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Aust Endod J 2013; 39: 159–163
ORIGINAL RESEARCH
Ultramicroscopic study of the interface and sealing ability of four root canal obturation methods: Resilon versus gutta-percha Pablo Castelo-Baz, DDS1; Benjamin Martin-Biedma, PhD1; Maria Manuela Lopes, PhD2; Luis Pires-Lopes, PhD2; Joao Silveira, DDS1; Elisardo López-Rosales, DDS1; and Purificación Varela-Patiño, PhD1 1 Unit of Dental Pathology and Therapeutics, Faculty of Medicine and Dentistry, University of Santiago de Compostela, Santiago de Compostela, La Coruña, Spain 2 Unit of Investigation and Oral and Biomedical Sciences, Faculty of Dental Medicine, University of Lisbon, Lisbon, Portugal
Keywords electron microscopy, RealSeal 1, Resilon, root canal obturation, System B, Thermafil. Correspondence Mr Pablo Castelo-Baz, Master of Endodontics, University of Santiago de Compostela, Rúa Entrerríos s/n, Santiago de Compostela, La Coruña 15770, Spain. Email: [email protected] doi:10.1111/j.1747-4477.2012.00370.x
Abstract Recently, filling materials have been introduced based on the dentine adhesion technologies used in conservative dentistry in an attempt to seal the root canal more effectively. The purpose of this study was to investigate the interface between the canal and root-filling material. Sealing ability of four root canal obturation methods was analysed by means of scanning electron microscopy. Extracted single-rooted teeth were endodontically treated and filled with gutta-percha/Pulp Canal Sealer using the Thermafil (TH) technique, guttapercha/Pulp Canal Sealer using the System B (SB) technique, Resilon points/ RealSeal (RS) and RealSeal 1/RealSeal (RS1). Specimen interfaces were analysed using field-emission scanning electron microscopy. The adhesive groups RS and RS1, formed hybrid layers but showed areas of separation (gaps) similar to those in the conventional obturation groups. The RS and RS1 groups showed less separation in the coronal third, but the separation was similar to that in the TH and SB groups in the middle and apical thirds. The sealing ability of Resilon is not superior to that of existing materials.
Introduction The three-dimensional obturation of the canal system after proper chemomechanical preparation is essential to achieve success in endodontics (1). The aim of endodontic treatment is to eliminate bacteria throughout the canal system (the primary aetiology of pulpal and radicular disease being bacterial) and to seal the access with various materials to prevent reinfection (2–4). Available data suggest that the root canal system cannot be totally cleaned and disinfected (5,6). Therefore, the canal system should be disinfected as much as possible and obturated to prevent coronal leakage and subsequent bacterial contamination, and the apex sealed to prevent contamination by periapical tissue fluids (7). Gutta-percha is the traditional filling material in endodontics, used in combination with cements composed of calcium hydroxide, zinc oxide/eugenol or epoxy resin. More recently, filling materials have been developed
© 2012 The Authors Australian Endodontic Journal © 2012 Australian Society of Endodontology
based on the dentine adhesion technologies used in conservative dentistry in an attempt to seal the root canal more effectively (8,9). Alternatives to gutta-percha, such as Resilon (Resilon Research LLC, Madison, CT, USA), were introduced in 2003. Resilon is a synthetic polymer-based thermoplastic polyester containing bioactive glass, bismuth oxychloride and barium sulfate. An alternative, RealSeal (RS; SybronEndo, Orange, CA, USA), is a dual-curing, resinbased composite sealer. The resin matrix is composed of bisphenol A glycidyl methacrylate (BisGMA), ethoxylated BisGMA, urethane dimethacrylate and hydrophilic bifunctional methacrylates. A new sealant, RS SE (SybronEndo) removes the need for a primer. The cement is applied in the conventional manner and is used to attach Resilon to the dentine (10). The aim of this study was to compare the interface between canal and obturating material. Sealing ability of four root canal obturation methods were analysed by means of scanning electron microscopy. 159
Resilon versus Gutta-percha
