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Influence of dentin pre-treatment with NaOCl on the morphology of adhesive interface of self-etching adhesive systems
Applied Surface Science 253 (2006) 1929–1933 www.elsevier.com/locate/apsusc
Influence of dentin pre-treatment with NaOCl on the morphology of adhesive interface of self-etching adhesive systems Carina Sincle´r Delfino *, Regina Guenka Palma-Dibb Department of Restorative Dentistry, School of Dentistry of Ribeira˜o Preto, University of Sa˜o Paulo, Ribeira˜o Preto, SP, Brazil Received 15 December 2005; accepted 15 March 2006 Available online 2 May 2006
Abstract The aim of this in vitro study was to evaluate the influence of pre-treatment using NaOCl in the morphology of dentin/resin interface. The three self-etching adhesive systems were selected: One-Up Bond F (Tokuyama, Tokyo, Japan), Prime & Bond NT/NRC (Dentsply, Konstanz, Germany) and Clearfil SE Bond (Kuraray, Osaka, Japan). Nine dentin disks were used in this study. Half disk was treated strictly following manufacturers’ instructions (control groups). The other half was treated with a solution of 2.5% NaOCl (experimental groups). After the bonding protocols were accomplished, a low viscosity resin (Flow-it/Jeneric Pentron) was inserted and light-cured. Specimens were prepared for SEM. Morphological aspects were observed, comparing both the groups. The analysis of the photomicrographs revealed formation of a hybrid layer for both controls groups along the interface. The experimental groups showed a resin/dentin interface more irregular and produced topographical features with funnel-shaped dentin tubules. Areas with absence of hybrid layer formation were observed, mainly for One-Up Bond F, although tubules their lateral branches were filled with Prime & Bond NT/NRC and Clearfil Se Bond adhesive systems. It was concluded that the use of NaOCl influenced negatively in the formation of the hybrid layer, mainly for the One-Up Bond F. # 2006 Elsevier B.V. All rights reserved. Keywords: Hybrid layer; Collagen layer; Sodium hypochlorite
1. Introduction The dentin adhesion does not depend only on the monomer micro-mechanical interaction on the de-mineralized substrate, as it occurs on enamel, but it needs to be diffused in the collagen fibers web, aiming to produce the hybrid layer [1,2]. However, the conditioned dentin shows a region that is more superficial and where a dense collagen web impregnated by monomer is observed, with no mineral contents and, in the subsequent portion can be observed a thin layer where the dentin is partially de-mineralized with hydroxyapatite crystals [1,3]. Even though, the collagen net can be exposed without the de-mineralized portion being completely filled by resin monomers due to the dentin low permeability or monomer diffusion deficiency [4].
* Corresponding author at: Rua Henrique Schaumann, 182, apto. 11, Pinheiros, 05413-010 Sa˜o Paulo, SP, Brazil. Tel.: +55 11 30863320; fax: +55 16 33366669. E-mail address: [email protected] (C.S. Delfino). 0169-4332/$ – see front matter # 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2006.03.037
Thus, a failure in the hydrolysis of collagen fibers not totally enveloped by monomers can happen in the adhesion process. In this way, the removal with sodium hypochlorite of the collagen net, may have some benefits, like dentin permeability increase and dentin composition change, making the surface closer to the surface observed on the conditioned enamel [4], which could increase the adhesive resistance [4,5] and decrease the marginal microleakage [6]. Moreover, another factor to be taken into consideration is that recent studies reported that the collagen layer does not have a direct quantitative contribution to adhesive interface [5,7–10]. This probably occurs due to the resin’s complete diffusion into the partially de-mineralized dentin pores [5,9,10]. Unfortunately, there are no studies that evaluate the interference of NaOCl application before the primer acid conditioning of the self-etching systems, in an attempt to provide a better interaction of these systems to dentin substrate. So, the aim of this in vitro study was to evaluate morphologically the resin/dentin interface using three selfetching adhesive systems after NaOCl treatment of the dentin surface.
