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The central aim of adhesive dentistry is to improve the compatibility between current adhesives and a range of substrates by employing diverse application techniques. Therefore, the overarching objective of this review is to offer a comprehensive analysis of dentin bonding systems, starting with an introduction to adhesion and a detailed overview of enamel and dentin structures, their histology, and the impact of dentin structure on resin–dentin bonding. It covers the mechanisms of resin–dentin bonding, including resin adhesive application, bonding mechanisms, and factors influencing efficacy. Further, this review explores the composition of resin adhesive systems, including acidic components, cross-linking monomers, solvents, and other critical elements. It also examines various adhesive strategies—etch-and-rinse, self-etch, and universal adhesives—highlighting their applications and advantages. The review extends to clinical applications of dental adhesion, including direct restorations, indirect restorations, and immediate dentin sealing (IDS), demonstrating the practical implications of adhesive systems in enhancing restoration longevity and performance. In conclusion, despite significant advancements, no gold-standard method for optimal adhesion exists. Each adhesive system has distinct strengths and limitations. The review emphasizes the importance of evaluating methods for achieving durable adhesion and staying current with technological advancements in adhesive systems. Summary: This review provides a thorough analysis of dentin bonding systems, delving into the structures and bonding mechanisms of both enamel and dentin. By exploring various adhesive systems and their components, it highlights the ongoing challenges in achieving optimal resin–dentin adhesion. The review also addresses the clinical applications of dental adhesion, including direct restorations, indirect restorations, and immediate dentin sealing (IDS), illustrating how different adhesive techniques impact clinical outcomes. It underscores the necessity for continuous innovation and assessment of adhesive systems to enhance long-term bonding effectiveness in clinical practice. [ABSTRACT FROM AUTHOR]

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

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Purpose: The purpose of this in vitro study was to compare the shear bond strength of different universal adhesives to enamel and dentin with and without additional phosphoric acid etching before and after thermocycling (TC). Materials and Methods: The mesial, distal, lingual, and buccal surfaces of the teeth were ground flat to expose two enamel areas and two dentin areas. Specimens were randomly divided into 36 groups (n = 10). Four adhesives were tested: Scotchbond Universal (SBU), Prime & Bond Elect (PBE), All-Bond Universal (ABU), and iBond Universal (IBU). The application was performed in the self-etch mode (SE) or in the etch-and-rinse mode (ER). Optibond FL (OFL) was used as an etch-and-rinse control. After composite buildups were made, half of the groups were tested before and the other half after TC. The failure mode was evaluated using a light microscope. Results: In enamel, mean bond strengths ranged from 13.4 to 21.9 MPa in the SE mode before TC. When used as an ER adhesive, mean bond strengths exceeded 30 MPa. TC did not influence the mean bond strengths in either application mode. Regarding dentin, significant differences in the SE mode were adhesive dependent. Differences were only detected between SBU and IBU before TC and were not present after TC. When SBU, PBE, and ABU were used as ER adhesives, no differences were detected before TC. TC only affected IBU when compared to the other adhesives. Conclusion: Universal adhesives benefit from phosphoric acid etching, as bond strengths increased especially at enamel surfaces. [ABSTRACT FROM AUTHOR]

The aim of this study was to review and analyze the evidence on the enamel acid etching time when bonding to primary teeth. The research question was: Does the acid-etching time affect the bond strength to primary enamel? A systematic search across PubMed, Web of Science, Scopus and Google Scholar databases was conducted up to April 2024 to select studies that compared acid etching times on the bond strength values of adhesive systems to the primary tooth enamel. Studies evaluating other materials than adhesive systems, absence of bond strength values as mean and standard deviation, or ineligible comparison between intervention and control were excluded. Two reviewers screened studies for eligibility and assessed risk of bias. Bond strength data was the primary outcome. From 411 screened studies, 7 reports were assessed for eligibility, and 5 studies were included in the systematic review. Four studies had a high risk of bias and one study had a moderate risk of bias. Acid etching times range from 5 to 60 s. Three studies considered 15 s as a shorter acid etching time and the time of 30 or 60 s as a control. Two studies evaluated the effect of acid etching times on bond strength by comparing the 5, 20, 30, and 60 s groups. Only one study found statistically significant differences between the acid etching times. The main limitation of the study was the inclusion of only 5 studies with a high or moderate risk of bias. Longer acid etching times do not appear to improve the enamel bond strength in primary teeth. This is the first comprehensive review of enamel acid etching time on bonding to primary teeth. It may support the similar acid etching time for primary and permanent tooth enamel. [ABSTRACT FROM AUTHOR]

