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The purpose of this study was to evaluate whether surface wetness would influence the bonding effectiveness of universal adhesives in etch-and-rinse mode. All-Bond Universal (AB), G-Premio Bond (GP), Prime & Bond Active (PB), and Scotchbond Universal Adhesive (SU) were evaluated. Initial bond strengths and bond-fatigue strengths of universal adhesives to both wet and dry enamel and dentin in etch-and-rinse mode were determined. Scanning electron microscopy observations of the adhesive interfaces were also conducted. The bond-fatigue durability of universal adhesive to enamel in etch-and-rinse mode was influenced by the surface wetness, unlike that to dentin. The bond fatigue durability of AB and GP to dentin in etch-and-rinse mode was different depending on the surface wetness, unlike that of PB and SU. The thicknesses of the adhesive or hybrid layer of resin-dentin interfaces were not influenced by the surface wetness, but the length of resin tags in the wet group was longer than in the dry group. Some universal adhesives with the addition of specific components and optimization of water content can achieve stable bonds regardless of surface wetness, but the surface wetness of dentin is still a significant factor for universal adhesive bonding in etch-and rinse mode, unlike that of enamel., (© 2018 Eur J Oral Sci.)

This study evaluated the simulated localized wear of resin luting cements for universal adhesive systems using different curing modes. Five resin luting cements for universal adhesive systems were evaluated and subsequently subjected to wear challenge in a Leinfelder-Suzuki wear simulation device. Overall, 20 specimens from each resin luting cement were photo-cured for 40 s (dual-cure group), and 20 specimens of each material were not photo-cured (chemical-cure group). Simulated localized wear was generated using a stainless steel ball-bearing antagonist in water slurry of polymethylmethacrylate beads. In addition, scanning electron microscopy (SEM) observations of resin luting cements and wear facets were conducted. Significant differences in simulated wear and SEM observations of wear facets were evident among the materials in the dual- and chemical-cure groups. The simulated wear and SEM observations of wear facets of G-CEM LinkForce and Panavia V5 were not influenced by the curing mode. SEM observations of resin luting cements were material dependent. In most cases, dual curing appears to ensure greater wear resistance of resin luting cements than chemical curing alone. The wear resistance of some resin luting cements appears to be material dependent and is not influenced by the curing mode.

Objectives: The purpose of this study was to determine the influence of different frequency rates on of bond durability of self-etch adhesives to enamel using shear fatigue strength (SFS) testing., Methods: A two-step self-etch adhesive (OX, OptiBond XTR), and two single step self-etch adhesives (GB, G-ӕnial Bond and SU, Scotchbond Universal) were used in this study. The shear fatigue strength (SFS) to enamel was obtained. A staircase method was used to determine the SFS values with 50,000 cycles or until failure occurred. Fatigue testing was performed at frequencies of 5Hz, 10Hz, and 20Hz. For each test condition, 30 specimens were prepared for the SFS testing., Results: Regardless of the bond strength test method, OX showed significantly higher SFS values than the two single-step self-etch adhesives. For each of the three individual self-etch adhesives, there was no significant difference in SFS depending on the frequency rate, although 20Hz results tended to be higher., Conclusions: Regardless of the self-etch adhesive system, frequencies of 5Hz, 10Hz, and 20Hz produced similar results in fatigue strength of resin composite bonded to enamel using 50,000 cycles or until bond failure., Significance: Accelerated fatigue testing provides valuable information regarding the long term durability of resin composite to enamel bonding using self-etch adhesive system., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

In this clinical study, we evaluated the 3-year clinical performance of a resin composite containing a surface-prereacted glass ionomer (S-PRG) filler (Beautifil II; Shofu Inc., Kyoto, Japan) placed with a single-step self-etch adhesive (BeautiBond; Shofu Inc.) in posterior restorations. Using modified US Public Health Service criteria, two experienced investigators performed clinical evaluations at the baseline, 6 months, 18 months, and 3 years. Color match, marginal adaptation, anatomical form, surface roughness, marginal discoloration, postoperative sensitivity, and secondary caries were evaluated. After 3 years, 26 patients attended the recall and 31 restorations were evaluated. No postoperative sensitivity or secondary caries was observed at any time point, and no restorations failed during the follow-up period. However, surface roughness, marginal adaptation, and marginal discoloration showed deterioration after 3 years. In conclusion, although some clinical changes were observed, resin composite containing S-PRG filler placed with self-etch adhesive exhibited acceptable clinical behavior in posterior restorations.

