Prior Etching Research Articles

Evaluation of adhesive bond strength of restorative materials to hard tissues of deciduous teeth based on adhesion technique

Relevance. Treating caries in deciduous teeth remains one of the most complex challenges in pediatric dentistry. The bond strength between the enamel and dentin of deciduous teeth and restorative materials is crucial for the durability of hard tissue restorations in these teeth. This article evaluates the adhesive strength of restorative materials to the enamel and dentin of deciduous teeth using a universal adhesive system, both with and without prior etching with orthophosphoric acid.Purpose. To assess the adhesive bond strength of dental filling materials to the hard tissues of deciduous teeth, contingent upon the enamel and dentin etching techniques used with a universal adhesive system.Materials and methods. This study measured the adhesive strength of a composite filling material to the enamel and dentin of deciduous teeth using a universal adhesive system. The methods included both the absence of preliminary etching with 37% orthophosphoric acid (self-etch technique) and the application of preliminary etching of enamel and dentin with 37% orthophosphoric acid (total-etch technique). Sixty extracted deciduous teeth from children aged 6-8 years were used. Adhesive strength was assessed using the shear test of the filling material in cylinder form against the substrate surface.Results. Significant differences were observed in the adhesive bond strength of the composite material to the hard tissues of deciduous teeth when using 37% orthophosphoric acid before applying the adhesive system (total-etch technique) compared to no preliminary etching (self-etch technique). When filling carious lesions in deciduous teeth, if the defect is within the enamel, etching the surface with 37% orthophosphoric acid significantly (by two-fold) enhances the adhesive strength of the bond with the composite material using a universal adhesive. However, when repairing defects located deeper than the enamel layer in deciduous teeth, no statistically significant differences were observed in the adhesive strength with or without dentin etching. The optimal adhesive bond strength of composite materials to the hard tissues of deciduous teeth under laboratory conditions was attained by selectively etching the enamel with 37% orthophosphoric acid, followed by the application of a universal adhesive system to both the enamel and dentin.

Wet and dry etching of ultrawide bandgap LiGa5O8 and LiGaO2

Crystalline thin films of LiGa5O8 have recently been realized through epitaxial growth via mist-chemical vapor deposition. The single crystal, spinel cubic LiGa5O8 films show promising fundamental material properties and, therefore, make LiGa5O8 a potential enabling material for power electronics. In this work, chemical resistance and etch susceptibility were investigated for the first time on crystalline LiGa5O8 thin films with various wet chemistries. It was found that LiGa5O8 is very chemically resistive to acid solutions, with no apparent etching effects observed when placed in concentrated acid solutions of HCl, H2SO4, HF, or H3PO4 at room temperature. In contrast, orthorhombic (010) LiGaO2 shows effective etching in HCl solutions at varying dilution concentrations, with etch rates measured between 8.6 [1000:1 (DI water: HCl concentration)] and 6092 nm/min (37 wt. % HCl). The inductively coupled plasma reactive ion etching (ICP-RIE) of LiGa5O8 using BCl3/Ar and CF4/Ar/O2 gas chemistries was investigated. The etching rate and surface morphology of etched surfaces were examined as a function of RIE and ICP power. Using a CF4/Ar/O2 gas chemistry with an RIE power of 75 W and an ICP power of 300 W resulted in smooth etched planar surfaces while maintaining an etch rate of ∼24.6 nm/min. Similar dry etching studies were performed for LiGaO2. It was found that the BCl3/Ar gas chemistry was better suited for LiGaO2 etching, with similar surface morphology quality being obtained after etching as prior etching when a RIE power of 15 W and an ICP power of 400 W is utilized.

Effect of Polymer Substrate on Adhesion of Electroless Plating in Irradiation-Based Direct Immobilization of Pd Nanoparticles Catalyst.

