Influence of a hydrophobic resin coating on the immediate and 6-month dentin bonding of three universal adhesives

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Available online at www.sciencedirect.com

ScienceDirect journal homepage: www.intl.elsevierhealth.com/journals/dema

Influence of a hydrophobic resin coating on the immediate and 6-month dentin bonding of three universal adhesives ˜ c, Ana Sezinando a , Issis Luque-Martinez b , Miguel Angel Munoz Alessandra Reis d , Alessandro D. Loguercio d , Jorge Perdigão e,∗ a

Department of Stomatology and Nursing, Health Sciences Faculty, Rey Juan Carlos University, Alcorcón, Madrid, Spain b Dentistry Academic Unit, Faculty of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile c School of Dentistry, Universidad de Valparaíso, Valparaíso, Chile d School of Dentistry, Department of Restorative Dentistry, State University of Ponta Grossa, Ponta Grossa, Paraná, Brazil e Department of Restorative Sciences, University of Minnesota, Minneapolis, MN, USA

a r t i c l e

i n f o

a b s t r a c t

Article history:

Objective. To test the influence of a hydrophobic resin coating (HC) on the immediate (24h)

Received 25 November 2014

and 6-month (6m) microtensile dentin bond strengths (␮TBS) and nanoleakage (NL) of three

Received in revised form 1 June 2015

universal adhesives applied in self-etch (SE) or in etch-and-rinse (ER) mode.

Accepted 8 July 2015

Methods. Sixty caries-free extracted third molars were assigned to 12 experimental groups

Available online xxx

resulting from the combination of the factors “adhesive system” (Scotchbond Universal Adhesive [SBU], 3M ESPE; All-Bond Universal [ABU], Bisco Inc.; and G-Bond Plus [GBP], GC

Keywords:

Corporation); “adhesive strategy” (SE or ER); “hydrophobic resin coating” [HC] (with or with-

Microtensile bond strength

out Heliobond, Ivoclar Vivadent); and “storage time” (24h or 6m). Specimens were prepared

Nanoleakage

for ␮TBS testing – (24h) half of the beams were immediately tested under tension; and

Dental bonding

(6m) the other half was stored in distilled water (37 ◦ C) for 6m prior to testing. For each

Hydrophobic resin coat

tooth, two beams were randomly selected for NL evaluation for both evaluation times. Data

Universal adhesive systems

were analyzed for each adhesive system using three-way ANOVA and Tukey’s post-hoc test (˛ = 0.05). Results. TBS: (24h): In SE mode, HC resulted in statistically greater mean ␮TBS for all adhesives. (6m): When HC was not used the mean ␮TBS for SBU/ER, ABU/ER, GBP/ER and SBU/SE decreased significantly. NL: (24h): SBU/ER, ABU/ER and GBP/SE resulted in a significant reduction in NL when HC was applied. (6m): No significant reduction was observed for SBU/ER or for SBU/SE regardless of the use of HC. Significance. The application of a hydrophobic resin coating improved the 24h and the 6m performances of all three adhesives systems in SE mode. © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

∗ Corresponding author at: Department of Restorative Sciences, University of Minnesota, 515 SE Delaware St, 8-450 Moos Tower, Minneapolis, MN 55455, USA. Tel.: +1 (612) 625 5432; fax: +1 (612) 625 7440. E-mail address: [email protected] (J. Perdigão).

http://dx.doi.org/10.1016/j.dental.2015.07.002 0109-5641/© 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Please cite this article in press as: Sezinando A, et al. Influence of a hydrophobic resin coating on the immediate and 6-month dentin bonding of three universal adhesives. Dent Mater (2015), http://dx.doi.org/10.1016/j.dental.2015.07.002

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1.

Introduction

The new simplified universal adhesives can be used as 2-step etch-and-rinse [ER] or as 1-step self-etch [SE] adhesives. This dual strategy is accomplished by using 1-step SE adhesives associated or not with previous phosphoric acid (PA) etching, which gives dentists a more versatile and attractive adhesive system that can also be used in selective etching mode [1–3]. PA etching, the first step in the ER strategy, removes the smear layer and demineralizes a few micrometers of the dentin surface [4]. After the removal of hydroxyapatite from the interfibrillar spaces, resin monomers infiltrate those spaces and impregnate collagen fibrils, leading to the formation of a thick hybrid layer of collagen and resin within the dentin substrate [5]. Dentin hybridization in simplified ER adhesives is a sensitive technique due to the potential for discrepancy between the etching depth and the effective adhesive impregnation of the exposed collagen fibril network [6,7]. SE adhesives, however, do no require preliminary PA etching, as dentin demineralization and priming may occur simultaneously [8]. The simultaneous etching and infiltration of SE adhesives into dentin does occur for all SE adhesives [9,10]. The idea of using the same adhesive solution for either adhesive strategy is not new. In fact, the application of PA with earlier versions of SE adhesives has resulted in debatable results [11–13], which may be a consequence of specific adhesive composition and technical application of the same adhesive under ER and SE strategies [14,15]. The inclusion of hydrophilic monomers in the composition of simplified adhesives has increased substantially within recent years with the objective of making these adhesives compatible with the inherently wet dentin substrate. The degradation potential of resin–dentin interfaces formed with hydrophilic simplified adhesives has been shown to enhance due to residual solvents and water entrapped in the polymer. In fact, water droplets are formed in 1-step SE adhesives as a result of water absorption from dentin through osmosis [16]. Water entrapment may hinder the formation of cross-linked polymers. This may occur via water-filled, nanometer-sized voids formed as a result of a decrease in the degree of conversion of the adhesive. A low degree of conversion affects the stability of the resin–dentin interface due to the elution on unreacted monomers and consequent formation of a porous hybrid layer [17,18]. One-step SE adhesives result in a thinner adhesive layer, being more susceptible to polymerization inhibition by oxygen [19]. The suboptimal polymerization is a drawback related to the use of universal adhesives as 1-step SE adhesives. A clinical alternative is the application of an additional layer of a hydrophobic resin coating (HC) over the polymerized simplified adhesive [20]. This extra resin coat aims at increasing the thickness and uniformity of the adhesive layer, as well as reducing the fluid flow across the adhesive interface [21]. Excellent in vitro and clinical results have been reported after placement of a HC over 1-step SE adhesives [22,23]. Additionally, promising results in terms of bond strength, nanoleakage, and degree of conversion inside the hybrid layer, have been recently reported for universal adhesives [24].

However, to the extent of our knowledge, studies on the longevity of this technique have not been carried out. The aim of this study was to evaluate the immediate (24h) and 6-month (6m) microtensile bond strength (␮TBS) and nanoleakage (NL) of universal adhesive systems used in the ER and SE approaches with or without an additional HC. The null hypotheses tested were that the use of an additional HC would not improve: (1) the immediate and 6-month bond strengths of universal adhesives used as ER or SE and; (2) the immediate and 6-month nanoleakage of resin–dentin interfaces formed with universal adhesives used as ER or SE.

2.

