One-step Self-etch Adhesives Research Articles

Prolonged Curing Time Reduces the Effects of Simulated Pulpal Pressure on the Bond Strength of One-step Self-etch Adhesives

The aim of this study was to evaluate the effects of extended light-curing procedures on the microtensile bond strength (μTBS) of one-step self-etch adhesives (1-SEAs) submitted to simulated pulpal pressure. Coronal deep-dentin specimens were bonded using Clearfil S3 Bond (S3), Adper Easy Bond (EB), or G-Bond Plus (GB) following the manufacturers' recommendations and light-cured for 10 seconds or 40 seconds. The dentin-bonded specimens were stored in distilled water for 24 hours without pulpal pressure (control) or submitted to 20 cm H2O simulated pulpal pressure for 24 hours. The specimens were cut into matchsticks and subjected to μTBS testing. The data were statistically analyzed using the three-way analysis of variance and Tukey's tests (p<0.05). Debonded sticks were investigated through scanning electron microscopy. EB obtained higher bond strengths than GB and S3. However, prolonged light activation (40 seconds) provided higher μTBS for all adhesives when submitted to pulpal pressure. Conversely, pulpal pressure caused a drop in μTBS in EB and S3 when light-cured for 10 seconds. A mixed failure mode was mainly attained for the control groups, whereas the specimens submitted to pulpal pressure failed in the adhesive mode. The μTBS of GB was not affected by pulpal pressure when light-cured for 10 seconds. Adhesive was the most prevalent failure mode, except when light-cured for 40 seconds, which showed predominantly cohesive failure. Extended curing times improved the resistance of 1-SEAs to simulated pulpal pressure.

Resistance to Degradation of Resin-Dentin Bonds Produced by One-Step Self-Etch Adhesives

The objective of this article is to evaluate the resistance to degradation of resin-dentin bonds formed with three one-step adhesives. Flat, mid-coronal dentin surfaces were bonded with the self-etching adhesives [Tokuyama Bond Force (TBF), One Up Bond F Plus (OUB), and G-Bond (GB)]. The bonded teeth were subjected to fatigue loading, chemical degradation, and stored in distilled water for four time periods (up to 12 months). Specimens were tested for microtensile bond strength and microleakage. Fractographic analysis was performed by scanning electron microscopy. Bonded interfaces were examined by light microscopy using Masson's trichrome staining. An atomic force microscope was employed to analyze phase separation and surface nanoroughness (Ra) at the polymers. Vickers microhardness and the degree of the conversion (DC) were also determined. ANOVA and multiple comparisons tests were performed. Bond strength significantly decreased after the chemical challenge, but not after load cycling. Aging decreased bond strength after 6 months in TBF and GB, in OUB after 12 months. An increase of the nonresin protected collagen zone occurred in all groups, after storing. TBF showed the highest roughness, microhardness, and DC values, and GB showed the lowest. Mild self-etch one-step adhesives (TBF/OUB) showed a higher degree of cure, lower hydrophilicity, and major resistance to degradation of resin-dentin bonds when compared to highly acidic self-etching adhesive (GB).

Effect of application mode on interfacial morphology and chemistry between dentine and self-etch adhesives

ObjectiveTo investigate the influence of application mode on the interfacial morphology and chemistry between dentine and self-etch adhesives with different aggressiveness. MethodsThe occlusal one-third of the crown was removed from un-erupted human third molars, followed by abrading with 600 grit SiC under water. Rectangular dentine slabs were prepared by sectioning the tooth specimens perpendicular to the abraded surfaces. The obtained dentine slabs were treated with one of the two one-step self-etch adhesives: Adper Easy Bond (AEB, pH∼2.5) and Adper Prompt L-Pop (APLP, pH∼0.8) with (15s, active application) or without (15s, inactive application) agitation. The dentine slabs were fractured and the exposed adhesive/dentine (A/D) interfaces were examined with micro-Raman spectroscopy and scanning electron microscopy (SEM). ResultsThe interfacial morphology, degree of dentine demineralization (DD) and degree of conversion (DC) of the strong self-etch adhesive APLP showed more significant dependence on the application mode than the mild AEB. APLP exhibited inferior bonding at the A/D interface if applied without agitation, evidenced by debonding from the dentine substrate. The DDs and DCs of the APLP with agitation were higher than those of without agitation in the interface, in contrast to the comparable DD and DC values of two AEB specimen groups with different application modes. Raman spectral analysis revealed the important role of chemical interaction between acid monomers of self-etch adhesives and dentine in the above observations. ConclusionThe chemical interaction with dentine is especially important for improving the DC of the strong self-etching adhesive at the A/D interface. Agitation could benefit polymerization efficacy of the strong self-etch adhesive through enhancing the chemical interaction with tooth substrate.

