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Basic Research—Technology
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he Root Canal Bonding of Chemical-curedotal-etch Resin Cementsikako Hayashi, DDS, PhD, Kenji Okamura, DDS, Hongxia Wu, DDS,utaka Takahashi, DDS, PhD, Evgeni V. Koytchev, DDS, PhD, Satoshi Imazato, DDS, PhD,nd Shigeyuki Ebisu, DDS, PhD
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bstractiscovering a durable restorative method to reconstructnd reinforce pulpless teeth is a vital key to helprevent root fractures. Complete and firm adhesion ofesin cement in root canal dentin using a post is criticalo achieve it. The null hypothesis in the present studyas that the bond strength of dual-cured and chemical-
ured adhesive resin cements to root canal dentin is notffected by their vertical locations in the root canal. Inhe experiments, extracted human incisors restoredith fiber-reinforced posts and adhesive resin cementsere subjected to microtensile bond strength testing.
hen, the failure modes and the dentin-bonding inter-aces were observed. Self-etch and self-adhesive dual-ured resin cements showed frequent pretesting failureespite using a silane coupling agent. Chemical-curedotal-etch adhesive material showed stable bondingerformances throughout the entire post space andhus has an advantage in post-core restorations. (Jndod 2008;34:583–586)
ey Wordshemical-cured, dual-cured, fiber-reinforced post, mi-rotensile bond strength, resin cement, root canal den-in, self-etch, silane coupling agent, total-etch
From the Department of Restorative Dentistry and Endod-ntology, Osaka University Graduate School of Dentistry,saka, Japan.
Supported in part by Grants-in-Aid for Scientific Researchnos. 19390842 and 19209060) from the Japan Society for theromotion of Science, by the 21st century COE program enti-led “Origination of Frontier BioDentistry” at Osaka Universityraduate School of Dentistry, and by the Japan-Chinaasakawa Medical Fellowship.
Address requests for reprints to Dr. Mikako Hayashi, De-artment of Restorative Dentistry and Endodontology, Osakaniversity Graduate School of Dentistry, 1-8 Yamadaoka,uita, Osaka 565-0871, Japan. E-mail address: [email protected]/$0 - see front matter
Copyright © 2008 by the American Association ofndodontists.oi:10.1016/j.joen.2008.02.003
s
OE — Volume 34, Number 5, May 2008
ulpless teeth restored with a combination of fiber reinforced posts (FRP) and resincores together with adhesive resin cements have shown excellent clinical perfor-
ances in several studies (1– 4). Particularly important for clinicians, those reportsuggest that the incidence of root fractures is low in such treated teeth. However,ebonding of the FRP from its post space was the most frequent failure pattern in thoseestorations (3, 5, 6). Therefore, more certain adhesion of post-core materials to rootanal dentin is essential to improve the fracture resistance of pulpless teeth and preventoot fracture.
One of the most influential factors compromising the bonding may be the intenseontraction stress generated when curing adhesive materials in the post space. Bouil-aguet et al. (7) conjectured that the unstable bonding performance of adhesive mate-ials in the post space may be attributed to the high configuration factor (C-factor). Theylso argued that when the C-factor is high, the use of slower setting materials couldeduce stress at the bonding interface by allowing the flow of the materials to relieveolymerization stress.
The difficulty in achieving high bond strength throughout an entire root canal haseen reported when using modern dentin bonding systems with FRP (7–17). Imperfecturing of the light-cured adhesives at the apical portions may be the cause of the inferiorond strengths. Therefore, using dual-cured and chemical-cured materials could haven advantage in root canal adhesion.
The null hypothesis in the present study was that the bond strength of dual-curednd chemical-cured adhesive materials to root canal dentin with FRP was not affected byhe vertical locations in a root canal.
Materials and MethodsA total of 54 human upper incisors, free of caries and fractures, were stored in
ank’s balanced salt solution at 4°C and used within 6 months of extraction. Thencisors were decoronated using a low-speed diamond saw (Isomet III; Buehler, Lakeluff, IL) under copious water cooling at the cement-enamel junction. A post space wasrepared in the root portions of the teeth with a depth of 10 mm and a diameter of 1.5 mmsing preparation drills (Para Post Drill #6; Coltene/Whaledent, Cuyahoga Falls, OH).
