were compacted into polyethylene molds. Samples were exposed to FBS or saline for 7 days. A universal testing machine was used to determine the compressive strengths. Results: QS had significantly lower compressive strength than all other materials (P < .001). White MTA and MTAP mixed with liquid had lower compressive strengths after exposure to FBS compared with saline (P = .003). ERRM, MTAP mixed with gel, and QS were not affected by the exposure to FBS. Conclusions: New silicate-based root-end filling materials, other than QS, have compressive strength similar to MTA. Within the limits of this study, premixed materials and those mixed with antiwashout gel maintain their compressive strength when exposed to biological fluids. (J Endod 2014;-:1–4)
Key Words Compressive strength, hydraulic silicate cement, MTA, root-end filling
From the Department of Endodontics, Texas A&M University Baylor College of Dentistry, Dallas, Texas. Address requests for reprints to Dr Jianing He, Department of Endodontics, Baylor College of Dentistry, 3302 Gaston Avenue, Dallas, TX 75246. E-mail address: [email protected] 0099-2399/$ - see front matter Copyright ª 2014 American Association of Endodontists. http://dx.doi.org/10.1016/j.joen.2013.11.018
JOE — Volume -, Number -, - 2014
T
he goal of endodontic surgery is to resolve periapical pathosis when orthograde endodontic treatment is no longer an option (1). The root-end filling material must possess adequate sealing properties, dimensional stability, radiopacity, and biocompatibility (1, 2). Many materials have been advocated for root-end fillings, but today hydraulic silicate cements are commonly used. ProRoot MTA (white mineral trioxide aggregate [WMTA]) (Dentsply International, Tulsa Dental Specialties, Johnson City, TN) is a commonly used hydraulic cement (3). These materials have also been recommended for apexification of immature teeth, perforation repair, and vital pulp therapy (4). Hydraulic silicate cements set in contact with moisture via a hydration reaction (3, 5, 6). Clinically, both the manufacturer’s liquid and biological fluids at the surgical site provide moisture for the setting of the material. These bodily fluids have been reported to affect the set of WMTA (7–9). Torabinejad et al (10) evaluated the effect of blood exposure on dye leakage, and they showed that blood has no effect on the sealing properties of gray mineral trioxide aggregate (MTA). Nekoofar et al (7) found that exposing WMTA to blood altered the physical properties and decreased the compressive strength of the material. Tingey et al (9) exposed WMTA samples to fetal bovine serum (FBS) and saline to evaluate any change in the surface microstructure. They found that exposing WMTA to blood significantly altered the surface morphology of the WMTA samples. WMTA has many desirable properties and continues to be the gold standard for root-end filling materials (3, 11, 12). Newer hydraulic silicate cements have recently been introduced to the marketplace to improve on the limitations of MTA such as the long setting time and difficult handling characteristics. One of these newer cements is MTA Plus (MTAP) (Avalon Biomed Inc, Bradenton, FL). MTAP is a tricalcium and dicalcium silicate–based cement that can be mixed with a liquid or a gel. The gel improves handling properties and washout resistance of the material (13). MTAP also has the benefit of decreased setting time of approximately 75 minutes compared with WMTA (14). Similarly, QuickSet (QS) (Avalon Biomed Inc, Bradenton, FL) is an experimental calcium aluminosilicate material that has a comparatively reduced setting time (15). When mixed with antiwashout gel, QS exhibits improved handling properties (16). Both MTAP and QS have shown similar biocompatibility to WMTA (15, 16). Another calcium silicate–based hydraulic cement is EndoSequence Root Repair Material (ERRM) (Brasseler USA, Savannah, GA). Unlike other products, it comes premixed in a ready-to-use container. ERRM is a calcium phosphate silicate material with a bioceramic component. It has similar biocompatibility compared with MTA and other calcium silicate–based materials (17–19). ERRM also overcomes the basic handling difficulties associated with MTA (19). Compressive strength is a measure of multiple material properties including the hydration reaction that is critical to the setting of hydraulic silicate cements (4, 20, 21). Compressive strength is an indirect measure of material setting (20, 21). Although dimensional stability and adequate sealing are of great importance to the clinician when choosing a root-end filling material, compressive strength is also an important property that may affect the clinical performance of the material (2). Compared with MTA, little research has been done involving the setting of these newer materials, and no study has compared the compressive strengths of these hydraulic silicate cements. This study evaluates and compares the compressive strengths of WMTA, MTAP, QS, and ERRM after exposure to saline and FBS.
