A comparative evaluation of 3 root canal filling systems Ruchika Roongta Nawal, MDS,a Mahantesh Parande, MD,b Ritu Sehgal,c Nageswar R. Rao, MDS,d and Aisha Naik,b New Delhi, India MAULANA AZAD INSTITUTE OF DENTAL SCIENCES, BELGAUM INSTITUTE OF MEDICAL SCIENCES, AND S.D.M. INSTITUTE OF DENTAL SCIENCES
Objective. This in vitro study was conducted to evaluate and compare the microbial leakage of a new obturation system: Guttaflow with resin-based Resilon cones and Epiphany sealer, keeping gutta-percha with AH plus sealer as the standard. Study design. The microbial leakage was tested using Enterococcus faecalis ATCC 29,212 as the bacterial marker in the microbial leakage test. These results were supplemented with scanning electron microscopy (SEM). Results and conclusion. The microbial leakage test indicated good sealing abilities for Resilon and Guttaflow, with the latter resisting microbial leakage for a longer period. AH plus with gutta-percha showed poor sealing ability. Results of the scanning electron microscopy correlated with the microbial leakage test. This study indicates that newer obturation systems like Guttaflow and Resilon cones with Epiphany provide better seal against microbial leakage than the standard obturation material, gutta-percha used with AH plus sealer. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2011;111:387-393)
Invasion of microorganisms or the leakage of their by-products into the periapical tissues is believed to be the predominant cause of periapical pathology.1-5 Healing of periapical disease involves a combination of bacterial eradication during treatment through chemomechanical means,6,7 along with sealing of both the root canal and access cavity with materials that will prevent bacterial reentry.8,9 To achieve complete healing, proper disinfection, 3-dimensional obturation, and adequate coronal sealing are essential. However, obturation materials and methods have failed to show a long-lasting perfect seal with the cavity wall.10,11 Eventually, a microscopic gap is formed at the material and tooth interface, which allows leakage of oral fluids and percolation followed by bacterial penetration and growth.2,12 To minimize the microbial leakage, many alterations are now being proposed to the “gold standard” technique of filling root canals with gutta-percha and sealer. a
Senior Lecturer, Department of Conservative Dentistry and Endodontics, Maulana Azad Institute of Dental Sciences, New Delhi, India. b Associate Professor, Department of Microbiology, Belgaum Institute of Medical Sciences, Belgaum, Karnataka, India. c Former Senior Lecturer, Department of Conservative Dentistry and Endodontics, Maulana Azad Institute of Dental Sciences, New Delhi, India. d Head of Department, S.D.M. Institute of Dental Sciences, Dharwad, Karnataka, India. Received for publication May 16, 2010; returned for revision Aug 8, 2010; accepted for publication Sep 23, 2010. 1079-2104/$ - see front matter © 2011 Mosby, Inc. All rights reserved. doi:10.1016/j.tripleo.2010.09.070
Among them, Guttaflow (Coltene Whaledent, DPI, Mumbai, India), a new flowable root canal filling paste, is a nonheated flowable obturation system that combines both the sealer and the gutta-percha in 1 injectable system. The sealer is silicone based with polymethyl hydrogen siloxane as its main component and the powder consists of finely ground gutta-percha (0.9 m). It is available in capsule, which is triturated for about 30 seconds and then inserted in the canal in combination with a single master gutta-percha cone. This material has shown good homogeneity and adaptation to the root canal walls owing to its better flow properties13 and is believed to flow into lateral grooves and depressions.14 Another group of root canal filling materials that has gained popularity are the resin-based filling materials. These materials have exhibited improved resistance to bacterial penetration through their strong bonding to the root canal dentin.15 Resilon, a thermoplastic synthetic polymer– based root canal filling material, is based on polymers of polyester and also contains bioactive glass, bismuth oxychloride, and barium sulfate. The overall filler content is 65% by weight. Epiphany sealer is a dual curable dental resin composite sealer. The resin matrix is a mixture of BisGMA, ethoxylated BisGMA, Udma, and hydrophilic difunctional methacrylates. It contains fillers of calcium hydroxide, barium sulfate, barium glass, and silica. The total filler content of the sealer is 70% by weight. This study was conducted to test the resistance to leakage through a microbial leakage model of conventional root canal filling materials: AH plus with gutta-percha with the newer materials Resilon387
