Basic Research—Technology

Comparison of Push-out Bond Strengths of Resilon withThree Different SealersDanielle Stiegemeier, DDS,* J. Craig Baumgartner, DDS, PhD,* and Jack Ferracane, PhD†

Abstract

Introduction: The purpose of this study was to evaluatethe push-out bond strengths of different obturatingmaterials. Methods: Forty single-rooted human ex-tracted teeth were used in this study. The teeth were in-strumented and irrigated by using 5.25% NaOCl, 15%ethylenediaminetetraacetic acid, and sterile water. Theteeth were then filled with Resilon/RealSeal, Resilon/RealSeal SE, Resilon/MetaSeal , or gutta-percha/KerrEWT sealer. The roots were then sectioned into 1-mm-thick slices and subjected to vertical loading to displacethe obturating material toward the coronal side of theslice. The bond strength was then calculated and sub-jected to statistical analysis. Slices were examined byusing a stereomicroscope at 30� to determine themode of failure. Results: The mean push-out bondstrengths were as follows: Resilon/RealSeal, 1.45 �0.99 MPa; RealSeal SE, 0.88� 0.49 MPa; Resilon/Meta-Seal, 2.41 � 1.7 MPa; and gutta-percha/Kerr EWTsealer, 2.32 � 0.74 MPa. Conclusions: The push-outbond strengths of Resilon/MetaSeal and gutta-percha/Kerr EWT were significantly (P < .05) higher than eitherResilon/RealSeal or Resilon/RealSeal SE. Resilon/Meta-Seal and gutta-percha/Kerr EWT did not differ signifi-cantly. (J Endod 2010;36:318–321)

Key WordsBond strength, MetaSeal, push-out test, RealSeal

From the *Department of Endodontology and †Departmentof Biomaterials and Biomechanics, Oregon Health and ScienceUniversity, Portland Oregon.

Dr Stiegemeier is currently in practice in Beachwood, OH.Address requests for reprints to Dr J. Craig Baumgartner,

Department of Endodontology, Oregon Health Sciences Univer-sity School of Dentistry, 611 SW Campus Dr, Room 130B, Port-land, OR 97201. E-mail address: baumgarc@ohsu.edu.0099-2399/$0 - see front matter

Copyright ª 2010 American Association of Endodontists.doi:10.1016/j.joen.2009.10.026

318 Stiegemeier et al.

The main objectives of root canal therapy are to thoroughly clean and shape the rootcanal system and to fully obturate the canal system in 3 dimensions, thus sealing off

the root canal from the periapical tissues (1). Gutta-percha has been the traditionalendodontic obturating material, used in combination with zinc oxide–eugenol, calciumhydroxide, or epoxy resin. In recent years obturating materials and sealers have beendeveloped on the basis of dentin adhesion technologies borrowed from restorativedentistry in an attempt to seal the root canal more effectively (2).

Recent research into bonding of root filling materials to dentin has shown thatdentin adhesives significantly reduce apical leakage (3–6) and increase fracture resis-tance of root-filled teeth (7, 8). Because epoxy resin sealers do not copolymerize withmethacrylate resin–based adhesives, a methacrylate resin sealer was developed witha self-etching primer that resulted in improvements of apical seal (9) and adhesionto root dentin (10).

Resilon (Resilon Research LLC, Madison, CT) is advertised as an alternative togutta-percha. Resilon is a thermoplastic synthetic polymer-based (polyester) root canalcore material that contains bioactive glass, bismuth oxychloride, and barium sulfate.The RealSeal sealer is a dual-curing, resin-based composite sealer. The resin matrixis composed of bisphenol A glycidyl methacrylate (BisGMA), ethoxylated BisGMA,urethane dimethacrylate (UDMA), and hydrophilic difunctional methacrylate. Thesealer with the aid of a primer adheres to the core material and dentin (11).