The cervical area of teeth is the most unpredictable region for durable adhesive bonding. This study evaluated the adhesion potential of resin cement to coronal and cervical/root structures with a focus on enamel, dentin and cementum using etch-and-rinse and self-etch adhesive systems. Anterior teeth (N = 60) were randomly divided into six groups for adhesion tests: (a) unprepared enamel (UE), (b) ground enamel (GE), (c) mid-coronal dentin (D), (d) cervical enamel 2 mm above cementoenamel junction (CE), (e) cementoenamel junction (CEJ), and (f) root cementum (RC). Enamel and dentin surfaces were conditioned using either an etch-and-rinse (Syntac Classic-SY) or self-etch (Clearfil S3 Bond Plus-CS3) adhesive system. Resin cement (Variolink Esthetic) was adhered to the different substrates using polyethylene molds and photo-polymerized. Bonded specimens were stored in water for 24 h at 37 °C. Microshear tests (µSBT) were conducted in a Universal Testing Machine (1 mm/min) and failure types were analyzed after debonding. Data were analyzed using two-way ANOVA and t-test (alpha = 0.05). While substrate type (p < 0.001) and adhesive system (p < 0.001) significantly affected the bond results, interaction terms were not significant (p = 0.063). Within SY adhesive system, adhesion to all substrates were not significant ranging between (8.07 ± 2.39–6.80 ± 4.60) (p > 0.05), except for CEJ (5.19 ± 1.39) and RC (4.08 ± 1.13). With the CS3 adhesive system, all groups presented non-significant results (4.15 ± 1.35–6.04 + 2.38) (p > 0.05), except for D (3.57 ± 1.84) and RC (3.21 ± 1.13) (p < 0.05). µSBT values for D (7.19 ± 2.31) and RC (4.08 ± 1.13) were significantly higher for SY compared to that of CS3 (3.57 ± 1.84–3.21 ± 1.13, respectively) (p < 0.05). [ABSTRACT FROM AUTHOR]

Purpose: To investigate the bonding of a new universal adhesive applied using different etching strategies on sound and caries-affected dentin of primary teeth. Materials and Methods: Flat dentin surfaces from 50 primary molars were randomly assigned to 10 groups according to substrate (sound dentin [SD] vs caries-affected dentin [CAD] pH cycled for 14 days) and bonding approach (Scotchbond Universal Adhesive: self-etching, vs dry or wet-bonding etch-and-rinse strategies; Adper Single Bond Plus [two-step etch-and-rinse adhesive] and Clearfil SE Bond [two-step self-etching system] as controls). After 24 h of water storage, bonded sticks with cross-sectional areas of 0.8 mm² were tested for microtensile bond strength (μTBS). Two sticks from each tooth were immersed in silver nitrate solution in order to evaluate nanoleakage (NL) with SEM. The μTBS means were analyzed using two-way ANOVA and Tukey's tests. For NL, the Kruskal-Wallis and Mann-Whitney tests were used (α = 0.05). Results: The influence of the etching strategy on the bonding performance of the universal adhesive was substrate dependent. The self-etching approach resulted in lower μTBS values and higher silver nitrate uptake into hybrid layers for Scotchbond Universal Adhesive on SD, while no difference among experimental groups was observed in CAD. Conclusion: It is preferable to use the universal adhesive following either a dry- or wet-bonding etch-and-rinse approach on both sound and caries-affected primary dentin. [ABSTRACT FROM AUTHOR]

