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Comparisons of the Retreatment Efficacy of Calcium Silicate and Epoxy Resin–based Sealers and Residual Sealer in Dentinal Tubules
Basic Research—Technology
Comparisons of the Retreatment Efficacy of Calcium Silicate and Epoxy Resin–based Sealers and Residual Sealer in Dentinal Tubules Hyunsuk Kim, DDS, MSD,* Euiseong Kim, DDS, PhD,† Seung-Jong Lee, DDS, PhD,† and Su-Jung Shin, DDS, PhD*‡ Abstract Introduction: The aim of this study was to evaluate the retreatment efficacy and amount of residual sealer in a single canal filled with either EndoSequence BC (Brasseler, Savannah, GA) or AH Plus (Dentsply DeTrey, Konstanz, Germany). Methods: Canal obturation with gutta-percha and sealer was performed in 28 human teeth using the continuous wave technique. Group 1 (n = 13) used AH Plus sealer, and group 2 (n = 15) used EndoSequence BC sealer. After 7 days, the root fillings were removed using Gates Glidden drills and a nickel-titanium rotary system. Retreatment time was measured in seconds. Canal cleanliness was examined by scanning electron microscopy. The remaining debris in the canal space and penetration into dentinal tubules were evaluated by confocal microscopy. Retreatment time was compared using the Student t test, and differences in sealer penetration and remaining debris between the groups were analyzed using the MannWhitney U test (P < .05). Results: There was no significant difference between the 2 groups in the amount of dentin penetration, amount of debris, or retreatment time. With respect to penetration depth, the AH Plus group showed a slightly higher percentage than the BC group, with a significant difference only in the portion 6 mm from the apex (P < .05). Scanning electron microscopic images showed significant debris remaining on canal walls in both groups, whereas canal patency in retreatment was achieved in every specimen. Conclusions: The present study shows that EndoSequence BC sealer and AH Plus sealer have similar efficacy in dentin penetration and retreatment efficacy. (J Endod 2015;-:1–6)
Key Words Calcium silicate, dentin penetration, endodontic sealer, retrievability
R
ecently, calcium silicate–based sealers such as MTA Plus (Prevest Denpro GmbH, Heidelberg, Germany), MTA Fillapex (Angelus, Londrina, Brazil), iRoot SP (Innovative BioCeramix, Vancouver, BC, Canada), and EndoSequence BC (Brassler USA, Savannah, GA) have been introduced. These products have shown low cytotoxicity, suitable bonding strength, and sealing ability (1–3). Moreover, some materials have been reported to induce biomineralization and hard tissue deposition (4). EndoSequence BC, 1 of the calcium silicate–based sealers, is composed of calcium silicates, calcium phosphate monobasic, zirconium oxide, tantalum oxide, and thickening agents. According to a recent study, EndoSequence BC sealed the root canal better than AH Plus sealer (Dentsply DeTrey, Konstanz, Germany) (5) and showed the highest bond strength under all moisture conditions (6). The material’s bond strengths were shown to be significantly higher than those of Sealapex (Kerr, Orange, CA) and EndoRez (Ultradent, South Jordan, UT) (7). Additionally, the material showed marginal adaptation similar to that of MTA (8). Zhang et al (9) reported EnodSequence BC’s cytotoxicity at 24 hours was much less than that of AH Plus, and it showed high biocompatibility. Moreover, although zinc oxide eugenol and AH Plus evoked greater calcitonin gene-related peptide release, EndoSequence BC sealer reduced basal calcitonin gene-related peptide release at all concentrations tested, indicating less potential for pain and neurogenic inflammation (10). It was also reported that BC sealer enhanced osteoblastic differentiation of periodontal ligament cells (11), induced dentin remineralization (12), and had strong antibacterial properties (13, 14). However, although the material’s clinical and biocompatibility features show promise in recently performed studies, studies on its retrievability are relatively few, and their results vary significantly. A calcium silicate–based sealer was shown to create hydroxyapatite crystals in the interface between dentin and sealer, and its retrieval from the dentinal wall and dentinal tubules may be challenging. Furthermore, the sealer’s ability to penetrate dentin is a property that may be related to the material’s retrievability. Although a dentin penetration property is not a shortcoming, the deep penetration depth of the material and dentinal tubule blockage may add challenges to canal retreatment. Only a few studies have focused on the retrievability and dentin penetration of calcium silicate sealers, and their results also vary significantly (15–17). Therefore, the purpose of this study was to evaluate and compare EndoSequence BC sealer and AH Plus sealer both in removal efficacy and the amount of residual filling material in the canal and dentinal tubules.