Material and methods Forty-eight permanent single-rooted human teeth extracted for periodontal or orthodontic reasons were stored in 0.2% chloramine at 4°C until endodontic preparation. Two radiographs, one from a mesiodistal direction and the other from a buccolingual direction, were made, confirming the presence of a single canal. The following procedures were carried out: disinfection, cleaning and removal of the crown; after cleaning and surface disinfection (with ultrasonics and 5% chlorhexidine), the crown of the tooth was cut at the cementoenamel junction to standardise the canal length to 14 mm, endodontic treatment; access and negotiation of the tooth and determination of the working length with a K-file (Flexofile #10; Dentsply Maillefer, Ballaigues, Switzerland) were performed such that the tip of the file was seen to protrude from the apical foramen under a clinical microscope (M525 F40; Leica, Heerbrugg, Switzerland). Hand preparation of the glide path with K-files (Flexofiles #15 and #20; Dentsply Maillefer) was then performed. Rotary instrumentation was carried out with the ProTaper Universal system (Dentsply Maillefer) following the sequence S1, S2, F1, F2 and F3. Irrigation was used throughout the process with 5.25% NaOCl, 2 ml for 1 min between each file use. Additionally, a final irrigation consisted of alternating 5.25% NaOCl (Niclor 5; OGNA, Muggiò, Italy), 3 ml for 1.5 min, 17% liquid EDTA (Tubuliclean; OGNA, Milan, Italy), 5 mL for 1 min and again 5.25% NaOCl (3 mL for 1.5 min). Both solutions were activated with ultrasound for 30 s with an ultrasonic tip (ISO 15, IrriSafe; Satelec, Actaeon Group, Merignac Cedex, France). The canal received a final wash with distilled water (1 mL for 1 min) applied to the working length with a 30-gauge needle (ProRinse; Dentsply Tulsa Dental Specialties, Tulsa, OK, USA) and canal drying; the canals were dried with absorbent F3 paper points (Dentsply Maillefer) and randomised into four groups of 12 teeth each, as described later.
Experimental groups Group 1: Obturation with System B (SB) Pulp Canal Sealer (Kerr, Romulus, MI, USA), a zinc oxide-eugenol sealer, was used as the sealing cement. Three paper points were placed within 1 mm of the working length: the first was used to apply the sealer, the second to distribute it and the third to remove the excess. A ProTaper F3 cone (Dentsply Maillefer) was placed 0.5 mm from the working length. Down-packing was performed with a 08 tapered plugger of the Elements Unit (SybronEndo) at 200°C to 4 mm from the working length, then backfilling was performed with hot gutta160
P. Castelo-Baz et al.
percha using the gun component of this unit and also using a Buchanan hand plugger (tip size 0.03/0.41).
Group 2: Obturation with Thermafil (TH) The same method previously described in-group 1 was used to place the sealer. The F3 verifier was used to check for appropriate fit and to assess whether the F3 TH (Dentsply Maillefer) was adequate (if not, the tooth was discarded). A ProTaper F3 obturator was heated in the ThermaPrep oven (Dentsply Maillefer) for 30 s (in accordance with the manufacturer’s recommendations) and then inserted into the tooth with a constant apical pressure for 6 s. The coronal excess was removed with a Thermacut bur (Dentsply Maillefer).
Group 3: RS In this group, RS self-etch cement (SybronEndo) was applied with paper points in the same way as for the previous groups. An RS (SybronEndo) cone was placed 0.5 mm from the working length. The Elements unit was then employed in the same way as in the first group.
Group 4: RealSeal 1 (RS1) After applying RS self-etch cement in the same way as in the previous group, a size 30 obturator was heated in the oven and then inserted in the tooth with a constant apical pressure for 6 s, as indicated by the manufacturer. The coronal excess was removed with a Thermacut bur (Dentsply Maillefer). The coronal portion was then photopolymerised for 40 s.
Subgroups The teeth from each group were then divided; morphological hybridisation was observed in nine teeth that were polished completely and three teeth that were left unpolished (to compare if the polish can modify the samples). Scanning electron microscopy was used to analyse the tooth/obturating material interface. Two disk-shaped samples were taken from the coronal area and the middle and apical regions of each specimen. Two areas in each disc were defined (A and B, always in the same position) and photographs were taken at 50, 200 and 1000 ¥ magnification. Areas where the cutting blade had not entered or finished were selected to avoid the creation of areas of drag or separation during sample preparation.
