Basic Research—Technology

In Vitro Fracture Resistance of Roots Obturated with EpoxyResin–based, Mineral Trioxide Aggregate–based, andBioceramic Root Canal SealersH€useyin Sinan Topcuo�glu, DDS, PhD,* €Oznur Tuncay, DDS,* Ertu�grul Karatas, DDS,†

Hakan Arslan, DDS, PhD,‡and K€ubra Yeter, DDS

†

Abstract

Introduction: The aim of this study was to evaluate thefracture resistance of teeth filled with 3 differentendodontic sealers. Methods: Seventy-five single-rooted extracted mandibular premolars were decoro-nated to a length of 13 mm. The teeth were randomlydivided into 5 groups (n = 15 for each group). In group1, the teeth were left unprepared and unfilled (negativecontrol), and in group 2, the teeth were left unobturated(positive control). The rest of the roots were prepared byusing the ProTaper System up to a master apical file sizeof F3: group 3, bioceramic sealer (Endosequence BCsealer) + gutta-percha; group 4, mineral trioxide aggre-gate–based sealer (Tech Biosealer Endo) + gutta-percha; and group 5, epoxy resin–based sealer (AHPlus Jet) + gutta-percha. All root specimens were storedfor 2 weeks at 100% humidity to allow the completesetting of the sealers. Each specimen was then sub-jected to fracture testing by using a universal testingmachine at a crosshead speed of 1.0 mm/min�1 untilthe root fractured. The force required to fracture eachspecimen was recorded, and the data were analyzedstatistically. Results: The fracture values of groups 3and 5 were significantly higher than those of group 4(P < .05). There was no significant difference betweengroups 3 and 5 (P > .05). Conclusions: In contrast toTech Biosealer Endo, Endosequence BC and AH PlusJet sealer increased the force to fracture in root-filledsingle-rooted premolar teeth. (J Endod 2013;39:1630–1633)

Key WordsEndodontics, fracture resistance, sealer

From the *Department of Endodontics, Faculty of Dentistry,Erciyes University, Kayseri; †Department of Endodontics, Facultyof Dentistry, Atat€urk University, Erzurum; and ‡Department ofEndodontics, Faculty of Dentistry, Katip Celebi University, Izmir,Turkey.

Address requests for reprints to Dr H€useyin Sinan Top-cuo�glu, Department of Endodontics, Faculty of Dentistry, Er-ciyes University, Melikgazi, Kayseri, Turkey 38039. E-mailaddress: topcuogluhs@hotmail.com0099-2399/$ - see front matter

Copyright ª 2013 American Association of Endodontists.http://dx.doi.org/10.1016/j.joen.2013.07.034

1630 Topcuo�glu et al.

It is commonly believed that endodontically treated teeth are weaker and more prone tofracture than vital teeth (1). There are several factors that affect the strength of endodon-tically treated teeth, including excessive loss of tooth structure because of caries or trauma,dehydration of dentin, access cavity preparation, instrumentation and irrigation of the rootcanal, excessive pressure during root obturation, and preparation of intraradicular postspace (2, 3). Reinforcement of the remaining tooth structure after endodontic proceduresis a major goal of root canal therapy (4). It has been suggested that sealers that can adhereto the root canal dentin surface will strengthen the remaining tooth structure, therebycontributing to the long-term success of an endodontically treated tooth (5, 6). In theliterature, conflicting reports have been published regarding effect of root canal sealerson the fracture resistance of roots. Some studies have indicated that neither zinc oxide-eugenol–based sealers nor epoxy resin–based sealers were able to strengthenendodontically treated roots significantly (7, 8), although other studies have reportedpositive results for epoxy resin–based sealers and glass ionomer sealers (9, 10).

Recently, a new bioceramic root canal sealer has been introduced, which is knowncommercially as Endosequence BC sealer (Brasseler USA, Savannah, GA). Endose-quence BC Sealer is a premixed and injectable endodontic sealer, and its nanoparticlesize allows it to flow readily into canal irregularities and dentinal tubules. It is hydro-philic and uses moisture in dentinal tubules to initiate and complete its setting reaction.In addition, no shrinkage occurs on setting, resulting in a gap-free interface between thegutta-percha, sealer, and dentin (11). The manufacturer also states that the sealer ishighly biocompatible and is antibacterial during the setting reaction because of its highlyalkaline pH (12, 13).