From the *Department of Conservative Dentistry and ‡Department of Conservative Dentistry and Oral Science Research Center, College of Dentistry, Gangnam Severance Hospital, Yonsei University, Seoul, Korea; and †Department of Conservative Dentistry and Oral Science Research Center, College of Dentistry, Yonsei University, Seoul, Korea. Address requests for reprints to Dr Su-Jung Shin, Department of Conservative Dentistry, Gangnam Severance Hospital, College of Dentistry,Yonsei University, 211 Eonjuro, Gangnam-gu, Seoul 135-720, Korea. E-mail address: [email protected] 0099-2399/$ - see front matter Copyright ª 2015 American Association of Endodontists. http://dx.doi.org/10.1016/j.joen.2015.08.030
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Basic Research—Technology Materials and Methods Preparation of Tooth Samples A total of 28 extracted single-rooted mature human teeth were used. The teeth were extracted for orthodontic and periodontal reasons, and the protocol was approved by the institutional review board committee at our institution (institutional review board approval no. 2-2015-0086). Teeth with microcracks were excluded from the study. Tooth crowns were removed using a water-cooled diamond bur to form standardized root samples of 13-mm lengths. K-file sizes #10 and #15 (Dentsply Maillefer, Ballaigues, Switzerland) were inserted into the canal to achieve the working length (WL). The canals were prepared using the ProFile rotary system (Dentsply Maillefer) to a size #35/0.06 taper according to the manufacturer’s instructions. Irrigation with a 3.25% sodium hypochlorite (NaOCl) solution was performed using a 27-G needle during filing. Finally, to remove the smear layer, 10 mL 17% EDTA solution was applied for 60 seconds. Then, the canals were flushed with 3.25% NaOCl and dried. Teeth were divided into 2 groups based on the sealer used during the root filling procedure: group 1 (n = 13) (AH Plus sealer) and group 2 (n = 15) (EndoSequence BC sealer). Both sealers were mixed with rhodamine B (Sigma-Aldrich, St Louis, MO) for fluorescence. Rhodamine B was mixed with sealer at a 1:100 ratio by weight. Both sealers were prepared according to the manufacturers’ instructions. In all samples, root canal walls were dried with paper points (#25, Dentsply Maillefer), and then a medium-sized gutta-percha cone (DiaDent, Cheongju-si, Korea) was coated with each sealer and inserted into the root canal. The canal filling process was performed using the continuous wave technique. The access cavities were temporarily sealed with Caviton (GC, Tokyo, Japan), and the teeth were then stored in a humidified chamber (100% humidity and 37 C) for 7 days. The root fillings were removed with #2, #3, and #4 Gates Glidden drills (Dentsply Maillefer) and ProFile rotary instruments. The rotary instruments were sequentially used in a crown-down manner. Retreatment progressed until a #40/0.06 tapered ProFile reached the WL. The achievement of patency was also recorded for each specimen. The time required to remove the root filling was recorded in seconds. No solvent was used to soften the gutta-percha. The canals were irrigated with 3.25% NaOCl between filings. A single operator performed all root canal instrumentation and retreatment procedures. Teeth without canal filling and teeth without retreatment after canal filling were used as controls. After these procedures, the canal orifice shapes of all teeth were examined. Microscopic photographs were taken, and the horizontal and vertical diameters of each tooth were measured. The shorter diameter was divided by the longer diameter (%, dS/dL) to determine whether each orifice was round or oval. This procedure was performed to determine whether there was a significant difference in anatomic morphology between the 2 groups. Retreatment Time The time required for retreatment was measured and recorded in seconds (n = 12 in the AH Plus group and n = 14 in the BC group). Retreatment time measurement began at the beginning of use of the Gates Glidden drills and ended when a #40/0.06 taper ProFile reached the WL. Scanning Electron Microscopy Canal cleanliness after retreatment was examined by scanning electron microscopy (n = 3 for each group). The retreated samples 2
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were embedded in clear resin and sectioned longitudinally. All samples were coated with gold by ion sputter (Eiko IB-3; Eiko Engineering Co Ltd, Hitachinaka, Japan), examined, and photographed with scanning electron microscopy (FE SEM S-800; Hitachi, Tokyo, Japan) at an acceleration voltage of 20 kV at various magnifications (25.0–25,000).
Confocal Microscopy Teeth were embedded in clear resin and sectioned horizontally 3 mm and 6 mm from the apex at a 100-mm thickness. All samples (n = 10 in the AH Plus group and n = 12 in the BC group) were evaluated under a confocal microscope (LSM 780; Zeiss, Jena, Germany) to calculate the amount of sealer remaining on the canal walls and in dentinal tubules. Photographs taken 10 mm below the surface at 20 with Zen 2012 (Zeiss) were analyzed using Metamorph software (Molecular Devices LLC, Sunnyvale, CA). The amount of debris remaining in the canal space was calculated as follows: amount of debris in the canal space divided by the total canal space 100 (%). The amount of residual sealer in the dentinal tubules was measured in 2 aspects: (1) the area of sealer penetration into the dentinal tubules (aP)/the area of the horizontal root section (aR) 100 (%); (2) the longest penetration depth was also measured (mm) (Fig. 1A–I). Statistical Analysis Retreatment time in each group and sealer penetration depth were compared using the Student t test (P < .05). The sealer penetration area and remaining debris were compared between the AH Plus group and the BC sealer group using the Mann-Whitney U test (P < .05).
Results There was no significant difference in canal orifice morphology between the 2 groups. The average retreatment times required in the AH Plus and BC groups were 323 and 337 seconds, respectively (P > .05) (Fig. 2). There was no significant difference in retreatment time between the 2 groups. Canal patency was achieved in all specimens. A scanning electron microscopic image of a retreated canal (Fig. 3A–F) reveals that canal cleanliness was not obtained at an ideal level, and the canal wall showed an irregular state of debris remaining in both groups. The amounts of debris on the root canal walls in the AH Plus and BC groups are shown in Figure 4A and B; there was no significant difference between sealer types at either level. The areas of sealer penetration (aP/aR %) in the AH Plus and BC groups are shown in Figure 4C and D. There was no significant difference between the groups in the dentin penetration area. Regarding the penetration depth of the sealer, the AH Plus group showed a slightly deeper percentage than the BC sealer at both 3 and 6 mm. The respective values in the AH Plus group and BC group were 1.16 0.02 mm and 0.800 0.099 mm in root dentin 3 mm from the apex (P > .05) and 1.14 0.17 mm and 0.573 0.099 mm in root dentin 6 mm from the apex (P < .05), with a statistically significant difference only observed at the 6-mm length (Fig. 4E and F).
