Role of the functional monomer 10-methacryloyloxydecyl dihydrogen phosphate in dentin bond durability of universal adhesives in etch-&-rinse mode.

This study aimed to determine the role of the 10-methacryloyloxydecyl dihydrogen phosphate (MDP) in dentin bond durability of universal adhesive in etch-&-rinse mode through bond strength tests after different degradation conditions. This study used the MDP-containing universal adhesive, Clearfil Universal Bond Quick (CU), and an experimental adhesive (NM) made with the same ingredients as CU, excluding MDP. Shear bond strength (SBS) to dentin were obtained in etch-&-rinse mode with or without MDP. CU in self-etch mode was used as a comparison. The groups were divided into three types: 1) subjected to thermal cycling; 2) subjected to long-term water storage; and 3) stored in water for 24 h, as a baseline. The discrepancies in the mean SBS of the CU and NM groups become prominent with prolonged degradation periods. This study indicates that the MDP in universal adhesive might play a key role in enhancing dentin bond quality even when etch-&-rinse mode is used.

SEM observation of novel characteristic of the dentin bond interfaces of universal adhesives.

OBJECTIVE: 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. METHODS: 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. RESULTS: 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 ∼1-2µm, with a high-density zone (reaction layer [RL]) below the HL. CONCLUSION: 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. SIGNIFICANCE: The RL might be a sign of chemical bonding even when using universal adhesives in ER mode.

Immediate enamel bond strength of universal adhesives to unground and ground surfaces in different etching modes.

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.

Interrelation among the handling, mechanical, and wear properties of the newly developed flowable resin composites.

OBJECTIVES: This study investigates the handling, mechanical, and wear properties of the newly developed flowable resin composites and elucidate the interrelations among the tested parameters. METHODS: Six flowable and two conventional resin composites are used. Five measurements are performed per resin composite to obtain the average inorganic filler content. Ten specimens per material are used to obtain the flexural strength, flexural modulus, and resilience. For sliding impact wear testing, twelve specimens are prepared. Noncontact profilometer and confocal laser scanning microscopy are used to determine the maximum facet depth and volume loss. Extrusion force and thread formation are used to measure the handling properties of the flowable resin composites. Six measurements are performed per flowable resin composite. Data evaluation is performed using analysis of variance and Tukey's honestly significant difference test at an α-level of 0.05. The correlation between the tested parameters is verified using the Pearson product-moment correlation coefficient. RESULTS: A subset of flowable resin composites exhibits higher flexural properties and wear resistance as compared to the conventional resin composites. The handling properties of the flowable resin composites are material dependent. CONCLUSION: While the resilience parameters exhibit an extremely strong and statistically significant correlation with the wear parameters, the handling properties exhibit no interrelation with the remaining parameters. SIGNIFICANCE: While the handling properties of the newly developed flowable resin composites did not correlate with the mechanical and wear properties, some new flowable resin composites have the potential for use in high-stress bearing areas, such as posterior lesions, because of the enhanced mechanical properties and wear resistance.

Influence of Application Time and Etching Mode of Universal Adhesives on Enamel Adhesion.

PURPOSE: To investigate the influence of application time and etching mode of universal adhesives on enamel adhesion. MATERIALS AND METHODS: Five universal adhesives, Adhese Universal, Bondmer Lightless, Clearfil Universal Bond Quick, G-Premio Bond, and Scotchbond Universal, were used. Bovine incisors were prepared and divided into four groups of ten teeth each. SBS, Ra, and SFE were determined after the following procedures: 1. self-etch mode with immediate air blowing after application (IA); 2. self-etch mode with prolonged application time (PA); 3. etch-and-rinse mode with IA; 4. etch-and-rinse mode with PA. After 24-h water storage, the bonded assemblies were subjected to shear bond strength (SBS) tests. For surface roughness (Ra) and surface free energy (SFE) measurements, the adhesives were simply applied to the enamel and rinsed with acetone and water before the measurements were carried out. RESULTS: Significantly higher SBS and Ra values were obtained with etch-and-rinse mode than with self-etch mode regardless of the application time or type of adhesive. Although most adhesives showed decreased SFE values with increased application time in self-etch mode, SFE values in etch-and-rinse mode were dependent on the adhesive type and application time. CONCLUSIONS: Etching mode, application time, and type of adhesive significantly influenced the SBS, Ra, and SFE values.

Bond durability of universal adhesive to bovine enamel using self-etch mode.

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.

Effect of double-layer application on bond quality of adhesive systems.

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.

Influence of different smear layers on bond durability of self-etch adhesives.

OBJECTIVE: The purpose of this study was to determine the influence of different smear layers on enamel and dentin bond durability of various types of self-etch adhesives. METHODS: Two universal adhesives, Scotchbond Universal (SU) and Prime & Bond elect (PE); a conventional single-step self-etch adhesive, G-ænial Bond (GB); and two two-step self-etch adhesives, Optibond XTR (OX) and Clearfil SE Bond (SE) were used in this study. Shear bond strengths (SBS) and shear fatigue strengths (SFS) to human enamel and dentin were determined with different smear layer conditions. The prepared specimens were divided into three groups. The bonding surfaces were prepared by grinding with either (1) #180, (2) #600, or (3) #4000-SiC papers before making the bonded assemblies. For each group, 15 specimens were prepared for the SBS and 30 specimens for the SFS. RESULTS: The two-step self-etch adhesives showed significantly higher SFS values than the single-step self-etch adhesives, regardless of the smear layer condition or substrate. Although most of the tested adhesives showed no significant differences in enamel SFS values among the smear layer groups, SU, GB, and SE showed significantly lower SFS values in the #180 in dentin groups than the #600 and #4000 groups. CONCLUSION: The influence of different smear layer conditions on bond durability was adhesive dependent. Furthermore, the smear layers generated on different substrates also influenced the bond quality of the self-etch adhesives. SIGNIFICANCE: Smear layer conditions of enamel and dentin influence the bond durability of universal adhesives and conventional single and two-step self-etch adhesives.