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Epiphany and Guttaflow. The microbial leakage was tested using Enterococcus faecalis ATCC 29,212 as the bacterial marker in the microbial leakage test, which was supplemented with scanning electron microscopy (SEM). MATERIALS AND METHODS Test for bacterial microleakage Forty caries-free, human maxillary incisors with straight roots, extracted for periodontal reasons, were used for the purpose of this study. The teeth were immersed in 5% sodium hypochlorite (NaOCl) for 15 minutes to remove organic material from the root surfaces. Any remaining tissue was mechanically removed using a curette, being careful not to damage the root surface. The teeth were then stored in sterile distilled water and kept moist throughout the course of this study. Preparation of the specimen. The test teeth were de-coronated near the cementoenamel junction in such a way that the root length for all specimens was standardized at 15 mm. Access to the root canals was gained from the coronal orifice of the roots using size # 4 and # 6 round burs in a high-speed hand-piece under copious water spray. Patency of the canals was verified by placing a # 15 K-file (0.02 taper) (Dentsply Maillefer, Mumbai, India). Working lengths were designated as 1 mm short of the point at which the # 15 K-file exited the apical foramen. Coronal flaring of all the canals was accomplished with # 1 to 3 Gates-Glidden drills (Mani, Mumbai, India). All the teeth were then instrumented with # 45 K-files (0.02 taper) apically to obtain a standardized diameter of the apical end of the canals. Approximately 2 mL of 2.5% NaOCl, delivered in a disposable syringe fitted with a 27-gauge needle, was used to flush the canal between each file size. For rinsing after instrumentation, 5 mL of 17% EDTA was used followed by 5 mL of 2.5% NaOCl rinse to remove the smear layer. The final rinse in all the canals was done with 5 mL of saline to remove any remnants of NaOCl. This ensured noninterference of NaOCl with the bonding of resin-based obturation system to the canal walls. After completing the preparation, # 15 K-file was passed through the apical foramen to ensure the patency in all the canals. Sterilization protocol. After biomechanical preparation, all the teeth were sterilized in an autoclave at 6.8 kg pressure for 20 minutes at 121°C. The teeth were then randomly divided into 5 groups. Obturation of the autoclaved teeth was carried out in a laminar airflow hood (Kartos, India) under aseptic conditions. Group 1 (10 teeth): lateral condensation of guttapercha with AH plus sealer. These samples were ob-
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turated with gutta-percha and AH plus sealer (Dentsply, India) using cold lateral condensation as described by Ingle et al.16 A 0.02-taper gutta-percha master point of # 45 size was fitted in the root canal at the working length and checked for tug-back criteria. AH plus sealer was applied to the root canal using a # 45 file size with counter-clockwise rotation. The apical part of the master point was coated with sealer and introduced slowly into the root canal until the working length was reached. Lateral condensation was done using standardized finger spreaders and corresponding cones (0.02 taper). Obturation was considered complete when the spreader could no longer penetrate the filling mass beyond the cervical part. Group 2 (10 teeth): lateral condensation of teeth using Resilon cones and Epiphany sealer. These samples were obturated using Resilon cones and Epiphany sealer using cold lateral condensation technique. A 0.02-taper Resilon master point of # 45 size was selected and checked for tug-back criteria. The canal was conditioned with 2 to 3 drops of self-etch primer dispensed with a pipette on orifice and applied evenly on the canal wall with the brush provided by the manufacturer. Any excess primer was removed with paper points. The sealer was then mixed and applied with a file size # 45 in a counter-clockwise direction. The apical part of the master point was coated with sealer and introduced in the canal until the working length was reached. Lateral condensation was done using standardized spreaders and corresponding Resilon cones (0.02 taper). Obturation was considered complete when the spreader could no longer penetrate the filling mass beyond the cervical part. Once the obturation was complete, the coronal surface was light-cured in the chamber for 40 seconds. Group 3: Guttaflow obturation system (10 teeth): teeth were obturated using the Guttaflow system as per the manufacturer’s instructions. Teeth were obturated using the Guttaflow system as per the manufacturer’s instructions. A # 45 size (0.02 taper) master cone was selected and checked for tug-back criteria. Guttaflow provided in single-use special capsules was mixed in the triturator for 30 seconds. The capsule was then loaded on the dispenser with attached canal tip. Guttaflow was layered slowly from the fine canal tip into the apical part. The selected master point was coated with Guttaflow paste in the apical third and placed in the canal. The canal tip was then inserted lateral to the master cone and the remaining canal was back-filled with Guttaflow paste. Group 4 (5 teeth): negative control. Following obturation by lateral condensation with gutta-percha and
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Fig. 1. High-power SEM (⫻750) micrograph of a longitudinal section of a root filled with Gutta-percha and AH plus sealer (A), Resilon and Epiphany sealer (B), and Guttaflow (C).
