Nanoleakage Evaluation of Resin Luting Systems to DentalEnamel and Leucite-Reinforced CeramicLUCIA TRAZZI PRIETO,1 EDUARDO JOSE SOUZA-JUNIOR,2 CINTIA TEREZA PIMENTA ARAUJO,1,4

ADRIANO FONSECA LIMA,1 CARLOS TADEU DIAS,3 AND LUIS ALEXANDRE MAFFEI SARTINI PAULILLO1*1Department of Restorative Dentistry, Piracicaba Dental School, State University of Campinas, SP-Brazil, Avenida Limeira, 901,Areiao, 13414-903, Piracicaba, SP, Brazil2Department of Restorative Dentistry, Dental Materials Division, Piracicaba Dental School, State University of Campinas, SP-BrazilAvenida Limeira, 901, Areiao, 13414-903, Piracicaba, SP, Brazil3Department of Statistical Mathematics, Luiz de Queiroz Higher School of Agriculture of the University of Sao Paulo (Esalq/USP),Avenida Padua Dias, 11—Piracicaba, SP, Brazi4Department of Dentistry, Faculty of Sciences of Health, Federal University of Jequitinhonha and Mucuri Valley -UFVJM, Diamantina,Minas Gerais, Brazil

KEY WORDS ceramic; adhesive system; enamel; nanoleakage; resin cement

ABSTRACT Purpose: The aim of this study was to evaluate the nanoleakage patterns betweendental enamel and reinforced leucite ceramic, bonded with resin luting systems and a flowablecomposite resin. Materials and Methods: Twelve crowns of bovine incisors were randomly dividedinto four groups (n 5 3) according to the luting procedure: Excite/Variolink II, Clearfil SE Bond/Panavia F, Scotchbond Multi-Purpose Plus/RelyX ARC, and Single Bond 2/Filtek Z350 Flow. Toevaluate the nanoleakage patterns, IPS Empress Esthetic disks (5 mm Ø and 1.2-mm thick) werebonded to enamel, and, after 24 h, the specimens were immersed in a 50% (w/v) solution of silvernitrate (24 h), fixed, dehydrated, and processed scanning electron microscopy (SEM). Results: Nonenanoleakage on interface of the groups that Single Bond 2 followed by the flowable composite wereused. The highest percentage of nanoleakage was shown by the Excite/Variolink II protocol. Also,in all conditions tested, none silver nitrate uptake was observed between the leucite-reinforced ce-ramic and the resin luting cement. Conclusions: The use of a two-step etch-and-rinse adhesivewith flowable composite was able to promote an adequate seal of the bond interface at the enamel.Moreover, the conventional dual-cured resin cements associated with simplified and dual-curedadhesives tested are also indicated to bond thin ceramics to enamel, since all presented low silvernitrate uptake. Microsc. Res. Tech. 00:000–000, 2011. VVC 2011 Wiley Periodicals, Inc.

INTRODUCTION

With the development of the adhesive dentistry,resin luting strategies have been widely used to bondindirect restorations to tooth structures. In this way,the dual-cured resin system aims to improve the poly-merization through the indirect restorations, since thelight attenuation caused by the ceramic can jeopardizethe degree of conversion of the luting materials. How-ever, the dual resin cements may have the originalcolor changed, due to oxidation of the amine compo-nent. This fact can compromise the final estheticappearance of the restoration, especially in cases ofthin ceramic veneers (Karaagaclioglu and Yilmaz,2008). To avoid this, some authors have suggested lut-ing thin ceramic veneers with flowable resin compo-sites (Moon et al., 2002). Flowable composites are light-cured materials, with a lower amount of amine coini-tiators, which may not affect the final esthetic appear-ance of the ceramic restoration over time.

The resinous luting approach traditionally requiresthe use of adhesive agents, which can be either total-etching or self-etching systems. The bond systems pre-senting a hydrophobic resin layer, such as the three-step etch-and-rinse and two-step self-etch, candecrease the adhesive film permeability, favoring bondstability over time (Carrilho et al., 2009; Reis et al.,

2008) Also, solvated bonding systems can compromisethe quality of the hybrid layers, due to the inferiorpolymer matrix formed, decreasing the bonding per-formance to dental substrate (Carrilho et al., 2009; Tayet al., 2003).