Compressive Strength of Root-end Filling Materials
1
Basic Research—Technology Materials and Methods Four hydraulic silicate cements were evaluated: WMTA, ERRM, MTAP, and QS. Cylindrical polyethylene molds with double open ends (length = 5 mm and diameter = 4.17 mm) were used to make samples with standardized size and shape. ERRM was removed from the container and placed directly into the mold. WMTA powder was mixed according to the manufacturer directions with the liquid from the provided ampoules. QS and MTAP powder were mixed with the antiwashout gel according to the manufacturer’s directions. In an additional group, MTAP was mixed with the liquid provided from the manufacturer. A single operator mixed all samples. All materials were mixed in a 3:1 powder:liquid/gel ratio by weight as recommended by the manufacturers. Freshly mixed materials were compacted into the molds using an amalgam plugger. Forty samples of each material were then divided into 2 groups: saline (0.9% Sodium Chloride Irrigation USP; B Braun Medical Inc, Irvine, CA) or FBS (Gibco, Life Technologies, Grand Island, NY). The filled molds were placed into floral foam soaked with either saline or FBS and maintained at 37 C at 100% humidity for 7 days. After 7 days, the ends of the hardened samples were sanded with fresh 400-grit sandpaper to remove any material flash from the ends of the molds. The samples were released from the mold with a Hu-Friedy PLG 1/2 NS amalgam plugger (Hu-Friedy, Chicago, IL). The compressive strengths of the samples were evaluated using a universal testing machine (The Mechanical Tester; TestResources Inc, Shakopee, MN). The machine measured the minimum force in N/mm2 required to break the samples at a speed of 1 mm/s. The minimum force required to fracture the samples was recorded using MTestWr software version R 1.3.6 (TestResources Inc, Shakopee, MN). The means and standard deviations were calculated. Statistical analysis included 2-way analysis of variance and Tukey multiple comparison post hoc with a significance level set at P < .05.
Results The results for mean compressive strength are displayed in Figure 1. All samples were completely set and able to be evaluated for compressive strength. QS had significantly lower compressive strength among all the other materials exposed to either saline or FBS (P < .001). MTAP with gel and ERRM had significantly higher mean compressive strength than WMTA and QS (P = .01). ERRM was not significantly different in mean compressive strength from MTAP with gel or liquid (P = .669 and .306).
WMTA was not significantly different in compressive strength from MTAP mixed with water (P = .671). MTAP mixed with gel had significantly higher mean compressive strength than MTAP with liquid (P < .05). The condition the materials were exposed to had a statistically significant impact on compressive strength (P = .003). Tukey post hoc test showed that WMTA and MTAP mixed with water had significantly lower compressive strength after the exposure to FBS compared with saline.