AH plus sealer, the entire length of the root was sealed with nail enamel. Group 5 (5 teeth): positive control. The group 5 teeth were those in which no obturation was done. Preparation of leakage apparatus. Bacterial leakage model was prepared according to previous experiments.17-19 It comprised 3 main parts, i.e., an upper chamber, the prepared tooth, and the lower chamber. After obturation, the outer surfaces of the teeth were coated with 2 layers of nail enamel except the apical 2 mm. Foley’s catheter tubes (20 no.) were cut into approximately 8-mm sections. Orthodontic ligature wires were passed through the upper part of each tube and attached to the rubber-stopper of the glass vials. These were then sterilized in an autoclave. The roots were then passed through the sterile tubes under laminar airflow. An excess 3 mm of each tube was left above the coronal portions of the teeth, which formed the upper chamber of the apparatus. The junction between the tube and the tooth was sealed with sterile cyanoacrylate. The cyanoacrylate was repeatedly tested and confirmed for sterile condition. The rubber stoppers with the attached teeth and tubings were placed in the sterile glass vials, creating 2 separate reservoirs. The glass vials were filled with 2 mL of sterile Brain Heart Infusion (BHI) broth, which formed the lower chamber of the apparatus (Fig. 1). These sterilized set-ups, along with the obturated teeth, were incubated at 37°C for 48 hours to allow the sealer to set and to ensure sterilization. Turbidity if observed in the lower chambers of any of these samples was considered as contamination. None of the apparatuses showed any contamination. Bacterial leakage test E. faecalis was used as an indicator of microbial leakage in this study. The strains used were obtained as clinical isolates from infected root canal cases, as in
previous studies.19,20 The isolates were incubated in BHI broth for 4 hours. The upper chambers of the apparatuses were filled with the 4-hour broth culture of E. faecalis, whereas the lower chambers contained the sterile BHI broth. The upper chambers of the apparatuses with the attached teeth were suspended such that the apical 2 mm of the tooth was immersed in the broth. The entire assembly was then incubated at 37°C and observed each day for turbidity in the lower chamber, for 30 days. The strain of E. faecalis was replenished every week to ensure the viability of the bacterial marker. Utmost care was taken to avoid spillage and accidental contamination of the lower chambers. Any turbidity in the sterile BHI broth of the lower chamber was considered as an indication of bacterial leakage from the upper to the lower chamber through obturation (Fig. 2). Turbidity in the lower chamber, if any, was tested for the presence of E. faecalis by standard microbiological techniques.20
Table I. Number of days from inoculation to bacterial leakage Specimen no.
GP ⫹ AH plus
Resilon ⫹ Epiphany
GP ⫹ Guttaflow
1 2 3 4 5 6 7 8 9 10
⫹30 10 15 7 10 ⫹30 ⫹30 10 17 21
17 ⫹30 ⫹30 10 ⫹30 ⫹30 ⫹30 18 ⫹30 ⫹30
⫹30 ⫹30 ⫹30 ⫹30 ⫹30 15 ⫹30 ⫹30 18 21
Samples that did not leak at all during the 30-day observation period are indicated as ⫹30.
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Table II. Descriptive statistics: minimum, median, maximum days at which microleakage occurred and the mean rank of comparisons among the experimental group Groups
A B C
7 10 15
31 31 31
14.8 26.1 27.2
8 31 31
9.45 18.25 18.80
Table III. Pair-wise comparison between the groups by Mann-Whitney U test Groups
S, significant; NS, not significant.