To evaluate the sealing ability of restoration by adhe-sive material and the quality of the polymer formed,nanoleakage is an important indicator (Sano et al.,1995). Based mainly on this technique, many studiesevaluating nanoleakage patterns for several bondingsystems (and their influence on bonding parameters)have been performed (Makishi et al., 2010; Reis et al.,2007, 2010). Silver nitrate has been accepted as a suit-able method for measuring interfacial leakage (Mala-carne-Zanon et al., 2010; Reis et al., 2007; Sano et al.,1995) due to the size of the silver ion dyes (0.059-nm di-ameter) compared to the size of a typical bacterium(0.5–1.0 nm). The small size of particles and the high,binding tightly to any exposed collagen fibrils not

*Correspondence to: Prof. Dr. Luıs Alexandre Maffei Sartini Paulillo, Depart-ment of Restorative Dentistry, Piracicaba School of Dentistry, State University ofCampinas—UNICAMP, Av: Limeira—Areiao. CEP: 13414-903, Piracicaba, SP,Brazil. E-mail: lapaulillo@gmail.com

Received 29 May 2011; accepted in revised form 26 September 2011

DOI 10.1002/jemt.21110

Published online inWiley Online Library (wileyonlinelibrary.com).

VVC 2011 WILEY PERIODICALS, INC.

MICROSCOPY RESEARCH AND TECHNIQUE 00:000–000 (2011)

enveloped by the adhesive resin, makes silver nitratethe most appropriate agent to detect the nanoporositieswithin the hybrid layer (Carrilho et al., 2007).

As there is no ideal material to bond indirect restora-tions to enamel, appropriate selection of these resinluting systems, according to the different clinical situa-tions, is required. Thus, the aim of this study was toevaluate the nanoleakage patterns of resin luting sys-tems, bonded to dental enamel and leucite-reinforcedceramic. The hypothesis tested was that the flowablecomposite would provide an effective seal for veneer ce-ramic cementation compared to the dual-cured resincements.

MATERIALS AND METHODSSpecimen Preparation

Twelve bovine incisors were selected, cleaned, andstored in 0.01% thymol solution at 378C for 2 weeks.The root was sectioned using a low-speed, double-faceddiamond saw (Isomet 1000, Buehler, Lake Bluff, IL).The buccal surface was ground flat with 400-, 600-, and1,200-grit aluminum oxide papers (Carborundum,Saint-Gobain Abrasives, Guarulhos, SP, Brazil), underconstant water-cooling. Next, the specimens were ran-domly distributed in experimental groups according tothe luting procedures (adhesive systems/resin cement):G1—Excite /Variolink II (EX/VR—Ivoclar-Vivadent,Schaan, Lietschestein); G2—Clearfil SE Bond/Panavia

F (CSE/PN—Kuraray, Tokyo, Japan); G3—AdperScotchbond Multi-Purpose Plus/RelyX ARC (SBMP/RX—3M/ESPE, St Paul, MN); G4—Adper Single Bond2/Filtek Z350 Flow (SB/FL—3M/ESPE). The composi-tion of the resin cements and adhesive systems arelisted in Tables 1 and 2. The adhesive systems andresin cements were applied following manufacturer’sinstructions, and are described in Table 3.

Ceramic disks (5-mm diameter, 0.6-mm-thick leu-cite-reinforced ceramic, and 0.6-mm-thick feldspar ce-ramic, totaling a ceramic specimen 1.2-mm thick) wereetched for 60 s using a 10% hydrofluoridric acid(Dentsply Caulk, Midford, DE), followed by silane(Monobond S, Ivoclar Vivadent, Schaan, Lietschestein)application for 60 s. The specimens were bonded toenamel surface, according to the manufacturer’sinstructions.

