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Objective: To investigate the effect of blue light photoactivated riboflavin modified universal adhesives on dentin collagen biodegradation resistance, dentin apparent elastic modulus, and resin-dentin bond strength with interfacial morphology., Methods: Dentin slabs were treated with 0.1% riboflavin-5-phosphate modified (powder added slowly while shaking and then sonicated to enhance the dispersion process) Universal Adhesive Scotch Bond and Zipbond™ along with control (non-modified) and experimental adhesives, photoactivated with blue light for 20s. Hydroxyproline (HYP) release was assessed after 1-week storage. Elastic-modulus testing was evaluated using universal testing machine at 24 h. Resin-dentin interfacial morphology was assessed with scanning electron-microscope, after 6-month storage. 0.1% rhodamine dye was added into each adhesive and analyzed using CLSM. Detection of free amino groups was carried out using ninhydrin and considered directly proportional to optical absorbance. Collagen molecular confirmation was determined using spectropolarimeter to evaluate and assess CD spectra. For molecular docking studies with riboflavin (PDB ID file), the binding pocket was selected with larger SiteScore and DScore using Schrodinger PB software. After curing, Raman shifts in Amide regions were obtained at 8 μm levels. Data were analyzed using Two-way analysis of variance (ANOVA, p ≤ 0.05) and Tukey-Kramer multiple comparison post hoc tests., Results: At baseline, bond strength reduced significantly (p ≤ 0.05) in control specimens. However, at 6 months' storage, UVA Zipbond™ had significantly higher μTBS. Resin was able to diffuse through the porous demineralized dentin creating adequate hybrid layers in both 0.1%RF modified adhesives in CLSM images. In riboflavin groups, hybrid layer and resin tags were more pronounced. The circular dichroism spectrum showed negative peaks for riboflavin adhesive specimens. Best fitted poses adopted by riboflavin compound are docked with MMP-2 and -9 proteases. Amide bands and CH 2 peaks followed the trend of being lowest for control UA Scotch bond adhesive specimens and increasing in Amides, proline, and CH 2 intensities in 0.1%RF modified adhesive specimens. All 0.1%RF application groups showed statistically significant (p < 0.05) less levels of HYP released compared to controls. Dentin E appr of riboflavin application was significantly (p < 0.05) more as compared to control groups., Conclusion: Blue light photoactivated 0.1% riboflavin modified adhesives improved the biochemical and biomechanical properties of demineralized dentin as well as the long-term resin-dentin interfacial integrity and bond strength of universal adhesive to dentin., (Copyright © 2020. Published by Elsevier Ltd.)

Objective: This study introduced the potential and proof-of-concept of high intensity focused ultrasound (HIFU) technology for dentin-surface treatment for resin-dentin bonding without acid-aided demineralization. This new strategy could provide a way to enhance interface-integrity and bond-durability by changing the nature of dentin-substrate; bonded-interface structure and properties; and minimizing denuded-collagen exposure., Methods: The interaction between HIFU waves and dentin-surface in terms of structural, mechanical and chemical variations were investigated by SEM, TEM, AFM, nano-indentation and Raman-analysis. The bonding between HIFU-treated dentin and two-step, etch-and-rinse, adhesive was preliminary explored by characterizing dentin-bound proteases activities, resin-dentin interfacial morphology and bond-durability with HIFU exposure at different time-points of 60, 90 and 120 s compared to conventional acid-etching technique., Results: With the increase in HIFU exposure-time from 60-to-120 s, HIFU waves were able to remove the smear-layer, expose dentinal-tubules and creating textured/rough dentin surface. In addition, dentin surfaces showed a pattern of interlocking ribbon-like minerals-coated collagen-fibrils protruding from the underlaying amorphous dentin-background with HIFU exposure for 90 s and 120 s. This characteristic pattern of dentin-surface showing inorganic-minerals associated/aligned with collagen-fibrils, with 90-to-120 s HIFU-treatment, was confirmed by the Raman-analysis. HIFU-treated specimens showed higher nano-indentation properties and lower concentrations of active MMP-2 and Cathepsin-K compared to the acid-etched specimens. The resin-dentin bonded interface revealed the partial/complete absence of the characteristic hybrid-layer formed with conventional etch-and-rinse bonding strategy. Additionally, resin-infiltration and resin-tags formation were enhanced with the increase in HIFU exposure-time to 120 s. Although, all groups showed significant decrease in bond-strength after 12 months compared to 24 h storage in artificial saliva, groups exposed to HIFU for 90 s and 120 s showed significantly higher μTBS compared to the control acid-etched group., Significance: The implementation of HIFU-technology for dental hard-tissues treatment could be of potential significance in adhesive/restorative dentistry owing to its ability of controlled, selective and localised combined tissue alteration/ablation effects., (Copyright © 2019 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.)