Discussion Under the conditions of the present study, there was no significant difference in retrievability between the AH Plus and BC sealer groups. The only statistically significant difference was in sealer penetration depth, which showed a significantly higher percentage in the AH Plus group. This may have been caused by the relatively higher fluidity of AH Plus (18). JOE — Volume -, Number -, - 2015
Basic Research—Technology
Figure 1. Confocal images of resected root surfaces after retreatment (20). (A) A scanned image of a resected root surface (20). (B) A confocal microscopic image overlapped with A shows debris in the canal (yellow arrow) and sealer penetrating into dentinal tubules, with red indicating the area of sealer mixed with rhodamine B. (C) A higher-magnification image shows debris remaining in the canal (yellow arrow) and dentinal tubules with sealer penetration. (D and E) Confocal microscopic imaging of the AH Plus group (D: at 6 mm from the apex and E: at 3 mm from the apex). (F) A higher-magnification image showing penetration of AH Plus sealer into the dentinal tubules. (G and H) Confocal microscopy imaging of the BC group (G: at 6 mm from the apex and H: at 3 mm from the apex). (I) A higher-magnification image showing penetration of BC sealer into the dentinal tubules.
A scanning electron microscopic image of retreated canal walls showed remaining debris after the retreatment procedure and dentinal tubules obstructed by a debris coating of remaining sealer and guttapercha.
Figure 2. Removal time (seconds) in the AH Plus and BC groups showing no significant difference.
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Retreatment was not entirely insufficient because patency was achieved in every specimen in this study. The results are in accordance with a previous study showing that both BC sealer and AH Plus were readily retreated using conventional retreatment methods with rotary instruments (19). This differs from the findings of a previous study by Hess et al (16) in which patency was regained in only 80% of the samples. This may have been caused by the fact that all procedures were performed using a single standardized method in this study unlike in Hess et al’s study in which groups were subdivided into samples with a gutta-percha cone placed at the WL or 2 mm short of the WL intentionally. Furthermore, specimens in both the AH Plus group and BC group were filled using the continuous wave technique, whereas in Hess et al’s study samples in the AH Plus group were filled using the warm vertical compaction method and those in the BC group were filled using a single cone. These findings are in accordance with previous studies on similar topics (15–17) because the results confirm that conventional retreatment techniques are not able to fully remove calcium silicate– based sealer. It was also confirmed that AH Plus, an epoxy resin– based sealer, was also difficult to remove completely. Furthermore, it
Retreatment of Calcium Silicate and Epoxy Resin–based Sealers
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Basic Research—Technology
Figure 3. Scanning electron microscopic imaging of retreated root dentin at various magnifications. (A) A low-magnification imaging view of a negative control in which the canal wall was unfilled, (B) images at a higher magnification of a negative control in which dentinal tubules are visible, (C) a low-magnification imaging view of a retreated canal wall from the AH Plus group, and (D) higher-magnification images showing debris. (E) A low-magnification imaging view of a retreated canal wall from the BC group and (F) higher-magnification images showing debris and dentinal tubule obstruction.
showed that AH Plus sealer penetrated slightly deeper into the dentin than the bioceramic sealer. Both sealers were shown to penetrate deep into the root dentin after the canal filling procedure and were impossible to remove completely because one would have to remove up to 40%–60% of additional root dentin to completely remove the penetrating sealer material. It cannot be concluded that a high degree of sealer remnants and penetration depth indicate retreatment failure. The main objective of sealer application is to achieve homogenous obturation to the apical constriction and a fluid-tight seal at the apical foramen. To achieve this goal, the degree of sealer penetration must be sufficient. According to 1 study, once the sealer penetrates into the dentinal tubule, its removal during retreatment is physically impossible, and some materials such as a zinc oxide–eugenol based sealer may negatively affect the bond strength of another sealer during a retreatment filling procedure (20). However, total removal of the root canal sealer is not an essential factor in endodontic retreatment, and not all sealer materials have negative effects during retreatment. Various methods have been applied in previous studies to investigate sealer penetration, such as computed tomographic imaging (15), scanning electron microscopy (16), and stereomicroscopy (17). In this study, confocal imaging was applied to effectively evaluate the extent of sealer penetration. This method was applied in a study (21) that investigated resin-dentin interfaces of different adhesive systems. It was shown that confocal imaging was effective in evaluating the depth and thickness of penetration into dentinal tubules made by a primer. In this study, confocal imaging was helpful in evaluating the extent of penetration by sealer material into dentinal tubules. This is distinct from previous studies (15–17, 21) in which the remaining sealer material could only be evaluated, classified, and scored based on the 4
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material’s presence. In this study, the degree of the materials’ presence and penetration were quantitatively evaluated (as percentages) based on the extent of dentin penetration visualized using a confocal microscope. A limitation of this study lies in the fact that the retreatment time and the amount of sealer material present were more dependent on the anatomic structure of the canal. It was shown in this study that samples with greater curvature and accessory microstructures were more likely to require greater retreatment time and leave behind more debris. To overcome this limitation, canal shape was evaluated in both groups, and there was no significant difference. A canal can be considered oval when the buccolingual dimension is more than 2.5 times larger than the mesiodistal diameter (<0.4 in the present study) (22). In this study, there was no significant difference in canal shape between the 2 experimental groups. Another limitation was that this study used the same filling method for both sealers, whereas the manufacturers’ recommendations are that one should apply the single-cone filling method for calcium silicate– based sealers. Moreover, there is a study advocating the application of the single-cone technique because calcium silicate sealers showed a decrease in bond strength when the continuous wave technique was applied (23). However, another study has described that a continuous wave of condensation was more effective in filling lateral canals than the single-point technique (24). Therefore, the best obturation technique for the material is still under debate. The present study is one of the first to use confocal microscopy to evaluate the percentage of penetration depth and area of sealer in dentinal tubules. As mentioned previously, there are only a few studies that focus on the retrievability of recent calcium silicate–based sealers. Further studies are necessary in this field. JOE — Volume -, Number -, - 2015
Basic Research—Technology
Figure 4. Remaining debris on the wall and residual sealer in dentinal tubules after retreatment. (A and B) Box plots represent the percentage of debris inside the canal space (aD/aC %) in the AH Plus and BC groups (A) for debris in the orifice 3 mm from the apex and (B) for debris in the orifice 6 mm from the apex. The horizontal bar inside the box indicates the median value. (C and D) Box plots represent the percentage of area of dentin penetration (aP/aR %) in the AH Plus and BC groups (C) for the penetration area in root dentin 3 mm from the apex and (D) for root dentin 6 mm from the apex. The horizontal bar inside the box indicates the median value. (E and F) Box plots of the depth of dentin penetration (mm) in the AH Plus and BC groups (E) for sealer penetration in root dentin 3 mm from the apex and (F) for penetration into the root dentin in which a significant difference between the 2 groups can be seen. The horizontal bar inside the box indicates the median value. *A significant difference between the groups.