The prepared roots with the post were randomly assigned into one of three groups,nd each group was treated with a dual-cured self-etch resin cement (Panavia F 2.0;uraray Medical, Tokyo, Japan [PNV]), a dual-cured self-adhesive resin cement (RelyUnicem; 3M ESPE, St. Paul, MN, USA [RXU]), or a chemical-cured total-etch resin
ealer (Super Bond Sealer; Sun Medical, Shiga, Japan [SBS]). Although SBS is anndodontic sealer, we used this material as an adhesive cement because of its advantagef an extended setting time. Each group was further subdivided, and half of the speci-ens were restored with glass FRP (Para Post Fiber White, Coltene/Whaledent) treated
y a silane-coupling agent (Clearfil Ceramic Primer, Kuraray Medical [SCA]), whereashe other specimens were restored with the FRP without the SCA.
In the group with PNV, a self-etching primer (ED Primer A and B, Kuraray Medical)as applied to the dentin surface in each post space for 20 seconds and dried by a paperoint and air blowing. Then, a dual-cured resin cement (PNV) and a glass FRP were
nserted into the post space consecutively, and the cement was light cured for 40
econds with an irradiation unit (Elipar Free Light 2, 3M ESPE) from the cervical orifice.Adhesion to Root Canal Dentin 583
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In the group with the dual-cured resin cement, RXU was applied toach post space without any pretreatment. After that, the FRP was placednto the post space, and the cement was light cured for 40 seconds.
In the chemical-cured resin sealer group, the prepared post spaceas treated with a 10% citric acid / 3% ferric chloride solution (Superond Green Activator, Sun Medical) for 10 seconds followed by copiousinsing with water and drying using a paper point and by air blowing.hen, 4META/TBB resin sealer (SBS) was applied to the post space, andn FRP was immediately inserted.
All specimens with the bonded fiber posts were stored under con-itions of 100% humidity at 37°C for 24 hours. Disk-shaped slabs withthickness of approximately 1.0 mm were sliced by using the low-speediamond saw perpendicular to the tooth axis. A total of seven slabs werebtained from each root, and the vertical locations of the seven slabs inhe root were maintained throughout the testing. Then, one hourglass-haped specimen was trimmed from each slab. A groove is madehrough the entire canal wall from two sides, leaving only the post
aterial and the luting cement to bear the load during testing. Inci-ences of bonding success or failure occurring during the trimming ofhe specimens were recorded in three categories: successful bondingn both sides, successful bonding on one side, and debonding on bothides. Distributions of the three different bonding statuses in the groups
ABLE 1. Bonding Statuses of Specimens before Microtensile Bond Strength Tes
Bonding statuses (Both
Materials PNV
Locations SCA (�) SCA (�)
Cervical1 3/6/0 4/5/02 2/6/1 1/7/13 4/5/0 3/6/04 4/5/0 2/6/15 7/2/0 4/4/16 4/5/0 5/3/17 3/5/1 4/5/0
ApicalTotal
n 27/34/2 23/36/4p � 0.59
Pretesting failure rate% 63.5 57.1
istributions of the specimens with the three different bonding statuses were compared between the g
%) � ([numbers of single-side bonding � numbers of both-side debonding]/total numbers) � 10
NV, Panavia F; RXU, Rely X Unicem; SBS, Super Bond Sealer; SCA, silane coupling agent.
ABLE 2. Microtensile Bond Strength of Specimens Successfully Bonded on Bo
PNV
Materials SCA (�) SCA (�) SCA (
Locations Mean (SD) n Mean (SD) n Mean (SD
Cervical1 10.8 (9.6) 3 17.1 (4.1) 4 — (—)2 7.5 (1.5) 2 15.3 (—) 1 — (—)3 12.1 (5.0) 4 8.3 (2.9) 3 11.9 (—)4 13.2 (3.8) 4 10.4 (6.5) 2 11.6 (6.65 11.1 (3.8) 7 11.3 (2.5) 4 9.7 (—)6 8.9 (2.8) 4 12.3 (4.6) 5 9.4 (8.77 13.0 (0.4) 3 11.0 (2.4) 4 6.4 (4.6
Apical
tatistical analyses, which compared the MTBS among the different vertical locations, were applied on
XU groups. Groups with the same letters (a and b) showed no significant differences in the MTBS b
D, standard deviation; PNV, Panavia F; RXU, Rely X Unicem; SBS; Super Bond Sealer; SCA, silane coupling ag
84 Hayashi et al.
ith and without SCA were compared by means of a chi-square test at a5% level of confidence.
