H3PO4 Etching Research Articles

Bond Strength to Lithium-Disilicate Ceramic after Different Surface Cleaning Approaches.

To evaluate the effect of different lithium-disilicate (LiSi) glass-ceramic surface decontamination procedures on the shear bond strength (SBS) to resin cement. Seventy CAD/CAM LiSi ceramic specimens (IPS e.max CAD, Ivoclar) were cut and sintered. Fifty specimens were treated with 5% hydrofluoric acid (HF) for 20 s, while 20 were left untreated. All 70 specimens were then contaminated with human saliva and try-in silicone paste. The following surface cleaning methods were investigated (n = 10): C: water rinsing (control); PA: 37% H3PO4 etching for 20 s; E: 70% ethanol applied for 20 s; CP: cleaning paste (Ivoclean, Ivoclar) brushed for 20 s; HFSEP: self-etching ceramic primer (Monobond Etch&Prime, Ivoclar) rubbed for 20 s; HF: 5% HF applied for 20 s or no HF etching prior to contamination; SEP: self-etching ceramic primer rubbed for 20 s and no HF etching prior to contamination. Composite cylinders were created and luted with an adhesive resin cement to the decontaminated surfaces. After storage for 24 h at 37°C, the SBS test was conducted. Two fractured specimens per group were observed under SEM to perform fractographic analysis. The data were statistically analyzed with p set at <0.05. The type of surface cleaning approach influenced bond strength (p < 0.001). HFSEP, SEP, and HF attained higher SBS (p < 0.001) compared to other groups. None of the approaches were able to completely remove contaminants from the ceramic surfaces. SEM images showed residual traces of contaminants on CP-treated surfaces. The self-etching ceramic primer enhanced bond strength to contaminated LiSi ceramic surfaces, irrespective of previous treatment with hydrofluoric acid.

Effects of Surface Pretreatments on Bond Strength and Morphology of Aprismatic Enamel.

To evaluate the effect of different pretreatment protocols and adhesives on the shear bond strength and surface morphology of aprismatic enamel. Human maxillary incisors (N = 120) were assigned to five different groups according to pretreatment: 1) no treatment; 2) glycine; 3) sodium bicarbonate; 4) Al2O3 and 5) extra-fine bur. Then the teeth were divided into three subgroups, according to the adhesive applied: 3-step etch-and-rinse (ER), universal adhesive in ER mode, and universal adhesive in self-etch (SE) mode. Shear bond strength (SBS) testing was performed with a universal testing machine. For SEM observation, fifteen human molars were collected and analyzed after pretreatment with/without etching with 37% H3PO4 for 30s. Al2O3 showed higher SBS than all other groups considered. Comparable SBS values were obtained for other pretreatments. Universal adhesive in E&R mode performed better than did 3-step E&R and universal adhesive in SE mode. SEM images showed visible differences in enamel surface roughness. Airborne-particle abrasion with Al2O3 followed by etching with H3PO4 increased SBS on aprismatic enamel. The combination of airborne-particle abrasion with alumina powder followed by 15 s of H3PO4 etching and application of a universal adhesive in E&R mode proved to be the most effective adhesive protocol.

Does the bonding effectiveness of a fiber post/resin composite benefit from mechanical or chemical treatment? Seven methods for saliva-contaminated surfaces.

This study examined four cleaning methods and three chemical treatments for artificial saliva-contaminated fiber posts in terms of bonding durability to resin composite core materials. Non-contaminated fiber posts (Tokuyama FR Post, Tokuyama Dental) and those contaminated (GC Fiber Post, GC) with artificial saliva (Saliveht Aerosol, Teijin Pharma) were used. Washing and drying (WD), alcohol cleaning (AlC), H3PO4 etching (P/WD), alumina blasting (B/D) for decontamination and silanization (Clearfil Ceramic Primer Plus, Kuraray Noritake Dental, Si), resin priming (HC Primer, Shofu, MMA), and bonding resin application (Clearfil Universal Bond Quick, Kuraray Noritake Dental, BR) for chemical treatment were performed. The treated fiber post was planted inside a cylindrical tube and filled with resin composite (DC Core Automix ONE, Kuraray Noritake Dental). The specimen was sectioned, and a push-out test was performed after 24 h, 1 month, and 3 months. The fracture surface was observed using a scanning electron microscope (SEM). Adhesion between the non-contaminated fiber post and resin composite did not improve by silanization and decreased by alumina blasting. SEM observations revealed a fractured glass fiber by alumina blasting. Saliva contamination decreased the bond strength between the fiber post and resin composite; however, recovery was achieved by WD, Alc, P/WD, and B/D. Compared to Si, BR (P = 0.009) was effective in restraining the long-term durability of bonding, whereas MMA (P = 0.99) was not. The application of bonding resin after alcohol cleaning is the most convenient and effective clinical procedure for fiber post surface treatment.