We examined the effect of warm air-drying on the enamel bond strengths and the surface free-energy of three single-step self-etch adhesives. Bovine mandibular incisors were mounted in self-curing resin and then wet ground with #600 silicon carbide (SiC) paper. The adhesives were applied according to the instructions of the respective manufacturers and then dried in a stream of normal (23°C) or warm (37°C) air for 5, 10, and 20 s. After visible-light irradiation of the adhesives, resin composites were condensed into a mold and polymerized. Ten samples per test group were stored in distilled water at 37°C for 24 h and then the bond strengths were measured. The surface free-energies were determined by measuring the contact angles of three test liquids placed on the cured adhesives. The enamel bond strengths varied according to the air-drying time and ranged from 15.8 to 19.1 MPa. The trends for the bond strengths were different among the materials. The value of the γS⁺ component increased slightly when drying was performed with a stream of warm air, whereas that of the γS⁻ component decreased significantly. These data suggest that warm air-drying is essential to obtain adequate enamel bond strengths, although increasing the drying time did not significantly influence the bond strength., (© 2013 Eur J Oral Sci.)

The purpose of this study was to determine ultrasonically the changes in elastic modulus of demineralized adhesive-infiltrated dentin. Dentin disks were obtained from bovine incisors and shaped into a rectangular form. The specimens were immersed in single-step self-etch adhesives, then stored in distilled water and run through thermal cycles between 5 and 60 degrees C. The longitudinal and shear wave sound velocities and the elastic modulus were determined using ultrasonic equipment composed of a pulser-receiver, transducers, and an oscilloscope. After 24 h of storage, the elastic modulus of mineralized dentin was 16.9 GPa and that of demineralized dentin was 2.1 GPa. The immersion of demineralized dentin in adhesives significantly increased the elastic modulus to 3.3-5.9 GPa. After 30,000 thermal cycles, the elastic modulus of dentin was 32.4 GPa, whereas that of demineralized adhesive infiltrated dentin was 3.1-4.1 GPa. Thermal stresses did not cause adhesive-infiltrated demineralized dentin to deteriorate, as measured by elastic modulus.

This study examined the effect of air-drying time of adhesives on the dentin bond strength of several single-application self-etch adhesive systems. The adhesive/resin composite combinations used were: Adper Prompt L-Pop/Filtek Z250 (AP), Clearfil Tri-S Bond/Clearfil AP-X (CT), Fluoro Bond Shake One/Beautifil (FB), G-Bond/Gradia Direct (GB) and One-Up Bond F Plus/Palfique Estelite (OF). Bovine mandibular incisors were mounted in self-curing resin and wet ground with #600 SiC to expose labial dentin. Adhesives were applied according to each manufacturer's instructions followed by air-drying time for 0 (without air-drying), 5 and 10 seconds. After light irradiation of the adhesives, the resin composites were condensed into a mold (phi4x2 mm) and polymerized. Ten samples per test group were stored in 37 degrees C distilled water for 24 hours; they were then shear tested at a crosshead speed of 1.0 mm/minute. One-way ANOVA followed by Tukey's HSD tests (alpha = 0.05) were done. FE-SEM observations of the resin/dentin interface were also conducted. Dentin bond strength varied with the different air drying times and ranged from 5.8 +/- 2.4 to 13.9 +/- 2.8 MPa for AP, 4.9 +/- 1.5 to 17.1 +/- 2.3 MPa for CT, 7.9 +/- 2.8 to 13.8 +/- 2.4 MPa for FB, 3.7 +/- 1.4 to 13.4 +/- 1.2 MPa for GB and 4.6 +/- 2.1 to 13.7 +/- 2.6 MPa for OF. With longer air drying of adhesives, no significant changes in bond strengths were found for the systems used except for OF. Significantly lower bond strengths were obtained for the 10-second air-drying group for OF. From FE-SEM observations, gaps between the cured adhesive and resin composites were observed for the specimens without the air drying of adhesives except for OF. The data suggests that, with four of the single-application self-etch adhesive systems, air drying is essential to obtain adequate dentin bond strengths, but increased drying time does not significantly influence bond strength. For the other system studied, the bond strength of the non-air dried group was not significantly different from the five second drying time, but prolonged drying was very detrimental to bond strength. For all five of the systems studied, a five-second air-drying time appeared to be appropriate.