Imperfect polymer formation as well as collagen's susceptibility to enzymatic degradation increase the vulnerability of hybrid layers over time. This study investigated the effect of new dimethyl sulfoxide (DMSO)-containing pretreatments on long-term bond strength, hybrid layer quality, monomer conversion and collagen structure. H 3 PO 4 -etched mid-coronal dentin surfaces from extracted human molars (n = 8) were randomly treated with aqueous and ethanolic DMSO solutions or following the ethanol-wet bonding technique. Dentin bonding was performed with a three-step etch-and-rinse adhesive. Resin-dentin beams (0.8 mm2) were stored in artificial saliva at 37 °C for 24 h and 2.5 years, submitted to microtensile bond strength testing at 0.5 mm/min and semi-quantitative SEM nanoleakage analysis (n = 8). Micro-Raman spectroscopy was used to determine the degree of conversion at different depths in the hybrid layer (n = 6). Changes in the apparent modulus of elasticity of demineralized collagen beams measuring 0.5 × 1.7 × 7 mm (n = 10) and loss of dry mass (n = 10) after 30 days were calculated via three-point bending and precision weighing, respectively. DMSO-containing pretreatments produced higher bond strengths, which did not change significantly over time presenting lower incidence of water-filled zones. Higher uniformity in monomer conversion across the hybrid layer occurred for all pretreatments. DMSO-induced collagen stiffening was reversible in water, but with lower peptide solubilization. Improved polymer formation and higher stability of the collagen-structure can be attributed to DMSO's unique ability to simultaneously modify both biological and resin components within the hybrid layer. Pretreatments composed of DMSO/ethanol may be a viable-effective alternative to extend the longevity of resin-dentin bonds. [ABSTRACT FROM AUTHOR]

The restoration longevity depends on a high dentin-composite bond quality. This study investigated learning outcomes when using etch-and-rinse and self-etch adhesives among general practitioners in a hands-on bonding test course. We recruited 30 general practitioners to perform shear bond strength (SBS) tests using five adhesives: one Peak® Universal Bond (PUB) etch-and-rinse and four Futurabond DC, Single Bond universal (SBU), Versa Optibond (VOB), and Tetric-N Bond Self-Etch (TNS) self-etch adhesives. SBS tests were conducted at pre-demonstration (pre-demo), post-demonstration (post-demo), and 24-h storage (delayed bonding) stages. SBS data were analyzed with paired Student's t -tests. We defined 17 MPa as "qualified bond strength (QBS)". The percentages of samples with SBS achieving QBS were analyzed using Mantel–Haenszel chi-square tests. The fracture surfaces of the samples were examined by scanning electron microscopy (SEM). Using PUB caused no significant differences in SBS between pre- and post-demo samples, whereas the SBS of the two self-etch adhesives (SBU and VOB) improved in post-demo samples (p < 0.05). SBU showed the highest percentage of samples with SBS achieving QBS in all three groups (pre-demo = 70%, post-demo = 83%, and delayed bonding = 76.5%). The QBS percentages of VOB and TNS notably improved from 0% (pre-demo) to 71.4% and 23.5% (post-demo), respectively. SEM indicated bubble-like defects at the dentin-resin interfaces in cases of low SBS. Bonding performance is both operator- and product-dependent. The continuing education hands-on course does help dentists to improve the bond strength especially when the self-etch system is used. [ABSTRACT FROM AUTHOR]

Abstract The objective of this study was to evaluate the effect of sonic application of universal adhesives on the enamel microshear bond strengths (µSBS), in situ degree of conversion (DC) and etching pattern. Ninety-six extracted third molars were sectioned in four parts (buccal, lingual, proximal) and divided into 12 groups, according to the combination of 1) adhesive system (All-Bond Universal [ABU], G-Bond Plus [GBP], Prime&Bond Elect (PBE), and Scotchbond Universal Adhesive [SBU]), and 2) adhesive application mode (manual active etch-and-rinse [M-ER], manual active self-etch [M-SE], and sonic vibration self-etch [S-SE]). Specimens were stored in water at 37 °C during 24 h and tested at 1.0 mm/min (µSBS). DC was evaluated in the enamel-resin interfaces using micro-Raman spectroscopy. The enamel-etching pattern was evaluated under a field- emission scanning electron microscope. Data were analyzed with two-way ANOVA and Tukey's test (α = 0.05). S-SE application increased µSBS and DC for all universal adhesives when compared to M-SE (p < 0.05). S-SE application resulted in mean bond strengths that were statistically similar to those obtained with the respective ER application mode (p > 0.05). A deeper enamel-etching pattern was observed for all universal adhesives in the etch-and-rinse strategy. An improvement in etching ability was observed in S-SE application compared to M-SE application. In light of the improved performance of universal adhesives when applied sonically in SE mode, selective enamel etching with phosphoric acid may not be crucial for their adhesion to enamel. The sonic application of universal adhesives in self-etch mode may be a practical alternative to enamel etching. [ABSTRACT FROM AUTHOR]