Fabrication and field emission properties of vertical, tapered GaN nanowires etched via phosphoric acid

The controlled fabrication of vertical, tapered, and high-aspect ratio GaN nanowires via a two-step top-down process consisting of an inductively coupled plasma reactive ion etch followed by a hot, 85% H3PO4 crystallographic wet etch is explored. The vertical nanowires are oriented in the direction and are bound by sidewalls comprising of semipolar planes which are at a 12° angle from the [0001] axis. High temperature H3PO4 etching between 60 °C and 95 °C result in smooth semipolar faceting with no visible micro-faceting, whereas a 50 °C etch reveals a micro-faceted etch evolution. High-angle annular dark-field scanning transmission electron microscopy imaging confirms nanowire tip dimensions down to 8–12 nanometers. The activation energy associated with the etch process is 0.90 ± 0.09 eV, which is consistent with a reaction-rate limited dissolution process. The exposure of the type planes is consistent with etching barrier index calculations. The field emission properties of the nanowires were investigated via a nanoprobe in a scanning electron microscope as well as by a vacuum field emission electron microscope. The measurements show a gap size dependent turn-on voltage, with a maximum current of 33 nA and turn-on field of 1.92 V nm−1 for a 50 nm gap, and uniform emission across the array.

Effect of customisation, root canal reshaping and acid etching on push-out bond strength of fiber post in flared, MTA repaired root canal.

Clinicians routinely encounter the endodontically treated teeth with wide flared canals and mineral trioxide aggregate (MTA) repair on the canal wall. To assess the effect of customized glass reinforced composite (FRC) post and reshaped root canal along with different acid etching protocol of MTA surface on push-out bond strength (PBS) in flared, MTA repaired root canal. Ninety recently extracted single-rooted premolar teeth were sequentially subjected to root canal obturation, post space preparation, flaring, and MTA application. The samples were randomly divided into 3 groups of control (no relining or reshaping), customized FRC post by relining with self-adhesive resin cement and reshaping the canal with flowable composite. Each group was subdivided into 3 subgroups (n= 10) as no surface treatment, 37% H3PO4 and 19% EDTA etching of MTA surface. Teeth samples cemented with FRC post were sectioned into 2 mm and push-out testing. Control group had the lowest PBS at 1.988 N. The PBS values for the groups with customized post relining were 8.489 N, 8.888 N and 7.911 N for control, H3PO4 etch and EDTA etch. The corresponding PBS values for root canal reshaping were 7.323 N, 8.318 N and 7.785 N. Customized FRC post with 37% H3PO4 etching is advised for the flared and MTA repaired root canals.

Selective electrochemical etching of epitaxial aluminum nitride thin film

Aluminum nitride (AlN) has an ultra-wide bandgap energy of 6.2 eV and is resistant to chemical etching owing to its high chemical stability, making it intractable in the device fabrication process. We developed a facile method of electrochemical (EC) etching of a high-quality AlN epitaxial layer, where both spatial selectivity and a controllable etch rate were achieved. Underneath porous metal electrodes, the lateral etch rate increased with the increasing external anodic bias, from 400 nm/min at 5 V to 700 nm/min at 15 V. Nonporous metal electrodes protected the AlN from etching in hot H3PO4, enabling the spatial selectivity. The high EC etch rate is attributed to the enhanced hole-assisted oxidation at the interface between the AlN and the etchant. The etch pit formed by EC etching exhibited an inverse hexagonal pyramid structure with {1 0 –1 −1} face. As an alternative to dry etching, our method can be applied to the low-damage patterning of AlN with a controllable etch rate.

