An In Vitro Comparison of the Intraradicular Dentin Bond Str

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An In Vitro Comparison of the Intraradicular Dentin BondStrength of Resilon and Gutta-Percha

Lance J. Skidmore, DDS, David W. Berzins, PhD, and James K. Bahcall, DMD, MS

Abstract

The purpose of this study was to compare the micro-push-out bond strength of Resilon to that of gutta-percha. Extracted human anterior teeth were used forevaluation. The crowns were removed and the rootcanals were instrumented with Gates Glidden drills and0.06 Profile rotary files. Instrumentation was performedwith 5.25% sodium hypochlorite irrigation and a finalrinse of 17% EDTA. The teeth were randomly dividedinto two groups. Gutta-percha group: obturation withgutta-percha and Kerr Pulp Canal Sealer EWT. Resilongroup: obturation with Resilon points, Epiphany Primer,and Root Canal Sealant. The teeth were cut perpendic-ular to their long axis to obtain a series of 1.0 mm thickdisks (n 15 per group). Micropush-out bondstrengths to root canal dentin were measured. Theresults show that the mean bond strength to root canaldentin was significantly higher (p 0.05) in the Resi-lon/Epiphany group as compared to the gutta-percha/Kerr Pulp Canal Sealer EWT group. (J Endod 2006;32:963966)

Key Words

Bond strength, Epiphany, micropush-out, Resilon

The principal objectives of endodontic therapy are to first chemomechanically cleanandshapetherootcanal system, andsecondto completely obturate the canal systemin three dimensions (1). Because bacteria and their byproducts have been shown tocause apical periodontitis and root canal failure (2 4), the objective of three dimen-sional obturation is to completely seal the canal system from any bacterial ingress fromthe oral cavity and periradicular tissues. Additionally, the obturating materials sealwithin the canal system any irritants that are not removed during chemomechanicalpreparation. Gutta-percha and traditional sealers have been the most commonly usedand accepted materials for the obturation of endodontically treated teeth. However,leakage and recontamination of the root-canal system continue to cause post treatment

complications (5).Khayat et al. (6) examined the microbial leakage of extracted maxillary and man-dibular molars and found that canals were completely contaminated on average within28 days regardless of the gutta-percha obturation method. To minimize the likelihoodof contamination, new materials and methods are continually developed to improve theseal of endodontic obturation.

Resilon (Resilon Research LLC, Madison, CT) is a new material that has beenintroduced for the obturation of endodontically treated teeth. Resilon is a syntheticpolycaprolactone polymer based on the polymers of polyester. This material containsdimethacylates and can bond to methacrylate-based resin sealers (7). Resilon pointslook and handle like gutta-percha, and when used with a self etch primer and a resinsealer, the manufacturer claims a bonded obturation between the intraradicular dentinand the root canal filling is formed.

Several studies have evaluated this material (812).Shipperetal.(8)usedasplitchamber microleakage test to compare the resistance to leakage of Resilon and Epiph-any sealer to that of gutta-percha and AH26 sealer and found Resilon had significantlylessleakageover30days.TheresultsofTayetal.(11)areincontrasttothoseofShipperet al. (8). Tay et al. found that the quality of apical seal with Resilon was not superior togutta-percha and a conventional epoxy-resin sealer when compared using a silvertracer penetration technique. Teixeira et al. (9) evaluated the fracture resistance ofendodontically treated teeth filled with either gutta-percha or Resilon and found that themean fracture loads of the gutta-percha groups were lower than the Resilon groups.However, the results of Gesi et al. (12) challenge the concept of the ability to increasefracture resistance of root canal treated teeth using Resilon, because their Resilon/Epiphany group exhibited significantly lower interfacial strength compared with gutta-percha/AH Plus group.