Objective: Four experimental blends of an organo-functional silane monomer with a non-functional cross-linking silane monomer (a novel silane system) were evaluated as adhesion promoters in an experiment in which a resin-composite cement was bonded to silica-coated titanium., Material and Methods: 3-Acryloyloxypropyltrimethoxysilane (as constant 1.0 vol%) was blended with 1,2-bis-(triethoxysilyl)ethane, where its concentration was 0.1, 0.2, 0.3, or 0.5 vol%. Titanium slides (n=20) were grit-blasted, silica-coated, and silanized with four experimental silane solutions, with a pre-activated silane Cimaratrade mark (VOCO, Germany) as control. After silanization, resin-composite cement stubs (Bifixtrade mark QM; VOCO, Germany) were photo-polymerized. The shear bond strength was measured after dry storage (24 h) or after thermo-cycling (6000 cycles between 5 degrees C and 55 degrees C). The resin stub failure mode was determined., Results: Statistical analysis (ANOVA) showed that type of storage (p <0.05) and concentration of cross-linker silane (p<0.005) both significantly affected the shear bond strength. The highest shear bond strength was obtained with a blend of 1.0 vol% 3-acryloyloxypropyltrimethoxysilane+0.3 vol% 1,2-bis-(triethoxysilyl)ethane, 15.9 MPa (standard deviation SD 3.4 MPa) for both the thermo-cycled group and after dry storage (24 h), 14.3 MPa (SD 4.1 MPa) (n=8/group). The lowest values were obtained with Cimaratrade mark silane 7.3 MPa (SD 2.2 MPa) in dry storage and 7.9 MPa (SD 2.0 MPa) obtained with 1.0 vol% 3-acryloyloxypropyltrimethoxysilane+0.1 vol% 1,2-bis-(triethoxysilyl)ethane. The failure type was mainly cohesive., Conclusion: A novel silane system with an optimal concentration of the cross-linking silane may produce significantly higher shear bond strength between silica-coated titanium and resin-composite cement compared to a pre-activated silane product.

The longevity of silane promoted adhesion of the surface conditioned etchable ceramic materials is a continuous and costly concern in dentistry. Moreover, it poses a functional and aesthetic dilemma both for the dentist and the patient. Several methods for surface conditioning exist, however some of them are not any more widely in clinical use. Tribochemical silica-coating combined with silane application, compared in vitro and in vivo to some other silanization protocols, is according to the literature a clinically proved, relevant adhesion promotion method to enhance bonding of resin composites to etchable ceramics. The repair of fractured ceramic with tribochemical silica-coating and followed by a silane application is, according to the literature a relevant adhesion promotion method in prosthetic dentistry. Silica-coating is followed by a silane coupling agent application. The bonding is adequate for clinical use according to the literature study.

Objectives: Three activated organofunctional silane coupling agents alone and blended with a non-functional cross-linker silane were evaluated as adhesion promoters in an experiment where a bis-GMA (bis-phenol-A-diglycidyldimethacrylate) resin was bonded to silicatized titanium. The adhesive performances of the silanes were assessed as shear bond strength values., Materials and Methods: 3-Methacryloyloxypropyltrimethoxysilane, N-[3-(trimethoxysilyl)propyl]ethylenediamine and [3-(triethoxysilyl)propyl]urea were prepared as 1.0vol.% solutions in 95 vol.% ethanol. They were each also blended with 1.0 vol.% 1,2-bis-(triethoxysilyl)ethane solutions that were activated for 1 or 24 h. Titanium slides were cleaned, silicatized, distributed randomly to study groups and silanized with nine silane solutions. After silanization experimental bis-GMA resin stubs were photo-polymerized and post-polymerized in a light-curing unit. The shear bond strength was measured as 'dry samples' and after thermo-cycling (6000 cycles at 5-55 degrees C)., Results: The type of silane affected significantly the shear bond strength (p<0.001) and the use of cross-linker silane (p<0.005) according to the statistical analysis (ANOVA). It showed that the highest shear bond strength for thermo-cycled resin stub samples (n=8/group) was obtained with a blend of 1.0vol.% 3-methacryloyloxypropyltrimethoxysilane+1.0 vol.% 1,2-bis-(triethoxysilyl)ethane blend (10.4+/-3.5 MPa). The lowest results were obtained with 1.0 vol.% [3-(triethoxysilyl)propyl]urea (4.5+/-1.0 MPa), and with 1.0 vol.% N-[3-(trimethoxysilyl)propyl]ethylenediamine (4.5+/-1.4 MPa)., Conclusions: Silanization with a blend of a functional silane and a cross-linker silane (a novel silane system) might improve the hydrolytic stability of a siloxane film between silicatized titanium and a bis-GMA resin.

