Adhesive Bond Strength Research Articles

Effects of etching mode on bond strength of universal adhesives

Effects of etching mode on bond strength of universal adhesives

Effect of Metalloproteinase Inhibitors on Bond Strength of a Self-etching Adhesive on Erosively Demineralized Dentin.

To analyze the influence of epigallocatechin-3-gallate (EGCG) and chlorhexidine (CHX) on adhesive-dentin bond strength of a self-etch adhesive to sound dentin (SD) and eroded dentin (ED). Thirty-six middle-dentin samples were assigned to six groups (n = 6) according to pretreatment (DW: distilled water, control; 0.1% EGCG; or 2% CHX) and erosive challenge (presence or absence). Specimens were subjected to 2-h acquired pellicle formation, then half of them were exposed to 1% citric acid three times a day for five days. SD and ED were treated with the tested solutions for 60 s, and then Clearfil SE Bond was applied before resin composite buildup. Bonded teeth were longitudinally sectioned into sticks and half were immediately tested, while the remaining specimens were tested after six months. The mode of fracture was examined and the microtensile bond strength (µTBS) measured. Statistical analysis was performed with ANOVA and Bonferroni tests. At both time periods, regardless of the dentin substrate, EGCG groups did not show bond strengths that were significantly different from those obtained with DW (p > 0.05), while CHX generated lower values than did DW (p < 0.05). On SD, there was a bond strength reduction only in the CHX groups after six months. However, for ED, the bond strength significantly decreased in all groups. CHX negatively affected both dentin substrates, while the pretreatment with EGCG did not affect µTBS over time on SD. µTBS may be influenced by the substrate over time and EGCG can be used as an alternative to CHX to maintain the bond strength of self-etching adhesives.

Universal Adhesives Benefit from an Extra Hydrophobic Adhesive Layer When Light Cured Beforehand.

To measure microtensile bond strength (μTBS) of universal adhesives immediately and after 6-month aging, with or without an additional adhesive layer applied on a separately light-cured or non-light-cured universal adhesive. Eighty human third molars were randomly assigned to 8 experimental groups. The universal adhesives Clearfil Universal Bond (Kuraray Noritake) and Single Bond Universal (3M Oral Care) were used in self-etch mode (following the manufacturer's directions), and either light cured or not before application of an extra hydrophobic adhesive layer (Clearfil SE Bond bond, Kuraray Noritake). The two-step self-etch adhesives Clearfil SE Bond (Kuraray Noritake) and OptiBond XTR (Kerr) were used as references. After composite buildups were bonded to mid-coronal occlusal dentin surfaces, the specimens were stored in water (37°C/24 h) and sectioned into microspecimens (0.96 ± 0.04 mm2). Half of the specimens were immediately subjected to μTBS testing (1.0 mm/min), while the other half was stored in water (37°C) for 6 months prior to testing. Failure analysis was performed using stereomicroscopy and SEM. Data were analyzed with two-way repeated measures ANOVA, Tukey's and paired t-tests (p = 0.05). The immediate μTBS was similar for the universal adhesives when applied following the different application strategies (p > 0.05). Application of an extra layer of hydrophobic adhesive improved the aged μTBS of the universal adhesives, which was statistically significant when the universal adhesives were first light cured (p < 0.05). The reference adhesives Clearfil SE Bond and OptiBond XTR exhibited a significantly higher immediate and aged μTBS to dentin than did the universal adhesives (p < 0.05). The bond durability of universal adhesives, applied in self-etch mode, was found to benefit from the application of an extra hydrophobic adhesive layer when the universal adhesives were first light cured.

New Approaches in Bonding to Glass-Ceramic: Self-Etch Glass-Ceramic Primer and Universal Adhesives.