One of the main claims of those advocating the use of Resilon is its ability toproduceabondedmonoblockfilling.ThisiscreatedbytheadhesionoftheResilonconeto the resin based sealer, which adheres to the dentinal wall and penetrates the dentinaltubules. Shipper et al. (10) referred to this bonded root canal filling as the ResilonMonoblock System (RMS). In their study, a dog model was used to compare theefficacy of gutta-percha and AH26 sealer versus RMS in preventing apical periodontitisafter coronal microbial inoculation. The results showed the RMS was associated withsignificantly (p 0.05) less periapical inflammation.

An improved bond and the creation of a monoblock root canal obturation wouldbe the main advantages of this newmaterial. Therefore, the purpose of this studywas toevaluate the bondability of this new material by comparing the micropush-out bondstrength of Resilon/Epiphany filled teeth to that of teeth filled with gutta-percha and KerrPulpCanal Sealer EWT(Kerr Corporation, Orange, CA). The nullhypothesis is thatthere

From the Department of Endodontics, Marquette Univer-sity, School of Dentistry, Milwaukee, Wisconsin.

Address requests for reprint to Dr. Lance J. Skidmore,Marquette University, School of Dentistry, Department ofEndodontics, 1801 West Wisconsin Avenue, Room 245, Mil-waukee, WI 53233. E-mail address: [email protected]/$0 - see front matter

Copyright 2006 by the American Association ofEndodontists.doi:10.1016/j.joen.2006.03.020

Basic ResearchTechnology

JOE Volume 32, Number 10, October 2006 Comparing Bond Strength of Resilon and Gutta-Percha 963


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is no difference in the micropush-out bond strength of Resilon andgutta-percha based obturating systems.

Materials and MethodsTwelve recently extracted human anterior teeth with straight roots

were used in this study. The crowns were removed at the cementoe-namel junction using a high-speed carbide bur with water coolant. A#15 K-type file was inserted until it could be seen at the apical foramen,

and then 1 mm was subtracted from this to determine the workinglength. The root canals were instrumented with Gates Glidden burs and0.06 Profile nickel-titanium rotary instruments (Dentsply Tulsa Dental,Tulsa,OK)toasize40fileatworkinglength.Toremovethesmearlayer,instrumentation was performed with 5.25% sodium hypochlorite irri-gation and a final rinse of 17% ethylene diamine tetra-acetic acid(EDTA) as per manufacturers instructions. Sodium hypochlorite wasnot used for final irrigation because it may negatively alter the bond ofthe sealer to the dentinal wall. The teeth were dried with paper pointsthen randomly divided into two equal groups.

Gutta-percha group: Obturation with gutta-percha and Kerr PulpCanal Sealer EWT using a warm vertical compaction technique.

Resilon group: Obturation with Resilon Points, Epiphany Primer,and Root Canal Sealant (Pentron Clinical Technologies, Walling-ford, CT) using a warm vertical compaction technique.

In the gutta-percha group, a #40 .06 tapered cone (Dentsply TulsaDental) was fit with tugback. Thepoint was coated with Kerr Pulp CanalSealer EWT (mixed according to manufacturers instructions) and in-troduced into the canal and pumped a few times. The cone was re-moved, re-coated with sealer, and inserted again to ensure adequatesealer coverage. A downpack and backfill were completed using a Sys-tem B (System B, SybronEndo, Orange, CA) and Obtura II (ObturaCorp., Fenton, MO).

In the Resilon group, the Epiphany self-etch primer was broughtinto thecanal by the insertion of a saturated fitted paper point. This step

was done two times to ensure adequate primer placement. Excessprimer, if any, was removed with a dry paper point. The sealer was thenexpressed using the auto mix syringe tip. The fitted master cone wascoated with the sealer and placed into the canal and pumped. The conewas removed, re-coated with sealer, and inserted again to ensure ade-quate sealer coverage. The downpack andbackfill were then completedusing the same technique as the gutta-percha group.