An addition to the Resilon system is a new sealer, RealSeal SE (SybronEndo,Orange, CA), that eliminates the primer from the series. This sealer is applied in themanner of traditional sealers and is used to bond dentin to Resilon.

Another sealer has been introduced with claims that it bonds both Resilon andgutta-percha as well as dentin. MetaSeal (Parkell Inc, Farmington, NY) is a 4-methacry-loyloxyethyl trimellitate anhydride (4-META) containing polymethylmethacrylate-based(PMMA) endodontic sealer. It is dual-cured and self-adhesive, thereby eliminating thepriming step. The manufacturer claims that MetaSeal bonds to gutta-percha by creatinga hybrid layer similar to that produced with dentin.

Only 2 studies to date have looked at the bond strength of MetaSeal, and 1 haslooked at RealSeal SE; thus the purpose of this study was to compare the push-outbond strength of Resilon/RealSeal, Resilon/RealSeal SE, Resilon/MetaSeal, and gutta-percha/Kerr EWT.

Materials and MethodsThe Institutional Review Board at Oregon Health & Science University approved

this study. Forty single-rooted extracted human teeth were used for this study. Eachtooth was radiographed buccolingually and mesiodistally to verify presence of a singlecanal. Before use each tooth was placed in NaOCl for 2 hours for surface disinfectionand periodontal ligament removal followed by storage in distilled water until use. Eachtooth was inspected under an operating microscope for presence of any cracks. Anaccess preparation was made with a high speed #4 round bur, pulp tissue was removedwith a barbed broach, and apical patency was confirmed with a #10 K-file. To providea definite apical stop, the working length (WL) was established by subtracting 1 mmfrom where the file was just visible at the foramen.

Each canal was instrumented by using a high torque DTC motor (Tulsa Dental,Tulsa, OK) at 300 rpm with 0.04 Profile Series 29 nickel-titanium rotary files. The fileswere used in a crown-down manner to WL and enlarged to a #7 Series 29 0.04 file.

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TABLE 1. Mean Bond Strength (MPa), SD, and Number of Samples per Group

GroupMean bond

strength (MPa) SD (MPa) N

Real Seal 1.447 � 0.99 10Real Seal SE 0.8782 � 0.49 10MetaSeal 2.411 � 1.74 10Gutta-percha/Kerr EWT 2.321 � 0.74 10

Basic Research—Technology

NaOCl (5.25%) was used as the irrigant between files for a total of 5 mL.The canals were then irrigated with 5 mL of 15% ethylenediaminetetra-acetic acid, 5 mL 5.25% NaOCl, and a final irrigation of 5 mL sterilesaline. A standardized method of irrigation was performed on all teethby using a 27-gauge Monoject endodontic needle (Sherwood Medical,St Louis, MO), with the needle placed as far into the canal as possiblewithout binding. The canals were dried with paper points, and the teethwere divided into 4 groups, with even distribution of tooth type in eachgroup: Resilon/RealSeal group, obturated with Resilon/RealSeal primerand sealer; Resilon/RealSeal SE group, obturated with Resilon/RealSealSelf Etch sealer; Resilon/MetaSeal group, obturated with Resilon/Meta-Seal; and gutta-percha/Kerr EWT group, obturated with gutta-percha/Kerr EWT pulp canal sealer.

In Resilon/RealSeal group (n = 10), continuous wave of conden-sation with Resilon/RealSeal Sealer was used according to manufac-turer’s instructions. After instrumentation, a size 40 Resilon mastercone was fit with tug-back to within 1 mm of WL. RealSeal self-etchingprimer was introduced into the canal by insertion of a saturated paperpoint and left in the canal for 30 seconds. Excess primer, if any, wasremoved with a dry paper point. The sealer was then expressed by usingthe auto-mix syringe tip. The master cone was coated with sealer, placedinto the canal, and pumped up and down to ensure coating of walls withsealer. Down-pack was completed with the System B unit (Analytic, Red-mond, WA) set at 160�C, with the .06 FM tip to within 4 mm of WL. Back-filling was done with the Obtura II (Obtura Spartan, Fenton, MO) set at150�C. The Resilon was placed in small increments and condensed withBuchanan pluggers (Sybron Endo, Orange, CA) until the cementoena-mel junction (CEJ) was reached.