The impact of etching time and material on bond strength of self-adhesive resin cement to eroded enamel.

The purpose of this study was to assess the effect of pre-etching time and material on shear bond strength (SBS) of self-adhesive resin cements to eroded and sound enamel. Eroded enamel specimens were assigned into 5 groups (n=20 each) based on enamel surface treatment as follow: Group N, eroded enamel (without surface pre-treatment); Group PH15, 35% H3PO4 etching for 15 s; Group PH30, 35% H3PO4 etching for 30 s; Group L30, 20% lactic acid etching for 30 s and Group L60, 20% lactic acid etching for 60 s.Composite blocks were fabricated and cemented to enamel surfaces with one of two self-adhesive cements. Notched-edge SBS was assessed. Bond strength of self-adhesive cement to eroded enamel surface significantly enhanced following application of 20% lactic acid for 30 s.

Self-template construction of honeycomb-like mesoporous YPO4:Ln3+ (Ln = Eu, Tb) phosphors with tuneable luminescent properties

Rare earth (RE)-based phosphors with mesoporous structure that can improve the absorption and utilization of light have attracted much attention recently. Herein, we develop a novel and facile self-template strategy to synthesize honeycomb-like mesoporous YPO4:Ln3+ (Ln = Eu, Tb) phosphors using Y4O(OH)9NO3: Ln3+ as the precursor through a simple H3PO4 etching process. The maximum specific surface area of the mesoporous YPO4:Ln3+ phosphors can reach 406 m2 g−1. The influence of mesoporous structure, crystallinity, and the concentration of rare earth ions on the photoluminescence performance of mesoporous YPO4:Ln3+ phosphors was investigated. The results of fluorescence measurements indicate the mesoporous YPO4:Ln3+ phosphors exhibit better photoluminescence performance after calcination at 900 °C due to the large surface area and high crystallinity. The optimum doped concentrations of Eu3+ ions and Tb3+ ions are 0.12 and 0.08, respectively, and the concentration quenching occurs among nearest-neighbor ions. This work provide a new sight on preparation of phosphors for white light-emitting diodes lamps.

Shear bond strength of one-step self-etch adhesives to dentin: Evaluation of NaOCl pretreatment.

BackgroundThe aim of this study was to evaluate the influence of dentin pretreatment with NaOCl on shear bond strength of four one-step self-etch adhesives with different pH values.Material and MethodsBovine permanent incisors were used. Four one-step self-etch adhesives were tested: Adper™ Easy Bond, Futurabond NR, G-aenial Bond, Clearfil S3 Bond. One two-step self-etch adhesive (Clearfil SE Bond) was used as control. Group 1- no pretreatment; group 2- pretratment with 5,25 % NaOCl; group 3- pretreatment with 37 % H3PO4 etching and 5,25 % NaOCl. A hybrid composite resin was inserted into the dentin surface. The specimens were tested in a universal testing machine. The examiners evaluated the fractured surfaces in optical microscope to determine failure modes, quantified with adhesive remnant index (ARI).ResultsDentin pretreatment variably influenced bond strength values of the different adhesive systems. When no dentin pretreatment was applied, no significant differences were found (P >.05) among four adhesives tested. No significant differences were recorded when comparing NaOCl pretreatment with H3PO4 + NaOCl pretreatment for all adhesive tested (P >.05) except Clearfil S3 Bond that showed higher shear bond strength values when H3PO4 was applied. Frequencies of ARI scores were calculated.ConclusionsThe influence of dentin pretreatment with NaOCl depends on the composition of each adhesive system used. There was no difference in bond strength values among self-etch adhesives with different pH values. Key words:Dentin, pretreatment, self-etch adhesives.