To investigate the tensile bond strength of silane-containing universal adhesives and self-etch glass-ceramic primer to lithium disilicate glass ceramics (LS2). 960 rectangular LS2 bars (7 mm x 3 mm x 9 mm, IPS e.max CAD, Ivoclar Vivadent) were manufactured and divided into 4 groups (n = 240). Group 1 was etched with ~5% hydrofluoric acid (HF) for 20 s (VITA Ceramics Etch, Vita Zahnfabrik), group 2 was etched with ~5% HF for 20 s and silanized (ESPE Sil, 3M Oral Care), group 3 was pre-treated with a self-etching glass-ceramic primer (Monobond Etch & Prime, Ivoclar Vivadent, and group 4 received no pre-treatment. Three universal adhesives (iBOND Universal, Heraeus Kulzer; Scotchbond Universal Adhesive, 3M Oral Care; Futurabond U, Voco) were applied to the differently pre-treated surfaces, with Heliobond (Ivoclar Vivadent) serving as control. The bars from each group were paired and luted perpendicularly, forming a square bonded area of 9 mm2, using Variolink II (Ivoclar Vivadent) with a constant pressure of 10 N, followed by light curing (40 s at 800 mW/cm2, Elipar Trilight, 3M Oral Care). The resulting specimens were stored for 24 h at 37°C in distilled water. Half of the specimens of each group were submitted to tensile bond strength testing, the other half were thermocycled ([TC] 5000 cycles, 5°C/55°C, 30-s dwell time) before testing. Data were analyzed using three-way ANOVA (α = 0.05). Group 2 (HF etched and silanized) and group 3 (self-etching glass-ceramic primer) reached significantly higher mean bond strengths than did groups 1 (only HF etched) and 4 (no pre-treatment). Additional silanization of HF-etched LS2 statistically signficantly improved the tensile bond strength of the silane-containing universal adhesive (Scotchbond Universal). The self-etching glass-ceramic primer Monobond Etch & Prime achieved mean bond strengths that did not differ significantly from HF-etched and silanized specimens.

Effect of Er:YAG and Burs on Coronal Dentin Bond Strength Stability.

To evaluate the immediate and aged bond strength and interfacial nanolaekage of different adhesives and protocols on dental elements prepared with diamond burs and Er:YAG laser. Forty molar crowns were flattened and a standardized smear layer was created. Teeth were divided into two main groups according to the dentin cutting technique: 1. Er:YAG laser for 30 s at 30 Hz repetition rate, 250 mJ energy per pulse, and water spray irrigation set at level 8; and 2. diamond bur. Each group was then divided into subgroups according to the adhesive protocol: SG1: dentin etching for 15 s followed by universal adhesive application (All Bond Universal, Bisco); SG2: universal adhesive application (All Bond Universal); SG3: two-step self-etch adhesive application (Clearfil SE Bond 2, Kuraray Noritake); SG4: etching followed by 3-step etch-and-rinse adhesive application (Optibond FL, Kerr). After curing the adhesives, resin composite buildups of 4 mm were made and specimens were sectioned to obtain 1-mm-thick sticks in accordance with the μTBS test technique. Sticks were stressed to failure at baseline and after 6 months of storage in artificial saliva. Three teeth per group were prepared for nanoleakage interfacial analyses. Data were statistically analyzed with three-way ANOVA and Tukey's post-hoc test (p < 0.05). A significant difference in bond strengths was found for treatment, aging, and adhesive protocol. Nanoleakage analysis showed higher marginal infiltration in Er:YAG-treated groups both at baseline and after aging. Surfaces prepared with diamond burs presented higher bond strengths than did those prepared with Er:YAG laser. Adhesive protocols and aging could influence the adhesive-dentin interface. Further studies are necessary to validate the results obtained.

A Comparative Study of Shear Bond Strength of Direct Bonding System with and without a Liquid Primer: An In Vitro Study.