Conclusion
References
On the basis of the study results, there was no significant difference in retrievability between the AH Plus sealer group and the BC sealer group although the AH Plus sealer group showed a significantly higher percentage in penetration depth of the coronal portion. It can be concluded that EndoSequence BC sealer and AH Plus sealer showed similar characteristics in retreatment procedures.
1. Silva EJ, Rosa TP, Herrera DR, et al. Evaluation of cytotoxicity and physicochemical properties of calcium silicate-based endodontic sealer MTA Fillapex. J Endod 2013; 39:274–7. 2. Gandolfi MG, Prati C. MTA and F-doped MTA cements used as sealers with warm gutta-percha. Long-term study of sealing ability. Int Endod J 2010;43:889–901. 3. Weller RN, Tay KC, Garrett LV, et al. Microscopic appearance and apical seal of root canals filled with gutta-percha and ProRoot endo sealer after immersion in a phophate-containing fluid. Int Endod J 2008;41:977–86. 4. Guven EP, Tash PN, Yalvac ME, et al. In vitro comparison of induction capacity and biomineralization ability of mineral trioxide aggregate and a bioceramic root canal sealer. Int Endod J 2013;46:1173–82. 5. Pawar SS, Pujar MA, Makandar SD. Evaluation of the apical sealing ability of bioceramic sealer, AH plus & epiphany: an in vitro study. J Conserv Dent 2014;17: 579–82. 6. Nagas E, Uyanik MO, Eymirli A, et al. Dentin moisture conditions affect the adhesion of root canal sealers. J Endod 2011;38:240–4.
Acknowledgments Supported by the Yonsei University College of Dentistry Fund (3-2015-0086). The authors thank Hanna Yoo for the statistical analysis. The authors deny any conflicts of interest related to this study. JOE — Volume -, Number -, - 2015
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Basic Research—Technology 7. Ersahan S, Avdin C. Dislocation of iRoot SP, a calcium silicate based sealer, from radicular dentine. J Endod 2010;36:2000–2. 8. Shokouhinejad N, Nekoofar MH, Ashoftehyazdi K, et al. Marginal adaptation of new bioceramic materials and mineral trioxide aggregate: a scanning electron microscopy study. Iran Endod J 2014;9:144–8. 9. Zhang W, Li Z, Peng B. Ex vivo cytotoxicity of a new calcium silicate-based canal filling material. Int Endod J 2010;43:769–74. 10. Ruparel NB, Ruparel SB, Chen PB, et al. Direct effect of endodontic sealers on trigeminal neuronal activity. J Endod 2014;40:683–7. 11. Chang SW, Lee SY, Kang SK, et al. In vitro biocompatibility, inflammatory response, and osteogenic potential of 4 root canal sealers: Sealapex, Sankin Apatite Root Sealer, MTA Fillapex, and iRoot SP Root canal sealer. J Endod 2014;40:1642–8. 12. Prati C, Gandolfi MG. Calcium silicate bioactive cements: biological perspectives and clinical applications. Dent Mater 2015;31:351–70. 13. Zhang H, Shen Y, Ruse ND, et al. Antibacterial activity of endodontic sealers by modified direct contact test against Enterococcus faecalis. J Endod 2009;35:1051–5. 14. Carpio-Perochena A, Kishen A, Shrestha A, et al. Antibacterial properties associated with chitosan nanoparticle treatment on root dentin and 2 types of endodontic sealers. J Endod 2015;41:1353–8. 15. Neelakantan P, Grotra D, Sharma S. Retreatability of 2 mineral trioxide aggregatebased root canal sealers: a cone-beam computed tomography analysis. J Endod 2013;39:893–6. 16. Hess D, Solomon E, Spears R, et al. Retreatability of a bioceramic root canal sealing material. J Endod 2011;37:1547–9.