Pd nanoparticles were directly immobilized on acrylonitrile-butadiene-styrene copolymer (ABS), acrylonitrile-styrene copolymer (AS), polystyrene (PS), polyphenylene sulfide (PPS), poly(vinyl chloride) (PVC), polypropylene (PP), and polyethylene (PE) polymer substrates via chemical reactions induced by ionizing irradiation. X-ray photoelectron spectroscopy analysis revealed that the chemical state of the immobilized Pd nanoparticles depended on the polymer substrate type. Electroless plating was performed using the immobilized Pd nanoparticles as the catalyst, and Cu-plating films were deposited on all polymer substrates. The results of the tape-peeling test suggested that the chemical state of the immobilized Pd nanoparticles on the polymer substrates affected the plating adhesion strength. Notably, ABS with immobilized Pd particles exhibited a high adhesion strength beyond the practical level, even without prior chemical etching. It was presumed that the high adhesion strength was owing to the anchoring effect of the holes generated on the ABS surface by ionizing irradiation.

Effect of Remnant Carbon and Etching of Particles on Pyrolysis Bonded Silicon Carbide (PBSC)

Silicon carbide (SiC) formed through pyrolysis of preceramic polymers loaded with SiC particles has gained significant attention for applications such as coatings, composite matrix modifications, and most importantly additive manufacturing. This work presents combined synchrotron XRD, Raman spectroscopy, scanning electron microscopy, nano-indentation, and Vickers indentation of pyrolysis bonded SiC to shed light on the changes of composition and mechanical properties of these materials. Characterization was performed on samples that were heat treated ranging from the synthesis 850 °C up to 1500 °C. Pre-treatments of the powders prior to pellet synthesis, such as heat treatment and etching using a hydrofluoric acid (HF), were investigated. It is shown that the degradation of mechanical properties when exposed to higher temperatures is due to the burnout of amorphous carbon clusters remnant of the pyrolysis process of the preceramic polymer. Furthermore, prior HF etching and removal of the native oxide layer of the powders showed improved density and hardness values in the final pellets. The average Vickers hardness of the control samples were 4.59 GPa and later 3.74 GPa when exposed to 1500 °C, while the samples synthesized using powders that were etched with HF had an average hardness value of 9.37 GPa and later 6.86 GPa when exposed to 1500 °C.

Study and characterization of GaN MOS capacitors: Planar vs trench topographies

Developing high quality GaN/dielectric interfaces is a fundamental step for manufacturing GaN vertical power transistors. In this paper, we quantitatively investigate the effect of planar etching treatment and trench formation on the performance of GaN-based MOS (metal oxide semiconductor) stacks. The results demonstrate that (i) blanket etching the GaN surface does not degrade the robustness of the deposited dielectric layer; (ii) the addition of the trench etch, while improving reproducibility, results in a decrease in the breakdown performance compared to the planar structures. (iii) For trench structures, the voltage for a 10 year lifetime is still above 20 V, indicating a good robustness. (iv) To review the trapping performance across the metal-dielectric-GaN stack, forward-reverse capacitance–voltage measurements with and without stress and photo-assistance are performed. Overall, as-grown planar capacitors devoid of prior etching steps show the lowest trapping, while trench capacitors have higher interface trapping and bulk trapping comparable to the blanket etched capacitors. (v) The nanostructure of the GaN/dielectric interface was characterized by high resolution scanning transmission electron microscopy. An increased roughness of 2–3 monolayers at the GaN surface was observed after blanket etching, which was correlated with the higher density of interface traps. The results presented in this paper give fundamental insight on how the etch and trench processing affects the trapping and robustness of trench-gate GaN-metal-oxide-semiconductor field effect transistors and provide guidance for the optimization of device performance.

No-primer adhesive vs. self-adhesive resin: bonding strength following LED curing.

