Fatigue of resin-dentin adhesive bonds is critical to the longevity of resin composite restorations. Objectives The objectives were to characterize the fatigue and fatigue crack growth resistance of resin-dentin bonds achieved using two different commercial adhesives and to identify apparent “weak-links”. Methods Bonded interface specimens were prepared using Adper Single Bond Plus (SB) or Adper Scotchbond Multi-Purpose (SBMP) adhesives and 3M Z100 resin composite according to the manufacturers instructions. The stress-life fatigue behavior was evaluated using the twin bonded interface approach and the fatigue crack growth resistance was examined using bonded interface Compact Tension (CT) specimens. Fatigue properties of the interfaces were compared to those of the resin-adhesive, resin composite and coronal dentin. Results The fatigue strength of the SBMP interface was significantly greater than that achieved by SB (p≤0.01). Both bonded interfaces exhibited significantly lower fatigue strength than that of the Z100 and dentin. Regarding the fatigue crack growth resistance, the stress intensity threshold (ΔKth) of the SB interface was significantly greater (p≤0.01) than that of the SBMP, whereas the ΔKth of the interfaces was more than twice that of the parent adhesives. Significance Collagen fibril reinforcement of the resin adhesive is essential to the fatigue crack growth resistance of resin-dentin bonds. Resin tags that are not well hybridized into the surrounding intertubular dentin and/or poor collagen integrity are detrimental to the bonded interface durability.

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Recent studies have shown that ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) inactivates endogenous dentin proteases, thereby preventing collagen degradation and improving the durability of adhesive bonds to dentin. Bond durability is routinely assessed by monotonic microtensile testing, which does not consider the cyclic nature of mastication. Objective to characterize the effect of an EDC pretreatment on the fatigue crack growth behavior of resin-dentin bonds. Methods Bonded interface Compact Tension (CT) specimens were prepared using a three-step etch-and-rinse adhesive and hybrid resin-composite. Adhesive bonding of the treated groups included a 1 min application of an experimental EDC conditioner to the acid-etched dentin. The control groups did not receive EDC treatment. The fatigue crack growth resistance was examined after storage in artificial saliva for 0, 3 and 6 months. Results There was no significant difference in the immediate fatigue crack growth resistance of the EDC-treated and control groups at 0 months. However, after the 3 and 6 months storage periods the EDC-treated groups exhibited significantly greater (p≤0.05) fatigue crack growth resistance than the control specimens. Significance Although the EDC treatment maintained the fatigue crack growth resistance of the dentin bonds through 6 months of storage, additional studies are needed to assess its effectiveness over longer periods and in relation to other cross-linking agents.

In this paper, we investigate the continuities of the metric projection in a nonreflexive Banach space X , which improve the results in [X.N. Fang, J.H. Wang, Convexity and continuity of metric projection, Math. Appl. 14 (1) (2001) 47-51; P.D. Liu, Y.L. Hou, A convergence theorem of martingales in the limit, Northeast. Math. J. 6 (2) (1990) 227-234; H.J. Wang, Some results on the continuity of metric projections, Math. Appl. 8 (1) (1995) [80][81][82][83][84]. Under the assumption that X has some convexities, we discuss the relationship between approximative compactness of a subset A of X and continuity of the metric projection P A . We also give a representation theorem for the metric projection to a hyperplane in dual space X * and discuss its continuity.

We discuss the relationships between τ -strongly Chebyshev, τ -approximative compactness, τ -strong proximinality, and proximinality, where τ stands for the norm topology or weak topology. We consider four examples which illustrate the differences, and a counterexample that shows the question regarding the approximative n-compact Chebyshev subset, raised by Bandayopadhyay et al., is negative.