Analysis of the interface using field-emission scanning electron microscopy Morphological hybridisation Teeth were sectioned perpendicularly to their long axis with a diamond saw (Isomet 1000; Buehler Ltd, Lake
© 2012 The Authors Australian Endodontic Journal © 2012 Australian Society of Endodontology
Resilon versus Gutta-percha
P. Castelo-Baz et al.
Bluff, IL, USA) under distilled water to obtain 1.5᎑to 2 mm thick slices. The specimens were immersed in 2.5% glutaraldehyde/2% paraformaldehyde in 0.1 mol sodium cacodylate buffer at pH 7.4 for 12 h at 4°C, and thoroughly processed by hexamethyldisilazane (HMDS; Ted Pella Inc., Redding, CA, USA) to drying (11). The disks were embedded in Epo-Thin epoxy resin (Buehler Ltd). After curing for 18 h, the surface of each epoxy cast was polished with wet SiC papers of decreasing abrasiveness (up to 1200 grit), and the soft tissue with increasingly fine diamond suspension to a 0.05᎑m size (Buehler Ltd). The specimens were sonicated in 100% ethanol for 5 min, demineralised in 6% NHCl (Acros Organics USA, Morris Plains, NJ, USA) for 30 s and deproteinised in 1% NaOCl for 10 min. The specimens were mounted on Al stubs and sputter-coated with Au-Pd in an E-5100 sputter-coater (Polaron Ltd, Watford, UK) at 40 mA for 90 s. Interfaces were observed under an S4700 Hitachi (Hitachi, Tokyo, Japan) field emission scanning electron microscopy (FESEM) at 4.0–5.0 kV.
Table 1 Mean and standard deviation of four groups in each thirds
Group
Third
Mean
Standard deviation
G1: SB
Coronal Middle Apical Coronal Middle Apical Coronal Middle Apical Coronal Middle Apical
28.56 8.58 9.19 21.96 10.09 8.74 14.23 9.50 8.44 12.49 8.38 7.45
6.35 2.23 3.59 6.29 3.87 2.78 3.20 3.83 3.20 5.04 2.74 1.69
G2: TH
G3: RS
G4: RS1
SB, System B; TH, Thermafil; RS, RealSeal; RS1, RealSeal 1.
a
b
c
d
Morphological hybridisation unpolished Three samples were not embedded in Epo-Thin resin (Buehler Ltd) and the surface was not polished with the wet SiC papers. After immersing the samples in HMDS, they were sonicated in 100% ethanol, demineralised, deproteinised and coated as previously described process of the morphological hybridisation. Interfaces were observed under the same FESEM.
Statistical analysis A one-factor analysis of variance and Turkey statistical methods were made to compare the groups in the three thirds (coronal, medial and apical). G-Stat program (Letón and Mariño, Department of Biometrics, GlaxoSmithKline, Madrid, Spain) was used to make this analysis.
Results Mean and standard deviation are shown in Table 1. The RS and RS1 adhesive groups formed hybrid layers (Fig. 1a) but showed areas of separation (gaps; Fig. 1b) similar to those of the conventional obturation groups (Fig. 1c,d). In all groups, the gap was located between the dentine and the sealer cement that remained attached to the obturating material (Fig. 2a,b). The RS and RS1 groups showed less separation in the coronal third (statistically significant F = 45.57, P < 0.001) than TH and SB groups. No statistical differences were found in all groups in medial (F = 1.47, P = 1.229) and apical thirds (F = 1.55, P = 0.2063). No statistical differences was observed between polished and unpolished teeth (Fig. 1e,f, P = 0.153) (Fig. 3a,b).
© 2012 The Authors Australian Endodontic Journal © 2012 Australian Society of Endodontology
Figure 1 (a) Coronal area of a specimen treated with RealSeal (RS), showing the hybrid layer. (b) Coronal area of a specimen treated with RS, showing a gap. (c) Coronal area of a specimen treated with RealSeal 1 (RS1), showing a gap. (d) Coronal area of a specimen treated with thermafil (TH), showing a gap. SEM, scanning electron microscopy.
Discussion Polymerisation shrinkage creates tensions that may be of sufficient magnitude to cause detachment of the resin from the canal wall dentine, thereby potentially opening a pathway for bacterial infiltration (12,13). Resilon/ Epiphany has been suggested to improve bacterial infiltration when it is compared with gutta-percha and traditional sealer (14–16). However, no statistically significant difference in infiltration between obturation techniques with Resilon and conventional gutta-percha has been reported in the recent literature (17,18,19). De-Deus et al. (20) showed that the interface adaptation 161
Resilon versus Gutta-percha
a
b
Figure 2 (a) Apical area of a specimen treated with System B (SB). (b) Apical area of a specimen treated with RealSeal 1 (RS1). SEM, scanning electron microscopy.