The goal of this study was to compare the shear bond strength (SBS) and failure modes of three different adhesive resins following the use of two different dental curing light units. A total of 160 human premolars were randomly divided into four groups (N = 40 for each): group1, Transbond™ XT (3M Unitek, Monrovia, CA, USA) adhesive paste; group2, Heliosit Orthodontic paste with no primer; group3, Maxcem Elite (Kerr, Orange, CA, USA) self-adhesive resin with prior etching; group4, Maxcem Elite self-adhesive resin with no etching. Each group was further divided into 2subgroups: half (named "a") were cured with VALO LED (Ultradent Products, South Jordan, UT, USA), and the other half (named "b") with the Elipar LED unit (3M Unitek LED, Monrovia, CA, USA). The brackets were submitted to SBS testing 24 h after bonding. Adhesive Remnant Index (ARI) scores and bonding time were also measured. Two-way analysis of variance (ANOVA) and Kruskal-Wallis tests were used for statistical analysis. No significant differences in SBS were observed when comparing the two different LED devices within the same bonding material. The mean SBS of group1 was significantly higher compared to groups2, 3, and 4 (p < 0.001). Mean SBS values of groups2 and 3 were significantly higher than that of group4 (p < 0.001). ARI scores were significantly different in groups4a and 4b compared to the other groups (p < 0.05). Group4a showed significantly lower bonding time/tooth compared to the other groups except to groups3a and 4b (p < 0.001). Decreasing curing time using high-power LED device did not significantly affect SBS. However, the composite type did affect SBS.

Improving Aluminum Ultraviolet Plasmonic Activity through a 1 nm ta-C Film.

Aluminum (Al) can actively support plasmonic response in the ultraviolet (UV) range compared to noble metals (e.g., Au, Ag) and thus has broad applications including UV sensing, displays, and photovoltaics. High-quality Al films with no oxidation are essential and critical in these applications. However, Al is very prone to fast oxidation in air, which critically depends on the fabrication process. Here, we report that by leveraging the in situ sputter etching and sputter deposition of a 1 nm tetrahedral amorphous carbon (ta-C) film on the Al nanostructures, Al plasmonic activity can be improved. The prior sputter etching process greatly reduces the oxidized layer of the Al films, and the subsequent sputter deposition of ta-C keeps Al oxidation-free. The ta-C film outperforms the naturally passivated Al2O3 layer on the Al film because the ta-C film has a denser structure, higher permittivity, and better biocompatibility. Therefore, it can effectively improve the plasmonic response of Al and be beneficial to molecule sensing, which is proved in our experiments and is also verified in simulations. Our results can enable the various applications based on plasmon resonance in the UV range.

Clinical Comparison of Fissure Sealants Retention Following Preparation with Seventh Generation Bonding Agent with Prior Etching and Conventional Acid Etch and Bond System (fifth Generation)

Introduction: Fissure sealant therapy is a preventive method relied on covering pits and fissures to prohibit bacteria from settling on tooth and producing acid, which cause tooth demineralization. The benefits of caries prevention could only be achieved when the sealants remain intact for a long time, thus long-lasting retention is mandatory. Despite recently achieved improvement in sealant quality, their retention in long course remains a challenging issue in dentistry. The purpose of our study was to compare the clinical efficacy of sealants after using seventh generation adhesive and additional etchant material with fifth generation bonding agent. Materials and Methods: In this randomized clinical trial, 40 patients in the age group of 7 to 12 years were randomly selected. All participants had a pair of sound first permanent molar in the mandible, which need fissure sealant therapy. For each patient, one tooth was treated with seventh generation bonding and separate etching material, and the counterpart tooth had undergone the fifth generation bonding system. A pediatric dentist did exert 6 and 12-mounth follow ups. Results: In 38 of 40 patients, who completed 6-month follow-up, the success rate of seventh generation adhesive was 84.2% and in the fifth generation group it was 76.3%. At 12-month follow-up, 36 patients were referred and success rate of fifth generation bonding was 52% and it was 36% in seventh generation adhesive. According to fisher test, the difference between two groups was not statistically significant. Conclusion: This study depicted that fissure sealant retention was equal after 6 and 12 months in both methods.

Does Rubbing of Universal Adhesive Reduce the Negative Effect of Saliva on Adhesion?