The investigators examining leakage during the 30 days were blinded to all the groups. Statistical analysis was performed using Kruskal-Wallis test for nonparametric data to determine any significant differences between groups. Pairs of groups were compared using Mann Whitney U test (P ⬍ .05). Scanning electron microscopy preparation On completion of the leakage test, 1 sample each from gutta-percha, Resilon, and Guttaflow groups was randomly chosen. Each specimen was longitudinally sectioned to obtain the dentin-filling interface. The entire root surface of both the split sections for each group was carefully studied by for scanning electron microscopy. This was used to detect the presence of any gap between the tooth surface and obturation throughout the length of the obturated root. RESULTS No growth was observed while checking for sterilization of the whole apparatus. The results obtained during the bacterial microleakage test for a period of 30 days are summarized in Table I. The positive control specimens leaked within 24 hours and none of the negative control specimens leaked during the 30 days. Group 1 showed leakage in 7 (70%) of 10, whereas both groups 2 and 3 showed leakage in 3 (30%) of 10 samples. According to the number of days at which the first leakage occurred, the AH plus group showed first leakage on the 7th day of observation, whereas the Resilon group leaked on the 10th day. The Guttaflow group showed first leakage on the 15th day. The median, mean, and maximum days of leakage and the mean rank for each leakage group are shown in Table II. Statistical analysis using the Kruskal-Wallis test revealed significant differences between groups 2 and 3 in relation to group 1. The difference between groups 2 and 3 was insignificant. The Mann-Whitney U test was used to compare the results, and both the Resilon and Guttaflow groups were found to be superior to the gutta-percha group with respect to the number and rate at which the samples leaked (Table III).
There was no statistical difference between Resilon and Guttaflow groups; however, the former showed leakage earlier than latter group. The dentin-filling interface of the longitudinal sections showed a uniform 12- gap in the gutta-percha specimens (Fig. 3, A). This gap was observed between the resin sealer that penetrated the dentin and the guttapercha filling. There was no gap at low- and high-power scanning electron microscopy for Resilon and Guttaflow groups (Fig. 3, B, C). The high-power scanning electron microscopy clearly showed excellent adaptation of the Guttaflow material to the canal walls (Fig. 3, C). This test further supplements the results of our microbial leakage test. DISCUSSION This study was conducted to test the resistance to microbial leakage of root canal filling materials: AH plus with gutta-percha, Resilon-Epiphany, and Guttaflow. The microbial leakage of the 3 root canal filling systems was evaluated by bacterial leakage method using Enterococcus faecalis ATCC 29,212 as the bacterial marker. Using bacteria itself as a marker is a clinically relevant demonstration of microbial leakage associated with root canal system. The gram-positive facultative bacteria E. faecalis used in this study is a common isolate from infected root canals.21 It is most often isolated in retreatment cases of apical periodontitis.22 Its prevalence ranges from 24% to 77%. This finding can be explained by its various virulence factors, including its ability to compete with other microorganisms, invade dentinal tubules, and resist nutritional deprivement.23 Thus, these bacteria seem relevant to clinical practice. For the purpose of the study, a clinical isolate of E. faecalis was used. To avoid anatomical variations and to standardize the leakage measurements in this study, the length and type of specimens was kept constant. For testing the microbial leakage in the experimental setup, the canals were cleaned with 17% EDTA and NaOCl to remove the
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smear layer.24,25 Smear layer may act as a barrier between obturating materials and the canal wall, which may make it difficult to create a seal and prevent coronal-to-apical leakage.19 Hence, its removal facilitates adherence of the sealer to the canal walls and its penetration in dentinal tubules, ensuring good bond strength.17,25 On completion of an evaluation period of 30 days, our results showed that 70% of samples leaked in the gutta-percha group (lateral condensation with AH plus sealer). This high percentage is comparable with that of the previous studies’ results. On the other hand, the Resilon groups with resin sealer and the silicone-based Guttaflow group showed leakage in 30% of cases, i.e., less than half of that in the gutta-percha group. When evaluated on the basis of the number of days at which the leakage occurred, the gutta-percha group was the first to show leakage, on the 7th day of obturation; the Resilon group showed the first sample leakage on the 10th day of obturation; whereas in the Guttaflow group the first sample leaked on the 15th day. Almost 70% of samples in both the Resilon and Guttaflow groups remained leakage free until the end of the 30-day observation period. Although the Resilon and Guttaflow groups showed similar results regarding the number of samples leaked, the samples of the Resilon group leaked earlier than the Guttaflow group. The positive controls (no obturation) leaked on the first day, whereas the negative controls did not leak at all until the end of the observation period. The results of the microbial leakage test, further confirmed by scanning electron microscopic analysis of the 3 groups, revealed that the gutta-percha group showed a clear gap at the dentin-filling interface, whereas both the Resilon and Guttaflow groups showed excellent adaptation to the canal wall. The better sealing ability exhibited by the Guttaflow root-canal filling material could be attributed to its ability to flow into the canal. The material has been shown to flow into lateral canals or any grooves in the canal wall and hence could fill the space between the master cone and canal wall.12 In a study by Leski et al.,26 it also showed good penetration into the dentinal tubules, which will also help in preventing leakage. Both gutta-percha with AH plus sealer and Resilon cones with Epiphany sealer, show a setting shrinkage following obturation. On the other hand, manufacturers claim that the Guttaflow obturation system exhibits a setting expansion of 0.2% following obturation in the canal.27 This property has been demonstrated by Hammad et al.28 These physical properties could contribute toward it, providing a good seal at the dentin interface and hence prevent leakage.