Tech Biosealer Endo (Isasan, Como, Italy) is a new endodontic sealer containingcalcium silicate. Calcium silicate mineral trioxide aggregate (MTA) cements areendodontic materials that have received increasing attention because of their high bio-logical compatibility and favorable biological response obtained in laboratory tests andclinical applications (14–16). According to the manufacturer, Tech Biosealer Endo hashigh antibacterial activity, perfect biocompatibility, excellent apical sealing, andradiopacity as a root canal filling material (17).

AH Plus Jet sealer (Dentsply De Trey, Konstanz, Germany) is a resin-based rootcanal sealer and has the same formulation as AH Plus sealer. According to the manu-facturer, it has an innovative delivery system that eliminates the need for manual mixingbefore use, while enabling direct and precise placement into the canal or onto a tradi-tional mixing pad. AH Plus Jet sealer features an innovative double-barrel syringe thatautomatically and precisely mixes the paste-to-paste formula in the necessary 1:1 ratio.

In the literature, there are few studies evaluating the effects of sealers on thefracture resistance of endodontically treated teeth. Therefore, the purpose of this studywas to evaluate in vitro the fracture resistance of roots filled with 1 of 3 different rootcanal sealers (Endosequence BC sealer, Tech Biosealer Endo, and AH Plus Jet).

Materials and MethodsSpecimen Selection and Preparation

Seventy-five single-rooted human mandibular premolar teeth recently extractedfrom patients between the ages of 40 and 45 years for periodontal reasons were selected

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Basic Research—Technology

and stored in 0.1% thymol until the beginning of experiment but nolonger than 30 days after extraction. The teeth were examined underan operating microscope (Zeiss, Oberkochen, Germany) to excludeany roots with immature apices, root caries, cracks, or fractures. Preop-erative radiographs were taken in the mesiodistal and buccolingualdirections to confirm the presence of a single canal without previousroot canal treatment, resorptions, or calcifications. The crowns of allthe teeth were removed by using a slow-speed diamond precision sawwith water cooling (Isomet 1000; Buehler, Lake Bluff, IL) to adjust thelength of the roots to a standardized length of 13 mm. The buccolingualand mesiodistal diameters of the coronal planes were measured by usinga digital caliper (Teknikel, Istanbul, Turkey). All the roots were of similardimensions measuring 5.21 � 0.5 mm buccolingually and 4.76 � 0.4mm mesiodistally. Except for 15 randomly selected teeth that formeda negative control group (group 1, unprepared and unfilled), theworking length was determined by subtracting 1 mm from the lengthof an inserted #10 K-file (Dentsply Maillefer, Ballaigues, Switzerland)with its tip visualized at the apical foramen. Sixty teeth were instrumentedup to a master apical file size of F3 with ProTaper rotary instruments(Dentsply Maillefer) by using a 16:1 reduction handpiece with a tor-que-controlled and speed-controlled electric motor (X Smart; DentsplyMaillefer). The speed and torque values were set as recommended by themanufacturer. The canals were irrigated by using 3 mL 5.25% sodiumhypochlorite (NaOCl) solution between each file size. After instrumenta-tion, the smear layer was removed by flushing the root canals with 5 mL17% EDTA solution. The canals were finally rinsed with 10 mL distilledwater and dried with ProTaper paper points (Dentsply Maillefer).

Fifteen teeth were randomly selected to serve as a positive controlgroup (group 2, unfilled). The 45 remaining teeth were then randomlyassigned into 3 experimental groups (n = 15 for each group). In all 3groups, the canals were obturated with sealer by using the matched-taper, single-cone technique. Table 1 shows composition of sealersused in this study.

In group 3, Endosequence BC sealer was introduced into the rootcanal via its intracanal tip. The tip was not inserted deeper into the canalthan the coronal one-third. An F3 master gutta-percha cone (DentsplyMaillefer) with good tug-back was then coated with sealer and slowlyinserted into the canal until the working length was reached.

In group 4, Tech Biosealer Endo was mixed according to themanufacturer’s instructions and introduced into the root canal by usinga lentulo spiral filler. An F3 master gutta-percha cone (Dentsply Mail-lefer) with good tug-back was coated with sealer and slowly insertedinto the canal until the working length was reached.

In group 5, AH Plus Jet was introduced into the root canal via itsintraoral tip. An F3 master gutta-percha cone (Dentsply Maillefer) withgood tug-back was coated with sealer and slowly inserted into the canaluntil the working length was reached.