To evaluate in vitro the effect of saliva contamination on bond strength of a universal adhesive applied with actively (with rubbing motion) and passively (without rubbing motion). A total of 144 bovine dentin samples were used, and the universal adhesive, Clearfil Universal Bond Quick, was either applied in accordance with the manufacturer's instructions (passive application) or applied with rubbing motion for 10 s (active application). These 2 groups were divided into 6 subgroups according to saliva contamination (n = 12): 1. control: etch-and-rinse (no saliva); 2. control: self-etch (no saliva); 3. etching/saliva/bonding; 4. etching/bonding/saliva; 5. saliva/bonding; 6. bonding/saliva. A resin composite, Filtek Ultimate, was filled into a polyethylene mold (0.9 mm diameter, 1.2 mm height) on the surfaces. Samples were subjected to microshear bond strength testing, and five specimens from each group were examined using SEM. Resin-dentin interfaces were also observed using transmission electron microscopy (TEM). All failure modes were determined using light microscopy. Statistical analyses were performed with two-way ANOVA, the Kruskall-Wallis test, and the Mann-Whitney U-test (p < 0.05). Active-application groups showed statistically significantly higher bond strengths than did passive groups, regardless of adhesive strategy and saliva contamination (p < 0.05). Application of Clearfil Universal Bond Quick in self-etch mode with rubbing motion improved the µSBS among control groups (p < 0.05). The active application did not make a significant difference among the active groups (p > 0.05), except in group 2. Groups 2 and 5 showed significantly higher µSBS than group 3 among the passive groups (p < 0.05). Rubbing the universal adhesives without any prior etching may increase the dentin bond strength. Following etching, passive application of the universal adhesive (without any additional rubbing motion) could affect the bonding to dentin in the presence of saliva.

Surface preparation by mechanical polishing of the 1.3-GHz mono-cell copper cavity substrate prior chemical etching for niobium coating

Surface quality of the substrate is widely acknowledged to be essential for the niobium thin film deposition. Much effort has thus been spent to improve the surface roughness by using various chemical etching techniques. However, surface preparation before the chemical etching also plays a part in obtaining a satisfactory substrate, but has rarely been studied before. This paper aims to define a specification for the pre-polished copper substrate prior chemical etching and searches for suitable alternative non-chemical grinding methods for the copper cavity. Copper samples were mechanically pre-polished at first by using flap sanding wheels of different grits and then chemically etched by using the well-established SUBU solutions. Surface roughness, as a figure of merit, was measured and compared before and after SUBU. Optimum practice for pre-polishing may therefore be determined. The mechanical grinding was subsequently applied on the 1.3-GHz mono-cell copper cavity. Meantime, the previously reported centrifugal barrel polishing method was also applied with new abrasive materials and modified schemes. A comprehensive study of etching rate, surface roughness and morphologies was conducted. The specification for surface roughness prior SUBU was determined. Due to a complex geometry and curved surfaces possessed by the 1.3-GHz copper cavity, the traditional mechanical grinding was proved to be not ideal. Satisfactory surface quality was obtained by using the alternative centrifugal barrel polishing on the cavity. The proposed new scheme and new abrasive materials were demonstrated to be effective, and a mirror-like surface was achieved on the copper cavity. The traditional mechanical grinding can therefore be replaced. This constitutes a dedicated study on pre-polishing of the 1.3-GHz copper cavity substrate prior chemical etching for niobium sputtering.

Adhesive restoration of molars affected by molar incisor hypomineralization: a randomized clinical trial.