Objectives: Five commercial dental silanes were evaluated in vitro as adhesion promoters bonding a luting cement to silica-coated titanium surfaces., Methods: Titanium slides (n=20) were cleaned with alumina sand and then silica-coated with a special sand consisting of alumina particles coated with silica. The bonding of a resin composite cement (3M ESPE, Seefeld, Germany) to silica-coated and silanized titanium was evaluated by using the dental silane (RelyX Ceramic Primer) that belongs to the RelyX ARC cementing kit, and comparing it to four other dental silanes (Bisco Porcelain Primer, Cimara, ESPE Sil, and Pulpdent Silane Bond Enhancer). The resin composite cement stubs (n=8) were light-polymerized onto a silanized silica-coated titanium surface. The shear bond strength of the cement stubs was measured after dry storage and thermo-cycling 6000 times between 5 and 55 degrees C. The silanes and their reactions were chemically monitored by using Fourier transform infrared analysis., Results: Statistical analysis using ANOVA revealed that the brand of silanes and the types of storage condition differ significantly (p<0.005). The highest shear bond strength was obtained with RelyX ceramic silane in dry conditions (19.5+/-4.3 MPa), and after thermo-cycling (16.6+/-3.5 MPa). The lowest results were obtained using Pulpdent Silane Bond Enhancer, in dry conditions (7.8+/-2.2 MPa), and after thermocycling (5.3+/-2.4 MPa). The analysis showed that silanes had different pH values. Some differences were detected between the silanes and their reactions., Conclusions: Dental silanes provide different bonding strengths and have differences in their pH, solvent system and silane concentration.

Objectives: The adhesive performance of 3-acryloyloxypropyltrimethoxysilane and a silane blend consisting of 3-acryloyloxypropyltrimethoxysilane and 1,2-bis(triethoxysilyl)ethane, adhering an experimental dendrimer-based resin to a silica-coated titanium surface, conditioned by CoJet method, was evaluated in vitro., Methods: 3-Acryloyloxypropyltrimethoxysilane (1.0 vol%) and a blend of 3-acryloyloxy-propyltrimethoxysilane and 1,2-bis(triethoxysilyl)ethane (both 1.0 vol%) were prepared in acidified 95 vol% ethanol. A commercial 3-methcryloyloxypropyltrimethoxysilane (ESPE Si) was used as control. The silanes were applied onto tribochemically silica-coated titanium surfaces. Fresh silane solution hydrolysis (activation) was monitored by Fourier transform infrared (FTIR) spectrometry. Experimental dendrimer resin stubs were applied and photo-polymerized on titanium. The specimens were thermocycled (6000 cycles, 5-55 degrees C). Before measuring shear bond strength of the resin to titanium, surface imaging was carried out with a scanning electron microscope (SEM) with elemental analysis applying energy dispersive X-ray analysis (EDXA)., Results: Statistical analysis (ANOVA) showed that the highest shear bond was obtained with 1.0 vol% 3-acryloyloxypropyltrimethoxysilane+1.0 vol% 1,2-bis(triethoxysilyl)ethane blend (5.2+/-1.3 MPa), and the lowest result with fresh commercial 3-methacryloyloxypropyltrimethoxysilane, ESPE Sil (2.1+/-0.8 MPa). 3-Acryloyloxypropyltrimethoxysilane yielded 4.1+/-1.0 MPa. The type of silane affected significantly the shear bond strength (ANOVA, p<0.001). All silanes were activated according to the infrared spectra. The SEM/EDXA analysis revealed an uneven distribution of titanium, silicon, and aluminum on silica-coated Ti surfaces., Conclusion: Silanization with 3-acryloyloxypropyltrimethoxysilane might offer better bonding of a novel dendrimer resin to silica-coated titanium than using a pre-hydrolyzed 3-methacryloyloxypropyltrimethoxysilane.

In dentistry, adhesion promotion with 3-methacryloyloxypropyltrimethoxysilane is usually sufficient, but its hydrolytic stability is a continuous concern. The hydrolytic stability of an alternative, 3-isocyanatopropyltriethoxysilane, was compared with that of conventional 3-methacryloyloxypropyltrimethoxysilane. Two silanes, both in 0.1 and 1.0 vol-% in ethanol-water, were evaluated in the attachment of an experimental bis-phenol-A-diglycidyldimethacrylate (Bis-GMA) resin to grit-blasted (with two different systems) titanium. Silane hydrolysis was monitored by FTIR spectrometry. Bis-GMA resin was applied and photo-polymerized on titanium. The specimens were thermocycled (6000 cycles, 5-55 degrees C). Surface analysis was carried out with scanning electron microscopy. Statistical analysis (ANOVA) showed that the highest shear bond was achieved with 0.1% 3-isocyanatopropyltriethoxysilane (12.5 MPa) with silica-coating, and the lowest with 1.0% 3-methacryloyloxypropyltrimethoxysilane (3.4 MPa) with alumina-coating. The silane, its concentration, and the grit-blasting method significantly affected the shear bond strength (p < 0.05). SEM images indicated cohesive failure of bonding, and, in conclusion, 3-isocyanatopropyltriethoxysilane is a potential coupling agent.