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Previous studies by Elayouti et al.13 and De Dues et al. demonstrated good adaptability to root canal walls with Guttaflow in accordance with this study. Brackett et al.30 found no significant difference in sealing ability between Guttaflow and vertically compacted, thermoplasticized gutta-percha and AH plus sealer when using a fluid filtration study. Kontakiotis et al.31 also found no difference at a short-term evaluation period. However, Guttaflow showed significantly better coronal seal at a long 12-month follow-up. Monticelli et al.,32 however, showed that teeth obturated with Guttaflow showed an equally good apical seal as compared with other groups, but its seal at a more coronal level was inferior as compared with teeth obturated with gutta-percha and AH plus by using a warm vertical technique. The difference in results of some studies could also be attributed to differences in methodologies used for testing coronal leakage. The mechanism of the sealing ability of Resilon cones with Epiphany sealer can be attributed to the mono-block created by the Resilon filling closely adapting to the Epiphany sealer, and in turn the Epiphany sealer adapting to the dentinal walls. This is facilitated by removal of the smear layer and application of the Epiphany primer. Epiphany primer is a self-etch primer that contains sulfonic acid terminated functional monomer, Hema, water, and polymerization initiator. The preparation of the dentin through these chemical agents prevents shrinkage of the resin filling away from the dentinal wall and aids in sealing the roots filled with Resilon. Epiphany sealer has also shown very good ability to flow into the canal, which may also help in providing a good seal.33 The coronal leakage results for Resilon and Epiphany in this study are consistent with previous studies by Shipper et al.23 and Tunga and Bodrumlu.34 Their studies showed that the gutta-percha group allowed bacterial penetration in a high proportion of cases, whereas the Resilon group resisted bacterial penetration. Stratton et al.,35 using fluid filtration test, also showed similar results. However, in a study by Tay et al.36 there was no difference in apical leakage by silver-tracer technique between gutta-percha with AH plus sealer and the Resilon group. Paque and Sirtes37 showed that Resilon, when used with a composite sealer (Epiphany), seals the apical root canal, as well as gutta-percha and AH plus in the short-term observation period. After 16 months, however, the Resilon/Epiphany groups leaked significantly more than the guttapercha/AH plus groups. This is an interesting observation and further studies with extended observation times are required for testing of these newer materials. Further comparison between the 2 newer materials: Epiphany and Guttaflow against each other, was also done. Previous studies comparing these 2 materials 29
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have given contradictory results. A microbial leakage study by Roggendorf et al.38 showed that Guttaflow had significantly better sealing properties as compared with Epiphany. This study, however, demonstrated the AH plus group to show minimum leakage, which was significantly superior to both Epiphany and Guttaflow groups. This is in contradiction with our study and many other studies previously mentioned that have clearly shown both Guttaflow and Epiphany to perform better than standard gutta-percha with AH plus sealer. Another dye penetration study by Taranu et al.39 also showed Guttaflow to be significantly superior to the Epiphany group in terms of leakage. Bouillaquet et al.40 compared AH plus, Epiphany, and Guttaflow sealer. They tested the leakage for an initial 24 hours and then long-term follow-up at 1 year by fluid filtration method. Their results indicated that AH plus showed more leakage in the initial 24 hours; however, no significant difference was found in leakage at 1-year follow-up among the 3 groups. In our study, the bacterial leakage model using E. faecalis as a marker was used to evaluate coronal leakage of both the newer materials. This method is considered to have more biological and clinical relevance than the dye leakage studies.41 The leakage was monitored continuously for 30 days, ensuring that any significant difference beyond the 24-hour time frame is captured for analysis of the superior sealer. The results of this study showed