In Resilon/RealSeal SE sealer group (n = 10), continuous wave ofcondensation with Resilon/RealSeal SE sealer was used. Obturation forthis group was identical to Resilon/RealSeal group; however, with thenew sealer there is no primer.

In Resilon/MetaSeal group (n = 10), a size 40 Resilon cone was fitto within 1 mm of WL with tug-back. MetaSeal was mixed according tomanufacturer’s instructions. The master cone was then coated with thesealer and placed into the canal. The gutta-percha cone was seared offwith System B just below CEJ.

In gutta-percha/Kerr EWT group (n = 10), continuous wave ofcondensation with gutta-percha/Kerr EWT sealer was used. After instru-mentation of the canal, a size 40 gutta-percha cone was fit with tug-backto within 1 mm of WL. Kerr EWT pulp canal sealer was mixed to manu-facturer’s instructions. The master cone was coated with sealer, insertedinto the canal, and pumped up and down. Down-pack and backfillingwere the same as for Resilon/RealSeal group except that the heat was setat 200�C for both System B and Obtura.

All access cavities were sealed with Cavit. The teeth were stored at37�C with 100% humidity for 1 week to allow sealers to fully set.

TABLE 2. Modes of Failure

Failuremode

RealSeal

RealSeal SE MetaSeal

Gutta-percha/Kerr EWT

Type 1,adhesive

49 45 2 50

Type 2,cohesive

0 0 20 0

Type 3,mixed

1 5 28 0

Totalsamples

50 50 50 50

Push-out Bond TestThe teeth were sectioned perpendicular to the long axis into

1-mm-thick disks by using an Isomet saw (Buehler Ltd, Lake Bluff,IL) under water lubrication. This yielded 5 samples from each tooth,giving a total of 50 samples for each group. If the sample consistedof noncircular shape filling material, they were discarded because ofthe fact that there would be nonuniform stress distributions duringtesting, and the stress value calculations would be inaccurate becausethey are based on circular cavities. The exact thickness of each diskwas measured with a digital caliper to within 0.1 mm. The sampleswere placed on top of a metallic jig with a hole to allow the filling mate-rial to fall through after failure of the bond. Three different-sizedplungers were used to closely match the size of the filling material.

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The plungers were connected to the load cell of a universal testingmachine (Instron Corp, Norwood, MA). A vertical load was appliedin an apical to coronal direction at a rate of 1.0 mm/min on the rootcanal filling. Failure was determined when the graph showed a reductionin load. The bond strength at failure was then calculated and expressedin MPa by dividing the load in newtons by the area of the bonded inter-face. The area of the bonded interface was calculated with the formulaArea = 2pr� h, where p = 3.14 and r and h are the measured radiusand height, respectively, in millimeters of the filling material pushed out.

After measurement of bond strength, both sides of the failed bondwere evaluated with 30� magnification to determine the mode offailure. Each sample was evaluated and placed into 1 of 3 failure modes:type 1, adhesive failure at sealer/dentin interface; type 2, cohesive failureat sealer to Resilon/gutta-percha interface; or type 3, mixed cohesiveand adhesive failure. The data were subjected to one-way analysis ofvariance and the post hoc Tukey test, with significance set at a = 0.05.

ResultsThe mean push-out bond strengths were as follows: Resilon/Real-

Seal group, 1.45� 0.99 MPa; Resilon/RealSeal SE group, 0.89� 0.49MPa; Resilon/MetaSeal group, 2.41� 1.7 MPa; and gutta-percha/KerrEWT group, 2.32 � 0.74 MPa (Table 1). Resilon/MetaSeal group andgutta-percha/Kerr EWT group both showed significantly higher bondstrength than either Resilon/RealSeal group or Resilon/RealSeal SEgroup. There was no difference in bond strength when comparing Re-silon/MetaSeal group with gutta-percha/Kerr EWT group.