This randomized clinical trial evaluated the survival of direct restorations on first permanent molars (FPMs) with molar incisor hypomineralization (MIH) and its impact on self-reported dental pain and dental anxiety. FPMs with MIH of 35 patients aged 7 to 16years were included. The FPMs were randomized into the following two groups: total-etch (TE-37% phosphoric acid etching) and self-etch (SE-no prior etching). The FPMs were restored with universal adhesive and bulk-fill resin composites. The restoration survival was evaluated according to USPHS criteria modified by a blinded examiner. Dental anxiety (Venham picture test) and dental pain (Faces pain scale-revised) were evaluated before treatment and at 1, 6, and 12months post-treatment. Survival rates were analyzed by the Kaplan-Meier method and the log-rank test. Nonparametric tests compared pain and anxiety in the follow-up periods. A total of 64 FPMs were restored (TE = 33; SE = 31). Survival rates were 96.9% (TE) and 96.7% (SE) after 1month, 90.5% (TE) and 80.6% (SE) after 6months, and 80.8% (TE) and 62.3% (SE) after 12months (p > 0.05). Self-reported dental pain and anxiety level decreased after treatment in both groups (p < 0.05). Self-reported pain decreased after 1month in SE, but it occurred at 6months in TE. Both restorative protocols presented similar longevity, decreasing self-reported pain and anxiety levels. A universal adhesive could be appropriate for restoration of MIH-affected teeth, and the survival of restorations could be higher in the total-etch technique, reducing dental pain and anxiety.

Process Development of Radical Based Dry Clean for Advanced 3D NAND Fabrication

As semiconductor device scaling marching toward sub-5 nm logic, 128+ layers 3D NAND, and advanced 1x nm DRAM technology nodes, wafer surface cleaning and residue removal in nanoscale, high aspect ratio structures become increasingly critical. Dry clean technologies are developed as alternatives for traditional wet clean applications with significant advantages in process extendibility and environmental friendliness. Furthermore, in comparison with gas only processes, radicals are considered as attractive precursors for dry clean applications due to their high reactivity en route to a high cleaning efficiency. In this work we report a novel inductively coupled remote plasma source design for radical based dry clean applications. The inductively couple plasma (ICP) source yields a high gas dissociation efficiency and a high radical density. Plasma potential and electron temperature are minimized with a unique grounded Faraday shield design and can be further suppressed with a pulsed plasma operation. Ions and electrons generated in the plasma are effectively filtered by charge separation grids, thus only leaving high flux radicals to impinge onto the wafer surface. Different radical chemistries are developed for selective removal of different dielectric, metal, and semiconductor materials, specifically for efficient cleaning inside nanoscale and high aspect ratio structures in advanced semiconductor devices. Here we report the following applications tailored toward 3D NAND manufacturing. Pre-epitaxial deposition clean in high-aspect-ratio channel holes: The requirements are to remove SiOx-like residues and damaged silicon layer at the bottom of high-aspect-ratio channel holes without damage to the exposed SiO2/SiN stacks. The aspect ratio of channel holes can exceed 50:1. A multi-step process is developed based on remote plasma chemistries containing hydrogen and fluorine radicals, in conjunction of a RF bias on wafer surface to improve directionality. SiOx-like residues of various thickness are initially completely removed at the bottom of high-aspect ratio structures. With a customized radical chemistry and a unique anisotropic process, there is no sidewall SiN/SiO2 damage and a minimal CD change. Followed by a selective removal of damaged silicon layer and surface contamination from prior etch process, a pristine and coherent surface can be prepared for the subsequent epitaxial deposition. Contact hole clean: The main objective is to remove amorphous silicon or silicon oxide interface layer at bottom of high aspect ratio contact hole structures in order to minimize metal contact resistance. The aspect ratio of contact hole structures can exceed 50:1 in advanced 3D NAND devices. Device process flow requires a high selectivity towards tungsten. A fluorine-containing remote plasma process was developed to effectively remove oxidized Si residues, create enough gouging depth, and maintain contact hole structure integrity at the same time. Contact resistance is significantly reduced with the radical based dry clean process.

Microtensile Bond Strength of Composite to Enamel Using Universal Adhesive with/without Acid Etching Compared To Etch and Rinse and Self-Etch Bonding Agents.