that both Epiphany and Guttaflow groups have good sealing ability, wherein Guttaflow showed superior sealing ability, as it resisted leakage for a longer period. This difference in the sealing ability of Epiphany can be attributed to the polymerization contraction of methacrylate-based resin sealer. Root canals have high cavity configuration factors that contribute to polymerization stresses created by resin-based sealers. Guttaflow paste, on the other hand, has exhibited expansion on setting, which could lead to better coronal sealing ability. However, it is important to note that Guttaflow, being a root canal paste, has a high risk of overfilling, as shown by some previous studies.42 Further studies are required to test the quality of seal of Guttaflow throughout the length of the canal especially at coronal levels. Similarly, Epiphany also warrants further support studies for long-term evaluation of its coronal seal. Any future studies to explore these properties of the 2 materials will be useful. CONCLUSIONS This study has attempted to evaluate clinically significant properties of obturation materials: AH plus with gutta-percha, Resilon cones with Epiphany sealer, and Guttaflow. The microbial leakage test indicated good sealing abilities for Guttaflow and Resilon groups,
with Guttaflow resisting bacterial leakage for a longer period. In the future, if its setting shrinkage could be compensated for, the Resilon group may show improvement in sealing ability. REFERENCES 1. Kakehashi S, Stanley H, Fitzgerald R. The effect of surgical exposures of dental pulps in germ free and conventional laboratory rats. Oral Surg Oral Med Oral Pathol 1965;20:340-9. 2. Brannstrom M, Nordenvall KJ. Bacterial penetration, pulpal reaction and the inner surface of concise enamel bond composite filling in etched and unetched cavities. J Dent Res 1978;57:3-10. 3. Sundqvist GK. Ecology of the root canal flora. J Endod 1992;18:427-30. 4. Baumgartner JC. Microbiologic and pathologic aspects of endodontics. Curr Opin Dent 1991;1:737-43. 5. Moller AJ, Fabricus L, Dahlen G, Heyden G. Influence on periradicular tissues of indigenous oral bacteria and necrotic pulp tissue in monkeys. Scand J Dent Res 1981;89:475-84. 6. Bystrom A, Sundqvist G. Bacteriologic evaluation of the effect of .5 percent sodium hypochlorite in endodontic therapy. Oral Surg Oral Med Oral Pathol 1983;55:307-12. 7. Bystrom A, Sundqvist G. The antibacterial action of sodium hypochlorite and EDTA in 60 cases of endodontic therapy. Int Endod J 1985;18:35-40. 8. Madison S, Wilcox LR. An evaluation of coronal microleakage in endodontically treated teeth. Part III. In vivo study. J Endod 1988;14:455-8. 9. Ray HA, Trope M. Peri-apical status of endodontically treated teeth in relation to the technical quality of the root filling and the coronal restoration. Int Endod J 1995;28:12-8. 10. Felton D, Bergenholtz G, Cox CF. Inhibition of bacterial growth under composite restorations following GLUMA pre-treatment. J Dent Res 1989;68:491-5. 11. Ben AA, Liberman R, Rothkoff Z, Cardash HS. Long term sealing properties of amalgam bond under amalgam restorations. Am J Dent 1994;7:141-3. 12. Wolcott JF, Hicks ML, Himel, VT. Evaluation of pigmented intraorifice barriers in endodontically treated teeth. J Endod 1999;25:589-92. 13. Elayouti A, Achleithner C, Lost C, Weiger R. Homogeneity and adaptation of a new gutta-percha paste to root canal walls. J Endod 2005;31:687-90. 14. Zielenski TM, Baumgartner JC, Marshall JG. An evaluation of guttaflow and guttapercha in the filling of lateral grooves and depressions. J Endod 2008;34:295-98. 15. Saunders WP, Saunders EM. Coronal leakage as a cause of failure in root canal therapy: a review. Endod Dent Traumatol 1994;10:105-8. 16. Ingle JI, Bakland LK. Endodontics. 5th ed. Hamilton, Ontario, London: 2002; Elsevier p. 599-615. 17. Timpawat S, Amornchat C, Trisuwan WR. Bacterial coronal leakage after obturation with three root canal sealers. J Endod 2001;27:36-9. 18. Chailertvanitkul P, Saunders WP, Mackenzie D. The effect of smear layer on microbial leakage of gutta-percha root fillings. Int Endod J 1996;29:242-8. 19. Clark-Holke D, Drake D, Walton R, Rivera E, Guthmiller JM. Bacterial penetration through canals of endodontically treated teeth in the presence or absence of the smear layer. J Dent 2003;31:275-81. 20. Koneman A, et al. Textbook of diagnostic microbiology. 5th ed. Philadelphia, PA: Lippincott Williams, Wilkins; 1997.
