A comparative evaluation of sealing ability of a new, self-etching, dual-curable sealer: Hybrid Root SEAL (MetaSEAL)

A comparative evaluation of sealing ability of a new, self-etching, dual-curable sealer: Hybrid Root SEAL (MetaSEAL)

A comparative evaluation of sealing ability of a new, selfetching, dual-curable sealer: Hybrid Root SEAL (MetaSEAL) Sema Belli, DDS, PhD, Erhan Ozcan,...

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A comparative evaluation of sealing ability of a new, selfetching, dual-curable sealer: Hybrid Root SEAL (MetaSEAL) Sema Belli, DDS, PhD, Erhan Ozcan, DDS, Oznur Derinbay, DDS, and Ayce Unverdi Eldeniz, DDS, PhD Konya, Turkey SELCUK UNIVERSITY

Objective. To assess the long-term sealing ability of a new dual-curable, self-etching, 4-META containing resin-based sealer: Hybrid Root SEAL (MetaSEAL in the United States) and compare with RealSeal and AH Plus sealers. Methodology. Root canals of 44 extracted and decoronated single-rooted human teeth were instrumented using a crown-down technique with ProFile 0.04 tapered NiTi rotary instruments to ISO size 30 and then to size 45 with Khand files. Four roots were selected and used as positive and negative controls (n ⫽ 2), the rest were randomly divided into 4 groups (n ⫽ 10) and filled using 0.04 tapered size 45 cones as follows: Group 1: AH Plus with guttapercha; Group 2: Hybrid Root SEAL (MetaSEAL) with gutta-percha; Group 3: Hybrid Root SEAL (MetaSEAL) with Resilon point; and Group 4: RealSeal with Resilon point. The quality of seal of each specimen was measured after 1, 4, 12, and 24 weeks using a fluid transport model. Measurements were made at 2-minute intervals for 8 minutes. The data were calculated as Lp and statistically analyzed using 2-way repeated measures of ANOVA and Bonferroni pairwise comparison tests (␣ ⫽ 0.05). Results. There were no significant differences among test materials in terms of fluid microleakage values (P ⫽ .126). There were statistically significant differences among the time periods (P ⫽ .009) and observed between 1- and 24week test periods. There was significant interaction between root canal filling materials and time of testing (P ⫽ .048). Conclusion. Within the limitations of this in vitro study, it was concluded that recently introduced Hybrid Root SEAL (MetaSEAL) showed similar sealing performance with RealSeal and AH Plus sealers when used either with gutta-percha or Resilon at 24 weeks. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008;106:e45-e52)

Complete and 3-dimensional impervious obturation of the root canal system is of prime clinical importance for the long-term success of endodontic treatment.1-3 Although a number of materials are used for obturation, the most common form of endodontic treatment uses the combination of gutta-percha cones and sealer.4 As gutta-percha does not bond to root canal walls, the use of sealers along with well-adapted gutta-percha has been recommended.5 To date, a great variety of endodontic materials are introduced to the dental community as a result of manufacturers’ attempts to develop new products having better physical properties than the commonly used materials. Resilon (Resilon Research LLC, Madison, CT) is the first bondable material that has the potential to challenge gutta-percha as a core.6,7 Its bonding ability is derived from the inclusion of resin with methacryloxy groups.8 When it is applied using a methacrylate-based sealer to self-etching primerSelcuk University, Faculty of Dentistry, Konya, Turkey. Received for publication Dec 13, 2007; returned for revision Jul 26, 2008; accepted for publication Jul 31, 2008. 1079-2104/$ - see front matter © 2008 All rights reserved. doi:10.1016/j.tripleo.2008.07.027

treated root dentin, it creates a secondary monoblock.9 Epiphany (Pentron Clinical Technologies, Wallingford, CT) and RealSeal (Sybron Endo, Orange, CA) sealers have similar chemical composition with different brand names and are designed for bonding simultaneously to intraradicular dentin and polycaprolactone-based Resilon.10 RealSeal exhibited rheological properties suitable for clinical use and defined as a dental resin composite material.11 Published literature about RealSeal is sparse and long-term evaluations are lacking. Hybrid Root SEAL (MetaSEAL) (Sun Medical, Tokyo, Japan; Parkell Inc., Farmingdale, NY) is a new dual-cure and self-etching resin cement, containing 4-methacryloyloxyethyl trimellitate anhydride (4-META) that can be used either with Resilon or gutta-percha according to the manufacturers. Four-methacryloyloxyethyl trimellitate anhydride is able to promote monomer diffusion into the acid-conditioned and underlying intact dentin and can produce functional hybridized dentin with the polymerization.12,13 The formation of hybridized dentin is the major mechanism of bonding14 and high-quality hybridized dentin resists acidic challenges.13 AH Plus sealer is known as an epoxy-resin– based sealer having excellent sealing properties15,16 and is e45

