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The dental adhesive market is constantly evolving to meet the demands of dentists and patients, but new products and upgrades should be rigorously evaluated before being used in clinical practice. This study investigated the physicomechanical properties and dentin bonding efficacy of a newly upgraded universal adhesive compared to its predecessor. Twenty-four molars were divided into four groups (n = 6/group) based on adhesive (new vs. predecessor) and application mode [self-etch (SE) vs. etch-and-rinse (ER)] for evaluating their dentin microtensile bond strength (μTBS), failure pattern, and bonding interface. Additional thirty-six molars' crowns were perpendicularly sectioned to obtain flat mid-coronal dentin discs. The opposing dentin surfaces of each disc received contrasting treatments (new/predecessor adhesive applied in SE/ER mode), resulting in six interventions. The bonded discs (n = 6/intervention) were used to assess the adhesives' survival probability employing a double-sided μTBS test. The other physicomechanical properties examined were adhesives' oxygen inhibition layer (OIL), viscosity, hardness, elastic modulus, degree of conversion (DC), and in-situ DC. Both adhesive versions showed similar μTBS (P > 0.05), failure pattern (P > 0.05), and survival probability (P > 0.008). ER mode promoted resin tag formation and exhibited a slender adhesive layer for both adhesives. The newer adhesive version showed a thinner adhesive layer in general with narrower OIL (P < 0.001), less viscosity (P < 0.001), higher hardness (P < 0.05), elastic modulus (P < 0.05), DC (P < 0.001), and in-situ DC (P < 0.001). While the newly updated adhesive had superior physicomechanical properties with more fluidity, its dentin bonding efficacy and survival probability were comparable to its predecessor. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate microtensile bond strength (µTBS) and ultra-morphological characteristic changes in sound dentin resulting from silver diamine fluoride (SDF) when using adhesives. Ninety-six extracted human third molars were divided into the SDF-contaminated dentin group and the sound dentin group. In the SDF-contaminated dentin group, 38% SDF was agitated for 1 min, left undisturbed for 2 min, and rinsed with distilled water for 30 s. Then, each group was further subdivided into six subgroups (n = 8 / group) according to application modes: self-etch mode (SE) and etch-and-rinse mode (ER) followed by three adhesives: (1) Scothbond Universal Plus Adhesive (SUP); (2) G2-Bond Universal Adhesive (G2B); and (3) Clearfil Mega Bond 2 (MB2). All specimens were restored with resin composite and were stored in distilled water for 24 h before μTBS testing. Data from the μTBS test were analyzed using Three-way ANOVA and Duncan test (p < 0.05). The morphology of fractured surface and adhesive-dentin interfaces were evaluated by SEM, TEM, and STEM. Further elemental analysis was done by EDX. All SDF-contaminated dentin groups demonstrated significantly lower μTBS than sound dentin groups. All ER groups had higher μTBS than SE groups, except for G2B in the sound dentin group. STEM/EDX revealed an SDF-dentin-reacted layer in the SDF-contaminated dentin group. SDF had an adverse effect on adhesives. Additionally, ER mode is preferable when bonded to SDF-contaminated dentin. A calcium and fluoride-contained layer was observed in all SDF-contaminated dentin. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: The objectives of this study were (1) to clarify the relationship between the duration of air-drying of one-step self-etch adhesives (1-SEAs) and the evaporation degree (ED) of solvents, and (2) to evaluate the effect of ED on the ultimate micro-tensile strength (μTS) of the adhesives. Methods: The ED of one HEMA-rich 1-SEA, Clearfil S3 Bond (Kuraray), and two HEMA-free 1-SEAs, iBond (Heraeus-Kulzer) and G-Bond (GC), was determined without air-drying and after, respectively, 5- and 10-s air-drying using a gravimetric method. Next, the μTS of the adhesives at ED equivalent to 0-, 5- and 10-s air-drying was measured. Results: The ED increased with extension of air-drying time. Among the adhesives tested, iBond showed the largest ED, followed by G-Bond and Clearfil S3 Bond in this order. A longer air-drying time for 10-s resulted in a statistically significantly higher μTS for the HEMA-rich Clearfil S3 Bond. The μTS of the latter was higher than that of the other two HEMA-free adhesives for each air-drying time. Significance: Air-drying of 1-SEAs had a significant effect on the degree of solvent evaporation (ED) and also on the mechanical properties (μTS) of the 1-SEAs upon setting. It is therefore beneficial to remove solvents of the 1-SEAs as much as possible by thorough, strong air-drying in order to achieve a strong adhesive layer at the interface. [Copyright &y& Elsevier]

Summary: Objective: The purpose of the present study was to evaluate the effect of evaporation of primer components on the ultimate tensile strength (UTS) of primer–adhesive mixtures. Methods: The UTSs of 1:3 by weight primer–adhesive mixtures and of the pure adhesives (controls) were measured after 0-, 2-, 5-min and 24-h storage in a 37°C oven for the three-step etch&rinse adhesive OptiBond FL (Kerr) and the two-step self-etch adhesive Clearfil SE (Kuraray). Results: Evaporation of primer components increased with time for both adhesives investigated. OptiBond FL showed a higher evaporation of primer components than Clearfil SE at the 2-, 5-min and 24-h storage time. As compared to the pure adhesive, the UTS of the primer–adhesive mixture was lower after 0- and 2-min storage for OptiBond FL and after 0-, 2- and 5-min storage for Clearfil SE. The UTS of OptiBond FL was higher than that of Clearfil SE at the 0- and 2-min storage time, though there was no difference at the 5-min and 24-h storage time. Significance: The degree of evaporation of primer components depended largely on the primer solvents employed. The significant decrease in UTS of adhesive resin when mixed with primer must be attributed to incomplete evaporation of primer components. Complete evaporation of solvents is hard to achieve, even by thorough air drying. [Copyright &y& Elsevier]

Summary: Objective: The purpose of this study was to measure the micro-tensile bond strength (μTBS) of two adhesives to dentin and to correlate this μTBS with the micro-tensile fracture strength (μTFS) of primer–adhesive mixtures of the two adhesives. Methods: The three-step etch&rinse adhesive OptiBond FL (Kerr) and the two-step self-etch adhesive Clearfil SE Bond (Kuraray) were used to bond Filtek Z100 (3M ESPE) to twenty mid-coronal dentin surfaces. The μTBS was determined at 1 and 24h after light-curing. In addition, the μTFS of primer–adhesive mixtures (primer:adhesive=1:3 by weight) and of the pure adhesives (controls) were measured after the same time intervals. Results: The μTBS to dentin of OptiBond FL at 24h was significantly higher than at 1h and than the μTBS of Clearfil SE Bond at 24h. The mean μTFS of the primer–adhesive mixtures was always lower than the μTFS of the respective adhesives. The highest reduction in μTFS due to mixing primer with the adhesive resin was measured for Clearfil SE Bond. Both the μTFS of the primer–adhesive mixtures and the pure adhesives of OptiBond FL and Clearfil SE Bond increased with time. Significance: The early 1h μTBS to dentin was lower than the 24h μTBS for OptiBond FL, but not for Clearfil SE Bond. Differences in polymerization efficiency as well as in the resulting interfacial strength may explain such varying early bond strengths to dentin. [Copyright &y& Elsevier]