On the durability of resin–dentin bonds: Identifying the weakest links

Abstract

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.

Fatigue behavior of resin-modified monolithic CAD–CAM RNC crowns and endocrowns

“…This scenario should not be used to predict real clinical premolar root failures as crack propagation under fatigue mechanism (or fatigue crack growth) inside a material is known to be influenced by several inherent material properties -diameter and orientation of tubuli in dentin, filler population and size in resin composite [40,41] as an exemple -and, except for the elastic modulus, the resin composite used in this in-vitro setup to simulate the roots displays features totally different to dentin. Also, the presence in current specimens of a resin-toresin bonding interface instead of a dentin-to-resin one could have had an influence on crack propagation [40,42]. However, it is reasonable to suppose that the particular design of a monolithic endocrown restoration, which clinically extends deeply inside the root and beyond the CEJ with an endo-core, could expose the root to irreversible fracture if the crack has already split the restoration.…”

Effect of carbodiimide on the fatigue crack growth resistance of resin–dentin bonds

“…Bonded interface Compact Tension (CT) specimens were prepared from the dentin sections using a special molding technique that has been described in detail in previous studies [28, 29]. Briefly, the dentin sections represented half of the completed CT specimen geometry (Fig.…”

“…Cyclic loading was continued until the specimen underwent complete fracture. These procedures have been used previously for evaluating the resin-dentin bonded interface [28, 29] and the fatigue crack growth resistance of dentin [30, 31]. …”

Fatigue resistance of dentin bonds prepared with two- vs. three-step adhesives: Effect of carbodiimide

“…Bonded interface Compact Tension (CT) specimens were prepared from the sections of dentin using a special molding technique described previously [18, 28]. As noted in Figure 1b, the dentin sections represented half of the completed CT specimen geometry.…”

“…This process triggers the gradual destruction of poorly infiltrated fibrils within the hybrid layers [15–17]. Resin tags that are not well anchored to collagen fibrils and/or poor collagen integrity are critical weak links of the bonded interface [18]. The degradation of collagen matrices resulting from endogenous protease activity can cause a decrease in bond strength over time and a reduction in the durability of resin-dentin bonds.…”