Material and methods

Sixty caries-free extracted human third molars were disinfected in 0.5% chloramine, stored in distilled water and used within 6 months after extraction. The teeth were collected after obtaining the patients’ informed consent under a protocol approved by the local Ethics Committee Review Board. A flat occlusal dentin surface was exposed in all teeth after wet-grinding the occlusal enamel with # 180 grit SiC paper. The exposed dentin surfaces were further polished with wet # 600-grit silicon-carbide paper for 60 s to standardize the smear layer [25].

2.1.

Experimental design and specimen preparation

The teeth were randomly assigned to 12 experimental conditions resulting from the combination of the factors “adhesive system” (Scotchbond Universal Adhesive [SBU, 3M ESPE, St. Paul, MN, USA – also known as Single Bond Universal in some countries], All-Bond Universal [ABU, Bisco Inc, Schaumburg, IL, USA], and G-Bond Plus [GBP, GC Corporation Tokyo, Japan – also known as G-ænial Bond]) (Table 1); “adhesive strategy” (ER or SE); “hydrophobic resin coating” [HC] (with or without, Heliobond, Ivoclar Vivadent, Schaan, Liechtenstein); and “storage time” (24h or 6m). The adhesive systems were applied according to the respective manufacturers’ instructions (Table 1), except for GBP, for which the manufacturer does not recommend dentin etching with phosphoric acid. Furthermore, the respective manufacturers do not recommend the application of HC (Table 1). Composite resin crowns were built with a nanofilled composite resin (Filtek Z350 XT, 3M ESPE, St. Paul, MN, USA; also named Filtek Supreme XTE or Filtek Supreme Plus) in two increments of 2 mm each. Each increment was light-cured for 40 s using a LED light-curing unit set at 1200 mW/cm2 (Radiical, SDI Limited, Bayswater, Victoria, Australia). After storage in distilled water for 24h at 37 ◦ C, the specimens were sectioned longitudinally in mesio-distal and buccal-lingual directions across the bonded interface with a slow-speed diamond saw (Isomet, Buehler Ltd., Lake Bluff, IL, USA) to obtain resin–dentin beams with a cross sectional area of approximately 0.8 mm2 measured with a digital caliper (Digimatic Caliper, Mitutoyo, Tokyo, Japan). Half of the beams from each tooth were used in the immediate time (24h) for the ␮TBS test, except two specimens that were randomly selected for measurement of NL. The other half were stored in distilled

Please cite this article in press as: Sezinando A, et al. Influence of a hydrophobic resin coating on the immediate and 6-month dentin bonding of three universal adhesives. Dent Mater (2015), http://dx.doi.org/10.1016/j.dental.2015.07.002

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Table 1 – Adhesive systems (batch number), chemical composition and application mode. Materials (batch number)

Composition

Application mode SE Without HC

Heliobond (N37749)

Scotchbond Universal Adhesive – SBU (448716)

All-Bond Universal – ABU (1200002722)

G-Bond Plus – GBP (1102221)

ER With HC

Without HC

With HC

bis-GMA, TEGDMA, initiators, stabilizers

1. Etchant: 32% phosphoric acid, water, synthetic amorphous silica, polyethylene glycol, aluminum oxide (Scotchbond Universal Etchant) 2. Adhesive: MDP phosphate monomer, dimethacrylate resins, HEMA, methacrylatemodified polyalkenoic acid copolymer, filler, ethanol, water, initiators, and silane 1. Etchant: 35% phosphoric acid, benzalkonium chloride, xanthan gum (SELECT HV-Etch) 2. Adhesive: MDP, bis-GMA, HEMA, ethanol, water, initiators

Acetone, dimethacrylate, 4 methacryloxyethyltrimellitate anhydride, phosphoric acid ester monomer, silicon dioxide, photo initiator, distilled water Note: The manufacturer does not recommend dentin conditioning with phosphoric acid

1. Apply the adhesive to the entire preparation with a microbrush and rub it in for 20 s 2. Direct a gentle stream of air over the liquid for about 5 s until it no longer moves and the solvent is evaporated completely 3. Light-cure for 10 s

1. Apply two separate coats of adhesive, scrubbing the preparation with a microbrush for 10–15 s per coat. Do not light cure between coats 2. Evaporate excess solvents by thoroughly air-drying with an air syringe for at least 10 s, there should be no visible movement of the material. The surface should have a uniform glossy appearance 3. Light cure for 10 s 1. Apply using a microbrush 2. Leave undisturbed for 10 s after the end of application 3. Dry thoroughly for 5 s with oil free air under maximum air pressure. Use vacuum suction to prevent splatter of the adhesive 4. Light-cure for 10 s

1. Apply the same self-etch mode 2. Apply a very thin layer of Heliobond with a microbrush on the dental surface 3. An air blower to achieve an optimally thin layer 4. Light-cure for 10 s

1. Apply etchant for 15 s 2. Rinse for 10 s 3. Air dry 5 s 4. Apply adhesive as for the self-etch mode

1. Apply the same etch-and-rinse mode 2. Apply a very thin layer of Heliobond with a microbrush on the dental surface 3. An air blower to achieve an optimally thin layer 4. Light-cure for 10 s

1. Apply the same self-etch mode 2. Apply a very thin layer of Heliobond with a microbrush on the dental surface 3. An air blower to achieve an optimally thin layer 4. Light-cure for 10 s

1. Apply etchant for 15 s 2. Rinse thoroughly 3. Remove excess water with absorbent pellet or high volume suction for 1–2 s 4. Apply adhesive as for the self-etch mode

1. Apply the same etch-and-rinse mode 2. Apply a very thin layer of Heliobond with a microbrush on the dental surface 3. An air blower to achieve an optimally thin layer 4. Light-cure for 10 s

1. Apply the same self-etch mode 2. Apply a very thin layer of Heliobond with a microbrush on the dental surface 3. An air blower to achieve an optimally thin layer 4. Light-cure for 10 s

1. Apply 32% phosphoric acid gel (Scotchbond Universal Etchant) for 10 s 2. Rinse for 5 s and gently dry 3. Apply adhesive as for the self-etch mode

1. Apply the same etch-and-rinse mode 2. Apply a very thin layer of Heliobond with a microbrush on the dental surface 3. An air blower to achieve an optimally thin layer 4. Light-cure for 10 s

bis-GMA = bisphenol glycidyl methacrylate; TEGDMA = tryethylene glycol dimethacrylate; MDP = methacryloyloxydecyl dihydrogen phosphate; HEMA = 2-hydroxyethyl methacrylate.

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Fig. 1 – Representative backscattered SEM images of resin–dentin interfaces of each experimental group at 24h (Co = composite resin; AL = adhesive layer; HL = hybrid layer; De = dentin). For SBU/ER and ABU/ER, a decrease in NL was observed when HC was used (B, E) compared with the respective controls (A, E). ABU/ER (E) resulted in higher silver nitrate infiltration at the bottom of the HL and resin tags compared with ABU/SE (G), for which a more linear deposition was observed at the base of the HL. For SBU/SE and ABU/SE, NL was observed despite the use of HC (arrows) (C, D, G, H). GBP/ER, with or without HC (I, J), and GBP/SE, without HC (K), resulted in abundant deposition of silver nitrate throughout the HL and resin tags, (arrows). NL deposition in the AL was observed as water-trees (pointer). GBP/SE with HC showed lower nanoleakage, which was similar to that of SBU/SE and ABU/SE, both with HC (D, HL). When used in SE mode with HC, all three adhesives resulted in globular deposition of silver nitrate at the base of the HL (arrows) (D, HL).

water (37 ◦ C) for 6m and tested for ␮TBS and NL in the same way.