This study investigated the effect of the bonding agent application method on the dentin bond durability of a two‐step adhesive utilizing a universal‐adhesive‐derived primer. The bonding durability of a universal adhesive was compared with those of two conventional two‐step adhesives by shear bond strength testing after thermal cycling. The primer was applied (with or without phosphoric acid pre‐etching), and the specimens were divided into three groups based on the bonding agent application method used as follows: (i) strong air‐flow application, (ii) gentle air‐flow application, and (iii) gentle air‐flow + second bonding application. The shear bond strength was determined after thermal cycling. All the factors (bonding agent application method, adhesive system, and storage condition) significantly influenced the dentin shear bond strength both with and without phosphoric acid pre‐etching. The specimens exposed to gentle air‐flow showed a higher shear bond strength than did those exposed to strong air‐flow and gentle air‐flow + second bonding. The bond durability of the tested adhesive systems was influenced by the bonding agent application method, and this trend was material dependent. The G2‐Bond Universal exhibited the same or greater dentin bond durability to the other two‐step adhesive systems. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate the bonding and wear properties of self‐adhesive flowable restorative materials. Five self‐adhesive flowable restorative materials were used. The study parameters were: (i) shear bond strengths; (ii) microleakage; (iii) occlusal wear; and (iv) qualitative evaluation of the bonding interface. The range of shear bond strengths of the materials was as follows: 7.4–12.2 MPa to ground enamel, 22.5–32.5 MPa to etched enamel, and 1.3–4.2 MPa to dentin. The microleakage scores of the materials did not show any statistically significant differences regardless of the presence or absence of etching. The wear facets on the materials showed 0.099–0.447 mm3 of volume loss and 148.6–365.3 µm maximum depth, with statistically significant differences between materials. Scanning electron microscopic images of the interfaces of the materials showed good adaptation regardless of substrate. The bonding and wear properties of self‐adhesive flowable restorative materials were still limited and showed lower values than previously reported results for nanofilled composites with an adhesive system. Selective enamel etching can improve the bonding performance of these materials. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effect of the adhesive application method on the durability of the enamel bond and the thickness of the adhesive layer. A new-generation two-step universal adhesive system, G2-Bond Universal, and two conventional two-step adhesive systems were utilized. The shear bond strength to bovine enamel was measured after thermal cycling in both etch-and-rinse and self-etch modes. Fifteen specimens were divided into three groups as follows: Group I, wherein a strong air stream was applied over the bonding agent for 5 s; Group II, wherein a gentle air stream was applied over the bonding agent for 5 s; and Group III, which was prepared as in Group II, followed by the application of a second layer of the bonding agent and a gentle air stream for 5 s. The durability of the enamel bond and thickness of the tested adhesives were influenced by the application method in both etching modes. The application method used in Group II appeared to be most suitable in terms of the bonding of the adhesives to the enamel. The new-generation two-step self-etch adhesive, comprising a universal adhesive-derived primer and a hydrophobic bonding agent, showed superior bond performance to the conventional two-step adhesive systems. [ABSTRACT FROM AUTHOR]

Objectives: The present study aimed to investigate the changes in the enamel bond strengths of universal adhesives in the early phase of specimen creation and evaluate the effect of double-layer application on enamel bond effectiveness using different etching modes. Method: Four universal adhesives, namely Clearfil Universal Bond Quick, G-Premio Bond, Scotchbond Universal, and Tokuyama Universal Bond, were used. Clearfil SE Bond two-step self-etch adhesive system was used as a comparison. Fifteen specimens per group were used for determining the shear bond strength (SBS) to bovine enamel in the etch-and-rinse or self-etch mode. The adhesive was applied to specimens in accordance with the manufacturers' instructions (single-layer application), or the adhesive was applied twice (double-layer application). The bonded specimens were stored in distilled water at 37 °C for 5 min or 1, 6, 12, or 24 h before SBS testing. The flexural properties of the resin composite Clearfil AP-X were measured for the same storage periods. Results: All universal adhesives exhibited increased SBS values with prolonged storage periods regardless of the application technique or etching mode used. Double-layer application was associated with higher SBS values than single-layer application for most universal adhesives over the same storage period. Conclusion: Phosphoric acid pre-etching and double-layer application of universal adhesives resulted in increased enamel bond strength in the early phase of specimen bonding. Clinical relevance: Care should be taken when using universal adhesives in the self-etch mode for enamel bonding because the enamel adhesion is sensitive to the duration after filling. [ABSTRACT FROM AUTHOR]