Background:A primer in dental bonding agents enhances the bond between the adhesive and the tooth by way of deriding the tooth surface of moisture and creating a hydrophobic surface for the adhesive to bond and by facilitating the flow of the adhesive into the etched tooth surface. In the orthodontic context, however, there have been debatable results in the published literature as to how significantly the use of primer affects the bond strength between the bracket and the tooth surface.Aims:This study aimed to evaluate and compare the shear bond strength of two commercially available direct bonding systems with and without using liquid primer and to record their adhesive remnant index scores.Settings and Design:A total of 100 natural human teeth, extracted for orthodontic therapies, had been selected as specimens for the study. They were equally divided into four categories. Two commercially available products were used to bond metallic orthodontic brackets to the teeth, both with the use of and without the use of a primer to test the shear bond strengths of the four types of adhesive-tooth complexes created. Shear bond strength was measured using universal testing machine, and Student’s t-test was applied for the comparison of the results.Materials and Methods:A total of 100 extracted human premolar teeth were divided into two groups: Group I and Group II, each of which contained two subgroups (with one subgroup pretreated with a primer and the other, not pretreated with the primer). All the teeth were divided equally among the subgroups and were mounted on color-coded acrylic blocks to aid in identification. Group I was bonded with Transbond XT Light Cure Adhesive (3M Unitek Orthodontic Products, Monrovia, California) and Group II was bonded using Phase II two-paste system (Reliance Orthodontic Products, Itasca, Illinois). The shear bond strength of Transbond XT Light Cure Adhesive used with Transbond XT primer and Phase II orthodontic two-paste system used with liquid primer was compared with that of those used without a liquid primer, respectively. The shear bond strength was evaluated using universal testing machine and the adhesive remnant scores were evaluated subsequently. The Student’s t-test was applied for comparison of the two groups.Statistical Analysis:Descriptive statistics, such as mean, standard deviation, and a standard error, were calculated for Transbond XT used with and without primer and for Phase II two-paste system used with and without a liquid resin. The Student’s t-test was applied for comparison of the two groups.Results:In Group I, the mean bond strength of Transbond XT without primer (12.5272MPa, 95% CI: 11.76–13.68) was compared to that of Transbond XT with XT primer (13.2028MPa, 95% CI: 12.39–14.06). In Group II, the mean shear bond strength of Phase II two-paste system without primer (10.66MPa, 95% CI: 10.13–11.18) was compared to that of Phase II two-paste system with primer (10.66MPa, 95% CI: 10.13–11.18), and the values were statistically insignificant.Conclusion:The shear bond strength of the brackets bonded with Transbond XT and Phase II without using the liquid primer was sufficient enough to withstand the masticatory forces, which implies the elimination of liquid primer during bonding.Clinical Significance:The development of the acid-etch technique and Bisphenol A-glycidyl methacrylate-based liquid resin has changed the practice of orthodontics over the years more than any other single principle formulated. Despite its wide popularity, the cytotoxicity, which stems from the use of liquid primer, needs attention.

Evaluation of the effect of chlorhexidine and sodium hypochlorite in adhesive cementation of fiber posts - in vitro study

Abstract Introduction The attachment of fiberglass posts is achieved through an adhesive process. Failures in adhesion may occur due to the hydrolytic degradation of the adhesives, or to the degradation of the collagen fibres of the hybrid layer by intrinsic enzymes. Objective To evaluate the effect of chlorhexidine and sodium hypochlorite treatment on bond strength to dentin. Material and method Thirty bovine roots were randomly distributed into 3 groups (n=10): a) Control, b) 2% Chlorhexidine, and c) 5% Sodium Hypochlorite. Next, RelyX® ARC resin cement was used to cement the post. Each specimen resulted in samples from the three root thirds that were submitted to the pushout test (MPa) at 24 hours and 12 months. Bond strength values were analysed using the Kolmogorov-Smirnov, 3-way ANOVA and Tukey tests. The fracture mode of the pin was also analysed using stereomicroscopy. Result There were no significant differences between treatments at the immediate time (p=0.0644) or in the interaction of factors (p=0.1935). After one year, the experimental groups showed no significant differences in bond strength in relation to the control group, with the exception of the cervical third of the chlorohexidine group in which there was a significant loss of adhesion. As for the fracture mode, there was a predominance of the mixed type in all groups and thirds. Conclusion The use of chlorhexidine or hypochlorite provides neither benefits nor losses in the adhesive bond strength of fiberglass posts. However, there is an influence of the root thirds, with the worst bond strength in the apical third.

Evaluation of the Bond Strength of Universal Tray Adhesives on Silicone Impression Materials Using an Acrylic Tray