2.2.

Microtensile bond strength (TBS)

The resin–dentin bonded beams were attached to a custommade grooved jig (Odeme, Biotechnology, Joac¸aba, SC, Brazil) with cyanoacrylate adhesive and tested under tension (Model 5565, Instron Co., Canton, MA, USA) at 0.5 mm/min until failure. The ␮TBS values were calculated by dividing the load at failure by the cross-sectional bonding area. The failure mode was classified as cohesive [C] failure (exclusively within dentin or resin composite), adhesive [A] failure (at the resin/dentin interface), or mixed [M] failure (at the resin/dentin interface that included cohesive failure of the neighboring substrates). The failure mode analysis was performed under a stereomicroscope at 100× magnification (Olympus SZ40, Tokyo, Japan). Specimens with premature failures (PF) were included in the tooth mean as 0 MPa and those with cohesive failures were excluded to avoid mean ␮TBS bias [26]. The ␮TBS values (MPa) of all beams from the same tooth were averaged for statistical purposes.

2.3.

Nanoleakage (NL)

Two resin-bonded beams from each tooth were used for NL evaluation. The beams were placed in an ammoniacal silver nitrate solution in darkness for 24 h [27], rinsed thoroughly in distilled water, and immersed in photo developing solution for 8 h under a fluorescent light to reduce silver ions into metallic silver grains. Specimens were polished with wet 600-, 1000-, 1200-, 1500-, 2000- and 2500-grit SiC paper and 0.25 ␮m diamond paste (Buehler Ltd., Lake Bluff, IL, USA) using a polishing cloth. Specimens were then ultrasonically cleaned, air dried, mounted on Al stubs, and coated with carbon-gold (MED 010, Balzers Union, Balzers, Liechtenstein). Resin–dentin interfaces were analyzed in a field-emission scanning electron microscope operated in the backscattered mode (LEO 435 VP, LEO Electron Microscopy Ltd., Cambridge, UK). Three micrographs of each resin–dentin bonded beam were obtained [28]. The first micrograph was taken in the center of the beam. The other two micrographs were taken 0.3 mm to the left and right of the first micrograph. A blinded operator measured the relative percentage of NL of the adhesive interface in each micrograph with the UTHSCSA ImageTool 3.0 software (University of Texas Health Science Center, San

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Fig. 2 – Representative backscattered SEM images of resin–dentin interfaces of each experimental group at 6m (Co = composite resin; AL = adhesive layer; HL = hybrid layer; De = dentin). Ageing specimens for 6m resulted in silver nitrate deposition for all adhesives regardless of the use of HC or of the adhesive strategy. However, NL decreased for SBU and ABU when HC was used compared with the respective controls (A, E, C, G), independently of the bonding strategy (B, F, D, H). Silver deposition occurred at the base of the HL (arrows). A dendritic pattern was depicted within the AL when ABU/ER was applied without HC (E). GBP resulted in greater NL at the base of the HL and resin tags (arrows) (I, J, L). Dendritic depositions within the AL were observed (J), as well glomerular-like spots (L) (pointer) and water-trees (K).

Antonio, TX, USA). The values originating from the same specimen were averaged for statistical purposes. The mean NL (%) of all beams from the same tooth was averaged for statistical purposes.

2.4.

Statistical analysis

The Kolmogorov–Smirnov test was used to assess whether the data followed a normal distribution. The Barletts’ test was computed to determine if the assumption of equal variances was valid. After observing the normality of the data distribution and the equality of the variances, data from ␮TBS (MPa) and NL (%), were analyzed separately for each adhesive system using three-way repeated measures ANOVA having the “adhesive strategy”, “hydrophobic resin coating” and “storage time” as independent variables. Tukey’s post-hoc multiple comparison test was used for pairwise comparisons at a level of significance of 5%.

3.

Results

The fracture pattern is shown in Table 2. Most specimens resulted in adhesive failures (Table 2).

3.1.

Microtensile bond strength (TBS)

3.1.1.

24h

For the ER strategy, HC resulted in statistically lower mean ␮TBS for ABU (Table 3; p = 0.001). There was no significant change in mean ␮TBS for SBU and for GBP (Table 3; p = 0.78 and p = 0.82, respectively). For the SE strategy, HC resulted in statistically greater mean ␮TBS for all three adhesives (Table 3; p = 0.00007 for ABU, p = 0.0003 for GBP, p = 0.01 for SBU).

3.1.2.

6m

For the ER strategy, 6m of water storage reduced significantly mean ␮TBS for all three adhesives when HC was not used (Table 3; p = 0.001 for ABU, p = 0.003 for GBP, p = 0.007 for SBU). When HC was applied, mean ␮TBS were significantly lower at 6m than at 24h only for SBU (Table 3; p = 0.002). For ABU and GBP, no significant changes in mean ␮TBS were observed from the 24h to 6m when HC was used (Table 3; p = 0.94 and p = 0.84, respectively). For the SE strategy, 6m of water storage reduced significantly mean ␮TBS only for SBU when HC was not used (Table 3; p = 0.01). When HC was used with SBU, the 6m mean ␮TBS were statistically similar to those obtained at 24h (Table 3; p = 0.32). For ABU and GBP, there was no statistical difference between mean ␮TBS obtained in 24h and those

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Table 2 – Number (%) of specimens according to fracture pattern mode for each experimental group. Adhesive system

Application mode

HC

Storage time

Fracture pattern A

SBU ER

SE

ABU ER

SE

GBP ER

SE

C

A/M

PF

Without With Without With Without With Without With

24h 24h 6m 6m 24h 24h 6m 6m

50 (72.5) 52 (73.2) 45 (70.3) 47 (82.5) 56 (77.8) 55 (84.6) 59 (83.1) 43 (68.3)

1 (1.4) 0 (0.0) 3 (4.7) 0 (0.0) 2 (2.8) 0 (0.0) 4 (5.6) 2 (3.2)

16 (23.3) 18 (25.4) 12 (18.8) 8 (14.0) 10 (13.9) 8 (12.3) 7 (9.9) 13 (20.6)

2 (2.8) 1 (1.4) 4 (6.2) 2 (3.5) 4 (5.5) 2 (3.1) 1 (1.4) 5 (9.6)

Without With Without With Without With Without With

24h 24h 6m 6m 24h 24h 6m 6m

54 (80.6) 46 (70.8) 60 (72.3) 49 (75.3) 62 (79.5) 55 (74.4) 52 (80.2) 48 (82.8)

0 (0.0) 1 (1.5) 0 (0.0) 2 (3.1) 0 (0.0) 1 (1.4) 4 (5.4) 0 (0.0)

10 (14.9) 17 (26.2) 18 (21.7) 12 (18.5) 11 (14.1) 14 (18.9) 15 (20.3) 6 (10.3)