Modes of failure are listed in Table 2. Microscopic examinationrevealed adhesive failure as the most common mode in all groupsexcept Resilon/MetaSeal group, in which failures were more cohesiveor mixed.

DiscussionThe results of this study showed that gutta-percha/Kerr EWT and

MetaSeal/Resilon have significantly higher bond strengths to root canaldentin than Resilon/RealSeal or Resilon/RealSeal SE. There was nodifference; however, in the bond strengths of Resilon/MetaSeal ascompared with gutta-percha/Kerr EWT. The results are in disagreementwith Lawson et al (12), who showed significantly higher push-out bondstrength of MetaSeal/gutta-percha compared with gutta-percha/AH

Push-out Bond Strengths of Different Obturating Materials 319

Basic Research—Technology

Plus. In this study we used Resilon/MetaSeal instead of gutta-percha.MetaSeal might have a stronger bond with Resilon than with gutta-per-cha, which increased the bond strength to a level comparable withgutta-percha/Kerr EWT. Because we used Kerr EWT versus AH Plus,it is possible that this produced the difference in results, althoughbecause Kerr EWT does not have any bonding properties to dentin,one would think it would have a lower bond strength than a sealerwith adhesive characteristics. Lawson et al also used different obturat-ing methods to include single cone technique for both groups as wellas warm vertical for both groups. To follow manufacturer’s recom-mendations, we used warm vertical compaction for all groups exceptfor MetaSeal.

A recent study conducted by Babb et al (13) compared the bondstrength of MetaSeal with the bond strength of EndoRez and RealSeal SE.They found that MetaSeal had higher push-out bond strength than Real-Seal SE or EndoRez. The authors did not use any core obturating mate-rial and explained their rationale by stating that a compressive load overa thermoplastic material can lead to erroneous results. Our study is inagreement with their findings that MetaSeal has higher bond strengthcompared with RealSeal SE, even with a core material.

ProRoot Endo Sealer is a recently developed calcium silicate–based root canal sealer. Huffman et al (14) found that ProRoot Sealerhad higher push-out bond strengths than either AH Plus or Pulp CanalSealer. That study did not include core obturating material, and theeffect of the bulk of sealer used might have affected the bond strengthresults. When using either gutta-percha or Resilon, the amount of sealeris thinned out, and this could reduce the bond strength.

Our study is in agreement with a number of other studiescomparing Resilon/Epiphany with gutta-percha and a variety of sealers.For the most part, these studies have shown gutta-percha/AH Plus tohave significantly greater push-out bond strength than Resilon/Epiphany (15–18). Skidmore et al (19) compared gutta-percha/KerrEWT and Resilon/Epiphany and found Resilon/Epiphany to have signif-icantly higher bond strength than gutta-percha/Kerr EWT. Theirprotocol was similar to the current study except the sealer was allowedto set for only 24 hours, whereas we let the sealer set for 1 week. Allow-ing the sealer to set for 24 hours might have provided for a higher bondstrength than allowing it to set for 1 week, because it has been shownthat Resilon and its sealer have the propensity to degrade over time(20, 21).

Another difference in the various studies is their use of differentobturating methods with different materials (22). The manufacturerof MetaSeal (Parkell) recommends using a single cone techniquewith their material because they state that heat will cause the sealer toset up too quickly and cause polymerization shrinkage. We used a singlecone technique for the MetaSeal group but a warm vertical technique forthe other 3 groups.