AIM:Considering the recent introduction of universal adhesives and the controversy regarding the use/no use of etchant prior to their application, this study sought to assess the microtensile bond strength of composite to enamel using universal adhesive with/without acid etching compared to three-step etch and rinse, two-step etch and rinse and two-step self-etch bonding agents.METHODS:This in vitro, an experimental study was conducted on 80 extracted sound human molars in five groups (16 each): Scotchbond Universal adhesive (3M) with/without prior etching, Adper Scthe otchbond Multi-Purpose, Single Bond and Clearfil SE Bond. Etching was performed with 37% phosphoric acid for 20 seconds followed by rinsing and drying. The bonding agent was then applied and light-cured. The e-lite composite was bonded to surfaces and light-cured. The teeth were then mounted, sectioned and subjected to microtensile bond strength test in a universal testing machine. The mode of failure was, determined under a stereomicroscope. Data were analysed using one-way ANOVA followed by Tukey’s test.RESULTS:Universal adhesive with prior etching yielded the highest bond strength (P = 0.03). Pairwise comparisons showed that the bond strength of this group was significantly higher than that of universal adhesive without prior etching (P = 0.04). No other significant differences were noted (P > 0.05). The modes of failure were significantly different among the groups (P = 0.003).CONCLUSION:Enamel etching with phosphoric acid can significantly increase the bond strength to universal adhesive. Universal adhesive without prior etching provided the bond strength as high as that provided by etching and rinse and self-etch bonding agents.

The effects of hybrid light activation and enamel acid etching on the effectiveness, stability and sensitivity after a single session in-office bleaching: A 12-month clinical trial.

The use of hybrid-light (HL) during in-office teeth bleaching can provide faster and reliable results after a single bleaching session, especially if associated with previous acid etching. The present in vivo, interventional, split-mouth, triple-blinded and randomized study evaluated the efficiency of a HL, with and without prior enamel acid etching, assessing the gel application time, degree of color change, sensitivity and treatment stability up to 12 months. Thirty-four patients were selected and randomly divided into four groups. The color was evaluated using a spectrophotometer with the CIELab color system, and a VAS questionnaire was used to evaluate the sensitivity. Both upper and lower hemiarches (GI and III) received enamel acid etching with 37% phosphoric acid for 15 s prior to the application of 35% hydrogen peroxide gel (HP). For GI and II, HP was applied on both dental arches for 3-4 consecutive applications and activated by HL (2 × 3' activations with 1' interval); and 3 × 15' (HP) for GIII and IV without HL. Patients returned in 24 h, 1 week, 1-, 6- and 12-months intervals. The clinical operator was different from the clinical measurements operator. After 3-way ANOVA, Tukey's, Wilcoxon and Mann-Whitney tests, all with p < 0.05, no statistical differences were observed between the groups regarding color change (ΔE) and sensitivity in all evaluations. The lowest gel application time was observed for GII (acid etch + HL), followed by GI (HL). The present study's results reveal the advantages of HL associated with acid etching prior to in office bleaching.

Repassivation Behavior of Individual Grain Facets on Dilute Ni–Cr and Ni–Cr–Mo Alloys in Acidified Chloride Solution

The effects of crystal orientation and prior etching on the polarization and repassivation behavior of Ni–Cr and Ni–Cr–Mo alloys have been investigated in acidic chloride environment using dc potentiostatic and ac single-frequency electrochemical impedance spectroscopy. Tests were conducted within the passive region at potentials where local oxide breakdown was possible. Surface morphologies of grains across a wide range of orientations were measured before and after passivation using atomic force microscopy. Oxide growth was monitored on isolated low- and high-index crystallographic planes as a function of repassivation time, enabling the independent measurement of the oxidation and total anodic current densities. Grains exhibited the tendency to either passivate with significant or minimal oxidation or instead resist active passivation and repassivation. The oxidation performance was a function of the crystallographic orientation of the exposed grain surface. The oxides grown on various-orientated surfa...