P. Castelo-Baz et al.
because of surface tensions, resulting in stress accumulation within the polymerisable resin. A similar pattern has been described when bonding fibre posts to root canal dentin (26). Apical gaps could occur in a clinical situation for the four obturation groups studied, potentially causing infiltration and endodontic treatment failure. Gap-free zones and areas with gaps at the interface have been associated with Resilon and gutta-percha/AH Plus (27). Perdigão et al. (22) also stated that despite hybridisation, a perfect seal of the root canal is difficult to achieve, possibly because of the complexity of the substrate and the high c-factor.
Conclusion a
b
Within the limitations of this study, it can be concluded that the sealing ability of new root canal obturating material (Resilon) is not superior to that of existing materials. Our future research will study the new obturating cements and the same samples with micro-computed tomography.
References Figure 3 (a,b) Polished and unpolished Thermafil (TH) samples. SEM, scanning electron microscopy.
of adhesive root sealants is compromised, even in teeth with simple anatomy and under well-monitored laboratory conditions. The results of this study agree with those of Hiraishi et al. (21) and Perdigão et al. (22), who reported gaps between Resilon and the sealant. This physical separation was not expected in view of the philosophy behind the concept of the monoblock. Tay et al. (23) have described the inability of Resilon to form a ‘monoblock’, possibly because of unfavourable root canal geometry for bonding filling material to dentine, and the potential to form gaps along the interface between the cement and dentine. The bond strength achieved between Resilon/Epiphany and intracanal dentine is not superior to that between guttapercha and epoxy resin sealer (24). The results of this study do not support the hypothesis that Resilon strengthens root canals. Bonding to the root canal wall is mechanically unfavourable because of a high configuration factor (c-factor), which leads to greater contraction stresses (25). This unfavourable c-factor within the canal may have led to high stresses that caused adhesive failure. Perdigão et al. (22) stated that the resin does not flow 162
1. Ray HA, Trope M. Periapical status of endodontically treated teeth in relation to technical quality of the root filling and the coronal restoration. Int Endod J 1995; 28: 12–8. 2. Schwartz RS, Fransman R. Adhesive dentistry and endodontics: materials, clinical strategies and procedures for restoration of access cavities: a review. J Endod 2005; 31: 151–65. 3. Kakehashi S, Stanley HR, Fitzgerald RJ. The effects of surgical exposures of dental pulps in germ-free and conventional laboratory rats. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1965; 20: 340–9. 4. Moeller AJR. Influence on periapical tissues of indigenous oral bacteria and necrotic pulp tissue in monkeys. Scand J Dent Res 1981; 89: 475–84. 5. Heard F, Walton RE. Scanning electron microscope study comparing four root canal preparation techniques in small curved canals. Int Endod J 1997; 30: 323–31. 6. Siqueira JF Jr, Araujo MC, García PF, Fraga RC, Dantas CJ. Histological evaluation of the effectiveness of five instrumentation techniques for cleaning the apical third of root canals. J Endod 1997; 23: 499–502. 7. Delivarnis PD, Mattison GD, Mendel RW. The survivability of F43 stain of Streptococcus sanguis in root canals filled with gutta-percha and Procosol cement. J Endod 1983; 9: 407–10. 8. Stiegemeier D, Baumgartner C, Ferracane J. Comparison of push-out bond strengths of resilon with three different sealers. J Endod 2010; 36: 318–21.