3 (4.5) 1 (1.5) 5 (6.0) 2 (3.1) 5 (6.4) 4 (5.4) 3 (4.1) 4 (6.9)

Without With Without With Without With Without With

24h 24h 6m 6m 24h 24h 6m 6m

58 (76.3) 54 (74.0) 43 (59.7) 61 (75.3) 53 (67.9) 43 (66.2) 54 (69.2) 59 (78.7)

4 (5.3) 6 (8.2) 6 (8.3) 8 (9.9) 5 (6.4) 3 (4.6) 5 (6.4) 7 (9.3)

8 (10.6) 11 (15.1) 15 (20.8) 7 (8.6) 16 (20.6) 12 (18.4) 19 (24.4) 4 (5.3)

6 (7.8) 2 (2.7) 8 (11.1) 5 (6.2) 4 (5.1) 7 (10.8) 0 (0.0) 5 (6.7)

A – adhesive fracture mode; C – cohesive fracture mode; A/M – adhesive/mixed fracture mode; PF – premature failure.

Table 3 – Microtensile bond strength (␮TBS) values (means ± standard deviations) of the different experimental groups* . Adhesive system

ER

SE

Without HC

SBU ABU GBP ∗

With HC

Without HC

With HC

24h

6m

24h

6m

24h

6m

24h

33.1 ± 4.1 B 41.1 ± 4.1 b 21.2 ± 4.1a

26.8 ± 3.6 C 32.2 ± 4.0 d 15.4 ± 2.7b

35.8 ± 4.6 B 35.2 ± 3.8 c,d 20.3 ± 3.4a

28.3 ± 3.6 C 38.4 ± 3.7 b,c 22.1 ± 3.8a

35.1 ± 3.4 B 24.1 ± 3.5 e 12.1 ± 3.9b,c

30.5 ± 4.5 C 23.9 ± 6.0 e 9.5 ± 2.4c

40.2 ± 6.1 A 47.3 ± 4.9 a 23.1 ± 5.1a

6m 36.2 ± 4.5 A,B 44.9 ± 5.4 a,b 24.5 ± 3.7a

Comparisons are valid only within rows. Means identified with the identical capital, lower case or superscript letters are statistically similar (p > 0.05).

obtained at 6m (Table 3; p = 0.78 and p = 0.98, respectively), regardless of the use of HC.

3.2.

Nanoleakage (NL)

3.2.1.

24h

SBU in ER or SE mode after 6m water storage regardless of the use of HC (Table 4; p > 0.32).

4. For the ER strategy significant reductions in 24h NL were observed for SBU and ABU when HC was applied (Table 4; p = 0.001 and p = 0.003, respectively) (Fig. 1). There was no significant change in mean NL values for GBP (Table 4; p = 0.96). For the SE strategy, the application of HC resulted in reduced 24h NL only for GBP (Table 4; p = 0.0001). There was no significant change in mean NL for SBU and for ABU (Table 4; p = 0.92 and p = 0.46, respectively).

3.2.2.

6m

For the ER strategy only ABU showed a significant increase in NL (Table 4; p = 0.003) after 6m water storage when HC was used (Fig. 2). No significant reduction in NL was observed for

Discussion

Bonding degradation typically occurs with hydrophilic simplified adhesives [29,30]. The demineralized collagen fibrils are vulnerable to time-dependent hydrolytic degradation by water, regardless of the bonding strategy. When the exposed collagen is not fully encapsulated by the polymerized adhesive monomers, nano-channels are left within the hybrid layer and/or demineralized dentin [31,32], disclosing areas of NL. Adhesive interfaces formed by simplified ER and SE adhesives behave as permeable membranes [33,34]. Once cured, SE adhesives allow transudation of dentinal fluid to the surface where it accumulates as droplets. However, degradation is less frequent when a more hydrophobic solvent-free adhesive coating is used [35,36]. HC has been shown to reduce

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Table 4 – Nanoleakage (NL) values (means ± standard deviations) of the different experimental groups* . Adhesive system

ER

SE

Without HC

SBU ABU GBP ∗

With HC

Without HC

With HC

24h

6m

24h

6m

24h

6m

24h

5.2 ± 3.0 B 9.3 ± 3.1 c 15.1 ± 4.1b,c

5.6 ± 2.1 B 10.3 ± 2.2 c 18.0 ± 2.9c

1.1 ± 2.0 A 4.2 ± 2.1 a 16.3 ± 3.6b,c

3.3 ± 2.3 A,B 9.4 ± 3.4 c 12.0 ± 2.8a,b

5.5 ± 3.5 B 6.2 ± 3.1 a,b 35.2 ± 5.8e

5.9 ± 3.5 B 7.0 ± 2.9 b 46.1 ± 6.2f

6.2 ± 3.4 B 9.1 ± 3.1 b,c 6.4 ± 3.4a

6m 4.9 ± 3.7 B 6.3 ± 2.9 a,b 23.1 ± 4.6d

Comparisons are valid only within rows. Means identified with the identical capital, lower case or superscript letters are statistically similar (p > 0.05).

the potential for hydrolytically degradation of the bonds and increase the longevity of resin–dentin interfaces both in vitro and in vivo [22,23,35–37]. An increase in silver penetration over time is correlated with a decrease in mean ␮TBS [38], but the issue is controversial [6,35]. In our study, a statistically significant cross-product interaction was observed for all adhesive systems, suggesting a strong relationship between “storage time” and “hydrophobic coating”. A 6-month in vitro evaluation of four adhesive systems, representing the four bonding strategies (3- and 2step etch-and- rinse; 2-and 1-step self-etch), from the same manufacturer, showed that aging stability was materialdependent [39]. However, adhesive systems that included a HC were more stable in water storage [39]. This study also revealed that a simplified self-etch adhesive outperformed the “golden standard” etch-and-rinse adhesive, which may indicate a tendency to improvements in chemistry of newest adhesives [40]. Our results are in line with these findings, as two of the three adhesives (SBU, ABU) reached mean ␮TBS as high as those of other contemporary adhesives, for either bonding strategy [41]. In our study, the use of HC did not improve the 24h or the 6m mean ␮TBS for any of the adhesives in ER mode. However, when HC was omitted, 6m of water storage reduced significantly mean ␮TBS for all three adhesives compared to 24h mean ␮TBS. This finding highlights the protective role that a HC may have on the adhesive interface when dentin is etched with phosphoric acid. In fact, both adhesives for which the respective manufacturer recommends the ER strategy, SBU and ABU, resulted in lower 24h NL when HC was used. For the SE strategy, the use of HC resulted in statistically greater immediate mean ␮TBS for all three adhesives. However, at 6m SBU/SE mean ␮TBS were significantly reduced when HC was not used. When HC was applied, the 6m mean ␮TBS were statistically similar to those obtained at 24h. For the other two adhesives, ABU and GBP, there was no statistical difference between mean ␮TBS obtained at 24h and those obtained at 6m, regardless of the use of HC. SBU was the first universal adhesive [2], which makes this adhesive the most prevalent universal adhesive in the peerreviewed literature [2,3,42–44]. An interesting observation is that mean ␮TBS for SBU/ER at 24h versus 6m showed a similar reduction, with or without HC. The same tendency was observed for SBU/SE without HC. Furthermore, NL was statistically similar in all SBU groups, with the exception for the significant reduction measured in SBU/ER with HC. A low variability may be indicative of low technique sensitivity of SBU