For the MTBS testing, each hourglass-shaped specimen was fixed to austom-made metallic jig with cyanoacrylate glue. Then, the testing wasonducted by means of a tabletop material testing machine (EZ test; Shi-adzu, Kyoto, Japan) with a crosshead speed of 1.0 mm/min. The MTBS
mong the groups with different vertical locations in the post space and withhe same adhesive materials were compared by means of the one-way anal-sis of variance and Scheffe’s F test at a 95% level of confidence. The fractureurfaces were observed by an optical microscope (SMZ-U; Nikon, Tokyo,apan) at a magnification of �20 to determine the failure modes.
To observe the details of the bonding interfaces, disk-shaped slabsere fabricated with the same methods as for the MTBS testing and
reated with a 50% phosphoric acid solution for 30 seconds and 5%aOCl for 2 minutes. Then, the bonding interfaces were observed by acanning electron microscope (SEM) (JSM9-840A; JOEL, Tokyo, Ja-an) at a magnification of �350 to �750.
ResultsPretesting failure was found less frequently in the groups with SBS
Table 1). In these groups, the use of the SCA significantly reduced the
bonding/Single-side bonding/Both-side debonding)
RXU SBS
SCA (�) SCA (�) SCA (�) SCA (�)
0/8/1 2/4/3 0/3/6 7/1/10/6/3 3/4/2 5/2/2 8/1/01/4/4 1/6/2 6/3/0 6/3/03/5/1 1/6/2 8/1/0 7/2/01/7/1 3/5/1 9/0/0 9/0/03/6/0 4/4/1 9/0/0 9/0/04/4/1 8/1/0 9/0/0 9/0/0
2/40/11 22/30/11 46/9/8 55/7/1p � 0.11 p � 0.05
81.0 65.1 27.0 12.7
ith and without the SCA by means of a chi-square test at a 95% level of confidence. Pretesting failure
s
RXU SBS
SCA (�) SCA (�) SCA (�)
n Mean (SD) n Mean (SD) n Mean (SD) n
0 7.2 (2.1) 2 — (—) 0 31.7 (17.1)a 70 6.7 (4.0) 3 7.7 (2.8)a 5 28.8 (11.4)a 81 12.5 (—) 1 12.3 (6.0)a,b 6 24.3 (11.9)a 63 19.9 (—) 1 11.7 (4.1)b 8 22.5 (8.3)a 71 13.6 (3.4) 3 14.2 (6.0)b 9 24.7 (11.3)a 93 10.3 (5.6) 4 12.2 (2.3)b 9 25.2 (11.7)a 94 15.9 (7.5) 8 13.8 (4.3)b 9 24.1 (7.0)a 9
e SBS groups because insufficient specimens with successful adhesion were obtained in the PNV and
of the one-way analysis of variance and the Scheffe’s F test at a 95% level of confidence.
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JOE — Volume 34, Number 5, May 2008
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Basic Research—Technology
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ncidence of pretesting failure from 27.0% to 12.7%. In the groups withNV and RXU, the incidences of pretesting failure were 57.1% and5.1%, respectively, despite using the SCA. The SCA did not significantlymprove the bonding in these groups.
The SBS group with the SCA showed MTBS in the range of 22.5Pa to 31.7 MPa, whereas the MTBS in other groups were below 20Pa (Table 2). The SBS group with the SCA showed that there were
o differences in the MTBS throughout an entire post space.In the PNV groups, approximately 85% of the specimens were
ractured at the interfaces between the dentin and the cement or be-ween the cement and the posts. In the RXU groups, more than two thirdsere fractured at the interfaces between the dentin and the cement. In
he SBS group without the SCA, 74.5% were fractured at the interfacesetween the cement and the posts. In the SBS group with the SCA, half ofhe specimens failed at the interfaces between the dentin and the ce-
ent, and the other half showed cohesive failure in the posts or mixedailure including cohesive failure in the posts.