1930
C.S. Delfino, R.G. Palma-Dibb / Applied Surface Science 253 (2006) 1929–1933
2. Materials and methods Nine extracted caries-free and non-restored human third molars stored in a 0.5% chloramine solution at 4 8C for up to 1 month after extraction, were used in this study. First, the occlusal overlying enamel was removed. Next, the teeth were individually fixed in a sectioning machine with a water-cooled diamond saw positioned parallel to the occlusal surface, obtaining a 1 mm thick (0.1 mm) disk from middle dentin, which had the bottom surface coated with two layers of cosmetic nail varnish. The disks were bisected and each half was manually ground under water using #120–#400-grit silicon carbide paper to provide a flattened and smooth dentin surface. A #600-grit SiC paper was used for 30 s to produce and standardize the smear layer. The hemi-disks were randomly assigned to three groups of equal size (n = 3), according to the adhesive systems tested (Table 1) and divided into two sub-groups according to the dentin treatment. Each disk was divided in two hemi-sections: one was assigned to the experimental group and other to the control group. The disk bottom surface was coated with two layers of cosmetic nail varnish. The adhesive systems applications were done strictly according to the manufacturer’s directions in one hemi-section (control group). The other hemi-section of the same tooth was treated with 2.5% NaOCl solution (with active application for 2 min, followed by water-rinsing for 1 min) before application of the adhesive (experimental group). Following this, a thin flowable resin layer (Flow-it/Jeneric Pentron) was inserted and photo-polymerized for 40 s by the photo-activating unit tip with a 450 mW/cm2 power output (XL-3000, 3M Dental Products). Specimens were embedded in a chemically activated acrylic resin into a silicone matrix. After resin polymerization, the specimens were sectioned at a 908 angle to the bonding surface and manually smoothened and polished with #1000–#4000-grit SiC paper. All specimens were fixed in a gluteraldehyde solution at 4 8C for 12 h and stored in distilled water for 1 h. The dentin/adhesive interface was conditioned with a 37%
Fig. 1. Resin/dentin interface produced by self-etching adhesive Prime & Bond NT. Well-defined hybrid layer (H.L.) with dentin tubules (T) completely filled with resin (X 3500).
phosphoric acid gel for 10 s, rinsed with distilled water and cleaned with an ultrasound apparatus (Ultrasonic Cleaner T1449-D, Odontobra´s Ind. e Com., Brazil) for 10 min, to remove any residues resulting from the sectioning procedure on the surface. The next step was rinsing the specimens in 10 mL (0.1 M) of a buffer sodium cacodylate solution (7.4 pH) for 1 h, followed by rinsing three times in distilled water for 1 min at 20-min intervals. The specimens were then de-hydrated by ethanol in increasing concentration solutions: 25% (20 min), 50% (20 min), 75% (20 min), 95% (30 min) and 100% (60 min). The last step was the immersion in a HMDS (hexamethyldisilazane) solution for 10 min, drying with absorbing paper, fixing on aluminum stubs and sputter-coated with gold. All adhesive/dentin interfaces were examined under a scanning electron microscope JSMT330A (JEOL Ltd., Tokyo 190-0012, Japan) operating at 15 kV. During the analysis, the dentin/adhesive system interface was photographed in different magnifications of the most representative areas of each group. The photographs were assessed by two previously calibrated
Table 1 Tested adhesive systems Adhesive system
Composition
Manufacturer
Batch number
One-Up Bond F (1 step)
Agent A: 100% methacrylate; Agent B: 74% methacrylate, 10% water, 16% fluoroalumino silicate glass filler Prime & Bond NT: di- and tri-methacrylate resins, acetone, functionalised amorphous silica, PENTA, cetylamine hydrofluoride NRC: organic acids/monomers in aqueous solution Primer: MDP, HEMA, hydrophilic dimethacrylate, water, DL-camphorquinone, NN-diethanol-p-toluidine; bond: MDP, bis-GMA, HEMA, hydrophobic dimethacrylate, DL-camphorquinone, NN diethanol-p-toluidine, silanated colloidal silica
Tokuyama, Tokyo, Japan
A: 034, B: 531
Dentsply, Konstanz,Germany
Prime & Bond NT: 0106001132, NRC: 0103801008
Kuraray, Osaka, Japan
Primer: 00157 A, Bond: 00127A
Prime & Bond NT /NRC (2 steps)
Clearfil SE Bond (2 steps)
C.S. Delfino, R.G. Palma-Dibb / Applied Surface Science 253 (2006) 1929–1933
Fig. 2. Resin/dentin interface produced by self-etching adhesive One-Up Bond F. Thin hybrid layer with absent areas (arrows) along the interface (X3500).
examiners relative to the presence or absence of hybrid layer, its integrity, thickness and homogeneity, as well as the existence of tags, their size, uniformity and disposition. 3. Results
1931
Fig. 4. Adhesive interface One-Up Bond F/dentin treated with NaOCl. Areas with lack of hybrid layer (arrows). Formation resin tags (T) into dentin tubules. Well-defined micro-tags (asterisk) into lateral branches and branch off the main resin (X3500).