[45]. In fact, the application mode or the degree of dentin moisture did not influence dentin ␮TBS of SBU in another study [2]. Additionally, the 18-month clinical performance of SBU in non-carious cervical lesions did not depend on the bonding strategy nor on the degree of dentin moisture [44]. The results of these two studies corroborate our findings. However, mean ␮TBS were generally higher [2] than those obtained in our study (SBU/SE = 54.4 MPa; SBU/ER, moist dentin = 54.0 MPa; SBU/ER, dry dentin = 53.9 MPa), which may be a consequence of operator variability [46]. Different experimental methodology, as 1 mm/min cross-head speed, may have resulted in a more uniform stress distribution [38]. One may think that SBU is more forgiving to variability in clinical procedures. Perdigão et al. speculated that the low variability of SBU might be due to its water content (10–15% by Wt) [2]. Water may plasticize the collapsed collagen network allowing re-expansion of the spatial interfibrillar spaces, and subsequent infiltration of resin monomers [47]. Water is an important component of 1-step self-etch adhesives as it allows their ionization and permeation through the smear layer and underlying mineralized dentin [14,15]. However, the intrinsic hydrophilicity of self-etch adhesives jeopardizes their in vitro [45] and clinical performance [48]. The application of HC over SBU improved 24h and 6m mean ␮TBS for the SE strategy. However, no differences were observed between 24h and 6m mean ␮TBS for the ER strategy when compared to the group without HC. SBU is an “ultra-mild” self-etch adhesive (pH 2.7), with a two-fold bonding ability: (1) mechanical-interlocking on dentin surface and (2) chemical interaction [49]. Stable calcium-methacryloyloxydecyl dihydrogen phosphate (MDP) complexes [50,51] form within the partial demineralized dentin through nano-layering [52]. A second additional chemical mechanism is associated to the interaction of a polyalkenoic acid co-polymer (also known as Vitrebond co-polymer, or VCP) with calcium in hydroxyapatite [53]. This self-adhesiveness may be responsible for the excellent long-term performance of polyakenoic-based materials [41,54,55]. As SBU, ABU is a “ultra-mild” MDP-containing 1-step selfetch adhesive (pH 3.1) that can chemically interact with calcium in hydroxyapatite [51]. However, ABU does not have a polyalkenoic acid copolymer, such as VCP, in its composition. The relevance of VCP was recently studied using ␮TBS [56]. The lack of the additional chemical bonding provided by VCP may be the reason why mean ␮TBS where lower for ABU/SE than for SBU/SE.

Please cite this article in press as: Sezinando A, et al. Influence of a hydrophobic resin coating on the immediate and 6-month dentin bonding of three universal adhesives. Dent Mater (2015), http://dx.doi.org/10.1016/j.dental.2015.07.002

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It is believed that the composition and the resulting mechanical strength of the adhesives are better predictors for the immediate bond strength than the acidity of the adhesive [57]. But chemical composition may be responsible for extent of diffusion-induced water movement and the amount of water within resin–dentin interfaces in the long-term [58]. When comparing manufacturers’ instructions, both ABU and GBP resulted in higher bond strength when applied in ER mode than in SE mode. These findings are in accordance with a previous in vitro study [3]. The smear layer removal through the etching step may have improved the impregnation of the hybrid layer by the universal adhesives ABU and GBP [3]. HC resulted in greater mean ␮TBS of SBU/SE and ABU/SE at 24h. The thickness of the adhesive layer may have increased [23] allowing the formation of a more densely packed hybrid layer with improved mechanical properties [21]. The HC also increased the 6m mean ␮TBS of SBU/SE and ABU/SE, which may have been a result of enhanced adhesive layer hydrophobicity. The adhesive layer becomes less permeable to water movement, and less susceptible to water degradation [23]. Coating with a hydrophobic layer may couple more unsolvated hydrophobic monomers to the adhesive interface through copolymerization with the uncured adhesive surface, decreasing the relative concentration of retained solvent and unreacted monomers, thus enhancing the in situ degree of conversion. The mean ␮TBS did not significantly decrease after 6m of water storage in the presence of the HC for the three adhesives studied. The monomer conversion continues after the polymerization process has finished, due to continuous propagation of free radicals, independently of the water storage conditions [59]. The hydrophobic layer may have protected the post-polymerization process. In a previous report, a 2-step mild self-etch adhesive (OptiBond XTR, Kerr Co., Orange, CA, USA) resulted in higher mean ␮TBS after 6 month water aging, in the same magnitude than the self-etch “golden standard” Clearfil SE Bond [39]. This may have been a result of the presence of the hydrophobic resin step in the 2-step self-etch adhesive, besides and a potential chemical bonding between a functional monomer molecule (GPDM, glycerol phosphate dimethacrylate) with calcium in hydroxyapatite. GBP is a HEMA-free 1-step 4-MET-derived self-etch adhesive, with a pH 1.5 [24]. GBP is not recommended in ER mode on dentin. However, we decided to experimentally apply GBP on phosphoric acid etched dentin, as some etching gels may inadvertently overflow to dentin during clinical procedures when selective enamel etching is used. GBP/SE resulted in statistically greater mean ␮TBS compare to GBP/ER without HC, which validates the respective manufacturer’s recommendation for not etching dentin, as well as, recently showed in the literature [24]. Regardless of the application mode, GBP had the poorest performance even when coated with HC. These findings are in agreement with previous studies [1,24]. Although Hanabusa et al. reported similar bond strengths for ER and SE strategies, they also reported a low-quality hybridization in the ER mode for GBP, specifically a resin-infiltrated collagen network with signs of adhesive incomplete infiltration [1]. Both SBU and ABU are HEMA-containing adhesives (Table 1), in opposition to GBP, which is a HEMA-free adhesive.