To evaluate the effect of SDF-based treatments following delayed bonding and surface treatment approaches on resin-dentin bonding efficiency of a universal adhesive under different application modes. Mid-coronal dentin surfaces from sound third molars were randomly treated with 38% silver diamine fluoride (SDF) and/or additionally with potassium iodide (SDF/KI). Untreated dentin served as control. SDF-treated teeth were assigned to groups according to surface treatment approaches (air-abrasion and water rinsing), the application mode of a mild universal adhesive (etch-and-rinse or self-etch) and delayed bonding (immediate, 7, 15 or 30 days). Microtensile bond strength (n = 5), SEM analyses of hybrid layer formation and dentin etching patterns and dentin permeability were evaluated. Data were analyzed with factorial ANOVA. SDF-based treatments affected dentin bonding depending on application mode and surface treatment approaches (p <0.001). Etch-and-rinse bonding was not affected by SDF-based treatments (p <0.05), producing more homogenous hybrid layers. While dentin etching patterns of etch-and-rinse application were not affected by SDF-based treatments, self-etching presented limitations. Bond strength reductions of self-etched dentin were restored by silver-removal strategies containing a water-rinsing step (p <0.05). Delayed bonding additionally reduced dentin permeability (p <0.05), further decreasing with longer periods (p <0.05). Although the negative effect of SDF-based treatments on resin-dentin bonding can be avoided by strategies incorporating water-rinsing before hybridization, delayed bonding brings additional advantages due to higher mineral deposition. While the etch-and-rinse technique avoids major bonding drawbacks to SDF-treated dentin, self-etch bonding requires removal of excess silver deposits before hybridization. Performing SDF-based treatments and dentin hybridization in separate sessions (>15 days apart) potentialize mineral deposition improving caries control and service life of composite restorations. • Resin bonding to SDF-treated dentin should not be underestimated. • Application mode affects bonding to SDF-treated dentin. • Strategies incorporating water rinsing before hybridization eliminate bonding issues. • Mineral deposition on SDF-treated dentin increases with time in wet environments. • Delayed bonding reduces permeability and reverts SDF-related bonding inefficiencies. [ABSTRACT FROM AUTHOR]

This study evaluate the effect of nanoparticles (Bi 2 O 3 - bismuth oxide; YbF 3 - ytterbium trifluoride; SiO 2 - silicon dioxide) on radiopacity (R), translucency parameter (TP), degree of conversion (DC), bond strength to dentin (µTBS), and quality of the adhesive interface of experimental two-step, etch-and-rinse adhesive systems. The R was evaluated using an x-ray equipment. TP was verified in five replications and DC was performed in triplicate. The µTBS was evaluated in specimens stored in distilled water after 24 h, 6, 12 and 24 months. The bonded interfaces were qualitatively examined by scanning electron microscopy (SEM), and using x-ray energy dispersive spectroscopy (EDS) for elemental analysis. Data were statistically analyzed at α = 0.05. YbF 3 resulted in statistically greater R when compared with all the other groups ( p = 0.024), which did not differ from each other. Bi 2 O 3 was the adhesive with lowest TP. For DC, the YbF 3 and C showed similar results ( p = 0.627). Similar µTBS was obtained between groups. The addition of nanoparticles affected the chemical-mechanical properties. The incorporation of YbF 3 could be considered a promising approach for the development of radiopaque dental adhesives. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the influence of CO2 9.3 μm short-pulsed laser irradiation on the shear bond strength of composite resin to enamel and dentin. Two hundred enamel and 210 dentin samples were irradiated with a 9.3 µm carbon dioxide laser (Solea, Convergent Dental, Inc., Natick, MA) with energies which either enhanced caries resistance or were effective for ablation. OptiBond Solo Plus [OptiBondTE] (Kerr Corporation, Orange, CA) and Peak Universal Bond light-cured adhesive [PeakTE] (Ultradent Products, South Jordan, UT) were used. In addition, Scotchbond Universal [ScotchbondSE] (3M ESPE, St. Paul, MN) and Peak SE self-etching primer with Peak Universal Bond light-cured adhesive [PeakSE] (Ultradent Products) were tested. Clearfil APX (Kuraray, New York, NY) was bonded to the samples. After 24 h, a single plane shear bond test was performed. Using the caries preventive setting on enamel resulted in increased shear bond strength for all bonding agents except for self-etch PeakSE. The highest overall bond strength was seen with PeakTE (41.29 ± 6.04 MPa). Etch-and-rinse systems achieved higher bond strength values to ablated enamel than the self-etch systems did. PeakTE showed the highest shear bond strength with 35.22 ± 4.40 MPa. OptiBondTE reached 93.8% of its control value. The self-etch system PeakSE presented significantly lower bond strength. The shear bond strength to dentin ranged between 19.15 ± 3.49 MPa for OptiBondTE and 43.94 ± 6.47 MPa for PeakSE. Etch-and-rinse systems had consistently higher bond strength to CO2 9.3 µm laser-ablated enamel. Using the maximum recommended energy for dentin ablation, the self-etch system PeakSE reached the highest bond strength (43.9 ± 6.5 MPa). [ABSTRACT FROM AUTHOR]