Nanoleakage Evaluation

After 24 h of the luting procedure, specimens werelongitudinally sectioned using a diamond saw. Next,each specimen was immersed in a 50% ammoniac sil-ver nitrate solution for 24 h in the dark at 378C (Tayet al., 2002). Afterward, the specimens were thor-oughly rinsed in distilled water for 2 min andimmersed in a photo-developing solution for 8 h (KodakDeveloper D--76-Kodak Brasileira Ind. e Com Ltda.,Sao Jose dos Campos, SP, Brazil) under fluorescent

TABLE 2. Adhesive systems used in the study with composition and manufacturer’s information

Adhesive systems Composition Manufacturer

ED Primer (Batch #01441) Primer A (Batch #00272A): 2-hydroxyethyl methacrylate (HEMA), MDP,NM-aminosalicylic acid, diethanol-p-toluidine, water. Primer B (Batch#00147A): NM-aminosalicylic acid, T-isopropilic benzenic sodium sulfinate,diethanol-p-toluidine, water

Kuraray Medical,Tokyo, Japan

Excite (Batch #1177) Phosphonic acid acrylate, HEMA, Bis-GMA, methacrylates, silicon dioxide,ethanol, catalysts and stabilizers

Ivoclar Vivadent,Schaan,Lietchtestein

Adper Single Bond 2(Batch #9XB)

Dimethacrylates, HEMA, Polyalkenoid acid copolymer, 5-nm silane-treatedcolloidal silica, ethanol, water, photoinitiator

3M ESPE, St Paul,Minesota, USA

Clearfil SE Bond Primer (Batch #00896A): water, MDP, HEMA, camphorquinone, hydrophilicdimethacrylate. Adhesive (Batch #01320A): MDP, bis-GMA, HEMA,camphorquinone, hydrophobic dimathacrylate, N,N-diethanol p-toluidine bond,colloidal silica.

Kuraray MedicalInc., Tokyo, Japan

Adper Scotchbond MultiPurpose (Batch #356B)

Primer:HEMA, water, copolymer of polycarboxilic acid. Adhesive: Bis-GMA,HEMA, polyalkenoic acid copolymer, CQ, EDMAB, DHEPT.

3M ESPE, St Paul,Minesota, USA

TABLE 1. Resin cements used in the study with composition and manufacturer’s information

Resin cements Composition Manufacturer

Variolink II (Batch#01441)

Base: Bis-GMA, UDMA and TEGDMA, barium glass, ytterbium trifluoride, glassfluorsilicate barium and aluminum oxides mixed spheroid. Catalyst: Bis-GMA, UDMAand TEGDMA, ytterbium trifluoride, glass and aluminum fluorsilicate barium andspheroid mixed oxide, benzoyl peroxide, stabilizer.

Ivoclar Vivadent,Schaan,Lietchtestein

RelyX ARC (Batch#GU9JG)

Paste A: Silane treated ceramic, Bis-GMA, TEGDMA, photoinitiators, amine, silanetreated silica, functionalized dimethacrylate polymer. Paste B: silane treated ceramic,TEGDMA, Bis-GMA, silane treated silica, benzoil peroxide, functionalizeddimethacrylate polymer.

3M ESPE, St Paul,Minesota, USA

Filtek Z350 flow(Batch:#N124855)

Matrix: BisGMA, TEGDMA, dimethacrylate polymer. Fillers: 47% zirconia/sılicafillers

3M ESPE, St Paul,Minesota, USA

Panavia F (Batch#00027B)

Paste A: 10-MDP, hydrophobic aromatic dimethacrylate, hydrophobic aliphaticdimethacrylate, hydrophilic dimethacrilate, silanated sılica, photoinitiators, dl-camphoroquinone, benzoil peroxide. Paste B: hydrophobic aromatic dimethacrylate,hydrophobic aliphatic dimethacrylate, hydrophilic dimethacrylate. Sodium aromaticsulfinate, accelerator, sodium fluoride, silanated barium glass.

Kuraray Medical,Tokyo, Japan

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2 L.T. PRIETO ET AL.

light, to reduce silver ions to metallic silver grainsalong bonded interface, adhesive resin, and cementpolymeric structure. Then, the stained specimens wereembedded in a polystyrene resin, and were wet-pol-

ished sequentially with aluminum oxide papers (600-,1,200-, and 2,000-grit) and felt disc with diamond pasteof decreasing grain (3.1 and 0.25 lm) using a metallo-graphic polisher (PL02, Arotec Equip, SP, Brazil). Thespecimens were immersed in distilled water and placedin ultrasonic baths (Ultrasone D 1440—OdontobrasInd. E Com Med Odont. Ltda., Rio Preto, Brazil) for 10min, after each step of the polishing procedure.