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considered as the gold standard against which all new sealers and bondable root canal obturation materials must be compared.17 Several investigations using different methodologies have been reported to test different properties of established resin-based sealers such as adhesion,18-21 adaptability,22 scanning electron microscope (SEM) or transmission electron microscope (TEM) interface evaluation studies,8 and leakage.23 The resistance to leakage is considered to be a basic property that needs to be evaluated for every new root canal filling material.24,25 It is also necessary to both assess long-term sealing ability of the sealers and short-term sealing as it may differ with time26 and different physical properties such as viscosity, flow, setting time, film thickness, and shrinkage of the sealers during setting leaving voids and gradual dissolution.27-30 To the authors’ knowledge, no research has been published yet about the short- and long-term sealing ability of Hybrid Root SEAL (MetaSEAL) sealer. Therefore the purposes of this in vitro study were to evaluate the following: 1. The sealing ability of Hybrid Root SEAL (MetaSEAL) in comparison with AH Plus and RealSeal/ Resilon system 2. To determine if Hybrid Root SEAL (MetaSEAL)/ Resilon combination is an effective method to reduce apical leakage 3. To evaluate if the leakage values change at different time intervals (1, 4, 12, and 24 weeks)

was enlarged with a 20 K-file. Working length was established by inserting the same file into the canal until it was just visible at the apical foramen and subtracting 1 mm from this length. The canals were then first instrumented using a crown-down technique with serially using ProFile 0.04 tapered nickel-titanium (NiTi) rotary instruments (Dentsply, Tulsa Dental, Tulsa, OK) 40/.04, 35/.04, 30/.04, 25/.04, 20/0.4, 25/.04, 30/.04 to apical size 30. Hand files with the size 35, 40, and 45 (Mani Inc., Tochigi-ken, Japan) were used at apical foramen to make more controlled enlargement. After instrumentation, the minor diameter was gauged to ensure that each foramen at working length was not greater than a size #45/.02 tapered file.31,32 If a #45/.02 file passed the working length, working length diameter was considered to be greater than an instrument size #45 and the root was not used. Root canals were irrigated with 3 mL of 5.25% NaOCl solution and 3 mL of 17% EDTA solution for smear layer removal and final rinse was done with 3 mL of distilled water. The canals were dried with paper points (Gapadent Co. Ltd., Xinkou Town, Tianjin, China). Four roots were selected for controls (negative and positive), kept unsealed, and the rest were randomly divided into 4 groups (n ⫽ 10). Tug back at working length was achieved with #45/0.04 taper cones; therefore, obturation of the roots was done using single cone technique with size #45/0.04 cones and one of the sealers given in Table I as follows: ●

The null hypothesis was that there are no differences in the leakage performance of Hybrid Root SEAL (MetaSEAL) versus RealSeal and AH Plus sealer when either used with Resilon or gutta-percha. MATERIALS AND METHODS Single-rooted permanent human teeth with straight root canals, extracted for periodontal reasons were radiographically examined to evaluate the root canal morphology and stored at ⫹4°C in a physiological saline solution. Teeth with caries, cracks, and immature apices were excluded from the study. Soft tissue remnants and calculus were removed. Forty-four roots were selected for this study and the crowns of the teeth were removed using a diamond disc under water cooling at the cement-enamel junction by leaving a root approximately 14 mm long. The canals were classified as being round or oval shaped according to the radiographs and root canal orifices. Each group was equally composed of 90% round and 10% relatively oval-shaped canals. The patency of the root canals was verified with #10 K-file (Dentsply Maillefer, Tulsa, OK) and to standardize the leakage, the apical foramen area of each root