Effects of Etch-and-Rinse and Self-etch Adhesives on Dentin MMP-2 and MMP-9

Auto-degradation of collagen matrices occurs within hybrid layers created by contemporary dentin bonding systems, by the slow action of host-derived matrix metalloproteinases (MMPs). This study tested the null hypothesis that there are no differences in the activities of MMP-2 and -9 after treatment with different etch-and-rinse or self-etch adhesives. Tested adhesives were: Adper Scotchbond 1XT (3M ESPE), PQ1 (Ultradent), Peak LC (Ultradent), Optibond Solo Plus (Kerr), Prime&Bond NT (Dentsply) (all 2-step etch-and-rinse adhesives), and Adper Easy Bond (3M ESPE), Tri-S (Kuraray), and Xeno-V (Dentsply) (1-step self-etch adhesives). MMP-2 and -9 activities were quantified in adhesive-treated dentin powder by means of an activity assay and gelatin zymography. MMP-2 and MMP-9 activities were found after treatment with all of the simplified etch-and-rinse and self-etch adhesives; however, the activation was adhesive-dependent. It is concluded that all two-step etch-and-rinse and the one-step self-etch adhesives tested can activate endogenous MMP-2 and MMP-9 in human dentin. These results support the role of endogenous MMPs in the degradation of hybrid layers created by these adhesives.

Effect of alternative modes of application on microleakage of one-step self-etch adhesives

Background/purposeContemporary one-step self-etch adhesives are certainly the most user-friendly adhesives; however, typically could not compete with the more traditional multi-step adhesives. This in vitro study evaluated the efficacy of two modes of application (double application or placement of a hydrophobic resin coating) for the reduction of microleakage, using three different one-step self-etch adhesives (AdheSE One VivaPen, Ivoclar Vivadent, Schaan, Liechtenstein; Xeno V, Dentsply De Trey, Konstanz, Germany; OptiBond All-In-One, Kerr Italia S.r.l, Scafati, Italy). Materials and methodsWe prepared Class V cavities with the occlusal margin in enamel and gingival margin in dentin on both buccal and lingual surfaces of 108 human molar teeth. Cavities were divided into nine groups according to the combination of adhesives and application modes used (n = 24). For applying adhesives, we followed three types of procedures: (1) according to the manufacturers’ directions; (2) using a double-application method; and (3) with the additional placement of a hydrophobic resin layer after following the manufacturers’ directions. We restored the cavities with a composite resin. After thermocycling (500 cycles at 5°C/55°C) and immersion in 0.5% basic fuchsin, we sectioned the teeth and evaluated them for microleakage using a stereo microscope (20×). Enamel and dentin margins were scored separately, and we analyzed the data using Kruskal–Wallis, Bonferroni-corrected Mann–Whitney U, and Wilcoxon signed-rank tests. ResultsApplication of a hydrophobic resin over the cured Xeno V adhesive decreased the amount of microleakage at the enamel margins, compared with the application according to the manufacturer’s instructions (P = 0.005). Both application modes decreased the amount of microleakage at the dentin margins with AdheSE One VivaPen adhesive, compared with application according to the manufacturer’s instructions (P < 0.001). With the OptiBond All-In-One adhesive, no significant difference between application modes was observed. ConclusionAlternative modes of application did not adversely affect the sealing ability of one-step self-etch adhesives. Depending on the type of adhesive, alternative modes of application may contribute to low microleakage values.