HEMA is a hydrophilic monomer added to self-etch adhesives to enhance dentin wettability and monomer infiltration [40] and prevent hydrophobic monomer/water phase separation [60]. The incorporation of poly-HEMA in the polymer network enhances water uptake after polymerization [40], due to poly-HEMA hydrolytic degradation and elution of by-products during long-term storage [61]. HEMA-containing adhesives are more hydrophilic and have higher water sorption [62]. In longterm water storage, the reduction in the tensile strength of adhesives increases with their hydrophilicity, reducing their mechanical properties [62,63]. The exclusion of HEMA within GBP composition has been suggested to have the potential of reducing the adhesive hydrophilic properties and, consequently, to avoid the decline in mechanical properties due to water sorption [61]. Water sorption and ultimate tensile strength of HEMA-free adhesives do not significantly change with water storage [61]. However, HEMA-free formulations do not produce bond strengths as higher as those of HEMAcontaining adhesives [26,64], which is in agreement with the results of our study. The paradox is that, to reach the acidic pH that allows the self-etching capability, hydrophilic properties cannot be avoided. In fact, acidic self-etch formulations (low pH as in GBP) need more hydrophilic and acidic resins blends [62]. The relatively low pH of 1.5 in GBP allows a more aggressive enamel and dentin demineralization [24,65] with less hydroxyapatite available for chemical interaction with the 4-MET, resulting in lower mean ␮TBS. If compared with the 10-MDP functional monomer, 4-MET is less hydrolytically stable [66], which also applies to the resulting 4-MET calcium complexes [67]. The 4MET functional monomer is not able to chemically interact with calcium in hydroxyapatite through nano-layering [67]. The lack chemical bonding to calcium by 4-MET may have been responsible for the lower mean ␮TBS of GBP/SE compared to those of GBP/ER. Furthermore, GBP has acetone as organic solvent, which might contribute to a higher susceptibility to the degree of moisture in dentin [1,62]. The performance of GBP improved after the application of HC. The GBP’s inherent hydrophilic nature may have been reduced by HC allowing a higher in situ degree of conversion [24]. However, we observed severe increase of NL within the hybrid layer for GBP/SE, which may have been a result of the hydrolysis of the phosphoric acid ester monomer, which may have caused dentin demineralization over time [10]. The instructions for use of GBP may have to be revised. The instructions for both SBU and ABU clearly state that these two universal adhesives must be applied actively, with two consecutive coats for ABU. Active application [68,69], double application [6,23,62,70], and a greater infiltration time [58] are known to improve the performance of self-etch adhesives. The manufacturer of GBP recommends applying GBP passively, with 10 s of infiltration compared to 20 s for SBU and 10–15 s for ABU, which may have adversely affected the interaction of GBP with dentin. GBP also resulted in higher nanoleakage with a water-tree pattern in the adhesive layer, characteristic of HEMA-free adhesives due to phase separation and residual water on the dentin surface [27]. The dendritic pattern may also have been a result of phase separation. When we analyzed the NL results for ER and SE, at 24h and 6m we were unable to find a cause–effect relationship from

Please cite this article in press as: Sezinando A, et al. Influence of a hydrophobic resin coating on the immediate and 6-month dentin bonding of three universal adhesives. Dent Mater (2015), http://dx.doi.org/10.1016/j.dental.2015.07.002

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the application of HC, as it occurred for ␮TBS. Some reductions were observed within groups with HC (SBU/ER, ABU/ER, GBP/SE). Immediate NL may be more related to the adhesive infiltration and sealing capability. It is well known that the quality of the resin–dentin bonds is affected by the extent of resin infiltration into the exposed collagen [6,58,71]. But in long-term water storage, the absorbed water in the polymerized adhesive causes gradual hydrolytic degradation, elution of the products and loss of collagen integrity [71]. For ER, peritubular hybridization of the resin tags may not occur. For SE, the weakest zone in aged specimens is below the hybrid layer, due to poorer polymerization of the monomers within the bottom of the hybrid layer [71]. These findings corroborate our NL pattern observations for both ER and SE modes. Even if resin hydrolysis may negatively affect the longterm bonding stability, collagen depletion may also occur due to enzymatic degradation. The activation of matrix metalloproteinases (MMP’s) is induced by adhesive chemical formulations on both mineralized and demineralized dentin, regardless of the bonding strategy [43]. However, MMP’s degradation is believed to be more destructive for ER hybrid layers than for mild SE hybrid layers, as SE adhesives bond to dentin with less demineralization [72]. The ABU etching gel contains benzalkonium chloride (BAC), that due to its antimicrobial properties and inhibition of MMP-2, -8, -9 activities, decreases resin–dentin interface degradation [73]. BAC might have contributed to the relative stable NL observed for ABU/ER with and without HC, at 24h compared to 6m. We partially failed to accept the first null hypothesis as the additional HC statistically improved mean ␮TBS at 24h and 6m, except for immediate mean ␮TBS in the ER mode. We failed to reject the second null hypothesis as the additional HC resulted in a decrease in NL for both storage times independent of the bonding strategy. Further in vitro experiments should be carried out to better understand the hydrolytic instability and degradation mechanism of universal adhesives on dentin. Furthermore, some modifications in the instructions for use should be considered to improve the performance of the specific universal adhesives used in this project.

5.

Conclusion

Within the limitation of this study, it was concluded that an extra hydrophobic layer coating improved the immediate and long-term in vitro performance (␮TBS and NL) of the universal adhesive systems studied in SE mode. However, NL pattern is material-dependent and aging stability seems not to be related with the adhesive strategy.

references

[1] Hanabusa M, Mine A, Kuboki T, Momoi Y, Van Ende A, Van Meerbeek B, et al. Bonding effectiveness of a new ‘multi-mode’ adhesive to enamel and dentine. J Dent 2012;40:475–84. [2] Perdigão J, Sezinando A, Monteiro PC. Laboratory bonding ability of a multi-purpose dentin adhesive. Am J Dent 2012;25:153–8.

xxx.e9

[3] Munoz MA, Luque I, Hass V, Reis A, Loguercio AD, Bombarda NH. Immediate bonding properties of universal adhesives to dentine. J Dent 2013;41:404–11. [4] Pashley DH. The effects of acid etching on the pulpodentin complex. Oper Dent 1992;17:229–42. [5] Van Meerbeek B, Inokoshi S, Braem M, Lambrechts P, Vanherle G. Morphological aspects of the resin-dentin interdiffusion zone with different dentin adhesive systems. J Dent Res 1992;71:1530–40. [6] Hashimoto M, De Munck J, Ito S, Sano H, Kaga M, Oguchi H, et al. In vitro effect of nanoleakage expression on resin-dentin bond strengths analyzed by microtensile bond test, SEM/EDX and TEM. Biomaterials 2004;25:5565–74. [7] Vaidyanathan TK, Vaidyanathan J. Recent advances in the theory and mechanism of adhesive resin bonding to dentin: a critical review. J Biomed Mater Res B Appl Biomater 2009;88:558–78. [8] De Munck J, Van Landuyt K, Peumans M, Poitevin A, Lambrechts P, Braem M, et al. A critical review of the durability of adhesion to tooth tissue: methods and results. J Dent Res 2005;84:118–32. [9] Carvalho RM, Chersoni S, Frankenberger R, Pashley DH, Prati C, Tay FR. A challenge to the conventional wisdom that simultaneous etching and resin infiltration always occurs in self-etch adhesives. Biomaterials 2005;26:1035–42. [10] Wang Y, Spencer P. Continuing etching of an all-in-one adhesive in wet dentin tubules. J Dent Res 2005;84: 350–4. [11] Van Landuyt KL, Peumans M, De Munck J, Lambrechts P, Van Meerbeek B. Extension of a one-step self-etch adhesive into a multi-step adhesive. Dent Mater 2006;22:533–44. [12] Erhardt MC, Osorio E, Aguilera FS, Proenca JP, Osorio R, Toledano M. Influence of dentin acid-etching and NaOCl-treatment on bond strengths of self-etch adhesives. Am J Dent 2008;21:44–8. [13] Proenca JP, Polido M, Osorio E, Erhardt MC, Aguilera FS, Garcia-Godoy F, et al. Dentin regional bond strength of self-etch and total-etch adhesive systems. Dent Mater 2007;23:1542–8. [14] Van Meerbeek B, Van Landuyt K, De Munck J, Hashimoto M, Peumans M, Lambrechts P, et al. Technique-sensitivity of contemporary adhesives. Dent Mater J 2005;24:1–13. [15] Perdigão J. New developments in dental adhesion. Dent Clin North Am 2007;51:333–57. [16] Van Landuyt KL, Snauwaert J, De Munck J, Coutinho E, Poitevin A, Yoshida Y, et al. Origin of interfacial droplets with one-step adhesives. J Dent Res 2007;86:739–44. [17] Breschi L, Mazzoni A, Ruggeri A, Cadenaro M, Di Lenarda R, De Stefano Dorigo E. Dental adhesion review: aging and stability of the bonded interface. Dent Mater 2008;24:90–101. [18] Reis A, Carrilho M, Breschi L, Loguercio AD. Overview of clinical alternatives to minimize the degradation of the resin-dentin bonds. Oper Dent 2013;38:E1–25. [19] Nunes TG, Ceballos L, Osorio R, Toledano M. Spatially resolved photopolymerization kinetics and oxygen inhibition in dental adhesives. Biomaterials 2005;26:1809–17. [20] King NM, Tay FR, Pashley DH, Hashimoto M, Ito S, Brackett WW, et al. Conversion of one-step to two-step self-etch adhesives for improved efficacy and extended application. Am J Dent 2005;18:126–34. [21] de Andrade e Silva SM, Carrilho MR, Marquezini Junior L, Garcia FC, Manso AP, Alves MC, et al. Effect of an additional hydrophilic versus hydrophobic coat on the quality of dentinal sealing provided by two-step etch-and-rinse adhesives. J Appl Oral Sci 2009;17:184–9. [22] Reis A, Leite TM, Matte K, Michels R, Amaral RC, Geraldeli S, et al. Improving clinical retention of one-step self-etching adhesive systems with an additional hydrophobic adhesive layer. J Am Dent Assoc 2009;140:877–85.