Objective: This study aimed to compare dentin bond durability under different degradation conditions between two etch-and-rinse (ER) systems and a universal adhesive in ER mode. Method: This study used a universal adhesive [Scotchbond Universal (SU)], a three-step ER adhesive [Scotchbond Multi-Purpose Plus (SM)], and a two-step ER adhesive [Single Bond Plus (SB)]. A phosphoric acid-etching agent was applied to bovine dentin prior to the application of either a primer or the adhesive. After acid etching, bonding procedures were conducted. The specimens were divided into three group classes: (1) subjected to 10,000, 30,000, or 50,000 thermal cycles (TC); (2) stored in distilled water at 37 °C for 6 months or 1 year (WS); and (3) stored in distilled water for 24 h (baseline). Shear bond strength (SBS) tests were conducted. Results: SB showed a higher baseline SBS than the other adhesives. Defining the baseline SBS value for each adhesive system as 100%, TC groups ranged from 56.1 to 70.3% for SM, from 98.4 to 103.7% for SB, and from 120.3 to 126.7% for SU. WS groups ranged from 66.2 to 71.4% for SM, from 98.1 to 103.3% for SB, and from 102.5 to 118.1% for SU. Conclusions: Although SB showed relatively stable dentin bond performance under all degradation conditions, SM showed decreased dentin SBS with prolonged degradation. SU did not show any significant decrease in SBS from the baseline under any degradation condition. Clinical relevance: The universal adhesive showed comparable adhesive performance with the two-step ER adhesive. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine the immediate bond effectiveness of universal adhesives to unground and ground enamel surfaces in different etching modes, through shear bond strength (SBS) tests and scanning electron microscopy observations. Three universal adhesives, a conventional two‐step self‐etch adhesive, and a conventional single‐step self‐etch adhesive were compared. Human enamel specimens from lower anterior teeth were divided into four groups and subjected to the following treatments: (i) unground enamel in self‐etch mode; (ii) ground enamel in self‐etch mode; (iii) unground enamel in etch‐&‐rinse mode; and (iv) ground enamel in etch‐&‐rinse mode. Bonded assemblies were subjected to SBS testing. All the adhesives showed significantly higher SBS values in etch‐&‐rinse mode than in self‐etch mode, regardless of whether enamel was unground or ground. The influence of the enamel surface condition on SBS was different in different etching modes. Without pre‐etching, all tested materials showed lower SBS values in unground enamel than in ground enamel. In etch‐&‐rinse mode, no significant differences in SBS values were observed between unground enamel and ground enamel for any of the adhesives tested. Phosphoric acid pre‐etching before application of self‐etch adhesives to an unground enamel surface is essential to enhance initial enamel bond effectiveness. [ABSTRACT FROM AUTHOR]

Objectives: The purpose of this study was to examine the enamel bond durability of universal adhesives in the self-etch mode under 2-year water storage and thermal cycling conditions.Materials and methods: Three commercially available universal adhesives and a gold standard two-step self-etch adhesive were used. Ten specimens of bovine enamel were prepared per test group, and shear bond strength (SBS) was measured to determine the bonding durability after thermal cycling (TC) or long-term water storage (WS). The bonded specimens were divided into three groups: (1) specimens subjected to TC, where the bonded specimens were stored in 37 °C distilled water for 24 h before being subjected to 3000, 10,000, 20,000 or 30,000 TC; (2) specimens stored in 37 °C distilled water for 3 months, 6 months, 1 year or 2 year; and (3) specimens stored in 37 °C distilled water for 24 h, serving as a baseline.Results: The two-step self-etch adhesive showed significantly higher SBS than the universal adhesives tested, regardless of the type of degradation method. All universal adhesives showed no significant enamel SBS reductions in TC and WS, when compared to baseline and the other degradation conditions.Conclusions: Compared to the bond strengths obtained with the two-step self-etch adhesive, significantly lower bond strengths were obtained with universal adhesives. However, the enamel bond durability of universal adhesives was relatively stable under both degradation conditions tested.Clinical relevance: The present data indicate that the enamel bond durability of universal adhesives in the self-etch mode might be sufficient for clinical use. [ABSTRACT FROM AUTHOR]