Prolonged exposure times of one-step self-etch adhesives on adhesive properties and durability of dentine bonds

ObjectivesTo evaluate the effect of prolonged exposure times on immediate and 6-month adhesive properties: degree of conversion (DC), nanoleakage (NL) and resin–dentine bond strength (μTBS) of three one-step self-etch adhesive systems (Adper Easy One [EO], Clearfil S3 Bond [CS3] and Go [GO]). Material and methodsThe adhesives were applied on exposed dentine surfaces of 90 human molars according to manufacturers’ instructions and light polymerized for 10, 20, and 40s at 600mW/cm2. Bonded teeth were sectioned to obtain stick-shaped specimens (0.8mm2) and tested under tensile stress (0.5mm/min) immediately (IM) or after 6 months of water storage. Two bonded sticks from each tooth at each storage time interval were analysed by SEM for NL evaluation. The in situ DC was evaluated by micro-Raman spectroscopy. Data were analysed by appropriate ANOVA and Tukey's test (α=0.05). ResultsProlonged exposure times significantly increased the DC (%) (10s [67.4±17.3]; 20s [85.9±8.9] and 40s [85.2±9.0]) and decreased the NL (%) (10s [24.8±13.2]; 20s [13.3±7.5] and 40s [13.5±9.3]) for all adhesives; however it did not increase the IM μTBS for two (EO, GO) out of the three adhesives. Furthermore, this technique did not minimize dentine bond degradation. ConclusionAlthough longer exposure times than those recommended could not prevent degradation of dentine bonds, they could increase DC within the hybrid layer and reduced NL for all adhesives tested.

Effect of waiting interval on chemical activation mode of dual-cure one-step self-etching adhesives on bonding to root canal dentin

ObjectivesThe purpose of this study was to evaluate the effect of waiting interval on the chemical activation of dual-cure one-step self-etching adhesives before placing resin core materials on the regional bond strength to root canal dentin. Materials and methodsForty-eight post spaces prepared in human lower premolars were applied with four dual-cure one-step self-etching adhesives Estelite Core Quick: ECB/ECQ, Clearfil DC Core Automix: CDB/CDC, Unifil Core EM: UNB/UNC, BeautiCore: BTB/BTC as the manufacturers’ instructions. These adhesives were cured with light activation for 10s, or chemical activation with 0, 10, and 30s waiting intervals prior to placing resin core material. Resin core materials were then placed into the post space and light-cured for 60s. After 24h water storage, each specimen was serially sliced into 8, 0.6mm×0.6mm thick beams for the μTBS test. The regional μTBS data were analyzed using three-way ANOVA and Dunnett's T3 test (p<0.05). ResultsFor the chemical activation with 10 and 30s waiting intervals, ECB and CDB exhibited significantly improved μTBS, whereas for UNB and BTB, the μTBS were not significantly different but increased with waiting interval. On the other hand, light-activation of all the adhesives produced significantly higher μTBS to root canal dentin than chemical activation (p<0.05), except for the UNB group. ConclusionsFor the chemical activation of dual-cure one-step self-etching adhesives, a waiting interval prior to placing resin core material improved μTBS to root canal dentin. Polymerising the adhesives before polymerisation reaction of resin core material would be effective for bonding to root canal dentin. Clinical relevanceFor chemical activation mode as well as light activation mode, pre-curing of adhesive layer before proceeding polymerisation of resin filling material would produce higher bonding performance to dentin in the cavity.

Effect of Calcium Salt of Functional Monomer on Bonding Performance

To determine the amount of 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-calcium (MDP-Ca) salt produced through the demineralization of enamel or dentin by MDP, we designed experimental MDP-based one-step adhesives with different amounts of MDP. The null hypotheses were that (1) the amount of MDP-Ca salt produced through the demineralization of enamel was the same as that for dentin, and (2) the amounts of MDP-Ca salt have no effect on bonding performance. Increases in the amount of MDP resulted in increased amounts of MDP-Ca salt. The production amount of MDP-Ca salt of the dentin was 1.3 times higher than that of the enamel. The predominant species of the MDP and enamel reactants was a calcium hydrogen phosphate of MDP. In contrast, the dentin yielded both calcium phosphate and calcium hydrogen phosphate of MDP. Increases in the amount of MDP-Ca salt decreased both enamel and dentin bond strengths. An optimal concentration of MDP exists in one-step self-etch adhesives.