© 2012 The Authors Australian Endodontic Journal © 2012 Australian Society of Endodontology
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9. Schwartz R. Adhesive density and endodontics: part 2 – bonding in the root canal system: the promise and the problems – a review. J Endod 2006; 32: 125–34. 10. Gogos C, Economides N, Stavrianos C, Kolokounis I, Kokorikos I. Adhesion of a new methacrylate resinbased sealer to human dentin. J Endod 2004; 30: 238–40. 11. Tay F, Pashley D, Yoshiyama M. Two models of nanoleakage expression in single-step adhesives. J Dent Res 2002; 81: 472–6. 12. Perdigão J, Lambrechts P, Van Meerbeek B, Vanherle G, Lopes ALB. A field emisión SEM comparison of four post-fixation drying techniques for human dentin. J Biomed Mater Res 1995; 29: 1111–20. 13. Tay FR, Loushine RJ, Lambrechts P, Weller RN, Pashley DH. Geometric factors affecting dentin bonding in root canals: a theoretical modeling approach. J Endod 2005; 31: 584–9. 14. Bergmans L, Moisiadis P, De Munck J, Van Meerbeek B, Lambrechts P. Effect of polymerization shrinkage on the sealing capacity of resin fillers for endodontic use. J Adhes Dent 2005; 7: 321–9. 15. Aptekar A, Ginnan K. Comparative analysis of microleakage and seal for 2 obturation materials: resilon/epiphany and gutta-percha. J Can Dent Assoc 2006; 72: 245. 16. Shipper G, Orstavik D, Teixeira F, Trope M. An evaluation of microbial leakage in roots filled with a thermoplastic synthetic polymer-based root canal filling material (resilon). J Endod 2004; 30: 342–7. 17. Wedding JR, Brown CE, Legan JL, Moore KB, Vail MM. An in vitro comparison of microleakage between resilon and gutta-percha with a fluid filtration model. J Endod 2007; 33: 1447–9. 18. Baumgartner G, Zehnder M, Paqué F. Enterococcus faecalis type leakage through root canals filled with
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Gutta-Percha/AH plus or Resilon/Epiphany. J Endod 2007; 33: 45–7. Fransen JN, Jianing HE, Glickman GN, Ríos A, Shulman JD, Honeyman A. Comparative assessment of active GP/Glass ionomer sealer, Resilon/Epiphany, and GuttaPercha/AH Plus Obturation: a Bacterial Leakage Study. J Endod 2008; 34: 725–7. De-Deus G, Reis C, Di Giorgi K, Brandao MC, Audi C, Fidel RA. Interfacial adaptation of the epiphany selfadhesive sealer to root dentin. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010; 111: 381–6. Hiraishi N, Papacchini F, Loushine RJ et al. Shear bond strength of Resilon to a methacrylate-based root canal sealer. Int Endod J 2005; 38: 753–63. Perdigão J, Lopes MM, Gomes G. Interfacial adaptation of adhesive materials to root canal dentin. J Endod 2007; 33: 259–63. Tay FR, Loushine RJ, Lambrecechts P, Weller RN, Pashley DH. Geometric factors affecting dentin bonding in root canals: a theoretical modeling approach. J Endod 2005; 31: 584–9. Gesi A, Ornella R, Goracci C, Pashley DH, Tay FR, Ferrari M. Interfacial strength of resilon and guttapercha to intraradicular dentin. J Endod 2005; 31: 809– 13. Bouillaguet S, Troesch S, Wataha JC, Krejci I, Meyer JM, Pashley DH. Microtensile bond strength between adhesive cements and root canal dentin. Dent Mater 2003; 19: 199–205. Timpawat S, Amornchat C, Trisuwan WR. Bacterial coronal leakage after obturation with three root canal sealers. J Endod 2001; 27: 36–9. Tay FR, Loushine RJ, Weller RN et al. Ultrastructural evaluation of the apical seal in roots filled with a polycaprolactone-based root canal filling material. J Endod 2005; 31: 514–9.
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Aust Endod J 2013; 39: 159–163
ORIGINAL RESEARCH
Ultramicroscopic study of the interface and sealing ability of four root canal obturation methods: Resilon versus gutta-percha Pablo Castelo-Baz, DDS1; Benjamin Martin-Biedma, PhD1; Maria Manuela Lopes, PhD2; Luis Pires-Lopes, PhD2; Joao Silveira, DDS1; Elisardo López-Rosales, DDS1; and Purificación Varela-Patiño, PhD1 1 Unit of Dental Pathology and Therapeutics, Faculty of Medicine and Dentistry, University of Santiago de Compostela, Santiago de Compostela, La Coruña, Spain 2 Unit of Investigation and Oral and Biomedical Sciences, Faculty of Dental Medicine, University of Lisbon, Lisbon, Portugal
Keywords electron microscopy, RealSeal 1, Resilon, root canal obturation, System B, Thermafil. Correspondence Mr Pablo Castelo-Baz, Master of Endodontics, University of Santiago de Compostela, Rúa Entrerríos s/n, Santiago de Compostela, La Coruña 15770, Spain. Email: [email protected] doi:10.1111/j.1747-4477.2012.00370.x
Abstract Recently, filling materials have been introduced based on the dentine adhesion technologies used in conservative dentistry in an attempt to seal the root canal more effectively. The purpose of this study was to investigate the interface between the canal and root-filling material. Sealing ability of four root canal obturation methods was analysed by means of scanning electron microscopy. Extracted single-rooted teeth were endodontically treated and filled with gutta-percha/Pulp Canal Sealer using the Thermafil (TH) technique, guttapercha/Pulp Canal Sealer using the System B (SB) technique, Resilon points/ RealSeal (RS) and RealSeal 1/RealSeal (RS1). Specimen interfaces were analysed using field-emission scanning electron microscopy. The adhesive groups RS and RS1, formed hybrid layers but showed areas of separation (gaps) similar to those in the conventional obturation groups. The RS and RS1 groups showed less separation in the coronal third, but the separation was similar to that in the TH and SB groups in the middle and apical thirds. The sealing ability of Resilon is not superior to that of existing materials.