Tuning the Threshold Voltage of Exfoliated β-Ga2O3 Flake-Based Field-Effect Transistors by Photo-Enhanced H3PO4 Wet Etching

Monoclinic β-Ga2O3 with an ultra-wide energy bandgap of ∼4.9 eV has facile cleavage planes because of the high anisotropy in the lattice structure. An exfoliated nanolayer flake of β-Ga2O3 can be used as an active channel layer in nanoelectronics. However, the mechanical exfoliation method used poses a fundamental issue in that the separated individual layer has a random thickness, which makes it challenging to obtain reproducible device performance. In our study, we demonstrated a photo-enhanced chemical etching technique to control the thickness of exfoliated β-Ga2O3 nanolayers, enabling us to adjust the threshold voltage of field-effect transistors (FETs) based on these nanolayers. Thickness-dependent device characteristics (threshold voltage, subthreshold swing, on/off ratio, and field-effect mobility) of the back-gated FETs were investigated as a function of the active channel layer (β-Ga2O3) thickness achieved by the photo-enhanced H3PO4 etching. Our study paves the way for the implementation of exfoliated β-Ga2O3 nanolayers in nanoelectronics.

Fabrication of Y doped BaZrO3 epitaxial film on YBa2Cu3Ox sacrificial buffer layer

Fabrication of highly oriented Y doped BaZrO3 (Ba(Zr,Y)O3:BZY) films on YBa2Cu3Ox (YBCO) sacrificial buffer layers was investigated. To clarify requirements of orientation control, BZY films were fabricated on various substrates using pulsed laser deposition (PLD). Cube-on-cube orientation relationship was obtained in BZY films on SrTiO3, LaAlO3, and MgO(100) regardless of PLD conditions, but orientation of BZY was strongly dependent on PLD conditions on yttria stabilized zirconia(YSZ) and CeO2(100), showing that perovskite structure or almost the same lattice parameter as BZY is needed to obtain cube-on-cube orientated BZY films. Cube-on-cube orientated BZY films were fabricated on YBCO, whose structure was perovskite, under wide ranging PLD conditions, showing that YBCO sufficiently controls crystalline orientation of BZY films. In addition, highly oriented BZY films were obtained on YBCO/YSZ/Si(100), demonstrating epitaxial BZY films on Si. Since good selective etching ability is also needed in sacrificial buffers, YBCO/BZY films were etched using H3PO4. H3PO4 etching removed the YBCO sacrificial buffers without damaging BZY with etching rate of ~30nm/s. The present results show that YBCO sacrificial buffer layers are promising for fabrication of the μSOFCs with highly oriented BZY.