All bonded samples were stored in 100% humidity for 24 h at37C. The samples were cut perpendicular to their long axis using anIsomet saw (Buehler Ltd., Lake Bluff, IL) with water lubrication. Thesamples in both groups were collected from the middle and coronalthirds of the canal. Because of thesmall size of the filling material in theapical 3 mm of the root, this portion was not evaluated using the mi-

cropush-out technique. If the sample contained filling material of anoncircular shape, it was discarded, as this would result in nonuniformstress distributions during testing and inaccurate measurements. Over-all, this step produced a series of 1.0 mm thick disks (n 15 pergroup) with seven and six of the 15 disks for the gutta-percha andResilon groups, respectively, arising from the middle third of the teeth.The exact dimensions of each disk were measured with a digital caliperto within 0.01 mm. The filling material was loaded with a 0.76 mmdiameter cylindrical stainless steel plunger that provided the most ex-tended coverage over the fillingmaterial withouttouching the canal wall(Fig. 1). The teeth were marked as to ensure that the direction of theplunger push was in the apical to coronal direction, to avoid any inter-ference owing to any root canal taper. Micropush-out bondstrengths toroot canal dentin were measured using a universal-testing machine

(Instron Corp., Norwood, MA) at a speed of 0.5 mm/min until bondfailure occurred. The bond strength expressed in MPa at failure wascalculated by dividing the load in Newtons by the area of the bondedinterface. The area of the bonded interface was calculated with the

formula, area 2r h, whereistheconstant3.14andrandharethe measured radius and height in millimeters of the fillingmaterial thatwas pushed out. The bond strength results were statistically evaluatedusing the Shapiro-Wilk test to determine whether the data were nor-mally distributed. As the data were not normally distributed, the Mann-Whitney test was performedwith statistical significance set at 95% (p0.05). For each group, bond strength data for the middle and coronallevels of the root were pooled as no difference (p 0.10) was foundbetween the different areas.

After the measurement of bond strength, both sides of the failedbond were evaluated microscopically to determine modes of bond fail-ure. Each sample was evaluated and placed into oneof 3 failure modes:type I, adhesive failure, at sealer and dentin interface; type II, cohesive

failure, within sealer or dentin; type III, mixed failure, failure in boththesealer and dentin.Four randomly selected intact and failed samples were prepared

for scanning electron microscopy (SEM) evaluation. Each sample wassputter coated with gold (Hummer I, Technics Electron MicroscopySystems, Inc., Munich, Germany) and evaluated under SEM (JSM-35,Jeol Ltd. Tokyo, Japan) at magnifications ranging from 300 to 2000.

ResultsThe mean micropush-out bond strength of the Resilon group

(1.51 1.22MPa) was significantly higher (p 0.05)than that of thegutta-percha group (0.66 0.39 MPa). Modes of failure are shown inTable 1. Inspection of the samples revealed the bond failure to bepredominantly adhesive between the sealer and dentin interface for

Figure 1. Schematic representation of tooth sample preparation and micro-push-out set-up used for testing the bond strength.


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In conclusion, the Resilon/Epiphany filled root canals have signif-icantly (p 0.05) higher mean micropush-out bond strength to in-traradiculardentinthan thatof gutta-percha andPulp Canal SealerEWT.However, SEM evaluation challenges the idea of producing a completemonoblock obturation without gaps. The clinical significance of thesefindings will require further in vivo evaluation.

AcknowledgmentsThe authors wish to thank Jim Brozek for the drawing and Dr.

Raymond A. Fournelle, Department of Mechanical and IndustrialEngineering, Marquette University, for use of the SEM.

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12. Gesi A, Raffaelli O, Goracci C, Pashley DH, Tay FR, Ferrari M. Interfacial strength ofResilon and gutta-percha to intraradicular dentin. J Endod 2005;31:80913.

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TABLE 2. Modes of bond failure

Failure mode Gutta-Percha group Resilon group

I - Adhesive 13 14II - Cohesive 0 0III - Mixed 2 1Total samples 15 15


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An In Vitro Comparison of the Intraradicular Dentin Bond Str

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