The shear bond strength of resin-based composite to white mineral trioxide aggregate

It is unknown if resin-based composite can be placed on top of mineral trioxide aggregate (MTA) immediately after placement of the MTA. The authors aimed to measure the bond strength of a resin-based composite to white MTA (WMTA) with different bonding strategies at different intervals. The authors bonded resin-based composite to MTA with three bonding protocols (n = 45 per group) (group 1, total-etching adhesive; group 2, two-step self-etching adhesive; or group 3, one-step self-etching adhesive), immediately (subgroup A), 45 minutes (subgroup B) or 24 hours (subgroup C) after placement of the MTA. The authors measured shear bond strength by means of a universal testing machine and performed statistical analysis of the data by means of two-way and one-way analysis of variance (P < .05). In all three groups, subgroup A demonstrated greater bond strengths than the other subgroups. Group/subgroup 3/A demonstrated the highest bond strength (mean [standard deviation] 49.2 [2.1] megapascals), which was significantly higher than that in all other groups (P < .05). This was followed by group/subgroup 1/A (40.2 [2.5] MPa), 2/A (38.4 [1.3] MPa) and 1/B (38.5 [1.91] MPa). The lowest bond strength was shown by group/subgroup 2/C (14.7 [1.90] MPa). There was a significant difference between the two-step and one-step self-etching adhesives at all three intervals (P < .05). Within the limitations of this study, the representative one-step self-etching adhesive demonstrated the strongest bond to WMTA immediately after fabrication of MTA samples. One-step self-etching adhesive may be used to bond resin-based composite to WMTA immediately after placement, thereby offsetting the need for a second appointment for permanent restoration.

Effect of thermal aging on the tensile bond strength at reduced areas of seven current adhesives

The purpose of this study was to determine the micro-tensile bond strength (MTBS) to dentin of seven adhesive systems (total and self-etch adhesives) after 24h and 5,000thermocycles. Dentin surfaces of human third molars were exposed and bonded with two total-etch adhesives (Adper Scotchbond 1 XT and XP Bond), two two-step self-etch adhesives (Adper Scotchbond SE and Filtek Silorane Adhesive System) and three one-step self-etch adhesives (G-Bond, Xeno V and Bond Force). All adhesive systems were applied following manufacturers' instructions. Composite buildups were constructed and the bonded teeth were then stored in water (24h, 37°C) or thermocycled (5,000cycles) before being sectioned and submitted to MTBS test. Two-way ANOVA and subsequent comparison tests were applied at α=0.05. Characteristic de-bonded specimens were analyzed using scanning electron microscopy (SEM). After 24h water storage, MTBS values were highest with XP Bond, Adper Scotchbond 1 XT, Filtek Silorane Adhesive System and Adper Scotchbond SE and lowest with the one-step self-etch adhesives Bond Force, Xeno V and G-Bond. After thermocycling, MTBS values were highest with XP Bond, followed by Filtek Silorane Adhesive System, Adper Scotchbond SE and Adper Scotchbond 1 XT and lowest with the one-step self-etch adhesives Bond Force, Xeno V and G-Bond. Thermal aging induced a significant decrease in MTBS values with all adhesives tested. The resistance of resin-dentin bonds to thermal-aging degradation was material dependent. One-step self-etch adhesives obtained the lowest MTBS results after both aging treatments, and their adhesive capacity was significantly reduced after thermocycling.

Bond strength of one-step self-etch adhesives and their predecessors to ground versus unground enamel

The aim of this study was to compare the shear bond strength of several self-etch adhesives to their two-step predecessors to ground and unground enamel. Seventy-five extracted, non-carious human third molar teeth were selected for this study. The buccal surfaces of each tooth were mechanically ground to obtain flat enamel surfaces (ground enamel), while the lingual surfaces were left intact (unground enamel). The teeth were randomly divided into five groups according to the adhesive systems (n=15): one-step self-etch adhesive - Clearfil S3 Bond, its two-step predecessor - Clearfil SE Bond, one-step self-etch adhesive - AdheSE One, and its two-step predecessor - AdheSE, and a two-step etch-and-rinse adhesive - Adper Single Bond 2(control). After application of the adhesives to the buccal and lingual enamel surfaces of each tooth, a cylindrical capsule filled with a hybrid composite resin (TPH) was seated against the surfaces. The specimens were stored in distilled water at 37°C for 24 hours, followed by thermocy-cling (5°C-55°C/500 cycles). They were subjected to shear bond strength test in a universal testing machine at a crosshead speed of 1.0 mm/minute. The data were compared using a two-way ANOVA, followed by Bonferroni test at P<.05. All adhesives exhibited statistically similar bond strengths to ground and unground enamel except for the etch-and-rinse adhesive that showed significantly higher bond strengths than the self-etch adhesives (P<.05). No significant differences in bond strength values were observed between ground and unground enamel for any of the adhesives tested (P=.17). Similar bond strengths to ground and unground enamel were achieved with one-step self-etch adhesives and their predecessors. Enamel preparation did not influence the bonding performance of the adhesives tested.