Bond F system (Fig. 4), although tubules and lateral ramifications have been completely filled with resin for the Prime & Bond NT/NRC and Clearfil SE Bond (Figs. 5 and 6).
Hybrid layer formation was observed for all the adhesive systems of the control group along the interface, being thicker and better defined for the Prime & Bond NT/NRC adhesive system (Fig. 1) than to the One-Up Bond F system, for in some areas (Fig. 2). The Clearfil SE Bond showed thin and homogenous hybrid layer, and tags of conical form, disposed regularly along the dentin surface and uniform in size were observed (Fig. 3). The experimental groups treated with NaOCl showed a more irregular inter-tubular dentin surface and topographical features comparable to the funnel-shaped dentin tubules. This surface showed areas with lack of hybrid layer, mainly for the One-Up
In the conditions exposed in the present study, the treatment with sodium hypochlorite influenced the hybrid layer formation, being more evident for the One-Up Bond F system which resulted in an interfacial morphology distinct from both studied groups but which presented no hybrid layer in the experimental group. This fact probably occurred because NaOCl, in concentrations varying from 1 to 10%, removes partially the organic portion from dentin superficial [11]. This dissolution action of organic portion can be observed by in the saponification reaction when sodium hypochlorite degrades
Fig. 3. Resin/dentin interface produced by self-etching adhesive Clearfil SE Bond. Hybrid layer (H.L.) with similar features were observed for Prime & Bond NT, although with an evident thickness (X3500).
Fig. 5. Adhesive interface Prime & Bond NT/dentin treated with NaOCl. The collagen was removed clearly revealing ‘‘tubule-wall hybridization’’ with resin tags triangularly (T) extends within the dentin tubules orifice walls and e microtags (asterisk) into lateral branches and branch off the main resin tags (X3500).
4. Discussion
1932
C.S. Delfino, R.G. Palma-Dibb / Applied Surface Science 253 (2006) 1929–1933
Fig. 6. Adhesive interface Clearfil SE Bond/dentin treated with NaOCl. Resin tags (T) into dentin tubules evident with absence of hybrid layer along the interface. Micro-tags (asterisk) into lateral branches and branch off the main resin (X3500).
lipids and fatty acids resulting in the formation soap and glycerol [12] and, consequently, it does not allow hybrid layer formation when adhesive systems are used. However this application can be promoted the increase restoration durability, preventing interface degradation due to non-protected collagen fibers hydrolysis. One-Up Bond F’s medium conditioning may have caused the different behavior between control and experimental groups. As it can be observed, the control group produced a thinner hybrid layer. Kubo et al. [13], reported similar results, in which One-Up Bond F exhibited areas with thin hybrid layer in normal dentin. Even though there is no correlation between hybrid layer thickness and adhesive resistance, the absence or non-uniformity of the hybrid layer could potentially lead to a poorer bond strength and increased likelihood of gap formation [14–16]. Apart from, this several studies reported that self-etching systems promote hybrid layer formation, but the depth of penetration of the acidic primer into the smear layer and dentinal substrate depends upon the thickness and packing density of the smear layer, concentration of the acidic component of the primer, viscosity and wetting characteristics of the primer, the diffusion coefficient of the acidic agent, application time and its pH [17]. Due to its high pH (1.8), OneUp Bond F may not be able to de-mineralize the dentin either removing or modifying the smear layer, compromising the monomer infiltration into the dentin. Primers with pH equal or less than 1.4, probably promote dentin de-mineralization in a more appropriate way [13,17]. On the other hand, Prime & Bond NT/NRC system showed a thicker hybrid layer and increased amount of resin tags in the lateral ramifications in both groups. This system has pH equal or less than 1.0 which, according to Van Meerbeek et al. [18], provides a high conditioning potential, de-mineralizing the smear layer and lower dentin layer, allowing the arise of an ultra-morphological dentin interface, similar to those produced