Etching of Silicon Nitride in 3D NAND Structures

3D NAND structures present a unique difficulty in semiconductor device manufacturing. One method of production consists of cylindrical structures made of alternating layers of silicon dioxide (SiO2) and silicon nitride (SiN) with a core of SiO2. As part of the device manufacturing process the SiN is etched away, leaving the SiO2 core with disc-shaped SiO2 fins. Due to material selectivity requirements of etching only the SiN while leaving the SiO2 unchanged, the process of choice is often immersion in a high-concentration hot phosphoric acid (H3PO4) bath with a silica additive to inhibit SiO2 etching, which with proper tuning can have selectivity of greater than 100:1 for etching SiN:SiO2. Like all wet etch processes, uniformity of the process is a constant concern. One of our goals in this paper is to show how we use experimental measurements and simulations to better understand what parameters have the most effect on the process, and how we can use that knowledge to improve the process. Experimentally we have measured the etch rate of blanket SiN and SiO2 wafers. We fit the etch rate data to Arrhenius models to quantify the etch rate of SiN and SiO2 films. Simulations of the etch process on both blanket wafers and patterned wafers showed that the etch rate is the same and doesn’t depend on feature geometry. In this paper we propose a simple chemical reaction and diffusion mechanism that explains the experimental observations of the etched structures. The uniformity of the SiN etching between the top and the bottom of the 3D NAND stacks indicates that the reaction rate is much slower than the rate of diffusion of reactants and products into and out of the structure, so the etching is a reaction-controlled mechanism. This indicates within-wafer uniformity and wafer-to-wafer uniformity variations as being primarily due to differences of temperature within the bath. We also conducted simulations of the etching of the SiN in the 3D NAND structure and the liquid flow in the bath to model and explain this mechanism. In these simulations we varied the rate of the surface reaction of H3PO4 etching SiN, and showed that for a fast reaction rate that the structure would etch from the top to the bottom as the overall reaction rate become diffusion limited, while for a slow reaction rate the entire structure would etch uniformly, showing it to be a reaction limited process. Another issue with SiN etching in an H3PO4 bath is that the etch rate of SiO2 depends highly on the concentration of silica, in fact the bath is generally pre-seeded with silica in order to achieve a lower SiO2 etch rate, though if above a critical concentration deposition is known to occur. Based on a study of silica chemistry, it may be possible for silica deposition to occur even when below the critical concentration. This would be a film that would grow on a SiO2 surface but would later dissolve back into solution. We propose a mechanism that explains the formation and later disappearance of the growth film on the SiO2 surface as a result of the etching of the SiN and the formation of silica byproducts into a sol/gel network. Sol/gels have the unique property of their ability to form in an area of locally high flux, and then later dissolve over a much longer time scale. The difference in forward and backward reaction rates of the sol/gel film formation and disillusion, respectively, are such that the system is never in equilibrium. Thus, even though all the silica can dissolve in the phosphoric acid at equilibrium, the silica formed from the SiN etching forms into a sol/gel polymer network that only slowly dissolves after SiN etching has stopped. We discuss the implications of this sol/gel oxide film for further process improvement. With better theoretical understanding of the SiN etching and possible silica sol/gel formation and dissolution process, we now have tools to better optimize the phosphoric acid bath, improving both etching uniformity and necessary process time. Figure 1

Effects of controlled surface states on the photoluminescence emission of GaN film

Hot phosphor acid (H3 PO4) etching and/or SiOxNy surface passivation are used to change the surface states of high-resistance intrinsic GaN films. The films are investigated to reveal the influence of controlled surface states on photoluminescence (PL) emission. It is found that H3 PO4 etching cannot improve the ultraviolet (UV) PL emission obviously, but the PL spectrum in the range of visible light is considerably enhanced. After passivation with SiOxNy film, the quantum efficiency of UV PL is increased by a factor of 12-13. Meanwhile, the visible PL is significantly enhanced. By analyzing the PL spectra of the etched and passivated samples obtained at room temperature and low temperatures, we discuss the role of surface states in PL emission in the range of UV, blue and yellow bands, and the related physical mechanisms.

Fabrication Mechanism for Patterned Sapphire Substrates by Wet Etching

Patterned sapphire substrate (PSS) was fabricated by wet etching solutions with different mixture ratios of H2SO4 to H3PO4 and different temperatures to investigate the fabrication mechanisms. It was found that the mixture ratio and temperature of the etching solutions affect the ratio of the pattern diameter to the pattern depth. In addition, the observed pattern shape was strongly affected by the mixture ratio. To discuss the reaction mechanisms of sapphire with H2SO4 and H3PO4 separately, we estimated the activation energies and reaction frequency factors for each reaction. By the estimated results, the behavior of the observed pattern shape for the etching conditions was well explained. To confirm the fabrication mechanism of pattern shape in the microscopic scale, the electron probe microanalysis (EPMA) inspection of the sapphire surface after H2SO4 and H3PO4 etching were carried out. As a result, it was indicated that the pattern shape is controlled by the step flow reaction with and without impurities in the etching solutions. From the observation of the pattern shape, the estimation of the activation energies and reaction frequency factors, and EPMA inspection of the reaction products for each reaction, a schematic model of the fabrication mechanisms for the wet etching of a PSS was established.