Group 1: Size #45/0.04 taper gutta-percha master cone was fitted to the working length with tug-back. An epoxy resin based sealer AH Plus was then placed into the root canal with the master cone. The excess material was cleaned with a heated instrument (Den Touch, Kfar-Saga, Israel) and cotton pellets. Group 2: Three drops of Hybrid Root SEAL (MetaSEAL) liquid and 1 cup of Hybrid Root SEAL (MetaSEAL) powder were mixed on a mixing pad. Size #45/0.04 taper gutta-percha points (Dentsply) were coated with the sealer and introduced into the sealer filled root canals. The excess material was removed and light-cured for 40 seconds. Excess guttapercha was then removed using the same device as in group 1. Group 3: Three drops of Hybrid Root SEAL (MetaSEAL) liquid and 1 cup of Hybrid Root SEAL (MetaSEAL) powder were mixed on a mixing pad and sealer mixture was applied to the canal with a lentulo spiral filler. A size #45/0.04 taper Resilon point was coated with the sealer and introduced into the root canal. The excess material was removed from the coronal surface and light-cured for 40 seconds.

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Table I. Resin-based root canal sealers evaluated in this study Sealer AH Plus

Hybrid Root SEAL (MetaSEAL)

RealSeal



Ingredients

Manufacturer

Paste A: Bisphenol-A epoxy resin, Bisphenol-F epoxy resin, Calcium tungstate, Zirconium oxide, Silica, Iron oxide pigments, Aerosil Paste B: N-Dibenziyl-5-oxanonane, TCD-Diamine, Aminoadamantane, Tricylodecane-diamine, Calcium tungstate, aerosil Zirconium oxide, Silica, Silicone oil. Liquid: 4-META, monofunctionalmethacrylate monomer, multifunctional macrylate monomers and photo-initiators; Powder: mixture of Zirconium oxide filler, SiO2 filler, and polymerization initiators. Mixture of PEGDMA, EBPADMA, EDMA, and BisGMA resins; silane-treated barium borosilicate glasses; barium sulphate; silica; calcium hydroxide; bismuth oxychloride with amines; peroxide; photo initator; stabilizers; and pigment.

De Trey / Dentsply, Konstanz, Germany

0602002055

Sun Medical, Tokyo, Japan; Parkell Inc., Farmingdale, NY

Powder: 060309 Liquid: 051004

SybronEndo, Orange, CA

103856

Group 4: RealSeal primer was introduced into the canal and excessive primer was removed with paper points. RealSeal sealer was applied to the canal with a lentulo spiral filler (Dentsply, Maillefer). A size #45/0.04 taper Resilon point was fitted to the working length with tug-back and RealSeal sealer was placed into the root canal with the master cone and excess gutta-percha was removed as in group 1. Then the roots were light-cured from the coronal side for 40 seconds using a halogen light-curing unit (Lunar, Benlioglu Dental, I˙stanbul, Turkey) at an intensity of 620 mW/cm2.

Coronal parts of all the roots were sealed with temporary filling material Cavit G (3M ESPE, Seefeld, Germany) and the specimens were then stored at 37°C and 100% humidity for 1 week. EVALUATION OF APICAL LEAKAGE A fluid filtration study design previously reported by Pashley and Depew33 was used to evaluate the leakage. Temporary filling materials were removed. Apical end of the roots were inserted 3 mm into a silicone tubing having an internal diameter of 3 mm and attached to the outer surface of the tube with a cyanoacrylate adhesive. The tube was then connected to a fluid filtration apparatus as described by Derkson et al.34 and modified by Wu et al.35 for endodontic studies. A polyethylene tubing (Fisher Scientific, Pittsburgh, PA) was used to connect the pressure reservoir to a 25-␮L micropipette (Microcaps, Fisher Scientific, Philadelphia, PA). Additional tubing connected the micropipette to a microsyringe (Gilmont Instruments Inc, Great Lakes, NY) and the silicone tube with the attached root. An air bubble was introduced into the system using the microsyringe and advanced into the micropipette. All tubing, pipette, and syringe were filled with distilled water under a pressure of 202 kPa via the use of O2 gas. The sealing