Please cite this article in press as: Sezinando A, et al. Influence of a hydrophobic resin coating on the immediate and 6-month dentin bonding of three universal adhesives. Dent Mater (2015), http://dx.doi.org/10.1016/j.dental.2015.07.002

DENTAL-2593; No. of Pages 11

ARTICLE IN PRESS

xxx.e10

d e n t a l m a t e r i a l s x x x ( 2 0 1 5 ) xxx.e1–xxx.e11

[23] Reis A, Albuquerque M, Pegoraro M, Mattei G, Bauer JR, Grande RH, et al. Can the durability of one-step self-etch adhesives be improved by double application or by an extra layer of hydrophobic resin? J Dent 2008;36:309–15. ˜ [24] Perdigão J, Munoz MA, Sezinando A, Luque-Martinez IV, Staichak R, Reis A, et al. Immediate adhesive properties to dentin and enamel of a universal adhesive associated with a hydrophobic resin coat. Oper Dent 2014;39:489–99. [25] Pashley DH, Tao L, Boyd L, King GE, Horner JA. Scanning electron microscopy of the substructure of smear layers in human dentine. Arch Oral Biol 1988;33:265–70. [26] Zander-Grande C, Loguercio AD, Stanislawczuk R, Martins GC, Gomes OM, Reis A. The effect of 6-month water storage on the bond strength of self-etch adhesives bonded to dentin. Am J Dent 2011;24:239–44. [27] Tay FR, Pashley DH, Yoshiyama M. Two modes of nanoleakage expression in single-step adhesives. J Dent Res 2002;81:472–6. [28] Reis A, Grande RH, Oliveira GM, Lopes GC, Loguercio AD. A 2-year evaluation of moisture on microtensile bond strength and nanoleakage. Dent Mater 2007;23:862–70. [29] Hashimoto M, Fujita S, Kaga M, Yawaka Y. In vitro durability of one-bottle resin adhesives bonded to dentin. Dent Mater J 2007;26:677–86. [30] Osorio R, Pisani-Proenca J, Erhardt MC, Osorio E, Aguilera FS, Tay FR, et al. Resistance of ten contemporary adhesives to resin-dentine bond degradation. J Dent 2008;36: 163–9. [31] Sano H, Shono T, Takatsu T, Hosodo H. Microporous dentin zone beneath resin-impregnated layer. Oper Dent 1994;19:59–64. [32] Sano H, Takatsu T, Ciucchi B, Horner JA, Matthews WG, Pashley DH. Nano-leakage: leakage within the hybrid layer. Oper Dent 1995;20:18–25. [33] Tay FR, Pashley DH, Suh BI, Carvalho RM, Itthagaruna A. Single-step adhesive are permeable membranes. J Dent 2002;30:371–82. [34] Tay FR, Pashley DH. Have dentin adhesives become too hydrophilic? J Can Dent Assoc 2003;69:726–31. [35] Gamborgi GP, Loguercio AD, Reis A. Influence of enamel border and regional variability on durability of resin-dentin bonds. J Dent 2007;35:371–6. [36] Abdalla AI, Feilzer AJ. Four-year water degradation of a total-etch and two self-etching adhesives bonded to dentin. J Dent 2008;36:611–7. [37] Feitosa VP, Leme AA, Sauro S, Correr-Sobrinho L, Watson TF, Sinhoreti MA, et al. Hydrolytic degradation of the resin-dentine interface induced by the simulated pulpal pressure, direct and indirect water ageing. J Dent 2012;40:1134–43. [38] Poitevin A, De Munck J, Van Landuyt K, Coutinho E, Peumans M, Lambrechts P, et al. Critical analysis of the influence of different parameters on the microtensile bond strength of adhesives to dentin. J Adhes Dent 2008;10:7–16. [39] Sezinando A, Perdigão J, Regalheiro R. Dentin bond strengths of four adhesion strategies after thermal fatigue and 6-month water storage. J Esthet Restor Dent 2012;20: 345–55. [40] Van Landuyt KL, Snauwaert J, De Munck J, Peumans M, Yoshida Y, Poitevin A, et al. Systematic review of the chemical composition of contemporary dental adhesives. Biomaterials 2007;28:3757–85. [41] Peumans M, Kanumilli P, De Munck J, Van Landuyt K, Lambrechts P, Van Meerbeek B. Clinical effectiveness of contemporary adhesives: a systematic review of current clinical trials. Dent Mater 2005;21:864–81. [42] Perdigao J, Loguercio AD. Universal or multi-mode adhesives: why and how? J Adhes Dent 2014;16:193–4.