The objective was to compare bond strengths of adhesives with/without thermocycling and to analyze the micromorphology of resindentin interfaces. Flat dentin surfaces were prepared and divided into eight groups to bond with four etch-and-rinse adhesives (Optibond FL, Adper Scotchbond Multi-Purpose, Optibond Solo Plus, and Single Bond 2) and four self-etch adhesives (Clearfil SE Bond, Adper SE Plus, Clearfil S3 Bond and Adper Easy Bond). Specimens were further divided into two subgroups subjected for with/ without thermocycling and then subjected to both micro-tensile test and resin-dentin interface evaluation. The results revealed that there were significant differences in bond strength between the groups with and without thermocycling for all etch-and-rinse groups and for the Adper Easy Bond self-etch group (p<0.01). Clearfil SE Bond demonstrated highly durable bond strengths. Furthermore, more silver ion uptake was observed at the resin-dentin interfaces for all etch-and-rinse adhesives and Adper SE Plus and Adper Easy Bond after thermocycling. [ABSTRACT FROM AUTHOR]

Background and aims. The aim was to evaluate the effect of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) on microtensile bond strength (µTBS) to carious affected dentin (CAD) using etch-and-rinse and self-etch adhesive systems. Materials and methods. The occlusal surface of 32 human molars with moderate occlusal caries was removed. Infected dentin was removed until reaching CAD and the teeth were randomly divided into two groups based on the Single Bond (SB) and Clearfil SE Bond (CSE) adhesive systems. Before composite resin bonding, each group was subdivided into three subgroups of ND, CAD and CPP-ACP-treated CAD (CAD-CPP) based on the dentin substrate. After dissecting samples to l-mm-thick cross-sections (each subgroup: n = 13), µTBS was measured at a strain rate of 0.5 mm/min. Data was analyzed using two-way ANOVA, independent samples t-test and post-hoc Tukey tests (α=0.05). Results. Bond strength of both adhesive systems to ND was significantly higher than that to CAD (P < 0.001) and CAD/CPP (P < 0.001). There were no significant differences between the µTBS of SB to CAD and CAD-CPP (P > 0.05). µTBS of CSE to CAD-CPP was higher than that to CAD; however, the difference was not significant (P > 0.05). Significant differences were found between SB and CSE systems only with CAD substrate (P < 0.001). Conclusion. Regardless of the adhesive system used, surface treatment of CAD with CPP-ACP did not have a significant effect on bond strength. However, bond strength to CAD was higher with SB rather than with CSE. [ABSTRACT FROM AUTHOR]