Marginal Sealing Durability of Two Contemporary Self-Etch Adhesives

Introduction. Sealing abilities of two self-etch adhesives were evaluated after two aging processes: storage in water and thermocycling. Materials and Methods. Cl V cavities were prepared on the buccal and lingual aspects of 48 human premolars, with cervical margins 1 mm below the CEJ. Clearfil Protect Bond (CPB) and BeautiBond (BB) (two-step and one-step self-etch adhesives, resp.) were applied, each to half of the cavities and restored with composite resin. Each group was randomly subdivided into 4 subgroups (n = 12) and evaluated for dye penetration after 24 hours, after 3000 thermocycling rounds, after a 6-month water storage, and after 3000 thermocycling rounds plus 6-month water storage, respectively. Data was analyzed using SPSS 11.5 and Kruskal-Wallis and Mann-Whitney U tests (α = 0.05). Results. There were no significant differences in enamel and dentin microleakage between the adhesives (P = 0.683; P = 0.154). Furthermore, no significant differences were observed in enamel microleakage of each one of CPB and BB (P = 0.061 and P = 0.318, resp.). However, significant decrease was observed in subgroups 3 and 4 (P = 0.001) for CPB dentinal margins. Conclusion. In this study, limited aging procedures had no influence on marginal integrity of composite resin restorations bonded with self-etch adhesives of CPB and BB. Furthermore, CPB dentinal sealing improved after aging.

Influence of preliminary etching on the stability of bonds created by one‐step self‐etch bonding systems

We evaluated the effects of preliminary etching of dentine on the stability of the bond created by one-step self-etch adhesives under different storage conditions. Adper Easy Bond (3M ESPE) and iBond Self-Etch (iBond SE; Heraeus Kulzer) were applied with an etch-and-rinse (i.e. after preliminary phosphoric acid etching for 15 s) or a self-etch approach. Resin-dentine bonded specimens were sectioned perpendicularly to the adhesive interface according to the 'non-trimming technique'. Beams were stored in artificial saliva for 24 h, 6 months, or 1 yr at 37°C, or in 10% NaOCl for 5 h at room temperature, and then stressed until failure; the microtensile bond strengths were calculated. Interfacial nanoleakage of additional teeth was evaluated using light microscopy or transmission electron microscopy. Adper Easy Bond showed higher bond strength than iBond SE, regardless of the dentine treatment. Similar microtensile bond strength results were obtained for teeth subjected to artificial ageing in 10% NaOCl for 5 h at room temperature and for teeth stored in artificial saliva for 6 months at 37°C. The additional etching step increased the microtensile bond strength for Adper Easy Bond and iBond SE. This study supports the use of one-step adhesives on etched dentine because of the increased bond strength compared with their application onto smear-layer-covered dentine, regardless of storage conditions.

Bond Strengths of One-Step Self-Etch Adhesives to Laser-Irradiated and Bur-Cut Dentin After Water Storage and Thermocycling

The objectives of this study were to evaluate the microtensile bond strength (μTBS) of one-step self-etch adhesive systems to Er:YAG laser-irradiated and bur-cut dentin after water storage and thermocycling. The Er:YAG laser is a promising alternative method for cavity preparation; however, no study has compared the effect of laser irradiation and aging procedures on the adhesion of one-step self-etch adhesives to dentin. Seventy-two third molars were selected and randomly divided according to cavity preparation method (Er:YAG laser and bur-cut). One-step self-etch adhesive systems (Clearfil S(3) Bond, AdheSE One and Adper Easy One) were used to bond the composite to dentin. Following the adhesive procedure, the specimens were subdivided according to aging conditions (24 h in water control [C], 6 months of water storage [WS] and 10.000 thermocycles [TC]). The μTBS was determined in a universal testing machine. Three-way ANOVA, independent samples t test, and post-hoc comparisons test (α=0.05) were performed on all data. There was no statistical difference in μTBS between Er:YAG laser-irradiated and bur-cut dentin (p>0.05). Similarly, no significant difference was found in μTBS between C, WS, and TC specimens (p>0.05). Moreover, Clearfil S(3) Bond presented the highest μTBS to dentin in both laser-irradiated and bur-cut cavity preparation methods. Neither bur-cut nor Er:YAG laser-irradiated dentin was affected by the aging methods used to simulate degradation of the adhesive interface. Er:YAG laser treatment may be used as an alternative cavity preparation method.