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17. Uzunoglu E, Yilmaz Z, Sungur DD, et al. Retreatability of root canals obturated using Gutta-Percha with Bioceramic, MTA and Resin-Based Sealers. Iran Endod J 2015; 10:93–8. 18. Sonntag D, Ritter A, Burkhart A, et al. Experimental amine-expoxide sealer: a physicochemical study in comparison with AH Plus and EasySeal. Int Endod J 2014;48: 747–56. 19. Ersev H, Yilmaz B, Dincol ME, et al. The efficacy of ProTaper University rotary retreatment instrumentation to remove single gutta-percha cones cemented with several endodontic sealers. Int Endod J 2012;45:756–62. 20. Rached-Junior FJ, Sousa-Neto MD, Souza-Gabriel AE, et al. Impact of remaining zinc oxide-eugenol-based sealer on the bond strength of a resinous sealer to dentine after root canal retreatment. Int Endod J 2014;47:463–9. 21. Bitter K, Paris S, Martus P, et al. A confocal laser scanning microscope investigation of different dental adhesives bonded to root canal dentine. Int Endod J 2004;37: 840–8. 22. De-Deus G, Barino B, Zamolyi RQ, et al. Suboptimal debridement quality produced by the single-file F2 ProTaper technique in oval-shaped canals. J Endod 2010;36: 1897–900. 23. DeLong C, He J, Woodmansey KF. The effect of obturation technique on the push-out bond strength of calcium silicate sealers. J Endod 2015;41:385–8. 24. Fernandez R, Restrepo JS, Aristizabal DC, et al. Evaluation of the filling ability of artificial lateral canals using calcium silicate-based and epoxy resin-based endodontic sealers and two gutta-percha filling techniques. Int Endod J 2015 Mar 31; http:// dx.doi.org/10.1111/iej.12454 [Epub ahead of print].
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Comparisons of the Retreatment Efficacy of Calcium Silicate and Epoxy Resin–based Sealers and Residual Sealer in Dentinal Tubules Hyunsuk Kim, DDS, MSD,* Euiseong Kim, DDS, PhD,† Seung-Jong Lee, DDS, PhD,† and Su-Jung Shin, DDS, PhD*‡ Abstract Introduction: The aim of this study was to evaluate the retreatment efficacy and amount of residual sealer in a single canal filled with either EndoSequence BC (Brasseler, Savannah, GA) or AH Plus (Dentsply DeTrey, Konstanz, Germany). Methods: Canal obturation with gutta-percha and sealer was performed in 28 human teeth using the continuous wave technique. Group 1 (n = 13) used AH Plus sealer, and group 2 (n = 15) used EndoSequence BC sealer. After 7 days, the root fillings were removed using Gates Glidden drills and a nickel-titanium rotary system. Retreatment time was measured in seconds. Canal cleanliness was examined by scanning electron microscopy. The remaining debris in the canal space and penetration into dentinal tubules were evaluated by confocal microscopy. Retreatment time was compared using the Student t test, and differences in sealer penetration and remaining debris between the groups were analyzed using the MannWhitney U test (P < .05). Results: There was no significant difference between the 2 groups in the amount of dentin penetration, amount of debris, or retreatment time. With respect to penetration depth, the AH Plus group showed a slightly higher percentage than the BC group, with a significant difference only in the portion 6 mm from the apex (P < .05). Scanning electron microscopic images showed significant debris remaining on canal walls in both groups, whereas canal patency in retreatment was achieved in every specimen. Conclusions: The present study shows that EndoSequence BC sealer and AH Plus sealer have similar efficacy in dentin penetration and retreatment efficacy. (J Endod 2015;-:1–6)
Key Words Calcium silicate, dentin penetration, endodontic sealer, retrievability
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ecently, calcium silicate–based sealers such as MTA Plus (Prevest Denpro GmbH, Heidelberg, Germany), MTA Fillapex (Angelus, Londrina, Brazil), iRoot SP (Innovative BioCeramix, Vancouver, BC, Canada), and EndoSequence BC (Brassler USA, Savannah, GA) have been introduced. These products have shown low cytotoxicity, suitable bonding strength, and sealing ability (1–3). Moreover, some materials have been reported to induce biomineralization and hard tissue deposition (4). EndoSequence BC, 1 of the calcium silicate–based sealers, is composed of calcium silicates, calcium phosphate monobasic, zirconium oxide, tantalum oxide, and thickening agents. According to a recent study, EndoSequence BC sealed the root canal better than AH Plus sealer (Dentsply DeTrey, Konstanz, Germany) (5) and showed the highest bond strength under all moisture conditions (6). The material’s bond strengths were shown to be significantly higher than those of Sealapex (Kerr, Orange, CA) and EndoRez (Ultradent, South Jordan, UT) (7). Additionally, the material showed marginal adaptation similar to that of MTA (8). Zhang et al (9) reported EnodSequence BC’s cytotoxicity at 24 hours was much less than that of AH Plus, and it showed high biocompatibility. Moreover, although zinc oxide eugenol and AH Plus evoked greater calcitonin gene-related peptide release, EndoSequence BC sealer reduced basal calcitonin gene-related peptide release at all concentrations tested, indicating less potential for pain and neurogenic inflammation (10). It was also reported that BC sealer enhanced osteoblastic differentiation of periodontal ligament cells (11), induced dentin remineralization (12), and had strong antibacterial properties (13, 14). However, although the material’s clinical and biocompatibility features show promise in recently performed studies, studies on its retrievability are relatively few, and their results vary significantly. A calcium silicate–based sealer was shown to create hydroxyapatite crystals in the interface between dentin and sealer, and its retrieval from the dentinal wall and dentinal tubules may be challenging. Furthermore, the sealer’s ability to penetrate dentin is a property that may be related to the material’s retrievability. Although a dentin penetration property is not a shortcoming, the deep penetration depth of the material and dentinal tubule blockage may add challenges to canal retreatment. Only a few studies have focused on the retrievability and dentin penetration of calcium silicate sealers, and their results also vary significantly (15–17). Therefore, the purpose of this study was to evaluate and compare EndoSequence BC sealer and AH Plus sealer both in removal efficacy and the amount of residual filling material in the canal and dentinal tubules.