Introduction The three-dimensional obturation of the canal system after proper chemomechanical preparation is essential to achieve success in endodontics (1). The aim of endodontic treatment is to eliminate bacteria throughout the canal system (the primary aetiology of pulpal and radicular disease being bacterial) and to seal the access with various materials to prevent reinfection (2–4). Available data suggest that the root canal system cannot be totally cleaned and disinfected (5,6). Therefore, the canal system should be disinfected as much as possible and obturated to prevent coronal leakage and subsequent bacterial contamination, and the apex sealed to prevent contamination by periapical tissue fluids (7). Gutta-percha is the traditional filling material in endodontics, used in combination with cements composed of calcium hydroxide, zinc oxide/eugenol or epoxy resin. More recently, filling materials have been developed
© 2012 The Authors Australian Endodontic Journal © 2012 Australian Society of Endodontology
based on the dentine adhesion technologies used in conservative dentistry in an attempt to seal the root canal more effectively (8,9). Alternatives to gutta-percha, such as Resilon (Resilon Research LLC, Madison, CT, USA), were introduced in 2003. Resilon is a synthetic polymer-based thermoplastic polyester containing bioactive glass, bismuth oxychloride and barium sulfate. An alternative, RealSeal (RS; SybronEndo, Orange, CA, USA), is a dual-curing, resinbased composite sealer. The resin matrix is composed of bisphenol A glycidyl methacrylate (BisGMA), ethoxylated BisGMA, urethane dimethacrylate and hydrophilic bifunctional methacrylates. A new sealant, RS SE (SybronEndo) removes the need for a primer. The cement is applied in the conventional manner and is used to attach Resilon to the dentine (10). The aim of this study was to compare the interface between canal and obturating material. Sealing ability of four root canal obturation methods were analysed by means of scanning electron microscopy. 159
Resilon versus Gutta-percha
Material and methods Forty-eight permanent single-rooted human teeth extracted for periodontal or orthodontic reasons were stored in 0.2% chloramine at 4°C until endodontic preparation. Two radiographs, one from a mesiodistal direction and the other from a buccolingual direction, were made, confirming the presence of a single canal. The following procedures were carried out: disinfection, cleaning and removal of the crown; after cleaning and surface disinfection (with ultrasonics and 5% chlorhexidine), the crown of the tooth was cut at the cementoenamel junction to standardise the canal length to 14 mm, endodontic treatment; access and negotiation of the tooth and determination of the working length with a K-file (Flexofile #10; Dentsply Maillefer, Ballaigues, Switzerland) were performed such that the tip of the file was seen to protrude from the apical foramen under a clinical microscope (M525 F40; Leica, Heerbrugg, Switzerland). Hand preparation of the glide path with K-files (Flexofiles #15 and #20; Dentsply Maillefer) was then performed. Rotary instrumentation was carried out with the ProTaper Universal system (Dentsply Maillefer) following the sequence S1, S2, F1, F2 and F3. Irrigation was used throughout the process with 5.25% NaOCl, 2 ml for 1 min between each file use. Additionally, a final irrigation consisted of alternating 5.25% NaOCl (Niclor 5; OGNA, Muggiò, Italy), 3 ml for 1.5 min, 17% liquid EDTA (Tubuliclean; OGNA, Milan, Italy), 5 mL for 1 min and again 5.25% NaOCl (3 mL for 1.5 min). Both solutions were activated with ultrasound for 30 s with an ultrasonic tip (ISO 15, IrriSafe; Satelec, Actaeon Group, Merignac Cedex, France). The canal received a final wash with distilled water (1 mL for 1 min) applied to the working length with a 30-gauge needle (ProRinse; Dentsply Tulsa Dental Specialties, Tulsa, OK, USA) and canal drying; the canals were dried with absorbent F3 paper points (Dentsply Maillefer) and randomised into four groups of 12 teeth each, as described later.