To evaluate the bond strength of two commercially available universal tray adhesives on polyvinylsiloxane addition silicone and condensation silicone impression materials to an autopolymerizing polymethyl methacrylate acrylic tray material. Sixty flat square specimens were fabricated from autopolymerizing polymethyl methacrylate tray material to which an eye hook was incorporated to serve as the point of attachment to a universal testing machine. A polyvinyl chloride (PVC) pipe of 15 mm diameter and 25 mm long was used to house the impression material, and a metal rod was inserted into two centered holes to provide retention that serves as the second point of attachment to the universal testing machine. The specimens were divided into 4 groups of 15 specimens each. The first and second groups of specimens were applied with Coltene and Zhermack universal tray adhesives and tested with addition silicone impression material. The third and fourth groups were coated with the above-mentioned adhesives, respectively, and tested with condensation silicone. Each specimen was then attached to the universal testing machine. The maximum force at which separation failure occurred was divided by the area of adhesion and recorded as the adhesive strength in MPa. A significant difference was observed between mean MPa values of Zhermack and Colten universal tray adhesives, where the F value of 1314.116 was found to be significant at 0.000 levels indicating that the Zhermack adhesive had higher MPa than Coltene adhesive. Impression material again indicated significant difference (F = 132.514; p = 0.000), where addition silicone had higher MPa value than condensation silicone. Also, the interaction between adhesive and impression material was found to be significant (F = 10.794; p = 0.002). The adhesive bond strength of Zhermack universal tray adhesive was higher compared to that of Coltene universal tray adhesive irrespective of the elastomeric impression material. It was also found that bond strength of Zhermack universal tray adhesive with addition silicone impression material was the highest and Coltene universal tray adhesive with condensation silicone impression material was the least of all the four groups. Tray adhesives need to be applied to the tray to obtain an accurate and consistent impression. If there is a separation of impression materials from the tray, it may results in a distorted impression leading to poor final restorations.

Do Products Preventing Demineralization Around Orthodontic Brackets Affect Adhesive Bond Strength?

Objective: This study investigated the effects, on the shear bond strength of orthodontic brackets, of using an antimicrobial selenium-containing sealant (DenteShieldTM) to serve dual functions of priming enamel prior to bonding and as a protective barrier against whitespot lesion formation. Materials and Methods: A total of 150 extracted human premolars were randomly assigned into 10 groups (n=15/group). Stainless steel brackets were bonded with two adhesive systems (DenteShieldTM or Transbond XT) after the enamel was conditioned with a primer (DenteShieldTM or Assure Universal) or a filled resin sealant (DenteShieldTM, Pro SealTM or Opal SealTM). The specimens were stored in deionized water at 37 °C for 24 hours and debonded with a universal testing machine. Results: The use of DenteShieldTM adhesive to bond orthodontic brackets to the enamel surface resulted in a significantly lower (P&lt;0.05), but clinically acceptable, shear bond strength (mean &amp; SD: 14.5±1.6 MPa) as compared with Transbond XT group (mean &amp; SD: 19.3±1.7 MPa). DenteShieldTM sealant used as primer resulted in shear bond strength values comparable to those of Pro SealTM and Opal SealTM. All adhesive-sealant and primer-sealant combinations tested in this study exhibited shear bond strength values greater than 9.6 MPa, sufficient for clinical orthodontic needs. Conclusion: DenteShieldTM sealant can serve as primer as well as anti-demineralization sealant during orthodontic treatment without adversely affecting the shear bond strength of the bracket.

The Influence of Cold Atmospheric Plasma Irradiation on the Adhesive Bond Strength in Non-Demineralized and Demineralized Human Dentin: An In Vitro Study

Purpose: While aiming at the use of Cold Atmospheric Plasmas (CAPs) in restorative dentistry, the present study intended to assess if plasma irradiation increases the Tensile Bond Strength (TBS) in non-demineralized and demineralized dentin. Materials and Methods: Forty-eight human dentin samples were assigned to three different treatment modalities: I: Plasma jet irradiation (CAP I); II: Dielectric barrier discharge plasma treatment (CAP II); and III: No plasma (control). In each group, half of the specimens had previously been demineralized. A fourth generation of adhesive and dental composite was applied to all of the samples. The testing of the TBS was performed after artificial aging. Results: In the non-demineralized dentin, the mean TBS values were significantly higher after using CAP II (16.95 MPa) than in the control samples (4.2 MPa; p = 0.001). Significantly higher TBS values were also obtained after irradiating the demineralized dentin with CAP I and CAP II (11.68 and 4.6 MPa) when compared to the control samples (0 MPa; p = 0.003 and 0.038). The differences between both of the plasma sources were only slightly significant (p = 0.05). Conclusion: CAPs can potentially enhance the adhesive/dentin interfacial bonding strength, whereby the underlying effects seem to depend on the type of plasma source and the degree of dentinal (de-) mineralization. In the non-demineralized dentin, after a complete caries excavation, dielectric barrier discharge devices might be favorable over the plasma jets, in order to improve the adhesive/dentin interfacial bonding. In contrast, the plasma jets could be more effective in the demineralized dentin after an incomplete caries excavation.