OOOOE Volume 111, Number 3 21. Sundqvist G. Ecology of the root canal flora. J Endod 1992; 18:427-30. 22. Charles HS, Scott AS, Thomas JB, Christopher BO. Enterococcus faecalis: its role in root canal treatment failure and current concepts in retreatment. J Endod 2006;32:93-8. 23. Shipper G, Orstavik D, Teixeira BF, Trope M. An evaluation of microbial leakage in roots filled with a thermoplastic synthetic polymer based root canal filling material (Resilon). J Endod 2004;30:342-47. 24. Taylor JK, Jeansonne BG, Lemon RR. Coronal leakage: effects of smear layer, obturation technique, sealer. J Endod 1997; 23:508-12. 25. Kouvas V, Liolios E, Vassiliadis L. Influence of smear layer on depth of penetration of three endodontic sealers: an SEM study. Endod Dent Traumatol 1998;14:191-5. 26. Leski M, Pawlicka H. A comparison of the penetration of three sealers into dentinal tubules: a SEM study. Int Endod J 2005;38:932. 27. Guttaflow. Instructions for use. Cuyahoga Falls (OH): Coltene/ Whaledent Inc.; 2006. 28. Hammad M, Qualtrough A, Silikas N. Extended shrinkage behaviour of endodontic sealers. J Endod 2008;34:90-3. 29. De Deus G, Brandao MC, Fidel RAS, Fidel SR. The sealing ability of Guttaflow in oval shaped canals; an ex vivo study using polymicrobial leakage model. Int Endod J 2007;40:794-99. 30. Brackett MG, Martin R, Sword J, Oxford C, Rueggeberg FA, Tay FR, et al. Comparison of seal after obturation techniques using a polydimethylsiloxane-based root canal sealer. J Endod 2006;32:1188-90. 31. Kontakiotis EG, Tzanetakis GN, Loizides AL. A L2-month longitudinal in vitro leakage study on a new silicon-based root canal filling material (Gutta-flow). Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2007;103:854-9. 32. Monticelli F, Sword J, Martin RL, Schuster GS, Weller RN, Ferrari M, et al. Sealing properties of two contemporary singlecone obturation systems. Int Endod J 2007;40:374-85.
Nawal et al. 393 33. Eldeniz AU, Orstavik D. Physical properties of newly developed root canal sealers. Int Endod J 2005;38:935. 34. Tunga U, Bodrumlu E. Assessment of the sealing ability of a new root canal obturation material. J Endod 2006;32:876-8. 35. Stratton RK, Apicella MJ, Mines P. A fluid filtration comparison of gutta-percha versus Resilon, a new soft resin endodontic obturation system. J Endod 2006;32:642-5. 36. Tay FR, Loushine RJ, Weller RN, Kimbrough WF, Pashley DH, Mak YF, 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. 37. Paqué F, Sirtes G. Apical sealing ability of Resilon/Epiphany versus gutta-percha/AH plus: immediate and 16-months leakage. Int Endod J 2007;40:722-9. 38. Roggendorf MJ, Ungvari S, Schoerner C, Ebert J, Petschelt A, Frankenberger R. Bacterial leakage in filled root canals using four root canal sealers. Int Endod J 2007;40:1005. 39. Taranu R, Wegerer U, Roggendorf MJ, Ebert J, Petschelt A, Frankenberger R. Leakage analysis of three modern root filling materials after 90 days of storage. Int Endod J 2005;38:928. 40. Bouillaguet S, Shaw L, Barthelemy J, Krejci I, Wataha JC. Long-term sealing ability of pulp canal sealer, AH-Plus, GuttaFlow and Epiphany. Int Endod J 2008;41:219-26. 41. Chailertvanitkul P, Saunders WP, Mackenzie D. Coronal leakage in teeth root filled with gutta-percha and two different sealers after long term storage. Endod Dent Traumatol 1997;13:82-7. 42. Lin JS, Haapasalo M. Quality of a new filling material GuttaFlowTM using a single gutta-percha cone cold flowable technique: a comparative in vitro study. J Endod 2008;34:369. Reprint requests: Ruchika Roongta Nawal, MDS Senior Lecturer Department of Conservative Dentistry and Endodontics Maulana Azad Institute of Dental Sciences New Delhi 110002, India [email protected]