This study evaluated the simulated localized wear of resin luting cements for universal adhesive systems using different curing modes. Five resin luting cements for universal adhesive systems were evaluated and subsequently subjected to wear challenge in a Leinfelder-Suzuki wear simulation device. Overall, 20 specimens from each resin luting cement were photo-cured for 40 s (dual-cure group), and 20 specimens of each material were not photo-cured (chemical-cure group). Simulated localized wear was generated using a stainless steel ball-bearing antagonist in water slurry of polymethylmethacrylate beads. In addition, scanning electron microscopy (SEM) observations of resin luting cements and wear facets were conducted. Significant differences in simulated wear and SEM observations of wear facets were evident among the materials in the dual- and chemical-cure groups. The simulated wear and SEM observations of wear facets of G-CEM LinkForce and Panavia V5 were not influenced by the curing mode. SEM observations of resin luting cements were material dependent. In most cases, dual curing appears to ensure greater wear resistance of resin luting cements than chemical curing alone. The wear resistance of some resin luting cements appears to be material dependent and is not influenced by the curing mode. [ABSTRACT FROM AUTHOR]

Objectives The aim of this study was to determine the effect of double-layer application of universal adhesives on the bond quality and compare to other adhesive systems. Methods Two universal adhesives used were in this study: Scotchbond Universal (SU), [3M ESPE] and Prime & Bond elect (PE), [Dentsply Caulk]. The conventional single-step self-etch adhesives G-ӕnial Bond (GB), [GC Corporation.] and BeautiBond (BB), [Shofu Inc.], and a two-step self-etch adhesive, Optibond XTR (OX), [Kerr Corporation], were used as comparison adhesives. Shear bond strengths (SBS) and shear fatigue strengths (SFS) to human enamel and dentin were measured in single application mode and double application mode. For each test condition, 15 specimens were prepared for SBS testing and 30 specimens for SFS testing. Results Enamel and dentin SBS of the universal adhesives in the double application mode were significantly higher than those of the single application mode. In addition, the universal adhesives in the double application mode had significantly higher dentin SFS values than those of the single application mode. The two-step self-etch adhesive OX tended to have lower bond strengths in the double application mode, regardless of the test method or adherent substrate. Conclusion The double application mode is effective in enhancing SBS and SFS of universal adhesives, but not conventional two-step self-etch adhesives. Significance These results suggest that, although the double application mode may enhance the bonding quality of a universal adhesive, it may be counter-productive for two-step self-etch adhesives in clinical use. [ABSTRACT FROM AUTHOR]