From the *Department of Conservative Dentistry and ‡Department of Conservative Dentistry and Oral Science Research Center, College of Dentistry, Gangnam Severance Hospital, Yonsei University, Seoul, Korea; and †Department of Conservative Dentistry and Oral Science Research Center, College of Dentistry, Yonsei University, Seoul, Korea. Address requests for reprints to Dr Su-Jung Shin, Department of Conservative Dentistry, Gangnam Severance Hospital, College of Dentistry,Yonsei University, 211 Eonjuro, Gangnam-gu, Seoul 135-720, Korea. E-mail address: [email protected] 0099-2399/$ - see front matter Copyright ª 2015 American Association of Endodontists. http://dx.doi.org/10.1016/j.joen.2015.08.030
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Retreatment of Calcium Silicate and Epoxy Resin–based Sealers
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Basic Research—Technology Materials and Methods Preparation of Tooth Samples A total of 28 extracted single-rooted mature human teeth were used. The teeth were extracted for orthodontic and periodontal reasons, and the protocol was approved by the institutional review board committee at our institution (institutional review board approval no. 2-2015-0086). Teeth with microcracks were excluded from the study. Tooth crowns were removed using a water-cooled diamond bur to form standardized root samples of 13-mm lengths. K-file sizes #10 and #15 (Dentsply Maillefer, Ballaigues, Switzerland) were inserted into the canal to achieve the working length (WL). The canals were prepared using the ProFile rotary system (Dentsply Maillefer) to a size #35/0.06 taper according to the manufacturer’s instructions. Irrigation with a 3.25% sodium hypochlorite (NaOCl) solution was performed using a 27-G needle during filing. Finally, to remove the smear layer, 10 mL 17% EDTA solution was applied for 60 seconds. Then, the canals were flushed with 3.25% NaOCl and dried. Teeth were divided into 2 groups based on the sealer used during the root filling procedure: group 1 (n = 13) (AH Plus sealer) and group 2 (n = 15) (EndoSequence BC sealer). Both sealers were mixed with rhodamine B (Sigma-Aldrich, St Louis, MO) for fluorescence. Rhodamine B was mixed with sealer at a 1:100 ratio by weight. Both sealers were prepared according to the manufacturers’ instructions. In all samples, root canal walls were dried with paper points (#25, Dentsply Maillefer), and then a medium-sized gutta-percha cone (DiaDent, Cheongju-si, Korea) was coated with each sealer and inserted into the root canal. The canal filling process was performed using the continuous wave technique. The access cavities were temporarily sealed with Caviton (GC, Tokyo, Japan), and the teeth were then stored in a humidified chamber (100% humidity and 37 C) for 7 days. The root fillings were removed with #2, #3, and #4 Gates Glidden drills (Dentsply Maillefer) and ProFile rotary instruments. The rotary instruments were sequentially used in a crown-down manner. Retreatment progressed until a #40/0.06 tapered ProFile reached the WL. The achievement of patency was also recorded for each specimen. The time required to remove the root filling was recorded in seconds. No solvent was used to soften the gutta-percha. The canals were irrigated with 3.25% NaOCl between filings. A single operator performed all root canal instrumentation and retreatment procedures. Teeth without canal filling and teeth without retreatment after canal filling were used as controls. After these procedures, the canal orifice shapes of all teeth were examined. Microscopic photographs were taken, and the horizontal and vertical diameters of each tooth were measured. The shorter diameter was divided by the longer diameter (%, dS/dL) to determine whether each orifice was round or oval. This procedure was performed to determine whether there was a significant difference in anatomic morphology between the 2 groups. Retreatment Time The time required for retreatment was measured and recorded in seconds (n = 12 in the AH Plus group and n = 14 in the BC group). Retreatment time measurement began at the beginning of use of the Gates Glidden drills and ended when a #40/0.06 taper ProFile reached the WL. Scanning Electron Microscopy Canal cleanliness after retreatment was examined by scanning electron microscopy (n = 3 for each group). The retreated samples 2
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were embedded in clear resin and sectioned longitudinally. All samples were coated with gold by ion sputter (Eiko IB-3; Eiko Engineering Co Ltd, Hitachinaka, Japan), examined, and photographed with scanning electron microscopy (FE SEM S-800; Hitachi, Tokyo, Japan) at an acceleration voltage of 20 kV at various magnifications (25.0–25,000).
Confocal Microscopy Teeth were embedded in clear resin and sectioned horizontally 3 mm and 6 mm from the apex at a 100-mm thickness. All samples (n = 10 in the AH Plus group and n = 12 in the BC group) were evaluated under a confocal microscope (LSM 780; Zeiss, Jena, Germany) to calculate the amount of sealer remaining on the canal walls and in dentinal tubules. Photographs taken 10 mm below the surface at 20 with Zen 2012 (Zeiss) were analyzed using Metamorph software (Molecular Devices LLC, Sunnyvale, CA). The amount of debris remaining in the canal space was calculated as follows: amount of debris in the canal space divided by the total canal space 100 (%). The amount of residual sealer in the dentinal tubules was measured in 2 aspects: (1) the area of sealer penetration into the dentinal tubules (aP)/the area of the horizontal root section (aR) 100 (%); (2) the longest penetration depth was also measured (mm) (Fig. 1A–I). Statistical Analysis Retreatment time in each group and sealer penetration depth were compared using the Student t test (P < .05). The sealer penetration area and remaining debris were compared between the AH Plus group and the BC sealer group using the Mann-Whitney U test (P < .05).