by total-etching systems, with abundant resin tags formation and a thicker hybrid layer. The Prime & Bond NT/NRC system promoted superficial dentin de-mineralization and the previous application of NaOCl resulted probably in an increase of dentin permeability and, consequently, better adhesive penetration into the substrate, originating a more homogeneous adhesive interface. The collagen removing can improve the adhesive contact to hydroxyapatite crystals [4], due to cleaning effect and the increase of dentin permeability, improving the adhesion [5]. As regards the control group, the conducted study observed results analogous to Tay and Pashley [19], in which the use of self-etching adhesive systems promoted a thin hybrid layer, but totally infiltrated by resin monomers. NaOCl application in the experimental groups removed partially the collagen web, according to Prati et al. [20], in which the collagen was probably only removed at the top of the smear layer when NaOCl was applied to smear layer covered dentin. Inter-tubular dentin surface was more irregular, and the tubule-wall hybridization aspect was evident. Tubule hybridization lateral aspect was observed in all experimental groups too. 5. Conclusion It was concluded that the self-etching adhesive systems promoted hybrid layer formation. However, the previous application of NaOCl influenced its formation, mainly for the One-Up Bond F adhesive system, in which no hybrid layer was observed. More in vivo and in vitro studies are required to elucidate the effectiveness of this treatment. References [1] N. Nakabayashi, K. Kojima, E. Masuhara, The promotion of adhesive by the infiltration of monomers into tooth structures, J. Biomed. Mater. Res. 16 (1982) 265–273. [2] B. Van Meerbeek, S. Inokoshi, M. Braem, P. Lambrechts, G. Vanherle, Morphological aspects of resin–dentin interdiffusion zone with different dentin adhesive systems, J. Dent. Res. 71 (1992) 1530–1540. [3] N. Nakabayashi, M. Ashizawa, M. Nakamura, Identification of a resin– dentin hybrid layer in vital human dentin created in vivo: durable bonding to vital dentin, Quintessence Int. 23 (1992) 135–141. [4] V.P. Saboia, A.L. Rodrigues Jr., L.A.F. Pimenta, Effect of collagen removal on shear bond strength of two single-bottle adhesive systems, Oper. Dent. 25 (2000) 395–400. [5] M.A. Vargas, D.S. Cobb, S.R. Armstrong, Resin–dentin shear bond strength and interfacial ultrastructure with and without a hybrid layer, Oper. Dent. 22 (1997) 159–166. [6] V.P. Saboia, L.A.F. Pimenta, G.M. Ambrosano, Effect of collagen removal in the microleakage of composite resin restorations, Oper. Dent. 27 (2002) 38–43. [7] S. Chersoni, C. Prati, G. Montanari, R. Mongiogi, Effect of collagen layer on self-etching bonding systems adhesion [abstract 1062], J. Dent. Res. 77 (1998) 238. [8] E. Fujita, A. Yamashita, S. Terada, K. Suzuki, Effect of NaOCl preconditioning to bovine root canal dentin [abstract 2990], J. Dent. Res. 75 (1996) 391. [9] A.J. Gwinnett, Altered tissue contribution to interfacial bond strength with acid conditioned dentin, Am. J. Dent. 7 (1994) 243–246. [10] S. Uno, W.J. Finger, Function of hybrid zone as a stress-absorbing layer in resin–dentin bonding, Quintessence Int. 26 (1995) 733–738.
C.S. Delfino, R.G. Palma-Dibb / Applied Surface Science 253 (2006) 1929–1933 [11] N. Inai, N. Kanemura, J. Tagami, L.G. Watanabe, S.J. Marshall, G.W. Marshall, Adhesion between collagen depleted dentin and dentin adhesives, Am. J. Dent. 11 (3) (1998) 123–127. [12] C. Estrela, C.R.A. Estrela, E.L. Barbin, J.C. Spano´, M.A. Marchesan, J.D. Pe´cora, Mechanism of action of sodium hypochlorite, Braz. Den. J. 13 (2) (2002) 113–117. [13] S. Kubo, H. Li, M.F. Burrow, M.J. Tyas, Nanoleakage of dentin adhesive systems bonded to carisolv-treated dentin, Oper. Dent. 27 (2002) 387–395. [14] J. Perdiga˜o, K.N. May Jr., A.D. Wilder Jr., M. Lopes, The effect of depth of dentin demineralization on bond strengths and morphology of the hybrid layer, Oper. Dent. 25 (2000) 186–194. [15] S. Phrukkanon, M.F. Burrow, M.J. Tyas, The effect of dentin location and tubule orientation on the bond strengths between resin and dentin, J. Dent. 27 (1999) 265–274.