Batch

qualities of the samples were quantitated by following the progress of this tiny air bubble traveling within the micropipette. “System leakage” was considered as “5 minutes” for each sample depending on 2 samples that were prepared as “negative control,” which do not leak. A small cavity was prepared on the apical end of these nonprepared and unfilled roots and the cavities were filled with SuperBond C&B (Sun Medical, Shiga, Japan) using a brush and powder-liquid technique. Apical parts were then covered with 2 layers of nail varnish. The fluid flow rate through the 2 unsealed root specimens was measured by weighing the amount of water that could flow through the needle in 1 minute. This value served both as a positive control and as 100% leakage, to which the sealed values could be expressed (as a percentage). Measurements of fluid movement were recorded at 2-minute intervals for 8 minutes and averaged. The quality of seal of each specimen was measured at 1, 4, 12, and 24 weeks. The access cavities were covered with temporary filling material after each measurement and 0.02% sodium azide was added to the storage solution to prevent bacterial colonization. The samples were kept in 100% humid conditions at 37°C throughout the experimental period. A 2-way repeated-measures analysis of variance (ANOVA) was used with time as the repetition factor to evaluate the data for significant differences. As 2-way repeated-measures ANOVA was taking averages of all apical leakage values obtained at different time periods, 1-way repeated measures ANOVA was also done to evaluate the differences in materials’ leakage with time. Multiple comparisons were done using Bonferroni pairwise comparison test at a significance level set at ␣ ⫽ 0.05. To evaluate the significant differences in leakage of different materials at different measurement periods 1-way ANOVA and Tukey HSD tests were done.

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Table II. Apical leakage values expressed in Lp (␮L/min⫺1 cm⫺2 cm H2O⫺1) for all test groups at 1, 4, 12, and 24 weeks Material period

AH Plus

Hybrid Root SEAL (MetaSEAL)-GP

Hybrid RootSEAL (MetaSEAL)-R

RealSeal

1 week 4 weeks 12 weeks 24 weeks

7.3 ⫻ 10⫺4 ⫾ 0.73 ⫻ 10⫺4 5.46 ⫻ 10⫺4 ⫾ 1.86 ⫻ 10⫺4 5.36 ⫻ 10⫺4 ⫾ 1.31 ⫻ 10⫺4 5.84 ⫻ 10⫺4 ⫾ 1.47 ⫻ 10⫺4

5.78 ⫻ 10⫺4 ⫾ 1.20 ⫻ 10⫺4 5.78 ⫻ 10⫺4 ⫾ 1.42 ⫻ 10⫺4 5.82 ⫻ 10⫺4 ⫾ 1.92 ⫻ 10⫺4 5.79 ⫻ 10⫺4 ⫾ 1.79 ⫻ 10⫺4

6.00 ⫻ 10⫺4 ⫾ 1.16 ⫻ 10⫺4 7.00 ⫻ 10⫺4 ⫾ 1.71 ⫻ 10⫺4 5.99 ⫻ 10⫺4 ⫾ 1.19 ⫻ 10⫺4 4.41 ⫻ 10⫺4 ⫾ 1.55 ⫻ 10⫺4

7.11 ⫻ 10⫺4 ⫾ 1.37 ⫻ 10⫺4 6.88 ⫻ 10⫺4 ⫾ 1.03 ⫻ 10⫺4 6.18 ⫻ 10⫺4 ⫾ 1.53 ⫻ 10⫺4 5.71 ⫻ 10⫺4 ⫾ 2.07 ⫻ 10⫺4

Values are means ⫾ SD (n ⫽ 10). GP, Gutta-percha; R, Resilon.

RESULTS The positive controls had grossly leaked as expected. The varnish-coated negative controls had no measurable bubble movement at all time periods. The means and standard deviations of the leakage values of the tested materials are shown in Table II. The 2-way repeated-measures ANOVA indicated that there were no significant differences among test materials in terms of fluid microleakage values (P ⫽ .126). There were statistically significant differences among the time periods since the P value is .009. To investigate which time periods were different in terms of mean leakage values, Bonferroni pairwise comparison tests were performed and statistically significant differences were observed in the 1-week and 24-week test periods (P ⫽ .005). There was significant interaction between root canal filling materials and test periods (P ⫽ .048). A graph showing mean apical leakage values of the all root canal filling materials at different time periods are given in Fig. 1 to show this interaction. Results of 1-way repeated measures ANOVA and Bonferroni pairwise comparison tests showed that leakage of the AH Plus group (Group 1) decreased significantly between 1- and 12-week time periods (P ⫽ .025). Leakage of the groups sealed with Hybrid Root SEAL (MetaSEAL)/Gutta Percha (Group 2) and RealSeal/Resilon (Group 4) did not change from the 1st to 24th weeks (P ⫽ 1 and P ⫽ .179 respectively). When Hybrid Root SEAL (MetaSEAL) was used with Resilon (Group 3), leakage significantly decreased between the 4th and 24th week measurement periods (P ⫽ .005). Results of 1-way ANOVA and Tukey HSD tests showed that at the first week, AH Plus group showed significantly more leakage than Hybrid Root SEAL (MetaSEAL)/Gutta Percha group (Group 2) (P ⫽ .025). No significant difference was obtained among materials for any other time period (P ⬎ .05). DISCUSSION To assess the sealing ability of root fillings, several in vitro methods have been designed and used in previous several investigations including dye penetration,