This aim of this study was to compare universal adhesives and two-step self-etch adhesives in terms of dentin bond fatigue durability in self-etch mode. Three universal adhesives - Clearfil Universal, G-Premio Bond, and Scotchbond Universal Adhesive - and three-two-step self-etch adhesives - Clearfil SE Bond, Clearfil SE Bond 2, and OptiBond XTR - were used. The initial shear bond strength and shear fatigue strength of resin composite bonded to adhesive on dentin in self-etch mode were determined. Scanning electron microscopy observations of fracture surfaces after bond strength tests were also made. The initial shear bond strength of universal adhesives was material dependent, unlike that of two-step self-etch adhesives. The shear fatigue strength of Scotchbond Universal Adhesive was not significantly different from that of two-step self-etch adhesives, unlike the other universal adhesives. The shear fatigue strength of universal adhesives differed depending on the type of adhesive, unlike those of two-step self-etch adhesives. The results of this study encourage the continued use of two-step self-etch adhesive over some universal adhesives but suggest that changes to the composition of universal adhesives may lead to a dentin bond fatigue durability similar to that of two-step self-etch adhesives. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine the relationship between mechanical properties and bond durability of short fiber-reinforced resin composite with universal adhesive. As controls, micro-hybrid and nano-hybrid resin composites were tested. The universal adhesives used were Scotchbond Universal, Adhese Universal, and G-Premio Bond. The fracture toughness and flexural properties of resin composites, and shear bond strength and shear fatigue strength of universal adhesive with resin composite using both total-etch and self-etch modes were determined. In the results, short fiber-reinforced resin composite showed significantly higher fracture toughness than did micro-hybrid and nano-hybrid resin composites. The flexural strength and modulus of short fiber-reinforced and nano-hybrid resin composites were significantly lower than were those of micro-hybrid resin composites. Regardless of etching mode, the shear bond strength of universal adhesives with short fiber-reinforced resin composite did not show any significant differences from micro-hybrid and nano-hybrid resin composites. The shear fatigue strength of universal adhesives with short fiber-reinforced resin composite and micro-hybrid resin composites were significantly higher than that of nano-hybrid resin composites. The results of this study suggest that the mechanical properties of short fiber-reinforced resin composite improve their bond durability with universal adhesive. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate the influence of duration of phosphoric acid pre-etching on the bond durability of universal adhesives and the surface free-energy characteristics of enamel. Three universal adhesives and extracted human molars were used. Two no-pre-etching groups were prepared: ground enamel; and enamel after ultrasonic cleaning with distilled water for 30 s to remove the smear layer. Four pre-etching groups were prepared: enamel pre-etched with phosphoric acid for 3, 5, 10, and 15 s. Shear bond strength ( SBS) values of universal adhesive after no thermal cycling and after 30,000 or 60,000 thermal cycles, and surface free-energy values of enamel surfaces, calculated from contact angle measurements, were determined. The specimens that had been pre-etched showed significantly higher SBS and surface free-energy values than the specimens that had not been pre-etched, regardless of the aging condition and adhesive type. The SBS and surface free-energy values did not increase for pre-etching times of longer than 3 s. There were no significant differences in SBS values and surface free-energy characteristics between the specimens with and without a smear layer. The results of this study suggest that phosphoric acid pre-etching of enamel improves the bond durability of universal adhesives and the surface free-energy characteristics of enamel, but these bonding properties do not increase for phosphoric acid pre-etching times of longer than 3 s. [ABSTRACT FROM AUTHOR]

The purpose of this study was to use shear bond strength ( SBS) and shear fatigue strength ( SFS) testing to determine the influence on dentin bonding of phosphoric acid pre-etching times before the application of self-etch adhesives. Two single-step self-etch universal adhesives [Prime & Bond Elect ( EL) and Scotchbond Universal ( SU)], a conventional single-step self-etch adhesive [G-ænial Bond ( GB)], and a two-step self-etch adhesive [OptiBond XTR ( OX)] were used. The SBS and SFS values were obtained with phosphoric acid pre-etching times of 3, 10, or 15 s before application of the adhesives, and for a control without pre-etching. For groups with 3 s of pre-etching, SU and EL showed higher SBS values than control groups. No significant difference was observed for GB among the 3 s, 10 s, and control groups, but the 15 s pre-etching group showed significantly lower SBS and SFS values than the control group. No significant difference was found for OX among the pre-etching groups. Reducing phosphoric acid pre-etching time can minimize the adverse effect on dentin bonding durability for the conventional self-etch adhesives. Furthermore, a short phosphoric acid pre-etching time enhances the dentin bonding performance of universal adhesives. [ABSTRACT FROM AUTHOR]

The influence of methyl mercaptan on the repair bond strength of composites fabricated using self-etch adhesives was investigated. The surface free-energies were determined by measuring the contact angles of test liquids placed on composites that had been immersed in different concentrations of methyl mercaptan (0.01, 0.1, and 1.0 M). To determine the repair bond strength, self-etch adhesives were applied to the aged composite, and then newly added composites were condensed. Ten samples of each specimen were subjected to shear testing at a crosshead speed of 1.0 mm min−1. Samples were analyzed using two-way anova followed by Tukey's honestly significant difference ( HSD) test. Although the dispersion force of the composites remained relatively constant, their polar force increased slightly as the concentration of methyl mercaptan increased. The hydrogen-bonding forces were significantly higher after immersion in 1.0 M methyl mercaptan, leading to higher surface-free energies. However, the repair bond strengths for the repair restorations prepared from composites immersed in 1.0 M methyl mercaptan were significantly lower than for those immersed in 0.01 and 0.10 M methyl mercaptan. Considering the results of this study, it can be concluded that the repair bond strengths of both the aged and newly added composites were affected by immersion in methyl mercaptan solutions. [ABSTRACT FROM AUTHOR]