Next, the specimens were dried with absorbentpapers and immersed in a solution of 50% phosphoricacid for 10 s, followed by rinsing in distilled water. Fordeproteinization, a 10% solution of sodium hypochlo-rite was used for 10 min. After this, the specimenswere rinsed and dried at room temperature (2 h) anddehydrated with ethanol at increasing concentrationsof 25, 50, 75, 90, and 100%, for 10-min each. The speci-mens were carbon coated (Bal-Tec SCD-050—Sputter-Coater) and analyzed in a scanning electron micro-scope (SEM—JEOL JSM—V 5600 LV, Tokyo, Japan),at 15 kV. The images of silver-infiltrated specimenswere taken to calculate the marked area using com-puter software Image Tool 3.0 (University of Texas,Health Science Center at San Antonio, TX). The inter-face length between enamel/adhesive and ceramic/resin cement was measured, and the percentage of theinfiltrated area calculated.

RESULTSNanoleakage Patterns

Descriptive analysis of the nanoleakage patternswas performed, as SEM evaluation showed a low per-centage of silver nitrate uptake; in most situations itwas 0%, excluding the statistical analysis. After analy-sis of the bonding interface between ceramic and resincement, none nanoleakage was observed in any speci-mens. Figures 1–4 show the bonded interface with sil-ver nitrate uptake (magnification 3200 and 31,400).Table 4 shows the percent values of nanoleakage at theenamel/adhesive interface. The association of Excite/Variolink showed higher silver nitrate uptake underthe adhesive layer (Fig. 1), followed by Clearfil SE

TABLE 3. Procedures for cementing systems adhesion

Luting systems Procedures for cementing

Adhesive system 1) Acid etching of enamel with 35%phosphoric acid (15 s) and washing withdistilled water for 15 s

Excite 2) Application of the adhesive system onenamel

Resin cement 3) Mild air streamVariolink 4) Light curing for 20 s(Ivoclar-Vivadent) 5) Mix of resin cement pastes (base 1

catalyst for 15 s)6) Light curing for 40 s.

Adhesive system 1) Primer application on enamel surface(Clearfil SE Bond) for 30 s

Clearfil SE bond 2) Bond application (Clearfil SE Bond) andlight curing for 10 s

ED primer 3) Application of the primer (Clearfil SEBond) 1 Porcelain Bond Activator mix for1 minute on ceramic surface for 1 min.

Resin cement 4) Mix of ED Primer A e B, and applicationon the adhesive layer on enamel

Panavia F 5) Mix of resin cement (20 s)(Kuraray) 6) Light curing for 40 sAdhesive system 1) Acid etching with 35% phosphoric acid

(15 s), and washing with distilled water(15 s)

Scotchbondmulti-uso Plus

2) Application of Activador Scotchbond andmild air stream (5 s)

Resin cement 3) Application of primer agent and air spray(5 s)

RelyX ARC 4) Catalyst application in ceramic surfaceand enamel

(3M/ESPE) 5) Mix of the resin cement (10 s)6) Light curing for 40 s.

Adhesive system 1) Acid etching with 35% phosphoric acid(15 s), and washing with distilled waterfor 15 s

Single bond 2) Application of two consecutives layer ofadhesive system

Resin Filtek Flow 3) Light curing for 10 s(3M/ESPE). 4) Application of the flowable resin

5) Light curing for 40 s.

Fig. 1. SEM photomicrography showing nanoleakage for the luting system Excite/Variolink II. (A)Can be noted as a silver deposition between the enamel and adhesive layer (arrows—3200). (B) Regionwith the silver infiltrated in the adhesive layer (31,400).

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3BONDING AND LEAKAGE TO ENAMEL/CERAMICS INTERFACE

Fig. 2. (A) Few points of silver deposition can be observed in the interface of Clearfil SE/Panavia(arrows—3200). (B) Region with the silver infiltrated points in the adhesive layer (arrows—31,400).

Fig. 3. (A) Interface Scotchbond MP Plus/ RelyX ARC showing silver deposition in few regions(arrows—3200). (B) The silver infiltrated can be noted in increased magnification (arrows—31,400).