[43] Marchesi G, Frassetto A, Mazzoni A, Apolonio F, Diolosà M, Cadenaro M, et al. Adhesive performance of a multi-mode adhesive system: 1-year in vitro study. J Dent 2014;42: 603–12. [44] Perdigão J, Kose C, Mena-Serrano AP, De Paula EA, Tay LY, Reis A, et al. A new universal simplified adhesive: 18-month clinical evaluation. Oper Dent 2014;39:113–27. [45] Van Landuyt KL, Mine A, De Munck J, Jaecques S, Peumans M, Lambrecths P, et al. Are one-step adhesives easier to use and better performing? Multifactorial assessment of contemporary one-step self-etching adhesives. J Adhes Dent 2009;11:175–90. [46] Heintze SD, Rousson V. Pooling of dentin microtensile bond strength data improves clinical correlation. J Adhes Dent 2011;13:107–10. [47] Maciel KT, Carvalho RM, Ringle RD, Preston CD, Russel CM, Pashley DH. The effects of acetone, ethanol, HEMA, and air on the stiffness of human decalcified dentin matrix. J Dent Res 1996;75:1851–8. [48] Perdigão J, Dutra-Corrêa M, Anauate-Netto C, Castilhos N, Carmo AR, Lewgoy HR, et al. Two-year clinical evaluation of self-etching adhesives in posterior restorations. J Adhes Dent 2009;11:149–59. [49] Peumans M, De Munck J, Van Landuyt KL, Poitevin A, Lambrechts P, Van Meerbeek B. Eight-year clinical evaluation of a 2-step self-etch adhesive with and without selective enamel etching. Dent Mater 2010;26:1176–84. [50] Perdigão J, Reis A, Loguercio AD. Dentin adhesion and MMPs: a comprehensive review. J Esthet Restor Dent 2013;25: 219–41. [51] Yoshihara K, Yoshida Y, Hayakawa S, Nagaoka N, Torii Y, Osaka A, et al. Self-etch monomer-calcium salt deposition on dentin. J Dent Res 2011;90:602–6. [52] Yoshida Y, Yoshihara K, Nagaoka N, Hayakawa S, Torii Y, Ogawa T, et al. Self-assembled nano-layering at the adhesive interface. J Dent Res 2012;91:376–81. [53] Fukuda R, Yoshida Y, Nakayama Y, Okazaki M, Inoue S, Sano H, et al. Bonding efficacy of polyalkenoic acids to hydroxyapatite, enamel and dentin. Biomaterials 2003;24:1861–7. [54] Mitra SB, Lee CY, Bui HT, Tantbirojn D, Rusin RP. Long-term adhesion and mechanism of bonding of a paste-liquid resin-modified glass-ionomer. Dent Mater 2009;25:459–66. [55] Trairatvorakul C, Itsaraviriyakul S, Wiboonchan W. Effect of glass-ionomer cement on the progression of proximal caries. J Dent Res 2010;90:99–103. [56] Perdigão J, Sezinando A, Monteiro PC. Effect of substrate age and adhesive composition on dentin bonding. Oper Dent 2013;38:267–74. [57] Ikeda T, De Munck J, Shirai K, Hikita K, Inoue S, Sano H, et al. Effect of fracture strength of primer-adhesive mixture on bonding effectiveness. Dent Mater 2005;21:413–20. [58] Hashimoto M, Tay FR, Sano H, Kaga M, Pashley DH. Diffusion-induced water movement within resin-dentin bonds during bonding. J Biomed Mater Res B Appl Biomater 2006;79:453–8. [59] Ye Q, Spencer P, Wang Y, Misra A. Relationship of solvent to the photopolymerization process, properties, and structure in model dentin adhesives. J Biomed Mater Res A 2007;80:342–50. [60] Van Landuyt KL, De Munck J, Snauwaert J, Coutinho E, Poitevin A, Yoshida Y, et al. Monomer-solvent phase separation in one-step self-etch adhesives. J Dent Res 2005;84:183–8. [61] Ito S, Hashimoto M, Wadgaonkar B, Svizero N, Carvalho RM, Yiu C, et al. Effects of resin hydrophilicity on water sorption and changes in modulus of elasticity. Biomaterials 2005;26:6445–59.

Please cite this article in press as: Sezinando A, et al. Influence of a hydrophobic resin coating on the immediate and 6-month dentin bonding of three universal adhesives. Dent Mater (2015), http://dx.doi.org/10.1016/j.dental.2015.07.002

DENTAL-2593; No. of Pages 11

ARTICLE IN PRESS d e n t a l m a t e r i a l s x x x ( 2 0 1 5 ) xxx.e1–xxx.e11

[62] Takahashi M, Nakajima M, Hosaka K, Ikeda M, Foxton RM, Tagami J. Long-term evaluation of water sorption and ultimate tensile strength of HEMA-containing/free one-step self-etch adhesive. J Dent 2011;39:506–12. [63] Malacarne J, Carvalho R, de Goes M, Svizero N, Pashley D, Tay F, et al. Water sorption/solubility of dental adhesive resins. Dent Mater 2006;22:973–80. [64] Cantanhede de Sá RB, Oliveira Carvalho A, Puppin-Rontain RM, Ambrosano GM, Nikaido T, Tagami J, et al. Effects of water storage on bond strength and dentin sealing ability promoted by adhesive systems. J Adhes Dent 2012;14: 543–9. [65] Tay FR, Pashley DH. Aggressiveness of contemporary self-etching systems. I: Depth of penetration beyond dentin smear layers. Dent Mater 2001;17:296–308. [66] Inoue S, Koshiro K, Yoshida Y, De Munck J, Nagakane K, Suzuki K, et al. Hydrolytic stability of self-etch adhesives bonded to dentin. J Dent Res 2005;84:1160–4. [67] Yoshihara K, Yoshida Y, Nagaoka N, Fukegawa D, Hayakawa S, Mine A, et al. Nano-controlled molecular interaction at adhesive interfaces for hard tissue reconstruction. Acta Biomater 2010;6:3573–82.

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[68] do Amaral RC, Stanislawczuk R, Zander-Grande C, Michel MD, Reis A, Loguercio AD. Active application improves the bonding performance of self-etch adhesives to dentin. J Dent 2009;37:82–90. [69] Loguercio AD, Stanislawczuk R, Mena-Serrano A, Reis A. Effect of 3-year water storage on the performance of one-step self-etch adhesives applied actively on dentine. J Dent 2011;39:578–87. [70] Taschner M, Kümmerling M, Lohbauer U, Breschi L, Petschelt A, Frankenberger R. Effect of double-layer application on dentin bond durability of one-step self-etch adhesives. Oper Dent 2014;39:416–26. [71] Kim J, Mai S, Carrilho MR, Yiu CK, Pashley DH, Tay FR. An all-in-one adhesive does not etch beyond hybrid layers. J Dent Res 2010;89:482–7. [72] Zheng P, Zaruba M, Attin T, Wiegand A. Effect of different matrix metalloproteinase inhibitors on microtensile bond strength of an etch-and-rinse and a self-etching adhesive to dentin. Oper Dent 2015;40:80–6. [73] Tezvergil-Mutluay A, Mutluay MM, Gu LS, Zhang K, Agee KA, Carvalho RM, et al. The anti-MMP activity of benzalkonium chloride. J Dent 2011;39:57–64.

Please cite this article in press as: Sezinando A, et al. Influence of a hydrophobic resin coating on the immediate and 6-month dentin bonding of three universal adhesives. Dent Mater (2015), http://dx.doi.org/10.1016/j.dental.2015.07.002