Effect of pulpal-pressure on dentin-bonding of one-step self-etching adhesives

Effect of pulpal-pressure on dentin-bonding of one-step self-etching adhesives

Effects of Surface Hydration State and Application Method on the Bond Strength of Self-etching Adhesives to Cut Enamel

To evaluate the effect of surface hydration state and application method on the microtensile bond strength of one-step self-etching adhesives systems to cut enamel. One hundred ninety-five bovine teeth were used. The enamel on the buccal side was flattened with 600-grit SiC paper. For the control group, 15 teeth received Adper Single Bond 2, applied according to manufacturer's recommendations. The other specimens were divided into three groups according to the adhesive system used: Futura Bond M (FM; Voco), Clearfil S3 Bond (CS; Kuraray), and Optibond All in One (OA; Kerr). For each group, two hydration states were tested: D: blown dry with air; W: the excess of water was removed with absorbent paper. Two application methods were tested: P (passive): the adhesive was simply left on the surface; A (active): the adhesive was rubbed with an applicator point. A coat of Grandio composite resin (Voco) was applied on the surface. The teeth were sectioned to obtain enamel-resin sticks (1 x 1 mm), which underwent microtensile bond testing. The data in MPa were submitted to a three-way ANOVA and Tukey's test (α = 5%). The ANOVA showed significant differences for application method and the type of adhesive, but not for hydration state. For the application method, the results of Tukey's test were: P: 31.46 (± 7.09)a; A: 34.04 (± 7.19)b. For the type of adhesive, the results were: OA: 31.29 (± 7.05)a; CS: 32.28 (± 7.14)a; FM: 34.68 (± 7.17)b; different lower-case letters indicate statistically significant differences. Active application improved the bond strength to cut enamel. The adhesive Futurabond M showed the highest bond strength to cut enamel.

Effect of different root canal irrigants on the sealing ability of two all-in-one self-etch adhesives: An in vitro study

Aim:To evaluate the effect of different root canal irrigants on the sealing ability of two self-etch adhesives, using dye penetration method, within the pulp chamber.Materials and Methods:72 extracted human molars were divided into six groups, according to the irrigant and self-etch adhesives used. After de-roofing the pulp chamber with a carborundum disc, the pulp was extirpated using excavator and broaches. In 36 samples, pulp chambers were bonded with Xeno V after irrigation with either 2% CHX (Group1: Xe-CHX) ; 17% EDTA + 5.25% NaOCl (Group2: Xe- EDTA + NaOCl) or normal saline (Group3: Xe-NS) and in other half samples, pulp chambers were bonded with Adper Easy One after irrigation with either 2% CHX (Group 4: Ad-CHX); 17%EDTA + 5.25% NaOCl (Group5: Ad-EDTA+NaOCl) or normal saline (Group 6: Ad-NS). All the samples were restored with Filtek Z350. Ten teeth from each group were assessed for dye penetration. Two samples in each group were viewed under scanning electron microscope to observe resin-dentin interfacial adaptation. Data was statistically analyzed using Mann–Whitney and Kruskal Wallis tests at a significance level of P < 0.05.Results:Mean microleakage scores and standard deviation observed were: Group 1 (Xe-CHX): 2.8 ± 0.42, Group 2 (Xe-EDTA + NaOCl): 2.3 ± 0.82, Group 3 (Xe-NS): 2.9 ± 0.31, Group 4 (Ad-CHX): 1.2 ± 0.91, Group 5 (Ad-EDTA + NaOCl): 0.8 ± 0.63, Group 6 (Ad-NS): 1.9 ± 0.99.Conclusions:Adper Easy One showed significantly less leakage than Xeno V when normal saline was used as an irrigant. EDTA treatment followed by NaOCl application significantly reduced microleakage and improved the interfacial adaptation with Adper Easy One. CHX did not significantly affect the sealing ability of both one-step self-etch adhesives tested.