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[16] C. Prati, S. Chersoni, R. Mongiorgi, D.H. Pashley, Resin-infiltrated dentin layer formation of new bonding system, Oper. Dent. 23 (1998) 185– 194. [17] M. Toledano, R. Osorio, G. de Leonardi, J.I. Rosales-Leal, L. Ceballos, M.A. Cabrerizo-Vilchez, Influence of self-etching primer on the resin adhesion to enamel and dentin, Am. J. Dent. 14 (2001) 205–210. [18] B. Van Meerbeek, M. Vargas, S. Inoue, Y. Yoshida, M. Peumans, P. Lambrechts, G. Vanherle, Adhesives and cements to promote preservation dentistry [supplement 06], Oper. Dent. (2001) 119–144. [19] F.R. Tay, D.H. Pashley, Aggressiveness of contemporary self-etching systems. I. Depth of penetration beyond dentin smear layers, Dent. Mater. 17 (2001) 296–308. [20] C. Prati, S. Chersoni, D.H. Pashley, Effect of removal of surface collagen fibrils on resin–dentin bonding, Dent. Mater. 15 (1999) 323–331.
Influence of dentin pre-treatment with NaOCl on the morphology of adhesive interface of self-etching adhesive systems Carina Sincle´r Delfino *, Regina Guenka Palma-Dibb Department of Restorative Dentistry, School of Dentistry of Ribeira˜o Preto, University of Sa˜o Paulo, Ribeira˜o Preto, SP, Brazil Received 15 December 2005; accepted 15 March 2006 Available online 2 May 2006
Abstract The aim of this in vitro study was to evaluate the influence of pre-treatment using NaOCl in the morphology of dentin/resin interface. The three self-etching adhesive systems were selected: One-Up Bond F (Tokuyama, Tokyo, Japan), Prime & Bond NT/NRC (Dentsply, Konstanz, Germany) and Clearfil SE Bond (Kuraray, Osaka, Japan). Nine dentin disks were used in this study. Half disk was treated strictly following manufacturers’ instructions (control groups). The other half was treated with a solution of 2.5% NaOCl (experimental groups). After the bonding protocols were accomplished, a low viscosity resin (Flow-it/Jeneric Pentron) was inserted and light-cured. Specimens were prepared for SEM. Morphological aspects were observed, comparing both the groups. The analysis of the photomicrographs revealed formation of a hybrid layer for both controls groups along the interface. The experimental groups showed a resin/dentin interface more irregular and produced topographical features with funnel-shaped dentin tubules. Areas with absence of hybrid layer formation were observed, mainly for One-Up Bond F, although tubules their lateral branches were filled with Prime & Bond NT/NRC and Clearfil Se Bond adhesive systems. It was concluded that the use of NaOCl influenced negatively in the formation of the hybrid layer, mainly for the One-Up Bond F. # 2006 Elsevier B.V. All rights reserved. Keywords: Hybrid layer; Collagen layer; Sodium hypochlorite
1. Introduction The dentin adhesion does not depend only on the monomer micro-mechanical interaction on the de-mineralized substrate, as it occurs on enamel, but it needs to be diffused in the collagen fibers web, aiming to produce the hybrid layer [1,2]. However, the conditioned dentin shows a region that is more superficial and where a dense collagen web impregnated by monomer is observed, with no mineral contents and, in the subsequent portion can be observed a thin layer where the dentin is partially de-mineralized with hydroxyapatite crystals [1,3]. Even though, the collagen net can be exposed without the de-mineralized portion being completely filled by resin monomers due to the dentin low permeability or monomer diffusion deficiency [4].