Results There was no significant difference in canal orifice morphology between the 2 groups. The average retreatment times required in the AH Plus and BC groups were 323 and 337 seconds, respectively (P > .05) (Fig. 2). There was no significant difference in retreatment time between the 2 groups. Canal patency was achieved in all specimens. A scanning electron microscopic image of a retreated canal (Fig. 3A–F) reveals that canal cleanliness was not obtained at an ideal level, and the canal wall showed an irregular state of debris remaining in both groups. The amounts of debris on the root canal walls in the AH Plus and BC groups are shown in Figure 4A and B; there was no significant difference between sealer types at either level. The areas of sealer penetration (aP/aR %) in the AH Plus and BC groups are shown in Figure 4C and D. There was no significant difference between the groups in the dentin penetration area. Regarding the penetration depth of the sealer, the AH Plus group showed a slightly deeper percentage than the BC sealer at both 3 and 6 mm. The respective values in the AH Plus group and BC group were 1.16 0.02 mm and 0.800 0.099 mm in root dentin 3 mm from the apex (P > .05) and 1.14 0.17 mm and 0.573 0.099 mm in root dentin 6 mm from the apex (P < .05), with a statistically significant difference only observed at the 6-mm length (Fig. 4E and F).
Discussion Under the conditions of the present study, there was no significant difference in retrievability between the AH Plus and BC sealer groups. The only statistically significant difference was in sealer penetration depth, which showed a significantly higher percentage in the AH Plus group. This may have been caused by the relatively higher fluidity of AH Plus (18). JOE — Volume -, Number -, - 2015
Basic Research—Technology
Figure 1. Confocal images of resected root surfaces after retreatment (20). (A) A scanned image of a resected root surface (20). (B) A confocal microscopic image overlapped with A shows debris in the canal (yellow arrow) and sealer penetrating into dentinal tubules, with red indicating the area of sealer mixed with rhodamine B. (C) A higher-magnification image shows debris remaining in the canal (yellow arrow) and dentinal tubules with sealer penetration. (D and E) Confocal microscopic imaging of the AH Plus group (D: at 6 mm from the apex and E: at 3 mm from the apex). (F) A higher-magnification image showing penetration of AH Plus sealer into the dentinal tubules. (G and H) Confocal microscopy imaging of the BC group (G: at 6 mm from the apex and H: at 3 mm from the apex). (I) A higher-magnification image showing penetration of BC sealer into the dentinal tubules.
A scanning electron microscopic image of retreated canal walls showed remaining debris after the retreatment procedure and dentinal tubules obstructed by a debris coating of remaining sealer and guttapercha.
Figure 2. Removal time (seconds) in the AH Plus and BC groups showing no significant difference.
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Retreatment was not entirely insufficient because patency was achieved in every specimen in this study. The results are in accordance with a previous study showing that both BC sealer and AH Plus were readily retreated using conventional retreatment methods with rotary instruments (19). This differs from the findings of a previous study by Hess et al (16) in which patency was regained in only 80% of the samples. This may have been caused by the fact that all procedures were performed using a single standardized method in this study unlike in Hess et al’s study in which groups were subdivided into samples with a gutta-percha cone placed at the WL or 2 mm short of the WL intentionally. Furthermore, specimens in both the AH Plus group and BC group were filled using the continuous wave technique, whereas in Hess et al’s study samples in the AH Plus group were filled using the warm vertical compaction method and those in the BC group were filled using a single cone. These findings are in accordance with previous studies on similar topics (15–17) because the results confirm that conventional retreatment techniques are not able to fully remove calcium silicate– based sealer. It was also confirmed that AH Plus, an epoxy resin– based sealer, was also difficult to remove completely. Furthermore, it
Retreatment of Calcium Silicate and Epoxy Resin–based Sealers
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Basic Research—Technology
Figure 3. Scanning electron microscopic imaging of retreated root dentin at various magnifications. (A) A low-magnification imaging view of a negative control in which the canal wall was unfilled, (B) images at a higher magnification of a negative control in which dentinal tubules are visible, (C) a low-magnification imaging view of a retreated canal wall from the AH Plus group, and (D) higher-magnification images showing debris. (E) A low-magnification imaging view of a retreated canal wall from the BC group and (F) higher-magnification images showing debris and dentinal tubule obstruction.