The bonding interfaces of the adhesive materials to root canal dentinhowed that no resin tag formation was found at the adhesive interfaces inhe PNV and RXU (Fig. 1A) groups, whereas stout resin tags extending over00 �m were observed in the SBS groups (Fig. 1B). Intertubular anasto-oses in lateral branches were also found in those resin tags.
DiscussionOur finding of frequent pretesting failures before conducting the
TBS testing with root canal dentin in post spaces is similar to thateported in other studies (9, 18, 19). Push-out testing has sometimeseen recommended as an alternative because of the low incidence ofretesting failure while preparing the specimens (9, 19). In the presenttudy, only 12.7% of the specimens in the SBS group with the SCAhowed pretesting failure, although all other groups showed frequentncidences. These results indicate that methods of the MTBS testing usedn the present study are superior as sensitive techniques to detect latentailures when compared with push-out testing. Our results revealed thatBS with SCA is a reliable bonding material for placing FRP because ithowed the fewest pretesting failures and also provided high bondingtrength throughout the entire post space.
This remarkably superior performance of the adhesion in the rootanal when using SBS can be explained by the unique characteristics of
igure 1. Bonding interfaces of the adhesive materials to root canal dentin. (A)n the SBS group, stout resin tags extending over 100 �m were found, and thedhesive material, (c) root canal dentin, and (d) resin tag.
his material. The dentin conditioner that is part of the SBS system,
OE — Volume 34, Number 5, May 2008
omposed of 10% citric acid/3% ferric chloride solution, removes themear layer and has an etching effect that opens the dentinal tubules.his then allows monomers with small molecular size to penetrate thepened tubules, leading to the formation of resin tags of over 100 �mFig. 1B). Such long resin tags with intertubular anastomoses in theirateral branches can counter the stress caused by the polymerizationhrinkage and contribute to enhancing the mechanical bondingtrength (20). Chemical curing may also have an advantage in promot-ng even distribution of the stress caused by the polymerization shrink-ge and inducing even bonding strength in the entire post space (21).
The application of the SCA was beneficial in improving the bondtrength in the SBS group because the most frequent failure mode in thisroup without SCA was adhesive failure at the interface between the postnd the sealer. Therefore, it is reasonable to conclude that the inci-ences of pretesting failure were significantly reduced and the MTBSere also markedly improved by applying the SCA. By contrast, theonding in the PNA and RXU groups was not improved by the SCAecause the fractures were found at the interface between the cementsnd the dentin in those groups without SCA. Improving the bonding ofNA and RXU cements to root canal dentin is a priority. Only when suchdhesion is achieved can SCA contribute to improve the bonding of FRPn a post space, as we showed in the SBS groups.
Another problematic consideration in achieving root canal bond-ng is the thick smear layer after the preparation of a post space. Goraccit al. (19) reported that a total-etch resin cement showed greater bond-ng potential than a self-etch cement when luting the FRP to root canalentin. It may be because acidic monomers responsible for substrateonditioning in the self-etch resin cement were less effective in etchinghrough the thick smear layer. This might have accounted for the sig-ificantly lower bond strength of the FRP to the root canal dentin in theresent study. Further studies need to be performed to identify theppropriate treatments to control the thick smear layer and to produceroper conditions for self-etch resin cement.
In conclusion, chemical-cured total-etch adhesive materials,hich showed stable bonding performances in an entire post space,learly have an advantage in post-core restorations.
References1. Qualtrough AJE, Mannocci F. Tooth-colored post systems: a review. Oper Dent
e RXU group, no resin tag formation was found at the adhesive interfaces. (B)ing intertubular anastomoses in lateral branches were observed (a) post, (b)
In thfollow
2003;28:86 –91.
Adhesion to Root Canal Dentin 585
1
1
1
1
1
1
1
1
1
1
2
2
Basic Research—Technology
5
2. Fredriksson M, Astback J, Pamenius M, Arvidson K. A retrospective study of 236patients with teeth restored by carbon fiber-reinforced epoxy resin posts. J ProsthetDent 1998;80:151–7.