Compositionally graded doped hydroxyapatite coating on titanium using laser and plasma spray deposition for bone implants

Plasma sprayed hydroxyapatite (HA) coating is known to improve the osteoconductivity of metallic implants. However, the adhesive bond strength of the coating is affected due to a mismatch in coefficients of thermal expansion (CTE) between the metal and HA ceramic. In this study, a gradient HA coating was prepared on Ti6Al4V by laser engineered net shaping (LENS™) followed by plasma spray deposition. In addition, 1 wt% MgO and 2 wt% Ag2O were mixed with HA to improve the biological and antibacterial properties of the coated implant. Results showed that the presence of an interfacial layer by LENS™ enhanced adhesive bond strength from 26 ± 2 MPa for just plasma spray coating to 39 ± 4 MPa for LENS™ and plasma spray coatings. Presence of MgO and Ag2O did not influence the adhesive bond strength. Also, Ag+ ions release dropped by 70% less with a gradient HA LENS™ layer due to enhanced crystallization of the HA layer. In vitro human osteoblast cell culture revealed presence of Ag2O had no deleterious effect on proliferation and differentiation when compared to pure HA as control and provided antibacterial properties against E. coli and S. aureus bacterial strands. This study presents an innovative way to improve interfacial mechanical and antibacterial properties of plasma sprayed HA coating for load-bearing orthopedic as well as dental implants. Statement of significanceImplants are commonly composed of metals that lack osteoconductivity. Osteoconductivity is a property where bone grows on the surface meaning the material is compatible with the surrounding bone tissue. Plasma sprayed hydroxyapatite (HA) coating improves the osteoconductivity of metallic implants, however, the adhesive bond strength can be weak. This study incorporates a gradient HA coating by using an additive manufacturing technique, laser engineered net shaping (LENS™), followed by plasma spray deposition to enhance the adhesive bond strength by incorporating a thermal barrier. The proposed system has not been well studied in the current literature and the results presented bring forth an innovative way to improve the interfacial mechanical and antibacterial properties of plasma sprayed HA coating for load-bearing orthopedic implants.

Effect of smear layer and surface roughness on resin-dentin bond strength of self-etching adhesives.

The purpose of this study was to evaluate the effect of surface roughness and smear layer on the micro-shear bond strength (µSBS) of two self-etching adhesives, Clearfil SE Bond (SE) and Clearfil Tri-S Bond (S3). Flat dentin surfaces were prepared with SiC papers (600-, 180- and 120-grit) and diamond burs (extra fine, medium and coarse). They were further divided into smear-covered and smear-free surfaces and bonded with respective adhesives. µSBS test was performed after water storage at 37ºC for 24 h. Smear layer thickness measurement was evaluated by scanning electron microscope (SEM). Surface roughness was examined by contact stylus profilometer. Smear layer thickness and surface roughness were significantly different among all groups (p<0.05). No difference in µSBS was observed among surface prepared by SiC whereas bur-cut smear layer had negative effect on µSBS, especially for S3. Surface roughness from different surface preparations had no influence on µSBS (p<0.05).

Effects of silver diammine fluoride on bond strength of adhesives to sound dentin.

This study evaluated bonding of adhesives to dentin treated with silver diammine fluoride (SDF). Micro-shear bond strength (MSBS) to sound human dentin was investigated for 3 adhesive systems: Clearfil SE bond 2 (CSE), and Scotchbond Universal in self-etching (SBU) and phosphoric acid-etching (SBT) modes, following 4 different SDF application protocols (n=10); Control: treated with deionized water. P1: SDF applied for 10-s, no rinse. P2: SDF applied for 10-s, rinsed off after 1-min. P3: superficial dentin polished off after 24-h following P1. MSBS data were obtained after 24-h water storage at 37°C. SDF significantly affected MSBS to dentin depending on the SDF protocol and adhesive system. Rinsing SDF off improved bond strength but superficial refreshing of SDFtreated dentin prior to bonding showed the highest bond strength. The two-step self-etch adhesive (CSE) and the universal adhesive in acid-etching mode (SBT) showed better performance than universal adhesive (SBU) alone on SDF treated dentin.