Discussion This study was the first to evaluate compressive strength of novel hydraulic silicate cements, and it replicated a clinical scenario in which serum and saline are present at the surgical site. Other studies have shown that MTA and related materials both have a decreased setting time and compressive strength in the presence of blood and blood components (7, 8). The current study confirmed the earlier findings and reports that WMTA was significantly affected by exposure to FBS. MTAP mixed with the liquid had lower compressive strength after exposure to FBS. This finding was similar to the WMTA group and earlier findings by Nekoofar et al (7). The current study mixed MTAP with both the proprietary liquid and gel. The data indicate that the MTAP mixed with gel was not negatively affected by the exposure to FBS. MTAP and QS mixed with gel maintained constant compressive strength when exposed to both saline and FBS. Gel products had more consistent compressive strength. It is possible that the gel provides some surface protection to the hydraulic cements that guards them from detrimental surface defects induced by the serum. It is also plausible that the liquid was less able to hydrate all molecules of the sample. This could result in a decreased hydration reaction and overall decreased compressive strength noted in the samples. The compressive strength of premixed ERRM was minimally affected by exposure to FBS. ERRM was premixed by the manufacturer, and it may have a more homogenous mixture. Products that require chairside mixing may have inconsistencies within the material because of variations in operator mixing. QS had lower compressive strength than any of the materials evaluated. The level of compressive strength required for root-end filling materials is unknown based on our current literature. Although QS has lower compressive strength, it may still be clinically sufficient. The accelerated setting time may be a more desirable property than compressive strength in clinical scenarios that cannot afford the longer setting times of other hydraulic silicates such as WMTA. Overall, the
Figure 1. Mean compressive strength values (N/mm2) with standard deviations. MTAPG and MTAPL are MTAP mixed with gel or liquid, respectively. *Statistically significant difference (P < .05).
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Figure 3. Color stability of ERRM with Ta2O5 radiopacifier (left). Discoloration of MTAP with Bi2O3 radiopacifier (right).
Figure 2. ERRM mushrooming above the polyethylene mold.
compressive strength of ERRM and MTAP performed similarly to the gold standard WMTA. This is an encouraging finding because these materials were created, in part, to overcome the limitations of WMTA such as the long setting time and difficult handling properties. They both have improved handling properties, and MTAP mixed with both proprietary liquid and gel handled better than WMTA. One important finding from the study was that compressive strength of ERRM and MTAP with gel was not negatively affected by exposure to FBS, suggesting these materials are suitable replacements for WMTA. A 7-day interval was chosen to allow each material adequate time for setting. The use of floral sponges soaked in saline or MTA was similar to previous studies evaluating MTA (8, 22). Floral foam was used to replicate in vivo surgical site moisture. Blood was not used as a test group because clotting would prevent longer incubation periods. In the course of this study, we also observed an interesting phenomenon where mushrooming occurred as ERRM expanded (Fig. 2) above the polyethylene mold. The expansion was observed consistently in all ESRRM samples in both saline and FBS. The height of the expansion was not measured but was typically between 1 and 3 mm above the upper edge of the molds. No previous authors have reported expansion of ERRM with either saline or FBS. A slight expansion in the material may be desirable to potentially improve marginal adaptation and seal. However, excessive expansion may increase the risk of root fracture. Another additional finding was that the materials containing bismuth oxide (Bi2O3), including WMTA, MTAP, and QS, were found to have surface discoloration (Fig. 3). Other authors have reported discoloration of WMTA both in vitro and in vivo (4, 23, 24). Studies have indicated that Bi2O3 used as a radiopacifier may contribute to the observed discoloration (23, 24). Bismuth has variable oxidation states that may allow for an interchange with compounds within the sponge. These compounds may not react equally with tantalum oxide (Ta2O5) or zirconium oxide (ZrO2). Compounds that use Ta2O5 or ZrO2, such as ERRM, display more color stability, and they do not have the ‘‘graying effect’’ seen by other Bi2O3-based root filling materials. It is the thought of the authors that this ‘‘graying effect’’ is directly correlated with the presence of Bi2O3. JOE — Volume -, Number -, - 2014
In conclusion, WMTA, MTAP, and ERRM have higher compressive strength than QS. In addition, premixed materials (ERRM) and materials mixed with an antiwashout gel (MTAP and QS) were not significantly affected by exposure to FBS. Further research is needed to further understand the clinical implications of hydraulic silicate cements. Clinical studies need to be conducted to evaluate the significance of compressive strengths in various clinical scenarios. Lastly, the expansion of ERRM must be addressed before it can be confidently used for root-end fillings and beneath coronal restorations.
Acknowledgments The authors thank Avalon Biomed Inc for supplying materials used in this study. Supported in part by a research grant from the AAE Foundation. The authors deny any conflicts of interest.