showed that AH Plus sealer penetrated slightly deeper into the dentin than the bioceramic sealer. Both sealers were shown to penetrate deep into the root dentin after the canal filling procedure and were impossible to remove completely because one would have to remove up to 40%–60% of additional root dentin to completely remove the penetrating sealer material. It cannot be concluded that a high degree of sealer remnants and penetration depth indicate retreatment failure. The main objective of sealer application is to achieve homogenous obturation to the apical constriction and a fluid-tight seal at the apical foramen. To achieve this goal, the degree of sealer penetration must be sufficient. According to 1 study, once the sealer penetrates into the dentinal tubule, its removal during retreatment is physically impossible, and some materials such as a zinc oxide–eugenol based sealer may negatively affect the bond strength of another sealer during a retreatment filling procedure (20). However, total removal of the root canal sealer is not an essential factor in endodontic retreatment, and not all sealer materials have negative effects during retreatment. Various methods have been applied in previous studies to investigate sealer penetration, such as computed tomographic imaging (15), scanning electron microscopy (16), and stereomicroscopy (17). In this study, confocal imaging was applied to effectively evaluate the extent of sealer penetration. This method was applied in a study (21) that investigated resin-dentin interfaces of different adhesive systems. It was shown that confocal imaging was effective in evaluating the depth and thickness of penetration into dentinal tubules made by a primer. In this study, confocal imaging was helpful in evaluating the extent of penetration by sealer material into dentinal tubules. This is distinct from previous studies (15–17, 21) in which the remaining sealer material could only be evaluated, classified, and scored based on the 4
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material’s presence. In this study, the degree of the materials’ presence and penetration were quantitatively evaluated (as percentages) based on the extent of dentin penetration visualized using a confocal microscope. A limitation of this study lies in the fact that the retreatment time and the amount of sealer material present were more dependent on the anatomic structure of the canal. It was shown in this study that samples with greater curvature and accessory microstructures were more likely to require greater retreatment time and leave behind more debris. To overcome this limitation, canal shape was evaluated in both groups, and there was no significant difference. A canal can be considered oval when the buccolingual dimension is more than 2.5 times larger than the mesiodistal diameter (<0.4 in the present study) (22). In this study, there was no significant difference in canal shape between the 2 experimental groups. Another limitation was that this study used the same filling method for both sealers, whereas the manufacturers’ recommendations are that one should apply the single-cone filling method for calcium silicate– based sealers. Moreover, there is a study advocating the application of the single-cone technique because calcium silicate sealers showed a decrease in bond strength when the continuous wave technique was applied (23). However, another study has described that a continuous wave of condensation was more effective in filling lateral canals than the single-point technique (24). Therefore, the best obturation technique for the material is still under debate. The present study is one of the first to use confocal microscopy to evaluate the percentage of penetration depth and area of sealer in dentinal tubules. As mentioned previously, there are only a few studies that focus on the retrievability of recent calcium silicate–based sealers. Further studies are necessary in this field. JOE — Volume -, Number -, - 2015
Basic Research—Technology
Figure 4. Remaining debris on the wall and residual sealer in dentinal tubules after retreatment. (A and B) Box plots represent the percentage of debris inside the canal space (aD/aC %) in the AH Plus and BC groups (A) for debris in the orifice 3 mm from the apex and (B) for debris in the orifice 6 mm from the apex. The horizontal bar inside the box indicates the median value. (C and D) Box plots represent the percentage of area of dentin penetration (aP/aR %) in the AH Plus and BC groups (C) for the penetration area in root dentin 3 mm from the apex and (D) for root dentin 6 mm from the apex. The horizontal bar inside the box indicates the median value. (E and F) Box plots of the depth of dentin penetration (mm) in the AH Plus and BC groups (E) for sealer penetration in root dentin 3 mm from the apex and (F) for penetration into the root dentin in which a significant difference between the 2 groups can be seen. The horizontal bar inside the box indicates the median value. *A significant difference between the groups.
Conclusion
References
On the basis of the study results, there was no significant difference in retrievability between the AH Plus sealer group and the BC sealer group although the AH Plus sealer group showed a significantly higher percentage in penetration depth of the coronal portion. It can be concluded that EndoSequence BC sealer and AH Plus sealer showed similar characteristics in retreatment procedures.
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Acknowledgments Supported by the Yonsei University College of Dentistry Fund (3-2015-0086). The authors thank Hanna Yoo for the statistical analysis. The authors deny any conflicts of interest related to this study. JOE — Volume -, Number -, - 2015
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17. Uzunoglu E, Yilmaz Z, Sungur DD, et al. Retreatability of root canals obturated using Gutta-Percha with Bioceramic, MTA and Resin-Based Sealers. Iran Endod J 2015; 10:93–8. 18. Sonntag D, Ritter A, Burkhart A, et al. Experimental amine-expoxide sealer: a physicochemical study in comparison with AH Plus and EasySeal. Int Endod J 2014;48: 747–56. 19. Ersev H, Yilmaz B, Dincol ME, et al. The efficacy of ProTaper University rotary retreatment instrumentation to remove single gutta-percha cones cemented with several endodontic sealers. Int Endod J 2012;45:756–62. 20. Rached-Junior FJ, Sousa-Neto MD, Souza-Gabriel AE, et al. Impact of remaining zinc oxide-eugenol-based sealer on the bond strength of a resinous sealer to dentine after root canal retreatment. Int Endod J 2014;47:463–9. 21. Bitter K, Paris S, Martus P, et al. A confocal laser scanning microscope investigation of different dental adhesives bonded to root canal dentine. Int Endod J 2004;37: 840–8. 22. De-Deus G, Barino B, Zamolyi RQ, et al. Suboptimal debridement quality produced by the single-file F2 ProTaper technique in oval-shaped canals. J Endod 2010;36: 1897–900. 23. DeLong C, He J, Woodmansey KF. The effect of obturation technique on the push-out bond strength of calcium silicate sealers. J Endod 2015;41:385–8. 24. Fernandez R, Restrepo JS, Aristizabal DC, et al. Evaluation of the filling ability of artificial lateral canals using calcium silicate-based and epoxy resin-based endodontic sealers and two gutta-percha filling techniques. Int Endod J 2015 Mar 31; http:// dx.doi.org/10.1111/iej.12454 [Epub ahead of print].
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