* Corresponding author at: Rua Henrique Schaumann, 182, apto. 11, Pinheiros, 05413-010 Sa˜o Paulo, SP, Brazil. Tel.: +55 11 30863320; fax: +55 16 33366669. E-mail address: [email protected] (C.S. Delfino). 0169-4332/$ – see front matter # 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2006.03.037
Thus, a failure in the hydrolysis of collagen fibers not totally enveloped by monomers can happen in the adhesion process. In this way, the removal with sodium hypochlorite of the collagen net, may have some benefits, like dentin permeability increase and dentin composition change, making the surface closer to the surface observed on the conditioned enamel [4], which could increase the adhesive resistance [4,5] and decrease the marginal microleakage [6]. Moreover, another factor to be taken into consideration is that recent studies reported that the collagen layer does not have a direct quantitative contribution to adhesive interface [5,7–10]. This probably occurs due to the resin’s complete diffusion into the partially de-mineralized dentin pores [5,9,10]. Unfortunately, there are no studies that evaluate the interference of NaOCl application before the primer acid conditioning of the self-etching systems, in an attempt to provide a better interaction of these systems to dentin substrate. So, the aim of this in vitro study was to evaluate morphologically the resin/dentin interface using three selfetching adhesive systems after NaOCl treatment of the dentin surface.
1930
C.S. Delfino, R.G. Palma-Dibb / Applied Surface Science 253 (2006) 1929–1933
2. Materials and methods Nine extracted caries-free and non-restored human third molars stored in a 0.5% chloramine solution at 4 8C for up to 1 month after extraction, were used in this study. First, the occlusal overlying enamel was removed. Next, the teeth were individually fixed in a sectioning machine with a water-cooled diamond saw positioned parallel to the occlusal surface, obtaining a 1 mm thick (0.1 mm) disk from middle dentin, which had the bottom surface coated with two layers of cosmetic nail varnish. The disks were bisected and each half was manually ground under water using #120–#400-grit silicon carbide paper to provide a flattened and smooth dentin surface. A #600-grit SiC paper was used for 30 s to produce and standardize the smear layer. The hemi-disks were randomly assigned to three groups of equal size (n = 3), according to the adhesive systems tested (Table 1) and divided into two sub-groups according to the dentin treatment. Each disk was divided in two hemi-sections: one was assigned to the experimental group and other to the control group. The disk bottom surface was coated with two layers of cosmetic nail varnish. The adhesive systems applications were done strictly according to the manufacturer’s directions in one hemi-section (control group). The other hemi-section of the same tooth was treated with 2.5% NaOCl solution (with active application for 2 min, followed by water-rinsing for 1 min) before application of the adhesive (experimental group). Following this, a thin flowable resin layer (Flow-it/Jeneric Pentron) was inserted and photo-polymerized for 40 s by the photo-activating unit tip with a 450 mW/cm2 power output (XL-3000, 3M Dental Products). Specimens were embedded in a chemically activated acrylic resin into a silicone matrix. After resin polymerization, the specimens were sectioned at a 908 angle to the bonding surface and manually smoothened and polished with #1000–#4000-grit SiC paper. All specimens were fixed in a gluteraldehyde solution at 4 8C for 12 h and stored in distilled water for 1 h. The dentin/adhesive interface was conditioned with a 37%
Fig. 1. Resin/dentin interface produced by self-etching adhesive Prime & Bond NT. Well-defined hybrid layer (H.L.) with dentin tubules (T) completely filled with resin (X 3500).
phosphoric acid gel for 10 s, rinsed with distilled water and cleaned with an ultrasound apparatus (Ultrasonic Cleaner T1449-D, Odontobra´s Ind. e Com., Brazil) for 10 min, to remove any residues resulting from the sectioning procedure on the surface. The next step was rinsing the specimens in 10 mL (0.1 M) of a buffer sodium cacodylate solution (7.4 pH) for 1 h, followed by rinsing three times in distilled water for 1 min at 20-min intervals. The specimens were then de-hydrated by ethanol in increasing concentration solutions: 25% (20 min), 50% (20 min), 75% (20 min), 95% (30 min) and 100% (60 min). The last step was the immersion in a HMDS (hexamethyldisilazane) solution for 10 min, drying with absorbing paper, fixing on aluminum stubs and sputter-coated with gold. All adhesive/dentin interfaces were examined under a scanning electron microscope JSMT330A (JEOL Ltd., Tokyo 190-0012, Japan) operating at 15 kV. During the analysis, the dentin/adhesive system interface was photographed in different magnifications of the most representative areas of each group. The photographs were assessed by two previously calibrated
Table 1 Tested adhesive systems Adhesive system
Composition
Manufacturer
Batch number
One-Up Bond F (1 step)
Agent A: 100% methacrylate; Agent B: 74% methacrylate, 10% water, 16% fluoroalumino silicate glass filler Prime & Bond NT: di- and tri-methacrylate resins, acetone, functionalised amorphous silica, PENTA, cetylamine hydrofluoride NRC: organic acids/monomers in aqueous solution Primer: MDP, HEMA, hydrophilic dimethacrylate, water, DL-camphorquinone, NN-diethanol-p-toluidine; bond: MDP, bis-GMA, HEMA, hydrophobic dimethacrylate, DL-camphorquinone, NN diethanol-p-toluidine, silanated colloidal silica
Tokuyama, Tokyo, Japan
A: 034, B: 531
Dentsply, Konstanz,Germany
Prime & Bond NT: 0106001132, NRC: 0103801008
Kuraray, Osaka, Japan
Primer: 00157 A, Bond: 00127A
Prime & Bond NT /NRC (2 steps)
Clearfil SE Bond (2 steps)
C.S. Delfino, R.G. Palma-Dibb / Applied Surface Science 253 (2006) 1929–1933
Fig. 2. Resin/dentin interface produced by self-etching adhesive One-Up Bond F. Thin hybrid layer with absent areas (arrows) along the interface (X3500).