Synthesis and electrochemical performance of phosphate-coated porous LiNi1/3Co1/3Mn1/3O2 cathode material for lithium ion batteries

Porous LiNi1/3Co1/3Mn1/3O2 microspheres were synthesized by a co-precipitation approach combined with high-temperature calcination. To improve the electrochemical performances, phosphate coating was formed on the surfaces of porous LiNi1/3Co1/3Mn1/3O2 microspheres by H3PO4 etching and subsequent annealing treatment. As anticipated, phosphate-coated LiNi1/3Co1/3Mn1/3O2 microspheres (2 mol.% H3PO4) delivered discharge capacity of 100. 1 mAh g−1 at 5 °C, which was higher than that of pristine LiNi1/3Co1/3Mn1/3O2 microspheres (64.8 mAh g−1). The improvement of rate capability and cycle stability of LiNi1/3Co1/3Mn1/3O2 microspheres could be attributed to the phosphate coating, which suppressed the side reaction between cathode and electrolyte. The phosphate surface modification has a promising application in improving the performance of layered oxide cathode materials for lithium ion batteries.

Influence of Surface Conditioning Protocols on Glass-Fiber Post Adhesion Performance After Aging and Flexural Strength

The effect of surface-conditioning of fiber-posts on the flexural strength of the post and on the adhesion between the root dentin and cement and between the fiber-post and the composite core were assessed. The fiber-posts were subjected to cleaning with alcohol (AL), treatment with AL + silane (SIL), sandblasting with Al2O3 particles + SIL, H2O2 etching + SIL, hydrofluoric acid etching + SIL, and H3PO4 etching + SIL. For comparison, another group of specimens was left unconditioned (control group). The conditioned fiber-posts were cemented to bovine roots, and standardized cylindrical resin cores were fabricated. The specimens were subjected to 106 mechanical pulses and then sectioned perpendicular to the long axis of the root. Push-out tests were conducted on the sliced root sections, and microtensile testing was applied to the trimmed sliced core sections. The posts were also subjected to three-point bending tests. The surface-conditioning did not have any significant effect on the push-out strength. However, silanization increased the microtensile strength at the resin core. Sandblasting significantly decreased the flexural strength as compared to other surface treatments. Our study indicates that post surface-conditioning did not improve the post retention in the root canal, although silanization enhanced the adhesion to the core resin. Sandblasting with 125-µm alumina particles should be avoided.

Does tin pre-treatment enhance the bond strength of adhesive systems to enamel?

ObjectivesThe study investigated the modification of composite-to-enamel bond strength by pre-treatment of enamel with a concentrated, acidic SnCl2-solution. MethodsSix groups of flat human enamel specimens (n=44 per group) were treated as follows: OB-H: H3PO4 etching, Optibond FL application (primer+adhesive; manufacturer's instructions); OB-S: SnCl2 pre-treatment, Optibond FL application (primer+adhesive); OB-HS: H3PO4 etching+SnCl2 pre-treatment, Optibond FL application (primer+adhesive); CF-N: Clearfil SE application (primer+bond; manufacturer's instructions); CF-H: H3PO4 etching, Clearfil SE application (primer+bond); CF-S: SnCl2 pre-treatment, Clearfil SE application (primer+bond). Enamel specimens were then built up with resin composite (Clearfil Majesty Esthetic) and stored (100% humidity, 37°C, 1 week). μTBS-measurement and failure mode analysis of one-half of the specimens were performed immediately after storage, while the other half was analysed after a thermocycling procedure (8500 cycles; 5°C and 55°C; dwell time 30s). Additional specimens were prepared for SEM- and EDX-analysis. ResultsHighest values were measured for OB-H before and after thermocycling, lowest values for CF-N. Compared to OB-H treatment, OB-S treatment reduced μTBS before/after thermocycling by 23%/28% and OB-HS treatment by 8%/24% (except for OB-SH before (n.s.), all p≤0.001 compared to OB-H). In the Clearfil SE treated groups pre-treatment increased μTBS significantly compared to CF-N (before/after: CF-H: +46%/+70%; CF-S: +51%/42%; all p≤0.001). ConclusionPre-treatment with H3PO4 or SnCl2 markedly increased the μTBS of Clearfil SE to enamel. However, thermocycling partly reduced the gain in μTBS obtained by SnCl2 pre-treatment. Clinical significanceThe application of an acidic and highly concentrated SnCl2 solution is a good option to increase the μTBS between enamel and a resin composite mediated by an adhesive system containing the multifunctional monomer MDP.