Fig. 1. Mean apical leakage values for all test groups at 4 time periods.

spectrometry of radioisotopes, fluorometric and electrochemical methods, gas chromatography, bacterial penetration, and fluid transport system.36-42 Fluid filtration method, in which the sealing capacity is measured by means of air bubble movement inside a capillary tube, was developed by Pashley’s group in 1986 to evaluate dentin permeability. The method was then modified by Wu et al.33 for endodontic leakage studies. Fluid transport takes into account all of the porosities of the interfaces between the filling material and tooth structure. This nondestructive technique allows repeated reproducible measurements of the same specimen for long-term evaluations.43,44 Despite it’s limitation in not providing information about the interface location of the leakage, it is still the most widely used and accepted leakage evaluation method.16,26,45-47 Thus, in the present study, a fluid transport model was used to evaluate leakage. To achieve maximum apical sealing and to allow satisfactory irrigation, a root canal preparation with taper is necessary.48 This preparation can easily be achieved with NiTi rotary systems having various tapered files. After NiTi rotary preparation of the canals, it is possible to fill tapered canals effectively with the

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combination of an appropriate gutta-percha cone with the same taper. Many dental companies introduced matching taper points that correspond to canal shapes created by similar tapered instruments. If a round shape is obtained during the canal preparation, an adequate obturation can be obtained with this technique49 over the whole length of the canal faster than the lateral condensation technique.50,51 Single-cone technique was used in this study during the obturation of the test groups either using a 0.04 tapered gutta-percha or Resilon point. Other condensation groups were not included because it was not the purpose of this study to compare the single-cone technique with other techniques. Wu et al.52 reported that in single-cone filled roots, more than half of the canal space is filled with sealer. After setting, most root canal sealers have weak matrices, and when they are subjected to oral fluids, sealer may have dissolved by that time; the singlecone fillings may contain wider voids than lateral or vertical compaction techniques.53 Furthermore, the sealer could be carried to the tooth with at most a couple of up and down strokes and this may increase sealer extrusion from the apical end when singlecone technique is used.53 In the current study, the master cone was coated with the sealer, placed into the canal 1 mm short of the apical foramen, and rotated slowly to deliver sealer everywhere in the canal. No extrusion of sealer was observed during the obturation procedure. All of the tested groups showed similar leakage values at the end of 24 weeks. When the voids or gaps were evaluated with the similar tested materials and single-cone technique, no significant difference was found among the groups and decreasing the sealer thickness with Resilon or gutta-percha could not prevent gap formation in Hybrid Root SEAL (MetaSEAL) (10%) and Epiphany groups (20%).54 However, in both studies, teeth with straight roots and canals were used and whether a good seal can be achieved with this technique in curved root canals is unknown and remains to be studied. Furthermore, human teeth were used to more closely simulate the clinical situation. To help reduce variability, multiple radiographs were taken from different directions to find similar root canal shapes. The roots having round-shape canal orifices were selected for this purpose and classified as being round or oval shaped according to the radiographs and root canal orifices. Each group was equally composed of 90% round and 10% relatively oval-shaped canals. Long-term sealing ability of the first epoxy-resin– based root canal sealer has been previously studied by Wu et al.55 and AH 26 demonstrated a reduction in