We compared the surface free energies and enamel bond strengths of single-step self-etch adhesives with and without an oxygen- inhibited layer. The adhesives were applied to the enamel surfaces of bovine incisors, light irradiated, and the oxygen-inhibited layer was either retained or removed with ethanol. The surface free energies and their components (γSLW, γS+, and γS-) were determined by measuring the contact angles of three test liquids placed on the cured adhesives. The enamel bond strengths of specimens with and without the oxygen-inhibited layer were measured. For all surfaces, the value of the estimated surface tension component γSLW was relatively constant. The value of the γS+ component increased slightly when the oxygen-inhibited layer was removed, whereas that of the γS- component decreased significantly. The enamel bond strengths of the self-etch adhesives were significantly lower in the specimens without an oxygen-inhibited layer. The oxygen-inhibited layer therefore appeared to promote higher enamel bond strength. [ABSTRACT FROM AUTHOR]

This study investigated the influence of the bonded surface area and the crosshead speed on the dentin bond strengths of self-etch adhesives. Bovine mandibular incisors were mounted in self-curing resin and the facial surfaces were wet ground with #600 silicon carbide (SiC) paper. The dentin surfaces were treated according to the manufacturer's instructions. Adhesives were applied, and the resin composites were condensed into molds (2.4 or 4.0 mm in internal diameter), placed on to the dentin, and then light activated. Ten samples per test group were shear tested at crosshead speeds of 0.1, 0.5, 1.0, 5.0, and 10.0 mm/mm. The results showed that higher crosshead speeds were associated with higher dentin bond strengths. This relationship was more significant for specimens with a smaller dentin bonding surface area. [ABSTRACT FROM AUTHOR]

Summary: Objectives. Adhesion of resin composites to dentin is currently believed to result from impregnation of adhesive resin into superficially demineralized dentin. The purpose of this study was to use micro-Raman spectroscopy and scanning electron microscopy (SEM) to investigate the extent of resin penetration into etched dentin with single-step adhesive systems. Methods. Adhesive systems used were One-Up Bond F (Tokuyama Dental) and Reactmer Bond (Shofu, Inc.). A self-etching primer system Mac Bond II (Tokuyama Dental) was employed as a control. Resin composites were bonded to bovine dentin with the adhesive systems, and specimens were sectioned parallel to dentinal tubules. Raman spectra were successively recorded along a line perpendicular to the dentin-adhesive interface in steps of 0.2μm and the spectra were obtained. SEM observations of the resin–dentin interface were also conducted. Results. The dentin–resin interface of single-step adhesive systems showed a gradual transition in the relative amount of adhesive from the resin side to dentin side. The widths of resin penetration into demineralized dentin detected by Raman microscopy were greater than those obtained by the morphological analysis using SEM. Conclusions. From the results of this study, a gradual variation in the composition of the dentin–resin interface was detected, and the degree of resin impregnation observed with SEM observation was less than that detected with the Raman microscopy. [Copyright &y& Elsevier]