examiners relative to the presence or absence of hybrid layer, its integrity, thickness and homogeneity, as well as the existence of tags, their size, uniformity and disposition. 3. Results
1931
Fig. 4. Adhesive interface One-Up Bond F/dentin treated with NaOCl. Areas with lack of hybrid layer (arrows). Formation resin tags (T) into dentin tubules. Well-defined micro-tags (asterisk) into lateral branches and branch off the main resin (X3500).
Bond F system (Fig. 4), although tubules and lateral ramifications have been completely filled with resin for the Prime & Bond NT/NRC and Clearfil SE Bond (Figs. 5 and 6).
Hybrid layer formation was observed for all the adhesive systems of the control group along the interface, being thicker and better defined for the Prime & Bond NT/NRC adhesive system (Fig. 1) than to the One-Up Bond F system, for in some areas (Fig. 2). The Clearfil SE Bond showed thin and homogenous hybrid layer, and tags of conical form, disposed regularly along the dentin surface and uniform in size were observed (Fig. 3). The experimental groups treated with NaOCl showed a more irregular inter-tubular dentin surface and topographical features comparable to the funnel-shaped dentin tubules. This surface showed areas with lack of hybrid layer, mainly for the One-Up
In the conditions exposed in the present study, the treatment with sodium hypochlorite influenced the hybrid layer formation, being more evident for the One-Up Bond F system which resulted in an interfacial morphology distinct from both studied groups but which presented no hybrid layer in the experimental group. This fact probably occurred because NaOCl, in concentrations varying from 1 to 10%, removes partially the organic portion from dentin superficial [11]. This dissolution action of organic portion can be observed by in the saponification reaction when sodium hypochlorite degrades
Fig. 3. Resin/dentin interface produced by self-etching adhesive Clearfil SE Bond. Hybrid layer (H.L.) with similar features were observed for Prime & Bond NT, although with an evident thickness (X3500).
Fig. 5. Adhesive interface Prime & Bond NT/dentin treated with NaOCl. The collagen was removed clearly revealing ‘‘tubule-wall hybridization’’ with resin tags triangularly (T) extends within the dentin tubules orifice walls and e microtags (asterisk) into lateral branches and branch off the main resin tags (X3500).
4. Discussion
1932
C.S. Delfino, R.G. Palma-Dibb / Applied Surface Science 253 (2006) 1929–1933
Fig. 6. Adhesive interface Clearfil SE Bond/dentin treated with NaOCl. Resin tags (T) into dentin tubules evident with absence of hybrid layer along the interface. Micro-tags (asterisk) into lateral branches and branch off the main resin (X3500).