Experimental groups Group 1: Obturation with System B (SB) Pulp Canal Sealer (Kerr, Romulus, MI, USA), a zinc oxide-eugenol sealer, was used as the sealing cement. Three paper points were placed within 1 mm of the working length: the first was used to apply the sealer, the second to distribute it and the third to remove the excess. A ProTaper F3 cone (Dentsply Maillefer) was placed 0.5 mm from the working length. Down-packing was performed with a 08 tapered plugger of the Elements Unit (SybronEndo) at 200°C to 4 mm from the working length, then backfilling was performed with hot gutta160
P. Castelo-Baz et al.
percha using the gun component of this unit and also using a Buchanan hand plugger (tip size 0.03/0.41).
Group 2: Obturation with Thermafil (TH) The same method previously described in-group 1 was used to place the sealer. The F3 verifier was used to check for appropriate fit and to assess whether the F3 TH (Dentsply Maillefer) was adequate (if not, the tooth was discarded). A ProTaper F3 obturator was heated in the ThermaPrep oven (Dentsply Maillefer) for 30 s (in accordance with the manufacturer’s recommendations) and then inserted into the tooth with a constant apical pressure for 6 s. The coronal excess was removed with a Thermacut bur (Dentsply Maillefer).
Group 3: RS In this group, RS self-etch cement (SybronEndo) was applied with paper points in the same way as for the previous groups. An RS (SybronEndo) cone was placed 0.5 mm from the working length. The Elements unit was then employed in the same way as in the first group.
Group 4: RealSeal 1 (RS1) After applying RS self-etch cement in the same way as in the previous group, a size 30 obturator was heated in the oven and then inserted in the tooth with a constant apical pressure for 6 s, as indicated by the manufacturer. The coronal excess was removed with a Thermacut bur (Dentsply Maillefer). The coronal portion was then photopolymerised for 40 s.
Subgroups The teeth from each group were then divided; morphological hybridisation was observed in nine teeth that were polished completely and three teeth that were left unpolished (to compare if the polish can modify the samples). Scanning electron microscopy was used to analyse the tooth/obturating material interface. Two disk-shaped samples were taken from the coronal area and the middle and apical regions of each specimen. Two areas in each disc were defined (A and B, always in the same position) and photographs were taken at 50, 200 and 1000 ¥ magnification. Areas where the cutting blade had not entered or finished were selected to avoid the creation of areas of drag or separation during sample preparation.
Analysis of the interface using field-emission scanning electron microscopy Morphological hybridisation Teeth were sectioned perpendicularly to their long axis with a diamond saw (Isomet 1000; Buehler Ltd, Lake
© 2012 The Authors Australian Endodontic Journal © 2012 Australian Society of Endodontology
Resilon versus Gutta-percha
P. Castelo-Baz et al.
Bluff, IL, USA) under distilled water to obtain 1.5᎑to 2 mm thick slices. The specimens were immersed in 2.5% glutaraldehyde/2% paraformaldehyde in 0.1 mol sodium cacodylate buffer at pH 7.4 for 12 h at 4°C, and thoroughly processed by hexamethyldisilazane (HMDS; Ted Pella Inc., Redding, CA, USA) to drying (11). The disks were embedded in Epo-Thin epoxy resin (Buehler Ltd). After curing for 18 h, the surface of each epoxy cast was polished with wet SiC papers of decreasing abrasiveness (up to 1200 grit), and the soft tissue with increasingly fine diamond suspension to a 0.05᎑m size (Buehler Ltd). The specimens were sonicated in 100% ethanol for 5 min, demineralised in 6% NHCl (Acros Organics USA, Morris Plains, NJ, USA) for 30 s and deproteinised in 1% NaOCl for 10 min. The specimens were mounted on Al stubs and sputter-coated with Au-Pd in an E-5100 sputter-coater (Polaron Ltd, Watford, UK) at 40 mA for 90 s. Interfaces were observed under an S4700 Hitachi (Hitachi, Tokyo, Japan) field emission scanning electron microscopy (FESEM) at 4.0–5.0 kV.
Table 1 Mean and standard deviation of four groups in each thirds
Group
Third
Mean
Standard deviation
G1: SB
Coronal Middle Apical Coronal Middle Apical Coronal Middle Apical Coronal Middle Apical
28.56 8.58 9.19 21.96 10.09 8.74 14.23 9.50 8.44 12.49 8.38 7.45
6.35 2.23 3.59 6.29 3.87 2.78 3.20 3.83 3.20 5.04 2.74 1.69
G2: TH
G3: RS
G4: RS1
SB, System B; TH, Thermafil; RS, RealSeal; RS1, RealSeal 1.
a
b
c
d
Morphological hybridisation unpolished Three samples were not embedded in Epo-Thin resin (Buehler Ltd) and the surface was not polished with the wet SiC papers. After immersing the samples in HMDS, they were sonicated in 100% ethanol, demineralised, deproteinised and coated as previously described process of the morphological hybridisation. Interfaces were observed under the same FESEM.