References 1. Kim S, Kratchman S. Modern endodontic surgery concepts and practice: a review. J Endod 2006;32:601–23. 2. Johnson BR. Considerations in the selection of a root-end filling material. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1999;87:398–404. 3. Darvell B, Wu R. ‘‘MTA’’—an hydraulic silicate cement: review update and setting reaction. Dent Mater 2011;27:407–22. 4. Parirokh M, Torabinejad M. Mineral trioxide aggregate: a comprehensive literature review—part III: clinical applications, drawbacks, and mechanism of action. J Endod 2010;36:400–13. 5. Camilleri J. Hydration mechanisms of mineral trioxide aggregate. Int Endod J 2007; 40:462–70. 6. Nair U, Ghattas S, Saber M, et al. A comparative evaluation of the sealing ability of 2 root-end filling materials: an in vitro leakage study using Enterococcus faecalis. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2011;112:74–7. 7. Nekoofar M, Stone D, Dummer P. The effect of blood contamination of the compressive strength and surface microstructure of mineral trioxide aggregate. Int Endod J 2010;43:782–91. 8. Kim Y, Kim S, Shin Y, et al. Failure of setting of mineral trioxide aggregate in the presence of fetal bovine serum and its prevention. J Endod 2012;34:536–40. 9. Tingey M, Bush P, Levine M. Analysis of mineral trioxide aggregate surface when set in the presence of fetal bovine serum. J Endod 2008;34:45–9. 10. Torabinejad M, Higa R, McKendry D, et al. Dye leakage of four root end filling materials: effects of blood contamination. J Endod 1994;20:159–63. 11. Torabinejad M, Parirokh M. Mineral trioxide aggregate: a comprehensive literature review—part II: leakage and biocompatibility. J Endod 2010;36:190–202. 12. Parirokh M, Torabinejad M. Mineral trioxide aggregate: a comprehensive literature review—part I: chemical, physical and antibacterial properties. J Endod 2010;36: 16–27. 13. Formosa L, Mallia B, Camilleri J. A quantitative method for determining the antiwashout characteristics of cement-based dental materials including mineral trioxide aggregate. Int Endod J 2013;46:179–86.
Compressive Strength of Root-end Filling Materials
3
Basic Research—Technology 14. Camilleri J, Formosa L, Damindot D. The setting characteristics of MTA Plus in different environmental conditions. Int Endod J 2013;46:831–40. 15. Avalon Biomed. Avalon Biomed Inc. Available at: http://avalonbiomed.com/quickset/. Accessed March 20, 2013. 16. Wei W, Qi Y, Nikonov S, et al. Effects of an experimental calcium aluminosilicate cement on the viability of murine odontoblast-like Cells. J Endod 2012;38:936–42. 17. Shokouhinejad N, Nekoofar MH, Razmi H, et al. Bioactivity of EndoSequence root repair material and bioaggregate. Int Endod J 2012;45:1127–34. 18. Hirschman WR, Wheater M, Bringas J, et al. Pulp-capping agents with a new bioceramic root repair putty. J. Endod 2012;38:385–8. 19. Damas M, Wheater M, Bringas J, et al. Cytotoxicity comparison of mineral trioxide aggregates and EndoSequence bioceramic root repair materials. J. Endod 2011;37: 372–5.
4
Walsh et al.
20. Danesh G, Dammaschke T, Gerth H, et al. A comparative study of selected properties of ProRoot mineral trioxide aggregate and two Portland cements. Int Endod J 2006; 39:213–9. 21. Kayahan M, Nekoofar M, Kazandag M, et al. Effect of acid-etching procedure on selected physical properties of mineral trioxide aggregate. Int Endod J 2009;42: 1004–14. 22. 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. 23. Watts JD, Holt DM, Beeson TJ, et al. Effects of ph and mixing agents on the temporal setting of tooth-colored and gray mineral trioxide aggregate. J Endod 2007;33: 970–3. 24. Krastl G, Allgayer N, Lenherr P, et al. Tooth discoloration induced by endodontic materials: a literature review. Dent Traumatol 2013;29:2–7.
JOE — Volume -, Number -, - 2014