Effect of multiple coats of ultra-mild all-in-one adhesives on bond strength to dentin covered with two different smear layer thicknesses.

To evaluate the effect on bond strength of 1, 2, or 3 coats of two one-step self-etching adhesives on dentin covered with two different smear layer thicknesses. Flat dentin surfaces from recently extracted third molars were wet ground with 60- or 600-grit SiC paper to produce smear layers of different thicknesses. Adper Easy Bond (3M ESPE) and Clearfil S3 Bond (Kuraray) were applied in 1, 2, or 3 consecutive coats after air drying each coat. ScotchBond Multi Purpose (3M) and Clearfil SE Bond (Kuraray) were used as controls. Composite resin crowns (Filtek Z250, 3M ESPE) were built up, stored for 24 h, and cut in x and y directions. Eight to twelve sticks (0.65 ± 0.05 mm2 of area) from the central area of each tooth were fractured in tension (0.5 mm/min). Sticks from each group were processed for interfacial micromorphological evaluation with SEM. Three-way ANOVA revealed a significant interaction between factors (p < 0.05). Tukey's post-hoc test showed that only when Adper Easy Bond was applied on dentin prepared with 600-grit SiC paper, microtensile bond strength was not significantly affected by the number of coatings. However, the effect of smear layer thickness was only statistically significant when the adhesives were applied in one coat, for both adhesives. When they were applied in two or three coats, smear layer thickness did not significantly affect bond strength (p > 0.05). The thickness of the smear layer affected the bond strength of both all-in-one adhesives. Additional coats can be beneficial to bond strength, especially with Clearfil S3 Bond.

Bond Strength and Interfacial Ultramorphology of Current Adhesive Systems

This study evaluated the bond strength and ultramorphology of the resin-dentin interfaces produced by current dental adhesive systems. Nine dentin bonding agents were investigated. Restored teeth were vertically, serially sectioned to obtain bonded slices for interfacial TEM analysis or to produce bonded beams for the microtensile bond strength test. The one-step self-etching adhesives (Futurabond® NR and Hybrid Bond®) showed lower bond strength values than the three-step etch-&-rinse adhesive system All-Bond 3. Most bonding agents presented statistically similar mean bond strength values, which ranged from 41.3 ± 17.9 to 35.0 ± 5.3 MPa. The thickness of the hybrid layer varied according to the type of adhesive system used. While the etch and rinse adhesives with alcohol as organic solvent showed bond strength means higher than 40 MPa, the self-etching systems showed bond strength lower than 40 MPa. Resin-dentin interdifusion zone and resin tags were noted in all bonded interfaces.

Influence of adhesive properties on resin-dentin bond strength of one-step self-etching adhesives.

To evaluate the association between the resin-dentin bond strength (microtensile bond strength, μTBS) and the physical properties (ultimate tensile strength [UTS] and microhardness [VHN]) of the cured adhesive resin using five commercial one-step self-etching systems. Futurabond NR, Go, G Bond, 1-step All Bond SE and Clearfil S3 Bond were applied on flat superficial dentin surfaces. Each adhesive system was applied in five teeth. A resin buildup was then made. After 24 h, resin-dentin beams (0.9 mm2) were prepared to be tested immediately at 0.5 mm/min. For the UTS measurement, hourglass specimens were prepared with each adhesive system (n = 5) to be tested under tensile stress at 0.5 mm/min. The fractured specimens from the UTS test were taken to a Vickers microhardness tester (25 gf/20 s). μTBS, UTS, and VHN values were submitted to a one-way ANOVA and Tukey's test (α = 0.05) for pairwise comparisons. Correlations between μTBS, UTS and VHN were analyzed using the Pearson product moment correlation test (α = 0.05). Significantly higher μTBS values were observed for 1-step All Bond SE and Clearfil S3 Bond (p > 0.05). The adhesive All Bond SE showed the highest UTSmean among all systems (p < 0.05). The adhesives All Bond SE and G-Bond showed the highest microhardness mean among all systems (p < 0.05). A strong (r = 0.93) and significant (p = 0.021) correlation was only found between the μTBS and UTS values. The ultimate tensile strength of one-step self-etching systems correlates with the resin-dentin bond strength values.