Vacuum-UV of polyetheretherketone (PEEK) as a surface pre-treatment for structural adhesive bonding

ABSTRACT Polyetheretherketone (PEEK) is known for its poor wettability and poor adhesive properties. Hence, for the creation of reliable high-strength structural adhesive bonded joints, surface treatment of PEEK is required. In this work high strength bondable PEEK surfaces were achieved through a vacuum-UV (VUV) treatment. Samples of amorphous and semi-crystalline PEEK films were exposed to different VUV radiation doses. Additionally oxygen low-pressure plasma (LPP) and untreated (as received) PEEK samples were investigated for comparison. Surfaces were characterized using x-ray photoelectron spectroscopy (XPS), contact angle measurements (CA), atomic force microscopy (AFM) and confocal laser scanning microscopy (CLSM). Tensile tests of the PEEK films were carried out, to investigate changes in the mechanical properties in the bulk of the PEEK films due to the VUV exposure. The adhesive bond strength of treated specimen was determined through two different test methods (tensile and shear). These strengths were compared to the created surface properties. A strong correlation between the contact angle and the creation of functional groups was observed. VUV radiation appears as a suitable pre-treatment method for PEEK, as adhesive bonds of high strength were achieved after 5 seconds. Additionally, the usage of a VUV excimer lamp is simple, cheap and easy for automation.

The improvement of biocompatibility of adhesives : The effects of resveratrol on biocompatibility and dentin micro-tensile bond strengths of self-etch adhesives.

The aim of this in vitro study is to evaluate the effects of resveratrol (RES) addition on the cytotoxicity and microtensile bond strength (μTBS) of different adhesives. Five self-etching adhesives (G-aenial Bond-GC, Optibond All in One-Kerr, Gluma Self Etch-Kulzer, Clearfil S3 Bond-Kuraray, and Nova Compo-B Plus-Imicryl) were tested. They were applied to L-929 cell culture by the extract method. In the test groups, 0.5μM RES (Sigma-Aldrich) was added into the medium. Cell viability was assessed by MTT assay after 24h. Human extracted third molars were used for μTBS test (n = 7). The adhesives with or without 0.5μM RES addition were applied on dentin surfaces. A composite build-up was constructed. Then, the specimens were sectioned into multiple beams with the non-trimming version of the microtensile test and subjected to microtensile forces. Statistical analysis was performed using ANOVA and post hoc Tukey test (p˂0.05). The extracts of all adhesives decreased the cell viability. However, RES addition increased the cell viability in all groups (p˂0.05). RES addition did not cause any decrease in μTBS values of the adhesives compared to baseline. Optibond All in One showed the highest μTBS after RES addition. It was followed by Clerafil S3 Bond and Nova Compo-B Plus. No difference was determined between the Optibond All in One and Clearfil S3 Bond. There was difference between Optibond All in One and Nova Compo-B Plus (p˂0.05). RES addition may improve the biocompatibility without causing negative influence on μTBS of the adhesives. RES addition has clinical applicable potential to overcome the adverse biocompatibility of adhesives.

Multivariate analysis of high through-put adhesively bonded single lap joints

The goal of this research was to experimentally demonstrate the correlations between processing variables (adhesive type, bondline thickness, adherend thickness, surface pretreatment, overflow fillet) and effective strength in adhesively bonded single lap joints. While generalizations between effective strength and individual joint design parameters have been assumed for decades, the multifaceted interplay between parameters is complex and remains difficult to understand. Traditionally reported studies of the adhesive bond strength of single lap joints are often limited in the sample size populations needed to statistically probe concurrent design variables. To overcome sample size limitations a test matrix of 1200 single lap joints, partitioned by 96 unique fabrication conditions, was processed and tested using a workflow protocol orchestrated through a relational database. The enhanced pedigree and integrity enabled by using a relational database centered workflow allowed for multivariate principal component analysis of the joint design parameters, with all experimental data input available for peer audit. The results of this study revealed that the adhesive type biases the remaining joint configuration variables towards more influence with respect to either mechanical load or displacement to failure.

Microshear bond strength of universal adhesives for use with artificially demineralized enamel, with and without pre-etching

The aim of this study was to investigate the microshear bond strength of five universal adhesives for use with demineralized enamel, with and without pre-etching. Using five universal adhesives (Single Bond Universal (SBU), Clearfil Universal (CU), Prime&Bond Elect Universal (PBU), Bisco All Bond Universal (ABU), Gluma Bond Universal (GU)), composite cylinders were bonded to the labial surfaces of extracted upper incisor teeth, with or without pre-etching. A micro-shear bond strength test was performed. The debonding surfaces were evaluated with the use of SEM. The data was analyzed using one-way ANOVA and Tukey’s Post-hoc tests. SBU, ABU, and PBU increased the bond strength statistically when used in etch&rinse mode (p < 0.05). GU and CU did not change the bond strength statistically with the use of pre-etching (p > 0.05). The bond strength of universal adhesives on demineralized enamel, with and without initial acid etching, depends on the type of adhesive system used.