Porous alumina thin films on conductive substrates for templated 1-dimensional nanostructuring

The growth of thin porous anodic aluminum oxide (AAO) films on silicon by anodizing Al on Ti/Au/Si and Ti/Pt/Si substrates in oxalic acid was demonstrated. Removal of the Al2O3 barrier layer was effected by selective chemical etching in H3PO4 and a reversed bias method in the anodizing solution. Ion transport and the influence of the Ti adhesion layer at the oxide–metal interface during the critical stages of anodization and pore opening were investigated. The AAO films may be exploited as templates in the creation of silicon-integrated nanostructured wire arrays. Electrodeposition of Pt into the AAO template yielded a nanowire array with superior methanol oxidation activity that can be integrated in a micro direct methanol fuel cell.

Bonding efficacy of an acetone/based etch-and-rinse adhesive after dentin deproteinization

Objectives: to evaluate the effect of sodium hypochlorite (NaOCl) treatment on dentin bonding by means of shear bond strength (SBS) measurements when using Prime&Bond NT (PB NT) adhesive. Ultrastructure of the interfaces was examined by scanning electron microscopy (SEM). Study design: Extracted human third molars were sectioned and ground to expose flat surfaces of superficial or deep dentin. Specimens were randomly assigned to two equal groups, and bonded as follows: (1) according to the manufacturers’ directions, after 35% H3PO4 etching, (2) 5% NaOCl treated for 2 minutes, after 35% H3PO4 etching. Each sample was embedded in a Watanabe shear test assembly for a single plane lap shear. After PB NT bonding, specimens were stored in water for 24 h at 37ºC and thermocycled (500x). Samples were tested in shear to failure using a universal testing machine at 0.75 mm/min. Data were analyzed with ANOVA and Newman-Keuls multiple comparison test procedures. Two samples of each group were randomly selected to investigate the morphologic aspect of the resin/dentin interface with SEM. Results: After etching and after aqueous sodium hypochlorite (NaOClaq) application, SBS values were similar on superficial than deep dentin (p>0.05). SEM findings shows for H3PO4 etching conditioned samples a detectable hybrid layer and long resin tags; for NaOCl treated specimens, it may be observed a non apparent hybrid layer, and the adhesive contact directly with the neck of the cylindrical resin tags. Conclusions: The use of 5% NaOCl for 2 min after dentin demineralization when PB NT was employed did not improve the bond strength to dentin, probably due to nanofiller content and/or oxidative changes on collagen-depleted dentin. Key words:Sodium hypochlorite, shear bond strength, SEM, Prime&Bond NT, superficial dentin, deep dentin.

Wetting ability of an acetone/based etch rinse adhesive after NaOCl-treatment

Objectives: to evaluate the effect of sodium hypochlorite (NaOCl) treatment on surface dentin roughness (Ra) and contact angle (CA) when using Prime&Bond NT adhesive (PB NT). Study Design: Extracted human third molars were sectioned to expose flat, superficial and deep dentin surfaces. CA and Ra were measured (1) before and (2) after 35% H3PO4 etching, and (3) H3PO4 etching + 5% NaOCl treated for 2 minutes before the application of PB NT. CA was measured by the Axisymmetric Drop Shape Analysis Technique using distilled and deionized water and PB NT. Roughness was evaluated with a profilometer, twelve radial measurements were performed in each treatment surface. Data were analyzed with two-way ANOVA and Newman-Keuls multiple comparison test procedures. Results: CA values decreased after acid etching and even more after NaOCl treatment on deep dentin when water was tested. With resin, there were not differences on CA results after H3PO4 neither after NaOCl treatment, in both dentin surfaces. Etching and NaOCl treatment resulted in surface roughness increase. Conclusions: In spite of the higher roughness after NaOCl treatment on superficial and deep dentin, the use of 5% NaOCl for 2 min after dentin demineralization when PB NT was employed did not improved the wettability of dentin, probably due to nanofiller content and/or hydrogen-bonding interactions with residues of the organic matrix on collagen-depleted dentin. Key words:Sodium hypochlorite, contact angle, roughness, Prime&Bond NT, superficial dentin, deep dentin.