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leakage after storage in high humidity at 37°C for 1 year. Subsequently developed AH Plus sealer showed diminished leakage at 1 week to 12 weeks in the present study, although this decrease was not significant at 24 weeks. This result can either be attributed to the volumetric increase of gutta-percha by water absorption25,55 or to the continuous expansion of AH Plus sealer with time.30 AH Plus sealer group provided comparable sealing values to Hybrid Root SEAL (MetaSEAL) and RealSeal groups from the 4-week measurement period and this could be due to the initial setting contraction and late expansion of AH Plus sealer that starts after 4 weeks of its setting.30 The result of the present study confirmed the findings of previous researchers in that the quality of apical seal achieved with Resilon core material and Epiphany (RealSeal) sealer is not superior to gutta-percha and AH Plus sealer.8,23 However, these findings are in contrast with the results reported by Stratton et al.46 and Tunga and Bodrumlu.56 Discrepancies between these studies could be because of differences in the methodology and measurement periods. Conventional or multistep adhesive systems may not fully infiltrate the demineralized dentin; furthermore, most of them require light-polymerization, which is not practical for endodontic sealing. In self-etching systems, demineralization of the dentin and infiltration of monomers may simultaneously occur. RealSeal and Hybrid Root SEAL (MetaSEAL) are self-etching sealers having dual-curable characteristics. Although it is believed that this dual-curable character gives a further advantage, when the results were evaluated, both sealers showed similar leakage values as epoxy-resin– based AH Plus sealer. This result can be explained by polymerization shrinkage of these methacrylate-based sealers57 following the increased sealer thickness as a result of single cone technique58 and/or by the high c-factor inside the root canals, which was previously reported by Morris et al.59 and Tay et al.10 Immediate light-curing from the coronal side of the roots may also create a large polymerization stress during setting by preventing flow of resin-based sealers and may lead to de-bonding of the resin from the root canal walls, which results in gap formation.10 The use of immediate light curing from the coronal side used in this study was done according to the recommendations of the manufacturers. The results might be different if the sealers were left to set without any light curing. Incomplete removal of the smear layer in isolated areas of the root canal is reported to prevent adhesive penetration into the dentinal tubules.60 Structural deficiencies originated from the air entrapped in the sealer mass during mixing or transferring the sealer61 may also delay the setting reaction and weaken the resin sealer and result in

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de-bonding between the resin cement and the root dentin providing an avenue for leakage.62 Onay et al.63 tested the apical sealing ability of Epiphany-Resilon using fluid filtration method and compared this root canal filling system with different pairings of AH Plus, gutta-percha, Epiphany, and Resilon. The results indicated that Epiphany– gutta-percha combination showed less leakage than the other test groups including AH Plus–Resilon combination and gutta-percha helped to reduce leakage when used with either Epiphany or AH Plus. In the present study, different pairs were not retested: RealSeal was used with Resilon and AH Plus was used with gutta-percha for clinical relevancy. However, the manufacturer of Hybrid Root SEAL (MetaSEAL) sealer proposed that this sealer can bond to both gutta-percha and Resilon point. Therefore, Hybrid Root SEAL (MetaSEAL) was tested with either gutta-percha or Resilon and similar leakage values were recorded and statistically no difference was found between the 2 groups. This confirmed the findings of Williams et al.64 who reported that Resilon and gutta-percha both demonstrate physical properties of elastomeric polymers and no significant difference was found between them clinically when mechanical properties of the 2 polymers were evaluated. On the other hand, some researchers demonstrated that Resilon had susceptibility to alkaline and enzymatic degradation and significant weight loss and surface thinning when compared with gutta-percha.65,66 This phenomenon may have an influence on the fluid penetration in the long term and may need further evaluation.67 CONCLUSION In the light of our findings, we must accept the null hypothesis that recently produced Hybrid Root SEAL (MetaSEAL) showed similar leakage performance with RealSeal and AH Plus sealers either with Resilon or gutta-percha at the end of 24 weeks. However, sealing is not the only required property for a root canal sealer and new sealers require further investigation into other properties essential for successful root canal treatment. This study was supported in part by Scientific Research Projects Coordination Center (BAP) of Selcuk University, Konya, Turkey, and the leakage test was done in Selcuk University, Faculty of Dentistry Research Laboratory. The authors would like to thank Sun Medical and SybronEndo companies for their generous material support to this work. They are also grateful to Professor Said Bodur and Assistant Professor Cos¸kun Kus¸ for their assistance in the statistics.

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Reprint requests: Sema Belli, DDS, PhD Selcuk University Faculty of Dentistry Endodontics Campus 42079 Konya Turkey [email protected]