Assessment of adhesive bond strength from ultrasonic tone-bursts.

A model for the amplitude and phase of ultrasonic tone-bursts incident on adherend-adhesive interfaces is developed for both reflected and transmitted waves. The model parameters include the interfacial stiffness constants, which characterize the elastic properties of idealized adherend-adhesive interfaces having a continuum of bonds. The ultrasonic model is linked to the more realistic physico-chemical model of adhesive bonding via a scaling equation that establishes the relationship between the interfacial stiffness constants of the ultrasonic model and the fraction of actual bonds in the physico-chemical model. The link to the physico-chemical model enables a quantitative assessment of the absolute bond strength. The ultrasonic model and scaling equation are applied to the simulation assessment of the absolute bond strength of two aluminum alloy adherends joined by an epoxy adhesive. Model input is obtained from the calculated phase of tone-bursts reflected from the adherend-adhesive interfaces as a function of the interfacial stiffness constants. The simulation shows that the reflected phase is dominated by the first interface encountered by the incident tone-burst with little contribution from the second interface. The simulation also shows that the accuracy in assessing the adhesive bond strength depends on the sensitivity of the reflected phase to variations in the interfacial stiffness constants, reflecting in part the nonlinearity of the scaling relationship.

Effect of moisture in aggregate on adhesive properties of warm-mix asphalt

Warm-mix asphalt (WMA) is one technology that has been found to have potential in minimizing the environmental harm caused by road construction activities. Its low mixing and compacting temperatures have opened great opportunities for more sustainable development. However, because WMA is mixed at low temperatures, the drying process of the aggregate may fail to dry the WMA completely. The binder-aggregate adhesion property can be damaged by moisture remaining from incomplete drying. The present study investigated the effects of aggregate moisture on the binder-aggregate interfacial characteristics of WMA by evaluating its surface free energy and adhesive bond strength. The results showed that for the Pen 60-70 binder type, the aggregate AG in general showed the higher bond energy and aggregate SD showed the lowest bond energy among three aggregate types. Also, the bond energy diminishes with increasing aggregate moisture contents but the percent drops in bond energy is less when WMA additives was included. For the PM binder, SL aggregate group showed the highest bond energy and SD aggregate group showed the lowest bond energy. For the work of adhesion, the results showed that with aggregate with 10% moisture contents has destructive effects on the work of adhesion which may decrease to 50% compare to dry aggregate condition. Finally, the four quadrant diagrams can be used to combine two distinct property of the bond energy and the work of adhesion as the hybrid performance indicator to rank the effect of moist aggregate to the adhesion properties at binder-aggregate interface.

Effect of air-blowing time and long-term storage on bond strength of universal adhesives to dentin.

To evaluate the effects of air-blowing time and storage time on microtensile bond strength (μTBS) of universal adhesives to dentin. Ninety flat dentin surfaces from extracted human third molars were bonded with three universal adhesives (Clearfil Universal Bond-CU; G-Premio Bond-GP; Scotchbond Universal Adhesives-SB). Bonded dentin surfaces were air-dried for 5s, 15s, or 30s followed by resin composite built-up. Resin-dentin beams were tested with μTBS test after different storage time in distilled water (24h and 1year). Data were analyzed by three-way ANOVA and Duncan test at (α = 0.05). Failure mode and resin-dentin interfaces were observed using a scanning electron microscope (SEM). Specific features of fractured beams after μTBS were further observed using SEM at high magnification. Extension of air-blowing time from 5s to 30s increased the 24h μTBS of CU only. Bond strength of all adhesives significantly decreased after 1-year storage except for CU at 5s and 30s of air-blowing time. One-year μTBS were significantly higher when air-blowing times were extended to 15s for SB and 30s for CU. Air-blowing time had no influence on GP. The effect of air-blowing time and storage time on resin-dentin bond was material-dependent. Extended air-blowing time increased the bond strength and bond durability of CU. Extension of air-blowing time to 15s and 30s improve the long-term bond strength of SB and CU, respectively.