Influence of application method on surface free-energy and bond strength of universal adhesive systems to enamel.

The aim of the present study was to determine the influence of different adhesive application methods and etching modes on enamel bond effectiveness of universal adhesives using shear bond strength (SBS) testing and surface free-energy (SFE) measurements. The adhesives Scotchbond Universal, All-Bond Universal, Adhese Universal, and G-Premio Bond were used. Prepared bovine enamel specimens were divided into four groups, based on type of adhesive, and subjected to the following surface treatments: (i) total-etch mode with active application; (ii) total-etch mode with inactive application; (iii) self-etch mode with active application; and (iv) self-etch mode with inactive application. Bonded specimens were subjected to SBS testing. The SFE of the enamel surfaces with adhesive was measured after rinsing with acetone and water. The SBS values in total-etch mode were significantly higher than those in self-etch mode. In total-etch mode, significantly lower SBS values were observed with active application compared with inactive application; in contrast, in self-etch mode there were no significant differences in SBS between active and inactive applications. A reduction in total SFE was observed for active application compared with inactive application. The interaction between etching mode and application method was statistically significant, and the application method significantly affected enamel bond strength in total-etch mode.

Influence of air-powder polishing on bond strength and surface-free energy of universal adhesive systems.

The influences of air-powder polishing with glycine or sodium bicarbonate powders on shear bond strengths (SBS) and surface-free energies of universal adhesives were examined. Scotchbond Universal Adhesive (SU, 3M ESPE), G-Premio Bond (GP, GC), Adhese Universal (AU, Ivoclar Vivadent), and All-Bond Universal (AB, Bisco) were used in this study. Bovine dentin surfaces were air polished with glycine or sodium bicarbonate powders prior to the bonding procedure, and resin pastes were bonded to the dentin surface using universal adhesives. SBSs were determined after 24-h storage in distilled water at 37°C. Surface-free energy was then determined by measuring contact angles using three test liquids on dentin surfaces. Significantly lower SBSs were observed for dentin that was air-powder polished and surface-free energies were concomitantly lowered. This study indicated that air-powder polishing influences SBSs and surface-free energies. However, glycine powder produced smaller changes in these surface parameters than sodium bicarbonate.

Ultrasonic monitoring of the setting of silicone elastomeric impression materials.

This study used an ultrasonic measurement device to monitor the setting behavior of silicone elastomeric impression materials, and the influence of temperature on setting behavior was determined. The ultrasonic device consisted of a pulser-receiver, transducers, and an oscilloscope. The two-way transit time through the mixing material was divided by two to account for the down-and-back travel path; then it was multiplied by the sonic velocity. Analysis of variance and the Tukey honest significant difference test were used. In the early stages of the setting process, most of the ultrasonic energy was absorbed by the elastomers and the second echoes were relatively weak. As the elastomers hardened, the sonic velocities increased until they plateaued. The changes in sonic velocities varied among the elastomers tested, and were affected by temperature conditions. The ultrasonic method used in this study has considerable potential for determining the setting processes of elastomeric impression materials.

Influence of degradation conditions on dentin bonding durability of three universal adhesives.

OBJECTIVES: This study aims to determine dentin bonding durability of universal adhesives using shear bond strength (SBS) tests under various degradation conditions. METHODS: G-Premio Bond (GP, GC), Scotchbond Universal (SU, 3M ESPE) and All Bond Universal (AB, Bisco) were compared with conventional two-step self-etch adhesive Clearfil SE Bond (SE, Kuraray Noritake Dental). Bonded specimens were divided into three groups of ten, and SBSs with bovine dentin were determined after the following treatments: 1) Storage in distilled water at 37°C for 24h followed by 3000, 10,000, 20,000 or 30,000 thermal cycles (TC group), 2) Storage in distilled water at 37°C for 3 months, 6 months or 1year (water storage, WS group) and 3) Storage in distilled water at 37°C for 24h (control). RESULTS: SE bonded specimens showed significantly higher SBSs than universal adhesives, regardless of TC or storage periods, although AB specimens showed significantly increased SBSs after 30,000 thermal cycles. In comparisons of universal adhesives under control and degradation conditions, SBS was only reduced in SU after 1year of WS. CONCLUSION: Following exposure of various adhesive systems to degradation conditions of thermal cycling and long term storage, SBS values of adhesive systems varied primarily with degradation period. CLINICAL SIGNIFICANCE: Although universal adhesives have lower SBSs than the two-step self-etch adhesive SE, the present data indicate that the dentin bonding durability of universal adhesives in self-etch mode is sufficient for clinical use.

Mapping the heparin-binding site of the osteoinductive protein NELL1 by site-directed mutagenesis.

Neural epidermal growth factor-like (NEL)-like 1 (NELL1) is a secretory osteogenic protein comprising an N-terminal thrombospondin-1-like (TSPN) domain, four von Willebrand factor type C domains, and six epidermal growth factor-like repeats. NELL1 shows heparin-binding activity; however, the biological significance remains to be explored. In this report, we demonstrate that NELL1 binds to cell surface proteoglycans through its TSPN domain. Major heparin-binding sites were identified on the three-dimensional structural model of the TSPN domain of NELL1. Mutant analysis of the heparin-binding sites indicated that the heparin-binding activity of the TSPN domain is involved in interaction of NELL1 with cell surface proteoglycans.