TABLE 1. Sealers Tested and Their Composition

Endodontic sealer Composition*

Endosequence BC Zirconium oxide, calcium silicates, calciummonobasic, calcium hydroxide, filler anagents

Tech Biosealer Endo Powder: white Portland cement, bismuthsodium fluoride. Liquid: Alfacaine SP sarticaine + 1/100,000 epinephrine)

AH Plus Jet Paste A: diepoxide, calcium tungstate, zisilica, iron oxide pigments. Paste B: 1-aamine, N,N-dibenzyl-5-oxa-nonandiamdiamine, calcium tungstate, zirconiumsilica, silicone oil

*Composition according to information provided by the manufacturers.

JOE — Volume 39, Number 12, December 2013

Mesiodistal and buccolingual radiographs were taken to confirmcomplete filling. After root filling, the coronal 1 mm of the filling mate-rials was removed, and the spaces were filled with a temporary fillingmaterial (Cavit; 3M ESPE, Seefeld, Germany). The teeth were storedat 37�C at 100% humidity for 14 days to allow the sealers to set.

Mechanical TestingTo simulate a periodontal membrane, the apical 5 mm of all roots

was covered with wax to obtain a 0.2- to 0.3-mm-thick layer beforeembedding the roots into acrylic resin. All the roots were then mountedvertically in copper rings (20 mm high and 20 mm diameter) and filledwith self-curing acrylic resin (Imicryl, Konya, Turkey), exposing 8 mmof the coronal parts of the roots. As soon as polymerization of the acrylicresin started, the roots were removed from the resin, and the wax wascleaned from the root surfaces by using a curette. The cleaned rootsurfaces were coated with a thin layer of polyvinylsiloxane impressionmaterial (Coltene\Whaledent AG, Altst€atten, Switzerland), and thenthey were again embedded into acrylic resin. A universal testingmachine (Instron Corp, Canton, MA) was used for the strength test.The acrylic blocks were placed on the lower plate of the machine.The upper plate consisted of a spherical steel tip with a diameter of 3mm. The tip was centered over the canal orifice, and a slowly increasingvertical force was exerted (1 mm/min�1) until fracture occurred. Thefracture moment was determined when a sudden drop in forceoccurred that was observed on the testing machine display. Themaximum force required to fracture each specimen was recorded innewtons. The data were analyzed statistically by using one-way analysisof variance with Tukey post hoc test for multiple comparisons. The levelof significance was set at P < .05.

ResultsThe mean values and their respective standard deviations of the

force required to fracture the roots are presented in Table 2. The stron-gest mean force required to fracture the roots was seen in the negativecontrol group, whereas the weakest force required was seen in the posi-tive control group. There was a significant difference between group 4(Tech Biosealer Endo) and the negative control group (P < .05).Among the experimental groups, group 3 (Endosequence BC sealer)had the highest fracture resistance, followed by group 5 (AH PlusJet) and then group 4 (Tech Biosealer Endo). The level of forcerequired to fracture the roots between groups 3 (Endosequence BCsealer) and 4 (Tech Biosealer Endo) was found to be statistically signif-icant (P < .05). In addition, there was significant difference betweengroups 4 (Tech Biosealer Endo) and 5 (AH Plus Jet) (P < .05). Twofracture modes were detected, a split vertical fracture that extendedalong the long axis of the root and a comminuted fracture that shattered

Manufacturer

phosphated thickening

Brasseler USA (Savannah, GA)

oxide, anhydride,olution (4%

Isasan (Como, Italy)

rconium oxide,damantaneine-1,9, TCD-oxide, aerosil

Dentsply De Trey, (Konstanz, Germany)

Fracture Resistance of Roots 1631

TABLE 2. Mean Fracture Resistance and Standard Deviation for theExperimental Groups

Groups NMean forces ± standarddeviation (newtons)

1. Negative control 15 470.68 � 110.89a

2. Positive control 15 320.19 � 49.45b

3. Endosequence BCsealer

15 457.61 � 111.61a

4. Tech Biosealer Endo 15 358.85 � 67.12b

5. AH Plus Jet 15 452.97 � 95.65a

The same superscript letters indicate no significant differences (P > .05).

Basic Research—Technology

the root into fragments. The most common fracture mode was the splitvertical fracture in buccolingual direction in all groups.

DiscussionChemomechanical preparation of root canals is an essential phase

in endodontic treatment. During chemomechanical preparation, exces-sive removal of dentin tissue, uncontrollable force during the root canalobturation, and prolonged exposure of the dentin to root canal irrigantsmay weaken the root and create an increased suspectibility to fracture(18–20).