Fig. 4. (A and B) Absence of silver deposition in the interface of flowable resin even in high magnifi-cation (3200 and31,400).

Microscopy Research and Technique

4 L.T. PRIETO ET AL.

Bond/Panavia F and Scotchbond Multi-Purpose Plus/RelyX ARC, which show few points of silver nitratepenetration in the adhesive layer (Figs. 2 and 3). Theflowable composite did not present nanoleakage pat-terns on the bond interface (tooth/adhesive; Fig. 4).

DISCUSSION

The luting systems selected for this study are suita-ble for fixing ceramic with different compositions. How-ever, the dual-cure resin cements can cause color alter-ation, due to the oxidation of the tertiary amine, lead-ing to color change of the prosthetic restorations(especially thin ceramic veneers), compromising the es-thetic appearance (Ghavam et al., 2010). Moreover,some manufacturers of flowable composite resin recom-mend this resin for luting thin indirect restorations. Inlight of these facts, the objective of the present studywas to compare the adhesive/flowable composite resinefficacy, a color-stable material, with different dual-cure luting systems, used for indirect restorations.

When the nanoleakage patterns between the leucite-reinforced ceramic and the resinous cements were eval-uated, no silver-tracing solution was found. This mightbe explained by the fact that some ceramic surfacetreatments, such as fluoridric acid etch, silanization,(Fabianelli et al., 2010) and, the application of a hydro-phobic resin layer (Naves et al., 2010) after the silani-zation approach, can guarantee adequate bonding andsealing ability, preventing the infiltration of silver ionsinside this interface.

Concerning nanoleakage evaluation, imagesobtained by SEM shown little or none penetration ofsilver nitrate at the bonding interfaces betweenenamel-luting systems, in most of the samples eval-uated. In this sense, the results of this study showedthat the hypothesis tested (that the flowable compositeresin could promote effective sealing when used for lut-ing ceramic veneers) was validated, as the interfacebonding agent/flowable resin presented no silveruptake along the interface with enamel.

It should be observed that the silver nitrate penetra-tion was observed in the interface enamel-bondingagent in nearly all specimens analyzed, but notbetween the adhesive system and resin cements. Thisfact demonstrated the reliable compatibility betweenthe systems regardless of the bonding protocol tested.

Although the SB adhesive is more susceptible towater sorption compared to the EX (Malacarne et al.,2006), the first adhesive presented lower silver nitrateuptake. One possible explanation for these results isthe amount of solvent content present in the SB. Thesolvent facilitates the diffusion of the agent into themicromechanical retention on enamel created by theacid etching, promoting better sealing of the interfaceenamel-adhesive.

The high concentration of hydrophobic monomers(BisGMA and UDMA) in EX, viscous monomers withhigh molecular weight (Van Landuyt et al., 2007), com-bined with the low concentration of diluents (HEMA)and solvent (ethanol), increase the viscosity of this ad-hesive, which can reduce the diffusion of the adhesiveto the microretention, decreasing the quality of adhe-sive interlocking, and, consequently, compromises thesealing ability of the adhesive.

The three-step etch-and-rinse and the two-step self-etch adhesives tested present a high amount of hydro-phobic monomers on the bond agent, which could com-promise sealing as with the EX. However, the primerapplication improves the bond penetration into theetched surface, which might explain the resultsobtained for the SBMP and CSE adhesives.

The present study showed that the flowable compos-ite resin associated with a simplified two-step etch-and-rinse bond system promotes better sealing of theceramic–tooth interface, an important factor for thelongevity of tooth veneers. In light of these facts, theuse of flowable resins to bond ceramic laminates shouldbe considered, as this material can provide bothadequate sealing and color stability.

CONCLUSIONS

The luting agents associated with the adhesive sys-tems showed high quality of the bonding to enamel andfew points of silver nitrate infiltration on the adhesiveinterface. The flowable resin is an alternative to lutingthin ceramic veneers to enamel, promoting adequatesealing between ceramic and tooth substrate.

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TABLE 4. Percentual of silver nitrate uptake at the tested groups

Luting system Silver nitrate uptake

Clearfil SE bond/Panavia F 2.30%Excite/Variolink 15.10%Scotchbond multi purpose /RelyX ARC 2.20%Single bond 2/Filtek Z350 Flow 0

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