Statistical analysis A one-factor analysis of variance and Turkey statistical methods were made to compare the groups in the three thirds (coronal, medial and apical). G-Stat program (Letón and Mariño, Department of Biometrics, GlaxoSmithKline, Madrid, Spain) was used to make this analysis.
Results Mean and standard deviation are shown in Table 1. The RS and RS1 adhesive groups formed hybrid layers (Fig. 1a) but showed areas of separation (gaps; Fig. 1b) similar to those of the conventional obturation groups (Fig. 1c,d). In all groups, the gap was located between the dentine and the sealer cement that remained attached to the obturating material (Fig. 2a,b). The RS and RS1 groups showed less separation in the coronal third (statistically significant F = 45.57, P < 0.001) than TH and SB groups. No statistical differences were found in all groups in medial (F = 1.47, P = 1.229) and apical thirds (F = 1.55, P = 0.2063). No statistical differences was observed between polished and unpolished teeth (Fig. 1e,f, P = 0.153) (Fig. 3a,b).
© 2012 The Authors Australian Endodontic Journal © 2012 Australian Society of Endodontology
Figure 1 (a) Coronal area of a specimen treated with RealSeal (RS), showing the hybrid layer. (b) Coronal area of a specimen treated with RS, showing a gap. (c) Coronal area of a specimen treated with RealSeal 1 (RS1), showing a gap. (d) Coronal area of a specimen treated with thermafil (TH), showing a gap. SEM, scanning electron microscopy.
Discussion Polymerisation shrinkage creates tensions that may be of sufficient magnitude to cause detachment of the resin from the canal wall dentine, thereby potentially opening a pathway for bacterial infiltration (12,13). Resilon/ Epiphany has been suggested to improve bacterial infiltration when it is compared with gutta-percha and traditional sealer (14–16). However, no statistically significant difference in infiltration between obturation techniques with Resilon and conventional gutta-percha has been reported in the recent literature (17,18,19). De-Deus et al. (20) showed that the interface adaptation 161
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a
b
Figure 2 (a) Apical area of a specimen treated with System B (SB). (b) Apical area of a specimen treated with RealSeal 1 (RS1). SEM, scanning electron microscopy.
P. Castelo-Baz et al.
because of surface tensions, resulting in stress accumulation within the polymerisable resin. A similar pattern has been described when bonding fibre posts to root canal dentin (26). Apical gaps could occur in a clinical situation for the four obturation groups studied, potentially causing infiltration and endodontic treatment failure. Gap-free zones and areas with gaps at the interface have been associated with Resilon and gutta-percha/AH Plus (27). Perdigão et al. (22) also stated that despite hybridisation, a perfect seal of the root canal is difficult to achieve, possibly because of the complexity of the substrate and the high c-factor.
Conclusion a
b
Within the limitations of this study, it can be concluded that the sealing ability of new root canal obturating material (Resilon) is not superior to that of existing materials. Our future research will study the new obturating cements and the same samples with micro-computed tomography.
References Figure 3 (a,b) Polished and unpolished Thermafil (TH) samples. SEM, scanning electron microscopy.
of adhesive root sealants is compromised, even in teeth with simple anatomy and under well-monitored laboratory conditions. The results of this study agree with those of Hiraishi et al. (21) and Perdigão et al. (22), who reported gaps between Resilon and the sealant. This physical separation was not expected in view of the philosophy behind the concept of the monoblock. Tay et al. (23) have described the inability of Resilon to form a ‘monoblock’, possibly because of unfavourable root canal geometry for bonding filling material to dentine, and the potential to form gaps along the interface between the cement and dentine. The bond strength achieved between Resilon/Epiphany and intracanal dentine is not superior to that between guttapercha and epoxy resin sealer (24). The results of this study do not support the hypothesis that Resilon strengthens root canals. Bonding to the root canal wall is mechanically unfavourable because of a high configuration factor (c-factor), which leads to greater contraction stresses (25). This unfavourable c-factor within the canal may have led to high stresses that caused adhesive failure. Perdigão et al. (22) stated that the resin does not flow 162
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