Various endodontic filling materials are used to improve thefracture resistance of endodontically treated teeth (21, 22). Most rootcanal filling methods use a root canal sealer as a complementary partof the obturation technique. The root canal sealer fills the gapsbetween gutta-percha cones and the walls of the root canal. It also fillsthe voids between individual gutta-percha cones applied during obtura-tion of the root canal system (23). Previous studies showed that epoxyresin–based sealers had higher adhesion to root canal dentin and deeperpenetration into dentinal tubules than zinc oxide-eugenol–based andglass ionomer–based sealers (24, 25). In addition, the epoxy resin–based sealers penetrate better into the microirregularities because oftheir creep capacity and long polymerization period (26). The retentionof the filling material may be improved by mechanical locking betweenthe canal walls and the sealers. As a result of the advantages of epoxyresin–based sealers, resistance to fracturing will increase (27).

In the present study, the effectiveness of Endosequence BC sealeron fracture resistance was compared with that of Tech Biosealer Endoand AH Plus Jet. The results showed that AH Plus Jet and EndosequenceBC sealer increased the fracture resistance of prepared teeth. However,Tech Biosealer Endo had no significant effect on fracture resistance.Sagsen et al (27) showed that AH Plus sealer increased the fractureresistance of instrumented root canals. Similarly, Ersev et al (28)reported that the group in which AH Plus was used with the matched-taper single-cone technique showed significantly higher fractureresistance than the instrumented but not obturated roots. The resultsof our study are compatible with those of these studies.

The introduction of bioceramic technology began to offer a newalternative to the other filling materials in endodontic obturation.Koch and Brave (29) stated that bioceramics have enhanced biocom-patibility, result in the possibly increased strength of the root after obtu-ration, have a high pH during the setting process (which is stronglyantibacterial), have a sealing ability, and are easy to use. Bioceramicroot canal sealers also exhibit chemical bonding to root canal dentinwalls (27). Cobankara et al (10) reported that chemical bondingenhances the fracture resistance of teeth with root canal filling. In thepresent study, this chemical bonding may have improved the fractureresistance of obturated teeth with Endosequence BC sealer. In addition,the deep penetration of the sealer into canal irregularities and dentinal

1632 Topcuo�glu et al.

tubules as a result of the sealer’s nanoparticles may be another factorassociated with increased fracture resistance.

In previous studies, the fracture resistance of endodonticallytreated teeth with MTA used as root canal obturation material was inves-tigated (30, 31). However, MTA-based root canal sealers have beenrecently used in root canal obturation. Tanalp et al (32) found thatMTA Fillapex did not improve the fracture resistance of immature teeth.In contrast, it was found that MTA Fillapex did increase the fractureresistance of endodontically prepared teeth (27). In the present study,the reinforcing effect of Tech Biosealer Endo as an MTA-based sealer onfracture resistance of root-filled teeth was evaluated. The results showedthat Tech Biosealer Endo did not increase the root fracture resistance ofprepared teeth. Unlike the other sealers used in this study, Tech Bio-sealer Endo is an endodontic sealer in the form of a powder and liquid.The ability of an endodontic material to penetrate dentinal tubules canbe attributed to the size of the dentinal tubules, the particle size of thematerial, and the setting reaction of the material (33). As a result ofdeep penetration of sealer into dentinal tubules, adhesion of the fillingmaterial is increased. Thus, increased mechanical locking may improveresistance to fracturing (27). The penetration depth of the sealers wasnot measured in the present study. However, the fact that sealers witha paste formulation increased fracture resistance may be due to thehigher flow and better penetration into dentinal tubules than sealerswith a powder/liquid formulation.

Regarding the fracture mode observed in the present study, a splitvertical fracture in buccolingual direction was the most commonlydetected type of fracture. Zamin et al (34) stated that the direction ofthe force application may influence the direction of the fracturesbecause fractures toward the buccolingual region are usually observedin studies (8, 35) applying a force vertically. According to the findings ofour study, the sealer type used in this study had no impact on thediversity of fracture.

ConclusionsWithin the limitation of this in vitro study, it may be concluded that

the Endosequence BC sealer and AH Plus Jet were able to increase theforce to fracture in single-rooted endodontically treated premolar teeth.Further research is required to validate the findings obtained in this study.

AcknowledgmentsThe authors deny any conflicts of interest related to this study.

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