The MetaSeal group had a very high standard deviation (SD)compared with the other 3 groups. This high SD might be attributedto the appearance of voids in the sealer that could be seen on sectioningthe tooth into the 1.0-mm-thick slices. Numerous voids were seen in thesealer around the core material, and this might have reduced the bondstrength in these particular slices, whereas when there were no voids,the bond strength was increased. An attempt was made when placingthe sealer and master cone to avoid producing voids in the sealer byensuring that the master cone was well-coated with sealer and seatedslowly into the canal, thus avoiding the entrapment of air. This isa concern in clinical practice, because these voids might provide a reser-voir for fluid or persistent bacteria and thus compromise the obturationand bacteriometric seal. It was noted through this push-out bond testthat MetaSeal did appear to bond to the dentin. Most of the failuresoccurred when the core material was pushed out, but the MetaSeal

320 Stiegemeier et al.

was still intact on the dental walls. In the other 3 groups, the failureswere mostly of an adhesive nature such that the bond between the dentinand sealer was broken. This bonding of MetaSeal to root canal dentinseems to be a desirable attribute. More research is needed to furtherunderstand the properties of MetaSeal. A recent study by De-Deuset al (23) found that AH Plus/gutta-percha had significantly higherpush-out strength than both Resilon/Epiphany and Resilon/EpiphanySE.

Creating an effective bond in the root canal is very challenging. Areview article by Schwartz (2) pointed out the difficulties associatedwith dentin bonding in the root canal space. These challenges includepolymerization shrinkage, C-factor (ratio of the bonded/nonbondedsurface area) of the root canal space, lack of evaporation of the alcoholcarrier for the sealer in the apical one third of the root canal, an oxida-tive layer left by irrigating solutions on the dentin, and calciumhydroxide remnant neutralization of the acid primer, thus reducingthe bond strength. A study by De-Deus et al (24) found that pretreatmentof dentin with 1-hydroxyethylidene-1-bisphosphonate (HEPB) opti-mized the bond quality compared with ethylenediaminetetraaceticacid or Biopure MTAD (Dentsply/Tulsa, Tulsa, OK). The lowest bondstrengths were with those treated with NaOCl (24).

ConclusionsBoth MetaSeal and gutta-percha/Kerr EWT had statistically higher

push-out bond strengths than either RealSeal group. However, the ques-tion of whether true dentin bonding occurs with these cements needs tobe addressed.

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723–44.2. Schwartz R. Adhesive density and endodontics: part 2—bonding in the root canal

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13. Babb BR, Loushine RJ, Bryan Ames JM, et al. Bonding of self-adhesive (Self-etching)root canal sealers to radicular dentin. J Endod 2009;35:578–82.

14. Huffman BP, Mai S, Pinna L, et al. Dislocation resistance of ProRoot endosealer, a calcium silicate-based root canal sealer, from radicular dentine. IntEndod J 2009;42:34–46.

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Basic Research—Technology

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obturation system (Resilon/Epiphany). J Endod 2007;33:160–2.18. Ureyen Kaya B, Kececi AD, Orhan H, Belli S. Micropush-out bond strengths of gutta-

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20. Tay FR, Pashley DH, Williams MC, et al. Susceptibility of a polycaprolactone-basedroot canal filling material to degradation: I—alkaline hydrolysis. J Endod 2005;31:593–8.

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21. Tay FR, Pashley DH, Yiu CKY, et al. Susceptibility of a polycaprolactone-based rootcanal filling material to degradation: II—gravimetric evaluation of enzymatic hydro-lysis. J Endod 2005;31:737–41.

22. Ungor M, Onay EO, Orucoglu H. Push-out bond strengths: the Epiphany-Resilonendodontic obturation system compared with different pairings of Epiphany, Re-silon, AH Plus, and gutta-percha. Int Endod J 2006;39:643–7.

23. De-Deus G, Di Giorgi K, Fidel S, Fidel RA, Paciornik S. Push-out bond strength ofResilon/Epiphany and Resilon/Epiphany self-etch to root dentin. J Endod 2009;35:1048–50.

24. De-Deus G, Namen F, Galan J, Zehnder M. Soft chelating irrigation protocol opti-mizes bondint quality of Resilon/Epiphany root fillings. J Endod 2008;34:703–5.

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