This in vitro study aimed to evaluate a pH‐cycling model for simulation of caries‐affected dentin (CAD) surfaces, by comparing the bond strength of etch‐and‐rinse adhesive systems on sound and artificially‐created CAD. Dentin substrates with different mineral contents and morphological patterns were created by submitting buccal bovine dentin to the following treatments: (1) immersion in artificial saliva during the experimental period (sound dentin, SD), or (2) induction to a CAD condition by means of a dynamic pH‐cycling model (8 cycles, demineralization for 3 h followed by mineralization for 45 h). The bond strength of Excite or Prime and Bond NT adhesive systems was assessed using the microtensile bond strength (μTBS) test. Dentin microhardness was determined by cross‐sectional Knoop evaluations. Resin–dentin morphology after the treatments was examined by scanning electron microscopy. SD produced significantly higher μTBS than CAD for both adhesives evaluated, without differences between materials. CAD exhibited lower microhardness than SD. Morphological analysis showed marked distinctions between SD and CAD bonded interfaces. Under the conditions of this study, differences in morphological pattern and dentin mineral content may help to explain resin–dentin bond strengths. The proposed pH‐cycling model may be a suitable method to simulate CAD surfaces for bonding evaluations. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008 [ABSTRACT FROM AUTHOR]

This study investigated the short- and long-term effects of dental adhesives doped with nano-sized bioactive glass 45S5 (BAG) on the resin–dentin interfacial bond strength. Two etch-and-rinse adhesives (Adper Scotchbond Multi-Purpose (ASB) and Solobond Plus (SB)) and one self-etch adhesive (Clearfil SE Bond (CF)) were doped with different concentrations of BAG (5, 10, and 20 wt%). The unmodified (0 wt% BAG) commercial adhesives served as control groups. Dentin of 120 molars (n = 10 per group) was treated with the different adhesives, followed by buildups with a conventional composite restorative material. From each tooth, 14 sticks were prepared for micro-tensile bond strength (µTBS) testing. The sticks were stored in simulated body fluid at 37 °C and tested after 24 h or six months for µTBS and failure mode. Data were analyzed using Kruskal–Wallis tests in combination with post-hoc Conover-tests and Wilcoxon signed-rank tests at a level of significance of α = 0.05. After 24 h and six months, both etch-and-rinse adhesives with a low BAG content (up to 10 wt% for ASB and 5 wt% for SB) showed similar µTBSs as their respective control groups (0 wt% BAG). CF showed a significant decrease in µTBS even after addition of 5 wt% BAG. At a high concentration of added BAG (20 wt%), all three adhesives showed a significant decrease in µTBS compared to the unmodified controls. The CF control group showed significantly lower µTBS after 6 months of storage than after 24 h. In contrast, the µTBS of all CF groups modified with BAG was unaffected by aging. In conclusion, the tested etch-and-rinse adhesives can be modified with up to 5 wt% (SB), or 10 wt% (ASB) of BAG without reducing their short- and long-term dentin bond strength. Moreover, the addition of nano-sized BAG may prevent long-term bond strength deterioration of a self-etch adhesive. [ABSTRACT FROM AUTHOR]

Multi-mode adhesives (MMA) with different adhesion protocols are postulated to improve bonding to enamel. Thus, this study compared the microshear bond strength (μSBS) of (MMA) and self-etch adhesive (SEA) to different regions and prism orientations of enamel. Thirty premolars were assigned for preparing 160 specimens for μSBS. Specimens were equally divided (n = 80) according to the enamel region evaluated: cuspal, and mid coronal enamel. Each group was divided into two subgroups according to the direction of tooth sectioning: axial, or tangential. Each subgroup was divided into two classes according to the applied adhesive system; either MMA or SEA. Finally; each class was divided into two subclasses (n = 10) according to the adhesion protocol utilized; self-etch adhesion protocol or with etch-and-rinse (pre-etching) adhesion protocol. Nano-filled flowable composite was used to prepare μSBS specimens. μSBS was measured using universal testing machine at a cross head speed of 0.5 mm/min until failure. Statistical analysis was carried out using four-way ANOVA test. Different enamel regions had no statistically significant effect at P-value 0.491. Direction of sectioning had a statistically significant effect at P-value <0.001. Adhesive systems had a statistically significant effect at P-value <0.001. Adhesion protocols had a statistically significant effect at P-value 0.001. Pre-etching of enamel before the application of the MMA improves the resin-enamel μSBS, while there was no advantage of the pre-etching step with the SEA. The μSBS of the tested adhesive systems were influenced by the direction of enamel prisms. The μSBS of the tested adhesive systems were not influenced by the enamel regions tested. [ABSTRACT FROM AUTHOR]