lipids and fatty acids resulting in the formation soap and glycerol [12] and, consequently, it does not allow hybrid layer formation when adhesive systems are used. However this application can be promoted the increase restoration durability, preventing interface degradation due to non-protected collagen fibers hydrolysis. One-Up Bond F’s medium conditioning may have caused the different behavior between control and experimental groups. As it can be observed, the control group produced a thinner hybrid layer. Kubo et al. [13], reported similar results, in which One-Up Bond F exhibited areas with thin hybrid layer in normal dentin. Even though there is no correlation between hybrid layer thickness and adhesive resistance, the absence or non-uniformity of the hybrid layer could potentially lead to a poorer bond strength and increased likelihood of gap formation [14–16]. Apart from, this several studies reported that self-etching systems promote hybrid layer formation, but the depth of penetration of the acidic primer into the smear layer and dentinal substrate depends upon the thickness and packing density of the smear layer, concentration of the acidic component of the primer, viscosity and wetting characteristics of the primer, the diffusion coefficient of the acidic agent, application time and its pH [17]. Due to its high pH (1.8), OneUp Bond F may not be able to de-mineralize the dentin either removing or modifying the smear layer, compromising the monomer infiltration into the dentin. Primers with pH equal or less than 1.4, probably promote dentin de-mineralization in a more appropriate way [13,17]. On the other hand, Prime & Bond NT/NRC system showed a thicker hybrid layer and increased amount of resin tags in the lateral ramifications in both groups. This system has pH equal or less than 1.0 which, according to Van Meerbeek et al. [18], provides a high conditioning potential, de-mineralizing the smear layer and lower dentin layer, allowing the arise of an ultra-morphological dentin interface, similar to those produced
by total-etching systems, with abundant resin tags formation and a thicker hybrid layer. The Prime & Bond NT/NRC system promoted superficial dentin de-mineralization and the previous application of NaOCl resulted probably in an increase of dentin permeability and, consequently, better adhesive penetration into the substrate, originating a more homogeneous adhesive interface. The collagen removing can improve the adhesive contact to hydroxyapatite crystals [4], due to cleaning effect and the increase of dentin permeability, improving the adhesion [5]. As regards the control group, the conducted study observed results analogous to Tay and Pashley [19], in which the use of self-etching adhesive systems promoted a thin hybrid layer, but totally infiltrated by resin monomers. NaOCl application in the experimental groups removed partially the collagen web, according to Prati et al. [20], in which the collagen was probably only removed at the top of the smear layer when NaOCl was applied to smear layer covered dentin. Inter-tubular dentin surface was more irregular, and the tubule-wall hybridization aspect was evident. Tubule hybridization lateral aspect was observed in all experimental groups too. 5. Conclusion It was concluded that the self-etching adhesive systems promoted hybrid layer formation. However, the previous application of NaOCl influenced its formation, mainly for the One-Up Bond F adhesive system, in which no hybrid layer was observed. More in vivo and in vitro studies are required to elucidate the effectiveness of this treatment. References [1] N. Nakabayashi, K. Kojima, E. Masuhara, The promotion of adhesive by the infiltration of monomers into tooth structures, J. Biomed. Mater. Res. 16 (1982) 265–273. [2] B. Van Meerbeek, S. Inokoshi, M. Braem, P. Lambrechts, G. Vanherle, Morphological aspects of resin–dentin interdiffusion zone with different dentin adhesive systems, J. Dent. Res. 71 (1992) 1530–1540. [3] N. Nakabayashi, M. Ashizawa, M. Nakamura, Identification of a resin– dentin hybrid layer in vital human dentin created in vivo: durable bonding to vital dentin, Quintessence Int. 23 (1992) 135–141. [4] V.P. Saboia, A.L. Rodrigues Jr., L.A.F. Pimenta, Effect of collagen removal on shear bond strength of two single-bottle adhesive systems, Oper. Dent. 25 (2000) 395–400. [5] M.A. Vargas, D.S. Cobb, S.R. Armstrong, Resin–dentin shear bond strength and interfacial ultrastructure with and without a hybrid layer, Oper. Dent. 22 (1997) 159–166. [6] V.P. Saboia, L.A.F. Pimenta, G.M. Ambrosano, Effect of collagen removal in the microleakage of composite resin restorations, Oper. Dent. 27 (2002) 38–43. [7] S. Chersoni, C. Prati, G. Montanari, R. Mongiogi, Effect of collagen layer on self-etching bonding systems adhesion [abstract 1062], J. Dent. Res. 77 (1998) 238. [8] E. Fujita, A. Yamashita, S. Terada, K. Suzuki, Effect of NaOCl preconditioning to bovine root canal dentin [abstract 2990], J. Dent. Res. 75 (1996) 391. [9] A.J. Gwinnett, Altered tissue contribution to interfacial bond strength with acid conditioned dentin, Am. J. Dent. 7 (1994) 243–246. [10] S. Uno, W.J. Finger, Function of hybrid zone as a stress-absorbing layer in resin–dentin bonding, Quintessence Int. 26 (1995) 733–738.
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