Epitaxial growth of Cu(001) thin films onto Si(001) using a single-step HiPIMS process

We report on a new route to grow epitaxial copper (Cu) ultra-thin films (up to 150 nm thick) at ambient temperature on Si(001) wafers covered with native oxide without any prior chemical etching or plasma cleaning of the substrate. It consists of a single-step deposition process using high power impulse magnetron sputtering (HiPIMS) and substrate biasing. For a direct current (DC) substrate bias voltage of −130 V, Cu/Si heteroepitaxial growth is achieved by HiPIMS following the Cu(001) [100]//Si(001) [110] orientation, while under the same average deposition conditions, but using conventional DC magnetron sputtering, polycrystalline Cu films with [111] preferred orientation are deposited. In addition, the intrinsic stress has been measured in situ during growth by real-time monitoring of the wafer curvature. For this particular HiPIMS case, the stress is slightly compressive (−0.1 GPa), but almost fully relaxes after growth is terminated. As a result of epitaxy, the Cu surface morphology exhibits a regular pattern consisting of square-shaped mounds with a lateral size of typically 150 nm. For all samples, X-ray diffraction pole figures and scanning/transmission electron microscopy reveal the formation of extensive twinning of the Cu {111} planes.

Active application of primer acid on acid-treated enamel: Influence on the bond effectiveness of self-etch adhesives systems.

Evaluate the composite-to-enamel bond after passive or active application of self-etching primer systems on polished or pre-etched enamel with phosphoric acid. Two self-etch adhesives systems (SEAS) were used: Clearfil SE Bond and Easy Bond. Third human molars were divided into 8 groups (N = 10). The crown of each tooth was sectioned into halves and the mesial/distal surfaces were used. The adhesives were actively or passively applied on enamel with or without prior phosphoric-acid etching. Resin composite cylinders were built after adhesive application. After stored in relative humidity for 24 hr/37°C the specimens were subjected to microshear test in universal testing a machine at a crosshead speed of 0.5 mm/minute. The results were analyzed with three-way ANOVA and the Tukey test. The enamel-etching pattern was evaluated under SEM. The 2-step SEAS system presented significantly higher adhesive bond strength means (47.37 MPa) than the 1-step (36.87 MPa). A poor enamel- etching pattern was observed in active mode showing irregular and short resin tags, however there was not compromised the bond strength. Active or passive application produced similar values of bond strength to enamel regardless of enamel pretreatment and type of SEAS.

Effectiveness of pit and fissure sealants bonded with different adhesive systems: a prospective randomized controlled trial.

To evaluate and compare the clinical retention of a resin-based fissure sealant placed with an intermediate layer of etch-and-rinse (ER) or self-etch (SE) adhesives. Two hundred twenty-eight sealants were placed in 57 children with previously unsealed, caries-free permanent first molars, employing a split-mouth design. The teeth were randomized into four groups (n=57 teeth/groups) according to the adhesive system placed under the tested sealant (Delton FS+; Dentsply). Group 1 (control): no bonding agent (conventional acid-etch sealant); group 2: prior enamel etch+ER adhesive (XP Bond; Dentsply); group 3: SE adhesive (Clearfil SE Bond; Kuraray) without prior etching; and group 4: prior enamel etch+SE adhesive (Clearfil SE Bond). Clinical assessments were performed according to modified USPHS criteria at 1, 3, 6, 12, 18, and 24months. The data were analyzed statistically using Fisher's Exact test, the Kaplan-Meier analysis, and the Log-rank test. At 24months, sealants bonded with XP Bond and Clearfil SE Bond with prior enamel etching showed similar retention rates (p>0.05), and these rates were significantly better than the rates of the conventional sealant and Clearfil-SE groups (p<0.05). There was no significant difference between the retention rates of the latter two groups (p>0.05). The cumulative survival rates on palatal/buccal surfaces showed similar outcomes as with occlusal surfaces: XP Bond (94%), Clearfil SE Bond+acid-etch (94%), conventional sealant (52%), and Clearfil SE Bond only (37%). Application of the tested ER adhesive and the SE adhesive with enamel etching significantly improved the clinical retention of Delton-FS over the 24-month period. The use of a resin-based fissure sealant placed with ER or SE adhesive with prior acid-etching yielded better retention than the conventional sealant over the 24-month period.

