Objective: To determine whether smear layer management, via conservative etching protocols, and the hydrophobic-rich content of hybrid layers would affect the fatigue strength of resin-dentin interfaces.
Methods: Bar-shaped dentin beams obtained from sound third molars were wet-polished for 30 s. Dentin was etched with 32 % ortho-phosphoric acid for 3 or 15 s, 10 % meta-phosphoric acid for 15 s or by a prime-and-rinse application using a mild universal adhesive (Scotchbond Universal, 3M ESPE). Self-etch application served as control. Coating was performed with a solvent-free bisGMA-based resin. Composite buildups were made with a nanofilled composite. Resin-dentin beams with twin-bonded interfaces were sectioned and stored in deionized water for 24 h at 37 ℃ before 4-point flexural quasi-static monotonic testing (n = 16). Stress-life fatigue behavior was evaluated under cyclic loading (n = 35) by the staircase method at 4 Hz. The tension side of cyclic-loaded unfractured beams were evaluated under SEM, along with the micro-morphology of etched dentin surfaces. Monotonic data was analyzed by two-way ANOVA followed by the Tukey Test and cyclic-loaded data by Kruskal-Wallis on Ranks (α = 0.05).
Results: Etching protocols and higher hydrophobic-rich content produced significantly higher fatigue life distributions (p < 0.05). Dentin demineralization was ranked as OPA 15 s > MPA 15 s > OPA 3 s > P + R > SE. Less aggressive etching and coating reduced crack formation at hybrid layers.
Significance: Current oversimplification trends in resin-dentin bonding constitute a trade-off between hybridization quality and easier adhesive handling. Controlled dentin etching and increasing the hydrophobic-rich content of hybrid layers may be necessary to extend the longevity of mild universal adhesives.
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http://dx.doi.org/10.1016/j.dental.2022.06.031 | DOI Listing |
Dent Mater
January 2024
Department of Restorative Dentistry and Cariology, Adhesive Dentistry Research Group, Institute of Dentistry, University of Turku, Turku, Finland; Turku University Hospital, TYKS, University of Turku, Turku, Finland.
Objectives: To examine whether dentin-etching extension and/or the hydrophobic-rich content of hybrid layers would affect fatigue strengths of a mild universal adhesive after long-term aging.
Methods: Twin-bonded resin-dentin interfaces were produced by etching sound midcoronal dentin beams with 32 % ortho-phosphoric acid for 15 s (OPA15s), 3 s (OPA3s) or 10 % meta-phosphoric acid for 15 s (MPA15s). Samples were bonded with a mild universal adhesive with or without additional coating using a solvent-free bisGMA-based bonding resin.
Dent Mater
August 2022
Department of Restorative Dentistry and Cariology, Adhesive Dentistry Research Group, Institute of Dentistry, University of Turku, Turku, Finland; Turku University Hospital, TYKS, University of Turku, Turku, Finland. Electronic address:
Objective: To determine whether smear layer management, via conservative etching protocols, and the hydrophobic-rich content of hybrid layers would affect the fatigue strength of resin-dentin interfaces.
Methods: Bar-shaped dentin beams obtained from sound third molars were wet-polished for 30 s. Dentin was etched with 32 % ortho-phosphoric acid for 3 or 15 s, 10 % meta-phosphoric acid for 15 s or by a prime-and-rinse application using a mild universal adhesive (Scotchbond Universal, 3M ESPE).
J Dent Res
March 2015
Bioengineering Research Center, University of Kansas, Lawrence, KS, USA Department of Mechanical Engineering, University of Kansas, Lawrence, KS, USA.
The 2-fold objectives of this study were 1) to understand whether model hydrophobic- and hydrophilic-rich phase mimics of dentin adhesive polymerize similarly and 2) to determine which factor, the dimethacrylate component, bisphenol A glycerolate dimethacrylate (BisGMA) or photoinitiator concentration, has greater influence on the polymerization of the hydrophilic-rich phase mimic. Current dentin adhesives are sensitive to moisture, as evidenced by nanoleakage in the hybrid layer and phase separation into hydrophobic- and hydrophilic-rich phases. Phase separation leads to limited availability of the cross-linkable dimethacrylate monomer and hydrophobic photoinitiators within the hydrophilic-rich phase.
View Article and Find Full Text PDFActa Biomater
July 2014
Bioengineering Research Center, University of Kansas, 1530 W. 15th Street, Lawrence, KS 66045-7609, USA; Department of Mechanical Engineering, University of Kansas, 1530 W. 15th Street, Lawrence, KS 66045-7609, USA.
Current dental resin undergoes phase separation into hydrophobic-rich and hydrophilic-rich phases during infiltration of the over-wet demineralized collagen matrix. Such phase separation undermines the integrity and durability of the bond at the composite/tooth interface. This study marks the first time that the polymerization kinetics of model hydrophilic-rich phase of dental adhesive has been determined.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
July 2009
Biophysics Program, Institute for Physical Science and Technology, University of Maryland, College Park, MD 20742, USA.
Sequence-dependent variations in the growth mechanism and stability of amyloid fibrils, which are implicated in a number of neurodegenerative diseases, are poorly understood. We have carried out extensive all-atom molecular dynamics simulations to monitor the structural changes that occur upon addition of random coil (RC) monomer fragments from the yeast prion Sup35 and Abeta-peptide onto a preformed fibril. Using the atomic resolution structures of the microcrystals as the starting points, we show that the RC --> beta-strand transition for the Sup35 fragment occurs abruptly over a very narrow time interval, whereas the acquisition of strand content is less dramatic for the hydrophobic-rich Abeta-peptide.
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