Purpose: To investigate the influence of thermal cycling on bond strength to dentin of 2-step bonding systems. Materials and Methods: The systems used were self-etching primer systems; Fluoro Bond (FB), Liner Bond II (LB), and Mac Bond II (MB); and self-priming adhesive systems; One-Step (OS), OptiBond Solo (OB), Prime & Bond 2.0 (PB), and Single Bond (SB). Bovine mandibular incisors were mounted in self-curing resin and the facial surfaces were wet ground with #600 SiC paper. Enamel and dentin surfaces were treated following each manufacturers' instructions. Adhesives were applied and composites were condensed into a Teflon mold (4x2 mm) placed on the dentin surface and light activated. Bonded specimens were divided into four groups; (a) stored in 37 °C water for 24 hours, (b) stored in 37 °C water for 24 hours followed by subjecting to thermal cycling between 5 °C and 60 °C for 3,000 times, (c) 10,000 times, and (d) 30,000 times. Twelve samples per test group were shear tested at a crosshead speed of 1.0 mm/minute. One-way ANOVAs followed by Duncan's multiple range test (P < 0.05) were performed. Results: For FB, LB, and MB, a small decrease in bond strength was observed and no significant differences were observed among the thermal cycling groups. For OS, OB, PB, and SB, a significant decrease in bond strength was observed for the 30,000 thermal cycling groups. The changes in bond strength after TC were different between the bonding systems. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the immediate dentin bond performance and bond durability of self-adhesive resin luting cements (RLCs) in combination with universal adhesives in different curing modes. Two self-adhesive RLCs were used with universal adhesives as primers. They were also used alone as self-adhesive RLCs. Two multiple-step RLC systems were used as comparison materials. To measure the shear bond strength (SBS) in different curing modes, 12 specimens were prepared for each group. Stainless-steel rods were bonded to bovine dentin, and the bonded specimens were assigned to the baseline group (stored for 24 h) and artificially aged group (thermal cycling [TC], 10,000 cycles). After each storage period, the SBS of the bonded specimens was measured. The Knoop hardness number (KHN) of the cured RLCs was measured with or without primer application in different curing modes at 24 h and after 10,000 TC. The representative RLC/dentin interfaces were observed using scanning electron microscopy (SEM). Dentin SBS was significantly influenced by the RLC system but not by the curing mode. Self-adhesive RLCs alone showed significantly lower SBS values than self-adhesive RLCs with primer regardless of the curing mode or storage period. The storage period, curing mode, and RLC system significantly influenced the KHN. The use of universal adhesives as a primer may help enhance the immediate dentin bond performance and bond durability of self-adhesive RLCs. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate dentin bonding durability of different etch-and-rinse (ER) adhesive systems under fatigue stress and to compare morphological features of resin/dentin interfaces using SEM. Two three-step ER adhesives, a two-step ER adhesive, and a universal adhesive in ER mode were evaluated. Before application of either primer or adhesive, phosphoric acid etching of human dentin was completed. Fifteen bonded specimens for each adhesive system were stored in distilled water at 37 °C for 24 h, then subjected to a shear bond strength (SBS) test. Bonding durability was assessed from the perspective of biomechanical stress. 25 bonded specimens for each adhesive system were subjected to shear fatigue strength (SFS) testing with a repeated subcritical load at a frequency of 20 Hz for 50,000 cycles or until failure. Mean SBS and SFS values ranged from 33.3 to 41.2 MPa, and from 18.3 to 20.3 MPa, respectively. Three-step adhesives showed higher SBS and SFS values than the other adhesive systems. Under SEM, resin tags in different adhesive systems showed similar features, but morphology below the hybrid layer was material dependent. The universal adhesive in ER mode showed an obvious thin, high-density reaction layer below the hybrid layer. Three-step adhesives showed higher dentin bond durability than the other ER adhesives; no significant differences in SFS were found between the universal adhesive in ER mode and the three-step ER adhesives. The results of this in vitro study indicate that some ER adhesives might establish chemical bonding with intact dentin below the hybrid layer in addition to micromechanical retention. [ABSTRACT FROM AUTHOR]

The aim of this study was to observe the resin/dentin interfaces of universal adhesives by using scanning electron microscopy (SEM), and to compare their morphologies with conventional etch & rinse (ER) and self-etch (SE) adhesive systems. Two three-step and one two-step ER adhesives and two two-step and two single-step SE adhesives were used for comparison with seven universal adhesives in ER mode and SE mode, respectively. Bonded surfaces with bovine teeth were longitudinally sectioned and mirror-polished. Half of the samples were treated with HCl and NaOCl solutions. The interfaces were subjected to argon ion beam etching and then observed by scanning electron microscopy. The thickness of the adhesive layer (AL) of most of the seven universal adhesives and single-step SE adhesives was similar. Universal adhesives in SE mode formed a hybrid smear layer as a high-density zone between the AL and dentin. The thickness of the hybrid layer (HL) of the universal adhesives in ER mode was ∼1–2 μm, with a high-density zone (reaction layer [RL]) below the HL. The morphological features of most universal adhesives in SE mode and single-step SE adhesives are similar. Although resin–dentin interfaces of universal adhesives in ER mode resemble those of ER adhesives, universal adhesives have a distinctive feature, an RL. The RL might be a sign of chemical bonding even when using universal adhesives in ER mode. [ABSTRACT FROM AUTHOR]