Penetration of resin-based materials into initial erosion lesion: A confocal microscopic study.

The application of resin-based materials is an alternative of treatment for eroded lesions. Nevertheless, there are no studies about the penetration of these materials into eroded lesion, which might affect its adhesion. Therefore, this study evaluated the penetration of four resin-based materials, with and without enamel etching. By using an in vitro protocol, types of treatment were studied at five levels (AdheSE(®) , Tetric N-Bond(®) , Single Bond 2(®) , Helioseal Clear(®) , Icon(®) ) and types of enamel etching in two levels (with and without). Materials were stained with 0.02 mg/mL ethanolic solution of tetramethylrhodamine isothiocyanate. Bovine enamel samples (4 × 4 mm) were immersed in 0.01 M HCl, pH 2.3, for 30 seconds to produce initial eroded lesions. Afterward, the materials were applied on half of sample enamel surface following the manufacturer's instructions. On the other half of sample, the materials were applied without etching the enamel. Materials penetration into the enamel was assessed by Confocal Laser Scanning Microscopy on reflection and fluorescence modes. The penetration depth (PD) was measured using ImageJ software. Data were analyzed by two-way ANOVA and Tukey test (P < 0.05). Regardless of the material, etched enamel resulted in higher PD than non-etched (P < 0.05). Icon(®) showed the highest PD in enamel followed by Helioseal Clear(®) (P < 0.05), with significant difference between them (P < 0.05) and no difference was found among AdheSE(®) , Tetric N-Bond(®) , and Single Bond 2(®) (P > 0.05). It can be concluded that prior enamel etching increased the materials penetration into eroded enamel and the Icon(®) -infiltrant presented highest penetration.

Heat treatment of pre-hydrolyzed silane increases adhesion of phosphate monomer-based resin cement to glass ceramic.

This study evaluated the influence of different forms of heat treatment on a pre-hydrolyzed silane to improve the adhesion of phosphate monomer-based (MDP) resin cement to glass ceramic. Resin and feldspathic ceramic blocks (n=48, n=6 for bond test, n=2 for microscopy) were randomly divided into 6 groups and subject to surface treatments: G1: Hydrofluoric acid (HF) 9.6% for 20 s + Silane + MDP resin cement (Panavia F); G2: HF 9.6% for 20 s + Silane + Heat Treatment (oven) + Panavia F; G3: Silane + Heat Treatment (oven) + Panavia F; G4: HF 9.6% for 20 s + Silane + Heat Treatment (hot air) + Panavia F; G5: Silane + Heat Treatment (hot air) + Panavia F; G6: Silane + Panavia F. Microtensile bond strength (MTBS) test was performed using a universal testing machine (1 mm/min). After debonding, the substrate and adherent surfaces were analyzed using stereomicroscope and scanning electron microscope (SEM) to categorize the failure types. Data were analyzed statistically using two-way test ANOVA and Tukey's test (=0.05). Heat treatment of the silane containing MDP, with prior etching with HF (G2: 13.15 ± 0.89a; G4: 12.58 ± 1.03a) presented significantly higher bond strength values than the control group (G1: 9.16 ± 0.64b). The groups without prior etching (G3: 10.47 ± 0.70b; G5: 9.47 ± 0.32b) showed statistically similar bond strength values between them and the control group (G1). The silane application without prior etching and heat treatment resulted in the lowest mean bond strength (G6: 8.05 ± 0.37c). SEM analysis showed predominantly adhesive failures and EDS analysis showed common elements of spectra (Si, Na, Al, K, O, C) characterizing the microstructure of the glass-ceramic studied. Heat treatment of the pre-hydrolyzed silane containing MDP in an oven at 100 °C for 2 min or with hot air application at 50 ± 5 ºC for 1 min, was effective in increasing the bond strength values between the ceramic and resin cement containing MDP.