3. Ferrari M, Vichi A, Mannocci F, Mason PN. Retrospective study of clinical perfor-mance of fiber posts. Am J Dent 2000;13:9B–13B.
4. Ferrari M, Vichi A, Garcia-Godoy F. Clinical evaluation of fiber-reinforced epoxy resinposts and cast post and cores. Am J Dent 2000;13:15B–18B.
5. Naumann M, Blankenstein F, Kiesling S, Dietrich T. Risk factors for failure of glassfiber-reinforced composite post restorations: a prospective observational clinicalstudy. Eur J Oral Sci 2005;113:519 –24.
6. Hayashi M, Takahashi Y, Imazato S, Ebisu S. Fracture resistance of pulpless teethrestored with post-cores and crowns. Dent Mater 2006;22:477– 85.
7. Bouillaguet S, Troesch S, Wataha JC, Krejci I, Meyer JM, Pashley DH. Microtensilebond strength between adhesive cements and root canal dentin. Dent Mater2003;19:199 –205.
8. Foxton RM, Nakajima M, Tagami J, Miura H. Bonding of photo and dual-cure adhe-sives to root canal dentin. Oper Dent 2003;28:543–51.
9. Goracci C, Tavares AU, Fabianelli A, et al. The adhesion between fiber posts and rootcanal walls: comparison between microtensile and push-out bond strength measure-ments. Eur J Oral Sci 2004;112:353– 61.
0. Foxton RM, Nakajima M, Tagami J, Miura H. Adhesion to root canal dentin using oneand two-step adhesives with dual-cured composite core materials. J Oral Rehabili2005;32:97–104.
1. Aksornmuang J, Nakajima M, Foxton RM, Tagami J. Regional bond strength of fourself-etching primer/adhesive systems to root canal dentin. Dent Mater J 2005;
24:261–7.86 Hayashi et al.
2. Akgungor G, Akkayan B. Influence of dentin bonding agents and polymerizationmodels on the bond strength between translucent fiber posts and three dentin regionswithin a post space. J Prosthet Dent 2006;95:368 –78.
3. Aksornmuang J, Nakajima M, Foxton RM, Tagami J. Effect of prolonged photo-irradiation time of three self-etch systems on the bonding to root canal dentin. J Dent2006;34:389 –97.
4. Mallmann A, Jacques LB, Valandro LF, Muench A. Microtensile bond strength ofphotoactivated and autopolymerized adhesive systems to root dentin using translu-cent and opaque fiber-reinforced composite posts. J Prosthet Dent 2007;97:165–72.
5. Aksornmuang J, Nakajima M, Foxton RM, Tagami J. Mechanical properties and bondstrength of dual-cure resin composites to root canal dentin. Dent Mater 2007;23:226–34.
6. Pirani C, Chersoni S, Foschi F, et al. Does hybridization of intraradicular dentin reallyimprove fiber post retention in endodontically treated teeth? J Endod 2005;31:891–4.
7. Faria e Silva AL, Casselli DS, Ambrosono GMB, Martins LRM. Effect of the adhesiveapplication mode and fiber post translucency on the push-out bond strength to denin.J Endod 2007;33:1078 – 81.
8. Mallmann A, Jacques LB, Valandro LF, Mathias P, Muench A. Microtensile bondstrength of light- and self-cured adhesive systems to intraradicular dentin using atranslucent fiber post. Oper Dent 2005;30:500 – 6.
9. Goracci C, Sadek FT, Fabianelli A, Tay FR, Ferrari M. Evaluation of the adhesion offiber posts to intraradicular dentin. Oper Dent 2005;30:627–35.
0. Hayashi M, Takahashi Y, Hirai M, Iwami Y, Imazato S, Ebisu S. Effect of endodonticirrigation on bonding of resin cement to radicular dentin. Eur J Oral Sci2005;113:70 – 6.
1. Braga RR, Ferracane JL. Alternative in polymerization contraction stress manage-
ment. Crit Rev Oral Biol Med 2004;15:176 – 84.JOE — Volume 34, Number 5, May 2008
